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Review ARTICLE
New tools for investigating astrocyte-to-neuron communication
- 1Biophysics of Gliotransmitter Release Team, Laboratory of Neurophysiology and New Microscopies, INSERM U603, CNRS UMR 8154, University Paris Descartes, Paris, France
- 2Glia-Glia and Glia-Neuron Interactions in Neurophysiopathology Team, Laboratory of Neurophysiology and New Microscopies, INSERM U603, CNRS UMR 8154, University Paris Descartes, Paris, France
Gray matter protoplasmic astrocytes extend very thin processes and establish close contacts with synapses. It has been suggested that the release of neuroactive gliotransmitters at the tripartite synapse contributes to information processing. However, the concept of calcium (Ca2+)-dependent gliotransmitter release from astrocytes, and the release mechanisms are being debated. Studying astrocytes in their natural environment is challenging because: (i) astrocytes are electrically silent; (ii) astrocytes and neurons express an overlapping repertoire of transmembrane receptors; (iii) the size of astrocyte processes in contact with synapses are below the resolution of confocal and two-photon microscopes (iv) bulk-loading techniques using fluorescent Ca2+ indicators lack cellular specificity. In this review, we will discuss some limitations of conventional methodologies and highlight the interest of novel tools and approaches for studying gliotransmission. Genetically encoded Ca2+ indicators (GECIs), light-gated channels, and exogenous receptors are being developed to selectively read out and stimulate astrocyte activity. Our review discusses emerging perspectives on: (i) the complexity of astrocyte Ca2+ signaling revealed by GECIs; (ii) new pharmacogenetic and optogenetic approaches to activate specific Ca2+ signaling pathways in astrocytes; (iii) classical and new techniques to monitor vesicle fusion in cultured astrocytes; (iv) possible strategies to express specifically reporter genes in astrocytes.
The concept of gliotransmission at the tripartite synapse developed more than 10 years ago (Araque et al., 1999; Perea and Araque, 2010) is very attractive: it suggests that cerebral gray matter protoplasmic astrocytes are not only supportive cells with homeostatic functions, but that they also play a role in information processing by responding to neuronal synaptic activity with Ca2+ elevations that induce the subsequent release of gliotransmitters and modulate neuronal excitability and synaptic plasticity [reviewed in (Angulo et al., 2008; Bergersen and Gundersen, 2009; Cali et al., 2009; Perea et al., 2009; Santello and Volterra, 2009; Halassa and Haydon, 2010; Perea and Araque, 2010; Parpura et al., 2011; Gucek et al., 2012; Zorec et al., 2012)]. However, the concept of gliotransmission is debated. First, the ability of astrocytes to release neuroactive compounds in a Ca2+-dependent manner has been questioned (Agulhon et al., 2008; Fiacco et al., 2009). Second, there is no consensus concerning the mechanisms of gliotransmitter release. In fact, studying astrocytes in situ is very challenging and an agreement is emerging that new methods are needed to selectively activate (Fiacco et al., 2009; Hamilton and Attwell, 2010) and read out Ca2+ signals in astrocytes in situ (Shigetomi et al., 2013b).
By gliotransmission, we mean Ca2+-dependant release of fast-acting neuroactive compounds, the gliotransmitters. Astrocytes can also release other molecules acting not only on neighboring neurons but also on nearby glial cells such as microglia, NG2 cells, and on cellular constituents of the blood brain barrier. Our review will focus on the fast acting gliotransmitter candidates, glutamate mostly, as well as D-serine, ATP, and GABA. Several pathways have been suggested for glutamate release: exocytosis, hemichannels, sodium-dependent transporters, volume-regulated anion channels, purine P2X7 receptor channel [reviewed in (Hamilton and Attwell, 2010)], and more recently the bestrophin 1 (Best1) chloride channel and the two-pore domain potassium TREK1 channel (Woo et al., 2012). The release of glutamate by Ca2+-regulated vesicular fusion is considered as an important pathway for gliotransmitter release because, by analogy with neuronal exocytosis, it appears to be the most suitable pathway for rapid information processing by astrocytes. Experimental evidence in favor of glutamate exocytosis has been provided using (i) dihydroxyphenylglycine (DHPG), mechanical stimulation, inositol triphosphate (IP3) and Ca2+ uncaging to activate astrocytes; (ii) Ca2+ buffering with BAPTA, VAMP2/3 cleaving with tetanus toxin (TeNT) or botulinum toxin (BoNT), and generating a dominant negative SNARE (dnSNARE)-expressing mouse line to inactivate vesicular release in astrocytes; (iii) fluoroacetate to inactivate astrocyte metabolism [reviewed in Bergersen and Gundersen, 2009; Cali et al., 2009; Gucek et al., 2012; Zorec et al., 2012], but contrasts with the relative absence on electron micrographs of small vesicles in astrocyte processes, when compared to the neuronal presynaptic terminal.
In this review, we discuss several new genetically encoded tools to read out astrocytic Ca2+ activity, to activate Ca2+ signals in astrocytes, and to monitor gliotransmitter release from astrocytes. Optical methods for astrocyte photoactivation and imaging, and strategies to selectively target the genes in astrocytes in their native environment are also reviewed.
Imaging Astrocyte Activity
Organic vs. Genetically Encoded Ca2+ Indicators
Protoplasmic astrocytes are electrically silent. However, they may be considered as excitable cells in the sense that they show Ca2+ signals, both spontaneously and in response to neuronal activity. In spite of the evidence suggesting that Ca2+ signals are necessary and sufficient to induce gliotransmitter release, many questions remain, concerning both the role and sources of Ca2+ signals in astrocytes (Agulhon et al., 2008; Fiacco et al., 2009; Parpura et al., 2011). One limiting factor to study Ca2+ signaling has been methodological. So far, most studies in acute brain slices and in vivo have been based on bulk-loaded membrane-permeable chemical Ca2+ indicators. There exist many organic Ca2+ indicators with different spectral properties and affinity for Ca2+ which can monitor either Ca2+-related fluorescence changes or, for the ratiometric probes, can be calibrated to provide absolute Ca2+ concentration [reviewed in (Paredes et al., 2008)]. The membrane-permeable acetoxymethyl (AM) esters, Fluo4-AM and Oregon Green BAPTA1-AM (OGB1-AM), the most popular dyes used to image Ca2+ activity in populations of astrocytes, allow imaging the somatic region and the larger proximal processes but leave the very thin distant processes that participate to the tripartite synapse unsampled (Reeves et al., 2011). At the laser powers, dye concentrations and integration times typically used and with the spatial resolution available, fluorescence changes in fine processes are generally not resolved (see below for a detailed discussion).
