Biomedical subjects

H K Mishima

Publications and source records attributed to H K Mishima.

At least 19 recordsLinked to original sources

PubMed1997

Cytokine- and neuropeptide-mediated differentiation in retinal pigment epithelial cells in vitro.

To determine the mechanism of growth and differentiation of retinal pigment epithelial (RPE) cells it is important to understand the pathogenesis of several retinal diseases. Recently it has been reported that several cytokines and neuropeptides regulate the growth of RPE cells. In this study, the role of cytokines and neuropeptides in melanin synthesis, which is one indication of the RPE cell differentiation, was examined using chick RPE cells in vitro IL-1beta, TNF-alpha, substance P, beta-endorphin and methionine-enkephalin stimulated the melanin synthesis of RPE cells in a dose-dependent manner. The most effective concentrations of these agents on RPE cell melanin synthesis were not the same as that for RPE cell proliferation. These results indicate that cytokines and neuropeptides play an important role not only for the growth but also for the differentiation of RPE cells.

Animals↗

PubMed1997

Circadian intraocular pressure management with latanoprost: diurnal and nocturnal intraocular pressure reduction and increased uveoscleral outflow.

Based on their mechanism of action, the most frequently used ocular hypertensive agents, the beta-blockers, cannot be assumed to reduce IOP during sleep. The need for drugs that reduce IOP around-the-clock is underscored, however, by the fact that inadequate nocturnal ocular perfusion pressure is considered to be one of the likely causes of glaucomatous optic neuropathy especially in some cases of normal tension glaucoma. The studies reviewed here demonstrate that latanoprost, a new ocular hypotensive prostaglandin F2 alpha analogue, applied once a day at a concentration of 0.005%, maintains a statistically highly significant IOP reduction around-the-clock. The magnitude of this IOP reduction was found to be essentially identical during the day and at night, both in patients maintained on timolol and in those not receiving other glaucoma medication. Latanoprost-induced IOP reduction was also found to be associated with increased uveoscleral outflow in normotensive volunteers, both during the day and at night. These circadian studies suggest that this new ocular hypotensive agent can be expected to be particularly useful for the medical management of some forms of glaucoma, such as normal tension glaucoma, when the cause of the glaucomatous damage cannot be linked specifically to diurnal IOP abnormalities.

Administration, Topical↗

PubMed1997

Purification and characterization of alpha,beta-ketoalkene double bond reductases from bovine eyes.

PURPOSE: To explore the alpha,beta-ketoalkene double bond reductases responsible for xenobiotic metabolism in bovine ocular tissues using trans-phenyl-l-propenyl ketone as a model substrate. METHODS: A mixture of trans-phenyl-l-propenyl ketone, NADPH or NADH, and an enzyme source in 0.1 M K,Na-phosphate buffer (pH 7.4) was incubated for 15 min at 37 degrees C. Phenyl propyl ketone formed was quantified by high performance liquid chromatography (HPLC). RESULTS: The lens, ciliary body, iris, retinal pigment epithelium (RPE)-choroid, retina, and cornea exhibited alpha,beta-ketoalkene double bond reductase activities in the presence of NADPH or NADH. An alpha,beta-ketoalkene double bond reductase was purified to homogeneity from the iris-ciliary body cytosol. The molecular weight was estimated to be 58,000 by gel filtration, and 40,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The enzyme activity was inhibited by dicumarol, quercitrin, indomethacin, disulfiram, and p-chloromercuribenzoic acid. The enzyme exhibited double bond reductase activity toward 2-alkenals as well as alpha,beta-ketoalkenes. Another alpha,beta-ketoalkene double bond reductase was also purified to homogeneity from the lens cytosol. The molecular weight was estimated to be 105,000 by gel filtration and 40,000 by SDS-PAGE. The enzyme activity was inhibited by dicumarol and quercitrin. The enzyme exhibited double bond reductase activity toward some alpha,beta-ketoalkenes. CONCLUSIONS: Two kinds of enzymes responsible for reduction of the carbon-carbon double bond of xenobiotics were purified for the first time from ocular tissues. The molecular weights, substrate specificities, and sensitivities to inhibitors of the enzymes were different from each other.

Alkenes↗

PubMed1997

Incidence of retinal vein occlusion at the Glaucoma Clinic of Hiroshima University.

