New ways of preventing HIV infection: thinking simply, simply thinking

HIV infection is the greatest health crisis in human history. It continues to spread unchecked among the poor in the developing world because we have failed to design simple preventative methods that are available and affordable to those living on under Dollars 2 a day. Five new methods are discussed. (i) A natural microbicide. Intravaginal lime or lemon juice has been used for centuries as a traditional contraceptive. The juice can also kill HIV in the laboratory, but clinical trials are needed to see if vaginal application is acceptable, safe and effective. (ii) Intravaginal oestrogen. Monkeys can be protected from Simian immunodeficiency virus (SIV) infection by keratinizing the vagina with topical oestrogen. If women take the oral contraceptive pill vaginally it retains its contraceptive efficacy, and the oestrogen it contains should thicken the vagina and protect against HIV infection. Clinical trials are needed. (iii) Male circumcision. Removal of the inner foreskin removes the main site of HIV entry into the penis, resulting in a sevenfold reduction in susceptibility to infection. The practice needs to be promoted. (iv) Post-coital penile hygiene. Wiping the penis immediately after intercourse with lime or lemon juice or vinegar should kill the virus before it has had a chance to infect. A clinical trial of efficacy is needed. (v) PhotoVoice. Asking schoolchildren in developing countries to photograph their impressions of HIV/AIDS is a powerful way of getting them to discuss the subject openly, and develop their own preventative strategies.     

“植物堂”于双语教学的实践与思考

双语教学是在现代教学经济国际化的影响下所形成的一种新兴教育形式。结合曲靖师范学院的植物学教学实践,总结和分析了植物学双语教学过程中的经验及其实施过程中遇到的主要困难。提出了引进并完善外文原版教材、加强教师队伍建设、提高学生综合素质、培养学生学习兴趣、实施多样化教学方式等完善植物学双语教学的相应对策。最后提出了“保持-过渡-双语思维”的双语教学改革模式,这对于双语教学理论系统化的形成有一定的参考价值。     

"植物学"双语教学的实践与思考

双语教学是在现代教学经济国际化的影响下所形成的一种新兴教育形式.结合曲靖师范学院的植物学教学实践,总结和分析了植物学双语教学过程中的经验及其实施过程中遇到的主要困难.提出了引进并完善外文原版教材、加强教师队伍建设、提高学生综合素质、培养学生学习兴趣、实施多样化教学方式等完善植物学双语教学的相应对策.最后提出了"保持-过渡-双语思维"的双语教学改革模式,这对于双语教学理论系统化的形成有一定的参考价值.     

Transport and function of syntaxin 3 in human epithelial intestinal cells

To follow the transport of human syntaxin (Syn) 3 to theapical surface of intestinal cells, we produced and expressed in Caco-2cells a chimera made of the entire Syn3 coding sequence and theextracellular domain of the human transferrin receptor (TfR). Thischimera (Syn3TfR) was localized to the apical membrane and wastransported along the direct apical pathway, suggesting that this isalso the case for endogenous Syn3. To test the potential role of Syn3in apical transport, we overexpressed it in Caco-2 cells and measuredthe efficiency of apical and basolateral delivery of several endogenousmarkers. We observed a strong inhibition of apical delivery ofsucrase-isomaltase (SI), an apical transmembrane protein, and of-glucosidase, an apically secreted protein. No effect was observedon the basolateral delivery of Ag525, a basolateral antigen, stronglysuggesting that Syn3 is necessary for efficient delivery of proteins tothe apical surface of intestinal cells.

     

关于生态学本科毕业设计(论文)教学的思考

本科毕业设计(论文)是本科实践教学的重要环节,对于提高本科教育质量和学生综合素质具有至关重要的作用。针对本科毕业设计(论文)方面存在选题盲目、时间安排不合理、写作不规范、缺乏创新等问题,利用新办专业在管理与课程设置方面处于调整阶段的优势,从课程培育、毕业论文时间延长、与在研课题相结合和全过程管理等方面,对如何提高本科毕业设计(论文)质量的方式、方法进行了深入的探讨。     

综合性大学“兽医微生物学”教学探究与思考

"兽医微生物学"是动物医学及相关专业的重要专业基础课程,为了培养具有创新性的高素质人才,我们在"兽医微生物学"的教学中进行了改革探究。分别从教学理念、教学模式和考核制度入手,由教师授课为主转变为引导学生主动学习,并将多种教学方法灵活地融入到各个知识点,同时实行知识和能力的全过程综合考核制度,以调动学生主动学习的积极性,发掘学生的学习兴趣,培养学生的自主学习能力、创新思维能力和动手实践能力,改变学生重结果轻过程的不良学习态度。实践结果获得了很好的教学效果,值得推广。     

