A rapid method for the flow microfluorometric determination of the DNA content per cell is described. Incubation of cells in a hypotonic solution of propidium iodide results in disruption of the cell membrane and rapid staining of nuclear chromatin. DNA distribution histograms generated from cells stained by this method are identical to those generated after fixation and RNase digestion. In contrast to some earlier described methods, the present technique is rapid (5 min of processing), requires a minimal amount of material, and avoids formation of cell clumps.

/pdf/rapid-flow-cytofluorometric-analysis-of-mammalian-cell-cycle-189iteqcl0.pdf

Rapid flow cytofluorometric analysis of mammalian cell cycle by propidium iodide staining.

Exposure of cultured human lymphoblasts to adriamycin (ADM) (0.1 μg/ml for 24 hr or 0.5 μg/ml for 1 hr) leads to an accumulation of cells with the DNA content of late S and G2. Higher concentrations of ADM (0.5 to 10 μg/ml) inhibit cell cycle traverse. Effect of ADM on cell cycle traverse, cell growth, and incorporation of labeled precursors into DNA is dependent on drug concentration and length of exposure to ADM. Synchronized cells in G1 or G2 part of the cell cycle are less sensitive to ADM than cells in S phase. Similarly, plateau-phase cells are less sensitive to ADM than cells from log-phase cultures.

https://cancerres.aacrjournals.org/content/canres/36/1/143.full.pdf

Effect of adriamycin on the cell cycle traverse and kinetics of cultured human lymphoblasts.

The inhibition of ribonucleoside diphosphate reductase by hydroxyurea, guanazole and pyrazoloimidazole (IMPY)

A graded series of drug-resistant Chinese hamster sublines has been examined for biochemical changes accompanying resistance to actinomycin D. The most highly resistant subline, DC-3F/AD X, is maintained at 10 µg/ml of the antibiotic. It was shown that over 250 times more actinomycin D is required to inhibit RNA synthesis in this subline than in the parental DC-3F line. The DC-3F/AD X subline was also shown to have a somewhat reduced capacity to transport uridine as compared to parental cells. Sensitive cells took up over 50 times more tritiated antibiotic than the most resistant cells, as determined in a 1-h assay. Uptake of actinomycin D was shown to be temperature-dependent in both resistant and sensitive cells and was not influenced by various metabolic inhibitors. Resistance could not be explained by a rapid uptake and release of the antibiotic, as demonstrated in efflux experiments, or by its metabolism. In addition, highly resistant cells which are cross-resistant to puromycin were shown to have a reduced capacity to take up labeled puromycin. These studies provide further evidence indicating that the mechanism of resistance to actinomycin D is reduced permeability to drug and suggesting that cell membrane alteration accounts for resistance to both actinomycin D and puromycin.

https://rupress.org/jcb/article-pdf/63/3/773/1266583/773.pdf

Lotti Möller

Papers

2,3-Dihydro-1H-imidazo(1,2-b)pyrazole: a new inhibitor of deoxyribonucleic acid synthesis.