摘要:

AbstractThe capacity of oligodendrocytes (OLs) and their progenitors to migrate, proliferate, and differentiate in vivo was evaluated by transplanting highly enriched populations of sequential stage of the OL lineage (A2B5+O4−, O4+GalC−, and GalC+) into the telencephalon of the hypomyelinating mouse, shiverer. The shiverer mouse neither expresses the major myelin basic protein (MBP) nor makes normal myelin due to a large deletion in the gene for MBP. Thirty days after transplantation, serial 225 μm sections of the host brain were immunostained with antiserum to MBP and analyzed by confocal microscopy. The presence of MBP+patches of myelin in the otherwise MBP−host brain allowed a retrospective analysis of the myelinogenic activity of the transplanted progenitors cells. Both the extent of MBP+myelin and the location of MBP+structures relative to the initial site of cell deposition were highly dependent on the developmental stage of the transplanted cells. Specifically, A2B5+O4−OL progenitors migrated distances of ≥ 600 μm and produced MBP+patches in nearly every slice of the host brain. An average of over 250 separate patches were found per host brain, some of which had cross‐sectional areas of>250,000 μm2containing as many as 60 MBP+OL cell bodies, and with densities of myelination rivaling that of normal brain. In marked contrast, transplantation of O4+GalC−cells produced only small (1,000–25,000 μm2), scattered (25–40 per brain) patches of MBP+myelin containing one to five cell bodies, all of which were within 50 μm of the needle track or the nearest ventricular surface. GalC+cells produced MBP+myelin at a level similar to that of O4+CalC−cells. These data suggest that the developmental transition of OL progenitors from the O4−to the O4+pheno‐type is accompanied by a dramatic reduction in the innate capacity of the cells to migrate and survive in vivo. The use of developmentally identified, enriched populations of OL progenitor cells offers the opportunity for more precise analyses of transplantation and remyelination behavior, and relates to clinically relevant studies indicating that contaminant cell types can seriously interfere with the stable integration of donor tissue into the

ISSN:0360-4012    

DOI:10.1002/jnr.490340102

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe effect of a permanent transection on myelin gene expression in a regenerating sciatic nerve and in an adult sciatic nerve was compared to establish the degree of axonal control exerted upon Schwann cells in each population. First, the adult sciatic nerve was crushed, and the distal segment allowed to regenerate. At 12 days post‐crush, the sciatic nerve was transected distal to the site of crush to disrupt the Schwann cell‐axonal contacts that had reformed. Messenger RNA (mRNA) levels coding for five myelin proteins were assayed in the distal segment of the crush‐transected nerve after 9 days and were compared to corresponding levels in the distal segments of sciatic nerves at 21 days post‐crush and 21 days post‐transection using Northern blot and slot‐blot analysis. Levels of mRNAs found in the distal segment of the transected and crush‐transected nerve suggested that Schwann cells in the regenerating nerve and in the mature adult nerve are equally responsive to axonal influences. The crush‐transected model allowed the genes that were studied to be classified according to their response to Schwann cell‐axonal contact. The levels of mRNAs were (1) down‐regulated to basal levels (PO and MBP mRNAs), (2) down‐regulated to undetectable levels (myelin‐associated glycoprotein mRNAs), (3) upregulated (mRNAs encoding 2′3′‐cyclic nucleotide phosphodiesterase and β‐actin), or (4) not stringently controlled by the removal of Schwann cell‐axonal contact (proteolipid protein mRNAs). This novel experimental model has thus provided evidence that the expression of some of the important myelin genes during peripheral nerve regeneration is dependent on continuous signals from the ingro

ISSN:0360-4012    

DOI:10.1002/jnr.490340103

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

年代:1993

数据来源: WILEY

摘要:

AbstractEnteric glia, the support cells of myenteric ganglia, have been widely studied with respect to their morphology and immunohistochemical phenotype, but little is known about their functional properties. We developed a method for the amplification of enteric glia from newborn guinea pigs to further characterize these cells. Treatment with a combination of basic fibroblast growth factor and the adenylate cyclase activator, cholera toxin, permitted expansion of enteric glial cultures to confluence and serial passage for up to 8 months. The long‐term cultured cells retained expression of (1) S100 protein, (2) GD3 ganglioside recognized by the monoclonal antibody LB1, and (3) the gene encoding glutamine synthetase. The electrophysiologic properties of cultured enteric glia were studied under whole‐cell patch clamp conditions. Most cells expressed “delayed rectifier”‐type potassium currents, and some also demonstrated tetrodotoxin‐sensitive sodium currents. Other subsets of voltage‐dependent potassium currents, calcium currents, and glutamate‐gated currents were not demonstrable. © 1993

ISSN:0360-4012    

DOI:10.1002/jnr.490340104

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

年代:1993

数据来源: WILEY

摘要:

AbstractIn contrast to the central nervous system (CNS), the peripheral nervous system (PNS) displays an important regenerative ability which is dependent, at least in part, on Schwann cell properties. The mechanisms which stimulate Schwann cells to adapt their behavior after a lesion to generate adequate conditions for PNS regeneration remain unknown.In this work, we report that adult rat dorsal root ganglion (DRG) neurons are able, after a lesion performed in vivo or when they are dissociated and cultured in vitro, to synthesize transforming growth factor β (TGFβ), a pleiotropic growth factor implicated in wound healing processes and in carcinogenesis. This TGFβ is tentatively identified as the β‐1 isoform. Adult rat DRG neurons release a biologically active form of TGFβ which is able to elicit multiple Schwann cell responses including a stimulation to proliferate. Moreover, purified TGFβ‐1 produces a Schwann cell morphology alteration and decreases the secretion of tissue‐type plasminogen activator (tPA) and enhances the secretion of plasminogen activator inhibitor (PAI) by Schwann cells. This generates conditions which are thought to favor a successful neuritic regrowth. Furthermore, purified TGFβ‐1 stimulates type IV collagen mRNA expression in Schwann cells. This subtype of collagen is associated with the process of myelinization. Finally, TGFβ‐1 decreases nerve growth factor (NGF) mRNA expression by Schwann cells, an effect which could participate in the maintenance of a distoproximal NGF gradient during nerve regeneration.We propose that neuronal TGFβ plays an essential role as a neuronoglial signal that modulates the response of Schwann cells to injury and participates in the successful regeneration processes observed in the PNS. © 1

ISSN:0360-4012    

DOI:10.1002/jnr.490340105

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe distribution of alpha 1 (α1)‐adrenoceptors along the different segments of the spinal cord (cervical, thoracic, lumbar, and sacral) of normal rats has been studied by quantitative autoradiography using the specific α‐antagonist [3H]Prazosin as a ligand. In addition, the influence of noradrenergic (NA) denervation [obtained either by complete transection of the spinal cord at vertebrae level T8‐T9 or by selective lesion of NA spinal cord system carried out by intracisternal injection of 6‐hydroxydopamine (6‐OHDA)]on eventual variations of α1‐adrenoceptor density at spinal cord target cells was studied in parallel.In control rats, the quantitative analysis of α1‐adrenoceptor densities revealed a widespread distribution of these receptors along all segments of the spinal cord with a similar pattern in the various subregions of gray matter studied. This distribution of α1‐adrenoceptors was quite well correlated with the distribution of NA terminals, when referring to previous descriptions by immunohistochemistry.After 6‐OHDA lesion, as well as caudally to the transection, a significant increase of α1‐adrenoceptor densities was observed in all spinal subregions thus evidencing supersensitivity.These results suggest that NA may act in the spinal cord, at least partly, via α‐adrenoceptors and that the expression of these receptors could be influenced by NA dysfunction, as demonstrated here through the effects observed in lesioned ani

ISSN:0360-4012    

DOI:10.1002/jnr.490340106

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

年代:1993

数据来源: WILEY

摘要:

AbstractNeurons in dissociated cell culture provide a favorable system for the quantitative analysis of structural changes and the examination of structure‐function relationships during development. Fragment C of tetanus toxin was used to label neurons in murine spinal cord cell cultures and dendrite outgrowth was monitored by a number of measures. The dissociated neurons increased in morphologic complexity from approximate spheres to highly branched structures during the first week in culture. Much of the structural complexity of the dendrite arbor, as quantified by fractal dimension, was established within 48 hr after plating, i.e., prior to the development of interneuronal contacts. During the first few days in culture, dendrite branching complexity increased more rapidly than dendrite size, whereas after 4 days, fractal dimension remained relatively constant while dendrites continued to grow. Fractal analysis has provided data which suggest that the early development of dendrite branching complexity is determined intrinsically. Fractal dimension, as an effective index of morphologic complexity, should be a useful tool for the further study of extrinsic signals which might modify the generation or stabilization of dendrite form. © 1993 Wiley‐Liss,

ISSN:0360-4012    

DOI:10.1002/jnr.490340107

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

年代:1993

数据来源: WILEY

摘要:

AbstractNoninnervated regenerating muscles are able to form focal postsynaptic‐like sarcolemmal specializations either in places of the former motor endplates ( “junctional” specializations) or elsewhere along the muscle fibers (extrajunctional specializations). The triple labeling histochemical method was introduced to analyse the congruity of focalization in such specializations of 3 synaptic components: acetylcholinesterase (AChE), acetylcholine receptor (AChR), and a specific synaptic glycoprotein which bindsDolichos bifloruslectin (DBAR). Noninnervated regenerating soleus and extensor digitorum longus (EDL) muscles of the rat were examined and compared with denervated muscles of neonatal and adult rats.All junctional sarcolemmal specializations in noninnervated regenerating muscles accumulated AChE and AChR. Localization of the 2 components was identical within the limits of resolution of the method. DBAR could not be demonstrated in junctional specializations in 17‐day‐old regenerating muscles. It seems that an agrin‐like inducing substance in the former junctional basal lamina invariably triggers the accumulation of both AChE and AChR in the underlying sarcolemma of the regenerating muscle fiber. However, accumulation of DBAR would probably require the presence of the motor nerve.In most of the extrajunctional sarcolemmal specializations in 8‐day‐old regenerating soleus and EDL muscles, both AChE and AChR accumulated. However, about 10 percent of AChE accumulations lacked AChR and about 35% of AChR accumulations lacked AChE. Even greater variability was observed in 17‐day‐old regenerating muscles. The presence of DBAR in the extrajunctional postsynaptic‐like sarcolemmal specializations could not be demonstrated. Similar extrajunctional sarcolemmal specializations were observed in denervated postnatal rat muscles. About 70% contained both AChE and AChR, and 30% contained only AChR, but none contained DBAR. In denervated mature muscles, sparse extrajunctional AChR accumulations did not contain detectable amounts of AChE. The ability to form complex postsynaptic‐like sarcolemmal specializations in the absence of nerve, which is probably inherent to noninnervated immature muscle fibers, may be reduced with muscle maturation. Variable accumulation of individual components in the postsynaptic‐like specializations indicates that different triggering factors may be involved in their accumulation or, at least, the mechanisms of their accumulation can function relatively independentl

ISSN:0360-4012    

DOI:10.1002/jnr.490340108

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

年代:1993

数据来源: WILEY

摘要:

AbstractRecent studies have established that pinealocytes of the mammalian pineal gland contain marker molecules of neuroendocrine cells or paraneurons like the synaptic vesicle‐associated protein synaptophysin (p38). The objective of this study was to identify the subcellular synaptophysin‐positive compartment and to characterize in detail the intracellular distribution of this protein in rat and gerbil pinealocytes. An analysis of serial semithin sections of plastic‐embedded pineals immunostained for synaptophysin, including computer‐assisted optical density measurements of synaptophysin immunoreactivities, demonstrated unequivocally that synaptosphysin was highly concentrated in dilated process terminals of the pinealocytes. More than 75% of these process terminals were found to border or lie within the pericapillary space. At the ultrastructural level, they contained accumulations of small clear vesicles of variable size that turned out to be the site of synaptosphysin immunoreactivity when immunogold staining was performed. In addition, microvesicles surrounding synaptic ribbons were also immunolabeled. Hence, the pinealocyte is the first neuroendocrine cell type that has now been shown to concentrate synaptophysin‐positive microvesicles in perivascular process endings. This observation lends strong support to the hypothesis that small clear vesicles in neuroendocrine cells in general, and in pinealocytes in particular, serve secretory functions. The quantitative analysis of completely sectioned process endings revealed that the microvesicles outnumber by far the amount of dense core vesicles and therefore cannot arise by endocytosis of dense core vesicle membranes. Thus, small synaptic‐like vesicles probably constitute an independent secretory pathway of the paraneuronal pinealocytes.In the present study, we could also establish the absence of immunoreactivity for synapsin I (belonging to a family of neuron‐specific nerve terminal phosphorproteins) from pinealocytes. Synapsin I immunoreactivity was only detectable in intrapineal nerve terminals and varicosities. Taken together, the immunostaining patterns of the pineal gland obtained with antibodies directed against synaptic vesicle‐associated proteins render the mammalian pinealocyte a very special type of neuroendocrine cell or paraneuron rather than a “classic” neuron. ©

