Records of anoplocephaline cestodes from wild rabbits and hares collected throughout Great Britain. Four species of anoplocephaline cestodes were found in wild rabbits collected throughout Britain in 1962 and 1972, i.e; since the great reduction in rabbit numbers following the introduction of myxomatosis, in 1953. They were Cittotaenia pectinata (Goeze, 1782), C. denticulata (Rudolphi, 1804), C. ctenoides (Rhiehm, 1881) and Andrya cuniculi (Blanchard 1891). C. pectinata and C. denticulata were relatively common with a respective prevalence of 25% and 8% in two samples totalling 442 rabbits and were widely distributed throughout Britain. C. ctenoides was rate and only recorded from seven localities, although these were spread throughout Britain A. cuniculi was also rate being known from four counties in England and five islands off southern England and Wales. C. pectinata was the only species found in hares and its prevalence was low at 6%. The records are shown plotted on to 10 km square distribution maps.


Studies on filariasis. IV. The rate of escape of the third-stage larvae of Brugia pahangi from the mouthpart of Aedes togoi during the blood meal. The rate of escape of the third-stage larvae of Brugia pahangi from Aedes togoi which were allowed to probe on a cat and a mouse at time intervals of 5, 10, 20, 30 and 60 seconds was studied. The rate of escape of third-stage larvae at all time intervals was greater during probing on the cat than on the mouse, and was in a logarithmic linear relation to the length of probing time by the mosquito host. The greatest loss (91.35%) of third-stage larvae was in mosquitoes which fed on a cat until fully gorged. There was a remarkable rate of escape (57.41%) within 5 seconds. This striking rate of escape of third-stage larvae may have important implications on filariasis transmission. Most larvae migrated towards the proboscis and head of mosquitoes during these feeding periods. Nearly equal numbers of third-stage larvae escaped from mosquitoes which fed to repletion for more than 60 seconds on a mouse and from those which probed fro more than 60 seconds on the same mouse but did not engorge. This confirmed our view that filling up of the stomach with blood does not constitute the single factor in causing the release of third-stage larvae from the mosquito host.


Application of immunoperoxidase techniques to localize horseradish peroxidase-tracer in the central nervous system. Immunoperoxidase techniques are presented which can be used to localize horseradish peroxidase-tracer in paraffin-embedded tissues of the central nervous system. Compared to histochemical methods using frozen sections, these immunologic techniques allow the use of stored, serial paraffin sections, and appear more sensitive for the demonstration of intraneuronal horseradish peroxidase after retrograde transport. The immunoperoxidase bridge techniques from reaction products of high quality which can easily be seen in fine processes.


Evaluation of silicon and germanium retention in rat tissues and diatoms during cell and organelle preparation for electron probe microanalysis. Chemical, radiochemical and x-ray microanalysis assays were used to define parameters of silicon (Si) retention during preparation og biologic samples (rat liver, spleen, kidney, lung, diatoms and cell organelles) for x-ray microanalysis, Due to its longer half-life 68-Fe was used in some cases to trace SI. Leaching of Si from cells and organelles by the aqueous preparation media was overcome by use of the freeze-substitution process. Cells were treated with 30% glycerol hypertonic sucrose medium to reduce ice damage. Embedment in Spurr's low viscosity epoxy resin medium caused no apparent Si loss. A semiquantitative evaluation showed 0.5 x 10-8 to 0.3 x 10-17 g detectable Si in isolated rat liver mitochondria in thin sections, which is within the instrument's range of detection. This study indicateds that the presence of Si in the mitochondria is not the rsult of contamination.


Centrifugal cytology. III. The utilization of centrifugal cytology for the preparation of fixed stained dispersions of cells separated by bovine serum albumin bouyant density centrifugation. This paper describes the modification of Centrifugal Cytology for the preparation of permanent, fixed, stained dispensions for both light and scanning electron microscopy of cells which have been isolated on bovine serum albumin (BSA) boyant density gradients. The principal problem with BSA gradient fractions is that the albumin which is present even after dilution is precipitated by the glutaraldehyde fixative. This problem has been solved by the layering of an intermediate D2O solution under the BSA and subsequent removal of the BSA solution and the underlaying with D2O containing glutaraldehyde. A special layering machine facilitates and expedites these operations. This technique has also been applied to BSA-seperated guinea pig and chicken bone marrow cells, as well as Ehrlich ascites tumor cells, hen and human blood cells. The number of celll present in each area of the slide is maintained at a constant value by utlizing a table of dilution factors. This table was generated by a computer program which calculates the concentration of cells present in the rractions and divides it by the number of celll desired.


Buoyant density separation of cells. I. The buoyant distribution of guinea pig bone marrow cells. Guinea pig bone marrow cells were separated by buoyant density utilizing linear gradients of bovine serum albumin (BSA). It has finally become possible to characterize the cells present in the density fractions in terms of classical morphology. The development of the Cell Type computer program which calculates the percentages of the individual types of cells present in the fractions and their buoyant density distributions and plots the data has greatly facilitated and improved the accuracy of these studies. Approximately 40 cell types were observed in guinea pig bone marrow. Cells with definitive morphologies such as erythrocytes, the neutrophilic series, the binucleate blast megakaryocyte precursor and cells in mitosis band as virtually single peaks. Cells which are parts of continua or can easily be wrongly classified are found in multiple peaks. The small lymphocytes which are known to be polydisperse are found as five peaks. Because of the very strong benzidine staining by the glutaraldehyde-fixed hemoglobin, some of the erythroblasts were wrongly staged, resulting in a multimodal distribution. The presence of macrocytes further complicated these distributions. The rule that the younger cells are always less dense than the mature cells was adhered to in those cases where the cells could be definitively characterized, such as the neutrophilic series and the blasts. These results indicate that morphology is a good first approximation of reality.


Genetic polymorphism of properdin factor B in the rhesus: evidence for single subunit structure in primates. Properdin Factor B shows genetic polymorphism in the human and the polymorphic patterns in agarose gel electrophoresis suggest a tetrameric structure. Factor B polymorphism in the rhesus monkey has been demonstrated in the present study to be genetically determined and under the control of a single autosomal locus, rhesus Bf. Six codominant alleles, Bf-F, Bf-G-1, Bf-G-2, Bf-S-1, Bf-S-2 have been recognized and the first five have been shown to have gene frequencies of 0.307,0.160,0.016,0.377, and 0.139. The electrophoretic appearance of the polymorphic patterns does not suggest a tetrameric structure in the rhesus. Structural studies show purified human factor B to exist as a single subunit of molecular weight 94,000 daltons so that a tetrameric structure appears highly unlikely.


Reversible restoration by thymosin of antigen-induced depression of spleen DNA synthesis in NZB mice. Antigen-induced depression of spleen DNA synthesis was studied in NZB and CBA/J mice. This phenomenon, a measure of T suppressor cell activity, normally decreases as a consequence of aging. However, NZB mice have an accelerated loss of antigen-induced depression that can be restored by treatment with thymosin or injection of 1-month-old NZB thymocytes. The restoration by thymosin declined between 1 and 2 weeks after treatment, but could be induced again after a second exposure to thymosin. These results suggest a potential for reversible but repeatable restoration of suppressor cell activity in NZB mice.


The structure and function of immunoglobulin domains. II. The importance of interchain disulfide bonds and the possible role of molecular flexibility in the interaction between immunoglobulin G and complement. The observation that reduction of the inter-chain disulfides in rabbit antibody destroys its ability to interact with complement was confirmed and shown to be true also of human meyloma IgG1 subclass proteins. In the latter case a C1-binding assay was used. Further studies indicated that it was the interheavy chain disulfides which were essential for complement-binding activity: Non-covalently reassembled IgG (LHHL) was devoid of C1-fixing activity whereas molecules formed from covalently linked heavy chain dimers, and reduced and alkylated light chains (ie., LH-HL) were as active as the parent intact IgG. Fc fragments from IgG1 bound C1 and this activity was insensitive to the presence or absence of intact interchain disulfides. These bonds therefore are neither directly involved in C1 binding nor essential for the integrity of the binding site. We have also shown that although IgG4 does not bind C1, Fc fragments derived from this subclass fix C1 with an affinity comparable to that of the corresponding fragment from IgG1. These data suggest that quaternary interaction with other regions of the molecule (ie., Fab) may modulate the activity of the C1-binding site.


IgE antibody-specific abrogation of an established immune response in mice by modified antigens. DBA/1 mice were immunized with low doses of ovalbumin and alumina gel to elicit an IgE response which could be augmented upon reimmunization. Treatment of IgE-producing mice with high doses of chemically modified ovalbumin preparations markedly reduced or eliminated the ability of the mice to respond to subsequent reimmunizations with low doses of ovalbumin. It was found that the primary structural requirement for efficacy of the modified ovalbumins was reduced antigenicity to prevent the anaphylactic demise of the animals. Cumulative doses of 0.5 mg or more given in several increments, i.v., afforded optimal protection. The protection was antigen-specific and persisted for 2 to 3 months regardless of intervening exposures of the animals to low doses of antigen. It could be extended by further courses of treatment. There was no correlation between the levels of circulating hemagglutinating or total antibody and the induction of unresponsiveness. Nor was the passive administration of antibody able to approximate the effects of the modified antigens. It is suggested that the induction of the IgE class specific unresponsiveness in responding animals may take p;ace via effects on T cells.


Receptors for immunoglobulin and complement on human alveolar macrophages. Specific cell membrane surface receptors for immunoglobulin and complement components were identified by rosette formation on in vitro cultured alveolar macrophages obtained from 24 humans and from rabbits. Respiratory macrophages have easily identified receptors for IgG and the C3b fragment of the third component of complement. A macrophage receptor for the C3d fragment was detected only when purified human complement components were used to form erythrocyte-antibody-C3 immune complexes but was not detected when whole human serum was used as the source of complement. No IgM cell receptor was identified. Thus, with respect to membrane receptors, alveolar macrophages resemble peripheral blood monocytes. These studies in addition emphasize the importance of using a variety of immune reagents, especially the use of human reagents, to determine correctly these cell receptors.


