Single pilus motor forces exceed 100 pN

Force production by type IV pilus retraction is critical for infectivity of Neisseria gonorrhoeae and DNA transfer. We investigated the roles of pilus number and the retraction motor, PilT, in force generation in vivo at the single-molecule level and found that individual retraction events are generated by a single pilus fiber, and only one PilT complex powers retraction. Retraction velocity is constant at low forces but decreases at forces greater than 40 pN, giving a remarkably high average stall force of 110 +/- 30 pN. Further insights into the molecular mechanism of force generation are gained from the effect of ATP-depletion, which reduces the rate of retraction but not the stall force. Energetic considerations suggest that more than one ATP is involved in the removal of a single pilin subunit from a pilus. The results are most consistent with a model in which the ATPase PilT forms an oligomer that disassembles the pilus by a cooperative conformational change.     

Transplantation of newborn thymus plus hematopoietic stem cells can rescue supralethally irradiated mice

We attempted to rescue supralethally irradiated (SLI) mice by transplantation of hematopoietic stem cells (HSCs) plus thymus from variously aged donors (fetus, newborn and adult). Although the transplantations of these kinds of HSCs alone showed a very short survival, newborn liver cells (NLCs) (as the source of HSCs) plus newborn thymus (NT) transplantation markedly improved the survival rate. The transplantation attenuated severe damage in the small intestine, which is one of the major causes of death by SLI. In addition, the donor-derived CD4(+) T cells significantly increased with additional NT transplantation. The production of interleukin (IL)-7 and keratinocyte growth factor, which plays a crucial role in protection against radiation injury in the intestine, was the highest in NT. Finally, SLI mice that had received NLC plus IL-7(-/-) NT transplantation plus IL-7 injection showed improved survival, weight recovery and an elevated number of CD4(+) T cells compared with the mice that had received NLC plus IL-7(-/-) NT or plus IL-7 injection alone. These findings suggest that NLCs plus NT transplantation can rescue SLI mice most effectively, and that high production of IL-7 in NT plays a crucial role with induction of CD4(+) T cells.     

Colonic delivery of dexamethasone from a prodrug accelerates healing of colitis in rats without adrenal suppression

Dexamethasone-β-d-glucuronide, a colon-specific prodrug of dexamethasone, may be useful in the treatment of ulcerative colitis and Crohn's colitis. The aim of this study was to evaluate colonic delivery and efficacy of this prodrug in the rat. Distribution of dexamethasone in luminal contents and tissues of the gastrointestinal tract and in plasma was measured after oral administration of dexamethasone-β-d-glucuronide or free dexamethasone. Efficacy of the prodrug and free drug was tested in an acetic acid-induced rat colitis model. Healing of induced colitis was assessed by measuring net intestinal fluid absorption, colonic surface area of ulceration, histology, and myeloperoxidase activity. Glucocorticosteroid toxicity was evaluated with serum corticosterone and plasma adrenocorticotropic hormone levels. The drug delivery index (a measure of relative targeting efficiency) was 6.7 and 8.6 in the cecal and colonic mucosa, respectively. The prodrug was significantly more potent than free drug in improving net colonic fluid absorption while significantly reducing surface area of ulceration and histological grade in colitic rats. Treatment with free dexamethasone significantly reduced serum corticosterone levels to subnormal levels, and treatment with the prodrug maintained serum corticosterone and plasma adrenocorticotropic hormone levels near control levels. The prodrug dexamethasone-β-d-glucuronide delivers efficacious amounts of dexamethasone to the large intestine from lower doses than free dexamethasone.     