We prospectively surveyed the incidence of retinal vein occlusion (RVO) at the glaucoma clinic of Hiroshima University between 1986 and 1991. Among 433 glaucoma patients, 18 (4.2%) subsequently presented with RVO, 9 had central retinal vein occlusion (CRVO) and 9 exhibited branch retinal vein occlusion (BRVO). Seven of 87 (8.1%) patients with primary angle closure glaucoma exhibited RVO, showing the highest incidence among glaucoma types. The incidence of RVO detected by the general outpatient clinic was 0.59% during the same period. The BRVO/CRVO ratio in the glaucoma clinic was 1.0, while it was 4.3 in the general outpatient clinic. Glaucoma is an important risk factor for the development of RVO, especially CRVO.

Adult↗

PubMed1996

A comparison of latanoprost and timolol in primary open-angle glaucoma and ocular hypertension. A 12-week study.

OBJECTIVE: To evaluate the intraocular pressure (IOP)-reducing effect and the side effects of latanoprost (PhXA41), a new phenyl-substituted prostaglandin F2 alpha-isopropyl ester analogue, in patients with elevated IOP, using timolol maleate as the reference drug. METHODS: A total of 184 patients with primary open-angle glaucoma or ocular hypertension at 35 medical centers participated in this randomized double-masked study. The patients were randomized to receive either 0.005% latanoprost once daily or 0.5% timolol maleate twice daily, for a period of 12 weeks. Intraocular pressure was measured 24 hours after the administration of timolol, at 2, 4, 8, and 12 weeks of treatment. RESULTS: Latanoprost reduced IOP at the end of 12 weeks by 6.2 +/- 2.7 mm Hg (mean +/- SD) (26.8%), while timolol reduced IOP by 4.4 +/- 2.3 mm Hg (19.9%). At all visits latanoprost reduced IOP significantly more than timolol did. The main ocular side effects observed in both groups were conjunctival hyperemia and smarting. The main systemic side effect was a reduced pulse rate, which occurred in patients treated with timolol. CONCLUSIONS: The results of this study demonstrated that 0.005% latanoprost taken once daily is well tolerated and more effective in reducing IOP than 0.5% timolol taken twice daily. Thus, latanoprost may become an important choice for the medical treatment of glaucoma.

Adrenergic beta-Antagonists↗

PubMed1996

Ultrasound biomicroscopic study of ciliary body thickness after topical application of pharmacologic agents.

PURPOSE: To examine the changes in ciliary body thickness after topical application of pilocarpine, cyclopentolate hydrochloride, and PhXA41, a prostaglandin F2alpha analog. METHOD: We used high-frequency Humphrey UBM840 ultrasound biomicroscope to examine 36 healthy young Japanese subjects. RESULTS: The mean ciliary body thickness increased from 0.67 +/- 0.07 mm to 0.073 +/- 0.08 mm (P < .01) after application of 2% pilocarpine; 1% cyclopentolate hydrochloride and 0.005% PhXA41 decreased the mean ciliary body thickness from 0.75 +/- 0.07 mm to 0.69 +/- 0.05 mm (P < .05) and from 0.78 +/- 0.06 mm to 0.75 +/- 0.06 mm (P < .01), respectively. CONCLUSIONS: Our ultrasound study clearly indicates that pilocarpine increased comparative thickness of the ciliary body by 8.3%, whereas PhXA41 decreased comparative thickness by 3.3% in a manner similar to cyclopentolate hydrochloride.

Administration, Topical↗

PubMed1996

Stimulation of retinal pigment epithelial cell growth by neuropeptides in vitro.

PURPOSE: The proliferation of many cell types are regulated by cytokines and neuropeptides by autocrine and paracrine mechanisms. Retinal pigment epithelial (RPE) cells are also regulated by cytokines. But RPE cells are very close to the neural retina which has some neuropeptides. The present study was to investigate the effects of neuropeptides on the growth of RPE cells. METHODS: RPE cells were obtained from the eyes of 11 day old chick embryos and cultured in Dulbecco's modified Eagle's culture medium containing 10% fetal calf serum. The growth of RPE cells was evaluated by [3H]-thymidine uptake. RESULTS: Substance P, beta-endorphin and calcitonin gene-related peptide markedly stimulated the growth of RPE cells. The effects of methionine-enkephalin, somatostatin and vasoactive intestinal peptide were intermediate. The strongest effects of substance P, beta-endorphin and calcitonin gene-related peptide were observed at 10(-6) to 10(-7) M. The stimulation of RPE cells with beta-endorphin was inhibited by naloxone, suggesting that the stimulation with beta-endorphin is mediated by an opioid receptor. beta-endorphin and substance P induced RPE cell growth stimulating activity. Leucine-enkephalin and neuropeptide Y did not affect the growth of RPE cells. CONCLUSIONS: These results suggest that neuropeptides play an important role in the regulation of RPE cell growth.

