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W C Duane

Publications and source records attributed to W C Duane.

At least 55 records · Page 3Linked to original sources
PubMed1986

Role of the unstirred layer in protecting the murine gastric mucosa from bile salt.

Bile salts disrupt a functional gastric mucosal barrier which normally minimizes back-diffusion of H+ into mucosa. Our previous studies have shown that ionized bile salts disrupt the barrier to H+ by dissolving membrane lipids. The presence of an unstirred water layer on the surface of the gastric mucosa could protect against bile salt injury either by creating a concentration gradient of bile salt from lumen to mucosal surface or by slowing diffusion of lipid-laden mixed micelles away from the mucosal surface. In the present study we investigated this possibility in the anesthetized rat. Measurements of H+ back-diffusion and Na+ forward-diffusion across the gastric mucosa were made before and after exposure to a bile salt solution that was either unmixed or mixed by continuous withdrawal and injection. Using carbon monoxide diffusion, we observed this method of mixing to decrease the unstirred layer thickness from 880 to 448 micron (p less than 0.02). Mixing increased mean H+ back-diffusion induced by a 10 mM mixture of six conjugated bile salts from -2.58 to -4.11 microEq/min (p less than 0.01) and increased mean forward-diffusion of Na+ from 1.81 to 3.27 microEq/min (p less than 0.01). Mixing also increased efflux of mucosal phospholipid (32.7 to 52.2 nmol/min, p less than 0.05) and of cholesterol (4.89 to 8.87 nmol/min, p less than 0.05) into the bile salt solution. Addition of saturation amounts of lecithin and cholesterol to the bile salt solution completely prevented disruption of the barrier whether the solution was mixed or not. Mixing also increased mucosal uptake of bile salt from 74.6 to 221.3 nmol/min (p less than 0.01) when no lipids were added. In the presence of lecithin and cholesterol, mixing increased absorption of bile salt from 63.5 to 165.6 (p less than 0.02). These findings further support the hypothesis that bile salts disrupt the gastric mucosal barrier by dissolution of mucosal membrane lipids, and provide evidence that the unstirred water layer helps protect the gastric mucosa from bile salt injury.

Animals↗
PubMed1986

Lysolecithin-lipid interactions in disruption of the canine gastric mucosal barrier.

Lysolecithin has been implicated in the pathogenesis of gastric ulcer and reflux gastritis. By use of canine Heidenhain pouches, we examined effects of lysolecithin on the gastric mucosal barrier both at neutral (PO4 buffer, pH 7) and acidic (0.15 M HCl) pH with respect to interaction of lysolecithin with membrane lipids. At both pH values, 2 mM lysolecithin significantly increased forward diffusion of Na+ and backdiffusion of H+. Both solutions also caused significant efflux of membrane phospholipid and cholesterol. Saturation of neutral and acidic lysolecithin solutions with either lecithin or cholesterol significantly diminished or completely prevented disruption of the barrier to H+ backdiffusion and Na+ forward diffusion. In agreement with other reports, we also demonstrated formation of soluble lysolecithin-lecithin mixed micelles but formation of insoluble lysolecithin-cholesterol complexes. Finally, by use of [3H]polyethylene glycol and [14C]lysolecithin, we demonstrated more rapid mucosal uptake of lysolecithin at acidic than at neutral pH for any given experimental condition. Specifically, mean mucosal uptake of lysolecithin from acidic solutions saturated with lecithin (which did not disrupt the gastric mucosal barrier) was greater than uptake from neutral solutions without added lipid (which did disrupt the barrier). These studies suggest that lysolecithin-lipid interactions play an important role in lysolecithin-induced injury to the gastric mucosa. The most important of these interactions appears to occur in luminal lysolecithin micelles rather than within mucosal membranes.

Animals↗
PubMed1984

A method for measurement of nanogram quantities of 3-methylcholanthrene in stool samples.

The carcinogen 3-methylcholanthrene can be produced from deoxycholic acid and is postulated by some investigators to play a role in the pathogenesis of colon carcinoma. The small quantities of this compound which could be carcinogenic have been difficult to measure in feces because of many potentially interfering compounds. Using 3-[6-14C]methylcholanthrene as an internal standard, petroleum ether extraction, C-18 SepPak separation, preparative high performance liquid chromatography, and gas-liquid chromatography-mass spectrometry with selected ion monitoring, we developed an assay capable of detecting less than 35 ng of 3-methylcholanthrene per gram of stool. Application of this technique to stools of five patients with colon carcinoma and two normal controls revealed no detectable 3-methylcholanthrene in any stool sample. This negative result was confirmed by incubating radiolabeled cholic acid in fecal homogenates. Although greater than 90% of this radiolabeled bile acid was converted to deoxycholic acid, none of the radioactivity was found in the thin-layer chromatography fraction corresponding to 3-methylcholanthrene. These observations provide evidence against a role for 3-methylcholanthrene in pathogenesis of human colon carcinoma. Similar assays could be used for analysis of other carcinogens in stool samples.

