高山嵩草种群在放牧干扰下遗传多样性的变化

利用SRAP (Sequence-related amplified polymorphism)分子标记, 对放牧干扰下的高山嵩草(Kobresia pygmaea)种群进行了遗传多样性研究, 获得了下述结果: 1) 20对SRAP引物组合共检测出448条清晰条带, 其中376条条带具有多态性, 多态位点百分率为83.93%, 随着放牧强度的增加, 高山嵩草种群多态位点百分数、Nei’s遗传多样性指数、Shannon信息指数均下降。2)高山嵩草种群具有较高的遗传多样性和较低的遗传分化(总的遗传多样性H_t为0.276 6, 种群内遗传多样性H_s为0.243 6, 遗传分化系数G_st为0.119 4, 基于G_st估计的基因流N_m^*为1.843 4), 但随着放牧强度的增加, G_st增加, N_m^*降低, 说明放牧限制了种群间的基因交流, 使种群发生遗传分化。3)不同放牧梯度的高山嵩草种群间的遗传距离很小, 但是随着放牧强度的增加, 种群间的遗传距离逐渐增加, 遗传一致度降低。根据遗传距离所构建的UPGMA聚类图中高山嵩草4个种群随着牧压的增加, 逐级聚在一起。     

水松自然种群和人工种群遗传多样性比较

采用ISSR分子标记技术分析水松不同起源种群的遗传多样性.结果表明:10条引物共检测出95个扩增位点,多态位点数占39.0%.与其他濒危裸子植物相比,水松的遗传多样性较低,遗传分化系数Gst为0.3982,基因流Nm仅0.3778,种群间存在一定程度的遗传分化,但种群内变异占主导地位;遗传距离与地理距离呈正相关关系.自然种群的多态位点百分率(P)、Nei的条带多样度(He)和Shannon信息指数(Ⅰ)平均值(39.3%、0.1499和0.2202)分别高于人工种群(30.7%、0.1265和0.1759).自然种群的遗传分化系数(Gst0.4513)和平均遗传距离(D=0.0301)也高于人工种群(Gst=0.3025,D=0.0192).     

籽蒿的地理分布与遗传分化

 对籽蒿(Artemisia sphaerocephala)的分布地点进行了调查,发现了籽蒿在浑善达克沙地的新分布, 绘制了籽蒿的分布图。在籽蒿集中分布的地区取了5个种群,新分布点取了一个种群,利用随机扩增多态性DNA（RAPD）方法进行了遗传分化的研究。15个引物共扩增出255条带,其中多态带232条,多态位点百分率为91%。各种群以乌海流动沙地种群最低, 多态位点百分率为66.7%, 沙坡头种群最高,多态位点百分率为83.4%。籽蒿种群间有着一定的遗传分化,遗传分化系数（Gst）为0.234 8, 表明76.52%的遗传变异存在于种群内。聚类分析显示,籽蒿种群之间的遗传距离与地理距离有着一定的相关性。而相隔很远的浑善达克沙地的锡林浩特种群与毛乌素沙地的榆林种群间的遗传距离较小,且被聚到了一起,表明两个草原区沙地籽蒿种群间的关系密切。     

观光木种群遗传多样性的ISSR研究

使用单因素筛选和均匀设计实验建立并优化了观光木ISSR—PCtL的最佳反应体系．从100条ISSR引物中筛选出8条多态性好、扩增稳定的ISSR引物,106份材料共扩增出12l条条带,其中109条呈现多态性,多态位点百分率（PPB）达90．08％。扩增片段为250～2000bp,平均每个引物扩增出15条片段．说明观光木种群间存在丰富的遗传多样性。观光木种群间的Nei’s基因多样性指数（He）=0．3557,Shannon信息指数（I）=0．5276,种群间的分化系数（Gst）=0．6480,而种群内的He=0．1261,I=0．1939,Gst=0．3520,说明观光木种群间的遗传多样性是观光木遗传变异的主要来源。     

美国白蛾种群遗传分化的RAPD分析

应用随机扩增多态性DNA(RAPD)技术,对9个不同地理种群美国白蛾进行了遗传多样性和UPMGA聚类分析.结果表明:25个RAPD引物共扩增191个位点,片段大小在200～2000 bp,其中158个是多态位点,多态百分率为82.72%,遗传距离指数在0.2043～0.5108,遗传相似性系数在0.4892～0.7957;9个不同地理种群的美国白蛾可以分成3类:辽宁省和山东类群、北京和天津类群、美国类群,表明美国白蛾不同地理种群间的遗传分化与地理位置相关.     

