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Biomedical subjects

A F Hofmann

Publications and source records attributed to A F Hofmann.

At least 163 records · Page 9Linked to original sources
PubMed1986

Biliary lipids support serum-free growth of Giardia lamblia.

Giardia lamblia has been grown in vitro only in media containing serum or serum fractions. How this pathogen can grow in the human small intestinal lumen without serum is not known. We found that samples of human hepatic or gall bladder bile maintained G. lamblia survival for 24 to 48 h in medium without serum but did not support growth. By contrast, an artificial biliary lipid dispersion containing six bile salts, phosphatidylcholine (PC), and cholesterol, in the ratios characteristic of human bile, supported parasite growth in medium without serum or serum fractions. To define the requirements, we showed that 1-palmitoyl-2-linoleoyl-PC or 1-palmitoyl-2-oleoyl-PC (which predominate in human bile) satisfied the requirement for PC. Moreover, either glycocholate or glycodeoxycholate could be substituted for the bile salt mixture. The finding that biliary lipids can support serum-free growth of G. lamblia may help explain why this parasite colonizes the upper small intestine.

Animals↗
PubMed1986

Intraductal mono-octanoin for the direct dissolution of bile duct stones: experience in 343 patients.

The efficacy and safety of mono-octanoin, a cholesterol solvent for the direct dissolution of stones in the biliary tract, was assessed by collating case reports on 343 patients provided by 222 physicians who used the material between 1977 and 1983. Most patients had previously undergone cholecystectomy, with common duct exploration, the majority within the preceding six weeks. In most, sphincterotomy was impossible or if carried out, had not induced stone passage. Stone dissolution was considered preferable to surgery, especially in patients who were frail, elderly, or had multiple medical problems. Treatment was unequivocally successful in 88 patients (26%) and was a valuable adjunct to interventional treatment in another 29 subjects (8%). In 70 patients (20%), calculi became smaller, but remained within the biliary tree. Thus, mono-octanoin was judged to have been useful in 54% of patients. Treatment was ineffective in 124 cases (36%). In the remaining 32 patients (9%), treatment was aborted because of side effects. Such side effects were common, occurring in 67% of cases, and in 41% of patients they were multiple. Abdominal pain was the most common complication. Other side effects reported were nausea, vomiting, and diarrhoea. Side effects were usually dose related and responded to reduction in infusion rate. Side effects were life threatening in 12 patients (5%), but there were no permanent sequelae and no deaths occurred. These data indicate that mono-octanoin is moderately effective, generally second line, but sometimes first line, treatment for retained biliary duct calculi.

Adolescent↗
PubMed1986

Diagnostic and therapeutic percutaneous gallbladder procedures.

The authors report their experience with 24 patients who underwent a variety of percutaneous procedures involving the gallbladder. Twenty diagnostic and 13 therapeutic procedures were performed under sonographic, computed tomographic (CT), or fluoroscopic guidance; these procedures included biopsy of the gallbladder, diagnostic cholecystography, diagnostic aspiration of bile, gallstone dissolution and removal, cholecystostomy for drainage, and gallbladder abscess drainage. The indications for percutaneous cholecystostomy (performed in 11 patients) included relief of hydrops and empyema, gallstone dissolution, mechanical gallstone removal, and drainage for malignant obstruction. Each procedure was successful. There was one complicating episode of cholecystitis and four previously described episodes of vagal hypotension. Bile peritonitis did not occur in any of the patients. The authors discuss the various percutaneous gallbladder procedures and specific technical considerations in performing them.

Adult↗
PubMed1986

Influence of the amino acid moiety on deconjugation of bile acid amidates by cholylglycine hydrolase or human fecal cultures.

