Concentration-dependent effects of eicosapentaenoic acid on very low density lipoprotein secretion by the isolated perfused rat liver

The effects of increasing concentrations of eicosapentaenoic acid (20∶5n?3; EPA) and oleic acid (18∶1n?9; OA) on esterification to triacylglycerols (TG) and phospholipids (PL), and the relationship to formation and secretion of the very low density lipoproteins (VLDL) were compared in the isolated perfused rat liver. Mixtures of EPA and OA were also studied to determine whether substrate levels of one fatty acid might influence the metabolism of the other. The basal perfusion medium, which contained 30% (vol/vol) washed bovine erythrocytes, 6% (wt/vol) bovine serum albumin (BSA), and 100 mg glucose/dL in Krebs-Henseleit bicarbonate buffer (pH 7.4) was recycled through the liver for 2 h. EPA or OA, as a complex with 6% BSA, was infused at rates of 70, 105, 140 and 210 μmol/h. In other experiments, mixtures of EPA and oleic acid (70 μmol total), with molar percentages of 100, 75, 50, 25 and 0% of each fatty acid were infused per hour. BSA (6%) in the buffer was infused alone and served as the control. At an infusion rate of 70 μmol EPA per hour, hepatic VLDL lipid output was not different from that when fatty acid was not infused (approximately half that when 70 μmol OA/h was infused). However, when larger amounts of EPA and OA were infused individually, rates of VLDL secretion were stimulated to a similar extent with either fatty acid. The apparent inhibitory influence of EPA on TG synthesis and VLDL lipid output when 70 μmol EPA were infused per hour could also be overcome by the presence of as little as 25 mol% OA in a mixture. Furthermore, the presence of EPA in the infused fatty acid mixture stimulated the incorporation of OA into TG, enhancing VLDL secretion. When EPA or OA was infused at rates exceeding 70 μmol/h, a constant amount of endogenously-derived fatty acids was incorporated into VLDL-TG, similar in amount to that when exogenous fatty acid was not supplied. However, when EPA was infused at a rate of 70 μmol/h, incorporation of endogenous fatty acid was depressed. AT this low rate of EPA infusion, esterification of EPA and endogenous fatty acid was inhibited. Conceivably, this may reflect the existence of independently-regulated pools of fatty acid (exogenous and endogenous), in that only exogenously available fatty acid preferentially enrich the secreted TG. Enrichment of PL by the infused fatty acid at the higher rates of fatty acid infusion showed similar, but much less pronounced, differences between VLDL and liver, compared to that for TG, providing additional evidence for a distinct metabolic pool of PL used for VLDL fabrication. It now appears that when EPA is available to the liver in high enough concentrations, or when OA (or other fatty acids?) is present in substrate amounts along with EPA, competing reactions and/or specific inhibitory influences of EPA on enzymatic reactions are overcome, and EPA can be utilized in a manner similar to OA for esterification to TG with subsequent enhanced VLDL formation and secretion.     

Influence of lipid peroxidation on lipoprotein secretion by isolated hepatocytes

Isolated rat liver cells have been exposed to 3 different lipid peroxidation-inducing agents, CCl₄, FeCl₃ and cumene hydroperoxide, and the rates of malonaldehyde production and of lipoprotein secretion have been compared. Results indicate that it is possible to induce a high degree of lipid peroxidation without inducing strong changes in lipoprotein secretion. Only in CCl₄-poisoned hepatocytes is lipoprotein secretion strongly impaired. In this experimental condition, the effect of free radical scavengers, or inhibitors of lipid peroxidation, has been studied; the degree of covalent binding of CCl₄ metabolites to hepatocyte proteins, as well as the behavior of both lipid peroxidation and lipoprotein secretion, have been evaluated. Promethazine and propyl gallate prevented malonaldehyde production, but neither agent reduced covalent binding nor improved secretion. Menadione, on the contrary, besides inhibiting malonaldehyde production, decreased covalent binding and protected against the impairment of secretion. These data lead to the conclusion that covalent binding of CCl₄ metabolites, rather than lipid peroxidation products, accounts for the derangement of lipoprotein secretion in CCl₄-poisoned liver cells. Presented in part at the ISF-AOCS World Congress, New York, April 1980.     

