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991.
S N Shchelkunov O I Riazankina P B Gashnikov A B Totmenin V E Chizhikov E G Malygin 《Molekuliarnaia biologiia》1991,25(2):396-404
Two genetics markers: the herpes simplex virus thymidine kinase and Escherichia coli beta-galactosidase genes were inserted into the 36K protein gene of vaccinia virus located in a HindIII-P DNA fragment. An unstability of recombinant viruses with Lac(+)-phenotype were discovered. A mechanism of viruses unstable variants formation was proposed, it was confirmed by the results of hybridisation analyses of virus recombinant genomes. The importance of a late nonstructural 36K protein gene for virus reproduction was demonstrated. 相似文献
992.
993.
In vitro exposure of PHA-stimulated human lymphocytes to organotin compounds resulted in statistically significant increases in the frequencies of hyperdiploid cells. When taken together with our previous study demonstrating spindle inhibiting effects of the same organotin compounds by an indirect method (Jensen et al., 1989), the present study strongly indicates that organotin compounds are able to induce aneuploidy, probably by affecting spindle function. 相似文献
994.
E. coli K12802 cells transformed by multicopy plasmid with phoA gene acquire the ability to oversynthesize alkaline phosphatase, secrete it into the cultural medium, and accumulate the precursor of this enzyme. The dynamics of enzyme production and secretion as well as cytomorphological changes revealed the existence of a mechanism of selective enzyme secretion into the medium. It is characterized by a decrease of enzyme specific activity in periplasm and its increase in cultural medium, appearance of numerous local zones of adhesion of cytoplasmic and outer membranes, formation of large extracellular outer membrane vesicles containing PhoA protein on the cell poles, and their release into the medium. We isolated the vesicles and found that they contain PhoA (in dominating quantity), several other periplasmic proteins, and matrix proteins of outer membranes. By their phospholipid and protein composition, they correspond to the fraction of outer membranes which have the largest density and sedimentation rate and, apparently, contain no lipoprotein. 相似文献
995.
We studied clastogenic effects in peripheral lymphocytes of cotton-field workers who were exposed to different pesticides. All the cells were grown in RPMI 1640 medium for 48 and 72 h. The type of aberrations observed in the exposed group are gaps, breaks, dicentrics, exchanges, rings and polyploidy. The frequency of total chromosomal aberrations increased significantly in male pesticide applicators when compared to controls. A significant decrease in mitotic index was observed in the exposed group as compared to the control group. The 48-h cultures showed high incidence of chromosomal aberrations and low mitotic index when compared to 72-h cultures. The difference in chromosomal aberrations between 48- and 72-h cultures was not significant. 24 out of 26 individuals showed ill health effects such as severe giddiness and nervous disorders. 相似文献
996.
We obtained a monoclonal antibody (TDM-1) binding to 313-nm UV-irradiated DNA in the presence of acetophenone. The binding of TDM-1 to 254-nm UV-irradiated DNA was not reduced with the subsequent irradiation of 313-nm UV. Furthermore, the treatment of UV-irradiated DNA with photolyase from E. coli and visible light exposure reduced both the antibody binding and the amount of thymine dimers in the DNA. A competitive inhibition assay revealed that the binding of TDM-1 to UV-irradiated DNA was inhibited with photolyase, but not with 64M-1 antibody specific for (6-4)photoproducts. These results suggest that TDM-1 antibody recognizes cyclobutane-type thymine dimers in DNA. Using TDM-1 and 64M-1 antibodies, we differentially measured each type of damage in DNA extracted from UV-irradiated mammalian cells. Repair experiments confirm that thymine dimers are excised from UV-irradiated cellular DNA more slowly than (6-4)photoproducts, and that the excision rates of thymine dimers and (6-4)photoproducts are lower in mouse NIH3T3 cells than in human cells. 相似文献
997.
