摘要:

AbstractImmunocytochemistry was used to establish the cellular localization of choline acetyltransferase [ChAT] throughout the rostrocaudal portions of the nuclei of the solitary tracts [NTS]in rat brain. By light microscopy, two distinct populations of ChAT‐positive cells were identified. The first consisted of relatively few, medium‐sized neurons located in the caudal one‐half of the medial NTS just dorsal to the dorsal motor nucleus of the vagus. The second population of ChAT‐labeled neurons was located more anteriorly and surrounded the medial and dorsal borders of the tractus solitarius. These cells were more abundant and smaller diameter than those located more caudally. Thick, non‐varicose processes with the light microscopic characteristics of dendrites also were selectively labeled for ChAT. A few of these processes were located near or were continuous with the labeled perikarya of the NTS. However, the vast majority of the immunoreactive processes could be traced from ChAT‐labeled perikarya in the ventrally adjacent dorsal motor nucleus of the vagus. These dorsally directed dendrites aborized extensively throughout the NTS, but they were densest in the rostral two‐thirds of the nucleus. Caudally, the labeled dendrites coursed horizontally, forming a commissure‐like structure between the two vagal motor nuclei.Electron microscopy confirmed the perikaryal and dendritic localization of ChAT in the NTS. The perikarya were characterized by dense peroxidase immunoreactivity throughout the cytoplasm, infolded nuclear membranes, and somatic synapses. The labeled dendritic profiles also were intensely immunoreactive and received synaptic input from unlabeled terminals. The unlabeled afferents to somata and dendrites contained large populations of small clear vesicles. The abundance of cholinergic dendrites and relative sparsity or absence of identified cholinergic axons suggests that the release of acetylcholine from dendrites of intrinsic neurons or from dendrites of neurons located within the dorsal motor nucleus of the vagus may be important for cholinergic modulation of visceral functions

ISSN:0360-4012    

DOI:10.1002/jnr.490200302

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

年代:1988

数据来源: WILEY

摘要:

AbstractRecent studies suggest that heterotypic cell‐cell interactions influence gliogenesis in the developing rat central nervous system. CNS neuron‐derived factors have been hypothesized to exist, and several have been identified and partially characterized which affect the number of oligodendrocytes in vitro. In order to study further the role of neurons in gliogenesis, we have used serumfree culture conditions, the B104 CNS neuronal cell line as a source of soluble factors, and dissociated neonatal rat brain cells as a source of glial cells. We have analyzed the response of the glial cells to serum‐free B104 conditioned medium using morphological, immunocytochemical, autoradiographic, and enzymatic methods. Dose‐dependent increases in the number of morphologically identified oligodendrocytes occur in response to this conditioned medium. Galactocerebroside (GalC) is a specific marker for oligodendrocytes, and the A2B5 antigen marks bipotential glial progenitor cells and their progeny: immature oligodendrocytes and type 2 astrocytes. In the presence of conditioned medium, the number of cells expressing GalC and/or A2B5 antigen increases over time when measured at 4, 8, and 12 days in vitro. A significantly weaker effect is seen if serum is also present. Since the vast majority of A2B5‐positive cells in conditioned medium treated cultures lack glial fibrillary acidic protein (GFA), indicative of type 2 astrocytes, they represent glial progenitors and immature oligodendrocytes. Double immunostaining combined with autoradiography suggests that the latter cell types are the target cells for the oligodendrocyte‐promoting activity. In addition, the conditioned medium markedly increases 2′,3′ cyclic nucleotide 3′‐phosphodiesterase (an oligodendrocyte marker) and to a lesser extent enhances glutamine synthetase activity (an astrocyte marker). Type 1 astrocytes are also more morphologically differentiated in this condition, and their percentage is decreased simulataneously. Conditioned medium from other donor neural cells either has no activity or is much less effective than B104 conditioned medium. The active factors are soluble, sensitive to both trypsin and 100°C treatment for 20 min, and appear to be 30–100 kilodaltons by stirred cell ultrafiltration. In summary, we have identified a potent source of growith‐stimulating factors that produce increased numbers of glial progenitor cells and oligodendrocytes; the same conditioned medium also appears to inhibit type 1

