DNA synthesis during the first stages of anterior regeneration in the polychaete annelid Owenia fusiformis (dedifferentiation and early phases of differentiation )

Development ◽  
1978 ◽  
Vol 44 (1) ◽  
pp. 81-92
Author(s):  
Monique Marilley ◽  
Yves Thouveny
Keyword(s):  
Dna Synthesis ◽  
Initial State ◽  
Cell Cycles ◽  
Small Areas ◽  
New Instrument ◽  
Dividing Cells ◽  
Marine Polychaete ◽  
The Moment ◽  
Early Phases ◽  
Anterior Regeneration

We have analysed DNA synthesis in early phases of regeneration in a marine Polychaete Annelid, Owenia fusiformis. The length and efficiency of the prereplicative phase was found to vary with the diurnal rhythm of activity of the animal; that is, it depends on the initial state of the cell population at the moment of the onset of proliferative stimulation. When animals were operated on at 12 a.m., the duration of the prereplicative phase of the first cells stimulated to proliferate was found to be 12 h. The remaining cells entered the S-phase progressively in waves until the 3rd day following amputation when nearly 100% of the blastema cells were stimulated. At that time the cell-cycles of these dividing cells were found to be highly synchronized. Blastema differentiation takes place on the 4th day and is initiated by stomodeum formation. During the differentiation phase, DNA synthesis is restricted to small areas of the regenerating part. The system described is viewed as a new instrument for investigating the control of the cell cycle in synchronized and subsequently differentiating tissue cells.

Incorporation of 3H-deoxynucleosides: changes in labelling indices during root development

1970 ◽  
Vol 48 (9) ◽  
pp. 1659-1663 ◽  
Author(s):  
R. D. MacLeod ◽  
D. Davidson
Keyword(s):  
Dna Synthesis ◽  
Root Development ◽  
Lateral Root ◽  
Developmental Stages ◽  
Root Systems ◽  
Interesting Aspect ◽  
Cell Cycles ◽  
Alternative Pathways ◽  
Dividing Cells

Whole root systems of Vicia faba were treated with 3H-TdR (tritiated deoxythymidine), 3H-AdR (tritiated deoxyadenosine), or 3H-CdR (tritiated deoxycytidine) solutions for 1 h. Labelling indices were determined immediately after treatment or up to 15 h later. Cells of lateral root meristems labelled immediately and most effectively with 3H-TdR. Lower levels of labelling were found in roots treated with 3H-AdR or 3H-CdR; these precursors, in particular 3H-CdR, appear to be unsuitable for the determination of any parameter of DNA synthesis. Cells of small primordia showed poor incorporation of labelled precursors immediately after a 1-h treatment but their labelling indices increased subsequently. It is suggested that pools of 3H-TdR and 3H-AdR are maintained and drawn upon by small primordia. Large primordia showed little or no incorporation of labelled precursors. The different responses of mitotically active cells taken from various developmental stages of a lateral root suggest that alternative pathways for the synthesis of DNA precursors are used to different extents during morphogenesis; the interesting aspect is that such changes can occur over a small number of cell cycles in a population of actively dividing cells.

Fluctuations of adenylate cyclase activity during anterior regeneration in Owenia fusiformis (Polychaete Annelid)

Development ◽  
1978 ◽  
Vol 48 (1) ◽  
pp. 73-78
Author(s):  
Josiane Coulon ◽  
Monique Marilley
Keyword(s):  
Cell Cycle ◽  
Cyclic Amp ◽  
Adenylate Cyclase ◽  
Cyclase Activity ◽  
Adenylate Cyclase Activity ◽  
Biochemical Assays ◽  
Strong Stimulation ◽  
Periodic Fluctuations ◽  
Early Phases ◽  
Anterior Regeneration

Biochemical assays of adenylate cyclase activity were performed during the early phases of regeneration in Owenia fusiformis (Polychaete Annelid). The results indicate the existence of a strong stimulation in an early phase following trauma. This stimulation is then followed by periodic fluctuations exhibiting a diurnal rhythm correlated with the cell cycle. Adenylate cyclase activity is also shown to be neurotransmitter-dependent. In this paper it is proposed that neurotransmitters might participate in the regulation of cyclic AMP formation, by means of adenylate cyclase acting on target blastema cells, undergoing the cell cycle.