Salinity effects on the degree of hydrophobicity and longevity for superhydrophobic fibrous coatings

Previous studies on submerged superhydrophobic surfaces focused on performance variables such as drag reduction and longevity. However, to use such surfaces for practical applications, environmental factors such as water salinity must be investigated and understood. In this work, experiments were carried out to investigate the impact of salt (sodium chloride, NaCl) concentrations in aqueous solutions on the hydrophobicity and longevity of polystyrene (PS) fibrous coatings. Rheological studies using salt water as a test fluid were performed to determine the effect of salt concentration on drag reduction. Contact‐angle measurements were used to validate the results from the rheometer. In situ noninvasive optical reflection was used to measure the longevity of the coating—time‐dependent loss of entrapped air within the coating—as a function of salinity. The superhydrophobic coating used herein consisted of PS fibers that were deposited using DC‐biased AC‐electrospinning. Electrospinning is scalable and far less expensive than conventional methods (e.g., microfabrication), bringing the technology closer to large‐scale submerged bodies such as submarines and ships. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

A simple method for labeling lipids in the bile lipoprotein

A simple method is proposed for the specific radioactive labeling of phosphatidylcholines and cholesterol in the bile lipoprotein complex. It can be used for human and animal bile samples and results in labeling with the desired specific radioactivity and position. Experiments which determined the intermicellar concentration of lipid constituents suggested that incorporation of radioactive lipids could occur through small dialyzable structures termed mixed premicelles in therm odynamic equilibrium with the bile lipoprotein complex.     

Ion-pair high-performance liquid chromatography of bile salt conjugates: Application to pig bile

The high-performance liquid chromatographic separation and quantitation of conjugated bile salts from pig bile is reported. Synthetic standards and bile samples were chromatographed on a C₁₈ reversed phase column using acetonitrile/water/tetrabutyl ammonium phosphate as an isocratic mobile phase at a flow rate of 1 mL/min. Detection of the ion-pairs was at 214 nm. The method permits efficient separation of all conjugated pig biliary bile salts without prior modification or treatment of the samples. Analysis of 12 pig biles showed that 85% of the bile salts are conjugated to glycine. The three main conjugated bile salts were glyco-3α,6α,7α-trihydroxy-5β-cholanoic acid (GHC), glyco-3α,7α-dihydroxy-5β-cholanoic acid (GCDC), and glyco-3α,6α-dihydroxy-5β-cholanoic acid (GHDC). Glyco-3α-hydroxy-6-oxo-5β-cholanoic acid (G3α6oxo), tauro-3α,7α-dihydroxy-5β-cholanoic acid (TCDC), tauro-3α,6α,7α-trihydroxy-5β-cholanoic acid (THC), and tauro-3α,6α-dihydroxy-5β-cholanoic acid (THDC) were found to contribute each for 4 to 5% ot the total. An excellent correlation was found between the sum of conjugated bile salts quantitated by high-performance liquid chromatography (HPLC) and values obtained by conventional enzymatic assay. Simplicity, efficiency and relative rapidity of the method render it suitable for routine analyses.     

Effects of various tocopherol-containing diets on tocopherol secretion into bile

γ-Tocopherol is abundant in common vegetable oil, but its concentration in plasma and liver is much lower than that of α-tocopherol. Discrimination between different forms of tocopherol is thought to take placevia the hepatic α-tocopherol transfer protein (α-TTP). γ-Tocopherol, with a low binding capacity to α-TTP, is thought to be excretedvia the bile. Our previous studies showed that γ-tocopherol administered with sesame seed exhibits significantly higher concentrations in the plasma and liver of rats than γ-tocopherol alone. Thus, we attempted to confirm whether a much higher amount of γ-tocopherol rather than γ-tocopherol would be secreted in the bile, and whether sesame seed would suppress the secretion of γ-tocopherol. In one experiment, we examined the concentrations of α-or γ-tocopherol in the plasma, liver, and bile of rats fed diets containing 300 mg/kg of α-tocopherol, 300 mg/kg of γ-tocopherol, or 300 mg/kg each of α-tocopherol+γ-tocopherol, and in the other experiment, we compared the γ-tocopherol concentrations of rats fed a diet of γ-tocopherol alone to those of rats fed a γ-tocopherol+sesame seed diet (each diet contained 300 mg/kg γ-tocopherol). The bile collection was done over 6 h. The γ-tocopherol concentration in the bile was markedly lower than that of α-tocopherol, paralleling the concentrations in the plasma and liver. Intake of α-tocopherol and γ-tocopherol together further lowered the concentration of γ-tocopherol in the bile as well as in the plasma and liver, compared to the intake of γ-tocopherol alone. The γ-tocopherol concentration in the bile, as well as in the plasma and liver, was markedly higher in the sesame seed-fed group than in the γ-tocopherol alone group. We found that the concentrations of α- or γ-tocopherol in the bile showed a good correlation with the concentrations of α- or γ-tocopherol in the liver, though the concentrations in the bile were substantially lower than those in the liver. These findings suggest that secretion into the bile is not a major metabolic route of α- or γ-tocopherol.     