濒危灌木长叶红砂遗传多样性的RAPD分析

应用RAPD分子标记对濒危灌木长叶红砂(Reaumuria trigyna)种群遗传多样性进行了分析.应用18条随机引物对长叶红砂5个种群的95个个体进行扩增,检测到118个位点,其中多态位点105个.结果表明:长叶红砂种群的多态位点比率(P)为88.98%,显示出长叶红砂种群存在较高的遗传多样性.Shannon多样性指数(0.4966)、Nei基因多样性指数(0.3303)和基因分化系数(Gst=0.1425)的分析结果显示,长叶红砂种群遗传变异大多存在于种群内,种群间的遗传分化占14.25%.聚类分析表明,长叶红砂种群遗传距离与地理距离之间无直接相关关系.遗传多样性水平与物种特性和所处不同群落有关,濒危植物并不一定表现为遗传变异水平的降低.     

Study on population genetic diversity of Camellia japonica in 5 islands between China and Japan

运用ISSR分子标记法对中、日两国5个岛屿天然山茶种群共150个个体进行遗传多样性分析.结果表明:筛选出的20条引物扩增得到205条清晰条带,其中183条为多态性条带,多态位点百分比(PPB)为89.27％.经POPGENE软件分析,山茶种群平均多态位点百分比(PPB)为72.00％,Nei's基因多样性指数(HE)为0.2743,Shannon信息多态性指数(H)为0.4023,种群水平遗传多样性较高.基因分化系数Gst=0.2033,表明遗传变异主要存在于种群内个体间.Mantel检验(r=0.7989,P＜0.05)和UPGMA聚类表明岛屿地理隔离对山茶种群遗传分化具有重要影响.基于岛屿山茶种群遗传结构的分析,建议加强我国岛屿自然种群的就地保护力度.     

引进天敌莲草直胸跳甲的遗传多样性

我国从美国引进天敌昆虫莲草直胸跳甲防治喜旱莲子草已有20多年历史.本研究采用随机引物扩增多态性DNA(RAPD)分析方法,对引入我国的4个莲草直胸跳甲地理种群(广州、重庆、昆明、福州)的遗传多样性情况进行分析,并以美国佛罗里达种群为参照,从分子水平上揭示其种群的遗传分化及其与环境之间的关系.从111条随机引物中选取13条条带清晰、重复性好的引物对5个种群的25个样本进行扩增.结果表明:总多态位点百分率为42.0％,其中美国佛罗里达种群的多态位点百分率显著高于我国的4个地理种群;25.5％遗传分化发生在4个群体间;对各地理种群间的遗传距离采用非加权配对算术平均法( UPGMA)进行聚类分析发现,遗传距离与种群空间分布距离呈正相关.     

舟山群岛野生山茶种群遗传多样性的ISSR分析

采用ISSR分子标记,利用筛选的20条引物对舟山群岛4个野生山茶（Camellia japonica）种群的遗传多样性进行分析。结果表明：山茶种群的多态位点百分比（PPB）为64.06％,Nei’s基因多样性指数（HE）为0.2390,Shannon信息多态性指数（H）为0.3548,种群水平遗传多样性较高。基因分化系数Gst = 0.2241,表明种群间具有较高的遗传分化。地理距离与遗传距离具有显著相关性（r = 0.9653,P<0.05）,表明岛屿隔离对山茶种群的遗传分化具有重要影响。UPGMA聚类表明同岛种群间的亲缘关系更近。基于舟山群岛山茶种群遗传结构分析,建议在其自然生长地加强就地保护。     

内蒙古中东部不同草原地带羊草种群遗传分化

运用 RAPD技术对内蒙古不同草原地带分布的 5个羊草种群 (共 10 0个个体 )的遗传多样性进行分析。 31个随机引物(10 nt)在 5个羊草种群中共检测到 4 96个扩增片断 ,其中多态性片断 4 89个 ,总的多态位点百分率达 98.6 %。利用 Nei指数和Shannon指数估算了 5个种群的遗传多样性 ,并计算种群相似系数和遗传距离运用 UPGMA法进行聚类分析。结果表明 :无论是种群内还是种群间 ,羊草均存在较高的遗传变异 ,大部分的遗传变异存在于种群内 (Nei指数和 Shannon指数估算结果分别为 85 .4 %和 72 .5 % ) ,只有少部分的遗传变异存在于种群间 ;不同种群的遗传多样性存在差异 ,各种群的遗传多样性与其所处的地理位置具有显著的相关性 ;5个种群的平均遗传距离为 0 .5 0 95 ,变异范围为 0 .4 6 84～ 0 .5 4 76 ;聚类分析结果显示地理距离较近的种群遗传距离较小 ,首先聚在一起 ,而地理距离较远的种群遗传距离较大 ,说明羊草种群间的遗传分化与地理距离存在一定相关性 ;但地理距离最近的两个种群并未最先聚集 ,说明羊草种群间的分化还与其生境的异质性有关     

