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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 179 (1989), S. 221-226 
    ISSN: 1432-0568
    Keywords: GABA ; Immunocytochemistry ; Gastrointestinal tract ; Epithelium ; Enteroendocrine cells ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Frozen sections of the corpus ventriculi, antrum pyloricum, duodenum, jejunum, ileum and colon from animals perfusion fixed with glutaraldehyde were treated with an antiserum specific for glutaraldehyde-fixed GABA and processed by the peroxidase antiperoxidase method. Semithin plastic sections from the antrum pyloricum were treated similarly. Stained cells appeared in the epithelium of all segments examined except the corpus ventriculi. The highest density of cells was observed along the major curvature of the antrum pyloricum. Here they were located in the bottom half of the gastric glands. Many of the cells showed a process extending towards the glandular lumen. No significant staining in the epithelium appeared when the antiserum was preincubated with glutaraldehyde-GABA complexes, nor when the anti-GABA serum was exchanged with anti-glycine or preimmune serum. The present findings and previous physiological data suggest that GABA may play a role in gut endocrine regulation.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0568
    Keywords: Glutamine ; Glutamate ; Cerebellum ; Immunocytochemistry ; Glia ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The cellular and subcellular localization of glutamine, a major glutamate precursor, was studied by means of an antiserum raised against glutaraldehydefixed glutamine. Ultrathin sections from the cerebellar cortex of rat and baboon (Papio anubis) were incubated sequentially in the primary antiserum and in a secondary antibody coupled to colloidal gold particles. The labelling intensity was quantified by computer-aided calculation of gold particle densities. High levels of immunoreactivity occurred in glial cells (Bergmann fibres, astrocytes, and oligodendrocytes), intermediate levels in cell bodies and processes of granule cells, and low levels in terminals of presumed GABAergic or glutamatergic fibres (terminals of basket and Golgi cells, and of parallel, mossy, and climbing fibres). The labelling intensity of Purkinje cells showed some variation, but never exceeded that in glial cells. Within the nerve fibre terminals, the glutamine-like immunoreactivity showed some preference for mitochondria, but was otherwise evenly distributed. The predominant glial localization of glutamine was also obvious in light microscopic preparations processed according to the postembedding peroxidase-antiperoxidase procedure. Gold particle densities over different types of profile in glutamine immunolabelled sections were compared with particle densities over the corresponding types of profiles in neighbouring sections labelled with an antiserum to glutaraldehyde-fixed glutamate. The glutamate/glutamine ratio, expressed arbitrarily by the ratio between the respective gold particle densities, varied by a factor of about 6, with the highest ratio in the putative glutamatergic mossy and parallel fibre terminals, and the lowest ratio in glial elements. The remaining tissue components displayed intermediate ratios. The present study provides direct morphological evidence for the existence in the brain of distinct compartments with differing glutamate/glutamine ratios.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 170 (1984), S. 197-207 
    ISSN: 1432-0568
    Keywords: Thalamus ; Pretectum ; GABA ; Glutaraldehyde ; Immunocytochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Antisera produced by immunizing rabbits with GABA conjugated to bovine serum albumin reacted, after purification, strongly with GABA fixed with glutaraldehyde to rat brain macromolecules, but insignificantly with other fixed amino acids (Storm-Mathisen et al. 1983). Sections through the diencephalon of perfusion-fixed mouse and rat brains showed a highly selective labeling pattern after incubation with these antisera. All cells of the reticular nucleus appeared to be stained. Smaller proportions of stained perikarya occurred in the dorsal and ventral subdivisions of the lateral geniculate body, in the medial geniculate body, in the lateroposterior nucleus, and in all nuclei of the pretectum. Labeled cell bodies were only rarely encountered in the ventrobasal complex, and were not found in the anterior and medial groups of thalamic nuclei. Stained axons were particularly concentrated in the ventrobasal complex, and in the stria medullaris, stria terminalis and inferior thalamic peduncle. The arrangement and density of labeled boutonlike dots varied markedly among nuclei, the highest densities occurring in the paraventricular and parataenial nuclei, and in the ventral subdivision of the lateral geniculate body. The mean staining intensity of the thalamic neuropil was lower than that of nearby structures, such as the hypothalamus and zona incerta. The present results on direct immunocytochemical detection of GABA are consistent with, and extend, data from immunocytochemical studies of the GABA-synthetizing enzyme, glutamic acid decarboxylase.