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Biomedical subjects

T A Davis

Publications and source records attributed to T A Davis.

118 records · Page 7Linked to original sources
PubMed1985

Muscle protein turnover: effects of exercise training and renal insufficiency.

Chronic renal failure is associated with an enhanced catabolism of muscle protein. To determine the effect of exercise training and moderate renal insufficiency on net protein catabolism and protein synthesis in isolated epitrochlearis muscles, three-fourth nephrectomized and control rats were exercise trained or remained sedentary. Net muscle protein degradation was determined by measuring the rates of release of phenylalanine and tyrosine. Protein synthesis was determined by measuring the incorporation of [U-14C]phenylalanine into muscle protein. Exercise training reduced the elevated protein degradation of uremia to control levels. In control rats, exercise training had no effect on protein degradation. Exercise training increased alanine release in control rats but did not further increase the elevated alanine release of uremia. Protein synthesis was unaffected by both uremia and exercise training. Exercise training in control and uremic rats moderately increased the responsiveness of muscle to insulin by reducing net protein degradation but did not further enhance the insulin-stimulated increase in protein synthesis. Thus exercise training ameliorates the enhanced muscle protein degradation of moderate renal insufficiency.

Alanine↗
PubMed1985

Weight loss improves lipoprotein lipid profiles in patients with hypercholesterolemia.

Risk for coronary artery disease is directly related to plasma levels of total and low-density lipoprotein (LDL) cholesterol and inversely related to high-density lipoprotein (HDL) cholesterol concentrations. Weight gain in four of five patients with hypercholesterolemia given colestipol for 37 +/- 6 months was associated with a decrease in HDL cholesterol levels and an increase in LDL cholesterol/HDL cholesterol ratios. Weight loss (-7 +/- 2 kg) in these five and two other patients given colestipol increased plasma HDL cholesterol (17% +/- 6%) and lowered total cholesterol (-8% +/- 1%), LDL cholesterol (-13% +/- 2%), and total triglyceride (-20% +/- 4%) concentrations. However, in six patients given treatment by diet alone (no colestipol), comparable weight loss (-6 +/- 1 kg) did not alter plasma HDL cholesterol or total triglyceride concentrations, but reduced total cholesterol (-9% +/- 3%) and LDL cholesterol (-11% +/- 3%) levels. These results suggest that weight reduction increases plasma HDL cholesterol levels only in those patients with hypercholesterolemia given colestipol but not in those given treatment by diet alone. Nevertheless, the effects of weight loss on plasma total cholesterol and LDL cholesterol levels were comparable in the two groups of patients. This indicates that weight loss is an important adjunct in the treatment of moderately obese patients with hypercholesterolemia and may reduce their risk for coronary artery disease by improving their lipid profiles.

Adult↗
PubMed1984

Artificial red cells with crosslinked hemoglobin membranes.

Artificial cells containing concentrated hemoglobin (Hb) solution were prepared by interfacial polymerization of Hb with glutaraldehyde (GA) in liquid membrane capsules (LMC). A solution containing 30% of Hb was emulsified in mineral oil as red cell-size microdroplets, and this emulsion was dispersed in an aqueous phase containing glutaraldehyde to form LMC. The LMC were semipermeable templates that held the microdroplets of Hb in suspension while GA diffused through the oil to the microdroplet surfaces. The GA crosslinked Hb at the surface of each microdroplet to form an artificial red-cell membrane encapsulating Hb solution. A water-soluble surfactant was used to eject the cells from the LMC and suspend them in saline. Several surfactants were evaluated. Cell size was controlled by agitation speed during preparation of the original emulsion. Cells of 2.52 = +/- 1.69 micron were prepared. The encapsulated Hb retained capacity to bind and release O2. The cells had a P50 of 8.9 torr (1200 Pa) and a capacity of 0.55 cc O2/g of total Hb, indicating that the crosslinked portion of the Hb did not contribute to O2 transport.