Summary
Pseudocyphellaria dissimilis, a foliose, cyanobacterial lichen, is shown not to fit into the normal ecological concept of lichens. This species is both extremely shade-tolerant and also more intolerant to drying than aquatic lichens previously thought to be the most desiccation-sensitive of lichens. Samples of P. dissimilis from a humid rain-forest site in New Zealand were transported in a moist state to Germany. Photosynthesis response curves were generated. The effect of desiccation was measured by comparing CO2 exchange before and after a standard 20-h drying routine. Lichen thalli could be equilibrated at 15° C to relative humidities (RH) from 5% to almost 100%. Photosynthesis was saturated at a photosynthetically active radiation (PAR) level of 20 mol m-2 s-1 (350 bar CO2) and PAR compensation was a very low 1 mol m-2 s-1. Photosynthesis did not saturate until 1500 bar CO2. Net photosynthesis was relatively unaffected by temperature between 10° C and 30° C with upper compensation at over 40° C. Temporary depression of photosynthesis occurred after a drying period of 20 h with equilibration at 45–65% relative humidity (RH). Sustained damage occurred at 15–25% RH and many samples died after equilibration at 5–16% RH. Microclimate studies of the lichen habitat below the evergreen, broadleaf forest canopy revealed consistently low PAR (normally below 10–20 mol m-2 s-1) and high humidities (over 80% RH even during the day time). The species shows many features of an extremely deep shade-adapted plant including low PAR saturation and compensation, low photosynthetic and respiratory rates and low dry weight per unit area. 相似文献
998.
From siliceous shales (Lower Carboniferous, Rheinisches Schiefergebirge), in direct neighborhood to a bed of allodapic limestone, the following fluontized radiolarian fauna has been extracted by chemical transformation of originally calcified skeletons:Albaillella cartalla, Latentifistula turgida, Eostylodktya cf. eccentrica, Tetragregnon sycamorensis sycamorensis, Belowea variabilis, Callela? hexactinia, Entactinia tortispina and Entactinia variospina. The limestone bed has been dated by calcareous foraminifera as being mid Visean in age (V 2b-3a, Cf 5-foraminiferal zone). The diagenetic calcification took place after the selective dissolution of the skeletons and was in itself not selective. 相似文献
999.
Quinovic acid glycosides from Uncaria guianensis. 总被引:1,自引:0,他引:1
A M Yépez O L de Ugaz C M Alvarez V De Feo R Aquino F De Simone C Pizza 《Phytochemistry》1991,30(5):1635-1637
From the bark of Uncaria guianensis, two new quinovic acid glycosides, quinovic acid 3 beta-O-beta-D-quinovopyranoside and quinovic acid 3 beta-O-beta-D-fucopyranosyl-(27----1)-beta-D-glucopyranosylester, have been isolated, in addition to known quinovic acid 3 beta-O-[beta-D-glucopyranosyl-(1----3)-beta-D-fucopyranosyl]-(27----1)- beta-D-glucopyranosylester and quinovic acid 3 beta-O-beta-D-fucopyranoside. Their structures were elucidated by spectral and chemical studies. 相似文献
1000.
Amine Accumulation in Acidic Vacuoles Protects the Halotolerant Alga Dunaliella salina Against Alkaline Stress 总被引:3,自引:3,他引:0 下载免费PDF全文
Amines at alkaline pH induce in cells of the halotolerant alga Dunaliella a transient stress that is manifested by a drop in ATP and an increase of cytoplasmic pH. As much as 300 millimolar NH4+ are taken up by the cells at pH 9. The uptake is not associated with gross changes in volume and is accompanied by K+ efflux. Most of the amine is not metabolized, and can be released by external acidification. Recovery of the cells from the amine-induced stress occurs within 30 to 60 minutes and is accompanied by massive swelling of vacuoles and by release of the fluorescent dye atebrin from these vacuoles, suggesting that amines are compartmentalized into acidic vacuoles. The time course of ammonia uptake into Dunaliella cells is biphasic—a rapid influx, associated with cytoplasmic alkalinization, followed by a temperature-dependent slow uptake phase, which is correlated with recovery of cellular ATP and cytoplasmic pH. The dependence of amine uptake on external pH indicates that it diffuses into the cells in the free amine form. Studies with lysed cell preparations, in which vacuoles become exposed but retain their capacity to accumulate amines, indicate that the permeability of the vacuolar membrane to amines is much higher than that of the plasma membrane. The results can be retionalized by assuming that the initial amine accumulation, which leads to rapid vacuolar alkalinization, activates metabolic reactions that further increase the capacity of the vacuoles to sequester most of the amine from the cytoplasm. The results indicate that acidic vacuoles in Dunaliella serve as a high-capacity buffering system for amines, and as a safeguard against cytoplasmic alkalinization and uncoupling of photosynthesis. 相似文献