Wrobel K H, Bickel D, Kujat R, Schimmel M
Institut für Anatomie, Universität Regensburg, Germany.
Cell Tissue Res. 1995 Aug;281(2):249-59. doi: 10.1007/BF00583394.
The spermatogonial stem cell line in prepubertal and adult bovine testis was studied by electron microscopy and protein gene product 9.5 immunohistochemistry. Three successive spermatogonia precursor cell configurations were observed. Small basal stem cells were found to possess a spherical shape and nuclei with two to three nucleoli. They were observed in prepubertal testes (25 and 30 weeks) and in low numbers during all the stages of the seminiferous epithelial cycle in the adult. Aggregated spermatogonia precursor cells are the dominating germ cell type in the 25-week-old and 30-week-old calf. In the adult seminiferous epithelium, they cause expansion of the basal tubular compartment as they form dense groups containing up to 15 cells. These groups are observed concomitantly with cycling A-spermatogonia and preleptotenes at the beginning of spermatocytogenesis. At the end of A-spermatogonia propagation, the aggregated spermatogonia precursor cells separate and intermingle with cycling A-spermatogonia. The spermatogonia precursor cells can later be found together with I-spermatogonia as members of an interconnected cellular network of medium-sized cells. When the I-spermatogonia divide to form the smaller B-spermatogonia, the precursor cells, which stay connected with the cycling spermatogonial population, pass through a growth phase. They can now be considered as committed spermatogonia precursor cells and are continuously being transformed into A1-spermatogonia to start a new round of spermatocytogenesis. Ultrastructurally, all members of the precursor cell line are similar. However, a number of features have been found to show a quantitative increase (endoplasmic reticulum, mitochondria) or to exhibit a rising degree of complexity (nucleolus) during the progression from basal stem cells to committed spermatogonia precursor cells.
通过电子显微镜和蛋白质基因产物9.5免疫组织化学方法，对青春期前和成年牛睾丸中的精原干细胞系进行了研究。观察到了三种连续的精原细胞前体细胞形态。发现小的基底干细胞呈球形，细胞核中有两到三个核仁。它们在青春期前的睾丸中（25周和30周）被观察到，在成年动物生精上皮周期的所有阶段数量都很少。聚集的精原细胞前体细胞是25周龄和30周龄小牛中主要的生殖细胞类型。在成年生精上皮中，它们形成含有多达15个细胞的密集群体，导致基底管状隔室扩张。这些群体在精子发生开始时与循环的A型精原细胞和前细线期细胞同时被观察到。在A型精原细胞增殖结束时，聚集的精原细胞前体细胞分离并与循环的A型精原细胞混合。精原细胞前体细胞后来可以作为中等大小细胞相互连接的细胞网络的成员，与I型精原细胞一起被发现。当I型精原细胞分裂形成较小的B型精原细胞时，与循环的精原细胞群体保持连接的前体细胞会经历一个生长阶段。它们现在可以被认为是定向的精原细胞前体细胞，并不断转化为A1型精原细胞，开始新一轮的精子发生。在超微结构上，前体细胞系的所有成员都相似。然而，已经发现一些特征在从基底干细胞到定向精原细胞前体细胞的过程中呈现出数量上的增加（内质网、线粒体）或复杂性程度的上升（核仁）。
