脑发育临界期的实验研究

昆明种小鼠随机分为四组(A、B、C、D),B、C、D三组在孕15天～生后30天内饲以0.2％甲硫嘧啶,同时C和D组分别于生后16～30天和1～15天注射甲状腺素。B组仔鼠在36天龄时呈克汀病样改变:体重及运动量降低,学习能力下降,脑湿重、全脑DNA和核密度低于对照组A。C组基本上同于B组,但DNA和核密度高于B组,低于A组。D组尽管体重和运动量降低,但脑重和学习能力接近于对照组A,明显高于C组。因此生后1～30天内的甲状腺素缺乏可以导致脑发育落后,在整个脑发育临界期内,生后1～15天对小鼠中枢神经系统的发育最为重要。

THE STUDY ON CRITICAL PERIOD OF BRAIN DEVELOPMENT

White mice, Kunming strain, were divided into four groups at random (A, B, C and D), Groups B, C and D were given 0.2% methylthiouracil from 15th day of pregnancy to 30th day postnatally, and groups C and D were injected thyroxine during 16th - 30th and 1st-15th day after birth respectively. The following results were noted: (1) The offsprings of group B showed cretinous defects at the age of 36 days: body underdevelopment, low motility, poor learning ability and decreased brain weight, total DNA and nuclear density as compared with the control group A. (2) Group C had the similar manifestations, not as severe as in group B, but total DNA and nuclear density were higher than those of group B. (3) Group C also had low body weight and motility; however, the brain weight and learning ability were near to those of group A and significantly higher than those of group C. In conclusion, thyroxine deficiency in 1st - 30th day postnatally led to brain retardation and 1st-15th day was more important to the brain development, compared with 16th-30th day.