Evaluation of the acrosome reaction can shed light on the fertilising competence of spermatozoa. To eliminate false-positive results when evaluating the acrosome status of human sperm cells, two viability probes propidium iodide (PI) and 7-amino-actinomycin D (7-AAD) were compared for their ability to stain nonviable cells post-fixation and permeabilisation. Both the mean fluorescence and % dea...

Chinese hamster cell lines resistant to daunomycin (DM) were developed by direct exposure to the antibiotic. Increase in resistance up to 883-fold was obtained. Evaluation of dose-response data for sensitive and resistant sublines revealed complete cross-resistance to the chemically closely related antibiotic adriamycin as well as considerable cross-resistance to actinomycin D. Radioautographic...

Using Chinese hamster cells in culture, we have measured the effectiveness of actinomycin D to suppress division as a function of the position, or age, of a cell in its growth cycle. Cells were first exposed to millimolar concentrations of hydroxyurea in order to produce a synchronized population just before the onset of DNA synthesis. Thereafter, the survival response after 30 min exposures to...

The decrease in protein synthesis which occurs in mammalian cells during cell division is associated with significant disaggregation of polyribosomes. For determining whether messenger RNA survives this disaggregation, the reformation of polyribosomes was investigated in synchronized HeLa cells as they progressed from metaphase into interphase in the presence of 2 microg/ml Actinomycin D. The p...

The yolk sac of the pregnant rat which functions as a true placenta is a target organ for vitamin D. This tissue can hydroxylate in position 24 both 25-hydroxy- and 1,25-dihydroxyvitamin D3 (25-OHD3 and 1,25-(OH)2D3). The present report describes an in vitro model for the study of 1,25-(OH)2D3 action on the further metabolism of 25-OH[3H]D3 and 1,25-(OH)2[3H]D3 by yolk sac. The tissue explants ...

Actinomycin D blocks DNA-dependent RNA synthesis by binding to DNA (Reich et al., reference 15). On a cellular level, several radioautographic studies have demonstrated the in vivo binding sites of radioactive actinomycin (de Vitry, reference 19; Fraccaro et al., reference 3; Goldstein et al., reference 8; Ro et al., reference 16; Rothstein et al., reference 17; Sonneborn and Rothstein, referen...

A microtechnique has been developed for the determination of specific activities of radioactive leucine in the nanogram range, with an accuracy of at least 7%. The technique depends onthe coupling of [3H]leucineto [W]Z ,4-dinitrofluorobenzene. By use of inulin in the incubation medium, a correction can be made for extracellular leucine contaminating the tissue, and thus the specific activity of...