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At least 253 records · Page 14Linked to original sources
PubMed1962

Studies on sulfhydryl groups during cell division of sea urchin egg. V. Change in contractility of the thread model in relation to cell division.

The contractility of the thread model prepared from the KCl-soluble proteins of the egg and in vivo factors for the contraction are investigated in Hemicentrotus, Anthocidaris, and Pseudocentrotus eggs. The contractility of the thread model induced by metal ions or cystine changes during development in the characteristic pattern of high at the metaphase and low at the monaster and the interkinetic stages. The change in contractility is paralleled by the change in the -SH content of the protein. The water-soluble fraction of the eggs has activity in causing contraction of the thread model. This activity changes during development in the same way as the contractility itself. The contraction of the thread induced by the water-soluble fractions is accompanied by a decrease in the -SH content of the thread. The activity of the water-soluble fraction in inducing the contraction is proportional to its ability to decrease the number of -SH groups. On boiling, the activity is largely destroyed. The activity is due to two components, one being non-dialyzable and the other dialyzable. Separately each component has little effect, but when mixed, the activity of the original sample is completely restored.

Animals↗
PubMed1986

Immediate effects of serum depletion on dissociation between growth in size and cell division in proliferating 3T3 cells.

Proliferating nonconfluent 3T3 cells become committed to proceed through the cell cycle or to enter G0 during the first post-mitotic part of G1 (G1pm). The decision to proceed through G1pm is dependent on the presence of serum growth factors in the culture medium. Cells that have passed this particular growth-factor-dependent cell cycle stage are independent of serum growth factors and undergo mitosis on schedule. We report here that G1ps, S, and G2 cells cease to increase in size when serum is withdrawn. As a result the mitotic cell size after 8 hours serum starvation is reduced to approximately 60% of the normal mitotic cell. This reduced growth in cell size is due to a rapid decrease in protein synthesis and some increase in protein degradation. This dissociation between growth in size and cell-cycle progression within a single cell cycle provides a new approach to study the two processes separately.

Animals↗
PubMed1995

Asymmetric cell division in human leukemic promyelocytic cells (HL-60).

Small cells accounted for 8-9% of the human leukemic promyelocytic cells (HL-60). The diameter of the small cells was 8.44 microns, whereas that of the large cells, which were heterogeneous in cells size, was 11.0 microns. The small cells were produced from the large cells through asymmetric cell division, which was demonstrated by cloning experiments and by microscopy.

Cell Division↗
PubMed1982

Increased expression of SV40 T antigen and cell division in skin fibroblast cell lines derived from a family at high risk of carcinoma (family G of Warthin).

T-antigen expression in 24 of 31 skin fibroblast cell lines from members of Family G was found to be significantly elevated compared with a healthy control population. However, the pattern of elevation did not appear to be associated with cancer risk. In addition, T-antigen values were independent of the age and sex, as well as the branch of family and generation of the cell donor. Cell lines from Family G tended to divide more frequently than cell lines from control donors. This tendency was negatively associated with elevated T-antigen expression in Family-G cell lines, while control cell lines showed no such correlation. These results demonstrate that caution must be taken in evaluating potential markers of cancer risk. Superficial analysis of the data would indicate the utility of the T-antigen assay as a marker for cancer family syndrome. However, consideration of additional factors, including pedigree relationships and cell biology in vitro, indicate that SV40 T-antigen expression is an ambiguous marker of this type of cancer risk, even when large groups are studied.

Adenocarcinoma↗
PubMed1994

Orientation of spindle axis and distribution of plasma membrane proteins during cell division in polarized MDCKII cells.

MDCKII cells differentiate into a simple columnar epithelium when grown on a permeable support; the monolayer is polarized for transport and secretion. Individual cells within the monolayer continue to divide at a low rate without disturbing the function of the epithelium as a barrier to solutes. This presents an interesting model for the study of mitosis in a differentiated epithelium which we have investigated by confocal immunofluorescence microscopy. We monitored the distribution of microtubules, centrioles, nucleus, tight junctions, and plasma membrane proteins that are specifically targeted to the apical and basolateral domains. The stable interphase microtubule cytoskeleton was rapidly disassembled at prophase onset and reassembled at cytokinesis. As the interphase microtubules disassembled at prophase, the centrioles moved from their interphase position at the apical membrane to the nucleus and acquired the ability to organize microtubule asters. Orientation of the spindle parallel to the plane of the monolayer occurred between late prophase and metaphase and persisted through cytokinesis. The cleavage furrow formed asymmetrically perpendicular to the plane of the monolayer initiating at the basolateral side and proceeding to the apical domain. The interphase microtubule network reformed after the centrioles migrated from the spindle poles to resume their interphase apical position. Tight junctions (ZO-1), which separate the apical from the basolateral domains, remained assembled throughout all phases of mitosis. E-cadherin and a 58-kD antigen maintained their basolateral plasma membrane distributions, and a 114-kD antigen remained polarized to the apical domain. These proteins were useful for monitoring the changes in shape of the mitotic cells relative to neighboring cells, especially during telophase when the cell shape changes dramatically. We discuss the changes in centriole position during the cell cycle, mechanisms of spindle orientation, and how the maintenance of polarized plasma membrane domains through mitosis may facilitate the rapid reformation of the polarized interphase cytoplasm.

Animals↗
PubMed2003

ANG II stimulates PKC-dependent ERK activation, DNA synthesis, and cell division in intestinal epithelial cells.

PKC, a major target for the tumor-promoting phorbol esters, has been implicated in the signal transduction pathways that mediate important functions in intestinal epithelial cells, including proliferation and carcinogenesis. With the use of IEC-18 cells arrested in G0/G1, addition of phorbol esters resulted in a modest increase in [3H]thymidine incorporation and a slight shift toward the S and G2/M phases of the cell cycle, whereas the combination of EGF and phorbol 12,13-dibutyrate (PDB) synergistically stimulated DNA synthesis. To investigate the effects of receptor-mediated PKC activation on mitogenesis, we demonstrated that ANG II induced ERK activation, a response completely blocked by pretreatment with mitogen/extracellular signal-regulated kinase inhibitors or specific PKC inhibitors. Furthermore, ANG II stimulated an over threefold increase in [3H]thymidine incorporation that was corroborated by flow cytometric analysis of the cell cycle to levels comparable to that achieved by the combination of EGF and PDB. Taken together, our results indicate that receptor-mediated PKC activation, as induced by ANG II, transduces mitogenic signals leading to DNA synthesis and cell proliferation in IEC-18 cells.

Angiotensin II↗
PubMed1994

Functions of the Golgi complex in cell division: formation of cell-matrix contacts and cell-cell communication channels in the terminal phase of cytokinesis.

The Golgi complex of mammalian cells is disorganized into dispersed vesicular and tubular elements during mitosis and is then reorganized into an interconnected system of cisternal stacks in each daughter cell during cytokinesis. Recent studies further indicate that the Golgi complex is typically relocated from the proximal to the distal side of the nucleus in the terminal phase of cytokinesis (as related to the intercellular bridge). Here, the functional role of this shift in position was approached using rat embryo fibroblasts synchronized with thymidine and nocodazole. Mitotic cells were collected by shaking and seeded in medium without or with brefeldin A (a fungal metabolite that inhibits protein secretion). They were fixed after one or two hours and stained for immunocytochemical demonstration of mannosidase II (a Golgi protein), fibronectin (an extracellular matrix protein), the fibronectin receptor (a member of the integrin family of proteins), and connexin 43 (a member of the connexin family of gap junction proteins). One hour after seeding, the cells had completed mitosis and progressed into cytokinesis. The Golgi complex was now usually located on the proximal side of the nucleus and overlapping fibrillar arrays of fibronectin and fibronectin receptors were observed in the contact zone between the daughter cells, while connexin 43 mainly occurred in fine dispersed spots. Two hours after seeding, the cells had spread out on the substrate and started to move apart. The Golgi complex was now usually located on the distal side of the nucleus. Moreover, fibronectin and fibronectin receptors were found to codistribute both in the contact zone between the daughter cells and in adhesive contacts beneath them, while connexin 43 was concentrated to plaques in the former zone. After treatment with brefeldin A, there was a diffuse cytoplasmic staining for mannosidase II and fibronectin and no distinct extracellular staining for fibronectin was noted. In addition, the connexin 43 positive plaques were reduced in size and number. Although the cells completed cytokinesis in the presence of the drug, they showed an increased tendency to detach from the substrate and locate on top of each other rather than to move apart normally. Taken together, the observations suggest that the change in position of the Golgi complex during cytokinesis serves the function to direct transport of secretory proteins as well as membrane constituents to different parts of the cell surface at different times.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2002

ICRF-193, a catalytic inhibitor of DNA topoisomerase II, inhibits re-entry into the cell division cycle from quiescent state in mammalian cells.

BACKGROUND: To describe the requirement of DNA topoisomerase II (topo II) during transition from the quiescent state (G0 phase) to the cell division cycle in mammalian cells, we examined the influence of ICRF-193, a catalytic inhibitor of topo II, on re-entry into the cell division cycle of quiescent cells in response to appropriate growth stimuli. RESULTS: The re-entry into the S phase of cultured cell lines arrested at the quiescent (G0) phase by serum-starvation was sensitive to 10 microm ICRF-193. DNA syntheses induced by lipopolysaccharide in murine spleen cells or by release from contact-inhibition were also inhibited by ICRF-193. The cell lines with a high-level of resistance toward ICRF-193 due to a point mutation in the topo IIalpha gene entered into the S phase from quiescence in the presence of ICRF-193. The drug did not inhibit entry into the S phase in cultured cells released from arrest at the metaphase or G1 phase. CONCLUSION: There is an ICRF-193-sensitive step during re-entry of quiescent mammalian cells into the cell division cycle upon growth stimulation and the drug targets topo IIalpha during the process.

3T3 Cells↗
PubMed1989

Possible role of phospholipase C in the regulation of cell division in normal and neoplastic cells.

It is proposed that a phosphatidylinositol-specific phospholipase C (PLC) enzyme may be present in abnormally high concentrations in certain cancer cells, and that the elevated activity may explain many, if not all, of the neoplastic characteristics of the cancer cells. There have thus far, been two reports in which PLC activity has been found to be elevated several fold in neoplastic cells. The products of the action of PLC on the phosphoinositides, including diglycerides and inositol phosphates, have been shown to activate the process of cell division by elevating the intracellular concentration of calcium ions and by stimulating the activity of protein kinase C. An elevated content of PLC in at least certain neoplastic cells could thus explain uncontrolled proliferative processes in those cells.

Calcium↗
PubMed1995

Effects of asbestos and man-made vitreous fibers on cell division in cultured human mesothelial cells in comparison to rodent cells.

We report the effects of chrysotile and crocidolite asbestos, and glass and rock wool fibers (man-made vitreous fibers, MMVF) on the induction of binucleate cells in vitro. The response of human mesothelial cells (target cells in fiber carcinogenesis) and rodent cells was compared. Human primary mesothelial cells, MeT-5A cells (an immortalized human mesothelial cell line), and rat liver epithelial (RLE) cells were exposed to asbestos and MMVF samples of similar size range. Milled glass wool, milled rock wool, and titanium dioxide were used as non-fibrous particle controls. All four fiber types caused statistically significant increases in the amount of binucleate cells in human primary mesothelial cells and MeT-5A cells (in the dose range 0.5-5.0 micrograms/cm2). Chrysotile and crocidolite asbestos were more effective (1.3-3.0-fold increases) than thin glass wool and thin rock wool fibers (1.3-2.2-fold increases). However, when the fiber doses were expressed as the number of fibers per culture area, the asbestos and MMVF appeared equally effective in human mesothelial cells. In RLE cells, chrysotile was the most potent inducer of binucleation (2.9-5.0-fold increases), but the response of the RLE cells to crocidolite, thin glass wool, and thin rock wool fibers was similar to the response of the human mesothelial cells. No statistically significant increases in the number of bi- or multinucleate cells were observed in human primary mesothelial cells or RLE cells exposed to the non-fibrous dusts. In MeT-5A cells exposed to 5 micrograms/cm2 of milled glass wool and milled rock wool, as well as in cultures exposed to 2 and 5 micrograms/cm2 of TiO2, significant increases were, however, observed. Our results show that rodent cells respond differently to mineral fibers than human cells. The results also add evidence to the suggested importance of disturbed cell division in fiber carcinogenesis.

Aneuploidy↗
PubMed1999

Effects of a pulsing electric signal on the cross membrane potential and the cell division potentiality of a single cell of tobacco.

A pulsing electric signal (pulse width 10 s) was applied to a single cell of cultured tobacco, line BY-2, by inserting a multifunctional microelectrode (MME) into the cell. The electric voltage (V(ET)) was loaded between the electrode terminals of the MME and the reference electrode situated in the extracellular medium. Since the electrical impedance of the MME was as large as that of the cell membrane, the effective potential acting across the cell membrane (V(CMP)) should be only some portion of V(ET). The MME enabled simultaneous measurement of V(ET) and V(CMP). When V(ET) was varied from 0 to -1 V, V(CMP) changed linearly in proportion to V(ET). When V(ET) variation range was enlarged (from 0 to -2 V), V(CMP) changing pattern became a declined curve. When V(ET) variation range was further enlarged (from 0 to -5 V), the V(CMP) changing pattern showed a saturation curve. Under this condition, the cell division potentiality decreased accordingly. Based on these results, the feasibility of V(CMP) as an indicator of the effective intensity of an electric stress signal is discussed. In the present case of a BY-2 cell, a proper intensity of V(CMP) that could cause an appreciable stress and not a lethal signal was estimated as -250 mV.

Amphotericin B↗
PubMed1975

The function of slime from Physarum flavicomum in the control of cell division.

A haploid cell of the myxomycete Physarum flavicomum undergoes cytokinesis, producing a large population of cells. However, after syngamy, cytokinesis no longer occurs but karyokinesis does and subsequent growth results in the formation of a diploid syncytial plasmodium. Slime, which is produced by the plasmodium but not the haploid cells, was aseptically isolated and purified, and tested for its effect as a cytokinetic regulator. Slime (a viscous, high molecular weight, acidic glycoprotein) affected cytokinesis of the haploid myxamoebae growing in pure culture in soluble media, and the effect was concentration dependent. In simple media, a slime concentration of about 6 10(-5) mug protein per cell suppressed cytokinesis about 50%, unequally inhibited the synthesis of protein, RNA, and DNA, but stimulated respiration. The biological activity of slime was not species specific and it also affected the bacterium Bacillus subtilis by inhibiting cytokinesis, stimulating oxygen uptake, and producing an aberrant cell morphology. Slime was inactivated by heat, fragmentation, and incubation with dithiothreitol, mercaptoethanol, and the proteolytic enzyme papain (EC 3.4.22.2). The inhibitory effect of slime on cell division of haploid cells could not be achieved using mucin or various polyanions. The possible role of slime in the production of the diploid syncytium is discussed.

Cell Division↗