Development and inhibition of cytotoxic antibody against spontaneous murine breast cancer. Increased cytolytic activity of mouse complement as a result of modified reaction conditions described permitted the detection of tumor-specific cytotoxic antibody in high dilutions of sera (1:100--1:000) from mice carrying spontaneously occuring autochthonous breast tumors, or primary syngeneic transplants of such tumors. However, these same sera failed to demonstrate cytotoxic antibody activity at low dilution (i.e., 1:10). Such a pattern of reactivity suggested the presence of an inhibitor of cytotoxic antibody in high concentrations of serum from tumor-bearing mice. Sequential measurements subsequent to primary tumor implantation revealed that, although the time of appearance of this inhibitor varied from tumor to tumor, it always became detectable simultaneously with significant levels of lymphocyte-blocking activity. Also like lymphocyte-blocking activity, the inhibitor of cytotoxic antibody disappeared following surgical tumor removal. In addition, the inhibitor of cytotoxic antibody activity was shown to operate through a competitive antigen-binding and blocking mechanism. This data suggests the possibility that a single serum moiety may be responsible for the efferent blocking of both the cellular and the humoral components of the immune tumor rejection response.


Kinetics of absorption of toxin of Vibrio cholerae. Autoradography of rabbit intestine exposed in vivo to purified tritiated toxin of Vibrio cholerae showed that pharmacologically important amounts of toxin can be rapidly absorbed despite the relatively large size of the toxin molecule and its affinity for binding to the brush border. Cholera toxin and tritiated nontoxic and tritiated nontoxic control substances of comparable size followed a similar time course in spreading down the surface of the villus, and with respect to the villus greater than crypt gradient of labeling of cytoplasm of the mucosal epithelial cells. Absorption of toxin or biologically active toxin fragments provides a mechanism whereby the basal and lateral areas of the cell, which are rich in adenyl cyclase, could participate in the hypersecretory process.


Antibiotic combinations in the treatment of experimental Staphylococcus aureus infection. A penicillin-sensitive strain of Staphylococcus aureus was used to evaluate the efficacy of six antibiotic combinations in the therapy of an experimental infection in mice. One hour after intraperitoneal infection, animals were treated with penicillin G, erythromycin, clindamycin, gentamcicin, or tobramycin singly or in various combinations of two of these drugs. Penicillin in combination with tobramycin, gentamicin, or ertyromycin significantly reduced mortality was compared with therapy with a single drug. Survival of animals treated with the combinations of penicillin and clindamycin, clindamycin and gentamicin, and erythromycin and gentamicin was not different from that seen with single-drug therapy. Pencillin plus either gentamicin or erythromycin significantly reduced the number of culturable organisms from livers and spleens of infected animals when compared with penicillin, gentamicin, or erythromycin alone. In vitro studies correlaed with some aspects of in vivo results but conflicted with others. Thus the combination of penicillin with either an aminoglycoside antibotic or erythromycin is more effective than a single drug in the therapy of infection caused by the Smith strain of S. aureus.


Pharmacokinetics of lincomycin and clindamycin phosphate in a canine model. Linomycin and clindamycin phosphate were studed in a canine model in which acute biliary obstruction was produced during iv infusion of antibiotic. Hepatic and renal extraction, bilary and renal excretion, and concentrations in liver and kidney were measured. Total and nonesterified clindamycin were assayed. The antibiotics were taken up by the liver at similar rates; however; the rates of excretion and concentration in bile were significantly higher for lincomycin  than for clindamycin. Biliary obstruction did not affect the concentration of either antibiotic in canalicular bile. Lincomycin was extracted by the kidneys and excreted into urine at a much higher rate than was clindamycin. Concentrations of nonesterified clindamycin in the hepatic vein were higher than those in the portal vein, an observation suggesting metabolic activation within the liver. This relation was reversed by bilary obstructon. The results in this canine model indicate a greater role for the kedney in the disposition of lincomycin than in that of clindamycin, major differences between the rates of biliary excretion of the two agents, and a probable change in the metabolism of clindamycin procued by acute bilary obstruction.


Decreased colonization of newborn infants with Staphylococcus aureus 80/81: Cincinnati General Hospital, 1960-1972. The changing pattern of colonization of newborn infants with Staphylococcus aureus was studied by examination of 25,662 nasal and umbilical cultures obtained at weekly intervals from 9,216 infants during 1960-1972. The frequency of colonization of infants in the newborn nursery with S. aureus 80/81 decreased significantly during 1963-1965 and has remained low since that time. This change in colonization was unrelated to the use of hexacholorophene for bathing infants or to changes in sensitivity to the commonly used systemic antibiotics, penicillin and kanamycin. A similar decrease occurred with S. aureus lysed by the group 2 phages, but this decrease rebounded to the earlier level after cessation of hexacholorphene use.


Infections of cerebrospinal fluid shunts: epidemiology, clinical manifestations, and therapy. During a 10-year period shunt infections occurred in 27% of the 289 hydrocephalic patients who had cerebrospinal fluid shunts inserted at Children's Hospital Medical Center. The rate of infection did not vary with the type of shunt. Staphylococcus epidermidis and Staphylococcus aureus were responsible for one-half and one-quarter of the infections, respectively. Removal of the infected shunt in conjunction with administration of systemic antibiotics was effective therapy. Use of systemic antibiotics alone was generally ineffective and was associated with an increased mortality rate. Infection itself was a significant risk factor, raising the mortality rate from 17% to 40%. Clustering of infection within two months of surgery and similar rates of infection for ventriculo-atrial and ventriculo-peritoneal shunts indicate that the infecting organisms are usually introduced during the perioperative period. The possibility that prophylactic antibiotics or different shunt materials might reduce the infection rate requires further study.


Prevention of streptococcal sequelae by penicillin prophylaxis: a reassessment. In conclusion, the diagnosis of streptococcal infection lacks precision, and as long as this is so, reliance must be placed on trained clinical judgement together with bacteriological studies. There is some evidence for an evolutionary drift in the relationship between the streptococcus and man, a drift that is compatible with the natural history of other diseases and with the accomodations observed in nature among other species during the course of evolutionary events. If, as a result of recent accomodations between man and the group A streptococcus, the risk of rheumatic fever is less, an undefinable risk nevertheless remains. There was even a military outbreak of rheumatic fever in England several years ago, and on that island--we are told--rheumatic fever has been banned for years. The current recommendations of the American Heart Association for the secondary prevention of rheumatic fever I judge acceptable for use in the United States. I have, however, raised the possibility that they may be inadequate for the prevention of second attacks in other populations where the environmental, socioeconomic, bacteriological, and nutritional circumstances are different from our own. Studies designed to reexamine these questions may, in the end, refocus our attention on the importance of host factors in the occurrence and pathogenesis of rheumatic fever.


The spectrum of colitis associated with lincomycin and clindamycin therapy. Ten cases of protracted diarrheal illness after the oral administration of lincomycin or clindamycin in standard dosages were observed in previously healthy subjects. An abrupt onset of diarrhea, crampy abdominal pain, fever, and leukocytosis was observed one to 12 days after discontinuation of the drug. Proctoscopic examination revealed erythematous friable mucosa covered with small raised, yellowish-white plaques that were sometimes confluent. Barium contrast studies of the colon demonstrated irregular shaggy mucosa, ulcerations, cobblestone appearance, and thumb printing. Rectal bipsy showed acute inflammation with pseudomembranes with focal or superficial ulcerations. All patients had a protracted course but recovered with supportive management. Follow-up barium enemas and proctoscopy were done on all patients and were normal. A history of diarrhea, fever, and mucosal changes seen on proctoscopy in a patient who has recently received one of these antibiotics should raise the possibility of colitis associated with clindamycin and lincomycin therapy.


Extraction of antibiotics from the circulation by liver and kidney: effect of probenecid. An experimental canine model was designed to measure directly the uptake, storage, and excretion of antibiotics by the liver and kidney. At equilibirum the rate of uptake of penicillin G, cephalothin, and nafcillin by these organs was about 80% of the rate of intravenous infusion of each antibiotic. Penicillin G and cephalothin were extracted mainly by the kidneys, and nafcillin by the liver. Injection of probenecid virtually abolished the difference in concentration of antibiotic between afferent and efferent vessels of the liver and kidney after 30-45 min. Renal tubular secretion of penicillin G and cephalothin was suppressed, and their levels in renal tissue were increased. These findings militate against any primary limitation by probenecid of access of antibiotic to the renal parenchyma. A marked sustained increase (60%-70%) in the rate of portal flow followed injection of probenecid, and the concomitant percentage of nafcillin extracted by the liver declined significantly. Because of the circulatory changes, a specific effect of probenecid on acess of nafcillin to the liver could not be proved.


Masking of the non-test ear in speech audiometry. Masking of the non-test ear is often needed in speech audiometry but the methods for such masking have not been well defined. 'White' or 'speech' noise is commonly provided by audiometers for this purpose, and the many problems and uncertainties in their calibration and effectiveness are discussed; data on these aspects are presented with respect to some current audiometers and Fry's and AB(S) PB-word lists. Formulae are given for estimating the possible need for masking, calculating the required dial level of masking noise for a given dial level of speech signal, and assessing the extent to which cross-masking may be affecting the results. The formulae presented are applicable for earphone listening only.


Masking of the non-test ear in tone decay, Békésy audiometry, and SISI tests. Masking of the non-test ear is frequently required in tone decay, Békésy audiometry and SISI tests; without it, serious misdiagnoses can result. Methods are given for calculating the dial levels of masking noises to be delivered and the extent of possible cross-masking. The methods are subdivided according to whether the tests to be employed are fixed-frequency or sweep-frequency, and to whether masking function data are available from previous use of shadow masking. In difficult cases, careful preliminary shadow-masking procedures and subsequent use of fixed-frequency tests is recommended.


