摘要:

AbstractThe adult rat dorsal root ganglion (DRG) produces mRNA for the neurotrophic factors nerve growth factor (NGF) and brain‐derived neurotrophic factor (BDNF) and contains large populations of neurons responsive to these factors. We report that following a focal crush injury of the sciatic nerve, NGF mRNA expression increases threefold and BDNF mRNA twofold, in the ipsilateral L4 and L5 DRGs. The mRNAs encoding the cognate neurotrophin receptors, p75NGFR, trkA, and trkB were expressed in the DRG throughout the post‐injury time course, suggesting that DRG neurons remain responsive to both NGF and BDNF. p75NGFRmRNA levels became transiently depressed in the DRG during the first several days after the lesion but returned to normal within 1 week.trkB mRNA was expressed in the normal sciatic nerve and levels were not altered by nerve crush. RNase protection assays detected both full‐length and truncatedtrkB transcripts in the DRG, but only truncatedtrkB mRNA, lacking the tyrosine kinase domain, was detected in the sciatic nerve. Likewise,trkA transcripts were not detected by RNase protection in normal sciatic nerve or in a segment of nerve distal to the crush site. These results are consistent with a model in which regenerating sensory neurons are supported by neurotrophic factors synthesized within the DRG. © 1993 Wiley‐L

ISSN:0360-4012    

DOI:10.1002/jnr.490360402

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe myelin‐associated glycoprotein (MAG) is a neural recognition molecule involved in heterophilic interactions between myelin‐forming cells and neurons. To characterize the molecular mechanisms underlying post‐translational modifications which may be instrumental in signal transduction following the recognition event, we have studied the stimuli leading to modification of32P‐orthophosphate incorporation into MAG in cultures of oligodendrocytes or transformed differentiated Schwann cells. Here we show that in oligodendrocytes both the 67 and 72 kD isoforms of MAG were phosphorylated exclusively on serine, while in the transformed Schwann cells only the 67 kD isoform was found to be present and phosphorylated. The phorbol‐12‐myristoyl‐13‐acetate (PMA) did not affect biosynthesis of the protein backbone, but enhanced incorporation of phosphate by a factor of 2–3, indicating the involvement of protein kinase C. Exclusive phosphorylation of serine residues was also observed, when purified MAG was incubated with protein kinase C in the presence of [γ‐32P] ATP. In searching for the physiological stimuli which may trigger phosphorylation of MAG, cultures of oligodendrocytes were exposed to extracellular signals, such as coculture with dorsal root ganglion and spinal cord neurons carrying the MAG receptor, to membrane fractions of these neurons, monoclonal MAG antibody 513 binding to the recognition site of MAG, or platelet‐derived growth factor. None of these additives modified the phosphorylation of MAG. These observations point to the possibility that phosphorylation of MAG is controlled by yet unknown intracellular cues rather than by extracellular signals interacting with cell surface receptors of oligodendrocytes.

ISSN:0360-4012    

DOI:10.1002/jnr.490360403

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

年代:1993

数据来源: WILEY

摘要:

AbstractGlial cells of the central nervous system (CNS) are postulated to function as immune accessory cells which may regulate immune reactivity occurring within the CNS, activating or alternatively inhibiting T cell responses. We have utilized surgically resected cerebral tissue derived from young adult humans to prepare dissociated cultures of glial cells (mixed astrocyte‐microglia‐oligodendrocyte cultures) and demonstrate that such cells are capable of acting as stimulators of primary T cell responses, using proliferation of T cells to allogeneic determinants on the glial cells as the test system. Studies of resected adult cerebral tissue indicated major histocompatibility complex (MHC) class II antigen expression on microglia in situ. Using a mixed lymphocyte reaction (MLR), we observed that enriched microglial cultures alone were capable of stimulating primary responses of freshly isolated T cells or the CD4+T cell subset, a response which could be inhibited with an anti‐MHC class II blocking antibody. In agreement with previous studies using rodent‐derived astrocytes, we found that human astrocytes (fetal), could not initiate a primary T cell response even after up‐regulation of MHC class II antigen expression with interferon gamma (IFNγ) and tumor necrosis factor alpha (TNFα). Our results indicate that a primary T cell response, as well as a secondary response to a recall antigen, can occur within the CNS; our data implicate microglia as the central cell involved in the former. © 1993 Wil

