摘要:

AbstractRecent patch‐clamp studies on freshly isolated mammalian Schwann cells suggest that voltage‐gated sodium and potassium channels, first demonstrated in cells under culture conditions, are present in vivo. The expression of these channels, at least at the cell body region, appears to be dependent on the myelinogenic and proliferative states of the Schwann cell. Specifically, myelin elaboration is accompanied by a down regulation of functional potassium channel density at the cell body. One possibility to account for this is a progressive regionalization of ion channels on a Schwann cell during myelin formation. In adult myelinating Schwann cells, voltage‐gated potassium channels appear to be localized at the paranodal region. Theoretical calculations have been made of activity‐dependent potassium accumulations in various compartments of a mature myelinated nerve fibre; the largest potassium accumulation occurs not at the nodal gap but rather at the adjacent 2–4 μm length of periaxonal space at the paranodal junction. Schwann cell potassium channels at the paranode may contribute to ionic regulation during nerve

ISSN:0894-1491    

DOI:10.1002/glia.440040602

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

年代:1991

数据来源: WILEY

摘要:

AbstractTo investigate the possible role of neurons and astrocytes for oligodendrocyte development we prepared a pure population of precursor cells positive for the precursor marker GD3 with the help of fluorescence‐activated cell sorting (FACS). Large numbers of highly purified cells were obtained from postnatal day 1 rat brainstems and cultured in different media and sera, and in conditioned media.As described in the literature for optic nerve O‐2A progenitors, GD3‐sorted brainstem cells cultured in medium containing 10% fetal calf serum (FCS) acquired a star‐shaped morphology and differentiated into GD3‐ and GFAP‐positive type‐2 astrocytes. On the other hand, in serum‐free medium, most of the cells differentiated into oligodendrocytes (O1‐/galactocerebroside‐positive).Sensory neuron conditioned media promoted survival and proliferation of the precursor cells. The spontaneous differentiation of progenitor cells into oligodendrocytes was retarded by the mitogen. Antibodies against platelet‐derived growth factor (PDGF) completely blocked the mitotic effect and allowed spontaneous oligodendrocyte differentiation to occur.Cultured astrocytes also secreted PDGF as a mitogen. However, postnatal astrocytes also released a potent signal promoting oligodendrocyte differentiation. The type of factor(s) released depended on the age of the astrocytes, since only conditioned medium of postnatal but not of embryonic astrocytes promoted oligodendrocyte differentiation, suggesting that astrocyte maturation directly influences oligodendrocyte differentiation. Different concentrations of PDGF could not reproduce this differentiation‐inducing effect.This study suggests that interactions between O‐2A progenitor cells, neurons, and astrocytes could be required to regulate and complete the oligodendrocyte developmental pathway. Astrocytes, themselves possibly under neuronal influences, might regulate first the proliferation of the precursor cells, and, later in development, the differentiation into mature oligodendroc

ISSN:0894-1491    

DOI:10.1002/glia.440040603

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

年代:1991

数据来源: WILEY

摘要:

AbstractGlial fibrillary acidic protein (GFAP) mRNA levels in the human astrocytoma line U‐373MG were examined to explore further the effects of agents that regulate protein kinase C. U‐373MG cells exhibit a biphasic change in steady‐state GFAP mRNA in the presence of the phorbol ester phorbol‐12‐myristate‐13‐acetate (PMA). Short‐term treatment with PMA results in increased GFAP mRNA, and long‐term treatment results in decreased GFAP mRNA. Nuclear run‐off experiments demonstrate that the PMA‐induced decrease in GFAP mRNA levels is not at the level of GFAP gene transcription. PMA exerts its effect in the presence of protein synthesis inhibitors, demonstrating that de novo protein synthesis is not required for the PMA‐induced changes in GFAP mRNA. Staurosporine, a protein kinase C inhibitor, reduces GFAP mRNA expression in a dose‐dependent manner; in the presence of PMA the effect is additive. By contrast HA1004, an inhibitor of cAMP‐dependent protein kinase, is not inhibitory to GFAP steady‐state mRNA. Total protein kinase C activity was determined to be 2,398.8 ± 94.3 pmol/min/mg protein, with most of the activity in the cytosol. Short‐term PMA treatment results in the translocation of the cytosolic protein kinase C activity to the membrane. Long‐term PMA treatment results in a decrease in total protein kinase C activity indicating that downregulation occurs. These studies demonstrate that in the U‐373MG cells, protein kinase C inhibitors and long treatment with PMA result in

