Zimmermann B
J Anat. 1984 Mar;138 ( Pt 2)(Pt 2):351-63.
During early chondrogenesis of the limb skeleton, cell condensations occur which are characterised by an increased density of cell packing, a decrease in the extent of the intercellular space and a drastic increase in the number of gap junctions. Electron microscopical investigations have been performed on the assembly and disassembly of these gap junctions in limb buds of mouse embryos during Days 10-12 of pregnancy. In undifferentiated mesenchyme, focal cell contacts occurred showing a gap of about 10 nm between adjacent cell membranes. During further development these contacts became broader, the intercellular gap decreased to 5 nm and gap junction structures were first formed at the ends of such cellular contacts. At the stage of maximum cell condensation, the blastemal cells were interconnected by large gap junctions, but there were also a considerable number of coiled gap junction structures present intracellularly. Near these coiled gap junctions, a well developed Golgi apparatus and many coated vesicles were generally detectable, indicating a fast turnover of cell membrane. The results suggest an insertion of gap junction components into the membrane during contact formation. Deposition of new cell membrane and coiling and invagination of gap junctions are discussed in the context of cell separation at the beginning of chondrogenesis.
在肢体骨骼的早期软骨形成过程中，会发生细胞凝聚，其特征是细胞堆积密度增加、细胞间间隙范围减小以及间隙连接数量急剧增加。对妊娠第10 - 12天小鼠胚胎肢体芽中这些间隙连接的组装和拆卸进行了电子显微镜研究。在未分化的间充质中，出现了局灶性细胞接触，相邻细胞膜之间显示出约10纳米的间隙。在进一步发育过程中，这些接触变得更宽，细胞间间隙减小到5纳米，间隙连接结构首先在这种细胞接触的末端形成。在细胞凝聚最大的阶段，胚基细胞通过大的间隙连接相互连接，但细胞内也存在相当数量的盘绕间隙连接结构。在这些盘绕间隙连接附近，通常可检测到发育良好的高尔基体和许多有被小泡，表明细胞膜有快速更新。结果表明在接触形成过程中间隙连接成分插入到膜中。在软骨形成开始时细胞分离的背景下，讨论了新细胞膜的沉积以及间隙连接的盘绕和内陷。
