bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synaptosomal plasma membrane transport of excitatory sulphur amino acid transmitter candidates: Kinetic characterisation and analysis of carrier specificity
Authors: Grieve A. , Butcher S. P. , Griffiths Roger 
Published: May 2005

AbstractThe transport kinetics of the excitatory sulphur‐containing amino acid (SAA) transmitter candidates, L‐cysteine sulphinate (L‐CSA), L‐cysteate (L‐CA), L‐homocysteine sulphinate (L‐HCSA), and L‐homocysteate (L‐HCA), together with their plasma membrane carrier specificity, was studied in cerebrocortical synaptosome fractions by a sensitive high performance liquid chromatographic assay. A high affinity uptake system could be demonstrated for L‐CSA (Km =; 57 ± 6 μM; Vmax =; 1.2 ± 0.1 nmol/min/mg protein) and L‐CA (Km =; 23 ± 3 μM; Vmax =; 3.6 ± 0.1 nmol/min/mg protein), whereas L‐HCSA (Km =; 502 ± 152 μM; Vmax =; 6.1 ± 1.3 nmol/min/mg protein) and L‐HCA (Km =; 1550 ± 169 μM; Vmax =; 10.3 ± 1.1 nmol/min/mg protein) exhibited much lower affinity as transport substrates. In all cases, only a single, saturable Na+‐dependent component of uptake could be identified, co‐existing with a non‐saturable, Na+‐independent influx component. Plasma membrane carrier specificity of the SAAs was established following comparison with other high‐affinity neurotransmitter systems. High‐affinity L‐CSA and L‐CA transport and low‐affinity L‐HCSA and L‐HCA transport demonstrate strong positive correlations in inhibition profiles when compared against each other or individually against the high‐affinity transport of L‐[3H]glutamate, L‐[3H]aspartate, or D‐[3H]aspartate. Moreover, the transport systems for the excitatory SAAs exhibited a negative correlation when compared in inhibition profiles with the high affinity transport of both [3H] γ‐aminobutyric acid (GABA) and [3H]taurine. Taken together, these results strongly suggest that L‐CSA, L‐CA, L‐HCSA, and L‐HCA share a common synaptosomal plasma membrane transport system with L‐glutamate, L‐aspartate, and D‐aspartate. © 1992 Wiley‐Liss, Inc.
Neuronal protein tyrosine kinases associated with synaptosomal glycoproteins
Authors: Hanissian S. H. , Sahyoun N. 
Published: May 2005

AbstractProtein tyrosine kinase (PTK) activity associated with synaptosomal membrane glycoprotein (SMGP) fractions of rat brain was examined. The synthetic substrate poly(Glu4‐Tyr) was phosphorylated by SMGP in the presence of Mg2+ and Mn2+, whose stimulatory effects were additive. In contrast, endogenous tyrosine phosphorylation in SMGPs was strictly dependent on Mn2+. Anti‐phosphotyrosine antibodies (PY20) immunoprecipitated two polypeptides in SMGPs of Mr 170K and 60K. Upon preincubation with IGF‐I, 97/90K polypeptides were phosphorylated, corresponding to the IGF‐I receptor beta‐subunits, and were immunoprecipitated with both PY20 and anti‐IGF‐I‐receptor antibodies. Immunoblot analysis using anti‐src antibody revealed that there was src protein associated with the glycoprotein fractions of solubilized synaptosomal membranes. Additional experiments revealed that the 60K tyrosine‐phosphorylated polypeptide present in the PY20 precipitates was indeed pp60 c‐src. This was confirmed by subjecting the PY20 immunoprecipitates to immunoblotting using anti‐src antibodies. In addition, src protein was directly immunoprecipitated by anti‐src antibodies from the SMGP preparations. Hence, IGF‐I receptors and glycoprotein‐associated PTKs in cluding pp60c‐src may play an important role in synaptic transmembrane signalling, plasticity, and neuronal survival. © 1992 Wiley‐Liss, Inc.
Phorbol esters modulate phospholipid metabolism in a human cholinergic cell line, LA‐N‐2: A possible role for the base exchange enzymes
Authors: Singh I. N. , McCartney D. G. , Sorrentino G. , Massarelli R. , Kanfer Julian N. 
Published: May 2005

