异育银鲫体内盐酸双氟沙星血浆蛋白结合率的变化与其药代动力学研究

为了研究盐酸双氟沙星(difloxacin, DIF)在异育银鲫体内血浆蛋白结合率的变化及其与药代动力学之间的关系, 实验采用超滤法测定了DIF在异育银鲫体内血浆蛋白结合率, 运用HPLC测定其对应时间点药物浓度, 并分析了血浆蛋白结合率变化对DIF体内处置的影响。实验以感染嗜水气单胞菌的异育银鲫为感染组, 健康异育银鲫为对照组。结果显示: 感染组各时间点DIF血浆蛋白结合率均高于对照组, 感染组与对照组DIF血浆蛋白结合率与总药物浓度呈对数关系: y=-9.01ln x+74.34和y=-4.81ln x+65.15, DIF血浆蛋白结合率与游离药物浓度的对数关系式分别为: y=-6.36ln x+64.91和y=-4.36ln x+ 60.63; 感染组和对照组血浆药时曲线均可使用开放性二室模型描述; 感染组DIF的吸收和消除慢于对照组, 其表观分布容积和曲线下面积大于对照组。结果显示异育银鲫体内感染嗜水气单胞菌促使DIF血浆蛋白结合率升高; 血浆蛋白结合率升高导致药物以结合药物的形式储存于血液中可能是导致药物组织分布受限、消除缓慢、长时间滞留于血液原因之一。     

酶标仪法测定氨茶碱血药浓度的研究

摘要 目的：通过酶标仪法,建立一种研究氨茶碱在新西兰兔体内的药代动力学参数及房室模型的分析方法。方法：新西兰兔以剂量15 mg/kg静脉注射氨茶碱后,应用酶标仪法,测定在274 nm 波长处吸光度值,采用直线相关与回归分析进行数据统计分析氨茶碱在体内的药代动力学参数、回收率实验及房室模型分析。结果：血清茶碱在浓度5～30 μg/mL范围内线性关系良好,回归方程为：A= 0.0013C+0.0074,r²=0.991。各浓度氨茶碱回收率均大于90%,平均回收率为95.83±3.83,RSD均小于15%,回收效果良好。通过氨茶碱体内房室模型拟合得：二室模型拟合显示：由消除相,得外推线浓度线性回归方程：lgC=-0.1271t+1.0562;由分布相,得残数浓度线性回归方程为：lgCr =-0.5829t+1.030,综合得其二室模型的药动学方程为：C=22.000e^-1.342t +11.381e^-0.292t 、T_1/2（α）= 0.516 h、T_1/2（β）= 2.369 h。一室模型拟合显示：一室模型药动学方程为：lgC= -0.2131t + 1.315,其药时方程为：C= 20.649e^-0.491t 、T_1/2= 1.412 h;结论：可以用酶标仪法测定氨茶碱体内药代动力学相关参数,其回收率良好,体内代谢符合二室模型,消除半衰期较长。     

黄土高原水蚀风蚀交错区坡地土壤剖面饱和导水率空间异质性

在黄土高原水蚀风蚀交错区坡面(40 m×350 m)尺度上进行网格(10 m×10 m)取样,用经典统计学和地统计学相结合研究了180个土壤剖面(0-200 cm)各土层扰动土饱和导水率(Ks) 的空间异质性及分布格局。结果表明: 0-20 cm土层的Ks值(5.36×10^-3 cm/s)最大,>20-200 cm各土层的Ks值均小于表层,其值介于4.32×10^-3-4.76×10^-3 cm/s之间。各土层Ks的变异程度相近,均属于中等变异。>20-200 cm各土层Ks 的Kriging 插值图分布格局也表现出一致性,因此可用>20-40 cm土层的Ks值来代表深层Ks值对土壤水分运动进行模拟。除了0-20 cm 的Ks的基台值(C +C₀)为0.154,其它各土层基台值介于0.202-0.276之间,说明0-20 cm的Ks空间异质性小于>20-200 cm各土层。从比值C/(C+C₀)来看, 0-20 cm属于中等自相关,>20-200 cm土层属于强的空间自相关性,同样也验证了黄土高原水蚀风蚀交错区土壤剖面饱和导水率具有空间变异特征。     

嘌呤生物合成调控——Ⅳ.purG OC突变位点及其与调节蛋白的结合功能研究

以野生型O⁺purG⁺和组成型O^C purG⁺为材料,通过体内克隆获得了初级克隆pLBG-1(O⁺)和pLBG-2(O^C),并对它们进行了亚克隆,得到可直接测定其5’调控区序列的亚克隆pLB1933(O⁺)和pLB1927(O^C).测序结果表明,O^C突变发生在purG5’端调控区的16bp PUR box上,使第3位的G变成了A.调节蛋白与PURbox的结合分析表明,调节蛋白能上O⁺purG⁺的PUR box结合,而不能和O⁺purG⁺的PUR box结合.这有力地证明了PUR box是调节蛋白的结合区,而PUR box的第3碱基是相对保守的,它的改变将直接导致PUR box功能的丧失.     

