Evolutionary rates for tuf genes in endosymbionts of aphids

The gene encoding elongation factor Tu (tuf) in aphid endosymbionts (genus Buchnera) evolves at rates of 1.3 x 10(-10) to 2.5 x 10(-10) nonsynonymous substitutions and 3.9 x 10(-9) to 8.0 x 10(-9) synonymous substitutions per position per year. These rates, which are at present among the most reliable substitution rates for protein-coding genes of bacteria, have been obtained by calibrating the nodes in the phylogenetic tree produced from the Buchnera EF-Tu sequences using divergence times for the corresponding ancestral aphid hosts. We also present data suggesting that the rates of nonsynonymous substitutions are significantly higher in the endosymbiont lineages than in the closely related free-living bacteria Escherichia coli and Salmonella typhimurium. Synonymous substitution rates for Buchnera approximate estimated mutation rates for E. coli and S. typhimurium, as expected if synonymous changes act as neutral mutations in Buchnera. We relate the observed differences in substitution frequencies to the absence of selective codon preferences in Buchnera and to the influence of Muller's ratchet on small asexual populations.      

1H-NMR spin-spin relaxation time assessment of the reflection coefficient of the Triticale seed cell wall–plasmalemma barrier to mannitol

The ¹H-NMR spin-spin relaxation time (T₂) in Triticale seeds swelling in external osmotica, polyethylene glycol 8000 or mannitol can identify both bound and free water. At the same water content, the free water spin-spin relaxation time increases for seeds imbibed with the mannitol solution, demonstrating inadequate water potential adjustment. The exchange rate of free/bound water molecules is apparently influenced by the driving force for water flow. The reciprocal lifetime of free water molecules, as a measure of water flow through the main cell barrier, was obtained. From a model of the seed as a resistance–capacitor network for water flow, a method was derived for calculating the reflection coefficient σ as a lifetime ratio of the free water molecules in seeds imbibed with two different osmotica (one penetrating across the main cell barrier and one not penetrating) at the same water potential. The ¹H-NMR method and the classical method based on volume rate changes yielded reflection coefficients for mannitol for the cell wall–plasmalemma barrier of 0.78 ± 0.08 and 0.68 ± 0.06, respectively.     

Glycine-dependent cryotransformation of Bacillus anthracis by DNA of various plasmids

The possibility of the 1,8-60,0 Md plasmids DNA transfer into the cells of different Bacillus anthracis strains has been established. A number of parameters of the procedure has been optimized. The including of PEG6000 into the cryomixture in the final concentration 10% has been demonstrated to be vital for increase in transformants yields. Under the described conditions the maximal efficiency of transformation (1,2.10(3)) has been registered for the DNA of the plasmid pUB110. The efficiency of the process decreased concomittant with the size of the transformed plasmids representing 2-4.10(-1) for the plasmid perlicon pXO2 (60 Md). The plasmids obtained by Bacillus anthracis cells retained the functional and structural stability.     

Sediment formation in Lake Baikal

The following stages in the formation of sediments in Lake Baikal have been distinguished. In the Middle Miocene lacustrine deposits accumulated in the southern depression. In Early and Middle Pliocene, as well as in Early-Middle Pleistocene the bottom of the southern and middle Baikal depressions was occupied by large lakes, but the northern basin was mainly dry with a system of small lakes, streams and rivers. This accounts for the great facies variety and the genetic heterogeneity of sediments in the northern depression. At the end of Middle and in the Late Pleistocene an abrupt warping of the depression took place, and a shore-line similar to the present one was formed. Sands in the upper part of the sediments are considered to be the product of intensive erosion which probably occurred in the pluvial epoch in the Late Pleistocene period.     

不同真菌纤维素酶一些生物化学性质的比较

比较了属于6个属,即青霉(Penicillium)、曲霉(Aspergillus)、木霉(Trichoderma)、漆斑菌(Myrothecium)、镰孢霉(Fusarium)和腐质霉(Humicola),总计9株真菌在麦麸液体培养基中所产纤维素酶的一些生物化学性质。此外,还比较了这9株真菌在麦麸固体培养基上所产纤维素酶的活力以及对脱脂棉、水曲柳木屑、水曲柳木粉、废报纸和玉米芯糠醛废渣的糖化能力。     

