Absorption and penetration of dinoprost (prostaglandin F2 alpha) and dinoprost methyl ester into perfused mesenteric circulation in rats. The absorption of dinoprost (prostaglandin F2 alpha) and its methyl ester in rat jejunum was studied. A 22-cm segment of rat jejunum was cannulated at both ends and connected to an oscillating perfusion pump system. The mesenteric vasculature supplying this isolated segment also was cannulated and perfused with Kreb's bicarbonate buffer with dextran. Solutions of 3H-dinoprost or its methyl ester were introduced into the lumen and oscillated through the segment. The disappearance of radioactivity from the lumen and the appearance of radioactivity in the vascular perfusate were monitored. The metabolite patterns in the vascular perfusate were analyzed by TLC. A lag between the time the drug disappeared from the lumen and the time it appeared in the mesenteric circulation was detected. This lag was longer for the methyl ester than for the free acid, even though the ester disappears from the lumen faster than does the free acid. Upon removal of dinoprost from the gut lumen, a gradual decrease in the amount of drug appearing in the mesenteric circulation could be detected. However, with the ester, a slight increase could be observed for approximately 0.5 hr, followed by a decrease. Metabolism by the gut wall appears to be greater for the ester than for the acid. The results suggest that, although the ester disappears from the lumen more quickly than does the acid, it actually penetrates to the blood at a slower rate and undergoes greater metabolism.


Effects of aspirin on 14C-pirprofen disposition in rats. The effects of aspirin on 14C-pirprofen disposition in the rat were studied. An oral 60-mg/kg dose of aspirin significantly reduced plasma radioactivity during the 1--8-hr interval after an intravenous 5-mg/kg injection of 14C-pirprofen. The aspirin-treated group had only 69% as much area under the radioactivity curve as the control group. The radioactive material in plasma consisted almost entirely of 14C-pirprofen, as shown by GLC. The plasma clearance of 14C-pirprofen was 7.4 ml/hr for the aspirin-treated group and 5.1 ml/hr for the control group, while the volumes of distribution were 0.32 and 0.20 liter/kg, respectively. The apparent elimination half-life was unchanged at 5.9 hr. 14C-Pirprofen was approximately 98.6% bound to plasma proteins, and the binding decreased to an average of 97.2% in the presence of salicylate. Binding to blood cellular constituents was insignificant. Rats give 14C-pirprofen by intravenous injection without aspirin secreted 36.0--42.8% of the dose radioactivity into bile during 4 hr while a comparable group given 60 mg of aspirin/kg secreted 46.4--70.8%. TLC and GLC demonstrated that the radioactivity in rat bile was 80--90% conjugated 14C-pirprofen. The increased radioactive material secretion into bile was compensated in the intact rat by reabsorption, since the total radioactive material excreted in urine was not changed by aspirin administration.


Doxycycline determination in human serum and urine by high-performance liquid chromatography. A reversed-phase high-performance liquid chromatographic method for quantitative doxycycline determination in human serum and urine is described. The drug was extracted from buffered (pH 6.1) serum or urine into ethyl acetate. A structural analog, demeclocycline, was added as the internal standard. A 10-cm X 2-mm i.d., 5-micrometers Lichrosorb RP8 column with acetonitrile-0.1 M citric acid as the eluent was used. The effluent was monitored at 350 nm. The extraction recovery from spiked serum was 87-8 +/- 4.3% (mean +/- SD, n = 11); for urine, a value of 92.2 +/-2.0% (mean +/- SD, n = 10) was found. Within-run and within-day relative standard deviations averaged (x = 2.5 micrograms/ml, n = 10) and 4.75% (x = 2.6 micrograms/ml, n = 9), respectively. The detection limit was estimated at 50 ng/ml of serum. No significant extra peaks were observed in chromatograms obtained on serum or urine extracts, suggesting the probable absence of metabolic processes in vivo.


Microiontophoretic studies on noradrenergic inhibition from locus coeruleus of spinal trigeminal nucleus neurons. Microiontophoretic studies using cats anesthetized with alpha-chloralose and local anaesthetic were undertaken in an attempt to determine whether or not norepinephrine (NE) derived from the locus coeruleus (LC) acts on neurons of the spinal trigeminal nucleus (STN) as an inhibitory transmitter. Both conditioning stimulation of the LC and iontophoretic application of NE inhibited orthodromic spike generation by interior alveolar nerve stimulation in 9 out of 14 STN relay neurons, without affecting antidromic spikes elicited by stimulation of the contralateral medial lemniscus. Glutamate-induced spike firing of the STN relay neurons, however, remained unaltered with iontophoretic application of NE up to 200 nA. The LC conditioning stimulation inhibited orthodromic spikes in 22 out of 25 type-B interneurons in the STN, while iontophoretic NE application seldom had an effect on orthodromic spikes and spontaneous firing of the interneurons. Only 5 out of the 25 interneurons exhibited an inhibition of orthodromic spike generation and spontaneous firing with iontophoretic NE. These neurons fired spikes upon orthodromic stimulation with a relatively short latency, compared with the spike latency of neurons unaffected by iontophoretic NE. The present results strongly suggest that NE released from the terminals of the LC neurons inhibits transmission of STN relay neurons, probably by acting on primary afferent terminals to produce presynaptic inhibition.


Clofibrate displaces warfarin from plasma proteins in man: an example of a pure displacement interaction. Clofibrate is known to potentiate the anticoagulant effect of warfarin during chronic administration. We examined the disposition of racemic warfarin in four healthy volunteers before and during clofibrate coadministration using an intravenous-continuous oral sequence of warfarin administration. An interaction between warfarin and clofibrate, evidenced by longer prothrombin and prothrombin-proconvertin times, was seen in all four subjects. Clofibrate caused a displacement of warfarin from plasma protein binding sites, with a 13% increase in the free drug fraction in plasma. As predicted from theoretical considerations, this displacement resulted in a small (18%) increase in the steady-state volume of distribution, and an increase in total plasma clearance, which, for warfarin, is independent on the free fraction of drug in plasma. The net effect of these changes is that the free concentration of warfarin was not changed during clofibrate coadministration, although total plasma concentrations were lower. This study documents the occurrence in man of a displacement pharmacokinetic interaction between clofibrate and warfarin. However, this pharmacokinetic interaction does not account for the clinical interaction between the two drugs, since free warfarin concentrations are unchanged.


Effects of clofibrate and warfarin alone and in combination on the disposition of vitamin K1. Clofibrate may interact with warfarin by potentiating its effects on vitamin K disposition. To examine this possibility, specifically labeled [3H]vitamin K was given intravenously to four healthy volunteers under conditions of no drug administration, administration of warfarin or clofibrate alone, or co-administration of both drugs. Clofibrate alone did not affect the disposition of tritiated vitamin K. Warfarin alone produced an accumulation in plasma of substantial amounts of vitamin K epoxide, a metabolite of vitamin K which is reconverted to vitamin K by a specific reductase. Although reconversion is apparently blocked to a large extent by warfarin, the plasma disappearance of tritiated vitamin K in the presence of warfarin is almost superimpossible to that observed in the absence of drugs. Clofibrate coadministration did not result in greater accumulation of vitamin K epoxide in plasma. These results indicate that clofibrate does not enhance the inhibition of the reductase enzyme. Analysis of the tritiated vitamin K plasma disappearance data indicates that the pool size of vitamin K in the body is small, and is turned over almost 10 times daily. The vitamin K epoxide data suggest that, in the absence of drugs, a relatively small proportion of the epoxide is reconverted to the vitamin.


Dissociation between opiate-like and antidiarrheal activities of antidiarrheal drugs. Three synthetic antidiarrheals, diphenoxylate, loperamide and SC 27166, and two narcotics, morphine and codeine, were evaluated in rats by the intravenous and oral route for specificity and duration of their antidiarrheal, opiate-like and acute toxic effects. The activity in the castor oil test, the tail withdrawal test and the acute toxicity test was used to determine the relative antidiarrheal specificity and relative safety margins. An analysis of animal and clinical data indicate these tests to be excellent indicators of clinical usefulness and specificity. Intravenously, all five agents induced opiate-like central effects, loperamide and SC 27166 at near toxic doses only. When administered orally loperamide and SC 27166 were devoid of opiate-like central nervous system activity. Analysis of the plasma levels after oral loperamide indicated that this drug does not attain a concentration high enough to induce opiate-like central effects. All agents were effective antidiarrheals by the oral route with loperamide being the most potent (ED50 = 0.15 mg/kg), longest acting (ED50 8 hr = 1.81 mg/kg) and most specific (relative antidiarrheal specificity, 8 hr greater than or equal to 88) and having the greatest relative safety margin (8 hr = 102).


Role of peripheral adrenoreceptors and vasopressin in the suppression of plasma renin activity by L-dopa in carbidopa-treated dogs. When extracerebral dopa decarboxylase is inhibited by carbidopa, L-dopa lowers plasma renin activity (PRA). The present study was designed to determine whether this suppression of PRA is mediated by the sympathetic nerves, and to identify the peripheral adrenergic receptor types involved. All experiments were performed in pentobarbital-anesthetized dogs in which changes in renal perfusion pressure were minimized by means of a suprarenal aortic clamp. Neither alpha adrenoreceptor blockage with phenoxybenzamine nor beta adrenoreceptor blockade with propranolol was by itself sufficient to block the suppression of PRA by L-dopa with carbidopa. However, combined alpha and beta adrenoreceptor blockade lowered PRA and completely prevented any further suppression of PRA by L-dopa with carbidopa. It was also observed that phenoxybenzamine decreased PRA by 48% when administered to propranolol-treated animals. Taken together, these data indicate that L-dopa with carbidopa suppresses PRA by decreasing sympathetic nerve stimulation of both alpha and beta adrenoreceptors. Plasma vasopressin concnetration was significantly decreased by L-dopa with carbidopa both in the control group and in animals with combined alpha and beta adrenoreceptor blockade. Because plasma vasopressin levels decreased after L-dopa, vasopressin is unlikely to play a causative role in the suppression of PRA.


Warfarin enantiomer disposition: determination by stereoselective radioimmunoassay. Immunoassay techniques offer promise for the selective analysis of enantiomeric substances without prior separation. In a demonstrationof this selective analysis, radioimmunoassays were developed for R- and S-warfarin. The 4'-carboxyethyl analog of R,S-warfarin was resolved and the enantiomeric acids were coupled to bovine serum albumin. Immunization of rabbits with the conjugates led to formation of antisera which selectively bound the predicted enantiomer. Cross-reactions with various metabolites of warfarin were low (0.1--4%) except for 4'-hydroxywarfarin, as were cross-reactions with the opposite enantiomer (0.3--3%). Assays were developed and used to determine enantiomer half-lives in rats dosed with racemic warfarin. Results were consistent with those found previously by administration of individual enantiomers, thus indicating the utility of the radioimmunoassay method.