Cholic Acid↗
PubMed1983

Regulation of bile acid synthesis in man. Presence of a diurnal rhythm.

Regulation of bile acid synthesis in man is incompletely understood, in part because of difficulty in making measurements over short time periods when the enterohepatic circulation is intact. We investigated the possibility of a diurnal rhythm of bile acid synthesis in three human subjects given [26-14C]cholesterol. When this isotope of cholesterol, which is randomly labeled in the 26 and 27 positions, is converted to bile acid, the 14C is released as propionic acid randomly labeled in the 1 and 3 positions. The labeled propionic acid is then oxidized to 14CO2, output of which is a function of bile acid synthesis. However, delays in transit of the 14C through propionic acid and CO2-HCO-3 pools would shift the phase and dampen the amplitude of 14CO2 output relative to an existing diurnal rhythm of bile acid synthesis. Therefore, using constant infusion methods, we determined the turnover constants for conversion to 14CO2 of [1-14C]propionic acid and [3-14C]propionic acid to be 0.36-0.59 h-1 and 0.14-0.16 h-1, respectively. Using these constants and modeling the diurnal rhythm as a cosine function, we determined that amplitude of 14CO2 output from [26-14C]cholesterol was reduced 35% and acrophase was delayed 2.4-3.0 h relative to the diurnal rhythm of bile acid synthesis. None of the diurnal rhythm in 14CO2 output from [26-14C]cholesterol resulted from diurnal variation in propionic acid or CO2-HCO-3 metabolism since constant infusion of [1-14C]propionic acid and [3-14C]propionic acid for 30 h revealed no diurnal variation in output of 14CO2. These studies demonstrate for the first time that humans with an intact enterohepatic circulation have a diurnal rhythm of bile acid synthesis with an amplitude of +/- 35-55% around mean synthesis, and an acrophase at about 9 a.m.

Adult↗
PubMed1983

Lack of effect of experimental ascorbic acid deficiency on bile acid metabolism, sterol balance, and biliary lipid composition in man.

Extensive studies in animal models indicate that subclinical ascorbic acid deficiency impairs the conversion of cholesterol to bile acid, elevates plasma cholesterol levels, and predisposes to development of cholesterol cholelithiasis. The present study was designed to see if this is also true in man. Five normal volunteers were hospitalized in a metabolic ward and placed on a controlled diet containing 3-4 mg of ascorbic acid each day. Ascorbic acid supplementation was given as follows: control period I (days 1-33), 75 mg/day; deficient period (days 34-96), 0 mg/day; and repletion period (days 97-101), 1000 mg/day. In addition, three of the subjects were studied during a second control period (days 102-139) during which they were given 75 mg/day of ascorbic acid. Ascorbate levels at the end of both control periods were 0.87-1.34 mg/dl in plasma and 19.4-29.5 micrograms/10(8) cells in leukocytes. At the end of the deficient period these levels were 0.09-0.15 mg/dl in plasma and 6.2-10.0 micrograms/10(8) cells in leukocytes, levels approaching those seen in scurvy. There was no effect of ascorbic acid deficiency on plasma cholesterol and triglycerides; plasma cholesterol in high, very low, and low density lipoprotein fractions; biliary lipid composition and saturation index of gallbladder bile; synthesis, fractional turnover, or pool size of either cholic or chenodeoxycholic acids; output of fecal acid or neutral sterols; and fecal sterol balance. Total bile acid pool size calculated by the one-sample technique was reduced 11% in the deficient period compared to control period I (P less than 0.005), and increased to 98.7% of the baseline levels in control period II. However, total bile acid pool calculated by the Lindstedt method did not change during deficiency. These data demonstrate that short-term subclinical ascorbic acid deficiency near the scorbutic range has no significant effect on bile acid and cholesterol metabolism in man.

Adult↗
PubMed1983

Taurocholate is more potent than cholate in suppression of bile salt synthesis in the rat.