低剂量UV-B辐射对乌拉尔甘草叶片光合机构的影响

为了探讨植物叶片对UV-B辐射增强的响应机制,采用叶绿素荧光测定技术,分别测定在人工模拟低剂量UV-B(2.4μW/cm~2)辐射条件下乌拉尔甘草叶片的叶绿素荧光诱导动力曲线、初始荧光(F_0)、最大荧光(F_m)、光合机构比活性参数(ABS/RC、TR_o/RC和ET_o/RC)和性能指数等变化规律。结果表明:(1)低剂量UV-B辐射未引起甘草叶片O-J-I-P叶绿素荧光诱导曲线中的相数发生改变,UV-B辐射对PSⅡ的影响主要发生在其受体侧,而非供体侧;(2)低剂量UV-B辐射引起了甘草叶片光合系统F_v/F_m以及F_m、F_0的明显变化,同时也影响了光合机构的开放程度和电子从Q_A向Q_B传递效率,从而影响了光转化效率;相应性能指数(PI_(abs)和PI_(total))的改变亦验证了此结果。研究认为,低剂量UV-B辐射抑制乌拉尔甘草叶片光合系统Ⅱ受体侧Q_A至PQ之间的电子传递效率,从而影响了Q_A之后的光化学反应及非光化学反应。     

猪蛔虫生长发育与繁殖力的研究

经对猪蛔虫雌虫体长,体重,子宫瞬间怀卵总量,相对毓力测定,发现怀卵总量与体长,体重有密切关系,呈正相关,还发现相对繁殖力,以体重１．０１－３．００ｇ,范围最佳,繁殖能力最强。     

Effect of small doses of interferon-alpha on food conditioning in young and ageing rats

Low doses (10 or 350 ME) of human interferon-alpha (HIA) were intranasally applied to young (3-4 months) and ageing (12-15 months) Wistar rats during food conditioning. In control groups, development of the conditioned reflex to acoustic stimulus (tone) did not differ significantly in young and ageing rats in the course of chronic applications of the HIA. However, the control ageing rats were better than young rats in time-interval conditioning. Small doses of HIA do not cause anorexia in rats whereas large doses do so. Tone-conditioning did not change in rats of both ages when they were treated with 10 ME of the HIA; moreover, 350 ME increased food motivation, especially in young rats. Time-interval conditioning in aging rats was descended by both doses to the level of young rats, whereas in young rats it did not change at all. We suggest that these differences between ages may by accounted for be different affinity and concentration of micro-opiod receptors (which are the targets for the HIA) in the brain structures responsible for food behaviour, and for counting time intervals.     

珍稀濒危植物蒙古扁桃花生物学特性

蒙古扁桃的植株可分为长花丝植株、短花丝植株和中花丝植株。群落花期约50d,单花花期约8d,分为露粉、微开、盛开、凋谢4个时期。过氧化物法测定4个时期花粉均具活力,可保持30d左右,联苯胺-过氧化氢测定柱头可授性,花粉活力与柱头可授性重叠,长花丝植株为8d左右,而中花丝约为5d。蒙古扁桃花一般在9:00开始泌蜜,11:00分泌量达到高峰,之后产蜜量减少直至停止,日泌蜜和散粉集中在10:00～14:00。蒙古扁桃开花受环境的影响。     

内蒙古阿鲁科尔沁国家级自然保护区景观动态及保护成效

快速评估自然保护区的保护成效,对科学地制定管理决策具有重要意义.本文通过遥感解译进行景观分类和景观动态变化分析,使用保护性景观质量指数、人工景观干扰指数和景观保护成效综合指数等开展内蒙古阿鲁科尔沁国家级自然保护区2004—2014年的保护成效研究.结果表明: 2004—2014年,该自然保护区内自然景观所占比例由92.2%增加到92.8%,天然草地和灌木林面积显著增加,但湖泊、河流快速减少;景观格局变化较大,主要景观类型面积转出率和转入率高,景观转类指数为0.33.自然保护区内各功能区的保护性景观及其占比均明显增加,保护性景观质量指数由24.37增长为25.36,景观质量得到提升.各功能区均存在不同程度的人工干扰,人工干扰景观面积增大;2004和2014年人工景观干扰指数分别为-0.79和-0.96,人工干扰强度变大.研究期间,内蒙古阿鲁科尔沁自然保护区的景观保护成效综合指数为3.5%,其景观保护成效达到“很好”,野生动植物生境趋于好转.