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Biomedical subjects

A Maiz

Publications and source records attributed to A Maiz.

At least 37 records · Page 2Linked to original sources
PubMed1986

Complications associated with the overfeeding of infected animals.

The effect of overfeeding on survival from peritoneal infection as well as changes in protein metabolism was evaluated. Rats were randomly divided into two groups and given for 6 days different quantities of a liquid diet containing 18% of the energy supplied as protein and 82% as carbohydrate and lipid via an implanted gastric tube. The control group received 301 +/- 4 kcal/kg/day which was equivalent to their mean voluntary intake and the overfeeding group received 528 +/- 8 kcal/kg/day (P less than 0.001). Following 6 days of enteral feeding, all rats received a jugular vein cannulation and cecal ligation with enterotomies. The overfeeding group showed a significantly (P less than 0.05) higher mortality rate to experimental peritonitis, a 24% lower leucine incorporation into whole body protein (P less than 0.05), and a 28% lower fractional synthetic rate of serum albumin (P less than 0.05). Although overfeeding in the rat increased body weight gain and was associated with significantly (P less than 0.001) greater nitrogen balance before infection, it can be concluded that such diets increase mortality to peritonitis and reduce whole body protein and serum albumin synthesis in response to such infections.

Animals↗
PubMed1986

Effect of DL-3-hydroxybutyrate infusions on leucine and glucose kinetics in burned rats receiving TPN.

Whole-body leucine and plasma glucose kinetics were simultaneously measured in burned rats after 2 d of total parenteral nutrition (TPN) containing sodium DL-3-hydroxybutyrate or sodium acetate to evaluate the ketone bodies as energy substrates during stress. TPN solutions consisted of dextrose and amino acids [200 kcal/(kg . d); 13 g amino acids/(kg . d)] and contained 34.3 mEq/(kg . d) either as sodium DL-3-hydroxybutyrate (n = 8) or sodium acetate (n = 7). Whole-body leucine appearance, incorporation into protein, release from protein breakdown and oxidation rates, as measured after a constant infusion of L-[1-14C]leucine did not significantly differ between the groups. In contrast, D-[6-3H]glucose appearance rates after constant infusion of this tracer were significantly higher in rats given sodium DL-3-hydroxybutyrate [209.3 +/- 3.8 mumol/(kg body weight . min)] than in those given sodium acetate [162.4 +/- 9.7 mumol/(kg body weight . min)] (P less than 0.01). Since leucine kinetics did not differ, the results suggest that sodium DL-3-hydroxybutyrate infusions increase endogenous glucose production [61.0 +/- 4.6 mumol/(100 kg body weight . min)] by enhancing glucose recycling. However, there was no unique protein-sparing effect of ketone bodies identified during injury.

3-Hydroxybutyric Acid↗
PubMed1985

Monoacetoacetin and protein metabolism during parenteral nutrition in burned rats.

The effect of intravenous infusion of monoacetoacetin (glycerol monoacetoacetate) as a non-protein energy source was evaluated in burned rats. During 3 days of parenteral nutrition, in which animals received 14 g of amino acids/kg body wt. per day exclusively (group I) or with the addition of isoenergetic amounts (523 kJ/kg per day) of dextrose (group II), a 1:1 mixture of dextrose and monoacetoacetin (group III) or monoacetoacetin (group IV), significant decreases in urinary nitrogen excretion and whole-body leucine oxidation were observed in the three groups given additional non-protein energy as compared with group I. Serum ketone bodies (acetoacetate and 3-hydroxybutyrate) were decreased in rats given dextrose, whereas glucose and insulin increased significantly. Monoacetoacetin-infused animals (group IV) had high concentrations of ketone bodies without changes in glucose and insulin, whereas animals infused with both monoacetoacetin and glucose (group III) showed intermediate values. On day 4 of nutritional support, whole-body L-leucine kinetics were measured by using a constant infusion of L-[1-14C]leucine. In comparison with group I, the addition of dextrose or monoacetoacetin produced a significant decrease in plasma leucine appearance and release from whole-body protein breakdown. Gastrocnemius-muscle protein-synthesis rates were also higher in the three groups receiving additional non-protein energy. These findings suggest that monoacetoacetin can effectively replace dextrose as an intravenous energy source in stressed rats. Both fuels are similar in decreasing weight loss, nitrogen excretion, leucine release from whole-body protein breakdown and oxidation, in spite of differences in energy substrate and insulin concentrations.

Acetoacetates↗
PubMed1984

Protein metabolism during total parenteral nutrition (TPN) in injured rats using medium-chain triglycerides.

