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51.
In vitro colonization ability of human colon mucosa by exogenous Lactobacillus strains 总被引:1,自引:0,他引:1
Leila-ouassila Sarem-Damerdji Farzin Sarem Luc Marchal Jean-Pierre Nicolas 《FEMS microbiology letters》1995,131(2):133-137
Abstract A 5.4 kb Hind III DNA fragment carrying the gene encoding raw starch-digesting α-amylase (RSDA), has been previously cloned from Bacillus circulans F-2 and expressed in Escherichia coli [Kim et al. (1990) Biochim. Biophys. Acta 1048, 2233–2238]. Interestingly, when the cell extract of E. coli harboring a plasmid carrying this fragment was incubated with l M NaCl, it exhibited about 10 times higher enzyme activity than when assayed without NaCl. Differential zymograms showed two different amylase activities: one for RSDA and the other for a salt-dependent a-amylase (SDA). Even though RSDA activity was detected without NaCl, SDA activity was detected only in high concentrations of NaCl. SDA activity was fully detected at above l M NaCl. Results from subcloning of the genes, fractionation analysis of cell extracts, and immunological assays clearly suggested that the two amylases are genetically distinct and that genes for both enzymes are closely linked on the 5.4 kb DNA fragment. 相似文献
52.
Catherine Iehl Sylvie Dlos Olivier Guirou Rothwell Tate Jean-Pierre Raynaud Pierre-Marie Martin 《The Journal of steroid biochemistry and molecular biology》1995,54(5-6)
The present study describes the independent expression of the type 1 and 2 isoforms of human 5α-reductase in the baculovirus-directed insect cell expression system and the selectivity of their inhibition. The catalytic properties and kinetic parameters of the recombinant isozymes were consistent with published data. The type 1 isoform displayed a neutral (range 6–8) pH optimum and the type 2 isoform an acidic (5–6) pH optimum. The type 2 isoform had higher affinity for testosterone than did the type 1 isoform (Km = 0.5 and 2.9 μM, respectively). Finasteride and turosteride were selective inhibitors of the type 2 isoform (Ki (type 2) = 7.3 and 21.7 nM compared to Ki (type 1) = 108 and 330 nM, respectively). 4-MA and the lipido-sterol extract of Serenoa repens (LSESr) markedly inhibited both isozymes (Ki (type 1) = 8.4 nM and 7.2 μg/ml, respectively; Ki (type 2) = 7.4 nM and 4.9 μg/ml, respectively). The three azasteroids were competitive inhibitors vs substrate, whereas LSESr displayed non-competitive inhibition of the type 1 isozyme and uncompetitive inhibition of the type 2 isozyme. These observations suggest that the lipid component of LSESr might be responsible for its inhibitory effect by modulating the membrane environment of 5α-reductase. Partially purified recombinant 5α-reductase type 1 activity was preserved by the presence of lipids indicating that lipids can exert either stimulatory or inhibitory effects on human 5α-reductase. 相似文献
53.
Plants and fungi possess an outwardly directed plasma membrane proton pump that may regulate intracellular pH. We provide the first demonstration that amoebae of the slime mould Dictyostelium discoideum also possess a similar proton pump. It can be assayed either as an ATPase activity in highly purified plasma membranes or as a proton pump, after solubilization and reconstruction into liposomes. The pump is inhibited by vanadate, diethylstilbestrol (DES) and miconazole but not by azide or ouabain. The proton pump described here may represent the target for the action of DES and miconazole, both of which have previously been shown to induce stalk cell formation during the in vitro development of Dictyostelium. 相似文献
54.
β-Sitosterol 1 is metabolised to cholesterol 5 by phytophagous insects. It has been previously shown that fucosterol-24,28 epoxide 3 is transformed into 5 in Locusta migratoria, desmosterol 4 being an intermediate. It is now established that locusts transform [3-3H] fucosterol propionate into the corresponding labelled epoxide 3, recovered as such or as an oxazoline derivative 11. 相似文献
55.
Jean-Pierre Thieuloy 《Geobios》1977,10(3):395-461
The boreal Ammonites (and the more or lessphylogenetically related ones) of the southeast France (Tethyan Realm) are described and figured. 24 forms are refered to, or compared with, previously identified species. 3 are left under open nomenclature, and 7 are new ones. Two new subgenus: Julianites (Paquiericeras) and Lemurostephanus (Olcostephanus) are also introduced.Their biostratigraphic position in the Frenchzonal scheme is detailed. Their contribution to the establishment of correlation between the Boreal and Tethyan provinces is stressed.The most interesting feature is the identification of a Prodichotomites horizon just below the Verrucosum zone, allowing comparison of the definition of the Lower-Upper Valanginian boundary in these two paleobiogeographic realms. 相似文献
56.