ISSN:0360-4012    

DOI:10.1002/jnr.490360404

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

年代:1993

数据来源: WILEY

摘要:

AbstractExperimental allergic neurities (EAN), an inflammatory demyelinating disorder of the peripheral nervous system, is preceded and accompanied by a massive microglial reaction in the spinal cord which occurs in the absence of inflammatory cells infiltrating the cord parenchyma. Since transforming growth factor beta (TGF‐β) has been shown to play a beneficial role in experimental autoimmune disease and might be involved in the regulation of glial activity, we have investigated the expression of TGF‐β in EAN spinal cord and nerve root tissue. Adoptive transfer EAN was induced by the injection of neurotogenic T‐cells specific for the P2myelin protein. In normal spinal cord tissue, both TGF‐β1 and TGF‐β3 mRNA were constitutively expressed at low levels. Already 3 days following injection of P2‐specific T‐cells, TGF‐β1 mRNA levels began to increase, peaked at day 6 at levels about tenfold above normal, and thereafter declined. TGF‐β3 was induced even earlier with a sharp rise at day 3 and a peak fourfold above normal at day 4. In situ hybridization for TGF‐β1 performed on spinal cord sections 6 days after injection of cells localized TGF‐β1 mRNA to many nonneuronal cells with the typical morphology of microglia. In addition, TGF‐β1 mRNA was observed in the meninges, and massive accumulation of signal was seen over inflammatory cells infiltrating the nerve roots. Our data indicate that TGF‐β1 and ‐β3 are involved in regulating the glial response in EAN and that activated microglial cells might control their own activity state by expressing TGF‐β1. The expression of TGF‐β1 by infiltrating inflammatory cells in the nerve roots might represent an important endogenous mechanism to limit the ex

ISSN:0360-4012    

DOI:10.1002/jnr.490360405

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

年代:1993

数据来源: WILEY

摘要:

AbstractGlucose deprivation was employed to model caloric undernutrition in newborn rat mixed glial cultures. Six day‐old cultures were placed in serum‐free media containing glucose concentrations from 0.55 mg/ml to 10 mg/ml. The expression of the myelin PLP, BP, and MAG genes was determined by Northern blot analysis. The activation of the myelin genes began at approximately 6 day in vitro (DIV), and a period of rapid upregulation followed through 14 DIV. The gene activity was directly related to the glucose concentrat.The increase in glucose concentration from 0.55 to 1.5 mg/ml (which spans the physiological range) resulted in 2–3 fold increases in expression of the myelin genes, whereas further increases in glucose (2–10 mg/ml) produced only slight additional elevation in the gene activity. We used high glucose (5–6 mg/ml) as control, or low glucose (0.55 mg/ml) as deprived, to delineate possible critical periods of oligodendrocytic differentiation. Cultures were deprived for 4‐day intervals, staggered from 6 to 22 DIV. Deprivation from 6 to 10 DIV produced an 80–90% suppression of the myelin gene upregulation at 22 DIV; deprivation from 10 to 14 DIV produced 60–70% suppression; whereas deprivation from 14 to 18 DIV was fully recoverable by 22 DIV. These results show that mixed glial cultures model the developmental pattern of myelin gene expression, as well as their vulnerability. Furthermore, the period of rapid upregulation of the myelin genes appears to be a critical period in development, during which glucose deprivation irreversibly alters oligodendrocyte differentiation. © 1993

ISSN:0360-4012    

DOI:10.1002/jnr.490360406

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

年代:1993

数据来源: WILEY

摘要:

AbstractWe describe a simple and reproducible acute demyelinating lesion of the rat brain stem induced by injection of ethidium bromide into the cisterna magna of young adult rats. Using immunofluorescence with a panel of antibodies to cell‐specific antigens we have studied the changes in cell populations that occur at various stages during lesion progression and repair. In particular we localized the expression of ganglioside GD3immunoreactivity, a marker for oligodendroglial progenitors in developing brain. Both astroglia (GFAP+) and oligodendroglia (CNP+) were destroyed during the early response to the ethidium bromide although axons were spared. Splitting of myelin lamellae occurred as early as 4 days post‐injection (DPI), with extensive demyelination of the inferior cerebellar peduncle following by 6 DPI. Large numbers of ED1+and OX‐42+macrophages were present in the lesion site at this stage. Astrogliosis occurred around the perimeter of the lesions. Two populations of GD3+cells appeared within and around the lesion sites during the demyelination. One population was identified by the phenotype GD3+ED1+and thus probably belonged to the macrophage/microglial lineage. In these cells both antigens appeared cytoplasmic. The second population of GD3+cells exhibited cell membrane GD3immunoreactivity but did not express the ED1 antigen. These cells are suggested to be oligodendroglial progenitors generated in response to the demyelination. No such cells were seen in control tissue. GD3+cells were present within the lesion sites from 6 DPI until 10–12.Following the clearance of myelin debris from the lesions, remyelination was a relatively rapid event with thin MBP+myelin sheaths first seen at 11–12 DPI. Remyelination, which was extensive by 25 DPI, was predominantly oligodendroglial in origin (MBP+Po−myelin) with only small pockets of peripheral myelin (MBP+Po+myelin) observed. The present study, in addition to identifying putative glial progenitors within a demyelinated lesion, also demonstrates the difficulties in unambiguously identifying such cells in the normal and damaged adult CNS. © 1993 Wil

ISSN:0360-4012    

DOI:10.1002/jnr.490360407

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

年代:1993

数据来源: WILEY

摘要:

AbstractPlexiform layer synaptic and photoreceptor cell components were investigated in retinas of Royal College of Surgeons (RCS) dystrophic rats transplanted with normal retinal pigment epithelial (RPE) cells by immunocytochemistry using previously characterized monoclonal antibodies. In retinas of normal adult rats and RPE‐cell transplanted retinas of 4 month‐old RCS rats, HNK‐1, a marker for a carbohydrate of the neural cell adhesion molecule (N‐CAM), was detected immunocytochemically in the inner and outer plexiform layers and ganglion cell bodies and their axons. HNK‐1 was also detected in the inner plexiform layer of nontreated retinas of 4 month‐old RCS rats, but was reduced to scattered patches in the outer plexiform layer. In addition, immunoreactivity for the SVP‐38 antibody recognizing synaptophysin was found in both plexiform layers of normal adult rat retinas and RPE‐transplanted retinas of 4 month‐old RCS rats. Furthermore, photoreceptor cell bodies and their inner and outer segments were immunostained for the opsin monoclonal antibody RET‐P1 in retinas of normal adult rats and RPE‐cell transplanted retinas of 4 month‐old RCS rats. However, in nontreated retinas of 4 month‐old RCS rats, only immunostained debris material was detected. These results strongly suggest that normal RPE transplants not only rescue photoreceptor cells in RCS rats, but also maintain an essential functional capacity, in this case, synaptic components in the plexiform layer

ISSN:0360-4012    

DOI:10.1002/jnr.490360408

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

年代:1993

数据来源: WILEY

摘要:

AbstractGelatinases in inflammatory demyelinating diseases of the central nervous system (CNS) were studied using actively induced experimental autoimmune encephalomyelitis (EAE) in mice as a model system. Clinical disease scores correlated in time and in intensity with pathology parameters such as cytosis in the cerebrospinal fluid (CSF), inflammatory infiltrates, and demyelination in the CNS. Zymographic analysis was employed to measure gelatinases A and B in the CSF from individual animals. According to their apparent molecular weight (MW), gelatinases A and B appeared with a MW of 65 and 95 kDa, respectively. The 65 kDa form was present in all samples, even in those derived from non‐induced animals, whereas the 95 kDa form was present only in samples from animals developing EAE. The levels of 95 and 65 kDa gelatinase correlated with the CSF cytosis. In vitro digestion of myelin basic protein (MBP) with gelatinase B and analysis of the cleavage products by protein sequence analysis pinpointed two cleavage sites in conserved regions of MBP. Gelatinase production within the CNS may constitute an important pathogenic mechanism for both the disruption of the blood‐brain barrier and the destruction of myelin, as observed in several neuroinflammatory disorders. © 1993 Wiley‐Lis

ISSN:0360-4012    

DOI:10.1002/jnr.490360409

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

年代:1993

数据来源: WILEY

摘要:

AbstractO‐2A progenitor cells were grown in medium containing either 1% or 10% fetal calf serum (FCS) for 4 weeks. The cells in 1% FCS were 75% oligodendrocytes by 3 weeks in culture. The cell population was so overgrown with astrocytes in the 10% medium that an accurate estimate of cell number could not be made. The activities of glycerophosphorylcholine phosphocholine phosphodiesterase (GPC‐PC‐PdE), p‐nitrophenylphosphorylcholine phosphodiesterase (pNPPC‐PC‐PdE), and ceramide UDP galactose galactosyl transferase (CGalT) were barely detectable in the cells grown in 10% FCS. The activities of these 3 enzymes were low in the cells grown in 1% FCS for the first 2 weeks and then all 3 increased manyfold. These observations reinforce the evidence previously accrued showing that these two phosphodiesterase activities (GPC‐PC‐PdE and pNPPC‐PC‐PdE) are markers of oligodendroglial cells as well as myelin. In contrast, glycerophosphorylcholine choline phosphodiesterase (GPC‐C‐PdE) activities were present in cells grown in both 1% and 10% FCS.

ISSN:0360-4012    

DOI:10.1002/jnr.490360410

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe ability of brain preparations from 20‐day‐old rat fetuses to synthesize prostanoids in vitro before and after interruption of the maternal‐fetal blood flow was examined using a radioimmunoassay technique. Synthesis of thromboxane B2(TxB; the stable thromboxane A2metabolite) decreased with increasing restriction time; conversely, it was elevated with reperfusion. Synthesis of 6‐keto prostaglandin F1α(PGF; the stable prostacyclin metabolite) and prostaglandin E2(PGE) prostanoids remained unchanged after 20 min restriction and through a 2 hr reperfusion period. Intraperitoneal administration of GM1 (45 mg/kg) into the pregnant rat, 3 hr before restriction, stimulated synthesis of PGE and reduced synthesis of TxB. A prostanoid vasoactive index (PVI), which reflects the relative proportion of the three prostanoids synthesized and asserts the vasoactive potential of the brain tissue, was established. A rise in this value was attained after intrafetal administration into the peritoneal cavity of either GM1, GM3, or isopropyl‐GM1 (AGF44) gangliosides, each given at 40μg dose in 5 μl volume, and N‐dichloroacetyl‐sphingosine (LIGA20; 15μg/5μl) ganglioside analog, 1 hr before restriction. The effect was primarily due to an increase in the capacity of fetal brain tissue to synthesize PGE and, to a lesser extent PGF, vasodilating prostanoids. The N‐methyl‐D‐aspartate (NMDA) receptor blocker MK801 (6.6 μg/μl) and the platelet activating factor (PAF) receptor antagonist BN52021 (0.1μmol/2μl), given by the same route, effectively raised by 60–80% the vasodilating potential of the brain tissue following ischemia. Based on the commonality seen with these chemically diverse anti‐ischemic agents, it is hypothesized that PGE and PGF elevation by gangliosides may be benefical rather than detrimental for the fetal ischem

ISSN:0360-4012    

DOI:10.1002/jnr.490360411

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

年代:1993

数据来源: WILEY