摘要:

AbstractThe neural cell adhesion molecule (NCAM) is found on cells as several related polypeptides formed by alternative splicing of the single NCAM gene. The alternatively spliced 30‐bp VASE exon in the fourth immunoglobulin‐like domain is the structural variation nearest those portions of the polypeptide proposed to mediate cell‐cell adhesion. To test the ability of distinct forms of the NCAM molecules to mediate cell adhesion, L cells were transfected with expression vectors encoding rat 140 kD NCAM ± the VASE exon. L cell lines which expressed these polypeptides were isolated and tested for self‐aggregation in a low shear, rapid aggregation assay. Increased cellular aggregation of the transfectants was observed to be a function of the NCAM molecule expressed. These transfected cells showed segregation in a long term co‐aggregation assay: cells expressing NCAM — VASE formed aggregates which tended to exclude cells expressing NCAM + VASE and vice versa. These results provide direct evidence that this small difference in NCAM structure is sufficient to allow segregation of cells. © 1994 Wi

ISSN:0360-4012    

DOI:10.1002/jnr.490380502

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

年代:1994

数据来源: WILEY

摘要:

AbstractEnolase (EC 4.2.1.11) is a glycolytic enzyme active as a dimer. In adult brain extracts, three forms, αα, αγ and γγ, have been described, with the αγ hybrid accounting for 30% of total enolase activity (Fletcher et al., Dev Biol 65:462–475, 1978; Lucas et al., Dev Neurosci 10:91–98, 1988). Previous biochemical studies strongly suggest that this hybrid is not generated artefactually during the extraction procedures (Keller et al., J Neurochem 36:1389–1397, 1981; Shimizu et al., BBA 748:278–284, 1983). Immunocytological observations have demonstrated the cell specific localization of the α subunit in astrocytes and of the γ subunit in neurons at the adult stage, but failed to identify a cell type containing both the α and γ subunits necessary for the formation of the αγ hybrid isoform (Ghandour et al., Exp Brain Res 41:271–279, 1981; Vinores et al., J Histochem Cytochem 32:1295–1302, 1984; Iwanaga et al., Arch Histol Cytol [Suppl] 52:13–24, 1989). We sought to approach this question by performing in situ hybridization studies in order to visualize the α and γ mRNAs. In agreement with the immunocytological reports, we observe a specific accumulation of the γ enolase transcripts in neurons and a high accumulation of α enolase transcripts in some glial cells such as the ependymocytes lining the ventricles.Our observations, following hybridization with35S labeled oligonucleotide specific probes on adjacent thin sections, demonstrate for the first time that transcription of both α and γ enolase genes occurs in many neurons of different brain regions. These results render highly probable the formation of the αγ hybrid in mature neurons.Furthermore, we observe a differential expression of the genes encoding the α and γ enolase subunits in various neuronal populations of the brain. The implications of these observations

ISSN:0360-4012    

DOI:10.1002/jnr.490380503

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

年代:1994

数据来源: WILEY

摘要:

AbstractAcetylcholinesterase (AChE) molecular forms were studied in normal (NM) and in dystrophic (DM) 129B6F1/J mouse muscle. Successive extractions of the tissue with saline and saline‐Triton X‐100 buffers yielded two soluble fractions, S1and S2. Forty percent of the AChE in NM was measured in S1and 60% in S2, and 65% and 35%, respectively, in extracts from DM. A12, A8, G4, G2, and G1forms of AChE were found in S1and S2from NM and DM. A similar content of asymmetric molecules was noticed between NM and DM. G4AChE was a minor species in DM, and G1and G2AChE were more abundant in DM than in NM. The amphiphilic properties of the several molecules were assessed by Triton X‐114 phase‐partitioning and hydrophobic chromatography. Thirty and 70% of the enzyme in a mixture of S1and S2partitioned in the detergent‐rich and in the detergent‐poor phases, respectively, whether the extracts were obtained from NM or DM. Asymmetric and G4AChE predominated in the aqueous phase and G1and G2in the detergent phase. Ten and 25% of the enzyme in S1from NM or DM, respectively, was adsorbed to the phenyl‐agarose. Elution of the retained enzyme followed by sedimentation analysis revealed that a certain amount of asymmetric and most of the G1and G2forms were associated with the matrix. The content of amphiphilic asymmetric and light globular forms was notably higher in DM than in NM. The results suggest that dystrophic muscle produces a specific pattern of molecular forms of AChE. © 1994 W

