Aminoacylation of Bisulphite-modified Yeast Tyrosine Transfer RNA

AS part of a search for the chemical rules underlying the recognition of a tRNA by its aminoacyl-tRNA ligase¹, we are examining the effect of C?U transitions on aminoacylation of tRNA. In this paper, we describe four well-characterized modifications of yeast tRNA^Tyr induced by reaction with bisulphite ions at pH 5.8. Three of the observed changes proved to be C-?U transitions produced by the series of reactions shown in Fig. 1 (refs. 2–5).     

Species Diversity and Floristic Characteristics of Vascular Plants in Nanji Island,Zhejiang Provience

A total of 393 species (sub type included) in 267 genera, 97 families were reported in Nanji Island, the main island of Nanji Islands National Nature Reserve. After eliminating all the cultivated and invasive species, there were still 304 species in 210 genera and 81 families belonging to wild vascular plants; To better understand the floristic characteristics of Nanji, we applied analysis in 3 levels: At family level, the largest families in pteridophyte were ranked as Pteridaceae、Thelypteridaceae、Lygodiaceae、Dryopteridaceae; In seed plants, almost the largest ones were Cosmopolitan, while the small ones dominented the most, quantitatively and proportionately; The characteristic families of seed flora were consisted of Liliaceae、Amaryllidaceae、Urticaceae、Verbenaceae, cause they got high ratio of VFICS/WFIW; At genus level, the Pantropical Distribution (3810%)、the North Temperate Distribution (1630%) and the East Asia distribution (1131%) formed the main part of seed flora; The proportion of the category of temperate distribution and tropical distribution was 6072% and 3928% respectively; Took 6 other sites as reference, through cluster analysis and R/T ratio comparisons, It was proved that Nanji Island were most similar to that of Wuyanling of Zhejiang Provience but showed more tropical affinities; At species level, wild seed plants can also be divided into 9 areal subtypes, The Yangtze River & Southern Proviences sub type dominented at 5390%, following by South China sub type at 2078%. The results showed that Nanji Island had a distinctive transitional characteristics of flora from north to south China with more tropical biological properties, thus the floristic division of Nanji should on the southern margin area of east China.     

迷走传入的投射区在电刺激颈迷走神经中枢端引起的降压反应中的作用

文献报道迷走传入直接或间接投射至多个脑区。本工作分别检验这些脑区在迷走传入引起的降压、降心率反应中的作用。在乌拉坦麻醉、双侧切断颈迷走神经的大鼠,将普鲁卡因微量注入孤束核或β-内啡肽抗血清注入延髓头端腹外侧区(RVL)均可明显减小电刺激预迷走神经中枢端引起的降压(DpV)和降心率反应,但分别将心得安、β-内啡肽抗血清注入室旁核或普鲁卡因注入最后区对DpV和心率减慢反应均无明显影响。保留右侧颈迷走神经的大鼠,在甲基阿托品(i.v.)阻断心迷走神经作用后DpV亦无明显变化,但心率减慢反应被衰减。鉴于我们以往的实验显示孤束核可通过其β-内啡肽能投射纤维作用于RVL而起降压作用,以上结果提示:迷走传入通过孤束核的β-内啡肽能神经元对RVL-交感兴奋神经元起抑制作用是引起降压反应的机制之一。     

大鼠下丘脑弓状核抑制蓝斑神经元放电的机制及其在电针效应中的作用

本工作在清醒箭毒化大鼠人工呼吸条件下进行。实验显示下丘脑弓状核(AR)内微量注射谷氨酸钠(Glut)所兴奋的 AR 神经元可以显著抑制蓝斑(LC)神经元放电。这一效应可被 LC内注射纳洛酮(Nx)或抗β-内啡肽(β-End)血清,以及切断支配 LC 的β-End 能束取消。这些结果提示它主要是通过兴奋β-End 能神经元,使其在 LC 内的轴突末梢释放β-End 而实现的。由于 LC 内单纯注射 Nx 时 LC 神经元放电率无可见变化,似可认为 AR 对 LC 无明显紧张性抑制作用。实验还显示 LC 内注抗β-End 血清后,电针兴奋 LC 的后期效应增加;如在电针的同时向 AR 内注 Glut 则电针兴奋 LC 的后期效应被取消;表明电针过程中有弓状核β-End 能神经元对 LC 的抑制作用参与。但此抑制作用似弱于电针对 LC 的兴奋效应,故只能取消(较弱的)电针的后期效应。不能取消(较强的)电针的早期效应。     

