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At least 19 recordsLinked to original sources
PubMed2000

Larval-to-adult conversion of a myogenic system in the frog, Xenopus laevis, by larval-type myoblast-specific control of cell division, cell differentiation, and programmed cell death by triiodo-L-thyronine.

For the clarification of larval-to-adult muscle conversion, the authors established primary culture methods for adult- and larval-type myoblasts in the frog, Xenopus laevis, and examined the hormonal response in each case. The cell types were enzymatically dissociated from adult frog leg and tadpole tail muscles, respectively. The cells became attached to culture plates, proliferated, and fused with each other to form multinucleated myotubes within one week. Five significant differences between the two cell types were noted. (1) Adult cells showed greater proliferation activity than larval cells, the former increasing 5.5-fold over 6 days while the latter increase only 2.5-fold. (2) Differentiation (fusion) of larval type myoblasts started earlier. Cell fusion began on day 2 or 3 in larval cells and on day 4 in adult cells. (3) The metamorphic hormone, triiodo-L-thyronine (T3) decreased larval cell numbers to 56% of that of control-cultures on day 7 but had no effect on adult cell number. DNA synthetic activity (3H-thymidine incorporation) in larval cells decreased under T3 (10(-8) M) to 45% of the control level on day 7. (4) Differentiation of adult myoblasts into myotubes was promoted by T3, whereas that of larval cells diminished by half. (5) Myotube death was induced by T3 specifically in larval but not in adult cultures. In addition to the myotube death, double staining with TUNEL (in situ DNA nick end labeling) and anti-desmin antibody indicated that T3 induces myoblast (desmin+ cell) death specifically in larval but not in adult cells. It is thus evident that the conversion of a larval-type myogenic system during metamorphosis becomes possible through nearly totally specific control of cell division, cell differentiation, and programmed cell death at a precursor cell level by T3.

Animals↗
PubMed1986

Effects of cell division, cell density, and cyclic nucleotides on choline acetyltransferase activity in a cholinergic neuroblastoma cell line (S-20Y).

We investigated the effects of a number of experimental perturbations on choline acetyltransferase (ChAT) in a cholinergic mouse neuroblastoma cell line (S-20Y). ChAT specific activity increased by 4.5-fold during growth, suggesting that enzyme activity is dependent on increased cell density. This was confirmed by assessing enzyme activity at differential initial seeding densities. ChAT activity was also markedly enhanced by 1 mM dibutyryl cyclic-3',5'-AMP (dBcAMP), an effect that was blocked by cycloheximide. Confirmation of the dBcAMP effect was achieved with forskolin, a compound known to enhance intracellular cyclic AMP; forskolin (100 microM) caused a significant increase in ChAT activity. After a 20-h latent interval ChAT activity was also enhanced significantly by cytosine arabinoside. The common element in these diverse effects on ChAT activity may be cessation of cell division, although cell-cell interactions at the level of the cell membrane may also be important in the control of ChAT in S-20Y.

Animals↗
PubMed1978

Cell division, cell elongation and the co-ordination of crystallin gene expression during lens morphogenesis in the rat.

A quantitative analysis of cell division and cell elongation was carried out during lens morphogenesis in the rat. At 13 days of development elongating cells in the posterior part of the lens vesicle (presumptive fibre cells) have a lower mitotic activity than cells in the anterior vesicle. By 14 days these elongating cells do not divide. Thus at 14 days of development the lens can be separated into two compartments; a proliferation compartment in the anterior lens and an elongation compartment in the posterior lens. The three main groups of lens-specific proteins, alpha-, beta- and gamma-crystallins, were localized by immunofluorescence. alpha-crystallin is the first crystallin to be detected and is localized in some lens pit cells at 12 days of development. By 14 days all lens cells contain alpha-crystallin. beta- and gamma-crystallins are detected later at 12 1/2 days and are localized in some cells situated primarily in the posterior part of the lens vesicle. At later stages of development these crystallins are restricted to cells of the elongation compartment, i.e. presumptive fibre and fibre cells. Possible mechanisms that govern the temporal and spatial distribution of crystallins are discussed.

Animals↗
PubMed1986

Effects of asbestos fibers on cell division, cell survival, and formation of thioguanine-resistant mutants in Chinese hamster ovary cells.

