Locomotion and cell-substratum contacts of XXXX epidermal cells in vitro and in situ.

@entity1238 @entity4530 @entity1579 @entity2701 @entity71610
Studies of tissue cell locomotion in culture have revealed much about cell motility, but whether behaviour in vitro resembles movement of the same cells in the animal is not clear. To investigate this, I compared the locomotion and cell-substratum contacts of epidermal cells from @entity1238 tadpoles, migrating from explants on glass and plastic, with the same cells spreading in vivo during wound closure. Time-lapse cinemicrography showed that in both cases, cells spread by extending broad lamellipodia across the substratum, and did not form microspikes, filopodia, or @entity4530 . The net rate of translocation was significantly slower in vitro, however, because cells both @entity71610 slower and spent more time stationary or withdrawing, compared with cells in situ. The increased fluctuation seemed in part due to greater @entity2701 within the expanding sheet in vitro, since when @entity2701 was reduced, for example by wounding, the cells spread with less fluctuation and at a greater rate (6.5 micrometers/min compared with 0.77 micrometers/min). Micromanipulation showed that cells adhered to the substratum, both in situ and in vitro, by a broad contact where @entity1579 ( @entity1579 ) of sectioned material showed the cells to be less than 30 nm from the substratum. A similar separation was observed beneath cells in vitro when viewed in life with interference-reflexion optics (IRM). A few focal contacts (adhesion plaques) were also seen with IRM and @entity1579 of cells in vitro, but were not seen with @entity1579 of cells in situ. Submarginal as well as marginal basal cells of the advancing sheet adhere and spread on the substratum in both situations, whereas cells of the outer layer are passive. Hence, the overall pattern of migration of these cells is similar in vitro and in situ; the differences in rates of movement may be explained in part by the different degree of @entity2701 in the epithelium under the 2 conditions.
