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481.
Cecil RL 《California and Western Medicine》1934,40(6):397-402
482.
483.
Venkataraman Balasubramanian Cecil H. Robinson 《Biochemical and biophysical research communications》1981,101(2):495-501
Novel 4,5-allenic 3β-hydroxy-5,10-secosteroids have been synthesized by sodium borohydride reduction of the corresponding conjugated allenic 3-oxo-5, 10-secosteroids. The secosteroid allenic alcohols are substrates for bovine adrenal and human placental Δ5-3β-hydroxysteroid dehydrogenases, and the resulting electrophilic conjugated allenic ketones are shown to inactivate these dehydrogenases in a time-dependent manner. Inactivated enzyme did not recover activity after filtration through Sephadex G-25. In contrast, the secosteroid allenic alcohols were not oxidized at C-3 by the bacterial 3β(and 17β)-hydroxysteroid dehydrogenase from , nor did the corresponding allenic ketones inactivate this enzyme when incubated directly. 相似文献
484.
The effect of retinoids on forelimb regeneration in the leopard frog, Rana pipiens, was examined by the topical application of a concentrated solution of vitamin A palmitate to the amputated left limb stumps of 30 froglets. This treatment resulted in the enhancement of regeneration; regenerative outgrowths of experimental frogs were more frequent, larger in size, and had improved morphology compared to their untreated control counterparts. We conclude that vitamin A palmitate, topically administered in concentrated dosages, exerts a positive effect on the regenerative capacity of Rana pipiens. 相似文献
485.
The process of epithelial cell attachment to glass surfaces studied by reflexion contrast microscopy
The process of attachment was studied in primary mouse kidney epithelial cell cultures by means of reflexion contrast microscopy, a method developed for studying the cell membrane-substrate relationship. The first in a series of events is simple adherence to the substrate, called close contact. This phenomenon is associated with the greatest extension of lamellar cytoplasm and the fewest number of cell nuclei/unit area. The nuclei of such cells are in close contact with the bottom portion of the cell membrane. Approx. 24 h after planting, as the cultures become more crowded, cells develop a different kind of attachment to the substrate—focal contacts—that are correlated with a decrease in lamellar cytoplasm. Cells detached from the substrate after close contact formation readily reattach, while cells detached after formation of focal contacts do not reattach. After incubation for periods greater than 5 days, the dense cultures degenerate and cells lose their attachment to the glass surface. 相似文献