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11.
12.
Cholinergic receptor sites in bovine cerebral arteries were analyzed using radioligand binding techniques with the cholinergic agonist, 3H-acetylcholine (ACh), as the ligand. Specific binding of 3H-ACh to membrane preparations of bovine cerebral arteries was saturable, of two binding sites, with dissociation constant (KD) values of 0.32 and 23.7 nM, and maximum binding capacity (Bmax) values of 67 and 252 fmol/mg protein, respectively. Specific binding of 3H-ACh was displaced effectively by muscarinic cholinergic agents and less effectively by nicotinic cholinergic agents. IC50 values of cholinergic drugs for 3H-ACh binding were as follows: atropine, 38.5 nM; ACh, 59.8 nM; oxotremorine, 293 nM; scopolamine 474 nM; carbamylcholine, 990 nM. IC50 values of nicotinic cholinergic agents such as nicotine, cytisine and alpha-bungarotoxin exceeded 50 microM. Choline acetyltransferase activity was 1.09 nmol/mg protein/hour in the cerebral arteries. These findings suggest that the cholinergic nerves innervate the bovine cerebral arteries and that there are at least two classes of ACh binding sites of different affinities on muscarinic receptors in these arteries.  相似文献   
13.
Several suggestions have been made about the functional significance of dendritic spines in connection with synaptic plasticity. We investigated transient electrical behavior of spines with bulbous terminals in neurons with arbitrary dendritic geometries. It is shown that postsynaptic potential transform caused by a synapse on a spine can be resolved into a product of two transfer functions and the synaptic input current transform. The first transfer function was determined to be independent of the spine. The second transfer function represents the straightforward attenuation effect of the spine, which determines the effective synaptic current reaching the parent dendrite. Using what is known of the size and the shape of spines from histology, we conclude that almost all of the synaptic current flow into the parent dendrite, and that therefore the straightforward attenuation effect is negligible. Consequently, when the synaptic current remained unaltered, as was the case for a large synaptic resistance as compared with the spine stem resistance, a morphological change of the spine did not produce an effective change in the postsynaptic potential. On the other hand, when the synaptic resistance is compared with the spine stem impedance, the morphological change of the spine might induce changes of the synaptic current and the postsynaptic potential.  相似文献   
14.
The molecular properties, such as molecular weight, N-and C-terminal amino acids, amino acid composition, and circular dichroism, of 1,2--mannosidase isolated from the culture filtrate ofAspergillus saitoi were determined.The enzyme had aK m of 0.67 mM andk cat of 1.27/s with mannobiose at pH 50.0 and 30°C. The anomeric configuration of the reaction products of the enzyme was examined by studying the -anomer. A single Manl2Man linkage in intact Taka-amylase A fromAspergillus oryzae was hydrolyzed, producing free mannose.  相似文献   
15.
Muscarinic cholinergic receptor sites in dog portal veins were analyzed directly using [3H]quinuclidinyl benzilate (QNB) as a ligand. Specific [3H]QNB binding to crude membrane preparations from the isolated veins was saturable, reversible and of high affinity (KD = 15.5 +/- 2.8 pM) with a Bmax of 110 +/- 14.7 fmol/mg protein. Scatchard and Hill plot analyses of the data indicated one class of binding sites. From kinetic analysis of the data, association and dissociation rate constants of 1.91 X 10(9) M-1 min-1 and 0.016 min-1, respectively, were calculated. The dissociation constant calculated from the equation KD = K-1/K+1 was 8.3 pM, such being in good agreement with the Scatchard estimate of KD (15.5 pM). Specific binding of [3H]QNB was displaced by muscarinic agents. Nicotinic cholinergic agents, alpha-bungarotoxin, nicotine and hexamethonium, were ineffective in displacing [3H]QNB binding at 10 microM. Our findings provide direct evidence for the existence of muscarinic cholinergic receptors in dog portal veins.  相似文献   
16.
The course of regeneration of aminergic nerves in rat cerebral arteries was studied by means of histochemical methods, after uni- or bilateral cervical sympathectomy. Degeneration of aminergic nerves started on day 1 and was complete between days 3 and 7 after surgery. Between weeks 4 and 6, regenerating nerves started to appear from the proximal internal carotid artery. Regenerated aminergic nerve fibres were generally unbeaded and intensity of fluorescence was weak. The circular nerves appeared earlier than the longitudinal ones. The number of regenerating nerves reached the maximum, between months 9 and 12, at about half the normal level. AChE activity of the cerebral arteries showed no significant changes at any stage.  相似文献   
17.
