Nucleic acid content and ultraviolet susceptibility of Tetrahymena pyriformis

Iverson, R.M.; Giese, Arthur C.

doi:10.1016/0014-4827(57)90001-0

Cited by 29 publications

(6 citation statements)

References 10 publications

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“…At the end of heat treatment, the average macronucleus contains 25/~g DNA and 690 ~#g historic. The value for DNA is favorably close to 55/~#g reported for Tetrahyrnena pyriformis W at the same time (17). These DNA and histone values decrease during the first 40 min and maximal levels occur 60 min after the end of heat treatment.…”

Section: Resultssupporting

confidence: 56%

“…Something similar occurs during the heat treatment, for although cell division processes are heat sensitive and come to a halt (35), cell volume continues to increase. The macronucleus also enlarges, to accommodate the DNA produced by at least one extra round of replication (17,35), and histone apparently increases to high levels by the end of heat treatment. Upon release of the heat treatment, cell division resumes at a more rapid than normal pace (35) in the enlarged cells, and produces the stepwise reduction of macronuclear volume and DNA and histone content.…”

Section: Discussionmentioning

confidence: 99%

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SIMULTANEOUS SYNTHESIS OF HISTONE AND DNA IN SYNCHRONOUSLY DIVIDING TETRAHYMENA PYRIFORMIS

Hardin

Einem

Lindsay

1967

The Journal of Cell Biology

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Histone and DNA syntheses have been studied in synchronously dividing Tetrahymena pyriformis GL. During the heat treatment necessary to synchronize cultures of this amicronucleate protozoan, the DNA content of the already polyploid macronucleus increases. When the cells begin synchronous division, their DNA content is reduced in a stepwise process which is closely paralleled by reduction of macronuclear histone content. During cell division, the contents of DNA and histone decrease by slightly more than twofold, and in the subsequent S phase, DNA and histone increase simultaneously to 85 % of the values expected if all chromosomes were to double. The first step in the process of reduction of DNA and histone contents is their decrease in excess of twofold, and this is accomplished by removal of extrusion bodies from the nuclei of dividing cells. The second step is a mechanism which allows, in effect, only 70 % of the chromatin in the average nucleus to duplicate. Such partial duplication suggests that both histone and DNA syntheses in synchronous Tetrahymena depend upon a regulatory mechanism, the mediating elements of which are localized in only certain chromosomes.

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Section: Resultssupporting

confidence: 56%

Section: Discussionmentioning

confidence: 99%

SIMULTANEOUS SYNTHESIS OF HISTONE AND DNA IN SYNCHRONOUSLY DIVIDING TETRAHYMENA PYRIFORMIS

Hardin

Einem

Lindsay

1967

The Journal of Cell Biology

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“…pages 1 -11 tinues asynchronously in the form of periodically occurring S periods while cell division is blocked during the heat-shock treatment . This suggestion explained biochemical DNA measurements (16,22,29,30,40) which revealed varying degrees of DNA accumulation (1 .7-to 4-fold) during the treatment, and microspectrophotometric observations (30) that DNA content rose above the normal G 2 complement in all cells by the end of the treatment (EST) .' Nonetheless, Byfield and Lee (3) have recently proposed that DNA synthesis proceeds only very slowly during the treatment and that some cells do not complete one S period .…”

Section: Introductionmentioning

confidence: 83%

ANALYSIS OF THE SCHEDULE OF DNA REPLICATION IN HEAT-SYNCHRONIZED TETRAHYMENA

Jeffery

Frankel

Bault

et al. 1973

The Journal of Cell Biology

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The temporal schedule of DNA replication in heat-synchronized Tetrahymena was studied by autoradiographic and cytofluorometric methods . It was shown that some cells, which were synchronized by selection of individual dividing cells or by temporary thymidine starvation, incorporated [3 H]thymidine into macronuclei in a periodic fashion during the heat-shock treatment . It was concluded that supernumerary S periods occurred while cell division was blocked by high temperature . The proportion of cells which initiated supernumerary S periods was found to be dependent on the duration of the heat-shock treatment and on the cell cycle stage when the first heat shock was applied . Cytofluorometric measurements of Feulgen-stained macronuclei during the heat-shock treatment indicated that the DNA complement of these cells was substantially increased and probably duplicated during the course of each S period . Estimates of DNA content also suggested that the rate of DNA synthesis progressively declined during long heat-shock treatments . These results indicate that the mechanism which brings about heat-induced division synchrony is not an interruption of the process of DNA replication. Further experiments were concerned with the regulation of DNA synthesis during the first synchronized division cycle . It was shown that participation in DNA synthesis at this time increased as more cells were able to conclude the terminal S period during the preceding heat-shock treatment . It is suggested that a discrete period of time is necessary after the completion of DNA synthesis before another round of DNA synthesis can be initiated .

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“…series of investigations has established that the metabolism A and the ultrastructure of Tetrahymena are altered markedly when the cells are removed from a nutrient medium and placed under starvation conditions (2,4,10,20,22,24,27,29). Protein (26) degradation takes place slowly while RNA loss proceeds rapidly.…”

Section: Relationship Of Cellular Energetics To Rna Metabolism Inmentioning

confidence: 99%

The Fate of RNA Degradation Products in Starved Cultures of Tetrahymena pyriformis W.*

Koroly

Conner

1974

The Journal of Protozoology

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SYNOPSIS. The RNA content of a population of Tetrahymena Pyriformis W was followed during the growth phases of the culture. The cellular RNA levels were found to reach a maximum in early log phase and to decrease throughout the remainder of the log and deceleration phases. There was a 25% decrease in RNA amount when cells in late stationary phase were compared to those in deceleration. This loss of RNA was mimicked when cells from the deceleration phase were suspended in a non-nutrient buffered medium.Procedures were established to determine RNA content and the intra-and extracellular distribution of RNA degradation products, namely purine and pyrimidine bases and orthophosphate. Balance sheets are presented to show that the decrease in RNA levels was accompanied by an equivalent increase in purine and pyrimidine bases and phosphorus derivatives. The validity of the procedures employed was demonstrated. The influence of magnesium, cholesterol and glucose on the cells suspended in a non-nutrient buffer was examined. Each was found to affect the ultimate distribution of RNA products in a characteristic fashion suggesting that each compound acts by a different mode of action.

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Nucleic acid content and ultraviolet susceptibility of Tetrahymena pyriformis

Cited by 29 publications

References 10 publications

SIMULTANEOUS SYNTHESIS OF HISTONE AND DNA IN SYNCHRONOUSLY DIVIDING TETRAHYMENA PYRIFORMIS

SIMULTANEOUS SYNTHESIS OF HISTONE AND DNA IN SYNCHRONOUSLY DIVIDING TETRAHYMENA PYRIFORMIS

ANALYSIS OF THE SCHEDULE OF DNA REPLICATION IN HEAT-SYNCHRONIZED TETRAHYMENA

The Fate of RNA Degradation Products in Starved Cultures of Tetrahymena pyriformis W.*

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