摘要:

AbstractA variety of prostaglandins and leukotrienes, together with thromboxane and prostacyclin metabolites, can be detected in central nervous tissues and in cerebrospinal fluid. Defined cultures of astrocytes have revealed these cells to be a major source of eicosanoids. In common with other eicosanoid‐producing cells, agents such as calcium ionophores and phorbol esters are potent stimuli for promoting release. While in other tissues agonists for receptors linked to calcium mobilisation prompt eicosanoid release, this does not seem to be the case in astrocytes, though a range of such receptors are present. The notable exceptions to this observation are adenosine triphosphate and adenosine diphosphate, presumably acting through P2 purinergic receptors. Many cell types in the CNS are targets for eicosanoids, possessing receptors linked to adenylate cyclase or phospholipase C. An appreciation of the functional significance of activation of these receptors in just now begining. Eicosanoids have effects in the CNS that involve not only the vascular supply but also synaptic modulation and immune regulatio

ISSN:0894-1491    

DOI:10.1002/glia.440010402

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

年代:1988

数据来源: WILEY

摘要:

AbstractIn the present study we investigated the Müller cell membrane of the mouse retina by freeze‐fracturing. The mouse retina is vascularized and the vessels running outside the nerve fiber layer are completely encased by Müller cell endfeet. Orthogonal arrays of particles (OAP) reside in all membrane areas of the Müller cells. The paravitreous as well as the pericapillary endfeet reveal a considerably higher density of OAP than the nonendfoot membranes including the perikaryal ones. This is in contrast to the Müller cell membrane of the rabbit retina studied previously (Wolburg and Berg:Neurosci. Lett., 82:273–277, 1987). There we found a completely different distribution of OAP; practically all OAP reside in the endfoot membrane facing the vitreous body. The nonendfoot and perikaryal membranes were devoid of OAP. The OAP distribution in both species corresponds roughly to the distribution of the K+conductances measured by Newman (J. Neurosci., 7:2423–2432, 1987). The putative relationship between OAP and K+channels, including functional aspects, is

ISSN:0894-1491    

DOI:10.1002/glia.440010403

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

年代:1988

数据来源: WILEY

摘要:

AbstractCultures of cerebral cells from 2‐day‐old jimpy (jp) and normal animals were immunocytochemically stained with antibodies to galactocerebroside, 2′, 3′‐cyclic nucleotide 3′‐phosphohydrolase and proteolipid protein (PLP). As the normal cultures mature, oligodendrocytes express these markers in cell bodies, in processes and in expansive membrane sheets produced along the lengths of cell processes. In contrast, oligodendrocytes from jp cultures do not produce large membrane sheets and their total numbers are reduced. Only rarely do jp oligodendrocytes exhibit immunostaining for PLP. Thus, jp oligodendrocytes grown in vitro mimic deficiencies of jp CNS in situ. In order to examine the effect of environment and cell‐cell interactions on expression of the jp mutation we grew jp cerebral cells in the presence of medium conditioned for short periods by normal cerebral cells. Under these conditions jp oligodendroglia appeared nearly normal by immunostaining criteria. Their numbers were increased; they were able to produce and maintain membrane sheets; and some cells expressed PLP. These results show that jp oligodendrocytes have the capacity to express certain normal phenotypic parameters, and when given an appropriate environment they do so. The effects of normal conditioned medium may be due to a secreted factor, possibly produced by the astrocytes, which constitute the vast majority of cells in the conditioning cultures. The dramatic effect of normal glial conditioned medium on jp oligodendrocytes suggests that the steps leading to hypomyelination in jp are exceedingly complex and may involve glial‐g

ISSN:0894-1491    

DOI:10.1002/glia.440010404

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

年代:1988

数据来源: WILEY

摘要:

AbstractCellular and subcellular distribution of adenylate cyclase (AC) and guanylate cyclase (GC) activities in crushed peripheral nerves during regeneration were studied at the electron microscope level. In unlesioned nerves, no AC reaction product could be evidenced, whereas GC was detectable on the plasma membranes of Schwann cells, myelinated and nonmyelinated fibers, and within nonmyelinated axons. At 24 hours after the crush, AC reaction product was found within axonal segments proximal to the zone of the crush in association with mitochondria. At this stage, macrophage‐like cells, which probably are transformed Schwann cells, polymorphonuclear leucocytes, and endothelial cells displaying an intense AC reaction product could be detected. On the other hand, at 24 hours after the crush, GC was no longer detectable, except on occasional unlesioned nerve fibers. At 48 hours after the lesion, AC reaction product was no longer detectable within axons, and all AC positivity was associated with plasma membranes of non‐neuronal cells, including transformed Schwann cells, occasional macrophages, polymorphonuclear leucocytes, fibroblasts, and elongated cells. As to GC, images similar to those obtained at 24 hours were observed until 48 hours after the crush. From the 7th to the 28th postlesion day, AC activity was localized exclusively to the plasma membranes of fibroblasts and elongated cells. Transformed Schwann cells were no longer detectable, whereas normal Schwann cells and regenerating axons could be seen, and these showed no AC reaction product in analogy to the absence of AC reaction product of unlesioned nerves. During the same period, GC again was detectable on regenerating fibers with the same subcellular localization as that of unlesioned nerves. The present results strongly suggest that starting from the second postcrush day, cells invading the lesioned zone and transformed Schwann cells, all taking part in the formation of the new perineurial tissue, display a high AC activity, which should be taken into account when measuring cyclic adenosine monophosphate (cAMP) levels under these conditions. Also, our data suggest that GC is involved primarily in regeneration processes that occur in crushed peripheral nerves. Thus, the pattern of AC distribution in peripheral unlesioned and lesioned nerves appears to be exactly the opposite of the GC localization examined under similar experimental conditions insofar as nervous fibers are concer