维生素A缺乏影响肠道屏障功能的研究进展

维生素A（vitamin A,VA）在维持肠道黏膜上皮屏障功能的完整性、调节黏膜免疫反应以及抗感染中起到重要的作用。肠道相关树突状细胞（dendritic cells,DCs）可表达合成视黄酸（retinoic acid,RA）所必需的酶（retinal dehydrogenase,RALDH）,合成RA。RA通过诱导T、B细胞产生整合素α4β7、CCR9,使其归巢到肠道,并提高肠道黏膜sIgA的水平。RA可增强天然CD4＋T细胞分化为Foxp3＋Treg细胞,抑制Th17细胞的生成。当机体VA缺乏时可降低肠道屏障功能,下调肠道黏膜免疫反应,增加肠道感染性疾病的易感性,容易导致腹泻。针对维生素A在肠道屏障功能的调节作用作一简要概述。     

TNFAIP3 maintains intestinal barrier function and supports epithelial cell tight junctions

Tight junctions between intestinal epithelial cells mediate the permeability of the intestinal barrier, and loss of intestinal barrier function mediated by TNF signaling is associated with the inflammatory pathophysiology observed in Crohn's disease and celiac disease. Thus, factors that modulate intestinal epithelial cell response to TNF may be critical for the maintenance of barrier function. TNF alpha-induced protein 3 (TNFAIP3) is a cytosolic protein that acts in a negative feedback loop to regulate cell signaling induced by Toll-like receptor ligands and TNF, suggesting that TNFAIP3 may play a role in regulating the intestinal barrier. To investigate the specific role of TNFAIP3 in intestinal barrier function we assessed barrier permeability in TNFAIP3(-/-) mice and LPS-treated villin-TNFAIP3 transgenic mice. TNFAIP3(-/-) mice had greater intestinal permeability compared to wild-type littermates, while villin-TNFAIP3 transgenic mice were protected from increases in permeability seen within LPS-treated wild-type littermates, indicating that barrier permeability is controlled by TNFAIP3. In cultured human intestinal epithelial cell lines, TNFAIP3 expression regulated both TNF-induced and myosin light chain kinase-regulated tight junction dynamics but did not affect myosin light chain kinase activity. Immunohistochemistry of mouse intestine revealed that TNFAIP3 expression inhibits LPS-induced loss of the tight junction protein occludin from the apical border of the intestinal epithelium. We also found that TNFAIP3 deubiquitinates polyubiquitinated occludin. These in vivo and in vitro studies support the role of TNFAIP3 in promoting intestinal epithelial barrier integrity and demonstrate its novel ability to maintain intestinal homeostasis through tight junction protein regulation.     

AhR activation protects intestinal epithelial barrier function through regulation of Par-6

The Par complex (Par-6/Par-3/aPKC) plays a key role in the maintenance of the intestinal barrier function through the regulation of epithelial junction formation. The aryl hydrocarbon receptor (AhR) has been shown to be an important regulator for intestinal homeostasis. In this study, we investigated the role of the AhR activation on the regulation of Par complex. AhR activation by 6-formylindolo (3,2-b) carbazole (FICZ) represses the abnormal expression of the Par complex in a mouse model of dextran sulphate sodium (DSS)-induced colitis. In T84 cells, overexpression of Par-6 causes intestinal barrier dysfunction. Lipopolysaccharide (LPS)-induced intestinal epithelial barrier dysfunction and increase in Par-6 expression was prevented by AhR activation. However, FICZ did not alter the expression of Par-3 or aPKC. Furthermore, AhR activation alleviated LPS-induced increase of Par-6 through repressing the expression of activating protein-2γ (Ap-2γ). These results reveal the protective effects of AhR activation on LPS induced disruption of intestinal epithelial barrier function through suppressing the expression of Par-6 expression. Our findings provide novel insights into the protective role of AhR in intestinal barrier function.     

Characterization of immunomodulatory properties and accessory cell function of small intestinal epithelial cells.

We have studied the immunomodulatory properties of epithelial cells from the small intestine on T cell immune function in vitro. Proliferation of lymph node cells stimulated either with antigen or with mitogen was inhibited by epithelial cells in a dose-dependent fashion. The epithelial cell-mediated suppression of lymphocyte proliferation was blocked by indomethacin, a cyclooxygenase pathway inhibitor, demonstrating that the suppressive effect of epithelial cells was related to prostaglandin secretion. Furthermore, the action of epithelial cell-secreted prostaglandin on lymphocytes was related to its effect on IL-2 as the suppressive effect of epithelial cells was abrogated by the addition of exogenous IL-2. As previously reported, epithelial cells constitutively express MHC class II and we found them able to present antigen in a class II-restricted fashion when their suppressive effects were blocked by indomethacin. Furthermore, epithelial cells activated by LPS secrete an IL-1 like molecule in a fashion analogous to other antigen-presenting cells. These results demonstrate that epithelial cells can both enhance and suppress in vitro T cell immune responses and further characterize the mechanisms by which intestinal epithelial cells may function in gut-associated immune responses.     

