Experimental analysiss of morphogenesis of hypothalamohypophyseal system

利用野生型(富含黑色素颗粒)和白化(不含黑色素颗粒)的中华大蟾蜍胚胎进行移植实验，以确定垂体细胞的来源。神经脊的前部几乎是上皮性垂体分泌细胞的唯一来源。在开放神经元期，垂体原基和下丘脑原基紧密对置。在神经管形成后很长一段时间内，观察到一些前神经脊起源的细胞群迁移到下丘脑。其中一种是已知的LHRH神经元。但还有另一个细胞群，当垂体原基附着在漏斗上时，它与垂体原基一起迁移，并穿透到下丘脑前部。虽然这些细胞没有特征，但它们很有可能分化为下丘脑神经元。因此，我们得出结论，下丘脑和垂体是一种密切的克隆关系。在未与下丘脑接触的垂体腺原基中，未见POMC细胞。在没有垂体原基的情况下，正中隆起和垂体性神经元的伸展都不会发生。这表明，诱导脑垂体和下丘脑分化的刺激信号是双向的；从下丘脑到脑垂体，反之亦然。

Using Bufo embryos of wild type (rich in melanin granules) and of albino (devoid of melanin granules) transplantation experiments were carried out to identify the origin of the pituitary cells. The anterior part of the neural ridge was found to be the almost exclusive source of the secretory cells in the epithelial pituitary. It was also found that the pituitary primordium and the anlage of the hypothalamus are closely apposed at the open neurula stage. Some of anterior neural ridge-originated cell groups were observed to migrate into the hypothalamus long after the formation of neural tube. One of them is known to be LHRH neurons. But there is another cell group which migrates together with the pituitary primordium and penetrates into the anterior hypothalamus when the pituitary primordium attaches to the infundibulum. Although these cells are not characterized, it is highly probable that they differentiate into hypothalamic neurons. Thus, we concluded that the hypothalamus and the hypophysis are in an intimate clonal relationship. In the hypophyseal primordium developed without contact with the hypothalamus, POMC cells did not appear. Without pituitary primordium, neither development of the median eminence nor extension of hypophysiotripic neurons occurred. This indicates that stimulatory signals that induce differentiation of the hypophysis and hypothalamus are bidirectional ; from hypothalamus to the hypophysis and vice versa.