Studies on lipid peroxidation in normal and tumour tissues. The Yoshida rat liver tumour.

Reduced rates of lipid peroxidation have been observed in Yoshida hepatoma cells and microsomes when compared with appropriate control tissue (normal rat liver) under the same pro-oxidant conditions. The pro-oxidant conditions used were incubation with NADPH+ADP+iron or ascorbate+iron or exposure to gamma-irradiation. As previously shown with the Novikoff hepatoma, the relative concentrations of alpha-tocopherol and polyunsaturated fatty acids are important in conferring resistance to lipid peroxidation in the Yoshida hepatoma. Furthermore, NADPH-cytochrome c reductase and the NADPH-cytochrome P-450 electron transport chain, which are involved in the initiation and propagation of certain types of lipid peroxidation, are found at very much reduced levels in the Yoshida hepatoma. The relative importance of these aberrations are discussed.     

Structure and dynamics of alpha-tocopherol in model membranes and in solution: a broad-line and high-resolution NMR study

Nuclear magnetic resonance has been applied to study the conformational dynamics of alpha-tocopherol (vitamin E) in solution and in model membranes. In nonviscous solution, 1H nuclear magnetic resonance (NMR) showed that alpha-tocopherol is in rapid equilibrium between two or more puckered conformers of its heterocyclic ring. The most likely conformers to be so involved are the two half-chair forms. Deuterium NMR spectra of specifically deuteriated alpha-tocopherol in multilamellar dispersions of egg phosphatidylcholine, measured in the liquid-crystalline state, were characteristic of axially symmetric motional averaging. The orientation of the rotational axis within the molecular framework was determined. Studies on oriented multilamellar membranes revealed that this axis is perpendicular to the surface of the membrane. The profile of quadrupolar splittings along the hydrophobic tail does not have a plateau, in contrast to that of the fatty acyl chains of the membrane lipids. Longitudinal relaxation times (T1) were short. The presence of a minimum in their temperature dependence shows that molecular motion with an effective correlation time tau eff approximately equal to 3 X 10(-9)s is responsible for relaxation. However, the temperatures and absolute values of the minima depend on the position of the deuterium in the molecule, demonstrating that tau eff represents a complex blend of motions.     

谷氨酸钠兴奋室旁核引起的升压效应及其与蓝斑-升压反应和A_1-降压反应间的关系

将L-谷氨酸钠(Glu)注入乌拉坦麻醉、箭毒化、人工呼吸大鼠的室旁核(NPV)或蓝斑内引起升压反应。蓝斑升压反应可被双侧室旁核内预先注射酚妥拉明或心得安明显衰减;双侧室旁核内预先注射酚妥拉明或荷包牡丹碱还可使Glu兴奋延髓A_1区引起的降压反应减小,但注射心得安对A_1-降压反应无明显影响。以上结果提示蓝斑-升压反应和A_1-降压反应均部分通过NPV实现,A_1降压过程中可能有NPV内GABA能抑制性中间神经元参与。     

顶核—延髓头端腹外侧区系统参与前庭降压降心率反应

实验用乌拉坦麻醉、箭毒化、人工呼吸的大鼠。将神经元胞体兴奋剂L-谷氨酸钠(Glu)微量注入顶核或前庭上核均引起血压下降;心率减慢。该顶核-和前庭上核-降压降心率反应均可被延髓头端腹外侧区内注射GABA受体阻断剂荷包牡丹碱阻断。顶核内注射普鲁卡因也能阻断Glu兴奋前庭上核的心血管反应。以上结果提示前庭-降压降心率反应可能通过顶核-延髓头端腹外侧区系统实现。静脉注射甲基阿托品也能衰减Glu兴奋顶核的心血管反应,显示迷走神经也参与前庭-顶核降压降心率反应。     