渗透胁迫和离子毒害对转Bt基因棉幼苗生长及离子分布的影响

研究了渗透和盐胁迫处理对转Bt基因抗虫棉(Gossypium hirsutum) 99B种子的萌发和幼苗生长的影响,以及幼苗不同器官离子吸收和分配的差异。结果表明:渗透和盐胁迫均对转Bt基因抗虫棉幼苗的生长有抑制作用,其中PEG的抑制作用最强,而3种盐的抑制程度以CaCl₂>NaCl>Na₂SO₄,且在Na⁺含量相同时,Cl^-的毒害大于SO₄^2-。渗透胁迫下使根、茎和叶中的Na⁺和Cl^-含量提高,K⁺、Ca²⁺、SO₄^2-含量和K⁺/Na⁺、Ca²⁺/Na⁺和SO₄^2-/Cl^-比值降低,且地上部的变化幅度大于地下部的,其中以PEG的影响最为显著,其次是CaCl₂,Na₂SO₄处理最弱。这些说明,转Bt基因抗虫棉99B的耐盐性较弱。     

不同耐盐植物根际土壤盐分的动态变化

以甘肃秦王川引大灌区盐渍化土壤为研究背景,用盆栽根袋法对4种耐盐植物根际和非根际土壤pH和盐分离子的动态变化进行了分析比较。结果表明:4种待测植物随着培养时间的延长土壤pH和EC值呈降低趋势。新疆大叶(Medicago Sativa L.cv.Xinjiangdaye)、向日葵(Helianthus annuus)和霸王(Zygophyllum xanthoxylum)生长90 d后根际土壤pH明显低于非根际,而裸麦(Hordeum vulgare var. vulgare)根际较非根际pH差异不大。霸王和新疆大叶根际土壤EC值较非根际高,而裸麦和向日葵的根际与非根际差异不大。4种供试植物根际K⁺均出现亏缺,Ca²⁺、Na⁺、Mg²⁺、SO^2-₄和Cl^-在新疆大叶、霸王和向日葵3种植物根际均出现富集,对于裸麦:Ca²⁺、Mg²⁺和SO^2-₄ 3种离子在植物根际富集,而Cl^-和Na⁺在根际亏缺。随着待测植物培养时间的增加Na⁺/K⁺、Na⁺/Ca²⁺和Na⁺/Mg²⁺ 这3个比值呈降低趋势,说明Na⁺相对于K⁺、Ca²⁺和Mg²⁺的含量降低,生物措施对Na⁺的移除效果较显著。     

拟水狼蛛对食物中镉的吸收和排泄及生物学响应

为明确拟水狼蛛对食物中镉的吸收和排泄及生物学响应,采用原子吸收光谱法检测了连续3代拟水狼蛛对食物中Cd²⁺的吸收和排泄情况,并测定了Cd²⁺对其生长发育、繁殖力和耐饥力的影响。结果表明:食物中过量的Cd²⁺能够通过食物链进行传递并在拟水狼蛛体内积累,积累量随拟水狼蛛代数的增加而增加,第2代和第3代拟水狼蛛体内Cd²⁺积累量浓度显著高于第1代中Cd²⁺积累量,第2代和第3代间差异不显著,积累量与消耗的黑腹果蝇数量极显著正相关,P<0.01;与消耗食物中Cd含量显著正相关,P<0.05。连续3代拟水狼蛛分别吸收了食物中65.4%、68.5%和69.1%的Cd,生物营养级放大因子分别为1.71、2.12和2.17。连续3代拟水狼蛛Cd排泄量极低。Cd处理能显著改变拟水狼蛛背胸甲宽、幼蛛存活率、生长历期和繁殖力。随拟水狼蛛受胁迫代数的增加,幼蛛存活率显著减少,生长历期显著延长。卵袋重量显著减轻,卵数目显著减少,卵体积显著升高。Cd处理还能显著降低拟水狼耐饥力。研究结果可为进一步研究环境中Cd沿土壤-昆虫-天敌传递、放大和生理耐受提供更为充分的理论依据。     