ISSN:0894-1491    

DOI:10.1002/glia.440010405

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe distribution of potassium conductance across the surface of retinal glial (Müller) cells was determined in three species of fishes: two teleosts, the goldfish (Carassius auratus) and the alewife (Alosa pseudoharengus), and an elasmobranch, the spiny dogfish (Squalus acanthias). Potassium conductance was measured by monitoring cell depolarizations evoked by focal ejections of a 15 mEq/L K+solution onto the surface of freshly dissociated cells. The K+conductance distributions observed in these three species resembled those found previously in other animals with avascular retinas. In both alewife and dogfish, K+conductance was highest in the endfoot; K+conductance in the distal half of these cells ranged from 7.0 to 22.9% of the endfoot conductance. In goldfish, in contrast, K+conductance was highest in the proximal region of the proximal process (114% of the endfoot conductance). As in the two other species, however, K+conductance in goldfish was low in the distal half of the cell (7.6 to 40.1% of endfoot conductance). Mean input resistance values of isolated cells were as follows: goldfish, 12.5 MΩ; alewife, 26.4 MΩ; dogfish, 38.0 MΩ. The high resistance of dogfish Müller cells lacking their endfeet (749 MΩ) indicates that 95% of the cell membrane conductance is located in or near the endfoot in this sp

ISSN:0894-1491    

DOI:10.1002/glia.440010406

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

年代:1988

数据来源: WILEY

摘要:

AbstractAuthentic β‐nerve growth factor mRNA, ∼1.35 kb in size, has been detected by Northern blot analysis in C6 glioma cells. Exposure of the cells to the β‐adrenergic agonist isoproterenol leads to a three‐ to fourfold increase in NGF mRNA, which reaches a peak by 2 hr. The EC50for this effect of isoproterenol is ∼2nM. The effect can be blocked by the β‐blocker propranolol but not by the α‐blocker phenoxybenzamine. Treatment of the cells with forskolin also increases NGF mRNA three‐ to fourfold, with a maximal effect by 2 hr. The stimulation of NGF mRNA by maximal concentrations of forskolin and isoproterenol is not additive; similarly, the two drugs have a nonadditive effect on cyclic AMP content. The results suggest that NGF gene transcription can be stimulated via increases in intracellular cyclic AMP and that regulation of NGF production by glial cells may occur via activation of cell‐surface neurotransmitter receptors such as the

ISSN:0894-1491    

DOI:10.1002/glia.440010407

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe ultrastructure of paranodal oligodendroglial cytoplasm, which is located in proximity to the forming myelin sheath, was studied during maturation of spinal motoneuron axons in rat. At 8 days postnatal, the paranodal oligodendroglial loops contain a network of membrane‐bound tubulovesicular elements. These membrane elaborations are most common in oligodendroglial loops attached to the outermost layers of the myelin sheath, i.e., paranodal loops closest to the nodal gap. The number of oligodendroglial cytoplasmic profiles per paranodal loop falls over the course of five to ten sequential paranodal loops, and these profiles are nearly absent in paranodal oligodendroglial cytoplasm located distant from the nodal gap. Oligodendrocytes in spinal cords of 14‐ and 20‐day‐old rats and of adult rats did not exhibit networks of tubulovesicular profiles. The appearance of these membrane organelles within oligodendroglial cytoplasm during myelin maturation suggests increased membrane turnover within paranodal cytoplasm located adjacent to the axon that is being myelinated. Membrane turnover within oligodendrocytes may reflect axonal modulation of glial function during myel

ISSN:0894-1491    

DOI:10.1002/glia.440010408

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

年代:1988

数据来源: WILEY

摘要:

AbstractWe have investigated the transfer of a fluorescent protein, the fluorescein isothiocyanate derivative of bovine serum albumin (FITC‐BSA), and a fluorescent carbohydrate, FITC‐dextran, from the crayflsh medial giant axon (MGA) to the periaxonal glial cells. The dialyzed tracer was injected into one of the two MGAs, and, after a transfer period of 15–60 min, the tissue was fixed for histological examination of fluorescence distribution. With each tracer, the periaxonal sheath of the injected MGA was specifically labeled. Similar results were obtained with several different fixatives. During the transfer period, there was no appreciable change in the resting potential or conducted action potential of the MGA or in the resting potentials of the adaxonal glial cells. Polyacrylamide gel electrophoresis indicated that the axoplasmic and sheath fluorescence was produced by the intact tracers. These results suggest that “foreign” macromolecules can be exchanged from crayfish axons to glia under physiological conditions. Such transfers may indicate a substantial intercellular traffic of molecules or a means whereby neurons can eliminate waste

ISSN:0894-1491    

DOI:10.1002/glia.440010409

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

年代:1988

数据来源: WILEY

ISSN:0894-1491    

DOI:10.1002/glia.440010401

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

年代:1988

数据来源: WILEY