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At least 289 records · Page 16Linked to original sources
PubMed2005

SspA, an outer membrane protein, is highly induced under salt-stressed conditions and is essential for growth under salt-stressed aerobic conditions in Rhodobacter sphaeroides f. sp. denitrificans.

We have previously shown that an outer membrane protein, SspA, is prominently induced by salt stress in a photosynthetic bacterium, Rhodobacter sphaeroides f. sp. denitrificans IL106 (R. sphaeroides). In this study, we investigated the physiological role of SspA under various stress conditions. Using recombinant SspA expressed in Escherichia coli as an antigen, the polyclonal antiserum of SspA was prepared. Western blot analysis demonstrated that SspA was highly induced by salt stress under both anaerobic and aerobic conditions. SspA was also induced, but to a lesser extent, by osmotic and acid stress. It is reduced under heat and cold compared to non-stressed conditions. While sspA-disrupted R. sphaeroides grew normally under anaerobic conditions in either the presence or absence of stress, it displayed significantly retarded growth under aerobic conditions in the dark, especially when osmotic or salt stress were imposed. In addition, the sspA disruptant, but not the wild type, formed cell aggregates when grown under both anaerobic and aerobic conditions, and this phenotype was significantly enhanced under salt-stressed aerobic conditions. Together, our findings suggest that SspA is critical under salt-stressed, aerobic growth conditions.

Acids↗
PubMed1977

Diffusion coefficients of single bile salt and bile salt-mixed lipid micelles in aqueous solution measured by quasielastic laser light scattering.

Diffusion coefficients of single bile salt micelles and mixed binary micelles consisting of single bile salts and phosphatidylcholine in the molar ratio 3 : 1 have been measured using quasielastic laser light scattering spectroscopy. Among single systems, marked concentration dependence of the diffusion coefficient was observed only in those containing sodium taurodeoxycholate. Micellar size correlates with bile salt molecular structure in a manner similar to that observed by earlier workers with some minor differences to towards a more consistent ordering. Phosphatidylcholine produces small increases in micellar size in most systems depending on bile salt structure, and seems most plausibly interpreted as simple swelling of the single species micelles. In some systems, when phosphatidylcholine is added, size or shape changes are indicated. Diffusion coefficients were also studied in the ternary systems bile salt-phosphatidylcholine-cholesterol which were saturated and metastably super-saturated with respect to cholesterol. The Stokes radii in both systems were the same within experimental error, 35 A. Our results indicate that intermicellar interactions significantly contributed to the measured diffusion coefficients in the ternary systems as well as in the single sodium taurodeoxycholate and binary sodium taurodeoxycholate-phosphatidylcholine systems in the concentration range studied.

Bile Acids and Salts↗
PubMed1995

Bile salt secretion by hepatocytes incubated with bile salts and liposomes or low density lipoproteins.

The purpose of this work was to determine the effect of exogenous unesterified cholesterol provided in either artificial liposomes or LDL on bile salt synthesis by isolated rat hepatocytes. Rates of de novo synthesis were determined in the presence of 300 or 600 microM taurocholate, 600 microM taurodehydrocholate, cholate, deoxycholate or chenodeoxycholate. There was no significant difference between the cholesterol uptake by hepatocytes when the degree of hydrophobicity of the bile salts changed (cholate vs deoxycholate or chenodeoxycholate). Compared to taurocholate, taurodehydrocholate lowered the hepatic incorporation of unesterified cholesterol for the first 60 minutes; compared to control, taurocholate stimulated the cholesterol incorporation for the first 20 minutes. A possible explanation for this finding would be an interaction between bile salts and exogenous cholesterol, depending on the kind of conjugated bile salt. Taurocholate increased the exchange of cholesterol between liposomes or LDL and hepatocyte membranes. It resulted in a significant increase of bile salt synthesis and secretion. This phenomenon was not observed with taurodehydrocholate.

Animals↗
PubMed1996

Effects of bile salt structure on chiral separations with mixed micelles of bile salts and polyoxyethylene ethers using micellar electrokinetic capillary chromatography.