Tympanoplasty in partial defects of the stapedial arch. A defective stapedial arch was found among 690 operated patients in 46 ears (6-7 per cent). Most often it was the stapedial head or anterior limb which was absent. The problems and results  of ossiculoplasty on a defective stapes are analyzed. Classical interposition of the incudal body on top of a defective stapes did not afford satisfactory results, as the incus had to be placed asymmetrically on top of the stapedial remnant, with a risk of fixation and tilting of the graft. Better results were obtained by interposition of the short process of the incus on the footplate in a way which gives the incus contact also with the remaining parts of the stapedial arch. If the neck and head of the stapes are absent, it is suggested that the ossicles be shaped in relation to the defect in such a way that contact between the stapedial remnant and the malleus will be stable and the risk of secondary fixation minimal. If there are partial defects of the stapedial limbs the columella should be in contact with the footplate as well as with the remaining parts of the limbs.


Effect of hyperbilirubinemia on the inner ear in Gunn rats. The effect of hyperbilirubinemia on the inner ear was studied in fifteen jaundiced homozygous Gunn rats. Seven non-jaundiced heterozygous littermates served as controls. Histopathological examination of the temporal bone in these animals showed normal sensory and neuronal structures of the inner ear. This cannot be taken as conclusive evidence that a central, rather than a peripheral, lesion is the cause of hearing loss in hyperbilirubinemia.


Stapedectomy--shorter prosthesis recommended. Based on some 4500 operations, a follow-up study has revealed certain recurring problems. Shorter than usual prostheses in Stapedectomy operations are strongly advised. A favourable influence on the later occurrence of Fistula and extrusion can be expected. Possible causes for extrusion are studied.


The treatment of a congenital laryngeal web. Past descriptions of the surgical treatment of congenital laryngeal webs have involved a laryngofissure to achieve division of the web and the insertion of a tantalum keel to prevent its reformation. The technique described below obviates the need for an open operation on the larynx. The web is divided under magnified vision through a laryngoscope using a Zeiss operating microscope. A silastic keel is secured between the vocal cords at the anterior commissure by means of a loop of nylon passing externally through the crico-thyroid and crico-hyoid membranes.


Exfoliative cytology in the diagnosis of laryngeal malignancy. In searching for a screening procedure in the diagnosis of laryngeal malignancy the authors have evaluated a cytological examination, adapted for indirect laryngoscopy, and present the results of 149 consecutive smears from the larynx. Forty-four per cent of the smears were false negative, and it is concluded that exfoliative cytology with this method has no place as a screening procedure in the diagnosis of laryngeal malignancy. The method is inferior to the evaluation of the clinical picture in indirect laryngoscopy, and the selection for direct laryngoscopy and biopsy for histological evaluation should be based upon the clinical evaluation.


Non-vegetable foreign bodies in the bronchopulmonary tract in children. A variety of 40 cases of non-vegetable foreign bodies inhaled by children are presented. These include: coins, washers, pins, reamers, nails, screws, wires, pencil caps, ball-point tip, worry beads, bones, broken tooth, small stones, and blades of broken foreign body forceps. The ages of the children ranged between 10 months and 8 years with average at 2 years and 9 months. Two methods are described for the removal of slippery beads, using a Fogarty Catheter and foreign body forceps technique. Emphasis is placed on the importance of bronchoscopy in all cases with definite or doubtful history of foreign body inhalation in spite of negative physical or roentgenological findings, particularly those cases diagnosed as upper respiratory infection, pneumonitis, bronchial asthma and whooping cough, and when there is no significant response to such treatment. Fluoroscopy with image intensifier is suggested for the localization of the pointed end of sharp pins which cannot be identified clearly through the bronchoscope. General anaesthesia was used in all the cases to ensure absolute immobility. Repeated bronchoscopies at close intervals were not advised and tracheostomy was suggested in subglottic oedema if asphyxia is threatening the life of the child. Immediate removal of foreign bodies is important so as to avoid unnecessary complications. Lobectomy was necessary in one case with an impacted screw and destroyed lobe. This stresses the importance of thoracotomy when several attempts fail to remove the foreign body.


Fibreoptic laryngoscopy in the assessment of laryngeal disorders. The fibreoptic laryngoscope is described, and its method of use detailed. Seventy patients were submitted to this examination. Its advantages and disadvantages in the assessment of the various groups of laryngeal disorders in these patients are discussed and compared with indirect and direct laryngoscopy. Its teaching and research possibilities are also mentioned. The technique shows considerable promise and will, we believe, achieve an accepted place as an addition to our diagnostic armamentarium in the investigation of laryngeal disorders.


Spontaneous rupture of the pharynx.

Spontaneous rupture of the pharynx. A case of spontaneous rupture of the pharynx is described occurring during the act of vomiting. Comparisons are made with the only known previously recorded case of spontaneous pharyngeal rupture.


Desmoplastic fibroma of maxilla.

Desmoplastic fibroma of maxilla. Desmoplastic fibroma of the long bones is very rare and has been mentioned in the literature, but there is no mention in the literature of desmoplastic fibroma occurring in relation to maxilla. The first case of desmoplastic fibroma of the maxilla is reported. Conservative surgery is recommended for desmoplastic fibroma of the maxilla to avoid facial deformity.


Quick hardening polymers in the surgical treatment of congenital neck fistulae. A method of filling up congenital fistulae of the neck by quick hardening polymers, immediately before the operation, is presented. Two cases are reported.


Fibrous dysplasia.

Fibrous dysplasia. Three cases of monostotic fibrous dysplasia of the cranial bones are presented. Several theories of the etiology of this uncommon condition are put forward and the relationship between monostotic and polyostotic fibrous dysplasia, Albright's disease, and hyperparathyroidism is examined. The difficulty in diagnosis and the ways they may present to the ear, nose and throat surgeon are discussed. It is suggested that conservative surgery is the best mode of treatment for maxillary or temporal lesions. However, ethmoid lesions, particularly when the optic foramen or base of skull are eroded, may need a neuro-surgical approach. The use of radiotherapy in any case is deprecated.


Prognosis of squamous-cell carcinoma of the gums with cytologically verified cervical lymph node metastases. A follow-up study was made of 125 patients with carcinoma of the gums treated from 1958 to 1969. Twenty-one of these patients with cytologically verified metastases of the neck at first visit were specially studied. The primary tumour was classified as T1 in three patients, T2 in one, T3 in nine, and T4 in eight patients. Twelve patients received radiotherapy, nine radiotherapy and surgery. The five-year determinate survival rate was 7 per cent in this group compared with 41 per cent for patients without cervical metastases. The importance of the use of fine-needle biopsy and cytology is stressed in the diagnosis of metastases of the neck for proper judgement of the prognosis and for selection of method for treatment.


Cysts of the parotid gland.

Cysts of the parotid gland. Simple cysts of the parotid gland are uncommon, and they have only rarely been reported. Two cases are reported here. The aetiology and management of parotid cysts is discussed.


Cysts of the parotid gland. Review and report of two unusual cases. Cysts of the major salivary glands are most frequent in the parotid where they form a small percentage of its benign tumours. They can be congenital or acquired and of parotid or extraparotid origin. Two unusual cysts are reported: a cholesteatoma arising from the ipsilateral mastoid, twenty years after successful radical mastoidectomy, and a deeply located cysts of probably congenital origin. The literature is reviewed and the management discussed. Parotidectomy, often with extensive dissection, remains in general the treatment of choice.


Nasopharyngeal craniopharyngioma.

Nasopharyngeal craniopharyngioma. Two cases of cranipharyngiomas which were mainly located in the nasopharynz have been reported. The cystic nature of the tumour with leakage of brownish-coloured fluid helped in arriving at the diagnosis, which was confirmed on histology. Marsupulization through a transpalatal approach seems to be the treatment of choice in such cases.


The internal auditory canal and sensori-neural hearing loss in homozygous sickle cell disease. The dimensions of the internal auditory canal were compared in patients with SS disease and with or without abnormal audiograms to investigate the role of auditory nerve compression by expansion of the petrous, temporal bone in hearing loss. There was no correlation between abnormal audiograms and narrowing of the internal auditory canals and it was concluded that this mechanism was not responsible for the hearing loss in SS disease.


Ameloblastoma of the upper jaw.

Ameloblastoma of the upper jaw. A clinical study was made of three cases of Ameloblastoma (Adamantinoma) of the maxilla. One case presented with oro-antral fistula following extraction of a molar tooth. Extensive bone destruction and involvement of ethmoidal air sinuses and nasal cavity was seen in one of the patients. At times histological diagnosis can be difficult; therefore, accurate diagnosis should be obtained by an experienced histopathologist. Partial maxillectomy with a wide margin of healthy bone should be the choice of treatment in the majority of cases. There tumours are sensitive to deep-X-ray to a varying degree. One should consider radiotherapy post-operatively if growth has been excised inadequately. Radiotherapy may be helpful when surgery is contraindicated.


Analysis of anomeric configurations in glyceroglycolipids and glycosphingolipids by chromium trioxide oxidation. Acetylation and CrO(3) oxidation in acetic acid (Angyal and James, Aust. J. Chem. 23: 1209-1221, 1970) was applied to 18 different glyceroglycolipids and glycosphingolipids of known structure. The lipids studied contained from one to five pyranosic monosaccharide units including alpha- and beta-linked glucose, galactose, mannose, and N-acetylgalactosamine and beta-linked N-acetylglucosamine. Monosaccharides bound to the lipids through beta-glycosidic linkages reacted to the extent of 80-97 percent, but in the case of alpha-glycosidic linkages the oxidation proceeded only to the extent of 0-6 percent. A partial reaction was observed in lipids in which a given monosaccharide unit was present in both anomeric forms. Therefore, oxidation with CrO(3) allows the determination of anomeric configurations in simple glycolipids. Samples of only 100-300 mug are required.


Demonstration of two pools of albumin-bound fatty acids. The uptakes of albumin-bound nonesterified fatty acids and of [1-14C]palmitic acid complexed to albumin by the isolated perfused rat liver were compared. During perfusion, the rate of uptake of nonesterified fatty acids decreased and became zero when the fatty acid:albumin molar ratio reached 0.3, but the rate of uptake of radioactive palmitic acid remained constant. This finding suggests the existence of two pools of fatty acids bound to albumin with different fractional turnover rates. This view was supported by the fact that when delipidated albumin complexed in vitro to radioactive and nonradioactive fatty acids was used no difference was observed between the uptakes of nonesterified fatty acids and radioactive fatty acids by perfused liver. Similar results were found with albumin-bound radioactive fatty acid in vivo (obtained from rats fed radioactive palmitic acid), showing a homogeneous distribution of the label in both pools. The existence of two nonesterified fatty acid pools in plasma would arise from the differences in the nature of bonds between fatty acid and albumin molecules, which could determine the rate of exchange of fatty acids between the albumin-bound and soluble forms preceding their uptake by the cells.