The influence of the chemical structure of the amino acid (or amino acid analogue) moiety of a number of synthetic cholyl amidates on deconjugation by cholylglycine hydrolase from Clostridium perfringens was studied in vitro at pH 5.4. Conjugates with alkyl homologues of glycine were hydrolyzed more slowly as the number of methylene units increased (cholylglycine greater than cholyl-beta-alanine greater than cholyl-gamma-aminobutyrate). In contrast, for conjugates with the alkyl homologues of taurine, cholylaminopropane sulfonate was hydrolyzed slightly faster than cholyltaurine, whereas cholylaminomethane sulfonate was hydrolyzed much more slowly. When glycine was replaced by other neutral alpha-amino acids, rates of hydrolysis decreased with increasing steric hindrance near the amide bond (cholyl-L-alpha-alanine much much greater than cholyl-L-leucine much greater than cholyl-L-valine greater than cholyl-L-tyrosine much greater than cholyl-D-valine). Conjugation with acidic or basic amino acids also greatly reduced the rates of hydrolysis, as cholyl-L-aspartate, cholyl-L-cysteate, cholyl-L-lysine, and cholyl-L-histidine were all hydrolyzed at a rate less than one-tenth that of cholylglycine. Methyl esterification of the carboxylic group of the amino acid moiety reduced the hydrolysis, but such substrates (cholylglycine methyl ester and cholyl-beta-alanine methyl ester) were completely hydrolyzed after overnight incubation with excess of enzyme. In contrast, cholyl-cholamine was not hydrolyzed at all, suggesting that a negative charge at the end of the side chain is required for optimal hydrolysis. Despite the lack of specificity for the amino acid moiety, a bile salt moiety was required, as the cholylglycine hydrolase did not display general carboxypeptidase activity for other non-bile acid substrates containing a terminal amide bond: hippuryl-L-phenylalanine and hippuryl-L-arginine, as well as oleyltaurine and oleylglycine, were not hydrolyzed. Fecal bacterial cultures from healthy volunteers also hydrolyzed cholyl-L-valine and cholyl-D-valine more slowly than cholylglycine, suggesting that cholylglycine hydrolase from Clostridium perfringens has a substrate specificity similar to that of the deconjugating enzymes of the fecal flora. The results indicate that modification of the position of the amide bond, introduction of steric hindrance near the amide bond, or loss of a negative charge on the terminal group of the amino acid moiety of the bile acid conjugate greatly reduces the rate of bacterial deconjugation in vitro when compared to that of the naturally occurring glycine and taurine conjugates.

Amides↗
PubMed1985

Polymeric dyes: useful nonabsorbable reference markers for intestinal perfusion studies in animals.

The properties of two polymeric dyes were examined to determine their suitability as nonabsorbable reference markers for intestinal perfusion studies. The first dye was a violet anthroquinone dye, R-478, named polyporphyre; the second was a blue anthroquinone dye, R-411, named polycyanine. The dyes could be determined spectrophotometrically over a concentration range of 0.03-5 microM (1-200 micrograms/mL) and had no appreciable osmotic effect. They were light stable and their absorption spectra did not change in solution over a pH range of 1-11. The dyes had a molecular weight of approximately 40,000 by gel permeation chromatography; they did not appear to have hydrophobic binding sites because they did not bind added dihydroxy bile acid or fatty acid anions. Determination of the dyes was not influenced by the presence of bilirubin when the latter was present at concentrations reported to occur in small intestinal content during digestion. The dyes did not interfere with an endpoint enzymatic determination of bile acids. The dyes caused little quenching of 3H- or 14C-radioactivity in a toluene-based liquid scintillation cocktail. Dyes were easily removed from aqueous solution by passage over a large-pore anion exchange column or by a BaCl2:ZnSO4 protein precipitation procedure. When tested in a rat jejunal perfusion model, changes in dye concentration evoked by hypotonic or hypertonic perfusates were identical to those of polyethylene glycol 4000, a commonly used reference marker. The dyes did not influence the rate of glucose absorption and did not bind to mucus.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Influence of side-chain charge on hepatic transport of bile acids and bile acid analogues.

The importance of side-chain charge on hepatic uptake and biliary secretion of bile acids and analogues was studied using the isolated, perfused rat liver and the anesthetized rat with a bile fistula. Derivatives of cholic acid with negative, neutral, zwitterionic, or positive charges on the side chain were synthesized and studied. Hepatic uptake by the isolated perfused liver, determined by measuring the rate of disappearance of a single 20-mumol bolus added to the perfusate, was strongly influenced by side-chain charge. A fully positively charged bile acid derivative (cholylcholamine) and two fully zwitterionic bile acid derivatives (CHAPS and cholyllysine) showed no appreciable uptake (less than 1% of the uptake rate of cholyltaurine). Bile acid derivatives existing mostly in cationic form (cholylamine) at pH 7.4, in neutral form (cholylglycylhistamine), or in divalent anion form (cholylaspartate and cholylcysteate) had an uptake rate that was greater but only 7-19% that of cholyltaurine. Side-chain charge also appeared to influence the rate of secretion into bile. Bile acids existing in mono- or dianionic form were well secreted (greater than 95% of dose in 2 h) into the bile, but all other derivatives had much lower secretion rates (less than 20% of dose in 2 h). When the biliary secretion of each bile acid derivative was expressed in relation to the amount that had entered the liver, relative secretion rates (presumably from liver cell) into bile decreased in the following order: cholyltaurine greater than cholylaspartate and cholylcysteate greater than CHAPS greater than cholyllysine greater than cholylglycylhistamine approximately equal to cholylamine. In bile fistula rats, cholylaspartate was quantitatively secreted into bile when infused at rates below its secretory maximum, whereas only very low biliary secretion rates of CHAPS were observed even during relatively high infusion rates; cholylamine was cholestatic. The above data show that, although uncharged and anionic derivatives of cholic acid may be taken up by the liver at a moderate rate, only anionic derivatives (both monovalent and divalent) are well secreted from within the liver cell into bile. A single negative charge on the side chain appears to be required for optimal transport of a bile acid from sinusoidal blood to bile.