Radiotelemetry Applied to Field Studies of Shrews

Abstract: Radiotelemetry is a widely used method to study ecology, behavior, and physiology of different animals but has rarely been used on shrews. Small body size, wide neck and narrow skull, high mobility, and fragility of shrews cause problems for both transmitter attachment and the safety of the animals. We developed a method for nonpermanent attachment of transmitters, which allowed us to track such small mammals as the Eurasian water shrews (Neomys fodiens; n = 39, mean body mass 14.9 g), Mediterranean water shrews (Neomys anomalus; n = 32, 10.9 g), and common shrews (Sorex araneus; n = 51, 8.1 g). We used microtransmitters weighing 0.47 g, but those we applied to the larger Neomys species were heavier (0.67 g) because we fortified them with a layer of hard material to prevent damage from biting. We glued a transmitter directly to the skin on a shrew's back, with the anterior edges particularly well sealed. We tracked shrews in the wild and in outdoor enclosures. Transmitters usually dropped off together with peeled skin (on average, after 56.0 hr, n = 92 observations), but if not dropped and if the signal was not lost, mean duration of monitoring was 96.7 hours (n = 37) and in 2 cases exceeded 194 hours. Other advantages of our attachment method were 1) it was less invasive and easier to apply than implantation of transmitters into the body cavity, and 2) we could find dropped transmitters and reuse them. We give suggestions on how to minimize the risk of injury to animals by correct handling, manipulation, and gluing. In conclusion, we recommend radiotelemetry as a useful technique for studying shrew behavior in both free-living populations and experimental enclosures.     

封育年限对毛竹林群落结构和林下植物多样性的影响

为探讨自然封育对毛竹林群落结构和林下植物多样性的影响,采用空间代替时间的方法,以浙江省杭州市余杭区常规经营(0年)和不同封育年限(10,20,30年)的毛竹林为对象,对毛竹林分结构和林下植物多样性进行了全面研究。结果表明:随着封育年限的延长,竹林密度增大,胸径变小;封育毛竹林中2度以上活立竹的密度显著高于常规经营(P<0.05),枯立竹的密度随着封育年限的延长而显著增加(P<0.05);封育20年后的2度以上活立竹和枯立竹的胸径显著减小(P<0.05)。封育0,10,20,30年的毛竹林下灌木种类分别为68,35,58,77种,而草本植物种类则分别为64,23,31,44种。封育10年的林下灌木的Simpson指数显著低于其他林分(P<0.05),封育20年后的Shannon-Wiener指数显著高于前期年份(P<0.05),封育显著提高了Pielou指数(P<0.05);封育显著降低了草本植物的Simpson指数(P<0.05),常规经营林下草本多样性指数Shannon-Wiener显著高于封育20年后的林分(P<0.05),封育10年...     

Oxygen sensitivity of C4 photosynthesis: evidence from gas exchange and chlorophyll fluorescence analyses with different C4 subtypes

