NMR and CD studies of triple-helical peptides.

Triple-helix formation of the peptide (Pro-Hyp-Gly)10 was monitored by nmr and CD spectroscopy. The two-dimensional nmr spectra indicated that the Gly C alpha H and Pro C delta H proton resonances shift upfield in going from the nonhelical to helical form, while hydroxy-proline resonances are unchanged. The integrated areas of the helical and nonhelical resonances could be monitored in the one-dimensional nmr spectrum, and indicate that in the (Pro-Hyp-Gly)10 about 90% of the residues are in a defined triple-helical conformation. The introduction of a glycine to alanine substitution or the deletion of a single hydroxyproline residue in the stable triple-helical peptide (Pro-Hyp-Gly)10 still allows trimers to be formed, but the trimers show a substantial loss of triple helix and decreased thermal stability compared with (Pro-Hyp-Gly)10. Two computer models were generated for the Gly----Ala peptide, one with the Ala side chains packed inside the helix and the other with the region containing the alanines forming a beta-bend that loops out from the helix. The nmr data is more consistent with the latter model.     

Screening and analysis of differentially expressed genes from an alien addition line of wheat Thinopyrum intermedium induced by barley yellow dwarf virus infection.

The alien addition line TAI-27 contains a pair of chromosomes of Thinopyrum intermedium that carry resistance against barley yellow dwarf virus (BYDV). A subtractive library was constructed using the leaves of TAI-27, which were infected by Schizaphis graminum carrying the GAV strain of BYDV, and the control at the three-leaf stage. Nine differentially expressed genes were identified from 100 randomly picked clones and sequenced. Two of the nine clones were highly homologous with known genes. Of the remaining seven cDNA clones, five clones matched with known expressed sequence tag (EST) sequences from wheat and (or) barley whereas the other two clones were unknown. Five of the nine differentially expressed sequences (WTJ9, WTJ11, WTJ15, WTJ19, and WTJ32) were highly homologous (identities >94%) with ESTs from wheat or barley challenged with pathogens. These five sequences and another one (WTJ18) were also highly homologous (identities >86%) with abiotic stress induced ESTs in wheat or barley. Reverse Northern hybridization showed that seven of the nine differentially expressed cDNA sequences hybridized with cDNA of T. intermedium infected by BYDV. Three of these also hybridized with cDNA of line 3B-2 (a parent of TAI-27) infected by BYDV. The alien chromosome in TAI-27 was microdissected. The second round linker adaptor mediated PCR products of the alien chromosomal DNA were labeled with digoxygenin and used as the probe to hybridize with the nine differentially expressed genes. The analysis showed that seven differentially expressed genes were homologous with the alien chromosome of TAI-27. These seven differentially expressed sequences could be used as ESTs of the alien chromosome of TAI-27. This research laid the foundation for screening and cloning of new specific functional genes conferring resistance to BYDV and probably other pathogens.     

Characterization of an Escherichia coli mutant, feeA, displaying resistance to the calmodulin inhibitor 48/80 and reduced expression of the rare tRNA3Leu

We previously described a mutation feeB1 conferring a temperature-sensitive filamentation phenotype and resistance to the calmodulin inhibitor 48/80 in Escherichia coli, which constitutes a single base change in the acceptor stem of the rare tRNA₃^Leu recognizing CUA codons. We now describe a second mutant, feeA1, unlinked to feeB, but displaying a similar phenotype, 48/80 resistance and a reduced growth rate at the permissive temperature, 30°C, and temperature-sensitive, forming short filaments at 42°C. In the feeA mutant, tRNA₃^Leu expression (but not that of tRNA₁^Leu) was reduced approximately fivefold relative to the wild type. We previously showed that the synthesis of β-galactosidase, which unusually requires the translation of 6-CUA codons, was substantially reduced, particularly at 42°C, in feeB mutants. The feeA mutant also shows drastically reduced synthesis of β-galactosidase at the non-permissive temperature and reduced levels even at the permissive temperature. We also show that increased copy numbers of the abundant tRNA₁^Leu, which can also read CUA codons at low efficiency, suppressed the effects of feeA1 under some conditions, providing further evidence that the mutant was deficient in CUA translation. This, and the previous study, demonstrates that mutations which either reduce the activity of tRNA₃^Leu or the cellular amount of tRNA₃^Leu confer resistance to the drug 48/80, with concomitant inhibition of cell division at 42°C.     

