摘要:

AbstractJanusin and tenascin are glia‐derived, structurally related, extracellular matrix glycoproteins of the J1 family that are expressed in vivo at times and in locations where active neurite outgrowth occurs, but also when the formation or stabilization of cytoarchitectonic boundaries appears to be in operation. To resolve this apparent functional dichotomy, we have studied the behavioral response of growth cones, growing in culture on the permissive substrate laminin, to janusin and tenascin, by video time lapse microscopy. When janusin and tenascin were offered as sharp substrate boundaries, dorsal root ganglion (DRG) and retinal ganglion neuron growth cones avoided growing on these molecules, but were not induced to collapse. On the other hand, when janusin and tenascin were offered, in a mixture with laminin, as uniform substrates, DRG growth cones displayed a collapsed morphology and were able to advance at a faster rate than on laminin alone. In contrast, the outgrowth of retinal ganglion neuron growth cones was completely inhibited under these conditions, underscoring a cell type specificity in the response of growth cones to these molecules. Using several monoclonal antibodies binding to distinct epitopes on the tenascin molecule, we have identified two domains responsible for growth cone repulsion, on epidermal growth factor (EGF)‐like repeats 3‐5 and fibronectin type III homologous repeats 4 and 5. These domains are different from the one previously recognized to be involved in neurite outgrowth on a uniform tenascin substrate. We conclude that both molecules may promote or retard growth cone advance, depending on the spatial expression pattern and the neuronal cell type. © 1993 Wiley‐L

ISSN:0360-4012    

DOI:10.1002/jnr.490350402

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe differentiation of skeletal muscle cells frommdxmice which lack dystrophin expression was examined after glucocorticoid treatment, namely α‐methylprednisolone (PDN). Primary skeletal muscle cell cultures were established from newbornmdx, congenic C57BL/10, and allogenic BALB/C mice. We show that PDN promotes the myogenesis of bothmdx‐ and control mice‐derived cultures as determined by (1) the number of myotubes, (2) acetylcholine receptors, and (3) dystrophin and dystrophin‐related protein levels. These results support the hypothesis that PDN could enhance the myogenesis of satellite cells and increase dystrophin‐related protein expression in DMD treated patients. © 1993 Wile

ISSN:0360-4012    

DOI:10.1002/jnr.490350403

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

年代:1993

数据来源: WILEY

摘要:

AbstractFollowing peripheral nerve injury, resident microglial cells proliferate and astrocytes undergo hypertrophy, as evidenced, e.g., by an increase in the levels of glial fibrillary acidic protein (GFAP). In a previous study we have shown that infusion of cytosine arabinoside (ARA‐C) into the rat brain blocks the axotomy‐induced proliferation of microglial cells. This experimental approach has been used in the present study in order to explore the issue of whether the reactive microglial cells are mediators of the increased GFAP expression in the hypoglossal nucleus of the rat following axotomy. Quantitative analysis of sections processed for immunocytochemistry or in situ hybridization demonstrated a marked increase in GFAP‐like immunoreactivity and GFAP‐mRNA, respectively, in the ipsilateral hypoglossal nucleus 4 and 7 days after axotomy in control experiments. These increases failed to occur in axotomized animals treated with ARA‐C. Therefore, our data are compatible with the hypothesis that activation of astrocytes following axotomy as measured by increased expression of GFAP and its mRNA is induced secondarily to the microglial response. © 1993 Wiley

ISSN:0360-4012    

DOI:10.1002/jnr.490350404

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

年代:1993

数据来源: WILEY

摘要:

AbstractMany studies provide evidence that retinoic acid (RA), an endogenous derivative of vitamin A, plays a role in the development of the nervous system. We now report that RA controls the neurotransmitter phenotype of post‐mitotic rat sympathetic neurons in cell culture. RA added to the culture medium increased the specific activity of choline acetyltransferase (ChAT) and the level of acetylcholine (ACh). Concomitantly, RA reduced the specific activities of two catecholamine synthetic enzymes, tyrosine hydroxylase (TH) and dopamine β‐hydroxylase (DBH) and the level of norepinephrine (NE). After a 2 week treatment with 5 μM RA, ChAT was increased by 5–10 fold, whereas TH and DBH were decreased by 10–15 fold and 2–3 fold, respectively, as compared to sympathetic neurons grown in the absence of RA. The modulation of the activity of the three enzymes was dose‐dependent and followed a similar time course. The decrease of TH expression was demonstrated to be due to a decreased number of TH molecules. © 1993 W

ISSN:0360-4012    

DOI:10.1002/jnr.490350405

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe C6 glial cell line has been used as a model cell system for the investigation of new glial produced neurotrophic and neurotropic molecules. By using the C6 cell line grown in a defined medium on collagen, this laboratory has isolated a distinct neurite promoting factor (NPF) that is potentiated by the presence of collagen (CPNPF). We have observed that C6 cells cultured in a defined medium on collagen (rat type‐I) slowed their growth rate and expressed an astrocytic‐ or oligodendrocytic‐like morphology. CPNPF, at this state of purity, appears to be a distinct NPF which induces neurite outgrowth (neurites of 1 or more somal diameters) in PC12 cells. These neurite promotion effects, however, appear to support the neuron morphology for only a short period (4 days) of time without the presence of neurotrophic factor (NTF). The neurite promoting activity is ineffective in inducing neurite outgrowth using mouse neuroblastoma cells (neuro‐2a). CPNPF appears to be a heat stable protein whose activity does not depend on the presence of intact collagen, heparin sulfate proteoglycan (HSPG), or chondroitin sulfate proteoglycan (CSPG). Exposure to dissociative conditions results in a loss of neurite promoting activity. CPNPF is not a glycoprotein that contains an accessible α‐D‐mannopyranosyl, α‐D‐glucopyranosyl, or a sterically related residue (hydroxyl groups in the C‐3,4, and 5 positions). Although these residues are not present on all glycoproteins, it does indicate that CPNPF is most likely not a glycoprotein. CPNPF activity is not blocked by neutralizing antibodies directed toward NGF, β‐FGF, IL‐1β, IL‐6, TGF‐β2, TGF‐β1.2, TGF‐β3, TGF‐β5, or EGF. CPNPF appears to either be oligomeric protein or a complex of proteins. On the basis of indirect evidence, it does not appear to be glial derived protease nexin‐I. The alteration in morphology of the C6 glial cell line by serum‐free conditions in the presence of collagen may have induced the production of a potentially new NPF not seen by pre

ISSN:0360-4012    

DOI:10.1002/jnr.490350406

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe possibility that cerebroside sulfates and myelin proteolipid (PLP) could be simultaneously located in transport vesicles destined to be assembled in myelin was investigated in the brain of 20 day old rats. The brain was homogenized and fractionated according to Burkart et al. (J Biol Chem257:3151–3156, 1982) to obtain a microsomal fraction that was further subfractionated in a linear sucrose density gradient following the procedure of Siegrist et al. (J Neurochem33:497–504, 1979) to obtain a vesicular fraction which has been shown to transport cerebroside sulfates (Burkart et al., as above). This fraction was associated with acid hydrolase activity and had a lipid composition different from that of myelin and microsomal fractions. Studied by slab gel electrophoresis, dot blot, and Western blot analysis, using a highly specific anti‐PLP antibody, it was found to contain myelin PLP. In view of previous findings of several laboratories including our own, the presence of myelin proteolipid in a vesicular fraction which is related to the transport of cerebroside sulfates gives further support to the hypothesis that the delivery of both constituents to the myelin membrane could be associated. © 1993 Wiley‐L

ISSN:0360-4012    

DOI:10.1002/jnr.490350407

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe effects of a neonatal dopaminergic deafferentation with the neurotoxin 6‐hydroxydopamine (6‐OHDA) on endogenous tissue levels of catecholamines, indoleamines, and amino acids were investigated in discrete rat brain regions. After producing the lesion at postnatal day 3 by intraventricular injections of 6‐OHDA, with a desipramine pretreatment to protect noradrenaline neurons, the animals were kept for 3 months. Their brains were dissected to obtain samples of neostriatum, Globus pallidus, Substantia nigra, and Raphe nuclei, which were then analyzed by high‐performance liquid chromatography, coupled either to electrochemical detection for aromatic monoamines, or to post‐column ninhydrin derivatization with spectrophotometry for amino acids. The neonatal 6‐OHDA treatment depleted dopamine (DA) levels in neostriatum, Globus pallidus, and Substantia nigra, but in Raphe nuclei DA was increased. The main metabolites of DA were also decreased in neostriatum, Globus pallidus, and Substantia nigra but remained unchanged in Raphe nuclei. Serotonin (5‐HT) and its metabolite 5‐hydroxyindole‐3‐acetic acid increased in neostriatum and Raphe nuclei; in Substantia nigra there was a slight increase in 5‐HT only. The 6‐OHDA lesion caused heterogeneous alterations in amino acid contents, which varied according to the region. In the neostriatum there were increases of γ‐aminobutyric acid (GABA), aspartic acid, and glycine. In the Globus pallidus taurine, GABA, glutamic acid, glutamine, aspartic acid, serine, and alanine were elevated. In the Substantia nigra only increases in taurine, GABA, glutamic acid, and glutamine could be documented. This study shows important changes in amino acid levels and in some of their ratios, occurring in different anatomical subdivisions of the basal ganglia and related brainstem nuclei following a neonatal treatment with 6‐OHDA. The results thus demonstrate major biochemical modifications in amino acids in the aftermath of a DA denervation and/or a 5‐HT hyperinnervation during an early developmental