Continuous DNA replication in the nucleus of the dinoflagellate Prorocentrum micans (Ehrenberg)

1977 ◽  
Vol 27 (1) ◽  
pp. 81-90
Author(s):  
S.A. Filfilan ◽  
D.C. Sigee
Keyword(s):  
Electron Microscope ◽  
Dna Synthesis ◽  
Nuclear Dna ◽  
Continuous Process ◽  
Prorocentrum Micans ◽  
Interphase Nuclei ◽  
Electron Microscope Autoradiography ◽  
Dividing Cells ◽  
High Degree ◽  
Very High

The uptake of tritiated thymine into cells of a heterogeneous population of Prorocentrum micans was investigated using light-microscope and electron-microscope autoradiography. Specificity of thymine uptake into DNA was demonstrated by the specific removal of label from wax-embedded material using DNase and by the high degree of localization of nuclear label to chromosomes in the electron-microscope autoradiographs. All nuclei, including both dividing and non-dividing cells, showed a substantial uptake of label, indicating that nuclear DNA synthesis in Prorocentrum micans is a continuous process. The level of DNA synthesis does show considerable variation, however, with very high levels in some interphase nuclei. The continuous replication of nuclear DNA provides further evidence of dinoflagellate affinity to the prokaryotes, and indicates that Prorocentrum micans is a very primitive eukaryote cell.

Maturation promoting factor and cell cycle regulation

Development ◽  
1985 ◽  
Vol 89 (Supplement) ◽  
pp. 271-284
Author(s):  
C. C. Ford
Keyword(s):  
Dna Synthesis ◽  
Cell Cycle Regulation ◽  
Nuclear Division ◽  
S Phase ◽  
Early Cleavage ◽  
Cell Cycles ◽  
Nuclear Envelope Breakdown ◽  
Cytostatic Factor ◽  
Cycle Regulation ◽  
Maturation Promoting Factor

Cell cycles in early amphibian embryos are characterized by the absence of G1 and G2 phases. The simple cycle of S phase and mitosis does show similarities with other systems, particularly in the presence of cytoplasmic components advancing nuclei into DNA synthesis and mitosis. Maturation-promoting factor induces nuclear envelope breakdown and subsequent chromosome condensation. Cytoplasmic factors appear during maturation which are capable of inducing DNA synthesis, and arrest of the nuclear division cycle in metaphase (cytostatic factor). The timing of appearance of these activities is considered and their relationship in integrating DNA synthesis during early cleavage is discussed.

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.

scholarly journals Stress states and moment rates of a two-asperity fault in the presence of viscoelastic relaxation

2015 ◽  
Vol 2 (1) ◽  
pp. 297-327
Author(s):  
M. Dragoni ◽  
E. Lorenzano
Keyword(s):  
Discrete Dynamical System ◽  
Constant Strain Rate ◽  
The State ◽  
Viscoelastic Deformation ◽  
Initial State ◽  
Tectonic Plates ◽  
Stress States ◽  
The Moment ◽  
Postseismic Relaxation ◽  
The Relationship

Abstract. A fault containing two asperities with different strengths is considered. The fault is embedded in a viscoelastic shear zone, subject to a constant strain rate by the motions of adjacent tectonic plates. The fault is modelled as a discrete dynamical system where the average values of stress, friction and slip on each asperity are considered. The state of the fault is described by three variables: the slip deficits of the asperities and the viscoelastic deformation. The system has four dynamic modes, for which the analytical solutions are calculated. The relationship between the state of the fault before a seismic event and the sequence of slipping modes in the event is enlightened. Since the moment rate depends on the number and sequence of slipping modes, the knowledge of the source function of an earthquake constrains the orbit of the system in the phase space. If the source functions of a larger number of consecutive earthquakes were known, the orbit could be constrained more and more and its evolution could be predicted with a smaller uncertainty. The model is applied to the 1964 Alaska earthquake, which was the effect of the failure of two asperities and for which a remarkable postseismic relaxation has been observed in the subsequent decades. The evolution of the system after the 1964 event depends on the state from which the event was originated, that is constrained by the observed moment rate. The possible durations of the interseismic interval and the possible moment rates of the next earthquake are calculated as functions of the initial state.