The ability of crocidolite fibers to induce point mutations and mitotic abnormalities in Chinese hamster ovary (CHO) cells was examined in cell cultures. The purpose has been to study the possibilities for establishing in vitro test methods to quantify genetic damage induced by asbestos and other mineral fibers. Results obtained with the CHO/hypoxanthine guanine phosphoribosyl transferase system indicated that crocidolite fibers per se do not significantly increase the number of thioguanine-resistant mutants. Crocidolite fibers also failed to potentiate the mutagenicity of benzo[a]pyrene. Time-lapse cinematography and microscopy showed that asbestos (crocidolite) fibers were markedly cytotoxic. Among surviving cells some underwent abnormal cell divisions which resulted in multi- and micronucleate cells. Many cells that contained a few asbestos fibers, however, underwent mitosis and successfully formed two mononucleate daughter cells capable of further divisions. Individual, fiber-containing cells were examined by time-lapse television recordings for 4-5 days. During this time period some cells underwent six divisions and generated an almost normal number of daughter cells. Cells which contained fibers that were longer or equivalent to the diameter of the mitotic cell (20 microns), showed different forms of mitotic abnormalities. The frequency of multinucleate cells was drastically increased following exposure to asbestos fibers. Only rarely, however, did these cells divide to produce viable daughter cells capable of continued cell multiplication. The frequency of multinucleate cells was dependent on the dose of exposure to asbestos fibers and could possibly be used as an index of the degree of mitotic disturbances induced by mineral fibers.

Animals↗
PubMed1989

Structural similarity among Escherichia coli FtsW and RodA proteins and Bacillus subtilis SpoVE protein, which function in cell division, cell elongation, and spore formation, respectively.

The Escherichia coli cell division gene ftsW (2 min) was cloned and sequenced. It encodes a hydrophobic protein(s) with 414 and/or 384 amino acid residues. The deduced amino acid sequence and the hydropathy profile of the protein showed high homology with those of the E. coli RodA protein functioning in determination of the cell shape and the Bacillus subtilis SpoVE protein functioning in spore formation. Probably similar functional membrane proteins are involved in these three cell cycle process.

Amino Acid Sequence↗
PubMed1994

EMB30 is essential for normal cell division, cell expansion, and cell adhesion in Arabidopsis and encodes a protein that has similarity to Sec7.

The EMB30 gene is involved in apical-basal pattern formation in the Arabidopsis embryo. Mutations in this locus produce mutants with a wide range of seedling phenotypes, but all of the mutants lack a root and a true hypocotyl. We have cloned the EMB30 gene, and it encodes a protein that has similarity to the yeast Sec7 protein and to two other open reading frames identified in clones from humans and C. elegans. We refer to the region of similarity among these four sequences as the Sec7 domain. The emb30-1 allele has a mutation in the Sec7 domain that alters a residue conserved in all four of these sequences, suggesting that this domain may be important for EMB30 function. Molecular data and microscopy studies of emb30 seedlings presented here indicate that EMB30 affects cell division, elongation, and adhesion and functions in seedling and adult plants as well as during embryogenic pattern formation.

Amino Acid Sequence↗
PubMed2003

Cerebral chemical dominance and neural regulation of cell division, cell proliferation, neoplastic transformation, and genomic function.

The study assessed the isoprenoid pathway, digoxin synthesis, and neurotransmitter patterns in individuals of differing hemispheric dominance, neurogenetic disorders, and neoplasms. The HMG CoA reductase activity, serum digoxin, magnesium, tryptophan catabolites, tyrosine catabolites, and RBC membrane Na+-K+ ATPase activity were measured in individuals of differing hemispheric dominance. The digoxin status, membrane Na+-K+ ATPase activity, and serum magnesium were assessed in Huntington's disease, trisomy 21, glioblastoma multiforme, and non-Hodgkin's lymphoma (high grade lymphoma). The results showed that right hemispheric, chemically dominant individuals had elevated digoxin synthesis, increased tryptophan catabolites, and reduced tyrosine catabolites, and membrane Na+-K+ ATPase with hypomagnesemia. Left hemispheric, chemically dominant individuals had the opposite patterns. In neurogenetic disorders and neo plasms also hyperdigoxinemia induced membrane Na+-K+ ATPase inhibition, and hypomagnesemia similar to right hemispheric chemical dominance could be demonstrated. The role of hemispheric chemical dominance and hypothalamic digoxin secretion play a key role in the regulation of cell differentiation/proliferation and genomic function. Ninety-five percent of the patients with neurogenetic disorders and neoplasms were right-handed/left hemispheric dominant by dichotic listening test. However, all of them had biochemical patterns similar to right hemispheric chemical dominance. Hemispheric chemical dominance has no correlation to cerebral dominance detected by handness/dichotic listening test.