导入TaNHX2基因提高了转基因普那菊苣的耐盐性

我国部分地区土地盐碱化的日益严重,对作物的生长和生态环境产生了显著影响,因此通过植物基因工程手段培育耐盐碱的转基因作物品种对改善作物的生存能力和生态环境,提高作物产量具有重要的意义。采用农杆菌介导法将来自小麦(Triticum aestivum Linn)的Na⁺ /H⁺逆向转运蛋白的基因(vacuolar Na⁺/H⁺ exchanger or antiporter,简称NHX、NHE或NHA),对普那菊苣(Cichorium intybus L.cv.Puna)植株进行了遗传转化。经抗生素筛选以及针对TaNHX2基因的PCR检测和Southern杂交分析,证明获得了28株转TaNHX2基因的普那菊苣植株。用不同浓度NaCl溶液对普那菊苣野生型和T₀代种子、愈伤组织和幼苗生长情况胁迫的研究,结果表明:转TaNHX2基因普那菊苣植株表现出一定的抗性,比野生型明显提高。在300 mmol/L NaCl胁迫下转基因植株种子的出芽率、外植体出愈率和分化率是野生型植株的2-4倍,而500 mmol/L NaCl浓度为野生型和转基因外植体能否生长的临界点。在此临界值下野生型外植体或不能形成愈伤组织、或幼苗不能正常生根、或已生根幼苗不能正常成长,而转基因外植体可以继续形成愈伤组织并正常生根生长。同时对500 mmol/L NaCl胁迫下野生型和转基因普那菊苣幼苗其体内丙二醛含量(MDA)、过氧化氢酶(POD)和超氧化物歧化酶(SOD)活性进行测定,结果表明 转基因植株比野生型植株的MDA含量降低了1-3倍,POD活性提高了1-3倍,SOD活性提高了2-3倍,分析发现普那菊苣的耐盐性与其体内的丙二醛含量(MDA)、过氧化氢酶(POD)和超氧化物歧化酶(SOD)活性密切相关。     

草鱼体内双氟沙星药代动力学研究

为研究双氟沙星（Difloxacin,DIF）在草鱼（Ctenopharynodon idellus）体内的药代动力学以及在各组织中的残留量,采用高效液相色谱法测定在15℃水温状态下单次给草鱼灌喂20 mg/kg剂量的双氟沙星后,得出双氟沙星在各组织以及血液中的药时曲线均都符合二室开放性模型,双氟沙星能够在草鱼体内快速吸收,并且血液及各组织中均有分布,双氟沙星在草鱼体内的药物动力学方程为C=5.056e-0.012t+19.041e-0.011t,其中双氟沙星在血液、肌肉、肝脏、肾脏中吸收半衰期（T_1/2α）分别为0.176h、0.562h、4.562h和1.477h,消除半衰期分别为（T_1/2β）69.492h、65.303h、218.412h和163.937h,总体消除率（CL）分别为0.495、11.181、10.789和7.102 L/（h·kg）,药时曲线下面积（AUC）分别为81.550、1277.55、807.470和1432.150 μg/（L·h）。根据相关规定肌肉中双氟沙星最大残留量300 μg/kg为标准,建议休药期26d以上。     

南方红壤典型水土流失区马尾松林地上林木碳储量的遥感监测——以长汀县河田镇为例

森林碳储量动态变化对揭示区域水土流失治理成效具有重要指示意义。以长汀县河田镇为例,2017年随机设置34个马尾松林样本作为建模集,分别与同期Landsat影像的原始波段、植被指数及主成分因子进行回归分析,构建马尾松（（Pinus massoniana））林地上林木碳储量的最佳反演模型,基于伪不变特征原理的线性归一化法实现该模型在2003、2010年影像上的适用性校正转换,实现研究区2003、2010、2017年马尾松林地上林木碳储量的反演及时空分异特征的研究。结果表明：研究区2017年马尾松林地上林木碳储量最佳遥感反演模型是以绿色植被指数（GNDVI）为自变量构建的指数模型：C₂₀₁₇=0.006e^{14.357GNDVI₂₀₁₇},该模型拟合的决定系数为0.57,平均相对精度为82.19%;2003年、2010年马尾松林地上林木碳储量遥感估测模型为：C₂₀₀₃=0.006e^{（16.4086GNDVI₂₀₀₃+1.1428）}、C₂₀₁₀=0.006e^{（15.1677GNDVI₂₀₁₀+1.5821）},两期校正模型的决定系数均在0.85以上;2003、2010及2017年碳储量分别为8.24 t/hm²、11.34t/hm²、16.14 t/hm²,整体呈上升趋势;地上林木碳储量随海拔、坡度的升高而增加,向阳坡地上林木碳储量高于背阴坡;碳储量增长率随海拔、坡度的升高而降低,背阴坡碳储量增长率高于向阳坡。     

