Episodic evolution mediates interspecies transfer of a murine coronavirus.

Molecular mechanisms permitting the establishment and dissemination of a virus within a newly adopted host species are poorly understood. Mouse hepatitis virus (MHV) strains (MHV-A59, MHV-JHM, and MHV-A59/MHV-JHM) were passaged in mixed cultures containing progressively increasing concentrations of nonpermissive Syrian baby hamster kidney (BHK) cells and decreasing concentrations of permissive murine DBT cells. From MHV-A59/MHV-JHM mixed infection, variant viruses (MHV-H1 and MHV-H2) which replicated efficiently in BHK cells were isolated. Under identical treatment conditions, the parental MHV-A59 or MHV-JHM strains failed to produce infectious virus or transcribe detectable levels of viral RNA or protein. The MHV-H isolates were polytrophic, replicating efficiently in normally nonpermissive Syrian hamster smooth muscle (DDT-1), Chinese hamster ovary (CHO), human adenocarcinoma (HRT), primate kidney (Vero), and murine 17Cl-1 cell lines. Little if any virus replication was detected in feline kidney (CRFK) and porcine testicular (ST) cell lines. The variant virus, MHV-H2, transcribed seven mRNAs equivalent in relative abundance and size to those synthesized by the parental virus strains. MHV-H2 was an RNA recombinant virus containing a crossover site in the S glycoprotein gene. At the molecular level, episodic evolution and positive Darwinian natural selection were apparent within the MHV-H2 S and HE glycoprotein genes. These findings differ from the hypothesis that neutral changes are the predominant feature of molecular evolution and argue that changing ecologies actuate episodic evolution in the MHV spike glycoprotein genes that govern interspecies transfer and spread into alternative hosts.     

Effects of chronic exercise and deconditioning on platelet function in women

Wang, Jong-Shyan, Chauying J. Jen, and Hsiun-Ing Chen.Effects of chronic exercise and deconditioning on plateletfunction in women. J. Appl. Physiol.83(6): 2080-2085, 1997.To investigate the effects of chronicexercise and deconditioning on platelet function in women, 16 healthysedentary women were divided into control and exercise groups. Theexercise group cycled on an ergometer at 50% maximal oxygenconsumption for 30 min/day, 5 days/wk, for two consecutive menstrualcycles and then were deconditioned for three menstrual cycles. Duringthis period, platelet adhesiveness on a fibrinogen-coated surface,ADP-induced platelet aggregation and intracellular calciumconcentration elevation, guanosine 3,5-cyclic monophosphate (cGMP) content in platelets, and plasma nitric oxide metabolite levels were measured before and immediately after a progressive exercise test in the midfollicular phase. Ourresults indicated that, after exercise training,1) resting heart rates and bloodpressures were reduced, and exercise performance was improved;2) resting platelet function wasdecreased, whereas plasma nitrite and nitrate levels and platelet cGMPcontents were enhanced; and 3) thepotentiation of platelet function by acute strenuous exercise wasdecreased, whereas the increases in plasma nitrite and nitrate levelsand platelet cGMP contents were enhanced by acuteexercise. Furthermore, deconditioning reversed these training effects. This implies that training-induced platelet functional changes in women in the midfollicular phase may be mediatedby nitric oxide.

     

Inputs from upper airway affect firing of respiratory-associated midbrain neurons