Michel Hughes Daniéle Duval Heidy Schmid Patrick Kitabgi Michel Lazdunski Jean-Pierre Vincent 《Life sciences》1982,31(5):437-443
This paper describes the interaction of apamin, the bee venom neurotoxin, with its receptor in the guinea pig colon. The pharmacological activity of the toxin was assayed by measuring its contracting effect on guinea pig colon preparations that had been previously relaxed by neurotensin. The IC50 value of apamin in this bioassay is 7 nM. These pharmacological data are compared to the binding properties of apamin to smooth muscle membranes prepared from guinea pig colon. The highly radiolabeled monoiododerivative of apamin binds to its colon receptor with a dissociation constant . The maximal binding capacity of colonic membranes is 30dfmol/mg of protein. The dissociation constant of the unmodified toxin is 23 pM. The difference between the toxin concentrations that produce half-maximal effects in the binding and pharmacological studies arises from the different experimental conditions used for the two assays. 相似文献
57.
Summary A microcalorimetric study is proposed to follow the degradation of straw by a mixed bacterial culture. The effect of an alkali pretreatment of straw is described. 相似文献
58.
Jacqueline Jollès Jean-Pierre Périn Pierre Jollès 《Molecular and cellular biochemistry》1977,17(1):39-44
Summary The purification of Ostrich (Struthio camelus) egg-white lysozyme is reported. The quantitative amino acid composition, the molecular weight, the N-terminal sequence (34 amino acids) as well as kinetic studies allow to range this enzyme among the goose type lysozymes.106th communication on lysozymes. 相似文献
59.
Monique Decastel Anh-Tuan Tran Jean-Pierre Frénoy 《Biochemical and biophysical research communications》1982,106(2):638-643
The binding of 4-methylumbelliferyl-α-D-galactopyranoside, -β-D-galactopyranoside and -D-Galβ(1→3)DGalNac to peanut agglutinin was studied by fluorescence. Peanut agglutinin quenched the fluorescence intensity of 4-methylumbelliferyl-α-D-galactopyranoside but enhanced that of the two 4-methylumbelliferyl-β-galactosides. For α-D-galactopyranoside, the association constants measured at 4 and 25°C were 3.4 × 103 and 1.7 × 103 M?1 respectively, and for D-Galβ(1→3)DGalNac, 1.5 × 105 and 3.3 × 104 M?1. The binding enthalpies estimated from these values are consistent with the existence of extended sugar binding sites in the peanut agglutinin molecule. 相似文献
60.
Neurotensin and Neuromedin N Are Differently Metabolized in Ventral Tegmental Area and Nucleus Accumbens 总被引:2,自引:2,他引:0
Frédéric Checler Pascale Dauch Yoshinori Masuo Jean-Pierre Vincent 《Journal of neurochemistry》1991,56(4):1320-1328
Whole homogenates and membrane-bound and cytosoluble fractions prepared from rat ventral tegmental area (VTA) and nucleus accumbens were examined for their content of peptidasic activities and for their ability to metabolize neurotensin and its natural related hexapeptide neuromedin N. No qualitative differences were observed between these two brain regions concerning the presence and the subcellular distribution of a series of activities able to hydrolyze various specific fluorimetric enzymatic substrates. However, aminopeptidase B, endopeptidase 24-15, and endopeptidase 24-11 were significantly lower in the VTA than in the nucleus accumbens membrane preparations, while proline endopeptidase was detected in significantly higher amount only in the cytosolic fraction prepared from nucleus accumbens. Both neurotensin and neuromedin N were metabolized more rapidly in the nucleus accumbens than in the VTA. Furthermore, the degradation rate of neuromedin N was considerably faster than that of neurotensin whatever the cerebral area examined. Studies carried out with highly specific peptidase inhibitors revealed that endopeptidase 24-15 mainly contributed to the catabolism of neurotensin in homogenates and membrane-bound preparations of nucleus accumbens and VTA, while aminopeptidase B appeared predominantly responsible for the rapid disappearance of neuromedin N in both cerebral tissues. The possibility that the different metabolic processes of the two peptide congeners could explain their distinct pharmacological profiles observed after their microinjection in the nucleus accumbens and in the VTA is discussed. 相似文献