Adult↗
PubMed1987

Effect of pseudopterosin A on cell division, cell cycle progression, DNA, and protein synthesis in cultured sea urchin embryos.

Pseudopterosin A is a diterpene riboside isolated from Pseudopterogorgia bipinata, a soft coral of the order Gorgonacea. Pseudopterosin A inhibits the first cleavage in fertilized sea urchin eggs (Strongylocentrotus purpuratus, Strongylocentrotus franciscanus, and Lytechinus pictus) with an IC50 of 25 microM. In time of addition studies, Pseudopterosin A (4 X 10(-5) M) progressively blocked the first cleavage when added within the first 50 min post fertilization; when added after 50 min the first division occurred normally. Cell cycle studies show that Pseudopterosin A had to be in continuous contact with the sea urchin eggs during the initial 45 min post fertilization to significantly inhibit the first cleavage. Shorter drug contact time progressively reduced the degree of inhibition, suggesting that inhibition of cytokinesis by Pseudopterosin A was correlated with mitosis. Pseudopterosin A (4 X 10(-5) M) inhibited the uptake and incorporation of [3H]thymidine during the S2 phase. This concentration of Pseudopterosin A also inhibits protein synthesis as measured by the uptake and incorporation of [3H]phenylalanine. In this case the inhibition started before the S1 phase. Cytological examination revealed that sea urchin embryos did not progress beyond early prophase. Notably, the nuclear envelope remained intact and chromatin was condensed into chromosomes in the arrested embryos. These synchronously dividing embryos did not show any abnormalities such as lysis, swelling, or morphological changes different from control embryos.

Animals↗
PubMed1986

Control of shoot apical development via cell division.

Cell division in plants not only partitions the protoplast but also provides the architectural framework for plant form. The shape of the shoot apical meristem is produced and maintained by gradients in the rate and plane of cell division, from the summit to the base of the apical dome, which also determine the region in which primordia can be formed. In Pisum leaf initiation is mainly the result of changes in the frequency of periclinal divisions at the leaf site whereas in Silene an increase in the rate of cell division seems more important since periclinal divisions are always present. Periclinal divisions may be permissive of primordium initiation rather than causal and may define the maximum area over which primordia can form. The occurrence in Pisum and Silene of periclinal divisions which do not seem to be related to concurrent outward growth suggests that the plane of division and the direction of growth may be controlled separately and in different ways. The control of outward growth during primordium initiation may lie in the epidermis, which necessarily grows faster at the leaf site. The initial orientation of epidermal growth at the primordial site, inferred as being normal to the plane of cell division, is predominantly longitudinal in Pisum but transverse in Silene. Longitudinal growth becomes dominant later in leaf development in Silene, as in Pisum. Several lines of evidence suggest a crucial role for the epidermis in the initial stages of primordium formation although the initial orientation of division planes in it may be concerned more with the shape of the young leaf than with initiation itself. In flower initiation primordial size becomes reduced, and in Silene there are alternations of higher and lower rates of cell division in successively initiated primordial types. A fuller understanding of the role of cell division in apical growth depends on better knowledge of the functional relationships between the plane of cell division, the orientation of microtubules and wall microfibrils, and the effect that division in one cell has on its neighbours.

Cell Division↗
PubMed1995

Thymic selection and cell division.

Cell division during thymic selection was studied with a system in which purified populations of T cell antigen receptor (TCR)- CD4+8+ (double-positive [DP]) cells and fetal thymic epithelial cells (TEC) were reaggregated in tissue culture. In this system, immature DP cells differentiate into mature single-positive (SP) CD4+8- and CD4-8+ TCRhi cells within 3-4 d, indicative of positive selection. By adding the DNA precursor, bromodeoxyuridine, to the cultures and staining cells for bromodeoxyuridine incorporation, T cell division in reaggregation cultures was found to be high on day 1, low on day 2, and high on days 4-5. Cell separation studies established that cell division on day 1 was restricted to DP blast cells. In the absence of blast cells, small DP cells failed to proliferate and differentiated into SP cells without cell division, thus indicating that proliferation is not an essential component of positive selection. This applied to SP cells generated within the first 2-3 d. Surprisingly, the SP cells generated later in culture showed a high rate of cell division; the proliferating SP cells were TCRhi and included both CD4+8- and CD4-8+ cells. Turnover of TCRhi SP cells was also prominent in the normal neonatal thymus and in TEC reaggregation cultures prepared with adult lymph node T cells. We speculate that division of mature SP cells in the perinatal thymic microenvironment is driven by stimulatory cytokines released from TEC. Such proliferation could be a device to expand the mature T cell repertoire before export to the periphery.

