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Anaerobic bacteria predominate in the normal human fecal flora, out-numbering aerobes at least 100 to one. The two most prevalent organisms are Bacteroides fragilis and Bifidobacterium. Ileostomy flora is, on the other hand, chiefly aerobic and the total count is lower (108 per ml of fluid, compared to 1010 per gram for feces). In normal people, small bowel bacterial counts are generally 105 per ml or less. The upper small bowel consists primarily of Gram-positive aerobes in small numbers. In the terminal ileum, counts are higher and aerobes and anaerobes are present in equal numbers. In the presence of acute obstruction and certain bowel stasis or other syndromes, the small bowel flora may become relatively profuse and fecal in type. The stomach normally has less than 103 organisms per ml but counts are higher in gastric samples with pH above 4.0.Intestinal bacteria are important in such processes as conversion of bilirubin to urobilinogen, supply of vitamin K to the host, defense against infection, bile acid deconjugation and conversion, infections related to the bowel, the malabsorption of blind loop and other bacterial overgrowth syndromes, and hepatic coma.  相似文献   
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The role of endogenous benzodiazepine receptor ligands in the pathogenesis of hepatic encephalopathy was studied in humans and in rat models of hepatic encephalopathy. Endogenous benzodiazepine ligands were extracted from rat brain and human CSF by acid treatment and purification by HPLC. Detection and partial characterization of these endogenous benzodiazepine ligands were carried out using both radioreceptor binding assays and radioimmunoassays with anti-benzodiazepine antibodies. Four different benzodiazepine receptor ligands were identified in human and rat tissue, two of which may be diazepam and desmethyldiazepam, based on elution profiles and anti-benzo-diazepine antibody reactivity. Human CSF and serum from patients with hepatic encephalopathy contained approximately 10 times more endogenous benzodiazepine receptor ligand than CSF from controls or nonencephalopathic patients with liver disease. The levels of brain benzodiazepine receptor ligand compounds were also increased approximately 10-fold in rats suffering from fulminant hepatic failure, but not in rats with portacaval shunts, a model of chronic hepatic disease. The increased concentrations of these substances could be behaviorally significant and may contribute to the pathogenesis of hepatic encephalopathy.  相似文献   
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Summary Using a combinatorial peptide library method, we identified YIYGSFK as an efficient and specific peptide substrate for pp60c-src protein tyrosine kinase (PTK) [Lam et al., Int. J. Pept. Protein Res., 45 (1995) 587]. Employing YIYGSFK as a template, we synthesized and evaluated a series of pseudosubstrate-based inhibitors for pp60c-src. We found that the efficiency of a given inhibitor was highly dependent on the specific tyrosine analog used at the phosphorylation site of the substrate. One of these pseudosubstrate inhibitors, YI(2-Nal)GSFK, selectively inhibited the kinase activity of pp60c-src, with a Ki of 24 M. This peptide inhibitor exhibited selectivity for pp60c-src as compared to other PTKs tested, such as c-Abl and Bcr-Abl. Our results suggest that selective inhibitors for a specific PTK can be developed when the structure of a specific and efficient small peptide substrate for this PTK can be used as a template for structure modification.Abbreviations 1-Nal l-1-naphthylalanine - 2-Nal l-2-naphthylalanine - BOP benzotriazolyl-N-oxy-tris(dimethylamino)-phosphonium hexafluorophosphate - BSA bovine serum albumin - cAPK cyclic AMP-dependent protein kinase - DIEA diisopropylethylamine - EGFR epidermal growth factor receptor - Fmoc fluorenylmethoxycarbonyl - HOBt 1-hydroxybenzotriazole - MES 2-[N-morpholino]ethanesulfonic acid - PBS phosphate-buffered salts - pCl l-p-chlorophenylalanine - pF l-p-fluorophenylalanine - PTK protein tyrosine kinase - TLC thin-layer chromatography  相似文献   
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Summary A study has been made of the insertional properties of transposon Tn7, a 14 kilobase transposable element encoding resistances to trimethoprim, streptomycin and specitinomycin. It has previously been shown that Tn7 transposes at a low frequency and with low specificity into multiple sites in large transmissible plasmids. However, Tn7 transposes with extrame specificity and at high efficiency into the E. coli chromosome. In all cases we have studied, insertion of Tn7 into the chromosome has occurred at a unique site and with a unique orientation. A combination of genetic and biochemical techniques have been used to precisely locate this site on the E. coli chromosome to minute 82 on the linkage map between markers glmS and uncA.To investigate the nature of this highly specific transpositional event, a small region of the E. coli chromosome that includes the unique site, was cloned into the plasmid vector pBR322. Subsequently a lkb restriction fragment, including the Tn7 insertion site, was sub-cloned from this plasmid into the plasmid pACYC184. We show that Tn7 transposes into both these plasmid recombinants with the frequency and specificity characteristie of the E. coli chromosome.  相似文献   
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