摘要:

Abstract:In a light and electron microscopic immunocytochemical study we have examined the distribution of myelin basic protein (MBP), 2′,3′‐cyclic nucleotide 3′‐phosphodiesterase (CNP), and myelin/oligodendroglial glycoprotein (MOG) within CNS myelin sheaths and oligodendrocytes of adult Sprague–Dawley rats. Ultrastructural immunocytochemistry allowed quantitative analysis of antigen density in different myelin and oligodendrocyte zones: MBP was detectable in high density over the whole myelin sheath, but not in regions of loops, somata, or the oligodendrocyte plasma membrane. CNP reactivity was highest at the myelin/axon interface, and found in lower concentration over the outer lamellae of myelin sheaths, at the cytoplasmic face of oligodendrocyte membranes, and throughout the compact myelin. MOG was preferentially detected at the extracellular surface of myelin sheaths and oligodendrocytes and in only low amounts in the lamellae of compacted myelin and the myelin/axon border zone. Our studies, thus, indicate further the presence of different molecular domains in compact myelin, which may be functionally relevant for the integrity and maintenance of the my

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1989.tb10930.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Abstract:The previous observation that a continuous chemical depolarization of aggregating rat brain cells with KCl alters the expression of opioid receptors was examined in more detail. In contrast to its significant and converse effect on forebrain and hindbrain cells cultured in serum‐containing medium, KCl had only a small and transient effect in serum‐free cultures of both types. The basal receptor density in serum‐free cultures was similar to the receptor density in KCl‐treated serum‐containing cultures, but medium conditioned by glial cells restored partially the effect of KCl in serum‐free cultures. The effect of KCl in serum‐containing forebrain cultures was enhanced by the voltage‐dependent calcium channel blocker verapamil, and magnesium and cadmium had a similar, though smaller, effect. The sodium channel activator veratridine had a profound and dose‐dependent inhibitory effect on the expression of the receptors in forebrain and hindbrain cultures, and tetrodotoxin blocked the veratridine effect. Information about the selectivity of the effect of neuronal activation on the various opioid receptor subtypes was obtained with the neuroblastoma X glioma hybrid M8 cells that possess only δ type opioid receptors. A Scatchard analysis of [3H]etorphine binding to these cells has shown that depolarization increased theBmax, but had little, if any, effect on the affinity (KD) of the ligand to the receptors. The significance of depolarization and voltage‐dependent sodium and calcium channels on the expression of different opioid receptor s

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1989.tb10931.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Abstract:Ependymins are thought to be implicated in fundamental processes involved in plasticity of the goldfish CNS. Gas‐phase sequencing of purified ependymins β and γ revealed that they share the same N‐terminal sequence. Each sequence displays microheterogeneities at several positions. Based on the protein sequences obtained, we constructed synthetic oligonucleotides and used them as hybridization probes for screening cDNA libraries of goldfish brain. In this article we describe the full‐length sequence of a mRNA encoding a precursor of ependymins. A cleavable signal sequence characteristic of secretory proteins is located at the N‐terminal end, followed directly by the ependymin sequence. Also, two potential N‐glycosylation sites were detected. A computer search revealed that ependymins form a novel family of uniq

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1989.tb10932.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Abstract:We have examined the development of γ‐aminobutyric acidB(GABAB) receptors in rat cerebrum using a binding assay that has achieved specific binding levels of ∼50% with the GABABligand (–)‐[3H]baclofen. As early as postnatal day 1, GABABreceptors are present and are linked to both calcium‐ and guanosine triphosphate‐binding protein (G protein)‐regulatory sites, as indicated by the stimulation of binding by calcium and the inhibition of binding by the guanine nucleotide guanosine 5′‐O‐(3‐thiotriphosphate) (GTPγS). However, whereas the EC50for the calcium effect was at a mature value in the neonate, the IC50for the inhibition of binding by GTPγS was not, and declined more than two orders of magnitude by adulthood. Moreover, while many previous studies had shown that manipulation of G proteins by guanine nucleotides affects receptor affinity rather than density, our saturation analysis of binding suggests that calcium affected GABABreceptor density rather than affinity. The results therefore suggest that calcium and the manipulation of G proteins by GTPγS may affect the GABABrecepto

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1989.tb10933.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Abstract:Myelin‐associated glycoprotein (MAG) was radioactively labelled with32P both in intact brain and in myelin membrane preparations. Chemical deglycosylation of the phosphorylated products revealed that only one of the MAG isoforms (L‐MAG) is labelled in vitro. Furthermore, the phosphorylation events in vivo and in vitro are confined to the cytoplasmic portion of the L‐MAG isoform. Tryptic mapping of L‐MAG labelled both in vivo and in vitro revealed that the majority of the sites phosphorylated in intact brain are also phosphorylated in myelin membrane preparations; however, the extent of phosphorylation at individual sites is variable. The results demonstrate that partially purified myelin membrane preparations can be used to study the enzymes responsible for MAG phosphorylation and dephosphorylation events

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1989.tb10934.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Abstract:Various steroids, including glucocorticoids, were observed to exert a direct effect on the rates of translation of several myelinprotein specific transcripts in a cell‐free, reticulocyte lysate system. Hydrocortisone caused a twofold stimulation in the translation of mRNAs of myelin basic protein and proteolipid protein. It inhibited the translation of 2′,3′‐cyclic nucleotide 3′‐phosphodiesterase mRNA by 50%, and had no effect on the translation of a number of other mRNAs. The data suggest that steroid‐mediated translational regulation may serve as a novel mechanism to modulate the expression of myelin protein genes at the transl

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1989.tb10935.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Abstract:An in vitro system has been devised to study the mitogenic effect of axolemma on cultured oligodendrocytes. Addition of axolemma‐enriched fraction to cultured oligodendrocytes results in a dose‐dependent mitotic response with an 11‐fold stimulation at a membrane concentration of 200 μg/ml. The interaction between oligodendrocytes and axolemma is specific, as myelin‐enriched fraction, astrocyte membrane, and red blood cell membrane showed little or no effect on the oligodendroglial proliferation under similar conditions. In addition, cultured astrocytes were tested with the same axolemma membrane, and no mitotic stimulation was observed. The mitogenicity of AEF membrane on cultured oligodendrocytes is sensitive to heat and trypsin treatment, suggesting that the axolemma mitogen may be a

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1989.tb10936.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1989.tb10937.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1989.tb13274.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY