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排序方式: 共有1727条查询结果,搜索用时 15 毫秒
1.
A model for determination of the admixture concentration in the secondary mother solution was developed. The concentration was determined depending on the solvent volume used for repulping the precipitate and on the impurity level of the initial antibiotic paste. When the values of X1 and X2 are known it is possible to estimate the amount of the admixtures remaining in the paste layer after separation of the secondary mother solution with regard to the volume of the latter in the precipitate pores. Optimization of paste repulping should be considered in combination with displacement washing and the apparatus used for separation of the phases, as well as the requirements for the purity level of the finished product. 相似文献
2.
Effect of anti-mosquito antibodies on the infectivity of the rodent malaria parasite Plasmodium berghei to Anopheles farauti 总被引:3,自引:0,他引:3
The effect of mouse anti-mosquito antibodies, present in the bloodmeal, on the infectivity of Plasmodium berghei Vincke to Anopheles farauti Laveran was investigated. Significantly fewer oocysts developed in mosquitoes feeding on mice immunized with sugar-fed mosquito midgut antigens than in mosquitoes feeding on control mice. Mosquitoes feeding on mice immunized with the midgut antigens derived from sugar-fed mosquitoes also showed reduced mortality and had lower infection rates than those fed on unimmunized mice. Blood-fed midgut antigen was less effective in producing these effects than sugar-fed midgut antigen. 相似文献
3.
Abstract. The techniques of molecular biology are being employed to investigate at the gene level the systemically mediated, wound-induced accumulation of two defensive proteinase inhibitor proteins in plant leaves. These techniques have added a new dimension to biochemical and physiological studies already underway to understand the mechanism of induction by wounding. The acquisition of cDNAs from the RNAs coding for the two inhibitors facilitated studies of mRNA synthesis in leaves in response to wounding, and provided probes to obtain wound-inducible proteinase inhibitor genes from tomato ( Lycopersicon esculentum ) and potato (Solarium tuberosum) genomes. Successful transformations of tobacco plants with fused genes, containing the 5' and 3' regions of the inhibitor genes with the open reading frame of the chloramphenicol acelyltransferase ( cat ) gene, have provided a wound-inducible chloramphenicol acetyltransferase (CATase) activity with which to seek cis- and transacting elements that regulate wound-inducibility to help to understand the interaction of cytoplasmic and nuclear components of the intracellular communication systems that activate the proteinase inhibitor genes in response to wounding by insect pests. 相似文献
4.
G L Piatigorskaia O Iu Zhilkova L M Murav'eva L F Sukhodub 《Molekuliarnaia biologiia》1986,20(2):423-429
DNA interaction with an alkylating antitumor drug N,N',N"-triethylenethiophosphoramide (thiotepa) in water-salt solutions at 37 degrees C has been studied by UV-spectroscopy, heat denaturation and electron microscopy methods. Changes of the DNA melting curve parameters provide information on the kinetics of alkylation. The dependence of the alkylation rate on DNA and thiotepa concentrations shows that the alkylation reaction is biomolecular. The increase of sodium chloride concentration from 10(-3) to 10(-1) M is accompanied by a drastic decrease of the alkylation rate. Thiotepa binding results in destabilization of the DNA secondary structure and formation of cross-links. An increased amount of bounded thiotepa results in DNA denaturation; prolonged alkylation causes breaks in the sugar-phosphate backbone. The results of the work are discussed in connection with the literature data on DNA interaction with thiotepa in vivo. 相似文献
5.
本工作应用心钠素放射免疫测定和分子杂交技术首次发现,吗啡耐受大鼠血浆心钠素水平显著降低,心房内心钠素含量明显升高,同时心房内心钠素特异性mRNA水平也相应提高,提示在吗啡耐受时大鼠心房内心钠素的合成和贮存增加,释放减少。 相似文献
6.
34Fusarium graminearum Schw isolates produced 4-deoxynivalenol to form significant amounts of 4, 7 — dideoxynivalenol and lesser amounts of 4 — deoxynivalenol monoacetates on grain substratesin vitro. This is the first report on the capability a large group of naturally occurring isolates to produce 4,7-dideoxynivalenol. The average levels of 4,7-dideoxynivalenol on rice, corn, barley, and wheat as a substrate were respectively 26.8, 14.0, 12.8, and 10.5% of the level of 4-deoxynivalenol. 4, 7 — dideoxynivalenol was present in all examined naturally contaminated wheat kernel samples at levels of 1.7 to 7.9% of the level of 4-deoxynivalenol. These findings suggest that more attention should be given to the occurrence of 4,7-dideoxynivalenol in cereals. 相似文献
7.
对兔核移植胚胎起始发育的超微结构变化进行电镜观察,并与供体桑椹胚细胞,受体卵母细胞及同期正常受精胚胎的超微结构进行比较,“原核”期兔核移植胚胎的超微结构明显不同于供体桑椹胚细胞及受体卵母细胞的超微结构,而与同期正常受精胚胎相似,但有些核移植胚胎中皮质反应,及核仁和线粒体中出电子致密的网眼结构,与正常受精卵存在差别,分裂至2-细胞期时,与正常2-细胞胚超微结构更相似,结果提示,兔胚胎细胞核移植后,供 相似文献
8.
蛋白分泌作为细胞之间传递信号的途径之一,在微生物生存竞争中也扮演着重要的角色。革兰氏阴性菌可以通过Ⅵ型分泌系统(type Ⅵ secretion system, T6SS)将效应蛋白传递至胞外或原核和真核微生物中,从而介导微生物间的竞争或宿主-细菌的相互作用,最终建立竞争优势。本文主要总结了T6SS的结构与组成,并重点对效应蛋白的装配以及其与免疫蛋白的作用机制的研究进展进行阐述,为以后靶向T6SS抗菌药物的研制提供新思路。 相似文献
9.
M N Zhadin B V Bakharev L I Murav'eva 《Zhurnal vysshe? nervno? deiatelnosti imeni I P Pavlova》1977,27(6):1173-1178
The average correlation coefficient between the EEG of different parts of the cortex gradually decreases as the rabbit is habituated to the experimental surroundings. Elaboration of an electo-defensive conditioned reflex leads to its enhancement which is replaced by a phase of temporary decrease, to be followed again by an enhancement of EEG correlation. The pronouncedness of theta-frequencies in the spectral and coherent functions behaves in a similar way. Successive changes of delta-activity level reveal no regularity. 相似文献
10.