The chiral resolving abilities of micellar solutions of four different bile salts alone and in mixtures with polyoxyethylene-4-dodecyl ether (C12E4) and methanol were investigated using MECC. The four bile salts investigated were the unconjugated sodium salts of cholic, deoxycholic, chenodeoxycholic and ursodeoxycholic acids. The test solutes included verapamil, norverapamil, gallopamil, bi-2-naphthol, atenolol and BAYK8644. The relative hydrophobicities of the micellar aggregates formed in solutions of binary mixtures of each bile salt with C12E4 were investigated by fluorescence spectroscopy using pyrene as a probe molecule. The observed enantiomeric resolution for the test compounds using these binary mixtures as MECC pseudo-stationary phases was determined. Correlations between micellar hydrophobicity for these solutions and chiral resolution of these test solutes are presented. The addition of C12E4 with or without methanol to solutions of sodium cholate and sodium deoxycholate enhanced the chiral resolution observed for compounds containing a longer hydrocarbon chain separating some of the major functional groups from the chiral center. The pure bile salt solutions generally provided better chiral resolution for the compounds where the major functional groups, such as aromatic rings, were closer to the chiral center.

Bile Acids and Salts↗
PubMed1997

The crystal structure of bovine bile salt activated lipase: insights into the bile salt activation mechanism.

BACKGROUND: The intestinally located pancreatic enzyme, bile salt activated lipase (BAL), possesses unique activities for digesting different kinds of lipids. It also differs from other lipases in a requirement of bile salts for activity. A structure-based explanation for these unique properties has not been reached so far due to the absence of a three-dimensional structure. RESULTS: The crystal structures of bovine BAL and its complex with taurocholate have been determined at 2.8 A resolution. The overall structure of BAL belongs to the alpha/beta hydrolase fold family. Two bile salt binding sites were found in each BAL molecule within the BAL-taurocholate complex structure. One of these sites is located close to a hairpin loop near the active site. Upon the binding of taurocholate, this loop becomes less mobile and assumes a different conformation. The other bile salt binding site is located remote from the active site. In both structures, BAL forms similar dimers with the active sites facing each other. CONCLUSIONS: Bile salts activate BAL by binding to a relatively short ten-residue loop near the active site, and stabilize the loop in an open conformation. Presumably, this conformational change leads to the formation of the substrate-binding site, as suggested from kinetic data. The BAL dimer observed in the crystal structure may also play a functional role under physiological conditions.

Animals↗
PubMed2006

Oxidative stress induces internalization of the bile salt export pump, Bsep, and bile salt secretory failure in isolated rat hepatocyte couplets: a role for protein kinase C and prevention by protein kinase A.

We have shown that Ca2+-mediated protein kinase C (PKC) activation induces impairment of bile salt secretory function and F-actin redistribution in hepatocyte couplets. Because oxidative stress induces Ca2+ elevation, we tested here whether PKC inhibition or protein kinase A (PKA) activation, which often counteracts PKC-dependent effects, can prevent and reverse these alterations. The pro-oxidant compounds tert-butylhydroperoxide (tBOOH, 100 microM) and 2,3-dimethoxy-1,4-naphthoquinone (30 microM), reduced by -41% and -29%, respectively, the percentage of couplets accumulating the fluorescent bile salt analog, cholyl-lysylfluorescein in their canalicular vacuoles (p < 0.01). tBOOH-induced bile salt secretory failure was accompanied by internalization of the canalicular bile salt export pump (Bsep), and disarrangement of cytoskeletal F-actin. All these deleterious effects were fully prevented by the intracellular Ca2+ chelator BAPTA/AM (20 microM), the pan-specific PKC inhibitors H7 (100 microM) and staurosporine (1 microM), the inhibitor of Ca2+-dependent PKCs, Gö6976 (2 microM), and the PKA activator dibutyryl-cAMP (500 microM). H7, Gö6976, and dibutyryl-cAMP not only prevented but also fully reversed the decrease in the cholyl-lysyl-fluorescein accumulation. In conclusion, these results suggest that low levels of oxidative stress impair bile salt secretion by internalizing Bsep through a Ca2+-dependent, PKC-mediated mechanism, and that inhibition of PKC, or activation of PKA, prevents and reverses these effects. Alterations in actin organization may be a causal factor.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1977

Bile salt metabolism. I. The physiology of bile salts.

