Masanori Okamoto

Dose-response relationship of γ-ray-induced reciprocal translocations at low doses in spermatogonia of the crab-eating monkey (Macaca fascicularis)

Abstract The yield of translocations induced by acute γ-irradiation at low doses (0.25 and 0.50 Gy) in the crab-eating monkeys (Macaca fascicularis) spermatogonia was examined. The frequencies of translocations per cell were 0.53% at 0.25 Gy and 1.07% at 0.50 Gy. Over the low dose range from 0 to 1 Gy, the dose-response relationship for translocation yield was a linear one with a regression coefficient of 1.79 · 10−2. To estimate the sensitivity to the induction of translocations in the crab-eating monkeys spermatogonia, the slope of the regression line was compared with those in other mammalian species. Consequently, over the low dose range below 1 Gy, the sensitivity of the crab-eating monkeys spermatogonia to translocation induction was similar to several mammalian species, the mouse. Chinese hamster, and the rabbit, but significantly higher than that of the rhesus monkey and lower than that of the marmoset.

Dose-response relationship for translocation induction in spermatogonia of the crab-eating monkey (Macaca fascicularis) by chronic γ-ray-irradiation

The induction of reciprocal translocations in spermatogonia of the crab-eating monkey (Macaca fascicularis) by chronic gamma-irradiation (1.8 x 10(-5) Gy/min, about 0.024 Gy/22 h/day) was examined. The frequencies of translocation per cell were 0.15% at 0.3 Gy, 0.27% at 1.0 Gy and 0.33% at 1.5 Gy. The dose-response relationship for translocation yield was a linear one with a regression coefficient (b) of 0.16 x 10(-2). When the slope (b) of the regression line was compared with that at a high dose rate (0.25 Gy/min, b = 1.79 x 10(-2), it was clear that the induction rate of translocations after chronic gamma-irradiation was only about one-tenth of that after high-dose-rate irradiation. Thus, there was evidence for a pronounced dose-rate effect in the crab-eating monkey.

Effects of Glucose and Pyruvate on the Sperm Pene- tration and Fertilization of Mouse Eggs In Vitro

体外におけるマウス卵子への精子侵入に必要な因子を解明する目的で,培地内に含まれるグルコースおよびピルビン酸の影響について検討した.JCL:ICR系成熟マウスの過排卵卵子と精巣上体精子を用いて,化学組成の明確な培地内で体外受精を行なった.ピルビン酸のみ添加したグルコースを欠く培地内では卵丘細胞の有無にかかわらず卵子への精子侵入は全く起こらなかった.一方,グルコースのみ添加した実験区では卵丘細胞を有する場合には,精子侵入卵の割合は95%と高い値を示したが,卵丘細胞を除去された裸化卵子では受精率は低く,前核形成には至らなかった.受精能獲得誘起のための精子前培養用培地はピルビン酸のみを含む場合でも,受精用培地にグルコースが存在すれば高い受精率が得られ,一方精子前培養用培地にグルコース,受精用培地にピルビン酸を添加した区では精子前培養時間の延長に伴って受精率が上昇した.さらに,ピルビン酸のみを含む培地内に卵子と精子を共存させ,次いでグルコースを添加したところ精子は卵子への侵入を開始した.これらの結果からグルコースはマウスの精巣上体精子が卵子へ侵入し受精を成立させるための必須の因子であり,その作用はピルビン酸では代替できないこと,およびグルコースは精子の受精能獲得の最終段階または精子の卵子透明帯通過に必要であると推察された.