AbstractIt was shown that in LA‐N‐2 cells prelabeled with [3H‐methyl]choline for 24 hr (Singh et al.: Mol Chem Neuropathol 14:53–66, 1991) the major intracellular and extracellular hydrophilic compound was phosphorylcholine. LA‐N‐2 cells were labeled with [14C‐methyl]choline for 24 hr, harvested, and incubated in Hepes/BSA/saline buffer for varying periods of time. The radioactive compound present in the cytosol and released into Hepes/BSA/saline buffer medium in the presence or absence of TPA was phosphorylcholine. There was a gradual increase in the appearance of radioactivity in the medium and this corresponded to a gradual decline in the radioactivity present in the cytosolic compartment with a statistically significant P value of <.005. Identical results were obtained with prelabeled cells subsequently incubated with TPA. There was no significant change in the amount of radioactivity associated with lipid suggesting that the phosphorylcholine may be released directly from the cytosolic compartment into the medium rather than originating through a phospholipase‐C catalyzed hydrolysis of phosphatidylcholine. This possibility received support from experiments in which cells were electropermeabilized in the presence of radioactive phosphorylacholine. It was found that the introduced [14C]phosphorylcholine was released intact into the incubation medium from the cytosolic compartment.The incorporation of [14C]choline, [14C]ethanolamine, and [14C]serine by LA‐N‐2 cells into their corresponding phospholipids was investigated in the presence or absence of TPA. The presence of TPA increased the amount of radioactivity incorporated into the phospholipids with a corresponding decrease in the amount of radioactivity in the cytosolic compartment compared to control cultures. There were no detectable differences between TPA exposed and control cells in the distribution of radioactivity in free choline, phosphorylcholine, or CDP‐choline of [14C] choline labeled cells. This indicates that the increased lipid labeling was not accompanied by enhanced labeling of the intermediates of the de novo pathway. This effect of TPA in altering the distribution of labeling of the cytosolic and lipid components was not demonstrable with cells grown in the presence of 10−5M retinoic acid. © 1992 Wiley‐Liss, Inc.
Ionic channel currents in cultured neurons from human cortex
Authors: Simard J. M. , Song Y. , Tewari K. , Dunn S. , Werrbach‐Perez K. , Perez‐Polo J. R. , Eisenberg H. M. 
Published: May 2005

AbstractIonic channels in human cortical neurons have not been studied extensively. HCN‐1 and HCN‐1A cells, which recently were established as continuous cultures from human cortical tissue, have been shown by histochemical and immunochemical methods to exhibit a neuronal phenotype, but expression of functional ionic channels was not demonstrated. For the present study, HCN‐1 and HCN‐1A cells were cultured in Dulbecco's modified Eagle's medium with 15% fetal calf serum, in some cases supplemented with 10 ng/ml nerve growth factor, 10 μM forskolin, and 1 mM dibutyryl cyclic adenosine monophosphate to promote differentiation. Cells or membrane patches were voltage clamped using conventional patch clamp techniques. In HCN‐1A cells, we identified a tetrodotoxin‐sensitive Na+ current, two types of Ca2+ channel current, including L‐type current and a second type that in some respects resembled N‐type current, and four types of K+ current, including a delayed outward rectifier that showed voltage‐dependent inactivation, two types of noninactivating Ca2+‐activated K+ channels with slope conductances of 146 and 23 pS (K+ iK+ o 145 mM/5 mM), and less frequently, a noninactivating, intermediate conductance channel that was not sensitive to internal Ca2+. When HCN‐1A cells were examined after 3 days of exposure to differentiating agents, pronounced morphological changes were evident but no differences in ionic currents were apparent. HCN‐1 cells also exhibited K+ and Ca2+ channel currents, but Na+ currents were not detected in these cells. Our data provide additional evidence indicating a functional neuronal phenotype for HCN‐1A cells, and represent the most comprehensive survey to date of the variety of ionic channels expressed by human cortical neurons. © 1993 Wiley‐Liss, Inc.
Identification of neuropeptide Y receptors in cultured astrocytes from neonatal rat brain
Authors: Gimpl G. , Kirchhoff F. , Lang R. E. , Kettenmann Helmut 
Published: May 2005