Bile salts are synthesized in the liver from cholesterol, conjugated with glycine or taurine and secreted in bile with cholesterol and lecithin. The molar concentrations of these three lipids determine solubility of cholesterol in bile. Within the gastrointestinal lumen bile salts play an essential role in lipid absorption and faty transport. An efficienct entero-hepatic circulation maintains hepatic bile salt secretion and provides a "feed-back" control of the bile salt and cholesterol metabolism. Potentially hepatotoxic lithocholic acid formed in the intestinal lumen by bacterial action on chenodeoxycholic acid is sulphated in the liver thus decreasing intestinal reabsorption. The total faecal excretion of bile salts balances hepatic synthesis and represents a major catabolic path in cholesterol metabolism.

Animals↗
PubMed1988

Solubilization of vitamin K1 by bile salts and phosphatidylcholine-bile salts mixed micelles.

The solubilization of vitamin K1 by bile salts (sodium deoxycholate, sodium cholate and their corresponding glycine conjugates) and phosphatidylcholine (egg)-bile salt mixed micelles has been investigated. The solubilization curves were not always linear with increasing bile salts, but the vitamin was appreciably solubilized in the region below their CMCs. In the bile salt solutions (20 mM, phosphate buffered saline, pH 7.5, ions strength 0.2), the solubilized vitamin ranged from 0.3 to 0.9 mM. With increasing phosphatidylcholine, the amount of vitamin solubilized was dramatically increased; at the molar ratio of 1:1 (both 20 mM), the amount of vitamin solubilized was about 25-30 times more than by the corresponding bile salts alone. There is a possibility that exogenous phospholipid given orally as liposomal forms assists the solubilization of vitamin K1, in the intestine. This characteristic is suggested as being responsible, in part, for the enhanced recovery of blood coagulation after oral administration of liposomal vitamin K1 to warfarin-treated rabbits.

Bile Acids and Salts↗
PubMed1994

Salt stress increases abundance and glycosylation of CFTR localized at apical surfaces of salt gland secretory cells.

Osmotic stress elicits hypertonic NaCl secretion and promotes structural and biochemical differentiation in avian salt glands. In addition to cholinergic control, Cl- secretion is stimulated by vasoactive intestinal peptide (VIP), suggesting that the cystic fibrosis transmembrane conductance regulator (CFTR) may be present and that its expression may be regulated by chronic salt stress. Anion efflux, assayed by 6-methoxy-N-(3-sulfopropyl)quinolinium fluorescence changes in single cells, was stimulated by VIP or 8-(4-chlorophenylthio)adenosine 3',5'-cyclic monophosphate. Immunoblots with a COOH-terminal peptide antibody to human CFTR revealed approximately 170- and approximately 180-kDa bands in lysates from control and salt-stressed glands, respectively. Both variants reduced to approximately 140 kDa after N-glycanase digestion and gave identical tryptic phosphopeptide maps after immunoprecipitation and phosphorylation by protein kinase A. CFTR was localized to apical membranes by immunofluorescence and, additionally, to subapical vesicles by immunoelectron microscopy. Salt stress induced an approximately twofold increase in CFTR abundance/cell protein (approximately 5-fold/cell) and intensified apical membrane immunofluorescence. For comparison, Na+ pump expression increased approximately fourfold per cell protein with little change in actin. Thus differentiation induced by salt stress is accompanied by alteration in CFTR abundance and glycosylation. Upregulation of CFTR likely contributes to increased efficiency of Cl- secretion.

Amidohydrolases↗
PubMed1983

Bile salt sulphation in man. Liver bile salt sulphotransferase activity in patients with primary biliary cirrhosis.

