西藏台错晚第四纪轮藻类的新类型

本文的研究材料来自西藏羌塘高原西部台错古湖一个3.69 m的天然剖面,其地层测年为32.6-4.5ka.从其156个样品中获取大量的轮藻类、介形类和腹足类及少量有孔虫等微体化石.据轮藻类藏卵器外形,顶部结构、螺旋细胞钙化式样等特征,该剖面的轮藻类应归属于轮藻科Characeae之轮藻属Chara.经研究得知,台错古湖在...     

陕南寒武系底部磷酸盐化保存的寒武松藻属化石新知

本文描述了产于我国陕西西乡寒武系底部磷矿层中的藻类化石,在标本中发现多种藻枝保存类型和可能的"固着器"等特征;由于藻体微小、藻管中空等特征而将其归入蓝菌类寒武松藻属;可为早寒武世早期的藻类繁盛提供了新的小生境和新的食物来源、加速了后生动物的进化。     

新疆塔里木盆地西部晚二叠世轮藻类

本文研究的晚二叠世轮藻化石产自新疆塔里木盆地西南部之地表及井下剖面中,计有2属4种,其中2新种(Stomochara kulunshanensis sp. nov., Porochara moyuensis sp. nov.)。这一化石组合不同于我国目前已知的晚二叠世轮藻类组合,而与欧洲同期轮藻类组合相近,可能反映了当时塔里木盆地与欧洲气候环境相近。文中还讨论了晚古生代末期轮藻类的演化关系,指出无顶孔的Paracuneatochara应起源于早二叠世早期或晚石炭世末期的Cuneatochara或与其性状相近的某属。     

浙江桐庐早二叠世船山组介形类化石

研究报道的介形类化石系采自浙江省桐庐县瑶林镇沈村剖面早二叠世船山组,计14 属4 亚属22 种,包括4新种和4未定种。其中12属4亚属和19种产自船山组第三段,并被归为Hollinella(Praehollinella) ema ciata Basslerella ola 组合,代表早二叠世船山世隆林期。牙形刺化石主要产自船山组第一段,带化石Streptogna thodus elegantulus 及其共生的其它牙形刺化石,指明船山组第一段的时代为中、晚卡西莫夫期到早格泽里期。根据介形类动物群生态组合和岩石特征,推测船山组第三段是在温暖的近岸浅水且为低能的开阔海环境下沉积的。     

广西晚二叠世早期蓝藻化石植物群及其在煤层底板形成中的作用

一、藻类化石的分布和保存 本文所记述的蓝藻类化石由湖北省地质科学研究所、广西地质科学研究所煤田专题研究组在广西河池白土、宜山六桥、凭祥、柳州三门江和贵县右榄上二叠统合山组采集的。现以宜山六桥剖面为代表,简介如下: 上覆地层 上二叠统长兴组,灰黑色含燧石条带泥晶生物屑灰岩,富含(竹蜓)类Palaeofusulina fusiformis Sheng     

贵州早寒武世早期黑色页岩中藻类及其环境意义*

贵州早寒武世早期黑色页岩中发现了丰富的宏观藻类及疑源类化石。描述了两个宏观藻类组合 ,1新属 2新种。这些宏观藻类和疑源类化石在剖面上具有一定的分布规律 ,并伴随其它动物化石大量出现 ,两者关系密切。通过对早寒武世早期牛蹄塘组和九门冲组中生物化石的分布特征研究 ,发现在早寒武世早期海侵引起的缺氧环境背景下曾发生一次短暂的海洋充氧期 ,就在这期间生物非常繁盛 ,可能是继小壳动物之后古生代第二个生物繁盛期 ,比筇竹寺期的澄江动物群时代可能还老 ,对研究早期后生生物的起源、演化以及震旦纪 -寒武纪之交古海洋演变都具有重要意义。     

