摘要:

AbstractGamma aminobutyric acid (GABA) is present in the central nervous system (CNS) during very early embryogenesis. It is therefore likely to play a role not only as a neurotransmitter but also as a signal molecule for neuronal differentiation, growth, and development. It has been firmly established that formation of synapses is strengthened by GABA, and the expression of certain subunits of the GABA type A (GABAA) receptor complex is clearly promoted by GABA. This latter effect of GABA may have profound implications for the functional activity of GABAergic synapses since the pharmacological properties of GABAA receptors are governed by the subunit composition of the receptor complex. Dynamic changes in GABAAreceptor expression and diversity during development and differentiation may therefore play important roles for the inhibitory potential of the CNS during mature stages. © 1995 Wiley‐Liss, I

ISSN:0360-4012    

DOI:10.1002/jnr.490410102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractInjection ofCorynebacterium parvuminto the rat dorsal root ganglion has previously been shown to cause an inflammatory reaction dominated by macrophages and to enhance regeneration of the central axons of primary sensory neurons. Here, neuronal mRNAs that are modified by nerve transection were analyzed by in situ hybridization following injection of C. parvum into the dorsal root ganglion. Neuronal concentrations of mRNAs for the growth‐associated protein (GAP‐43) and the immediate early gene c‐jun were increased by a local inflammatory response just as after axotomy. The concentration of mRNA for calcitonin gene‐related peptide (CGRP) was also increased in a constant subpopulation of sensory neurons after injection of C. parvum in contrast to its decrease following axotomy. The results are consistent with the hypothesis that some of the responses to sensory neurons to axotomy are sustained by macrophages which accumulate within the dorsal root ganglion after nerve injury. © 1995 Wiley

ISSN:0360-4012    

DOI:10.1002/jnr.490410103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractF1‐20/AP‐3 is a synapse‐specific phosphoprotein. In this study we characterize the ability of bacterially expressed F1‐20/AP‐3 to bind and assemble clathrin cages. We find that both of two bacterially expressed alternatively spliced isoforms of F1‐20/AP‐3 can bind and assemble clathrin as efficiently as preparations of F1‐20/AP‐3 from bovine brain. This establishes that the clathrin assembly activity found in F1‐20/AP‐3 preparations from brain extracts is indeed encoded by the cloned gene for F1‐20/AP‐3. It also demonstrates that posttranslation modification is not required for activation of the clathrin binding or assembly function of F1‐20/AP‐3. Ultrastructural analyses of the clathrin cages assembled by bacterially expressed F1‐20/AP‐3 reveals a strikingly narrow size distribution. This may be important for the regulation of quantal size during neurotransmission. We also express the 33 kD NH2‐terminus of F1‐20/AP‐3 in E. coli, and measure its ability to bind to clathrin triskelia, to bind to clathrin cages, and to assemble clathrin triskelia into clathrin cages. It has been suggested that the 33 kD NH2‐terminus of F1‐20/AP‐3 constitutes a clathrin binding domain. We find that the bacterially expressed 33 kD NH2‐terminus of Fl20/AP‐3 binds to clathrin triskelia, fails to bind to preassembled clathrin cages, and is not sufficient for clathrin assembly. The finding that the 33 kD NH2‐terminus of F1‐20/AP‐3 binds to clathrin triskelia but fails to assemble clathrin triskelia into clathrin cages is consistent with the published proteolysis studies. The finding that the 33 kD NH2‐terminus of F1‐20/AP‐3 fails to bind to clathrin cages is novel and potentially important. It is clear from these experiments that the 33 kD NH2‐terminus of F1‐20/AP‐3 is sufficient to carry out some aspects of clathrin binding; however it appears that defining the regions of the protein involved in clathrin binding and assembly may

ISSN:0360-4012    

DOI:10.1002/jnr.490410104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe relative expression of large (L) and small (S) iso‐forms of the myelin‐associated glycoprotein (MAG) and their glycosylation were compared in developing spinal cord of quaking and control mice. Using anti‐sera specific for L‐ and S‐MAG, respectively, it was shown that S‐MAG is the principal isoform in quaking mice at all ages between 13 and 72 days, although L‐MAG was just detectable by western blotting at the early ages. Both L‐ and S‐MAG have higher apparent molecular weights in quaking mice than in controls. Experiments involving lectin binding and glycosidase treatment demonstrated that the higher molecular weight of MAG in the quaking mutant was due to a higher content of N‐acetyineuraminic acid residues linked α2‐3 to galactose as well as to more branching of oligosaccharide moieties indicated by a higher content of subterminal galactose residues. The total sialic acid measured by HPAE‐chromatography in purified quaking MAG was 40% higher than in control MAG. By contrast, quaking MAG contained less of the adhesion‐related, HNK‐1 carbohydrate epitope. Another difference was that a lower molecular weight form of MAG with predominantly high mannose oli‐gosaccharides was prominent in young quaking mice, but not in controls. The abnormalities of MAG expression related to splicing of its mRNA and glycosylation may contribute to the myelin pathology in quaking m

