北京地区黑线仓鼠年龄鉴定及种群年龄组成的研究

鼠类种群年龄组成的研究是种群生态学的基础内容。种群年龄组成的变化,直接关系到鼠类数量的波动。黑线仓鼠(Cricetulus barabensis)是北京地区农田的主要害鼠之一,为探讨该鼠种在农田生态系统中的作用,并控制其危害,研究其种群年龄组成及变化是非常必要的。     

仙湖苏铁种群年龄判断及年龄结构特征

根据苏铁类植株体残存的营养叶叶基数、开花痕数以及生长单元发生率等茎干特征, 建立了仙湖苏铁种群年龄判断方法,计算出该种群年龄. 进一步采用年龄结构图、年龄分布 曲线和曲线估计等方法,从基株和无性系水平探讨了仙湖苏铁种群的年龄结构特征.年龄结构 图显示,仙湖苏铁无性系种群为稳定种群,基株种群为衰退种群;年龄分布曲线和曲线估计结 果则表明仙湖苏铁无性系和基株种群均为衰退种群. 综合3种方法的分析结果,仙湖苏铁 种群为衰退种群,必须采取一定措施予以保护.     

黑线仓鼠种群年龄组成及其数量季节消长的研究

本文对黑线仓鼠的上臼齿磨损程度进行了系统观察,共采标本553只,结合生殖系统的解剖记录,确定以右侧上臼齿的磨损程度将黑线仓鼠划分为5个年龄组。探讨了年龄与体长、体重及繁殖力的相互关系,以及种群数量季节消长与气候条件及种群结构的关系。结果表明,黑线仓鼠年龄越大,雌鼠的繁殖力越高,但平均怀仔量并不随年龄增大而增加。体重、体长不易作为划分黑线仓鼠年龄组的指标。种群数量与大降雨量呈明显的负相关,但种群的年龄结构对数量消长起着主要作用。     

大沙鼠的年龄鉴定与种群年龄组成

在鼠类生态学的研究中 ,对鼠类年龄的鉴定是一项重要的工作。年龄组成是种群的重要特征之一 ,它有助于了解种群的年龄结构以及种群数量变动的规律。大沙鼠 (Ｒｈｏｍｂｏｍｙｓｏｐｉｍｕｓ)是中亚地区荒漠及半荒漠草原的重要害鼠之一 ,在内蒙古西部的梭梭 (Ｈａｌｏｘｙｌｏｎａｍｍｏｄｅｎｄｒｏｎ)林区 ,由于大沙鼠的啃咬 ,影响了该地区梭梭林的正常结实 ,从而降低了结实量[1 ] 。同时 ,大沙鼠又是鼠疫和皮肤利什曼病的重要宿主。对大沙鼠的年龄鉴定与种群年龄组成进行研究 ,将有助于了解其种群数量变动的规律 ,从而为有效防治大沙鼠鼠…     

黄胸鼠的年龄鉴定和种群年龄组成

本文经晶体干重法鉴定黄胸鼠的年龄,分析其种群年龄组成,并与其他年龄鉴定方法如体重法、体长法、臼齿磨损法进行了比较。     

格氏栲种群个体年龄与胸径的时间序列模型研究

本文提出格氏栲种群以年轮确定种群个体年龄并与胸径、树高确定种群个体年龄有机结合的时间序列预测个体年龄方法。通过时间序列分析,确定出格氏栲种群个体年龄与胸径关系的ＡＲＩＭＡ（１,２,０）模型,经检验该模型的相似性系数为９３．４８％,即该模型预测胸径生长量是可靠的。同时,通过ＡＲＩ－ＭＡ（１,２,０）模型预测结果与实际调查材料组合起来,建立较为准确反映个体年龄的组合模型：Ａ＝１０．１５４５１＋１．１１３８５１Ｄ＋０．０４２２００４９Ｄ２－０．０００２２７３０３Ｄ３式中Ｄ为格氏栲种群个体胸径,Ａ为格氏栲种群个体年龄,相关指数为０．９９９８。可见,组合模型的格氏栲种群个体胸径与年龄回归关系极显著,效果理想,为相应研究提供一个较为可靠的方法。     

