Biomedical subjects

Hiroyuki Koike

Publications and source records attributed to Hiroyuki Koike.

21 records · Page 2Linked to original sources

PubMed2002

Temperature acclimation of photosynthesis and related changes in photosystem II electron transport in winter wheat.

Winter wheat (Triticum aestivum L. cv Norin No. 61) was grown at 25 degrees C until the third leaves reached about 10 cm in length and then at 15 degrees C, 25 degrees C, or 35 degrees C until full development of the third leaves (about 1 week at 25 degrees C, but 2-3 weeks at 15 degrees C or 35 degrees C). In the leaves developed at 15 degrees C, 25 degrees C, and 35 degrees C, the optimum temperature for CO(2)-saturated photosynthesis was 15 degrees C to 20 degrees C, 25 degrees C to 30 degrees C, and 35 degrees C, respectively. The photosystem II (PS II) electron transport, determined either polarographically with isolated thylakoids or by measuring the modulated chlorophyll a fluorescence in leaves, also showed the maximum rate near the temperature at which the leaves had developed. Maximum rates of CO(2)-saturated photosynthesis and PS II electron transport determined at respective optimum temperatures were the highest in the leaves developed at 25 degrees C and lowest in the leaves developed at 35 degrees C. So were the levels of chlorophyll, photosystem I and PS II, whereas the level of Rubisco decreased with increasing temperature at which the leaves had developed. Kinetic analyses of chlorophyll a fluorescence changes and P700 reduction showed that the temperature dependence of electron transport at the plastoquinone and water-oxidation sites was modulated by the temperature at which the leaves had developed. These results indicate that the major factor that contributes to thermal acclimation of photosynthesis in winter wheat is the plastic response of PS II electron transport to environmental temperature.

Acclimatization↗

PubMed2002

Renoprotective effects of blockade of angiotensin II AT1 receptors in an animal model of type 2 diabetes.

To evaluate the efficacy of angiotensin II receptor blockers (ARBs) for use in the treatment of diabetic nephropathy, we examined the effects of olmesartan medoxomil (olmesartan), an angiotensin II type 1 (AT1) specific ARB, on the progression of nephropathy in Zucker diabetic fatty (ZDF) rats, an animal model of type 2 diabetes. We used 2 doses of olmesartan, a sub-antihypertensive dose and an antihypertensive dose, to specifically examine whether the drug exerts beneficial effects on the kidney without lowering blood pressure. Olmesartan mixed in the diet at a concentration of 0.001% (approximately 0.6 mg/kg/day) or 0.01% (approximately 6 mg/kg/day) was administered for 19 weeks starting from 12 weeks of age, when the animals developed microalbuminuria. Lean non-diabetic rats served as controls. ZDF rats had hyperglycemia, hyperinsulinemia, and moderate hypertension as compared to lean control rats. Plasma glucose and insulin concentrations were not affected by olmesartan, and blood pressure was lowered only by the high dose of olmesartan. Progressive proteinuria in ZDF rats was greatly (about 70%) suppressed by the high dose of olmesartan and moderately (about 30%) suppressed by the low dose that did not significantly lower blood pressure. ZDF rats exhibited hyperlipidemia and hypoalbuminemia, both of which were substantially corrected by treatment with olmesartan. The histological evidence of glomerular and tubular damage in the ZDF rats was also reduced by the drug. These results indicate that AT1 receptor blockade with olmesartan retards the progression of nephropathy associated with type 2 diabetes without affecting glucose metabolism, and that this renal protective effect is at least partly independent of the antihypertensive effect of the drug.

Angiotensin Receptor Antagonists↗

PubMedDate not supplied

CS-088, an angiotensin type 1 receptor antagonist, ameliorated the impaired blood flow in the optic nerve head of rabbits.

The effect of CS-088, an angiotensin type 1 receptor antagonist, on optic nerve head (ONH) circulation was investigated in anesthetized rabbits. ONH blood flow was measured for 3 h using laser Doppler flowmetry. ONH blood flow disturbance was induced by intravenous injection of endothelin-1. Blood flow was decreased by 30%; this decrease was reversed by the injection of CS-088. A single injection of CS-088, however, did not alter the baseline ONH blood flow. It is concluded that CS-088 can have a beneficial effect on disturbed ONH blood flow.

Angiotensin II Type 1 Receptor Blockers↗