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991.
T G Rossman M Molina L Meyer P Boone C B Klein Z Wang F Li W C Lin P L Kinney 《Mutation research》1991,260(4):349-367
The Microscreen assay was developed as a means of testing very small samples, as in complex mixture fractionation. It is a multi-endpoint assay which utilizes E. coli WP2s(lambda). Exposure takes place to serial dilutions of the test compound in microtitre wells (250 microliters) followed by sampling from wells in which growth has occurred ('non-toxic wells'). Although a number of different endpoints can be measured, only the prophage induction endpoint (the first one developed) has been extensively tested. Results with 133 compounds are presented. These include 111 compounds which have been tested in the S. typhimurium assay and 66 compounds for which both rodent bioassay and S. typhimurium assay data exists. The concordance for the Microscreen assay and the S. typhimurium assay was 71%. For this group of compounds, the sensitivity of the Microscreen assay in detecting carcinogens was 76% compared with 58% for the S. typhimurium assay. However, the S. typhimurium assay was somewhat more specific (69%) compared with the Microscreen (56%). The overall association between carcinogenicity and Microscreen results was statistically significant (p = 0.029), whereas for the S. typhimurium assay the association with carcinogenicity was non-significant (p = 0.086). The Microscreen assay was able to detect halogenated compounds better than the S. typhimurium assay. The Microscreen assay should prove useful in complex mixture fractionation, or in other situations where sample size is limiting. 相似文献
992.
M De Ferrari M Artuso S Bonassi S Bonatti Z Cavalieri D Pescatore E Marchini V Pisano A Abbondandolo 《Mutation research》1991,260(1):105-113
Chromosome aberrations (CA) and sister-chromatid exchanges (SCE) were measured in lymphocytes of (A) 32 healthy individuals working in the flower industry and exposed to pesticides, (B) 32 individuals exposed as above and hospitalized for bladder cancer, and (C) 31 controls. Compounds to which floriculturists were exposed included 18 nitro-organic herbicides and fungicides, 9 nitro-organic fungicides, 12 organophosphate and organothiophosphate insecticides, 4 hydrocarbon derivative herbicides and 5 inorganic fungicides and insecticides. 150 and 70 metaphases per individual were scored for CA and SCE, respectively. A significant increase in the incidence of CA and SCE was observed in both exposed groups. Cancer patients showed the presence of rare rearrangements (dicentrics, rings and quadriradials) that were not observed in controls and were present at a lower frequency in healthy exposed people. Hyperdiploid and polyploid metaphases were also significantly increased in the 2 exposed groups compared to controls. Stratifying for age or smoking habits, although affecting the significance of individual data, did not change the substance of the results. 相似文献
993.
Arndt Brüning 《Oecologia》1991,86(4):478-483
Summary The predation on spiders in a forest ecosystem by a colony of red wood ants, Formica polyctena, was estimated using a barrier to isolate the colony. Of the ants' total prey, 4.6% were spiders. In order to estimate the effect of F. polyctena within their hunting area on the spider population, the spiders' population density was studied inside and outside the hunting area. Samples of the forest floor were taken, spider webs were counted and pitfall traps were used. No significant difference was found in density or composition of the spider fauna inside and outside the hunting area. 相似文献
994.
An endemic brackish water faunule consisting of three taxa of bivalves,Hudsonella sinensis (Chen) n. gen.,Hudsonella sp., andProtocardia hepingxiangensis Chen & Lin occurs in the Bajocian of the southern Qinghai province, China.Hudsonella sinensis is a very variable species with a hinge structure characteristic of the subfamily Pachydontinae of the family Corbulidae. According to both geochemical data (stable carbon isotopes and the strontium/barium ratio) and ecological data the faunule lived in a brackish water embayment of mesohaline salinity (5#x2013;18 per mil) burrowing in soft substrate. 相似文献
995.
Proton and sucrose transport in isolated tonoplast vesicles from sugarcane stalk tissue 总被引:1,自引:0,他引:1
Tonoplast vesicles prepared from immature sugarcane ( Saccharum spp., hybrid cv. H65–7052) tissue and purified on a discontinuous dextran gradient take up sucrose. Uptake was stimulated by MgATP. Evidence that the mechanism is linked to proton transport is derived from "pH jump'data and from inhibition of ATP-stimulated sucrose transport by the protonophore carbonyl cyanide m -chlorophenylhydrazone (CCCP) and by the proton-channel blocker of proton-linked ATPases. N. N '-dicyclo-hexylcarbodiimide (DCCD). A saturable phase of sucrose uptake was found at low substrate concentrations, and a linear phase characterized uptake at higher concentrations. Uptake was specific for sucrose, as demonstrated by competition experiments with various sugars. Sucrose uptake by the vesicle fraction was inhibited by KNO3 , protonophores and protein modifying reagents, whereas sodium orthovanadate had no effect. Overall, the evidence suggests an ATP-hydrolysis-dependent tonoplasl antiport for sucrose transport, although a more direct influence of ATP on conformational changes in relevant tonoplast proteins cannot be ruled out. 相似文献
996.
