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Biomedical subjects

M Koike

Publications and source records attributed to M Koike.

At least 469 records · Page 26Linked to original sources
PubMed1976

Structure, assembly and function of mammalian alpha-keto acid dehydrogenase complexes.

An attempt has been made to provide a description of the mammalian alpha-keto acid dehydrogenase multienzyme complexes, especially with respect to the structure, assembly and function of PDC and OGDC based on the investigation carried out in this laboratory over the last 14 years. Special efforts have been focused on the purification, characterization, and stoichiometric resolution into component enzymes, and the reassembling process to produce these multienzyme complexes. Studies of the macroorganization and the mechanism of regulation of these multienzyme complexes still remains a most challenging question.

Acetyltransferases↗
PubMed1975

A kinetic study of the alpha-keto acid dehydrogenase complexes from pig heart mitochondria.

The kinetic mechanisms of the 2-oxoglutarate and pyruvate dehydrogenease complexes from pig heart mitochondria were studied at pH 7.5 and 25 degrees. A three-site ping-pong mechanism for the actin of both complexes was proposed on the basis of the parallel lines obtained when 1/v was plotted against 2-oxoglutarate or pyruvate concentration for various levels of CoA and a level of NAD+ near its Michaelis constant value. Rate equations were derived from the proposed mechanism. Michaelis constants for the reactants of the 2-oxoglutarate dehydrogenase complex reaction are: 2-oxoglutarate, 0.220 mM; CoA, 0.025 mM; NAD+, 0.050 mM. Those of the pyruvate dehydrogenase complex are: pyruvate, 0.015 mM; CoA, 0.021 mM; NAD+, 0.079 mM. Product inhibition studies showed that succinyl-CoA or acetyl-CoA was competitive with respect to CoA, and NADH was competitive with respect to NAD+ in both overall reactions, and that succinyl-CoA or acetyl-CoA and NADH were uncompetitive with respect to 2-oxoglutarate or pyruvate, respectively. However, noncompetitive (rather than uncompetitive) inhibition patterns were observed for succinyl-CoA or acetyl-CoA versus NAD+ and for NADH versus CoA. These results are consistent with the proposed mechanisms.

Acetyl Coenzyme A↗
PubMed1975

Noninvasive evaluation of cardiac function in patients with ischemic heart disease by the subclavian arterial blood flow response to exercise.

To evaluate cardiac function, the regional blood flow of the subclavian artery as a parameter of cardiac output was measured instead of measuring cardiac output itself in 12 normal subjects and 17 patients with ischemic heart disease. The measurement of the subclavian arterial blood flow was continuously and noninvasively made utilizing the Doppler ultrasonic flowmeter before, during and after exercise. The exercise was performed in the upright position on a bicycle ergometer for 3 minutes at the work load of 230 Kpm/min. Delta F Ratio, that is, the ratio of the increased blood flow during the exercise to the increased blood flow during the first 3 minutes after the termination of the exercise, was calculated in all subjects. Delta F Ratio as well as the response pattern of the blood flow to exercise was investigated. In patients with ischemic heart disease, the increase in the subclavian arterial blood flow during the exercise was slow, and the time required to return to the pre-exercise level was remarkably prolonged in comparison with normal subjects. The mean delta F Ratio of the younger normal group was 7.43, and that of the older normal group was 5.53. While in patients with ischemic heart disease, markedly lower values were observed. The mean delta F Ratio of the following subgroups of patients with ischemic heart disease, the myocardial infarction group, the angina pectoris group, and the group of ischemic heart disease without pain, were 1.25, 1.97, and 2.52 respectively. The difference in the mean delta F Ratio between the older normal group and each subgroup of ischemic heart disease was statistically significant. Low delta F Ratio in patients with ischemic heart disease is supposed to be the manifestation of diminished cardiac reserve due to decreased myocardial contractility. As a simple parameter of cardiac output, the continuous measurement of the subclavian arterial blood flow by the Doppler flowmeter is a useful method for the noninvasive evaluation of cardiac function. Especially, the calculation of delta F Ratio may provide the numerical presentation of cardiac function.

Adult↗