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Biomedical subjects

A F Hofmann

Publications and source records attributed to A F Hofmann.

At least 199 records · Page 11Linked to original sources
PubMed1982

Bioluminescence measurement of primary bile acids using immobilized 7 alpha-hydroxysteroid dehydrogenase: application to serum bile acids.

A simple, rapid, and sensitive bioluminescence method for measuring primary bile acids has been developed and validated. The method is based on enzymatic dehydrogenation of bile acids using a bacterial 7 alpha-hydroxysteroid dehydrogenase that is co-immobilized on Sepharose 4B beads with NADH:FMN oxidoreductase and a bacterial luciferase. The assay is specific for 7 alpha-hydroxy bile acids and has a detection limit of 0.5 pmol/tube, with a linear range of 0.5-50 pmol/tube. The assay shows good precision (6-8% intra-assay; 8-10% inter-assay). The values obtained with the bioluminescence assay showed good agreement with those obtained by gas-liquid chromatography, radioimmunoassay, or endpoint enzymatic assays. When applied to the measurement of serum bile acids, there was no interference from serum albumin, and the effect of other dehydrogenase activity in serum could be eliminated by heating the sample prior to assay. Since the method is rapid (1 minute), extremely sensitive (requires only 10 microliters of serum), and specific, it appears to be the best method currently available for the measurement of serum primary bile acids.

Bile Acids and Salts↗
PubMed1982

Pretreatment biliary lipid composition in white patients with radiolucent gallstones in the National Cooperative Gallstone Study.

Biliary lipid classes (bile acids, phospholipids, cholesterol) as well as individual biliary bile acids were measured in duodenal bile samples obtained before treatment from 284 white men and 264 white women participating in the National Cooperative Gallstone Study. The patients had radiolucent gallstones present in visualizing gallbladders. Calculated biliary cholesterol saturation was significantly higher in women (143 +/- 43, mean +/- SD, vs. 132 +/- 39 for men). Chenodeoxycholic acid was the major biliary bile acid in both sexes (40.0 +/- 9.9 in men; 38.8 +/- 9.3 in women, NS). Cholic acid was the second most common bile acid, constituting 32.9 +/- 8.8 in men and 31.8 +/- 8.9 in women (NS). When other demographic and clinical characteristics, including serum lipids, were related with biliary lipid composition, only percent ideal body weight correlated significantly. The partial correlation coefficient adjusted for percent ideal body weight indicated that the proportion of chenodeoxycholic acid correlated negatively with the mole fraction of cholesterol in bile in men, but not in women. Multiple regression analyses showed that bile saturation could not be predicted reliably from any clinical, chemical, or radiologic measurement in either sex. Published data for biliary lipid composition in individuals with biliary disease showed considerable overlap with the National Cooperative Gallstone Study data reported here, suggesting that cholesterol gallstone disease is not caused solely by increased biliary cholesterol saturation.

Adult↗
PubMed1981

Retained biliary tract stones. Nonsurgical treatment with capmul 8210, a new cholesterol gallstone dissolution agent.

The ability of Capmul 8210, a commercial solvent that predominantly consists of glyceryl 1-mono-octanoate, to dissolve retained common duct stones by direct infusion into the T-tube was tested in 20 patients with a total of 43 stones. Of 19 patients who completed their infusion, stone disappearance was observed in 15, giving a success rate of 79%. The dissolution time for a single stone averaged four days. A slight rise in serum alkaline phosphatase and amylase levels occurred in some patients, and rapidly returned to normal when treatment was concluded. Other side effects, such as nausea and vomiting epigastric discomfort, or diarrhea, occurred occasionally but were easily controlled medically. We believe that this agent is a useful adjunct in the management of postoperative choledocholithiasis in the patient with an indwelling T-tube.

Alkaline Phosphatase↗
PubMed1981

Effective therapy of enteric hyperoxaluria: in vitro binding of oxalate by anion-exchange resins and aluminum hydroxide.

Hyperabsorption of dietary oxalate is a major factor in the pathogenesis of enteric hyperoxaluria and a frequent complication of inflammatory bowel disease and ileojejunal bypass surgery. Successful treatment requires reduction in oxalate intake or inhibition of absorption of dietary oxalate by oral ingestion of oxalate binding agents. To identify such agents, oxalate binding by anion-exchange resins, gums, and aluminum hydroxide was measured under conditions that simulated those present in the intestinal lumen. Of the agents tested, those that bound oxalate best were colestipol and aluminum hydroxide. Strongly basic anion-exchange resins readily bound oxalate only in the absence of chloride. These results suggest that colestipol and aluminum hydroxide administration might reduce dietary oxalate absorption in patients with enteric hyperoxaluria.

Adsorption↗
PubMed1981

Altered bile acid metabolism in primary biliary cirrhosis.