scholarly journals Multiple roles for protein phosphatase 1 in regulating the Xenopus early embryonic cell cycle.

1992 ◽  
Vol 3 (6) ◽  
pp. 687-698 ◽  
Author(s):  
D H Walker ◽  
A A DePaoli-Roach ◽  
J L Maller
Keyword(s):  
Dna Synthesis ◽  
Protein Phosphatase ◽  
Specific Inhibitor ◽  
Embryonic Cell ◽  
S Phase ◽  
Multiple Roles ◽  
Protein Phosphatase 1 ◽  
Cell Cycles ◽  
M Phase ◽  
Cytostatic Factor

Using cytostatic factor metaphase II-arrested extracts as a model system, we show that protein phosphatase 1 is regulated during early embryonic cell cycles in Xenopus. Phosphatase 1 activity peaks during interphase and decreases shortly before the onset of mitosis. A second peak of activity appears in mitosis at about the same time that cdc2 becomes active. If extracts are inhibited in S-phase with aphidicolin, then phosphatase 1 activity remains high. The activity of phosphatase 1 appears to determine the timing of exit from S-phase and entry into M-phase; inhibition of phosphatase 1 by the specific inhibitor, inhibitor 2 (Inh-2), causes premature entry into mitosis, whereas exogenously added phosphatase 1 lengthens the interphase period. Analysis of DNA synthesis in extracts treated with Inh-2, but lacking the A- and B-type cyclins, shows that phosphatase 1 is also required for the process of DNA replication. These data indicate that phosphatase 1 is a component of the signaling pathway that ensures that M-phase is not initiated until DNA synthesis is complete.

The induction of DNA synthesis in the chick red cell nucleus in heterokaryons during the first cell cycle after fusion with HeLa cells

1975 ◽  
Vol 18 (3) ◽  
pp. 455-490
Author(s):  
R.T. Johnson ◽  
A.M. Mullinger
Keyword(s):  
Cell Cycle ◽  
Dna Synthesis ◽  
Hela Cells ◽  
S Phase ◽  
Red Cells ◽  
Red Cell ◽  
Embryonic Chick ◽  
Cell Cycles ◽  
Phase Protein ◽  
Different Parts

Induction of DNA synthesis in embryonic chick red cells has been examined during the first and second cell cycles after fusion with HeLa cells synchronized in different parts of G1 and S-phase. The data indicate that: (i) the younger the embryonic blood the more rapidly the red cells are induced into DNA synthesis; (ii) the greater the ratio of HeLa to chick nuclei in the heterokaryon, the more rapidly the induction occurs; (iii) DNA synthesis in the chick nucleus can continue after the HeLa nucleus has left S-phase and entered either G2 or mitosis; (iv) the induction potential of late S-phase HeLa is somewhat lower than that of early or mid S-phase cells; (v) less than 10% of the chick DNA is replicated during the first cycle after fusion and only a small proportion (15%) of the chick nuclei approach the 4C value of DNA during the second cycle after fusion; (vi) the newly synthesized DNA is associated either with the condensed regions of the nucleus or with the boundaries between condensed and non-condensed regions; (vii) the chick chromosomes at the first and second mitosis after fusion are in the form of PCC prematurely condensed chromosomes); they are never fully replicated and are often fragmentary; (viii) DNA synthesis in the chick nuclei is accompanied by an influx of protein (both G1 and S-phase protein) from the HeLa component of the heterokaryon.

