摘要:

AbstractThe X‐linked mutation rumpshaker (rsh), which is probably an allele of jimpy (jp), causes hypomyelination in the CNS of mice. This study examines the developmental expression of the morphology, glial cells, and immunostaining of myelin proteins in the optic nerve and spinal cord. The optic nerve contains varying numbers of amyelinated and myelinated fibres. The majority of such sheaths are of normal thickness whereas in the spinal cord most axons are associated with a disproportionately thin sheath which changes little in thickness during development. In the optic nerve glial cell numbers are elevated in mutants during early and peak myelination but then fall slightly below normal in adults. In contrast, the number of glial cells is consistently elevated after 16 days of age in the spinal cord. The majority of the alterations to total glial cells are due to corresponding changes in the oligodendrocyte population. Immunostaining intensity is somewhat reduced for myelin basic protein (MBP) and the C‐terminal common to proteolipid protein (PLP) and DM‐20 and profoundly decreased for the PLP‐specific peptide. Glial fibrillary acidic protein (GFAP) is increased inrsh. It is probable that some of the variation in myelination between optic nerve and cord inrshis related to the difference in axon diameter in the two locations, as there are adequate numbers of oligodendrocytes at the time of myelination. However, the effect of the mutation on cell development in the brain and the spinal cord may be different. The immunostaining indicates a marked deficiency in PLP in myelin but suggests that DM‐20 levels may be relatively normal.rshshows several major differences fromjpand other X‐linked myelin mutants, particularly in relation to oligodendrocyte numbers, and will be useful to elucidate the role of the PLP gene in influencing oligodendrocyte differentiation a

ISSN:0894-1491    

DOI:10.1002/glia.440050302

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

年代:1992

数据来源: WILEY

摘要:

AbstractWe have investigated the time of appearance of the earliest differentiating glial cell types of human spinal cord using a panel of antigenic markers to identify them in cultures from 6‐ to 9‐week‐old human embryos. Immunolabeling performed at 14 h in vitro with the O4 mAb, an early oligodendrocyte marker, showed the presence of oligodendrocytes during the 7th week of age. At 8 weeks only a few of the O4+cells expressed galactocerebroside (GalC), a marker of more differentiated oligodendrocytes. All the O4+and GalC+cells were vimentin+and some of the GalC+cells were A2B5+, GD3+and SSEA‐1+. During the first week in vitro many of the O4+cells exhibiting a more immature, bi‐ or tri‐polar morphology incorporated [3H]thymidine into their nuclei. Cells expressing the astrocyte‐specific marker GFAP could be first observed at 8 weeks; almost all of these GFAP+cells, which should correspond to radial glia on the basis of the current literature, were vimentin+, A2B5+, GD3+, and SSEA‐1+. At 2 days in vitro incorporation of [3H]thymidine could be shown in a small fraction of these cells. The finding that radial glia and oligodendrocytes expressed similar antigenic features and the additional observation that a small, but consistent fraction of the cells were simultaneously labeled by O4 and anti‐GFAP antibodies support the hypothesis that, in the human spinal cord, radial glial cells can give rise to both oligodendrocytes and astrocytes; in this respect, radial glial cells may be similar to the A2B5+, GD3+, vimentin+bipotential glial progenitors previously identified in cultures from developing rat CNS, which also express A2B5,

ISSN:0894-1491    

DOI:10.1002/glia.440050303

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe neuronal cell surface is believed to carry a mitogenic signal for peripheral glial cells. We have purified a mitogen from fetal bovine brain membranes that, in common with the PNS neuronal mitogen, stimulates the proliferation of Schwann cells in vitro and binds heparin. The purified mitogen has an apparent molecular weight of 50,000 daltons as estimated by elution of activity from non‐reducing polyacrylamide gels. Since the developing central nervous system is a rich source of mitogen, we tested whether the protein is mitogenic for one or more cell types isolated from the developing brain. Purified mitogen was added to enriched cultures of astrocytes or developing oligodendrocytes, or to microglial cells. The analyses demonstrated that the protein is mitogenic for developing oligodendrocytes but not astrocytes or microglial cells. These results suggest that during development a membrane‐associated mitogen present in the brain might regulate the proliferation of developing oligodendrocytes, and consequently, the population size of oligodendrocytes in the br

