Cytotoxicity assessment of three therapeutic agents, cyclosporin-A, cisplatin and doxorubicin, with the ciliated protozoan Tetrahymena pyriformis

The cortex of the ciliated protozoan Tetrahymena contains a number of fibrous elements, including a network of filaments that pervades the feeding organelle of this organism. The cluster of polypeptides (79–89K; K = 10(3) Mr) in Tetrahymena pyriformis GL-C that constitute these filaments has been purified by in vitro assembly after solubilization in 1.0 M KI. Four distinct sets of these polypeptides, designated ‘tetrins’, have been shown to be distinguishable from each other by immunochemical and biochemical criteria. The smallest filaments reassembled in vitro were 3–4 nm in diameter and these fine filaments were seen to be bundled together into thicker strands of varying diameters, similar to those within the cell. The thicker filament bundles were clearly distinguishable from intermediate filaments, but fine filaments in these bundles were superficially similar to the 2–5 nm filaments described as microtubule-associated proteins in other organisms. The ultrastructure of the tetrin filaments localized within the feeding organelle reveals a substantial presence of these filaments apart from microtubules. In addition, circular dichroism measurements indicate a relatively low alpha-helical content for these filaments and suggest that the tetrins may be substantially different from other fine filament proteins such as the tektins and giardins.

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Morphogenetic Events in Normal and Synchronously Dividing Tetrahymena

Development ◽

10.1242/dev.7.2.241 ◽

1959 ◽

Vol 7 (2) ◽

pp. 241-256

Author(s):

Norman E. Williams ◽

Otto H. Scherbaum

Keyword(s):

Daughter Cell ◽

Tetrahymena Pyriformis ◽

Building Blocks ◽

Specific Pattern ◽

Central Position ◽

Parent Cell ◽

Ciliated Protozoan ◽

Mass Cultures ◽

Synchronous Cell ◽

Species Specific

Synchronous cell-division has been induced in mass cultures of the small ciliated protozoan Tetrahymena pyriformis (Scherbaum & Zeuthen, 1954). While it is known that cells grow in a characteristic way during the synchronizing treatment the effect on the morphogenetic events associated with the cell cycle is not clear. Studies in ciliate morphogenesis generally have established the central position of the ciliary basal body, or kinetosome, in developmental processes. The kinetosomes are believed to be self-duplicating structures, the kinetosomal population of a daughter cell arising directly by kinetosomal reproduction in the parent cell. The species-specific pattern of the ectoplasmic cortex is largely a matter of the distribution of kinetosomes. Further, the kinetosomes appear to function either as building blocks or ‘local organizers’ in most, if not all, structural syntheses occurring in the cortex, i.e. in the production cilia, cirri, membranelles, trichocysts, and other ciliate structures (see Weisz, 1954).

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Effect of cell population density on G2 arrest in Tetrahymena.

The Journal of Cell Biology ◽

10.1083/jcb.67.3.518 ◽

1975 ◽

Vol 67 (3) ◽

pp. 518-522 ◽

Cited By ~ 13

Author(s):

I L Cameron ◽

N C Bols

Keyword(s):

Cell Cycle ◽

Population Density ◽

Cell Population ◽

Tritiated Thymidine ◽

Tetrahymena Pyriformis ◽

High Cell ◽

Ciliated Protozoan ◽

G2 Phase ◽

Cell Densities ◽

Two Peaks

The ciliated protozoan, Tetrahymena pyriformis strain GL-C, has been used to study the effect of cell population density during starvation on the synchrony obtained after refeeding and on the number of cells arrested in G2 phase of the cell cycle. At high cell densities two peaks of division indices were observed after refeeding while only one was observed at low cell densities. Cell division began earlier in cultures starved at high cell densities. Most importantly, the proportion of cells in G2 was considerably higher in populations starved at high cell densities. When tritiated thymidine was present during the refeeding period, radioautographs of cell samples at different times showed that the first cells to exhibit division furrows contained unlabeled nuclei. The first peak in the division index after refeeding was observed only at higher cell densities and is attributed to the cells arrested in G2. These results suggest that Tetrahymena is an excellent organism to study the concept of resting stages in the cell cycle and their control.

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