鸭跖草科杜若(Pollia japonica Thunb.)的减数分裂研究

首次对鸭跖草科杜若(Pollia japonicaThunb.)进行了花粉母细胞减数分裂观察,并重新报道了该种的染色体数目为2n=32。结果显示,减数分裂中期I构型为16Ⅱ,并且观察到次级联会现象。减数分裂后期I和后期Ⅱ存在落后染色体、染色体断片、二次分裂不同步等异常现象,统计各时期畸形率都低于10%。随机统计花粉粒活性,成熟率达到90%以上。这说明杜若的减数分裂过程基本正常,也证明了2n=32的体细胞染色体数目是可信的。     

蓼科羊蹄减数分裂过程的观察

首次对蓼科酸模属植物羊蹄（Rumex japonicus Houtt．）进行了花粉母细胞减数分裂观察。减数分裂后期Ⅰ和后期Ⅱ存在染色体桥、染色体断片和落后染色体等异常现象,统计各时期畸形率都低于5％。随机统计花粉粒活性,成熟率达到95％。羊蹄的减数分裂过程基本正常,也证实了羊蹄的体细胞染色体数目2n=2x=100是可信的。     

斑叶蒲公英的核型分析和花粉母细胞的减数分裂观察

采用根尖压片法确定斑叶蒲公英的染色体数目,通过分析斑叶蒲公英核型及花粉母细胞减数分裂过程,以确定其倍性水平。结果表明:(1)斑叶蒲公英根尖细胞染色体数目为32条,核型公式为2n=3x+x′=32=(18m+6sm)+(3m+4sm+1T),属于2A型。(2)斑叶蒲公英花粉母细胞减数分裂为同时型胞质分裂,四分体的排列方式以正四面体型居多,十字交叉型偏少,偶见左右对称型。(3)前期Ι染色体的构型复杂,中期Ι和中期Ⅱ有赤道板外染色体;后期Ι和后期Ⅱ出现落后染色体、染色体桥及断片;后期Ⅱ和末期Ⅱ还出现染色体分离不同步及不均等分裂的现象;四分体时期出现二分体、三分体、含微核的异常四分体及多分体等异常现象。(4)对其花粉进行离体萌发试验,花粉萌发率只有26.3%,说明斑叶蒲公英是异源四倍体,32条染色体不均等的减数分裂异常,造成花粉活性较低。     

秤锤树的核型研究及其减数分裂过程的观察

观察研究了秤锤树有丝分裂和减数分裂的细胞学特征。秤锤树核型为2n=2x=24=4m 7sm(2SAT) 1st,属于较为原始的2A型。有丝分裂间期核为复杂染色中心型,前期出现B染色体,中期染色体中等大小。减数分裂中期具12对正常的二价体,但后期I和后期Ⅱ均有染色体异常现象发生。统计断片、落后染色体和染色体桥出现的比例与花粉粒败育性比例比较一致,表明秤锤树的小孢子在发生和发育过程中较高频率的败育现象可能存存一常的细胞学原因．     

黄芩的花粉母细胞减数分裂及核型分析

采用压片法,对黄芩花粉母细胞减数分裂及核型进行了研究。结果表明:黄芩的大多数花粉母细胞减数分裂中染色体的行为正常,在终变期同源染色体配对后可形成9个二价体,后期Ⅰ染色体以9∶9的方式向细胞两极分离,其减数分裂为同时型;在少数花粉母细胞减数分裂中观察到落后染色体、染色体桥等异常行为;其花粉粒育性为76.49%。黄芩的染色体数目为2n=2X=18,核型公式为K(2n)=2X=18=16m+2 sm,染色体相对长度组成为2n=1 s+4M1+3M2+1L,其核型为"1A"型。     

石竹花粉母细胞减数分裂的观察

采用常规压片法对石竹(Dianthus chinensis L.)花粉母细胞减数分裂进行了细胞学观察。结果表明,减数分裂过程中存在二价体提前分离、赤道板外染色体、落后染色体、染色体不均等分离等异常现象,各时期的畸形率都低于3%,石竹的减数分裂过程基本正常,石竹染色体数目2n=2x=30。     

白花丹参的核型分析及小孢子发生过程观察

对白花丹参(Salvia miltiorrhiza f.alba)进行了核型分析及小孢子发生过程观察.结果表明,白花丹参染色体数目为2n=16,核型公式为2n=16=8m+8sm,其中2条染色体具有随体,没有观察到多倍体细胞和B染色体;16条染色体在减数分裂中期I正常配对形成8个二价体,减数分裂的胞质分裂属于同时型;在白花丹参的减数分裂前期I观察到频率较高的细胞融合现象.白花丹参的核型为2B型,其花粉母细胞中的细胞融合现象为首次报道.     

关于2n和n在减数分裂中用法的商榷

在科学研究论文、高中生物、大学细胞生物学和遗传学减数分裂教学中,减数分裂I终变期细胞中的染色体数目的表示是用n还是用2n,目前还比较混乱,有的用n表示,但也有的用2n表示。该文通过对减数分裂I终变期细胞染色体行为和数目的分析,认为减数分裂I终变期细胞中的染色体数目应该用2n表示。     

白菜型油菜(B. Chinensis)与海甘蓝(Crambe abyssinica)属间杂种的细胞学观察

白菜型油菜与海甘蓝属间杂种F₁代染色体数目早期为2n=55。经多代组培无性繁殖后,杂种染色体大量减少,数目变化于25～28条间,平均为26条。杂种PMC减数分裂中,平均配对构型为0.06Ⅲ+11.26Ⅱ+3.80Ⅰ,二价体数目变化于8～13之间,以10Ⅱ、11Ⅱ、12Ⅱ的细胞出现频率较高,分别为26.60%,23.91%和30.98%,单价体数目变化于0～8个之间。杂种染色体数目减少,二价体个数较高,这说明海甘蓝染色体在大量丢失的同时,白菜型油菜的染色体组发生了自然加倍。在后期Ⅱ观察到三分体、染色体落后、染色体桥等异常现象。      

麦蓝菜的花粉母细胞减数分裂及核型分析

采用压片法,对麦蓝菜的花粉母细胞减数分裂及体细胞核型进行了研究。结果表明,麦蓝菜的绝大多数花粉母细胞减数分裂中染色体的行为正常,在终变期同源染色体配对后可形成15个二价体;在少数花粉母细胞减数分裂中观察到落后染色体、染色体桥等异常行为;其减数分裂为同时型,其花粉粒育性为88.04%。麦蓝菜的染色体数目为2n=2X=30,核型公式为K(2n)=2X=30=22m(2SAT)+8 sm,染色体相对长度组成为2n=16M2+14M1,其核型为"1A"型。     

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.