Animals↗

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↗

PubMed1995

Isoforms of glucose transporter in the iris-ciliary body.

Isoforms of the facilitated glucose transporter (GLUT) were identified in the iris-ciliary body. Western blot analysis showed that GLUT1 and GLUT4 proteins were expressed in the rat iris-ciliary body. In addition, the content of GLUT proteins in the rabbit iris-ciliary body was estimated by specific [3H]cytochalasin B binding assay. The content of GLUT proteins was found to be more abundant in the iris-ciliary body than in the cerebral cortex. The utilization of glucose in the iris-ciliary body and the transport of glucose into the aqueous humor are suggested to be mediated by GLUT1 and GLUT4 proteins.

Animals↗

PubMed1995

Ca2+/calmodulin effects on cAMP response in cultured chick ciliary epithelial cells.

The authors investigated the influence of the elevation of intracellular Ca2+ concentration on the production of cyclic adenosine 3',5'-monophosphate (cAMP) using cultured chick embryo ciliary epithelium (CE). We examined the effects of calcium ionophore (A23187) on cAMP production after incubation with vasoactive intestinal peptide (VIP), isoproterenol (ISO), sodium fluoride (NaF) or forskolin (FSK). A23187 had no effect on the basal cAMP level, or the NaF- and FSK-stimulated responses for cAMP level; but A23187 potentiated VIP- and ISO-stimulated cAMP responses. Calmodulin antagonist (W-7) was very effective in inhibiting the potentiating effects of A23187 on VIP and ISO-stimulated production of cAMP. Our present findings suggested that Ca2+/calmodulin may potentiate the receptor-mediated cAMP pathway through Ca2+/calmodulin-dependent protein kinase in the CE.

1-Methyl-3-isobutylxanthine↗

PubMed1995

The effects of prostaglandins on the blood-ocular barrier.

The effects of prostaglandins (PGs) and PG-related compounds on the blood-ocular barriers were examined using pigmented rabbits. Latanoprost (PhXA41), PGF2(alpha)-isopropyl ester (PGF2(alpha)-IE) or PGE2 was topically applied once only or once daily for 8 weeks. Aqueous flare was measured with a laser flare-cell meter, and morphological changes in the ciliary processes after repeated applications of a test drug were investigated by means of light or electron microscopy using horseradish peroxidase (HRP) as a tracer. PGF2(alpha)-IE and PGE2, but not PhXA41, caused an initial rise in the aqueous flare after application. On the other hand, no morphological changes were found in the ciliary processes after 8-week PhXA41 application. After 8-week application of PGF2(alpha)-IE or PGE2 dilation of ciliary channels in the ciliary processes were found. Leakage of intravenously injected fluorescein was measured by a vitreous fluorophotometer after an intravitreal injection of PGE2, PGF2(alpha), or PhXA41. Vitreous fluorescence was significantly higher in treated eyes than in controls after intravitreal injection of PGE2 or PGF2(alpha), while it showed no significant change after intravitreal injection of PhXA41. Only PGE2 caused morphological changes in the retina. These results suggest that PhXA41 does not compromise the integrity of the blood-ocular barriers, and has a potential as a future anti-glaucoma eyedrop.

Administration, Topical↗

PubMed1994

Growth regulation of retinal pigment epithelial (RPE) cells in vitro.

Studies of growth factor production by chick embryo retinal pigment epithelial (RPE) cells and the effects of cytokines on chick and human RPE cells were performed in vitro. RPE cell growth was evaluated by tritiated thymidine uptake. Chick RPE cells produced growth factors whose molecular weights were 15 and 108 kD. These fractions contained interleukin (IL)-1-like activity which stimulated murine thymocyte proliferation. 100-150 U/ml human IL-1 beta, interferon (IFN)-beta, IFN-gamma and tumor necrosis factor (TNF)-alpha stimulated the growth of both RPE cells. The activity of IFN-beta was the most potent of these cytokines, while IL-2 and IFN-alpha had no effect in chick RPE cells. 100-150 U/ml transforming growth factor (TGF)-beta 1 suppressed cytokine-induced growth of both RPE cells. RPE cells therefore produce growth factors, respond to several growth factors and are regulated by a network of cytokines.

Aged↗

PubMed1994

Effect of cytokines and prostaglandins on the growth of chick retinal pigment epithelial cells.

