摘要:

AbstractNa+channel expression was studied in cultures of rat optic nerve astrocytes using whole‐cell voltage‐clamp recordings. Astrocytes from postnatal day 7 rat optic nerve (RON) expressed two distinct types of Na+currents, which had significantly differenth∞curves. Stellate, GFAP+/A2B5+astrocytes showed currents with h∞curve midpoints close to−65 mV, similar to Na+currents in most neurons. In contrast, flat fibroblast‐like GFAP+/A2B5−astrocytes showed Na+currents withh∞midpoints around −85 mV, almost 20 mV more hyperpolarized than in neurons or A2B5+astrocytes. Interestingly, Na+current expression was maintained in A2B5 Na+astrocytes but began to decrease in A2B5−astrocytes after 6 days in vitro (DIV) and fell to or below the level of detection (i.e., 1 pA/pF) at 12 DIV. Astrocytes cultured from neonatal rats (P0) are almost exclusively GFAP+/A2B5‐. These cells did not display measurable Na+currents when studied at 2 DIV; however, Na+current was observed after 5 DIV in A2B5−astrocytes from these neonatal (P0) cultures. These findings were substantiated by immunocytochemical experiments using 7493, an antibody raised against purified rat brain Na+channels; in P0‐derived astrocyte cultures 7493 antibody staining was initially lacking (up to 3 DIV), but it was prominent in cultures after 5 DIV, suggesting that Na+current expression in RON astr

ISSN:0360-4012    

DOI:10.1002/jnr.490300202

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

年代:1991

数据来源: WILEY

摘要:

AbstractA long‐term culture system of dissociated rat dorsal root (DRG) and trigeminal ganglion cells with high cell density has been developed. Two to 3 weeks after plating, the cultures consist of a nearly pure population of sensory neurons, which can be kept for more than 2 months in culture.Cultured neurons synthesize and release the tachykinins substance P (SP) and substance K (SK, neurokinin A) with a time course similar to that observed in vivo. High‐pressure liquid chromatography (HPLC) analysis of peptides extracted from neuronal cultures and synthetic tachykinins revealed identical retention characteristics. Northern blot analysis of mRNAs from cultured cells with a specific tachykinin‐probe demonstrated that the preprotachykinin‐gene is expressed in preparations of both DRG and trigeminal ganglia cells.Depolarizing stimuli such as high potassium (47 mM) evoked a peptide release from cultured neurons in a strictly Ca++‐dependent manner. Capsaicin, a compound known to stimulate nociceptive sensory neurons, dose‐dependently released tachykinins in concentrations as low as 10−9M. Only total absence of Ca++ions from the incubation medium abolished the capsaicin‐induced peptide release. Nifedipine, a blocker of voltage‐dependent L‐type Ca++‐channels, completely blocked the potassium‐induced release of SP but did not reduce the capsaicin‐evoked release.Mediator substances of pain and inflammation, such as bradykinin, serotonin, and histamine, triggered the release of tachykinins from sensory neurons in vitro. These results clearly demonstrate that the neurons characterized express properties similar to those of sensory neurons in vivo and provide model systems for detailed studies of the biosynthesis and release of neuropeptides as well as the participation of sensory neurons in pain a

ISSN:0360-4012    

DOI:10.1002/jnr.490300203

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

年代:1991

数据来源: WILEY

摘要:

AbstractNeuronal growth can be controlled in vitro by plating cells at low density and by differential adhesion between the cell and substrate. Primary cultures of rat hippocampal neurons were grown in serum‐free culture on polylysine‐coated glass coverslips patterned by selective laser ablation so as to leave grids of polylysine with varying linewidths (3, 5, and 10 μM), intersection distance (80, 120, and 160 μM), and nodal (intersection) diameter (5, 10, and 20 μM). Not only did somae strongly prefer the unablated polylysine areas, but they also migrated to foci where the local area of unablated polylysine was higher. These loci were the nodes, as opposed to the narrow connecting paths, and larger nodes, as compared with smaller nodes. Maximum migration to nodes of 88% occurred for a combination of 5‐μM pathwidth, 20‐μm node diameter, and 80‐μM pathlength. Daily observations indicated active migration to larger adhesive areas, which explains the differen

