Autoradiographic detection of the uptake of the label from bacterial3H-DNA in relation to the kinetics of the mitotic cycle in barley embryos

1979 ◽  
Vol 21 (1) ◽  
pp. 35-41 ◽  
Author(s):  
P. Tichý ◽  
M. Ondřej ◽  
Květuše Schwammenhöferová
Keyword(s):  
Mitotic Cycle ◽  
Kinetics Of ◽  
Autoradiographic Detection

scholarly journals INTRAPOPULATION KINETICS OF THE MITOTIC CYCLE

1965 ◽  
Vol 25 (2) ◽  
pp. 179-189 ◽  
Author(s):  
Jesse E. Sisken ◽  
Luciano Morasca
Keyword(s):  
Generation Time ◽  
Mitotic Cycle ◽  
Tritiated Thymidine ◽  
Age Distribution ◽  
Time Lapse ◽  
Human Amnion ◽  
Generation Times ◽  
The Right ◽  
Kinetics Of ◽  
Autoradiographic Detection

Data obtained with time lapse cinemicrographic techniques showed that the distribution of generation times for exponentially proliferating human amnion cells in culture is skewed to the right and that reciprocals of generation times appear normally distributed. As shown for bacteria, the true age distribution is much broader than theoretical distributions which fail to take into account the dispersion of generation times. By means of the technique utilizing autoradiographic detection of tritiated thymidine in cells whose mitotic histories were recorded by time lapse cinemicrography, it was shown that the G1 distribution is similar to the generation time distribution but is more variable. In our experiments, the G2 + prophase distribution resembled the generation time and G1 distributions. The data suggested two possibilities for S: either it is relatively constant, or it is inversely related to the lengths of G1 and G2 + prophase. Since G1 is more variable than the total cycle, and G2 + prophase more variable than the computed sum of S + G2 + prophase + metaphase, it was concluded that the relationships between parts of the cycle are non-random and that compensating mechanisms apparently help regulate the lengths of successive parts of the mitotic cycle in individual cells.

scholarly journals CELL POPULATION KINETICS OF EXCISED ROOTS OF PISUM SATIVUM

1965 ◽  
Vol 27 (1) ◽  
pp. 179-189 ◽  
Author(s):  
Jack Van't Hof
Keyword(s):  
Cell Population ◽  
Mitotic Cycle ◽  
Sucrose Concentration ◽  
Tritiated Thymidine ◽  
Cycle Duration ◽  
Population Kinetics ◽  
Pea Roots ◽  
Mitotic Figures ◽  
Kinetics Of ◽  
Subsequent Rise

The cell population kinetics of excised, cultured pea roots was studied with the use of tritiated thymidine and colchicine to determine (1) the influence of excision, (2) the influence of sucrose concentration, (3) the average mitotic cycle duration, and (4) the duration of mitosis and the G1, S, and G2 periods of interphase.1 The results indicate that the process of excision causes a drop in the frequency of mitotic figures when performed either at the beginning of the culture period or after 100 hours in culture. This initial decrease in frequency of cell division is independent of sucrose concentration, but the subsequent rise in frequency of division, after 12 hours in culture, is dependent upon sucrose concentration. Two per cent sucrose maintains the shortest mitotic cycle duration. The use of colchicine indicated an average cycle duration of 20 hours, whereas the use of tritiated thymidine produced an average cycle duration of 17 hours.

DURATION OF MITOTIC CYCLE AND REGULATION OF DNA REPLICATION IN NICOTIANA PLUMBAGINIFOLIA AND A HYBRID DERIVATIVE OF N. TABACUM SHOWING CHROMOSOME INSTABILITY

1969 ◽  
Vol 11 (1) ◽  
pp. 133-142 ◽  
Author(s):  
S. B. Gupta
Keyword(s):  
Mitotic Cycle ◽  
Chromosome Instability ◽  
Nicotiana Plumbaginifolia ◽  
Root Tips ◽  
Time Intervals ◽  
Pulse Label ◽  
Significant Difference ◽  
Synthetic Phase ◽  
Autoradiographic Detection ◽  
Hybrid Derivative

