Cholesterol and bile acid turnover in miniature swine

Miniature swine were fitted with indwelling cannulae at two sites in the gut and catheters in the aorta and portal vein. Ring labeled cholesterol was administered via jejunum and portal vein and various parameters of disappearance measured over 17–66 days. Conversion of cholesterol to bile acids and their subsequent disappearance from gut lumen were measured. Cholesterol disappearance was found to follow a two component exponential in serum and three components in gut. The serum curves were similar to those reported for humans. It was concluded that the minipig is an advantageous model for cholesterol turnover studies and that serum and gut cholesterol dynamics are different.     

谷胱甘肽生物合成过程中酸胁迫的作用及其机制

以产朊假丝酵母Candida utilis SZU 07-01产谷胱甘肽（GSH）为研究对象,分析比较了恒定pH和不控制pH条件下GSH的分批发酵过程,确定pH3.5和pH1.5分别为弱酸胁迫和强酸胁迫条件。通过对C.utilis SZU 07-01恒化培养过程进行分析,选择合适的酸胁迫时间分别为弱酸胁迫6 h和强酸胁迫2 h。采用分批补料培养方式,比较了不同酸胁迫条件下的GSH生物合成情况,发现长时间弱酸胁迫比短时间强酸胁迫和不胁迫更有利于GSH的过量合成。最后,分别从分批发酵动力学、胞内辅因子（NADH、ATP）以及各关键代谢物的代谢通量变化规律等角度对弱酸胁迫促进GSH过量合成的机理进行了定量分析。     

Enterohepatic circulation of cholic acid and cholesterol metabolism in the rat

A role for cholic acid in the regulation of body cholesterol levels is emphasized by the following experiment and findings. Fifteen rats with biliary and duodenal fistulae were divided into three groups. 4-¹⁴C-cholesterol was admistered intravenously to all animals on day 1. Two groups received a duodenal infusion of either sodium taurocholate or of cholesterol at the same time and thereafter daily. Bile samples were collected daily for 15 consecutive days. Cholic, chenode-oxycholic acid and cholesterol were the major labeled compounds in the bile. Labeled cholic acid disappeared from the bile of control animals after day 8 while it persisted in the group receiving unlabeled cholic acid up to day 15. The decrease of specific radioactivity of labeled biliary cholic acid in the rats receiving unlabeled cholesterol corresponded to that of control animals. A significant increase in the concentration of cholesterol was found in the plasma of animals receiving cholic acid and in the liver of those receiving unlabeled cholesterol. A preliminary report was presented at the 49th Annual Meeting of the Federation of American Societies for Experimental Biology, Atlantic City, 1965.     

Gastroprotection of DNA with a synthetic cholic acid analog

The oral delivery of functional DNA to the gastrointestinal system would constitute a desirable, noninvasive method for potentially treating a variety of diseases. The digestive process, however, remains a formidable barrier. This dilemma may be addressed by using targeted liposomes both to protect the polynucleotide and to deliver the therapeutic DNA with high tissue specificity. The present study represents the initial steps toward developing a novel gene delivery system designed to interact with the enterohepatic receptors of the small intestine. Two cholic acid esters were synthetically modified at position C(3) to incorporate a DNA-binding domain. These novel compounds were evaluated for their ability to protect DNA from the nucleases found in gastrointestinal segments. Additionally, the compounds were screened as a component of a gene delivery vector. Formulations containing the new bile salt derivatives protected DNA from degradation for more than 2 h and were capable of transfecting cultured NIH 3T3 cells.     

Bile acid metabolism in mammals: IX. Conversion of chenodeoxycholic acid to cholic acid by isolated perfused rat liver

Current dogma of bile acid synthesis in mammals insists that hydroxylation of the ring structure at C-12 precedes side chain oxidation, and that chenodeoxycholic acid is not converted to cholic acid under normal conditions. This report concerns the conversion of chenodeoxycholic acid to cholic acid by isolated, perfused rat liver. Results indicate that isolated perfused rat liver has a definite, but limited, capacity for synthesis of cholic acid from chenodeoxycholic acid.     

