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71.
Three experiments are reported as a contribution to the validation of the multiple treatment protocol presently under discussion. (1) In the single treatment experiment with hydroquinone (HQ) the time of maximum micronucleus response was determined to be 24 h with a dose of 75 mg/kg given intraperitoneally. In the subsequent dose-response study at the 24-h interval the lowest positive dose was 50 mg/kg of HQ (P less than 0.01). The increase in micronucleus frequencies was non-linear. (2) Daily treatments with 15 or 75 mg/kg of HQ and bone marrow sampling on days 2-4 after the start of treatment resulted in an increased micronucleus yield for the lower dose (P less than 0.05) and a decrease in micronucleus frequencies at the higher dose (P less than 0.01) with increasing numbers of treatments. At the same time no change in the composition of the erythrocyte population was observed. (3) With 25 mg/kg of cyclophosphamide (CP) the micronucleus yields increased from 1 to 3 daily doses but dropped significantly from 3 to 4 daily doses (P less than 0.01). The polychromatic to normochromatic erythrocyte ratio was significantly decreased after single (P less than 0.01) and marginally lower than the control value after 4 daily treatments with CP. The present data suggest that the response of the bone marrow micronucleus assay to multiple treatments may depend on the dose employed and may differ from chemical to chemical. The specific clastogenic action or other cellular effects of a chemical may influence the micronucleus yields of an individual chemical and it may be difficult to generate a strict protocol recommendation. 相似文献
72.
中国特产雉类—褐马鸡,藏马鸡和蓝马鸡卵壳的电镜观察 总被引:16,自引:4,他引:12
迄今为止,在国内有关野生鸟类卵壳的超微结构报道尚少。我们对中国特产鸡类——三种马鸡卵壳的表皮、气孔、木栅层、锥体层、乳头结、壳膜和基帽进行了扫描巨镜观察,并对结果进行了比较、讨论。认为三种马鸡不同结构的形态,对研究它们的亲缘关系提供了新的价值。 相似文献
73.
Sequence-specific nuclear magnetic resonances assignments have been obtained for the protons of kistrin. Kistrin is a small naturally occurring snake venom protein that inhibits platelet aggregation by blocking the interaction of fibrinogen with the membrane-bound glycoprotein IIb-IIIa (GP IIb-IIIa), a receptor from the integrin family. Kistrin has an Arg-Gly-Asp sequence which is believed to form an adhesion recognition sequence that is essential for activity. Therefore, the interaction between kistrin and GP IIb-IIIa may provide important information on the motif used by integrins to recognize their target proteins which bear RGD sequences. Kistrin consists of 68 residues and contains six intramolecular disulfide bonds. Although one-third of the amide protons are protected from exchange with the solvent, there appears to be little or no regular secondary structure. The large number of NOE's between residues separated by two and three positions in the sequence indicates that the protein contains a large number of tightly packed loops. Along with the sequential assignments, this paper also discusses the construction and use of computerized data bases for manipulating NMR results. A strategy for computer-assisted sequential resonance using these data bases is also presented. 相似文献
74.
Robert Dudley Gregory H. Adler 《Biological journal of the Linnean Society. Linnean Society of London》1996,57(4):317-326
Distributions of danaine butterfly species and associated mimetic patterns were compared among fifteen archipelagos of the tropical Pacific Ocean, and within five major archipelagos (the Bismarcks, Fiji, East and West Solomon Islands, and Vanuatu). Using both simple and stepwise linear regression analysis, variation in the total number of danaine species and number of mimetic patterns was assessed with respect to island size, isolation and elevation. Relative to interarchipelago distributions, the distribution of danaine species and number of mimetic patterns on islands within archipelagos exhibited less dependence upon interisland distance and island area. Geographical features influencing the number of mimetic patterns were similar to those of danaines as a whole. Analysis of residuals from stepwise linear regression suggested that factors influencing danaine distributions were different from those for non-danaine butterflies. This result is consistent with the hypothesis of enhancement of danaine species establishment through Müllerian mimicry, although other factors such as host plant availability and similar habitat use may also be important. 相似文献
75.