[U-14C]glucose metabolism in vivo in rats rendered obese by a high fat diet. Estimates of the glucose pool, the glucose space, the turnover rate, and the recycling of glucose were made after the injection of [U-14C]glucose into (a) obese rats fed a high fat diet and (b) rats fed a carbohydrate diet. The specific activity--time curve consisted of two components. Physiological parameters were calculated by using a two-compartment model. The glucose pool and glucose space were the same in both groups of rats. The turnover rate was 1.96 mg. min-1 for the carbohydrate-fed rats and 1.55 mg. min-1 for the fat-fed rats. There was about 12 percent recycling in both groups. In the carbohydrate-fed group, another approach based on simultaneous use of [6-14C]glucose and [6-3H]glucose yielded nearly the same values for these parameters. Respiratory excretion of CO2 and the incorporation of labeled glucose into lipids of some tissues were also measured. The rate of excretion of labeled CO2 and the conversion of labeled glucose into fatty acids in fat-fed rats were lower than in the carbohydrate-fed rats by 50 percent and 80 percent, respectively. More glucose was diverted into glyceride glycerol in the fat-fed group. It is suggested on the basis of the results that glyceride glycerol can serve as a gluconeogenic substrate in these rats where the turnover rate of glucose is much higher than the daily intake of carbohydrates.


Hepatic fine structure in young and aging rats treated with oxandrolone: a morphometric study. Hepatic fine structural alterations induced by shortterm administration of the hypolipidemic drug oxandrolone were evaluated using morphometric techniques. These changes are described in the livers of normolipidemic young adult and hyperlipidemic retired breeder male rats. Retired breeder rats, characterized by hyperlipidemia and a high incidence of arteriosclerosis, are thought to undergo premature aging. A previous morphometric study has shown that the hepatocytes of retired breeder rats are larger, contain a greater volume fraction of lysosomes, and have significantly less smooth-surfaced endoplasmic reticulum than those of young adult rats. However, after oxandrolone administration, the livers of these two animal groups were no longer distinguishable on the basis of these morphometric parameters. Unlike a number of other hypolipidemic drugs, oxandrolone does not induce a marked proliferation of hepatic microbodies. The effect of oxandrolone on the livers of prematurely aging rats suggests that the age-related fine structural changes are not the result of irreversible alterations in the genome or translation-transcription apparatus but may actually represent secondary reactions to extrahepatic and/or endocrine metabolic changes. The relationship between (1) aging and hyperlipidemia and (2) aging and the reduced hepatic capacity to metabolize drugs suggest a need to evaluate the effects of lipid-lowering drugs on the livers of old as well as young animal models.


Thin-layer chromatographic separation of sulfated and nonsulfated lithocholic acids and their glycine and taurine conjugates. A method for superior thin-layer chromatographic separation of lithocholic acid and its N-glycine and N-taurine conjugates, as well as their respective 3alpha-sulfates, is described. A solvent system of chloroform-methanol-acetic acid-water 65:24:15:9 (v/v) is used with air-dried plates of silicic acid containing calcium sulfate (10% by weight) under conditions of chamber saturation.


Isotope derivative assay of microsomal cholesterol 7 alpha-hydroxylase. A rapid method was developed to measure cholesterol 7 alpha-hydroxylase activity of hepatic microsomes by the direct determination of the mass of 7 alpha-hydroxycholesterol formed. The method is based on the quantitative acetylation of the incubation mixture with [-3H]acetic anhydride and the separation of the biosynthetic 7 alpha-hydroxycholesterol as its diacetate by thin-layer chromatography on alumina. Amounts of 7 alpha-hydroxycholesterol as low as 0.1 nmole could be measured. A comparison of the proposed isotope derivative method with the previously used isotope incorporation method showed that the latter underestimated the enzyme activity by about 20 percent.


Metabolism of retinol-binding protein and vitamin A during hypervitaminosis A in the rat. Vitamin A is normally transported in plasma as retinol bound to a specific protein, retinol-binding protein (RBP). Detailed studies were conducted to examine the effects of excess vitamin A on the plasma concentration and metabolism of RBP, and to obtain information about vitamin A transport in the hypervitaminotic state. Two separate experiments were conducted. In the first (Study I, 99 days), plasma RBP and vitamin A levels were compared in three groups of rats fed 0.14 mg (control), 7.3 mg (group 2), or 41 mg (group 3) of vitamin A per day. After day 50 of the study, the administration of excess vitamin A to hypervitaminotic rats (groups 2 and 3) was discontinued and the rats were allowed to recover from vitamin A toxicity. In the second, shorter experiment (Study II), serum vitamin A and RBP levels were compared in control and hypervitaminotic (34 mg of retinyl acetate per day) rats. The rats in this study were also given [3-H]retinyl acetate daily to determine the distribution of retinyl esters and retinol between the lipoprotein and nonlipoprotein protein fractions of plasma. In both studies, administration of large, excessive doses of vitamin A resulted in substantial and significant decreases in the levels of serum RBP. Excessive doses of vitamin A produced fatty liver in the rats, in association with a normal (group 2, Study I) or with a decreased (group 3, Study I) level of RBP in the liver. It is possible that excess vitamin A leads to decreased rates of RBP synthesis in, and of RBP secretion from, the liver. Administration of excessive doses of vitamin A also resulted in elevations of serum vitamin A levels, which were mainly due to large increases in the circulating levels of retinyl esters. In the hypervitaminotic rats, most of the serum vitamin A, and virtually all of the retinyl esters, was found in association with the serum lipoproteins of hydrated density less than 1.21. These results demonstrate that the serum lipoproteins play an important role in the transport of the vitamin A that accumulates in serum in hypervitaminosis A. We suggest that the toxic manifestations of hypervitaminosis A occur when vitamin A circulates in plasma and is presented to membranes in a form other than bound to RBP. Plasma lipoproteins may nonspecificially deliver vitamin A to biological membranes and hence lead to vitamin A toxicity.


Regulation of cholesterol synthesis and storage in fat cells. The fat cells of rat epididymal adipose tissue contain an average of 0.5 mg of cholesterol per gram of triglyceride. Of this cholesterol, 90% is nonesterified and 80% is located in the lipid storage compartment. The fat cell cholesterol content correlated positively with cell size. During fasting the free cholesterol of the adipocyte decreased in parallel with triglyceride, whereas the amount of esterified cholesterol did not change. The fat cell cholesterol content is independent of the amount of dietary cholesterol. On in vitro incubation of rat fat cells with radiolabeled acetate, mevalonate, glucose, leucine, or water, labeled cholesterol was synthesized. The rate of cholesterol synthesis increased with fat cell size. Fasting suppressed cholesterol synthesis by 90%, whereas refeeding stimulated the synthesis above values found in normally fed rats. Stimulation of lipolysis with theophylline or with dibutyryl cyclic AMP markedly inhibited cholesterol synthesis in fat cells. Insulin increased the incorporation of glucose and leucine into fat cell cholesterol. The cholesterol synthesis in fat cells was not suppressed by a high cholesterol diet. Addition of very low or low density lipoprotein into the incubation medium suppressed fat cell cholesterol synthesis whereas high density lipoprotein did not. The lipoprotein-free serum stimulated cholesterol synthesis compared with serum-free medium. The rate of cholesterol synthesis in total adipose tissue of rat was estimated to be 4% of that in the liver. It seems unlikely that the increased body cholesterol turnover present in obesity is accounted for by the enhanced cholesterol formation in the enlarged adipose tissue.


Characterization of lung surfactant: factors promoting formation of artifactual lipid-protein complexes. Because uncertainty exists as to whether dipalmitoyl phosphatidylcholine, the major component of lung surfactant, is part of a lipoprotein molecule, a study was designed to investigate the relationships between the phospholipids and proteins of rabbit lung washings obtained by lavage with aqueous solutions. Surface-active sediments contained phospholipid and protein in ratios directly dependent upon the ratios in the washings from which they were obtained. Comparison of negatively stained lung washings and sediments revealed that sedimentation caused extensive aggregation of surfactant "liposomes". Analytical ultracentrifugation revealed that both cell-free washings from lungs and suspension of pure phosphatidylcholine contained components with flotation rates ranging from 25 to 400. Density gradient centrifugation of washings, without prior sedimentation, resulted in the appearance of a phospholipid band associated with only a small amount of protein. The density of the band varied depending upon temperature. No qualitative differences in the protein compositions of the phospholipid band and other gradient fractions were found by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Albumin, IgG, IgM, and several nonplasma proteins were present. These results indicate that little, if any, protein is specifically attached to the phospholipids of lung surfactant; rather, the lipid-protein complexes of lung washings are the result of a nonspecific association caused by removal of water-soluble surfactant from the lung and promoted by sedimentation.


Identification of a novel cell type in peripheral lymphoid organs of mice. IV. Identification and distribution in mouse spleen. White pulp nodules of mouse spleen contain a minor population of cells with morphologic features that are identical to those of dendritic cells, a cell type recently described in vitro. They have characteristic large, irregularly shaped nuclei with distinctive chromatin patterns and small nucleoli. The cytoplasm is extended in processes that contain relatively few organelles. These presumptive dendritic cells can be distinguished from other cell types that are known to exist in spleen including those that have irregular or branching cell shapes. In particular, dendritic cells do not contain the large number of lysosomes seen in phagocytes, and do not actively interiorize intravenously administered colloidal thorium dioxide particles. They also lack the well developed secretory apparatus (rough endoplasmic reticulum and Golgi zone) and microfilament bundles that are noted in connective tissue cells. These morphologic observations, combined with previous in vitro work, substantiate the existence of a novel class of cells in mouse lymphoid organs.


