Wood A, Thorogood P
J Cell Sci. 1984 Mar;66:205-22. doi: 10.1242/jcs.66.1.205.
In the teleost embryo the pectoral fin bud initially displays an apical ectodermal ridge along its entire distal margin. The ridge subsequently becomes transformed into an apical fold as the distal ectodermal epithelium grows and folds to enclose an extracellular space between the apposed basal surfaces of the epithelium. Collagen fibrils up to 2 micron in diameter, termed 'actinotrichia', are deposited along the proximo-distal axis in two (dorsal and ventral) arrays. The actinotrichia are aligned parallel to one another with a regular spacing along the greater part of their length. Mesenchymal cells migrating distally from the base of the fin bud encounter the dorsal and ventral arrays of actinotrichia and move between them apparently using the fibrils as a substratum. The entire structure is transparent and, using the killifish Aphyosemion scheeli, we have investigated the migration of the mesenchymal cells between 135 and 220 h of development, using Nomarski interference contrast microscopy and time-lapse video recording. The number of cellular processes per cell increased significantly during the period of observation. These processes could be graded according to their diameters. Processes of diameter greater than 2 micron were not usually aligned along actinotrichia and arose at any aspect of the cell body. In contrast, processes with diameters less than 2 micron appeared to be confined to the distal aspects of the migrating cells and showed an increasing tendency to become aligned as development progressed. Time-lapse video recordings revealed that such aligned processes move faster (mean speed 17.98 (+/- 2.25) micron/h) than non-aligned processes (mean speed 4.66 (+/- 0.67) micron/h). Whole cell translocation was generally slower than rates of process movement: the lowest mean value (1.52(+/- 0.36) micron/h) was recorded between 135 and 160 h of development rising to a maximum mean rate (4.72(+/- 0.42) micron/h) between 195 and 220 h; the period of the fastest rate of cell translocation correlated with maximum process alignment along actinotrichia. Thin 1 micron plastic sections revealed that, generally, aligned processes were in close association with the surface of the actinotrichial fibrils and not the spaces between them.
在硬骨鱼胚胎中，胸鳍芽最初在其整个远缘显示出一条顶端外胚层嵴。随着远端外胚层上皮生长并折叠以包围上皮相对基底面之间的细胞外空间，该嵴随后转变为顶端褶皱。直径达2微米的胶原纤维，称为“鳍条”，沿近远轴以两个（背侧和腹侧）阵列沉积。鳍条在其大部分长度上彼此平行排列，间距规则。从鳍芽基部向远端迁移的间充质细胞遇到背侧和腹侧的鳍条阵列，并显然以这些纤维为基质在它们之间移动。整个结构是透明的，我们使用鳉鱼Aphyosemion scheeli，通过微分干涉相差显微镜和延时视频记录，研究了发育135至220小时期间间充质细胞的迁移。在观察期间，每个细胞的细胞突起数量显著增加。这些突起可以根据其直径进行分级。直径大于2微米的突起通常不沿鳍条排列，而是在细胞体的任何部位出现。相反，直径小于2微米的突起似乎局限于迁移细胞的远端，并且随着发育的进行，排列的趋势增加。延时视频记录显示，这种排列的突起移动速度（平均速度17.98（±2.25）微米/小时）比未排列的突起（平均速度4.66（±0.67）微米/小时）快。整个细胞的移位通常比突起移动的速度慢：在发育135至160小时之间记录到最低平均值（1.52（±0.36）微米/小时），在195至220小时之间上升到最大平均速率（4.72（±0.42）微米/小时）；细胞移位最快的时期与沿鳍条的最大突起排列相关。1微米厚的塑料切片显示，通常，排列的突起与鳍条纤维的表面紧密相关，而不是与它们之间的空间相关。