ISSN:0360-4012    

DOI:10.1002/jnr.490380504

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

年代:1994

数据来源: WILEY

摘要:

AbstractQuantitative morphological changes of the developing Purkinje cells were studied from 6 to 90 postnatal (PN) days in the IVth lobule of vermis in the cerebellum of rats. The soma size (mean diameter) of Purkinje cells increased rapidly between 6 PN (on average 10 μm) and 18 PN (about 17 μm) days; it did not change between 18 and 25 PN days, but increased moderately again between 25 and 48 PN days (22–23 μm) and stabilized on the same value. In contrast, the number of Purkinje cells/100 μm (the “linear density”) decreased rapidly from 6 to 18 PN days. The molecular layer area belonging to 1 Purkinje cell increased rapidly from 6 to 25 PN days (from about 370 to 6,200 μm2) and less rapidly between PN days 30 to 48 (up to 9,300 μm2), followed by a moderate decrease at PN day 90 (about 6,600 μm2). The volume belonging to 1 Purkinje cell dendritic arbor was about 5,500 μm3at PN day 6,93,000 μm3at PN day 25, and 100,000 μm3at PN day 90. The numerical density of dendritic spines in the molecular layer showed a biphasic curve: a rapid increase from PN days 6 to 21 followed by a significant but short decrease at PN day 25, moderate rise from PN days 25 to 48, and a subsequent decline between PN days 48 and 90. The number of spines belonging to 1 Purkinje cell showed two developmental “peaks”: the first peak at 21 PN days was moderate (5.6 × 104spines/Purkinje cell) while the second maximum at 48 PN days was more significant (1.2 × 105spines/Purkinje cell), which then declined to 6.3 × 104spines/Purkinje cell at PN day 90. It is suggested that the temporary overproduction and the following decline in the number of Purkinje dendritic spines during the development of the cerebellar cortex may be the morphological indicator of the dynamics of synaptogenetic and of synaptic stabilization processes.

ISSN:0360-4012    

DOI:10.1002/jnr.490380505

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

年代:1994

数据来源: WILEY

摘要:

AbstractMonoamine‐activated α2‐macroglobulin (α2M) has been shown to inhibit choline acetyltransferase in basal forebrain neurons as well as neurotrophin‐dependent neuronal functions. The objective of this study was to determine whether monoamine‐activated α2M can affect the caudate putamen (CP) dopaminergic system in vivo. Male rats received intracranial infusions of methylamine‐activated α2M (0.6 nmole) and contralateral infusions of its vehicle, phosphate‐buffered saline (PBS). Five days following infusion, the animals were killed, the CP dissected into three rostral‐caudal segments, and assayed for dopamine (DA) using a high‐performance liquid chromatography system. Within the two rostral CP segments (the approximate site of cannula placement), statistically significant (26%) reductions of DA concentrations were obtained on the α2M‐infused side of the CP with 90–100% of the animals showing decreases. At a more distal (caudal) site of the CP, DA concentrations showed only an insignificant (12%) reduction. No differences in DA concentrations between sides infused with bovine serum albumin versus PBS or from olfactory tubercle samples were obtained in these animals. These results demonstrate that monoamine‐activated α2M is capable of producing significant degeneration of the nigrostriatal dopaminergic system in vivo and suggest that this factor may play a role in age‐related neurodegenerative disorders such as Parkinson's di

ISSN:0360-4012    

DOI:10.1002/jnr.490380506

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

年代:1994

数据来源: WILEY

摘要:

AbstractThis paper describes a novel monoclonal antibody (C1G5F2) derived from mice splenocytes immunized in vitro with a wheat germ agglutinin glycoprotein fraction isolated from bovine central nervous system (CNS) myelin. Immunohistochemical reactions with C1G5F2 were investigated on rat brain sections during the active period of myelination. From day 10 to 13 postnatally, no stained structures were observed throughout the whole brain. The first immunolabeled myelin fibers were detected within the pons at day 14, and the white matter areas in the cerebrum started to be stained some days later. White matter areas of the cerebellum were clearly immunopositive after the third week. There was a strong positive signal on myelin fibers in the cerebrum at day 30. By contrast, no immunolabeled cell bodies of oligodendrocytes were observed throughout the brain. The other neural cell types were also not labeled. This C1G5F2 monoclonal antibody bound mainly to the extracytosolic membrane surface of the processes of live cultured oligodendrocytes derived from newborn rat brain but was unreactive with live or fixed astrocytes and neurons maintained in culture. No immunostaining was detected in the peripheral nervous system or in the spleen, liver, or pancreas. The C1G5F2 epitope containing antigen may therefore be considered as a CNS myelin/oligodendrocyte specific molecule. Sodium deoxycholate‐Tween 20 extracts of secondary oligodendrocyte cultures, biotinylated with biotin hydrazide, were used to attempt the purification of the antigen with C1G5F2 IgMs linked to antimouse IgM agarose. A main broad biotinylated protein band of 54–58 kDa molecular mass was noted. In a second approach, the antigen was immunopurified from cultured oligodendrocytes as an immune complex using biotinylated C1G5F2 IgMs. A distinct protein doublet of 53–56 kDa was also observed. It is postulated that this antigen may play an essential role in myelin formation and could be a possible target in diseases restricted to CNS myelin. © 1994 Wiley‐L

ISSN:0360-4012    

DOI:10.1002/jnr.490380507

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe neostriatal distribution of D2dopamine receptor protein has been assessed using subtype‐selective polyclonal antibodies generated against three unique polypeptide sequences of the receptor. The experimental tissues were processed by peroxidase based immunohistochemical procedures for routine light microscopy, Golgi impregnation‐gold toned morphological characterization, and correlative light/electron microscopy. The results demonstrated a regional gradient of D2‐like dopamine receptor expression in the neostriatum, where lateral portions in the nucleus exhibited more reactive cell bodies than medial portions. D2‐like expression was detected in the three populations of neostriatal neurons, i. e., the medium‐sized spiny projections neurons, and the medium‐ and large‐sized aspiny interneuron types. Morphometric measurements of labeled neurons verified that medium and large diameter neurons expressed the D2‐like receptor subtype. D2‐like immunoreactivity was distributed throughout the cytoplasm in dendritic processes, and in presynaptic terminal boutons. Immunoreactivity for the receptor protein was also detected in small, thinly myelinated axons, suggesting the possibilities of anterograde transport of the receptor from cell bodies in the substantia nigra to their neostriatal terminal fields, as well as from local axon collaterals of neostriatal projections neurons. These findings provide evidence of widespread distribution of the D2‐like receptor protein in neostriatal neurons, and showed that the presynaptic D2receptors contain analogous epitopes to the postsynaptic receptor subtype. ©

ISSN:0360-4012    

DOI:10.1002/jnr.490380508

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

年代:1994

数据来源: WILEY

摘要:

AbstractThree experiments were conducted to examine the role of histamine in neuronal degeneration in a rat model of Wernick's encephalopathy induced by an acute bout of pyrithiamine‐induced thiamine deficiency (PTD). In the first experiment, histamine levels in medial thalamus of freely moving PTD rats measured by microdialysis were increased (180% of controls) at a prelesion stage of thiamine deficiency (treatment day 12) and further elevated 48 hr later (380%) in the same animals when necrosis was evident. Histamine levels in dialysates of the hippocampus collected simultaneously from the same animals were unchanged at either stage of thiamine deficiency. Glutamate levels in microdialysates from the same animals were unchanged at the prelesion stage but were significantly elevated on the second collection day. In a second experiment, separate groups of PTD and pairfed control (CT) rats were infused continuously with either α‐fluoromethylhistidine (FMH; 80 mg/day, i. p.), an irreversible inhibitor of histamine synthesis, or saline. FMH pretreatment produced a significant protection against PTD‐induced neuronal loss within the midline‐intralaminar and anteromedial thalamic nuclei, but had no effect on damage to ventrolateral nuclei, anteroventral nucleus, or the mammillary bodies. In a third study, histamine (80 μg, free base) or vehicle was directly infused into the same region of medial thalamus dialyzed in experiments 1. Histamine infusion into prelesion PTD but not CT animals resulted in severe neuronal loss and gliosis. Infusion of vehicle into the same regions of PTD and CT rats produced a mild gliosis restricted to the needle tract with no evidence of neuronal loss. These observations together with recent evidence of a histamine enhancement of glutamate receptor activation suggest that early histamine release may contribute significantly to glutamate‐N‐methyl‐D‐aspartate (NMDA)‐mediated excitotoxic neuronal death in thiamine deficiency‐induced Wernicke's encephalopathy.

ISSN:0360-4012    

DOI:10.1002/jnr.490380509

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

年代:1994

数据来源: WILEY

摘要:

AbstractWe have examined the regulation of growth‐associated protein 43 kD (GAP‐43) in rat Schwann cells. In unlesioned adult nerves, GAP‐43‐immunoreactivity was restricted to non‐myelinating Schwann cells and unmyelinated axons. When adult nerves were transected to cause permanent axotomy, previously myelinating Schwann cells expressed progressively more GAP‐43‐immunoreactivity over 3 weeks and GAP‐43 mRNA levels increased over a similar time course. The peak level of GAP‐43 mRNA occurred at least 2 weeks later than that of nerve growth factor receptor, another marker of denervated Schwann cells. In contrast, after nerve‐crush, which allows axonal regeneration, many fewer Schwann cells had GAP‐43‐immunoreactivity, and the amount of GAP‐43 mRNA was markedly lower than in transected nerves. Forskolin, a drug that activates adenylate cyclase and mimics many effects of axon‐Schwann cell interactions, markedly reduced GAP‐43‐immunoreactivity and mRNA expression in cultured Schwann cells, whereas interleukin‐1 had no effect. These data demonstrate that axon‐Schwann cell interactions inhibit the expression of GAP‐43 in Schwann cells and that this effect is mimicked

ISSN:0360-4012    

DOI:10.1002/jnr.490380510

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe PC12 rat pheochromocytoma cell line is widely used to study neuronal differentiation by growth factors. In response to nerve growth factor (NGF) and basic fibroblast growth factor (bFGF), PC12 cells differentiate into sympathetic‐like neurons and become electrically excitable. Using whole cell patch‐clamp recording, with barium as a charge carrier, we looked at the effects of bFGF on calcium channel expression as reflected by changes in barium current amplitudes normalized to cell membrane area. Similar to the effect reported for NGF, we show that 7 day treatment with bFGF increased the barium current approximately 4‐fold. The largest contributor to the increase in barium current with bFGF treatment is a 6‐fold increase in the high threshold voltage activated Ω‐conotoxin sensitive barium current. Smaller increases in current produced by bFGF treatment of PC12 cells are observed for the dihydropyridine sensitive and dihydropyridine/conotoxin insensitive currents. The bFGF‐induced increases in barium currents are dependent on tyrosine phosphorylation, since the effects of bFGF are blocked by genistein, a tyrosine kinase inhibitor. This system will ultimately be useful in understanding the signaling pathways that control calcium channel expression in response to growth factors. © 1994 Wi

ISSN:0360-4012    

DOI:10.1002/jnr.490380511

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

年代:1994

数据来源: WILEY