Occurrence of pollen and spores in relation to present-day vegetation in a Dutch heathland area

Abstract. Pollen, spores and fungal remains in moss cushions along a transect, traversing a Betula-Quercus forest and a surrounding heathland, were analysed in order to study the relation between present-day vegetation and recent pollen deposition. Pollen and spores are divided into local types from plant species encountered along the transect and regional types, not present along the transect. Relative percentages and absolute concentration of the palynomorphs were estimated. Radiocaesium activity in the moss was measured to assess the minimal duration of palynomorph accumulation (i.e. the age of the moss samples). The absence of simultaneous trends in the regional pollen types indicates that the samples do not have major differences in age. The moss represents the later stages in the heath mosaic cycle. This is supported by the radiocaesium content of the moss. Thus, in this case the concentration values of regional pollen approach deposition values. The values of the local pollen types calculated on such a rather constant regional pollen flux is considered to represent real differences in the local deposition. The local pollen types can be arranged topographically into five groups characteristic of the local vegetation types and their ecotones. The arrangement of the curves of types from phyco-, zoo-, and myco-coenoses suggests their possible origin, either locally from the heath area or from the Betula-Quercus forest, or regionally from elsewhere. Analyses and topographical arrangement of the curves of unknown types contribute in this way to their identification and their possible source of origin.     

Clarke-Carbon公式的推导

Clarke-Carbon公式用于估计一个完整的基因文库所需的最少克隆数。本文通过建立基因克隆的统计模型,利用二项分布原理对该公式进行了推导,从而有利于在教学过程中对这一公式的确切理解。 Abstract:Clarke-Carbon equation can give a good estimation for the necessary number of recombinants in a gene library.By establishing a statistical model of process of cloning, a deduction and interpretation of this equation can be obtained according to the principle of binomial distribution.This will help to understand the equation more accurately for the teachers and learners.     

国产湖瓜草,球柱草和芙兰草三属果皮微形态特征初探

首次对国产莎草科湖瓜草属、球柱草属和芙兰草属植物的果皮微形态特征进行了扫描电镜的比较观察。结果表明,上述三属果皮纹饰有三种类型：即网状纹饰、疣状纹饰和复合纹饰。其微形态特征存在着明显的种间区别,可为种的划分提供重要依据。研究结果为上述三属植物的分类提供新的佐证,亦为系统演化和亲缘关系的研究提供有价值的资料。     

Dragons in Distress: Naturalists as Bioactivists in the Campaign to Save the American Alligator

This article explores the scientific and environmental activism of a group of naturalists who not only studied but also advocated on behalf of an unlikely organism: the American alligator (Alligator mississippiensis). A large, toothy reptile that once inhabited wetlands across much of the southeastern United States, the alligator had long been reviled as a fearsome predator and pursued as a valuable commodity. At the end of the nineteenth and the beginning of the twentieth centuries, a small group of naturalists began to note its precipitous decline and to issue calls for its protection. Initially they tended to do so working individually, largely within the pages of scientific and governmental publications devoted to the species. By the middle of the twentieth century, however, as habitat destruction joined commodification to further threaten the alligator, naturalists banded together with state officials, conservationists, and other wildlife enthusiasts to form the American Alligator Council. That organization not only promoted research on the alligator but also secured local, state, and federal protection of the increasingly beleaguered species, thereby snatching it from the jaws of impending extinction. The naturalists examined in this article were not only producers and purveyors of knowledge, then; they were also bioactivists, biologists with a strong political agenda who firmly embraced the practice of engaging in the public sphere.     

杜鹃花科Vaccinium wardii Adamson的订正

通过对模式标本和原始文献的研究,确认Vaccinium wardii Adamson 是红粉白珠(Gaultheria hookeri C. B. Clarke)的异名,而不是乌鸦果(Vaccinium fragile Franch.)的异名.     