There are metabolic limitations to the infusion of large quantities of dextrose in critically ill patients receiving total parenteral nutrition. Of the alternative, nonprotein lipid sources, medium chain triglycerides (carbon chain length 8 and 10) are more rapidly oxidized and are deposited in the adipose tissue at rates much less than long chain triglycerides. In rats with burn injury receiving hypocaloric (dextrose and amino acids) parenteral feeding, we studied the changes in protein metabolism as a result of increasing the caloric intake by 33% by the addition of either dextrose, a soybean oil emulsion, a medium chain triglyceride emulsion, or a structured lipid emulsion of triglycerides synthesized from safflower oil (40%) and medium chain triglycerides (60%). Changes in body weight, blood glucose concentration, beta-hydroxybutyrate, lactate, amino acids, insulin, albumin, liver protein content, and nitrogen balance were measured during three days of feeding. Whole body leucine kinetics and muscle protein fractional synthetic rate were evaluated using a constant intravenous infusion of L-[1-14C]leucine. The addition of dextrose or soybean oil emulsion produced a significant increase in body weight and liver nitrogen but did not change albumin concentrations or leucine kinetics compared to those of the hypocaloric feeding group. Rats receiving medium chain triglycerides and structured lipid emulsions showed a reduction in branched chain amino acid concentrations and an improvement in serum albumin levels. However, the rats receiving the structured lipid emulsion also showed increased body weight, had a significant decrease in leucine oxidation, and showed a three day cumulative nitrogen balance significantly greater than zero.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Structured medium-chain and long-chain triglyceride emulsions are superior to physical mixtures in sparing body protein in the burned rat.

The present study was undertaken to compare the effectiveness of a physical mixture of long-chain and medium-chain triglycerides with an emulsion consisting of chemically synthesized triglycerides composed of medium-chain and long-chain fatty acids in similar proportions. Sprague-Dawley rats received a 25% body surface area full-thickness scald burn on the dorsum. For the next three days, all rats received 300 kcal/kg/day as 160 kcal/kg/day glucose, 50 kcal/kg/day amino acid, and an additional 90 kcal/kg/day lipid emulsion as either long-chain triglyceride, medium-chain triglyceride, a 1:1 physical mix of medium-chain and long-chain triglycerides or a chemically structured triglyceride made up of 60% medium-chain fatty acid and a 40% safflower oil. Rats receiving the chemically structured lipid emulsion showed the greatest gain in body weight, the greatest positive nitrogen balance, and the highest serum albumin concentration, outstripping rats receiving the long-chain triglyceride, medium-chain triglyceride, and even the physical mixture long-chain and medium-chain triglycerides (P less than 0.01). A 30% increase in oxygen consumption and 35% increase in energy expenditure in rats given the medium-chain triglyceride emulsion alone (P less than 0.01) was observed. This study confirms that the metabolism of chemically structured triglycerides composed of medium-chain and long-chain fatty acids markedly differs from similar physical mixtures. For these reasons, the new structured lipid emulsions may prove advantageous in feeding the severely injured patient.

Amino Acids↗
PubMed1984

Protein dynamics during refeeding of protein-depleted rats: effects of increasing amino acid intake by TPN or enteral continuous feeding.

The effect of increasing nitrogen intake with constant calorie supply was studied in protein-depleted rats. Animals were randomized into three paired groups to receive either total parenteral nutrition (TPN) or enteral (EF) isocaloric feedings (240 kcal X kg-1 X day-1) differing only in their amount of amino acids. The diets, composed of dextrose, a safflower oil emulsion and crystalline amino acids, were infused continuously for 5 days. Daily nitrogen intakes were for controls (EF, n = 7; TPN, n = 6) 0.25 g/kg; for groups 1 (EF, n = 7; TPN, n = 8) 1.4 g/kg and for groups 2 (EF, n = 7; TPN, n = 7) 2.5 g/kg. The rats in groups 1 and 2 obtained significant protein repletion in terms of body weight, nitrogen retention, liver protein and serum albumin regardless of the route of nutrient delivery. However, rats in groups 2 (higher nitrogen intake) presented a more rapid and greater recovery despite a reduction in nitrogen utilization. Whole-body leucine kinetics studied at the end of controlled feeding periods were similar for EF and TPN rats. However, increasing nitrogen intake (1 and 2) increased whole-body leucine flux and incorporation into protein resulting in a better balance, since leucine release from protein breakdown was comparable to controls. Liver protein fractional synthetic rates were reduced in EF while remaining at a high rate in TPN group 2 and still more elevated in TPN group 1, suggesting a preferential support of liver protein by enteral feeding or the effect of TPN as a non-physiologic route.

Amino Acids↗