Animals↗
PubMed1976

On the mode of action of 5-diazouracil on bacterial cell division.

Cell division by strains of Escherichia coli and Salmonella typhimurium is inhibited by 5-diazouracil (5-DU). Division recovers in the presence of the inhibitor after a period which is temperature-dependent. Recovery is probably due to breakdown of 5-DU and the rate of this breakdown is apparently increased at alkaline pH. Growth with 5-DU caused only a slight reduction in the rate of murein synthesis and no alteration in the properties or composition of membranes of S. typhimurium. The agent caused chaining in Streptococcus fecalis and inhibition of the penicillin-induced lysis of S. typhimurium. These effects may have been due to direct inhibition of lysin activity but an indirect effect seems more likely. The most marked effect of 5-DU on S. typhimurium was to cause a transient inhibition of DNA synthesis. Since 5-DU did not stop uncoupled cell division (i.e. division occurring independently of DNA replication) and since lon- strains were more sensitive to 5-DU than lon+ strains, it was concluded that 5-DU acts on cell division via an inhibitory effect on DNA replication.

Azo Compounds↗
PubMed1977

Epigenetic variation of cultured somatic cells: evidence for gradual changes in the requirement for factors promoting cell division.

Cells of higher plant species in culture sometimes lose their requirement for an exogenous supply of a cell division factor that, thereafter, they are able to produce. This heritable change, known as cytokinin habituation, appears to be an epigenetic one rather than a classical mutation because it is directed, potentially reversible, leaves the cell totipotent, and involves the expression of a latent differentiated function. By using cloned cell lines derived from pith parenchyma of tobacco, we have obtained evidence that the habituation process is gradual rather than all-or-none and leads to progressively more autotrophic tissues. Cells in culture show reversible shifts among a range of habituated states but remain totipotent and can be induced to regain their requirement for a cell division factor. Thus, it appears that habituation involves epigenetic changes in a quantitative cellular phenotype. Our findings support the hypothesis that tumor progression in crown gall, a neoplastic disease of higher plants, can be accounted for by heritable changes in the pattern of gene expression.

Cell Differentiation↗
PubMed1995

Age-related alterations in cell division and cell cycle kinetics in control and trimethyltin-treated lymphocytes of human individuals.

Trimethyltin chloride induced age-related suppression of cell division and cell cycle kinetics in human peripheral blood lymphocytes cultured in RPMI 1640 culture medium supplemented with human AB serum, phytohemagglutinin and bromodeoxyuridine. A high frequency of M1 (first metaphase) cells was seen in cultures treated with a high dose (C1 = 1.0 microgram per culture) and in lymphocytes from donors in the age range 40-70 years. The delay in cell division and cell cycle kinetics may indicate a longer duration in DNA synthesis induced by trimethyltin chloride in aged lymphocytes.

Adenosine Triphosphate↗
PubMed1984

Inhibition of lateral wall elongation by mecillinam stimulates cell division in certain cell division conditional mutants of Escherichia coli.

The effect of mecillinam, a beta-lactam antibiotic that specifically binds penicillin-binding protein 2 of Escherichia coli, causes transition from rod to coccal shape, and inhibits cell division in sensitive cells, has been tested on three different E. coli temperature-sensitive cell division mutants. At the nonpermissive temperature, the antibiotic allows an increase in cell number for strains BUG6 and AX655 but not for AX621. In strain AX655, the cell division stimulation was observed only if the antibiotic was added immediately after shifting to the nonpermissive temperature, whereas in BUG6, the rise in cell number was observed also when mecillinam was added after 90 min of incubation at the nonpermissive temperature. In all cases, cell division began occurring 30 min after addition of the antibiotic. Mecillinam had no effect on division of dnaA, dnaB temperature-sensitive mutants or on division of BUG6 derivatives made resistant to this antibiotic. Other beta-lactam antibiotics such as penicillin, ampicillin, cephalexin, and piperacillin and non beta-lactam antibiotics such as fosfomycin, teichomycin, and vancomycin that inhibit cell wall synthesis did not show any effect on cell division for any of the mutants. The response of the three cell division mutants to mecillinam is interpreted in terms of a recently proposed model for shape regulation in bacteria.

Amdinocillin↗