ULTRASTRUCTURAL CHANGES OF NUCLEI AFTER TREATMENT WITH MESODERMAL INDUCING SUBSTANCE

Ultrastructural changes occur in the nuclei of the presumptive ectoderm cells of theearly gastrula of Cynops orientalis after treatment with a mesodermal inducing substance(guinea pig bone marrow extract). The large condensed chromatin masses in the nuclei ofthe control series are no longer found; they become more or less dispersed. The successivechanges of chromatin from condensed to dispersed have been observed. And in connectionwith the observations on neural induction after Ca-free treatment, the transformation fromheterochromatin to euchromatin as the initiation of cell differentiation has been discussed.     

早期发育细胞间相互关系的电子显微学研究

根据电镜观察，结合在两栖类胚胎进行的在体和离体实验的结果，认为，在胚胎发育的早期，“决定”和“分化”两个过程中细胸间的相互关系不同，不但相互作用的细胞类别不同，方式也不一样。在“决定”过程中，主要的影响自相邻细胞，也就是不同类别的细胞，方式可能是多样的。     

EFFECT OF ANTIBODIES AGAINST THE GAP JUNCTION PROTEIN ON DIFFERENTIATION OF INDUCED EMBRYONIC CELLS

Microinjections of antibodies against gap junction prorein to early blastomcres of Xenopus laevis were succeeded by the treatments of mesodermal inductor. It was found that induction was not affected by the injection of the antibodies but the differentiation of notochord and muscle was impeded at different degrees. Cell interactions via gap junction communication seem to be involved in the differentiation of the induced cells.     

POLARIZATION OF TIGHT JUNCTION DURING THE PROCESS OF ITS FORMATION

By the freeze-etching technique, electron microscopic observations of the formation of the tight junction of embryonic cells of Cynops orientalis were carried out. Three states were recorded: isolated fragments of junctional strands occurred at the lateral membrane, the isolated fragments connected to form a more or less continuous band and finally a typical bandlike structure was observed at the apical border of the cell. They represent the transitional stages of the polarization of the tight junction. The dependence of the polarization on the appearance of the segmentation cavity and the interrelationship between the polarization and the domains of the epithelial cells were discussed.     

紧密连接形成过程中的极性化现象

本文用冰冻蚀刻的技术,观察了东方蝾螈早期胚胎细胞中紧密连接的形成过程。看到了它们处于三种状态:在侧膜上存在着分散的条索片段,分散的片段连成断断续续的连接结构,最后在细胞顶端形成典型的带状结构。它们代表紧密连接的极性化过程。结合分裂腔的出现讨论了紧密连接极性化的产生,以及极性化与上皮细胞领区划分的相互关系。     

抗间隙连接蛋白抗体对胚胎细胞诱导分化的影响

本文用爪蟾胚胎,先给早期裂球微量注射抗间隙连接抗体,待胚胎发育到原肠早期,割取外胚层,用中胚层诱导物质处理。结果发现,抗体注射不影响诱导作用,但是,诱导形成的脊索和肌肉细胞的分化却受到不同程度的阻抑。通过间隙连接的细胞间相互作用很可能在诱导形成的细胞分化中起一定作用。     

中胚层诱导物质处理后细胞核的超微观察

本文证明蝾螈原肠早期的预定外胚层经中胚层诱导物质(豚鼠骨髓抽提液)处理后,细胞核的超微结构出现了变化。对照组细胞核中体积较大的、浓缩的染色质团块不再存在,而是出现比较小而疏散的团块,以至分散的染色质纤维。这可能代表染色质松散的过程。结合以往缺钙处理引起神经诱导的观察,认为这种异染色质向常染色质的转变应该是诱导刺激引起细胞分化的征兆。     

类β-内啡肽物质在两栖类胚胎表皮细胞的免疫电镜定位

本文用免疫电镜包埋后技术研究了类β－内啡肽物质在两栖类胚胎表皮细胞中的定位。观察到类β－内啡肽物质主要分布在胚胎表皮外层细胞的外缘部位。除在囊泡状结构内含物上、囊泡壁以及附近,在细胞卢的外缘和细胞外分泌物上也都观察到金颗粒的分布。认为,类β－内啡肽物质在表皮细胞中,首先集中在外层细胞的囊泡状结构内,然后释放到细胞外。