Biomedical subjects

D H Shi

Publications and source records attributed to D H Shi.

3 recordsLinked to original sources

PubMed1996

Potassium channel openers inhibit ATP-induced cytosolic free calcium increase in cultured rabbit aortic smooth muscle cells.

AIM: To study the effects of potassium channel openers (PCO) on cytosolic free calcium ([Ca2+]i) changes and their possible mechanisms in vascular smooth muscle cells (VSMC). METHODS: Cultured rabbit aortic VSMC were treated with Fura-2 AM 2.5 mumol.L-1 at 37 degrees C for 50 min. The PCO were pinacidil (Pin), nicorandil (Nic), lemakalim (Lem), and RP 49356 (RP). [Ca2+]i level was measured by fluorospectrometer. RESULTS: [Ca2+]i increase induced by K+ 30 mmol.L-1 was weakly inhibited by Pin, Nic, Lem, and RP (441 +/- 23, 455 +/- 48, 451 +/- 22, 370 +/- 31 vs 544 +/- 40 nmol.L-1, P < 0.01). ATP (0.1 mmol.L-1)-induced peak and sustained [Ca2+]i increase were inhibited by these agents in a concentration-dependent manner. The effects of Pin, Lem, and RP were completely canceled (peak phase: 549 +/- 39, 540 +/- 30, 564 +/- 13 vs 541 +/- 39 nmol.L-1; sustained phase: 413 +/- 25, 364 +/- 16, 377 +/- 11 vs 380 +/- 8 nmol.L-1), but that of Nic was only partially blocked (peak phase: 453 +/- 31 vs 541 nmol.L-1; sustained phase: 348 +/- 19 vs 380 +/- 8 nmol.L-1, P < 0.01) by glibenclamide (Gli, 10 mumol.L-1). Pretreated with the Pin, Nic, Lem, and RP (10 mumol.L-1), the peak [Ca2+]i elevation induced by ATP was reduced in the Ca(2+)-free solution (129 +/- 17, 142 +/- 21, 136 +/- 14, 114 +/- 9 vs 258 +/- 32 nmol.L-1, P < 0.01). CONCLUSION: Pin, Nic, Lem, and RP inhibited ATP-induced [Ca2+]i increase, associated with decreases of both Ca2+ release from intracellular store and Ca2+ influx from extracellular store.

Adenosine Triphosphate↗

PubMed1996

Inhibitory effect of potassium channel openers on proliferation of cultured rabbit aortic smooth muscle cells.

AIM: To study the effects of pinacidil (Pin), nicorandil (Nic), RP 49356 (RP), and lemakalim (Lem) on phenylephrine (PE)-induced proliferation of cultured rabbit aortic smooth muscle cells (ASMC). METHODS: The [3H]thymidine incorporation into DNA and number of ASMC were measured. RESULTS: [3H]Thymidine uptake induced by PE was markedly inhibited by Pin, Nic, RP, and Lem (0.1-10 mumol.L-1). Only RP inhibited [3H]thymidine uptake without PE-pretreatment. Cell growth induced by PE was completely inhibited by Pin. CONCLUSION: Pin, Nic, RP, and Lem showed potent antiproliferation of ASMC.

Animals↗

PubMed1991

Edge extraction by active defocusing.

A novel edge extraction method that employs an active defocusing technique is presented. The method is based on the principle that a Laplacian-of-Gaussian (LOG) operation can be approximated by a Difference-of-Gaussian (DOG) operation. While such an operation is usually done in digital image processing, it can also be very effective conducted in a combination of optical techniques and digital processing. In this edge extraction method, a focused image of an object in a scene is first acquired. The image of the scene is then slightly defocused by changing the focal length of the camera. A real time subtraction operation is applied to subtract the defocused image from the previously acquired image. It produces a residual image that emphasizes abrupt intensity variations. An objective evaluation, called an edge index, is performed on the resulting image. The amount of defocusing is carefully adjusted according to this measurement so that a desired edge image is generated. Boundaries of objects can then be obtained by further enhancement of the edge image. Since this edge detection method is an optical-based process aided by digital processing, it is fast and relatively inexpensive.

Artificial Intelligence↗