ISSN:0022-3042    

DOI:10.1046/j.1471-4159.1995.65041431.x

出版商:Blackwell Science Ltd    

年代:1995

数据来源: WILEY

ISSN:0022-3042    

DOI:10.1046/j.1471-4159.1995.65041445.x

出版商:Blackwell Science Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract:The turnover of a CNS‐specific cell adhesion glycoprotein, ependymin, has earlier been found to increase during periods of neuronal plasticity. Here, ependymin mRNA expression was analyzed by semiquantitative in situ hybridization in goldfish. Learning of an active avoidance response resulted in a significant increase in ependymin mRNA expression 20 min to 4 h after acquisition of the task. In contrast, yoked control animals that were exposed to the same numbers of conditioned and unconditioned stimuli in a random, unpaired manner exhibited a strong down‐regulation of ependymin mRNA. Hybridization signals were also increased by injection of anti‐ependymin antiserum into brain ventricles. Ependymin mRNA was exclusively localized to reticular‐shaped fibroblasts of the inner endomeningeal cell layer. Immunoelectron microscopic investigation, however, revealed ependymin also in distinct neuronal and glial cell populations in which no ependymin mRNA had been detected. Uptake of meningeal protein factors into glial and neuronal cells may therefore be of functional importance for plastic adaptations of

ISSN:0022-3042    

DOI:10.1046/j.1471-4159.1995.65041456.x

出版商:Blackwell Science Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract:A rapid increase in ependymin mRNA expression demonstrated by semiquantitative in situ hybridization after avoidance conditioning on goldfish suggested a molecular demand for newly synthesized ependymin translation product. To inhibit de novo synthesis of ependymin molecules without interference with preexisting ones, 18 mer anti‐ependymin mRNA‐phosphorothioate oligodeoxynucleotides (S‐ODNs) were injected into the perimeningeal brain fluid before active avoidance training. S‐ODN‐injected animals learned the avoidance response; however, they were amnesic in the test. When injected into overtrained animals, S‐ODNs did not interfere with retrieval or performance of the avoidance response. Fish treated with randomized S‐ODN sequences served as further controls. Incorporation of S‐ODNs was analyzed by injection of fluorescein isothiocyanate (FITC)‐conjugated oligodeoxynucleotide probes. Microscopic observation revealed strong FITC‐S‐ODN fluorescence in reticular‐shaped fibroblasts, the only known site of ependymin synthesis. Results demonstrate that selective inhibition of ependymin gene expression in vivo can specifically prevent memory formation. We conclude that in particular the newly synthesized ependymin molecules are involved in memory consolidation, possibly because they have not yet undergone irreversible molecular changes, which have been reported of this glycoprotein in a low

ISSN:0022-3042    

DOI:10.1046/j.1471-4159.1995.65041465.x

出版商:Blackwell Science Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract:Three unique 5′ untranslated regions (UTRs) have been characterized for human microtubule‐associated protein‐2 (MAP‐2) transcripts. All three UTRs shared a common 171‐bp sequence adjacent to the MAP‐2 coding region and then diverged upstream. The size of the unique upstream sequence was 281, 146, or 104 bp. PCR of genomic DNA demonstrated that the 5′ UTRs span multiple exons. The unique region of the UTRs recognizes a 9.5‐ and a 6‐kb MAP‐2 transcript in poly(A)+mRNA isolated from human MSN cells, and PCR analysis demonstrated that each unique UTR is contained in multiple high‐ and low‐molecular‐weight MAP‐2 transcripts. Reverse transcription‐PCR (RT‐PCR) performed on MSN mRNA isolated from polysomes demonstrated that all three of the UTRs contained within multiple MAP‐2 transcripts were associated with polysomes and hence translated. RT‐PCR from human fetal spinal cord and adult brain mRNA demonstrated that all of the UTRs are expressed

ISSN:0022-3042    

DOI:10.1046/j.1471-4159.1995.65041472.x

出版商:Blackwell Science Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract:Previously, opioid peptide analogues, β‐endorphin, and synthetic opiates were found to inhibit DNA synthesis in 7‐day fetal rat brain cell aggregates via κ‐and μ‐opioid receptors. Here dynorphins and other endogenous opioid peptides were investigated for their effect on DNA synthesis in rat and guinea pig brain cell aggregates. At 1 µM, all dynorphins tested and β‐endorphin inhibited [3H]thymidine incorporation into DNA by 20–38% in 7‐day rat brain cell aggregates. The putative ε‐antagonist β‐endorphin (1–27) did not prevent the effect of β‐endorphin, suggesting that the ε‐receptor is not involved in opioid inhibition of DNA synthesis. The κ‐selective antagonist norbinaltorphimine blocked dynorphin A or B inhibition of DNA synthesis, implicating a κ‐opioid receptor. In dose‐dependency studies, dynorphin B was three orders of magnitude more potent than dynorphin A in the attenuation of thymidine incorporation, indicative of the mediation of its action by a discrete κ‐receptor subtype. The IC50value of 0.1 nMestimated for dynorphin B is in the physiological range for dynorphins in developing brain. In guinea pig brain cell aggregates, the κ‐receptor agonists U50488, U69593, and dynorphin B reduced thymidine incorporation by 40%. When 21‐day aggregates were treated with dynorphins, a 33–86% enhancement of thymidine incorporation was observed. Because both 7‐ and 21‐day aggregates correspond to stages in development when glial cell proliferation is prevalent and glia preferentially express κ‐receptors in rat brain, these findings support the hypothesis that dyno

