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Biomedical subjects

G E Mitchell

Publications and source records attributed to G E Mitchell.

At least 55 records · Page 3Linked to original sources
PubMed1985

The effect of dietary cholesterol, energy intake, and oxygen consumption on cholesterol metabolism in the chick.

This experiment, involving 320 chicks, was conducted to determine the effects of dietary cholesterol, restricted caloric intake, and genetic lines on cholesterol metabolism in the bird. The two lines of chicks studied had been divergently selected for oxygen consumption and had been shown to differ significantly (P less than .01) in weight gain and carcass lipid deposition. The dietary treatments, administered for a 2-week period, consisted of two levels of dietary cholesterol (none and supplemented) for each of two levels of energy (ad libitum and restricted). At the end of this 2-week period, the birds were injected intravenously with 1-14C-acetate and their livers removed 4 hr later. Hepatic cholesterol and lipid synthesis were measured by the uptake of acetate. Added dietary cholesterol significantly (P less than .01) decreased hepatic cholesterol synthesis, lipid synthesis, and specific activity of hepatic cholesterol but increased plasma and liver cholesterol. However, the elevation in plasma and liver cholesterol represented only .9 and 1.8% respectively, of the increase in total intake of dietary cholesterol. Metabolizable energy of diets fed ad libitum was also significantly (P less than .01) reduced with supplemented dietary cholesterol. A significant (P less than .01) difference in body weight was present between the two lines, with low oxygen consuming (LOC) birds exhibiting heavier body weights than high oxygen consuming (HOC) birds. A significant interaction between line and energy intake (P less than .05) was present for hepatic cholesterol levels; LOC birds exhibited higher levels of hepatic cholesterol than HOC birds when both groups were fed at restricted levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Acetate and propionate production in the cecum and proximal colon of lambs.

A modified single-injection isotope dilution technique measured acetate and propionate production rates in the cecum and proximal colon of 14 lambs fed a forage (hay) or high corn (concentrate) diet. The modified isotope dilution appeared to have merit. Volatile fatty acid pool sizes were stable and apparently absorption of fermentation products occurred to prevent end product inhibition. Propionate pool sizes were greater (P less than .01) while acetate pool sizes were not significantly greater when lambs received the concentrate diet. Apparent acetate production was higher (P less than .05) in lambs fed the concentrate diet than in forage-fed lambs (239.4 vs 189.5 mmol/d, respectively). Apparent propionate production was also greater (P less than .01) when lambs were fed the concentrate diet rather than the forage diet (431.4 vs 180.7 mmol/d, respectively). These results indicate that acetate and propionate produced in the cecum and proximal colon may be a considerable source of energy and glucose precursors for the growing lamb.

Acetates↗
PubMed1984

Essential fatty acid status and characteristics associated with colostrum-deprived gnotobiotic and conventional lambs. Growth, organ development, cell membrane integrity and factors associated with lower bowel function.

A factorial experiment involving gnotobiotic (GN) and conventional (CV) colostrum-deprived lambs and diets formulated to be adequate or deficient in linoleic acid was conducted to determine the effect(s) of the intestinal microflora on the essential fatty acid (EFA) status of the host and subsequent physiological consequences, i.e., growth, organ development, cell membrane integrity and lower bowel function. Lambs were obtained by sterile surgical procedures and housed in sterile isolators or in conventional metabolism stalls for 60 d. Skimmed cow's milk with 6% hydrogenated coconut oil and vitamins A, D and E added with and without .32% of the total calories as linoleic acid was homogenized, bottled and autoclaved, then fed to appetite three to four times daily. The GN lambs supplemented with linoleic acid gained significantly faster between 13 and 41 d of age and more efficiently between 27 and 41 d than the other treatment groups. The absence of dietary linoleic acid decreased liver and spleen weights and, in general, suppressed development of organs except the brain. Red blood cell hemolysis was not affected by treatment. Although showing signs of chronic mild diarrhea, the GN neonatal ruminant differed in Cl- concentration and dry matter percentage of its lower bowel contents from the "classic rodent model." The results indicate that neonatal colostrum-deprived lambs have an EFA requirement, as evidenced by decreased growth and performance characteristics in the GN linoleic deficient vs GN supplemented group, and suggests that the required level is in excess of .32% of the total caloric intake as linoleic acid.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Cholesterol metabolism in the laying hen as influenced by dietary cholesterol, caloric intake, and genotype.

Three trials, each with 24 hens, were conducted to determine the effects of dietary cholesterol, caloric intake, and genotype on the synthesis, storage, and excretion of cholesterol in the laying hen. The two genotypes of birds used in this experiment had been divergently selected for high and low oxygen consumption and had been shown to differ significantly (P less than .01) in body weight gain and carcass lipid deposition from 0 to 4 weeks of age. The dietary treatment, administered for a 2-week period to birds in each genotype, consisted of two levels of dietary cholesterol (0 and 1% added) and two energy intakes (ad libitum and 75% ad libitum). The experimental design was a 2 X 2 X 2 factorial. One percent added cholesterol versus none supplemented produced a significant (P less than .01) decrease in available metabolizable energy and uptake of acetate into liver cholesterol while causing significant (P less than .01) increases in egg and liver cholesterol but not in plasma cholesterol. Restricting caloric intake, as compared to ad libitum feeding, resulted in significantly (P less than .01) decreased egg production and total amount of cholesterol excreted via the egg with significantly (P less than .05) increased plasma and liver cholesterol levels but no change in egg cholesterol concentration. Differences were significant (P less than .05) between the two genotypes in feed intake and hepatic cholesterol and lipid synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Effect of dietary cholesterol and genotype on cholesterol metabolism in roosters.

An experiment, involving 32 roosters, was designed to study the interaction of dietary cholesterol and genotype on cholesterol metabolism in roosters. The two lines of birds used in this study had been divergently selected for high and low oxygen consumption and had been shown to differ significantly (P less than .01) in body weight gain and carcass lipid deposition from hatch to 4 weeks of age. The dietary treatments, administered for a 2-week period, were 0 and 1% dietary cholesterol added to a basal mash diet. Two separate trials were run, each with 16 roosters, resulting in four replicates of each treatment per line for each trial (block). After the trial period, the birds were injected with 1-(14)C-acetate and livers were removed; hepatic cholesterol synthesis was measured by the uptake of labeled acetate into liver digitonin precipitable sterols. Plasma and liver cholesterol levels were also measured. The data were analyzed as a randomized complete block design. Added dietary cholesterol significantly (P less than .01) increased both plasma and liver cholesterol levels over the control while significantly (P less than .01) decreasing the uptake of acetate into hepatic cholesterol in both lines by about 7-fold. Plasma cholesterol was significantly (P less than .05) greater in the high than low oxygen-consuming birds, and liver cholesterol was higher (P less than .10) in the low than high oxygen-consuming line.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1982

Plasma magnesium levels as influenced by cold exposure in fed or fasted sheep.

Eight ewes weighing about 52 kg were used in a 2 X 2 factorial arrangement of treatments replicated with temperature reversal to determine the effect of cold exposure on plasma Mg, Ca, free fatty acids (FFA), glucose and insulin concentrations and on renal clearance of Mg and Ca. Closely sheared ewes were fed a complete mixed diet at either 1.5% of body weight with no pretreatment fast or fed ad libitum followed by fasting 3 days before initiation of temperature treatments. Fasting superimposed on cold exposure reduced (P less than 0.01) plasma Mg at 1 hour after exposure to cold, and this effect continued during the cold treatment period, whereas Mg concentration was not significantly affected in fed sheep. Plasma FFA measured across temperature treatments was increased (P less than 0.01) by fasting. FFA measured across dietary treatments was only slightly increased by cold exposure. Plasma glucose levels of fasting sheep were lower (P less than 0.05) than those of fed sheep; however, levels rose (P less than 0.05) after exposure to cold. A tendency for plasma insulin to increase after cold stress was observed. Renal clearances of Mg and Ca were markedly reduced (P less than 0.01) by fasting, but clearance was not changed by cold stress. These results suggest that exposure to cold (2-5 degrees) and a deficient dietary intake synergistically reduce plasma Mg in sheep.

Animals↗
PubMed1982

Influence of bilateral nephrectomy on selected gastrointestinal bacteria in the rat.