Effect of eicosapentaenoic acid-derived prostaglandin E3 on intestinal epithelial barrier function

Prostaglandins (PG) are inflammatory mediators derived from arachidonic or eicosapentaenoic acid giving rise to the 2-series or the 3-series prostanoids, respectively. Previously, we have observed that PGE₂ disrupts epithelial barrier function. Considering the beneficial effect of fish oil consumption in intestinal inflammatory processes, the aim of this study was to assess the role of PGE₃ on epithelial barrier function assessed from transepithelial electrical resistance and dextran fluxes in Caco-2 cells. The results indicate that PGE₃ increased paracellular permeability (PP) to the same extent as PGE₂, through the interaction with EP₁ and EP₄ receptors and with intracellular Ca²⁺ and cAMP as the downstream targets. Moreover, we observed a redistribution of tight junction proteins, occludin and claudin-4. In conclusion, PGE₃ is able to increase PP thus leading to reconsider the role of PGE₂/PGE₃ ratio in the beneficial effects of dietary fish oil supplementation in the disruption of barrier function.     

Th2 cytokines down-regulate TLR expression and function in human intestinal epithelial cells

TLRs serve important immune and nonimmune functions in human intestinal epithelial cells (IECs). Proinflammatory Th1 cytokines have been shown to promote TLR expression and function in IECs, but the effect of key Th2 cytokines (IL-4, IL-5, IL-13) on TLR signaling in IECs has not been elucidated so far. We stimulated human model IECs with Th2 cytokines and examined TLR mRNA and protein expression by Northern blotting, RT-PCR, real-time RT-PCR, Western blotting, and flow cytometry. TLR function was determined by I-kappaBalpha phosphorylation assays, ELISA for IL-8 secretion after stimulation with TLR ligands and flow cytometry for LPS uptake. IL-4 and IL-13 significantly decreased TLR3 and TLR4 mRNA and protein expression including the requisite TLR4 coreceptor MD-2. TLR4/MD-2-mediated LPS uptake and TLR ligand-induced I-kappaBalpha phosphorylation and IL-8 secretion were significantly diminished in Th2 cytokine-primed IECs. The down-regulatory effect of Th2 cytokines on TLR expression and function in IECs also counteracted enhanced TLR signaling induced by stimulation with the hallmark Th1 cytokine IFN-gamma. In summary, Th2 cytokines appear to dampen TLR expression and function in resting and Th1 cytokine-primed human IECs. Diminished TLR function in IECs under the influence of Th2 cytokines may protect the host from excessive TLR signaling, but likely also impairs the host intestinal innate immune defense and increases IEC susceptibility to chronic inflammation in response to the intestinal microenvironment. Taken together, our data underscore the important role of Th2 cytokines in balancing TLR signaling in human IECs.     

Regulation of intestinal epithelial intercellular adhesion and barrier function by desmosomal cadherin desmocollin-2

The role of desmosomal cadherin desmocollin-2 (Dsc2) in regulating barrier function in intestinal epithelial cells (IECs) is not well understood. Here, we report the consequences of silencing Dsc2 on IEC barrier function in vivo using mice with inducible intestinal–epithelial-specific Dsc2 knockdown (KD) (Dsc2^ERΔIEC). While the small intestinal gross architecture was maintained, loss of epithelial Dsc2 influenced desmosomal plaque structure, which was smaller in size and had increased intermembrane space between adjacent epithelial cells. Functional analysis revealed that loss of Dsc2 increased intestinal permeability in vivo, supporting a role for Dsc2 in the regulation of intestinal epithelial barrier function. These results were corroborated in model human IECs in which Dsc2 KD resulted in decreased cell–cell adhesion and impaired barrier function. It is noteworthy that Dsc2 KD cells exhibited delayed recruitment of desmoglein-2 (Dsg2) to the plasma membrane after calcium switch-induced intercellular junction reassembly, while E-cadherin accumulation was unaffected. Mechanistically, loss of Dsc2 increased desmoplakin (DP I/II) protein expression and promoted intermediate filament interaction with DP I/II and was associated with enhanced tension on desmosomes as measured by a Dsg2-tension sensor. In conclusion, we provide new insights on Dsc2 regulation of mechanical tension, adhesion, and barrier function in IECs.     

p27(Kip1) is an inducer of intestinal epithelial cell differentiation

Constant renewal of the intestinal epitheliumis a highly coordinated process that has been subject to intenseinvestigation, but its regulatory mechanisms are still essentiallyunknown. In this study, we have demonstrated that forced expression ofthe cyclin-dependent kinase inhibitors (CKIs) p27^Kip1 andp21^Cip1/WAF1 in human intestinal epithelial cells led toexpression of differentiation markers at both the mRNA and proteinlevels. Cell differentiation was temporally dissociated from inhibitionof retinoblastoma protein phosphorylation and growth arrest, alreadyestablished 1 day after infection with recombinant adenoviruses.p27^Kip1 proved significantly more efficient thanp21^Cip1/WAF1 in induction of cell differentiation. Incontrast, forced expression of p16^INK4a resulted in growtharrest without induction of differentiation markers. These resultsimplicate both p27^Kip1 and p21^Cip1/WAF1 in thedifferentiation-timing process, but p21^Cip1/WAF1 may actindirectly by increasing p27^Kip1 levels. These results alsosuggest that induction of intestinal epithelial cell differentiation byCKIs is not related to their effects on the cell cycle and may involveinteractions with cellular components other than cyclins andcyclin-dependent kinases.