三号胆盐的研制

研究建立了一种三号胆盐（ＢＳＮＴ）的制备工艺，本工艺ＢＮＳＴ产品的化学组成及其各项理化指标均达到了进口三号胆盐（ＩＢＳＮＴ）的水平，可以考虑代替ＩＢＳＮＴ使用。     

Dietary protein effects on cholelithiasis in hamsters: Interaction with amino acids and bile acids

The objective of this experiment was to study the effects of dietary cottonseed protein and casein on plasma and biliary lipids, plasma amino acids and gallstones in hamsters. Thirty-four male hamsters (60 ± 5 g) were fed either the lithogenic “Dam Diet” (containing 20% casein, 74.3% sucrose and 5.7% vitamin-mineral mix) or a similar diet that contained 20% cottonseed protein for 30 days. Both diets contained protein as a protein isolate. The concentration of alpha-aminobutyric acid was significantly elevated in the casein-fed group. Significant differences in the total plasma cholesterol or lipoprotein cholesterol concentrations were not observed between the two dietary groups. A significant elevation in the absolute concentration of biliary cholesterol was observed in the casein-fed hamsters. Cottonseed protein-fed animals exhibited a significantly elevated concentration of bile acids. The ratio of glycochenodeoxycholic:glycocholic acid was significantly higher in the cotton-seed protein-fed group. This study reports that an elevated concentration of biliary cholesterol with a concomitant decrease in bile acid concentration yields a condition favorable to gallstone formation. It is proposed that cottonseed protein may have a specific effect on the bile acid pool by increasing the ratio of glycochenodeoxycholic acid:glycocholic acid which, in turn, prevents formation of cholesterol gallstones.     

Recombinant protein secretion via the type III secretion system

The type III secretion system (T3SS) is a mechanism by which bacteria export proteins from the cytoplasm, through the membranes, to the extracellular environment. T3SS is made up of more than 20 different proteins, about half of which maintain conserved sequences. This review summarizes the features of this novel apparatus and discusses the potential of utilizing T3SS to export recombinant proteins into the external environment, and the impact this system will have on protein production technology.     

Oleic acid modulates the partitioning of cholesterol from micellar bile salt solution

The effects of monounsaturated fatty acid (oleic acid) on cholesterol monomer activity and on the rate of cholesterol influx were studied in vitro. A polyethylene disc method was employed to determine cholesterol monomer activity in constant sodium taurocholate-cholesterol micellar solution containing different oleic acid concentration levels at pH 5.5, 6.5 and 7.2. In addition, the effect of oleic acid on the rates of cholesterol influx was determined using an everted rat jejunal sac technique. At pH 5.5, increased oleic acid concentration from 5 to 10 mM resulted in significant decreased apparent cholesterol monomer activity (3.8±0.21 nmol/disc vs 1.0±0.08, P<0.001). At pH 6.5, apparent cholesterol monomer activity was 2.3±0.19 nmol/disc at 5 mM and 0.5±0.09 at 16 mM oleic acid level (P<0.001). Apparent monomer activity of cholesterol in micellar solutions at pH 7.2 used for the influx study at 5 and 15 mM oleic acid concentration level was 1.8±0.14 and 0.7±0.08 nmol/disc, respectively (P<0.001). Thus there was a significant decrease in cholesterol monomer activity by the addition of oleic acid at each pH. The rate of cholesterol influx across the brush border membrane of the rat jejunum at 5 and 15 mM oleic acid concentration level was 3.2±0.31 and 1.5±0.21 nmol/100 mg dry weight tissues/min, respectively (P<0.001). It is concluded that the addition of oleic acid decreases both monomer activity and the rate of influx of cholesterol from micellar solution. This effect is primarily attributable to the inhibition of the release of cholesterol monomers from the mixed micelle.     

One-step analysis of major bile components in human bile using 1H NMR spectroscopy

Human gallbladder bile dissolved in dimethyl-sulfoxide provides sharp and resolved signals for major bile components in ¹H NMR spectra. Characteristic well-resolved marker signals that invariably appear in ¹H NMR spectra of bile were identified for cholesterol (H18 methyl signal at 0.643 ppm), lipids (glycerol CH signal at 5.064 ppm), total bile acids (H18 signals in the range 0.520–0.626 ppm), total glycine conjugated bile acids (NH signal at 6.958 ppm), total taurine conjugated bile acids (NH signal at 7.646 ppm), and urea (NH₂ signal near 5.48 ppm), which enabled their rapid and accurate analysis. Excellent linearity and precision of quantitative analysis was observed for all the identified bile components (R ²>0.99 for all). The method was demonstrated on gallbladder bile from 19 patients with gallbladder diseases. Urea in bile was identified by NMR for the first time and its quantitative analysis, along with several other bile components, is presented. The majority of the bile components could be analyzed in a single step. Accurate and rapid quantification of several bile components noninvasively by using the method presented herein may have far-reaching implications in the study of bile acid metabolism and pathophysiology of various hepatobiliary and gastrointestinal diseases.     

