摘要:

SPATIAL distribution of the cAMP-gated channel was investigated in amphibian olfactory receptor cells. Low doses of cAMP applied to the cytoplasmic side of a membrane patch excised from cilia produced single channel activity of unitary conductance 28pS. Variance analysis showed that the ciliary membrane contained 920 cAMP gated-channels/μm2in the newt and 2400 channels/μm2in the toad. In contrast, the membrane of the dendrite and cell body contained only 2 cAMP-gated channels/μm2(newt) and 6 channels/μm2(toad). Thus, there is a high density of cAMP-gated channels in the cilia where olfactory transduction is thought to take place.

ISSN:0959-4965    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

THE glomerular layer of the olfactory bulb contains a substantial population of dopaminergic neurons. We determined the quantity and location of D1 and D2 dopamine receptors which are the presumed targets of these neurons. Binding of the D1 selective ligand [3H]SCH23390 was slightly above background and was distributed through all layers of the bulb except the olfactory nerve layer. In contrast there were relatively high levels of [3H]spiperone binding to D2 DA receptors in the glomerular and olfactory nerve layers. The presence of relatively high concentrations of D2 DA receptors in both the nerve layer and glomerular layer suggests the novel hypothesis that these receptors may be localized on terminals of the olfactory nerve.

ISSN:0959-4965    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

SYNAPTOSOMAL plasma membranes (SPMs) from adult rat brain tested for fibronectin binding and antigenicity toward antibodies against integrin-type fibronectin receptors. Binding (1–10 pmol mg-1protein) was considerably greater in SPMs than in homogenates for hippocampus and neocortex but not for brain stem. The tetrapeptide L-arginyl-glycyl-L-aspartyl-L-serine blocked up to 90% of the binding indicating that integrin-type receptors are present. Antibodies against two sub-classes of integrins detected high Mr integrin subunits in homogenates but not in SPMs. However, antibodies against hamster ovarian fibronectin receptor reacted intensely with polypeptides of 55000 and 40000 Mr that were concentrated 20 to 40-fold in SPMs compared to homogenates. These peptides may constitute a new class of matrix receptor involved in synaptic adhesion.

ISSN:0959-4965    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

WE usedin-situhybridization to study the effect of acute stress on induction of the immediate early genes (IEGs), c-fos and zif/268, in the rat brain. After one hour of restraint plus intermittent tail shock, messenger RNA (mRNA) levels for both genes were significantly increased bilaterally in the neocortex, particularly in layers IV, V and VI, and in the CA1 region of the hippocampus. This regionally-specific response suggests that IEGs may have a role in the mediation of acute stress responses in the central nervous system.

ISSN:0959-4965    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

NEURO-2A neuroblastoma cells were differentiated by the addition of dibutyryl-cyclic AMP, resulting in an increase in transcription of mRNA coding for the two neurofilament polypeptides NF-L and NF-M. The mRNAs for these two polypeptides appeared to be co-expressed with both being switched on at 24 h after the addition of drug. This was in contrast to NF-H whose induction was only seen at 60 h following addition of drug. These results are in good agreement with the expression time course previously reportedin-vivoand suggest that the neurofilament triplet polypeptides can be divided into two subsets which appear to be under different genetic control mechanisms according to their time course of expression.

ISSN:0959-4965    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

THE mRNA levels of the acetylcholine receptor α-subunit gene and of four members of the MyoD1 gene family, which code for candidate transcriptional activators of the former gene, were compared in the mouse during postnatal development and after denervation in the adult. During post-natal development, mRNA levels of myogenin, MyoD1, and Myf5 decrease in parallel with α-subunit mRNA whereas MRF4 mRNA level remains nearly constant. After denervation, increases in the levels of mRNAs coding for myogenin, MyoD1 and MRF4 accompany that of α-subunit mRNA, while Myf5 mRNA level varied little. A possible role of these myogenic genes in mediating nerve influence on the state of muscle differentiation and AChR α-subunit gene expression is discussed.

ISSN:0959-4965    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

IONIC currents elicited by N-phthalamoyl-L-glutamic acid (PhGA) were investigated on freshly isolated hippocampal neurons with the whole-cell voltage clamp and concentration clamp techniques. PhGA elicited desensitizing inward currents in Mg2+-free salines only in the presence of glycine. The dose-response relationship for PhGA was close to a Langmuir isotherm with Kd= 3.7 mM and saturating level 0.75 of that for L-aspartate (L-Asp). PhGA-activated currents were blocked by Mg2+, D-2-amino-5-phosphonovalerate and kynurenate, and had the same reversal potential as L-Asp-activated currents. Complete cross-desensitization was obtained between the responses to PhGA and L-Asp. We conclude that PhGA is a new selective ‘superacidic’ agonist of the N-methyl-D-aspartate type of glutamate receptor

ISSN:0959-4965    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

TETANUS and botulinum A neurotoxins block exocytosis of noradrenaline in chromaffin cells. During exocytosis vesicles fuse with the plasma membrane. This requires an intact cytoskeleton. The cytoskeleton can be displayed by rhodamine-labelled phalloidin binding to F-actin. When chromaffin cells are stimulated with carbachol, F-actin forms clusters close to the plasma membrane. On withdrawal of the secretagogue the stimulated cells revert to their original appearance. The conversions, like exocytosis, depend on the presence of Ca2+, indicating the association of exocytosis with F-actin arrangement. When exocytosis is blocked in chromaffin cells by tetanus or botulinum A neurotoxins, F-actin fails to cluster during nicotinic stimulation. Thus, the toxins act somewhere between the rise in intracellular free Ca2+and the rearrangement of F-actin.

ISSN:0959-4965    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

REINNERVATION of sweat glands, skeletal muscle and skin was studied in the mouse paw after section of the sciatic nerve and repair by entubulation with collagen conduits, with and without a coating of laminin. After operation, sweat glands activated by pilocarpine reappeared at 32 days and increased in number to 67% of control counts. Muscle action potentials (during sciatic nerve stimulation) were recorded from the interosseus muscle at 39 days. The potential amplitudes increased to 30% of controls. The first withdrawal response from pin prick to the paw was observed at about 34 days, the response score increasing to 66% of control. There were no significant differences at any test interval between the control group and the group with laminin added.

ISSN:0959-4965    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

THE central control of brown fat thermogenesis was evaluated in seventeen rats with moveable electrodes implanted in the ventromedial hypothalamus (VMH) and adjacent structures. Brown adipose tissue and core body temperatures were monitored in response to VMH stimulation; sites which elicited a rise in brown fat temperature were observed in the dorsomedial and anterior ventromedial hypothalamus, with BAT temperature profiles varying widely in duration and peak values. Given the complexity of BAT responses to endogenous VMH signals, these varied profiles may be mediated by dissimilar VMH signals, which remain to be characterized.

ISSN:0959-4965    

出版商:OVID    

年代:1991

数据来源: OVID