摘要:

AbstractThe cell surface characteristics of degenerating cells and phagocytes, as well as the participation of lysosomes in the cell death process associated with the early embryogenesis of chick lens rudiment, were studied by means of scanning electron microscopy and cytochemically using the Gomori‐b̃‐glycerophosphate method for acid phosphatase.The prospective dying columnar epithelial cells lose their apical and basal processes and become rounded. The rounded, isolated, dying cells initially show a rough surface with some cytoplasmic constrictions followed by progressive break‐up into several pitted fragments. Coincident with the loss of the columnar cell shape, acid phosphatase is localized within the Golgi apparatus and autophagic vacuoles which progressively increase in size. In contrast, the isolated dying cells and fragments do not show significant acid phosphatase activity. The role of lysosomes in this degenerative process is discussed.Neighboring epithelial cells phagocytose the dead cell fragments, becoming nonspecialized phagocytes. These consist of columnar epithelial cells and free cells which have migrated from the lens epithelium. Two mechanisms of internalization are observed. The most frequent mechanism takes place in both the columnar epithelial cells and the free cells, and consists of the progressive engulfment of the fragments into craters of the cell surface. The other mechanism is only detected in the free cells and takes place by pseudopod engulfment. We suggest that both phagocytic procedures could be related to the degree of intercellular connection. The presence of phagocytic internalization by crater formation in the epithelial cells could be a mechanism preserving the epithelial stability, which is necessary for a normal morphogenesis. Small microprocesses binding the surface of the phagocyte and the fragment are present prior to the internalization process.In the lens stalk and in the space located between the ectoderm and the lens vesicle, there are some cells displaying migratory characteristics. This fact suggests that an active migration of epithelial cells from the lens stalk could account for the process of detachment of lens vesicle from the ectoderm. The free cells appear to undergo an in situ progressive degene

ISSN:0003-276X    

DOI:10.1002/ar.1092080113

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

摘要:

AbstractThe occurrence of a sequential bone remodeling activity, similar to what is observed in human bone, is demonstrated in rat trabecular bone at the level of the secondary spongiosa. A complete dynamic histomorphometric analysis of the remodeling activity, using undecalcified sections and double fluorescent labels, has consequently been performed in young adults (220 g, 8 weeks old) and in more mature animals (320 g, 12 weeks old). The results showed that, despite a similar trabecular bone volume, younger animals had a five times higher bone formation rate and five times more osteoclasts than more mature animals. The higher bone formation rate was due in part to a threefold higher extent of double‐labeled trabecular bone surface and in part to a 1.5‐fold faster mineralization rate. These results therefore demonstrate a marked slowing down of bone turnover during skeletal maturation in the rat. The values obtained in this study have been compared with measurements made in other parts of the skeleton in the same species (Vignery and Baron 1978, 1980b; Tran Van et al., 1982a) or in humans. This comparison indicated that 12‐week‐old rats had a turnover rate very similar to values observed in iliac crest trabecular bone in adult humans. The rat is therefore a good experimental animal for the study of trabecular bone remodeling but since large variations occur during skeletal maturation, care should be taken in the selection of an age group relevant to the type of questions bein

ISSN:0003-276X    

DOI:10.1002/ar.1092080114

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

ISSN:0003-276X    

DOI:10.1002/ar.1092080115

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY

ISSN:0003-276X    

DOI:10.1002/ar.1092080102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1984

数据来源: WILEY