ISSN:0022-3042    

DOI:10.1046/j.1471-4159.1995.65041481.x

出版商:Blackwell Science Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract:β‐Amyloid (Aβ) is a 39–42 amino acid that is the primary component of plaques in Alzheimer's disease (AD). Previous studies from our laboratory and others have shown that Aβ induces neurodegeneration via apoptosis in vitro, suggesting that Aβ may also initiate an apoptotic pathway of cell death in AD. Apoptosis has been suggested to proceed by a gene‐directed program in several systems. Accordingly, we have investigated whether Aβ‐mediated apoptosis is associated with the induction of genes that may regulate or play a role in cell death in vitro. Immediate early genes (IEGs) respond to cellular stimuli and participate in cellular signaling pathways. The protein products of some IEGs, e.g., c‐jun, are capable of forming dimers and acting as transcriptional regulatory proteins, and have been implicated in apoptosis in both nonneuronal and neuronal cells. In this study, we report a selective and abnormally sustained induction of c‐Jun in cultured hippocampal neurons treated with Aβ. In addition, we describe the lack of induction of c‐Jun in neurons that are relatively resistant to Aβ‐mediated toxicity, and a correspondence between immunoreactivity for c‐Jun and changes in nuclear morphology that are indicative of apoptosis. These data demonstrate that c‐Jun is induced in cultured neurons that undergo Aβ‐mediated apoptosis and suggest that c‐Jun may participate in a cell

ISSN:0022-3042    

DOI:10.1046/j.1471-4159.1995.65041487.x

出版商:Blackwell Science Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract:The signal pathway for light‐induced expression of c‐fosand the neuropeptide somatostatin (SS) in rat retinal cells was investigated. Flashing light induced c‐fosand SS mRNA in the inner nuclear layer and the ganglion cell layer. As both c‐fosand SS genes have a cyclic AMP response element (CRE) in their promoters, CRE‐binding protein (CREB) phosphorylation in retinal cells was examined with a phospho‐CREB‐specific antibody. Both flashing light and administration of the L‐type Ca2+channel activator Bay K 8644 induced phosphorylation of CREB in the nuclei of the amacrine cells and the ganglion cells where c‐fos/SS mRNAs were expressed. These cells could be double‐stained with anti‐calmodulin kinase II (anti‐CaM kinase II) monoclonal antibody and phospho‐CREB‐specific polyclonal antiserum after Bay K 8644 administration, indicating the colocalization of phosphorylated CREB at Ser133and CaM kin

ISSN:0022-3042    

DOI:10.1046/j.1471-4159.1995.65041499.x

出版商:Blackwell Science Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract:In this study we examined the effects of staurosporine, a potent inhibitor of protein kinase C (PKC), on the differentiation of C6 glial cells and on the expression and cellular distribution of specific PKC isoforms. Staurosporine reduced cell proliferation and induced distinctive changes in the morphological appearance of the cells to that characteristic of cells exhibiting astrocytic phenotypes. The differentiative effect of staurosporine was further indicated by the increased expression of two proteins related to astrocytic phenotypes, glial fibrillary acidic protein (GFAP) and glutamine synthetase. Thus, staurosporine induced a dose‐dependent increase both in GFAP immunoreactivity and in the activity and protein levels of glutamine synthetase. Staurosporine also induced a decrease in the expression of PKC‐β2and an increase in that of PKC‐γ. In addition, it induced translocation of PKC‐ε from the membrane to the cytosol, whereas no differences were observed in the distribution of the other PKC isoforms. The results of our study indicate that staurosporine induced astrocytic phenotypes in glial cells and that changes in the expression and cellular distribution of these PKC isoforms may be related to astrocytic diffe

ISSN:0022-3042    

DOI:10.1046/j.1471-4159.1995.65041505.x

出版商:Blackwell Science Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract:Cultured astroglia express both adenosine and ATP purinergic receptors that are coupled to increases in intracellular calcium concentration ([Ca2+]i). Currently, there is little evidence that such purinergic receptors exist on astrocytes in vivo. To address this issue, calcium‐sensitive fluorescent dyes were used in conjunction with confocal microscopy and immunocytochemistry to examine the responsiveness of astrocytes in acutely isolated hippocampal slices to purinergic neuroligands. Both ATP and adenosine induced dynamic increases in astrocytic [Ca2+]ithat were blocked by the adenosine receptor antagonist 8‐(p‐sulfophenyl)theophylline. The responses to adenosine were not blocked by tetrodotoxin, 8‐cyclopentyltheophylline, 8‐(3‐chlorostyryl)caffeine, dipyridamole, or removal of extracellular calcium. The P2Y‐selective agonist 2‐methylthioadenosine triphosphate was unable to induce increases in astrocytic [Ca2+]i, whereas the P2agonist adenosine 5′‐O‐(2‐thiodiphosphate) induced astrocytic responses in a low percentage of astrocytes. These results indicate that the majority of hippocampal astrocytes in situ contain P1purinergic receptors coupled to increases in [Ca2+]i, whereas a small minority appear to contain P2purinergic receptors. Furthermore, individual hippocampal astrocytes responded to adenosine, glutamate, and depolarization with increases in [Ca2+]i. The existence of both purinergic and glutamatergic receptors on individual astrocytes in situ suggests that astrocytes in vivo are able to integrate information derived from glutamate and adenosi

ISSN:0022-3042    

DOI:10.1046/j.1471-4159.1995.65041515.x

出版商:Blackwell Science Ltd    

年代:1995

数据来源: WILEY