ISSN:0360-4012    

DOI:10.1002/jnr.490350408

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

年代:1993

数据来源: WILEY

摘要:

AbstractNeurotrophins may have a neuroprotective role and are probably involved in the control of axonal sprouting and synaptic plasticity. An antibody raised against a pro‐sequence of nerve growth factor (NGF) was tested. In control undisturbed rats, a strong immunoreactivity was detected in scattered cells in and around the pyramidal and granule cell layer of the hippocampus and a moderate labeling was found in the reticular thalamic nucleus. In situ hybridization showed specific expression of NGF mRNA in a similar population of scattered cells in the hippocampal formation but not in the reticular thalamic nucleus. Acute epileptic seizures, induced by a convulsive dose of 50 mg/kg pentylenetetrazol (PTZ), strongly in creased NGF mRNA in neurons of the granular layer of the dentate gyrus 3 hr but not 6 hr after the injection. No change in pro‐NGF‐like immunoreactivity was observed in the hippocampus or reticular thalamic nucleus after acute seizures. Chemical kindling was induced by daily injections of subconvulsive doses (30 mg/kg) of PTZ for 4 weeks. This treatment significantly increased pro‐NGF‐like immunoreactivity in the reticular thalamic nucleus but did not affect NGF mRNA. These data strengthen a role for the reticular thalamic nucleus and NGF in PTZ kindling. © 1993 Wiley

ISSN:0360-4012    

DOI:10.1002/jnr.490350409

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

年代:1993

数据来源: WILEY

摘要:

AbstractWe have studied the behavior of Schwann cells transplanted at a distance from an induced myelin lesion of the adult mouse spinal cord. These transplanted cells were mouse Schwann cells arising from an immortalized cell line (MSC80) which expresses several Schwann cell phenotypes including the ability to produce myelin. The behavior of MSC80 cells was compared to that of purified rat Schwann cells transplanted in the same conditions. Schwann cells were labeled in vitro with the nuclear fluorochrome Hoechst 33342 and were transplanted at distances of 2‐8 mm from a lysolecithin‐induced myelin lesion in the spinal cord of shiverer and normal mice. Our results show that transplanted MSC80 cells migrated toward the lesion, in both shiverer and normal mouse spinal cord, preferentially along the ependyma, meninges, and blood vessels. They also migrated along white matter tracts but traveled a longer distance in shiverer (8 mm) than in normal (2‐3 mm) white matter. Using these different pathways, MSC80 cells arrived within the lesion of shiverer and normal mouse spinal cord at the average speed of 166 p, m/hr (8 mm/48 hr). Migration was most efficient along the ependyma and the meninges where it attained up to 250 μm/hr. Migration was much slower in white matter tracts (95 μm/hr ± 54 in the shiverer and only 38 pm/hr ± 3 in the normal mouse). We also provide evidence for the specific attraction of MSC80 cells by the lysolecithin‐induced lesion since (1) their number increased progressively with time in the lesion, and (2) MSC80 cells left their preferential pathways of migration specifically at the level of the lesion. Finally, combining the Hoechst Schwann cell labeling method with the immunohistochemical detection of the peripheral myelin protein, PO, we show that some of the MSC80 cells which have reached the lesion participate in myelin repair in both shiverer and normal lesioned mouse spinal cord. A series of control experiments performed with rat Schwann cells indicate that the migrating behavior of transplanted MSC80 cells was identical to that of purified but non‐immortalized rat Schwann cells. © 1993 W

ISSN:0360-4012    

DOI:10.1002/jnr.490350410

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

年代:1993

数据来源: WILEY

摘要:

AbstractAbnormally phosphorylated tau protein is a major component of the cytoskeletal pathology of Alzheimer's disease (AD) found in the neurofibrillary tangle (NFT) and neuritic plaque (NP). Identification of the kinase responsible for this phosphorylation has been difficult. In the test tube, several proline‐directed kinases, particularly mitogen‐activated protein (MAP) and cdc2 kinase, phosphorylate tau on sites that appear to mimic the abnormally phosphcrylated sites in AD. Important unanswered issues include: (1) whether this phosphorylation event occurs in the tightly regulated environment of a living cell; (2) whether this phosphorylation of tau affects its functional properties; and (3) what is the subcellular relationship of proline‐directed kinases and tau. We show here that tau can be phosphorylated in cultured hippocampal neurons by the MAP kinase p44mpkand phosphorylation of tau compromises its functional ability to assemble microtubules. We show further that MAP kinase copurifies with microtubule fractions where it is tyrosine phosphorylated and presumably active. These studies address and raise several important issues regarding the regulation of tau phosphorylation in normal and AD brain. © 1993 Wiley‐L

ISSN:0360-4012    

DOI:10.1002/jnr.490350411

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

年代:1993

数据来源: WILEY