Induction of nucleolar segregation in adrenal fasciculata cells by actinomycin D

RNA synthesis inhibitors on young rat adrenal in primary culture. An ultrastructural study

Adrenal cells of newborn rat adrenals in primary tissue culture were treated with actinomycin D (2, 10 and 25 micrograms/ml), alpha-amanitin (5 and 50 micrograms/ml) and cordycepin (100 micrograms/ml) and studied with the electron microscope. The most striking changes observed with the three drugs were localized on the nucleoli, and consisted, respectively, of segregation (actinomycin D), fragmentation (alpha-amanitin) and microsegregation (cordycepin). These results are consistent with the molecular sites of action of the drugs and are comparable to previous in vivo findings.

Effects of alpha-amanitin on the fine structure of adrenal fasciculata cells in the young rat

The administration of 0.2 micrograms/g/bw of alpha-amanitin to approximately 20 g rats provoked the following nuclear modifications in rat adrenal fasciculata cells at 60 min: chromatin condensation, nucleolar fragmentation, increase in the number of PCG and clumping of ICG in the center of the nucleus. At longer time intervals (2.5 and 4.5 hr) these alterations were more evident, but at 24 hr the nuclear structure was back to normal with the exception of a persistent increased number of PCG. After injection of 0.75 micrograms/g/bw and at 2.5 hr, there was pulverization of condensed chromatin, fragmentation and partial segregation of the nucleolus with increased density of the fibrillar component. Cytoplasmic alterations were severe including cap-shaped mitochondria with electron-dense matrix surrounding lipid droplets, reduced endoplasmic reticulum of vesicular type and clusters of microvesicles with dense content in the Golgi trans-area. At 24 hr, the nuclear and cytoplasmic morphology returned to normal. These findings are interpreted as the morphological counterpart of a disturbance of extranucleolar and nucleolar RNA synthesis, as well as of lipid and lipoprotein metabolism, brought about by the drug.

Inhibition of protein synthesis and cell proliferation in cultured human breast cancer cells treated with mitoxantrone

Mitoxantrone suppresses cell proliferation, inhibits protein synthesis and induces ultrastructural alterations in the T-47D and MDA-MB-231 breast cancer cell lines. After 24 h treatment with 10(-9), 10(-7) and 10(-5) M drug and 8 h incubation with [35S]methionine, protein synthesis declined rapidly. While a 10-15% decrease in protein synthesis at 10(-9) M was observed, more than 95% inhibition of protein synthesis occurred at 10(-5) M mitoxantrone in both cell lines. Sodium dodecylsulfate (SDS) gel electrophoresis of labeled proteins revealed no qualitative changes in either cell line. However, only trace amounts of several proteins were present in T-47D cells treated with 10(-5) M drug. At 10(-9) M mitoxantrone had little effect on cell proliferation. At 10(-7) M, 25% and 35% growth inhibition in T-47D and MDA-MB-231 cells was observed, respectively. Cell growth at 10(-5) M was abolished. Cytotoxicity was evident at drug concentrations above 10(-5) M. Ultrastructural alterations in the nucleoli of both cell lines included disintegration and segregation of granular and fibrillar components and the disappearance of nucleolar organizers at 10(-7)-10(-5) M mitoxantrone.