Murine terminal deoxynucleotidyl transferase: cellular distribution and response to cortisone. The mouse thymus contains two forms of terminal deoxynucleotidyl transferase (TdT) which are distinguishable by the salt concentration necessary to elute them from a phosphocellulose column, by their distrubtion among the thymocyte subpopulations, and by their sensitivity to cortisone treatment. In the whole thymus the later eluting peak (peak II) is the predominant one with about 3-10% of the total activity appearing in peak I. Both peak I and peak II activities are most sensitively assayed by the polymerization of dGMP onto an oligo(dA) primer. The minor population of thymocytes which is less dense and cortisone-resistant contains a higher specific activity of peak I TdT. The majority of TdT activity is, however, found in the major population of thymocytes which occurs in the center region of a bovine serum albumin gradient and is cortisone-sensitive. A very low level of an activity indistinguishable from peak II TdT activity is also detected in the mouse bone marrow. Other tissues, such as spleen, liver, heart, and brain lack detectable amounts of TdT activity.


Association of HL-A 5 and immune responsiveness in vitro to streptococcal antigens. Lymphocytes, from randomly selected individuals having normal immune function, when incubated in vitro with varying concentrations of streptococcal antigens, responded in three ways: (a) response over the entire antigen concentration range, i.e., responders; (b) low response to only the highest antigen concentrations; and (c) no response at any antigen concentration. Frequency distribution analysis of these groups indicated that a significant association occurred between the ability to respond and HL-A 5.


Studies of the macrophage complement receptor. Alteration of receptor function upon macrophage activation. We have examined the roles of Fc receptors and complement receptors in mediating the interaction of sensitized sheep erythrocytes (E) with activated and with nonactivated mouse peritoneal macrophages. Both activated and nonactivated macrophages ingest IgG-coated erythrocytes [E(IgG)]; activated cells intest 1.5-2 times as man E(IgG) as do nonactivated macrophages. Thus, there is a quantitative difference in Fc receptor-mediated ingestion between activated and nonactivated macrophages. There is, however, a qualitative difference in function of complement receptors of activated and nonactivated macrophages. Nonactivated macrophages avidly bind complement-coated E [E(IgM)Ia1, but do not ingest them to a significant degree. Activated macrophages, on the other hand, bind and ingest E(IgM)C. The possibility of Fc receptor participation in mediating ingestion of E(IgM)C by activated macrophages was eliminated by blocking Fc receptors with an antimacrophage IgG fraction. Activated macrophages treated with antimacrophage IgG did not ingest E(igG) but did ingest both E(IgM)C AND E(IgM)C. Nonactivated macrophages treated with antimacrophage IgG did not interact at all with E(IgG). These cells bound, but did not ingest, E(IgM)C and E(IgM)C. Complement receptor-mediated ingestion is a marker for macrophage activation and may be physiologically important in the elimination of complement-coated particles.


Experimental autoimmune myasthenia: A model of myasthenia gravis in rats and guinea pigs. Immunization of animals with acetylcholine receptor (AChR) protein from the electric organs of Electrophorus electricus and Torpedo californica induces an autoimmune response to the AChR of mammalian skeletal muscle. Rats and guinea pigs develop experimental autoimmune myasthenia gravis (EAMG) after a single inoculation with small quantities of AChR and adjuvant. The indicence and severity of disease appears to depend on the dose of AChR and stability of the emulsion. EAMG is strikingly similar to myasthenia gravis (MG) of man in its clinical picture and its electrophysiological abnormalities. The presence of antibodies to syngeneic rat muscle AChR in the serum of rats with EAMG documents the existence of autoimmunity in the experimental disease. A common immunopathogenesis is suggested for both EAMG and mg.


Polymorphonulcear leukocyte chemotaxis toward oxidized lipid components of cell membranes. Polymorphonuclear leukocyte chemotaxis has been elicited by oxidized arachidonic acid and other oxidized polyenoic lipids in the Boyden micropore filter assay system. This chemotactic activity was observed in the absence of serum and chemotactic proteins. The esterfied arachidonic acid present in plasma membranes may be a precursor of chemotactic messages as well as prostaglandins in vivo.


Nonallelic behavior of rabbit variable-region allotypes. Group a allotypes not detected by qualitative typing or anticipated from breeding data (latent allotypes) were detected at low levels in 50% of normal rabbit sera tested. The latent allotypes, which were serologically identical to allotypes of pooled IgG, were detected in sera from rabbits with all possible combinations of group a allotypes and their occurrence in individual rabbits was transitory and sporadic. These findings give reason to question the assumption that the synthesis of immunoglobulin allotypes is directed by allelic structural genes.


Hereditary C2 deficiency: Genetic studies and association with the HL-A system. Herediatary C2-deficiency has been shown to be transmitted asn an autosomal recessive characteristic. Recent evidence indicates that some genetic factors involved in the control of the complement (C) system in both man and mice are governed by genes localized within the major histocompatibility regionmthis study describes a large pedigree of the paternal family of a C2-deficient patient with systemic lupus erythematosusl It is shown that this condition is transmitted as an autosomal recessive trait, the heterozygous carriers having approximately half normal levels of C2. Furthermore, this trait was shown to be inherited in close linkage with an infrequent HL-A typw, 2,4A2. The maternal, C2-defective chromosome was shown to be transmitted by HL-AW10, W18 haplotypemthis same haplotype was described in a similar study by Fu et al. (6) to be associated with C2 deficiencymfinally, a third haplotype HL-A2,W18 carrying a defective C2 gene was demonstrated in a part of this pedigree.


Informed consent and its implications in family practice. The doctrine of informed consent has had its practical introduction to medical malpractice litigation in the past five years. Its definition has not changed since the days when its definitive application was only a fond dream of the malpractice plaintiffs attorneys. However, with neh new methods of presenting this theory to the courts, and with the newly emerging practice fo having rulings on matters of law substituted by judges for prevailing standards of medical practice, the implications for family physicians have become tremendous. Hopefullum by understanding the principles involved in its application in the pertinent landmark cases, family physicians will be better able to abid the pitfalls engendered by the doctrine of informed consent.


A predoctoral curriculum in family medicine. Development of a new discipline, such as family medicine, requires careful definition of scope and purpose. This must be followed by delineation of specific education objectives. The teaching program is often carried out by people experienced as clinicans but not as teachers and requires selection of methods most natural to this kind of faculty. This article describes the current stage of curricular development at the institution with the longest experience in predoctoral family medicine in the United States. Based on seven years' experimentation, this paper provides an overview of the philosophy behind this particular curriculum and describes, in brief, four educational methods which have proven useful. These methods will be discussed in greater detail in subsequent articles focusing on specific educational objectives, illustrative examples, and evaluative methods.


The first-year family practice resident. An identity crisis. A definite identity crisis was recognized among first-year family practice residents prior to this year. A specific solution was found through a carefully planned one month family practice rotation that enabled the residents to become fully acquainted with the Family Practice Clinic operation while firmly establishing their identity as unique family practice residents. There is good evidence that this approach has been highly successful in dealing with the problem, and the alleviation of identity crises in first-year residents has, in addition, strengthened other areas of the residency program.


Toward clarification of objectives for family practice and family medicine. This paper analyzes the social boundaries derived from an adequate definition of family practice and family medicine and explores the social dynamics between them and other social institutions and disciplines, More precise objectives  for family practice and family medicine are delineated using a model which specifies social targets, methods, and purpose of intervention. Implication for further research in family medicine are discussed as well as their future effect on family practice.


A new look at continuing education in family practice. The rapid increase of medical knowledge in recent years, together with continuously changing methods and patterns of practice, have made continuing medical education today a critical and challenging problem. It is now recognized that the large majority of a physician's medical knowledge over a practice career is derived from postgraduate learning after his initial formal undergraduate and graduate medical education. Despite the present importance of continuing medical education, we still have a relatively ineffective system which is not easily accessible to the practicing physician and which often fails to meet his individual learning needs. This paper critiques our past efforts in this area, describes some principles of learning, and suggests some new approaches to make continuing education in family practice more accessible and effective.


A critical review of periodic health screening using specific screening criteria. Part 2: Selected endocrine, metabolic and gastrointestinal diseases. Despite the increasing interest in recent years in prevention and early recognition of asymptomatic disease, there has been a lag in development of a sound scientific basis for efforts in this area. No objectively based program for periodic health screening of asymptomatic adults has yet been proposed for the primary care physician. This is the second in a series of four articles which will critically examine the feasibility of screening procedures for 36 selected diseases. Six basic criteria are adopted as necessary to justify periodic screening. Specific screening recommendations are made for each disease, and a longitudinal screening program for asymptomatic adults will be proposed in the concluding article of this series.


The unwanted pregnancy in adolescence.

The unwanted pregnancy in adolescence. The unwanted pregnancy in adolescence is a crisis during which the adolescent woman often seeks help from an agency or physician. Frequently the option chosen is termination by therapeutic abortion. This option should be offered in a nonjudgmental manner with an attempt to understand and monitor the adolescent's emotional status. Psychiatric consultation should be sought only under specific circumstances is described which will help the adolescent with unwanted pregnancy resolve this life crisis constructively.


The role of the family physician in the crisis of impending divorce. The divorce rate in the United States is approaching 30 to 40 percent. Because the family physician cares for the entire family, he often finds himself in the midst of the turmoil created by the crisis of impending divorce. Using a case presentation, we have offered some specific suggestions to help the family physician manage this common problem. Few traditional training programs have adequately prepared the primary physician to be effective in marriage counseling. The integration of the behavioral sciences with the medical sciences should be a major goal of the developing discipline of family medicine. If training programs in family medicine successfully develop curricula that teach the skills required to support a troubled marriage, the family physician of the future may make a more significant contribution towards the preservation of the nuclear family.