Investigation of the drug-binding defect in plasma from rats with glycerol-induced acute renal failure. The binding defect in plasma from rats with glycerol-induced acute renal failure has been studied. The protein binding of phenytoin, salicylic acid, o-methyl red and methyl orange in uremic rat plasma, measured by equilibrium dialysis at 37 degrees C, was significantly decreased. Analysis of the data by a modified Scatchard plot revealed that in uremic plasma the total binding capacity (nkP) was decreased mainly as the result of a decrease in apparent association constant (k). Charcoal extraction significantly increased the ability of uremic rat plasma to bind the four ligands and restored the binding to about that of the control plasma. Extraction with organic solvents or silicic acid and pre-dialysis against defatted human albumin produced no significant removal of the binding defect. The thiol concentrations of male rat plasma and female rat serum were significantly decreased in uremia. Dithiothreitol decreased the binding of o-methyl red to both control and uremic rat plasma and thereby largely removed the pretreatment difference in unbound fraction of dye. The results suggest the presence of endogenous binding inhibitors.


The influence of endogenous glucagon release on hyperglycemic responses to catecholamines in normal fed and diabetic rats. The present study provides evidence that changes in glucagon secretion are influential in determining the hyperglycemic activity of catecholamines in normal and diabetic rats. In normal fed rats, epinephrine (EPI) stimulated large increments in glucagon release and inhibited insulin secretion. In contrast, the modest hyperglycemic activity of isoproterenol (ISO) in normal fed rats correlated with its weak glucagon-releasing activity and its strong insulin-releasing activity. In alloxan-diabetic rats, the augmented hyperglycemic response to ISO was accompanied by larger increments in plasma glucagon levels than the catecholamine produced in normal fed rats. When glucagon release was inhibited by a concurrent infusion of somatostatin, the hyperglycemic responses of normal fed rats to EPI were reduced by approximately 67%. ISO-induced hyperglycemia in alloxan-diabetic rats was even more sensitive to inhibition by somatostatin since this response was reduced by approximately 90% when glucagon release was inhibited by somatostatin. These findings indicate that more than half of the hyperglycemic response to EPI in normal fed rats and nearly all of the hyperglycemia produced by ISO in diabetic rats result from increased glucagon release. Moreover, the impotence of ISO as a hyperglycemic agent in normal fed rats is probably due to insulin release which tends to suppress glucagon release.


Size, scatter and coverage of ganglion cell receptive field centres in the cat retina. 1. Receptive field centre sizes of brisk-sustained (X) and brisk-transient (Y) ganglion cells of the cat retina were assessed by three different methods: small spot mapping, area threshold method and spatial resolution. 2. Centre sizes of brisk-sustained (X) cells increased from 20' in the central area to about 70' at an eccentricity of 4.5 mm, centre sizes of brisk-transient (Y) cells from 50' in the central area to about 140' at 5 mm eccentricity. 3. The scatter of centre sizes at one retinal location was measured by recording as many ganglion cells as possible in one cat in a small field of retina. The centre sizes of the individual classes were homogeneous and exhibited only a small amount of scatter. 4. The coverage of the retina by the different ganglion cell classes was assessed from their density and their receptive field centre area. At every retinal location the receptive field centres of seven to twenty brisk-sustained (X) cells and of three to six brisk-transient (Y) cells were found to overlap. Sluggish concentric and non-concentric cells taken together have a coverage factor of about 60.


Dependence of motoneurone properties on the length of immobilized muscle. 1. The soleus muscle of adult cats was fixed in a shortened or lengthened position for 2 weeks by immobilizing the leg with a plaster cast. To eliminate the effects of reflex activity arising from the muscle, the lumbosacral dorsal roots were sectioned on the side of leg immobilization.2. The soleus muscle showed a significant decrease in weight after immobilization in a shortened position. Immobilization of the muscle in a lengthened position produced no significant changes in its weight.3. Two weeks after transection of the throacic spinal cord, the soleus muscle showed a significant decrease in weight. This decrease was prevented by immobilization of the muscle in a lengthened position. Immobilization in a shortened position caused no further muscle atrophy in cord-transected animals.4. Soleus motoneurones showed a significant decrease in the duration of after-hyperpolarization (a.h.p.) 2 weeks after immobilization of the muscle in a shortened position, whereas immobilization of the muscle in a lengthened position caused no significant changes in the duration of a.h.p.5. A decrease in the duration of a.h.p. of soleus motoneurones induced by cord transection was significantly prevented by immobilization of the muscle in a lengthened position but not by immobilization in a shortened position.6. In a variety of experimental conditions, the mean duration of a.h.p. of soleus motoneurones was significantly correlated with the soleus muscle: body wt. ratio.7. It is concluded that certain motoneurone properties depend upon the condition of the innervated muscle and that the primary factor responsible for the trophic influence is metabolic change in the muscle rather than contractile activity itself.


The excitation and depression of spinal neurones by ibotenic acid. 1. The firing of spinal interneurones and Renshaw cells by microelectrophoretic (+/-)-ibotenate, which was approximately eight times more active as an excitant than L-glutamate, was followed by prolonged depression of the sensitivity of the neurones to excitant amino acids and acetylcholine. 2. The depression, which lasted for 15--30 min when ibotenate was ejected for 3--6 min, was blocked by the GABA-antagonist bicuculline methochloride, and was independent of prior firing since it occurred with subthreshold concentrations of ibotenate and when ibotenate firing had been blocked by DL-alpha-aminoadipate. 3. When administered electrophoretically for 5 min, muscimol, a potent GABA  agonist, reduced neuronal excitability for prolonged periods and this effect was also prevented by bicuculline methochloride. 4. The depression of neuronal excitability produced by GABA, taurine, isoguvacine or 3-aminopropane sulphonate, ejected for periods of 5--6 min, recovered rapidly. 5. It is suggested that ibotenate is converted in vivo to muscimol or a related compound which has a prolonged, bicuculline-sensitive depressant action on the excitability of neurones.


Contribution of calcium and potassium permeability changes to the off response of scallop hyperpolarizing photoreceptors. 1. The membrane response of the distal photoreceptors in the retina of the scallop Pectin irradians to the termination of a bright white light (off response) is shown to be composed of the decay of the hyperpolarizing receptor potential and an action potential with slow kinetics. 2. The action potential can be produced in darkness in the absence of external Na+ ions by membrane depolarization. 3. The action potential is maintained by replacement of external Ca2+ with Sr2+ or Ba2+, but not by Mg2+. In normal external Ca2+ (9mM), the action potential is abolished by the addition of the Ca2+ inhibitors, La3+, Co2+, and Mn2+ or the organic Ca2+ antagonist D-600. 4. Elevated external Ca2+ concentrations increase the rate of rise and peak amplitude of the action potential as well as the rate of repolarization and after hyperpolarization, but decrease the duration. 5. The rate of rise and peak amplitude of the action potential are increased by the K+ antagonists tetraethylammonium (TEA) 4-amino-phyridine (4-AP), Ba2+ and procaine. The antagonists have different effects on subsequent phases of the response, however. External TEA and Ba2+ increase the duration, but decrease the rate of repolarization and abolish the after hyperpolarization, whereas external 4-AP and procaine increase the rate of repolarization, decrease the duration and increase the after hyperpolarization. 6. The ratio of the Ca2+ to K+ permeability (P Ca/P K) estimated from the constant field equation at the peak of the action potential in different external Ca2+ concentrations is close to 1. 7. The maximum rate of rise and the peak amplitude of the action potential are increased by membrane hyperpolarization and decreased by membrane depolarization. They are decreased by background light intensity relative to their value in the dark. 8. In normal ASW the action potential can be identified during the off response as a small overshoot of membrane potential relative to its value in the dark. 9. The rate of repolarization of the off response in normal ASW is reduced by agents or conditions which inhibit or reduce Ca2+ permeability changes, e.g. external Co2+ and La2+ or zero external Ca2+. 10. Our results suggest that a voltage-dependent increase in membrane permeability to Ca2+ and to K+ ions modifies the repolarizing phase of the receptor potential.


The responses of afferent fibres from the glabrous skin of the hand during voluntary finger movements in man. 1. Afferent activity of 111 single units from the glabrous skin area was recorded percutaneously in the median nerve of human subjects, using tungsten electrodes. 2. The majority of the units (103) were classified as low-threshold mechano-sensitive units belonging to one of the four categories previously described: rapidly adapting with small receptive fields (RA), rapidly adapting with large receptive fields (PC, presumed Pacinian corpuscle units), slowly adapting with small fields (SA I), and slowly adapting with large fields (SA II). The size of the responses (in number of impulses) to indentation and stretching of the skin was compared with that of the responses elicited during voluntary isotonic finger movements, which avoided trivial excitation of the units by direct touch. 3. All four types of units, and 77% of the single units, were activated by isotonic movements. The decreasing order of responsiveness was PC, SA II, SA I, RA. 4. Almost all responsive units were excited during the dynamic phase of ramp and smooth oscillatory movements. Static responses, on the other hand, occurred only with 50% of the slowly adapting units, corresponding to a third of the total sample (SA II, 81%; SA I, 17%. 5. For all four types of units the dynamic responses to movements were of similar size as the responses to localized skin indentation with a von Frey hair at five times threshold. 6. The results are discussed with regard to the possible implications for kinaesthesia and motor control.


