Biomedical subjects

A B Thomson

Publications and source records attributed to A B Thomson.

At least 217 records · Page 12Linked to original sources

PubMed1987

Spectrum of effects of dietary long-chain fatty acids on rat intestinal glucose and lipid uptake.

Isocaloric modification in the ratio of dietary polyunsaturated-to-saturated fatty acids influences intestinal uptake of actively and passively transported nutrients. This study was undertaken to determine which dietary fatty acid was responsible for these alterations in absorption. Adult female rats were fed isocaloric semisynthetic diets high in palmitic and stearic acids (SFA), oleic acid (OA), linoleic acid (LA), or linolenic acid (LNA). An in vitro technique was used to measure the uptake of varying concentrations of glucose as well as a series of fatty acids and cholesterol. Jejunal uptake of 40 mM glucose was highest in rats fed SFA and lowest in those fed LA; ileal glucose uptake was similar in OA, LA, and LNA, but was lowest in SFA. Jejunal uptake of medium-chain fatty acids (8:0-12:0) was higher in OA than in other diet groups; ileal uptake of medium-chain fatty acids was unaffected by diet. Jejunal and ileal uptake of 18:2 was higher in LNA than in SFA or OA; the uptake of the other long-chain saturated or unsaturated fatty acids was unchanged by diet. The ileal but not the jejunal uptake of cholesterol was increased in LA as compared with SFA or OA, and reduced in LNA as compared with LA. These transport changes were not explained by differences in the animals' food consumption, body weight gain, intestinal mass, or mucosal surface area. We postulate that these diet-induced transport alterations may be mediated via changes in brush border membrane phospholipid fatty acyl composition. Thus, intestinal transport of nutrients may be varied by isocaloric changes in the dietary content of individual fatty acids.

Animals↗

PubMed1987

A high linoleic acid diet diminishes enhanced intestinal uptake of sugars in diabetic rats.

Intestinal absorption is altered in rats by diabetes and by dietary manipulation. For 5 wk rats were fed chow (C) or semisynthetic diets containing isocaloric amounts of a high content of either polyunsaturated (P) or saturated (S) fatty acids; then half were rendered hyperglycemic with streptozotocin while the remaining half served as nondiabetic controls. Studies were performed after a total of 8 wk on C, P, or S. Jejunal villous surface area was greater in diabetic rats than in control rats fed C or S, whereas the jejunal mucosal surface area was significantly greater in diabetic animals than in control animals only when they were fed S. Ileal mucosal surface area was similar in diabetic and in control rats fed C, S, or P; although ileal villous surface area was greater in diabetic than in control rats only when they were fed C. The jejunal and ileal uptake of varying concentrations of glucose and galactose was higher in diabetic rats than controls fed C or S. In contrast, the enhanced uptake of these sugars was reduced or normalized in diabetic rats fed P. The jejunal brush-border membrane (BBM) content of phospholipids was higher in diabetic than in control rats fed chow, but there was no difference in diabetic vs. control animals fed P or S in BBM total free fatty acids, phospholipids, or cholesterol. Thus feeding a high linoleic acid diet diminishes the enhanced intestinal uptake of glucose and galactose in diabetic rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1987

Vitamin A status in 137 patients with Crohn's disease.

Serum retinol and serum carotene concentrations were determined over a 6-month period in 137 outpatients with Crohn's disease. Serum retinol measurements were within the reference range for all patients at each assessment period, while serum carotene levels were low in about one quarter of the patients. Of the 56 patients who completed 48-hour stool collections, 41% had stool fat values exceeding the reference value. Serum retinol concentrations were not significantly correlated with the serum carotene concentrations, with the 48-hour stool fat content, or with the Crohn's disease activity. In contrast serum retinol concentrations were correlated with the dietary levels of vitamin A. Serum carotene concentrations were inversely correlated with the stool fat content but were not related to Crohn's disease activity or dietary levels of carotene or total vitamin A. Thus: (1) serum retinol concentrations were normal in this moderately large group of patients with Crohn's disease and did not reflect a low dietary vitamin A intake by 34% of the population; (2) serum carotene levels were frequently low in patients with Crohn's disease, possibly due to the presence of steatorrhea, but were not related to low dietary intakes of carotene or to active Crohn's disease, and (3) a low serum level of carotene does not indicate that the patient is at risk of developing vitamin A deficiency.

Adult↗

PubMed1987

Feeding rats diets containing cheno- or ursodeoxycholic acid or cholestyramine modifies intestinal uptake of glucose and lipids.