ISSN:0360-4012    

DOI:10.1002/jnr.490200303

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe neural cell adhesion molecule (NCAM) is thought to mediate cell–cell adhesion by a homophilic mechanism involving binding sites located in the N‐terminal region of the protein. This region of the molecule consists of five domains that are homologous to each other and share conserved residues with immunoglobulin domains. We report here secondary structure predictions for the five NCAM domains and three‐dimensional models for two of them. The results are entirely consistent with an immunoglobulin‐like folding of the NCAM domains into seven strands forming two b̃‐sheets. NCAM–NCAM binding may thus be analogous to the pairwise associations of immunoglobulin constant domains, which are involved in dimer formation. Insertions and deletions are located mostly in b̃‐turn regions. Two α‐helical regions in the third and fourth domain are predicted with high probability. NCAM bears two kinds of functionally important sugar side chains, sialic acid polymers in the fifth domain, which modulate NCAM binding, and the L2 moiety, which is involved in cell adhesion and can be assigned to the third domain. Three‐dimensional modelling of the corresponding domains indicates that two of the three sites for N‐linked glycosylation in the fifth and the single site in the third domain are located on he face of the domain, which in immunoglobulin contant regions engages in inter

ISSN:0360-4012    

DOI:10.1002/jnr.490200304

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

年代:1988

数据来源: WILEY

摘要:

AbstractGD3is a major ganglioside of the immature vertebrate CNS, and its expression is suggested to be characteristic of immature neuroectodermal cells. Using immunocytochemistry on cryostat sections of developing rat cerebellum with a monoclonal antibody specific for GD3, we have found that GD3begins to be expressed on the plasma membrane of Purkinje cell bodies and dendrites beginning at postnatal day 7. Staining became brighter as the dendritic tree of the cells enlarged. As the Purkinje cells began to mature in different folia, they became GD3+, until by 15 days postnatal all Purkinje cells were GD3+. Positive staining of the dendritic tree was still present in the adult cerebellum. Using a monoclonal antibody 7–8D2, which recognizes cerebellar granule cells and their axons (the parallel fibres), and polyclonal antibodies against a synaptic vesicle component synaptophysin, double‐immunofluorescence staining together with anti‐GD3antibodies suggested that the appearance of GD3immunoreactivity did not correlate either with the ingrowth of parallel fibres or the presence of their synapses on Purkinje cell dendrites. However, comparison with earlier morphological studies showed that the appearance of GD3immunoreactivity correlated well with the formation of climbing fibre synapses on Purkinje cell dendrites and the onset of the rapid expansion of the dendritic tree. These results are in keeping with the idea that elevated GD3concentrations are found in certain cell types during periods of rapid growth or high metabolic activity but also show that this is not only restricted to immature

ISSN:0360-4012    

DOI:10.1002/jnr.490200305

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

年代:1988

数据来源: WILEY

摘要:

AbstractWe have developed a silicone nerve regeneration chamber that is partitioned into two compartments by a strip of nitrocellulose paper. The modified two‐compartment chamber allows the investigation of the effects on rat sciatic nerve regeneration of trophic or growth factors that are initially bound to the nitrocellulose partition. In this study we compared the effects of untreated nitrocellulose, a siliconized nitrocellulose strip, and a strip that had been soaked in a basic fibroblast growth factor (FGF) solution. FGF is a known angiogenic factor and a mitogen for endothelial cells, fibroblasts, and Schwann cells. All of these cell types are present in the peripheral nerve. In vitro analyses, using 3T3 cells as test cells, showed that some of the bound FGF remained active on the nitrocellulose paper for at least 8–10 days. In vivo experiments, examined at 16 days post‐implantation, revealed that spatial migration of all cellular elements (perineurial‐like cells, vasculature, and Schwann cells) across the chamber gap was slower with untreated nitrocellulose strips than with siliconized strips but was most advanced with FGF‐treated ones. Most striking was the well‐developed vascular arborization of the regenerate within the FGF chambers. Histologic sections from the proximal one‐half of the chamber revealed that the regenerate in untreated strip chambers consisted of fibrin matrix and erythrocytes, whereas a welldeveloped structure with all the cellular elements of a regenerating nerve was seen in several of the FGF strip chambers. We conclude that FGF stimulates peripheral nerve regeneration