On the separability of two mechanisms involved in the detection of grating patterns in humans. 1. The detectability of contrast modulation (M) of sinusoidal gratings was explored at the rate of 8 Hz. The luminance profile of a contrast modulated sinusoidal grating is L = L(1 + C cos 2 pi F chi). This stimulus may also be regarded as the sum of a steady grating pattern and counter phase flicker of the same spatial frequency. 2. Contrast modulation sensitivity (1/M) was established in five observers at several levels of constract and over a range of spatial frequencies, where M = delta C/C of delta C is the just detectable contrast change and C is the mean contrast of the grating. The slope of a modulation sensitivity function (C/delta C vs. C) is 1 (i.e. delta C = constant) near threshold contrast at each spatial frequency, but in the suprathreshold contrast range the slope flattens from close to 1 at 1.5 c/deg to almost 0 (delta C/C = constant) at 12 c/deg. 3. Adaptation to a high contrast steady grating of the same spatial frequency as the contrast modulated test gratings shifts each modulation sensitivity function to the right at low contrasts, but not at high. As a result the adapted curves cross their corresponding unadapted ones. At each spatial frequency the modulation sensitivity function is now fitted by a straight line of slope 1. While delta C needs to be higher than half the detection threshold of the same grating at spatial frequencies above 3 c/deg, in the adapted condition the values are nearly equal at each frequency. Thus pattern adaptation unmasks the threshold of the counterphase component of the contrast modulated grating near threshold contrast as well as above it. The phase of the steady adapting grating, relative to the steady component of the test grating, does not make any difference. 4. Apparently contrast modulation reveals differences beyond threshold sensitivity between spatial frequencies adjacent to the peak of the contrast sensitivity curve. For each spatial frequency channel there must be different neural coupling between steady and modulated inputs. Electrophysiological studies using contrast modulated gratings would be useful in the exploration of individual and ensemble properties of neurones of the visual cortex.


Intraventricular microinjections of a stable analogue of prostaglandin endoperoxide cause fever in rabbits. 1. Derivatives of arachidonic acid other than prostaglandin are pyrogenic, the likely candidates being the prostaglandin endoperoxides and/or the thromboxanes. 2. Intraventricular microinjections in rabbits of a stable analogue of prostaglandin endoperoxide resulted in dose-dependent increases of rectal temperature. The pyrexia was delayed in onset; no significant change in body temperature occurred for at least an hour. 3. The pyrexia was unaltered by simultaneous injection of the potent prostaglandin synthetase inhibitor indomethacin. 4. We suggest that both prostaglandins and prostaglandin endoperoxides may be implicated in fever.


Lysine transport across rat jejunum: distribution between the transcellular and the paracellular routes. Transport of lysine across the rat jejunum has been studied measuring transmural fluxes, Jms and Jsm, under short-circuit conditions, influx across the brush-border membrane, Jmc, under open-circuit and voltage-clamp conditions, and steady-state uptake by the isolated mucosa. 1. Jlysmc can be described as the sum of a saturable process with a Kt of 3 mM and a Jmax of 2.25 micromole/cm2.hr and a diffusional component corresponding to a lysine permeability of 0.014 cm/hr. Also Jlysms is well described as the sum of a saturable process and a diffusional contribution described by the same permeability as for Jlysmc. 2. The effects of the transmural p.d. on Jlysmc indicate that at 60 mM this flux includes a diffusional contribution, which corresponds to a lysine permeability of 0.014 cm/hr. 3. The passage of an electrical current across the gut wall changes the electrical conductance as expected for a cation-selective epithelium. The effect of a mucosa to serosa current on the Jms value of mannitol provides confirmation of the expected current effect on transepithelial volume flow. These effects on conductance and solute flux, together with the electrostatic effect on lysine movements, suffice to account for the p.d. effects on Jmc, Jms, and Jsm of lysine. 4. Jlyssm is in a saturable manner stimulated by increasing concentrations of D-glucose. At higher (10 mM) concentrations of lysine this effect leads to a net secretion of lysine. Qualitatively and quantitatively these effects are consistent with the model of a glucose-induced fluid circuit between the mucosal solution and the lateral intercellular spaces. 5. All observations are consistent with a paracellular, transepithelial pathway for lysine, which includes the lateral intercellular spaces. 6. The transport of lysine across the basolateral membrane is analysed. Togethet the data on transcellular passage of lysine are very similar to those reported for rabbit ileum, except that more than one transport process could not be demonstrated.


Assessment of the pulmonary origin of bronchoconstrictor vagal tone. 1. In anaesthetized spontaneously breathing cats, the sensory component of the vagal nerves was sectioned at the level of nodose ganglion, using a method described previously (Mei, 1966; Mei & Dussardier, 1966).2. The strength of the Hering-Breuer reflex (inhibitory ratio, i.e. T(1)/T(0)) provided a test for effectiveness of section of vagal afferents, particularly respiratory afferents. On the other hand, by studying the cardiac and bronchomotor effects induced by electrical stimulation of the supranodose portion of the vagal nerve, it was possible to test the integrity of the efferent vagal component.3. Unilateral right sensory vagotomy was followed by a 29% reduction in total pulmonary resistance.4. Section of the contralateral sensory vagal component (sensory bivagotomy), produced a weak supplementary effect (total decrease of total pulmonary resistance: 31%).5. No additive bronchomotor effect could be observed after the bilateral section of efferent vagal fibres (total bivagotomy).6. In intact cats, blockade of the two vagal nerves by procaine induced a decrease in pulmonary resistance similar to those produced by the sensory bivagotomy (23%). This bronchodilatator effect was concomitant with a complete disappearance of the C wave of the compound vagal potential.7. Intravenous injection of phenyl diguanide, immediately after the blockade of the C vagal fibres by procaine did not modify bronchomotor tone. This result confirms that the C pulmonary afferents, which are activated by phenyl diguanide, are mainly involved in this mechanism.8. The pulmonary irritant receptors seem to play a minor role. In fact, the I.V. administration of histamine under the same conditions, provides evidence that the corresponding neurones (small sized myelinated fibres) are potent during the procaine application.9. From these results, it appears that bronchoconstrictor vagal tone has an exclusive peripheral origin and that pulmonary endings, in particular those connected with non-medullated fibres, are probably involved in this mechanism.


Intracellular citrate or externaly applied tetraethylammonium ions produce calcium-dependent action potentials in an insect motoneurone cell body. 1. Electrophysiological observations have been made upon the cell body of an identified motoneurone of the cockroach, Periplaneta americana. Normal responses were compared with those observed after intracellular injection of citrate anions or when the preparation was bathed in solutions containing tetraethylammonium ions (TEA+).2. Normally when depolarized, the motoneurone soma gave a series of damped oscillations; the amplitude of these responses increased with increase in the applied current.3. After citrate ions had been injected into the neurone soma, all-or-none action potentials were evoked by depolarization; such responses appeared about 5-10 min after the onset of citrate injection. Injection of EGTA produced similar effects. Citrate and EGTA probably produce their effect through a reduction in the intracellular free calcium concentration.4. When preparations were bathed in saline solution containing 50 mM-TEA+, soma depolarization produced prolonged all-or-none action potentials (up to approximately 100 msec duration).5. The action potentials produced by citrate injection or externally applied TEA+ appeared to have a similar ionic mechanism; they were not depressed by sodium-free solutions or by tetrodotoxin (4 x 10(-6)M) but were reversibly blocked in saline solution containing 40 mM-manganous chloride.6. The overshoot amplitude of action potentials recorded after injection of citrate anions or in solutions containing TEA+ showed a 22.5 mV change for a ten-fold change in the external calcium concentration.7. Both intracellular citrate and external TEA+ caused a significant increase in the input resistance and membrane time constant of the motoneurone.8. It is concluded that action potentials generated under various experimental conditions in the soma of this insect motoneurone map have differing ionic mechanisms.


Discharge patterns of Purkinje cells in cats anaesthetized with alpha-chloralose. 1. Micro-electrodes have been used to record from 119 Purkinje (P) cells in the paramedian lobule of the cerebellum in cats anaesthetized with alpha-chloralose. 2. The spontaneous discharge rate and degree of irregularity of the discharge varied very much from one cell to another; the over-all mean rate (about 25/sec) was a little lower than has been reported either for barbiturate anaesthetized or for decerebrate unanaesthetized preparations. 3. Following electrical stimulation of a peripheral nerve, most P cells responded with both simple spikes and a climbing fibre response. This initial response was usually succeeded by a prolonged period of silence (over-all mean duration 350 msec) before resumption of the tonic simple spike discharge. Similar response-silence sequences could also be evoked by mechanical stimulation such as a tap applied to the pads of the forepaw. 4. Electrical stimulation of the inferior olive evoked climbing fibre responses followed by a prolonged pause in the simple spike discharge of the cell. 5. In six individual preparations, recordings were made both from P cells of the paramedian lobule and from neurones of nucleus interpositus (to which the former project). Comparison of the responses of the two types of neurone to peripheral nerve and inferior olivary stimulation showed that the end of the pauses in P cell firing correlated well with the end of a prolonged period of facilitation of the interpositus neurones. 6. These results support the hypothesis advanced in an earlier report (Armstrong, Cogdell & Harvey, 1975) that the prolonged facilitatory responses of interpositus neurones are essentially disinhibitory responses resulting from reduction in the activity of overlying cells, and that responses of P cells and of interpositus neurones consist, in general, of modulations of activity which are mutually out of phase.


Functional characteristics of slowly adapting pulmonary stretch receptors in the turtle (Chrysemys picta). 1. Single nerve fibre discharge has been recorded from slowly adapting pulmonary stretch receptors in single-pithed turtles on artificial ventilation. 2. Receptor discharge during static and dynamic lung inflations showed that lung volume was the major stimulus of these receptors. The rate and degree of change in transpulmonary pressure were without direct effect. 3. The response of these receptors to static and dynamic lung inflation differed only quantitatively from those of bronchopulmonary stretch receptors in mammals. The lower discharge frequencies and sensitivities of the turtle receptors may arise from the low body temperature of these animals. 4. The sensitivity of turtle pulmonary receptors to CO2 was greater than that recorded for bronchopulmonary receptors of mammals although the effects of CO2 on receptor discharge were qualitatively similar. In several instances, receptor discharge was totally inhibited throughout the ventilatory cycle by inflation with 5--10% CO2 in air.


The nature of the atrial receptors responsible for a reflex increase in heart rate in the dog. 1. In dogs anaesthetized with chloralose, small latex balloons were positioned at the left pulmonary vein-atrial junctions so as to stretch this region. By recording action potentials from slips of the cervical vagi it was established that distension of these balloons stimulated receptor endings in the atrial endocardium which discharged into the myelinated branches of the vagi i.e. Paintal type A, type B and Intermediate type receptors. 2. In other dogs, cooling the cervical vagus in steps of 2 degrees C reduced this response in vagal myelinated fibres. With twelve receptors the response to distension was reduced by 30% when the vagus was cooled to 16 degrees C, by 70% when cooled to 12 degrees C and abolished at 8--12 degrees C. 3. In a third group of dogs, distension of balloons at the pulmonary vein-atrial junctions resulted in a reflex increase in heart rate. Cooling the cervical vagi in these dogs in stages to 8 degrees C reduced this increase in heart rate. In nine dogs the response was reduced by 20% when the vagi was cooled to 16 degrees C, by 70% when cooled to 12 degrees C and abolished between 12 and 8 degrees C. 4. In a fourth group of dogs, distension of balloons at the pulmonary vein-atrial junctions was shown also to activate receptor endings in the atria which discharged into non-myelinated branches of the Vagi. In twelve receptors, cooling the cervical vagus in steps of 2 degrees C reduced this evoked increase in activity in non-myelinated fibres. These responses were abolished over a wide range of temperature unlike the responses observed above. 5. It is concluded that the increase in heart rate which follows distension of balloons at the pulmonary vein-atrial junctions is mediated solely by the Paintal-type receptors which discharge into the myelinated fibres in the vagi.


