Molecular divergence of the sia locus in different serogroups of Neisseria meningitidis expressing polysialic acid capsules

The serogroups B, C, W135 and Y of Neisseria meningitidis express chemically and immunologically distinct capsular polysaccharides containing sialic acid. In the case of serogroup B meningococci sialic acid is synthesized by the gene products of a locus termed sia and forms the homopolymers of the capsule. The organization of the genes required for sialic acid synthesis in serogroups B, C, W135 and Y was elucidated by PCR technology. Cloning, sequencing and the functional expression of the polysialyltransferase (PST) genes of serogroups B and C demonstrated that the difference in capsule composition derives from the presence of related, but distinct siaD genes coding for PSTs. Analysis of meningococci of serogroups W135 and Y expressing sialic acid heteropolymers revealed that the DNA sequences of the corresponding genetic loci in these serogroups were highly homologous, but differed completely from the siaD genes of serogroups B and C. This finding suggests that enzymes unrelated to those of serogroups B and C are required for the formation of sialic acid heteropolymers characteristic of the capsules of serogroups W135 and Y. Received: 24 June 1997 / Accepted: 23 September 1997     

单气囊小肠镜与胶囊内镜对不明原因消化道出血的诊断价值

目的:探讨单气囊小肠镜(SBE)与胶囊内镜(CE)对不明原因消化道出血(OGffi)患者的诊断价值。方法:将在我院治疗的100例OGIB患者按照诊断方式的不同分为SBE组和CE组各50例。对两组的病灶检出率病因诊断率以及安全性进行比较。结果SBE组病因诊断率为78.0%;CE组病因诊断率为60.0%,两组病因诊断率比较差异无统计学意义(P0.05)。SBE组病灶检出率为80.0%(40/50),CE组病灶检出率为86.0%(43/50),两组病灶检出率比较差异无统计学意义(P0.05)。SBE组患者检查较顺利,CE组胶囊滞留率为4.0%。所有患者检查后均未出现不良反应及并发症。结论:息肉及粘膜糜烂渍疡病变的OGIB患者在SBE与CE检查方法中较为常见,CE病灶检出率与SBE相当,两种检查方法均较可靠,CE检查更为方便。     

薄层层析-紫外分光光度法测定十全大补胶囊中芍药苷含量

目的 建立薄层层析-紫外分光光度法测定十全大补胶囊中芍药苷含量的方法。方法 使用硅胶GF254薄层板,醋酸乙酯：甲酸：冰醋酸：水(30：2：2：4)为展开剂,在紫外光灯(254nm)下定位,230nm波长处检测。结果 点样量在25～125μg范围内呈现良好的线性关系,其回归方程为Y=0．004658C-0．01959,r=0．9994,平均回收率为99．20％,RSD=1．19％。结论 本法准确,适用于该药的质量控制。     

A disulfide bridge network within the soluble periplasmic domain determines structure and function of the outer membrane protein RCSF

RcsF, a proposed auxiliary regulator of the regulation of capsule synthesis (rcs) phosphorelay system, is a key element for understanding the RcsC-D-A/B signaling cascade, which is responsible for the regulation of more than 100 genes and is involved in cell division, motility, biofilm formation, and virulence. The RcsC-D-A/B system is one of the most complex bacterial signal transduction pathways, consisting of several membrane-bound and soluble proteins. RcsF is a lipoprotein attached to the outer membrane and plays an important role in activating the RcsC-d-A/B pathway. The exact mechanism of activation of the rcs phosphorelay by RcsF, however, remains unknown. We have analyzed the sequence of RcsF and identified three structural elements: 1) an N-terminal membrane-anchored helix (residues 3-13), 2) a loop (residues 14-48), and 3) a C-terminal folded domain (residues 49-134). We have determined the structure of this C-terminal domain and started to investigate its interaction with potential partners. Important features of its structure are two disulfide bridges between Cys-74 and Cys-118 and between Cys-109 and Cys-124. To evaluate the importance of this RcsF disulfide bridge network in vivo, we have examined the ability of the full-length protein and of specific Cys mutants to initiate the rcs signaling cascade. The results indicate that the Cys-74/Cys-118 and the Cys-109/Cys-124 residues correlate pairwise with the activity of RcsF. Interaction studies showed a weak interaction with an RNA hairpin. However, no interaction could be detected with reagents that are believed to activate the rcs phosphorelay, such as lysozyme, glucose, or Zn(2+) ions.     