Synthesis of bile salts is regulated through negative feedback inhibition by bile salts returning to the liver. Individual bile salts have not been distinguished with regard to inhibitory potential. We assessed inhibition of bile salt synthesis by either cholate or its taurine conjugate in bile fistula rats. After allowing synthesis to maximize, baseline synthesis was determined by measuring bile salt output in four consecutive 6-hr periods. Next, sodium cholate (+[(14)C]cholate) or taurocholate (+[(14)C]taurocholate) was infused into the jugular vein for 36 hr and bile was collected in 6-hr aliquots. Hepatic flux of exogenous bile salt was determined by measuring output of radioactivity in bile divided by specific activity of the infusate. Synthesis was determined during the last four 6-hr periods of infusion by subtracting exogenous bile salt secretion from the total bile salt output. Thirteen studies using cholate and 13 using taurocholate were performed. Hepatic flux of infused bile salt varied from 1 to 12 micro mol/100 g per rat per hr. Percent suppression of synthesis varied directly with hepatic flux of exogenous bile salt for both cholate and taurocholate in a linear fashion (r = 0.66, P < 0.01 and r = 0.87, P < 0.0005, respectively). Slope of the taurocholate line was 7.82 (% suppression/ micro mol per 100 g per hr), while slope of the cholate line was 3.66 (P < 0.05), indicating that taurocholate was approximately twice as potent as cholate in suppression of synthesis. At fluxes of 10-12 micro mol/100 g per hr, taurocholate suppressed synthesis 84 +/- 8 (SEM) % while cholate suppressed synthesis only 42 +/- 12% (P < 0.02). The x-intercept of the taurocholate line was 0.65 ( micro mol/100 g per hr), while that of the cholate line was -1.01 (NS) suggesting that the threshold for initial suppression of synthesis did not differ for these two bile salts. We conclude that taurocholate is a more effective inhibitor of hepatic bile salt synthesis than cholate, and that intestinal deconjugation of bile salts may play a role in the regulation of synthesis.-Pries, J. M., A. Gustafson, D. Wiegand, and W. C. Duane. Taurocholate is more potent than cholate in suppression of bile salt synthesis in the rat.

Animals↗
PubMed1982

Comparison of bile acid synthesis determined by isotope dilution versus fecal acidic sterol output in human subjects.

Fecal acidic sterol output has been found to be much lower than bile acid synthesis determined by isotope dilution (J. Lipid Res. 17: 17, 1976). Because of this confusing discrepancy, we compared these 2 measurements done simultaneously on 13 occasions in 5 normal volunteers. In contrast to previous findings, bile acid synthesis by the Lindstedt isotope dilution method averaged 16.3% lower than synthesis simultaneously determined by fecal acidic sterol output (95% confidence limit for the difference - 22.2 to -10.4%). When one-sample determinations of bile acid pools were substituted for Lindstedt pools, bile acid synthesis by isotope dilution averaged 5.6% higher than synthesis by fecal acidic sterol output (95% confidence limits -4.9 to 16.1%). These data indicate that the 2 methods yield values in reasonably close agreement with one another. If anything, fecal acidic sterol outputs are slightly higher than synthesis by isotope dilution.

Bile Acids and Salts↗
PubMed1982

Lack of effect of subclinical ascorbic acid deficiency upon antipyrine metabolism in man.

The influence of experimentally induced subclinical ascorbic acid deficiency upon antipyrine metabolism was assessed in five healthy male volunteers maintained in a hospital metabolic ward and fed a controlled diet deficient in ascorbic acid. Antipyrine pharmacokinetic parameters were determined four times during the study: at the end of an initial control period, after 28 and 63 days of depletion, and at the end of a second control period. No differences in antipyrine metabolism were observed despite the fact that the subjects had plasma ascorbate levels indicative of vitamin C deficiency (i.e., plasma levels less than 0.3 mg/dl) for 5 days (28 day-depletion) or 40 days (63 day-depletion). This experiment demonstrates that pronounced ascorbic acid deficiency of relatively short duration does not alter antipyrine metabolism in man.

Adult↗
PubMed1982

Human T-cell function in experimental ascorbic acid deficiency and spontaneous scurvy.

Studies in animal models suggest that ascorbic deficiency impairs T-cell-mediated immunity. We studied five normal volunteers hospitalized on a metabolic unit and consuming a strictly controlled diet deficient in ascorbic acid I) after a 5-wk control period of ascorbic acid supplementation (75 mg/day) and 2) after a 9-wk period of no supplementation. Three of the subjects were restudied after a 5-wk period of ascorbic acid supplementation after the deficient period. At the end of both control periods ascorbic acid levels in plasma ranged from 0.9 to 1.3 mg/dl and in leukocytes from 19 to 30 microgram/10(8) cells. At the end of the deficient period levels of ascorbic acid in plasma ranged from 0.09 to 0.15 mg/dl and in leukocytes from 6.2 to 10 microgram/10(8) cells, levels at or below those frequently found in frank scurvy. None of the T-cell parameters tested including mitogen responsiveness to phytohemagglutinin and percentage of T-cells bearing receptors for IgM (helper cells) and IgG (suppressor cells) was different in the deficient period compared to the control periods. One patient with spontaneous scurvy (plasma ascorbic acid 0.07 mg/dl, leukocytic ascorbic acid 4.9 microgram/10(8) cells) was studied at the time of admission and after vigorous ascorbic acid repletion. All T-cell parameters after repletion were unchanged from admission. We conclude that in man ascorbic acid deficiency, even at the scorbutic level, does not alter T-cell numbers or impair in vitro T-cell function.

