失血性休克引起大鼠肠系膜动脉平滑肌依钙K^＋通道活动改变

在由股动脉放血制备的失血性休克大鼠模型急性分离的肠系膜动脉平滑肌细胞上,利用膜片箝单通道记录技术观察了血管平滑肌依钙K^ 通道（BKca)的活动,发现在对去甲肾上腺素（NE）反应性增高的休克代偿期,BKca的开放概率（P0)和单位电导都显著较正常动物的低,P0的改变主要是由通道的慢关闭时间常数（τcs)增大引起关闭时间延长所致;而处于对NE反应性降低的休克失代偿期,BKca的P0和单位电导都高于正常动物,P0的变化也主要是τcs减小所致。     

肾缺血增强大鼠延髓腹外侧头端区神经元电话动和Fos蛋白表达

在67只切断两侧缓冲神经的麻醉Sprague-Dawley大鼠,应用细胞外记录的电生理方法和免疫组织化学技术,分别观察肾缺血对延髓腹外侧头端区巨细胞旁外侧核神经元自发放电活动和Fos蛋白表达的影响.所得结果如下(1)左肾动脉阻断后,28个单位的放电频率由11.40±1.08增至21.1±1.74spikes/s(P<0.001),血压和心率无明显变化(P>0.05);(2)在17个放电单位中,应用腺苷受体拮抗剂8-苯茶碱(8-phenyltheophylline,10mg/kg)可明显抑制肾缺血的兴奋效应(P<0.05);(3)肾缺血后,延髓腹外侧头端区的Fos蛋白样免疫反应神经元显著增加(P<0.01);(4)预先应用8-苯茶碱可明显减弱肾缺血所激活的Fos蛋白表达反应(P<0.05).以上结果提示肾缺血增强延髓腹外侧头端区神经元的放电活动和Fos蛋白表达,而此作用可能与肾脏缺血所产生的腺苷激活肾内感受器有关.     

颈动脉注射辣椒素对脑干心血管相关核团一氧化氮合酶和Fos表达的影响

实验采用NADPH－d组化技术和Fos蛋白免疫组化技术相结合的方法,观察了颈动脉注射辣椒不时,大鼠脑干心血管相关核团内NOS和Fos蛋白的分布以及两者的共存关系。结果显示：（1）颈动脉注射辣椒不可诱发脑干中最后区（AP）、孤束核（NTS）、巨细胞旁外侧核（PGL）和蓝斑（LC）等多个部位Fos样免疫反应（FLI)神经元显著增加 中脑中央灰质（PAG）和中缝核群（RN）的FLI神经元无明显改变。（2）PGL和NTS内NO合成神经元以及PGL内双标神经元数量也明显增加,而AG和RN中NO合成神经元无明显变化,在LC和AP仅偶见或未见NO合成神经元。（3）预先应用辣椒素受体阻断剂钌红或NMDA受体阻断剂MK－801,则明显减弱辣椒素的上述效应,以上结果表明,颈动脉注射辣椒素可兴奋脑干心血管活动相关核团神经元,NO在脑干核团对辣椒素的反应中发挥间接的调制作用,辣椒素的效应由香草酸受体（辣椒素受体）介导并有谷氨酸参与。     

The C-terminal cytoplasmic Lys-thr-X-X-X-Trp motif in frizzled receptors mediates Wnt/beta-catenin signalling

Frizzled receptors are components of the Wnt signalling pathway, but how they activate the canonical Wnt/beta-catenin pathway is not clear. Here we use three distinct vertebrate frizzled receptors (Xfz3, Xfz4 and Xfz7) and describe whether and how their C-terminal cytoplasmic regions transduce the Wnt/beta-catenin signal. We show that Xfz3 activates this pathway in the absence of exogenous ligands, while Xfz4 and Xfz7 interact with Xwnt5A to activate this pathway. Analysis using chimeric receptors reveals that their C-terminal cytoplasmic regions are functionally equivalent in Wnt/beta-catenin signalling. Furthermore, a conserved motif (Lys-Thr-X-X-X-Trp) located two amino acids after the seventh transmembrane domain is required for activation of the Wnt/beta-catenin pathway and for membrane relocalization and phosphorylation of Dishevelled. Frizzled receptors with point mutations affecting either of the three conserved residues are defective in Wnt/beta-catenin signalling. These findings provide functional evidence supporting a role of this conserved motif in the modulation of Wnt signalling. They are consistent with the genetic features exhibited by Drosophila Dfz3 and Caenorhabditis elegans mom-5 in which the tryptophan is substituted by a tyrosine.     