Because photosynthetic rates in C₄ plants are the same at normal levels of O₂ (c, 20 kPa) and at c, 2 kPa O₂ (a conventional test for evaluating photorespiration in C₃ plants) it has been thought that C₄ photosynthesis is O₂ insensitive. However, we have found a dual effect of O₂ on the net rate of CO₂ assimilation among species representing all three C₄ subtypes from both monocots and dicots. The optimum O₂ partial pressure for C₄ photosynthesis at 30 °C, atmospheric CO₂ level, and half full sunlight (1000 μmol quanta m^?2 s^?1) was about 5–10 kPa. Photosynthesis was inhibited by O₂ below or above the optimum partial pressure. Decreasing CO₂ levels from ambient levels (32.6 Pa) to 9.3 Pa caused a substantial increase in the degree of inhibition of photosynthesis by supra-optimum levels of O₂ and a large decrease in the ratio of quantum yield of CO₂ fixation/quantum yield of photosystem II (PSII) measured by chlorophyll a fluorescence. Photosystem II activity, measured from chlorophyll a fluorescence analysis, was not inhibited at levels of O₂ that were above the optimum for CO₂ assimilation, which is consistent with a compensating, alternative electron How as net CO₂ assimilation is inhibited. At suboptimum levels of O₂, however, the inhibition of photosynthesis was paralleled by an inhibition of PSII quantum yield, increased state of reduction of quinone A, and decreased efficiency of open PSII centres. These results with different C₄ types suggest that inhibition of net CO₂ assimilation with increasing O₂ partial pressure above the optimum is associated with photorespiration, and that inhibition below the optimum O₂ may be caused by a reduced supply of ATP to the C₄ cycle as a result of inhibition of its production photochemically.     

转C4光合酶基因水稻的CO2交换和荧光特性

用转PEPC、PPDK、NADP_ME、PEPC PPDK酶基因水稻 (OryzasativaL .)及原种为材料 ,研究了光合作用对光照、温度、CO2 的响应和光抑制条件下的叶绿素荧光特性 ,结果如下 :1.转C4 光合酶基因水稻的饱和光合速率比原种高 ,其中转PEPC、PEPC PPDK双基因水稻的光饱和点比原种高 2 0 0 μmol·m-2 ·s-1,饱和光合速率比原种分别高5 1.6 %和 5 8.5 % ;转PEPC基因水稻的羧化效率比原种高 49.3% ,CO2 补偿点降低 2 6 .2 % ;在高温 (35℃ )下 ,转PEPC基因水稻的光合速率比原种高 17.5 %。 2 .经光抑制处理 8d后 ,转PEPC、PEPC PPDK酶基因水稻的PSⅡ光化学效率 (Fv/Fm)和光化学猝灭 (qP)下降 2 0 % - 30 % ,非光化学猝灭 (qN)增加了约 30 % ;但原种的Fv/Fm 和qP下降了 5 0 %多 ,qN变化不明显 ,表明转C4 光合基因水稻耐光抑制能力增强。这些结果为用生物技术提高水稻光合效率研究提供了新的依据和途径     

The Effect of Interleukin-2 on Parasitemia and Myocarditis in Experimental Chagas' Disease

Previous investigations showed that interleukin-2 (IL-2) administered in vivo into mice infected with Trypanosoma cruzi reduced levels of parasitemia and increased longevity. Present experiments examined the effect of administration of different doses of IL-2 at different times during infection in mice on parasitemia and histopathoiogy of heart tissue. Two different doses of IL-2 (1,500 or 10,000 U) given at 3 different times during infection were equivalent in reducing parasitemia. All of the IL-2 treated groups of mice had significantly lower numbers of circulating trypomastigotes as compared with controls not receiving this fymphokine. This IL-2 treatment of T . crazi-infected mice resulted also in lower numbers of pseudocysts in all 4 ventricular regions in the hearts. This was particularly evident in the more severely infected right ventricular wall; however, a similar decrease was not as apparent in the less severely infected left ventricular wall. The IL-2 treated, infected mice showed minimal or no effect in reducing inflammation of myocardial cells. However, the mildest inflammation of ventricular wall tended to occur in mice receiving IL-2 treatment either as a low dose (1,500 U) or a high dose (10,000 U) at 5, 7 and 9 days after infection as compared with mice treated later on. It was concluded that IL-2 treatment of infected mice produced a significant decrease in parasitemia and decreased infection of myocardial cells. Key words. Heart, histopathoiogy, inflammation, lymphokine, myocardial cells, pseudocyst, Trypanosoma cruzi .