[Cell division in Drosophila neurogenesis: cell cycle control/asymmetric cell division].
Explore the source record for details and available documents.
Animals↗
SEARCH · Search PubMed
Results for “CELL DIVISION”
Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Mathematical modeling of vascular endothelial layer maintenance: the role of endothelial cell division, progenitor cell homing, and telomere shortening.
Maintenance of the endothelial cell (EC) layer of the vessel wall is essential for proper functioning of the vessel and prevention of vascular disorders. Replacement of damaged ECs could occur through division of surrounding ECs. Furthermore, EC progenitor cells (EPCs), derived from the bone marrow and circulating in the bloodstream, can differentiate into ECs. Therefore, these cells might also play a role in maintenance of the endothelial layer in the vascular system. The proliferative potential of both cell types is limited by shortening of telomeric DNA. Accelerated telomere shortening might lead to senescent vascular wall cells and eventually to the inability of the endothelium to maintain a continuous monolayer. The aim of this study was to describe the dynamics of EC damage and repair and telomere shortening by a mathematical model. In the model, ECs were integrated in a two-dimensional structure resembling the endothelium in a large artery. Telomere shortening was described as a stochastic process with oxidative damage as the main cause of attrition. Simulating the model illustrated that increased cellular turnover or elevated levels of oxidative stress could lead to critical telomere shortening and senescence at an age of 65 yr. The model predicted that under those conditions the EC layer could display defects, which could initiate severe vascular wall damage in reality. Furthermore, simulations showed that 5% progenitor cell homing/yr can significantly delay the EC layer defects. This stresses the potential importance of EPC number and function to the maintenance of vascular wall integrity during the human life span.
Arteriosclerosis↗
Inhibition of DNA synthesis and cell division by a cell surface sialoglycopeptide.
We have isolated and purified a cell surface sialoglycopeptide (SGP) from bovine cerebral cortex cells that previously was shown to be a potent inhibitor of cellular protein synthesis. The following studies were carried out to characterize the potential ability of the SGP to inhibit DNA synthesis and to arrest cell division. Treatment of exponentially proliferating Swiss 3T3 cells with the SGP inhibitor resulted in a marked inhibition of thymidine incorporation within 24 h. When the SGP was removed from inhibited cultures, a sharp rise in 3H-thymidine incorporation followed within 3-4 h that peaked well above that measured in exponentially growing cultures, suggesting that the inhibitory action of the SGP was reversible and that a significant proportion of the arrested cells was synchronized in the mitotic cycle. In addition to DNA synthesis, the inhibitory action of the SGP was monitored by direct measurement of cell number. Consistent with the thymidine incorporation data, the SGP completely inhibited 3T3 cell division 20 h after its addition to exponentially growing cultures. Upon reversal there was a delay of 15 h before cell division resumed, when the arrested cells quickly doubled. Most, if not all, of the growth-arrested cells appeared to have been synchronized by the SGP. The SGP inhibited DNA synthesis in a surprisingly wide variety of target cells, and the relative degree of their sensitivity to the inhibitor was remarkably similar. Cells sensitive to the SGP ranged from vertebrate to invertebrate cells, fibroblast and epitheliallike cells, primary cells and established cell cultures, as well as a wide range of transformed cell lines.
Animals↗
Identification of new genes in a cell envelope-cell division gene cluster of Escherichia coli: cell division gene ftsQ.
We report the identification, cloning, and mapping of a new cell division gene, ftsQ. This gene formed part of a cluster of three division genes (in the order ftsQ ftsA ftsZ) which itself formed part of a larger cluster of at least 10 genes, all of which were involved in some step in cell division, cell envelope synthesis, or both. The ftsQAZ group was transcribed from at least two independent promoters.
Cell Division↗
Coupling of cell division to cell growth by translational control of the G1 cyclin CLN3 in yeast.
The eukaryotic cell cycle is driven by a cascade of cyclins and kinase partners including the G1 cyclin Cln3p in yeast. As the first step in this cascade, Cln3p is uniquely positioned to determine the critical growth-rate threshold for division. To analyze factors regulating CLN3 expression, we identified a short upstream open reading frame (uORF) in the 5' leader of CLN3 mRNA as a translational control element. This control element is critical for the growth-dependent regulation of Cln3p synthesis because it specifically represses CLN3 expression during conditions of diminished protein synthesis or slow growth. Inactivation of the uORF accelerates the completion of Start and entry into the cell cycle suggesting that translational regulation of CLN3 provides a mechanism coupling cell growth and division.
Antifungal Agents↗
Development of a novel, multi-analyte biosensor system for assaying cell division: identification of cell proliferation/death precursor events.
A novel, miniaturized biosensor system was created by combining the electrophysiological response of immobilized cells with superoxide-sensing technology, optical and fluorescence microscopy. Vero cells were immobilized in a calcium alginate matrix (at a density of 1.7 x 10(6) cells ml(-1)). A 0.5 cm x 0.5 cm piece of cell-containing gel matrix was aseptically adhered on a glass microscope slide with a microfabricated gold electrode array, sealed with a cover slip and provided with Dulbecco's medium +10% (v/v) fetal calf serum every day by means of a capillary feeding tube. During a culture period of 7 days, the membrane potential of immobilized cells was continuously monitored, while cell division was assayed with an optical microscope. In addition, daily measurements of immobilized cell membrane potential, viability, RNA and calcium concentration, radical oxygen species (ROS) and glutathione accumulation, were conducted by fluorescence microscopy after provision of an appropriate dye. Superoxide accumulation was assayed by covering the electrodes with superoxide dismutase (SOD). Maximum cell membrane potential values and superoxide production were observed upon initiation of cell division. Using the novel biosensor, we were able to correlate seven different cell physiological parameters to each other and formulate a model for ROS-mediated signaling function on cell division and death. In addition, we were able to predict cell proliferation or death by comparing the relative response of the electrophysiological and superoxide sensor during the culture period.
Animals↗
Light, flies and cell division. Workshop: regulation of cell division in Drosophila.
Explore the source record for details and available documents.
Animals↗
The Arabidopsis PILZ group genes encode tubulin-folding cofactor orthologs required for cell division but not cell growth.
Plant microtubules are organized into specific cell cycle-dependent arrays that have been implicated in diverse cellular processes, including cell division and organized cell expansion. Mutations in four Arabidopsis genes collectively called the PILZ group result in lethal embryos that consist of one or a few grossly enlarged cells. The mutant embryos lack microtubules but not actin filaments. Whereas the cytokinesis-specific syntaxin KNOLLE is not localized properly, trafficking of the putative auxin efflux carrier PIN1 to the plasma membrane is normal. The four PILZ group genes were isolated by map-based cloning and are shown to encode orthologs of mammalian tubulin-folding cofactors (TFCs) C, D, and E, and associated small G-protein Arl2 that mediate the formation of alpha/beta-tubulin heterodimers in vitro. The TFC C ortholog, PORCINO, was detected in cytosolic protein complexes and did not colocalize with microtubules. Another gene with a related, although weaker, embryo-lethal phenotype, KIESEL, was shown to encode a TFC A ortholog. Our genetic ablation of microtubules shows their requirement in cell division and vesicle trafficking during cytokinesis, whereas cell growth is mediated by microtubule-independent vesicle trafficking to the plasma membrane during interphase.
Arabidopsis↗
Effects of nitrogen on mesophyll cell division and epidermal cell elongation in tall fescue leaf blades.
Leaf elongation rate (LER) in grasses is dependent on epidermal cell supply (number) and on rate and duration of epidermal cell elongation. Nitrogen (N) fertilization increases LER. Longitudinal sections from two genotypes of tall fescue (Festuca arundinacea Schreb.), which differ by 50% in LER, were used to quantify the effects of N on the components of epidermal cell elongation and on mesophyll cell division. Rate and duration of epidermal cell elongation were determined by using a relationship between cell length and displacement velocity derived from the continuity equation. Rate of epidermal cell elongation was exponential. Relative rates of epidermal cell elongation increased by 9% with high N, even though high N increased LER by 89%. Duration of cell elongation was approximately 20 h longer in the high- than in the low-LER genotype regardless of N treatment. The percentage of mesophyll cells in division was greater in the high- than in the low-LER genotype. This increased with high N in both genotypes, indicating that LER increased with cell supply. Division of mesophyll cells adjacent to abaxial epidermal cells continued after epidermal cell division stopped, until epidermal cells had elongated to a mean length of 40 micrometers in the high-LER and a mean length of 50 micrometers in the low-LER genotype. The cell cycle length for mesophyll cells was calculated to be 12 to 13 hours. Nitrogen increased mesophyll cell number more than epidermal cell number: in both genotypes, the final number of mesophyll cells adjacent to each abaxial epidermal cell was 10 with low N and 14 with high N. A spatial model is used to describe three cell development processes relevant to leaf growth. It illustrates the overlap of mesophyll cell division and epidermal cell elongation, and the transition from epidermal cell elongation to secondary cell wall deposition.
Journal Article↗
Cellular immune response in vitro: I. A requirement for time-dependent T-lymphocyte cell division of cytotoxic cells in the allogeneic response.