Mutual Exclusivity of Hyaluronan and Hyaluronidase in Invasive Group A Streptococcus

A recent analysis of group A Streptococcus (GAS) invasive infections in Australia has shown a predominance of M4 GAS, a serotype recently reported to lack the antiphagocytic hyaluronic acid (HA) capsule. Here, we use molecular genetics and bioinformatics techniques to characterize 17 clinical M4 isolates associated with invasive disease in children during this recent epidemiology. All M4 isolates lacked HA capsule, and whole genome sequence analysis of two isolates revealed the complete absence of the hasABC capsule biosynthesis operon. Conversely, M4 isolates possess a functional HA-degrading hyaluronate lyase (HylA) enzyme that is rendered nonfunctional in other GAS through a point mutation. Transformation with a plasmid expressing hasABC restored partial encapsulation in wild-type (WT) M4 GAS, and full encapsulation in an isogenic M4 mutant lacking HylA. However, partial encapsulation reduced binding to human complement regulatory protein C4BP, did not enhance survival in whole human blood, and did not increase virulence of WT M4 GAS in a mouse model of systemic infection. Bioinformatics analysis found no hasABC homologs in closely related species, suggesting that this operon was a recent acquisition. These data showcase a mutually exclusive interaction of HA capsule and active HylA among strains of this leading human pathogen.     

双歧杆菌三联活菌胶囊对肝性脑病患者 肠黏膜屏障功能及血氨的影响

目的探讨双歧杆菌三联活菌胶囊对肝性脑病患者肠屏障功能及血氨的影响。方法选取100例确诊为肝性脑病的患者,随机分为对照组和治疗组各50例。对照组患者给予肝性脑病常规综合治疗,治疗组在常规综合治疗的基础上同时口服双歧杆菌三联活菌胶囊进行治疗。治疗前及治疗两周后分别检测两组患者肠黏膜屏障功能及血氨水平并比较其变化。结果治疗前两组患者肠屏障功能及血氨水平差异无统计学意义(P0.05);治疗2周后,治疗组患者的血氨水平、血清二胺氧化酶(DAO)水平、血清内毒素水平(LPS)及肿瘤坏死因子-α(TNF-α)水平较治疗前显著降低,且较对照组治疗后的水平亦有明显的降低(P0.05)。结论肝性脑病患者在常规综合治疗的基础上,加用双歧杆菌三联活菌胶囊可以明显改善患者肠黏膜屏障功能,减少肠源性血氨的生成,临床疗效确切。     

顺天胶囊药理学实验研究Ⅱ.顺天胶囊对幼鼠性功能及抗疲劳作用的影响

本文探讨了顺天胶囊对幼鼠性机能的影响和抗疲劳等作用。实验结果表明,本品对雌性幼鼠性机能无明显影响作用,但能明显提高雄性幼鼠前列腺一精囊重量和睾丸酮水平,明显延长小鼠游泳时间。提示本品具有提高雄性动物性机能及明显抗疲劳作用。     

Effects of crowding on life history parameters of four green leafhoppers,Nephotettix spp. (Homoptera: Cicadellidae)

The effects of intraspecific crowding on the different life history parameters of the three tropical and subtropical green leafhoppers, Nephotettix virescensStål ,N. nigropictusDistant and N. malayanusIshihara etKawase , and one temperate species, N. cincticepsUhler , were studied under 25±1°C using the susceptible Japonica rice variety “Nipponbare”. Crowding during the immature stages of the four species prolonged the nymphal developmental period and resulted to smaller adults with reduced fecundity and shorter life span. Similarly, crowding during the adult stage also shortened the life span of both sexes of adults and decreased the fecundity of females of the four species. The effect of crowding during the adult stage was more adverse than the effect of crowding during the immature stages. N. cincticeps seemed more sensitive to crowding even at lower densities whereas the three tropical species were sensitive mostly at higher densities.     

植物人工种子研究进展

在我国高技术的发展规划中,生物技术是被重视的首领技术之一。植物人工种子正是在创建中的生物技术,由于其具有重大的实践意义和经济价值,目前美国、日本、法国等都相继地开展了此方面的广泛研究,并在胡萝卜、芹菜、苜蓿、花椰菜、西红柿等植物中获得成功。我国从事此方面研究很少,从1985年开始中科院植物所探索了西洋参、玉米、芹菜等植物人工种子的研究,取得可喜成绩。本文阐述植物人工种子发展历程,人工种子的概念,使用的可行性,优越性及对人工种子技术发展中现存的问题,前景给以了乐观的估计。     

Heterotylenchus antumnalis. Hemocytic reactions and capsule formation in the host, Musca domestica

Failure of the nematode H. autumnalis to develop in M. domestica is attributed to the defense reaction of host larvae to the infective, gamogenetic stage of the parasite. The defense reaction involves melanization and encapsulation of the parasite, and is manifested as changes in the hemocyte picture of the host.