We wished to test the hypothesis that variations in the luminal content of bile acid produced by feeding chenodeoxycholic acid (CDC), ursodeoxycholic acid (UDC) or cholestyramine (C) alter intestinal transport properties and morphology. Rats were fed standard chow pellets containing 0.5% CDC, 0.5% UDC or 2% C for a period of 2 weeks, and the in vitro uptake of glucose, cholesterol, bile acids and a homologous series of fatty acids was assessed. The food consumption was similar in animals fed chow, CDC, UDC and C, yet rats fed CDC or UDC gained less weight, and the weight of the jejunal and ileal mucosa was lower in animals fed CDC or C than in those fed chow or UDC. Ileal but not jejunal uptake of glucose was reduced in animals fed UDC, CDC or C. The active ileal uptake of bile acids was enhanced by UDC, CDC or C, whereas the jejunal passive permeability to bile acids was reduced by feeding C. Feeding C inhibited the jejunal and ileal uptake of cholesterol; C, UDC and CDC had a variable effect on the intestinal uptake of the fatty acids 10:0-18:0. The jejunal mucosal surface area was lower in groups fed CDC or UDC as compared with rats fed chow or C, and the ileal mucosal surface area was lower in rats fed CDC. However, the altered intestinal transport could not be explained by the altered morphology. Thus, (1) chronic variations in the intestinal luminal content of bile acids produced by the feeding of CDC, UDC or C resulted in alterations in the active and passive transport properties of the intestine, and (2) these changes differed between the jejunum and the ileum and were not explained simply by alterations in the animals' food intake or mucosal morphology. These studies suggest that chronic variations in the bile acids in the intestinal lumen may be one of the factors independently influencing the transport properties and mucosal surface area of the intestine. The long-term effect of changes in luminal bile acid content on intestinal function in man remains to be established.

Animals↗

PubMed1987

Early feeding of a high-cholesterol diet enhances intestinal permeability to lipids in rabbits.

This study was undertaken in young and growing rabbits to establish the of feeding a high- (2%) cholesterol diet (HC) on the intestinal in vitro uptake of a homologous series of saturated fatty acids, dodecanol, cholesterol, and bile acids. In the jejunum there was an increase in the uptake of myristic acid and dodecanol in HC as compared with animals fed Purina Chow, whereas in the ileum the uptake of stearic acid, cholesterol, and taurocholic acid was reduced. There was increased jejunal uptake of medium-chain length fatty acids, increased incremental change in free energy (integral of delta Fw----l), increased uptake of palmitic, taurocholic acid, and glycocholic acid and reduced uptake of myristic acid and dodecanol in animals fed the high-cholesterol diet for 10 days followed by Purina Chow for 18 days (HC-chow), as compared with HC. There was also increased ileal uptake of palmitic acid in HC-chow as compared with HC but reduced ileal uptake of stearic acid, cholesterol, taurocholic acid, and glycocholic acid. In the colon, there was increased uptake of stearic acid and dodecanol in HC-C as compared with HC, but reduced uptake of cholesterol, taurocholic acid and glycocholic acid. These changes in lipid uptake were not explained by alterations in the mucosal surface area or in the animals' body weight gain. It is proposed that early feeding experiences with a high-cholesterol diet may alter the normal development of intestinal transport of lipids with increased jejunal permeability to medium-chain fatty acids and increased effective resistance of the intestinal unstirred water layer.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1987

Endothelium-dependent relaxation in aorta of BB rat.

The study was undertaken to determine whether the phenomenon of endothelium-dependent relaxation was impaired in the spontaneously diabetic BB Wistar rat. Endothelium-dependent relaxation in the aorta of overtly diabetic animals was compared with that in nondiabetic BB rats. The relaxative responses were elicited in vitro to acetylcholine (-8.0 to -5.5 log M) and histamine (-7.0 to -3.0 log M) after precontraction with norepinephrine (-6.0 log M). The maximum relaxations produced by both acetylcholine and histamine expressed as percentages of the contractions to norepinephrine were significantly lower in diabetic than in nondiabetic rats. Scanning electron microscopy revealed that in diabetic BB rats there was consistent evidence of swollen cells, raised nuclei, and sloughing of nuclei in endothelial cells of the aorta. In nondiabetic animals these features were not evident. These findings suggest the presence of a functional and morphological defect in endothelial cells in the aorta of the BB rat.

Acetylcholine↗

PubMed1987

Pharmacological management of patients with peptic ulcer disease: prospects for the late 1980's.