Gastric emptying and secretion in the calf on duodenal infusion of tryptophan, tryptamine and 5-hydroxytryptamine. 1. Gastric emptying, gastric acid and pepsinogen secretion were assessed simultaneously in the conscious calf using the test meal and duodenal perfusion technique (Bell & Mostaghni, 1975).2. When 60 mM-HCl was infused into the duodenum, gastric emptying was arrested but both acid and pepsinogen secretion continued at a low level. Duodenal infusion with isotonic NaHCO(3) caused rapid exponential emptying of the test meal and acid and pepsinogen output was more than doubled.3. Duodenal infusion of amino acids in isotonic NaHCO(3) did not affect the rapid emptying, except infusion with tryptophan, which caused a measureable degree of inhibition of emptying, with concomitant effects on acid and pepsinogen secretion4. Tryptamine and 5-hydroxytryptamine (5-HT) incorporated in low concentration into isotonic NaHCO(3) also produced depression of gastric emptying, acid and pepsinogen levels comparable to the response initiated by acid infusate. Tryptophan was effective only in non-physiological amounts while 5-HT and tryptamine were active in smaller doses.5. Our results suggest that the inhibition of gastric emptying following duodenal infusion of tryptophan noted by Stephens, Woolson & Cooke (1975) may be due to the duodenal synthesis of its biogenic amine derivatives tryptamine and 5-HT.6. The level of activity of the three gastric functions, emptying, acid secretion and pepsinogen secretion appears to be linked. A single stimulus, therefore, could evoke a duodenal receptor or receptors to mediate or suppress activity of the gastric smooth muscle and secretory cells through interrelated mechanisms. The effect of some duodenal infusates, however, produces some variability in response which suggests differential activation of different receptors with consequent variable motor activity on effector cells.


Inhibition of gamma motoneurone discharge by contraction of the homonymous muscle in the decerebrated cat. 1. The aim of this study has been to determine the autogenetic reflex effects of tendon organ stimulation upon gamma motoneurones in the decerebrated cat. 2. Tendon organs serving a muscle were excited by isometric twitch contractions of some motor units of that muscle. Contractions were elicited by electrical stimulation of the cut peripheral end of part of the ventral root supply, using a stimulus strength at or below maximum for alpha motoneurone axons. Afferent recordings in the same cats as were used to study reflexes of gamma motoneurones showed that tendon organs were powerfully excited during twitch contractions of their muscle. Early discharges were also elicited in both tendon organs and spindle primary afferents. 3. Background discharges of forty-seven triceps surae gamma motoneurones, ranging in axonal conduction velocity from 17 to 40 m/sec, were recorded from filaments of the muscle nerve. The initial response of twenty-two (47%) neurones to twitches of the triceps surae was inhibition of their discharge. The latency from time of stimulation of the ventral root ranged from 10 to 22 msec. The lowered probability of firing lasted an average of 25 msec and, occasionally, was seen as a short silent period. 4. The inhibition was reduced in duration by decreasing the resting muscle length so that less active tension was developed during contraction. 5. The inhibition was observed, in one instance, in the spinally transected decerebrated cat. 6. We argue the case that early discharges in tendon organ afferents give rise to the onset of inhibition and that tension dependent discharges of tendon organs contribute further inhibition of gamma motoneurones. 7. Sixteen gamma motoneurones were not affected by contraction but seventeen showed a period of facilitation. The facilitation could occur after a period of inhibition (eight neurones) or as the sole response to contraction. In either case facilitation occurred mainly during relaxation of the muscle and may, in part, be attributable to increased spindle primary ending firing at this time. 8. In discussion a comparision is made of the reflex effects of muscle afferent discharges on alpha and gamma motoneurones.


Relationship between calcium release and potassium release in rat parotid gland. 1. A study was made of the role of Ca release in mediating the sustained phase of K release (86 Rb release) in the rat parotid gland due to receptor activation. 2. Sr could substitute for Ca in supporting the sustained phase of the 86Rb release due to carbachol. Sr was less effective than Ca, while Ba was ineffective. 3. Sr could also restore responsiveness of the transient phase to agonists in media lacking Ca. Again, Sr was less effective than Ca, and Ba was without effect. 4. Carbachol stimulated release of 45Ca from parotid gland slices. The amount of Ca released (about 0.2 micromole/g) was much greater than the estimated Ca influx for the same period. 5. Release of 45Ca by carbachol prevented release due to a subsequent exposure to substance P. 6. Release of 45Ca due to substance P was significantly increased if muscarinic receptors were activated during tissue labelling. 7. These results support an earlier hypothesis whereby different agonists (such as carbachol and substance P) stimulate the release of Ca from a common pool and the release of this Ca mediates the transient phase of the K release response.


Sodium and calcium gating currents in an Aplysia neurone. 1. Currents generated by depolarizing the hyperpolarizing voltage pulses were recorded at temperatures of 4--12 degrees C in the voltage-clamped soma of R15 in aplysia abdominal ganglia exposed to solutions which suppressed ionic currents. 2. Subtraction of linear capacitive and leakage currents from current generated by voltage pulses to levels more positive than -20mV revealed non-linear transient outward displacement currents at the onset of the clamp step (on-current) and transient inward displacement currents after the membrane potential returned to the holding potential (off-current). Only on-currents were studied. 3. Pulses to membrane potentials of -20 to 0 mV generated a displacement current with rapid onset and exponential decay. At membrane potentials more positive than o mV a second displacement current with a much slower onset and slower exponential decay was seen. Because the different threshold potentials for the two displacement currents were close to the different threshold potentials for Na and Ca ion currents, the two displacement currents were called Na and Ca 'gating' currents. 4. The amount of charge transfer during Ca gating currents increased sigmoidally with increasing depolarization, reaching a maximum at +30 to +40 mV. Half-maximum charge transfer occurred at +15 mV. 5. Total charge movement during Ca gating currents was maximal with holding potentials of -30 to -40 mV. More positive or more negative holding potentials produced a decrease in charge movement. 6. The time course of the gating currents, but not the total charge displaced, was very sensitive to temperature. The time constant of decay of Ca gating currents had a Q10 of about 3, whereas the total amount of charge displaced had a Q10 of 1.2. 7. The charge transfer during both Na and Ca gating currents and the amplitude of Na and Ca (but not K) ionic currents were reduced in solutions containing 1 mm-n-octanol.


Inactivation of delayed outward current in molluscan neurone somata. 1. Inactivation of delayed outward current was studied by voltage clamp of isolated neurone somata of the molluscs Archidoris and Anisodoris. During prolonged voltage clamp steps in normal artificial sea water delayed outward current rises to a peak and then declines to a non-zero steady-state. During repetitive clamp pulses at repetition rates slower than 2/sec, the amplitude of peak outward current in the second pulse is commonly less than the amplitude at the end of the preceding pulse, giving the impression of continued inactivation during the repolarized interval. We have termed this property cumulative inactivation. 2. Two components of delayed outward current were separated using tetraethyl ammonium ions (TEA) and cobalt ions (Co). External TEA blocks 90% of a voltage and time dependent outward current termed K current (IK). External Co blocks 85% of a Ca activated delayed outward current termed Ca current (ICa does not inactivate during prolonged or repetitive voltage clamp pulses. IK, however, inactivates during prolonged voltage clamp steps and shows cumulative inactivation during repetitive voltage clamp pulses. 3. Inactivation of IK is voltage and time dependent and does not require influx of Ca ions. 4. As measured by a prepulse method, the onset of inactivation is characterized by a two time constant process. Fast inactivation occurs with a time course comparable to the rate of rise of outward current and can account for 90% of total inactivation. 5. Recovery from inactivation is slow with a time constant approximately an order of magnitude slower than the onset of inactivation. 6. The current-voltage (I-V) curve for peak IK can be N-shaped, with a region of negative slope resistance in the range of +30 to +80 mV. The I-V curve for steady-state IK, however, shows little or no tendency to form a local maximum. 7. The pattern of delayed outward current varies considerably between cells. A major contributing factor to this variability appears to be the relative contributions of ICa and IK to delayed outward current.


Mechanism of frequency-dependent broadening of molluscan neurone soma spikes. 1. Action potentials recorded from isolated dorid neurone somata increase in duration, i.e. broaden, during low frequency repetitive firing. Spike broadening is substantially reduced by external Co ions and implicates an inward Ca current. 2. During repetitive voltage clamp steps at frequencies slower than 1 Hz, in 100 mM-tetraethyl ammonium ions (TEA) inward Ca currents do not increase in amplitude. 3. Repetitive action potentials result in inactivation of delayed outward current. Likewise, repetitive voltage clamp steps which cause inactivation of delayed outward current also result in longer duration action potentials. 4. The frequency dependence of spike broadening and inactivation of the voltage dependent component (IK) of delayed outward current are similar. 5. Inactivation of IK is observed in all cells, however, only cells with relative large inward Ca currents show significant spike broadening. Spike broadening apparently results from the frequency dependent inactivation of IK which increases the expression of inward Ca current as a prominent shoulder on the repolarizing phase of the action potential. In addition, the presence of a prolonged Ca current increases the duration of the first action potential thereby allowing sufficient time for inactivation of IK.