Trifluoromethanesulfonamide, diphenylphosphoramide and diphenylthiophosphoramide of (R)-(+)-1,1'-binaphthyl-2,2'-diamine as chiral catalyst ligands for the titanium(IV) alkoxide-promoted addition of diethylzinc to aldehydes

Chiral trifluoromethanesulfonamide 4, diphenylphosphoramides 5 and 6, and phenylthiophosphoramide 7 were prepared from the reaction of trifluoromethanesulfonic anhydride, diphenylphosphinic chloride, and diphenylthiophosphinic chloride with (R)-(+)-1,1'-binaphthyl-2, 2'-diamine, respectively. They were used as catalytic chiral ligands in the asymmetric addition reaction of diethylzinc to aldehydes in the presence of titanium(IV) isopropoxide to give the corresponding sec-alcohols with 43-54%, 18-22%, 30-34%, and 52-64% enantiomeric excess, respectively. Copyright 2000 Wiley-Liss, Inc.     

Porphyromonas gingivalis proteinases as virulence determinants in progression of periodontal diseases

Porphyromonas gingivalis, one of the major causative agents of periodontal diseases, produces large amounts of arginine- and lysine-specific cysteine proteinases in cell-associated and secretory forms, which are now referred to as Arg-gingipain (Rgp) and Lys-gingipain (Kgp), respectively. A number of studies have revealed that these proteinases are closely associated with the periodontopathogenesis of this bacterium: destruction of periodontal connective tissues, disruption of host defense mechanisms, and development and maintenance of inflammation in periodontal pockets. With respect to the physiology of the bacterium, Rgp and Kgp are indispensable for it to obtain nutrients from the environment, since it cannot utilize saccharides as carbon/energy sources for growth and totally depends on peptides and amino acids that are provided from environmental proteins by Rgp and Kgp. Furthermore, proteolytic activities of Rgp and Kgp contribute to processing/maturation of various cell-surface proteins of P. gingivalis, such as fimA fimbrilin (a subunit of major fimbriae), 75-kDa protein (a subunit of minor fimbriae), hemagglutinins, and the hemoglobin receptor protein, which are important for the bacterium to colonize and proliferate in the gingival crevice and to invade the periodontium. These findings strongly indicate critical roles of Rgp and Kgp in the virulence of P. gingivalis.     

Characterization of the functionally related sites in the neural inducing gene noggin

Previously we have shown that blocking bone morphogenetic protein (BMP) receptor signaling by a dominant negative BMP receptor causes neurogenesis in Xenopus animal caps (ACs), whereas the physiological neural inducer noggin acts as a homodimer physically binding to BMP-4 and disrupting its signaling at the ligand level. The present study attempted to elucidate the relationship between the structure and function of noggin. By replacing some cysteine residues with serine residues through a site-directed mutagenesis strategy, we generated three noggin mutants, C145S, C205S, and C(218, 220, 222)S (3CS). Although mRNAs encoded by these mutants were translated as efficiently as wild-type (WT) noggin mRNA, they behaved differently when expressed in vivo. Expression of WT noggin or C205S in Xenopus ACs converted the explants (prospective ectoderm) into neural tissue, indicated by the neural-like morphology and expression of the pan neural marker NCAM in the ACs. In contrast, ACs expressing C145S or 3CS sustained an epidermal fate like the control caps. Similar results were observed in the mesoderm where C205S (but not C145S and 3CS) displayed dorsalizing activity as well as WT noggin. Altogether, our results suggest that Cys145 alone or Cys(218, 220, 222) as a whole in noggin protein is required for the biological activities of noggin, probably participating in the dimerization of noggin with BMP-4 or itself.