The effects of a companion animal on distress in children undergoing dental procedures.

The purpose of our pilot study was to evaluate the effects of a companion animal (dog) on physiologic arousal and behavioral distress among children undergoing a dental procedure. A repeated measures experimental design was used to study 40 children between the ages of 7 and 11 years who were undergoing procedures in a pediatric dental clinic. Half the children had the dog present during the procedure and half did not. Data were obtained before, during, and after the procedure. Behavioral distress was measured using the Observational Scale of Behavioral Distress; procedures were videotaped. Physiologic arousal was measured using a YSI telethermometer taped to the child's index finger. Student's t-test and repeated measures analysis of variance were used to answer the research question. No significant differences in behavioral distress or physiologic arousal were found between experimental and control groups. Further analysis revealed that for children who initially verbalized distress on arrival at the clinic, the presence of the dog decreased physiologic arousal during the time the child was on the dental table waiting for the dentist to arrive. Further research should be conducted to verify the effect of a companion animal on initial stress experienced by children for whom the visit to the dentist is most stressful.

Amino acid administration enhances renal protein metabolism after acute tubular necrosis.

The capacity of exogenous amino acids to alter renal protein metabolism was studied during renal regeneration after mercuric chloride-induced acute tubular necrosis in the rat. In regenerating cortical tissue, the free leucine concentration was 17% lower than normal, and was decreased further after glucose infusion. The concentration was raised above normal by amino acid infusion thereby ameliorating the deficit of this amino acid. Synthesis and degradation of rapidly-turning over proteins in renal cortical cells was examined in vitro. Renal protein synthesis in cortical slices was assessed by measurements of tissue leucine specific radioactivity and cycloheximide-inhibitable [14C]leucine incorporation into protein. Protein synthesis in regenerating tissue was 52% higher than normal and was not increased further by glucose infusion. In contrast, amino acid infusion increased the rate 47% above that observed after an isocaloric glucose infusion, thereby demonstrating that amino acid enhancement of protein synthesis is superimposed upon the increased synthetic rate observed during renal regeneration. Renal protein degradation remained at the normal rate after amino acid infusion, but was increased in regenerating tissue and after glucose infusion. These results indicate that infused amino acids act on the kidney to enhance protein synthesis and reduce protein degradation in regenerating renal cells after acute tubular necrosis.

Amino acid modulation of renal phosphatidylcholine biosynthesis in the rat.

The hypothesis that amino acids act as modifiers of phospholipid biosynthesis was tested in renal cortical cells from normal rats. The rate of [14C]-choline incorporation into phospholipid in cortical slices was enhanced by the addition of lysine or arginine to the incubation medium, and reduced by phenylalanine, aspartic acid, or four other amino acids. Lysine and aspartic acid appeared to modify the cholinephosphotransferase reaction in which cytidine 5'-diphosphocholine (CDP-choline) and 1,2-diacylglycerol react to form phosphatidylcholine, the major phospholipid of renal membranes. Since this enzymatic reaction takes place in the endoplasmic reticulum, the effect of single amino acids on microsomal preparations was examined. Lysine increased CDP-choline:1,2-diacylglycerol cholinephosphotransferase activity by 95%, whereas aspartic acid reduced activity by 65%, in a concentration-dependent manner. For both substrates in the reaction, amino acids modulated enzyme activity by altering the maximum velocity without changing the apparent Km. These observations in intact renal cells and in microsomal preparations indicate that changes in cellular amino acid concentrations could modify the biosynthetic rate of phosphatidylcholine, and suggest a mechanism that could coordinate the biosynthesis of phospholipid and protein.

Amino acid-mediated stimulation of renal phospholipid biosynthesis after acute tubular necrosis.

