胸内正压对正常人左室功能影响及其力学原理

目的：探讨胸内正压对正常人左室射血及充盈的影响及其力学原理。方法：超声心动图观测30例正常人初始时与标准乏氏动作张力期10s时左室舒张末容积（LVEDV）、左室收缩末容积（LVESV）、每搏量（SV）、射血分值（EF）、流入道血流速度（E峰、A峰）、E／A值、二尖瓣环舒张早期运动速度（e）及舒张早期充盈压（E/e）的变化。结果：与初始时比较,标准乏氏动作张力期LVEDV、LVESV及SV减低而心率（陬）增快（P均〈0．001）,EF值增加,但无统计学意义（P〉0．05）;E峰与E／A值减低（P均〈O．05）;e没有变化（P〉0．05）．E／e值减低（P〈O．05）。结论：胸内正压对左室游离壁的力学作用促进了左室收缩运动而阻碍了左室舒张运动,会引起EF值增加,E峰及E／A值减低;2,胸内正压降低了肺静脉系统与心脏的跨壁压力,增加了血流阻力也是导致肺静脉系统与左室血液回流减少．E峰减低．E／e值减低的一个原因。     

Host reproductive phenology drives seasonal patterns of host use in mosquitoes

Seasonal shifts in host use by mosquitoes from birds to mammals drive the timing and intensity of annual epidemics of mosquito-borne viruses, such as West Nile virus, in North America. The biological mechanism underlying these shifts has been a matter of debate, with hypotheses falling into two camps: (1) the shift is driven by changes in host abundance, or (2) the shift is driven by seasonal changes in the foraging behavior of mosquitoes. Here we explored the idea that seasonal changes in host use by mosquitoes are driven by temporal patterns of host reproduction. We investigated the relationship between seasonal patterns of host use by mosquitoes and host reproductive phenology by examining a seven-year dataset of blood meal identifications from a site in Tuskegee National Forest, Alabama USA and data on reproduction from the most commonly utilized endothermic (white-tailed deer, great blue heron, yellow-crowned night heron) and ectothermic (frogs) hosts. Our analysis revealed that feeding on each host peaked during periods of reproductive activity. Specifically, mosquitoes utilized herons in the spring and early summer, during periods of peak nest occupancy, whereas deer were fed upon most during the late summer and fall, the period corresponding to the peak in births for deer. For frogs, however, feeding on early- and late-season breeders paralleled peaks in male vocalization. We demonstrate for the first time that seasonal patterns of host use by mosquitoes track the reproductive phenology of the hosts. Peaks in relative mosquito feeding on each host during reproductive phases are likely the result of increased tolerance and decreased vigilance to attacking mosquitoes by nestlings and brooding adults (avian hosts), quiescent young (avian and mammalian hosts), and mate-seeking males (frogs).     

Energy Crop and Biotechnology for Biofuel Production

Selection of energy crops is the first priority for large-scale biofuel production in China. As a major topic, it was extensively discussed in the Second International Symposium on Bioen-     

COMPARISONS OF OBSERVED PHYLOGENETIC TOPOLOGIES WITH NULL EXPECTATIONS AMONG THREE MONOPHYLETIC LINEAGES

Three null models have been proposed to predict the relative frequencies of topologies of phylogenetic trees. One null model assumes each distinguishable n-member tree is equally likely (proportional-to-distinguishable-arrangements model). A second model assumes that each topological type is equally likely (equiprobable model). A third model assumes that the probability of each topological type is determined by random speciation (Markov model). We sampled published phylogenetic trees from three major groups of organisms: division Angiospermae, class Insecta, and superclass Tetrapoda. Our sampling was more restricted than previous studies and was designed to test whether observed topological frequencies were distinguishable from those predicted by the three null models. The pattern of evolution reflected in five-member phylogenetic trees is different from predictions of the equiprobable and Markov model but is indistinguishable from the proportional-to-distinguishable-arrangements model. This indicates that 1) speciation (and/or extinction) is not equally likely among all taxa, even for small phylogenies; or 2) systematists' attempts at reconstructing small phylogenies are, on average, indistinguishable from those expected if they had merely selected a tree at random from the pool of all possible trees. The topology frequencies were not different among the three groups of organisms, suggesting that factors shaping patterns of speciation and extinction are consistent among major taxonomic groups.     

Chronic stress and its effects on adrenal cortex apoptosis in pregnant rats

The model of chronic intermittent stress by immobilization during pregnancy may produce alterations in the mechanisms that maintain adrenal gland homeostasis. In earlier investigations using this model, significant variations in plasma prolactin and corticosterone levels, and adrenal gland weights were observed. We hypothesized that chronic stress causes changes in apoptosis in the adrenal glands of pregnant rats. We identified and quantified apoptotic cells in the adrenal cortex and examined their ultrastructural characteristics using transmission electron microscopy. Adrenal glands of pregnant rats at gestation days 12, 17 and 21 were studied for control and experimental (stressed) rats. Immunolabelling techniques, stereological analysis and image quantification of adrenal gland sections were combined to determine differences in apoptosis in the different cell populations of the adrenal cortex. The apoptotic index of the experimental rats showed a significant reduction at gestation day 17, while at days 12 and 21 there were no differences from controls. Moreover, the apoptotic index of the reticular zones in control and experimental animals showed a significant increase compared to the glomerular and fascicular zones at the three gestation times studied. Chronic stress by immobilization reduced the caspase-dependent apoptotic index at gestation day 17, which may be related to variations in plasma concentrations of estrogens and prolactin.     