ISSN:0360-4012    

DOI:10.1002/jnr.490300204

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe epitope specificities of myelin basic protein (BP) specific T cell lines derived from the spinal cords (SC) and lymph nodes (LN) of rats with experimental autoimmune encephalomyelitis (EAE) were compared. To induce EAE, Lewis rats were immunized with guinea pig (GP)‐BP and complete Freund's adjuvant. Mononuclear cells from the SC and LN of these animals proliferated in response to BP and the purified protein derivative (PPD) of mycobacterium. After initially being cultured in growth medium, SC mononuclear cells had an enhanced response to BP and lost their response to PPD. LN cells cultured in identical conditions lost their response to both BP and PPD. LN‐derived BP specific cell lines recognized only two epitopes of GP‐BP: an encephalitogenic epitope in residues 72–89 and a non‐encephalitogenic epitope in residues 43–68. SC‐derived BP specific cell lines and clones recognized the 72–89 epitope and a second encephalitogenic epitope contained in residues 87–99 but not the non‐encephalitogenic 43–68 epitope. Unlike those from LN, BP‐specific T cell lines and clones derived from the CNS appear to recognize only encephalitogenic epitopes, including epitopes not

ISSN:0360-4012    

DOI:10.1002/jnr.490300205

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

年代:1991

数据来源: WILEY

摘要:

AbstractTo analyze the cross‐reactivity between serotonin (5‐HT) and histamine, the in vitro transcribed RNA for the 5‐HT1creceptor was functionally expressed inXenopus oocytes. 5‐HT significantly increased45Ca2+efflux in RNA‐injected oocytes, but not in uninjected and water‐injected control oocytes. Furthermore, histamine and the H1receptor agonists, but not the H2and H3agonists, significantly induced45Ca2+efflux in 5‐HT1c receptor RNA‐injected oocytes, but not in uninjected and water‐injected oocytes. However, the H1, H2, and H3antagonists failed to inhibit histamine‐induced45Ca2+efflux at 10−6M. This finding suggests that the 5‐HT1creceptor can be activated by both 5‐HT and histamine, although the action of histamine is different from class

ISSN:0360-4012    

DOI:10.1002/jnr.490300206

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

年代:1991

数据来源: WILEY

摘要:

AbstractRat sciatic nerve Schwann cells either do not proliferate, or proliferate very slowly, in medium containing 10% fetal bovine serum (FBS). They were previously shown to respond only to a limited number of mitogens associated with cells of central and peripheral nervous systems, which appeared to be distinct from FGFs and PDGF, and to agents that raise intracellular cAMP levels. In a basal medium consisting of 75% DMEM, 25% Ham's F‐12, 5 nM sodium selenite, 50 μM 2‐amino ethanol, and 2 mM histidine, supplemented with 5% FBS, we showed that aFGF, bFGF, and PDGF were all capable of stimulating Schwann cell growth and the stimulation was greatly potentiated by forskolin and dibutyryl‐cAMP. In addition, pretreating culture surface with purified matrix proteins such as laminin, fibronectin, or type 1 collagen, was necessary for obtaining a better cellular response to the mitogenesis of these growth factors even in 10% FBS. Our results clearly indicated that providing a suitable medium and substratum, aFGF, bFGF and PDGF are mitogens for rat sciatic nerve Schwann cells in medium with and without forskolin or dibutyry

ISSN:0360-4012    

DOI:10.1002/jnr.490300207

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe ability of cells of the immune system, immunocytes, to receive signals from the nervous as well as the endocrine system is dependent on the cells' expression of receptors for neurotransmitters and neurohormones. The number of receptors, especially beta adrenergic receptors (BARs), varies with the functional subset of immunocytes. However, little is known about how receptor number may vary during the life span (stem cell to mature activated immunocyte) of a given cell type. In this study, we have addressed this question by examining the affinities (Kd's) and the changes in receptor number (Bmax) on (1) clones of T cells and macrophages, (2) fresh thymocytes and splenocytes before and after activation with Concanavalin A (Con A) and phorbol myristate acetate (PMA)/ Ca+2ionophore (A23187), and (3) the cloned human monocyte U937 and the murine thymic lymphoma cell BW5147, in the presence and absence of PMA and A23187 ionophore.Drug treatments of fresh and cloned immunocytes alter the number but not the affinity of β‐receptors. Con A increases the number of β‐adrenergic receptors per cell, whereas PMA/ionophore decreases it. Similar decreases in BAR number are induced by PMA on cell lines BW5147 and U937. These data indicate that changes in receptor number can be regulated with different states of cell maturation and function. Thus, the immunological status of a given cell can influence the expression of BARs, thereby modulating its ability to respond to signals from the nervous and endocrine sy

