Dose response kinetics of serum vitellogenin, liver DNA, RNA, protein and lipid after induction by estradiol-17β in male flounders (Platichthys flesus L.)

1979 ◽  
Vol 63 (1) ◽  
pp. 1-6 ◽  
Author(s):  
Julius Emmersen ◽  
Bodil Korsgaard ◽  
Ingrid Petersen
Keyword(s):  
Dose Response ◽  
Platichthys Flesus ◽  
Kinetics Of ◽  
Estradiol 17Β

Kinetics of DNA Repair Under Chronic Irradiation at Low and Medium Dose Rates in Repair Proficient and Repair Compromised Normal Fibroblasts

2021 ◽  
Author(s):  
Elena K. Zaharieva ◽  
Megumi Sasatani ◽  
Kenji Kamiya
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Dose Rate ◽  
Dose Response ◽  
Chronic Irradiation ◽  
Dose Rates ◽  
Chronic Radiation ◽  
Damage Repair ◽  
Kinetics Of ◽  
Medium Dose

We present time and dose dependencies for the formation of 53BP1 and γH2AX DNA damage repair foci after chronic radiation exposure at dose rates of 140, 250 and 450 mGy/day from 3 to 96 h, in human and mouse repair proficient and ATM or DNA-PK deficient repair compromised cell models. We describe the time/dose-response curves using a mathematical equation which contains a linear component for the induction of DNA damage repair foci after irradiation, and an exponential component for their resolution. We show that under conditions of chronic irradiation at low and medium dose rates, the processes of DNA double-strand breaks (DSBs) induction and repair establish an equilibrium, which in repair proficient cells manifests as a plateau-shaped dose-response where the plateau is reached within the first 24 h postirradiation, and its height is proportionate to the radiation dose rate. In contrast, in repair compromised cells, where the rate of repair may be exceeded by the DSB induction rate, DNA damage accumulates with time of exposure and total absorbed dose. In addition, we discuss the biological meaning of the observed dependencies by presenting the frequency of micronuclei formation under the same irradiation conditions as a marker of radiation-induced genomic instability. We believe that the data and analysis presented here shed light on the kinetics of DNA repair under chronic radiation and are useful for future studies in the low-to-medium dose rate range.

Charakterisierung und Kinetik des in der Rattenplacenta vorkommenden mikrosomalen Enzyms, das den Wasserstoff-Transfer von Oestradiol auf Androstendion katalysiert / Characterization and Kinetics of the Microsomal Enzyme of Rat Placenta which Functions as a “Transhydrogenase” between Estradiol-17β and Androstenedione

1971 ◽  
Vol 26 (7) ◽  
pp. 710-719 ◽  
Author(s):  
Kunhard Pollow ◽  
Barbara Pollow
Keyword(s):  
Hydrogen Transfer ◽  
Microsomal Fraction ◽  
Close Relation ◽  
Inhibitory Effect ◽  
Magnesium Ions ◽  
Michaelis Constant ◽  
Temperature Optimum ◽  
Optimum Ph ◽  
Kinetics Of ◽  
Estradiol 17Β

The microsomal fraction of rat placenta contains a 17β-hydroxysteroid-oxidoreductase which transfers hydrogen from position 17 of estradiol to androstenedione. This hydrogen transfer is dependent on NAD, NADP as cofactor is without effect. The optimum pH is at 6,9. In the presence of NAD the Michaelis constant for estradiol is 4,17 · 10-5м at pH 7,4. In the presence of androstenedione in the incubation medium the Km-value for estradiol is decreased, which indicates an increased affinity for the enzyme. The temperature optimum of the enzyme is 38 °C. Addition of SH-blocking agents inhibited the enzyme activity. Zinc and magnesium ions had an inhibitory effect on the “transhydrogenase” and B-NADPT specifically labelled from [1-T]-glucose showed that the non-effect of NADP on transhydrogenation from estradiol to androstenedione resulting in reduction of position 17 is not due to different stereospecifity.The results show a close relation between the oxidative metabolism of estradiol and the reduction of androstenedione, indicating that estradiol-17β, as the preferred hydrogen-donating substrate, is an essential component of the androstenedione-hydrogenating system in the microsomal fraction of rat placenta.

GnRH-FSH and LH Dose-Response Relationships in Anestrous Sheep and Effects of Estradiol-17β and Progesterone Pretreatment

1982 ◽  
Vol 55 (2) ◽  
pp. 384-390 ◽  
Author(s):  
J. E. Wheaton ◽  
S. E. Recabarren ◽  
Mary A. Mullett
Keyword(s):  
Dose Response ◽  
Estradiol 17Β

Short Communication: Effect of silymarin (Silybum marianum) treatment on prolactin concentrations in cyclic sows

2013 ◽  
Vol 93 (2) ◽  
pp. 227-230 ◽  
Author(s):  
F. Loisel ◽  
H. Quesnel ◽  
C. Farmer
Keyword(s):  
Dose Response ◽  
Short Communication ◽  
The Other ◽  
Milk Thistle ◽  
Silybum Marianum ◽  
Blood Samples ◽  
Communication Effect ◽  
Dose Response Study ◽  
Estradiol 17Β

Loisel, F., Quesnel, H. and Farmer, C. 2013. Short Communication: Effect of silymarin (Silybum marianum) treatment on prolactin concentrations in cyclic sows. Can. J. Anim. Sci. 93: 227–230. An extract (silymarin) from the plant Silybum marianum (milk thistle) was shown to increase circulating concentrations of prolactin in cycling rats. A dose-response study was undertaken to determine if silymarin does have hyperprolactinemic properties in cycling swine. Forty-four weaned sows were allotted to four groups receiving 0, 1, 2 or 4 g d−1 of silymarin over a period of 8 d. Blood samples were obtained on days 1 (first day of treatment starting 24 to 48 h after the onset of the standing estrus), 2, 3, and 9. Prolactin, progesterone, estradiol-17β and leptin concentrations were determined. Silymarin did not increase prolactin concentrations at any of the doses studied, nor did it affect concentrations of the other hormones (P>0.1).

Dose response and kinetics of foci disappearance following exposure to high- and low-LET ionizing radiation

2009 ◽  
Vol 85 (10) ◽  
pp. 872-882 ◽  
Author(s):  
Rasa Ugenskiene ◽  
Kevin Prise ◽  
Melvyn Folkard ◽  
Janusz Lekki ◽  
Zbigniew Stachura ◽  
...  
Keyword(s):  
Ionizing Radiation ◽  
Dose Response ◽  
Kinetics Of

Kinetics of edema formation in rats as influenced by critical doses of dextran

1960 ◽  
Vol 199 (4) ◽  
pp. 657-660 ◽  
Author(s):  
L. Kátó ◽  
B. Gözsy
Keyword(s):  
Dose Response ◽  
Response Curve ◽  
Dose Response Curve ◽  
Edema Formation ◽  
Critical Dose ◽  
Small Doses ◽  
Full Intensity ◽  
Kinetics Of

The severity and time of edema formation is characteristically influenced by doses of dextran if injected intravenously into rats. The dose-response curve revealed that small doses of dextrans (0.1–0.8 mg/100 gm) provoke maximal edema formation within 10 minutes, while increasing doses produce less severe edema and delay in its appearance, until a critical dose is arrived at, which provokes no hyperemia and no edema at all. Further increase in dose provokes edema again. The critical dose is relatively sharp and characteristic for each type of dextrans. If antihistamines are injected simultaneously with the critical dose, edema appears with full intensity. Experiments suggest that dextrans contain two fractions with opposite effects, one which provokes the edema formation and another which inhibits the response.

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