Host susceptibility to the attaching and effacing bacterial pathogen Citrobacter rodentium

Many studies have shown that genetic susceptibility plays a key role in determining whether bacterial pathogens successfully infect and cause disease in potential hosts. Surprisingly, whether host genetics influence the pathogenesis of attaching and effacing (A/E) bacteria such as enteropathogenic and enterohemorrhagic Escherichia coli has not been examined. To address this issue, we infected various mouse strains with Citrobacter rodentium, a member of the A/E pathogen family. Of the strains tested, the lipopolysaccharide (LPS) nonresponder C3H/HeJ mouse strain experienced more rapid and extensive bacterial colonization than did other strains. Moreover, the high bacterial load in these mice was associated with accelerated crypt hyperplasia, mucosal ulceration, and bleeding, together with very high mortality rates. Interestingly, the basis for the increased susceptibility was not due to LPS hyporesponsiveness, as the genetically related but LPS-responsive C3H/HeOuJ and C3H/HeN mouse strains were also susceptible to infection. Analysis of the intestinal pathology in these susceptible strains revealed significant crypt epithelial cell apoptosis (terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end label staining) as well as bacterial translocation to the mesenteric lymph nodes. Further studies with infection of SCID (T- and B-lymphocyte-deficient) C3H/HeJ mice demonstrated that loss of lymphocytes had no effect on bacterial numbers but did reduce crypt cell apoptosis and delayed mortality. These studies thus identify the adaptive immune system, crypt cell apoptosis, and bacterial translocation but not LPS responsiveness as contributing to the tissue pathology and mortality seen during C. rodentium infection of highly susceptible mouse strains. Determining the basis for these strains' susceptibility to intestinal colonization by an A/E pathogen will be the focus of future studies.     

A CdtA-CdtC complex can block killing of HeLa cells by Haemophilus ducreyi cytolethal distending toxin

The cytolethal distending toxin (CDT) of Haemophilus ducreyi is comprised of the CdtA, CdtB, and CdtC proteins, with the CdtB protein having demonstrated enzymatic (i.e., DNase) activity. Using a single recombinant Escherichia coli strain with two plasmids individually containing the H. ducreyi cdtA and cdtC genes, we purified a noncovalent CdtA-CdtC complex. Incubation of this CdtA-CdtC complex with HeLa cells blocked killing of these cells by CDT holotoxin. Furthermore, the addition of purified recombinant CdtB to HeLa cells preincubated with the CdtA-CdtC complex resulted in the killing of these human epithelial cells.     

上矢状窦旁桥静脉的显微解剖与影像学观察

目的:通过对上矢状窦(SSS)旁大脑桥静脉的显微解剖、影像学观察及其对照研究,为各种纵裂间手术入路中桥静脉的保护提供基础。方法:分别对30例(60侧)上矢状窦和颈内静脉内灌注蓝色乳胶的成人头颅湿标本、40侧DSA静脉相和16侧CTV进行显微解剖和影像学观察。结果:上矢状窦前部和后部分别有一缺乏桥静脉注入段,显微解剖、DSA和CTV观察上矢状窦旁桥静脉的数量分别为11.2支、8.9支和7.0支,DSA和CTV观察发现桥静脉注入上矢状窦处常显示不清。结论:熟悉和比较上矢状窦旁桥静脉的解剖学和影像学特征有利于各种纵裂间手术入路和手术过程中桥静脉的保护。     

IL-1β诱导体外培养的大鼠中脑黑质神经元c-jun表达

应用细胞原位杂交技术，观察经重组小鼠白细胞介素-19（IL-1β）处理后的体外培养的新生1d大鼠中脑黑质神经元c－jun基因的表达．结果显示，培养的黑质细胞多为酪氨酸羟化酶阳性神经元，IL-1β可诱导体外培养的黑质神经元c－junmRNA表达，高水平的表达出现在IL-1β处理后2～4h。说明IL－1β有兴奋黑质神经元的作用，并提示黑质神经元上可能存在IL－1β受体．     

羊精子在成熟和获能过程中表面的凝集素标记变化

用辣根过氧化物酶结合的麦芽凝集素和大豆凝集素，对绵羊睾丸和附睾内精子及体外获能精子细胞化学标记，麦芽凝集素在睾丸内精子的顶体区有强标记，在附睾头前段精子顶体区的标记减弱，但在附睾头后段精子顶体区的标记又增强，且尾部也出现弱标记，获能后部分精子的顶体后区出现弱至中等标记。大豆凝集素在睾丸内精子的顶体区有中等标记，在附睾体出现强标记，但获能后标记减至很弱，结果提示，麦芽凝集素记糖复合物可能与肥精有关。     

Evidence for a major gene underlying bone size variation in the Chinese

Osteoporosis is a major public health problem defined as a loss of bone strength, of which bone size is an important determinant. In the present study, familial correlation and segregation analyses for the spine and hip bone sizes were performed for the first time in a Chinese sample composed of 393 nuclear families with a total of 1,193 individuals. The results indicate a major gene of codominant inheritance for spine bone size; however, there is no evidence of a major gene influencing hip bone size. Significant familial residual effects are found for both traits, suggesting their polygenic inheritance. Heritability estimates (±SE) for spine and hip bone size were 0.62 (0.13) and 0.59 (0.12), respectively. Sex and age differences in genotype‐specific average bone size were observed. Compared with our previous study on bone mineral density (BMD) in the same population, this study suggests that genetic determination of bone size may be different from that of BMD, and thus studying bone size as one surrogate phenotype for osteoporotic fractures may be necessary. Am. J. Hum. Biol. 16:68–77, 2004. © 2003 Wiley‐Liss, Inc.     