水产用聚维酮碘对异育银鲫养殖的安全性评价

评价水产用聚维酮碘对异育银鲫(Carassius auratus gibelio)养殖的安全性,为其在异育银鲫养殖中的安全应用提供了重要的科学依据,本研究参照国家标准及相关法规,在观察了聚维酮碘对小球藻(Chlorella sp.)生长抑制作用、对水产益生菌抑菌效果以及对大型蚤(Daphnia magna straus)、斑马鱼(Brachydanio rerio)和异育银鲫的急性毒性的基础上,分析其对异育银鲫及其养殖水体主要有害理化因子的影响.实验结果表明,聚维酮碘在终浓度为6.00 ～ 14.00 mg/L时对小球藻生长具有促进作用,对小球藻的半数抑制浓度大于14.00 mg/L,对水产益生菌的最小抑菌浓度为128～512 mg/L,对大型蚤、斑马鱼的半数致死浓度分别为13.44 mg/L、17.63 mg/L.此外,聚维酮碘对异育银鲫的半数致死浓度为74.77 mg/L,而且在养殖水体中加入聚维酮碘至终浓度为0.20 ～ 1.40 mg/L后14 d内,随着聚维酮碘浓度的增加,各浓度组异育银鲫养殖水体的氨氮含量、亚硝酸盐含量均缓慢下降.本研究证实聚维酮碘低毒,但考虑到其可能对异育银鲫养殖水体中大型蚤等浮游动物存在潜在影响,建议其在异育银鲫养殖中的安全应用浓度应不高于1.34 mg/L,在该安全应用浓度内不会引起养殖水中氨氮、亚硝酸盐等有害因子含量的增加.     

蕙兰病株根部内生细菌种群变化

为了研究褐斑病与蕙兰根部内生细菌群落结构和多样性的关联,从野生蕙兰健株和褐斑病株根部分离出内生细菌112株,采用核糖体DNA扩增片段限制性酶切分析(ARDRA),研究了健株和病株内生细菌多样性与群落结构。将内生细菌纯培养物扩增近全长的16S rDNA,并用ARDRA (Amplified Ribosomal DNA Restriction Analysis) 对所分离的菌株进行分型,根据酶切图谱的差异,将健株中的内生细菌分成8个ARDRA型,病株分成13个ARDRA型。并选取代表性菌株进行16S rDNA序列测定。结果表明,健株分离出内生细菌6个属,优势菌群为Bacillus;病株分离出11个属,优势菌群为 Mitsuaria和Flavobacterium。通过回接兰花植物和初步拮抗实验发现,从病株分离出的H5号菌株 (Flavobacterium resistens)使兰花产生病症,而健株中的B02 (Bacillus cereus) 和B22号菌株 (Burkholderia stabilis) 对菌株H5有拮抗作用。     

Reclassification of Aeromonas hydrophila subsp. dhakensis Huys et al. 2002 and Aeromonas aquariorum Martínez-Murcia et al. 2008 as Aeromonas dhakensis sp. nov. comb nov. and emendation of the species Aeromonas hydrophila

Previous studies indicate that Aeromonas aquariorum and Aeromonas hydrophila subsp. dhakensis are the same taxon and suggest that they should be synonymized. Using a polyphasic approach, the phenotypic and phylogenetic relationship of A. aquariorum with the 3 defined A. hydrophila subspecies (i.e. dhakensis, hydrophila, ranae) was investigated. Phylogenetic trees derived from the 16S rRNA, rpoD or gyrB genes and a multilocus phylogenetic analysis (with the concatenated sequences of gyrB, rpoD, recA, dnaJ and gyrA) confirmed that both A. aquariorum and A. hydrophila subsp. dhakensis are a unique taxon, different from the other A. hydrophila subspecies, corroborating the phenotypic and DNA–DNA hybridization (DDH) results. A formal synonymization of A. aquariorum and A. hydrophila subsp. dhakensis and a reclassification of both as Aeromonas dhakensis sp. nov. comb nov. is therefore proposed.     

