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At least 235 records · Page 13Linked to original sources
PubMed1996

Solution and solid state structure of an aib-containing cyclodecapeptide inhibiting the cholate uptake in hepatocytes.

The conformational analysis of synthetic cyclodecapeptide c(Pro-Phe-phe-Aib-Leu)2 related to the cyclolinopeptide A, in the solid state and solution, has been carried out by x-ray diffraction and nmr spectroscopy. The structure of the monoclinic form obtained from methanol [a = 11.351 (5) A, b = 27.455 (2) A, c = 12.716 (8) A, beta = 99.65 (3) degrees; space group P2(1); Z = 2] shows the presence of six intramolecular NH...CO hydrogen bonds, with formation of four turns (three of type I and one of type III) and two C16 ring structures. All peptide units are trans. The solution structure, as found by nmr, indicates that, at room temperature, the peptide is conformationally homogeneous; the structure determined is perfectly symmetrical and topologically similar to that found in the solid state. The cyclodecapeptide exhibits similar biological activity to cyclolinopeptide A.

Animals↗
PubMed1975

The removal of retained gallstones from the common bile duct: experience with sodium cholate infusion and the Burhenne catheter.

The use of cholic acid T tube infusion and of the Burhenne catheter has been investigated in the management of gallstones retained in the common bile duct following biliary surgery in 9 patients. Four of 7 patients treated with cholic acid infusion showed disappearance of the stones during treatment. The stones in a fifth subject were removed by a combination of cholic acid infusion (1 stone disappeared) and instrumentation with a Burhenne catheter (a second stone removed). Use of a Burhenne catheter was unsuccessful in 3 of 4 patients. Details of the technique of cholic acid infusion are given, and possible complications of the treatment are discussed. The use of cholic acid infusion for the dissolution of stones in the common bile duct is recommended.

Catheterization↗
PubMedDate not supplied

Molecular organization in phases of lecithin-cholate-water as studied by nuclear magnetic resonance.

The molecular organization in the liquid crystalline phases and the micellar solution phase has been investigated using numerous nuclear magnetic resonance techniques. A brief review of previous studies on the lamellar, hexagonal and cubic liquid crystalline phases is given. Mixed micelles were studied by measurements of 2H T1 and T2 nuclear magnetic resonance relaxation times of 2H-labeled phosphatidylcholine. Using simple and rough models, the size and shape of the micellar aggregate were estimated.

Cholic Acids↗
PubMedDate not supplied

Regulation of bile acid synthesis. I. Effects of conjugated ursodeoxycholate and cholate on bile acid synthesis in chronic bile fistula rat.

Bile acid synthesis is thought to be regulated by a negative feedback mechanism which is presumably dependent upon the flux of bile acids in the enterohepatic circulation. To characterize further the role of bile acids in regulation of bile acid synthesis, we have administered pure taurine or glycine conjugates of ursodeoxycholic acid or cholic acid to chronic bile fistula rats by continuous intraduodenal infusion, thus simulating restoration of the enterohepatic circulation. The effects of these bile salt infusions on bile acid synthesis, biliary cholesterol and phospholipid secretion and on the activities of the hepatic microsomal enzymes cholesterol 7 alpha-hydroxylase and HMG-CoA reductase were evaluated. Because the rate of biliary bile salt secretion in rats with intact exteriorized enterohepatic circulation averaged 27.1 +/- 1.4 mumoles per 100 gm rat per hr, infusion rates for bile fistula studies were chosen to match (24 to 36 mumoles per 100 gm rat per hr) or exceed (48 mumoles per 100 gm rat per hr) this physiological flux. Infusion of tauroursodeoxycholic acid for 48 hr at 24 and 48 mumoles per 100 gm rat per hr failed to suppress cholic acid synthesis. Bile flow and biliary cholesterol and phospholipid secretion exhibited small, dose-dependent increases with tauroursodeoxycholic acid infusions. No suppression of cholesterol 7 alpha-hydroxylase or HMG-CoA reductase activity was observed. By contrast, taurocholic acid inhibited synthesis of chenodeoxycholate and its metabolites alpha- and beta-muricholate by 10% (NS), 66% (p less than 0.05) and 75% (p less than 0.05) at infusion rates of 24, 36 and 48 mumoles per 100 gm rat per hr, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1976

The correlation between the protein composition of cytoplasmic membranes and the formation of nitrate reductase A, chlorate reductase C and tetrathionate reductase in Proteus mirabilis wild type and some cholate resistant mutants.

Three genotypically different chlorate resistant mutants, chl I, chl II and chl III, appeared to lack completely nitrate reductase A, chlorate reductase C and tetrathionate reductase activity. Fumarate reductase is only partially affected in chl I and chl III and unaffected in chl II. Formate dehydrogenase is only partially diminished in chl II, hydrogenase is diminished in chl I and chl II and completely absent in chl III. Subunits of nitrate reductase A, chlorate reductase C and tetrathionate reductase have been identified in protein profiles of purified cytoplasmic membranes from the wild type and the three mutant strains, grown under various conditions. Only the presence and absence of the largest subunits of these enzymes appeared to be correlated with their repression and derepression in the wild type membranes. On the cytoplasmic membranes of the chl I and chl III mutants these subunits lack for the greater part. In the chl II mutant, however, these subunits are inserted in the membrane all together after anaerobic growth with or without nitrate. A model for the repression/derepression mechanism for the reductases has been proposed. It includes repression by cytochrome b components, whereas the redox-state of the nitrate reductase A molecule itself is also involved in its derepression under anaerobic conditions.

Anaerobiosis↗