Zavala G, Vázquez-Nin G H
Department of Biology, Faculty of Sciences UNAM, Mexico City, Mexico.
Biol Cell. 1997 Jul;89(4):245-55.
The nuclear structure of the epiblast and skin cells was studied during the development of the chick embryo (Gallus domesticus). Ribonucleoproteic structures (RNPs) and chromatin were characterized with preferential staining techniques. The changes of the frequency of a type of RNP particle, the perichromatin granule, from gastrulating embryos to newly hatched chick, were analyzed by electron microscopic quantitative stereology. The changes of nuclear and nucleolar volume were estimated using the light microscope. The differentiation of ectoderm from epiblast is characterized by a significant increase in the nucleolar volume and in the frequency of perichromatin granules. These features suggest that ectoderm differentiation involves a general increment of mRNA and rRNA transcription. At the beginning the synthesis of a sulfhydryl-rich protein, which is coincident with the thickening of the bilayered epithelium to a multilayered epithelium, a large increase of the numerical density of perichromatin granules not accompanied by any modification of the nucleolar volume was found. The same changes characterize the acquisition of epidermal mature cell features immediately after hatching. These findings as well as previous results concerning the differentiation of central nervous system and striated muscle suggest that the increases of the number of perichromatin granules take place during the acquisition of new cytophysiological states related to functional maturation and not to early stages of cell differentiation.
在鸡胚（家鸡）发育过程中，研究了上胚层和皮肤细胞的核结构。采用优先染色技术对核糖核蛋白结构（RNPs）和染色质进行了表征。通过电子显微镜定量体视学分析了从原肠胚形成的胚胎到刚孵出的小鸡，一种核糖核蛋白颗粒即染色质周围颗粒的频率变化。使用光学显微镜估计核和核仁体积的变化。上胚层向外胚层的分化特征是核仁体积和染色质周围颗粒频率显著增加。这些特征表明外胚层分化涉及mRNA和rRNA转录的普遍增加。在富含巯基蛋白合成开始时，这与双层上皮增厚为多层上皮同时发生，发现染色质周围颗粒的数量密度大幅增加，而核仁体积没有任何变化。相同的变化特征也出现在刚孵出后表皮成熟细胞特征的获得过程中。这些发现以及先前关于中枢神经系统和横纹肌分化的结果表明，染色质周围颗粒数量的增加发生在与功能成熟相关的新细胞生理状态的获得过程中，而不是在细胞分化的早期阶段。