ISSN:0360-4012    

DOI:10.1002/jnr.490410105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractChicken ovalbumin upstream promoter‐transcription factors (COUP‐TF) are expressed in the developing nervous system and interact with nuclear hormone receptors to regulate expression of different genes. The role of COUP‐TF orphan receptors in neurogenesis is virtually unknown. To study the possible function of COUP‐TF I during neuronal differentiation, we generated COUP‐TF I overexpressing teratocarcinoma PCC7 cell lines and analyzed retinoic acid (RA)‐induced neuronal differentiation of these cells. COUP‐TF I overexpression results in the blockade of morphological differentiation after induction to differentiate. COUP‐TF I represses expression of micro‐tubule‐associated protein 2 (MAP2) gene and delays induction of growth‐associated protein 43 (GAP43) gene expression. In contrast, expression of the neurofilament light subunit (NF‐L) gene is not affected by COUP‐TF I overexpression during neuronal differentiation. Also, cells overexpressing COUP‐TF I do not stop proliferating after RA and dBcAMP treatment and possess suppressed transcriptional activation from different RA response elements. These results suggest that COUP‐TF I plays an important role in regulating RA‐induced neuronal differe

ISSN:0360-4012    

DOI:10.1002/jnr.490410106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractIn the present study we have characterized the major proteoglycans of chick brain, focusing on their pattern of expression in development and on identifying the heparan sulfate proteoglycan (HSPG) that binds to the neural cell adhesion molecule (NCAM). The major chondroitin sulfate proteoglycans (CSPG) are a heterogeneous group of molecules with an average MW of 450 kDa. Protein core analysis reveals multiple protein cores between 100 and 350 k Da, The HSPGs are somewhat smaller, with an average MW of 350 kDa, and the major brain HSPG possesses a 250 kDa protein core. During development the relative percentage of HSPG decreases from approximately 50% of total sulfate‐labeled PG at E6 to 25% by E10. In order to begin to characterize the HSPG that interacts with NCAM, we initially used an antiserum produced against a HSPG which was previously shown to copurify with NCAM (Cole and Burg: Exp Cell Res 182:44‐60, 1989). This antiserum immunoprecipitated a HSPG core protein of 250 kDa, corresponding to the major HSPG of chick brain. We also show that the major brain HSPG binds to a synthetic peptide that encodes the heparan sulfate‐binding domain of NC AM, and that monoclonal antibodies to a recently identified chick retinal HSPG recognize this NCAM‐binding HSPG. This HSPG was immunopurified from E10 chick brain using the 6D2 monoclonal antibody, and has been shown to bind an affinity column containing the heparan sulfate‐binding peptide of NCAM. Consistent with its ability to bind NCAM, we show that the intact 6D2 HSPG inhibits cell adhesion to a HBD peptide substratum, and also binds chick brain cells when employed as a substratum. © 1995 Wiley

ISSN:0360-4012    

DOI:10.1002/jnr.490410107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe activation of GABABreceptors of adrenal chomaffin cells produces an increase of [Ca2+]imeasured by fura‐2 AM techniques. GABABagonists 3‐aminopropylphosphinic acid or (‐)baclofen, at concentrations of 0.5 mM, increased basal Ca2+, values 332 ± 60.9 and 306 ± 40.5 nM, respectively, in cells suspended in a 2.5 mM Ca2+buffer.The GABAB‐induced increase of [Ca2+]iseemed to have two different components. The first was due to an entry from the extracellular medium mainly through L‐type voltage‐dependent Ca2+channels as the dihydropiridine nifedipine 50 μM was able to decrease it more than 60%, while ω‐conotoxin, which blocks N‐type channels, did not produce any change in the GABAB‐evoked Ca2+increment. The second component was due to a release of Ca2+from intracellular pools and was about one‐third of the total GABAB‐induced increase of [Ca2+]i. GABABreceptors stimulated inositol 1,4,5‐trisphosphate‐sensitive and not the caffeine‐sensitive Ca2+store. In a low Ca2+buffer after treatment with 2 μM angiotensin II, neither 0.5 mM 3‐APPA nor baclofen were able to produce an additional increase of [Ca2+]i, whereas 4 mM caffeine had no effect on GABABresponse. This intracellular Ca2+mobilization could be due to inositol 1,4,5‐trisphosphate accumulation produced by the activation of GABABreceptors. In fact, the specific agonists after 10 minutes incubation produced a dosedependent increase of inositol 1,4,5‐trisphosphate. The maximal effect was obtained at 100 μM baclofen and 3‐APPA, and it was 3.63 ± 0.75 and 3.2 ± 1.5 times the basal levels (7.3 ± 0.3 pmol/106cells), respectively.In the absence of extracellular Ca2+, GABAB‐evoked catecholamine secretion and cyclic AMP formation were reduced more than 70%, suggesting an important role of extracellular Ca2+in GABABmechanisms in ad

