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31.
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
32.
Luc Cynober Jean-Louis Auget Jean Agneray Ohvanesse G. Ekindjian 《Biochemical and biophysical research communications》1984,123(2):535-542
2-deoxyglucose uptake rates at low sugar concentrations (less than 500 μM) appeared to be lower than those predicted by the Michaelis-Menten model which correctly described higher concentrations. This phenomenon which we will call concentration-dependent transport lag, was also observed for L-glucose uptake which suggest that this phenomenon is carrier-independent. A model involving the perimembrane space is developed which, for L-glucose, gives k1 = 0.931 ± 0.072 × 10?6 l. mg protein?1. minute?1, k2 = 2.97 ± 0.19 × 10?7 l. mg protein?1. minute?1 and So = 88,8 ± 4,3 μM; where k1 is the diffusion constant in the cell membrane, k2 is the diffusion constant in the perimembrane space and So the sugar concentration required in the external medium in order to provide an équivalent sugar concentration in the transport carrier area. 相似文献
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34.
Juan Ortín Concepción Martínez Lucía del Río Mercedes Dávila Cecilio López-Galíndez Nieves Villanueva Esteban Domingo 《Gene》1983,23(2):233-239
The complete genetic information contained in the influenza virus RNA segment 7 of the A/Bangkok/ (H3N2) strain has been cloned by in vitro synthesis of the complementary dsDNA and its insertion into plasmid pBR322. The nucleotide sequence of the viral RNA segment has been determined from the cDNA insert. It is 1027 nucleotides long, and contains two open reading frames, as shown for other influenza virus strains. When compared with the previously published sequence for the A/Udorn/72 (H3N2) strain, 15 nucleotide exchanges are observed, most of them silent mutations, and only two causing amino acid changes in each of the M1 and M2 protein sequences. 相似文献
35.
Pyrolytic Methylation-Gas Chromatography of Whole Bacterial Cells for Rapid Profiling of Cellular Fatty Acids
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A novel, on-line derivatization technique has been developed which enables generation of fatty acid methyl ester (FAME) profiles from microorganisms by gas chromatography-mass spectrometry without the need for laborious and time-consuming sample preparation. Microgram amounts of bacterial cells are directly applied to a thin ferromagnetic filament and covered with a single drop of methanolic solution of tetramethylammonium hydroxide. After air drying, the filament is inserted into a special gas chromatograph inlet equipped with a high-frequency coil, thus enabling rapid inductive heating of the ferromagnetic filament. This so-called Curie-point heating technique is shown to produce patterns of bacterial FAMEs which are qualitatively and quantitatively nearly identical to those obtained from extracts of methylated lipids prepared by conventional sample pretreatment methods. Relatively minor differences involve the loss of hydroxy-substituted fatty acids by the pyrolytic approach as well as strongly enhanced signals of FAMEs derived from mycolic acids. This type of pyrolysis enables on-line derivatization and thermal extraction of volatile derivatives for analysis, whereas the residual components remain on a disposable probe (ferromagnetic wire) of a pyrolytic device. The reduced sample size (micrograms instead of milligrams) and the lack of sample preparation requirements open up the possibility of rapid microbiological identification of single colonies (thus overcoming the need for time-consuming subculturing) as well as analysis of FAME profiles directly from complex environmental samples. 相似文献
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37.
Role of glycerol 3-phosphate and glycerophosphate acyltransferase in the nutritional control of hepatic triacylglycerol synthesis 总被引:7,自引:7,他引:0
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![点击此处可从《The Biochemical journal》网站下载免费的PDF全文](/ch/ext_images/free.gif)
1. Glycerol 3-phosphate content of isolated hepatocytes from starved rats and of glycogen-depleted hepatocytes from fed rats was low and severely limited triacylglycerol synthesis. 2. Raising the glycerol 3-phosphate content by addition of precursors to the cells resulted in a hyperbolic-like relationship between triacylglycerol synthesis and cellular glycerol 3-phosphate content. Statistical analysis of the curves showed no significant differences between the nutritional states either at saturating or at subsaturating glycerol 3-phosphate content. 3. Vmax. of glycerophosphate acyltransferase measured in homogenized hepatocytes was decreased by 30–40% in starvation. There was no change in apparent Km for glycerol 3-phosphate. Since at saturating glycerol 3-phosphate content esterification rates in hepatocytes of both nutritional states were identical, the enzyme is not limiting esterification under this condition. 4. At subsaturating glycerol 3-phosphate content the flux through glycerophosphate acyltransferase necessarily limits esterification. Therefore one would expect a decrease in esterification in starvation under this condition. This was the case when triacylglycerol synthesis was plotted against intracellular glycerol 3-phosphate concentration, calculated from the cellular glycerol 3-phosphate content and the intracellular water space, which was smaller in hepatocytes from starved rats. 5. The data obtained in hepatocytes were extrapolated to the intact liver by using the number of parenchymal cells per g of liver as determined from marker-enzyme analysis and the liver weight per 100g body weight. The extrapolation suggested that glycerol 3-phosphate is limiting esterification in vivo for contents below 0.3–0.4 and 0.5–0.65μmol/g for livers from fed and starved animals respectively. Also for a given fatty acid load and a glycerol 3-phosphate content below 0.3μmol/g the liver may esterify less in the starved state. However, at the glycerol 3-phosphate contents measured in freeze-clamped livers (0.30 and 0.44μmol/g for the fed and starved state respectively), livers in both nutritional states seemed capable of esterifying similar amounts of fatty acids. 相似文献
38.
Marina Bandeira Marc-André Bouchard Luc Granger 《Applied psychophysiology and biofeedback》1982,7(3):317-330
This paper discusses the general methodological controversy between individual and group research approaches by comparing the main characteristics of these two methods as applied to the specific context of basic research on voluntary heart rate control. A review of the literature published over the past 19 years in this area of study shows an imbalance in the frequency of utilization of these two methods that strongly favors short-term group designs. Implications of this research tendency are discussed. The relevance and the advantages of applying the individual approach to voluntary autonomic control research are outlined. This area is particularly amenable to the individual approach because the phenomena under study seem to be characterized by, among other things, a smaller intrasubject than intersubject variability. It is suggested that the present imbalanced tendency in the choice of a research method be corrected and that researchers adopt a more flexible attitude in the choice of the best method for studying each specific problem. 相似文献
39.
Claire-Michelle Calberg-Bacq Camille Francois Luc Gosselin Paul M. Osterrieth Francoise Renteir-Delrue 《生物化学与生物物理学报:生物膜》1976,419(3):458-478
Milk fat globule membranes and mammary tumour virus particles (d = 1.17 g/cm3) have been obtained from the milk of a Swiss albino mice strain. Comparitive biochemistry shows that these two structures differ significantly in the phospholipid, polypeptide and glycopolypeptide patterns and enzymatic activities. However, the lipid profile and the morphology of both structures suggest a filiation with the plasma membrane. Density fractions obtained from the crude virus preparation have been thoroughly investigated. The results suggest that most of these fractions represent degraded virus and/or atypical virus assembly. 相似文献
40.