用粪便形态特征初步研究新疆塔里木马鹿种群年龄和性别

塔里木马鹿分布在干旱地区,是唯一的适应干旱荒漠环境的特殊马鹿亚种之一.目前,塔里木马鹿种群面临着栖息地退缩和片段化的双重影响,这不仅导致了种群数量的锐减,而且也因物种遗传漂变和近亲繁殖的不断增加,进一步加剧其濒危程度.为了有效地保护该物种,全面了解种群结构是至关重要.对塔里木马鹿粪便的长度、宽度、长度/宽度比例和体积等参数进行了测量,并采用判别分析方法划分种群年龄.结果表明,塔里木马鹿粪便形态在不同性别之间有差异,一般雌性的粪便大于雄性(P<0.05).同时根据粪便形态对种群年龄划分为成年雄性、成年雌性和幼体等3个年龄组.     

紫萁年龄判断及其种群年龄结构分析初探

根据紫萁地下根状茎长度、叶残基痕迹及叶柄基径等与年龄相关的性状特征,该文建立了紫萁年龄判断模型,用以计算广西越城岭地区紫萁种群个体年龄,并采用年龄结构图方法,探讨该地区紫萁种群的年龄结构特征。结果表明:紫萁这种多年生草本蕨类植物达到一定年龄后,地上部分性状趋于稳定,对其年龄判断,只能选择地下根状茎作为研究对象;蕨类植物没有活跃的维管形成层,不能形成完整的次生维管结构,其地下根状茎的直径与年龄之间无显著相关关系,判断其年龄可根据地下根状茎的长度确定。越城岭山脉一带的紫萁种群趋于老龄化,幼龄级个体缺乏,更新能力弱,大量采摘或挖掘紫萁植株,极大地影响了紫萁天然更新和种群结构。     

用鳞片和耳石鉴定鲫年龄的比较研究

两观测者独立观测了分别采自洪湖的175尾和洞庭湖的168尾鲫样本的鲜片和耳石,结果显示鳞片适于鉴定年龄组成简单、生长较快的洞庭湖鲫种群的年龄,两观测者年轮读数的总吻合率可达90.5%,与耳石上年轮读数的吻合率也可高达91.7%;但用鳞片鉴定年龄结构复杂、生长缓慢的洪湖鲫种群年龄,两观测者总吻合率只有50.9%,各龄组吻合率随年龄上升而迅速下降。与耳石上年轮读数总吻合率也仅为56.6A%,存在比耳石低估高龄个体年龄的问题,用耳石鉴定鲫年龄具有易于识别、精确度高的优点,用之鉴定洪湖和洞庭湖鲫种群年龄,两观测者年轮读数的总吻合率都很高,分别为92.7%和97.0%,且随年龄上升,依然可保持较高的精确度,对洪湖鲫种群应用耳石为宜。     

水毛茛种群生态学研究

本文根据6年定位研究结果,讨论了东北山溪激流中整株越冬的草本植物─-水毛茛的有关种群生态方面的问题;诸如水毛茛种群的空间分布格局、种群年龄区段结构和种群数量的周期性变动等;并利用观测数据编制了水毛茛种群的静态生命表,绘制了种群的存活曲线和死亡动态曲线,根据种群生殖力表计算了种群的内禀增长能力.利用逻辑斯蒂标准曲线对植物种群数量增长曲线进行拟合.最后对年龄区段的划分及其在生命表中的作用、种群数量变动及其影响因素、迁入与迁出对水毛茛种群大小的影响等进行了探讨.       

Recent advances in the study of Kaposi's sarcoma-associated herpesvirus replication and pathogenesis

It has now been over twenty years since a novel herpesviral genome was identified in Kaposi's sarcoma biopsies. Since then, the cumulative research effort by molecular biologists, virologists, clinicians, and epidemiologists alike has led to the extensive characterization of this tumor virus, Kaposi's sarcoma-associated herpesvirus(KSHV; also known as human herpesvirus 8(HHV-8)), and its associated diseases. Here we review the current knowledge of KSHV biology and pathogenesis, with a particular emphasis on new and exciting advances in the field of epigenetics. We also discuss the development and practicality of various cell culture and animal model systems to study KSHV replication and pathogenesis.     