ISSN:0894-1491    

DOI:10.1002/glia.440050304

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

年代:1992

数据来源: WILEY

摘要:

AbstractWe used double‐barrelled, neutral carrier, pH‐sensitive microelectrodes to study the mechanisms by which the intracellular pH (pHi) is regulated in the connective glial cells if the medicinal leech. In HEPES‐buffered, nominally CO2/HCO3−‐free solutions the recovery of pHifrom intracellular acidosis is Na+‐dependent and reduced by at least half in the presence of amiloride, suggesting the action of Na+:H+exchange. The rate of pHirecovery by this mechanism can be increased by raising the extracellular buffering power or by increasing extracellular pH. The presence of CO2/HCO3−greatly increases the rate of pHirocovery from intracellular acidosis. This CO2/HCO3−‐stimulated recovery is also dependent on external Na+, largely Cl−‐independent, inhibited by DIDS, and accompanied by membrane hyperpolarization. This is consistent with it being mediated by the electrogenic cotransport of Na+and HCO3−into the cells. A Cl−‐dependen component to Na+‐ and HCO3−‐dependent regulation is most easily explained by the added presence of a Na+

ISSN:0894-1491    

DOI:10.1002/glia.440050305

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

年代:1992

数据来源: WILEY

摘要:

AbstractCytosolic Ca2+([Ca2+]i) activity was measured in individual type 1 astroglial cells in primary culture after exposure to glutamate (Glu), quisqualate (QA), γ‐aminobutyric acid (GABA), 5‐hydroxytryptamine (5HT), and noradrenaline (NA) by using the Ca2+indicator dye fura‐2/AM in a computerized microspectrofluorimetric system. Various patterns of Ca2+transients were observed, but the most common was biphasic, having an initial sharp peak, rising immediately after stimulation, and then declining to a lower but sustained Ca2+level. The only substance that diverged from this pattern was GABA, which induced a Ca2+response with longer latency and a single‐phase curve. The effects of the anticonvulsive drug Na+‐valproate (VPA) were also investigated. After both acute and chronic (5–7 days) exposure to 10−4M VPA, the GABA‐evoked rises in [Ca2+]iwere completely inhibited. VPA also had acute effects on the 5HT‐ and Glu‐evoked Ca2+spikes. The Ca2+responses after 5HT stimulation were greatly reduced after exposure to 10‐4M VPA. The responses after glutamate stimulation were, on the contrary, increased after a similar exposure. No VPA effects were seen on the curve patterns of QA and NA stimulations. The most frequent agonist‐evoked responses were seen after stimulation with 5HT and NA, where over 80% of the tested cells responded. For QA and Glu, the response frequencies were about 40% each, while for GABA it was 20%. The responses after 5HT and NA stimulation were blocked to baseline levels after exposure to ketanserin (5HT2receptor antagonist) and a combination of prazosin, yohimbine, and propranolol (α1, α2, and β adrenoceptor antagonists, respectively). The rises in [Ca2+]iafter stimulation with QA, Glu, and GABA were partly antagonized by 6‐nitro‐7‐cyano‐quinoxaline‐2,3‐dione (CNQX; a QA receptor antagonist, also tested on the glutamate responses) and bicuculline (GABA receptor antagonists). The biphasic curve forms, after stimulation with Glu, QA, 5HT, and NA, were reduced to single‐phase curves with unaffected or slightly reduced initial peaks when the stimulations were performed in Ca2+‐free medium. Interestingly, in some cells Glu induced a curve form that, different from the other Glu‐evoked responses, consisted of an immediate rise in [Ca2+]i, which persisted at the level of maximal response. Furthermore, this response was completely inhibited in Ca2+‐free buffer. The GABA response was also totally inhibited in Ca2+‐free buffer.The results suggest that astrocytes in primary culture respond differently to various receptor agonists, with regard to both the intracellular Ca2+spiking behavior and the response frequency. Furthermore, the data also show that certain agonist‐evoked rises in [Ca2+]ican be s

