Search PubMed⌕ Search

Biomedical subjects

W E Connor

Publications and source records attributed to W E Connor.

At least 217 records · Page 12Linked to original sources
PubMed1973

The different effects on the serum lipids and fecal steroids of high carbohydrate diets given orally or intravenously.

The hypothesis that diets high in carbohydrate produce hyperlipidemia in man was tested in new experiments which provided all calories either by the intravenous route or orally. After a base-line general diet, eight healthy men were fed fat-free diets consisting of 80% of the calories from glucose and 20% from an amino acid hydrolysate. The calories were adequate to maintain body weight. The solutions (1 cal/ml) were infused by constant drip over a 24 h period through either a superior vena cava catheter or a nasogastric tube. Each feeding was for 12 days in sequence but assigned in random order. The high CHO diet given orally, as expected, increased the mean base-line serum triglyceride level from 176+/-29 (SE) to 274+/-47. The identical diet given intravenously (i.v.) failed to produce hypertriglyceridemia; triglyceride levels were not significantly changed, 154+/-37, nor were blood glucose levels. Serum insulin levels were higher during the intravenous feeding. In contrast, both i.v. and oral feedings greatly lowered mean serum cholesterol concentration from the base-line value of 220+/-13 mg/100 ml to 135+/-11 and 151+/-13, respectively. However, the serum cholesterol level was significantly lower (P < 0.01) with the intravenous feeding than with the oral feeding. In addition, the fecal excretion of both neutral sterols and bile acids diminished greatly during the period of intravenous feeding. The fecal mass was likewise decreased. The bacterial conversion of cholesterol to conprostanol did not occur with either intravenous or oral feeding, but with both regimens secondary bile acids predominated, as usual, in the bile acid fraction of the stool. These results emphasize the key role of the intestinal mucosa in the etiology of carbohydrate-induced hypertriglyceridemia and as a direct or indirect contributor to plasma triglyceride and cholesterol levels in the absence of dietary lipids. When the gut mucosa was bypassed, carbohydrate-induced hypertriglyceridemia did not occur and both serum triglyceride and serum cholesterol levels decreased greatly at a time when the excretion of steroids in the stool was also reduced.

Administration, Oral↗
PubMed1972

The formation of abnormal bile and cholesterol gallstones from dietary cholesterol in the prairie dog.

To study the pathogenesis of cholesterol gallstones, we fed 24 adult male prairie dogs a high cholesterol, egg yolk diet. 13 control animals received a cholesterol-free diet. All animals fed the egg yolk diet formed multiple gallstones in 2-6 months' time. These stones contained cholesterol, 77+/-14% by dry weight. No stones ocurred in the control group. The egg yolk-fed animals developed bile of altered chemical composition. The cholesterol concentration of hepatic and gallbladder bile increased significantly. The molar ratios of bile acid/cholesterol and phospholipid/cholesterol decreased in hepatic and gallbladder bile. The predominant bile acid shifted from cholic acid, 78% of the total bile acids, to chenodeoxycholic acid, 60% of the total. In common bile duct cannulated animals the high cholesterol diet produced increased secretion of cholesterol by the liver and increased bile flow. In animals fed the egg yolk diet for 2 months, cholesterol-4-(14)C was included in the daily diet for the next 4 months to establish an isotopic steady state. At autopsy the mean specific activity of cholesterol was similar in serum, liver, hepatic bile, gallbladder bile, and gallstones. Thus the cholesterol of gallstones apparently equilibrated constantly throughout the study and was not sequestrated as a static pool. The high cholesterol, egg yolk diet caused the secretion of an "abnormal bile" which led to precipitation of cholesterol from micellar solution. The increased bile cholesterol relative to bile acid and phospholipid favored stone formation. This dietary induction of cholesterol gallstones provided a unique animal model, in part but not completely analogous to human cholelithiasis.

Animals↗
PubMed1972

Excretion of sterols from the skin of normal and hypercholesterolemic humans. Implications for sterol balance studies.

The 24 hr sterol excretion from the entire skin surface was determined in six normal and five hypercholesterolemic (Type II) patients fed a controlled, eucaloric diet containing 400 mg of plant sterols. All subjects received radiolabeled cholesterol intravenously in order to measure cholesterol turnover and exchange. The 24 hr skin surface lipids were collected subsequently at intervals of 7-10 days. Sterols were quantified and identified by a combination of thin-layer and gas-liquid chromatographic methods. The mean 24 hr excretion of cholesterol in milligrams was 82.6 in the normal subjects and 82.7 in the hypercholesterolemic patients. Cholesterol constituted 89% of the total sterol excretion through the skin surface in both groups. The specific radioactivity of cholesterol in the skin surface lipids increased gradually after the intravenous administration of the isotope. Within 4-5 wk the specific activity equaled and then remained higher than that of the plasma up to 10 wk. These specific activity curves suggested that, for at least some of skin surface cholesterol, there was a precursor-product relationship between the plasma cholesterol and the skin cholesterol. The presence of plant sterols, beta-sitosterol, campesterol, and stigmasterol in the skin surface lipids of man has not been reported previously. We identified these sterols in the skin surface lipids of all of our subjects. They constituted about 7% of the total skin surface sterols. The occurrence of plant sterols in the skin surface lipids suggested that plasma sterols were transferred from the plasma into the skin. 1-2% of the skin surface sterols were tentatively identified as lathosterol and lanosterol. The present study documented that a significant amount of cholesterol was excreted from the skin surface and that probably there was a net transfer of plasma cholesterol into the skin surface lipids. Both normal subjects and hypercholesterolemic patients excreted similar amounts of cholesterol per day into the skin surface lipids. We suggest that this daily loss of cholesterol from the skin surface may need to be considered in sterol balance studies.

