Evolution ofMHC polymorphism: Extensive sharing of polymorphic sequence motifs between human and bovine DRB alleles

The evolution ofMHC polymorphism has been studied by comparing the amino acid and nucleotide sequences of 14 bovine and 32 humanDRB alleles. The comparison revealed an extensive sharing of polymorphic sequence motifs in the two species. Almost identical sets of residues were found at several highly polymorphic amino acid positions in the putative antigen recognition site. Consequently, certain bovine alleles were found to be more similar to certain human alleles than to other bovine alleles. In contrast, the frequencies of silent nucleotide substitutions were found to be much higher in comparisons between species than within species implying that none of the human or bovine DRB alleles originated before the divergence of these distantly related species. The results suggest that the observed similarity inDRB polymorphism is due to convergent evolution and possibly the sharing of short ancestral sequence motifs. However, the relative role of the latter mechanism is difficult to assess due to the biased base composition in the first domain exon of polymorphic class 11 genes. The frequency of silent substitutions betweenDRB alleles was markedly lower in cattle than in man suggesting that theDRB diversity has evolved more rapidly in the former species.     

新疆博格达山地面生地衣群落数量分类及物种多样性

根据对新疆博格达山地面生地衣群落27个样点(20 m×20 m)调查的数据,以各地衣种的盖度为指标结合双向指示种分析方法(TWINSPAN)和除趋势对应分析法(DCA)对博格达山地面生地衣群落进行数量分类并分析了群落结构特征及其多样性和相似性。采用典范对应分析法(CCA)对各群落的物种分布格局与环境因子的关系进行了探讨。结果表明,TWINSPAN分析和DCA排序将分布在博格达山的37种地面生地衣分为以下5个群丛。群丛1:膜地卷(Peltigera membranacea)+伴藓大孢蜈蚣衣(Physconia muscigena)群丛;群丛2:地卷(Peltigera rufescens)+伴藓大孢蜈蚣衣(Physconia muscigena)群丛;群丛3:裂边地卷(Peltigera degenii)+平盘软地卷(Peltigera elisabethae)群丛;群丛4:喇叭石蕊(Cladonia pyxidata)+犬地卷(Peltigera canina)群丛;群丛5:盾鳞衣(Placidium squamulosum)+缠结茸枝衣(Seirophora contortuplic...     

新疆褐家鼠种群生命表及其在干旱区的生存能力分析

从2000年至今,曾于野外捕捉的褐家鼠3 837只,其中雌鼠2 685只,雄鼠1 152只,经鉴定划分为幼年组(Ⅰ)、亚成年组(Ⅱ)、成年Ⅰ组(Ⅲ)、成年Ⅱ组Ⅳ、老年组(Ⅴ)等5个年龄组,其年龄结构探讨种群数量动态,结果表明,种群中Ⅱ龄的平均生命期望值最高1.0357,其次为Ⅲ龄0.9488。该种群中1龄个体占优势地位,种群属于增长性种群,种群内禀增长率rm为0.2789/年,年周限增长率λ为1.3217,世代时间T为2.623年,种群经一世代的净增殖率R0为2.0782。     

Fear-conditioning mechanisms associated with trait vulnerability to anxiety in humans

Investigations of fear conditioning in rodents and humans have illuminated the neural mechanisms underlying cued and contextual fear. A critical question is how personality dimensions such as trait anxiety act through these mechanisms to confer vulnerability to anxiety disorders, and whether humans' ability to overcome acquired fears depends on regulatory skills not characterized in animal models. In a neuroimaging study of fear conditioning in humans, we found evidence for two independent dimensions of neurocognitive function associated with trait vulnerability to anxiety. The first entailed increased amygdala responsivity to phasic fear cues. The second involved impoverished ventral prefrontal cortical (vPFC) recruitment to downregulate both cued and contextual fear prior to omission (extinction) of the aversive unconditioned stimulus. These two dimensions may contribute to symptomatology differences across anxiety disorders; the amygdala mechanism affecting the development of phobic fear and the frontal mechanism influencing the maintenance of both specific fears and generalized anxiety.     

