Benzyladenine-stimulation of nuclear DNA synthesis and cell division in germinating maize

1991 ◽  
Vol 1 (2) ◽  
pp. 113-117 ◽  
Author(s):  
J. Reyes ◽  
L. F. Jiménez-García ◽  
M. A. Gonzalez ◽  
J. M. Vázquez-Ramos
Keyword(s):  
Cell Division ◽  
Dna Replication ◽  
Dna Synthesis ◽  
Mitotic Index ◽  
Nuclear Dna ◽  
Fold Increase ◽  
Mechanisms Of Action ◽  
Dna Metabolism ◽  
Stimulation Of

AbstractWe have studied by means of cytology and autoradiography the effect of benzyladenine (BA, a synthetic cytokinin) on DNA metabolism during early maize germination.The data indicate that BA stimulates nuclear DNA replication. The doubling of the amount of nuclear DNA in BA-treated axes occurs earlier than in nontreated axes, and there is a three-fold increase in the mitotic index at 24 h of germination. These results provide further corroboration for the suggestion that the stimulation of DNA synthesis observed relates to a nuclear replicative type of synthesis. Possible mechanisms of action of BA are discussed.

Stimulation of cell division and DNA replication inPrototheca richardsiby passage through larval amphibian guts

Parasitology ◽  
1993 ◽  
Vol 107 (2) ◽  
pp. 119-124 ◽  
Author(s):  
T. J. C. Beebee ◽  
A. L.-C. Wong
Keyword(s):  
Cell Division ◽  
Dna Replication ◽  
Growth Inhibition ◽  
Dna Synthesis ◽  
Free Living ◽  
Leucine Uptake ◽  
Amphibian Larvae ◽  
Larval Amphibian ◽  
Stimulation Of

SUMMARYPrototheca richardsi, an unpigmented heterotrophic alga, causes growth inhibition in amphibian larvae and has proved refractory to culturein Vitro.P. richardsireplication is dependent on regular passaging through tadpole digestive systems; uptake of thymidine by free-livingProtothecacells and incorporation into DNA are very low by comparison with leucine uptake and incorporation into protein, but DNA synthesis is detectable in cells isolated from tadpole intestines. DNA replication was elicited 6–8 h after ingestion in protothecans fed to tadpoles and subsequently re-isolated from them, providing that the tadpoles were fed subsequent to the ingestion. It appears that passaging through tadpole intestines provides an essential stimulus to maintaining an active cell division cycle inP. richardsi.

scholarly journals MACROMOLECULAR EVENTS LEADING TO CELL DIVISION IN TETRAHYMENA PYRIFORMIS AFTER REMOVAL AND REPLACEMENT OF REQUIRED PYRIMIDINES

1965 ◽  
Vol 25 (2) ◽  
pp. 9-19 ◽  
Author(s):  
Ivan L. Cameron
Keyword(s):  
Cell Division ◽  
Dna Replication ◽  
Dna Synthesis ◽  
Nuclear Dna ◽  
Early Period ◽  
Tetrahymena Pyriformis ◽  
Cell Number ◽  
Cellular Protein ◽  
Cellular Content ◽  
Endogenous Protein

Tetrahymena pyriformis were brought to a non-growing state by removal of pyrimidines from their growth medium. During pyrimidine deprivation cell number increased 3- to 4 fold, and this increase was accompanied by one or more complete cycles of macronuclear DNA replication. Autoradiographic studies show that endogenous protein and RNA were turning over throughout starvation and that RNA breakdown products were used to support the DNA synthesis that occurred during the early period of starvation. However, after 72 hours of starvation all DNA synthesis and cell division had ceased. Feulgen microspectrophotometry shows the macronuclei of these cells to have been stopped at a point prior to DNA replication (G1 stage). After pyrimidine replacement the incorporation of H3-uridine, H3-adenosine, and H3-leucine was measured by the autoradiographic grain counting method. The results indicate that RNA synthesis began to increase almost immediately, but that there was a lag of almost an hour before an increase in protein synthesis. In agreement with the autoradiographic data, chemical data also show that cellular content of RNA began to increase shortly after pyrimidine replacement but that cellular protein content did not increase until about one hour later. Pulse labeling of the cells with H3-thymidine at intervals after pyrimidine replacement shows that labeled macronuclei first began to appear at 150 minutes; that 98 per cent of the macronuclei were in DNA synthesis at 240 to 270 minutes; and that the percentage then began to decrease from 300 to 390 minutes, at which time only 25 per cent of the macronuclei were labeled. Cellular content of DNA did not increase for at least 135 minutes after pyrimidine replacement; however, just before the first cells divided (360 minutes) the DNA content had doubled. After pyrimidine replacement the cells first began to divide at 360 minutes, and 50 per cent had divided at 420 minutes; however, all cells had not divided until 573 minutes. This technique of chemical synchronization of cells in mass cultures makes feasible detailed biochemical analysis of events leading to nuclear DNA replication and cell division.