The effect of cytokines and prostaglandins on the growth of chick retinal pigment epithelial (RPE) cells was studied in vitro. The growth of RPE cells was evaluated by [3H]-thymidine uptake. Human recombinant interleukin-1 beta, interferon-beta and tumor necrosis factor-alpha stimulated the growth of RPE cells at 50-200 units/ml. Prostaglandins such as PGE1, PGE2 and PGF2 alpha suppressed RPE cell growth at 10(-5) approximately (-6)M. Indomethacin, an inhibitor of cyclooxygenase, did not affect the spontaneous RPE cell growth at 10(-7) approximately (-9) M. However, 10(-7) M indomethacin enhanced RPE cell growth stimulated by cytokines synergistically. The addition of 10(-6) M PGF2 alpha suppressed the enhanced growth of RPE cells which was induced with cytokines and indomethacin. Furthermore, RPE cells stimulated with cytokines produced PGE2. These results suggest that RPE cells produce prostaglandins which have a negative regulatory role in RPE cell growth.

Animals↗

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

15-Ketoprostaglandin delta 13-reductase activity in bovine ocular tissues.

The present study provides the first evidence for delta 13-reduction of 15-ketoprostaglandins (15-keto-PGs) by bovine ocular tissues. The 9,000xg supernatants of cornea, iris, ciliary body, retina, and RPE-choroid except lens exhibited delta 13-reductase activity toward 15-keto-PG E2 and F2 alpha in the presence of NADPH or NADH as an electron donor. Among the tissues tested, the highest activity was observed in ciliary body and iris, followed by RPE-choroid, retina, and cornea. The NADPH- and NADH-linked double bond reductase activities were inhibited by dicumarol, quercitrin, indomethacin and disulfiram, but not by potassium cyanide. NADPH-linked 15-keto-PG F2 alpha delta 13-reductase was purified from bovine iris-ciliary body cytosol by fractionation with ammonium sulfate and high performance liquid chromatography (HPLC) with TSK gel DEAE-5PW, and TSK gel Blue-5PW. The purified enzyme was homogenous by the criterion of sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Its molecular weight was estimated to be about 57,000 by electrophoresis, and about 55,000 by gel filtration HPLC with Superose 12.

15-Oxoprostaglandin 13-Reductase↗

PubMed1993

Binding of antiglaucomatous drugs to synthetic melanin and their hypotensive effects on pigmented and nonpigmented rabbit eyes.

The binding of ocular hypotensive drugs to synthetic melanin was studied spectrophotometrically in vitro. The ocular hypotensive effects of the drugs, namely, timolol, befunolol, carteolol, pilocarpine, epinephrine, prostaglandin A2, F2 alpha and E2, also were compared in vivo on eyes of pigmented and albino rabbits. At an initial concentration of 10(-4) M, each of the three beta-blockers exhibited a binding rate of 80-85% as compared to only 40% for pilocarpine and 50% for epinephrine. Almost none of the prostaglandins were found to bind to synthetic melanin. Topically applied, 0.5% timolol and 3% pilocarpine significantly lowered the intraocular pressure in albino but not in pigmented rabbits. Epinephrine (1%) caused a significant reduction in the intraocular pressure both in albino and pigmented rabbits; however, the maximum reduction was greater in albino than in pigmented rabbits. Intraocular pressure was reduced to the same extent and with a similar time-course in both albino and pigmented rabbits by 0.02% prostaglandin A2, F2 alpha and E2. These findings show that several ocular hypotensive drugs bind to melanin and suggest that this process can modify the extent of their pharmacological effects when tested in a single dose, or the time-course of their effects when used to treat chronic conditions.

Adrenergic beta-Antagonists↗

PubMed1993

Ophthalmic diseases in bedridden patients with severe dementia.

Ophthalmologic examinations were performed on the 176 eyes of 88 bedridden patients with severe dementia. There were some pathologic changes in the external and anterior segments of 93 eyes. We observed infectious external and anterior segment eye diseases in 80 of these 93 eyes (86.0%). Fundus diseases were found in 34 eyes, but treatment was not necessary. Infectious eye diseases appeared to be the most prevalent ocular problem in these patients. Cultures of conjunctival swabs commonly demonstrated Staphylococcus aureus. No differences were noted in tear secretion rate or lysozyme concentrations in tears between eyes with and without infection. The blinking frequency was significantly reduced in infected eyes compared to normal eyes. Failure of the lacrimal drainage system was observed more often in infected eyes than in normal eyes. This study demonstrated that bedridden patients with severe dementia develop infectious eye diseases easily, to which stasis of tear flow seems to predispose. In caring for bedridden patients with severe dementia, ophthalmologists must be concerned with controlling infectious eye diseases.

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↗