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The use of conventional and zonal centrifugation to study the life cycle of mammalian cells. Phospholipid and macromolecular synthesis in neoplastic mast cells.

ABSTRACT: 1. Conventional gradient centrifugation has been used to separate cells according to their position in the cell cycle, and to obtain synchronously growing cells. Analysis of prelabelled cells by gradient centrifugation confirms that phospholipid, protein and RNA synthesis is continuous throughout the cell cycle and shows that the rate of synthesis begins to increase already during the G(1) phase. The pattern of phospholipid degradation follows that of synthesis. 2. The limitations of conventional gradient centrifugation have been overcome by use of a zonal rotor. Analysis of prelabelled cells confirms the results obtained by conventional centrifugation and in addition shows that the rates of phospholipid, protein and RNA synthesis decrease during the G(2) phase. The mean cell volume and the net amount of phospholipid, protein and RNA, unlike that of DNA, are found to increase continuously throughout the intermitotic period. 3. These results show that the synthesis of macromolecules, and probably that of membranes also, is controlled by a mechanism other than that of gene dosage.

SUBMITTER: Warmsley AM

PROVIDER: S-EPMC1179379 | biostudies-other | 1970 Sep

REPOSITORIES: biostudies-other

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Changes in nuclear protein during the cell cycle in cultured mast cells separated by zonal centrifugation.

Project description:1. Exponentially grown mouse mast cells (cell line P815, strain Y) were separated by zonal centrifugation on a Ficoll gradient. Fractions were allocated to different phases of the cell cycle according to the specific radioactivity of their DNA. 2. Histones were extracted and their thiol content was analysed. The proportion of reduced thiol increased in S phase, decreasing subsequently. 3. The phosphate content of histone F1 and of the other histones reached a peak in early and later S phase respectively. The incorporation of (32)P into these fractions showed a corresponding increase. 4. The timing of histone synthesis was examined. Incorporation of (14)C-labelled amino acids into the histone fractions took place at the same times as phosphorylation. 5. Acid nuclear proteins differ from the histones in incorporating labelled amino acids and (32)P fairly constantly through the cell cycle.

| S-EPMC1174009 | biostudies-other

Metabolism of macromolecular heparin in mouse neoplastic mast cells.

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| S-EPMC1172761 | biostudies-other

The fractionation of nuclei from mammalian cells by zonal centrifugation.

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| S-EPMC1186761 | biostudies-other

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| S-EPMC1179376 | biostudies-other

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| S-EPMC1179660 | biostudies-other

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| S-EPMC7443435 | biostudies-literature

mTORC1 and mTORC2 differentially regulate homeostasis of neoplastic and non-neoplastic human mast cells.

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| S-EPMC3245204 | biostudies-literature

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| S-EPMC6392733 | biostudies-literature

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