AbstractSpecific binding sites for neuropeptide Y could be demonstrated in primary cultures of astrocytes from neonatal rat brain. Neuropeptide Y binding was saturable, reversible, and temperature dependent as revealed by saturation studies and kinetic experiments. Scatchard analysis of equilibrium binding data indicated a single population of high‐affinity binding sites with respective KD and Bmax values of 0.43 nM and 6.9 fmol/2.7 × 105 cells. Physiological responses induced by neuropeptide Y could be detected in a distinct subpopulation of cultured astrocytes on the basis of two criteria: (1) electrophysiological responses and (2) single cell measurements of changes in [Ca2+]i. In that fraction of cells responding (20–70%, varying among cultures from different preparations), brief application of neuropeptide Y led to a membrane potential depolarization, lasting several minutes. When the membrane was clamped close to the resting membrane potential using the whole‐cell patch‐clamp technique, neuropeptide Y induced an inward current with a similar time course as the neuropeptide Y‐induced membrane depolarization. As detected by single cell microfluorimetric (fura‐2) measurements neuropeptide Y induced an increase of [Ca2+]i which was caused by the entry of extracellular Ca2+. Both the [Ca2+]i increase and the electrophysiological responses were unaffected by pretreatment of the astrocytes with pertussis toxin. © 1993 Wiley‐Liss, Inc.
Molecular biology of vertebrate learning: Is c‐fos a new beginning?
Authors: Kaczmarek L. 
Published: May 2005

AbstractAn elevated expression of c‐fos nuclear protooncogene (immediate early gene) has been shown repeatedly to correlate with long‐term neuronal responses. This paper reviews recent data suggesting that neuronal plasticity, including learning and memory formation, may involve c‐fos expression as well. On the basis of biological functions of the Fos protein, well known to be a component of a transcription factor, AP‐1, (activator protein 1) a hypothesis suggesting a role of transcription factors in the integration of information during learning processes is proposed. © 1993 Wiley‐Liss, Inc.
FGF‐2‐mediated protection of cultured mesencephalic dopaminergic neurons against MPTP and MPP+: Specificity and impact of culture conditions, non‐dopaminergic neurons, and astroglial cells
Authors: Otto Dörte , Unsicker K. 
Published: May 2005

AbstractThe protective role of basic fibroblast growth factor (FGF‐2) for 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP)‐ and methylpyridiniumion (MPP+)‐lesioned dopaminergic (DAergic) nigrostriatal neurons was studied, using dissociated cell cultures of embryonic day (E) 14 rat mesencephalon. Cells were grown in different culture media and received FGF‐2 (5 ng/ml) and/or the toxins (5 μM) at various schedules, but were consistently allowed to differentiate for 3 days prior to becoming exposed to the toxin. Survival of tyrosine hydroxylase (TH)‐immunoreactive cells at 7 days was only markedly impaired by MPTP, if horse serum (HS) or bovine serum albumine (BSA) were omitted from the culture medium. FGF‐2 increased the number of TH‐immunoreactive cells, and this increase not diminished by MPTP under any culture condition. Uptake of 3H‐DA was significantly reduced by MPTP in HS‐ and BSA‐containing, but not in protein‐less cultures. A protective effect by FGF‐2 was only seen in the presence of BSA. MPP+ caused a more pronounced reduction in 3H‐DA uptake than MPTP, and this effect was partially reversed by the addition of FGF‐2, unless cultures contained HS. Neurofilament protein (NF), an indirect measure for the total number of neurons present in the cultures, was not significantly reduced by MPTP or MPP+ corroborating the specificity of the toxin for DAergic neurons, which constitute only a minor fraction in these cultures. In line with the wide spectrum of target neurons of FGF‐2, this factor significantly increased NF contents under any culture condition. Quantification of the amounts of glial fibrillary acidic protein (GFAP) revealed stimulatory effects of FGF‐2 (2.5‐ to 4‐fold) and at least 10‐fold higher levels in the presence as compared to the absence of HS. These data show that FGF‐2 can protect DAergic neurons against MPTP‐ and MPP+‐mediated damage. However, the effects of the toxins as well as of FGF‐2 are partially dependent on culture conditions. Variations in the effectiveness of toxins and FGF‐2 are not overtly related to the total numbers of neurons or astroglial cells, but may reflect culture type‐dependent alterations of neuronal and glial metabolism. © 1993 Wiley‐Liss, Inc.
Reactive astrocytes involved in the formation of lesional scars differ in the mediobasal hypothalamus and in other forebrain regions
Authors: Alonso G. , Privat A. 
Published: May 2005