Bile salt sulphation in primary biliary cirrhosis was studied by measurements of the liver bile salt sulphotransferase levels in 16 patients. Although the enzyme activity varied among the patients it did not correlate with the severity of cholestasis. Furthermore, the mean bile salt sulphotransferase magnitude in patients with primary biliary cirrhosis did not differ significantly from corresponding enzyme activity in patients with non-cholestatic, alcohol induced liver disease. The present data indicates that chronic cholestasis, as evidenced in patients with primary biliary cirrhosis, does not lead to increased levels of liver bile salt sulphotransferase. It is suggested that mechanisms other than enzymic induction are responsible for the increased bile salt sulphate synthesis as observed in primary biliary cirrhosis.

Adult↗
PubMed1976

Enhancement of solubility of drug salts by hydrophilic counterions: properties of organic salts of an antimalarial drug.

Judicious choice of the salt form of a drug can greatly affect the aqueous solubility and formulation of the compound. The objective of this work was to demonstrate the effect of various counteranions on the aqueous solubility of the antimalarial agent alpha-(2-piperidyl)-3, 6-bis(trifluoromethyl)-9-phenanthrenemethanol. Several organic salts of this drug were studied. The methods of synthesis, the apparent aqueous solubilities, and in vitro dissolution tests for these salts are reported. The lactate salt was 200 times as soluble as the hydrochloride salt. This enhanced solubility suggests that parenteral administration of this drug may now be feasible.

Antimalarials↗
PubMed1986

Effect of salt loading and salt deprivation on the vasopressin and oxytocin content of the median eminence and the neural lobe in adrenalectomized rats.

In adrenalectomized rats the influence of salt loading or salt deprivation on the vasopressin and oxytocin content of the median eminence (ME) and the neural lobe (NL) was studied by means of various methods: morphometric and microphotometric analysis of aldehyde fuchsin-stained sections of ME and NL; immunohistochemical demonstration of neurophysin, oxytocin, and vasopressin in the ME and in the NL; radioimmunological measurement of oxytocin and vasopressin in the ME and in the NL. Adrenalectomy in salt-substituted rats raised the vasopressin content of the outer layer of the ME (OLME) but had no influence on the amount of vasopressin in the inner layer of the ME and in the NL. Osmotic stimulation of adrenalectomized rats by hypertonic saline markedly diminished vasopressin and oxytocin in the inner layer of the ME and in the NL but did not, or only slightly reduced vasopressin in the OLME. Withdrawal of salt supplementation in adrenalectomized rats resulted in a decrease of plasma sodium and plasma volume. It did not change the vasopressin or oxytocin content of the inner layer of the ME and of the NL, but it was correlated with a decrease of vasopressin in the OLME. The present findings may suggest that vasopressin in the OLME is involved in salt and/or volume regulation by influencing the hypophysial-adrenal axis.

Adrenalectomy↗
PubMedDate not supplied

[Urinary excretion of fluorides in inhabitants of the Canton Vaud who consume fluoridated salt as compared with that of the inhabitants of neighboring cantons who consume nonfluoridated salt].