The duration of the mitotic cycle with its component phases in Nicotiana plumbaginifolia (pbg, 2n = 20) and a hybrid derivative of N. tabacum (tbc, 2n = 48 and N. plumbaginifolia was determined from the root tips. A 30 minute pulse label of H3-thymidine was employed for the autoradiographic detection of the labeled prophases.The time intervals, for the total generation time (T), postsynthetic phase (G2), prophase, synthetic phase (S), and the combined presynthetic phase, metaphase, anaphase, telophase (G1 + M + A + T) in N. plumbaginifolia were estimated as 11.0, 3.4, 1.3, 5.7 and 0 6 hours, respectively. In the hybrid derivative the corresponding estimates were 9.0, 1.4, 0.8, 3.8 and 3.0 hours.The G1, S and G2 periods of N. plumbaginifolia were found significantly different from those of the hybrid derivative, but the duration of the mitotic cycle did not show a significant difference. On the basis of the distribution of heterochromatin and its late replication in N. plumbaginifolia chromosomes, possible causes of instability of alien pbg chromosomes in N. tabacum nuclei are discussed.

Direct observations of radiation-enhanced transformations in glass

1983 ◽  
Vol 41 ◽  
pp. 354-355
Author(s):  
J. F. DeNatale ◽  
D. G. Howitt
Keyword(s):  
Glass Matrix ◽  
Diffusion Mechanism ◽  
Bubble Formation ◽  
Silicate Glasses ◽  
Phase Decomposition ◽  
Direct Observations ◽  
Thin Foils ◽  
Oxygen Bubble ◽  
Electron Energy Loss ◽  
Kinetics Of

The electron irradiation of silicate glasses containing metal cations produces various types of phase separation and decomposition which includes oxygen bubble formation at intermediate temperatures figure I. The kinetics of bubble formation are too rapid to be accounted for by oxygen diffusion but the behavior is consistent with a cation diffusion mechanism if the amount of oxygen in the bubble is not significantly different from that in the same volume of silicate glass. The formation of oxygen bubbles is often accompanied by precipitation of crystalline phases and/or amorphous phase decomposition in the regions between the bubbles and the detection of differences in oxygen concentration between the bubble and matrix by electron energy loss spectroscopy cannot be discerned (figure 2) even when the bubble occupies the majority of the foil depth.The oxygen bubbles are stable, even in the thin foils, months after irradiation and if van der Waals behavior of the interior gas is assumed an oxygen pressure of about 4000 atmospheres must be sustained for a 100 bubble if the surface tension with the glass matrix is to balance against it at intermediate temperatures.

Irradiation behavior of pyrolytic silicon carbide

1983 ◽  
Vol 41 ◽  
pp. 72-73
Author(s):  
R. J. Lauf
Keyword(s):  
Silicon Carbide ◽  
Fission Products ◽  
Thermodynamics And Kinetics ◽  
Neutron Fluences ◽  
Fuel Particles ◽  
Sic Coatings ◽  
Irradiation Behavior ◽  
Kinetics Of ◽  
Htgr Fuel

Fuel particles for the High-Temperature Gas-Cooled Reactor (HTGR) contain a layer of pyrolytic silicon carbide to act as a miniature pressure vessel and primary fission product barrier. Optimization of the SiC with respect to fuel performance involves four areas of study: (a) characterization of as-deposited SiC coatings; (b) thermodynamics and kinetics of chemical reactions between SiC and fission products; (c) irradiation behavior of SiC in the absence of fission products; and (d) combined effects of irradiation and fission products. This paper reports the behavior of SiC deposited on inert microspheres and irradiated to fast neutron fluences typical of HTGR fuel at end-of-life.

The Ordered Phase Formation in Ti-Al-Ga Alloys

1970 ◽  
Vol 28 ◽  
pp. 440-441
Author(s):  
Shiro Fujishiro ◽  
Harold L. Gegel
Keyword(s):  
Thermal Stability ◽  
High Temperature ◽  
Titanium Alloys ◽  
Growth Kinetics ◽  
Stoichiometric Composition ◽  
Good Potential ◽  
Alpha Titanium ◽  
Cold Rolled ◽  
Kinetics Of ◽  
Thermal Stability Of

Ordered-alpha titanium alloys having a DO19 type structure have good potential for high temperature (600°C) applications, due to the thermal stability of the ordered phase and the inherent resistance to recrystallization of these alloys. Five different Ti-Al-Ga alloys consisting of equal atomic percents of aluminum and gallium solute additions up to the stoichiometric composition, Ti3(Al, Ga), were used to study the growth kinetics of the ordered phase and the nature of its interface.The alloys were homogenized in the beta region in a vacuum of about 5×10-7 torr, furnace cooled; reheated in air to 50°C below the alpha transus for hot working. The alloys were subsequently acid cleaned, annealed in vacuo, and cold rolled to about. 050 inch prior to additional homogenization

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