Adult↗
PubMed1972

Cholesterol metabolism and placental transfer in the pregnant Rhesus monkey.

The placental transfer of cholesterol (5-cholesten-3beta-ol) was investigated by giving pregnant rhesus monkeys cholesterol-1alpha-(3)H or cholesterol-4-(14)C and then determining the cholesterol specific activity (SA) in maternal serum and in fetal serum and tissues. An isotopic steady state was established in five pregnant animals by the daily feeding of a tracer dose of cholesterol-4-(14)C. Comparison of maternal and fetal serum cholesterol SA revealed that an average of 42.6% of the serum cholesterol in the term fetus originated by transfer from the maternal blood. The remainder presumably arose by fetal synthesis de novo. Fetal tissues had cholesterol SA equal to or slightly less than that of fetal serum, except for brain which had a SA only 5% that of fetal serum. In other studies a single intravenous dose of radioactive cholesterol was given to either mother or fetus in late pregnancy. The time for detectable passage across the placenta in either direction was between 4 and 24 hr. With maternal administration of the isotope, there was equilibration of maternal and fetal serum cholesterol SA after 10-12 days. With fetal injection of isotopic cholesterol, however, the maternal cholesterol SA never attained a level more than 5% of fetal SA. This indicated that the net cholesterol flux was strongly in the direction of mother to fetus. Serum cholesterol levels were significantly greater in maternal than in fetal serum (80.3+/-18.5 vs. 59.6+/-15.6 mg/100 ml). Maternal serum cholesterol concentration in the monkey was significantly lower in late pregnancy than during the puerperium. Studies of breast milk indicated that approximately two-thirds of milk cholesterol was transferred from the maternal blood.

Administration, Oral↗
PubMed1970

Effect of cellulose in the diet on the recovery of dietary plant sterols from the feces.

In one normal subject, J.S., fed several formula diets in a sterol balance study, only 25-58% of the ingested plant sterols were recovered from the stool. The dietary plant sterols were completely recovered from the stools of five other men. Plant sterol recovery was complete in all men when a diet of mixed general foods was consumed. Since the chief differences in composition of the formula and the diet of mixed general foods were related to the different contents of cellulose and lactose, these components were added to the formula diet of J.S., and plant sterol balance studies were then carried out. The addition of fresh celery or pulverized cellulose to the formula diet partially corrected the usual fecal loss of plant sterols (80% being recovered). Lactose in the formula was only slightly corrective. However, the addition of both cellulose and lactose led to complete recovery of the ingested plant sterols in the feces. Bacterial cultures of stools were incubated with added cholesterol-4-(14)C, and a linear relationship between losses of sterol during balance studies and in vitro incubations was observed; that is, a considerable loss of the labeled cholesterol from cultures after the formula diet, but not after the diet of mixed general foods. This in vitro loss was also corrected by the addition of cellulose and lactose to the formula diet. The loss of the sterol nucleus in the intestinal tract may occur at times because of the lack of certain dietary constituents. It is hypothesized that the metabolism of intestinal tract bacteria is altered when certain constituents are not present in the diet, and that these bacteria may then degrade the sterol nucleus.

Carbon Isotopes↗
PubMed1969

Cholesterol balance and fecal neutral steroid and bile acid excretion in normal men fed dietary fats of different fatty acid composition.

Six normal men were fed formula diets containing either highly saturated fat (cocoa butter, iodine value 32) or polyunsaturated fat (corn oil, iodine value 125). The sterol balance technique was used to compare the changes in serum cholesterol concentration with the excretion of fecal steroids. The method used for the analysis of fecal steroids was chemical, with a final identification and quantification by gas-liquid chromatography. It was confirmed that the chemical method for fecal steroid analysis was accurate and reproducible. The three dietary periods were each 3 wk in length. In sequence, cocoa butter (period I), corn oil, and cocoa butter (period III) were fed at 40% of the total calories. All diets were cholesterol free, contained similar amounts of plant sterols, and were identical in other nutrients. Corn oil had a hypocholesterolemic effect. Mean serum cholesterol concentrations were 222 mg/100 ml (cocoa butter, period I), 177 during corn oil, and 225 after the return to cocoa butter. Individual fecal steroids were determined from stools pooled for 7 days. Both neutral steroids and bile acids were altered significantly by dietary polyunsaturated fat. The change in bile acid excretion was considerably greater than the change in neutral steroids. Corn oil caused a greater fecal excretion of both deoxycholic and lithocholic acids. The total mean excretion (milligrams per day) of fecal steroids was 709 for cocoa butter (period I), 915 for corn oil, and 629 for the second cocoa butter period. The enhanced total fecal steroid excretion by the polyunsaturated fat of corn oil created a negative cholesterol balance vis-à-vis the saturated fat of cocoa butter. The hypocholesterolemic effect of polyunsaturated fat was associated with total fecal sterol excretion twice greater than the amount of cholesterol calculated to leave the plasma. This finding suggested possible loss of cholesterol from the tissues as well.

Adult↗