scholarly journals ANALYSIS OF THE SCHEDULE OF DNA REPLICATION IN HEAT-SYNCHRONIZED TETRAHYMENA

1973 ◽  
Vol 59 (1) ◽  
pp. 1-11 ◽  
Author(s):  
William R. Jeffery ◽  
Joseph Frankel ◽  
Lawrence E. de Bault ◽  
Leslie M. Jenkins
Keyword(s):  
Cell Cycle ◽  
High Temperature ◽  
Dna Replication ◽  
Heat Shock ◽  
Dna Synthesis ◽  
Shock Treatment ◽  
Heat Shock Treatment ◽  
Dividing Cells ◽  
S Period ◽  
Selection Of

The temporal schedule of DNA replication in heat-synchronized Tetrahymena was studied by autoradiographic and cytofluorometric methods. It was shown that some cells, which were synchronized by selection of individual dividing cells or by temporary thymidine starvation, incorporated [3H]thymidine into macronuclei in a periodic fashion during the heat-shock treatment. It was concluded that supernumerary S periods occurred while cell division was blocked by high temperature. The proportion of cells which initiated supernumerary S periods was found to be dependent on the duration of the heat-shock treatment and on the cell cycle stage when the first heat shock was applied. Cytofluorometric measurements of Feulgen-stained macronuclei during the heat-shock treatment indicated that the DNA complement of these cells was substantially increased and probably duplicated during the course of each S period. Estimates of DNA content also suggested that the rate of DNA synthesis progressively declined during long heat-shock treatments. These results indicate that the mechanism which brings about heat-induced division synchrony is not an interruption of the process of DNA replication. Further experiments were concerned with the regulation of DNA synthesis during the first synchronized division cycle. It was shown that participation in DNA synthesis at this time increased as more cells were able to conclude the terminal S period during the preceding heat-shock treatment. It is suggested that a discrete period of time is necessary after the completion of DNA synthesis before another round of DNA synthesis can be initiated.

Inhibition of Cell Division by High External NaCl Concentrations in Synchronized Cultures of Chlorella emersonii

1982 ◽  
Vol 9 (2) ◽  
pp. 179 ◽  
Author(s):  
T.L Setter ◽  
H Greenway ◽  
J Kuo
Keyword(s):  
Electron Microscopy ◽  
Cell Division ◽  
Dna Synthesis ◽  
Dna Content ◽  
Cell Cycles ◽  
Daughter Cells ◽  
Specific Effects ◽  
Rna And Dna ◽  
Synchronized Cultures ◽  
In Cells

Effects of high external NaCl concentrations on growth were examined in the unicellular freshwater alga Cldorella emevsonii during different phases of cell development, using synchronized cultures obtained by alternating light-dark cycles. Growth of cultures synchronized at 1 mM NaCl [external osmotic pressure (next=) 0.08 MPa] was compared with (i) cultures synchronized at 200 mM NaCl (n,,, = 1.01 MPa) and (ii) cultures synchronized at 1 mM NaCl from which the daughter cells were suddenly transferred to 100, 150 or 200 mM NaCl. The effects of these two treatments on synthesis of protein, RNA and DNA during cell cycles were similar, and are attributed to the high nexta nd not to specific effects of Na+ and C1-. Growth inhibitions in cells at 200 mM NaCl relative to 1 mM NaCl occurred mainly via effects on cell division; this was confirmed by electron microscopy. There was a lag before net DNA synthesis commenced, and there were reductions in rates of net DNA synthesis in cells at 200 mM NaCl relative to 1 mM NaC1. Rates of increase in cell volume and in protein and RNA content per cell were little affected by high external NaCl concentrations. Consequently, daughter cells at 200 mM NaCl were approximately twice the volume and contained twice as much protein and RNA as daughter cells at 1 mM NaCl, while DNA content was equal in daughter cells at 1 and 200 mM NaCl.

Sign in / Sign up

Export Citation Format

Share Document