Biochemical and genetic characterization of three hamster cell mutants resistant to diphtheria toxin

We describe here three different hamster cell mutants which are resistant to diphtheria toxin and which provide models for investigating some of the functions required by the toxin inactivates elongation factor 2 (EF-2). Cell-free extracts from mutants Dtx(r)-3 was codominant. The evidence suggests that the codominant phenotype is the result of a mutation in a gene coding for EF-2. The recessive phenotype might arise by alteration of an enzyme which modifies the structure of EF-2 so that it becomes a substrate for reaction with the toxin. Another mutant, Dtx(r)-2, contained EF-2 that was sensitive to the toxin and this phenotype was recessive. Pseudomonas aeruginosa exotoxin is known to inactivate EF-2 as does diphtheria toxin and we tested the mutants for cross-resistance to pseudomonas exotoxin. Dtx(r)-1 and Dtx(r)-3 were cross-resistant while Dtx(r)-2 was not. It is known that diphtheria toxin does not penetrate to the cytoplasm of mouse cells and that these cell have a naturally occurring phenotype of diphtheria toxin resistance. We fused each of the mutants with mouse 3T3 cells and measured the resistance. We fused each of the mutants with mouse 3T3 cells and measured the resistance of the hybrid cells to diphtheria toxin. Intraspecies hybrids containing the genome of mutants Dtx(r)-1 and Dtx(r)-3 had some resistance while those formed with Dtx(r)-2 were as sensitive as hybrids derived from fusions between wild-type hamster cells and mouse 3T3 cells.     

Multiple infection diagnosis of intestinal helminthiasis in the assessment of health and environmental effect of development projects in Nigeria

Patterns of intestinal helminth infections among school-aged children have been assessed in Eko-ende and Ore, as part of an overall assessment of the public health impact of Erinle Dam Reservoir in Osun State, Nigeria. The investigation was carried out between January and May 2005 using the Kato Katz thick smear technique and simple questionnaire for information on the bio-data, knowledge, attitude and practice of individuals towards disease transmission and control. Ascaris lumbricoides, hookworm, Trichuris trichiura, Taenia spp., Strongyloides stercoralis and Schistosoma mansoni were recovered at an overall prevalence of 78.3% among 309 children examined. Ascaris lumbricoides, hookworm, T. trichiura and S. mansoni were the most common infections while S. stercoralis and Taenia spp. were found only among a few children. Infection patterns of the common diseases were age-specific with peaks in the 11-15 age bracket. Children not attending school were significantly (P < 0.05) more at risk of infection than those attending school. Multiple infections were pronounced with over 54% double infections and 6% four parasites or more infections. The need for urgent intervention to arrest the obviously serious public health situation attributable to Erinle Dam is emphasized.     

ANTIPYRETIC ACTION OF DEXAMETHASONE ON EGTAZIC ACIDINDUCED FEVER IN RABBITS

本文用脑室灌注和Ｆｕｒａ２测定细胞内游离钙技术观察了地塞米松（ｄｅｘａｍｅｔｈａｓｏｎｅ,ＤＥＸ）对家兔乙二醇双（２氨基乙醚）四乙酸性发热效应和下丘脑细胞内游离钙浓度（［Ｃａ２＋］ｉ）的影响,借此深入探讨地塞米松解热作用的中枢机制。结果发现：脑室灌注乙二醇双（２氨基乙醚）四乙酸（０６ｎｍｏｌ）引起家兔结肠温度明显升高,静脉注射地塞米松（５ｍｇ／ｋｇ）显著抑制家兔乙二醇双（２氨基乙醚）四乙酸性发热,地塞米松（６０～１２０μｍｏｌ／Ｌ）并不影响下丘脑细胞内［Ｃａ２＋］ｉ,而事先脑室灌注抑制基因转录的放线菌素Ｄ（３ｎｍｏｌ）则完全取消了地塞米松对乙二醇双（２氨基乙醚）四乙酸性发热的解热作用。这些结果提示：地塞米松显著抑制家兔乙二醇双（２氨基乙醚）四乙酸性发热,其机制与地塞米松激活脑内某些基因的表达有关,而与下丘脑神经细胞跨膜钙离子流无关。     

Instant success for Instant Pharmacology

Instant Pharmacology (1999). Saeb-Parsy K, Assomull RG, Kahn FZ, Saeb-Parsy K, and Kelly E. John Wiley and Sons 349 pp. £19.99 pbk; ISBN 0471976393 © 1999 John Wiley & Sons, Inc.     

人眼微光下夜近视机制的研究

本文利用激光散斑屈光测试系统详细探讨了夜近视(night myopia)的产生机制。夜近视在环境亮度降低到产生暗视觉时出现,并随亮度继续降低而增大,平均值为1.35D。实验证明眼睛球差和色差不是造成夜近视的主要因素。夜近视数值在暗适应过程中呈增大的趋势。在暗视觉时,由于视野中缺少适宜的刺激,眼睛处于暗焦(dark focus)休止状态,这是造成夜近视的主要原因。     

Risk factors for tungiasis in Nigeria: identification of targets for effective intervention

Background

The parasitic skin disease tungiasis (caused by the flea Tunga penetrans) affects resource-poor communities in Latin America, the Caribbean and sub-Saharan Africa. Prevalences in endemic areas are high, and severe pathology occurs commonly. However, risk factors for infestation have never been assessed in Africa.