Immunocompetent lymphoid cells cultured in vitro with allogeneic stimulator cells have been shown to produce T-lymphocyte populations which are specifically cytotoxic in vitro to the stimulatory cells whether normal or malignant. Although the culture requirements as well as the allogeneic requirements are known, the events leading to the production of T-lymphocyte cytotoxic cells is poorly understood. This study examines the role of cell division in the production of allogeneic cytotoxic T-cells in vitro. The elimination of cell division during the first 24 hr of allogeneic culture does not affect the cell-mediated cytotoxic immune response in vitro. Cell division is required, however, from 24 hr through 96 hr in culture and not necessary after 96 hr.
Animals↗
Regulation of cell division of mature B cells by ionomycin and phorbol ester.
The growth of a human B lymphoma cell line B104, an experimental model for mature B cells, was inhibited by ionomycin but not 12-O-tetradecanoylphorbol-13-acetate (TPA). Ionomycin inhibited B104 cells from entering into the M phase of the cell cycle without affecting DNA synthesis. The inhibition of cell division of B104 cells by ionomycin occurred within 24 h after stimulation. Because such a mode of action resembles that of anti-IgM antibodies, signals transduced by Ca2+ may be responsible for the inhibition of cell division of B104 cells by anti-IgM antibodies. Indeed, EGTA suppressed the inhibition of cell division of B104 cells caused not only by ionomycin, but also by anti-IgM antibody. Although TPA itself did not have any ability to promote the growth of B104 cells, it could cancel the inhibition of cell division of B104 cells by ionomycin and increase the proportion of B104 cells entering into the M phase of the cell cycle. Staphylococcus aureus Cowan I causes the greatest proliferation of normal human peripheral blood B cells during the period from 48 to 72 h after stimulation. When ionomycin was added to S. aureus Cowan I-stimulated peripheral blood B cells at 48 h of culture, it inhibited cell division during this period without affecting DNA synthesis. In the presence of TPA, this activity of ionomycin was suppressed, and the proportion of M-phase cells increased. These results suggest that cell division of mature B cells is regulated by the signals mediated by Ca2+ and protein kinase C in a mode quite different from that of regulation of DNA synthesis.
B-Lymphocytes↗
Organization and transcription of the division cell wall (dcw) cluster in Neisseria gonorrhoeae.
A cluster of genes involved in cell division and cell wall (dcw) biosynthesis was identified in Neisseria gonorrhoeae using genomic analysis and through verification of gene order by polymerase chain reaction (PCR) analysis. The gonococcal dcw cluster consists of 17 genes, in the order 5'-mraZ-mraW-ftsI-murE-hyp1-murF- mraY-hyp2-murD-ftsW-murG-murC-ddl -ft sQ-ftsA-ftsZ-hyp3-3'. The gene organization of the dcw cluster of N. gonorrhoeae is more similar to that observed in Gram-negative rods such as Escherichia coli and Haemophilus influenzae than in Gram-positive bacteria. The cluster is characterized by several intergenic spaces. Compared with E. coli, two genes, ftsL and envA, are absent in the gonococcal dcw cluster and three hypothetical genes are novel to the cluster. The cluster is flanked by two transcriptional terminators consisting of paired neisserial uptake sequences and also includes four internal terminators, three of which are paired neisserial uptake sequences. We also found that a repeated sequence on the gonococcal genome, commonly called a Correia element, acts as the fourth transcriptional terminator. All termination sequences were shown to be fully functional by using reverse transcription PCR experiments. Transcriptional start sites upstream of ftsQ, ftsA and ftsZ were determined by primer extension and six promoters were identified; three promoters were located upstream of ftsZ in the intergenic space, two were upstream of ftsA within ftsQ and one was upstream of ftsQ within ddl. Some of these promoters were preferentially used under anaerobic conditions. The location of these promoters differed from those described in E. coli indicating dissimilar transcriptional regulation.
Base Sequence↗
The orientation of cell division influences cell-fate choice in the developing mammalian retina.
Asymmetric segregation of cell-fate determinants during cell division plays an important part in generating cell diversity in invertebrates. We showed previously that cells in the neonatal rat retina divide at various orientations and that some dividing cells asymmetrically distribute the cell-fate determinant Numb to the two daughter cells. Here, we test the possibility that such asymmetric divisions contribute to retinal cell diversification. We have used long-term videomicroscopy of green-fluorescent-protein (GFP)-labeled retinal explants from neonatal rats to visualize the plane of cell division and follow the differentiation of the daughter cells. We found that cells that divided with a horizontal mitotic spindle, where both daughter cells should inherit Numb, tended to produce daughters that became the same cell type, whereas cells that divided with a vertical mitotic spindle, where only one daughter cell should inherit Numb, tended to produce daughters that became different. Moreover, overexpression of Numb in the dividing cells promoted the development of photoreceptor cells at the expense of interneurons and Müller glial cells. These findings indicate that the plane of cell division influences cell-fate choice in the neonatal rat retina and support the hypothesis that the asymmetric segregation of Numb normally influences some of these choices.
Animals↗
Lack of correlation between agglutinability, the surface distribution of con A and post-confluence inhibition of cell division in ten cell lines.
Agglutinability by concanavalin A, distribution of surface-bound concanavalin A, and maximal cell density in monolayer culture were examined under similar conditions in parallel cultures of ten established cell lines. The degree of agglutinability of the cell lines did not correlate with the presence or absence of patching of concanavalin A bound to the cell surface, as determined with a hemocyanin marker. Agglutinability was also not always correlated with the loss of post-confluence inhibition of cell division. Two clones of mouse 3T3 fibroblasts that maintained post-confluence inhibition of cell division and low agglutinability differed substantially with respect to the surface distribution of concanavalin A. Patching of concanavalin A binding sites is neither necessary nor sufficient to explain differences in agglutinability between cell lines.
Agglutination↗
Identification of Salmonella functions critical for bacterial cell division within eukaryotic cells.
Salmonella typhimurium multiplication inside eukaryotic host cells is critical for virulence. Salmonella typhimurium strain SL1344 appears as filaments upon growth in macrophages and MelJuSo cells, a human melanoma cell line, indicating a specific blockage in the bacterial cell division process. Several studies have investigated the host cell response impairing bacterial division. However, none looked at the bacterial factors involved in inhibition of Salmonella division inside eukaryotic cells. We show here that blockage in the bacterial division process is sulA-independent and takes place after FtsZ-ring assembly. Salmonella typhimurium genes in which mutations lead to filamentous growth within host cells were identified by a large scale mutagenesis approach on strain 12023, revealing bacterial functions crucial for cell division within eukaryotic cells. We finally demonstrate that SL1344 filamentation is a result of hisG mutation, requires the activity of an enzyme of the histidine biosynthetic pathway HisFH and is specific for the vacuolar environment.
Aminohydrolases↗
The uncoupling of macromolecular synthesis from cell division in SV3T3 cells by glucocorticoids: the imposition of a G2 block.
Through a receptor-mediated process glucocorticosteroids block cell division by 20-45 hours in SV40-transformed 3T3 (SV3T3) mouse fibroblasts growing in a low calf serum (0.30% v/v) medium containing biotin. However, the rate of DNA synthesis, determined at various times after dexamethasone addition by the incorporation of radioactive thymidine into acid-insoluble material, is not inhibited by this steroid as late as 66 hours. A modest decrease is observable by 91 hours. There is also no reduction in the uptake of exogenous thymidine into acid-soluble cellular pools. Similarly, RNA synthesis and the uptake of radioactive uridine are not affected by the glucocorticoid up to 69 hours. Measurements of the amounts of cellular DNA (by the fluorescent dye, 4', 6-diamidino-2-phenylindole) and protein revealed that both macromolecules are present in elevated quantities in steroid-treated cells. (The constancy of the protein content in the nonproliferative stage suggests that protein synthesis and degradation are occurring at equal rates.) If the steroid is removed and fresh 10% calf serum medium added, cell division commences (even if nearly 90% of protein synthesis is inhibited by cycloheximide) as early as 45 minutes later such that by 2 hours the viable cell count increases by as much as 70%. Since the growth curve after recovery resembles a step function, it appears that the cells are partially synchronized by the glucocorticoid. These results demonstrate that the glucocorticoid cytostatic effect in SV3T3 cells is the result of a block not in G1, as previously thought, but in G2.
Animals↗
Alkaline phosphatase activity in normal and scorbutic bones.
Explore the source record for details and available documents.
Alkaline Phosphatase↗
Cortical domains and the mechanisms of asymmetric cell division.
Asymmetric cell divisions are central to the generation of cell-fate diversity because factors that are present in a mother cell and distributed unequally at cell division can generate distinct daughters. The process o f asymmetric cell division can be described as consisting of three steps: setting up an asymmetric cue in the mother cell, localizing factors with respect to this cue, and positioning the plane o f cell division so that localized factors are partitioned asymmetrically between daughters. This review describes how specialized cortical domains play a key role in each of these steps and discusses our current understanding of the molecular nature o f cortical domains and the mechanisms by which they may orchestrate asymmetric cell divisions.
Journal Article↗