Nucleoprotein changes during the mitotic cycle in Paramecium aurelia

Woodard, John; Gelber, Beatrice; Swift, Hewson

doi:10.1016/0014-4827(61)90036-2

Cited by 77 publications

(29 citation statements)

References 11 publications

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“…At division, total nuclear protein is divided equally between the two daughter macronuclei. The pattern of increase in labeled protein is somewhat similar to the course of increase of macronuclear proteins measured microspectrophotometrically in Paramecium (6). The primary difference is a rapid increase in rate of protein increase just before division in Paramecium.…”

Section: Synthesis Of Total Macronuclear Proteinsupporting

confidence: 71%

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THE SYNTHESES OF TOTAL MACRONUCLEAR PROTEIN, HISTONE, AND DNA DURING THE CELL CYCLE IN EUPLOTES EURYSTOMUS

Prescott

1966

The Journal of Cell Biology

136

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The syntheses of histone, total protein, and DNA during the cell cycle were measured in the macronucleus of Euplotes eurystomus by assaying the incorporation of tritiated amino acids and tritiated thymidine in groups of 800 to 1000 synchronized cells. The synthesis of DNA begins at 30% completion of the cell cycle, proceeds at a constant rate, and ends very shortly before the beginning of macronuclear division. Histone labeling is absent during G1, begins in phase with DNA synthesis, continues at an unchanging rate during the S phase, and ends with the completion of DNA synthesis. The results support the view that the syntheses of histone and DNA are closely coupled events. Label in total protein accumulates at a constant rate during G1 and appears to shift to a slightly higher rate when histone synthesis begins. At division, radioactive DNA, histone, and total protein are distributed equally between the daughter macronuclei without loss of radioactivity. Radioautographic analysis showed that protein labeling occurs throughout the macronucleus during the entire life cycle. There was no clear difference in the degree of protein labeling between replicated and unreplicated regions of the macronucleus. The distribution of label suggests that most of macronuclear protein labeling during the cell cycle is concerned with the events of transcription rather than replication.

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Section: Synthesis Of Total Macronuclear Proteinsupporting

confidence: 71%

“…The rate of synthesis shows no deviation from a linear course. Such constancy in the rate of DNA synthesis has previously been described for Paramecium (6). Cytological observations of the replication bands in Euplo~es gave the impression that the rate of DNA synthesis increased toward the end of S, but this proves not to be so.…”

Section: Synthesis Of Dnasupporting

confidence: 54%

THE SYNTHESES OF TOTAL MACRONUCLEAR PROTEIN, HISTONE, AND DNA DURING THE CELL CYCLE IN EUPLOTES EURYSTOMUS

Prescott

1966

The Journal of Cell Biology

136

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“…4). The micronuclear mitosis takes place in the last sixth of the interfission interval but it is completed before the fission furrow forms (Woodard et al 1961).…”

Section: O B S E R V a T I O N Smentioning

confidence: 99%

“…across a minor diameter. It has been estimated that the macronucleus contains about 430 times as much DNA as the micronucleus (Woodard, Gelber & Swift, 1961;Woodard, Woodard, Gelber & Swift, I 966). The macronucleus rather than the micronucleus must be concerned with growth and fission since Sonneborn ( I 938) showed that animals could survive for over a hundred fissions without a micronucleus but could not survive for more than one or two fission cycles without a macronucleus.…”

Section: Introductionmentioning

confidence: 99%

Ultrastructure of the Nuclei and Intranuclear Microtubules of Paramecium aurelia

Jurand¹,

Selman²

1970

Journal of General Microbiology

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SUMMARYElectron microscope observations on the micronucleus of Paramecium aurelia showed that the mitotic spindle was organized within the nuclear envelope. At the intranuclear metaphase plate stage some microtubules were attached to chromosomes by localized centromeres and other interzonal microtubules ran between the chromosomes. The interzonal microtubules elongated tenfold during telophase and were tightly packed in a narrow cylindrical membrane-limited stem of the spindle. Some microtubules persisted in the micronucleus during interphase and formed a layer near the nuclear envelope. There were scattered groups of microtubules in the isthmus of the macronucleus during its amitosis. The nuclear envelope remained intact. Large and small bodies persisted throughout the amitosis and the microtubules pass between them. Before the first postconjugal fission there was a stage during which the two macronuclear anlagen were separated by a sheet of cytoplasm only 0.3 pm. wide.

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“…The role of the microtubules is, however, obscure. The occurrence of macronuclear regeneration, in which one fragment can reconstitute an entire macronucleus (Sonne- born 1947} shows also that each fragment has sufficient genetic information to control cell functions, but this might be expected since if there are 30 fragments, each would have 25 times the haploid complement of DNA, since the mature macronucleus has about 860 times the haploid complement of the micronucleus (Woodard, Gelber, and Swift 1961).…”

Section: Discussionmentioning

confidence: 99%

Ultrastructure of Nuclear Division in Paramecium Aurelia III. Meiosis in the Micronucleus During Conjugation

Stevenson¹

1972

Aust. Jnl. Of Bio. Sci.

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Ab8tractUltrastructural features of micronuclear meiosis occurring during conjugation of the ciliate P. aurelia are described. Following pair formation the micronuclei enter prophase. The core of condensed chromatin in the micronucleus fragments, and almost the whole nucleus becomes filled with coiled and twisted chromatin elements. After about 1· 5 hr of pairing regions of condensed chromatin appear linked into strands 1-2 p;m long. Somewhat later, ill-defined, synaptinemal, complex-like material lies between paired masses of chromatin. Only a few synaptinemal complexlike structures can be seen in the nucleus. A short while later, synaptinemal complexlike material may be seen free in the nucleoplasm. After about 2·5 hr of pairing, the micronucleus expands into the crescent stage. Microtubules appear in the nucleus, which expands rapidly to a length of about 20 /Lm, usually oriented along the long axis of the cell. Concurrently with expansion the chromatin becomes diffuse and spreads along the length of the nucleus. This stage probably corresponds to diplotene. The nuoleus then shrinks, miorotubules reappear, and metaphase of the first meiotic division oocurs. A large number of chromosomes, with indistinct kinetochores, can be seen. At telophase the nucleus is 15-20 /Lm long and dumbbell-shaped. It breaks into two parts, there being no separation spindle, in contrast to mioronuclear mitosis. The seoond meiotic division occurs immediately. Ultrastructurally it resembles the first with respeot to metaphase, anaphase, and telophase. Since P. aurelia has two micronuclei, there are eight haploid meiotic products. The one nearest the paroral cone survives and the other seven disintegrate and are resorbed. The remaining nucleus undergoes a modified mitotic division. One of the two final produots becomes a stationary ("female") pronucleus, while the other becomes a migratory ("male") pronuoleus. Male pronuclei are exchanged aoross the fused paroral oone regions of the partners. The male pronucleus contains microtubules during its migration. After fusion to produce the synkaryon, the conjugants separate.The maoronuclei of oonjugants also undergo a series of changes. At metaphase of the first micronuolear division they become irregular in outline. During the second meiotio division the nucleus becomes a twisted skein 40-50 p;m long. As the third mioronuolear division becomes imminent the macronucleus fragments into 30 or 40 pieoes, microtubules being apparent in small numbers at this time.

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Nucleoprotein changes during the mitotic cycle in Paramecium aurelia

Cited by 77 publications

References 11 publications

THE SYNTHESES OF TOTAL MACRONUCLEAR PROTEIN, HISTONE, AND DNA DURING THE CELL CYCLE IN EUPLOTES EURYSTOMUS

THE SYNTHESES OF TOTAL MACRONUCLEAR PROTEIN, HISTONE, AND DNA DURING THE CELL CYCLE IN EUPLOTES EURYSTOMUS

Ultrastructure of the Nuclei and Intranuclear Microtubules of Paramecium aurelia

Ultrastructure of Nuclear Division in Paramecium Aurelia III. Meiosis in the Micronucleus During Conjugation

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