Over the past ten years there have been major advances in the physician's ability to treat patients with peptic ulcer disease. Cimetidine continues to be the standard against which newer therapies are generally compared, although ranitidine is equally effective for short-term therapy, more effective for maintenance therapy, and has a superior safety profile. Famotidine is an even more potent H2 receptor antagonist, and initial clinical studies are promising. The initial concern for the development of gastric carcinoid lesions in rodents, maintained for long periods on high doses of omeprazole, defused the initial enthusiasm for this hydrogen-potassium ATPase "proton pump" inhibitor, but recent studies continue to show a marked efficacy of this agent for the short-term care of patients with gastric or duodenal ulcers and for the management of patients with the Zollinger-Ellison syndrome. Sulcrate continues to enjoy wide popularity for acute and chronic care of acid peptic disorders because of its local action and minimal adverse effects. Pirenzepine is effective in achieving and maintaining healing, but prevalence of anticholinergic side-effects has hampered enthusiasm for its widespread use. The 2 forerunners in the prostaglandin analogues arena, misoprostol and enprostil, are antisecretory agents when given in sufficiently high doses. These orally administered prostaglandins have a favourable safety profile, and their only adverse effect is that of the development of transient mild diarrhea. Finally, while antacids continue to be used in large amounts because of their over-the-counter availability, their clinical usefulness is limited by their unpalatable taste and the relatively large amounts usually required to achieve ulcer healing.

Alprostadil↗

PubMed1987

The assessment of recovery of the intestine after acute radiation injury.

Several aspects of intestinal function and morphology are affected by acute radiation damage, including changes in the activity of proliferative cells in the crypts, immune cell populations, and the transport of various substrates. This study was designed to compare the time course of the recovery of intestinal proliferation, transport, and leukocyte population following radiation injury. Rats received a single dose of 6 Gy to the abdomen from a 137Cs source and were studied 3, 7, and 14 days later. No changes in the passive uptake of L-glucose or D-leucine were observed in the jejunum. Active transport of D-glucose and maximal water uptake were reduced at 3 days but had returned to normal by 7 days, whereas L-leucine uptake required more than 7 days to return to control levels. Mucosal permeability, assessed by an in vivo potential difference technique, remained increased 7 days after irradiation. Ornithine decarboxylase, an indicator of DNA synthetic activity, was elevated following radiation treatment and remained so even after 14 days. By comparison, myeloperoxidase activity, used as a quantitative monitor of granulocyte numbers, was still reduced after 7 days. These data indicate that while certain parameters of gut function may return to normal soon after radiation injury, the recovery of other factors is more prolonged. Thus the return of transport function to normal values post irradiation may be viewed as an adaptive change rather than simply the recovery of the tissue.

Animals↗

PubMed1987

Effect of diet on islet cell transplantation.

Transplantation of adequate numbers of islets can normalize the clinical parameters during normal chow feeding and modified diets of cholesterol, carbohydrate and protein. The transplantation of 3,000 fresh islets gives a clinical response that is the same as the normal controls. Animals transplanted with insufficient number of islets are unable to tolerate dietary stress, which eventually exhausts the beta cells, so that insufficient insulin is secreted to normalize the transplanted animals. Diabetic animals are unable to tolerate diet modification with many of the animals dying during or shortly after the diet's modification.

Animals↗

PubMed1987

Isocal and Portagen alter intestinal uptake of sugars but not mucosal surface area in rabbits with an intact intestinal tract and following ileal resection.

This study was undertaken to examine the effect of feeding 2 defined-formula diets, Isocal and Portagen, on intestinal morphology and transport function in rabbits subjected to an ileal resection, and in control animals with an intact intestinal tract. Neither ileal resection nor feeding Isocal or Portagen significantly altered jejunal mucosal surface area. In animals with an intact intestinal tract, feeding Isocal was associated with decreased jejunal uptake of 2 mM glucose, whereas both Isocal and Portagen were associated with increased jejunal uptake of 40 mM glucose, and increased ileal uptake of 2 mM glucose, as compared with rabbits fed chow. In animals with an ileal resection, feeding Isocal was associated with increased jejunal and colonic uptake of galactose, whereas jejunal uptake of glucose was unaffected. Thus, (1) feeding defined-formula diets alters the intestinal active uptake of sugars without altering intestinal mucosal surface area; (2) sugar uptake rates were generally higher in animals fed Isocal than in those fed Portagen; (3) ileal resection obscured the differences in the jejunal uptake of higher concentrations of glucose observed in control rabbits (with an intact intestinal tract) fed these defined-formula diets; and (4) the differences in the effects of defined-formula diets on sugar uptake in control and resected animals was likely due to a direct effect on the glucose and galactose carrier(s), rather than to an indirect effect on food consumption, body weight gain, intestinal morphology, or the effective resistance of the intestinal unstirred water layer. It is suggested that the functional differences observed between animals fed Isocal versus Portagen may be due to the varying source of lipids and proteins in these diets, their different ratios of saturated-to-polyunsaturated fatty acids, and their different percent content of carbohydrate.

