In vitro colonization ability of human colon mucosa by exogenous Lactobacillus strains

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.     

Human prostatic steroid 5α-reductase isoforms—A comparative study of selective inhibitors

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 (K_m = 0.5 and 2.9 μM, respectively). Finasteride and turosteride were selective inhibitors of the type 2 isoform (K_i (type 2) = 7.3 and 21.7 nM compared to K_i (type 1) = 108 and 330 nM, respectively). 4-MA and the lipido-sterol extract of Serenoa repens (LSESr) markedly inhibited both isozymes (K_i (type 1) = 8.4 nM and 7.2 μg/ml, respectively; K_i (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.     

An electrogenic proton pump in plasma membranes from the cellular slime mould Dictyostelium discoideum

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.     

Recognition of sodium- and potassium-dependent adenosine triphosphatase on mouse lymphoid cells by means of a monoclonal antibody

Summary Previous evidence has established the similarity between (Na⁺+K⁺)-ATPase (ATP phosphohydrolase, EC.3.6.1.3) and the antigen recognized by the rat antimouse monoclonal antibody anti-BSP-3. This antibody has been used for investigation of the surface expression and biochemical analysis of the enzyme in different mouse lymphoid populations. The BSP-3 determinant is found on almost all thymocytes and concanavalin A-induced thymocytes, to a lesser extent on bone marrow cells and also on a minor population of spleen cells. Spleen cells from athymic mice are negative. The (Na⁺+ K⁺)-ATPase purified from mouse thymus by affinity chromatography migrates in SDS-polyacrylamide gels in the form of two polypeptide chains of 105000 and 51000 daltons. Chains of the same molecular weight, fractionated on SDS-PAGE from microsomes of mouse thymuses, are shown to react with subunit-specific polyclonal antisera against ATPase in immunoblotting experiments. Immunoprecipitation with anti-BSP-3 from surface iodinated thymocytes yields only the small subunit. Comparison of the chains isolated from thymus and brain shows molecular weight differences in both subunits. These results, and variations in the reactivity pattern of the anti-BSP-3 antibody on several cell types, may indicate a possible heterogeneity of the (Na⁺+K⁺)ATPase expressed by various tissues and cells.     

Le fucosterol-24,28 epoxyde,intermediaire dans la biodegradation oxydative du fucosterol en cholesterol par le criquet Locusta migratoria (R. ET F.)

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.     

Les ammonites boréales des formationsnéocomiennes du Sud-Est français (province subméditerranéenne)

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.     

Specific binding and pharmacological interactions of apamin,the neurotoxin from bee venom,with guinea pig colon

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 $\text{in vitro}$ 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 $\text{K}{}_{\mathrm{<mtext>d</mtext>}}{}^1\text{= 36}\text{pM}$. The maximal binding capacity of colonic membranes is 30^dfmol/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.     

Changes in cell-wall polysaccharide composition of developingNitella internodes

Changes in the uronide, neutral-polysacharide, and cellulose composition of the cell wall ofNitella axillaris Braun were followed throughout development of the internodes and correlated with changes in growth rate. As the cells increased in length from 4 to 80 mm during development, the relative growth rate decreased. Cell wall thickness, as measured by wall density, increased in direct proportion to diameter, indicating that cell-wall stress did not change during elogation. Cell-wall analyses were adapted to allow determination of the composition of the wall of single cells. The total amounts of uronides, neutral sugars and cellulose all increased during development. However, as the growth rate decreased, the relative proportions of uronides and neutral sugars, expressed as percent of the dry weight of the wall, decreased, while the proportion of cellulose increased. The neutral sugars liberated upon hydrolysis ofNitella walls are qualitatively similar to those found in hydrolysates of higher plant cell walls: glucose, xylose, mannose, galactose, arabinose fucose and rhamnose. Only the percentage of galactose was found to increase in walls of mature cells, while the percentage of all other sugars decreased. The rate of apposition (g of wall material deposited per unit wall surface area per hour) of neutral polysaccharides decreased rapidly with decreasing growth rate during the early stages of development. The rate of apposition of uronides decreased more steadily throughout development, while that of cellulose, after an early decline, remained constant until dropping off at the end of the elongation period. These correlations between decreasing growth rate and decreasing rate of apposition of neutral sugars and uronides indicate that synthesis of these cell-wall components could be involved in the regulation of the rate of cell elongation inNitella.     

Microcalorimetric evaluation of the efficacy of the alkaline treatment on the fermentation of straw

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.