In the Swiss canton of Vaud (512000 inhabitants) the salt available for human consumption has been fluoridated since 1969 by adding 250 mg F- per kg of salt. The urinary excretion of fluoride has been investigated in large samples of the population in 1970 and in 1974. The present study reports the results of the 1974 study, in which the urinary fluoride excretion of persons living in the canton of Vaud was compared to that of a smaller sample of people living in small townships across the border of the canton, in which neither edible salt nor water are fluoridated. The concentration of fluoride in 444 single samples of urine from adult persons living in the canton of Vaud was 1.06 +/- 0.03 mg/l, in 40 subjects living two townships across the border 0.62 +/- 0.06 mg/l. The excretion of fluoride per 24 hrs has been evaluated by measuring simultaneously the creatinine concentration in the urine samples under the assumption of constant creatinine and fluoride excretion within 24 hour periods. The calculated fluoride excretion in 366 subjects living in the canton of Vaud was 1.14 +/- 0.03 mg/24 hrs, that of 40 subjects living outside of the canton 0.60 +/- 0.05 mg/24 hrs when the figure inserted for the excretion of creatinine within 24 hours was taken from a study of Rowe [9]. A few data reported suggest that the mean excretion of creatinine in the urine of normal subjects living in Switzerland was only 67% of that measured in the U.S. by Rowe. Total fluoride excretions calculated under this assumption were 0.76 +/- 0.02 mg/24 hrs for persons living in Vaud vs. 0.40 +/- 0.04 mg/24 hrs in the subjects living outside of Vaud. The concentrations of fluoride found in the urine of the adult subjects of the present study did not differ significantly from those found in school children aged 7-15 living in the same communities. Concentrations of fluoride in urine appear to have increased since 1970 in subjects living in the canton of Vaud. This fact may indicate that a steady state equality between intake and urinary excretion of fluoride had not yet been reached in 1970. In 366 urine samples of subjects living in Vaud in 1974, the concentration of fluoride in urine could be represented as a linear regression on the concentration of creatinine. The slope of this regression was smaller than unity indicating an enhanced fluoride excretion at higher rates of urine flow and a depressed excretion at low rates of urine flow. The occurrence of diurnal variations in the urinary excretion of fluoride or of creatinine could not be excluded in the present study. The urinary excretion of fluoride exceeded 2.5 mg/24 hr in approximately 2% of the subjects living in the canton of Vaud but was smaller than 0.8 mg/24 hr in approximately 18%. It was concluded that fluoridation of salt at the level indicated should be an effective measure for the prevention of dental caries. It was, furthermore, concluded that salt fluoridation at the level indicated does not present any risk of toxicity.

Adult↗
PubMed1989

Inhibition of human milk bile-salt-dependent lipase by boronic acids. Implication to the bile salts activator effect.

The bile-salt-dependent lipase from human milk, which catalyzes the hydrolysis of the water-soluble substrate 4-nitrophenyl acetate and the water-insoluble substrate tributyrin, is competitively inhibited by phenyl boronic acid. This inhibitor does not interfere with the interaction of lipase either with the siliconized glass beads/water interface or with the activator bile-salt binding site. The boronic acid binds near or at the active site serine, since modification of this residue by diisopropylphosphofluoridate (DFP) was prevented by phenyl boronic acid. Phenyl boronic acid binds 15-fold as tightly to bile-salt-dependent lipase as does 4-nitrophenyl acetate. Therefore, phenyl boronic acid bears analogy to a substrate rather than to a tetrahedral intermediate analog. Bile salts such as sodium taurocholate which are non-essential activators for the milk lipase activity on water-soluble substrates decrease the Km as well as the enzyme inhibitor dissociation constant (Ki). They have a slight effect on kcat. These results are interpreted in terms of an increase of the stability of the enzyme-substrate tetrahedral intermediate and in general of any transition states for the formation and for the decomposition of these intermediates upon the enzyme bile salts interaction.

Adsorption↗
PubMed1992

Characterization of salt-tolerant and salt-sensitive mutants of Rhizobium leguminosarum biovar viciae strain C1204b.

Spontaneous mutants of Rhizobium leguminosarum biovar viciae strain C1204b were selected for their ability to tolerate 0.2 M NaCl, a growth-inhibiting level of salt for the parental strain. Transposon-mediated salt-sensitive mutants of strain C1204b were screened for their inability to grow in 0.08 M NaCl. Quantitation of the free-amino acid pools in the mutants grown in NaCl revealed a dramatic increase in glutamine, serine, glutamate and proline, and to a lesser extent alanine and glycine in the salt-tolerant mutants in comparison with the parental strain exposed to NaCl; but only glutamate and proline increased in the salt-sensitive mutants under NaCl stress. Extracellular polysaccharide levels were quantitated for the salt-tolerant mutants and determined to be approximately two-fold higher than for the parental strain. Although the mutations that occurred in the NaCl-tolerant and NaCl-sensitive strains did not interfere with nodule formation, no nitrogenase activity could be observed in the NaCl tolerant mutants as evaluated by acetylene reduction.

Amino Acids↗
PubMed2006

Enhanced humoral and memory B cellular immunity using HPV16/18 L1 VLP vaccine formulated with the MPL/aluminium salt combination (AS04) compared to aluminium salt only.