Another limiting factor has been the lack of specificity of these membrane-permeable Ca2+ indicators, which label both neurons and astrocytes (Garaschuk et al., 2006) with cell-type preferences, depending on the indicator, the protocol of application, and the age of the animal. Therefore, sulforhodamine 101 (SR101) that is specifically taken up by astrocytes has been generally used as a secondary fluorescent marker for astrocyte identification. The deep-red emission of SR101 can be detected with negligible spectral overlap with GFP or green fluorescein-based membrane-permeable Ca2+ indicators (Nimmerjahn et al., 2004). However, SR101 uptake is age-dependent (Kafitz et al., 2008) and it does not work in all brain regions (Schnell et al., 2012). Also, at concentrations needed for astrocyte labeling, SR101 leads to increases of neuronal excitability and long-term potentiation (Kang et al., 2010; Garaschuk, 2013), and thus might affect functional studies. As an alternative, transgenic (Tg) mouse lines (Nolte et al., 2001; Vives et al., 2003; Heintz, 2004; Zuo et al., 2004; Regan et al., 2007) expressing a green/yellow fluorescent protein (GFP/YFP) or Discosoma red protein (DsRed) under astrocyte-specific promoters (GFAP, S100β, GLT-1, ALDH1L1) can be used to identify astrocytes.
In this context, the recent genetically encoded Ca2+ indicators (GECI) provide a new alternative for non-invasive imaging of Ca2+ activity in vivo and in brain slices [reviewed in (Knopfel, 2012; Looger and Griesbeck, 2012)]. Their level of expression can be stable for months in the absence of apparent adverse effect (Zariwala et al., 2012). GECIs can be targeted to the plasma membrane of astrocytes (Shigetomi et al., 2010) and their specific expression by astrocytes in vivo is being developed using viral constructs and Tg mouse lines (see below). Finally new GECI variants are being generated having greater signal to noise ratio, different Ca2+-binding affinities, and different spectral properties (Horikawa et al., 2010; Zhao et al., 2011; Ohkura et al., 2012; Akerboom et al., 2013; Chen et al., 2013b) which further enlarge their utility for studying the role of astrocytes on synaptic transmission (Tong et al., 2013).
Among the most recent GECIs, several variants of the original GFP-based Ca2+ sensor GCaMP1 (Nakai et al., 2001) have been tested in astrocytes: GCaMP2 (Hoogland et al., 2009), GCaMP3 (Shigetomi et al., 2010, 2013b; Tong et al., 2013), GCaMP5 (Akerboom et al., 2012), and red GECIs (Akerboom et al., 2013), as well as Case12 (Souslova et al., 2007; Gourine et al., 2010), and yellow Cameleon YC3.60 (Atkin et al., 2009). In neurons GCaMP5G and GCaMP6 variants have been shown to produce a higher signal-to-noise ratio than GCaMP3 and can detect Ca2+ changes evoked by single action potential (Akerboom et al., 2012). GCaMP3, GCaMP5G, and GCaMP6 are all compatible with two-photon excitation at 910-930 nm (Akerboom et al., 2012; Mutze et al., 2012). Recently, Khakh's group (Tian et al., 2009; Shigetomi et al., 2010, 2013b) compared Ca2+ changes in astrocytes using a membrane-permeable Ca2+ indicator (Fluo4-AM) with those detected with two GECIs, the cytosolic GCaMP3 and a membrane-targeted Lck-GCaMP3 (Figure 1). Ca2+ signals were recorded with a confocal microscope at the surface of acute hippocampal slices from adult mice. Specific astrocytic targeting of GCaMP3 and Lck-GCaMP3 was obtained using a short version (gfaABC1D) of the human glial fibrillary acidic (hGFAP) promoter. Unlike Fluo4-AM which diffuses poorly to the thin astrocyte processes (Reeves et al., 2011), both GCaMP3 and Lck-GCaMP3 reported a wealth of Ca2+ signals in distant thin astrocytic processes with relatively less activity in the soma and proximal processes. Interestingly, (i) spontaneous Ca2+ rises recorded with the GCaMP3 are highly localized and desynchronized, as suggested previously from whole-cell dye loading single astrocytes with higher dye concentrations through the patch pipette (Nett et al., 2002; Di Castro et al., 2011; Panatier et al., 2011); (ii) spontaneous somatic activity does not appear to integrate the signals generated locally in the thin processes; (iii) using Lck-GCaMP3, a new Ca2+ signaling pathway has been suggested in astrocytes involving the A1 transient receptor potential (TRPA1) channel (Shigetomi et al., 2011) that has been proposed to contribute to D-serine release (Shigetomi et al., 2013a). In summary, earlier studies using membrane-permeable Ca2+ indicators may have underestimated the variety of Ca2+ signaling mechanisms, and missed local interactions between astrocytes and neurones.
Figure 1. Expression of GCAMP3 in astrocytes and comparison of Ca2+ signals detected with Fluo-4, cyto-GCAMP3, and Lck-GCAMP3. (A,B) Illustration of the membrane-targeted Lck-GCAMP3 and cytosolic non-targeted Cyto-GCAMP3. (C) Protocol of AAV2/5 injections into a mouse hippocampus. (D) Confocal images in CA1 stratum radiatum for Lck-GCaMP3 and cyto-GCaMP3. (E) Colocalization between Lck-GCaMP3 and cyto-GCaMP3 with the astrocytic marker GFAP. (F) Ca2+ signals imaged with Fluo-4 (black traces), cyto-GCaMP3 (green traces), and Lck-GCaMP3 (red traces). Top, representative images of astrocytes loaded with Fluo-4AM, Lck-GCaMP3 or cyto-GCaMP3. ROIs are shown in each image, and their time-lapse intensities are shown below. Adapted from (Shigetomi et al., 2013b).
GECIs have been introduced only recently compared to chemical Ca2+ indicators that have been used since the 80s. Therefore, their photophysical properties and impact on intracellular Ca2+ homeostasis have not yet been characterized to the same extent as their chemical counterparts (Perez Koldenkova and Nagai, 2013). For example, the Ca2+affinity of many GECIs has not been yet determined in the complex intracellular milieu; their binding kinetics (on- and off-rates for Ca2+ binding), as well as their aggregation and bleaching rates are not well established. Open questions concern their precise mobility, local concentration, Ca2+ buffer capacity and subcellular localization, which can be engineered by adding genetically encoded targeting sequences, as done with Lck-GCaMP3 (Shigetomi et al., 2010). However, the capacity of GECIs to specifically detect local Ca2+ signals in a population of astrocytes together with their low photobleaching and high signal-to-noise ratio seem to outweigh these limitations. Indeed experiments become feasible that were simply not possible with earlier small-molecule chemical indicators. The new Ca2+ data with the GECIs provide intriguing clues to explore astrocyte functions but also present new challenges. New tools will be needed to reliably detect and quantify the wealth of rapid asynchronous and local fluorescence changes. The mechanisms and functional significance of these Ca2+ signals are far from being understood. Given the striking difference between fluorimetric Ca2+ signals detected with chemical Ca2+ indicators and GECIs, the relation between neuronal activity and astrocytic Ca2+ signals needs to be re-investigated under physiological and pathological conditions using acute brain slices, and anesthetized or non-anesthetized mouse preparations.