Spatio-temporal changes in the shapes of the epithelial cells in culture were followed with the aid of scanning electron microscopy. On a substratum that enables the epithelium to spread extensively, the first remarkable change in shapes of the cells occurred at the margin of epithelium at 12 h of culture. The marginal cells formed leading edges with filo- or lamellipodia, flattened, and lost microvilli on surface. In accordance with those changes, the borderlines among cells became almost indiscrenible. Flattening of the cells was the essential characteristic associated with active epithelial spreading throughout the culture period. Elongation of cells of intermediate zone at right angles to the direction of the locomotion of the marginal cells at 24 h of culture was the second significant change. As the third, the change from the ordinary pentagonal or hexagonal to extraordinary tetragonal or other polygonal shapes, with or without irregular margins, began in cells of the intermediate area at 24 h and propagated to those in inner area. The active deformation of the inner cells with no space in which to move was considered to play some role in the extensive epithelial spreading.  相似文献   
18.
Grooming initiation among adult males and females of a Japanese macaque troop was analyzed during the non-mating season. Some gestures (“solicitation”) elicited grooming from partners at a high rate. Grooming initiation patterns were divided into two main types: (1) a male often solicited a female to groom him immediately after approaching her and was groomed by her; and (2) a female approached an alpha male selectively, and immediately groomed him. After a female groomed a male, she rarely solicited him to groom her and instead often moved away from him. These results indicated that males were motivated to be groomed, while females were more highly motivated to groom. Sex differences in grooming motivation can be explained by sex differences in the benefit to be groomed.  相似文献   
19.
The mechanism of known receptor-mediated androgen effects on the endometrial stroma was studied in endometrial fibroblasts derived from human uterus. 17-Estradiol (E) induced the expressions of androgen receptor (AR) mRNA, and predominantly increased the level of testosterone-binding sites (TBS) in uterine endometrial fibroblasts. The effect on the level of dihydrotestosterone-binding sites (DHTBS) was similar but smaller. This result suggests that the AR mRNA expressed might encode TBS, but probably not DHTBS. The TBS level increased by estrogen was down-regulated by testosterone (T) + E, but the AR mRNA expression increased by E was not down-regulated by E + T in the fibroblasts. Although the synthesis rate of AR was slightly increased (p<0.05) by E alone or E + T, the degradation rate of AR was significantly accelerated (p<0.05) by E + T in the fibroblasts. This result suggests that T might stimulate the metabolic rate of TBS, but does not inhibit the synthesis rate of AR mRNA to TBS in endometrial fibroblasts.  相似文献   
20.
Cellular mechanisms responsible for the termination of ET-1 signal are poorly understood. In order to examine the hypothesis that nitric oxide serves as a physiological brake of ET- 1 signaling, Chinese hamster ovary (CHO) cells stably transfected with the ETA receptor cDNA (CHO-ET) were studied. CHO-ET responded to ET-1 with robust [Ca2+], transients and developed a long-lasting homologous desensitization. Donors of nitric oxide (NO), 3-morpholino-sydnonimine HCl(SIN-1), or sodium nitroprusside (SNP) reduced the amplitude of these responses, accelerated the rate of [Ca2+], recovery, and counteracted the development of homologous desensitization by a cyclic GMP-independent mechanism, suggesting an alternative mode for NO modulation of ET-1 responses. Stimulation of CHO-ET cells with mastoparan, a wasp venom acting directly on G proteins (bypassing receptor activation), was inhibited by NO, revealing a postreceptoral target for NO-induced modulation of [Ca2+] mobilization. Using a lys9-biotinylated ET-1 (ET-1 [BtK9]), binding sites were “mapped” in CHO-ET cells. Receptor-ligand complexes did not exhibit spontaneous dissociation during 60min observations. Quantitative fluorescence microscopy revealed that SNP or SIN-1 caused a rapid, concentration-dependent, and reversible dissociation of biotinylated ET- 1 from ETA receptor (EC50 = 75 μM and 6 μM, respectively), an effect that was not mimicked by 8-bromo-cyclic GMP. “Sandwich” co-culture of endothelial cells with CHO-ET showed that activation of NO production by endothelial cells similarly resulted in dissociation of ET-1 [BtK9] from ETA receptors. We hypothesize that NO plays a role in physiological termination of ET-1 signalling by dual mechanisms: (1) displacement of bound ET-1 from its receptor, thus preventing homologous desensitization, and (2) interference with the postreceptoral pathway for [Ca2+] mobilization, hence inhibiting end-responses to ET-1. © 1994 Wiley-Liss, Inc.  相似文献   
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