ISSN:0360-4012    

DOI:10.1002/jnr.490200306

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe present study examined the cellular mechanisms underlying the generation of neuroarchitecture. IdentifiedHelisomaneurons in isolated cell culture normally require factors present in brain‐conditioned medium (CM) in order to display the different components of neurite outgrowth (sprouting, elongation, branching, and growth cone motility), which ultimately determine their overall architecture. We report here that cell calcium and cell‐substrate interactions can play quite specific roles in the regulation of these different components of neuronal outgrowth. CM‐induced neurite outgrowth was inhibited by calcium ionophore A23187. In the absence of CM the calcium channel blocker La3+(10μM) reduced intracellular calcium levels and induced neurite sprouting and elongation; growth cone motility and branching were greatly reduced in the La3+‐induced neurites. Neurons plated into an environment containing La3+and a fibronectin substrate exhibited all of the components of neuronal outgrowth normally seen in response to CM. Fibronectin alone had little outgrowthpromoting activity. Neurite elongation rates and branching were increased by exposure to La3+in neurons on either a CM or fibronectin substrate. The neurons growing on CM or fibronectin whose outgrowth was accelerated by La3+elaborated neuritic arbors that differed from those of neurons grown in resposne to CM; differences were seen in neurite length, area of outgrowth, branching frequency, and varicosity numbers. Taken together, these results indicate that (1) calcium and the growth substrate can exert specific effects on neurite sprouting, elongation, growth cone motility, and branching; (2) appropriate levels of activation of these two sytems can elicit neurite outgrowth that closely resembles that induced by endogenous growth factors; (3) both the differential expression of the separate components of outgrowth and the kinetics of outgrowth determine a neuron' mo

ISSN:0360-4012    

DOI:10.1002/jnr.490200307

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe association of several phosphoproteins with the synaptosomal plasma membrane (SPM) was investigated by phosphorylating SPM fractions from neonatal rat brain in the presence of Ca2+and then exposing these to a variety of agents. Extraction of the major acidic phosphoproteins, GAP‐43, pp40, and pp80, was assessed by two‐dimensional gel electrophoresis and fluorography. All three proteins were best extracted from the membrane by high pH and by guanidine hydrochloride. GAP‐43 was not extracted in the presence of either low‐or high‐ionic‐strength buffers, reducing agents, or chelating agents; pp80 and pp40, however, showed a significant extraction even under low‐ionic‐strength conditions. Partition experiments with Triton X‐114 revealed an amphiphilic behavior for GAP‐43 and a strong affinity for hydrophobic environments for pp80 and pp40. None of the phosphoproteins was released from the membrane by the use of a phosphatidylinositol‐specific phospholipase C. The extraction properties of GAP‐43, pp80, and pp40 are similar to those of known extrinsic membrane proteins and therefore suggest that these phosphoproteins are peripheral rather than integral to t

ISSN:0360-4012    

DOI:10.1002/jnr.490200308

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe activity of calcium‐activated neutral proteinase (mMCANP) was determined in subcellular fractions of rat brain. The CANP activity in whole homogenate and its membrane fractions including myelin was increased tenfold following treatment with Triton X‐100. The majority of the activity (60%) was in the primary particulate fractions P1(nuclear), P2(mitochondrial), and P3(microsomal). Following subfractionation of each particulate fraction, most of the activity (50%) was found in the myelin‐enriched fractions (P1A, P2A, and P3A) and separated at the interface of 0.32–0.85 M sucrose. Only 20–30% of the total homogenate activity was in cytosol. The enrichment in the myelin fractions resembled that for 2′, 3′‐cyclic nucleotide 3′‐phosphohydrolase (CNPase) activity.Immunoblotting revealed that the CANP was mainly in myelin and cytosol. In addition to the presence of 72–76 Kd and 80 Kd bands, there were faint highmolecular‐weight CANP bands ranging from 110–150 Kd and lower‐molecular‐weight forms in the region of 30–50 Kd in both purified myelin and cytosol. These studies suggested that CANP is present in myelin and cytosol and that it exists in the brain in

ISSN:0360-4012    

DOI:10.1002/jnr.490200309

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

年代:1988

数据来源: WILEY

摘要:

AbstractMonoclonal antibody mabQ113 recognizes a 120‐kilodalton polypeptide which, in the cerebellar cortex, is confined exclusively to a subset of Purkinje cells which are organized in parasagittal bands (Hawkes et al.:Brain Research333:359–365, 1985). In all other areas of the adult rat brain examined the localization of the mabQ113 epitope was marked by regional neuronal and glial coexpression (Plioplys and Hawkes:Brain Research375:1–12, 1986).Similar neuronal‐glial co‐expression was characteristic of the adult rat cerebral cortex. Intriguingly, mabQ113 revealed a unique differential sublamination of layer I. In the neocortex, layer I was split into two sublayers, with the more superficial sublayer weakly stained and the deeper sublayer stained more intensely, whereas in the pyriform cortex, layer I was split into three. These sublaminations do not correspond to previously described subdivisions of layer I.In the developing cortex, the mabQ113 epitope is found in radial glial fibers. Stained radial fibers are first seen beginning at E17, reach a maximum at P4 and finally disappear between P12 and P14. The laminar distribution of mabQ113‐immunoreactivity emerges earlier in the pyriform cortex than the neocortex: the sublamination of layer I is seen at P4 in the pyriform cortex but not until P8 in the neocortex.The significance of these observations i

ISSN:0360-4012    

DOI:10.1002/jnr.490200310

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

年代:1988

数据来源: WILEY

摘要:

AbstractIn a previous work we found that the activity of glutamate decarboxylase (GAD), the enzyme responsible for the synthesis of the inhibitory neurotransmitter γ‐aminobutyric acid (GABA), is decreased in comatose cirrhotic rats after chronic treatment with CCl4. In the present report we studied the participation of pyridoxal phosphate in the inhibition of GAD, as well as the concentration of this coenzyme and the activity of its synthesizing enzyme, pyridoxal kinase, in the brain of the cirrhotic rats. Furthermore, cirrhotic animals were treated with three inhibitors of GAD, and the effects of such treatment were compared to those of ammonium. Liver failure resulted in a 25% inhibition of GAD activity when measured in the absence of added pyridoxal phosphate. Treatment with the GAD inhibitors thiosemicarbazide or 3‐mercaptopropionic acid enhanced this inhibition and produced convulsions at a dose that had no behavioral effects in control rats. Treatment with ammonia resulted in a comatose state and in a 25–40% inhibition of GAD. Both pyridoxal kinase activity and pyridoxal phosphate levels were found to be decreased by 15–20% in the brain of the cirrhotic rats. We concluded that chronic liver failure results in a decreased pyridoxal phosphate and GABA synthesis in brain, with a consequent diminished efficiency of GA‐BAergic neurotransmission; these effects are probably related to the manifestations of neuronal hyperexcitability that are frequently seen in human hepatic ence

ISSN:0360-4012    

DOI:10.1002/jnr.490200311

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

年代:1988

数据来源: WILEY