ISSN:0894-1491    

DOI:10.1002/glia.440050306

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe ability of embryonic day 12 and 13 optic tectum cells to replace depleted A2B5(+) cells and neurons was tested by immunomagnetic cell separation. Nearly all purified surface A2B5(−) cells were identified as glia by immunoreactivity for either glutamine synthetase of galactocerebroside. Most (∼80%) of the purified A2B5(−) cells became A2B5(+) after 1 day in culture, although no increase in the percentage of A2B5(+) cells (from 45%) was observed in control cultures of unpurified cells. Long‐term monolayer cultures from purified cells contained A2B5(+) cells with mostly flattened glial‐like or round process‐free morphology, whereas those from unpurified cells contained many A2B5(+) neurons. The non‐neuronal A2B5(+) cells frequently reacted with antibodies against glial fibrillary acidic protein and another marker expressed by embryonic brain glia, 5A11. Additionally, some flattened glia‐like cells exhibited elaborate networks of anti‐neurofilament‐M‐reactive filaments. We believe these unusual pheno‐types, which appeared only in cultures of purified A2B5(−) cells, arose in response to the immunomagnetic removal of neurons. In conjunction with previous findings, we conclude that the abnormal phenotypes in purified cell cultures represent glia that were unsuccessful in attempting to replenish the depleted neuronal population. This may reflect restricted developmental potentials that ar

ISSN:0894-1491    

DOI:10.1002/glia.440050307

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

年代:1992

数据来源: WILEY

摘要:

AbstractActivation of adenylate cyclase in astroglial cells in culture results in a rapid change in cell shape that appears to occur by the active movement of cytoplasm from peripheral cell regions to the perinuclear space with processes being formed along regions that remain extended. Three series of experiments were designed to determine how shape change occurred. First, the Ca2+‐dependency of shape change was determined by reducing intracellular Ca2+concentrations to ≤50 nM or increasing intracellular Ca2+concentrations to ≥1 μM. Neither of these changes significantly affected the rate of receptor‐mediated shape change. Second the role that longer‐lived, acetylated microtubules play in receptor‐mediated shape change was assessed by visualizing microtubules using a polyclonal antibody to brain 6S tubulin or a monoclonal antibody to oligomers of tubulin to monitor total tubulin distribution and a monoclonal antibody to acetylated tubulin to describe the distribution of these microtubules. Three‐dimensional distribution of microtubules was observed by optical sectioning of cultures using a laser scanning confocal imaging system. The distribution of acetylated tubules in control cells was similar to that observed with the antibodies to tubulin. Following treatment with 100 nM isoproterenol to stimulate shape change, there was a dramatic redistribution of microtubules; however, the distribution of acetylated tubules was again similar to the total microtubules. Analysis of the optical sections recorded using the confocal attachment revealed that while control cells were relatively flat (cell height = 4 μm), the perinuclear region of isoproterenol‐treated cells extended much higher above the substrate (cell height = 13 μm). Third, the role of microtubule assembly and disassembly were assessed using colchicine and taxol. Results from these experiments suggest that microtubule reassembly is necessary for receptor‐mediated shape change. Control experiments indicated that colchicine or taxol treatment did not inhibit either cAMP synthesis or another cAMP‐dependent process, receptor‐mediated taurine release. Together these results indicate that receptor‐mediated shape change in astroglial cells occurs by a Ca2+‐independent mechanism that results in active movement of cytoplasm to the perinuclear region. This process is dependent on microtubule reassembly suggesting that shape change may occur by active movement of material along microtubules or b

ISSN:0894-1491    

DOI:10.1002/glia.440050308

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

年代:1992

数据来源: WILEY

ISSN:0894-1491    

DOI:10.1002/glia.440050301

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

年代:1992

数据来源: WILEY