Characteristics of the membranes of the pellicle of the ciliatePseudomicrothorax dubius

Summary The membranes of the pellicle of the ciliatePseudomicrothorax dubius are investigated using thin section electron microscopy and freeze-fracture replicas. The plasma membrane is covered by a surface coat and is connected to the outer alveolar membrane by short, sometimes branched, bridges. The inner alveolar membrane is coated on both sides. The epiplasm lies in intimate contact with the cytoplasmic surface of this membrane, and there is a corresponding deposit on the other surface. This deposit is regularly striated.The epiplasmic layer and the alveoli are interrupted at sites of cytotic activity,e.g., the attachment sites of trichocysts, the cytoproct, and the parasomal sacs. The striated deposit ends where the epiplasm ends, indicating a direct relationship between these two epimembranous layers.There is a deposit along the sides of the first part of the tip of the trichocysts, and in this region the trichocyst membrane is free of intramembranous particles.The membrane of the parasomal sacs has a coat on both surfaces. That on the extraplasmic surface is similar to the surface coat of the plasma membrane. The origin of the cytoplasmic coat is unknown. The cytotic activity of these sacs is indicated by their highly irregular profiles.     

The early development of the tail and the transformation of the shape of the nucleus of the spermatid of the domestic fowl,Gallus gallus

Summary The differentiation of the spermatid, especially in reference to the formation of the flagellum, and transformation of the shape of the nucleus was investigated in the domestic fowl.In the early stage of the spermatid, a prominent Golgi apparatus appears around the centrioles. The Golgi vesicles then surround the axial-filament complex which develops from the distal centriole. These vesicles fuse to form continuous membrane at the earliest stage of flagellar formation, and in the succeeding stage Golgi lamellae are attached to the plasma membrane of the developing flagellum. From these observations, it is assumed that Golgi apparatus may be a source of the membrane system of the flagellum.The microtubules distributed around the nucleus form the circular manchette. The anterior region of the nucleus with the manchette is cylindrical in shape and the posterior region without it remains irregular in shape. When the circular manchette has been completed, the whole nucleus acquires a slender cylindrical shape. The circular manchette then changes into the longitudinal manchette. The nuclei of spermatids without a longitudinal manchette are abnormal in shape. In view of these observations it is assumed that the nuclear shaping of the spermatid may be accomplished by circular manchette and the maintenance of shape of the elongated nucleus by longitudinal manchette.The authors wish to thank Mr. Takayuki Mori for his helpful suggestions and technical advices     

Observations on the permeability of the choriocapillaris of the eye

Summary The choriocapillaris is a fenestrated capillary bed located posterior to the retinal pigment epithelium. It serves as the main source of supply to the photoreceptors, retinal pigment epithelium, and other cells of the outer retina. The permeability of these capillaries to intravenously injected ferritin (MW — approx. 480,000; mol. diam. 11 nm) was examined in the mouse, rabbit, and guinea pig, each of which is characterized by a different type of retinal vascularization. In all three species, the bulk of the ferritin remained in the capillary lumina, where it appeared to be blocked at the level of the diaphragmed fenestrae. Some ferritin was present in endothelial cell vacuoles. The results confirm previous work on the rat choriocapillaris and indicate that the barrier function of the choriocapillary endothelium is present even among species in which the retinal circulation differs significantly.Supported by NIH grant EY03418     

Separation of the pineal vesicle from the wall of the third ventricle during the post-hatching development of the chicken

Summary According to light- and electron-microscopic observations the pineal organ of the 3-day-old chicken consists of a prominent end vesicle and a tapering parenchymal stalk. During this stage the pineal lumen is in open communication with the third ventricle. However, in the 40-day-old chicken, which still possesses a well-developed end vesicle, the proximal portion of the pineal stalk displays regressive changes leading to local fragmentation. At this stage the pineal stalk is reduced, and the pineal lumen is missing. In 1-year-old chickens the parenchyma of the proximal portion of the stalk is further diminished, and in 3-year-old domestic fowl is completely displaced by bundles of collagenous fibers, only some nerve fibers being present. This post-hatching pineal development may reflect the sequence of changes leading from pineal sense organs to pineal glands.This work was supported by a grant-in-aid for Scientific Research from the Ministry of Education, Science and Culture of Japan