Methods and Findings

A cross-sectional study was conducted in Erekiti, a rural community in Lagos State (Nigeria), where tungiasis is endemic. Individuals were examined clinically for the presence of tungiasis, and a questionnaire was applied. Data from 643 individuals (86.6% of the target population) were analyzed; 252 (42.5%) were infested with T. penetrans. In the multivariate logistic regression analysis, presence of pigs on the compounds (adjusted odds ratio = 17.98; 95% confidence interval: 5.55–58.23), sand or clay floor inside houses (9.33; 5.06–17.19), and having the common resting place outside the house (7.14; 4.0–14.29) were the most important risk factors identified. The regular use of closed footwear (0.34; 0.18–0.62) and the use of insecticides indoors (0.2; 0.05–0.83) were protective against infestation. The population attributable fractions associated with tungiasis were: sand or clay floor inside the house (73.7%), resting usually outside the house (65.5%), no regular use of closed footwear (51.1%), and pigs on the compound (37.9%).

Conclusion

The presence of tungiasis in Erekiti is determined to an important extent by a limited number of modifiable variables. Effective and sustainable intervention measures addressing these factors need to be implemented in this and other West African communities with high disease burden.     

瓜类枯萎病研究进展(综述)

瓜类枯萎病是由尖孢镰刀菌Fusarium oxysporum侵染引起,在全球大部分瓜类产区均有发生。该病已成为影响我国瓜类品质和产量的重要病害。本文从瓜类作物枯萎病的防治方法、致病机理和分子生物学研究等方面综述其研究现状,并对今后的研究方向进行展望。     

beta1,6 N-acetylglucosaminyltransferase (core 2 GlcNAc-T) expression in normal rat tissues and different cell lines: evidence for complex mechanisms of regulation

The distribution of the Golgi enzyme beta1, 6-N- acetylglucosaminyltransferase (core 2 GlcNAc-T for short) has been investigated in several tissue and cell systems by combining the potentials of a polyclonal antibody and a novel, sensitive fluorescent enzyme assay. In normal rat tissues, levels of the protein were found to vary and as a general trend did not correlate with enzyme activities. Additionally, we observed tissue-specific core 2 GlcNAc-T forms of various size: 75 kDa (liver), 70 kDa (spleen), 60 kDA (heart), and 50 kDa (heart and lung). These forms might arise from differential protein modifications; alternatively, the smaller form may be a product of proteolytic cleavage, given the presence of a catalytically inactive 50 kDa species in rat serum. Chinese hamster ovary (CHO), MDAY-D2, PSA- 5E, and PYS-2 cell lines consistently displayed a 70 kDa enzyme. When induced to retrodifferentiate in the presence of butyrate + cholera toxin, CHO cells exhibited a 21-fold increase in enzyme activity, while protein levels remained constant. A similar trend was observed in the embryonal endoderm cell lines PSA-5E and PYS-2, where an approximately 100-fold difference in core 2 GlcNAc-T activity was found notwithstanding unchanged amounts of the protein and identical mRNA levels, as evidenced by RT-PCR. In contrast, levels of core 2 GlcNAc-T activity in MDAY-D2 cells correlated well with protein expression. Taken together, these observations demonstrate that core 2 GlcNAc-T expression may be subjected to multiple mechanisms of regulation and suggest that in at least some instances (i.e., PSA-5E and PYS-2 cells) expression may be regulated exclusively via posttranslational mechanism(s) of control.      

Epidemiology of intestinal helminth parasites in stray dogs from markets in south-eastern Nigeria

A survey of gastrointestinal helminth parasites of stray dogs (Canis familiaris) was conducted at Obollo-Afor and Ekwulobia markets, in Enugu and Anambra States, south-eastern Nigeria, respectively, to determine the patterns of infection among dogs in different parts of south-eastern Nigeria. Faecal samples collected, using long forceps, from every dog encountered in the markets between June 2007 and December 2008 were analysed by the Kato-Katz technique. Out of 413 dogs examined in both markets, 217 (52.6%) were infected with at least one of five parasites (Toxocara spp., Dipylidium caninum, Ancylostoma caninum, Taenia spp. and Trichuris vulpis). Overall faecal egg intensity of infection was 49.9?±?58.7 eggs/g (epg). The prevalence of infection was comparable between the markets and between the male and female dogs, but varied significantly (P?相似文献   

人胎儿脑的一个cDNA编码序列及其蛋白质预测

用 m RNA差异显示 PCR技术 ,从人 1 8周、2 2周胎儿脑和肝肾组织的 m RNA逆转录产物得到一些特异性显示的片段 .其中一个随机片段 GC1 0 2作为探针 ,从本实验室构建的 1 8周胎儿脑c DNA基因文库进行杂交筛选 ,得到一个阳性克隆λ gt1 0 /GC1 0 2 .该克隆内插入的 c DNA片段长2 .9kb,经过 DNA测序 ,显示具有一个开放阅读框架 ,编码 1 37个氨基酸的肽链 .用蛋白质结构的建模软件预测了该肽链的立体结构初步模型 .