Adult↗
PubMed1982

Bile acid and bile salt disrupt gastric mucosal barrier in the dog by different mechanisms.

The present study was undertaken to assess the mechanism by which protonated taurocholic acid disrupts the gastric mucosal barrier. By the criterion of lecithin solubilization, the critical micellar concentration of taurocholic acid (pH 1) was 4.5 mM, as opposed to 3.0 mM for sodium taurocholate (pH 7). In canine Heidenhain pouches, taurocholic acid significantly increased net forward diffusion of Na+ and backdiffusion of H+ at concentrations of 9, 4.5, and 3.5 mM, indicating that micelle formation was not required for disruption of the gastric mucosal barrier by this bile acid. Saturation of the 9 mM taurocholic acid solution with lecithin (and cholesterol) did not prevent disruption of the gastric mucosal barrier. At 9 mM, taurocholic acid was absorbed from the pouches at a mean rate of 1,150 +/- 115 nmol/min in contrast to an absorption rate of 225 +/- 10 nmol/min for sodium taurocholate at the same concentration. These findings indicate that, unlike ionized bile salts, disruption of the gastric mucosal barrier by taurocholic acid is mediated largely by uptake of bile acid by the gastric mucosa rather than dissolution of mucosal membrane lipids.

Absorption↗
PubMed1982

Inhibition of gallstone formation by sphincterotomy in the prairie dog: reversal by atropine.

Sphincterotomy has previously been shown to decrease gallbladder volume and gallbladder bile stasis while inhibiting gallstone formation in the prairie dog. We tested the possibility that atropine administration might reverse the effects of sphincterotomy on gallbladder mechanical function and gallbladder bile stasis and thereby reverse the inhibition of gallstone formation seen after sphincterotomy. Sixteen prairie dogs underwent sphincterotomy and were placed on a high cholesterol diet known to consistently induce gallstone formation. After 6 wk, in addition to the lithogenic diet, 8 animals were administered atropine. A control group of 8 animals was continued on the lithogenic diet. At death, animals that had undergone sphincterotomy and received atropine had a larger mean gallbladder volume (2.7 +/- 0.4 ml) than sphincterotomized control animals (0.66 +/- 0.2 ml, p less than 0.005), more total lipid stored in the gallbladder (176.1 +/- 33.9 mumol, sphincterotomy and atropine vs. 42.8 +/- 17.3 mumol, sphincterotomy, p less than 0.005), and a larger fraction of administered radiolabeled bile salt stored in the gallbladder (51.5 /- 7.3%, sphincterotomy and atropine vs. 24.5 +/- 10.7 sphincterotomy, p less than 0.05). The ratio of the fraction of [3H]cholic acid in the gallbladder (given 1 day before death) to the fraction of [14C]cholic acid in the gallbladder (given 4 days earlier) was lower for animals that underwent sphincterotomy and received atropine (0.63 +/- 0.04) than for sphincterotomized control animals (1.0 +/- 0.15, p less than 0.05), indicating a return of gallbladder bile stasis in the atropine-treated group. Confirming our previous work, only 1 of 8 animals that underwent sphincterotomy had gallstones. In contrast, 8 of 8 atropine-treated animals formed stones (p less than 0.005). Gallbladder bile of both groups were equally supersaturated with cholesterol. These findings provide direct support for the role of gallbladder bile stasis in the pathogenesis of cholesterol gallstone formation in this model.

Ampulla of Vater↗
PubMed1981

Effect of sorbitol on psychomotor function: its use in alcoholic cirrhosis.