Cholesterol and fatty acid synthesis in swine

In incubation studies with swine tissue slices, acetate-1-¹⁴C or glucose-U-¹⁴C as substrates were incorporated more readily into fatty acids and cholesterol in adipose tissue than other tissues tested. Cholesterol and fatty acid synthesizing activity was substantial in the small intestine. When acetate was available, liver, small intestine, and adipose tissue were important sites for cholesterol synthesis. Heart and aortic tissue had marginal levels of cholesterol synthesizing ability. Lipogenesis in adult swine liver, heart, and aortic tissue was extremely low. As in tissue slices, incorporation of acetyl-1-¹⁴C CoA into fatty acids by adipose homogenates indicated high lipogenic activity. Subcellular fractionations of heart and aortic tissue indicated that the heart microsomal fraction had the highest lipogenic activity as measured by the incorporation of acetyl-1-¹⁴C CoA into fatty acids. In adult swine adipose tissue, the incorporation of glucose-U-¹⁴C into fatty acid was higher than its incorporation into glyceride-glycerol. The synthesis of glyceride-glycerol from glucose-U-¹⁴C or acetate-1-¹⁴C in liver was higher than for fatty acid synthesis. The activity of acetyl CoA carboxylase, fatty acid synthetase, citrate cleavage enzyme, nicotinamide adenine dinucleotide phosphate-malate dehydrogenase, glucose-6-phosphate dehydrogenase, and 6-phosphogluconate dehydrogenase was considerably higher in adipose tissue than in other tissues tested, paralleling its high lipogenic capacity. A preliminary report of this paper was given at the AOCS 66th Annual Spring Meeting, Dallas, Texas, April 30, 1975, Abstr. No. 109. In partial fulfillment of the requirement for the PhD degree in Nutritional Sciences at the University of Illinois at Urbana-Champaign.     

Cholelithiasis in hamsters: Effects of cholic acid and calcium on gallstone formation

Dietary cholic acid (0.1%) and/or calcium (2.6% as calcium carbonate) were added to a semipurified diet containing cholesterol and ethynyl estradiol to determine whether the incidence of pigment and/or cholesterol gallstones would be changed. Male golden Syrian hamsters were fed the experimental diets for 96 days (Group 1, control; Group 3, cholic acid plus calcium) or only an average of 60 days (Group 2, 0.1% cholic acid). Animals in Group 2 became ill (weight loss, low food intake, diarrhea) possibly due to cholic acid (or deoxycholic acid) toxicity. Cholesterol gallstones and crystals were absent in all experimental groups. The incidence of pigment gallstones was: control, Group 1, 12/16; 0.1% cholic acid, Group 2, 3/13; and 0.1% cholic acid plus calcium, Group 3, 11/22. Cholic acid with or without calcium produced an elevation of both liver and plasma cholesterol: Group 2, 80.1 mg/g and 501 mg/dl; Group 3, 103.7 mg/g and 475 mg/dl vs Group 1, 65 mg/g and 209 mg/dl, respectively. The lithogenic indices of the bile were lower in Groups 2 and 3 compared to Group 1, controls, 0.45 and 0.58 vs 1.16, respectively. The extent of the portal tract pathology could not be correlated with the presence or absence of pigment gallstones or with the levels of lithocholic acid in the hamster bile. In summary, when semipurified diets were supplemented with ethynyl estradiol and cholic acid, with and without calcium supplementation, no cholesterol gallstones formed and the incidence of pigment gallstones was not altered.     

