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Biomedical subjects

Y Koh

Publications and source records attributed to Y Koh.

At least 127 records · Page 7Linked to original sources

Surgery for ascending aortic aneurysm with aortic regurgitation.

We reviewed 22 consecutive patients undergoing surgery during 13 years from 1968 to 1981 for ascending aortic aneurysms associated with aortic regurgitation due primarily to idiopathic medionecrosis resulting in annuloaortic ectasia. Chronic aortic dissection was accompanied in 45% of the patients. The operative period was divided into 2 stages, the first from 1968 to 1976, and the second from 1977 to 1981. In the earlier period, the operative mortality was 42%, and it improved significantly to 0% (p less than 0.05) in the later period. The reasons for improved surgical results are 1) the employment of the Bentall operation with some technical modifications and 2) the use of better myocardial protection method with cold potassium cardioplegia. The postoperative hemodynamic and clinical improvements were significant. The left ventricular improved toward normal (p less than 0.05 and p less than 0.001). Operative survivors showed a clinical improvement from NYHA class 3 to 1.3 on an average. The actuarial survival rate at 6 years after operation was 64.3% in the entire series, and 71.1% in patients with the Bentall operation. In patients with type I aortic dissection, a false lumen remained patent after operation and may progress to cause late morbidity or mortality. Surgery should be performed earlier than aortic dissection takes place whenever feasible. The Bentall operation can now be performed with a low risk, and can improve the clinical and hemodynamic states and very possibly prolong the longevity of the patients.

Adult↗

A new antitumor antibiotic, stubomycin.

A new antibiotic, stubomycin, was isolated from the culture broth and mycelia of Streptomyces strain No. KG-2245. Stubomycin was prepared as colorless plates and has the empirical formula C29H35NO5. The antibiotic possesses growth inhibitory activity against Gram-positive bacteria and transplantable murine tumors, such as Ehrlich carcinoma, and leukemia P388. The antibiotic also shows direct cytotoxic activity against HeLa cells in vitro.

Animals↗

A nuclear mutation conferring aurovertin resistance to yeast mitochondrial adenosine triphosphatase.

A single gene nuclear yeast mutant was isolated whose mitochondrial F1-ATPase was resistant to the specific F1 inhibitor aurovertin. The mutant enzyme was not cross-resistant to other F1 inhibitors. The binding of aurovertin to F1 and to the two largest F1 subunits (alpha and beta) was measured by enhancement of aurovertin fluorescence. Aurovertin bound to wild type F1-ATPase and to its monomeric beta subunit with about the same binding constant. It failed to bind to wild type alpha subunit or to either F1 or F1 subunits from the mutant. The aurovertin-resistant mutant thus contains an altered nuclear gene which specifies the structure of the beta subunit of F1.

Adenosine Triphosphatases↗

Aurovertin binds to the beta subunit of yeast mitochondrial ATPase.

Isolated beta subunit of ATPase (F1) from yeast mitochondria does not catalyze an ATPase reaction but still binds the specific F1 inhibitor aurovertin. Binding was measured by enhancement of aurovertin fluorescence; it was as tight as that to F1-ATPase. No binding was observed with F1 or with isolated beta subunit from a single-gene nuclear yeast mutant whose F1-ATPase was resistant to aurovertin.

Adenosine Triphosphatases↗