Identification and immunochemical characterization of spermatogenic cell surface antigens that appear during early meiotic prophase

Three spermatogenic cell populations isolated from prepuberal mice--type B spermatogonia, preleptotene spermatocytes, and leptotene/zygotene spermatocytes--were used to elicit distinct polyclonal antisera. Surface binding specificities were determined for purified IgGs by indirect immunofluorescence and rosette assays on live cells. Binding activities were assayed both before and after absorptions with a variety of somatic and spermatogenic cells. Each of these antisera binds to surface antigens that are present on germ cells throughout spermatogenesis and are not shared by splenocytes, thymocytes, and erythrocytes. Only the antiserum raised against leptotene and zygotene spermatocytes (ALZ) recognizes a stage-specific subset of surface determinants. After appropriate absorptions, ALZ binds to the surface of early pachytene spermatocytes and germ cells at subsequent stages of differentiation, including vas deferens spermatozoa. Antigens which react with this absorbed IgG are not detected on the surface of spermatogonia or meiotic cells prior to pachynema, including leptotene and zygotene spermatocytes. The observed binding specificities may result from the synthesis of one or more surface molecules during the early meiotic stages, followed by delayed insertion into the plasma membrane during the pachytene stage of meiotic prophase. Stage-specific antigens recognized by ALZ, including both protein and probably lipid, have been localized immunochemically on nitrocellulose blots from one-dimensional SDS gels. A dithiothreitol-sensitive constituent (Mr approximately 39,000) recognized by ALZ has been identified as the major protein determinant present in early meiotic cells but absent in 8-day-old seminiferous cell suspensions containing spermatogonia and Sertoli cells. This determinant is present in populations of preleptotene, leptotene/zygotene, and early pachytene spermatocytes isolated from 17-day-old animals, an observation consistent with the hypothesis of delayed insertion into the plasma membrane.     

Reduction and Subsequent Binding of Ruthenium Ions Catalyzed by Subcellular Components

The reduction of Cl(NH₃)₅Ru(III) and subsequent binding of heterocyclic ligands by the resultant (H₂O)(NH₃)₅Ru(II) ion is shown to be catalyzed by components of rat-liver cells. The presence of air significantly decreases the rate of heterocyclic ligand binding. In the case of microsome and soluble component catalysis, this is probably due to oxidation of the Ru(II) ion prior to complexation. Various inhibitors of electron-transfer proteins were employed in an effort to determine the preferred reducing species. These results lend support to the hypothesis that the antitumor activity of acido ruthenium(III) ammine complexes involves activation by reduction in vivo prior to metal coordination to nucleic acids. Anticancer drugs functioning by this mechanism may be preferentially toxic to or may localize in hypoxic areas of tumors.     

中国篦齿蕨属植物（水龙骨科）一新组合种

根据叶绿体rbcL和rps4-trnS序列及叶脉类型、孢子纹饰特征等证据,栗柄水龙骨Polypodiodes microrhizoma（C.B.Clarke ex Baker）Ching属于篦齿蕨属Metapolypodium Ching的范畴,因此将其组合到篦齿蕨属MetapolypodiumChing之下更合理。文中报道了该新组合种,即栗柄篦齿蕨Metapolypodium microrhizomum（C.B.Clarke ex Baker）S.G.Lu et L.H.Yang。     

白叶蒿挥发油成分研究

目的：分析白叶蒿的化学成分。方法：采用水蒸气蒸馏法提取,运用毛细管气相色谱-质谱联用法对白叶蒿挥发性化学成分进行了分析,用气相色谱面积归一化法测定了各成分的相对百分含量。结果：经毛细管色谱分离出31个峰,并鉴定出峰所对应的化合物。其主要化学成分为2,5-辛二烯（41．41％）;（z,z）-3,5辛二烯（17．87％）;桉油醇（6．75％）;3,3,6-三甲基-1,5-庚二烯-4-酮（3．26％）;1-甲氧基-4-（2-丙烯基）-苯（2．79％）;3,3,4,4-四甲基己烷（2．71％）;1R—α-蒎烯（2．67％）;（1-甲基-1,2-丙二烯基）环丙烷（2．61％）;7,11-二甲基-3-亚甲基-1,6,10-十二碳三烯（2．30％）等。结论：报道了白叶蒿的化学成分,为进一步开发利用提供了科学依据。