Optical Methods for Imaging Astrocyte Activity
Imaging GECIs with two-photon microscopy holds important potential for monitoring astrocytic Ca2+ signals in situ. However, major challenges remain when imaging astrocyte signals in the neuropil. The limited spatial resolution is an issue when it comes to tell apart morphological changes and Ca2+ signals. An astrocyte process occupies only a small fraction of the two-photon excitation volume and, this fraction will become smaller with increasing imaging depth, for which two-photon resolution degrades due to scattering and wave front aberrations (Chaigneau et al., 2011). Thus, subtle morphological changes expected to modulate synapse coverage and modulate astrocyte-neuron interactions are unlikely to be resolved in two-photon microscopy and will be confounded with Ca2+ changes.
Two-photon microscopy combined with two-photon stimulated emission depletion (STED) (Ding et al., 2009; Li et al., 2009b; Moneron and Hell, 2009; Nägerl and Bonhoeffer, 2010) increases lateral resolution and super-resolution imaging of dendritic spines in live mouse brain in vivo has been recently reported (Berning et al., 2012). Two-photon-STED is attractive because it brings two-photon resolution closer to typical dimensions of astrocyte processes but it aggravates the temporal resolution problem inherent to scanning microscopies where temporal resolution depends on the number of pixels (i.e., the sampling rate imposed by the spatial resolution) and the dwell time per pixel (i.e., the number of photons available). As spatial resolution is privileged in 2PE-STED, the number of image pixels increases as the resolution gain squared, and the temporal resolution drops accordingly. Simultaneous multi-spot detection (Cheng et al., 2011; Grosberg et al., 2012; Ducros et al., 2013) speeds up image acquisition by an order of magnitude compared to conventional raster scanning, but does not fundamentally address the temporal undersampling problem. Finally, STED resolution scales with the square-root of power of the depletion beam so that STED increases the already high light burden of two-photon imaging (Koester et al., 1999). Faster imaging, i.e., shorter pixel dwell times will thus require better fluorophores with higher fluorescence quantum yield, greater depletion efficiency, and higher photostability, all at the same time. Also, while these arguments already hold for imaging a single focal plane, their weight increases when it comes to imaging Ca2+ changes in three dimensions along a branch or an entire astrocyte. In summary, major technological advances are still needed to image small signals in fine astrocyte processes and track their subtle morphological changes.
Activation of Astrocytes
Following neuronal activity, the activation of astrocytes is mediated by neurotransmitter released from synaptic terminals (Porter and McCarthy, 1996; Wang et al., 2006). The subsequent release of gliotransmitters from mature protoplasmic astrocytes has been reported to depend upon Gq GPCR activation leading to astrocytic type-2 IP3 receptor (IP3R2) activation and Ca2+ release from the endoplasmic reticulum [reviewed in (Halassa et al., 2007)]. While this pathway has been implicated in gliotransmitter release, the mechanisms and the concept of gliotransmission remains debated (Agulhon et al., 2008; Fiacco et al., 2009; Hamilton and Attwell, 2010) in part because of our inability to selectively activate Ca2+ signals in astrocytes. The exogenous generation of Ca2+ signals that mimic those evoked by neuronal stimuli should clarify the interactions between neurons and astrocytes.
Since most cell types in the brain express an overlapping array of GPCRs, conventional pharmacological approaches consisting of bath application or local pipette perfusion of Gq GPCR agonists to evoke Ca2+ elevations in astrocytes in situ lack cellular selectivity, For instance, one of the agonists most frequently used to stimulate astrocytes, dihydroxyphenylglycine (DHPG), a group I metabotropic receptor (mGluR) agonist, has direct effects on neurons, and elicits neuronal Ca2+ elevations, long-term depolarization (Mannaioni et al., 2001; Rae and Irving, 2004), and potentiation of N-methyl-D-aspartate (NMDA) receptor-mediated currents (Benquet et al., 2002). Therefore, the use of Gq GPCR agonists, not only DHPG but also many other agonists, will lead to direct activation of neuronal receptors.
To overcome these limitations, a novel Tg mouse model was created (Fiacco et al., 2007) using the Gq GPCR MrgA1 receptor normally expressed by nociceptive sensory neurons (Dong et al., 2001). In the MrgA1 mouse model: (i) the GFP-tagged MrgA1 receptor is expressed selectively by astrocytes using an inducible tet-off system transcribed from a tet (tetO) minimal promoter; (ii) it is not activated by endogenous ligands found in brain; (iii) its ligand, the FMRF peptide, does not activate any endogenous brain Gq GPCRs. These mice were crossed with mice in which the tetracycline transactivator (tTA) is targeted to astrocytes using the hGFAP promoter. In the absence of doxycycline, tTA binds to tetO and drives expression of the MrgA1-GFP construct selectively in astrocytes and the MrgA1 receptor is functional in most astrocytes (Fiacco et al., 2007).
MrgA1-receptor-mediated Ca2+ release from astrocytic internal Ca2+ stores did not affect synaptic transmission and plasticity (Fiacco et al., 2007; Agulhon et al., 2010), raising questions about the ability of astrocytes to undergo Ca2+-dependent gliotransmitter release. Using the same MrgA1 mouse model, it was later shown that instead, astrocytic MrgA1R-mediated Ca2+ elevations potentiate glutamate and K+ uptake (Wang et al., 2012; Devaraju et al., 2013). The MrgA1 Tg mouse model demonstrates the interest of a pharmacogenetic approach to investigate the role of astrocytic Ca2+ in acute slices and in vivo. However, astrocytes are heterogeneous (Zhang and Barres, 2010) and they are likely to exhibit different functions depending on the brain area. Consequently, continued improvements are needed to activate discrete populations of astrocytes in specific brain areas. The combination of pharmacogenetic with the use of adeno-associated viral technology to deliver the expression of genetically engineered new Gq GPCRs (Wess et al., 2013) is a promising approach (see below). Additionally, two-photon uncaging of caged FMRF at the vicinity of thin astrocyte processes should better mimic synaptically-induced Gq GPCR activation and therefore help addressing further the role of this signaling pathway in astrocyte physiology.