Changes of the DNA content of differentiating and adult macronuclei of the ciliate Loxodes magnus (Karyorelictida)

1980 ◽  
Vol 44 (1) ◽  
pp. 375-394
Author(s):  
N.N. Bobyleva ◽  
B.N. Kudrjavtsev ◽  
I.B. Raikov
Keyword(s):  
Cell Division ◽  
Dna Replication ◽  
Hydrochloric Acid ◽  
Dna Synthesis ◽  
Acid Hydrolysis ◽  
Gene Amplification ◽  
Dna Content

The DNA content of isolated micronuclei, differentiating macronuclei (macronuclear Anlagen), and adult macronuclei of Loxodes magnus was measured cytofluorimetrically in preparations stained with a Schiff-type reagent, auramine-SO2, following hydrochloric acid hydrolysis. The DNA content of the youngest macronuclear Anlagen proved to be the same as that of telophasic micronuclei (2 c). The Anlagen thus differentiate from micronuclei which are still in G1. The quantity of DNA in the macronuclear Anlagen thereafter rises to the 4-c level, simultaneously with DNA replication in the micronuclei which immediately follows mitosis. In non-dividing animals most micronuclei are already in G2. Adult macronuclei here contain on average 1.5 times more DNA than the micronuclei; their DNA content is about 5–6 c (in some individual nuclei, up to 10 c). These data are consistent with autoradiographic evidence indicating a weak DNA synthesis in the macronuclei of Loxodes and make likely the existence of partial DNA replication (e.g. gene amplification) in the macronuclei. The DNA content of adult macronuclei isolated from dividing animals proved to be significantly smaller than that of macronuclei isolated from non-dividing specimens of the same clone. In 3 clones studied, the former value amounted on average to 71–79, 78 and 95% of the latter, respectively. This drop of DNA content cannot be explained by ‘dilution’ of the old macronuclei with newly formed ones. The quantity of DNA in adult macronuclei thus seems to undergo cyclical changes correlated with cytokinesis, despite the fact that, in Loxodes magnus, the macronuclei themselves never divide and are simply segregated at every cell division. The macronuclei of Loxodes can be termed paradiploid or hyperdiploid.

Stimulation of DNA Synthesis by Mouse DNA Helicase B in a DNA Replication System Containing Eukaryotic Replication Origins

Biochemistry ◽  
1995 ◽  
Vol 34 (24) ◽  
pp. 7913-7922 ◽  
Author(s):  
Ken Matsumoto ◽  
Masayuki Seki ◽  
Chikahide Masutani ◽  
Shusuke Tada ◽  
Takemi Enomoto ◽  
...  
Keyword(s):  
Dna Replication ◽  
Dna Synthesis ◽  
Dna Helicase ◽  
Replication Origins ◽  
Replication System ◽  
Stimulation Of

Functions of cytokinins

1978 ◽  
Vol 284 (1002) ◽  
pp. 449-457 ◽  
Keyword(s):  
Cell Division ◽  
Binding Protein ◽  
Leaf Tissue ◽  
Mechanisms Of Action ◽  
Transfer Rna ◽  
Biological Functions ◽  
Higher Plant ◽  
Rna Molecules ◽  
Plant Ribosomes ◽  
Stimulation Of

Mechanisms of action of cytokinins at the cellular and molecular levels are still unknown. Biological functions of cytokinins are presented through specific bioassay systems which are regarded as standard (delay of senescence of leaf tissue and stimulation of cell division) and which have been or may be biochemically investigated. These ‘biochemical functions’ of cytokinins are reviewed. The biochemical significance of the specific occurrence of cytokinins in transfer RNA molecules is discussed with respect to the question of the incorporation of labelled cytokinins into RNA molecules. Also, the significance of the cytokinin binding protein recently isolated from higher plant ribosomes is discussed.

Abstract 1359: Only the Catalytic p110alpha Isoform Mediates Class IA PI 3-Kinase-Induced Atherogenic Signals in Vascular Smooth Muscle Cells

Circulation ◽  
2008 ◽  
Vol 118 (suppl_18) ◽  
Author(s):  
Marius Vantler ◽  
Lenard Mustafov ◽  
Evren Caglayan ◽  
Stephan Rosenkranz
Keyword(s):  
Smooth Muscle ◽  
Growth Factor ◽  
Vascular Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Dna Synthesis ◽  
Vascular Smooth Muscle Cells ◽  
Fold Increase ◽  
And Migration ◽  
Induced Apoptosis ◽  
Stimulation Of

