Replication and Functions of Macronuclear Dna in Synchronously Growing Populations of Tetrahymena Pyriformis
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Regulation of ribosomal RNA synthesis in Tetrahymena pyriformis.
Ribosomal RNA is synthesized at constant rate during most of the cell cycle in heat-shock synchronized populations of Tetrahymena pyriformis. Early in each macronuclear S-period the rate of synthesis increases abruptly, concomitant with replication of the genes coding for ribosomal RNA. The increase is prevented by inhibitors of DNA replication, added prior to the S-period. Similarly, in cultur...
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Utilization of temperature-sensitive mutants of Tetrahymena pyriformis affected in cell division or developmental pathway selection has permitted elucidation of causal dependencies interrelating micronuclear and macronuclear replication and division, oral development, and cytokinesis. In those mutants in which cell division is specifically blocked at restrictive temperatures, micronuclear divis...
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The fine structure of the nuclei of logarithmically growing Tetrahymena pyriformis, strain HSM, was studied at 30-minute intervals throughout the cell cycle. Organisms were selected at similar stages of cytokinesis by means of a braking pipette, incubated, fixed in OsO(4), and embedded in agar to facilitate subsequent preparation for electron microscopy. Aggregates of micronuclear chromatin und...
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This report describes an ultrastructural investigation of macronuclear development following conjugation in Stylonycltia mytilus (a spirotrichous ciliate) and Tetrahymena pyriformis (a holotrichous ciliate). In S. mytilus, polytene chromosomes are formed in the young macronucleus (macronuclear Anlage). They are subsequently broken between the bands by 'membranous' partitions; the assembly of th...
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In a preceding publication a method was reported by which fragments of the nuclear envelopes of Tetrahymena pyriformis could be isolated (10). When macronuclear envelopes were isolated from exponentially growing cultures of the amicronucleate Tetrahymena pyriformis strain GL, two types of envelope pieces were observed which differed markedly in the structure of their pore complexes. Type A cont...
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