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Biomedical subjects

K K Koh

Publications and source records attributed to K K Koh.

45 records · Page 3Linked to original sources
PubMed1993

Coronary vasospasm, multiple coronary thrombosis, unstable angina and essential thrombocytosis.

Rarely, essential thrombocythemia has led to coronary artery occlusion. Only one patient has been described, in whom coronary angiography demonstrated multiple coronary thrombosis. We report a case of coronary vasospasm, multiple coronary thrombosis involving right and left coronary artery and possibly leading to myocardial infarction and unstable angina pectoris in a woman with migraine, Raynaud's phenomenon, and essential thrombocytosis.

Angina, Unstable↗
PubMed1993

Isolated left main coronary ostial stenosis in Oriental people: operative, histopathologic and clinical findings in six patients.

OBJECTIVES: This study was performed to determine whether there are differences in the operative, histopathologic, angiographic and clinical findings of isolated ostial stenosis between Oriental and western patients. BACKGROUND: Angiographic, clinical and histologic findings in isolated ostial stenosis have been reported in western but not in Oriental patients. METHODS: Six patients, all women (0.88% of a total of 684 patients who underwent coronary angiography between March 1989 and July 1991), were found to have isolated left main coronary ostial stenosis. We performed surgical ostial angioplasty with the autologous pericardial or saphenous venous patch and biopsy at the aortic arteriotomy site in four of the six patients. RESULTS: All six patients presented with severe angina (angina class III or IV) of short duration (mean +/- SD 6.2 +/- 6.2 months) and had a very low incidence of risk factors, although histopathologic examination showed typical atherosclerosis in four of the six patients. They were young to middle-aged women (mean 45 +/- 3 years) except for Patient 6 (62 years). Exercise duration was short and ST segment depression, accompanied by typical angina, was observed in many leads in the warm-up period or stage I. Despite the crucial location of the lesion, most patients had well preserved left ventricular function and normal wall motion. There was no angiographically definable collateral circulation from either ipsilateral or contralateral vessels except for grade I collateral circulation in Patient 5. Operative findings demonstrated mostly yellow atheroma in the aortic wall and left coronary ostium. Coronary angiography showed only ostial stenosis of the left coronary artery in all six patients, but operative findings documented atheromatous change in the left main coronary artery in two of the six. CONCLUSIONS: The clinical, angiographic, histopathologic and operative findings of Oriental patients were similar to those reported in western patients, but the incidence of isolated left main coronary ostial stenosis was higher in the Oriental group. Angiographically definable isolated coronary ostial stenosis may often not be true isolated ostial stenosis.

Cardiac Catheterization↗
PubMed1992

Various 12-lead electrocardiographic findings of diffuse three-vessel coronary artery spasm.

Electrocardiographic signs of diffuse three-vessel coronary artery spasm may show various findings including no ST segment changes, according to whether or not a difference of an electrical gradient develops between the anterior and inferior regions because of global ischemia. This study suggests that diffuse three-vessel coronary artery spasm must be considered when the 12-lead electrocardiogram (ECG) shows no important ST segment changes with episodes of angina and diffuse coronary artery spasm during an ergonovine provocation test in patients with strongly suspected variant angina.

Adult↗
PubMedDate not supplied

Implications for atypical antioxidative properties of manganese in iron-induced brain lipid peroxidation and copper-dependent low density lipoprotein conjugation.

Our group recently observed that manganese prevents oxidative brain injury in the iron-induced parkinsonian animal model. It has also been suggested that manganese retards while copper promotes the development of atherosclerosis. In this report, we provide further evidence to support a controversial notion that manganese is an atypical antioxidant. Among transition metals, Cu2+ and Fe2+ (0.1 to 125 microM), but not Mn2+, converted hydrogen peroxide to reactive hydroxyl radicals via the Fenton reaction at pH 7.4. Iron's pro-oxidative rate is relatively slow, but it is accelerated further by ascorbate (50 microM) in 37 degrees C Dulbecco's phosphate buffered saline. Moreover, Mn2+ (0-80 microM) concentration dependently retarded diene conjugation of human low density lipoproteins stimulated by 5 microM Cu2+. This new result is consistent with our recent finding that Mn2+ (0 to 20 microM) does not initiate brain lipid peroxidation while it inhibits iron-induced peroxidation of polyunsaturated fatty acids. These unexpected manganese results are somewhat at odds with a prominent theory that manganese is a prooxidative transition metal. Furthermore, iron and copper induced free radical generation and lipid peroxidation are suppressed by lowering the incubation temperature; this suggests that hypothermia may decrease the oxidative stress and damage in vivo. In conclusion, normal dietary intake of manganese may protect cells and neurons from oxidant stress through the inhibition of propagation of lipid peroxidation caused by hydroxyl radicals generated by pro-oxidative transition metals such as iron and copper. Potential therapeutical uses of manganese, manganese SOD mimetics and hypothermia for protecting brain neurons and vascular endothelial cells against oxidative stress and damage have been successfully demonstrated in both animal models and clinical trials.

Animals↗