非线性映射和聚类分析在中风病证候分类中的应用

本文用非线性映射和聚类分析方法,给出了中风病的四个类型,为中风病的证候分类提供了分析方法和信息．     

成人革兰阴性杆菌肺炎23例临床分析

本文以临床体征,胸片和连续二次以上细菌培养阳性为诊断标准,报告革兰阴性杆菌肺炎２３例,并就其临床表现,并发症及预后进行分析,提出８种情况应考虑革兰阴性杆菌肺炎,对临床诊断和治疗有指导意义．     

Yeast mRNA cap methyltransferase is a 50-kilodalton protein encoded by an essential gene.

RNA (guanine-7-)methyltransferase, the enzyme responsible for methylating the 5' cap structure of eukaryotic mRNA, was isolated from extracts of Saccharomyces cerevisiae. The yeast enzyme catalyzed methyl group transfer from S-adenosyl-L-methionine to the guanosine base of capped, unmethylated poly(A). Cap methylation was stimulated by low concentrations of salt and was inhibited by S-adenosyl-L-homocysteine, a presumptive product of the reaction, but not by S-adenosyl-D-homocysteine. The methyltransferase sedimented in a glycerol gradient as a single discrete component of 3.2S. A likely candidate for the gene encoding yeast cap methyltransferase was singled out on phylogenetic grounds. The ABD1 gene, located on yeast chromosome II, encodes a 436-amino-acid (50-kDa) polypeptide that displays regional similarity to the catalytic domain of the vaccinia virus cap methyltransferase. That the ABD1 gene product is indeed RNA (guanine-7-)methyltransferase was established by expressing the ABD1 protein in bacteria, purifying the protein to homogeneity, and characterizing the cap methyltransferase activity intrinsic to recombinant ABD1. The physical and biochemical properties of recombinant ABD1 methyltransferase were indistinguishable from those of the cap methyltransferase isolated and partially purified from whole-cell yeast extracts. Our finding that the ABD1 gene is required for yeast growth provides the first genetic evidence that a cap methyltransferase (and, by inference, the cap methyl group) plays an essential role in cellular function in vivo.     

Aggression and preputial gland of male mice affected by the presence of other males

The level of aggressiveness and the weight of preputial gland and testis in male mice (Mus musculus) were influenced by housing condition, especially by the presence of cohabitant males. In this study, the relation between aggressiveness and the preputial gland and testis weight was studied for various housing conditions. The mouse individually housed in a cage that was linked to another cage containing another male separated by wire net was more aggressive than isolated or paired mice. The preputial gland weight also showed the same tendency, suggesting that the odor from other males promotes pituitary-gonadal activity in males, and that long-term cohabitance inhibits it.     

短盖巨脂鲤卵巢发育组织学研究

通过对短盖巨脂鲤各个生长时期卵巢组织学研究以及成熟卵超微结构观察,获得短盖巨脂鲤生长发育过程中卵巢发育规律;同时对卵母细胞核仁排出物与核质关系及在卵黄形成中的作用等问题作了初步探讨;并根据卵巢的卵母细胞组成确定了其产卵类型。     

Adventitious regeneration of Juglans nigra L. (eastern black walnut)

Somatic embryos and adventitious shoots were initiated from immature cotyledons 10–14 weeks after anthesis. Maximum embryogenesis occurred 12 weeks after anthesis and maximum shoot organogenesis occurred 14 weeks after anthesis. The best treatment for induction of somatic embryos and adventitious shoots from immature cotyledon explants was on agar-solidified WPM supplemented with 0.1 M 2,4-D and 5.0 M TDZ and incubated in light for the first four weeks. Rooting of adventitious shoots was best if they were quickdipped in 2.5 mM IBA and 1.25 mM NAA in 1% dimethyl formamide and 3.9% ethanol (120 Wood's Rooting Compound: water, by volume). Plantlets from rooted adventitious shoots were acclimatized to the greenhouse.Abbreviations BA Benzyladenine - 2,4-D 2,4-dichlorophenoxyacetic acid - DKW Driver and Kuniyuki (1984) walnut medium - IBA indolebutyric acid - LP Long and Preece medium described herein - NAA naphthaleneacetic acid - PPF photosynthetic photon flux - TDZ thidiazuron - WPM Woody Plant Medium of Lloyd and McCown (1980)