ISSN:0360-4012    

DOI:10.1002/jnr.490300208

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe potential of immature glial cells to differentiate into astrocytes (ASs) or oligodendrocytes (OLs) has been examined using a monoclonal antibody (007) that is specific for OLs in vivo. Cells were dissociated from 2‐day postnatal mouse cortex and labeled with the 007 antibody 2 hr after plating. The cells which were labeled during this single, brief exposure to the antibody retained the antibody on their surfaces over the course of the experiments. Cells were double stained at various timepoints for residual 007 antibody and either galactocerebroside (GC) or glial fibrillary acidic protein (GFAP). Shortly after plating, most 007 + cells were GC − and none expressed GFAP. These cells were round, although some had begun to extend very short processes. After 96 hr,>95% of cells with residual 007 on their surfaces also expressed GC. By this time, all the 007 + cells had several processes of varying lengths extending from their cell bodies. Cells expressing both 007 and GFAP were never seen. The 007 + /GC + OLs were not induced to differentiate from 007 + bipotential progenitors since they were grown in fetal calf serum. These results show that under our culture conditions the 007 antibody is OL specific. Immunostaining for bromodeoxyuridine, a marker for dividing cells, revealed that some 007 + cells were proliferating. The majority of these proliferating cells had already extended three or more processes. We therefore conclude that immature, process‐bearing cells can be committed to the OL lineage at times before they express detectable amounts of GC. Since these young 007 + OLs are actively proliferating, committed cells can serve as an important source of ne

ISSN:0360-4012    

DOI:10.1002/jnr.490300209

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

年代:1991

数据来源: WILEY

摘要:

AbstractMost previous studies on Schwann cell proliferation in vitro have used serum‐containing media. This complicates the analysis of agents required for cell division since serum contains an ill‐defined mixture of hormones and growth factors. Serum‐free medium has therefore been used to analyse the response of Schwann cell to previously identified Schwann cell mitogens.Serum factors were not necessary for DNA synthesis in response to platelet‐derived growth factor, basic fibroblast growth factor, or glial growth factor, provided they were used in combination with forskolin to elevate intracellular cAMP. Transforming growth factor β1, a Schwann cell mitogen in serum, was not mitogenic under these conditions. Neither the growth factors nor forskolin were effective when used alone. Growth control was analysed further using long‐term cultured Schwann cells that had spontaneously immortalized. Measurements of endogenous cAMP levels in short‐ and long‐term Schwann cells revealed that long‐term cells had two to three times higher basal cAMP levels. As predicted by these findings, platelet‐derived growth factor, basic fibroblast growth factor, and glial growth factor stimulated DNA synthesis in long‐term cells without requiring costimulation by agents which elevate cAMP (while transforming growth factor β1had no effect).These results show first that in rat Schwann cells activation of at least two intracellular pathways, one of which is cAMP dependent, is required for stimulation of DNA synthesis, second that serum factors are not necessary for the synergy between cAMP and platelet‐derived growth factor, basic fibroblast growth factor, or glial growth factor, and third that the mitogenic stimulation by transforming growth factor β1is more complex, requiring serum factors in addit

ISSN:0360-4012    

DOI:10.1002/jnr.490300210

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

年代:1991

数据来源: WILEY

摘要:

AbstractPrimary cultures enriched in neurons dissociated from embryonic rat cerebra were used to demonstrate that platelet activating factor and the structurally related ether glycerolipid, dodecylglycerol, are readily taken up in small amounts by neurons and that they stimulate the differentiation of neurons. The stimulation of neuronal differentiation was observed as a precocious development of axon‐like extensions which correlated with a concentration — dependent increase in neuronal‐specific enzyme activities. This stimulation of morphological and neurochemical factors by either platelet activating factor or dodecylglycerol was almost completely abolished by triazolam, a known inhibitor of platelet activating factor function. Neither platelet activating factor nor dodecylglycerol at the concentrations used to achieve stimulation of neuronal differentiation compromised the plasma membrane, as indicated by the lack of leakage of cytoplasmic lactic acid dehydrog

ISSN:0360-4012    

DOI:10.1002/jnr.490300211

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

年代:1991

数据来源: WILEY