抗巨噬细胞表面分子Mac-1单克隆抗体对利什曼原虫入侵巨噬细胞的抑制作用

应用抗巨噬细胞表面分子Mac-1单克隆抗体（M1／70和M18／2）处理巨噬细胞，观察M1／70和M18／2对杜氏利曼原虫前鞭毛体入侵巨噬细胞的抑制作用。结果，经上述单抗处理后巨噬细胞，对杜氏利什曼原虫的易感性明显降低，其原虫感染率和受染巨噬细胞内入侵的原虫数量减低，原虫对巨噬细胞的入侵过程及速度也减慢。M1／70和M18／2两种单抗同时应用，则对原虫侵入巨噬细胞的抑制作用更为显著，巨噬细胞受染率为13．8％，且受染巨噬细胞内入侵的原虫数量大多仅有1～2个。提示，M1／70和M18／2单克隆抗体可以通过与巨噬细胞表面Mac－1的结合，干扰巨噬细胞表面分子上与利什曼原虫相结合的连接位点，抑制利什曼原虫对巨噬细胞的入侵。     

The evolution of courtship behaviors through the origination of a new gene in Drosophila

New genes can originate by the combination of sequences from unrelated genes or their duplicates to form a chimeric structure. These chimeric genes often evolve rapidly, suggesting that they undergo adaptive evolution and may therefore be involved in novel phenotypes. Their functions, however, are rarely known. Here, we describe the phenotypic effects of a chimeric gene, sphinx, that has recently evolved in Drosophila melanogaster. We show that a knockout of this gene leads to increased male-male courtship in D. melanogaster, although it leaves other aspects of mating behavior unchanged. Comparative studies of courtship behavior in other closely related Drosophila species suggest that this mutant phenotype of male-male courtship is the ancestral condition because these related species show much higher levels of male-male courtship than D. melanogaster. D. melanogaster therefore seems to have evolved in its courtship behaviors by the recruitment of a new chimeric gene.     

宁夏银川市2006-2011年伤害监测病例流行病学特征分析

目的了解2006-2011年宁夏银川市伤害监测病例流行病学分布特征,为制定伤害预防控制策略提供科学依据。方法收集银川市3家伤害哨点监测医院2006-2011年的伤害报告卡资料,按照WHO伤害监测指南分类标准进行归类。统计分析使用全国伤害管理软件及Excel2010。结果 2006-2011年共收集伤害病例70 404例,男女性别比为2.17︰1,其中25~44岁组病例数所占比例最高(42.93%),职业以商业、服务业人员和在校学生居多;伤害发生原因前3位依次为道路交通伤害(33.30%)、跌倒/坠落(22.30%)和钝器伤(16.46%);伤害发生地点主要为公路/街道(38.36%)、家中(21.33%)和公共居住场所(14.09%);伤害病例以非故意伤害(94.95%)和轻度伤害(71.55%)为主。历年数据显示,伤害报告数量逐年稳步增加,各年度伤害病例分布特征无明显变化。结论数据分析显示,银川市伤害发生的人群主要为青壮年,发生的地点主要为公路/街道,发生的原因主要为道路交通伤害,为制定有针对性的伤害预防控制策略提供了科学依据。     

两种敷料对层流手术间动态下空气质量的影响

目的研究无纺布手术衣及敷料与棉织布手术衣及敷料对层流手术室动态下空气质量的影响,为提高层流手术间动态空气质量措施提供科学依据。方法选取医院2013年2-10月骨科全髋关节置换手术患者100例,随机分成A、B两组,每组各50例,A组用无纺布手术衣及敷料,B组用棉织布手术衣及敷料;采用沉降法和浮游法对两组手术间动态空气质量进行监测,并将监测结果进行比较。结果沉降法监测中A、B两组手术间平均空气沉降菌菌落数整体比较差异有统计学意义(t=3.12,P<0.01),在不同时点比较中,麻醉前A、B两组手术间空气沉降菌菌落数比较差异无统计学意义,在切皮前、手术中、缝合前及手术结束后各时点两组比较差异均有统计学意义(P<0.05);浮游法监测中A、B两组手术间平均空气浮游菌菌落数整体比较差异有统计学意义(t=3.78,P<0.01),在不同时点比较中,麻醉前A、B两组手术间空气浮游菌菌落数比较差异无统计学意义,在切皮前、手术中、缝合前、手术结束后各时点两组比较差异均有统计学意义(P<0.05)。结论使用无纺布手术衣及敷料的手术其手术间动态空气质量明显优于使用传统棉织布手术衣及敷料。