Development of in vitro toxicity tests with cultures of freshly isolated rat hepatocytes

Summary Freshly isolated and cultured hepatocytes were analyzed by two-parameter flow cytometry. The combined analysis of DNA and cellular protein content allowed the contribution of ploidy classes and of subpopulations within a ploidy class to be defined. Analysis of hepatocytes during exposure to dimethylsulfoxide (DMSO), phenobarbital (PB), low oxygen tension (5% O₂) or fetal calf serum (FCS), provided insight into the dynamic response of individual ploidy classes as a function of culture time. By analogy with the age-dependent ploidy shifts in vivo, hepatocyte-cultures shift towards adult animals during exposure to DMSO and towards young animals when cultured at low pO₂ (4% O₂). FCS and phenobarbital disturb this constitutive ploidy balance. FCS increased the 2 N cell population, where stem cells probably respond to the proliferative stimuli provided by growth factors in the serum. Phenobarbital affects the liver-specific 4 N hepatocytes, which agrees with effects seen in liver after exposure in vivo. It is suggested that drug-induced pathological alterations in ploidy in hepatocyte cultures could serve as indicators of compounds, such as liver tumor promoters, which interfere with cell differentiation in liver. The heterotypic cell-cell interaction of freshly isolated hepatocytes with isolated, in vitro cultured, rat liver epithelial cells in co-cultures proved to be a valuable concept in toxicity testing: aldrin epoxidase, an enzyme system involved in xenobiotic metabolism, was stabilized for more than two weeks. After exposure to the three chemicals, 2-acetylaminofluoren, procarbazine and cyproterone-acetate, a preferential toxicity for each compound and cell population was established. Thus heterotypic cell cultures can considerably increase the amount of information available from in vitro studies.The final concept, combining monitoring of cellular DNA (ploidy) and protein content in hepatocyte cultures during and after exposure to a given test compound at tissue oxygen tension with the heterotypic cell-cell interaction, would create a more in vivo-like culture system. This would enhance the predictability of hepatocyte cultures and contribute to a more widespread use of the test system and as a result help to reduce the number of whole-animal tests.     

对申小龙文化语言学的认识

80年代，中国语言学研究领域出现了文化语言学的热潮．申小龙举起大旗，深入民间，轰轰烈烈地倡导文化语言学，引起了强烈反响。时至今日，我们回头重新审视这一热潮，不无启示作用。     

应用PCR技术检测结核菌的临床研究

应用聚合酶链反应（ＰＣＲ）技术对２４４例呼吸疾病患者临床标本进行结核菌ＤＮＡ检测，并同时与涂片抗酸染色结果进行比较。结果显示：１１２例结核标本涂片和ＰＣＲ检测阳性率分别为１６．１％和５２．７％，两者差别有显著性（Ｐ＜０．０１）。９４例涂阴结核标本ＰＣＲ阳性达４５．７％。结果表明应用ＰＣＲ技术检测结核杆菌ＤＮＡ具有快速敏感、特异性较高等优点，尤其对涂阴病人具有较大诊断价值     

Mitochondrial DNA variation in geographic populations of Colorado potato beetle,Leptinotarsa decemlineata (Coleoptera; Chrysomelidae)

Summary This study demonstrates variability in restriction enzyme cleavage sites of mitochondrial DNA (mtDNA) among four popalations of Colorado potato beetle (CPB). A suite of three enzymes (EcoRI,HpaI,PstI) was sufficient to discriminate among the populations tested. Individuals heteroplasmic for restriction enzyme patterns were found in some populations. Variability in CPB mtDNA should prove useful in efforts to trace the origin and dispersal of the species in North America.     

EC109细胞株细胞周期DNA代谢和形态改变的研究

人食管癌细胞株 EC109以显微分光光度计测定癌细胞核 DNA 含量,以放射自显影测定细胞核摄取~3H-TdR 和扫描电镜检查细胞表面的超微结构.大多数 EC109瘤细胞间期细胞核的 DNA 含量增加,主要干系细胞 DNA 含量为2 C,属 G_1期,也可见低于四倍体(3 C),高于四倍体(>4 C).甚至多倍体(>8 C)的瘤细胞.~3H-TdR 加入培养基10分钟后,许多瘤细胞核有银粒出现(S 期细胞).大量细胞进入细胞周期反映其恶性程度高.扫描电镜可见 EC109在细胞周期不同阶段其细胞大小形状和微绒毛也不同.本文结果说明用细胞核 DAN 含量测定,~3H-TdR 掺入和细胞表面超微结构可测定肿瘤周期.也可用这些方法判定瘤细胞的恶性程度.     

PCR技术对肺炎支原体DNA的检测

作者首次在国内利用自己的条件完成了肺炎支原体从培养基制备、实验室培养、菌种检定、引物设计、ＤＮＡ提取．到ＰＣＲ扩增条件的摸索、产物检测等一整套技术,与非肺炎支原体、部分相关细菌进行了鉴别,并同时进行了临床样品和模拟样品的实验,结果表明该方法的特异性和灵敏性都是好的．     

Phylogeny and rapid Northern and Southern Hemisphere speciation of goldfinches during the Miocene and Pliocene Epochs

Mitochondrial cytochrome b (cyt b) from 25 out of 31 extant goldfinches, siskins, greenfinches and redpolls (genus Carduelis) has been sequenced from living samples taken around the world, specimens have also been photographed. Phylogenetic analysis consistently gave the same groups of birds, and this grouping was generally related to geographical proximity. It has been supposed that Pleistocene glaciations played a crucial role in the origin of extant diversity and distribution of Northern Hemisphere vertebrates. Molecular comparison of most extant songbird species belonging to the genus Carduelis does not support this assertion. The fossil record of chicken and pheasant divergence time has been used to calibrate the molecular clock; cyt b DNA dendrograms suggest that speciation in Carduelinae birds occurred during the Miocene and Pliocene Epochs (9 – 2 million years ago) in both the Northern and Southern Hemispheres. Only about 4% average amount of nucleotide substitution per lineage is found between the most distant Carduelis species; this suggests a remarkably rapid radiation when compared with the radiation of other passerine songbird genera. In addition, a continuum of small songbird speciation may be found during the Miocene Epoch in parallel with speciation of other orders (i.e. Galliformes, chicken/pheasant). Pleistocene glaciations may have been important in subspeciation (i.e. Eastern European grey-headed goldfinches/Western European black-headed goldfinches) and also in ice-induced vicariance (isolation) (i.e. siskin in Western Europe vs. siskin in Far East Asia) around the world. European isolated Serinus citrinella (citril finch) is not a canary, but a true goldfinch. South American siskins have quickly radiated in the last 4 million years coinciding with the emergence of the Isthmus of Panama; probably, a North American siskin related to C. notata invaded a suitable and varied biotope (the South American island) for Carduelis birds. North American goldfinches may be renamed as siskins, because they have a distant genetic relationship with European goldfinches. Genus Acanthis could be dropped, and thus redpolls should be separated from twite and linnet, the latter (Europeans) probably being related to American goldfinches. Also, reproductive barriers are observed between closely related species and not between other more distant ones. Finally, a tentative classification for genus Carduelis species is suggested. Received 6 March 1998; received after revision 3 July 1998; accepted 7 July 1998