Biomedical subjects

S R Yeh

Publications and source records attributed to S R Yeh.

21 records · Page 2Linked to original sources

PubMed1991

Effects of insulin on glucose uptake in cultured cells from the central nervous system of rodent.

1. Incubation of C6 glioma cultures with insulin resulted in a time and dose-dependent stimulation of 2-deoxy-D-glucose uptake. The maximal stimulation (160% of the control) was observed with 1 nM insulin and 0.05 nM caused half-maximum effect. 2. Incubation of NG 108-15 (neuroblastoma x glioma hybrid) and N2 neuroblastoma cells with 160 nM insulin did not result in a significant stimulation of this glucose uptake. 3. The basal level and stimulatory effect by insulin on this glucose uptake observed in C6 glioma cells were dependent on the presence of calcium in the medium. 4. Such an increase in glucose uptake in C6 glioma cells was also observed in the presence of diacylglycerol (DG) generating agents, such as carbachol (1 mM) and phospholipase C (0.05 unit/ml) or of DG analogs, such as sn-1,2-dioctanoyl glycerol (250 microM) and phorbol myristate acetate (1 microM). 5. Our results indicated that both calcium ion and DG levels play important roles in the regulation of glucose uptake in the glial cells, but not in neuronal cells from the brain.

Animals↗

PubMed1991

Evidence for the coupling of muscarinic M3 receptor to cyclic AMP formation and poly-phosphatidylinositol turnover in rat salivary glands.

The biochemical events which are coupled to the subtypes of muscarinic cholinergic receptors in rat salivary glands were studied. The subtype property of this receptor system was characterized by the use of 3H-QNB binding to glandular membrane homogenates. The Kd and Bmax values of this binding were found to be 0.2 nM and 210 fmole/mg protein respectively. In the drug-displacement study on the 3H-QNB binding the following potency order was obtained (based on the IC50 values calculated from each individual dose-response curve): Atropine greater than 4-DAMP greater than HHSiD greater than Pirenzepine greater than AF-DX 116. This order is a typical M3 muscarinic subtype, according to the recent consensus. Carbachol (0.1 mM) caused a 4.4-fold increased in IP3 production over the basal level, when tissue fragments were prelabeled with 3H-inositol. The above mentioned cholinergic antagonists could block this event in a similar potency order. Carbachol (0.1 mM) did not have a significant effect on the basal level of cAMP formation of these tissue homogenates. On the other hand, it had a 33% reduction of isoproterenol (10 microM)-enhancing cAMP formation. The reduction effect of carbachol on cAMP formation could also be blocked by the above mentioned cholinergic antagonists in a similar order. Our results indicated that rat salivary glands have M3 muscarinic receptors and the activation of these receptors causes changes in both phosphatidylinositol turnover and cAMP formation.

Animals↗

PubMed1991

Biochemical events coupled to the activation of serotonin receptors in brain regions of the rat.

Effects of serotonin on the levels of inositol phosphate and cyclic AMP in certain brain regions of the rat were studied. When brain slices were treated with serotonin (10(-4) or 10(-5) M), it caused significant increases in inositol phosphate levels in cerebral cortex, hippocampus, midbrain and brain stem, but not in cerebellum. Serotonin itself did not have a significant effect on the basal levels of cAMP in most of these regions, except in midbrain in which it had stimulatory effect. However, serotonin also had significant inhibitory effect on forskolin-induced cAMP formation in cerebral cortex, hippocampus and brain stem but not in midbrain in which an increase instead. Effects of serotonin on both biochemical events were in dose-dependent manner, and their maximal responses were at doses between 10(-4) and 10(-3) M. The rank order of the maximal response to serotonin on inositol phosphate production in these regions was cerebral cortex greater than hippocampus greater than midbrain greater than brain stem greater than cerebellum. On the other hand, the rank order of the maximal response to serotonin on inhibiting forskolin-induced cAMP formation was cerebral cortex = brain stem greater than hippocampus. Our data revealed that there is a regional difference in serotonin-induced inositol phosphate and cAMP responses. This difference is likely due to a differential distribution of serotonergic receptor subtypes and densities in different regions of rat brain.

Adenylyl Cyclases↗