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Results for “CELL DIVISION”

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At least 361 records · Page 20Linked to original sources
PubMed1987

The effect of automobile exhaust particulates on cell viability, plating efficiency and cell division of mammalian tissue culture cells.

Extract of particulate matter (EPM) of gasoline engine exhaust induced only a slight loss of cell viability of mouse macrophages (line IC-21) in vitro, while a strong dose-dependent reduction of plating efficiency of human cell line A-549 and of Syrian hamster line 14-1b occurred. Cytological investigations of exposed macrophages of line IC-21 revealed an increase in the mitotic index from 1.5% of control values up to 14.6% at the highest tested concentration of EPM. Mitotic arrest is based almost exclusively on C-type mitoses occurring dose-dependently in the presence of EPM. Results indicate disturbances of the spindle apparatus in the presence of EPM.

Animals↗
PubMed1984

Comparative studies on the heat-induced thermotolerance of protein synthesis and cell division in synchronized mouse neuroblastoma cells.

Mouse neuroblastoma (N2A) cells react to a heat treatment by inhibition of DNA and protein synthesis and induction of cell cycle progression delay. Mitotic delay of heat-treated G1 cells correlates with reduction of protein synthesis and is due to an extensive delay of entrance into S phase, while the G2 phase of these cells is shortened. Mitotic delay of heat-treated G2 cells is more than in G1 cells and no correlation with protein synthesis reduction is found. In heat-treated G1 phase cells, both protein synthesis and cell cycle progression become thermotolerant to a second incubation at increased temperature. Moreover, the process of DNA synthesis becomes thermotolerant. In contrast, when heat-treated G1 phase cells have progressed into G2 phase and are then incubated at increased temperature, this G2 phase delay is not diminished. Apparently, additional targets for hyperthermia are present in late S and G2 phase cells.

Acclimatization↗
PubMed1988

Photodynamic effects of Photofrin II on cell division in human NHIK 3025 cells.

Human cervix carcinoma cells of the line NHIK 3025 were exposed to light after 18 h incubation with Photofrin II. After this photodynamic treatment cells in the interphase were retarded with respect to entry into mitosis for a period which increased with increasing light dose. Following the prolonged interphase, an increase in the mitotic index was observed, giving rise to a 3-fold higher level of mitotic cells compared to the control level. Staining of methanol-fixed cells with the DNA-specific dye mithramycin indicated that the increase in mitotic index was due to a prolongation of the metaphase. For all the light doses studied most of the metaphase cells could be characterized as three-group metaphases or c-metaphase-like structures for the first 8 h after treatment. An approximately 10-fold increase above the control level in the number of tripolar mitoses was also observed. A 2h incubation in a Photofrin II-free medium after the 18 h incubation with Photofrin II and before light exposure reduced the fluorescence of the cells by 30 per cent. However, this wash-out period had no effect on the increase in mitotic index after light exposure. A light dose corresponding to 80 per cent survival (as assayed on asynchronous cells) was given to cells in mitosis after Photofrin II incubation. This treatment delayed more than 90 per cent of the metaphase cells from entering the anaphase for at least 1 h. Cells photodynamically treated in the anaphase and telophase entered the interphase at a similar rate as control cells. These observations indicate a temporary block in the initiation of the anaphase and a prolongation of the metaphase. A microscopic study of cells immunologically stained for beta-tubulin 1 h after photodynamic treatment indicated that the organization of the spindle apparatus was disturbed by the photodynamic treatment. Such perturbations are suggested to be the cause of the observed accumulation of cells in mitosis.

Cell Division↗
PubMed1973

Dibutyryl cyclic adenosine 3'5' monophosphate, sugar transport, and regulatory control of cell division in normal and transformed cells.

Swiss 3T3 cells exhibit contact-regulated cell growth and have a lower ability to transport 2-deoxyglucose than polyoma (Py)-transformed 3T3 cells. Py3T3 cells treated with dibutyryl cyclic adenosine 3'5' monophosphate (dBcAMP) and theophylline have reduced cell growth and transport 2-deoxyglucose at the same rate as normal 3T3 cells. Evidence that the cessation of cell growth and reduced transport abilities in Py3T3 cells does not represent a return to contact-regulated growth comes from the following observations. First, treating high density Py3T3 cells with dBcAMP allows more than two doublings of cell number, even though ability to transport 2-deoxyglucose is returned to levels equal to those of normal 3T3 cells. Second, dBcAMP prevents serum-stimulated increases in 2-deoxyglucose transport in Py3T3 but not in 3T3 cells.

Agglutination↗
PubMed1980

Rate of thymidine incorporation and incidence of parenchymal cell division in adult rat hypophyseal cell cultures. Effect of thyroliberin and somatostatin.

Cell suspensions derived from adult rat anterior pituitary glands were cultured for up to eight days. Prolactin immunoreactivity and/or tritiated thymidine incorporation into DNA of cell nuclei were demonstrated in cells with and without thyroliberin (TRH) and somatostatin (SRIF) treatment. It has been established that (a) TRH, which is effective in releasing both thyrotropin and prolactin, may stimulate cell proliferation in other than its target cells; that (b) SRIF has no effect on lactotropic cell proliferation and augments thymidine incorporation into DNA of unidentified cells; that (c) immunoreactive lactotropic cells with tritium-labelled nuclei are present in each culture, independent of hypothalamic hormone treatments.

Animals↗
PubMed1983

The stimulation of the initiation of DNA synthesis and cell division in Swiss mouse 3T3 cells by prostaglandin F2 alpha requires specific functional groups in the molecule.

Among a number of prostaglandins, PGF2 alpha had the highest specific activity for stimulating the initiation of DNA synthesis in confluent resting Swiss 3T3 cells. At a saturating concentration of 8.5 X 10(-7) M, PGF2 alpha stimulated 21% of the cells to incorporate [ methyl-3H ]thymidine within 28 h. To elicit similar effects, prostaglandins F1 alpha, E1, E2, and D2 were required in 10-fold higher concentrations. Prostaglandins A1, A2, B1, and prostacyclin had no mitogenic activity. Insulin at 10(-8) M enhanced the stimulatory effect of PGF2 alpha and also of prostaglandins F1 alpha, E1, E2, and D2 by increasing the fraction of labeled nuclei. Methyl derivatives of PGF2 alpha were as effective as PGF2 alpha. Epimerization of the hydroxyl group at C-9 abolished the activity of the molecule. In contrast, upon epimerization at C-11 and C-15, some mitogenic activity was retained. In the presence of insulin, the latter molecules were as active as PGF2 alpha. Oxidation of the hydroxyl group at C-15 to a ketone abolished the mitogenic effect, while methyl ether formation led to only a slight loss of activity. Reduction of the delta 13 double bond also led only to a small reduction of activity. Similar differences in the activity of the various prostaglandins and analogues of PGF2 alpha were observed for 2-deoxyglucose uptake and increases in cell number. The relationships between structure and activity of prostaglandins suggest the existence of some specific receptor for PGF2 alpha to confer mitogenic response.

Animals↗
PubMed1998

Plant nuclear gene knockout reveals a role in plastid division for the homolog of the bacterial cell division protein FtsZ, an ancestral tubulin.

Little is known about the division of eukaryotic cell organelles and up to now neither in animals nor in plants has a gene product been shown to mediate this process. A cDNA encoding a homolog of the bacterial cell division protein FtsZ, an ancestral tubulin, was isolated from the eukaryote Physcomitrella patens and used to disrupt efficiently the genomic locus in this terrestrial seedless plant. Seven out of 51 transgenics obtained were knockout plants generated by homologous recombination; they were specifically impeded in plastid division with no detectable effect on mitochondrial division or plant morphology. Implications on the theory of endosymbiosis and on the use of reverse genetics in plants are discussed.

Amino Acid Sequence↗
PubMed1992

The proper ratio of FtsZ to FtsA is required for cell division to occur in Escherichia coli.

Interactions among cell division genes in Escherichia coli were investigated by examining the effect on cell division of increasing the expression of the ftsZ, ftsA, or ftsQ genes. We determined that cell division was quite sensitive to the levels of FtsZ and FtsA but much less so to FtsQ. Inhibition of cell division due to an increase in FtsZ could be suppressed by an increase in FtsA. Inhibition of cell division due to increased FtsA could be suppressed by an increase in FtsZ. In addition, although wild-type strains were relatively insensitive to overexpression of ftsQ, we observed that cell division was sensitized to ftsQ overexpression in ftsI, ftsA, and ftsZ mutants. Among these, the ftsI mutant was the most sensitive. These results suggest that these gene products may interact and that the proper ratio of FtsZ to FtsA is critical for cell division to occur.

Bacterial Proteins↗
PubMed1990

FtsZ regulates frequency of cell division in Escherichia coli.

Cell division is regulated so that it occurs only once per cell cycle. In Escherichia coli, a rod-shaped bacterium, division normally takes place at the center of the long axis of the cell; however, in the minicell mutant, division can also take place at the cell pole. Such divisions take place at the expense of normal divisions, resulting in an overall increase in nucleated cell length. We report here that increasing the level of FtsZ can completely suppress the cell length of the minicell mutant by increasing the frequency at which cell division events take place. This result suggests that the level of FtsZ controls the frequency of cell division in E. coli.

Bacterial Proteins↗