Cytology of cultured cells surviving actinomycin D.

Abstract

free media, about 80 per cent of the initial cell population is killed within 24 hours. In contrast, XAMD in the samer dosage causes virtually no mortality in stationary phase cultures of primary hurmani amnioni cells in contact inhibition. In the surviving cells of both HeLa anrd primary amnion cultures, RNA synthesis per cell measured 24 hours after the beginning of treatment declines to less than 10 per cent of initial control values, while protein synthesis per cell is then only 20 per cent (in amnion: cells) anid 50 per cent (in HeLa cells) of the initial control values. (Synthetic capacity was determined by liquid scintillation counting of replicate niumbers of cells extracted with cold trichloracetic acid that had been previously exposed to a pulse of tritiated uridine or of C14-labeled amino acid mixture.) The chondriome of AMD-treated He:La cells beginis to increase withill the first 12 hours, arid by 24 hours the mitochondria have attained remarkable lengths (Fig. 1). In some cells these long mitochondria are disposed in what appears to be anastamosing networks. The mitochondria of AMD-treated cells are demonstrable in living cells with the phase-contrast rnicroscope, by conventional staining methods (e.g., osmication, Regaud's iron hernatoxylin), anid by the histochemical techniques for adenosine triphosphatase8' 9 arrd succinic dehydrogenase.10 To assess the extent of the increase in chondriome, the total length of filamentous mitochondria per cell was summated using a map measure on phase-contrast photomicrographs of osmium-fixed cells at X 1000 magnification. The mean total length of chondriome per cell had increased by 185 per cent over control values in HeLa cells and by 230 per cent in primary amnion cells when measured 26 hours after