Daikoku S, Kinutani M, Sako M
Cell Tissue Res. 1977 Mar 30;179(1):77-86. doi: 10.1007/BF00278463.
The adrenal medullae of rats were studied electron microscopically from day 13.5 of gestation. Synapses with thickening of pre-and post-synaptic membranes were first evidenced on the medullary cells of 15.5-day-old fetuses. They increased gradually in number with advancing age. In the medullary cells, a few membrane-limited granules were recognized on day 13.5 of gestation, and thereafter they increased in number. The appearance of the granules was not uniform; some of the granular contents consisted of fine or coarse particles and others contained homogeneous material of varying electron-densities. The population of these granules in the cytoplasm was different from cell to cell. Thus, the discrimination of cell types (NA-and A-cells) was not possible in the prenatal period. Granular discharge of the cells was totally absent in the normal untreated fetuses. However upon the intraperitoneal administration of insulin to the fetus on day 16.5, 18.5, or 21.5 of gestation, discharge by reverse pinocytosis was first evidenced in the medullary cells of the 21.5-day-old fetus.
从妊娠第13.5天开始，对大鼠肾上腺髓质进行了电子显微镜研究。在15.5天大的胎儿髓质细胞上首次发现突触前膜和突触后膜增厚的突触。随着年龄的增长，它们的数量逐渐增加。在妊娠第13.5天，在髓质细胞中可识别出一些膜包颗粒，此后其数量增加。这些颗粒的外观并不一致；一些颗粒内容物由细颗粒或粗颗粒组成，另一些则含有电子密度不同的均质物质。这些颗粒在细胞质中的数量因细胞而异。因此，在产前阶段无法区分细胞类型（去甲肾上腺素细胞和肾上腺素细胞）。在未经处理的正常胎儿中，细胞的颗粒释放完全不存在。然而，在妊娠第16.5天、18.5天或21.5天对胎儿腹腔注射胰岛素后，在21.5天大的胎儿髓质细胞中首次发现通过反向胞饮作用的释放。