Panting thresholds of lizards. IV. The effect of dehydration on the panting threshold of Amphibolurus barbatus and Amphibolurus muricatus. Amphibolurus barbatus which occupies arid and mesic habitats elevates its panting threshold with increasing loss of body water, thereby minimizing water loss at the expense of thermoregulatory effectiveness. Change in panting threshold is greatest up to losses of body water of 6-8% of hydrated weight, after which adjustment of the threshold is of lesser magnitude. Amphibolurus muricatus, a species restricted to the more mesic regions of Australia, does not show any change of panting threshold with progressive dehydration.


An analysis of nuclear numbers in individual muscle fibers during differentiation and growth: a satellite cell-muscle fiber growth unit. A numerical analysis of changes in the populations of nuclei in individual, intact muscle fibers was made to study how multinucleation arises during normal differentiation and growth. Gastrocnemius muscle fibers from pre- and post-natal mice were isolated with guanidine (Cardasis and Cooper, '75) and examined. Satellite cells associated with muscle fibers were first observed at 19 days of gestation. The number of nuclei per muscle fiber (muscle + satellite cell nuclei) averages 83 at this age, 157 at birth and continues to increase to 354 by 63 days of age. However, the rate of increase during growth is not constant. Estimates of satellite cell and muscle nuclei in histological cross sections indicate that there is a decrease in the percentage of satellite cells from 32% at birth to 6% in the adult. However, the numbers of satellite cells associated with individual muscle fibers, calculated from these percentages and the nuclear counts on whole fibers, decreases only between 2 and 4 weeks of age. Cytosine arabinoside was injected subcutaneously during the first two weeks of age. Pairs of satellite cells, abnormal nuclei and elevated percentages of satellite cells were observed. This evidence as well as the numerical analysis of nuclear populations in whole fibers lends further support to the hypothesis that satellite cells account for the increase in muscle nuclei from birth to maturity.


Eye disk differentiation in the wax moth: induction in vitro. Ecdysterone-induced differentiation of Galleria mellonella compound eyes in vitro is critically dependent on the age of the donor. It is greatest in explants from young prepupae, decreases with increasing donor age, and is absent in explants from 4-6 hour pupae. Failure of eye disks from pupae to differentiate in vitro seems to be the consequence of exposing them to culture conditions at a susceptible time in their development for, unlike eye disks from prepupae, they do not develop when removed from the medium and implanted into competent hosts. The explants most responsive in vitro are more liable to submerge, with resulting inhibition of development. Three media allow differentiation of adult eye structures, and one of these is suitable without adding macromolecular compounds. Ecdysterone is essential, and will elicit ommatidia formation when it is added to the medium at concentrations ranging from 0.1-20 mug/ml. Rubrosterone is ineffective at 1.0 mug/ml of medium. In the best-differentiated explants each ommatidium consists of 8-10 pigmented retinal cells surrounding a rhabdom-like core, and their axons can be traced to an enlarged optic nerve. Crystalline cones, adult cuticle in the form of facets (corneal lenses), and pigment cells also are formed.


Limb development in diplopodia4: a polydactylous mutation in the chicken. In a study of the polydactylous mutation of the domestic chicken, diplopodia4, we have found that the genetic lesion affects primarily the mesoderm and only secondarily the ectoderm. The effect of this mutant mesenchyme on overlying ectodermal ridge, either mutant or normal, is to thicken the ridge preaxially, leading to increased outgrowth and preaxial polydactylism. A "zone of polarizing activity" in the normal limb-bud seems to have a role in the control of its anteroposterior polarity. We have examined diplopodia4 limb-buds for polarizing activity and found it to be normal in its activity and distribution. These results suggest that the supernumerary outgrowth in the mutant limbs result from increased ridge mainon of the polarizing zone.


Electron microscopic study of erythrocytes in developing rainbow trouts, Salmo gairdnerii irideus, with particular reference to changes in the cell line. The fine structure of the first erythroid cells in the embryonic circulation of the rainbow trout and new erythroid cells appearing after hatching was examined by scanning and transmission electron microscopy. The first erythroid cells in the embryos, where circulation has just begun, are very immature in ultrastructural characteristics; they are spherical, relatively large, and contain a large nucleus with diffuse chromatin and numerous free ribosomes mostly occurring as polyribosomes. The cells divide in the circulatory system. As development proceeds, the entire population undergoes a synchronous maturation, i.e., transformation into round and flat discs, progressive heterochromatization, reduction in number of cytoplasmic organelles, especially of ribosomes, and a concomitant increase of hemoglobin content. The fully mature first erythroid cells persist until after hatching and are gradually replaced by a new population of erythroid cells which begin to appear in the circulatory system within a few days after hatching. The new cells are at first small and spherical, and show immature ultrastructural features, but no dividing cells were encountered. The cytological changes accompanying maturation are almost parallel to those seen in the first class of erythroid cells. In the circulatory system of fry, where yolk absorption has just been completed, almost all the erythroid cells are mature. These cells are uniformly flat and elliptical discs. The differences in ribosome numbers in electron micrographs of erythroid cells from different stages of development are also consistent with the existence of two series of erythroid cell maturation in the peripheral blood of the developing rainbow trout.


The changes in cell shape during pigment migration in melanophores of a teleost, Oryzias latipes. The changes in cell shape of fish melanophores during pigment displacement, and the effects of colchicine and cytochalasin B on the surface morphology were studied by scanning electron microscopy. Dispersed melanophores are generally flat, with thick radiating dendritic processes. Aggregated melanophores are characterized by their swollen, hemispherical centrospheres and thin, collapsed dendrites. Colchicine induces a flattening of the entire surface of the cell while cytochalasin B elicits the swelling of the centrosphere accompanied by a partial migration (aggregation) of melanosomes.


The ontogeny of L-alpha-hydroxyacid oxidase isozymes in the mouse. Mouse liver hydroxyacid oxidase isozymes are present at low levels at birth and increase in activity until day 13 after which HAOX-B almost disappears and HZOS-A is reduced to approximately one half the maximum level in the adultkidney. HAOX-G appears near day 13 post partum and increases until adult levels are reached, the female having four times the activity of the male. The pregnant female has significantly lower levels of HAOX-A and HAOX-B in the liver and higher activity of HAOX-B in the kidney. Developmental changes occur in the extent of epigenetic modification of mouse liver HAOX-A during the early neonatal period.


Studies on differentiation of Mûllerian ducts in the quail, Coturnix coturnix japonica. II. Effects of sex hormones on nucleic acid synthesis in isolated female ducts. The present investigations were carried out in an effort to determine the mechanisms underlying differentiation in the avian Müllerian duct, especially the asymmetrical differentiation of the female ducts. Using the isolated female ducts of Japanese quail, the incorporations of 3H-uridine and 14C-thymidine were determined in vitro at several embryonic stages. Incorporation of 3H-uridine was altered with some synchronous fluctuation during the embryonic period in both the left and right ducts, while 14C-thymidine incorporation first decreased rapidly and subsequently, only slightly, during the same period. By administering sex hormones in vitro nucleotide incorporation was affected to an appreciable extent characteristic of the duct at each stage. This hormonal susceptibility was also periodically altered during duct differentiation. The growing left duct continued to receive an apparent stimulation under the hormonal conditions, while the involuting right duct was sometimes inhibited under the same conditions. Such hormonal susceptibilities may explain the asymmetrical differentiation of the female left and right ducts during this embryonic period.


Hybrid desmosomes in aggregated chick and mouse cells. Mouse embryo skin epidermis has been examined during maturation, and stages have been found when desmosomes are first scarce, then increasing in frequency and finally numerous. Cells of skin epithelium from these stages have been combined in reaggregates with cells of the 15-day chick corneal epithelium which also form desmosomes readily. When these two cell types are reaggregated in the presence of cytochalasin B which inhibits cell sorting, they form numerous junctions with each other. Desmosomes in mouse and chick appear similar morphologically except for certain cytoplasmic components. Mouse skin epidermis cells combined with cardiac muscle or intestinal epithelium formed imperfect or no specialized contacts. The possible role of junctions in cell sorting in reaggregates is discussed.


Morphogenetic gradients in moltiple-graft Hydra viridis. I. The effects of colcemid and colchicine. The morphogenesis of so-called secondary (2 degree) heads, budding regions and feet, and separations at graft borders, is studied in multiple-graft animals containing three gastric regions (3g animals) treated with Colcemid or colchicine. Control animals consist of three non-treated pieces. Animals consisting of two non-treated and one treated piece are also employed. The main effects of Colcemid are the promotion of graft healing at the distal graft border, and of 2 degree head formation on the proximal gastric region (g-1). Colchicine also promotes graft healing at the distal graft border, but in contrast to the effect of Colcemid, promotes the formation of ectopic feet (tertiary feet) and inhibits head regeneration at the distal end of the middle gastric region (g-2). Colchicine also accelerates an inversion of polarity in 2 degree budding regions on the g-2 pieces of animals with 2 degree heads on their g-1 pieces. Treatment of a distal graft piece with Colcemid promotes 2 degree head formation on the nearest proximal piece which is not treated, but the inhibition of 2 degree head formation by colchicine occurs only on colchicine treated pieces. The morphogenetic effects of the drugs are interpreted as consequences of their actions on nerve differentiation and cell division. The paper argues that homeostatic control of a hydra's cell population depends on dividing cells influencing cell loss, and that similar mechanisms are involved in the rejection of a graft and the separation of a bud.


Ontogenetic expression of larval and adult hemoglobin phenotypes in the intergeneric salmonid hybrids. Ontogeny of the hemoglobins of Honmasu (Oncorhynchus rhodurus, HXH),brook trout (Salvelinus fontinalis, BXB) and their reciprocal hybrids (HXB and BXH) was examined electrophoretically as well as spectrophotometrically. All of these fish have electrophoretically distinct larval and adult type hemoglobins and the transition from one type to the other occurred early during post-hatching development. In the case of larval hemoglobins, the electrophoretic pattern of a hybrid, BXH, resembled that of the maternal parent, brook trout (BXB), while the hemoglobin of the reciprocal hybrid, HXB, differed markedly from that of the maternal parent, Honmasu (HXH), in that it possesses a diffuse pattern. Spectrophotometric examinations indicated that this was mostly methemoglobin. Adult type hemoglobins at more advanced stages of both hybrids were electrophoretically resolved into the parental hemoglobins. However, no "hybrid" hemoglobins were detected. Because there was abnormal hemoglobin formation in the larval erythrocytes (erythrocytes L) of the HXB hybrid, and then normal hemoglobin synthesis in the adult erythrocytes (erythrocytes A) of the same fish at later developmental stages, it appears that the paternal effects upon the hemoglobin differed in these two erythroid cell lines of the developing trout.