Selected aspects of bile acid metabolism were assessed in six women with primary biliary cirrhosis and varying degrees of cholestasis. Urinary bile acid excretion was markedly increased and correlated highly with serum levels. In three patients in whom urinary bile acids were separated by chromatography, the majority of urinary bile acids were monosulfated (34%, 42%, 32%) or polysulfated and/or glucuronidated (30%, 20%, 38%). The monosulfates of chenodeoxycholic acid were conjugated at either the 3 position (67%, 68%, 73%) or the 7 position (33%, 32%, 27%); similarly, the monosulfates of cholic acid were conjugated at the 3 position (65%, 58%, 68%) or the 7 position (35%, 42%, 32%). The position of sulfation was not markedly influenced by the mode of amidation with glycine or taurine. Chenodeoxycholic exchangeable pool size, turnover rate, and synthesis were measured by isotope dilution and found to be well within normal limits, despite the cholestasis. The fraction of chenodeoxycholic acid synthesis excreted in urine ranged from 9 to 48%; 4--38% of chenodeoxycholic acid synthesis was sulfated. These data indicate that the major abnormalities in bile acid metabolism in patients with cholestasis secondary to primary biliary cirrhosis are formation of sulfated bile acids in greatly increased amounts, elevation of blood levels of primary bile acids, and a shift to renal excretion as a major mechanism for bile acid elimination. Chenodeoxycholic acid synthesis continues at its usual rate despite cholestasis. Whether these changes, including the formation of 7-monosulfated bile acids, occur in other forms of cholestasis and whether either the persistance of unchanged chenodeoxycholic acid synthesis or the formation of such novel conjugates has any pathophysiological significance remain to be investigated.

Adult↗
PubMed1981

Hyperoxaluria associated with intestinal bypass surgery for morbid obesity: occurrence, pathogenesis and approaches to treatment.

Hyperoxaluria occurs in most patients after the conventional jejunoileal bypass procedure for obesity. The mechanism of hyperoxaluria is complex, involving persistence of dietary oxalate in solution as well as increased colonic permeability to oxalate. Endogenous oxalate formation also contributes to hyperoxaluria. Treatment is unsatisfactory and involves a low-oxalate diet and simultaneous administration of agents which bind oxalate and bile acids, such as aluminum hydroxide. Hyperoxaluria was not present in 21 of 22 patients who had undergone the pancreato-biliary bypass procedure.

Biliary Tract Surgical Procedures↗
PubMed1981

Enzymatic measurement of choline-containing phospholipids in bile.

An enzymatic method, previously used to determine choline-containing phospholipids in serum, was applied to the estimation of phospholipid concentration in bile. The method combines three enzymatic reactions: a) release of choline by phospholipase D; b) choline oxidation by choline oxidase, a reaction which generates hydrogen peroxide; and c) formation of a red quinone dye by peroxidase. The method is an endpoint, spectrophotometric determination. It is simple, sensitive, and reproducible. Accuracy was demonstrated both by linear recoveries of the choline-containing phospholipids in bile and a good correlation with a chemical determination. No interferences by bile acids and/or cholesterol were observed; bile pigment interference was removed by bleaching with white light. This method which determines lipid choline is simpler than the widely used chemical determination of lipid phosphorus.

Alcohol Oxidoreductases↗
PubMed1980

Silencing the beeper.

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Hospital Communication Systems↗
PubMed1980

Metabolism in man of 7-ketolithocholic acid: precursor of cheno- and ursodeoxycholic acids.

To define the metabolism of 7-ketolithocholic acid in man, studies were carried out in gallstone patients with normal liver function. 7-[24-14C]ketolithocholic acid or its glycine or taurine conjugates were injected intravenously, and the chemical form of radioactivity appearing in bile was determined to define hepatic biotransformation. To study intestinal absorption 7-[24-14C]ketolithocholic acid was infused into the jejunum and ileum, respectively, and the chemical form of radioactivity appearing in peripheral blood and bile was assessed. 7-Ketolithocholic acid was extensively reduced in the liver to chenic acid and, to lesser extent, to ursodeoxycholic acid. Hepatic reduction was similar for both unconjugated as well as glycine- and taurine-conjugated 7-ketolithocholic acid. 7-Ketolithocholic acid was well absorbed. There was no biotransformation in the small intestinal lumen or during absorption, because all radioactivity recovered from the lumen or in peripheral blood was in unchanged 7-ketolithocholic acid. Biotransformation products in bile after jejunal infusion were similar to those after intravenous injection. The studies indicate that 7-ketolithocholic acid is likely to be a physiological precursor of ursodeoxycholic acid in healthy man.

Carbon Radioisotopes↗
PubMed1980

Spectrophotometric determination of urinary oxalate with oxalate oxidase prepared from moss.

A novel spectrophotometric enzymic procedure for estimating oxalic acid in urine is described. Oxalate oxidase, prepared from moss species, converts oxalic acid to hydrogen peroxide and carbon dioxide. Hydrogen peroxide is determined enzymatically with horseradish peroxidase, by oxidative coupling of 3-methyl-2-benzothiazolinone hydrazone with N,N-dimethylaniline; the resulting indamine due is determined spectrophotometrically at 595 nm. Interfering substances are removed by adsorption to ion-exchange resins and oxidation with charcoal, thus avoiding oxalate recovery problems accompanying oxalate isolation. The procedure is rapid, sensitive, linear, and precise. Results agreed well with those obtained with a widely used chemical technique.

Adult↗