AbstractThe fine organization of lesional scars was studied in adult rats at the level of 2 types of surgical cuts aimed at deafferentating the dorsal hypothalamus from its neuropeptide‐Y innervation. These included (i) lesions located dorsolateral to the dorsal hypothalamus, which were shown to form a permanent obstacle to the regeneration of transected neuropeptide‐Y‐fibers, and (ii) lesions located in the ventromedial hypothalamus, where transected neuropeptide‐Y‐fibers were shown to penetrate and eventually cross the lesional area. Double labeling immunocytochemistry and conventional electron microscopy were used to identify various molecules produced by reactive astrocytes and to visualize their ultrastructural organization within the scars, respectively. In the different portions of the dorsolateral scars, the large majority of reactive astrocytes was characterized by a strong immunoreactivity to glial fibrillary acidic protein, vimentin, and embryonic (polysialilated) NCAM. Intense laminin‐immunoreactivity was also observed over large patches included in the scar. Electron microscope observations further indicated that the matrix of the scar was mainly composed of tightly packed astrocytic perikarya and processes connected by extended gap junctions. All around the extracellular and perivascular spaces, these astrocyte profiles were bordered by a thick basal lamina. Only scarce axonal profiles were detected in the core of the scar, most of which exhibited degenerative features. In the ventromedial hypothalamic scars, reactive astrocytes were found to exhibit intense immunoreactivity to both glial fibrillary acidic protein and vimentin. On the other hand, only slight immunostaining to embryonic NCAM and laminin were associated with this type of lesional scar. At the ultrastructural level, the main differences with the dorsolateral scars concerned (i) the gap junctions, which were less frequent and involved shorter portions of adjacent membranes; (ii) the basal lamina, which was essentially localized to the perivascular spaces; and (iii) the axonal profiles, which were frequently observed throughout the scar matrix. These data indicate that reactive astrocytes that formed the glial scar differ in the mediobasal hypothalamus and in other forebrain regions. This provides strong support for the hypothesis that the regeneration of neuropeptide‐Y axons through a mediobasal hypothalamic surgical cut depends mainly on the particular organization of the astroglial scar. © 1993 Wiley‐Liss, Inc.
Rat cerebral cortical neurons in primary culture release a mitogen specific for early (GD3+/04−) oligodendroglial progenitors
Authors: Hardy R. , Reynolds Richard 
Published: May 2005

AbstractThe development of cells of the oligodendroglial lineage, from immature progenitor to myelinating cells, occurs largely in a neuronal environment, yet little is known about specific interactions between these 2 cell types. We have tested the effects of medium conditioned by cultures of rat cerebral cortical neurons (CCM), cerebellar granule interneurons (GCM), and a dorsal root ganglion derived cell line (NDCM) on cells of the oligodendroglial lineage in culture. Different stages of the lineage were defined using the cell surface antigens GD3, 04, and GalC. CCM and NDCM were mitogenic for the early GD3+/04− oligodendroglial progenitor, whereas GCM was mitogenic for the later GD3+/04+ stage. Neutralising antibodies to PDGF and bFGF were able to eliminate the mitogenic activity of NDCM and GCM, respectively, but did not abolish the mitogenic effect of CCM. We have demonstrated that neurons in primary culture from distinct CNS regions exert diffent influences on cells of the oligodendroglial lineage, and specifically that cortical neurons release an unknown mitogen for GD3+/04− oligodendroglial progenitors. © 1993 Wiley‐Liss, Inc.
Alteration of carnosine expression in olfactory system of mouse after unilateral naris closure and partial bulbectomy
Authors: Sakai M. , Nagatsu I. 
Published: May 2005

AbstractTo investigate the function of the dipeptide carnosine in the olfactory system, alterations of carnosine in the primary olfactory nerve after unilateral naris closure or olfactory bulb semilesion were studied by means of immunocytochemistry. After unilateral naris closure, carnosine staining showed no alteration, but immunoreactivity of tyrosine hydroxylase (TH), the rate‐limiting enzyme for biosynthesis of dopamine in dopaminergic neurons, decreased dramatically in periglomerular neurons. This behavior of carnosine is consistent with that reported for the olfactory marker protein (OMP). On the other hand, following partial lesion of the olfactory bulb, ordinary to strong carnosine expression was seen in newly innervated glomeruli that exceeded that seen in the conventional targets. Ectopic, TH‐positive, periglomerular cell‐like neurons appeared around the newly formed glomeruli. These data suggest that carnosine may have some role in regulating TH expression in post‐synaptic neurons. © 1993 Wiley‐Liss, Inc.
Association of glucocorticoid receptor immunoreactivity with cell membrane and transport vesicles in hippocampal and hypothalamic neurons of the rat
Authors: Liposits Zs. , Bohn M. C. 
Published: May 2005