Proliferation, migration, and apoptosis of vascular smooth muscle cells (VSMC) are pivotal determinants of the pathogenesis of vascular diseases, which are mainly controlled by growth factor dependent activation of PI 3-Kinase (PI3K). Growth factors like platelet-derived growth factor (PDGF) activate class IA PI3Ks containing one of three p110 catalytic subunits (p110alpha, p110beta, and p110delta). We investigated the specific function of these isoforms for PDGF-controlled proliferation, migration, and apoptosis of VSMC using novel isoform-specific inhibitors. PDGF-dependent proliferation and migration solely depended on p110alpha. Stimulation of VSMC with PDGF-BB (50 ng/ml) mediated a 2.5±0.4 increase ( p <0.05) of DNA-synthesis (BrdU incorporation assay) and induced a 3.4+/−0.7 fold increase ( p <0.05) of VSMC migration (modified Boyden-chamber). Inhibition of p110alpha with PIK075 (1 μ M, Ki=100 nM) completely abrogated PDGF-dependent DNA-synthesis and migration ( p <0,05), whereas inhibitors against p110beta (TGX 221, 1 μ M) or p110delta (IC87114 1 μ M) had no influence. Consistently, PDGF-induced DNA-synthesis and migration were suppressed by siRNA-dependent downregulation of p110alpha ( p <0,05) whereas p110beta or p110delta knockdown had no effect. Interestingly, stimulation of VSMC with PDGF-BB (50 ng/ml) induced anti- or proapoptotic effects depending on the duration of PDGFR activation. Incubation of VSMC with H 2 O 2 (50 μ M, 16h) led to a 2.8±0.7 fold increase ( p >0.05) of apoptosis (Cell Death Detection ELISA). Simultanous addition of PDGF-BB (50 ng/ml) significantly diminished the H 2 O 2 -induced apoptosis (52±7%, p >0.05). In contrast, prestimulation with PDGF-BB 24h prior to the addition of H 2 O 2 led to an increase of H 2 O 2 -induced apoptosis (7.8±1.3, p >0.05). The anti- as well as the proapoptotic effect depended strictly on p110alpha as PIK075 (1 μ M, p <0,05) or p110alpha specific siRNA completely abrogated PDGF-BB-mediated pro- as well as antiapoptotic effects. Our results demonstrate that only the catalytical PI3K subunit p110alpha mediates the growth factor-induced atherogenic responses. Therefore, p110alpha represents an interesting therapeutic target for prevention of atherosclerosis and restenosis formation.

Cytofluorimetric analysis of nuclear DNA during meiosis, fertilization and macronuclear development in the ciliate Tetrahymena pyriformis, syngen 1

1975 ◽  
Vol 17 (3) ◽  
pp. 471-493 ◽  
Author(s):  
F.P. Doerder ◽  
L.E. Debault
Keyword(s):  
Cell Division ◽  
Dna Synthesis ◽  
Nuclear Dna ◽  
Nuclear Dna Content ◽  
Tetrahymena Pyriformis ◽  
Cell Cycles ◽  
Macronuclear Development ◽  
Sister Chromatids ◽  
Nuclear Development ◽  
S Period

Fluorescence cytophotometry was used to study nuclear DNA content and synthesis patterns during meiosis, fertilization and macronuclear development in the ciliated protozoon, Tetrahymena pyriformis, syngen 1. It was found that cells entered conjugation with a G1 (45C) macronucleus and a G2 (4C) micronucleus. During meiosis the micronucleus was reduced to 4 haploid nuclei, each with a 1C amount of DNA; each meiotic product then replicated to 2C, but only the nucleus next to the attachment membrane in each conjugant divided to form the two 1C gametic nuclei. The gametic nuclei replicated to 2C prior to fertilization; hence there was no S-period in the 4C fertilization nucleus (synkaryon). The first postzygotic division products immediately entered an S-period to become 4C, and at the second postzygotic division, each of the two 4C nuclei in each conjugant divided to form one 2C micronucleus and one 2C macronuclear Anlage. The macronuclear Anlagen began DNA synthesis immediately and were about 8C at the completion of conjugation; the micronuclei did not undergo rapid DNA doubling and measured between 2C and 3C when the conjugants separated. The old macronucleus did not participate in any S-period during conjugation and began to decompose after the second postzygotic division; it contained an average of 24C at the end of conjugation. From this sequence of nuclear divisions a pattern emerges that, unless a general cytoplasmic signal for DNA synthesis is suppressed, DNA synthesis always occurs in micronuclear division products immediately following separation of sister chromatids. Nuclear development continued in the first two cell cycles after conjugation. In exconjugants (the first cycle), macronuclear Anlagen underwent two rounds of DNA synthesis to become 32C and both micronuclei also underwent DNA synthesis. However, prior to the first cell division, one micronucleus and the old macronucleus completely disintegrated, and at the first cell division the remaining 4C micronucleus divided and one macronuclear Anlage was distributed to each resulting caryonide. At the end of the second cell cycle, the dividing macronucleus of each caryonide contained about 128C. These results relate to the question of ploidy of macronuclear subunits. It is argued that the G1 macronucleus contains 22 or 23 diploid subunits, each subunit being a copy of the diploid micronuclear genome. It is suggested that unequal macronuclear division relates to the question of subunit ploidy by playing a role in the phenomenon of macronuclear assortment.

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