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Biomedical subjects

R H Dowling

Publications and source records attributed to R H Dowling.

At least 145 records · Page 8Linked to original sources
PubMed1972

Lithogenic bile in patients with ileal dysfunction.

Ileal disease or resection causes bile salt malabsorption and a reduction in the bile salt content of bile. Since cholesterol solubility requires adequate bile salt concentrations, depletion of the bile salt content of bile might, therefore, jeopardize cholesterol solubility and predispose to cholesterol gallstone formation. To study this, we examined biliary lipid composition in 10 patients with ileal dysfunction and in 25 healthy controls. Biliary lipid composition, as analysed in cholecystokinin-stimulated, bile-rich duodenal fluid, was shown to be representative of gallbladder bile and reproducible on repeat duodenal intubation. Nine of the 10 patients with ileal dysfunction had an abnormal, supersaturated bile in which the limits of cholesterol solubility were exceeded, and while nine of 25 control subjects also had an unstable bile, the mean bile composition in the ileal dysfunction group was significantly different from the control population. These studies provide a physicochemical explanation for the clinical observation that patients with ileal dysfunction have an increased incidence of gallstones.

Adult↗
PubMed1971

Endocrine tumour in kidney affecting small bowel structure, motility, and absorptive function.

A 44-year-old woman is described with an endocrine tumour arising in the kidney. There were associated abnormalities of small intestinal morphology, motility, and absorptive function. These abnormalities reversed on removal of the tumour. Detailed studies showed that the tumour contained, and was secreting, glucagon. It is postulated that the intestinal abnormalities may have resulted from glucagon itself or another, as yet unidentified, hormone.

Adult↗
PubMed1971

Action of neomycin on the intraluminal phase of lipid absorption.

Administration of a single 1 g dose of neomycin sulfate to five healthy subjects simultaneously with a test meal caused a marked increase in the proportion of fatty acid and bile acid in the ultracentrifuged deposit of aspirated intestinal contents. Labeled cholesterol was precipitated in a similar manner in two hypercholesterolemic patients. Neomycin had no effect on the pancreatic lipase concentration or on the pH of intestinal contents. These results confirm that the ability of neomycin to precipitate micellar lipids is due to interaction between the polybasic neomycin molecule and ionized fatty acids and bile acids. This mechanism provides an explanation for both the steatorrhea and hypocholesterolemia induced by this compound.

Administration, Oral↗
PubMed1971

Biliary lipid secretion and bile composition after acute and chronic interruption of the enterohepatic circulation in the Rhesus monkey. IV. Primate biliary physiology.

Bile salts and phospholipids are both required to solubilize biliary cholesterol. Since interruption of the enterohepatic circulation (EHC) depletes bile of bile salts, we have examined in the rhesus monkey the effects of controlled interruption of the EHC on biliary secretion of bile salt, phospholipid, and cholesterol and on the relative proportions of these components in bile. Immediately after complete interruption of the EHC, bile secretion and bile composition remained normal for 2-3 hr. During the next 3 hr, however, secretion of all components decreased. Bile salt decreased to a greater extent than phospholipid and cholesterol, and the bile was now supersaturated with cholesterol. 12-24 hr after interruption of the EHC, a new steady state was reached in which there was a relative deficiency of bile salt and a relative increase in phospholipid and cholesterol. The resulting bile, although somewhat more saturated with cholesterol, was not supersaturated with cholesterol but was stable with respect to cholesterol solubility. Thus, bile instability conducive to gallstone formation occurs transiently within hours after interruption of the EHC. Prolonged large interruptions in the steady state animal also produce a relative bile salt deficiency, but in this situation cholesterol remains soluble in the bile of these animals because there occurs a concomitant relative increase in phospholipid. When the EHC was only partially interrupted, secretion rates and the relative concentration of bile salt, phospholipid, and cholesterol did not change significantly from control values until more than 20% of the bile was diverted. Modest changes in the relative composition of bile occurred when 33 and 66% of the bile was diverted, and these changes were very similar to those produced by resection of the distal small bowel.

Animals↗
PubMed1970

Effects of controlled interruption of the enterohepatic circulation of bile salts by biliary diversion and by ileal resection on bile salt secretion, synthesis, and pool size in the rhesus monkey.

The effects of controlled interruption of the enterohepatic circulation (EHC) of bile salts by biliary diversion on bile volume, bile salt secretion and synthesis rates, bile salt pool size, and the relationship to fecal fat excretion were studied in 16 rhesus monkeys. Bile from a chronic bile fistula was returned to the intestine through an electronic stream-splitter which, by diverting different percentages of bile to a collecting system, provided graded and controlled interruption of the EHC. The increase in hepatic bile salt synthesis in response to interruption of the EHC was limited and reached a maximum rate at 20% interruption of the EHC. Up to this level of biliary diversion, the increased hepatic synthesis compensated for bile salt loss so that bile salt secretion and pool size were maintained at normal levels. With diversion of 33% or more, there was no further increase in hepatic bile salt synthesis to compensate for external loss, and as a result there was diminished bile salt secretion, a reduction in bile salt pool size, and steatorrhea was observed. The effects of interruption of the EHC by the streamsplitter were compared with those produced by resection of the distal one-third or two-thirds of small bowel. While ileal resection appreciably reduced bile salt secretion, the EHC was by no means abolished. Bile salt reabsorption from the residual intestine was greater after one-third than after two-thirds small bowel resection. These observations suggest that jejunal reabsorption of bile salts occurs and may well contribute to the normal EHC.

Animals↗