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Biomedical subjects

R E Tucker

Publications and source records attributed to R E Tucker.

At least 37 records · Page 2Linked to original sources
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↗
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↗
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↗
PubMed1979

Mammary transfer of vitamin E in cows treated with vitamin A or linoleic acid.

The effect of an intravenous injection of vitamin A alcohol and subcutaneous injections of linoleic acid on the mammary transfer of an intravenous injection of vitamin E acetate was studied with 15 Holstein cows. The cows received either an intravenous injection of 3 g vitamin E acetate (controls), intravenous injections of 3 g vitamin E acetate and 1 million IU vitamin A alcohol, or an intravenous injection of 3 g vitamin E acetate and subcutaneous injections totaling 40 g of linoleic acid. Milk samples were at 12-h intervals, two prior to and six following treatment. The main influence of vitamin A alcohol and linoleic acid on mammary transfer of vitamin E was to delay secretion of vitamin E in milk. However, total secretion of vitamin E was not reduced by injection of either vitamin A alcohol or linoleic acid. Vitamin E injection produced substantial increases in vitamin E in milk, but less than 1% of the dose could be accounted for in the milk.

Animals↗
PubMed1979

Bioassay of vitamin A in liquid supplements.

Vitamin A bioassay techniques based on liver storage in the chick were adapted for the assay of vitamin A in molasses based liquid supplements for cattle. Methods of administering the assayed supplement to the chicks were: 1) direct dosing of the supplement via four crop infusions at hourly intervals and 2) ether extraction, suspension in cottonseed oil with solvent removal in vacuo followed by direct crop dosing. The last method allowed a larger dosage with fewer analytical problems. Five sequential extractions were required for 97% recovery of the vitamin A from the molasses supplement. With the higher dosage range, the variance of response was a function of dose level. Transformation to a log dose - log response curve allowed a linear plot with homogeneity of variance. Detection of a 10% loss of vitamin A potency (P less than .10) was estimated to require 27 chicks per treatment by the slope ratio bioassay procedure.

Animal Feed↗
PubMed1976

Mammary transfer of vitamin A alcohol and ester in lactating dairy cows.

The effect of intravenous injection of vitamin A alcohol and vitamin A ester on the vitamin A concentration of bovine milk was studied. Holstein cows received either an intravenous injection of 1 million international units (IU) of vitamin A alcohol, 1 million international units of vitamin A palmitate, or served as controls. Blood serum and milk were sampled at intervals prior to and following injection. Mean concentrations of vitamin A in milk at time 0 were 59.0, 52.0, and 58.4 mug/100 ml for the control, alcohol, and palmitate treatments. Mean contrations of vitamin A in milk, expressed as mug/100 ml or mug/g fat of cows receiving vitamin A alcohol at +195, +451, and +678 min postinjection, were greater than concentrations for either control cows or cows receiving palmitate. Partition of milk Vitamin A at +195 min postinjection for cows injected with vitamin A alcohol showed 4.1% of the recovered vitamin A in the alcohol and 95.9% in the ester form. Injection of vitamin A palmitate had little effect on milk vitamin A concentration. Vitamin A in serum (mug/100 ml) at 195 min after vitamin A alcohol injection was higher (100.4) than for either control (84.0) or cows injected with vitamin A palmitate (89.0).

Animals↗