Metabolic engineering of Aeromonas hydrophila 4AK4 for production of copolymers of 3-hydroxybutyrate and medium-chain-length 3-hydroxyalkanoate

A mutant termed Aeromonas hydrophila AKLF was constructed by deleting acetic acid pathway related genes pta and ackA in A. hydrophila 4AK4. Accumulation of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) in A. hydrophila AKLF was increased by 47% from 2.11 to 3.10 g/L associated with a reduction on acetic acid formation compared with A. hydrophila 4AK4 when lauric acid was used as carbon resource. A. hydrophila AKLF harboring pVGAB encoding Vitreoscilla hemoglobin, β-ketothiolase and acetoacetyl-CoA reductase was found to produce 85% more PHBHHx compared to its wild type. Expression of plasmid pD_EcL_Pp harboring genes related to fatty acid metabolism in A. hydrophila AKLF led to 63% more PHBHHx production than A. hydrophila 4AK4. Replacing phaC in A. hydrophila AKLF with a mutant phaC2 from Pseudomonas stutzeri 1317 resulted in enhanced production of copolymers of 3-hydroxybutyrate and medium-chain-length 3-hydroxyalkanoates compared to A. hydrophila 4AK4 harboring the mutant phaC2 in the chromosome as control.     

Giardia duodenalis: Kinetics of cyst elimination and the systemic humoral and intestinal secretory immune responses in gerbils (Meriones unguiculatus) experimentally infected

This study aimed to determine the pre-patent period and to evaluate the kinetics of cyst elimination and the systemic humoral (IgA, IgG₁, IgG_2a, IgM, IgE) and intestinal secretory (IgA) immune responses in gerbils (Meriones unguiculatus) experimentally innoculated with different doses of Giardia duodenalis trophozoites. Forty-eight animals aged 6-8 weeks were used, equally distributed among six groups, five groups innoculated with different doses of trophozoites (10¹, 10², 10³, 10⁴, 10⁵) and one control (non-infected) group. Coproparasitological examinations were carried out daily up to 91 days after inoculation (d.a.i.) to determine the pre-patent period and the kinetics of cyst elimination. Blood and stool samples were weekly collected for antibody assays. The pre-patent period was observed from the 9 d.a.i. onwards, with intermittent elimination of variable quantities of cysts up to 27 d.a.i.. All infected gerbils, irrespective of the dose received, were able to mount systemic humoral immune responses as evidenced by specific IgM titers from 7 to 28 d.a.i., corresponding to the peak of cyst elimination, followed by high and persistent IgG1 titers. Intestinal secretory responses were also seen with two peaks of fecal IgA titers, corresponding to IgM and IgG1response peaks, respectively. In conclusion, systemic and intestinal humoral immune responses were related to the control of giardiasis in this experimental model.     

Fabacyl acetate, a germination stimulant for root parasitic plants from Pisum sativum

A germination stimulant, fabacyl acetate, was purified from root exudates of pea (Pisum sativum L.) and its structure was determined as ent-2′-epi-4a,8a-epoxyorobanchyl acetate [(3aR,4R,4aR,8bS,E)-4a,8a-epoxy-8,8-dimethyl-3-(((R)-4-methyl-5-oxo-2,5-dihydrofuran-2-yloxy)methylene)-2-oxo-3,3a,4,5,6,7,8,8b-decahydro-2H-indeno[1,2-b]furan-4-yl acetate], by 1D and 2D NMR spectroscopic, ESI- and EI-MS spectrometric, X-ray crystallographic analyses, and by comparing the ¹H NMR spectroscopic data and relative retention times (RR_t) in LC-MS and GC-MS with those of synthetic standards prepared from (+)-orobanchol and (+)-2′-epiorobanchol. The ¹H NMR spectroscopic data and RR_t of fabacyl acetate were identical with those of an isomer prepared from (+)-2′-epiorobanchol except for the opposite sign in CD spectra. This is the first natural ent-strigolactone containing an epoxide group. Fabacyl acetate was previously detected in root exudates of other Fabaceae plants including faba bean (Vicia faba L.) and alfalfa (Medicago sativa L.).     

