Biomedical subjects

Y Hotehama

Publications and source records attributed to Y Hotehama.

4 recordsLinked to original sources

PubMed1995

Characterization of ciliary muscle relaxation induced by various agents in cats.

PURPOSE: To understand the cellular mechanism underlying the relaxation of ciliary muscle, relaxation induced by prostaglandins (PGs) and some other agents was characterized in the cat. METHODS: Tone of isolated ciliary muscle was measured by means of a force-displacement transducer. Adenylate cyclase activity was determined with membrane fraction of ciliary muscle by measuring the formation of cyclic adenosine monophosphate (cAMP). RESULTS: The addition of various PGs and isoproterenol relaxed the ciliary muscle that had been precontracted with 3 x 10(-6) M carbachol. The relaxation was dose dependent, with an EC50 of 2 x 10(-7) M for PGE2. The rank order of potency by which PGs induced relaxation (PGE2 = E1 > D2 > F2 alpha > I2) was identical with that reported for EP type prostaglandin receptor-mediated responses except for PGD2, which was more potent than expected. Agents that increased cellular cAMP, such as forskolin and IBMX, also relaxed the precontracted muscle. Nitric oxide donors, such as sodium nitroprusside and S-nitroso-N-acetyl-DL-penicillamine (SNAP), also caused dose-dependent relaxation. PGs and isoproterenol, but not nitroprusside, stimulated adenylate cyclase. The rank order of potency by which PGs stimulate adenylate cyclase was similar to that observed for muscle relaxation, suggesting that cAMP is the cellular second messenger for the PG-induced muscle relaxation and thus that PG receptors of EP2 and DP type are involved. CONCLUSIONS: Relaxation of cat ciliary muscle is mediated by two independent mechanisms: a cAMP-dependent one, which includes beta-adrenergic, EP2, and DP receptor-mediated responses, and a cAMP-independent one, which includes the nitric oxide-induced mechanism.

Adenylyl Cyclases↗

PubMed1994

Exercise intensity determines the magnitude of IOP decrease after running.

The effects of the intensity, duration and quantity (intensity x duration) of exercise on the reduction of intraocular pressure (IOP) in healthy and physically fit individuals were studied. Five minutes after 15 minutes of exercise at 70%, 55% and 40% of maximum exercise load (%HRmax) the IOP decreased 4.3 +/- 0.7 mmHg, 2.2 +/- 0.7 mmHg and 0.6 +/- 0.5 mmHg, respectively. The magnitude of IOP reduction increased with exercise load. Running for 7.5 minutes at 70%HRmax decreased IOP comparable to 15 minutes of running at the same exercise load (4.4 +/- 0.6 mmHg). Twenty-five minutes of running at 40%HRmax is almost the same quantity of exercise as 15 minutes of running at 70%HRmax. However, the former did not result in IOP reductions to equal the latter (2.3 +/- 0.5 vs 4.4 +/- 0.6 mmHg). The amount of IOP reduction after short-term exercise seems to depend on the intensity of exercise, not on the duration of exercise or the quantity of exercise.

Adult↗

PubMed1993

Clinical efficacy of PhXA34 and PhXA41, two novel prostaglandin F2 alpha-isopropyl ester analogues for glaucoma treatment.

Four clinical studies were performed in 54 healthy Japanese volunteers to assess the efficacy and the safety of two phenyl-substituted PGF2 alpha-isopropyl ester analogues, PhXA34 and PhXA41 after both single and repeated administrations. PhXA34 and PhXA41 reduced intraocular pressure (IOP) significantly in a dose-dependent way. The maximum IOP reductions were 14.5% to 17.5% with baseline adjustment at 10 to 12 hours after a single administration. No transient early elevation in IOP after treatment was observed. Based on the maximum IOP reducing effect of 1 microgram of PhXA34 and PhXA41, PhXA41 appeared to be at least 1.5 times more active than PhXA34. Tachyphylaxis of the ocular hypotensive effect did not develop during repeated administration for 5 days. A mild conjunctival hyperemia occurred in some subjects at high doses; it tended to diminish with time during the repeated administration of both drugs. Neither PhXA34 nor PhXA41 caused any change at any time in the aqueous flare intensity measured with a laser flare-cell meter. There were no changes in pupillary diameter after treatment. Each drug was well tolerated and caused no other ocular or systemic side effects.

Adolescent↗

PubMed1993

Ocular hypotensive effect of PhXA41 in patients with ocular hypertension or primary open-angle glaucoma.

A study was carried out to assess the clinical efficacy of PhXA41, a new phenyl-substituted prostaglandin F2 alpha-isopropyl ester analogue, using a single administration in 35 subjects with ocular hypertension or primary open-angle glaucoma. PhXA41 caused a dose-dependent intraocular pressure (IOP) reduction which continued 24 hours or more after administration. The mean IOP reduction 8 hours after treatment compared with the baseline IOP was 3.4, 4.9 and 5.9 mmHg for the doses of 25, 50 and 100 micrograms/ml, respectively. Although slight conjunctival hyperemia occurred in some patients, it disappeared by the next day with no treatment. No aqueous flare or cells were detected, no significant change in pupillary diameter was found, and no systemic symptom was reported. Thus, PhXA41 was well tolerated in subjects with ocular hypertension or primary open-angle glaucoma. Furthermore, its IOP-reducing effect was so long-lasting that a once daily application may suffice for clinical use.

Adult↗