Over the last decade, the development of new photoswitchable genetically encoded channels and receptors to activate and inactivate specific neuronal subtypes had a significant impact on Neuroscience. The simultaneous methodological advances in several fields: (i) optics for photoactivation and imaging in situ, (ii) molecular engineering for developing new photoswitchable proteins, (iii) molecular biology for specific targeting of the light sensitive proteins, have been instrumental for the success of optogenetics in elucidating the function of neuronal circuits (Szobota and Isacoff, 2010; Fenno et al., 2011; Miesenbock, 2011). The most popular photoswitchable channel to activate neurons is the H314R channelrhodopsin 2 [ChR2(H314R)], a variant of the wild type ChR2 with reduced desensitization (Nagel et al., 2005). ChR2 is a cationic channel highly permeable to proton (P+H/P+Na ~ 106) but weakly permeable to Ca2+ (P2+Ca/P+Na ~ 0.117) (Nagel et al., 2003; Lin et al., 2009). In neurons, its photoactivation triggers Ca2+ elevations which depend mainly on the secondary activation of voltage-gated Ca2+ channels (VGCC) (Nagel et al., 2003; Zhang and Oertner, 2007; Li et al., 2012).
Attempts have been made to photoactivate protoplasmic astrocytes. In situ experiments suggest that the photoactivation of ChR2-expressing astrocytes can trigger gliotransmitter release (Gradinaru et al., 2009; Gourine et al., 2010; Sasaki et al., 2012; Chen et al., 2013a). In the rat brain stem retrotapezoid nucleus, ChR2-expressing astrocytes responded to long lasting (20–60 s) illumination by slow Ca2+ rises that lasted for minutes (Gourine et al., 2010). In the hippocampal CA1 region, blue light pulses induce rapid time-locked Ca2+ signals in astrocytes (Chen et al., 2013a). However, our own experiments using mouse cortical astrocytes in culture, show that ChR2 activation induces variable and weak Ca2+ elevations (Li et al., 2012). Instead we found that the activation of the Ca2+-permeable light-gated glutamate receptor (LiGluR) [reviewed in (Szobota and Isacoff, 2010)], and the Ca2+-translocating ChR2 (CatCh) (Kleinlogel et al., 2011) evokes reliable and robust Ca2+ signals in astrocytes (Figure 2). We attributed the low efficacy of ChR2 in astrocytes to its relatively weak Ca2+ permeability (Nagel et al., 2003; Lin et al., 2009), and to the absence of VGCC in protoplasmic astrocytes (Carmignoto et al., 1998; Parpura and Verkhratsky, 2012). Interestingly, LiGluR can be rapidly switched ON and OFF to mimic endogenous Ca2+ signals recorded with the GCaMP3 (Shigetomi et al., 2013b). Finally, LiGluR activation induces a large Ca2+ influx that is further shaped by internal stores, while CatCh activation generates a Ca2+ influx insensitive to internal Ca2+ store depletion, indicating that LiGluR and CatCh are interesting tools to activate differentially selective Ca2+ signaling pathways and to study their downstream effects.
Figure 2. Ca2+ signals recorded in mouse cortical astrocytes in culture using LiGluR, ChR2(H134R) and CatCh photoactivation. (A) Light-gated Ca2+ rises in an astrocyte expressing LiGluR-mRFP. Ca2+ rises were imaged with dual-color TIRFM and repetitively switched on and off by 385-nm (violet arrows, 0.3 mW/mm2, 50 ms) and 488-nm (blue arrows, 39.1 mW/mm2, 200 ms) light pulses, respectively. (B) LiGluR(GFP)-gated astrocytic Ca2+ elevations monitored with the red-fluorescent Ca2+ dye Xrhod-1. (C) In astrocytes expressing ChR2(H134R), short photoactivation (458-nm, 27.3 mW/mm2, 500 ms) of ChR2 failed to evoke near-membrane Ca2+ elevation (top). Longer light pulses (458-nm, 1 s) evoked variable Ca2+ signals (bottom). (D) Comparison of the percentage of astrocytes showing light-gated Ca2+ rises, and of the amplitude of Ca2+ responses in LiGluR- and ChR2-expressing astrocytes. LiGluR evokes more reliable and reproducible Ca2+ rises in astrocytes. (E) CatCh-evoked astrocyte Ca2+ elevations following blue light photoactivation (1 s, 458-nm). (F) CatCh-induced Ca2+ signaling was abolished in the absence of extracellular Ca2+, but unaffected when ER Ca2+ store is perturbed by thapsigargin (TG). Bars, 10 μm. Adapted from (Li et al., 2012).
Astrocytes express a rich repertoire of metabotropic Gq, Gi/o, and Gs GPCRs (Porter and McCarthy, 1997). New light-gated proteins that mimic these GPCR-mediated pathways have been developed (Schroder-Lang et al., 2007; Airan et al., 2009; Ryu et al., 2010; Gutierrez et al., 2011; Stierl et al., 2011; Levitz et al., 2013), but they have not yet been tested on astrocytes. Since astrocytes express store-operated Ca2+ channels Orai1 (Akita and Okada, 2011; Linde et al., 2011; Moreno et al., 2012), it should also be of interest to activate them with the new photosensitive synthetic protein LOVS1K that reversibly translocates to Orai1 channels and generates either local Ca2+ signals at the plasma membrane or global Ca2+ signals upon repeated photoactivation (Pham et al., 2011).
Optical Methods to Photoactivate Astrocytes
While imaging morphological dynamics of astrocytic fine processes may not yet be possible, stimulating astrocytes locally with light is more promising because the astrocyte-specific expression of light-sensitive Ca2+-permeable ion channels circumvents the optical resolution problem, and therefore even one-photon whole-field illumination is sufficient to stimulate specifically the astrocytes. A more specific photoactivation of a subset of cells, and the local subcellular stimulation of a single astrocyte can be achieved using spatial light modulators [reviewed in (Maurer et al., 2011)] to shape the light (Shoham, 2010; Vaziri and Emiliani, 2012; Papagiakoumou, 2013). One-photon digital holography allows photoactivation within precisely shaped regions of interest at or near the tissue surface.