An effective virus-like particle (VLP) based prophylactic vaccine designed to protect against persistent infection with human papillomavirus (HPV) types 16 and 18 and subsequent lesion development will need to induce a strong humoral and cellular immune response capable of providing long-term protection. Our objective was to evaluate the ability of an HPV16/18 L1 VLP vaccine formulated with the AS04 adjuvant system (3-O-desacyl-4'-monophosphoryl lipid A (MPL) and aluminium salt) to induce an immune response of higher magnitude and persistence compared to a vaccine formulated with aluminium salt only. We demonstrated that MPL adsorbed onto aluminium salt retains its capacity to activate an innate immune response as assessed by the production of TNFalpha by human monocytes (U937). In addition, vaccination of mice, monkeys or human subjects with AS04 formulations induced higher total anti-L1 VLP16 and L1 VLP18 antibody responses (1.6-8.5-fold) than the aluminium salt only formulations. The enhanced antibody response induced by the AS04 vaccine formulation (1.6-4.1-fold) in monkeys and humans was shown to be targeted to functional neutralising L1 VLP16 and L1 VLP18 epitopes as assessed by V5/J4 specific ELISAs or HPV16 and HPV18 pseudo-neutralization assays. The enhanced immune profile observed with the AS04 formulation in terms of both total, V5/J4 specific and neutralizing antibodies was shown to persist for at least 3.5-year post-vaccination in human subjects. Finally, using the newly developed B cell ELISPOT assay we also demonstrated that the AS04 formulation elicited an increased frequency (2.2-5.2-fold) of HPV L1 VLP specific memory B cells when compared with the aluminium salt only formulations. These data strongly support the role of the AS04 adjuvant, which includes the immunostimulant MPL, in triggering a persistent vaccine-induced immune response of high quality.

Adjuvants, Immunologic↗
PubMed1979

Retention of biologic characteristics of zona pellucida in highly concentrated salt solution: the use of salt-stored eggs for assessing the fertilizing capacity of spermatozoa.

When unfertilized hamster eggs are placed in highly concentrated solutions of neutral salts (e.g., 2 M ammonium sulfate), the egg proper, or vitellus, shrinks, creating a large perivitelline space; the zona pellucida remains unchanged in appearance under the light microscope. When these eggs are inseminated, many spermatozoa attach to and penetrate the zona. The specificity as well as several physical and chemical characteristics of the zona seem to remain unchanged during storage of the eggs in salt solutions. The properties of the human zona pellucida which allow the attachment and penetration of human spermatozoa are also retained in concentrated salt solutions. Shipment of salt-stored human eggs at ambient temperature to any part of the world is feasible and inexpensive. The present study suggests that salt-stored eggs can be used as substitutes for fresh living eggs in the preliminary assessment of fertilizing capacity of spermatozoa when collection of a large number of fresh unfertilized eggs, particularly in humans, is not practical.

Animals↗
PubMed1984

Dietary salt and doca-salt treatments modify ethanol self-selection in rats.

The effect of a salt supplemented diet on the voluntary intake of ethanol in male Wistar rats was examined in two experiments. In Experiment 1, the addition of 3% sodium chloride to the diet selectively increased the intake of moderately concentrated ethanol solutions (3 and 6%) while leaving the choice of a 12% solution unaffected. The choice and intake of water in the two former groups declined. In a second experiment four different groups of rats were offered the 3% salt supplemented diet in combination with daily injections of the synthetic salt-retaining mineralocorticoid desoxycorticosterone acetate (0.5, 1.5, and 6.0 mg/day). Ethanol intake again tended to increase in the 3 and 6% groups but in contrast to the results of Experiment 1 water intake also increased significantly. When desoxycorticosterone was administered without the salt supplemented diet, ethanol intake was significantly depressed while water intake increased. These findings indicate that a salt supplemented diet can significantly and selectively enhance the intake of moderately concentrated ethanol solutions and that while the addition of desoxycorticosterone injections to this diet has its effect primarily on water intake, these injections alone can also suppress ethanol intake indirectly by shifting the animals choice toward water and away from ethanol.

Alcohol Drinking↗