Heat Shock Proteins in Two Lines of Zea mays L. That Differ in Drought and Heat Resistance 总被引:2,自引:0,他引:2 下载免费PDF全文
Synthesis of heat shock proteins (HSPs) in the leaves of a drought- and heat-resistant (line ZPBL 1304), and a drought- and heat-sensitive (line ZPL 389) line of maize (Zea mays L.) was studied under two environmental stress treatments: (a) soil drying and high temperature and (b) high temperature. In the first treatment 13-day-old plants were exposed to 7-day soil drying followed by high temperature stress (45°C), and in the second treatment 20-day-old plants were exposed to high temperature stress (45°C). Second leaves were labeled with [35S]methionine. During the labeling period line ZPBL 1304 showed no signs of leaf dehydration under soil drying and high temperature stress conditions. In contrast, line ZPL 389 was dehydrated 23%, as determined by relative water content. Incorporation of [35S]methionine into protein was greater in the resistant than in the sensitive line in both treatments. The pattern of synthesis of HSPs in the two lines was similar in treatments 1 and 2. Both lines synthesized a high molecular mass set and a low molecular mass set of HSPs. Proteins from both sets from both lines of maize appeared similar to each other, with respect to the molecular mass. Heated plants of the drought- and heat-resistant line ZPBL 1304 synthesized a band of HSP(s) of approximately 45 kilodaltons which was not found in heated plants of the drought and heat sensitive line ZPL 389. This is the first report on qualitative intraspecific difference in the synthesis of HSPs in maize. 相似文献
997.
An experiment to study the effects of Mg nutrition on root and shoot development of the Al-sensitive sorghum (Sorghum bicolor (L.) Moench) genotype CV323 grown in pots of sandy loam under different acid soil stress is reported. This experiment had
a factorial design: four rates of liming were combined with four rates of Mg fertilization. When no Mg was added, the pH of
the soil solutions (collected in ceramic cups) increased from 4.0 (unlimed) to 4.2, 4.7 and 5.9 at the increasing rates of
liming. After 30 days of growth dry matter yields of the limed treatments were 40%, 115% and 199% higher than that of the
unlimed treatment. Without liming and at the highest liming rate, adding Mg did not affect plant biomass significantly. At
the two intermediate levels of liming, however, 11.3 mg extra Mg per kg soil increased dry matter yield to the same levels
as found at the highest liming rate. Concentrations of Mg in the soil solution rose after Mg was added and fell when lime
was added, but adding both Mg and lime increased Mg concentrations in the plant shoots. In plants of the limed treatments,
dry matter yield was correlated closely with the Mg concentration in the shoot. This was not so in the unlimed treatment.
Furthermore, in the unlimed treatments root development was inhibited, but reduced Mg uptake by the plants resulted mainly
from the direct effect of Al- (or H-) ions in the soil solution rather than from impaired root development. It is concluded
that Mg fertilization counteracted the interfering effects of Al- and H ions on Mg uptake. 相似文献
998.
999.
1000.
The effects of the local anesthetic dibucaine on coupling between electron transport and ATP synthesis-hydrolysis by the coupling-factor complex (CF0CF1 ATPase) were investigated in thylakoid membranes from Spinacia oleracea L. cv. Monatol. Evidence is presented that inhibition of ATP synthesis was produced by a specific uncoupling mechanism which was based on dibucaine-membrane surface interactions rather than on the interaction of dibucaine with the ATPase complex. Dibucaine reduced the osmotic space of thylakoid vesicles. At low pH of the medium it stimulated ATP hydrolysis beyond the rates obtained with optimum concentrations of ‘classical’ uncouplers. After addition of dibucaine, there was displacement of membrane-bound Mg2+ and strong thylakoid stacking in the presence of only low Mg2+ concentrations. Inhibition of ATP synthesis and transmembrane pH gradient increased with medium pH. Hydrolysis of ATP by isolated CF1 and the CF0CF1 complex was only slightly affected by dibucaine. The data are discussed assuming the involvement of localized proton channels on the membrane surface in protonic coupling of electron transport and ATP synthesis. A hypothesis for the mechanisms of action of local anesthetics at the thylakoid membrane is presented. 相似文献