Combining digital holography and two-photon excitation with temporal focusing to modulate the temporal width of the pulsed laser, several groups reported shaped two-photon excitation deep inside scattering tissue (Andrasfalvy et al., 2010; Papagiakoumou et al., 2010). The spatial patterns thus generated are robust against scattering and remained confined at depths of 100 μm (Papagiakoumou, 2013). Combining optogenetics, shaped photoactivation and two-photon imaging for the optical readout of astrocytes (combined with electrophysiology for recording neuronal signals) holds important promises for interrogating interactions between neurons and astrocytes in intact brain tissue. To probe specific signaling pathways, wave-front light shaping can be combined with uncaging of classical IP3 and Ca2+ cages (Ellis-Davies, 2011), and new endothelin cage (Bourgault et al., 2007).
Monitoring Gliotransmitter Release
Among the mechanisms of gliotransmitter release, Ca2+-regulated exocytosis of synaptic-like small vesicles has been proposed as a major pathway (Cali et al., 2009). Total internal reflection fluorescence microscopy (TIRFM) is a powerful technique to monitor single-vesicle behavior and to study the mechanisms of vesicular docking and fusion in cultured cells (Holz and Axelrod, 2008). Since cultured astrocytes may differ from their in situ counterparts, the physiological relevance of the findings made in culture with TIRFM need to be validated in situ using other approaches.
TIRFM has been used to visualize near membrane single vesicles and monitor single vesicle fusion in cultured astrocytes (Bezzi et al., 2004; Zhang et al., 2004; Bowser and Khakh, 2007; Li et al., 2008; Malarkey and Parpura, 2011; Potokar et al., 2013). In early experiments (Bezzi et al., 2004), the fluorescent weak base acridine orange (AO) was used to report exocytosis, and the vesicular glutamate transporter (VGLUT) tagged with the enhanced GFP (EGFP) was overexpressed to identify the AO-positive vesicles. Following DHPG application, rapid millisecond Ca2+-dependent flashes of AO-labeled vesicles were detected and interpreted as the exocytosis of glutamatergic vesicles (Bezzi et al., 2004; Domercq et al., 2006). This interpretation was soon complicated by studies showing that AO metachromasy results in its simultaneous emission of green and red fluorescence, which invalidates the identification of the AO-positive vesicles with EGFP labeling (Nadrigny et al., 2006, 2007). It has also been shown that the flash events of AO-loaded astrocyte vesicles are not solely due to exocytosis but also reflect intracellular vesicle photolysis (Jaiswal et al., 2007; Li et al., 2008), due to the action of AO as a photosensitizer. Styryl pyridinium FM dyes, established markers of vesicular release in neurons (Rizzoli and Betz, 2005), were also used to label the astrocytic vesicular compartments and report exocytosis. However, FM dyes are handled differently by neurons and astrocytes (Li et al., 2009a) and they label mainly lysosomes (Zhang et al., 2007; Li et al., 2008; Liu et al., 2011).
Later, the genetically encoded exocytotic reporter, pHluorin, has emerged as a valuable tool to monitor astrocyte vesicle exocytosis. As a pH-sensitive GFP mutant, pHluorin fluorescence is quenched in the acidic vesicle lumen and becomes bright upon vesicle fusion when the fluorescent protein is exposed to external neutral pH (Miesenbock et al., 1998). Since there was evidence that astrocytes release glutamate via Ca2+-regulated exocytosis (Cali et al., 2009), pHluorin was targeted to the lumen of putative glutamatergic vesicles in astrocytes by using the fusion protein VGLUT1-pHluorin (Marchaland et al., 2008). TIRFM imaging of single vesicles in cultured astrocytes labeled with VGLUT1-pHluorin revealed fusion events occurring within hundreds of milliseconds after Ca2+ rise evoked by either mGluR (Marchaland et al., 2008) or purinergic P2Y1 receptor activation (Santello et al., 2011). These results were consistent with those obtained by the same lab using AO-labeled (Bezzi et al., 2004; Domercq et al., 2006), and FM-labelled astrocytes (Cali et al., 2008).
Different kinetics have been reported for the exocytosis of the putative glutamatergic vesicles in astrocytes when using another pHluorin-based exocytotic reporter synaptopHluorin (spH), a chimeric construct tagging the luminal side of synaptobrevin 2 (Burrone et al., 2006). As synaptobrevin 2 appears to colocalize with VGLUT1 on the same vesicles in astrocytes (Montana et al., 2004; Zhang et al., 2004; Liu et al., 2011), expressing spH in astrocytes leads to the labeling of VGLUT1-positive vesicles (Bowser and Khakh, 2007; Liu et al., 2011). However, unlike VGLUT1-phluorin that reports fast millisecond kinetics of exocytosis (Cali et al., 2008; Santello et al., 2011), spH-labeled vesicles undergo slow exocytosis that is loosely coupled to stimulation, with most events occurring ~2 min after P2 receptor-mediated Ca2+ rise (Malarkey and Parpura, 2011), and within hundreds of milliseconds following Ca2+ increase evoked by mechanical stimulation (Liu et al., 2011; Malarkey and Parpura, 2011).
Genetically encoded reporters of exocytosis set the stage for investigating the mechanisms of astrocyte exocytosis and for addressing several remaining questions. First, the reasons for the variable fusion kinetics of putative VGLUT-positive vesicles remain to be elucidated. Second, several studies failed to detect the presence of VGLUT expression in astrocytes (Cahoy et al., 2008; Juge et al., 2010; Li et al., 2013), therefore, new experiments are needed to clarify the molecular identity of the VGLUT-positive vesicles. Recently, a new genetically encoded red pH-sensitive probe, pHTomato, has been introduced to image single vesicle exocytosis (Li and Tsien, 2012). It should allow monitoring exocytosis, and, simultaneously, activating Ca2+ signal with optogenetic tools that typically require blue light illumination (Li et al., 2012). Finally, the new genetically encoded glutamate sensor, iGluSnFR, shows fast kinetics (Marvin et al., 2013) and is potentially suitable for fast real-time recording of glutamate release from astrocytes. Combining it with TIRFM detection of single vesicle exocytosis would help to clarify the relative contribution of vesicular vs. non-vesicular release pathways to glutamate release (Kimelberg et al., 2006; Li et al., 2012; Woo et al., 2012). Fourth, a combination of fast two-photon imaging, local photoactivation and genetically targeted expression of pHluorins in slice and in vivo must validate earlier findings from cell-culture studies.
