Effect of alkylresorcin on biological membranes during activation of lipid peroxidation

The effect of alkyl resorcin isolated from the cells of Azotobacter chroococcum and of its structural analog devoid of the alkyl chain (resorcin) on liver microsomes and brain synaptosomes of the rat as well as on rabbit skeletal muscle sarcoplasmic reticulum fragments during activation of lipid peroxidation was studied. Alkyl resorcin was shown to produce a much more potent antioxidant effect as compared with resorcin, since it inhibited lipid peroxidation in all the three types of membranes under study at much lower concentrations. Both alkyl resorcin and resorcin which inhibit lipid peroxidation prevented lipid peroxidation-induced structural-functional damages of synaptosomal and sarcoplasmic reticulum fragment membranes. Unlike resorcin, alkyl resorcin exerted an additional effect on brain synaptosomal membranes which consisted in the stabilization of barrier functions of membranes during incomplete inhibition of lipid peroxidation. The cumulative data suggest that stabilization necessitates the presence of both resorcin radical and alkyl chain in the alkyl resorcin molecule.     

Nonhyperbolic kinetics of Na,K-ATPase--a new viewpoint]

The kinetics of the 130 kDa monomer obtained by treatment of duck salt gland Na,K-ATPase with C12E8 was compared with that of the membrane-bound enzyme. The shapes of the substrate-velocity curves for the membrane-bound and solubilized forms were quite different: a hyperbolic one for the monomeric Na,K-ATPase and a nonhyperbolic one for the native enzyme. A reaction scheme for ATP hydrolysis based on a comparative analysis of kinetic properties of these two forms is proposed. Experimental evidence in favour of this hypothesis is presented.     

Effect of anti-mosquito antibodies on the infectivity of the rodent malaria parasite Plasmodium berghei to Anopheles farauti

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.     

Antioxidative properties of histidine-containing dipeptides from skeletal muscles of vertebrates

1. Ascorbate-dependent peroxidation of lipid components of biological membranes is inhibited by the natural histidine-containing dipeptides, carnosine and anserine, used at physiological concentrations. 2. Carnosine and anserine exhibit an equal antioxidative activity, whereas the preventing effect of homocarnosine is manifested only at low concentrations of oxidized lipid material. 3. The inhibiting effect of the dipeptides is enhanced either by the rise in the dipeptide concentration or by the decrease in the level of membrane components. 4. Addition of the dipeptides results in a marked decrease in the level of primary molecular products of lipid peroxidation. 5. In this case the optical spectrum of primary molecular products of polyunsaturated fatty acids changes significantly.     

Molecular biology of wound-inducible proteinase inhibitors in plants

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.     

How the activity of membrane enzymes is regulated

The pattern of dependence of catalytic function for a number of key membrane bound enzymes on the state and properties of their lipid environment is analysed in the review presented. Using hexokinase, cytochrome c-oxidase, transport ATPases and other membrane bound oligomeric systems it has been shown that phospholipid bilayer regulates the interaction of protein components of these ensembles in the bilayer. This feature of membrane structures regulates the substrate accessibility and affinity to the corresponding active centres, the formation and a life-time of the oligomeric associates (that is especially important for membrane channels), their stability and so on. As the microviscosity of membrane bilayer is strongly modified not only in the course of pathologic but also in the process of adaptive alterations as well as depending on the day time, season and as a result of action of biologically active substance on membrane, the regulation of the functional activity of membrane proteins by this factor is an effective mode for metabolic control.     

Endogenous ouabain-like substances in animal tissues

Methods of purification and properties of the digitalis-like substances from different animal-origin sources are considered. Possible mechanisms of the cardiac glycoside-effect on the cardiac muscle and endogenous digitalis-like factors' effect on the smooth muscles of the blood vessels are discussed. Criteria that may be used to characterize the digitalis-like activity in samples and extracts obtained from different tissues are presented. The role of these substances in some types of pathologies, especially in the development of hypertension, is considered.     

吗啡耐受大鼠心房心钠素的释放及其基因转录

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。     

Production of DON-related trichothecenes byFusarium graminearum Schw from Krasnodarski krai of the USSR

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.     

兔核移植胚胎起始发育的超微结构研究

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