Animals↗

PubMed1987

Diet counseling modifies nutrient intake of patients with Crohn's disease.

The nutrient intake of 137 outpatients with Crohn's disease was recorded, and the effect of diet counseling was assessed. Half the patients received monthly diet counseling that was individualized and aimed at normalizing nutrient intake; the other half of the patients received no diet counseling and served as controls. Over the 6-month study period, the mean nutrient intakes met or exceeded the 1980 U.S. Recommended Dietary Allowances (RDAs) for all nutrients except folate in the men and iron and folate in the women. However, at study entry, for each nutrient there was a substantial proportion of patients whose intake did not meet the full RDA. Less than 50% of the men consumed the full RDA for energy and folate, and less than 50% of the women consumed the full RDA for energy, folate, calcium, iron, thiamin, and vitamin B-12. Monthly diet counseling sessions were associated with increases in the mean intake of most nutrients, whereas similar improvement was not observed in the control group members, who did not receive counseling. By 6 months, significantly more counseled than non-counseled patients were consuming the full RDA for protein, riboflavin, and vitamin C (p less than .05). Thus, diet counseling was found to be an important tool for improving the nutrient intake of outpatients with Crohn's disease.

Adolescent↗

PubMed1987

Iron, folate, vitamin B-12, zinc, and copper status in outpatients with Crohn's disease: effect of diet counseling.

Iron, folate, and vitamin B-12 status was found to be poor in a substantial proportion of outpatients with generally inactive Crohn's disease. Diet counseling was associated with a normalization of TIBC and serum folate over a 6-month period, but no other consistent benefits were noted despite moderate improvements in intake. The outpatients appeared to be at low risk of developing a zinc or copper deficiency.

Adult↗

PubMed1986

Treatment of duodenal ulcer with enprostil, a synthetic prostaglandin E2 analogue.

Enprostil is a synthetic prostaglandin E2 analogue developed by Syntex. In a randomized, double-blind trial involving 128 patients with duodenal ulcer disease, four weeks of treatment with enprostil at doses of 70 micrograms twice daily and 35 micrograms twice daily produced healing rates (78 percent and 65 percent, respectively) that were statistically significantly higher than the placebo rate (39 percent; p less than 0.05). In a subgroup of smokers, ulcer healing occurred with statistically significantly greater frequency at both the high dose (70 percent) and the low dose (60 percent) when compared with the rate in the placebo group (32 percent; p less than 0.05). The only clinically important side effect was diarrhea, which was generally mild, self-limited, and of short duration. This study demonstrated that enprostil is highly effective in the treatment of duodenal ulcer and has a favorable safety profile.

Adolescent↗

PubMed1986

Uptake of lipids into rabbit jejunum and colon following ileal resection. Effect of variations in dietary content of carbohydrate.

This study was undertaken to determine the effect of variations in the dietary content of carbohydrate (sucrose) and intestinal resection on the passive jejunal and colonic uptake of short-, medium-, and long-chain length fatty acids, cholesterol, and decanol. A previously validated in vitro technique was used, and studies were performed in sham-operated control animals and in rabbits submitted to the surgical removal of the distal half of the small intestine. After six weeks feeding of a high- or low-carbohydrate diet, the uptake of lipids was altered, but the direction and extent of changes was different among jejunum, ileum, and colon in control animals, and between the jejunum or colon of control vs resected animals. The intestinal membrane is likely heterogeneous with respect to passive permeability pathways since dietary manipulation of sucrose had a different effect on the uptake of each lipid probe. The finding of lower jejunal and colonic cholesterol uptake in animals fed a high- as compared with a low-carbohydrate diet reflects the importance of dietary effects on intestinal permeation. Studies must now be performed to establish the mechanisms responsible for these diet-related changes in intestinal permeability.

Animals↗

PubMed1986

Defined formula diets alter jejunal and colonic uptake of lipids in rabbits with intact intestinal tract and following ileal resection.