Chen, Zibin, and Frederic L. Eldridge. Inputs fromupper airway affect firing of respiratory-associated midbrain neurons. J. Appl. Physiol. 83(1): 196-203, 1997.In 16 decerebrated unanesthetized cats, we studied effects ofneural inputs from upper airway on firing of 62 mesencephalic neuronsthat also developed respiratory-associated (RA) rhythmic firing whenrespiratory drive was high [Z. Chen, F. L. Eldridge, and P.G.Wagner. J. Physiol. (Lond.) 437:305-325, 1991] and on firing of 16 neurons that did notdevelop the rhythmic firing (non-RA neurons). Activity in RA neuronsincreased after mechanical expansion of pharynx (45% of those tested)or larynx (68%) and after stimulation of glossopharyngeal (50%) orsuperior laryngeal nerves (77%). The increased neuronal firingoccurred despite decreases or abolition of respiratory activity(expressed in phrenic nerve). Neuronal firing also increased aftermechanical stimulation of nasal mucosa (66%) or by jetsof air directed into the nares (48%) and after lightbrushing of nasal skin (~40%). Most stimuli led to decreased firingin a smaller number of neurons, and some neurons showed no response.None of the non-RA neurons developed an increase of firing after any ofthe stimuli, although one had decreased firing after stimulation of thesuperior laryngeal nerve. We conclude that inputs from the upper airwayand nasal skin have independent modulatory effects on the samemesencephalic neurons that are stimulated by ascending rhythmic RAinput from the medulla. These findings may have relevance to generationof the sensation of dyspnea.

     

Evidence for Linkage of Bipolar Disorder to Chromosome 18 with a Parent-of-Origin Effect

A susceptibility gene on chromosome 18 and a parent-of-origin effect have been suggested for bipolar affective disorder (BPAD). We have studied 28 nuclear families selected for apparent unilineal transmission of the BPAD phenotype, by using 31 polymorphic markers spanning chromosome 18. Evidence for linkage was tested with affected-sib-pair and LOD score methods under two definitions of the affected phenotype. The affected-sib-pair analyses indicated excess allele sharing for markers on 18p within the region reported previously. The greatest sharing was at D18S37: 64% in bipolar and recurrent unipolar (RUP) sib pairs (P = .0006). In addition, excess sharing of the paternally, but not maternally, transmitted alleles was observed at three markers on 18q: at D18S41, 51 bipolar and RUP sib pairs were concordant for paternally transmitted alleles, and 21 pairs were discordant (P = .0004). The evidence for linkage to loci on both 18p and 18q was strongest in the 11 paternal pedigrees, i.e., those in which the father or one of the father's sibs is affected. In these pedigrees, the greatest allele sharing (81%; P = .00002) and the highest LOD score (3.51; θ = 0.0) were observed at D18S41. Our results provide further support for linkage of BPAD to chromosome 18 and the first molecular evidence for a parent-of-origin effect operating in this disorder. The number of loci involved, and their precise location, require further study.     

Analysis of mtDNA variation in African populations reveals the most ancient of all human continent-specific haplogroups.

mtDNA sequence variation was examined in 140 Africans, including Pygmies from Zaire and Central African Republic (C.A.R.) and Mandenkalu, Wolof, and Pular from Senegal. More than 76% of the African mtDNAs (100% of the Pygmies and 67.3% of the Senegalese) formed one major mtDNA cluster (haplogroup L) defined by an African-specific HpaI site gain at nucleotide pair (np) 3592. Additional mutations subdivided haplogroup L into two subhaplogroups, each encompassing both Pygmy and Senegalese mtDNAs. A novel 12-bp homoplasmic insertion in the intergenic region between tRNA(Tyr) and cytochrome oxidase I (COI) genes was also observed in 17.6% of the Pygmies from C.A.R. This insertion is one of the largest observed in human mtDNAs. Another 25% of the Pygmy mtDNAs harbored a 9-bp deletion between the cytochrome oxidase II (COII) and tRNA(Lys) genes, a length polymorphism previously reported in non-African populations. In addition to haplogroup L, other haplogroups were observed in the Senegalese. These haplogroups were more similar to those observed in Europeans and Asians than to haplogroup L mtDNAs, suggesting that the African mtDNAs without the HpaI np 3592 site could be the ancestral types from which European and Asian mtDNAs were derived. Comparison of the intrapopulation sequence divergence in African and non-African populations confirms that African populations exhibit the largest extent of mtDNA variation, a result that further supports the hypothesis that Africans represent the most ancient human group and that all modern humans have a common and recent African origin. The age of the total African variation was estimated to be 101,000-133,000 years before present (YBP), while the age of haplogroup L was estimated at 98,000-130,000 YBP. These values substantially exceed the ages of all Asian- and European-specific mtDNA haplogroups.     