盐生植物角果碱蓬种子二型性对环境的适应策略

角果碱蓬(Suaeda corniculata)是藜科一年生盐生植物, 在我国分布于北方盐碱滩涂和盐碱荒漠地区。角果碱蓬具有棕色和黑色两种异型体种子(简称棕色和黑色种子)。对采自内蒙古鄂托克前旗盐渍化生境的角果碱蓬二型种子的形态、休眠和萌发特性开展对比研究, 测定了二型种子休眠和萌发行为对温度、光照和盐分(NaCl)的响应, 以揭示盐生植物异型种子对温带盐漠生境的适应对策。结果表明: (1)二型性种子在大小、种皮特性和结实比例方面有显著差异。与黑色种子相比, 棕色种子个体较大, 种皮透水性强。黑色种子与棕色种子的结实比例约为5.6 : 1。(2)新成熟的棕色种子的萌发对各温度梯度和光照条件不敏感, 萌发率较高(84%-100%); 而新成熟的黑色种子萌发率较低(8%-78%), 萌发对光照敏感。(3)黑色种子具有浅度生理休眠, 种皮划破、赤霉素处理和低温层积均可有效地提高种子的萌发率。(4)二型种子萌发对土壤盐分的胁迫具有不同的响应。与黑色种子相比, 棕色种子对盐分胁迫不敏感, 在较高的盐分浓度下仍有较高的萌发率, 低温层积处理能够降低黑色种子对盐胁迫的敏感性, 有效地提高种子的初始萌发率、萌发恢复率和最终萌发率。角果碱蓬二型种子不同的形态、休眠和萌发特性, 提高了该物种在高度异质性生境中的适合度, 对种群成功地适应温带盐漠环境具有重要的意义。     

尼古丁在帕金森病中的神经保护作用

帕金森病(Parkinson’s disease,PD)是常见的中老年神经退行性疾病。研究表明,尼古丁具有抵抗黑质多巴胺神经元损伤的作用,其通过烟碱型乙酰胆碱受体(nicotinic acetylcholine receptor,nAChR)途径与非受体途径抑制帕金森病的发生与发展。本文就尼古丁在帕金森病中的神经保护作用以及保护机制的相关研究进行综述。     

丝素蛋白/羟基磷灰石复合物对磷酸钙骨水泥性能的影响

目的：磷酸钙骨水泥（Calcium phosphate cement,CPC）以其诸多优点正得到了越来越多的应用,但其较差的力学性能表现也限制了它的使用范围。本研究目的在于改善磷酸钙骨水泥的力学性能,同时评估改性后的磷酸钙骨水泥的其他性能。方法：通过丝素蛋白（Silk fibroin,SF）的矿化自组装方法制备丝素蛋白／羟基磷灰石复合物（silk fibroin/hydroxyapitite composite, SF/HA）。按照1％、2％、3％、4％的质量分数加入磷酸钙骨水泥中,与磷酸钙骨水泥组对比。比较内容包括力学强度、抗渍散性能及细胞毒性。结果：以丝素蛋白溶液为液相组的磷酸钙骨水泥强度大约为35MPa。随后随着添加丝素蛋白／羟基磷灰石复合物的质量分数从1％增至3％,磷酸钙骨水泥的强度逐渐增加（P〈0．05）,最高约至45MPa。而当丝素蛋白／羟基磷灰石的质量分数达到4％时,磷酸钙骨水泥的强度较质量分数3％组小幅度下降至43MPa（P〈0．05）。以丝素蛋白溶液作为液相时,磷酸钙骨水泥的抗溃散能力也得到了加强。在MTT法测定细胞活力的对照实验中,无论是加入丝素蛋白溶液或丝素蛋白／羟基磷灰石复合物,都未观察到细胞毒性。结论：在磷酸钙骨水泥中加入3％质量分数的丝素蛋白／羟基磷灰石复合物,能显著提高磷酸钙骨水泥的抗压强度。而丝素蛋白溶液作为液相可改善磷酸钙骨水泥的抗溃散能力。同时,丝素蛋白和丝素蛋白／羟基磷灰石复合物都不表现出细胞毒性。更理想的力学强度和更强的抗溃散能力,大大扩展了磷酸钙骨水泥的应用范围。     

Insect cell expression of recombinant imidazoleglycerolphosphate dehydratase of Arabidopsis and wheat and inhibition by triazole herbicides.

Imidazoleglycerolphosphate dehydratase (IGPD; EC 4.2.1.19), which is involved in the histidine biosynthetic pathway of Arabidopsis thaliana and wheat (Triticum aestivum), has been expressed in insect cells using the baculovirus expression vector system. N-terminal amino acid sequencing indicated that recombinant IGPDs (rIGPDs) were produced as mature forms via nonspecific proteolytic cleavages in the putative transit peptide region. The wheat rIGPD contained one Mn atom per subunit, and the Mn was involved in the assembly of the subunits to form active IGPDs. Protein-blotting analysis, using antibodies raised against the wheat rIGPD, indicated that IGPD was located in the chloroplasts of wheat. The rIGPDs of Arabidopsis and wheat, which were 86% identical in their primary structures deduced from the cDNAs, exhibited similar properties in terms of the molecular mass, pH optimum, and the Km for the substrate, imidazoleglycerolphosphate. However, the nonselective herbicides 3-amino-1,2,4-triazole and a newly synthesized triazole [(1R*, 3R*)-[3-hydroxy-3-(2H-[1,2,4]triazole-3-yl)-cyclohexyl]- phosphonic acid], inhibited Arabidopsis and wheat IGPDs in a mixed-type and a competitive manner, respectively.