A series of experiments was designed to investigate the influence of acute renal failure on selected gastrointestinal bacteria. Sprague-Dawley male rats were bilaterally nephrectomized to induce acute renal failure, with sham-operated animals serving as controls. After 48 h animals were sacrificed and the stomachs, upper and lower small intestines, ceca, and colons were excised and subjected to microbial analyses. Lactobacilli and streptococci including enterococci, were 1-2 log counts higher in the stomachs of anephric rats than those of sham-operated controls; lactobacilli were increased similarly in the upper small intestines of these animals. Coliforms including Escherichia coli, and Proteus were 1-2 log counts higher in the lower small intestine of anephric rats than those of sham-operated rats. The decreased gastric pH, increased cecal pH, hypothermia, and delayed gastric emptying observed in nephrectomized rats could partly explain the different microfloras in these animals.

Animals↗
PubMed1982

Carbohydrate fermentation in the large intestine of lambs.

In one of two experiments, six 4-mo-old wethers fitted with ileal and cecal cannulas were fed three levels of concentrate (0, 40 or 80% corn) with forage in a replicated 3 X 3 Latin square design. Chromic oxide was fed as a marker. Quantities of starch recovered at the ileum and digested in the large intestine increased (P less than .05) with increased starch intake. Quantities of acid detergent fiber (ADF) recovered at the ileum increased with increased ADF intake; however; ADF digestion (grams) in the large intestine was highest (P less than .05) when the 80% corn diet was fed. Cecal total VFA concentrations, butyrate molar proportions and lactic acid concentrations were highest (P less than .05), and cecal acetate to propionate (C2:C3) ratios and pH values were lowest, in lambs fed 80% corn. In Exp. 2, 14 wethers (4-mo-old) were fed a forage (alfalfa hay) or a concentrate (80% corn) diet containing chromic oxide as a marker. Digesta grab samples were obtained by surgical procedure. The amounts of starch recovered at the abomasum and ileum and the amounts digested in the rumen, small intestine and large intestine were greater (P less than .05) when lambs were fed the concentrate. Large intestinal total VFA concentrations and butyrate molar proportions were higher (P less than .01) when the concentrate diet was fed; pH values were lower (P less than .01). Lambs fed the concentrate diet had lower (P less than .01) large intestinal and ruminal C2:C3 ratios of VFA.

Abomasum↗
PubMed1982

Renal function and magnesium clearance in young and old cows given potassium chloride and sodium citrate.

Six young (3 yr old) and six old (8 to 11 yr old) cows were used to examine renal function, KCl and sodium citrate effects on Mg clearance rate and the relation of parathyroid hormone (PTH) to Mg reabsorption. The treatments were 1.5 g KCl/kg body weight (BW) and 1.5 g Na citrate/kg BW. Inulin and p-aminohippuric acid (PAH) clearance rates were used as measures of glomerular filtration rate (GFR) and effective renal plasma flow (ERPF), respectively, in control cows on each treatment day. Creatinine clearance rate was also used as a measure of GFR in all cows. Magnesium loading (2.4 mg/kg BW) through continuous intrajugular infusion of MgCl2 facilitated the measurement of changes in Mg clearance rate and reabsorption due to treatment. Inulin and creatinine clearance rates were not different as measures of GFR, and there were no differences in ERPF between young and old cows. Old cows had lower (P less than .05) GFR, creatinine to PAH clearance ratios and tubular reabsorption of Mg than young cows. Intraruminal infusion of KCl and Na citrate increased (P less than .05) the GFR. Potassium chloride increased plasma K concentration (P less than .001), plasma K clearance rate (P less than .002), plasma Na clearance rate (P less than .03), plasma Mg concentration (P less than .05), net tubular reabsorption of Mg (P less than .02), maximum tubular reabsorption of Mg (P less than .002) and plasma PTH concentration (P less than .03). Plasma Mg clearance rate was increased only by Na citrate (P less than .05). These results suggest a possible relationship between age, renal function, Mg antagonists and PTH in Mg homeostasis and in the etiology of hypomagnesemic tetany.

Animals↗
PubMed1982

Plasma glucose and insulin responses to propionate in preruminating calves.

Eighteen preruminating calves obtained at approximately 38 d of age were used to determine whether the ruminant insulin response to propionate is an inherent response or one that is acquired because of ruminal propionate production. A liquid milk replacer diet was fed alone or with isocaloric additions of propionate [50 mmol . (kg BW . 75-1 . d-1] or glucose. Both additions caused a strong insulin response, but the response by propionate-fed calves appeared to be independent of plasma glucose concentrations during the early post-feeding hours. After receiving the experimental diets for 18 d, all calves were given an iv infusion or propionate [.035 mmol propionate . (kg BW . 75-1 . min-1 for 20 min]. All calves demonstrated a plasma insulin rise and glucose decline due to the infusions, but glucose-fed and propionate-fed calves appeared less sensitive to the iv propionate than the calves fed only milk replacer.