Sorbitol solution has been used to a control substance of evaluating the efficacy of lactulose therapy for hepatic encephalopathy (HE). However, recent in vitro studies suggested that sorbitol may be an inert placebo and may have therapeutic relevance. We evaluated in vivo metabolism of sorbitol in healthy volunteers and alcoholic cirrhotic patients and found that sorbitol was metabolized by gut bacteria in a similar manner to lactulose. We next evaluated the effect of sorbitol treatment on five psychomotor performances tests in cirrhotic patients. Patients receiving sorbitol demonstrated improvement in all psychomotor tests, whereas similar patients not receiving sorbitol showed no improvement. We conclude the following: sorbitol is metabolized by gut bacteria in man, sorbitol therapy improved psychomotor performance in cirrhotic patients, and previous studies using sorbitol as a control underestimated the beneficial effects of lactulose.

Humans↗
PubMed1980

Mechanism by which bile salt disrupts the gastric mucosal barrier in the dog.

Bile salts disrupt a functional "gastric mucosal barrier" increasing net forward-diffusion (+) of Na+ and back-diffusion (-) of H+. Studying canine Heidenhain pouches, we attempted to distinguish between two possible mechanisms for this effect: (a) mucosal uptake of bile salt with subsequent cellular injury or (b) dissolution of mucosal lipids by intralumenal bile salt. A 10 mM mixture of six conjugated bile salts simulating the proportions found in human bile induced net Na+ flux of 15.5 +/- 3.2 and net H+ flux of -9.9 +/- 3.3 mueq/min. This change was accompanied by an increase in phospholipid efflux out of gastric mucosa from a base-line value of 13.2 +/- 2.7 to 54.8 +/- 2.8 nmol/min (P < 0.001) and an increase in cholesterol efflux from 11.7 +/- 3.8 to 36.3 +/- 3.2 nmol/min (P < 0.001). Saturation with lecithin (25 mM) and cholesterol (50 mM) blocked disruption of the gastric mucosal barrier by bile salt (Na+ flux - 1.2 +/- 0.9, H+ flux 0.6 +/- 1.8 mueq/min). A 10 mM solution of taurodehydrocholate, a bile salt that does not form micelles, induced no net Na+ (-0.3 +/- 0.8) or H+ flux (-0.7 +/- 1.4) and did not increase efflux of phospholipid (11.3 +/- 1.7) or cholesterol (10.4 +/- 2.0) over base line. Bile salt was absorbed from the mixture of six conjugates at 752 +/- 85 nmol/min. Addition of subsaturation amounts of lecithin (4 mM) reduced bile salt absorption three fold to 252 +/- 57 (P < 0.001), but abnormal Na+ flux (14.1 +/- 3.4) and H+ flux (-15.6 +/- 3.5) persisted. Taurodehydrocholate was absorbed to an intermediate extent (467 +/- 116). Dissolution of mucosal lipids is apparently the mechanism by which bile salt disrupts the gastric mucosal barrier, and presumably at least one mechanism by which bile salt can injure the gastric mucosa.

Animals↗
PubMed1979

Diurnal rhythms of bile acid production in the rat.

Diurnal rhythms of bile acid synthesis were studied in Sprague-Dawley rats maintained in 12 h of illumination and 12 h of darkness each day. Synthesis, measured as output from a chronic bile fistula, underwent a consistent diurnal change with an amplitude of about 20% around mean daily synthesis and a peak in the dark period. The peak in cholate synthesis preceded the peak in chenodeoxycholate synthesis which preceded the peak in alpha-muricholate synthesis which preceded the peak in beta-muricholate synthesis. Fasting, intravenous infusion of dexamethasone (100 microgram/kg . h), adrenalectomy, and ocular enucleation all failed to abolish the diurnal rhythm in synthesis. In one rat studied 30 days after ocular enucleation the diurnal rhythm in synthesis persisted; however, relative to 4 days after enucleation the phase of the rhythm shifted about 90 degrees suggesting that light deprivation caused the rhythm to become free-running with a period slightly different from 24 h.

Adrenal Glands↗
PubMed1978

Sex differences in the size of bile acid pools.

In view of the excess prevalence of gallstones among women and the association of gallstones with diminished bile acid pool size, we measured bile acid pools in 27 male and 25 female healthy human volunteers. The average bile acid pool in the women was significantly smaller than in the men (2.25 +/- .12 g versus 2.88 +/- .16 g; p = 0.003). Chenodeoxycholic acid pool size, computed from bile acid composition data available in 43 of these subjects, was also smaller in women than men (0.94 +/- 0.06 versus 1.22 +/- 0.07 g; p = 0.004). Age, race, and body size bore no statistically significant relationship to bile acid pool size. Biliary cholesterol saturation was positively correlated with weight and obesity and showed a significant inverse correlation with chenodeoxycholic acid pool size, but not with total bile acid pool size. These findings suggest a possible mechanism for the higher prevalence of gallstones among women.

Adolescent↗