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Reversible Inhibition of RNA Synthesis in Tetrahymena pyriformis GL by Dimethyl Sulphoxide: An Electron Microscope Autoradiographic Study

Jytte R. Nilsson
Transactions of the American Microscopical Society
Vol. 95, No. 3 (Jul., 1976), pp. 403-414
Published by: Wiley on behalf of American Microscopical Society
DOI: 10.2307/3225134
Stable URL: http://www.jstor.org/stable/3225134
Page Count: 12
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Reversible Inhibition of RNA Synthesis in Tetrahymena pyriformis GL by Dimethyl Sulphoxide: An Electron Microscope Autoradiographic Study
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Abstract

Dimethyl sulphoxide (DMSO) was added in the following concentrations: 2.5%, 5.0%, and 7.5% (v/v) to exponentially multiplying Tetrahymena pyriformis GL cultures to determine the effect on cell proliferation. As studied over a 5-hr period the rate of cell proliferation is slower in 2.5% DMSO than in untreated controls, whereas no increase in cell number occurs in the presence of 5.0% or 7.5% DMSO. The effect of DMSO on the rate of RNA synthesis was studied by electron microscope autoradiography. After a 1-hr exposure to DMSO in the above-mentioned concentrations the cells were exposed to tritiated uridine for 10 min. Furthermore, a cell sample was first exposed to 7.5% DMSO for 1 hr and then left to recover for 1 hr after removal of DMSO before being exposed to tritiated uridine for 10 min. Investigation of the autoradiograms (at least 10 cells per sample) revealed a low rate of incorporation of labeled material in the presence of 5.0% and 7.5% DMSO. Semi-quantitative determination of the amount of incorporation was made by counts of silver grains above measured nuclear and cytoplasmic areas. Using the former data, a linear response of the rate of RNA synthesis is found with increasing concentrations of DMSO. Furthermore, the rate of RNA synthesis in the cells treated with the high concentration of DMSO and left to recover for 1 hr is increased above the value found in untreated control cells. The finding indicates that renewed synthesis is correlated with the recovery from the effects of DMSO.

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