福尔马林致痛提高大鼠中枢μ阿片受体密度及电针的加强作用 总被引:7,自引:0,他引:7
用放射自显影方法观察到;(1)大鼠脚掌注射福尔马林后,某些与镇痛有关的脑区如尾核头部、伏隔核、杏仁核、中央灰质、脚间核、中缝大核、脊髓背角等结构中μ阿片受体密度明显增加(P<0.05,P<0.01);(2)给予电针抑制痛反应的大鼠,在其大部分上述结构及扣带回、隔区、视前内侧区、内膝体、上丘、中缝背核及中央上核受体密度明显增加;与福尔马林注射组相比,脚间核、中央灰质尾端腹外侧区、腰膨大背角的受体密度进一步增加。从而在受体水平支持伤害性刺激可以激活体内内阿片肽能活动,而电针可以加强这一活动的设想。 相似文献
76.
The ability of a chimeric HP1-Polycomb (Pc) protein to bind both to heterochromatin and to euchromatic sites of Pc protein binding was exploited to detect stable protein-protein interactions in vivo. Previously, we showed that endogenous Pc protein was recruited to ectopic heterochromatic binding sites by the chimeric protein. Here, we examine the association of other Pc group (Pc-G) proteins. We show that Posterior sex combs (Psc) protein also is recruited to heterochromatin by the chimeric protein, demonstrating that Psc protein participates in direct protein-protein interaction with Pc protein or Pc-associated protein. In flies carrying temperature-sensitive alleles of Enhancer of zeste[E(z)] the general decondensation of polytene chromosomes that occurs at the restrictive temperature is associated with loss of binding of endogenous Pc and chimeric HP1-Polycomb protein to euchromatin, but binding of HP1 and chimeric HP1-Polycomb protein to the heterochromatin is maintained. The E(z) mutation also results in the loss of chimera-dependent binding to heterochromatin by endogenous Pc and Psc proteins at the restrictive temperature, suggesting that interaction of these proteins is mediated by E(z) protein. A myc-tagged full-length Suppressor 2 of zeste [Su(z)2] protein interacts poorly or not at all with ectopic Pc-G complexes, but a truncated Su(z)2 protein is strongly recruited to all sites of chimeric protein binding. Trithorax protein is not recruited to the heterochromatin by the chimeric HP1-Polycomb protein, suggesting either that this protein does not interact directly with Pc-G complexes or that such interactions are regulated. Ectopic binding of chimeric chromosomal proteins provides a useful tool for distinguishing specific protein-protein interactions from specific protein-DNA interactions important for complex assembly in vivo. 相似文献
77.
78.
游离氨基酸组分分析表明,水稻培养细胞中谷氨酸和丙氨酸含量很高,占氨基酸总量的40%。高脯氨酸愈伤组织变异体总游离氨基酸含量比原型高45.5%,其中脯氨酸增加最多,其次是雨氨酸和谷氨酸。当NaCl100mmol/L处理时变异体和原型的总氨基酸都增加,而变异体的增量约为原型增量的3倍。蛋白水解氨基酸组分中变异体和原型各氨基酸的相对含量无大差异。蛋白质双向电泳表明,高脯氨酸变异体的蛋白组分发生变化,明显比原型多4个蛋白点。在NaCl100mmol/L处理下原型亦产生53.3kD蛋白,变异体中该蛋白的含量变得更多。盐胁迫下变异体和原型的蛋白质组分变化的差异十分显著,主要表现在蛋白质等电点的变化不同。 相似文献
79.
中国大痣小蜂属食植群记述(膜翅目:长尾小蜂科) 总被引:7,自引:1,他引:6
本文报导中国大痣小蜂属Megastigmus食植群Phytophagous group 12种,其中包括5新种:黄杉大痣小蜂Megastigmus pseudotsugaphilus sp.nov.(寄生华东黄杉Pseudotsugagassenii),拟海棠大痣小蜂Megastigmus pseudomali sp.n.(寄主不明),基室大痣小蜂Megastigmus cellus sp.nov 相似文献
80.
Na2SO3对热-DTT活化的游离CF1及类囊体膜上CF1-ATPase活力均有显著的促进作用,NaHCO3亦有明显的促进作用。Na2SO3和NaHCO3的促进作用与它们解除Mg2+的抑制作用有关。从NaHCO3和Na2SO3及它们与Mg2+之间的竞争性关系,表明三者是结合在酶的同一部位上。Na2SO3可明显降低热-DTT活化的游禹CF1-ATPase催化反应的活化能,这可能与促进产物ADP的释放有关。 相似文献