Inhibition and induction of bile acid synthesis by ketoconazole effects on bile formation in the rat

The effects of ketoconazole, an antimycotic agent, and metyrapone, an inhibitor of mixed function oxidases, on bile acid synthesis were compared in the rat bothin vitro andin vivo. In rat liver microsomes, ketoconazole was much more potent than metyrapone in inhibiting the activity of cholesterol 7α-hydroxylase, the rate-limiting enzyme in the synthesis of bile acids. The I₅₀ values were 0.42 μM and 0.91 mM for ketoconazole and metyrapone, respectively. Intraduodenal administration of ketoconazole caused a rapid, dose-dependent reduction of bile acid synthesis in eight-day bile diverted rats. A single dose of 50 mg/kg reduced bile acid synthesis to 5% of control value; the same dose of metyrapone caused a reduction to only 85%. Inhibition of bile acid synthesis by ketoconazole was followed by a marked overshoot. At 28 hr after injection of 50 mg/kg of the drug, formation of bile acids was stimulated maximally by 45% compared to control value and remained elevated for more than 20 hr thereafter. Synthesis of all primary bile acids was affected to the same extent. Cholesterol 7α-hydroxylase activity in livers of ketoconazole treated (30 mg/kg) rats with an intact enterohepatic circulation was increased by 70% at 16 hr after i.p. injection of the drug. During the very large decrease of biliary bile acid output with ketoconazole, bile flow rate was relatively increased, due to stimulation of the bile acid-independent fraction of bile flow. The latter effect can probably be explained as caused by biliary secretion of osmotically active metabolites of ketoconazole.     

Helix stability and hydrophobicity in the folding mechanism of the bacterial immunity protein Im9

Recent models suggest that the mechanism of protein folding is determined by the balance between the stability of secondary structural elements and the hydrophobicity of the sequence. Here we determine the role of these factors in the folding kinetics of Im9* by altering the secondary structure propensity or hydrophobicity of helices I, II or IV by the substitution of residues at solvent exposed sites. The folding kinetics of each variant were measured at pH 7.0 and 10 degrees C, under which conditions wild-type Im9* folds with two-state kinetics. We show that increasing the helicity of these sequences in regions known to be structured in the folding intermediate of Im7*, switches the folding of Im9* from a two- to three-state mechanism. By contrast, increasing the hydrophobicity of helices I or IV has no effect on the kinetic folding mechanism. Interestingly, however, increasing the hydrophobicity of solvent-exposed residues in helix II stabilizes the folding intermediate and the rate-limiting transition state, consistent with the view that this helix makes significant non-native interactions during folding. The results highlight the generic importance of intermediates in folding and show that such species can be populated by increasing helical propensity or by stabilizing inter-helix contacts through non-native interactions.     

无机盐复配对马拉色菌的抑菌作用研究

寻找一种无副作用洗发水祛屑和防腐二合一添加剂,通过NaC l与ZnSO4、ZnC l2、MgSO4和MgC l2等无机盐复配体系抑制马拉色菌和化妆品腐败菌的作用表明,当总无机盐含量在8%,NaC l与0.05%的锌盐复配时,能有效地杀死导致产生头皮屑的马拉色菌落和抑制洗发水腐败菌落的生长,抑菌效果达国家优级标准,可以作为洗发产品良好的添加剂。     

微孔硅酸钙憎水性研究

针对微孔硅酸钙制品吸湿吸水性大的特点，采用有机硅渗透处理，在制品表层生成一层憎水薄膜。结果表明：其憎水效果优良。本文还对其憎水机理进行了分析。     

Effects of ethylp-chlorophenoxyisobutyrate on biliary secretion of bile acids,cholesterol and phosphatidyl choline

The effect of chronic administration of ethylp-chlorophenoxyisobutyrate (CPIB) on the secretion of bile lipids was studied in four dogs with surgically implanted Thomas cannulae for periods of 2–7 months. The concentration of cholesterol, triglycerides andp-chlorophenoxyisobutyric acid in serum and of bile acids, cholesterol and phospholipids (phosphatidyl cholines) in bile were measured. Chronic administration of CPIB resulted in a marked increase in the concentration of cholesterol, bile acids and phosphatidyl cholines in the bile of all dogs, and a decrease in serum cholesterol and triglyceride concentration in serum in three of the four dogs. Serum concentrations ofp-chlorophenoxyisobutyric acid were monitored to insure the presence of the drug in the dogs; however, no correlation between serum levels ofp-chlorophenoxyisobutyric acid and the concentration of biliary lipids was noted. The bile acids andp-chlorophenoxyisobutyric acid were determined by gas chromatographic procedures and the structures were confirmed by gas chromatography-mass spectrometry. One of eight papers presented at the symposium “Recent Advances in Drugs Affecting Lipid Metabolism,” AOCS Meeting, Houston, May 1971.     