Blood Substitutes↗
PubMed1983

Differential effects of dietary caloric and protein restriction in the aging rat.

Numerous studies have shown caloric restriction retards the physiological decline and increases the life span of animals. However, in these studies protein consumption was also reduced; thus, whether the beneficial effects were due to caloric or to protein restriction is unclear. To examine independently the effects of caloric and protein restriction on growth, renal function, and survival, caloric restricted male rats were fed 18, 30 or 42 percent casein diets that provided two-thirds of the quantity of diet consumed by groups fed 12, 20, or 28 percent casein diets ad libitum, respectively. Hence, caloric restricted groups consumed the same amount of protein as their paired ad libitum fed groups but one-third fewer calories. The results showed that caloric restriction decreased mature body weight, increased the rate of attaining mature body weight, retarded the age-associated decline in renal function, and increased survival. Protein restriction had no effect on mature body weight, decreased maturation rate, improved renal function, and decreased survival. Thus, protein restriction did not contribute to the survival-promoting effects of caloric restriction in rats.

Aging↗
PubMed1983

Effects of exercise training on muscle protein catabolism in uremia.

The effects of exercise training on muscle protein catabolism in uremia were studied in female rats. Rats made uremic by 3/4 nephrectomy were compared with sham-operated control female rats under conditions of exercise training by swimming or no exercise. The release of amino acids from epitrochlearis muscle in vitro was measured. Body weight epitrochlearis muscle weight, and epitrochlearis protein content were similar among groups. Uremia increased the release of phenylalanine and tyrosine 33% and alanine 50% from muscle of sedentary rats. Citrate synthase activity and glycogen content of muscle were increased twofold by exercise in both controls and uremics. Exercise increased the release of alanine (60%), glutamine (50%), and pyruvate (30%) from muscles of control rats, but it decreased to control levels the release of phenylalanine and tyrosine in uremic rats. Alanine release remained elevated. To determine if exercise training increases in vitro muscle sensitivity to insulin, we incubated muscle with and without 0.01 U/ml of insulin. Phenylalanine and tyrosine release was reduced minimally by insulin in both sedentary uremic and control groups. Glucose uptake was enhanced by 55% in both groups. But in the exercised uremic and control groups, insulin reduced phenylalanine and tyrosine release by 50% and increased glucose uptake by 75%. These results suggest that exercise training reduces muscle protein catabolism in uremia; and this reduction is associated with enhanced muscle response to pharmacologic doses of insulin in control and uremic rats.

Amino Acids↗
PubMedDate not supplied

Orally administered IL-6 induces elevated intestinal GM-CSF gene expression and splenic CFU-GM.

Orally administered interleukin (IL)-6 has been shown to be of benefit in eliminating Campylobacter infection and in preventing sepsis following hemorrhage. In related experiments, it was seen that proliferating cells were found in the spleens of untreated mice given IL-6 by oral gavage. Injection of the DNA label, BrdU, showed that significant proliferation began at 4 h and peaked at 24 h in the splenic red pulp of animals given oral IL-6. Mice given saline showed no increase in splenic BrdU uptake. Histological analysis suggested a hematopoietic lineage for these cells. Clonogenic assays performed on spleen cells taken from mice given oral IL-6 revealed that increased granulocyte-macrophage colony forming units (GM-CFU) were present at 24 h post-IL-6 administration. No increase in GM colonies occurred in mice fed IL-3, granulocyte-colony stimulating factor (G-CSF) or granulocyte-macrophage (GM)-CSF. RT-PCR analysis of intestinal mRNA from treated mice revealed that GM-CSF mRNA was elevated at 4 h after oral IL-6 administration, but not in mice fed other cytokines. It is suggested that oral administration of IL-6 induces both proliferation and a brief elevation of GM-CFU in the hematopoietic spleens of mice. This increase appears to be the result of increased GM-CSF mRNA production in the intestines of mice fed IL-6.

Administration, Oral↗