An in vitro technique was used to measure the jejunal and colonic uptake of fatty acids, decanol and cholesterol in sham-operated control (CONT) rabbits and in animals with a surgical resection of the distal half of the small intestine (RES). CONT and RES were fed standard Purina chow, Ensure, or Flexical HN for 2 weeks. The animals fed Ensure or Flexical HN consumed half the number of calories as the chow-fed rabbits and failed to gain weight. The mean of the jejunal dry weights were unchanged by diet or by ileal resection, although the height of the villi was lower in the animals fed the defined formula diets. Restricting chow intake to match the body weight gain of the animals fed Ensure or Flexical HN was associated with alterations in the uptake of lipids, but the pattern of changes was dissimilar to the pattern of changes observed in the resected animals or in the rabbits fed Ensure or Flexical HN. Ileal resection was associated with changes in the jejunal uptake of lipids and the influence of the defined formula diets on the uptake of short-, medium- and long-chain length fatty acids, decanol and cholesterol varied depending upon whether the animal had an intact intestinal tract or whether the animal had an ileal resection. It is concluded that the passive uptake of a homologous series of saturated fatty acids, cholesterol, and decanol into the jejunum and colon is modified by ad libitum feeding of Ensure or Flexical HN; the functional adaptation of the intestine and colon to dietary modification is influenced by the previous resection of the distal half of the small intestine; and these changes in the uptake of lipids are not explained solely by alterations in food intake, body weight gain, or intestinal morphology.

Animals↗

PubMed1986

Uptake of hexoses and lipids into rabbit jejunum and colon following ileal resection: effect of variations in the cholesterol and fat content of the diet.

After 6 weeks feeding on either a high-cholesterol/fat (H) or a low-cholesterol/fat (L) diet, jejunal and colonic uptake was measured using a previously validated in vitro technique in control rabbits with an intact intestinal tract (C) and in animals submitted to the surgical removal of the distal half of the small intestine (R). The uptake of hexoses and fatty acids was influenced by ileal resection and by diet. Dietary manipulation altered the passive and active transport properties of the intestine and had a different effect on intestinal transport in animals with an ileal resection than in animals with an intact small intestine.

Animals↗

PubMed1986

Fractionated low doses of abdominal irradiation alters jejunal uptake of nutrients.

Abdominal radiation is associated with changes in intestinal uptake of nutrients that begins within three days and persist for over 33 weeks. Clinically, fractionated doses of radiation (FDR) are used in an attempt to minimize the complications of this therapy, but the effects of fractionated doses of radiation on intestinal transport have not been defined. Accordingly, an in vitro technique was used to assess the jejunal and ileal uptake of varying concentrations of glucose and leucine, as well as the uptake of single concentrations of fatty acids and decanol in rats exposed 3, 7, and 14 days previously to a course of 200 cGy given on each of five consecutive days. FDR was associated with an increase in the uptake of decanol, and therefore a decrease in the effective resistance of the unstirred water layer. FDR had a variable effect on the uptake of glucose and leucine, with a decline in the value of the Michaelis constant (Km) and the passive permeability coefficient for glucose (Pd), whereas the Km for leucine was unchanged and the Pd for leucine was variably affected by FDR. The maximal transport rate (Jdm) for leucine progressively rose following FDR, whereas the Jdm for glucose initially rose, then fell. The uptake of galactose and medium chain-length fatty acids was unchanged by FDR, whereas the jejunal uptake of myristic acid rose, and the uptake of cholic acid declined, then returned to normal. FDR was associated with greater body weight gain and jejunal and ileal weight, but these changes did not adequately explain the variable alterations in the kinetics of uptake. The changes in nutrient uptake following FDR differed from the absorption changes occurring after a single dose of radiation. Thus, fractionated doses of abdominal radiation produce complex changes in the intestinal uptake of actively and passively transported nutrients, and these variable changes are influenced by the time following radiation exposure and by the solute studied.

Abdomen↗

PubMed1986

Limitations in the use of 14C-glycocholate breath and stool bile acid determinations in patients with chronic diarrhea.

Analysis of a modified 14C-glycocholate breath test on 165 consecutive in-patients being investigated for chronic diarrhea showed that the measurement of 14CO2 between 3 and 6 h after oral dosing of 5 microCi of 14C-glycocholic acid was of only limited use to distinguish between patients with Crohn's disease (CD), idiopathic bile salt wastage (IBW), or ileal resection (IR) from those with the irritable bowel syndrome (IBS). Continuing 14CO2 collections for up to 24 h was of little more help in establishing the presence of bacterial overgrowth syndrome (BOS) and in distinguishing between BOS and CD. Stool bile acid measurements were of use in differentiating between IBW and IBS, but did not distinguish between CD and BOS or between CD and IR. Since the range of normal values was defined by measurements in the IBS group, a positive test was specific for an organic cause of chronic diarrhea. Even so, the sensitivity of the test was relatively low: CD, 53%; IR, 23%; IBW, 14%; and BOS, 10%. We believe that the 24-h 14C-glycocholic breath test combined with the measurement of stool bile acids represents a screening test of only limited use for the identification of organic causes of chronic diarrhea.

Bile Acids and Salts↗