Effects of salt content on secondary formation of hydrates in complex systems

The phenomenon of ‘memory effect’ exists in the secondary generation of natural gas hydrates, which is mainly manifested in the fact that the induction time required for the nucleation of hydrates in the secondary generation of hydrates is significantly shorter than that of the primary generation, thus accelerating the generation of hydrates. At present, the research on the memory effect phenomenon has been proven to exist, and its influencing factors have become a research hotspot. In order to study the influence of decomposition time and salt content on the memory effect, the hydrate was generated under the system of porous medium alumina complexed with surfactant SDS, and hydrate secondary generation experiments were carried out by adding different contents of NaCl according to four different decomposition times. The influence of four different decomposition times on the memory effect phenomenon in the secondary generation of hydrates and the influence of different salt contents on the memory effect phenomenon were analyzed by observing the pressure drop changes in the reactor during the hydrate generation process and calculating the methane gas consumption. The experimental results show that different decomposition times can affect the effect and time of the memory effect, and the effect of decomposition time on the memory effect does not show a linear relationship. The addition of salt may have an inhibitory effect on the memory effect.     

Effect of surface microstructure on the hydrophobicity of coatings

In this paper, coatings adopted SiO₂ nanoparticles ranging from 1 wt% to 7 wt% were in situ polymerized with low surface energy polymer, and different surface microstructures were built automatically during painting film. Copper microstructure surface was also achieved by chemical etching method and then was modified by low surface energy resin as contrast. The contact angle and the peel strength between the coating and bio-gooey simulacrum were studied. The results showed that the hydrophobicity of the coating was remarkably affected by the surface microstructure. The coating containing 5 wt% SiO₂ nanoparticles was covered with micro- and nano-scale salience and holes, and had the maximum contact angle and the minimum peel strength. Copper slices presented uniform micron and sub-micron structure surface when etching for 15 min and the contact angle reached a maximum of 125° after being modified.     

进口三号胆盐的色谱法分离与鉴定

利用薄层层析(TLC)、氨基酸分析和高效液相(HPLC)联合色谱对进口三号胆盐进行了分离鉴定。三号胆盐的主要成分是胆酸(CA)、去氧胆酸(DCA)与 Na~+结合形成的盐。其中 CA 63.92%、DCA 18.89%。     

The effects of boron derivatives on lipid absorption from the intestine and on bile lipids and bile acids of sprague dawley rats

N,N-dimethyl-n-octadecylamine borane 1 at 8 mg/kg/day, tetrakis-u-(trimethylamine boranecarboxylato)-bis(trimethyl-carboxyborane)-dicopper(II) 2 at 2.5 mg/kg/day and trimethylamine-carboxyborane 3 at 8 mg/kg/day were evaluated for their effects on bile lipids, bile acids, small intestinal absorption of cholesterol and cholic acid and liver and small intestinal enzyme activities involved in lipid metabolism. The agent administered orally elevated rat bile excretion of lipids, e.g. cholesterol and phospholipids, and compounds 2 and 3 increased the bile flow rate. These agents altered the composition of the bile acids, but there was no significant increase in lithocholic acid which is most lithogenic agent in rats. The three agents did decrease cholesterol absorption from isolated in situ intestinal duodenum loops in the presence of drug. Hepatic and small intestinal mucosa enzyme activities, e.g. ATP-dependent citrate lyase, acyl CoA cholesterol acyl transferase, cholsterol-7-alpha -hydroxylase, sn glycerol-3-phosphate acyl transferase, phosphatidylate phosphohydrolase, and lipoprotein lipase, were reduced. However, the boron derivatives 1 and 3 decreased hepatic HMG-CoA reductase activity, the regulatory enzyme for cholesterol synthesis, but the compounds had no effects on small intestinal mucosa HMG-CoA reductase activity. There was no evidence of hepatic cell damage afforded by the drugs based on clinical chemistry values which would induce alterations in bile acid concentrations after treatment of the rat.