Comparison of phenotypical and genetic identification of Aeromonas strains isolated from diseased fish

Phenotypicaly identified Aeromonas strains (n=119) recovered mainly from diseased fish were genetically re-identified and the concordance between the results was analysed. Molecular characterization based on the GCAT genus specific gene showed that only 90 (75.6%) strains belonged to the genus Aeromonas. The 16S rDNA-RFLP method identified correctly most of the strains with the exception of a few that belonged to A. bestiarum, A. salmonicida or A. piscicola. Separation of these 3 species was correctly assessed with the rpoD gene sequences, which revealed that 5 strains with the RFLP pattern of A. salmonicida belonged to A. piscicola, as did 1 strain with the pattern of A. bestiarum. Correct phenotypic identification occurred in only 32 (35.5%) of the 90 strains. Only 14 (21.8%) of the 64 phenotypically identified A. hydrophila strains belonged to this species. However, coincident results were obtained in 88% (15/17) of the genetically identified A. salmonicida strains. Phenotypic tests were re-evaluated on the 90 genetically characterized Aeromonas strains and there were contradictions in the species A. sobria for a number of previously published species-specific traits. After genetic identification, the prevailing species were A. sobria, A. salmonicida, A. bestiarum, A. hydrophila, A. piscicola and A. media but we could also identify a new isolate of the recently described species A. tecta. This work emphasizes the need to rely on the 16S rDNA-RFLP method and sequencing of housekeeping genes such as rpoD for the correct identification of Aeromonas strains.     

Pharmacokinetics, tissue distribution and excretion study of dl-praeruptorin A of Peucedanum praeruptorum in rats by liquid chromatography tandem mass spectrometry

dl-Praeruptorin A (Pd-Ia), isolated from Chinese traditional herbal medicine Peucedanum praeruptorum Dunn, has been proved to be a novel Ca²⁺-influx blocker and K⁺-channel opener, and displayed bright prospects in prevention and therapy of cardiac diseases. The aim of this study was to investigate the pharmacokinetics, tissue distribution and excretion of Pd-Ia in rats following a single intravenous (i.v.) administration. The levels of Pd-Ia in plasma, tissues, bile, urine and feces were measured by a rapid and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. The results showed that Pd-Ia was rapidly distributed and then eliminated from rat plasma and manifested linear dynamics in dose range of 5-20 mg/kg. The mean elimination half-life (t_1/2) of Pd-Ia for 5, 10 and 20 mg/kg dose were 57.46, 60.87 and 59.01 min, respectively. The major distribution tissues of Pd-Ia in rats were spleen, heart and lung, and low polarity enabled Pd-Ia to cross the blood-brain barrier. There was no long-term accumulation of Pd-Ia in rat tissues. Total recoveries of Pd-Ia within 24 h were low (0.097% in bile, 0.120% in urine and 0.009% in feces), which might be resulted from liver first pass effect.     

Epithelial transport and barrier function in occludin-deficient mice

Background and Aims

This study aimed at functional characterization of the tight junction protein occludin using the occludin-deficient mouse model.

Methods

Epithelial transport and barrier functions were characterized in Ussing chambers. Impedance analysis revealed the ionic permeability of the epithelium (R^e, epithelial resistance). Conductance scanning differentiated transcellular (G^c) and tight junctional conductance (G^tj). The pH-stat technique quantified gastric acid secretion.

Results

In occludin+/+ mice, R^e was 23±5 Ω cm² in jejunum, 66±5 Ω cm² in distal colon and 33±6 Ω cm² in gastric corpus and was not altered in heterozygotic occludin+/− or homozygotic occludin−/− mice. Additionally, [³H]mannitol fluxes were unaltered. In the control colon, G^c and G^tj were 7.6±1.0 and 0.3±0.1 mS/cm² and not different in occludin deficiency. Epithelial resistance after mechanical perturbation or EGTA exposition (low calcium switch) was not more affected in occludin−/− mice than in control. Barrier function was measured in the urinary bladder, a tight epithelium, and in the stomach. Control R^t was 5.8±0.8 kΩ cm² in urinary bladder and 33±6 Ω cm² in stomach and not altered in occludin−/− mice. In gastric corpus mucosa, the glandular structure exhibited a complete loss of parietal cells and mucus cell hyperplasia, as a result of which acid secretion was virtually abolished in occludin−/− mice.

Conclusion

Epithelial barrier characterization in occludin-deficiency points against an essential barrier function of occludin within the tight junction strands or to a substitutional redundancy of single tight junction molecules like occludin. A dramatic change in gastric morphology and secretory function indicates that occludin is involved in gastric epithelial differentiation.