The role of circulating renin in drinking in response to isoprenaline. 1. In nephrectomized rats, S.C. (0.12 mg. kg body wt.(-1)) or intracerebroventricular (I.C.V.: 0.03 mg. kg(-1)), isoprenaline failed to elicit drinking. However, when preceded (5-20 min) by a non-dipsogenic dose of I.V. pig renin, S.C. isoprenaline induced a marked, and I.C.V. isoprenaline a smaller drinking response. 2 hr after I.V. renin, S.C. isoprenaline no longer caused drinking.2. Pig renin did not enhance drinking in response to 0.12 mg. kg(-1) isoprenaline S.C. in intact or sham-operated rats.3. Isoprenaline (0.12 mg. kg body wt.(-1), S.C.) caused a larger fall of blood pressure in unanaesthetized nephrectomized than in intact unanaesthetized rats, but it was not the resulting hypotension that interfered with the nephrectomized rats' ability to drink, since intact rats with similar falls in blood pressure drank avidly in response to large doses of isoprenaline.4. Since the rate of inactivation of pig renin in nephrectomized rats was not modified by isoprenaline, drinking in nephrectomized animals in response to renin+isoprenaline was not attributable to increased plasma renin levels.5. Since isoprenaline induces drinking in the presence of circulating renin, but in the absence of renin release from kidneys, renin plays a permissive role in isoprenaline-induced drinking. Angiotensin and isoprenaline may interact at the level of intracranial receptors.


Achievement, aggression, and perceived adult age stages. A questionnaire was administered to 173 male and female undergraduates to contrast their perceptions of the transition periods of young, middle age, and old adulthood stages of aging. A comparison of the perceived stages was then made with the personality dimensions of achievement and aggression. A 2 X 2 X 3 analysis of variance was computed for sex of S, sex of the perceived individual, and three adult stages. In addition, coefficients of correlation were obtained for 24 variables. The analysis of variance resulted in finding several significant main effects and interactions. Male judged the transition of age periods earlier than females for young and middle age adults, and females were perceived as entering the stage of old age at an earlier date than males. A directionality of establishing earlier transition ages by high scorers on the achievement dimension was also noted.


The effects of age and sex on the factor structure of the Wechsler Memory Scale. Memory is one of the central intellectual functions characteristic of human behavior. Increasing age affects memory processes by requiring more time and increased learning trials in such tasks as memory for digits, symbols, and figures, and in the acquisition of new information. Factor analytic studies of the Wechsler Memory Scale (WMS) have been contradictory because of the confounding effects of subject age and sex. Principal component analyses with oblique rotations were performed 16 times on independent and random samples of males and females, and of males and females at each of three developmental age levels: 13-39, 40-59, and 60-88 years. For total male and female samples, a two-factor structure of general retentiveness and memory was found. For both males and females at 13-39 and 40-59 years, the same factor structure was obtained. The two-factor structure did not occur at age 60-88 for males or females. These findings confirm Wechsler's hypothesis as to the structure of the WMS, and Guilford's hypothesis as to the effect of age upon memory.


Effects of model warmth on acquisition and performance of modeled behavior in chronic psychotics. Hypotheses derived from an earlier study were tested in experimental dyads with 32 adult chronic psychotic state hospital residents of both sexes. Patients either interacted with an adult model who was noncontingently warm and rewarding, or were not exposed initially to a model. In a second phase, the model displayed task responses and novel behaviors incidental to the task, and the patient's subsequent imitation of the model under minimal demand conditions was recorded. In a third phase, the model again displayed the same behaviors, whereupon half the patients in each group were subjected to moderate (explicit verbal request) or high (verbal request plus material rewards) incentives to imitate. Under strong incentive conditions, initial differences between groups on incidental imitation vanished, indicating that a previously positive relationship with a model facilitates imitative performance but not learning.


Attention to stimulus presentation mode as a function of sex. This study investigated sex differences in attention to verbal stimuli presented in auditory and visual modes. Ss were 996 male and female students, ages 7 through 17, who observed different forms of a sound motion picture film. One control film contained auditory verbal stimuli only, the other control film contained visual verbal stimuli only, and the experimental film contained simultaneous, conflicting auditory and visual verbal stimuli. Attending behavior was quantified as the number of stimulus specific answers on a paper-and-pencil test administered after presentation of the film. Prior results had indicated that experimental Ss under the age of 12 attended auditory stimuli significantly more often, and those over the age of 13 attended visual stimuli significantly more often. The present experiment concerned sex differences in attending behavior during the crossover period: it was found that females switched their preference for auditory stimuli to visual stimuli earlier (age 11.5) than males (age 13.5). The significant differences between sexes (p less than .05) were attributed to differential conditioning of attitudes, reinforcements, and discriminations regarding the stimulus presentation mode, as well as biological factors.


Sex differences and the incidence of left-handedness. The higher incidence of left-handedness among males still remains a manifest and interesting phenomenon. For instance, Clark indicated that 7.84% of her male respondents were left-handed compared to 3.91% of the females. A study in South Africa among 882 students (mean age 13 years) yielded similar results: 11.13% of the males were left-handed compared to 7.69% of the females.


Frustration-instigated behavior and learned helplessness. This paper compares Seligman's recent work on learned helplessness with N. R. F. Maier's work on frustration-instigated behavior published some 30 years ago. Some striking similarities are noted between the two approaches, and it is concluded that some of the differences are more apparent than real and that the learned helplessness model could provide an explanation for the "abnormal fixations" reported by Maier.


Empirically derived personality types among male and female college students. Data on the 16 PF obtained from 130 male and female college students were cluster analyzed to produce an empirical personality typology. Two different clustering algorithms were compared. Seven personality types emerged: 1) Well-Adjusted Conservative, 2) Ego-Involved Neurotic, 3) Norm Independent, 4) Socially-Detached Neurotic, 5) Superego Controlled, 6) Self-Assured Experimenter, and 7) Tough-Minded Controlled. Not only did the types differ significantly in personality, but they also were found to be significantly different on nine different measures of interpersonal orientation. Since the types did give intuitive insight into the nature of personality as particular combinations of personality traits and also were different on variables other than those used for the classification, the scientific utility of the typological approach received support.


Discrimination learning in preschool children as a function of the stimulus and relevant dimension. The purpose of the present study was to determine discrimination learning rates as a function of the nature of the stimulus and the relevant dimension. Ss were 160 preschool boys and girls. The design consisted of two stimuli (faces and cups), two constant dimensions (size and form), and two relevant dimensions (form and color when the size dimension was held constant, and size and color when the form dimension was held constant). The errors to criterion scores revealed that for cup stimuli the color dimension was learned more rapidly than size and form, while for face stimuli the dimensions of size and form were learned more rapidly than color.


Attempted cross-transmission of coccidia between sheep and goats and description of Eimeria ovinoidalis sp. n. Attempted infection of 2 young lambs with oocysts of Eimeria christenseni from a goat was unsuccessful. Negative results were obtained also when young kids were fed oocysts of Eimeria ninakohlyakimovae from sheep. There was no difficulty in infecting lambs with the sheep coccidium resembling E. ninakohlyakimovae nor goats with the goat coccidium E. christenseni. Oocysts from the goat measured 38.4 X 26.7 microns, but were easily distinguished from Eimeria ahsata from the sheep by sporocyst size and shape, and from Eimeria ovina by oocyst size. Eimeria ninakohlyakimovae-like oocysts from sheep averaged 23.0 X 18.2 microns and were morphologically indistinguishable from previously reported goat coccidia. Since no cross infections of sheep and goats could be accomplished with oocysts of Eimeria sp. characteristic of one or the other host, I concluded that sheep coccidia previously known as E. ninakohlykimovae are distinct from morphologically similar goat coccidia and therefore constitute a separate species. Since the name E. ninakohlyakimovae was first used for coccidia from the goat, the sheep coccidium is renamed Eimeria ovinoidalis with oocyst structure and endogenous stages similar to those previously described from the sheep.


Toxoplasma gondii-vertebrate cell interactions. II. The intracellular reproductive phase. The reproduction of Toxoplasma gondii RH-strain in vertebrate cells was studied in a controlled-environment culture system. The lag period before reproduction and the doubling time of individual parasites were determined using a least-squares linear regression method of analysis which does not artificially constrain the data. In the majority of cases, the time intercept of the linear regression line was either zero, implying the lack of a lag phase before reproduction, or negative, implying the parasite had completed part of its reproductive cycle before entering the host cell. The mean doubling time of T. gondii is 10.9 h in bovine embryo skeletal muscle cells and 8.3 h in HeLa cells. This difference is not significant at the 5% level. The population doubling times of mouse-derived parasites is best described by a gamma distribution.


An experimental investigation of the modifiability of the temporal structure of spontaneous speech. This study attempted to test the hypothesis that the temporal structure of spontaneous speech is modifiable by reinforcing and punishing pauses, of a certain duration, in an operant conditioning situation. Pause rate was significantly affected by these contingencies: moreover, rate of change was rapid, indicating a "prepared" association between pausing and such contingencies. This study also attempted to test the hypothesis that there is a class of noncognitive pauses in monologue by punishing UPs to determine if UPs can be eliminated without affecting speech content. Although this manipulation did lead to a decline in pause rate, a significant increase in the amount of filled hesitation, particularly in repetition, resulted. This suggests that the overall amount of hesitation is fixed by the cognitive demands of the task but that a speaker is able to adapt to different interactional contexts by varying the category of hesitation used for cognitive planning.


Urine microscopy and infection in general practice. To test the value of urine microscopy 100 consecutive specimens were examined in the surgery and the results correlated with the subsequent laboratory culture reports.An assessment of the degree of pyuria was made by low power microscopy of a thick drop of fresh urine. A second specimen was examined under high power for the presence or absence of motile bacilli. The techniques used are described and quantified.The laboratory report was definitive in 88 of the 100 cultures. All the 33 specimens with 10(5) bacteriuria had some degree of pyuria and in 27 (82 per cent) motile bacilli had been found. In the 50 with no significant bacteriuria no motile bacilli had been seen in 38 (76 per cent).In these 88 specimens a diagnosis made in the surgery based entirely on bacterial microscopy would have been correct in 80 per cent, combined with cytological microscopy in 87 per cent, and with the addition of clinical features in 92 per cent.In the remaining 12 cases the laboratory report was inconclusive and would have made no difference to my conclusions.


Intuition and problem solving.

Intuition and problem solving. General practitioners use the hypothetico-deductive method of scientific reasoning to solve problems. In the first few minutes of their consultations physicians form initial hypotheses about their patients' problems. This process has childlike, imaginative qualities based on intuition. It is often outside consciousness and probably based on pattern recognition. It has been neglected from study and analysis because of these ;mystical' qualities. Yet it is the key to fast and efficient problem solving. If the process could be understood, its efficiency would be improved. This paper is an attempt to explore the nature of general practitioners' intuition.