DNA synthesis during lens regeneration in larval Xenopus laevis. Larvae of Xenopus laevis at stages 50-53 were lentectomized and then injected with tritiated thymidine at various times after lentectomy. In series I, the animals were injected 1,2,3,4,6,8,10,12,15, or 17 days after lens removal and fixed three hours after injection. Autoradiograpns of serial cross sections through the eyes were prepared. Increased incorporation of thymidine in the cells of the regenerating lens was first observed two days (stage 2) after lentectomy. All of the cells of the lens vesicle incorporated H3 thymidine until stage 4 at which time the cells in the inner wall of the vesicle began to differentiate into lens fibers. Labelling then became restricted to the peripheral cells (prospective lens epithelium and prospective lens fibers). At stage 5 of regeneration, only cells of the lens epithelium incorporated H3 thymidine. In Series II, animals injected three or four days after lentectomy were fixed daily from one to seven days after injection. Many stage 3 and stage 4 regenerates were recovered with label throughout and stage 5 regenerates were found, seven days after injection, with label over the lens fibers as well as over the lens epithelium.


Parthenogenic development after chemical treatment of Xenopus laevis spermatozoa. Eggs of Xenopus laevis were fertilized in vitro by spermatozoa pre-treated with various concentrations of aziridinyl urea (ethyleneurea) for between 30 and 120 minutes. At 2 and 4 mg/ml for 30 minutes there was a high incidence of abnormal embryos, few of which developed into tadpoles; after 6 and 8 mg/ml no tadpoles were produced. However, the highest concentration 10 mg/ml, yielded 66% of tadpoles, only 7% of which were obviously abnormal. With increasing time the same pattern of events was obtained except for a displacement towards the lower concentration ranges. Tadpoles developing from these latter experiments were found to be haploid. The results resemble those obtained by exposure of Rana pipiens spermatozoa to X-rays and ultraviolet light, with the production of gynogenetic embryos, usually referred to as the Hertwig effect.


Urea excretion in the hibernating Columbian ground squirrel (Spermophilus columbianus). Hibernation was induced in Columbian ground squirrels by placing them in refrigerated cages equipped with urine-collection pans. On arousal, urine and blood were collected from each animal, which was then allowed to reenter hibernation. After several days the animal was sacrificed and bladder urine and another blood sample were taken. In addition, four active non-hibernating ground squirrels were placed in a cage at room temperature with neither food or water. Urine was collected at 9 and 26 hours and blood was collected at 0 and 26 hours. Although only seven of ten hibernating squirrels had a higher blood-urea level when sacrificed than during the previous arousal, the other three had very high levels in the arousal period and probably further excreted urea before entering hibernation. When total body urea was calculated on a body weight basis, all except one animal showed a greater level of urea during hibernation than in the previous arousal. During their period of dehydration, the non-hibernating summer squirrels showed a marked decrease in blood urea. The osmotic concentration of the urine from these squirrels was due less to urea than that excreted during arousal by hibernating squirrels. Thus, it appears that urea accumulates in the blood during hibernation and is excreted in the urine during arousal.


Ultrastructural analysis of artificially activated rabbit eggs. Ultrastructural investigations have been carried out on parthenogenetic rabbit eggs in an effort to elucidate events occurring during artificial activation and their similarity to processes of fertilization and embryogenesis. Rabbit eggs were artificially activated by culturing at 10 degrees C for 24 hours followed by incubation at 37 degrees C for 2 to 24 hours. Examination of eggs immediately after incubation at 10 degrees C for 24 hours indicates that activation is initiated when the chromosomes coalesce to form a reticulum which is either surrounded completely by two parallel membranes or incompletely by cisternae of smooth endoplasmic reticulum. Aggregation of the chromosomes occurs as a result of a reduction in the number of microtubules making up the meiotic spindle. When cold treated ova are subsequently incubated at 37 degrees C a nucleus is formed which moves central where it may participate in the cleavage of the egg. Formation of a second polar body and release of the contents of the cortical granules as reported for inseminated eggs was not found to be a part of activation of the egg by cold treatment. Approximately 95% of the ova cultured at 10 degrees C for 24 hours followed by 37 degrees C for 12 hours were activated, i.e., they possessed a nucleus or they had cleaved. Many of the activated eggs cultured for short periods at 37 degrees C were structurally similar to fertilized ova, with further incubation fragmented eggs and abnormal multicellular stages predominated.


Abnormal neuronal responses during evolution of a penicillin epileptic focus in cat visual cortex. After defining the receptive fields of single units in cortical area 17 of anesthetized cats, recurrent on-off stimulation with bars of light of optimal configuration win from a second micropipette; Progressively, three distinct alterations of neuronal activity developed. The most longlasting and usually the earliest abnormality was an increase in the number and frequency of spikes comprising a neuron's response to stimuli that were effective prior to iontophoresis. This enhanced physiologic response (EPR) could be elicited from a cell independently of the discharge activity of an induced focus, but only with stimuli appropriate for the cell's receptive field. With additional iontophoresis an entirely new response developed, which was consistent with an extracellular paroxysmal depolarization shift (PDS). This high-frequency burst of spikes appeared only in association with an ECoG interictal potential. It could be triggered, however, by stimuli which were previously effective or ineffective, as well as occur spontaneously. Characteristics which further distinguished the PDS from EPR included a longer and more-variable latency, a longer recovery period, and a different sensitivity to changes of stimulus intensity. A period of response inhibition also accompanied each interictal potential and persisted with a variable duration afterward. It was most noticeable as an interruption in the activity of tonically responding neurons and was often present before the cell began to generate PDSs. It was concluded that the EPR represents a direct effect of penicillin on the cell or its immediate synaptic connections, while the PDS appears dependent on the altered interactions within a population of such affected cells. The inhibitory phenomenon, in addition, seems a result of projected influences from cells more fully involved with the developing focus. A dynamic model of the EPR-PDS relationship is proposed.


Responses of rabbit superior colliculus neurons to repeated visual stimuli. It has been shown that cells in the superficial layers of the superior colliculus exhibit response decrements when a visual stimulus is repeated. These response decrements have some of the properties associated with habituation, in particular, 1) spontaneous recovery and 2) habituation rate dependent on stimulus frequency. These observations have been made in two classes of neurons; direction-selective cells and so-called modified concentric cells. All of these neurons had small receptive fields and well-defined response properties. Some neurons in both the direction-selective and modified concentric groups do not show habituation. On the basis of area-threshold curves and other observations, it is suggested that those neurons which habituate possess strong inhibitory inputs which are weak or lacking in thenonhabituating neurons. This generalization leads to a hypothesis that inhibition in the superior colliculus has a long decay time and that a response to a given stimulus is affected by inhibition activated by preceding stimuli.


Disinhibition in cat motor cortex by ammonia. The effect of intravenously administered ammonium salts on postsynaptic inhibition of pyramidal tract cells was investigated in cat motor cortex. Extracellular recordings revealed that pyramidally or thalamically mediated inhibition of antidromic action potentials is abolished by ammonia. Intracellular recordings demonstrated that hyperpolarizing IPSPs vanished and EPSPs appeared while the inhibitory stimuli still triggered a decrease of neuronal resistance and the resting membrane potential was unchanged. It is concluded that ammonia disinhibited action-potential generation and EPSPs by shifting E(IPSP) to the level of the resting membrane potential. With disinhibition and facilitation replacing inhibitation of action potentials, ammonia clearly disturbs those cortical functions involving postsynaptic inhibition.


Spatial limits of epileptogenic cortex: its relationship to ectopic spike generation. In order to investigate if ectopic spike generation was ubiquitous in and specific generation was ubiquitous in and specific to epileptogenic cortex, a method was devised to determine the limits of such an area based on a well-accepted physiologic characteristic of epileptogenicity. The limits of the penicillin-induced epileptogenic cortex were defined in terms of a retinal activation field; this is a circumscribed area whose stimulation by light evokes a characteristic cortical epileptiform wave. All lateral geniculate nucleus (LGN) neurons manifesting ectopic spike generation during interictal epileptiform waves had receptive fields within the activation field. During organized seizures, ectopic spike generation was observed in neurons with receptive fields outside the activation field. Because of these findings it was concluded that ectopic spike generation is a characteristic and specific feature of epileptogenic cortex and that it is a characteristic of the epeleptogenic process rather than a peripheral event related entirely to the direct effect of penicillin on neurons.


Responses of single units in cerebellar vermis of the cat to monaural and binaural stimuli. The responses of 146 cerebellar neurons to tone stimuli were studied in 29 cats anesthetized with chloralose-urethan and in 7 decerebrate preparations. Units were classified as onset or sustained firing. Onset spikes occurred on stimulation of either ear and showed binaural facilitation, while sustained discharges were frequently only excited by monaural stimulation. The latent periods of sustained discharges appeared to be shorter than those of onset responses, and sustained discharges were also more sharply tuned than the onset units. Evidence was presented suggesting that onset responses reflected input from the inferior colliculus and sustained responses, the cochlear nucleus. The sterotyped facilitatory behavior of onset units suggested that a maximal discharge might occur if sounds were of equal intensity at each ear; 26 neurons were examined with variable interaural time or intensity differences and 10 of these exhibited maximal firing when the interaural time and intensity difference was zero--i.e., if the sound was located directly in front of the head.


