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为了探讨高原低氧对机体无氧代谢阈值(AT)的影响,本研究采用Wasserman无创性方法,分别测定了11名新兵在平原(四川淮口,海拔500m)和经空运进驻高原 (西藏错那,海拔4370m)后的第3、5、7和14天的AT。结果表明:新兵进驻高原后AT由平原的813.6±147.4kg·m/min降低到395.5±194.5 kg·m/min(P<0.01);高原低氧引起AT的降低幅度与受试者平原AT的高低呈正相关(r=0.933,P<0.01);进驻高原后第3、5、7天AT维持在较低水平,随后呈上升趋势。但移居高原1年战士的AT仍低于平原水平(P<0.05)。提示,高原低氧能够显著地降低机体的AT,并且AT越高的个体进驻高原后受低氧环境的影响程度越大。 相似文献
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Selective esterification reactions of 1,6-anhydro-3-deoxy-β-D-xylo-hexopyranose(1), 1,6-anhydro-β-D-glucopyranose (7), and several derivatives of 7, were conducted with an acid chloride or acid anhydride in pyridine. Reaction of 1 with p-toluenesulfonyl chloride and with benzoyl chloride gave 70 and 63%, respectively, of the 2-esters. The 2-methyl and 2-benzyl ethers of 7, both having strongly hydrogen-bonded C-4 hydroxyl group, reacted with p-toluenesulfonyl chloride to yield the 4-monosulfonates (71 and 74%, respectively). Esterification of the 2-methyl ether and 2-p-toluenesulfonate of 7 with p-toluenesulfonic anhydride instead of with p-toluenesulfonyl chloride led to increased yields of the 4-p-toluenesulfonates after a shorter reaction-time. 相似文献
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白翅叶蝉是福建省水稻的重要害虫,苗期受害严重者,整片稻苗苍白,甚至枯死;早稻孕穗、抽穗期常大量发生为害,影响谷粒饱满度,造成减产。福州和闽侯地区一年发生4代,部分5代。成虫越冬。冬季日平均温度达11℃以上时仍能取食为害。春季成虫侵入稻田,4月下旬前后大量产卵,5月中旬虫数激增,5月下旬或6月初达到高峰。早稻收割时由于农事活动引致若虫大量死亡。晚稻田于8、9月虫数较多,但危害不如早稻严重。10月中旬以后成虫逐渐离开稻田,迁往越冬场所。 寄主植物幼嫩茂密和较大湿度的小生境有利于白翅叶蝉的发育繁殖。大发生的气候因子主要是春季多雨。适宜的温湿度范围为温度20—25℃,相对湿度85—90%。 DDT单独使用或DDT与666混用防治白翅叶蝉都能收到满意的效果。早稻秧田宜在播种后两周施药防治;本田于5月中旬虫口密度开始增长之际施药,亦能抑制为害。冬季小麦出土以前清除田边杂草,也是一项有效的防治措施 相似文献
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P. C. Rathke Erinita Seib K. Weber Mary Osborn W. W. Franke 《Experimental cell research》1977,105(2):253-262
Immunofluorescence microscopy using antibody against actin has been used to study the expression of microfilamentous material in cells of a cloned mouse 3T3 line during cytochalasin A (CA) induced cell contraction. A conspicuous modification of the structure of the microfilament bundles is observed. Actin containing rod-like elements can be visualized both by phase contrast and immunofluorescence microscopy. These actin containing rods are of rather defined length (approximate length 5 μm) and seem to be derived as subunits from the original microfilament bundles. In some cells the rods were in the same orientation as the microfilament bundles in control cells, whereas other cells showed scattered arrangements. The phenomenon suggests intrafibrillar periodical heterogeneity in the microfilament bundles. 相似文献
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New evidence for a role of vessel-associated cells and phloem in the rapid xylem refilling of cavitated stems of Laurus nobilis L. 总被引:2,自引:1,他引:2
Xylem recovery from embolism was studied in Laurus nobilis L. stems that were induced to cavitate by combining negative xylem pressure potentials (PX = ?1.1 MPa) with positive air pressures (PC) applied using a pressure collar. Xylem refilling was measured by recording the percentage loss of hydraulic conductance (PLC) with respect to the maximum 2 min, 20 min and 15 h after pressure release. Sodium orthovanadate (an inhibitor of many ATP‐ases) strongly inhibited xylem refilling while fusicoccin (a stimulator of the plasma membrane H+‐ATPase) promoted complete embolism reversal. So, the refilling process was interpreted to result from energy‐dependent mechanisms. Stem girdling induced progressively larger inhibition to refilling the nearer to the embolized stem segment phloem was removed. The starch content of wood parenchyma was estimated as percentages of ray and vasicentric cells with high starch content with respect to the total, before and after stem embolism was induced. A closely linear positive relationship was found to exist between recovery from PLC and starch hydrolysis. This, was especially evident in vasicentric cells. A mechanism for xylem refilling based upon starch to sugar conversion and transport into embolized conduits, assisted by phloem pressure‐driven radial mass flow is proposed. 相似文献
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ANDREA NARDINI FABIO RAIMONDO MARIA A. LO GULLO SEBASTIANO SALLEO 《Plant, cell & environment》2010,33(7):1091-1100
Leaf hydraulics of Aesculus hippocastanum L. were measured over the growing season and during extensive leaf mining by the larvae of an invasive moth (Cameraria ohridella Deschka et Dimic) that specifically destroy the palisade tissue. Leaves showed seasonal changes in hydraulic resistance (Rlamina) which were related to ontogeny. After leaf expansion was complete, the hydraulic resistance of leaves and the partitioning of resistances between vascular and extra‐vascular compartments remained unchanged despite extensive disruption of the palisade by leafminers (up to 50%). This finding suggests that water flow from the petiole to the evaporation sites might not directly involve the palisade cells. The analysis of the temperature dependence of Rlamina in terms of Q10 revealed that at least one transmembrane step was involved in water transport outside the leaf vasculature. Anatomical analysis suggested that this symplastic step may be located at the bundle sheath where the apoplast is interrupted by hydrophobic thickening of cell walls. Our findings offer some support to the view of a compartmentalization of leaves into well‐organized water pools so that the transpiration stream would involve veins, bundle sheath and spongy parenchyma, while the palisade tissue would be largely by‐passed with the possible advantage of protecting cells from short‐term fluctuations in water status. 相似文献