ISSN:0360-4012    

DOI:10.1002/jnr.490340109

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe localization of versican, a large hyaluronatebinding fibroblast proteoglycan, was studies in rat prenatal and postnatal development. In adult rat white matter and cerebellum, the distribution of versican was identical to that previously reported for brain‐specific glial hyaluronate‐binding protein (GHAP). Versican was also found in gray matter where it formed characteristic coats around large neurons. It was also found in peripheral tissues, namely, kidney medulla, myotendinous junctions, and endoneurial and endomysial sheaths. In rat embryo the most notable finding was the presence of large amounts of versican immunoreactive material in precartilaginous mesenchyma. In embryonal CNS, versican was mainly confined to the marginal zone on the surface of the cerebral hemispheres. Versican expression mainly occurred postnatally in brain and spinal cord. In spinal cord white matter, versican immunoreactivity was already present in 3‐day‐old rats and preceded the appearance of GHAP, which was first detected on day 13 after the onset of myelination. Versican expression was markedly delayed in gray matter. The characteristic perineuronal coats were first observed on day 21 in the cerebral cortex. It is concluded that, with the exception of hyaluronate, brain extracellular matrix (ECM) is mainly produced postnatally and that the ECM protein produced by brain cells, most likely astrocytes, is similar to that produced by precartilaginous mesenchyma. © 1993 Wiley

ISSN:0360-4012    

DOI:10.1002/jnr.490340110

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe salicylate trapping method was used to investigate the changes in hydroxyl radical (·OH) levels in the selectively vulnerable hippocampus compared to the cerebral cortex of gerbils subjected to a 10 min period of near complete forebrain ischemia. Salicylate‐derived 2,5‐dihydroxybenzoic acid (2,5‐DHBA) was measured in sham‐operated animals and at 1, 5, and 15 min of reperfusion. A basal level of 2,5‐DHBA was also seen in non‐ischemic gerbil brain, both in the hippocampus and cortex. The hippocampal basal level was 160% higher than in the cortex (P<.01). Treatment with the cytochrome P450 inhibitor SKF‐525A (50 mg/kg s.c. 30 min before measurement) did not affect this basal level in either hippocampus or cortex, which argues against a contribution of metabolic salicylate hydroxylation as its source. In contrast, pretreatment with the arachidonic acid cyclo‐oxygenase inhibitor ibuprofen (20 mg/kg s.c.) decreased (−68.8%) the level of salicylate hydroxylation in the hippocampus, but not the cortex. In animals subjected to 10 min of forebrain ischemia, a selective increase in 2,5‐DHBA was observed in the hippocampus at 1 min of reprerfusion which subsided by 5 min. No increase in salicylate hydroxylation was apparent in the cortex within the same time frame. The increase in ·OH in the hippocampus at 1 min of reperfusion was accompanied by a significant decrease (−15%;P<.03) in the hippocampal levels of vitamin E. No loss of vitamin E was observed in the cortex at the same time. It is hypothesized that the selective ischemic vulnerability of the hippocampus is mechanistically related to a selective post‐ischemic burst in ·OH in that region. Moreover, this may be based upon an intrinsically higher level of oxidative stress in that region as a by‐product of greater arachidonic acid turn

ISSN:0360-4012    

DOI:10.1002/jnr.490340111

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

年代:1993

数据来源: WILEY