Targeting Genetically Encoded Proteins to Astrocytes
Most optical techniques available today lack the spatial resolution for imaging thin astrocyte processes. Bulk-loaded Ca2+ indicators that label both astrocytes and neurons, report mixed signals. However, using GECIs targeted selectively to astrocytes, it becomes possible to record astrocyte-specific Ca2+ signals with standard imaging techniques, like confocal, spinning-disk confocal, and two-photon microscopies. Similarly by targeting the light-gated proteins, selective photoactivation of astrocytes can be achieved (see below). Therefore, targeting the GECIs and the light-gated channels/receptors to astrocytes in situ is a critical step, and several strategies have been used. First, plasmids can be electroporated in utero (Yoshida et al., 2010) but the yield of electroporation is variable, therefore, protocols using intracerebral and intravenous injections of viral constructs and Tg mouse lines are being favored.
Viral constructs are relatively easy to generate and adeno-associated virus (AAV) are the most widely used for astrocyte infection (Table 1). Intracerebral injections of lentivirus (LV) and adenovirus (AV) (Liu et al., 2008; Colin et al., 2009; Gourine et al., 2010) have been limited due to their possible toxic effects. Among the AAV variants, the serotype 5 with a high tropism for astrocytes (Ortinski et al., 2010), is commonly used for packaging the DNA constructs. Following intracerebral viral injections, the area of infection extends well beyond the injection site and the expression of the reporter genes is stable for months. In adult mice, intravenous injections of AAV serotype 9 labels mostly astrocytes rather than neurons (Foust et al., 2009). Intraventricular injection of AAV serotype 8 at postnatal day 3 (P3) labels preferentially astrocytes (Kim et al., 2013). New serotypes have been developed using a directed evolution approach with higher transduction level for astrocytes leading to 94% specific expression in retinal Müller glial cells after intravitreal injection (Klimczak et al., 2009). This seems to be promising to reduce the virus titer needed for expression. More specific targeting can be achieved by inserting an astrocyte-specific promoter. The 2.2 kb hGFAP promoter targets selectively ChR2 to astrocytes using LV constructs (Gradinaru et al., 2009). However, since AAVs cannot carry constructs larger than 4.7 kb, a shorter 681 bp hGFAP promoter (gfaABC1D also called gfa104) (Lee et al., 2008) has been used to target selectively EGFP, ChR2, GECIs (case12, GCaMP3, Lck-GCaMP3), and a pleckstrin homology (PH) domain of phospholipase C-like protein p130 (p130PH) to astrocytes (Ortinski et al., 2010; Xie et al., 2010; Shigetomi et al., 2013b).
Gene targeting of viral constructs can also be achieved by the Cre-Lox or tetO-tTA strategies injecting floxed (or flexed) viral constructs in Cre mouse lines, or tetO virus in the tTA mouse lines (Pfrieger and Slezak, 2012). Several astrocyte-specific Cre- and tTA-expressing mouse lines have been generated (Table 2). When a Cre-dependent ChR2-expressing virus was injected in hippocampus (Chen et al., 2013a) of a P14 hGFAP mouse line (Casper and McCarthy, 2006), selective expression of ChR2 was obtained in the astrocytes.
Yet an important limitation of the viral delivery strategies needs to be taken into account. Following intracerebral injection of AAV2/5-gfa104-EGFP construct, a significant dose-dependent reactive gliosis has been observed (Reimsnider et al., 2007; Klein et al., 2008; Ortinski et al., 2010). Since gliosis is associated with changes of several signaling pathways in astrocytes (Hamby et al., 2012), it will be important to develop alternative approaches to study the role of astrocytes in physiological conditions. Introducing a sequence encoding the VIVIT peptide that interferes with the calcineurin/nuclear factor of activated T-cells signaling pathway and down regulates GFAP overexpression (Furman et al., 2012), may reduce AAV-induced gliosis. Replacing viral constructs by Tg floxed/tetO mouse lines is a very promising approach to control gliosis. Several floxed (Slezak et al., 2012; Zariwala et al., 2012) and tetO (Fiacco et al., 2007; Agulhon et al., 2010) mouse lines of interest have been generated. With a hGFAP-CreERT2 mouse line in which the recombination can be induced in juvenile or adult mice by tamoxifen injections, astrocyte-specific targeting has been obtained in cortex, hippocampal CA1 region, cerebellum, diencephalon and brain stem, with weaker levels of recombination in cortex (Hirrlinger et al., 2006; Lioy et al., 2011). In glutamate-aspartate transporter (GLAST)- and connexin 30 (Cx30)-CreERT2 mouse lines, astrocyte-specific recombination occurs in cortex, hippocampal CA1 region, and cerebellum. But in GLAST-CreERT2 and hGFAP-CreERT2 mouse lines, the recombination is not astrocyte-specific in brain regions including the olfactory bulb and hippocampal dentate gyrus, where neurons are also labeled (Mori et al., 2006; Slezak et al., 2007). The floxed/tetO strategy is advantageous since it does not require surgery for viral injections. A Ai38 floxed GCaMP3 reporter mouse line was generated by a knockin strategy to insert GCaMP3 into the ROSA26 locus (Zariwala et al., 2012). When the Ai38 mouse was crossed with an inducible Wfs1-Tg2-CreERT2 mouse line, a uniform expression of the reporter genes was obtained in cortical excitatory neurons without over expression of GCaMP3 in the nucleus as observed after cortical injection of an AAV-syn-GCaMP3 construct (Figure 3). Importantly, it appears that various Cre- and tTA-dependent mouse lines differ in their ability to induce recombination, and also the specificity of recombination can vary with the brain region, and with the age. Therefore, in order to ascertain specificity of astrocytic signal measurement and photoactivation, it will be critical to carefully validate astrocyte-specific expression, for example, by using cell type-specific antibodies and confocal microscopy.
Figure 3. Stable expression levels in the Ai38 ROSA26-GCaMP3 mouse line over months. Native GCaMP3 fluorescence in layer2/3 excitatory neurons of visual cortex from Wfs1-Tg2-CreERT2:Ai38 mice (A,B) and adult wild-type mice injected with AAV-syn-GCaMP3 (C,D). (E) Quantification of neuronal brightness. Error bars correspond to SEM. From (Zariwala et al., 2012), with permission.
In conclusion, new genetically targeted optical and pharmacological tools allow the selective measurement and activation of astrocytic Ca2+ signals. These tools should be of value for studying the mechanisms of gliotransmitter release, the role of astrocytes, and more specifically the bidirectional communication between astrocytes and neurons.
Conflict of Interest Statement
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
We thank Karine Hérault for her permanent support, Jonathan Bradley and Deniz Dalkara for their advice on viral vectors, Ehud Isacoff for his expertise on light-gated channels, Christian Giaume and Etienne Audinat for discussions, Florent Jean and Patrice Jegouzo for technical assistance. Our work is supported by grants from the Agence Nationale de la Recherche (ANR) to Nicole Ropert; France-BioImaging (FBI) to Martin Oheim; a Ph.D. fellowship from the Fondation pour la Recherche Médicale (FRM) to Elke Schmidt; a Chair of Excellence from the Paris School of Neuroscience (Ecole des Neurosciences de Paris, ENP) and a Marie Curie Career Integration grant to Cendra Agulhon.