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 47 (1986), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Na+-dependent “binding” of acidic amino acids in brain plasma membranes was examined by procedures similar to those employed in earlier studies, using the metabolically inert D-[3H]aspartate as a probe. The “binding” showed characteristics similar to those described before in terms of affinity (KD, 400 nM). density of sites (Bmax, 300 pmol/mg protein), sensitivity to D,L-threo-3-hydroxyaspartate. and requirement for Na+. It turned out that the “binding” represents uptake into membrane-bounded saccules (which according to the inulin and H2O spaces constituted 3.4 μ/mg protein and comprised about 50% of the volume of the sedimented membranes), rather than binding to the transport carrier. This conclusion is based on the observations that the “binding” of D-aspartate (1) was released by osmotic shock; (2) was abolished by thorough washing of membranes in H2O prior to assay, Which removed endogenous contents of amino acids, and could be recovered by loading the washed membranes with glutamate; (3) was reduced by prior freezing and thawing; (4) was low on incubation at 0°C; (5) had a bell-shaped time course similar to that reported for uptake; and (6) had a slow rate of reversal compared to the apparent KD. True binding would have considerably lower apparent Bmax than the carrier-mediated uptake. This and its likely rapid rate of dissociation would make binding to the carrier difficult to detect by the methods used up to now.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 47 (1986), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Na+-dependent uptake of dicarboxylic amino acids in membrane saccules, due to exchange diffusion and independent of ion gradients, was highly sensitive to inhibition by K+. The IC50 was 1–2 mM under a variety of conditions (i.e., whole tissue or synaptic membranes, frozen/thawed or fresh, D-[3H]aspartate (10–1000 nM) or L-[3H]glutamate (100 nM), phosphate or Tris buffer, NaCl or Na acetate, presence or absence of Ca2+ and Mg2+). The degree of inhibition by K+ was also not affected on removal of ion gradients by ionophores, or by extensive washing with H2O and reloading of membrane saccules with glutamate and incubation medium in the presence or absence of K+ (3 mM, i.e., IC70). Rb+, NH4+, and, to a lesser degree Cs+, but not Li+, could substitute for K+. [K+] showed a competitive relationship to [Na+]2. Incubation with K+ before or after uptake suggested that the ion acts in part by allowing net efflux, thus reducing the internal pool of amino acid against which D-[3H]aspartate exchanges, and in part by inhibiting the interaction of Na+ and D-[3H]aspartate with the transporter. The current model of the Na+-dependent high-affinity acidic amino acid transport carrier allows the observations to be explained and reconciled with previous seemingly conflicting reports on stimulation of acidic amino acid uptake by low concentrations of K+. The findings correct the interpretation of recent reports on a K+-induced inhibition of Na+-dependent “binding” of glutamate and aspartate, and partly elucidate the mechanism of action.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: To characterize glutamate/aspartate uptake activity in various cellular and subcellular elements in the striatum, rat striatal slices were exposed to 10 and 50 μM exogenous D-aspartate. After fixation with glutaraldehyde/ formaldehyde the distribution of D-aspartate was analysed by postembedding immunocytochemistry and the ultrastructural distribution was compared with the distributions of endogenous glutamate and GABA. Light microscopically, D-aspartate-like immunoreactivity was localized in conspicuous dots along very weakly labelled dendritic profiles and neuron cell bodies. At the electron microscope level gold particles signalling D-aspartate occurred at highest density in nerve terminals making asymmetrical contacts with postsynaptic spines (i.e. resembling synapses of cortical afferents). Astrocytic processes also contained gold particles, but at a lower density than nerve endings. In contrast, dendritic spines were only weakly D-aspartate–positive. The difference in labelling at 10 and 50 μM D-aspartate was consistent with‘high-affinity’uptake. Neighbouring sections processed with other antibodies showed that the D-aspartate labelling occurred in nerve terminals strongly immunoreactive for glutamate, rather than in terminals very weakly glutamate-immunopositive or in nerve endings immunoreactive for GABA. Glutamate labelling of perfusion-fixed striatum confirmed that terminals forming asymmetrical synaptic contacts with spines were enriched with gold particles, suggesting that these terminals use glutamate as a transmitter. This study demonstrates that high-affinity uptake sites for excitatory amino acids in the striatum are most strongly expressed on presumed glutamatergic nerve terminals and on astrocytes.