ISSN:0360-4012    

DOI:10.1002/jnr.490410108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractNerve growth factor (NGF) has been well‐characterized with respect to its role as a trophic agent for various peripheral nervous system (PNS) and central nervous system (CNS) neuronal populations. Recent evidence indicates that NGF may also play a functional role in endocrine systems, although investigations in this field are only beginning to define sites of action and molecular mechanisms involved in NGF endocrine interactions. A potential site for such an interaction to occur is within the pituitary. Previous investigations have demonstrated the presence of NGF and NGF receptors in the pituitary and our group has recently reported the presence of NGF‐like immunoreactivity exclusively within the thyrotrophic cells of the anterior pituitary of the adult rat. Since many questions regarding how NGF interacts in the anterior pituitary will be more efficiently addressed using an in vitro system, it was necessary to first determine if cultured adult anterior pituitary cells retain the NGF‐like staining and unique association of NGF with thyroid‐stimulating hormone‐producing cells seen in vivo. Results of the present investigation confirm that cultured anterior pituitary cells retain the characteristics previously observed in vivo and further demonstrate the stability of these cells and their specific NGF and pituitary hormone contents in culture for as long as 6 days. © 1995 Wile

ISSN:0360-4012    

DOI:10.1002/jnr.490410109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractIn the present study, following previous experience with electrolytic lesion of the rat brain, and subsequent reduction of reactive gliosis with 7b̃‐hydroxycholesterol derivatives (Bochelen et al.: Neuroscience 51:827‐834, 1992), we have performed a hemisection of the spinal cord in adult rats and investigated the influence of 7b̃‐hydroxycholesteryl‐3‐oleate (oxysterol) on the intensity of the astrocytic reaction and the axonal regeneration. We have shown here that local administration of liposomes containing this oxysterol reduced the intensity of the astroglial reaction on the sectioned side, as seen with immunocytochemical detection of glial fibrillary acidic protein (GFAP) and by in situ hybridization with a specific RNA probe. Moreover, radioautographic evaluation of astrocyte proliferation with tritiated thymidine evidenced a reduction of the astrocyte labelling index. In addition, double immunocytochemical detection of GFAP and polysialylated neural cell adhesion molecule (E‐NCAM) revealed a decrease of the expression of this molecule in reactive astrocytes of the treated animals. Finally, immunocytochemical detection of serotonin (5HT) was determined in the raphespinal projections, which constitute a major descending system. In treated animals, serotonergic axons originating from the intact side reinnervated the dorsal horn of the sectioned side, below the hemisection.These results demonstrate that 7b̃‐hydroxycholesteryl‐3‐oleate can reduce the astrocytic reaction following spinal cord injury, promoting the serotonergic reinnervation of a denervated territory. ©

ISSN:0360-4012    

DOI:10.1002/jnr.490410110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe proteolipid proteins play a major role in the structure of the CNS myelin sheath, but they have also been implicated in the oligodendrocyte development leading to myelination. Mutations in the PLP gene result in severe dysmyelination and a paucity of mature oligodendrocytes. The myelin deficient (md) rat, carrying a Thr75? Pro substitution present in both isoforms of proteolipid protein (PLP and DM20), is the most severely affected of the PLP mutants described to date. The expression of myelin associated genes was quantitated to determine the effect of the mutation on oligodendrocyte development in vivo. At 5 days postnatal, gene expression in the and rat approximated that in age‐matched control rats, but as they matured, there was a progressive inhibition of gene expression in the and rats. The genes expressed late in the myelination program (PLP and MBP) were affected more dramatically than those expressed earlier in oligodendrocyte development (CNP and GPDH). The results indicate that the later stages of oligodendrocyte maturation and myelin elaboration are inhibited. © 1995 Wiley‐Liss,

ISSN:0360-4012    

DOI:10.1002/jnr.490410111

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY