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At least 217 records · Page 12Linked to original sources
PubMed2005

The C. elegans RUNX transcription factor RNT-1/MAB-2 is required for asymmetrical cell division of the T blast cell.

The RUNX genes encode conserved transcription factors, which play vital roles in the development of various animals and human diseases. Drosophila runt is a secondary pair-rule gene, which regulates embryo segmentation. Human RUNX1, previously known as AML1, is essential for hematopoiesis. C. elegans rnt-1 is co-orthologous to the human RUNX genes. We found that RNT-1Colon, two colonsGFP is expressed in the H0-2, V1-6, and T blast cells in the embryo, and predominantly in the seam cells during larval to adult stages. rnt-1 mutants exhibit a loss of polarity in the asymmetrical T cell division in hermaphrodites and abnormal ray morphology in the male tail. Genetic and molecular analysis revealed that rnt-1 is allelic to mab-2. Mutant analysis suggested that rnt-1/mab-2 is involved in regulating T blast cell polarity in cooperation with the Wnt signaling pathway. Expression studies of GFPColon, two colonsPOP-1 and TLP-1Colon, two colonsGFP reporters in rnt-1/mab-2 mutants indicated that this gene functions upstream of tlp-1 and downstream, or in parallel to, pop-1 in the genetic cascade that controls asymmetry of the T cell division. All our data suggest that RNT-1/MAB-2 functions with POP-1 to control the asymmetry of the T cell division.

Amino Acid Sequence↗
PubMed2002

Penaeid (Penaeus japonicus) lymphoid cells replicate by cell division in vitro.

Penaeid cell culture has gained much attention as a potential model to facilitate researches on the characterization of the virus and to develop more sophisticated and improved diagnostic procedures for use in the aquaculture industry. However, to date, cell division processes of cultured penaeid cells have not been found, which is suggested as one of the reasons that block the establishment of the continuous penaeid cell lines. We reported here the cell division processes of cultured lymphoid cells of Penaeus japonicus. The culture medium used was based on M199 and was modified by supplementing saline components. Cultures were incubated at 25 degrees C, and 5% CO2 was supplemented. In primary cultured lymphoid cells, dividing cells in different shapes were found. Cell division processes of 12 dividing lymphoid cells were tracked. After cell division, their daughter cells turned into fibroblast-like or epithelioid cells. These results proved that the culture conditions used were suitable for lymphoid cells of I japonicus to proliferate in vitro and that cultured lymphoid cells still had the ability to carry out cell division. These findings would give light to the establishment of continuous penaeid cell lines and would also provide us with the knowledge of cell division processes of the penaeid.

Animals↗
PubMed2002

Influence of lineage-specific cytokines on commitment and asymmetric cell division of haematopoietic progenitor cells.

We examined the influence of cytokines on erythroid- and myeloid-lineage development of AC133+ cells during primary and secondary cultures. Cells cultured for 14 d in liquid medium containing erythropoietin (EPO) were amplified 831-fold with 98.2% erythroid cells. A similar culture exposed to granulocyte colony-stimulating factor (G-CSF) grew 1350-fold with 97.4% myeloid cells. To assess whether the cells with EPO inducement could respond at this point to G-CSF signal, or vice versa, the EPO-stimulated population was re-grown with G-CSF, constituting 95.2% myeloid, of 5075-fold, cells after 14 d of re-culture. Conversely, reculture of the G-CSF-stimulated population with EPO resulted in a 4083-fold growth with 81.4% erythroid cells. Semisolid culture containing EPO orG-CSF showed that some individual colonies had self- renewal potential after 14 d culture and could be induced todevelop into a different lineage. Analysis of primitive markers, CD34 and Notch1, or lineage markers, EPO-R and CD13, by single-cell reverse transcription polymerase chain reaction showed that individual colonies of 2-16 cells contained at least one CD34-positive cell with expression ofNotch1 and co-expression of EPO-R and CD13 appeared on either CD34-positive or CD34-negative cells. In situ hybridization with the same cell surface markers in cell populations confirmed the asymmetric cell division and co-expression from single cell data. The study provides a useful model for the analysis of multipotential progenitor development, and indicates that progenitor cells co-express genes from different lineage pathways before commitment and that cytokines influence lineage commitment.

AC133 Antigen↗
PubMed2004

Development of gliomas: potential role of asymmetrical cell division of neural stem cells.

Asymmetrical cell division is a mechanism that gives rise to two daughter cells with different proliferative and differentiative fates. It occurs mainly during development and in adult stem cells. Accumulating evidence suggests that tumour cells arise from the transformation of normal stem cells. Here, we propose that the asymmetrical mitosis potential of stem cells is associated with the generation of migrating tumour progenitors. Application of this speculative model to glioma proposes that the sites where tumour-initiating stem cells reside are indolent and distinct from the tumour mass, and implies that the tumour mass is continuously replenished with new migrating tumour cells from these clinically silent regions. This hypothesis offers explanations for our inability to cure glioblastoma and points to asymmetrical division as a new potential therapeutic target.