Sublocalization of an Ataxia-Telangiectasia Gene Distal to D11S384 by Ancestral Haplotyping In Costa Rican Families

In an effort to localize a gene for ataxia-telangiectasia (A-T), we have genotyped 27 affected Costa Rican families, with 13 markers, in the chromosome 11q22-23 region. Significant linkage disequilibrium was detected for 9/13 markers between D11S1816 and D11S1391. Recombination events observed in these pedigrees places A-T between D11S1819 and D11S1960. One ancestral haplotype is common to 24/54 affected chromosomes and roughly two-thirds of the families. Inferred (ancestral) recombination events involving this common haplotype in earlier generations suggest that A-T is distal to D11S384 and proximal to D11S1960. Several other common haplotypes were identified, consistent with multiple mutations in a single gene. When considered together with all other evidence, this study further sublocalizes the major A-T locus to ≈200 kb, between markers S384 and S535.     

摇蚊幼虫对底泥中氮、磷释放作用的研究

本文研究了摇蚊幼虫对底泥中氮、磷释放的影响,初步探讨了摇蚊在湖泊富营养化过程中的生态作用。结果表明,摇蚊幼虫能明显促进底泥中氮、磷的释放,而释放到水层中的氮、磷又容易被藻类吸收利用,从而促进藻类生长。这种生态效应与水体营养循环和富营养化的发生及发展过程间存在着重要的关系。     

濒危植物——长喙毛茛泽泻的雌雄配子体发育

长喙毛茛泽泻 Ranalisma rostratum stapf 小孢子母细胞的减数分裂过程为连续型,四分体为左右对称型。成熟花粉为三胞花粉。花药绒毡层为变形绒毡层。雌蕊由多数单室子房构成,每子房中含一具双珠被、薄珠心的倒生胚珠。胚囊发育为葱型。成熟胚囊中三个反足细胞退化;二个极核分别位于中央细胞的两端,其体积相差明显。这种极核分布可能与反足细胞过早退化有关。     

籼稻的抗冷性与亲本的关系

四个籼稻（Ｏｒｙｚａ ｓａｔｉｖａ Ｌ．）品种幼苗经１℃黑暗或光照２５０ μｍ ｏｌ·ｍ － ２·ｓ－ １处理后,抗冷的“桂山矮选３”比不抗冷的“青华６ 号”幼苗存活率高,其子代是以“桂山矮选３”为母本的比“青华６ 号”为母本的存活率较高。抽穗期剑叶经光照低温处理１２、２４ 和３６ ｈ 后,光合作用是“桂山矮选３”和以“桂山矮选３”为母本的子代比“青华６ 号”和以“青华６ 号”为母本的子代下降较少。呼吸作用是前者比后者在处理１２ ｈ 时有明显升高现象。荧光参数Ｆｖ／Ｆｏ和Ｆｖ／Ｆｍ比值在处理２４ ｈ 时前者比后者下降明显,但在常温下恢复则是前者比后者明显较快。自然低温（寒露风）对叶绿素荧光的影响亦有相似的规律。对水稻后代的抗冷性倾向于母本进行了讨论     

脱落酸对线粒体Na^＋—K^＋ATPase活性的影响

在提取大豆（Ｇｌｙｃｉｎｅ ｍ ａｘ）黄化子叶的线粒体时,于清洗和悬浮介质中加入ＡＢＡ,发现４０ μｍ ｏｌ／Ｌ（±） ＡＢＡ 对线粒体膜结合Ｎａ＋ －Ｋ＋ ＡＴＰａｓｅ 活性及线粒体吸氧速率有明显的促进作用。ＡＢＡ 可使１６℃与２７℃培养的大豆子叶线粒体膜结合Ｎａ＋ －Ｋ＋ ＡＴＰａｓｅ Ａｒｒｈｅｎｉｕｓ图的折点温度分别下降６．３℃和５．９℃,并将该酶的底物动力学曲线由正协同曲线转变为非协同曲线。表明ＡＢＡ 可降低线粒体的膜相变温度