The doctor/patient relationship and its effect upon outcome. The study of 299 chronically ill patients examined the doctor/patient relationship by asking two questions: first, what factors affect the quality of the relationship and secondly, does the doctor/patient relationship affect outcome for the patient? The doctor/patient relationship was measured by indicators of the doctor's awareness of the patient's problems.The following factors were found to be positively associated with the doctor's awareness: a small number of patient problems, a large number of recent visits, and the patient, rather than the doctor, initiating the consultation. The patient's age and education, the completeness of family care, and duration of care were not found to influence awareness. After eliminating the effect of confounding variables, the relationship between the doctor's awareness and the patient's recovery was maintained for some groups of patients. Awareness did not significantly affect the patient's satisfaction. We list some practical recommendations to aid doctors in increasing their knowledge of their patients.


An evaluation of the A4 folder system in general practice. All 63 general practices known to have introduced the A4 folder system were asked to complete questionnaires comparing A4 records with the traditional medical records envelope system. Of the 77 per cent who replied, an overwhelming majority favoured the A4 system and felt that it helped them to obtain higher standards of care for patients.


Some difficulties in comparing morbidity between countries. During a two-month period in general practice we compared morbidity records from the teaching practices at Southampton, UK, and Nijmegen, The Netherlands. Although the commonest conditions - emotional disorders, upper respiratory tract infection, and musculo-skeletal disorders - were equally prevalent, obesity was five times as prevalent and hypertension and urinary tract infection were twice as prevalent in Nijmegen as in Southampton. The Dutch doctors were far more ready to prescribe oral contraception to women over 50 years old. We met many difficulties in what had appeared to be a simple project and our results may reflect important differences about doctors' attitudes to care as well as differences in morbidity.


The distribution of carnitine and acetylcarnitine in the rabbit epididymis and the carnitine content of rabbit spermatozoa during maturation. The highest levels of carnitine and acetylcarnitine were found in the cauda, and spermatozoa from the proximal cauda contained significantly greater amounts of carnitine than those removed from the corpus or caput epididymidis. Acetylcarnitine levels (as a % of the total carnitine pool) were greater in all regions of the rabbit epididymis than has been reported in other species. It is suggested that the accumulation of carnitine is involved in sperm maturation.


Plasma relaxin immunoactivity in the pig at parturition and during nuzzling and suckling. One sow bled at 30--60-min intervals for 48 h at 5 and 4 days before parturition had mean +/- s.e.m. relaxin levels of 5.0 +/- 0.48 ng/ml and 5.5 +/- 0.44 ng/ml for each 24-h period respectively. This sow and another were bled at frequent intervals during parturition; both showed considerable fluctuations in their relaxin levels but no consistent peaks in relation to each birth. Mean levels during parturition were 10.7 +/- 0.46 ng/ml and 13.4 +/- 0.81 ng/ml respectively, both significantly higher than the levels at 4 and 5 days before birth. Relaxin levels in two lactating sows rose acutely during nursing, showing a 3-fold rise in one animal and an 8-fold rise in the other. Results from a third sow during an extended period of nuzzling and sucking by the piglets showed multiple peaks of relaxin immunoactivity associated with each nuzzling/sucking stimulus.


The effect of pregnancy on the interval between one oestrus and the next in the tammar wallaby, Macropus eugenii. In females mated to vasectomized males the interval between oestrous periods was 30.6 +/- 1.17 (s.d.) days but when mated to intact males and pregnancy intervened, it was 29. +/- 1.26 days (P less than 0.0025). After removal of pouch young, females carrying diapausing blastocysts gave birth 26.2 days later and came into oestrus 26.4 +/- 0.57 (s.d.) days later. When post-partum fertilization was prevented, removal of pouch young was followed by oestrus 30.4 +/- 0.99 days later (P less than 0.0005). These results indicate an influence of the conceptus upon the oestrous cycle of Macropus eugenii.


Synthesis of steroids by echidna (Tachyglossus aculeatus) testis and the effects of gonadotrophin administration. After administration of hCG and PMSG to male echidnas (in non-breeding state) the testis to body weight ratio increased 3-fold and the diameter of the seminiferous tubules doubled, but spermatogenesis was not induced. The major conversion product of testicular homogenate with [4-14C]progesterone as substrate was 17 alpha-hydroxyprogesterone (4% in untreated and 29% in treated echidnas). Testosterone (5%), androstenedione (16%) and 17 alpha,20 beta-dihydroxypregn-4-en-3-one (7%) were also obtained in gonadotrophin-treated animals. In untreated animals these steroids were present in minor amounts (less than 1%).


Time requirement for capacitation of boar spermatozoa assessed by their ability to penetrate the zona-free hamster egg. Boar spermatozoa were preincubated for various times in the isolated uterus and oviduct from a maturing gilt and used to inseminate zona-free hamster eggs. The proportions of eggs penetrated and activated were increased, and the interval between insemination and sperm penetration was shortened when the spermatozoa were preincubated for 4--5.5 h instead of 2--.5 h. Overall penetration rates were higher and sperm penetration occurred about 1 h earlier when the eggs were inseminated with spermatozoa preincubated in the uterus than in the oviduct. It is concluded that the change in ability of boar spermatozoa to penetrate zona-free hamster eggs is due to capcitation which requires 4--4.5 h and 5--5.5 h of preincubation in the isolated uterus and oviduct, respectively.


Mechanism of liquefaction of the human ejaculate. I. Changes of the ejaculate proteins. The spontaneous liquefaction of the human ejaculate in vitro was studied by macroscopic inspection, disc electrophoresis of the ejaculate proteins, free amino acid and nitrogen determinations and by electron microscopy. Liquefaction occurred in three phases. Phase 1 was characterized by the macroscopic solubilization of the gelatinous material and by disappearance of its granular ultrastructure. Zn++, Hg++ and Cu++ completely inhibited the first step of the liquefraction, which could be reversed by Na2EDTA. The factor(s) involved is most probably a proteolytic enzyme(s) which is tightly incorporated into the gelatinous material. In Phase 2 of liquefaction solubilized proteins were degraded to peptides and in Phase 3 these peptides were degraded to amino acids. Factor(s) responsible for these two steps of liquefaction could be removed by washing the gelatinous material.


Catecholamine requirement for hamster sperm motility in vitro. Homogenates of hamster and bovine glands contain a "sperm motility factor" (SMF) that stimulates the motility of hamster epididymal spermatozoa in vitro. The potency of these adrenal preparations was severely attenuated after gel filtration on a Sephadex G-10 column. This loss of activity was ascribed to the retardation and separation of co-factors for SMF which appeared to be catecholamines. The sperm motility-stimulating activity of the SMF-containing fractions was fully restored by addition of either the 'retarded' fractions or catecholamines (epinephrine or norepinephrine). Neither the catecholamines nor the 'retarded' fractions were able to sustain vigorous sperm motility in the absence of the SMF-containing fractions. The potentiating action of catecholamines on SMF was mimicked by the adrenergic agonists isoproterenol and phenylephrine and inhibited by the alpha-adrenergic antagonist phentolamine, but not by the beta-adrenergic antagonist propranolol. Our results indicate that one or more catecholamines are essential co-factors of SMF and demonstrate that hamster spermatozoa require catecholamines for their motility in vitro.


Serum gonadotrophin levels in prepubertally castrated male sheep treated for long periods with propionated testosterone, dihydrotestosterone, 19-hydroxytestosterone or oestradiol. At different times of the year, groups of wethers were treated with 20 mg testosterone, dihydrotestosterone or 19-hydroxytestosterone propionates/day or 2 mg oestradiol dipropionate/day, or the oil vehicle, for 6 weeks after a 2-week control period. LH and FSH values were determined by radioimmunoassay of serum samples collected at regular intervals. Oestradiol and dihydrotestosterone reduced LH and FSH concentrations whereas 19-hydroxytestosterone and testosterone had no effect.


The effect of ouabain on membrane potential and flagellar wave in ejaculated bull spermatozoa. Ejaculated bull spermatozoa were exposed to various concentrations of ouabain to ascertain the effect on membrane potential, intracellular concentrations of sodium and potassium and motility. Membrane potenital, measured by electrophysiological methods, decreased. Intracellular potassium decreased and intracellular sodium increased. Progressive motility decreased. In addition, the motility change produced by ouabain was identified as a decrease both in beat frequency and in wave amplitude.


Affinity of uterine luminal proteins for rat blastocysts. The binding of 125I-labelled rat uterine luminal proteins from Day-5 pregnant rats showed higher binding affinity to blastocysts than did the binding of proteins in uterine fluid from pro-oestrous rats (Day 0), rat serum albumin (RSA) or bovine serum albumin (BSA). Apparently little uptake of proteins into cells by phagocytosis or entry into the blastocoelic cavity occurred since similar results were obtained in the presence of sodium azide or cytochalasin B. Autoradiographic studies showed that the proteins were localized on the outer surface of the blastocyst. The binding was Ca2+-dependent. Denaturation of Day-5 uterine proteins at 80 degrees C reduced the counts to the values obtained with undenatured RSA and Day-0 fluids; this residual binding was considered as non-specific. The binding of labelled Day-5 uterine proteins was substantially reduced in the presence of unlabelled Day-5 proteins but to a lesser extent in the presence of RSA or rat serum. The dissociation of the bound labelled Day-5 uterine proteins occurred most rapidly in the presence of unlabelled Day-5 proteins. However, dissociation occurred within 2 h in the presence of other macromolecules, suggesting that the binding was not strong.


Altered response of cervical and vaginal epithelia to oestradiol benzoate in ewes after prolonged exposure to oestrogenic pasture. Ovariectomized ewes, 10 clover disease infertility and 10 controls, were injected daily for 3 days with 25 micrograms oestradiol benzoate. At the end of this period, the Spinnbarkeit of cervical mucus and the keratinization of the vaginal epithelium were less in the infertile ewes. It is suggested that the infertility in  clover-affected ewes is due to an inability of target organs to give a continued response to the 'priming' action of oestrogen.


The movement of pyruvate, lactate and lactate dehydrogenase into rabbit oviductal fluid. Pyruvate, lactate and lactate dehydrogenase appeared linearly in 2 ml 0.9% NaCl recirculated through the rabbit oviduct for 4 h in vivo. In oviducts from rabbits injected 3 days previously with 100 i.u. hCG, the rate of appearance of all three constituents was considerably reduced. It is considered unlikely that the lactate dehydrogenase secreted brings about the interconversion of pyruvate and lactate in the oviduct lumen.