Brain Neoplasms↗
PubMed1978

The waste-product theory of aging: waste dilution by cell division.

When cells divide, the quantity of waste material per cell decreases because the wastes are "diluted" by apportionment between the daughters which result from the division. The quantity of waste present in a symmetrically or asymmetrically dividing population of cells is governed by a first-order non-linear differential equation. In the derivation of the equation, it is assumed (a) that waste is created at a rate which is either constant or proportional to the amount of waste already formed, (b) that waste is neither destroyed nor transported across cell walls, and (c) that the rate of cell division at large values of time is inversely proportional to the amount of waste per cell raised to a power. Relations among the parameters of the differential equation specify conditions under which its solutions rise to a critical value. If the amount of waste per cell given by a solution of the differential equation exceeds this value, it is assumed that deleterious effects become evident and that cell death follows. Decreases in the cell division rate leading to a cessation of population growth may occur at lower levels of waste accumulation.

Cell Division↗
PubMed1966

Relationship between RNA synthesis, cell division, and morphology of mammalian cells. I. Puromycin aminonucleoside as an inhibitor of RNA synthesis and division in HeLa cells.

Logarithmically growing HeLa cell monolayers were treated with a range of concentrations of puromycin aminonucleoside (AMS). The effects of AMS were studied by the following means: microscope examination of treated cells; enumeration of the cell number using an electronic particle counter; analyses for DNA, RNA, and protein content; incorporation of P(32) and H(3)-thymidine into nucleic acids; and fractionation of nucleic acids by column chromatography. Taking the rate of incorporation of the isotopic precursor as a measure of nucleic acid synthesis, it was found that concentrations of the inhibitor which had a rapid effect on the rate of cell division inhibited the synthesis of all types of nucleic acids and of protein, but depressed ribosomal RNA synthesis most markedly. Lower concentrations of AMS selectively inhibited ribosomal RNA and, to a lesser extent, transfer RNA synthesis. Partial inhibition of ribosomal RNA synthesis with low doses had no effect on the rate of cell division within the period studied (3 generation times). The cell content of RNA returned to normal when the inhibitor was removed.

Cell Division↗
PubMed2004

Equilibrium between cell division and apoptosis in immortal cells as an alternative to the G1 restriction mechanism in mammalian cells.

Starvation arrests cultured mammalian cells in the G(1) restriction point of the cell cycle, whereas cancer cells generally lose the regulatory control of the cell cycle. Human lymphocytes, infected with Epstein-Barr virus (EBV), also lose their cell cycle control and produce immortal lymphoblastoid cell lines. We show that during starvation, EBV-lymphoblasts override the cell cycle arrest in the G(1) restriction point and continue cell division. Simultaneously, starvation activates apoptosis in an approximately half of the daughter cells in each cell generation. Continuos cell division and partial removal of cells by apoptosis results in stabilization of viable cell numbers, where a majority of viable cells are in the G(1) phase of the cell cycle. In contrast to starvation, anticancer drug etoposide activates apoptosis indiscriminately in all EBV-lymphoblasts and convertes all the viable cells into apoptotic. We conclude that the removal of surplus cells by apoptosis may represent a survival mechanism of transformed (i.e., cancer) cell population in nutrient restricted conditions, whereas nontransformed mammalian cells are arrested in the G(1) restriction point of the cell cycle.

Antineoplastic Agents↗
PubMed2006

Not so divided: the common basis of plant and animal cell division.

Plant cells do not have centrioles and their mitosis is frequently likened to the chromosome-based mechanism seen in acentriolar animal cells. However, this is a false analogy. Although plants can use this mechanism, they generally divide by a method that uses bipolar mitotic caps, which is more similar to the canonical centrosome-based method of animals.

Animals↗
PubMedDate not supplied

Effects of cadA gene on cell division phenotype.

Studying cell division regulatory mechanisms in Escherichia coli an important role of cad operon was discovered. The cadA gene is part of the cad operon. The promotor of cad operon (pBA) regulates two genes, cadB (the first gene in the cad operon) and cadA (the second one). The cadB encodes the lysine-cadaverine antiporter. The cadA gene encodes enzyme lysine decarboxylase that turns lysine into cadaverine and carbon dioxide. The expression of cadA is activated by several different environmental parameters, such as low pH, low oxygen, and excess lysine. Regulation of any of these parameters depends on the presence of cadC gene, encoding the regulator of the operon. It is located upstream of cad operon. The aim of this study is to investigate if the effect upon the cell division rate was caused by the induction of cadA. Specific aims were to obtain structural gene of cadA and construct a plasmid (pAM1) that contains cadA under the control of the arabinose inducibile promoter pARA, and complement the cell division phenotype of a cadA mutant by providing cadA on the inducibile plasmid. Activation of the pAM1 with 0.05% arabinose reduced the cell division rate that confirms the inhibitory effect of the pAM1.

Cell Division↗
PubMed2003

The gene expression and enzyme activity of plant 3-deoxy-D-manno-2-octulosonic acid-8-phosphate synthase are preferentially associated with cell division in a cell cycle-dependent manner.

3-deoxy-D-manno-2-octulosonic acid-8-phosphate (Kdo-8-P) synthase catalyzes the condensation of phosphoenolpyruvate with D-arabinose-5-phosphate to yield Kdo-8-P. Kdo-8-P is the phosphorylated precursor of Kdo, a rare sugar only found in the rhamnogalacturonan II pectic fraction of the primary cell walls of higher plants and of cell wall polysaccharides of some green algae. A cDNA named LekdsA (accession no. AJ294902) encoding tomato (Lycopersicon esculentum) Kdo-8-P synthase has been isolated. The recombinant protein rescued a kdsA thermosensitive mutant of Salmonella typhimurium impaired in the synthesis of a functional Kdo-8-P synthase. Using site-directed mutagenesis of LekdsA cDNA, the tomato Kdo-8-P synthase was shown to possess the same essential amino acids that form the active sites in the bacterial enzymes. The tomato kdsA gene expression and the relevant Kdo-8-P synthase activity were preferentially associated to dividing cells, in the course of the early development of tomato fruit and in meristematic tissues. Furthermore, the transcription of the kdsA gene was found to oscillate during the cell cycle in tobacco (Nicotiana tabacum) Bright-Yellow 2 synchronized cells with a maximum during mitosis.

Aldehyde-Lyases↗
PubMed1987

A quantitative histological study of cell division and changes in cell number in the meningeal sheath of the embryonic human optic nerve.

Mitotic cells are present in all layers of the meninges of the human optic nerve between 8 and 18 weeks post-conception. The number of meningeal cells per section remains constant between 8 and 12 weeks before rising rapidly from 234 at 12 weeks to 747 at 18 weeks. The mitotic index is only 0.17% at 8 weeks but rises to 1.02% at 10 weeks before falling gradually to 0.29% at 18 weeks. A comparison of the results of this study with a previous one on gliogenesis in the same nerves (Sturrock, 1975) leads to the tentative conclusion that mitotic activity in the layers of the meninges is probably sufficient to account for the increase in meningeal cell number between 8 and 18 weeks. The substantial increase in thickness of the meninges found between 14 and 15 weeks is due to a large increase in the amount of collagen in the developing dural layer rather than the modest increase in cell number. During mitosis meningeal cells do not retract their processes and cell division usually occurs tangentially.

Cell Count↗
PubMed2000

The SCHIZOID gene regulates differentiation and cell division in Arabidopsis thaliana shoots.

Cell division and cell differentiation are key processes in shoot development. The Arabidopsis thaliana (L.) Heynh. SCHIZOID (SHZ) gene appears to influence cell differentiation and cell division in the shoot. The shz-2 mutant is notable in that distinct phenotypes develop, depending on the environment in which the plants are grown. When shz-2 mutants are grown in petri dishes, callus develops from the petiole and hypocotyl. In contrast, when the mutants are grown on soil, shoots appear externally stunted with malformed leaves. However, detailed examination of soil-grown mutants shows that the two phenotypes are related. Soil-grown mutants form adventitious meristems, produce a large amount of vascular tissues and have aberrant cell divisions in the meristem. Cells with abnormal cell-division patterns were found in the apical and vascular meristems, suggesting SHZ influences cell division. Development of callus in petri dishes, development of adventitious meristems and aberrations in leaves on soil suggest that SHZ influences cell differentiation. The distinct, but related phenotypes on soil and in petri dishes suggests that SHZ normally functions to regulate differentiation and/or cell division in a manner that is responsive to environmental conditions.

Arabidopsis↗
PubMed1999

Phosphate as a limiting factor for the cell division of tobacco BY-2 cells.

The re-addition of phosphate to tobacco BY-2 cells deprived of phosphate for 3 d induced cells to semi-synchronously re-enter the cell cycle from a static state. Though the addition of auxin to auxin-starved tobacco BY-2 cells also induced cell division (Ishida et al. 1993), some major differences were observed between these two systems. BY-2 cells lost the ability to re-enter the cell cycle after prolonged periods of auxin deprivation, but in contrast retained this ability after longer periods in the absence of phosphate. By differential cDNA screening we identified a phosphate-induced gene phi-1. phi-1 was rapidly induced by the addition of phosphate with transcript levels starting to decrease by the start of DNA synthesis. phi-1 does not share any significant homology with any gene with known functions over its full length. However, the N-terminus shared some homology with plasma membrane ATPases suggesting that it may be involved in some process of phosphorylation. Immunolocalization of the phi-1 gene product revealed that it rapidly accumulated in the cytoplasm prior to the start of plastid and nuclear DNA synthesis. These results are discussed in relation to the role of phosphate in inducing plant cell division.

Amino Acid Sequence↗