The structure, reproduction and taxonomy of Vidalia and Osmundaria (Rhodophyta, Rhodomelaceae)

Comprises species occurring mostly in subtidal habitats in tropical, subtropical and warm-temperate areas of the world. An analysis of the type species, V. spiralis (Sonder) Lamouroux ex J. Agardh, a species from Australia, establishes basic characters for distinguishing species in the genus. These characters are (1) branching patterns of thalli, (2) flat blades that may be spiralled on their axis, (3) width of the blade, (4) primary or secondary derivation of sterile and fertile branchlets and (5) position of sterile and fertile branchlets on the thalli. Application of the latter two characters provides an important basic method for separation of species into three major groups. Osmundaria , a genus known only in southern Australia, was studied in relation to Vidalia , and its separation from the Vidalia assemblage is not accepted. Species of Vidalia therefore are transferred to the older genus name, Osmundaria. Two new species, Osmundaria papenfussii and Osmundaria oliveae are described from Natal. Confusion in the usage of the epithet, Vidalia fimbriala Brown ex Turner has been clarified, and Vidalia gregaria Falkenberg, described as an epiphyte on Osmundaria pro/ifera Lamouroux, is revealed to be young branches of the host, Osmundaria prolifera.     

New or rare chromosome counts in Artemisia L. (Asteraceae, Anthemideae) and related genera from Kazakhstan

Fifteen chromosome counts of six Artemisia taxa and one species of each of the genera Brachanthemum, Hippolytia, Kaschgaria, Lepidolopsis and Turaniphytum are reported from Kazakhstan. Three of them are new reports, two are not consistent with previous counts and the remainder are confirmations of very scarce (one to four) earlier records. All the populations studied have the same basic chromosome number, x = 9, with ploidy levels ranging from 2x to 6x. Some correlations between ploidy level, morphological characters and distribution are noted.     

肝癌中HBV和HCV基因和抗原的分布及意义

采用原位分子杂交方法检测HCV RNA及HBV X基因;采用免疫组织化学方法研究HCV核心抗原,非结构区C33c抗原及HBxAg在肝细胞肝癌中的定位及分布.结果表明(1)HCV RNA、HBV X基因在肝细胞肝癌组织检出率分别为40%(55/136)和82%(112/136).HCV RNA定位于癌细胞的胞浆内,阳性细胞呈散在、灶状及弥漫分布三种形式;HBV X基因在肝癌细胞中的分布呈胞浆型、核型及核浆型,阳性细胞也呈上述三种分布形式;(2)HCV C33c抗原、核心抗原在肝细胞肝癌中的阳性率为81%(133/164)及86%(141/164).C33c抗原定位于癌细胞及肝细胞的胞浆内;核心抗原既定位于癌细胞核中,又可定位于胞浆中.C33c抗原阳性细胞以灶状分布为主;而核心抗原阳性细     

Selection with two alleles and complete dominance

For a plant selection model with frequency-independent viabilities, fertilities and selfing rates, it is shown that apart from global fixation, for certain parameter combinations a protected polymorphism and facultative fixation (either allele may become fixed according to initial frequencies) may both occur. Facultative fixation requires different selling rates for the dominant and recessive type. Protection of the polymorphism requires resource allocation for male and female function. In this connection the problem of purely genetically caused population extinction is discussed.
For general frequency dependence and regular segregation, the chances for establishment of a completely recessive gene are compared to those of a completely dominant gene. It is proven that the process of establishment of the recessive gene, despite a fitness advantage, may be considerably endangered by drift effects if random mating prevails. The recessive gene may reach the same effectivity in establishment as a dominant gene, only if the recessive homozygote mates exclusively with its own type during the period of establishment.