ISSN:0894-1491    

DOI:10.1002/glia.440040604

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

年代:1991

数据来源: WILEY

摘要:

AbstractFragments of neural tissue from normal newborn mouse were stained with Hoechst 33342 dye before transplantation into the newborn shiverer mouse brain. Combination of this technique with immunohistochemistry demonstrated that, after transplantation, these cells are able to survive as long as unstained cells and to myelinate in the shiverer mouse host brain. Stained cells express the normal sequence of differentiation in terms of chronology of differentiation marker expression [04, galactocerebroside (GalC), myelin basic protein (MBP)], as normal cell do in situ. It has thus been possible by this technique to show the migration pathways of transplanted cells and to correlate them with the expression of specific markers: long distance migration along white matter axonal pathways occurs when cells are o4‐positive, GalC‐negative. By contrast, only GalC‐positive cells are able to migrate across the grey matter in the absence of radial glia. Finally, it has been possible to propose a migration and differentiation sequence of these cells, suggesting that MBP‐positive oligodendrocytes divide after migration in the targ

ISSN:0894-1491    

DOI:10.1002/glia.440040605

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

年代:1991

数据来源: WILEY

摘要:

AbstractMammalian central nervous system (CNS) axons are virtually incapable of regenerating after injury. However, CNS neurons of lower vertebrates, such as fish and amphibians, are endowed with a high regenerative capacity. Lately, the glial cells have been credited with the regenerative ability of any specific CNS. We have previously demonstrated that many oligodendrocytes are recovered in cultures of injured rat optic nerve, while only a few oligodendrocytes are recovered from injured fish optic nerve in culture. We further demonstrated that medium conditioned by regenerating fish optic nerves (CM), which has been shown to cause axonal elongation in injured rabbit optic nerves, causes a decrease in the number of oligodendrocytes in rat glial cultures. In the present study, we demonstrate that soluble factors in the CM are capable of reducing the number of fish oligodendrocytes in fish optic nerve cultures. In addition, an inverse relationship was found between the number of macrophages and the number of oligodendrocytes. These results thus suggest that macrophages and/or activated resident microglial cells are directly or indirectly responsible for the presence of these soluble factor(s) that regulate the postinjury number of oligodendrocytes in the fish optic nerves.

ISSN:0894-1491    

DOI:10.1002/glia.440040606

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

年代:1991

数据来源: WILEY

摘要:

AbstractA series of frozen and vibratome coronal sections of the rat brain were examined by immunocytochemistry for the presence of a cysteine‐rich metal binding protein, metallothionein (MT). Astrocytes throughout the brain and brainstem stained positively for MT; neurons and oligodendroglia were unstained. Ependymal cells and tanycyte processes in the hypothalamus were also immunoreactive, along with a narrow zone of immunopositivity along the margins of the area postrema. Gomori‐positive astrocytes in the hypothalamus, identifiable by toluidine blue staining, metal‐containing cytoplasmic granules, represented a subset of MT‐positive astrocytes that may be involved in reactions to blood‐borne metal compounds that penetrate into circumventricular organs of

ISSN:0894-1491    

DOI:10.1002/glia.440040607

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe membrane potential of cultured rat sciatic nerve Schwann cells was determined with conventional microelectrode and voltage‐sensitive fluorescent dye, Di‐S‐C3(5), optical techniques. The value for membrane potential obtained with microelectrodes was −42.1 ± 4.7 mV (n = 8). Using optically determined fluorescent intensity changes caused by changes in external potassium ion concentration, in the presence or absence of valinomycin (null point method), the membrane potential was estimated at −45.7 ± 6.2 mV (n = 7); with a gramicidin and valinomycin double ionophore method it was −52.2 ± 9.1 (n = 4). The membrane potential of Schwann cells was found to be potassium sensitive at and above the physiological range of [K+] at 27.5 mV/10 × Δ[K+], which is approximately half the Nernstian value. This result suggests that other ion permeabilities strongly influence the resting membrane potential of cultured Schwann cells. Since Na+had little effect on the membrane potential, it is concluded that Cl−is a likely candidate for the other permeant ionic species. The optical method has been shown to be a useful tool for the systematic study of the membrane potential of Schwann cells in culture and for the characterization of its ionic ba

ISSN:0894-1491    

DOI:10.1002/glia.440040608

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

年代:1991

数据来源: WILEY

ISSN:0894-1491    

DOI:10.1002/glia.440040601

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

年代:1991

数据来源: WILEY