Animals↗
PubMed1985

Mass spectrometry identification of biliary bile acids in bile from patients with gallstones before and during treatment with chenodeoxycholic acid. An ancillary study of the National Cooperative Gallstone Study.

The chemical structure of individual bile acids in 255 duodenal bile samples obtained from patients with radiolucent gallstones before and during treatment with chenodeoxycholic acid (375 or 750 mg/day) was determined by coupled gas chromatography/mass spectrometry. The two primary bile acids, cholic acid and chenodeoxycholic acid, and their metabolic products, deoxycholic acid, lithocholic acid, and ursodeoxycholic acid, were present in all bile samples and constituted greater than 97% of all bile acids. In pretreatment samples, the 12-oxo derivative of deoxycholic acid (3 alpha-hydroxy-12-oxo-cholanoic acid) was the next most abundant bile acid, being present in 62% of the samples; the average concentration was 1%, but three individuals had 6% to 8% of this bile acid. The 7-oxo derivative of chenodeoxycholic acid was also present in the majority of samples, but at a lower proportion (0.3%); five individuals had 2% to 3%. The 7-oxo derivative of cholic acid was present in a minority of samples (37%) in trace concentrations; isodeoxycholic acid and the 3-oxo derivatives of chenodeoxycholic acid and deoxycholic acid were also present in trace amounts. Four patients had 1% to 11% ursocholic acid in bile. During treatment with chenodeoxycholic acid, bile became enriched in it in direct relation to dosage; the concentration of its bacterial metabolites increased, and the proportion of cholic acid and its bacterial metabolites showed a reciprocal decrease. No unusual bile acids appeared, indicating that treatment with these doses of chenodeoxycholic acid does not result in the occurrence of additional uncommon bile acids in bile. It is suggested that the paucity of uncommon bile acids in bile, which contrasts strikingly with the great variety of uncommon bile acids known to be present in urine and feces, is the result of two factors: (1) the conversion of uncommon bile acids to common bile acids by reduction, hydroxylation, or epimerization during hepatic passage; and (2) efficient hepatic transport of common but not uncommon bile acids into bile.

Bile↗
PubMed1984

Physicochemical properties of bile acids and their relationship to biological properties: an overview of the problem.

The structure of the bile acid molecule is described and correlated with physiochemical properties of bile acids such as solubility, ionization, and micelle formation. Recent measurements of the critical micellar concentration (CMC) of a large number of bile acids indicate that the CMC is influenced by both side chain and nuclear structure. Bile acids with hydroxy substituents on both sides of the steroid nucleus are non-amphipathic and do not form micelles, and decreasing the length of the side chain causes an exponential increase in the CMC. Bile acid ionization, measured by titration in alcohol-water mixtures, is shown to be uninfluenced by nuclear substituents; the pKa of all unconjugated bile acids is about 5. Interactions of bile acid solutions with Ca2+ are discussed; recent work indicates that cholyl conjugates bind Ca2+ as monomers in solution. Model systems relevant to biological processes are classified, as are some of the physicochemical parameters of these systems. Biological processes involving bile acids are tabulated, and corresponding model systems are assigned to each. Some biological processes such as bile acid transport show marked species differences, suggesting that physicochemical parameters are insufficient to explain biological differences. It is recommended that the physical chemist study a variety of bile acids, that the biologist study a variety of species, and that both collaborate to attempt to factor out the extent to which physicochemical properties of bile acids can explain their biological properties.

Bile Acids and Salts↗
PubMed1984

A bioluminescence assay for total 3 alpha-hydroxy bile acids in serum using immobilized enzymes.

