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1.
Levans produced by four Zymomonas mobilis strains showed antitumour activity against sarcoma 180 and Ehrlich carcinoma in Swiss albino mice. Levans from two strains (ZAP and CP4) had the highest effects. NMR analysis showed that the polymers were composed only of fructose units. The results suggested that the antineoplasic effect is associated to the polysaccharide molecular weight and that a particular molecular weight range may be responsible for this effect. 相似文献
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The amount of calliphorin, its biosynthesis, and the levels of translatable calliphorin-mRNA have been determined during the postembryonic development of Calliphora vicina R.-D. The amount of calliphorin increases in early third-instar larvae, reaching maximal levels in 6-day-old animals. It continuously decreases during late larval and pupal development to approximately one-half of the maximal levels and abruptly sinks during eclosion. The biosynthesis of calliphorin takes place only in 3- to 5-day-old larvae. Poly(A)+-RNA has been translated into proteins in a wheat germ cell-free system. Calliphorin-mRNA can be detected in 3- to 7-day-old larvae; maximal concentrations are observed in 4- and 5-day-old animals. No calliphorin-mRNA can be detected in prepupae, pupae, or imagos. The biosynthesis of calliphorin in blowfly larvae stops before a decrease of translatable calliphorin-mRNA is observed. This finding raises the question of the mechanism of in vivo inactivation of this specific mRNA. 相似文献
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Immunofluorescence microscopy has been applied to detect glucocorticoid receptors in rat thymocytes, HeLa cells and human mononuclear cells from peripheral blood. Blast formation induced in human mononuclear cells by PHA results in increased receptor concentration in the cytoplasm, as suggested from the immunofluorescence technique. Incubation of the blast cells with 10−7 M dexamethasone at 37°C within 15 min leads to decrease of staining in the cytoplasm and concomitant increase in the nucleus, indicative of a translocation of the cytoplasmic receptor into the nucleus. 相似文献
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Induction of dopa (3,4-dihydroxyphenylalanine) decarboxylase in blowfly integument by ecdysone. A demonstration of synthesis of the enzyme de novo. 下载免费PDF全文
The activity of the enzyme dopa (3,4-dihydroxyphenylalanine) decarboxylase, present in the epidermis cells of blowfly larvae, increases during the late third instar under the influence of the steroid hormone, ecdysone. By using the double-labelling technique and immune precipitation with univalent antibody to dopa decarboxylase, we demonstrated that the increase in enzyme activity was due to a stimulation of synthesis of enzyme molecules de novo. In this respect, the action of ecdysone is similar to the action of other steroid hormones. 相似文献
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采用随机扩增多态 DNA(RAPD)分析研究了中国3种珍稀濒危兰科植物硬叶兜兰(Paphiopedilum micranthum Tang et Wang)、麻栗坡兜兰(P. malipoense S.C.Chen et Tsi)和独花兰(Changnienia amoena Chien)的遗传多样性与群体遗传结构.12个RAPD引物在2种兜兰中共扩增出131条带.对4个硬叶兜兰群体的检测表明其物种水平的多态条带百分率(PPB)为 71.6%,Nei 的基因多样度(h)为 0.217 1,Shannon多样性指数 (I) 为 0.330 1;4个群体的平均多样性水平为 PPB = 45.2%,h = 0.145 7,I = 0.220 4,低于远交兰花的平均水平.在总遗传变异中,群体间遗传变异占20.31%,略高于远交物种的平均水平.在物种水平上,麻栗坡兜兰的PPB为49.5%,h为0.117 4,I为0.176 4,均大大低于硬叶兜兰.对11个独花兰群体采用16个RAPD引物共扩增出119条带.物种水平PPB=76.5%,h=0.194 1,I=0.305 8;在群体水平上,上述3个指标的平均值则分别为37.2%、0.119 7和0.181 0,均低于远交兰花的平均水平.群体间的遗传变异占45.27%,遗传分化明显高于远交物种的平均水平.导致3个物种遗传多样性偏低而群体间遗传分化较高的主要原因在于人为的过度采挖和生境的片断化.研究结果为兰花保护策略和措施的制定提供了理论基础. 相似文献
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Variation in heat shock proteins within tropical and desert species of poeciliid fishes 总被引:8,自引:0,他引:8
Norris CE; diIorio PJ; Schultz RJ; Hightower LE 《Molecular biology and evolution》1995,12(6):1048-1062
The 70-kilodalton heat shock protein (hsp70) family of molecular
chaperones, which contains both stress-inducible and normally abundant
constitutive members, is highly conserved across distantly related taxa.
Analysis of this protein family in individuals from an outbred population
of tropical topminnows, Poeciliopsis gracilis, showed that while
constitutive hsp70 family members showed no variation in protein isoforms,
inducibly synthesized hsp70 was polymorphic. Several species of
Poeciliopsis adapted to desert environments exhibited lower levels of
inducible hsp70 polymorphism than the tropical species, but constitutive
forms were identical to those in P. gracilis, as they were in the
confamilial species Gambusia affinis. These differences suggest that
inducible and constitutive members of this family are under different
evolutionary constraints and may indicate differences in their function
within the cell. Also, northern desert species of Poeciliopsis synthesize a
subset of the inducible hsp70 isoforms seen in tropical species. This
distribution supports the theory that ancestral tropical fish migrated
northward and colonized desert streams; the subsequent decrease in
variation of inducible hsp70 may have been due to genetic drift or a
consequence of adaptation to the desert environment. Higher levels of
variability were found when the 30- kilodalton heat shock protein (hsp30)
family was analyzed within different strains of two desert species of
Poeciliopsis and also in wild-caught individuals of Gambusia affinis. In
both cases the distribution of hsp30 isoform diversity was similar to that
seen previously with allozyme polymorphisms.
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