In vivo studies of the biosynthesis of vernolic acid in the seed of Vernonia galamensis

In vivo radiotracer experiments using [1-¹⁴C]acetate as the precursor were conducted to investigate the biosynthesis of vernolic acid (12, 13-epoxy-cis-9-octadecenoic acid) in the seeds of Vernonia galamensis. The acetate precursor radioactively labeled vernolate in phosphatidylcholine (PC), diacylglycerol, and triacylglycerol. Time-course kinetics of the incorporation of the radioactive tracer indicated that vernolate is synthesized while the acyl moiety is esterified to PC. Pulsechase experiments provided additional supporting evidence that vernolate is synthesized while esterified to PC. These results are consistent with the hypothesis that linoleoyl PC is the precursor of vernoleoyl-PC. Subsequently, vernolate is quickly moved from the PC pool to the triacylglycerol pool, where it accumulates.     

抗氧化剂α-硫辛酸的生物合成研究进展

α-硫辛酸及其还原态二氢硫辛酸具有极强的抗氧化性,可改善葡萄糖代谢,减弱氧化应激,对糖尿病性白内障、糖尿病多发性神经病及心血管损伤等糖尿病并发症具有较好的预防和治疗作用。概述了α-硫辛酸的作用机制、生物合成途径及应用,重点综述了具有良好应用前景的生物法生产α-硫辛酸工艺。     

Studies on biosynthesis of waxes by developing jojoba seed. II. the demonstration of wax biosynthesis by cell-free homogenates

The following enzyme activities were demonstrated in cell-free homogenates from developing jojoba cotyledons: 1) elongation of long chain acyl-CoAs in the presence of malonyl-CoA and NADPH (or NADH), 2) NADPH-dependent reduction of long chain acyl-CoAs to the corresponding alcohols, 3) esterification of long chain acyl-CoAs and the alcohols produced from them into wax, 4) elongation of stearoyl-ACP to eicosanoate and docosanoate as well as reduction to stearyl alcohol, 5) desaturation of stearoyl-ACP to oleate in the presence of reduced ferredoxin, and 6) incorporation of malonyl-CoA into long chain fatty acids and alcohols in the presence of added acyl carrier protein. These activities were associated entirely with the floating wax pad after centrifugation of the cell-free homogenate at 12,000 g for 20 min. The relevance of the above reactions (1–6) to wax biosynthesis in vivo is discussed. Production of oleate from acetate by enzymes utilizing ACP-thioesters as substrates followed by conversion of oleyl-ACP to oleoyl-CoA (via free oleic acid) for subsequent elongation, reduction, and esterification, is presented as the most probable in vivo pathway, for wax biosynthesis. The substrate specificities of the elongation and reduction reactions utilizing acyl-CoAs as substrates are examined in terms of wax composition.     

Potentiometric and polarographic studies of cadmium(II) complexes with tetraethylenepentamineheptaacetic acid

Stability constants for cadmium(II) complexes with tetraethylenepentamineheptaacetic acid (TPHA, H₇L) were determined by the pH titration method. In an aqueous solution (μ = 0.1), three complex species, CdH₂L, CdHL and CdL are confirmed. The structure of uninuclear complexes are discussed. The formation constants of the complexes stated above have been calculated as follows (at 25 ± 0.1°C): log K_CdL = 15.35, log K_CdHL = 13.33 and log K_CdH2L = 7.89. The polarographic behaviour of the cadmium(II) in the presence of TPHA was studied over the pH range 3–5. Mechanisms of the electrode processes were elucidated and electrochemical kinetic parameters were evaluated from dependence of the half-wave potentials on the hydrogen ion and TPHA concentration. In the presence of an excess of TPHA, the wave B is assigned to the irreversible reductions of the complex, CdH₂L^3? (pH range 3–4) or CdHL^4? (pH range 4–5). The electrode reaction can be written:

and

Where k_e (the rate constant) = 2.3 × 10^?2 cm s^?1 and k′_e = 1.59 × 10^?4 cm s^?1. The other polarographic methods were also used in the elucidation of the electrode process.     

Stimulatory effects of tannins and cholic acid on tryptic hydrolysis of proteins: Ecological implications

The biochemical basis for considering tannins as digestion inhibitors has been reexamined. Both stimulatory and inhibitory effects of tannins on tryptic hydrolysis are reported. We show how stimulation may result from tannin-induced structural changes in the substrate protein, effectively denaturing it. The surfactant and bile constituent cholic acid also produced similar stimulatory effects. These results have considerable implications for normal digestive physiology as well as for the impact of tannins on argicultural and natural herbivore populations.     