The mechanism by which amino acid infusion stimulates membrane physpholipid biosynthesis during renal regeneration after mercuric-chloride-induced acute tubular necrosis was studied in the rat. Amino acids can act directly on regenerating renal tissue to enhance net phospholipid synthesis because preincubation of cortical slices with amino acids induced an increase in [14C]-choline incorporation into phospholipid without altering the rate of breakdown. This amino acid stimulation of phospholipid biosynthesis was studied further by measuring [14C]-choline accumulation and its sequential conversion to phosphorylcholine, cytidine diphosphocholine (CDP-choline), and phosphatidylcholine via the Kennedy pathway in regenerating renal tissue. [14C]-Choline accumulation was increased after amino acid infusion, compared to glucose infusion. There were also increments in the Vmax of the choline kinase reaction, which converts entering [14C]-choline into [14C]-phosphorylcholine, and of the cholinephosphotransferase reaction in which [14C]-CDP-choline is incorporated into [14C]-phosphatidylcholine, whereas the apparent Km of each reaction was unchanged. Thus, amino acids infused after tubular necrosis can act directly on regenerating renal cells to increase precursor availability and augment two reactions of the phospholipid biosynthetic pathway.

Stimulation of renal phospholipid formation during potassium depletion.

Potassium depletion induces increased membrane phospholipid formation and renal growth in rats. To determine the mechanism by which potassium depletion augments phospholipid formation, the metabolism of radioactive choline, a precursor of choline-containing phospholipids, was studied in renal slices. Cortical and medullary tissue from potassium-depleted and control animals accumulated extracellular choline and sequentially converted it to phosphorylcholine, cytidine diphosphocholine (CDP-choline), and choline phosphoglyceride, thereby demonstrating that renal cells can utilize the Kennedy pathway for phospholipid synthesis. [14C]Choline uptake into intracellular fluid was increased in cortical slices from potassium-depleted animals. The apparent Km and Vmax of the kinase reaction which converts entering [14C]choline to [14C]phosphorylcholine were unchanged during potassium depletion. The rate of [14C]phosphorylcholine conversion to [14C]CDP-choline was also unchanged. In contrast, the Vmax of [14C]choline phosphoglyceride formation from [14C]CDP-choline was increased, whereas the apparent Km for this reaction was unchanged. These results indicate that increased renal choline phosphoglyceride formation during potassium depletion can occur via the Kennedy pathway and appears to be mediated by increases in choline uptake and the rate of CDP-choline incorporation into phospholipid, the first and last steps of the pathway.

Phospholipid metabolism during renal regeneration after acute tubular necrosis.

Renal function, structure, and membrane metabolism were studied during regeneration of proximal tubular cells in rats. A reversible syndrome of nonoliguric acute renal failure was induced by the intravenous administration of a low dose of mercuric chloride (1.0 mg Hg/kg). At day 1 there was a marked increase in serum urea nitrogen concentration (SUN), decrease in food intake, and a zone of proximal tubular cell necrosis in the inner cortex. By day 3 low cuboidal epithelial cells were seen, indicating that regeneration had been initiated despite decreased food intake and increasing SUN. Phospholipid synthesis for new membrane formation in regenerating cells was studied by using [14C] choline as a precursor of phosphorylcholine and cytidine diphosphocholine (CDP-choline), which are intermediates in the synthesis of renal choline-containing phospholipid. The rate of [14C]choline incorporation into phospholipids in inner cortical slices was lowest 1 day after mercury administration, then increased constantly for the next 4 days to reach a maximal value 104% above control. The rate declined slowly for the next 11 days and returned to normal by 28 days. The increased rate represented choline phosphoglyceride synthesis, since degradation was unchanged. The entire increment in choline radioactivity in regenerating tissue 2 and 3 days after mercury administration was in phospholipid or CDP-choline, which suggests that the increased number of choline molecules entering the growing cells were trapped in these two forms. The results indicate that renal regeneration is associated with a specific enhancement of the synthesis of choline-containing phospholipids. This anabolic response of the kidney occurs in the presence of systemic catabolism and progressive renal functional insufficiency.