低氧致鼠腺泡内肺动脉PDGF—B链蛋白表达的变化

目的：探讨血小板源性生长因子（ＰＤＧＦ）在低氧肺动脉高压血管构形重建发生中的作用。方法：应用免疫组化技术结合计算机图像分析，检测了低氧大鼠腺泡内肺动脉（ＩＡＰＡ）ＰＤＧＦ－Ｂ链蛋白表达水平。结果：常氧时，ＩＡＰＡ仅有ＰＤＧＦ－Ｂ链蛋白弱表达；低氧１天时，ＩＡＰＡ便有较强的ＰＤＧＦ－Ｂ链蛋白表达，定位于ＩＡＰＡ的内皮和中膜，低氧３天至１４天仅分布于中膜；低氧１、３、５、７、１４天各时间点ＰＤＧＦ－Ｂ链蛋白表达分别为常氧组的１．５３、１．５９、１．５６、１．６２和１．４２倍，差异有显著性（Ｐ＜０．０１）。结论：ＰＤＧＦ－Ｂ链蛋白可能参与了低氧肺动脉高压血管构形重建的发病过程     

人胚胎肺内神经内分泌细胞电镜观察

用透射电镜对不同胎龄的人胚胎肺内神经内分泌细胞进行了发生和超微结构观察。肺内支气管上皮内未分化细胞，第八周开始向神经内分泌细胞转化，提示神经内分泌细胞对早期胚胎肺的发生、发育有特殊意义。神经内分泌细胞内致密核心小泡（ＤＣＶ）及其它与内分泌活动有关的各种细胞器发达。能见到Ｐ０细胞、Ｐ１细胞、Ｐ２细胞及Ｐ３细胞等四种类型的神经内分泌细胞。Ｐ０细胞的发生及分化程度表明它可能是一种前细胞，它可以进一步转化     

Recombinant single-chain variable fragment antibodies directed against Clostridium difficile toxin B produced by use of an optimized phage display system

Recombinant antibody cloning and phage display technologies were used to produce single-chain antibodies (scFv) against Clostridium difficile toxin B. The starting material was the mouse B cell hybridoma line 5A8, which generates a monoclonal antibody against the toxin. The integrated cloning, screening, and phage display system of Krebber et al. (J. Immunol. Methods 201:35-55, 1997) allowed us to rapidly obtain toxin B-binding scFv sequences derived from the hybridoma cell line. The best candidate scFv sequences, based on preliminary enzyme-linked immunosorbent assay (ELISA) screening data were then subcloned into the compatible expression vector. Recombinant single-chain antibodies were expressed in Escherichia coli. A 29-kDa band was observed on polyacrylamide gel electrophoresis as predicted. The expressed product was characterized by immunoblotting and detection with an anti-FLAG antibody. The toxin B-binding function of the single-chain antibody was shown by a sandwich ELISA. The antibody was highly specific for toxin B and did not cross-react with material isolated from a toxin B-negative C. difficile strain. The sensitivity of the soluble single-chain antibody is significantly higher than the original monoclonal antibody based on ELISA data and could detect a minimum of 10 ng of toxin B/well. Competitive ELISAs established that the affinity of the 5A8 parent antibody and the best representative (clone 10) of the single-chain antibodies were similar and in the range of 10(-8) M. We propose that recombinant antibody technology is a rapid and effective approach to the development of the next generation of immunodiagnostic reagents.     

Monte Carlo based treatment planning for modulated electron beam radiation therapy

A Monte Carlo based treatment planning system for modulated electron radiation therapy (MERT) is presented. This new variation of intensity modulated radiation therapy (IMRT) utilizes an electron multileaf collimator (eMLC) to deliver non-uniform intensity maps at several electron energies. In this way, conformal dose distributions are delivered to irregular targets located a few centimetres below the surface while sparing deeper-lying normal anatomy. Planning for MERT begins with Monte Carlo generation of electron beamlets. Electrons are transported with proper in-air scattering and the dose is tallied in the phantom for each beamlet. An optimized beamlet plan may be calculated using inverse-planning methods. Step-and-shoot leaf sequences are generated for the intensity maps and dose distributions recalculated using Monte Carlo simulations. Here, scatter and leakage from the leaves are properly accounted for by transporting electrons through the eMLC geometry. The weights for the segments of the plan are re-optimized with the leaf positions fixed and bremsstrahlung leakage and electron scatter doses included. This optimization gives the final optimized plan. It is shown that a significant portion of the calculation time is spent transporting particles in the leaves. However, this is necessary since optimizing segment weights based on a model in which leaf transport is ignored results in an improperly optimized plan with overdosing of target and critical structures. A method of rapidly calculating the bremsstrahlung contribution is presented and shown to be an efficient solution to this problem. A homogeneous model target and a 2D breast plan are presented. The potential use of this tool in clinical planning is discussed.