Cell Division In Tetrahymena Research Articles

Mode of Action of Alkylating Agents Using a Ciliate Protozoan as a Model System VI.Inhibition of Synthesis of Macromolecules by Metepa in Tetrahymena pyriformis (Ciliata)

Tetrahymena pyriformis , when exposed to metepa (tris-2(methyl-l-aziridinyl) phosphine oxide), showed a drastic reduction in the synthesis of DNA, RNA and proteins.The inhibitory effect was found to be dependent on the duration of metepa treatment and its concentration.Metepa also induced some quantitative changes in the histones but the extent of the effect varied depending on the particular histone fraction.It is evident that metepa inhibits cell division in Tetrahymena by inhibiting the syntheses of nucleic acids and proteins which are the necessary prerequisites for cell dvision.

CAMP uncouples DNA synthesis and cell division in Tetrahymena

Tetrahymena cells were synchronized by a differential density labeling method. Millimolar concentrations of db-cAMP will cause a delay in the division of the synchronized cells only if added before late S period. The effective concentrations will also cause a precocious initiation of DNA synthesis during G2 just prior to cell division, suggesting that the cyclic nucleotide causes an uncoupling of the program of DNA synthesis and that of karyo- and cytokinesis.

Changes in calcium and magnesium levels during heat-shock synchronized cell division in Tetrahymena

Calcium and magnesium contents were measured in cells of Tetrahymena pyriformis induced to divide synchronously by a multi-heat-shock procedure. During free-running synchronized cell division in complex proteose peptone medium, significant peaks of both calcium and magnesium were observed at points in the cell cycle just prior to division. No such peaks were detected in cells dividing asynchronously in proteose peptone. When synchronized cell division was followed after transfer to an inorganic medium, cell calcium and magnesium levels were observed to decrease in relation to the corresponding cell number increase, indicating that in concentration terms, calcium and magnesium remain fairly constant. This latter result suggests that neither calcium nor magnesium influxes act as triggers for cell division in Tetrahymena and that the fluctuations of these metals seen during the synchronized division cycle in complex medium represent an effect rather than a cause.

A synchronizing effect of carbon dioxide on cell division in Tetrahymena

A synchronizing effect of carbon dioxide on cell division in Tetrahymena

Quinacrine: inhibition of synchronized cell divisioion in tetrahymena.

Quinacrine: inhibition of synchronized cell divisioion in tetrahymena.

Synchronous DNA synthesis following heat-synchronized cell division in Tetrahymena

Synchronous DNA synthesis following heat-synchronized cell division in Tetrahymena

The effect of high hydrostatic pressure on the cell division and growth of Tetrahymena pyriformis

1. 1. An apparatus for monitoring numbers and sizes of cells in suspension is described. The apparatus has been used to monitor the growth of a population of Tetrahymena inside a pressure vessel. 2. 2. 250 atm immediately arrests cell division whilst 100 atm has little effect. 3. 3. 175 atm has no immediate effect on division. After an hour an abrupt inhibition to 10 per cent of the control rate of division sets in. Growth in cell volume continues and leads to a 30 per cent increase in mean cell volume after four hours. 4. 4. The results are interpreted in accordance with current ideas on sol-gel equilibria and the preparation for cell division in Tetrahymena.

Cell division in Tetrahymena adapting to p- dl-fluorophenylalanine

Cell division in Tetrahymena adapting to p- dl-fluorophenylalanine

INHIBITION OF SYNCHRONIZED CELL DIVISION IN TETRAHYMENA BY ACTINOMYCIN D.

The effects of actinomycin D on RNA and protein synthesis have been investigated in Tetrahymena pyriformis. The extent of inhibition of total RNA synthesis and the time before inhibition occurs are both dependent on the concentration of the drug over the range 0.5–10 μg/ml. In contrast to reports on mammalian systems, actinomycin D at low doses is not a selective inhibitor of rRNA synthesis in Tetrahymena; at all doses tested, poly(A+) RNA and poly(A−) RNA syntheses were reduced to similar extents.Finally, the action of actinomycin D was studied in conjunction with γ-radiation which alone causes a transient disaggregation of the polysomes. Actinomycin D partially inhibits the reassociation of polysomes in irradiated cells, but after recovery, the polysome content of the irradiated and drug-treated cells is greater than that of cells treated only with actinomycin D. The results support both a direct action of actinomycin D on translation and secondary effects resulting from inhibition of transcription.The effect of actinomycin D on protein synthesis was determined by two independent methods. 1.1. Investigation of drug-induced alterations in polysome content showed that as the dose increases (a) the lag period before observable polysome dissociation decreases; (b) the rate of polysome dissociation increases; and (c) the final extent of polysome loss increases.2.2. By measuring the relative rates of incorporation of [35S]methionine into N-terminal and internal positions of nascent peptides, it was determined that actinomycin D inhibits initiation and elongation to similar extents.