AAV, adeno-associated virus; ACR, astrocyte Cre reporter; ALDH1L1, aldehyde dehydrogenase 1 L1; AM, acetoxymethyl; AV, adenovirus; CatCh calcium-translocating channelrhodopsin 2; ChR, channelrhodopsin; CMV, cytomegalovirus; Cx30, connexin 30; DHPG, dihydroxyphenylglycine; DsRed, discosoma red protein; EGFP, enhanced green fluorescent protein; GCaMP, green fluorescent protein-based Ca2+ sensor; GECI, genetically encoded calcium indicator; GFAP, glial fibrillary acidic protein; GFP, green fluorescent protein; GLAST, glutamate-aspartate transporter; GLT-1, glutamate transporter 1; hGFAP, human glial fibrillary acidic protein; IP3, inositol triphosphate; LiGluR, light-gated glutamate receptor; LimGluR, light-gated metabotropic glutamate receptor; LV, lentivirus; mGluR, metabotropic glutamate receptor; Mlc1, megalencephalic leukoencephalopathy with subcortical cysts 1; MrgA1, Mas-related gene A1; OGB1, oregon green BAPTA1; STED, stimulated emission depletion; TIRF(M), total internal reflection fluorescence (microscopy); TA, tetracycline transactivator; TetO, tetracycline operator; Tg, transgenic; YFP, yellow fluorescent protein
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Keywords: photoactivation, pharmacogenetics, optogenetics, gliotransmission, GCaMP, LiGluR, CatCh, ChR2
Citation: Li D, Agulhon C, Schmidt E, Oheim M and Ropert N (2013) New tools for investigating astrocyte-to-neuron communication. Front. Cell. Neurosci. 7:193. doi: 10.3389/fncel.2013.00193
Received: 03 July 2013; Accepted: 07 October 2013;
Published online: 29 October 2013.
Edited by:Carole Escartin, MIRCen, France
Reviewed by:Baljit S. Khakh, Brain Research Institute, USA
Richard Robitaille, Université de Montréal, Canada
Frank Kirchhoff, University of Saarland, Germany
Copyright © 2013 Li, Agulhon, Schmidt, Oheim and Ropert. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
*Correspondence: Nicole Ropert, Laboratory of Neurophysiology and New Microscopies, Université Paris Descartes, INSERM U603, CNRS UMR8154, 45 rue des Saints Pères, 75006, Paris, France e-mail: firstname.lastname@example.com


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Electric vehicles are coming closer to being a more affordable option as more companies work on them. Now we have Lucid Motors bringing the Air to market in 2018 with a 400 mile range. Even though the car is in the luxury class, it's another step in perfecting the tech. As it gets easier to make these cars, the price will come down across the board.
Size and Design
With cars like Tesla's Model S already up for sale, we have a handy comparison for Lucid's Air. It features an exterior marked with sleek lines as well as a futuristic feeling shape. The outside profile is that of a smaller sedan but the interior volume is still large for its class.
The smaller form factor and roomy interior is possible thanks to the clever move of floor mounting batteries. This eliminates the need for a longer nose or tail section and spreads the weight more evenly. This also allow for all four seats to have ample room to move around and be comfortable.

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GMV is a supplier not only lift (elevator) systems, but also escalators and autowalks (moving walks). It is an important step towards the investors and architects who expect the complex solutions from such respectable lift manufacturer as GMV. Our solutions find its way in commercial buildings: trade galleries, exhibition centers or office buildings and in public transport objects such as: subway, railway stations and airports.
The GMV escalators are adapted to operation in closed objects and outdoors, in places without roofing, and exist in two basic versions:LMG – designed for usual use (commercial buildings),
LMU / LMU-YG - designed for intensive operation (public transport buildings).
The GMV moving walks are divided into angular (inclination: 10° or 12°) and horizontal (inclination: 0°).
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Saturday, June 12, 2010
Children's Joy Foundation
11:56 AM - kayray - 0 Comments
Last June 9, 2010, Chummy Chum visited 100 kids at the CHILDREN'S JOY FOUNDATION. All kids were ready to have fun when Chummy Chum arrived. The program was started by doing lots of parlor games. After that, the kids displayed their talents in dancing, singing, and playing instruments such as the rondallia.
Chummy Chum admires the kids for being so talented. He also gave out popcorn and cotton candy. Also, solar calculator pencil cases, coloring books and crayons were given out.
The children of the foundation also remember Chummy Chum's first visit to them in 2007. :)
Children's Joy Foundation is located at # 6 Brown Swiss St. Short Torn Congressional Road, Proj. 8, QC.
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That' s it for the installation, now we should be able to use the driver. DLL Note: The Microsoft CompCheck tool for ODBC - see microsoft. Other languages that can use ODBC include COBOL Perl, PHP Python. Temporary views in Spark SQL are session- scoped and will disappear if the session that creates it terminates.
0 for Linux along with its functionality is now. The Microsoft ODBC Driver for SQL Server provides native connectivity from Windows to Microsoft SQL Server and Windows Azure SQL Database. Download ODBC Driver for SQL Server. I don' t SQLGetFunctions in that list.
Oct 22, · Thanks for listing the SQL Server - SQL Native Client 10. 03/ 13/ ; 2 minutes to read; Contributors. The Qt SQL module uses driver plugins to communicate with the different database APIs. May 04, · Optimize access to Microsoft SQL Server when using the Microsoft SQL Server ODBC driver.
Using the Microsoft SQL Server ODBC driver for Linux. You can always enable ODBC tracing in the driver manager it will show what ODBC calls are made what the result was. Sql odbc driver version 10. The 64 bit version of the Microsoft SQL Server ODBC Driver for Linux provides. New key features for the Windows version. Mar 05, · The Microsoft SQL Server ODBC Driver for Linux provides native.
If you want to have a temporary view that is shared among all sessions keep alive until the Spark application terminates you can create a global temporary view. Connection string options and links to more detailed resources. Loading DocCommentXchange. Mar 02 · The Microsoft ODBC Driver for SQL Server provides native connectivity from Windows to Microsoft SQL Server Windows Azure SQL Database. Global Temporary View.
