摘要:

Basic fibroblast growth factor (bFGF) is a multifunctional protein that stimulates proliferation, migration and differentiation of various cell types of the mammalian brain. In rat astrocyte cell cultures bFGF stimulates DNA synthesis after exogenous addition. This article will focus on the endogenous pathway of bFGF in rat astrocytes in cell cultures. After a single administration of bFGF antisense phosphorothioate oligodeoxynucleotide (PTO) a significant inhibition of DNA synthesis was observed. A control oligodeoxynucleotide does not inhibit DNA synthesis, while specific antisense c-myc PTO did inhibit DNA synthesis. Addition of anti bFGF PTO suppresses the expression of bFGF protein in Western blot analysis. These results suggest that bFGF may be an endogenous growth signal in developing astrocytes.

ISSN:0959-4965    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Crush injury to rat sciatic nerves results in a 10-fold increase in the post-translational arginylation of proteins. In other systems,N-terminal arginylation leads to ubiquitination and proteolysis of the arginylated proteins. In the present experiments, proteins obtained from the 150 kg supernatant of crushed sciatic nerves were posttranslationally modified by3H-arginine. These arginine modified proteins formed aggregates (precipitated at 20 kg) which then partially separated by SDS-PAGE were immunoreactive to a monoclonal antibody to ubiquitin. The results indicate that following injury to sciatic nerves, certain proteins are arginylated and ubiquitinated, probably targeting them for degradation. It is likely that these reactions help to rid cells of proteins damaged by the crush which would otherwise be cytotoxic.

ISSN:0959-4965    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

The left somatosensory cortex of PVG/C rats was subjected to a transcranial cold lesion, spontaneous and evoked cortical activity was studied 2–3 weeks after the lesion. The spontaneous activity underwent a depression at the focus of the lesion. Close to the epicentre of the lesion, the amplitude of the potentials evoked by electrical stimulation of the contralateral whisker pad was considerably smaller than in the controls and an almost complete reduction of the initial positive phase was found. Perifocally, 3—4 mm from the epicentre, evoked potentials with enhanced amplitudes were recorded in all experiments. It seems that considerable damage took place at the epicentre of the lesion, while perifocally an excitatory (and/or inhibitory?) mechanism was activated.

ISSN:0959-4965    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Microdialysis in combination with HPLC and fluorescence detection was used to measure the release of endogenous amino acids from the region of the intermediolateral cell column of rat thoracic spinal cord in response to electrical stimulation of the rostral ventrolateral medulla (RVLM). Stimulation of the RVLM led to a marked rise in blood pressure (74 \pm 6 mm Hg) accompanied by an immediate increase in the release of glutamate (80%) and aspartate (50%). Small increases in the release of glycine and taurine were found, but there were no changes in alanine and serine release. These results suggest that the RVLM pressor pathway to the thoracic spinal cord may use, at least in part, excitatory amino acids as neurotransmitters, supporting previous pharmacological and neuroanatomical investigations of this bulbospinal pathway.

ISSN:0959-4965    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

The effects of intracerebroventricular (ICV) administration of 5-hydroxytryptaminecreatinine sulphate complex (5-HT), 35–140nmol, on food intake in genetically obese (ob/ob) and lean mice were investigated. 5-HT (70–140 nmol) decreased feeding in a dose-related manner on 1 h and 2 h postinjection measures. Intake in lean mice was reduced by over 70% of the control condition. Obese mice, however, demonstrated a reduced sensitivity to the anorectic effect of 5-HT, and reduced 1 h intake by only 40% of saline control. Although these results are consisted with a role for serotonin in the control of food intake in mice, the altered sensitivity of theob/obto serotonergic stimulation may result in part, from an impaired satiety control mechanism in this mutant.

ISSN:0959-4965    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

The aim of the present study was to determine whether the hyperphagia produced by systemic administration of 8-OH-DPAT is independent of drug-induced chewing or gnawing behaviour. The effects of 8-OH-DPAT (15.625–500$mUkg-1s.c.) were therefore investigated on operant food intake in non-deprived rats. Low doses (i.e. 15.625–62.5$mU kg-1) increased operant food intake. Drug-induced stereotypy disrupted operant responding at the higher doses. The results thus suggest that 8-OH-DPAT-induced hyperphagia is independent of chewing or gnawing behaviour.

ISSN:0959-4965    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Computer simulations of the spontaneous pacemaker oscillations observed in thalamocortical (TC) cells were performed using a biophysical model that included the low voltage activated, Ca2+current,lpand the mixed Na+/K+, inward rectifying current,Ih. The simulations accurately reproduced the waveform and voltage-dependence of the pacemaker oscillations, hence the transition from tonic firing to burst firing which is a peculiar feature of the electrical activity of TC cells bothin vivoandin vitro.The results provide further support to the suggestion thatI, andIbare essential for the presence of the packmaker oscillations, and indicate that our model is a useful tool for the study of spontaneous, low-frequency oscillatory activities in TC cells.

ISSN:0959-4965    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

The visual cortex contains regular arrangements of neurons responding to specific types of visual stimulation, such as ocular dominance columns and orientation columns. These columnar structures can be considered as the functional architecture for early visual information processing. The model of activity-dependent self-organization reported here demonstrates that both response properties of neurons to visual stimulation and the related columnar organization can be reproduced based on the competition between ON- and OFF-center inputs. Furthermore, the relationships between anatomical neural organization and its physiological response properties are clarified. This model also predicts new columnar organization linking the symmetry of receptive fields, which has never been examined. A hypercolumn, composed of orientation columns and symmetry columns, is suggested to serve as a basis for the representation of visual information.

ISSN:0959-4965    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

Development of orientation-selective receptive fields in primary visual cortex of higher mammals can occur through activity-dependent competition between ON-center and OFF-center inputs. This competition yields orientation and spatial-frequency-selective `simple cells' if the dark activity of ON (or OFF)-center inputs is best correlated with that of other ON (or OFF)-center inputs at small retinotopic separations and with that of OFF (ON)-center inputs at larger separations. Features of cat and monkey cortical organization emerge, including continuous and periodic arrangement of preferred orientation across the cortex. A new feature, systematic variation of receptive field spatial phase, is predicted. Experimental tests of this hypothesis are proposed.

ISSN:0959-4965    

出版商:OVID    

年代:1992

数据来源: OVID

摘要:

The effects of a nitric oxide (NO) donor, sodium nitroprusside (SNP), onN-methyl-D-aspartate (NMDA) receptors were assessed by optical measurements of intracellular calcium concentration ([Ca2+];) and patch-clamp techniques in cultured central neurons. SNP selectively blocked NMDA-mediated currents and increases in [Ca2+]i*SNP inhibited the binding of [3H]-CGS 19755. The blockade of NMDA responses by SNP was prevented by CPP or APV which are selective competitive NMDA receptor antagonists. These effects were not necessarily mediated by NO, since they were mimicked by ferrocyanide ions, the NO companion photolysis product of SNP.

ISSN:0959-4965    

出版商:OVID    

年代:1992

数据来源: OVID