The movement of amino acids into rabbit oviductal fluid. Twenty-three amino acids appeared linearly in oviduct fluid to reach an average concentration 27% of that in the plasma, with glycine and alanine present in greatest amount. In contrast, the concentration of urea in the fluid approached its plasma concentration after 1 h, and remained at this level for the duration of the experiment. The oviduct was unable to bring the overall uphill transport of amino acids from plasma to oviduct lumen. The amounts of amino acids appearing in the oviduct lumen of rabbits injected 3 days previously with hCG were mostly similar to those of the controls, but the movements of 6 neutral amino acids appeared to be enhanced relative to their plasma concentrations following ovulation.


The effect of sympathomimetic drugs on contractility of the vas deferens in vitro and in vivo. The sympathomimetic drugs noradrenaline, methoxamine, tyramine and norephedrine caused rhythmic contractions in isolated human vasa deferentia. Provided the drug was not washed out, these contractions lasted for the entire duration of the experiment (4-6 h). These contractions were mediated via alpha-adrenoreceptors. Intravenous administration of methoxamine or oxymetazolene to rats or guinea-pigs produced contractions of the vas deferens in vivo in some experiments but was accompanied by severe cardiovascular side effects. A local method of application was developed, using mixtures of tyramine with Silastic prepared as collars specially designed to fit round the vas deferens. Acute and chronic insertion of these slow-releasing devices around the vas deferens of rats produced rhythmic contractions of the vas deferens without any serious side effects.


Antifertility effect of sympathomimetic drugs on male rats when applied locally to the vas deferens. Local application of collars containing 25% methoxamine, 50% or 75% tyramine or 50% norephedrine to both vasa deferentia of rats caused a reduction in fertility but not in their ability to mate. A gradual return to fertility was seen in those animals which received the lower dose of tyramine or norephedrine, while the other treatments caused a permanent reduction in fertility. The cause of sterility was production of azoospermic ejaculates resulting from either a block in sperm transport in the vas deferens or from a deficiency in the ejaculatory mechanism. Only methoxamine caused a mechanical obstruction of the vas deferens, but it is possible that the other drugs caused a sustained spasm. An emission defect could have been due to transmitter depletion, receptor-specific desensitization or presynaptic alpha-adrenoreceptor-mediated inhibition. Spermatozoa from the cauda epididymidis were immotile following the treatments.


Induction of meiosis in fetal mouse testis in vitro by rete testis tissue from pubertal mice and bulls. To test whether a meiosis-inducing substance (MIS) is responsible for the induction of meiosis in the testis at puberty, pubertal mouse rete testis was grown with (1) fetal undifferentiated mouse testis attached to the other side of a filter and (2) the used medium obtained from culture of the rete testis of a pubertal bull for 2 days. In both systems meiosis was induced in the fetal testis showing that MIS is not species specific. No meiosis-preventing effect was seen and it is concluded that meiosis in the testis is triggered at puberty as a result of the activity of the MIS concomitant with decreased activity of the meiosis-preventing substance.


Carnitine, acetylcarnitine and the activity of carnitine acyltransferases in seminal plasma and spermatozoa of men, rams and rats. The concentration of total carnitine (i.e. carnitine plus acetylcarnitine) was measured in seminal plasma and spermatozoa of men and rams. In ram semen, there was a close correlation between the concentration of spermatozoa and that of total carnitine in the seminal plasma, indicating that the epididymal secretion was the sole source of seminal carnitine. The percentage of total carnitine present as acetylcarnitine was 40% in seminal plasma and 70-80% in spermatozoa. The acetylation state of carnitine in seminal plasma was apparently not influenced by the metabolic activity of spermatozoa in ejaculated ram semen as no change was found in the plasma concentration of carnitine or acetylcarnitine up to 45 min after ejaculation. In spermatozoa, the activity of carnitine acetyltransferase (EC 2.3.1.7) was approximately equivalent to that of carnitine palmitoyltransferase (EC 2.3.1.21); and the activity of these enzymes was similar in ram and human spermatozoa but greater in rat spermatozoa. It is concluded that there is no correlation between the content of either total carnitine or the carnitine acyltransferases and the respiratory capacity of spermatozoa.


A high incidence of abdominal pregnancy in the Djungarian hamster (Phodopus sungorus). Eight animals with abdominal fetuses were found in a relatively small colony of Djungarian hamsters. All the fetuses were macerated. Some had remains of an amniotic sac with an umbilical attachment to a placenta adherent to the peritoneum, but others were without placental remains. Gross and histological examinations failed to reveal any ruptures of the uterus or oviducts. It was not possible to decide whether the abdominal pregnancies were primary or secondary.


Effect of exogenous gonadotrophin (PMSG) on the antral follicle population in the sheep. Follicles were obtained from the ovaries of four groups of 15 ewes. Ewes in the control group were ovariectomized on the 12th day of the oestrous cycle. The other ewes were all given PMSG on the 12th day of the cycle; some were ovariectomized 24 or 40 h later, the others were given prostaglandin followed by hCG and were ovariectomized 6 or 12 h after the hCG injection. All follicles greater than 2 mm in diameter were measured and examined macroscopically for signs of atresia. Some were subjected to detailed morphological examination, the pattern of steroid secretion was determined in others. All the evidence from these three approaches suggested that, in vivo, reversal of the atretic process ('rescue') plays no part in the increase in the number of follicles observed following administration of PMSG.


Maternal nest building by pseudopregnant mice. Pseudopregnant mice displayed maternal nest-building behaviour. Their nests were smaller but qualitatively identical to those constructed by pregnant animals.


Embryo survival in heifers after transfer of an egg to the uterine horn contralateral to the corpus luteum and the effect of treatments with progesterone or hCG on pregnancy rates. Day 7 eggs (oestrus = Day 0) were surgically transferred singly to the uterine horn contralateral to the CL and heifers were either slaughtered on Day 24-26 (Group 1) or palpated per rectum on Day 42 (Group 2) to determine the presence of a developing conceptus and a maintained corpus luteum. There was a fall in pregnancy rate of the control heifers in Groups 1a (6/10) and 2a (2/10) (P = 0.085). Pregnancy rate was unaffected by progesterone treatments from Day 13 to the day before slaughter in Group 1b (8/10), or to Day 23 in Group 2b (2/10). Two of the conceptuses recovered in Group 1b were developing in the presence of regressed corpora lutea. There was, however, an increase in pregnancy rate in Group 2d (6/10) compared with Group 2a (2/10) when heifers were treated with hCG from Days 13 to 35 (P = 0.085). The results indicated that embryonic death is occurring after Day 24 and suggest that a change in the nature of the embryonic signal may be occurring at this time.


Chronic guanethidine treatment of female rats including effects on the fetus. Adult virgin female rats were injected daily with low doses (5 or 10 mg/kg) or a high dose (30 mg/kg) of guanethidine for 12 or 18 weeks respectively. 'Short' and 'long' noradrenergic neurones were unaffected by low doeses. This contrasts markedly to earlier findings in male rats in which long-term damage of 'short' noradrenergic neurones occurred, and indicates a basic difference between 'short' noradrenergic neurones in male and female rats. Widespread degeneration of both types of neurones followed treatment with high doses and little reinnervation was observed 8 weeks after cessation of treatment. Fertility, pregnancy and litter size were apparently unaffected. Some teratogenic effects were observed in the offspring of female rats treated with guanethidine (10 or 25 mg/kg/day) before and throughout pregnancy. However, these effects had largely disappeared by the time the offspring were 10 weeks old. Since noradrenergic neurones of newborn rats are particularly sensitive to damage by guanethidine it would appear that either very little guanethidine crosses the placental barrier or that noradrenergic neurones are not susceptible during prenatal development to the cytotoxic effects of guanethidine.


Study of U.S. Medical School Applicants, 1977--78. This annual report on applicants to the 1977--78 U.S. medical school freshman class describes the first substantial decline in applicants during the past quarter century. Since the decline was accompanied by the opening of several new medical schools, the chances of gaining admission improved to 39 percent, the highest in six years. For applicants making their first attempt the acceptance rate was 43 percent. There was no loss of qualified applicants, however; the 1977--78 pool presented record-high entrance test scores and undergraduate college grades. In the report comparisons are made with activity in 1974--75--the peak year for medical school spplicants--in order to measure the impact of the decline on individual medical schools and geographical regions and on various applicant subpopulations.


Group experience as a means of training medical students. All medical students in a six-week psychiatric clerkship met once a week in "experiential groups." One week after the last group session a concluding and evaluative discussion was held. A detailed description of the students' responses and reactions is given. The results indicate that for the majority of the students, the experiential group was the most significant personal and learning experience they had during the clerkship. It effected better interpersonal communication among the students and improved their humane skill, empathy, and sensitivity.


Psychological aspects of medical care: a training seminar for primary care providers. A seminar devoted to the psychological aspects of medical care has formed the major portion of the psychiatric training of primary care internal medicine residents at the Kenmore Center of the Harvard Community Health Plan since 1973. The group includes a psychiatrist, a psychiatric nurse, staff physicians, residents, and nurse practitioners. The atmosphere is open and supportive, and discussion focuses on particular situations causing discomfort to members. Content issues include professional identity, relationships with co-workers, and difficulties in handling patients. The group teaches the value of communication and sharing and improves skills in caring for patients.


The first pelvic examination: helping students cope with their emotional reactions. The author has conducted seminars with small groups of medical students beginning their training on an obstetrics and gynecology service. Six characteristic responses of students to performing their first pelvic examination are described. Within the framework of the seminar discussion, an attempt is made to help the students cope with those reactions that could impair their ability to perform competent gynecological examinations.


Electrical properties of the cellular transepithelial pathway in Necturus gallbladder: III. Ionic permeability of the basolateral cell membrane. The ionic permeability of the basolateral membrane of Necturus gallbladder epithelium was studied with intracellular microelectrode techniques. After removal of most of the subepithelial tissue (to reduce unstirred layer thickness), impalements were performed from the serosal side, and ionic substitutions were made in the serosal solution while a microelectrode was kept in a cell. Thus, it was possible to obtain continuous (and reversible) records of transepithelial and cell membrane potentials and to measure intermittently the transepithelial resistance and the ratio of cell membrane resistances. From these data and the mean value of the equivalent resistance of the cell membranes in parallel (obtained from cable analysis in a different group of tissues), absolute cell membrane and shunt resistances and equivalent electromotive forces (emfs) were calculated. From the changes of basolateral membrane emf (Eb) produced by the substitutions, the conductance (G) and permeability (P) of the membrane for K, Cl and Na were estimated. Potassium-for-sodium substitutions produced large reductions of both cell membrane potentials, of Eb, and of the resistance of the basolateral membrane (Rb), indicating high GK and PK. Chloride substitution with isethionate or sulfate resulted in smaller changes of cell membrane potentials and Eb and in no significant change of Rb, indicating small but measurable values of GCl and PCl. Sodium substitutions with N-methyl-D-glucamine (NMDG) resulted in cell potential changes entirely attributable to the biionic potential produced in the shunt pathway (PNa greater than PNMDG), and in no significant changes of Rb or Eb, indicating that GNa and PNa are undetectable. The question of the mechanism of Cl transport across the basolateral membrane was addressed by comparing the mean rate of transepithelial Cl transport : formula, see text: and the predicted passive Cl flux across the basolateral membrane (from the membrane Cl conductance, potential, and Cl equilibrium potential). The conclusion is that only a very small fraction of the Cl flux across the basolateral membrane can be electrodiffusional. Since the paracellular Cl conductance is also too low to account for : formula, see text:, these results suggest the presence of a neutral mechanism of Cl extrusion from the cells. This could be a NaCl pump, a downhill KCl transport mechanism, or a Cl-HCO3 exchange mechanism.


Slowing of the time course of the excitation of squid giant axons in viscous solutions. The time course of excitation of intracellularly perfused squid giant axons was slowed as the solution viscosity was raised by adding neutral molecules, i.e., glucose and glycerol. By twofold increase of the solution viscosity, the duration of action potential was prolonged to 2.7-fold and the maximum rate of rise decreased to one-half. At the same time, the membrane resistance at resting state increased by 60%. These effects were reversible. The time course of inward and outward currents was slowed also. When the solution viscosity increased to twofold, the time to peak inward current increased by 80%, and the amplitudes of peak inward and steady outward currents decreased by 60% and by 70%, respectively. These effects were not specific for the sodium or the potassium channel. Effects of solution viscosity occurred in both hypotonic and hypertonic solutions. Q10 values of temperature dependence of the time course of the action potential were equal in any viscous solutions. These effects in viscous solutions were explained by the change in solution viscosity but not by the change in solution osmolarities, ionic activities, or solution resistivity.


Reversible electrical breakdown of lipid bilayer membranes: a charge-pulse relaxation study. Charge-pulse experiments were performed with lipid bilayer membranes from oxidized cholesterol/n-decane at relatively high voltages (several hundred mV). The membranes show an irreversible mechanical rupture if the membrane is charged to voltages on the order of 300 mV. In the case of the mechanical rupture, the voltage across the membrane needs about 50-200 musec to decay completely to zero. At much higher voltages, applied to the membrane by charge pulses of about 500 nsec duration, a decrease of the specific resistance of the membranes by nine orders of magnitude is observed (from 10(8) to 0.1 omega cm2), which is correlated with the reversible electrical breakdown of the lipid bilayer membrane. Due to the high conductance increase (breakdown) of the bilayer it is not possible to charge the membrane to a larger value than the critical potential difference Vc. For 1 M alkali ion chlorides Vc was about 1 V. The temperature dependence of the electrical breakdown voltage Vc is comparable to that being observed with cell membranes. Vc decreases between 2 and 48 degrees C from 1.5 to 0.6 V in the presence of 1 M KCl. Breakdown experiments were also performed with lipid bilayer membrane composed of other lipids. The fast decay of the voltage (current) in the 100-nsec range after application of a charge pulse was very similar in these experiments compared with experiments with membranes made from oxidized cholesterol. However, the membranes made from other lipids show a mechanical breakdown after the electrical breakdown, whereas with one single membrane from oxidized cholesterol more than twenty reproducible breakdown experiments could be repeated without a visible disturbance of the membrane stability. The reversible electrical breakdown of the membrane is discussed in terms of both compression of the membrane (electromechanical model) and ion movement through the membrane induced by high electric field strength (Born energy).


Volume flows across gallbladder epithelium induced by small hydrostatic and osmotic gradients. The hydraulic conductivity of rabbit gallbladder epithelium has been studied using a continuous volumetric method based on capacitance measurements. The time resolution for measuring osmotic flows is in the range of seconds. Volume flows have been induced by osmotic gradients between 0 and 100 mosmol. In this range the flow-force relation is linear and the Pf value is 9.3 X 10(-3) cm/sec. After correction for solute polarization effects, the Pf value amounts to 0.05 cm/sec. The observed flow is constant between 5 sec up to 20 min after a sudden increase in the osmolarity of the mucosal solution. The wet weight of the gallbladder tissue decreases by 22% and increases by 30% during osmotic flows from mucosa to serosa, respectively. Volume flows induced by hydrostatic pressure gradients on the mucosal surface are linearly related to the driving forces between 0 and 40 mbar. The Pf value is 0.15 cm/sec. The volume flows are constant between 2 sec and 15 min after pressure application. The flow-force relation for pressure gradients on the serosal surface is markedly nonlinear for gradients greater than 5 mbar. Below 5 mbar the Pf value is 4.5 cm/sec. From electrical measurements, e.g., resistance and streaming potentials, and from flux studies with inulin and polyethylene glycol 4000, it is concluded that hydrostatic and osmotic gradients are not comparable when they are applied to gallbladder epithelium. They induce volume flows across different pathways, e.g., osmosis predominantly across the cellular route and pressure filtration predominantly across paracellular routes.


Characteristics of anion transport in cat and dog red blood cells. Self-exchange of chloride and sulfate in dog and cat red cells has been measured under equilibrium conditions. The rats of efflux for these anions are approximately twofold higher in dog compared to cat red blood cells. Although the rates differ, the anion exchange systems of these two red cell types exhibit many common properties. The dependence of 35SO4 efflux on the intracellular SO4 concentration, the pH dependence and the inhibition of 35SO4 efflux by Cl and SITS are almost identical in dog and cat red cells. Nystatin treatment was used to study the dependence of 36Cl efflux on internal Cl. Chloride efflux exhibits saturation in both cell types with dog red cells possessing a higher Vmax and K1/2 than cat red cells. The number of anion transport sites was estimated by extrapolation to the number of molecules of dihydro DIDS (H2DIDS, where DIDS is 4,4'-diisothiocyano-2,2' stilbene-disulfonic acid) which were bound at 100% inhibition of transport. The results indicate that either the turnover numbers for anion transport differ in dog, cat, and human red cells or that there is heterogeneity in the function of the membrane components which bind H2DIDS.


Fluorescent probes for asymmetric lipid bilayers: synthesis and properties in phosphatidyl choline liposomes and erythrocyte membranes. We have synthesized three sets of fluorescent probes which we believe will be useful in studies of asymmetric membranes and have studied their interactions with model lipid bilayers and erythrocyte membranes. The probes were designed to partition preferentially into one face of a lipid bilayer with asymmetrically disposed phospholipids and to report lipid transitions in that monolayer. We synthesized more than twenty probes containing anthroyl-, dansyl-, or pyrene rings with acidic, basic, and neutral functional groups and alkyl "spacers" of various lengths. The interactions of these probes with liposomes of phosphatidyl choline and with erythrocyte membranes were characterized to determine whether probe insertion was asymmetric, how deeply the probe penetrated the bilayer, and whether the probe reflected thermotropic phase transitions in model membranes. The set of variously charged anthroyl esters, analogs of local anaesthetics, appears to be promising for studies of asymmetric membranes. Fluorescent probes have been used extensively to provide information on the lipid regions of biological membranes. Membrane fluidity, a composite of molecular packing and motion of acyl chains in lipid bilayers, has been assessed with a variety of fluorescent probes, the fluorescence of which undergoes some measurable change at the temperature of the membrane's thermotropic phase transition. A large number of fluorescent probes have been used for this purpose. Bashford, Morgan and Radda (Bashford, C.L., Morgan, C.G., Radda, G.K. 1976; Biochim. Biophys. Acta 426:157) and Thulborn and Sawyer (Thulborn, K.R., Sawyer, W. H. 1978; Biochim. Biophys. Acta 511:125) synthesized several fatty acid derivatives in which an anthracene group is attached (in ester linkage) along the acyl chain at various positions, and have shown that this set of probes may be useful in probing membrane fluidity at different depths within the bilayer. This report  describes the synthesis and properties of several sets of amphipathic fluorescent probes, which may partition unequally into the two faces of an asymmetric lipid bilayer, and may therefore provide information about membranes complementary to that obtainable with existing probes.


Zinc-dependent action potentials in giant neurons of the snail, Euhadra quaestia. In giant neurons of subesophageal ganglion of the Japanese land snail, Euhadra quaestia Deshayes, permeation of Zn ions through Ca channels were investigated with a conventional current clamp method. All-or-none action potentials of long duration (90 to 120 sec) were evoked in 24 mM Zn containing salines. The overshoots were about +10 mV and the maximum rate of rises (MRRs) was about 2.9 V/sec. The amplitudes and the MRRs of the action potentials depended on external Zn ion concentrations. The action potentials were suppressed by specific Ca-channel inhibitors such as Co2+, La3+ and Verapamil, but they were resistant to Na-channel inhibitor, tetrodotoxin, even at 30 microM. It is concluded that these action potentials are generated by Zn ions permeating Ca channels in snail neuronal membrane. On the basis of Hagiwara and Takahashi's (S. Hagiwara & K. Takahashi, 1967, J. Gen. Physiol. 50:583) model of Ca channels, it is inferred that Zn ions are 5 to 10 times stronger in affinity to Ca channels than Ca ions, but 10 to 20 times less permeable.


Relationship of California group virus infection and mental retardation: seroepidemiological observations. A plaque reduction neutralisation test was utilised to determine the prevalence of antibodies to California group virus (LaCrosse subtype) among 612 moderately to profoundly retarded subjects resident in two Wisconsin state institutions. Neutralising antibodies were detected in the sera of fifty-one (8 per cent) of the subjects tested. Age and sex differences in antibody distribution were not significant. When sero-logical data correlated with clinical case history records, antibody was found in the sera of 13 per cent (24/188) of a group in which mental retardation (MR) was attributed to "presumed psychological causes" and in 8 per cent (12/158) of a group for which the aetiology of MR was "encephalopathy". In a group of 254 subjects with MR of unknown aetiology, none of the sixty subjects with cranial anomaly and only two of the ninety-five (2.1 per cent) subjects with Down's syndrome were positive for antibody to CEV, while thirteen of ninety-nine (13.1 per cent) subjects diagnosed as "other cerebral defects" had CEV antibody. In a majority of the subjects with CEV neutralising antibody, MR was attributed to perinatal influences.