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I Tobari

Publications and source records attributed to I Tobari.

57 records · Page 4Linked to original sources

Studies on chromosome aberrations in the eggs of mice fertilized in vitro after irradiation. I. Chromosome aberrations induced in sperm after X-irradiation.

The induction of chromosome aberrations in eggs of mice fertilized with X-irradiated sperm was performed by using an in vitro fertilization technique. Capacitated mature sperm was irradiated with various doses of X-rays and cytological analysis of the first cleavage metaphase of in vitro fertilized eggs was made. The frequencies of chromosome aberrations increased exponentially with dose and the dose-response relationship for overall breaks fitted well to a quadratic equation. The chromosome aberrations were mainly chromosome-type (82.1%), and the majority of aberrations were fragments.

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Effects of tranilast on cultured rabbit corneal keratocytes and corneal haze after photorefractive keratectomy.

PURPOSE: In vitro and in vivo studies were performed to elucidate the effects of tranilast on cellular proliferation and collagen synthesis. METHODS: Subculturing was carried out using keratocytes from rabbits that underwent photorefractive keratectomy (PRK) and developed corneal haze, and keratocytes from normal rabbit cornea. RESULTS: Tranilast suppressed proliferation in cultured keratocytes from the corneal haze region at doses of 30 and 300 micromol/L and collagen synthesis at doses of 3, 30, and 300 micromol/L. Normal corneal cultures showed suppression of keratocyte proliferation and collagen synthesis only at a high dose of tranilast (300 micromol/L). Betamethasone suppressed proliferation of keratocytes in both haze and normal cornea at a dose of 10 micromol/L, as well as collagen synthesis at respective doses of 1 and 10 micromol/L. Diclofenac sodium suppressed collagen synthesis of keratocytes in haze cornea at a high dose of 100 micromol/L, and in keratocytes in normal cornea, at doses of 10 and 100 micromol/L. In an in vivo study, either 0.5% tranilast, 0.1% betamethasone phosphate eye drops, or a tranilast base solution (control) was instilled four times daily to rabbits that had undergone PRK. Weekly evaluation of the inhibitory effect of these drugs on the development of haze was performed 2 weeks after surgery. Tranilast suppressed haze 6-13 weeks after PRK, but betamethasone phosphate showed no effect. CONCLUSION: These results indicate that tranilast is potentially effective for inhibiting the corneal haze that occurs after PRK.

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In vitro fertilization rate of mouse eggs with sperm after X-irradiation at various spermatogenetic stages.

The frequency of in vitro fertilization of mouse eggs using sperm obtained weekly (for 1-9 weeks) from epididymis after testicular X-irradiation (200 rad) was observed. The sperm concentrations for insemination were 100, 200 and 300/mm3. The number of fertilized eggs seemed to remain constant almost at control level (90-98%) until the 4th week after X-irradiation. Thereafter, the number declined to reach a minimum level (about 30-50%) in the 6th week; they then recovered completely in the 8th week. This tendency was found at all sperm concentrations used. This result indicates that the most sensitive stage for the fertilization capacity of sperm to X-rays was the early spermatocytes or the late spermatogonia. The high radiosensitivity of the fertilization capacity of sperm irradiated during the early-spermatocyte to late-spermatogonial stage, corresponded well with the rate of induction of sperm abnormalities and spermatogenetic cell killing. The in vitro fertilization rate was not restored by an increase in sperm concentration at insemination; it is, therefore, likely that the in vitro fertilization frequency depends on the proportion of sperm with abnormal morphology and abnormal fertilization ability, and sperm number seems to have hardly any influence on the fertilization rate, as far as the in vitro fertilization experiment is concerned.

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