Age Factors↗
PubMed1982

Reversible hepatotoxicity associated with hepatic vitamin A accumulation in a protein-deficient patient.

A 62-yr-old white male presented with edema, protein malnutrition, and abnormal liver function. He had ingested from 40,000-50,000 IU of vitamin A per day for 7 yr. Examination of liver tissue by light and electron microscopy revealed findings characteristic of an excessive accumulation of vitamin A. Liver tissue contained massive amounts of vitamin A (19,000 IU/g); however, both the serum concentration of vitamin A and retinol-binding protein were below normal, and serum RBP was not saturated. On a normal diet the patient was able to mobilize hepatic vitamin A, as indicated 71 days later by a repeat biopsy of the liver, which then contained 9000 IU of vitamin A/g. During this time his nutrition improved, serum vitamin A rose, and serum RBP became transiently saturated. The amount of vitamin A ingested by this patient was less than that usually producing recognizable hepatotoxicity, and he had no extra hepatic manifestations of vitamin toxicity, consistent with a low serum vitamin A concentration and a low vitamin A to retinol-binding protein ratio. At presentation he was apparently unable to normally mobilize vitamin A from his liver, which may have been due to an accompanying protein deficiency.

Biopsy↗
PubMed1981

Misleading density of mediastinal cysts on computerized tomography.

Five patients seen with roentgenographic evidence of smooth, rounded mediastinal masses were evaluated by computerized tomographic (CT) scanning. Density readings from the lesion were interpreted in all patients as being equivalent to solid tissue. With these findings, thoracotomy seemed necessary for definitive diagnosis. All 5 lesions were found to be thin-walled cystic structures containing thick viscid fluid. Contrary to views expressed in the radiology literature, we conclude that computerized tomography does not differentiate reliably between solid and cystic mediastinal masses.

Adolescent↗
PubMed1981

Plasma parathyroid hormone and insulin concentrations in cows administered potassium chloride and sodium citrate.

Two age group of nonpregnant cows were used to study plasma changes in parathyroid hormone, insulin, and glucose, and renal clearance rates of magnesium, calcium, and inorganic phosphorus after intraruminal administration of 1.5 g potassium chloride (KCl)/kg body weight (BW) or 1.5 g sodium citrate/kg BW. Magnesium (2.4 mg/kg BW) was simultaneously infused intravenously for 120 minutes to facilitate the measurement of changes in magnesium clearance rate and kidney tubular resorption due to the treatments. Elevated plasma concentrations of potassium from intraruminal infusion of KCl increased plasma parathyroid hormone, insulin glucose, and magnesium levels. Net tubular resorption of magnesium (TMg) was also increased after potassium dosing, and the old cows had lower TMg values compared with the young cows. Plasma magnesium and calcium clearance rates were increased only by citrate, while phosphorous was not influenced by either treatment. These results provide evidence for a relationship between potassium and the endocrine factors, parathyroid hormone, and insulin; citrate appears to antagonize tubular resorption of magnesium and calcium.

Animals↗
PubMed1981

Solitary hepatic cyst and benign bile duct polyp: a heretofore unheralded association.

Solitary hepatic cysts are uncommon lesions that can produce jaundice by extrinsic compression on the extrahepatic biliary tree. In two recent cases of solitary hepatic cyst with jaundice, an intraluminal polypoid adenoma that obstructed the common hepatic duct was discovered. Concurrence of these two unusual lesions suggests that they may be associated. The importance of recognizing this association is illustrated by two case reports. In case 1, extrinsic compression by the cyst on the common hepatic duct was identified as the cause of jaundice at the initial operation. In case 2, choledocholithiasis was the initial explanation for the jaundice. In both cases, palpation and exploration of the proximal bile ducts with probes and catheters failed to discover the polyp. However, jaundice persisted postoperatively in both cases, and subsequent contrast radiography revealed an intraluminal filling defect in the common hepatic duct. In both cases, reoperation was required, and a benign bile duct polyp was discovered and excised. Thus, the presence of jaundice in a patient with a cystic hepatic mass should suggest the possibility of a concurrent bile duct polyp. Awareness of this possibility should permit recognition of such a polyp at initial operation.

Adenoma↗