During natural metamorphosis, concomitant, linear increases were found in tadpole liver for the activities of the five enzymes in the ornithine-urea cycle: carbamyl phosphate synthetase I, omithine transcarbamylase, argininosuccinate synthetase, argininosuccinate lyase, and arginase. Upon immersion in 2.6 X 10M8 M L-thyroxine for two weeks, the biochemical changes which occur during natural met...

1. Carbamoyl phosphate synthetase, ornithine transcarbamoylase, the arginine-synthetase system and arginase were measured in the livers of ammoniotelic, ureotelic and uricotelic animals. The chelonian reptiles, whose nitrogen excretory patterns vary according to the habitat, and the Mexican axolotl, a neotenic species, were also studied. 2. The levels of the activities of the first three enzyme...

Most conditions detected by expanded newborn screening result from deficiency of one of the enzymes that degrade acyl-coenzyme A (CoA) esters in mitochondria. The role of acyl-CoAs in the pathophysiology of these disorders is poorly understood, in part because CoA esters are intracellular and samples are not generally available from human patients. We created a mouse model of one such condition...

Urea cycle defects (UCDs) typically present with hyperammonemia, the duration and peak levels of which are directly related to the neurologic outcome. Liver transplantation can cure the underlying defect for some conditions, but the preexisting neurologic status is a major factor in the final outcome. Multicenter data indicate that most of the children who receive transplants remain significant...

Collagen-binding activity (CBA) and FRETS-VWF73 assays are widely adopted methods for the measurement of the plasmatic activity of ADAMTS13, the von Willebrand factor (VWF) cleaving-protease. Accurately assessing the severe deficiency of ADAMTS13 is important in the management of thrombotic thrombocytopenic purpura (TTP). However, non-concordant results between the two assays have been reported...

The present study investigated the role of ammonia as a trigger for hatching, mechanisms of ammonia detoxification and the localization of urea cycle enzymes in the early life stages of freshwater rainbow trout (Oncorhynchus mykiss). The key urea cycle enzyme carbamoyl phosphate synthetase III was found exclusively in the embryonic body (non-hepatic tissues); related enzymes were distributed be...

The effect of two levels of dietary protein energy, moderate (20%; MP) and high (70%; HP), on urea kinetics in eleven domestic cats was studied. After a 3-week prefeed, a single dose of [(15)N(15)N]urea was administered, and urine and faeces collected over the subsequent 5 d. For each 24 h period, total urea and enrichment of [(15)N(15)N]- and [(15)N(14)N]urea in urine were determined, and a mo...

The regulation of ornithine delta-aminotransferase (OAT) expression is poorly characterized in humans, but in rat there are tissue-specific responses to nutritional and hormonal stimuli. We analyzed 1.3 kilobases of 5'-flanking sequence and part of intron 1 of the human OAT gene and found several candidate regulatory sequences including four copies of a motif also present in the promoters of th...

A characteristic consequence of a biotin deficiency in animals is a decreased ability to fix C402 into various tissue components including the amino acid arginine (1). Carbon dioxide is incorporated into arginine as a result of the conversion of ornithine to citrulline in the Krebs-Henseleit urea cycle (2). The methods developed by Cohen and Hayano (3, 4) for the synthesis of citrulline from or...

We have shown that first-pass intestinal metabolism is necessary for approximately 50% of whole body arginine synthesis from its major precursor proline in neonatal piglets. Furthermore, the intestine is not the site of increased arginine synthesis observed during dietary arginine deficiency. Primed constant intravenous (iv) and intraportal (ip) infusions of L-[U-14C]proline, and iv infusion of...