植物分类学在化石珊瑚藻(珊瑚藻目,红藻门)中的应用

最近有人认为将化石藻类的分类归入现生藻类分类单元有利于珊瑚藻作为古环境的标志,便于理解该类群的演化。然而,这样分类可能很难,因为并不是所有现生藻类分类特征都能在化石种中保存下来。Sporolithacea科的钙化部分(独立或者聚集的孢子囊群)的出现,可以把它们与这个类群的另一个现生科Corallinaceae区别开,这个科在生殖窠中产生孢子囊。节片的有无,丝间细胞的联系类型,生殖窠中孢子囊释放的数目都是用来划分Coral1inaceae科的亚科的标准,在化石样品中也可以用合适的条件进行观察。在大多数情况下,对现生珊瑚藻类属的划分特征可以在化石藻类中鉴别出来,但在几种现生珊瑚藻没有钙化的生殖结构或发育特征。因此,它们生殖结构无法与相应的化石藻类进行对比,也不能进行化石藻类的分类。近年来的趋势认为生殖结构和发育特征是对现生珊瑚藻进行分类的优先鉴定标准,然而,某些特征的稳定性在属的划分上仍然存在争论。在许多情况下,现生藻类的分类标准特征都不能在化石中保存,对古生物化石的分类标准的最佳选择是在化石藻类中选择辅助的,并且可以识别的其它鉴定特征,或者应用非正式的比现生藻类代表定义更宽的属名。     

浙江和江西二叠/三叠系界线以下的软骨鱼类微体化石——华南二叠/三叠系界线上下鱼类序列研究之五

记述了浙江长兴县煤山剖面、江西修水县四都乡东岭剖面和信丰县铁石口镇铁石口剖面二叠/三叠系界线以下的软骨鱼类10个类别的微体化石,包含5科6属5种,其中有3新属5新种,它们是:刘氏煤山鲨(Meishanselache liuigen.et sp.nov.)、王氏长兴鲨(Changxingsela-che wangigen.et sp.nov.)、东岭中华尖齿鲨(Sinacrodus donglingensis gen.et sp.nov.)、修水滑齿鲨(Lissodus xiushuiensis sp.nov.)和江西多尖齿鲨(Polyacrodus jiangxiensis sp.nov.)。浙、赣两省的这批软骨鱼类微体化石显示两个特点:组成以弓鲛超科化石为主;发现于特提斯区三叠纪的鲨类与发现于中国南方晚二叠世的鲨类具有密切的亲缘关系。这是包含全球二叠/三叠系界线层型剖面和点位(GSSP)在内的全球二叠/三叠系界线以下软骨鱼类微体化石序列的首次报道。软骨鱼类是我国鱼类化石研究中最为薄弱的一个环节,本文化石的记述大大地填补了这个薄弱环节。     

川西北上三叠统卡尼阶马鞍塘组中部硅质海绵礁

川西北地区绵竹汉旺青岩沟、观音崖以及安县雎水剖面三叠纪卡尼期马鞍塘组硅质海绵礁群生长于碳酸盐岩缓坡带,可划分为礁基、礁核、礁翼、礁间沉积等亚相,据内碎屑含量、化石埋葬学特征以及灰泥等基质比例厘定岩相和群落特征。礁灰岩主要为海绵格架岩和钙质微生物凝块岩,附礁生物类型包括有孔虫类、双壳类、棘皮类、介形类、腕足类、粗枝藻类、钙质海绵等。马鞍塘组海绵礁终结之后上覆黑色页岩沉积。晚三叠世卡尼期气候骤变在全球生物圈引发广泛的效应,海平面升降速率相对海绵礁的生长速率较大,加之构造活动频繁,大火山岩省集中爆发以及超级季风盛行,从而导致了硅质海绵礁灭绝。     

黔桂皖二叠纪末期硅泥质岩相地层中的介形类

对广西柳桥剖面、贵州晒瓦剖面和安徽平顶山西剖面晚二叠世末期硅泥质岩相地层中产出的介形类化石进行了系统分类学研究,共鉴定介形类化石30属86种,其中包括1个新属Denticupachydomella Yuan gen.nov.和2个新种Pseudobythocypris guiqianensis Yuan sp.nov.和Denticupachydomella spinosa Yuan sp.nov..该动物群主要由薄壳和个体较小的介形类组成,呈现出以古生代分子为主,同时含有少量典型中生代先驱分子(如:Abrobairdia,Lobobairdia)的混合动物群面貌.通过这些剖面之间的对比以及与前人研究资料对比,发现各剖面产出的介形类动物群具有强烈的地方性,三个剖面之间无相同分子,亦仅有20种曾报道于欧洲和东南亚等地区晚石炭世-晚二叠世地层.     

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.