21:T438,The appearance of DNA strand breaks during apoptosis was detected in individual cells, in relation to the cell cycle phase, by a novel assay based on labeling 3'-OH termini with biotinylated dUTP using exogenous terminal transferase or DNA polymerase. Apoptosis was induced in HL-60 cells by the DNA topoisomerase I and II inhibitors, and in rat thymocytes by prednisolone. Formation of strand breaks was prevented by the serine protease irreversible inhibitors diisopropyl fluorophosphate (DFP), L-1-tosylamido-2-phenylethyl chloromethyl ketone (TPCK), N-p-tosyl-L-lysine chloromethyl ketone (TLCK) and by the substrates N-alpha-tosyl-L-arginine methyl ester (TAME) and N-benzoyl-L-tyrosine ethyl ester (BTEE). The data indicate that initiation of DNA degradation during apoptosis is preceded by a proteolytic step and suggest that apoptosis starts with activation (e.g. by DNA lesions) of a serine protease which hydrolyses protein(s) associated with the internucleosomal linker DNA sections, thus increasing accessibility of linker DNA to the apoptosis-associated endonuclease.22:T42d,Quantitative determinations of the absorption of ultraviolet radiations by different structures of the eye are of importance, since various pathologic conditions, such as cataract,¹retinal damage²and functional visual disturbances,³have been variously ascribed to these radiations. The measurements of absorption of ultraviolet radiations by ocular media made heretofore have been limited to photographing narrow bands of radiations transmitted through the eye. As pointed out by the author of one of these papers,⁴the data obtained by this means are qualitative, since it is difficult to estimate the proportion of the radiations which is transmitted through the ocular structures. In the present study quantitative information was obtained by measuring photoelectrically the fraction of radiation which was transmitted.

MATERIALS AND METHODS

All the measurements were made on the eyes of young adult albino rabbits, weighing approximately 2 Kg. Technics used in determining the absorption of ultraviolet radiations

	Year	Citations

Abstract

References