A bioluminescence assay for bile acids was developed using a co-immobilized 3 alpha-hydroxysteroid dehydrogenase, diaphorase, and bacterial luciferase. The assay was specific for bile acids containing a free 3 alpha-hydroxyl group, as well as androsterone. Light output was linear over a bile acid concentration range of 1-20 000 pmol. Intra-assay precision was 6.2-8.2% and the recovery of added standards was 92-110%. Comparison of results using the bioluminescence assay with those using gas liquid chromatography revealed an excellent correlation (r = 0.99, n = 31). Since the bioluminescence assay is rapid, sensitive, specific, and uses inexpensive reagents, it appears to be an ideal method for the measurement of total bile acids in serum.

3-Hydroxysteroid Dehydrogenases↗
PubMed1984

Mesophase formation during cholesterol gallstone dissolution in human bile: effect of bile acid composition.

Duodenal bile obtained from patients with gallstones who were acutely infused with chenodeoxycholic acid, ursodeoxycholic acid, or cholic acid were examined for the propensity toward the formation of a liquid crystalline mesomorphic phase when cholesterol gallstones were incubated in these bile acids. Bile taken from patients infused with ursodeoxycholic acid was found to be enriched in ursodeoxycholic acid; mesophase formation was detected in these samples but not in bile from patients infused with chenodeoxycholic acid or cholic acid.

Bile↗
PubMed1984

Major issues in the organization and implementation of the National Cooperative Gallstone Study (NCGS).

The National Cooperative Gallstone Study (NCGS) was a cooperative, randomized, controlled trial of a drug, chenodiol, for the medical dissolution of gallstones. The design and procedures of the NCGS were complex, having developed as a result of extensive involvement of many experts in the field of gallstone disease and biliary lipids. During the design and implementation of the protocol, many important issues required consideration and resolution. The aim of this article is to review these issues and the deliberations surrounding their resolution and provide personal conclusions and recommendations that may be helpful to other investigators involved in cooperative, controlled trials.

Chenodeoxycholic Acid↗
PubMed1984

Differing effects of norcholate and cholate on bile flow and biliary lipid secretion in the rat.

The effects of norcholate (a C23 bile acid that differs from cholate in having a side chain containing four rather than five carbon atoms) on bile flow and biliary lipid secretion were compared with those of cholate, using the anesthetized rat with a bile fistula. Norcholate and cholate were infused intravenously over the range of 0.6-6.0 mumol X min-1 X kg-1. Both bile acids were quantitatively secreted into bile; norcholate was secreted predominantly in unconjugated form in contrast to cholate, which was secreted predominantly as its taurine or glycine conjugates. The increase in bile flow per unit increase in bile acid secretion induced by norcholate infusion [17 +/- 3.2 (SD) microliters/mumol, n = 8] was much greater than that induced by cholate infusion (8.6 +/- 0.9 microliters/mumol, n = 9) (P less than 0.001). Both bile acids induced phospholipid and cholesterol secretion. For an increase in bile acid secretion (above control values) of 1 mumol X min-1 X kg-1, the increases in phospholipid secretion [0.052 +/- 0.024 (SD) mumol X min-1 X kg-1, n = 9] and cholesterol secretion (0.0071 +/- 0.0033 mumol X min-1 X kg-1, n = 9) induced by norcholate infusion were much less than those induced by cholate infusion (0.197 +/- 0.05 mumol X min-1 X kg-1, n = 9, and 0.024 +/- 0.011 mumol X min-1 X kg-1, n = 9, respectively; P less than 0.001 for both phospholipid and cholesterol). The strikingly different effects of norcholate on bile flow and biliary lipid secretion were attributed mainly to its possessing a considerably higher critical micellar concentration than cholate.

Animals↗
PubMed1984

Differing effects of hydroxy-7-oxotaurine-conjugated bile acids on bile flow and biliary lipid secretion in dogs.