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The large so-called type I afferents of the cochlear nerve carry the majority of the auditory input from the cochlea to the cochlear nuclei in the brainstem. These fibres are excitatory and previous studies have suggested they may use glutamate as their neurotransmitter. In the present investigation therefore, antibodies to glutamate and to the glutamate precursor, glutamine, were applied to resin sections of perfusion-fixed brains and of in vitro brain slices subjected to depolarizing levels of potassium before fixation to study glutamate handling and synaptic release. Ultrathin sections were labelled by the immunogold technique, and the immunoreactivity was quantified by recording the density of gold particles over the various tissue profiles. Non-primary, presumably inhibitory, terminals and glial processes were used as reference structures. The cochlear primary terminals proved to be strongly immunoreactive for glutamate. The density of glutamate labelling was higher in primary terminals than in non-primary ones, and lowest in glial processes. The ratio between the mean glutamate and glutamine labelling densities was also higher in primary terminals than in non-primary ones, and lowest in glial processes in each case. In the primary terminals, the glutamate immunoreactivity was higher over vesicle-containing regions than over vesicle-free regions, whilst glutamine was evenly distributed throughout. The in vitro brain slices showed a potassium-induced, partly calcium-dependent depletion of glutamate from the primary terminals but not from the non-primary ones. These observations strongly support the conclusion that glutamate is a neurotransmitter of type I cochlear afferents.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Glutamine is involved in a variety of metabolic processes, including recycling of the neurotransmitters glutamate and γ-aminobutyric acid (GABA). The system N transporter SN1 mediates efflux as well as influx of glutamine in glial cells [Chaudhry et al. (1999), Cell, 99, 769–780]. We here report qualitative and quantitative data on SN1 protein expression in rat. The total tissue concentrations of SN1 in brain and in kidney are half and one-quarter, respectively, of that in liver, but the average concentration of SN1 could be higher in astrocytes than in hepatocytes. Light and electron microscopic immunocytochemistry shows that glutamatergic, GABAergic and, surprisingly, purely glycinergic boutons are ensheathed by astrocytic SN1 laden processes, indicating a role of glutamine in the production of all three rapid transmitters. A dedication of SN1 to neurotransmitter recycling is further supported by the lack of SN1 immunoreactivity in oligodendrocytes (cells rich in glutamine but without perisynaptic processes). All neuronal structures appear unlabelled implying that a different protein mediates glutamine uptake into nerve endings. In several regions, SN1 immunoreactivity is higher in association with GABAergic than glutamatergic synapses, in agreement with observations that exogenous glutamine increases output of transmitter glutamate but not GABA. Nerve terminals with low transmitter reuptake or high prevailing firing frequency are associated with high SN1 immunoreactivity in adjacent glia. Bergmann glia and certain other astroglia contain very low levels of SN1 immunoreactivity compared to most astroglia, including retinal Müller cells, indicating the possible existence of SN isoforms and alternative mechanisms for transmitter recycling.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 98 (1994), S. 342-354 
    ISSN: 1432-1106
    Keywords: Glutamate ; Glycine ; Bipolar Cells ; Retina ; Human ; Colocalization ; Terminals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Human retinae from surgical specimens rapidly fixed in a glutaraldehyde/formaldehyde mixture were subjected to postembedding, immunogold immunocytochemistry of glutamate and glycine, and subsequently analysed in an electron microscope. The two amino acids were visualised in the same tissue sections by the use of two different gold particle sizes. All bipolar cell perikarya and terminals showed significant glutamate labelling with mean gold particle densities 3–4 times higher than those of the retinal, non-neural pigment epithelial and Müller cells. Bipolar cell terminals displayed significantly higher glutamate labelling density than the bipolar cell bodies, as would be expected of glutamatergic neurons. A subpopulation of the glutamate-immunolabelled bipolar cell bodies (18%) and terminals (32%) also exhibited strong glycine labelling (7–8 times that of pigment epithelial and Müller cells). These glutamate-glycine positive terminals established contacts with amacrine cell processes and ganglion cell dendrites and were localised almost exclusively at between 44% and 88% depth of the inner plexiform layer, indicating that they belong to the “ON” cone bipolar system. This subpopulation of terminals was endowed with significantly higher glycine labelling density than the glycine positive bipolar cell bodies. These results show that human bipolar cell terminals colocalise glutamate and glycine and provide the first direct demonstration of an enrichment of these two amino acids in the same presynaptic element.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Fig. 1 Specificity of antisera tested by staining 'antigen'-bearing Sepharose gel beads by the peroxidase-antiperoxidase (PAP) method3. Supernatants (l,000g) of water homogenates of rat cerebral cortex, including the hippocampus, were dialysed against tap water followed by 0.1MNaHCO3 containing ...
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