In this article Microsoft ODBC Driver 17 for SQL Server Windows. So I am searching for download trying to install IBM DB2 driver as Microsoft ODBC driver for.Info examples downloads for ' SQL Server Native Client 10. Apr 03, · We are pleased to announce an update to the Microsoft ODBC Driver 17 for SQL Server! There is an ODBC driver for most data sources. Sql odbc driver version 10. Download the Microsoft ODBC Driver 17 for SQL Server on Windows. 1 brings a couple of added features and several fixed issues. Jan 22, · Microsoft SQL Server ODBC Driver 1. The operation of Microsoft SQL Server version 6.
After the installation, we can start using the driver for whatever purpose we installed it. The Oracle ODBC Driver enables ODBC applications on Microsoft Windows Solaris, IBM Advanced Interactive eXecutive ( AIX) read , as well as UNIX platforms like Linux write access to Oracle® databases through the ODBC interface using Oracle Net Services software.
Since Qt' s SQL Module API is database- independent, all database- specific code is contained within these drivers. Com/ kb/ 301202 checks for the lastest version of ODBC and other drivers.
Selected Version SQL Server. In computing, Open Database Connectivity ( ODBC) is a standard application programming interface ( API) for accessing database management systems ( DBMS).


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How To Install And Use Solar EnergySolar energy is one of the great technological advances of our time. It saves average people a lot of money and helps large corporations operate in an environmentally friendly manner. If you are considering making the switch to solar, read on. This article will show you the benefits and how you can make them work for you.
If your roof cannot to support the weight of photo-voltaic solar panels, you can save a lot of money by investing in thin film solar panels. These panels are very light and flexible, which makes the installation much easier and affordable. Their higher price is also justified by their efficiency.
The efficiency of a solar energy system varies a lot depending on its exposure to the sun. If you live in a sunny area, your system should produce enough energy to cover all your needs but solar energy might not be such a good investment if you live in an area where the sky is usually filled with clouds.
Money can be saved on your energy bills if you install solar panels where you live or if you use solar water heating. Photo-voltraic panels work best in areas that get 5 hours of direct sunlight daily. If you have a heated swimming pool, consider installing solar water heaters to cut down on heating costs.
Before you pull the trigger and buy a system, take a look at how long the manufacturer guarantees the product for. You want a fairly long warranty because the system will have to pay for itself over time and help you begin to generate a profit. Therefore, make sure the warranty is for at least 25 years.
To help keep your solar energy panels running efficiently, keep a record of your solar panels performance. On this record, note when the days are overcast and how much energy your panels produced. This will help you plan your energy consumption better. For example, if the forecast is cloudy, then you should wait to do household chores that use a lot of energy.
Keep your solar panels clean. If your solar panels are dirty or obstructed in any way, they won't work as well. Keep an eye on your solar panels and clean them if they're not quite looking their best. Hosing them down occasionally will ensure that they are much more efficient.
Shopping For Solar Panels - 3 Helpful Tips
Outdoor lighting is among the simplest methods of implementing solar energy in your home. These tiny lamps take in the sun's energy during the light hours and then shine it along your path when dark. Not only are they easy to install, they will also add some charm to your landscape.
If you have animals that require electric fencing to contain them, use solar powered fencing units to provide power for them. A great advantage to these systems is that they are completely mobile, and can be easily moved. If you are a horse owner who enjoys overnight horse-camping, the fencer can be easily taken along.
Don't assume that just because a company sells and installs solar panels means they are good and trustworthy people. Shop around. Get a minimum of three quotes. Read all contracts. Check backgrounds of potential contractors. Deal with this like any other home-improvement project that you would otherwise do.
Always look for a good and qualified contractor to install your solar system. Just because you are having a new technology installed on your home, does not mean that you should look for new contractors. The type of work is very specialized and having a quality contractor with a proven track record is critical to having your system installed properly
You need to think seriously about the benefits of a good solar water heater. Even the best models will only reduce your power consumption by 1/3. It is also important to remember that just because you are showering while it is still dark out that you will not have hot water. Water heated by solar power should stay warm for 24 hours.
Try not to step on the solar panels. You have to protect them at all costs. If you must step on them, make sure that you avoid walking at the ends of the panels since this is the part that is more likely to break.
Solar energy is something in which lots of people are developing a keen interest. The fact remains, however, that many individuals need to acquire a bit more education before they jump in. With any luck, the tips and advice above have provided you with just the sort of start you needed to begin.


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2008 NEWS 2008-07-13 - NEW MODULE: Uize.Xml
A new
Uize.Xml utility module has been added, with static methods for serializing objects to attributes strings, decoding attributes strings into attributes objects, and encoding and decoding attribute values.
In time, more features related to dealing with data in XML format will be added to this package. Documentation is complete.


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KD Cycle has the experience.
KD Cycle has an experienced staff of mechanics who can get you up and running whether it is just for the duner broken down to the local enthusiasts who needs a complete over haul, to complete performance engines. We work on all models of ATV, Side by Side, Dirt Bike, Street Bike & Golf Cars'. We offer preventative maintenance inspection and service on all units, as well as diagnosis of your issue and offer quality service and repair. Cylinder boring and porting services are available as well. Our staff is here to help you.


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ISRN Pediatrics
Volume 2012, Article ID 307039, 7 pages
Risk Factors at Birth for Permanent Obstetric Brachial Plexus Injury and Associated Osseous Deformities
Research Division, Texas Nerve and Paralysis Institute, Houston, TX 77030, USA
Received 12 September 2011; Accepted 31 October 2011
Academic Editor: G. J. Casimir
Copyright © 2012 Rahul K. Nath et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Purpose. To examine the most prevalent risk factors found in patients with permanent obstetric brachial plexus injury (OBPI) to identify better predictors of injury. Methods. A population-based study was performed on 241 OBPI patients who underwent surgical treatment at the Texas Nerve and Paralysis Institute. Results. Shoulder dystocia (97%) was the most prevalent risk factor. We found that 80% of the patients in this study were not macrosomic, and 43% weighed less than 4000 g at birth. The rate of instrument use was 41% , which is 4-fold higher than the 10% predicted for all vaginal deliveries in the United States. Posterior subluxation and glenoid version measurements in children with no finger movement at birth indicated a less severe shoulder deformity in comparison with those with finger movement. Conclusions. The average birth weight in this study was indistinguishable from the average birth weight reported for all brachial plexus injuries. Higher birth weight does not, therefore, affect the prognosis of brachial plexus injury. We found forceps/vacuum delivery to be an independent risk factor for OBPI, regardless of birth weight. Permanently injured patients with finger movement at birth develop more severe bony deformities of the shoulder than patients without finger movement.