AbstractThe aim of the present study was to reveal at the ultrastructural level cytoplasmic loci that display glucocorticoid receptor (GR) immunoreactivity in pyramidal neurons of the CA1 sector of the hippocampus and in cells of the medial parvicellular subnucleus of the hypothalamic paraventricular nucleus (PVN). Adrenalectomized male rats were injected intraperitoneally with corticosterone (CS) (1 mg/100 g bw) and sacrificed within 4 hr. Vibratome sections of the perfusion‐fixed forebrains were processed for immunocytochemical detection of type 2 GR by means of the BuGr, anti‐rat liver GR monoclonal antibody and silver‐gold‐intensified diaminobenzidine chromogen. The corticosterone administration gradually shifted the GR immunoreactivity (IR) from the cytoplasm to the nucleus. Samples taken 20–40 min after the steroid treatment demonstrated pyramidal cells expressing GR IR in both the cytoplasmic and nuclear pools. Although the chromatin‐associated appearance of GR in the nucleus was identifiable at the light microscopic level, the nature of immunoreactive intracytoplasmic loci was not. Ultrastructural analysis of the cytoplasm indicated that fine silver‐gold grains marking GR‐immunoreactive sites associated with the plasma membrane and coated and regular vesicles. Noted occasionally beneath the plasma membrane of the cell bodies and dendrites, the vesicles also appeared at deeper locations in dendritic processes and around the cell nuclei.These results suggest that glucocorticoid receptors participate in signal transduction at the level of the cell membrane, as well as at the level of the genome in the cell nucleus. Published 1993 by Wiley‐Liss, Inc.
Effects of nerve growth factor on the survival of primary cultured adult and aged mouse sensory neurons
Authors: Jiang Z.‐G. , Smith R. A. 
Published: May 2005

AbstractThis study investigated the effects of exogenous nerve growth factor (NGF) on the survival and differentiation in primary culture of sensory neurons isolated from adult (6 months) and aged (2 years) mice. For neurons prepared from adult mice, a concentration effect was evident during a 2 week culture period: Neuronal counts in cultures supplemented with 25 and 50 ng/ml NGF did not differ significantly from those of control cultures without exogenous NGF or those with anti‐NGF included in the culture medium, whereas cultures supplemented with either 100 or 200 ng/ml NGF contained higher numbers of neurons throughout the culture period. Cultures prepared from aged mice contained less neurons than those from adult mice, although those supplemented with 100 ng/ml NGF retained higher neuronal numbers than cultures from aged mice which did not receive exogenous NGF. Neuronal diameters were measured to investigate whether specific subpopulations of neurons were more dependent on NGF; the results indicate that neurons of a medium‐larger diameter were more prevalent than cells with a smaller diameter following NGF administration. A shape index was calculated for each culture regimen; with longer culture periods a higher proportion of spindle‐shaped neurons was observed. © 1993 Wiley‐Liss, Inc.
Identification of membrane‐bound carbonic anhydrase in white matter coated vesicles: The fate of carbonic anhydrase and other white matter coated vesicle proteins in triethyl tin‐induced leukoencephalopathy
Authors: Sapirstein V. S. , Durrie R. , Nolan C. E. , Marks N. 
Published: May 2005

AbstractWe have extended our studies on the content of white matter derived coated vesicles (WMCVs) to show that they are enriched in membrane‐bound carbonic anhydrase. Within the myelin complex membrane‐bound carbonic anhydrase is concentrated in the periaxolemmal domain; however, this protein is enriched almost sevenfold in the bilayer of coated vesicles even relative to this myelin membrane region. These data suggest that some vesicles are derived from a site at which this enzyme is highly localized. The enrichment observed for membrane‐bound carbonic anhydrase is unique since other periaxolemmal proteins such as CNPase and plasmolipin are only present in equal amounts in periaxolemmal‐myelin fractions and WMCVs. Based on their known localization, the presence of CNPase coupled with the absence of MAG in WMCVs suggest that these vesicles are derived from the paranodal region. The identification in WMCVs of periaxolemmal‐myelin proteins associated with ion and fluid movement, such as carbonic anhydrase, Na+, K+ ATPase, and the putative K+ channel protein plasmolipin, prompted us to examine the status of these vesicles in triethyl tin (TET)‐induced myelin edema. Coated vesicles and other membrane fractions were isolated from whole brains of control and TET‐treated rats. Whole brains were used so we could compare the effects of TET on WMCV proteins with the effect on proteins enriched in gray matter coated vesicles. The results indicated that TET had no detectable effect on compact or periaxolemmal‐myelin, however, Western blot analysis showed that WMCV proteins, such as carbonic anhydrase, CNPase, and plasmolipin, were virtually absent or greatly diminished from the whole brain coated vesicle fraction. In contrast, gray matter coated vesicle proteins such as synaptophysin, SV2, and the general vesicle protein, cation‐independent mannose‐6‐phosphate receptor were unchanged. These results indicate that coated vesicles may be a useful probe for membrane changes associated with leukopathologies. © 1993 Wiley‐Liss, Inc.