Feeding or Resting? The Strategy of Rutting Male Alpine Chamois

Optimal foraging theory suggests that animals normally maximize energy intake to optimize their energy balance. However, when efficiency to assimilate energy falls below the level necessary to ascertain basal energetic requirements, they should shift to an energy saving strategy. Males of many ruminant species considerably reduce their food intake during the rut. Nevertheless, they are commonly assumed to maximize energy intake besides their investments in rutting activities. Based on predictions of optimal foraging theory and the specific ruminant digestive physiology, we propose, however, that rutting males in polygynous species with time consuming mating tactics should instead use an energy saving strategy. Particularly, we predict this to be the case in Alpine chamois (Rupicapra rupicapra rupicapra), a highly polygynous mountain ungulate, of which the males defend mating territories during the rut. By combining observational and telemetry data of eight radio‐collared males we constructed individual 24‐h time budgets, and compared the behavior of males before, during and after the rut. Males spent significantly less time feeding during the rut (0.9 h) compared with before (8.5 h) and afterwards (6.4 and 7.5 h, respectively), whereas time spent lying remained more or less unchanged (pre‐rut; 12.7 h, rut; 13.3 h, post‐rut; 12.9 and 13.9 h, respectively). The ratio of time spent feeding to lying dropped from 0.67 in the pre‐rut period to 0.05 in the rutting period. As a result, males allocated on average approx. 90% of their non‐rutting time to lying, and a negative relationship between rutting and lying time emerged. Hence, males seemed to trade lying time against rutting time. We conclude from these results that male Alpine chamois do not maximize their energy intake during the rut, but rather adopt an energy saving strategy to optimize their energy balance.     

植物FLOWERING LOCUS T/TERMINAL FLOWER1基因家族的研究进展

植物FLOWERING LOCUS T/TERMINAL FLOWER1(FT/TFL1)基因家族是一个进化上高度保守的基因家族,它在植物的花发育过程中具有重要作用:其成员FT基因编码的蛋白产物是可以长距离转运的成花激素,在花形成过程中起关键作用;另一成员TFL1基因则在花序的形成和维持过程中起重要作用.本文就近年来国内外对植物FT/TFL1基因家族的结构、成员,以及各个成员在花发育转换过程中的功能等研究现状进行综述,并对该基因家族的研究前景提出展望.     

High molecular mass glycans are major structural elements associated with the laminated layer of in vitro cultivated Echinococcus multilocularis metacestodes

The laminated layer of the larval stage (metacestode) of the cestode parasite Echinococcus multilocularis is composed largely of carbohydrates, which form a tight microfibrillar meshwork around the entire metacestode. Since this laminated layer is the only parasite structure which is in constant contact with host immune and non-immune cells, and appears largely resistant to physiological and immunological reactions of the host, it most likely carries out important functions with regard to host-parasite interactions. In infected hosts, the metacestode is usually concentrically covered by host connective tissue cells and large amounts of collagen, causing a dense scar-like fibrosis, and it is likely that host-derived components are incorporated into the laminated layer at the host-parasite interface. Therefore, in order to obtain information on the molecular composition of this structure, we used parasite larvae which were generated through in vitro cultivation and thus were largely devoid of interfering host components. Lectin fluorescence on section-labelling of metacestodes embedded in LR-White suggested that the laminated layer is largely composed of N-acetyl-beta-D-galactosaminyl, and alpha- and beta-D-galactosyl residues, as well as of the core structure of O-linked carbohydrate chains, N-acetylgalactosamine-beta-1.3-galactose, while N-linked glycopeptides and alpha-D-mannosyl residues and/or glucosyl residues were found mainly within the germinal layer, and within the cellular mass and the surface of developing protoscoleces. Lectin-gold EM confirmed these findings. The laminated layer was isolated from in vitro cultivated metacestodes by urea extraction, and the ultrastructure of the purified laminated layer was assessed comparatively with respect to the laminated layer of intact parasites. The glycan composition was determined using SDS-PAGE and lectin blotting. This work has laid the basis for a more detailed dissection of the molecular composition of the laminated layer.     

植物Shaker K+通道的研究进展

钾离子通道是植物钾离子吸收的重要途径之一。Shaker K+家族通道是K+通道中最早发现、且研究最深入的K+通道家族。近年来,已从多种植物或同种植物的不同组织器官中分离得到多个Shaker K+钾离子通道基因,如AKT1,AtKC1,QsAKT1,GORK,AKT2等。从结构、表达部位、生理功能和调控等方面介绍了植物Shaker K+通道的研究进展。