圈养塔里木马鹿白昼活动时间分配及行为格局的初步研究

2004年10月3日至12日,在新疆南部且末县塔特让乡塔里木马鹿人工饲养场对15只圈养塔里木马鹿的活动时间分配及种群的站立和运动、休息(静卧)、摄食和饮水、反刍等4种行为,采用目标及扫描取样方法进行了观察,并对各行为的发生率进行了统计分析．结果表明：圈养塔里木马鹿白天用大多数时间来休息和静卧,摄食集中于早晨和晚上,反刍行为出现在摄食后,通常在中午和下午的高温下,停止摄食活动,进行反刍．另外圈养塔里木马鹿对栖息地环境有明显的选择行为,其喜好程度依次为干土地、摄食区、沼泽地、水泥地、水沟．     

Monodehydroascorbate Reductase in Spinach Chloroplasts and Its Participation in Regeneration of Ascorbate for Scavenging Hydrogen Peroxide

The primary reaction product of chloroplast ascorbate peroxidaseactivity was shown to be monodehydroascorbate radical (MDA).MDA reductase (EC 1.6.5.4 [EC] ) was localized in spinach chloroplaststroma. The MDA reductase activity of spinach chloroplasts,using NAD(P)H as electron donor, could account for the regenerationof ascorbate from MDA produced by ascorbate peroxidase activity.In the absence of MDA reductase, MDA disproportionated to ascorbate(AsA) and dehydroascorbate (DHA). The DHA was reduced to AsAby DHA reductase (EC 1.8.5.1 [EC] ) in chloroplasts. Both NADH andNADPH served as the electron donor of partially purified MDAreductase from spinach leaves. (Received September 24, 1983; Accepted January 23, 1984)     

LC-MS/MS-based metabolic profiling of Escherichia coli under heterologous gene expression stress

Escherichia coli is frequently exploited for genetic manipulations and heterologous gene expression studies. We have evaluated the metabolic profile of E. coli strain BL21 (DE3) RIL CodonPlus after genetic modifications and subjecting to the production of recombinant protein. Three genetically variable E. coli cell types were studied, normal cells (susceptible to antibiotics) cultured in simple LB medium, cells harboring ampicillin-resistant plasmid pET21a (+), grown under antibiotic stress, and cells having recombinant plasmid pET21a (+) ligated with bacterial lactate dehydrogenase gene grown under ampicillin and standard isopropyl thiogalactoside (IPTG)-induced gene expression conditions. A total of 592 metabolites were identified through liquid chromatography-mass spectrometry/mass spectrometry analysis, feature and peak detection using XCMS and CAMERA followed by precursor identification by METLIN-based procedures. Overall, 107 metabolites were found differentially regulated among genetically modified cells. Quantitative analysis has shown a significant modulation in DHNA-CoA, p-aminobenzoic acid, and citrulline levels, indicating an alteration in vitamin K, folic acid biosynthesis, and urea cycle of E. coli cells during heterologous gene expression. Modulations in energy metabolites including NADH, AMP, ADP, ATP, carbohydrate, terpenoids, fatty acid metabolites, diadenosine tetraphosphate (Ap4A), and l -carnitine advocate major metabolic rearrangements. Our study provides a broader insight into the metabolic adaptations of bacterial cells during gene manipulation experiments that can be prolonged to improve the yield of heterologous gene products and concomitant production of valuable biomolecules.     

Rutin as promising drug for the treatment of Parkinson’s disease: an assessment of MAO-B inhibitory potential by docking,molecular dynamics and DFT studies

ABSTRACT

Inhibitors of monoamine oxidase (MAO)-B have been used for many years in the therapy of Parkinson’s disease (PD). Owing to the safety concerns of the currently used agents, the discovery of novel scaffolds is of considerable interest. MAO-B inhibitory potential of rutin, a flavonoid derived from natural sources, has been established in experimental findings. Hence, the current study seeks to examine the interactions between rutin and crystal structure of human MAO-B enzyme. Molecular docking calculations, as well as molecular dynamics simulations, were employed to investigate the binding mode and the stability of the rutin/MAO-B complex. Energies of highest occupied/lowest unoccupied molecular orbitals were computed through DFT studies and used to calculate electron affinity, hardness, chemical potential, electronegativity, and electrophilicity index in order to investigate the capability of these parameters to influence the ligand–receptor interactions. It was found that rutin traverses both the entrance cavity and the substrate cavity, forcing the Ile-199 ‘gate’ to rotate into its open conformation. It results in the fusion of the two cavities of the MAO-B binding site and directly leads to better binding interactions. Results of the current study can be used for lead modification and development of novel drugs for the treatment of PD.