The effects on bile flow and biliary lipid secretion of two taurine-conjugated 7-oxo bile acids, 3 alpha-hydroxy-7-oxocholanoyltaurine (I) and 3 alpha,12 alpha-dihydroxy-7-oxocholanoyltaurine (II), were measured in the unanesthetized, chronic bile fistula dog. Each synthetically prepared compound, or cholyltaurine as control, was infused intravenously at a physiological rate of 1 mumol X kg-1 X min-1 for randomized 90-min periods. Bile samples were collected and analyzed for biliary lipids (bile acids, phospholipid, and cholesterol) and bile acid composition. Both compounds were secreted efficiently in bile, recovery averaging 90%. The trisubstituted compound (II) induced a greater choleresis and less phospholipid and cholesterol secretion than the disubstituted compound (I) or cholyltaurine. Each oxo compound was partially reduced during hepatic passage: about 47% of I (to mostly chenodeoxycholyltaurine) and about 30% of II (to mostly cholyltaurine). The effect of the individual bile acids on biliary lipid secretion was then calculated by assuming that a) the infused bile acid induced biliary lipid secretion after its hepatic biotransformation and b) each bile acid or its biotransformation product exerted an independent effect on biliary lipid secretion (expressed as a linkage coefficient, e.g., phospholipid secretion/bile acid secretion). For phospholipid, the calculated linkage coefficient for I was 0.31; for II, 0.07. For cholesterol, the calculated linkage coefficient for I was 0.014; for II, 0.003. In vitro studies indicated that the critical micellar concentration (CMC) in 0.15 M Na+ was 22 mM for I and 40 mM for II (compared with 6 mM for cholyltaurine.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Influence of bile acid structure on bile flow and biliary lipid secretion in the hamster.

A comprehensive study of the influence of bile acid structure on bile flow and biliary lipid secretion was carried out by infusing pure bile acids at a physiological rate into the proximal small intestine of a bile fistula hamster. Twelve individual bile acids, cholate (C), ursocholate (UC), chenodeoxycholate (CDC), and ursodeoxycholate (UDC) as their glycine (G), taurine (T), or unconjugated form, were studied so that influence of the hydroxy substituents as well as side-chain structure could be defined. The pattern of bile acid output was dependent on bile acid structure and reflected the site and rate of intestinal absorption. Conjugated bile acid output was delayed because of late ileal absorption, and TUC was poorly absorbed. Unconjugated trihydroxy bile acids, C and UC, also exhibited a delay in absorption, while CDC and UDC were absorbed immediately and achieved the highest bile acid output. Unconjugated bile acids were conjugated initially mostly with taurine and then mostly with glycine. The effect of glycine conjugates of each bile acid on bile flow and biliary lipid secretion was similar to that of their corresponding taurine conjugates. All conjugated bile acids induced a similar rate of bile flow (9-15 microliter bile/mumol bile acid), but unconjugated bile acids other than C induced more flow (20-25 microliter bile/mumol bile acid) than their corresponding conjugates. Conjugates of the dihydroxy bile acids induced a greater secretion of phospholipid and cholesterol than cholyl conjugates, whereas conjugates of UC were unique in inducing extremely low phospholipid and cholesterol secretion. For an increase of 1 mumol X min-1 X kg-1 in bile acid output, the increase in phospholipid secretion was 0.072 mumol X min X kg for GCDC and TCDC; 0.051 mumol X min-1 X kg-1 for GUDC and TUDC; and 0.030 mumol X min-1 X kg-1 for GC and TC. Increase in cholesterol output per mumol X min-1 X kg-1 of bile acid output was 0.013 mumol X min-1 X kg-1 for GCDC and TCDC, 0.011 mumol X min-1 X kg-1 for GUDC and TUDC, and 0.005 mumol X min-1 X kg-1 for GC and TC. In general, unconjugated bile acids induced more phospholipid and cholesterol than their corresponding conjugates; however, the rank-order effect of the steroid nucleus substituents was similar to that observed for the respective conjugates. These results indicate that both nuclear and side-chain structure influence the enterohepatic circulation and biliary secretory properties of bile acids.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1984

Low-dose chenodiol to prevent gallstone recurrence after dissolution therapy.

Chenodiol is a safe and effective agent for the medical dissolution of gallstones in selected patients; however, after dissolution and cessation of treatment, gallstones recur. This study was done to determine the recurrence rate after successful medical treatment and cessation of chenodiol therapy; compare the efficacy and safety of low-dose chenodiol, as compared to placebo, for prophylaxis against recurrence; and identify factors predictive of recurrence. In a randomized, double-blind fashion, 53 patients with gallstone dissolution received either chenodiol, 375 mg/d, or placebo, for at least 2 years. Standardized oral cholecystograms were done at 6 months, 1 year, and then yearly thereafter. Routine laboratory testing was done every 6 months. The cumulative rate of recurrence (life-table) was 27% in patients followed for up to 3.5 years. Chenodiol, 375 mg/d, was ineffective in preventing the recurrence of gallstones. No demographic, clinical, roentgenographic, or biochemical characteristics were predictive of recurrence.

Aged↗