Toxicology studies. II. The laboratory animal

The laboratory animal can be thought of as the toxicologist's major instrument for use in a safety evaluation programme. Consequently, to obtain reliable results from such an ‘instrument’, the toxicologist must obtain animals of the highest quality available, and maintain as well as monitor them in such a manner that intercurrent infections or latent diseases do not produce effects leading to erroneous conclusions. The procedures described will enhance the reliability of the results obtained in toxicological studies.     

Isomerization studies: II. Thermal alteration of oleic acid and methyl oleate in the presence of mineral catalysts

A structure analysis has been conducted on the distillable fraction (67–71%) obtained from the clay catalyzed isomerization of methyl oleate and oleic acid. The method of analysis involved the combined use of reductive ozonolysis, urea adduction, and gas liquid chromatography-mass spectrometry. The results of this study indicate that the original unsaturation of the fatty acid is mostly retained, but less than the theoretical amount of hydrogen is absorbed when the products are subjected to low pressure catalytic hydrogenation. These results in conjunction with the gas liquid chromatography-mass spectrometry data suggest that branching of the carbon chain has occurred.     

Specific binding of cholic acid by cross-linked polymers prepared by the hybrid imprinting method

A cholic acid-imprinted polymer has been prepared by a hybrid imprinting method involving the use of a template-containing monomer, 3α-methacryloyl cholic acid methyl ester. The removal of the template can afford the polymer with cavities and carboxylic acid groups well positioned in these cavities for the specific binding of cholic acid via hydrogen bonding. The maximum binding capabilities for the imprinted and non-imprinted polymers were determined to be 344.8 and 43.6 μmol/g, respectively. Scatchard analysis indicates the existence of two kinds of binding sites on the imprinted polymer. The imprinted polymers exhibit high affinity and good recognition selectivity for cholic acid in comparison to other compounds with similar molecular structures. The size-specific binding and hydrogen bonding may be both important for the binding of cholic acid by the imprinted polymers.     

Cholesterol interference in analysis of fatty acid methyl esters

In the course of isolating and analyzing the fatty acid methyl esters (FAME) from steelhead trout (Salmo gairdneri) eggs and sac fry, a component was found on gas liquid chromatography to have a retention time longer than any characteristic polyunsaturated fatty acid previously encountered in trout. Subsequent purification and analysis demonstrated this component to be cholesterol. Thus, cholesterol and related compounds can interfere in the analysis of FAME when the methyl esters are prepared by transesterification.     

Modeling and experimental studies of emulsion copolymerization systems. II. Styrenics

Using a model previously published, predictions for evolution of conversion and average particle diameter in batch experiments are compared against experimental data for four emulsion copolymerizations of styrene with the following monomers: (1) methyl methacrylate, (2) butyl acrylate, (3) butadiene, and (4) acrylic acid. For each copolymerization system the experiments covered simultaneous variations in five variables: initiator and surfactant concentrations, water to monomer ratio, monomer composition, and temperature. It is shown that after data fitting for unknown or uncertain parameters, the model is capable of explaining quantitatively the experimental observations for conversion evolution and only qualitatively the particle size evolution data. This points out to the possible contribution of particle nucleation mechanisms other than the micellar one, which is the only mechanism included in the model. Some of the adjustable parameter values were found to depend on the copolymer composition. The only case in which the model does not perform well is in the prediction of the effect of initiator concentration on the copolymerization rate for butadiene‐rich formulations. It is also found that the model predictions are very sensitive to the value of the diffusion coefficients of monomeric radicals in the copolymer particle, which are not readily available in the literature. It is concluded that it is important to independently measure these parameters in order to enhance the predictive power of models. It is also concluded that the model can be useful for practical applications. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2380–2397, 2001