摘要:

AbstractThe methylation status of a 4.4‐kb 5′ end of the myelin‐associated glycoprotein (MAG) gene was assessed in cells with different levels of transcriptional activity of the gene, i.e., liver, brain, O‐2A oligodendrocyte precursors cells, mature oligodendrocytes, and glioma C6 cells. Purified DNA was digested with methylation‐sensitive restriction enzymes, and the cuts were mapped by the indirect end‐labeling technique. The restriction sites within the 4.4‐kb fragment revealed a highly heterogenous methylation pattern among cells and tissues, and liver DNA was the most heavily methylated. Most of the restriction sites were partly demethylated in the nervous system cells. Notably, two adjacent Hha1 sites at +94 and +96 were fully methylated in liver, but partially demethylated in the brain, OL, and O2A. Two Hpa2 site located at −1836 and at −39 were progressively demethylated in oligodendrocyte lineage cells, indicating specific hypomethylation associated with the oligodendrocytic differentiation. Most of the restriction sites were weakly methylated in the DNA from neoplastic C6 cells, although the Hha1 sites were fully methylated. No clear‐cut correlation between the extent of CpG dinucleotide methylation and the chromatin conformation was found. For example, out of four heavily methylated sites only two comapped with MNase hypersensitive sites. Also, the −1836 Hpa2 site whose demethylation is concomitant with oligodendrocytic differentiation seems to be localized within precisely positioned nucleosomal arrays of the MAG gene chromatin.The results indicate that the MAG gene undergoes progressive demethylation concomitant with the oligodendrocyte differentiation/maturation. However, certain CpG dinucleotides remain heavily methylated even in the fully active gene in mature oligodendrocytes, indicating that they may be essential in maintaining proper chromatin structure.

ISSN:0360-4012    

DOI:10.1002/jnr.490390302

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

年代:1994

数据来源: WILEY

摘要:

AbstractIn nasal chemosensory systems, glandular proteins associated with the vomeronasal and olfactory epithelia perform specific perireceptor functions associated with sensory transduction. Vomeromodulin, a recently identified glycoprotein synthesized by the lateral nasal glands, is proposed to be a pheromone transporter (Khew‐Goodall et al.,FASEB J5:2976–2982, 1991). In our study, we have investigated its expression in vomeronasal, olfactory, and respiratory nasal mucosae of rats and humans using in situ hybridization and immunocytochemical techniques. In the rat, vomeromodulin mRNA and protein were localized abundantly in the glandular acini of the maxillary sinus component of the lateral nasal glands. In addition, the vomeronasal and posterior glands of the nasal septum also expressed vomeromodulin mRNA and protein. Vomeromodulin immunoreactivity was localized extracellularly in the mucus of the sensory and non‐sensory epithelia of the vomeronasal organ, and in the mucociliary complex of the olfactory, respiratory, and associated nasal epithelia. In human nasal mucosae, vomeromodulin immunoreactivity was localized in the mucociliary complex of the vomeronasal and respiratory epithelia. Comparison of the localization of vomeromodulin with that of odorantbinding protein, which is also synthesized in the lateral nasal glands of rats, revealed that odorant‐binding protein was expressed in a completely separate glandular region, namely the ventral component. In the septal glands, vomeromodulin was expressed in the posterior glands whereas odorant‐binding protein was localized in the anterior glands. Odorant‐binding protein immunoreactivity was not observed in the vomeronasal glands. In contrast, both proteins were localized in the mucus of vomeronasal, olfactory, and respiratory epithelia. Our results suggest that vomeromodulin, like odorant‐binding protein, functions as a chemosensory stimulus transporter associated with perireceptor processes in vomeronasal and olfactory transduction. Copyright © 1994 W

ISSN:0360-4012    

DOI:10.1002/jnr.490390303

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

年代:1994

数据来源: WILEY

摘要:

AbstractPhenotypic expression and proliferative capacity of the cells of oligodendrocyte lineage were investigated in primary cultures isolated from fetal human brains of 12–15 weeks' gestation using double immunolabeling with Ranscht‐monoclonal antibody (R‐mAb) or O4 and antibromodeoxyuridine (BrdU) antibody. Cultured cells of oligodendrocyte lineage consisted of a major population of R‐mAb+O4−cells and minor populations of R‐mAb−O4+and R‐mAb+O4+cells. Most of the R‐mAb+O4−cells exhibited a uni‐, bi‐, or tripolar immature morphology, while the majority of the R‐mAb+O4+cells exhibited a multipolar mature morphology. R‐mAb−O4+cells contained a mixture of immature and mature cell types. When incubated in serum‐free culture medium containing BrdU for 4 days, 42% of total oligodendrocytes expressed nuclear BrdU immunolabeling. R‐mAb+cells exhibited a higher degree of BrdU immunolabeling, indicating that they have greater capacities for proliferation than O4+cells. The large majority of BrdU+cells exhibited an immature morphology. Inclusion of insulin, insulin‐like growth factor (IGF)‐I, basic fibroblast growth factor (bFGF), or fetal bovine serum in culture medium did not stimulate proliferation of oligodendrocytes, while platelet‐derived growth factor (PDGF) of PDGF plus bFGF increased the number of R‐mAb+BrdU+and O4+BrdU+cells over control, even though the results were not statistically significant. In addition, insulin and IGF‐I induced a 3‐fold increase in the number of R‐mAb+O4+cells, indicating that they promoted differentiation of oligodendrocytes. The present study indicates that fetal human oligodendrocytes in culture exhibit a considerable degree of proliferative capacity without requirement of exogenous growth factors and that both insulin and IGF‐I prom

ISSN:0360-4012    

DOI:10.1002/jnr.490390304

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

年代:1994

数据来源: WILEY

摘要:

AbstractMyelin gene expression in normal oligodendrocytes (OLG) depends on developmentally regulated protein kinase C (PKC) enzyme activity (Asotra and Macklin: J Neurosci Res 34:571–588, 1993). We studied the developmental expression of the Ca++‐dependent PKC‐α, ‐βI, ‐βIIand ‐γ isozymes, and the Ca++‐independent PKC‐δ, ‐ϵ, ‐ζ and ‐η isozymes in enriched rat brain OLG cultures. In A2B5+O‐2A progenitors, only PKC‐δ, PKC‐ϵ and PKC‐ζ were detected immunocytochemically. In 04+proligondendrocytes, PKC‐βI, ‐δ and ‐ζ were expressed moderately and low levels of PKC‐α and ‐ϵ were detected. GD3+OLG, GC+OLG and MBP+OLG showed increased levels of PKC‐α, ‐βI, ‐δ and ‐ζ isozymes. PKC‐βII, ‐γ and ‐η were poorly expressed in OLG. On immunoblots, PKC‐α was present early and increased continually up to 18 days but PKC‐βIincreased until 12 days in cultured OLG. High levels of PKC‐δ, PKC‐ϵ and PKC‐η, the most abundant PKC isozymes in OLG, were maintained up to 12 days and were then slightly reduced. Interestingly, relatively high levels of PKC‐α, PKC‐βI, PKC‐βII, PKC‐γ and PKC‐ϵ isozymes were detected in purified myelin membrane although greater levels of PKC‐δ were found in OLG than in purified myelin. Thus, most of the PKC isozymes found in cultured OLG were also present in myelin, although at different levels. Treatment with 50 nM 4β‐phorbol‐12,13‐dibutyrate (PDB) caused a delayed downregulation of PKC‐δ levels after 8 hr without modulating the expression of other PKC isozymes in 1‐day OLG; in the 3‐day‐old and 6‐day‐old OLG, PDB downmodulated PKC‐βI, ‐δ and ϵ isozymes with only a minor effect on PKC‐α and no reduction in PKC‐ζ. Induction or downmodulation of individual PKC isozymes by phorbol esters appears to depend on the differentiation state of OLG. These data suggest that PKC‐βI, ‐δ and ‐ϵ isozymes have an important function in different cellular events of OLG differentiation. We conclude that the PKC‐dependent modulation of myelin gene expression in OLG results predominantly from the Ca++‐dependent PKC‐βIisozyme activity and the Ca++‐independent PKC‐δ and PKC‐ϵ activities in a cell differentiation state‐dependent manner. Because of continuous presence of PKC‐ζ isozyme in all the

ISSN:0360-4012    

DOI:10.1002/jnr.490390305

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

年代:1994

数据来源: WILEY

摘要:

AbstractWe have already shown that alkylcatechol markedly enhances synthesis/secretion of nerve growth factor (NGF) in cultured mouse fibroblasts and astroglial cells through immediate accumulation of NGF mRNA and that the stimulatory effect of alkylcatechol on NGF synthesis/secretion is synergistically enhanced by the coadministration of phorbol 12‐myristate 13‐acetate (PMA). The stimulatory effect on NGF mRNA expression of astroglial cells in culture by 4‐methylcatechol (MC), an alkylcatechol, and/or PMA was blocked by treatment of the cells with cycloheximide, suggesting de novo synthesis of some cellular protein(s) is essential for the observed increase in the NGF mRNA level. The exposure to MC and/or PMA caused a rapid increase in c‐fosmRNA content, which was immediately followed by an increase in c‐junmRNA, prior to NGF mRNA elevation. The expression of c‐fosmRNA was transiently enhanced in all cases of the treatment with MC and/or PMA. The c‐junmRNA expression was also observed transiently when the cells were treated with PMA alone, while the expression of c‐junmRNA was pronounced and long‐lasting after the treatment with MC, which was much further enhanced by the coadministration of PMA. The result that the profile of the change in c‐junmRNA expression resembled that in NGF mRNA expression suggests that the increase in c‐junmRNA is responsible for the subsequent increase in NGF mRNA after MC treatment. The cotransfection of mouse astroglial cells with expression plasmids of c‐fosand/or c‐junand NGF promoter gene showed that simultaneous expression of both c‐fosand c‐jungenes was necessary to enhance NGF promoter activity. These results suggest that alkylcatechol induces NGF mRNA by means of transient induction of c‐fosmRNA and long‐lasting induction of

ISSN:0360-4012    

DOI:10.1002/jnr.490390306

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

年代:1994

数据来源: WILEY

摘要:

AbstractUnilateral combined transections of the fimbriafornix and angular bundle in adult Fischer 344 rats were used to study the effects of deafferentation on hippocampal expression of calretinin, calbindin D‐28k, and parvalbumin. Reflecting the widespread degeneration of synaptic contacts, immunostaining for glial fibrillary acidic protein 6 days after the lesions was increased in lacunosum‐molecular and oriens layers of CA1, 2, and 3 in ipsi‐ and contralateral hippocampus and in the ipsilateral dentate gyrus outer molecular layer. At 21 days the immunoreactivity had decreased to control levels except for a still slightly increased signal in the oriens layer of CA1‐3. At 6 and 21 days after the combined lesions the numbers of hippocampal neurons containing calretinin, parvalbumin, and calbindin D‐28k was unaltered. The combined lesions abolished calretinin containing terminals in the dentate gyrus inner molecular layer on the deafferentated side. This could be reproduced by single unilateral fimbria‐fornix transections, suggesting that the axons of these calretinin positive terminals project to the hippocampus through the fimbria‐fornix. The most likely origin of the calretinin positive terminals are neurons in the supramammillary hypothalamic nucleus. Our findings demonstrate that the extensive lesion‐induced synaptic rearrangements in the adult hippocampus do not induce degeneration of hippocampal neurons expressing calretinin, calbindin D‐28k, and parvalbumin, but do remove calretinin containing terminals which reach their targets in the hippocampus through the fimbria‐fornix. ©

ISSN:0360-4012    

DOI:10.1002/jnr.490390307

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

年代:1994

数据来源: WILEY

摘要:

AbstractDissociated septal and hippocampal neurons from E18 fetal rats were cultured with varying concentrations of ethanol (0.6–2.4 g/dl) and in cultures containing ethanol plus nerve growth factor (NGF) or basic fibroblast growth factor (bFGF). These substances have been shown to provide neurotrophic support for these populations and to afford neuroprotection against certain toxic substances or conditions applied to some neuronal populations. Both the septal and hippocampal neurons responded to ethanol in a dosedependent manner. Survival of septal neurons was generally unaffected by initial ethanol concentrations of 0.6 and 1.2 g/dl but was considerably impaired by higher concentrations (1.8 and 2.4 g/dl), while neurite outgrowth was compromised by all ethanol concentrations except the lowest one applied. The hippocampal neurons survived ethanol concentrations up to 2.4 g/dl, although process extension was decreased in concentrations of 1.2 g/dl and higher. NGF or bFGF in the culture medium (in cultures without ethanol) did not affect neuronal survival or process outgrowth in either population, probably owing to the relatively high plating densities of the cultures. NGF did tend to have a moderate ameliorative effect on the ethanol neurotoxicity in the septal cultures, however, and was slightly effective in this regard in hippocampal cultures at intermediate ethanol concentrations (1.8 g/dl). High concentrations of ethanol (2.4 g/dl) reduced the proportion of cholinergic cells in the septal preparations by approximately 50%. This neuronal loss could be reversed by inclusion of high concentrations of NGF in the culture medium (100 ng/ml) but not by a lower concentration (20 ng/ml). bFGF provided some protection against ethanol cytotoxicity with respect to both populations. The implications of these results for studies of fetal alcohol effects are discussed, as well as their relation to prior reports of trophic factor neuroprotection. © 1994 Wiley‐Liss,

ISSN:0360-4012    

DOI:10.1002/jnr.490390308

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe distribution of alpha 2 (α2)‐adrenoceptors along cervical, thoracic, lumbar, and sacral segments of the spinal cord of normal rats has been studied by quantitative autoradiography using the specific α2‐antagonist [3H]rauwolscine 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 α2‐adrenoceptor density at spinal cord target cells was studied in parallel.In control rats, the quantitative analysis of α2‐adrenoceptor densities revealed the presence of these receptors throughout the whole gray matter with a preferential location in the superficial dorsal horn. This pattern was the same at all rostro‐caudal levels of the cord and appeared very well correlated with the distribution of NA terminals revealed by immunohistochemistry, particularly in the supeficial layers of the dorsal horn.After total transection of the spinal cord (caudally to the section) and 6‐OHDA‐induced lesion, an increase of α2‐adrenoceptor density was mainly observed within the distal dorsal horn thus evidencing supersensitivity in this area, while modifications were not detectable in other regions of the spinal gray matter, except at the lumbar level where other dorsal, central, and intermediate zones were significantly enrich

ISSN:0360-4012    

DOI:10.1002/jnr.490390309

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe inhibitor preparation of the UDP‐N‐acetylgalactosamine: GM3, N‐acetylgalactosaminyltransferase (EC 2.4.1.92) (GalNAc‐T) produces effects on the neurons and the glial (astrocytes) cells of the cerebrum in culture. The effect in culture is evidenced by aneuritogenesis, deficiency in the GalNAc‐T activity, and decrease in the content of gangliosides, proteins, and lipids. In isolated glial cells the effect is evidenced by cytoplasm vesiculation and premature cessation of proliferation compared with control culture. The pattern of gangliosides in the inhibited culture shows a decrease in the amount of GD1a with respect to GD3; this is compatible with the notion that the effect is due to an inhibitor of the GM2 synthase. The inhibitor effects are reverted when it is eliminated after 24 or 48 hr in the culture medium. © 1994 Wiley

ISSN:0360-4012    

DOI:10.1002/jnr.490390310

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

年代:1994

数据来源: WILEY

摘要:

AbstractNerve growth factor (NGF), in addition to being a neurotrophic substance, has effects on the endocrine and immune systems. For example, intravenous injection of NGF results in a cascade of events leading to an increase in glucocorticoid secretion. While this response appears to be mediated centrally, there has been no evidence that circulating NGF has access to the CNS. Using intravenous injections of125I‐NGF, we find specific uptake at 1 hr but none at 6 hr, into homogenates of the basal forebrain, cerebellum, frontal cortex, hippocampus, and olfactory bulb. By autoradiography, uptake is localized to circumventricular organs, deep layers of the cerebellum, and all layers of the hippocampal region CA1, but not the dentate gyrus. Thus, uptake of blood‐borne NGF could affect the hypothalamic‐pituitary‐adrenal axis via binding to NGF receptors present in the hippocampus. However, the sources of endogenous NGF, the mechanism of access through the blood‐brain barrier, the eventual fate of NGF entering from the blood, and the physiological significance of this uptake remain to be elucidated. © 1994 Wiley

ISSN:0360-4012    

DOI:10.1002/jnr.490390311

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

年代:1994

数据来源: WILEY