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1.
Tannin, a naturally occurring polyphenolic compound, was found to inhibit the activity of purified poly(ADP-ribose) glycohydrolase from human placenta. The inhibition was dose-dependent and half maximal with 2.8 micrograms/ml of tannin. The inhibitory effect of tannin was two and three orders of magnitude more than those of ADP-ribose and cAMP, respectively. Kinetic analysis revealed that the inhibition by tannin was competitive with respect to the substrate poly(ADP-ribose). 相似文献
2.
Y J Tsai H Abe H Maruta T Hatano H Nishina H Sakagami T Okuda S Tanuma 《Biochemistry international》1991,24(5):889-897
Three classes of chemically defined tannins, gallotannins, ellagitannins and condensed tannins were examined for their inhibitory activities against purified poly (ADP-ribose) glycohydrolase. Ellagitannins showed higher inhibitory activities than gallotannins. In contrast, condensed tannins, which consist of an epicathechin gallate (ECG) oligomer without a glucose core were not appreciably inhibitory. Kinetic analysis revealed that the inhibition of ellagitannins was competitive with respect to the substrate poly(ADP-ribose), whereas gallotannins exhibited mixed-type inhibition. These results suggest that conjugation with glucose of hexahydroxy-diphenoyl (HHDP) group, which is a unique component of ellagitannins, potentiated the inhibitory activity, and that the structure of ellagitannins may have a functional domain which competes with poly(ADP-ribose) on the poly(ADP-ribose) glycohydrolase molecule. 相似文献
3.
Summary The changes in ovarian activity in the life cycle of the eusocial halictine beeLasioglossum (Evylaeus) duplex (Dalla Torre) was studied in both queens and workers by examining the stages of the terminal follicle in each of the six ovarioles. By
this method, ovarian activities of both queens and workers were more quantitatively determined than by observation of gross
ovarian features as usually conducted. Queen ovaries clearly exhibited two active periods, corresponding to the spring solitary
phase and the summer eusocial phase, with distinctly greater activity in the latter. In ovaries of overwintering queens oosorption
of young follicle was observed. Worker ovaries were found more active in orphan than in queenright colonies. The order of
ovarian activity obtained from pooled data, summer queens>spring queens>orphan workers>queenright workers, was also recognized
by comparison of individual females.
Bionomics of the eusocial halictine beeLasioglossum duplex IX.
Contribution No. 3107 from the Inst. Low Temp. Sci. 相似文献
4.
Cholesterol esterification in rat-liver cell sap 总被引:2,自引:0,他引:2
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The fluorimetric method of Correa-Freire et al. (Correa-Freire, M.C., Barenholz, Y. and Thompson, T.E. (1982) Biochemistry 21, 1244-1248) to measure glucosylceramide transfer between phospholipid bilayers has been applied to the determination of the activity of glycolipid transfer protein purified from pig brain. The transfer of pyrene-labeled galactosylceramide (PyrGalCer) from donor to acceptor vesicles was measured by a decrease in the intensity ratio of eximer (E) to excited monomer (M). A sensitive determination of the glycolipid transfer activity is possible by the fluorimetric method without separation of the donor and acceptor vesicles. The newly developed fluorimetric assay of glycolipid transfer protein was used to study the effects of N-ethylmaleimide, HgCl2 and sugars on the transfer activity. The treatment with N-ethylmaleimide inactivated the activity to about 40%. The activity was almost completely inactivated by the treatment with HgCl2. Monosaccharides and methyl-alpha-D-glucoside had no inhibitory effect on the transfer activity. A marked and immediate drop of the E/M ratio was observed by the addition of glycolipid transfer protein to vesicles containing PyrGalCer at a protein-to-PyrGalCer molar ratio of 1.56:1. The result suggests a complex formation of glycolipid transfer protein with PyrGalCer. 相似文献
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V. Svoboda Z. Kotašková V. Lenger J. Thomas 《Radiation and environmental biophysics》1979,16(4):339-345
Summary Repopulative activity of hemopoietic stem cells of mice given i.v. 5 kBq239Pu/mouse (166.5 kBq/kg) was followed. The activity retained was measured in the whole mouse, the skeleton and the liver. Simultaneously average cumulative skeletal dose was calculated. Quantitative parameters of the stem cell compartment and the marrow cellularity were studied in variously arranged bones (femur, pelvis, lumbar vertebra) using the exocolonizing test and cytological techniques. The effects of radiation were most marked in lumbar vertebra, less serious changes were found in pelvis and only a moderate response was present in femur. The bone marrow hemopoiesis is damaged in various bone sites to different degrees and the percentage of cells at risk appears higher in trabecular than in cortical bone. 相似文献