An electrically mediated inhibition in goldfish medulla. 1. Passive hyperpolarizing potentials (PHPs) have been recorded intracellularly from goldfish medullary neurons in the vicinity of the Mauthner cell (M-cell). They are evoked when this cell is activated antidromically by stimulation of the spinal cord, and orthodromically via the ipsilateral eighth nerve; when appropriately timed they block or delay spikes induced both directly and transsynaptically. 2. Since the PHPs and the M-cell spike have the same latency, time course, and all-or-none character, they cannot be generated by chemically mediated synaptic transmission. This conclusion is further supported by the evidence that PHP amplitude and time course are independent of membrane potential. 3. The analysis of the mechanism underlying PHP generation has been based on the hypothesis that they are brought about by the extracellular currents flowing to the axon cap during an M-cell action potential. Specifically, it was postulated that some of this current is channeled back to the axon cap region intracellularly through processes of PHP-exhibiting neurons, and that these cells are passively hyperpolarized by the associated inward transmembrane current flow. This model would require that PHP-exhibiting neurons send processes into the axon cap. This hypothesis is confirmed by the following: a) When the PHP is timed to occur during the conductance increase associated with a spike after hyperpolarization, it is reduced, as would be expected for a passive current flow across a membrane resistance. b) PHPs are not found in all medullary neurons in the vicinity of the M-cell, but rather in a specific neuronal population. c) PHP-exhibiting neurons have been identified following Procion yellow injections; as predicted, they issue one process, presumably the axon, which projects toward the M-cell axon cap area. d) The PHP can be stimulated by passing a cathodal current from a microelectrode located in the axon cap; it is not mimicked when the cathodal electrode is moved outside this region. The currents necessary to mimic a PHP are comparable to the estimated current flowing back to the axon cap during an M-cell action potential. 4. The input resistance of PHP-exhibiting neurons is in the range of 4 M alpha, and their estimated specific membrane resistance is in the range of 900-2,000 alpha-cm-2, which is not an unusually low value for neuronal membranes. By contrast, the intracellular channeling of current during a PHP can rather be attributed to a high extracellular tissue resistance within the axon cap, which was found to be at least 2.5 times that of the surrounding medullary tissue..


Visual activation of neurons in inferotemporal cortex depends on striate cortex and forebrain commissures. Neurons in inferotemporal cortex respond only to visual stimuli and a majority have receptive fields that extend well into both visual half-fields. After bilateral removal of striate cortex, no inferotemporal neurons responded to visual stimuli. After unilateral removal of striate cortex, inferotemporal neurons in both hemispheres responded only to stimuli in the hemifield contralateral to the intact striate cortex. After section of the corpus callosum and anterior commissure, inferotemporal neurons in both hemispheres responded only to stimuli in the hemifield contralateral to the recording site. These results indicate that inferotemporal cortex visual information from striate cortex and that the pathway from striate cortex to the contralateral inferotemporal cortex includes the forebrain commissures. This same striate-temporal pathway is also necessary for normal discrimination learning. We suggest that the converging input onto single inferotemporal neurons from widely separated retinal areas may provide a mechanism for stimulus equivalence over different parts of the visual field, and it may be the absence of such a mechanism that contributes to the visual discrimination deficit that follows inferotemporal lesions.


Neural implications of different profiles between treadmill and overground locomotion timings in cats. A cinematographic comparison of treadmill and overground performances by the cat revealed considerable flexibility in the neural control program for locomotion. For the single limb's step cycle, swing duration (time foot is off the surface) was approximately equal in both situations, as has been found previously. Subcomponents of the swing (flexion duration and timings between joints during the transition from flexion to extension) differed, however. Interlimb timings also responded to situation. The interval between touchdown of one hindlimb and the ipsilateral forelimb was reduced for treadmill stepping. An ipsilateral coupling interval also differed that had been previously reported to involve propriospinal activity, the time for onset of extension during the swing phase of the hindlimb to the onset of flexion at the beginning of the swing phase in the forelimb. Segmental afferent input, visual and other suprasegmental inputs, and motivational variables probably all contribute to the separation of treadmill and overground timing profiles.


Mauthner neuron field potential in newly hatched larvae of the zebra fish. 1. Extracellular unit recording was done in the brain and spinal cord of unanesthesized zebra fish larvae embedded in a drop of gelatin under a compound microscope. Startle responses were elicited either by vibrating a stylus against the ear vesicle, or by direct electrical stimulation of the spinal cord. 2. As in adult fish, the Mauthner neurons produced a prominent negative potential (0.5-1 mV) which occurred at the beginning of the startle reflex. The axonal conduction velocity was 1.7-3.7 m/s. 3. With vibratory stimulation, the startle reflex was elicited most reliably at rates of 1/min or less, though the Mauthner cells would follow stimulation rates of 1/s when the spinal cord was stimulated electrically. At this rate there was considerable fatigue of the spike itself, which became smaller in amplitude and longer in duration. 4. The auditory system functions during vibratory stimulation of the ear vesicle, and probably activates the Mauthner cells, though it was not concluded that this was an exclusive excitatory pathway during these experiments. Lateral line or purely tactile receptors might also be involved. The latency of the Mauthner spike varied inversely (range, 6-17.5 ms) with the intensity of the vibratory stimulus. Muscle contractions began 2 ms after the Mauthner spike. 5. We recorded several forms of startle behavior, including a single tail flip or a tail flip followed by regular or irregular tail movements. The Mauthner neuron almost always fired at the beginning of the response, but it never fired again during subsequent movements. This supports an earlier contention that the Mauthner cell initiates the tail flip but is not involved in iterative swimming behavior.


Reticulospinal neurons with and without monosynaptic inputs from cerebellar nuclei. An account is given of the responses of 557 medial reticular neurons with axons projecting down the spinal cord. All 30 experiments were on decerebrated unanesthetized cats paralyzed by Flaxedil. Recording from single neurons was by extracellular glass microelectrodes. Identification was first by location (confirmed by subsequent histology) in the medial reticular nucleus of medulla or pons, and second by antidromic activation from cord stimulation at C2 and L2 segmental levels. Axonal conduction velocities were calculated from the latency differential between L2 and C2 antidromic responses, and were usually in the range of 90-140 m/s; but about 25% were slower, ranging down to 30 m/s. Stimulation by electrodes in the ipsilateral and contralateral fastigial nuclei differentiated reticulospinal neurons into two classes according to whether they did or did not receive monosynaptic inputs, the respective populations of fully investigated neurons being 270 and 174. The fastigioreticular neurons were distinguished by a higher background frequency with mean values of 28 as against 15/s. There were also significant diffences in both the excitatory and inhibitory responses to afferent volleys from forelimb and hindlimb nerves. Comparison of the respective latency histograms showed that the responses of neurons with a fastigial input had an excess of latencies in the ranges that can be correlated with the latency histograms observed for fastigial responses. Thus, there is evidence for the effectiveness of the fastigial input and so for the pathway with monosynaptic linkage: Purkinje cells of cerebellar vermis yields fastigial neurons yields medial reticular neurons projecting down the spinal cord. Adequate stimulation of cutaneous receptors by pad taps and air-jet stimulation of hairy skin in a disppointingly small action when compared with fastigical responses. Explanations of this deficiency are suggested. Another discrpancy from the fastigial responses is that the medial reticular neurons have much wider receptive fields with little discrimination between ipsilateral and contralateral and between forelimb and hindlimb. Stimulation of the ipsilateral tegmental tract was tested on 183 reticulospinal neurons, 112 being with fastigial inputs. In about half there was a powerful monosynaptic excitation, which would identify such neurons as being on the pathway from mesencephalic and diencephalic centers to the spinal cord. There is a general discussion of transmission across successive synaptic relays, where specificity is sacrificed to integration.


Medial recticular neurons projecting Rostrally. 1. In the latter part of investigations on the medial reticular neurons, stimulation was applied to the ipsilateral tegmental tract in the upper pontine level. Of the 426 neurons in this series, 56 had rostrally projecting axons as evidenced by their antidromic responses. 2. Of these 56 neurons, 41 were activated by limb nerve stimulation, usually very strongly, and so qualify as units in the reticular activating system. Fastigial stimulation monosynaptically excited 14 of these reticular activating neurons, so providing and ascending pathway from the cerebellar vermis. 3. Axonal branching has been demonstrated by antidromic testing in four reticular neurons with ascending axons. In two there were branches to the fastigial nucleus and in two, down the spinal cord. 4. The latency histograms of the excitatory and inhibitory responses resembled those for reticular neurons with descending axons except for the poverty of inhibitory responses in neurons not receiving a fastigial projection.


Capacities of humans and monkeys to discriminate vibratory stimuli of different frequency and amplitude: a correlation between neural events and psychological measurements. The capacities of monkeys and humans to discriminate between mechanical sinusoids differing in amplitude or frequency were measured in a two-alternative, forced-choice task. The difference limen for amplitude discrimination for both species remained constant near 10% of the standard amplitude over the range of 17-30 dB, relative to detection threshold. Equal subjective intensity curves in the 20-40 Hz range were determined at 20 and 29 dB, relative to detection threshold. These curves followed the threshold curve and were identical for the two species. The difference limen for frequency discrimination averaged 1.8 Hz for humans and 2.7 Hz for monkeys; the range of values for the two species overlapped nearly completely. The small sizes of these difference limens indicate, we believe, the capacity of highly trained individuals of either species to ascertain small differences in the temporal order of somesthetic stimuli and of the neural events evoked by them. In one series of experiments we demonstrated that subjects of both species possess two threshold for two different aspects of flutter-vibration which are displaced from each other along the intensive continuum. For either species, the minimum level of stimulus amplitude required for threshold frequency discrimination is about 8 dB above that sufficient for detection. This difference in amplitude is called the atonal interval and matches that observed between absolute and tuning thresholds for quickly adapting, mechanoreceptor afferents (the Meissner afferents) which innervate the glabrous skin of the monkey hand. These and previous findings have permitted a number of direct correlations between behavioral and neural events as regards the sense of flutter. The neural codes for the intensity and frequency of flutter appear to be different. The capacity to detect the presence of a mechanical sinusoid and the capacity to judge its subjective intensity are likely to depend on criterion levels of activity in the total population of Meissner afferents, the former on the appearance of any activity (absolute threshold) in a small population of the most sensitive of these fibers and the latter on the overall size of the active population of neuronal elements at each level of amplitude. The total activity in the relevant neural population elicited by sinusoids of increasing amplitude defines a prothetic continuum along which subjects can judge the magnitude of sensation..