Daily metabolism and hepatic balance studies of plasma cortisol and aldosterone in the preruminant calf

Intestinal and hepatic catabolism of cortisol and aldosterone were studied in the calf using blood samples from the mesenteric artery and portal and hepatic veins collected over 24 h, the hepatic blood flow being continuously recorded during this period. The total hepatic blood flow remained broadly constant over the 24 h, although meals were followed by decreasing flow in the portal vein and by increasing flow in the hepatic artery. The intestinal tract catabolizes cortisol as intensively as the liver (both 13% of cortisol reaching the organ). The part played by the gut and the liver in the catabolism of aldosterone were also equivalent (both 30% of aldosterone reaching the organ). This 24-h study demonstrated that a constant ratio existed between secretion and catabolism of cortisol while the hepatic balance of aldosterone seemed to be modified during the night.     

Free amino acids in calf embryos

In this work have been reported the research results tending to establish the free amino acidis concentration, existing in the calf embryos. The free embryonal amino acidis composition has been determined through an analysis effected with "Amino Acid Analyzer". Such studies, which conern the researches under execution in our Institute on the chemical composition of the calf embryos furnish the biochemical determination of a biological material, used in some Nations like a commercial product.     

Transport of neutral amino acids by human erythrocytes

The transport of several neutral amino acids by human erythrocytes in vitro was studied. The measurements made included steady-state distributions, kinetics of initial rates of uptake, effects of monovalent cations and anions, general mutual inhibitory interactions, kinetics of inhibitions, effluxes, ability to produce accelerative exchange diffusion, and the inhibitory action of the thiol reagent N-ethylmaleimide. The results are interpreted as showing that the human erythrocyte membrane possesses several distinct transport systems for these amino acids, including one Na⁺-dependent system and one dependent on both Na⁺ and a suitable anion, that are qualitatively similar to those systems previously described in pigeon erythrocytes and mammalian reticulocytes. Quantitatively, however, the systems differ among the different kinds of red cell and a major difference lies in their abilities to produce accelerative exchange diffusion.     

Transitory postnatal hemolysis of calf red cells by amino acids

Summary Among the amino acids which can be solubilized to give a concentration of 300 mM at near physiological pH, histidine and proline caused a complete hemolysis of newborn calf but not of adult cow red cells within 20 to 30 minutes at 38°C. While hydroxyproline, valine, and serine resulted in a partial lysis of calf cells, threonine, glutamine, and glycine were inefective. In this communication, emphasis has been focused on the mode of the lytic process by histidine, which was found to be affected by several governing parameters including the pH, temperature and the extracellular salts in the solution. Unlike human red cells suspended in isotonic histidine, both calf and cow cells lost little Na and K ions. In the presence of 300 mM histidine, both calf and cow cells displayed an instantaneous uptake of histidine amounting to 20 to 45 moles/ml RBC followed by a slow influx rate of 0.25 to 0.5 moles/ml RBC×min. The extent to which histidine entry was allowed by the cell was counterbalanced by Cl^– efflux, resulting in little change in cell volume prior to hemolysis. Moreover, histidine-induced hemolysis can by prevented by 1 mM or lower PCMBS without at discernible effect on histidine influx suggesting a possible membrane lesion or damage at the outer surface of the cell.Hemolysis induced by histidine decreased substantially when a calf reached two months of age which time the red cells containing the fetal hemoglobin are virtually depleted. The results of hemoglobin electroiphoresis obtained during this postnatal period revealed that those cells resistant to histidine hemolysis almost invariably contain the adult type hemoglobin suggesting a selective, speicific action of the amin acid on the featal cells.A preliminary report of these data has been presented at the 19th Annual Meeting (1975) of the Biophysical Society, Philadelphia, Pennsylvania.     

Free amino acids in the blood plasma of lampreys, frogs and rats

Free amino acids in the blood plasma of lampreys, frogs and rats were determined by HPLC. In spite of quantitative differences in the total pool of free amino acids, the specific content of physiologically important amino acids is quite similar in representatives of different classes of vertebrates, from cyclostomes to mammals.     

Measurement of branched chain amino acids in blood plasma by high performance liquid chromatography

A simple and rapid high performance liquid chromatographic technique is described for the separation and quantitation of plasma branched chain amino acids. After addition of a norleucine internal standard, plasma samples are acidified with acetic acid, and amino acids are separated from proteins and other plasma components by passage of the acidified plasma through an ion exchange resin. The ammonium hydroxide eluate from the resin is dried, phenylisothiocyanate derivatives are prepared, and the amino acids are separated on a Waters reverse-phase "Pico-Tag" column with an ultraviolet detector set at 254 nm. In addition to the branched chain amino acids (leucine, valine, and isoleucine), aspartate, glutamate, serine, threonine, alanine, and methionine are quantitated with high precision and accuracy, as verified by quantitative recovery and comparison with an automatic amino acid analyzer. The advantages of the method are its simplicity, speed, stability of derivatives, high reproducibility, low per-sample cost, and the use of a simple fixed-wavelength ultraviolet detector.     

Oxidation of glutamine by the splanchnic bed in humans

[1,2-(13)C(2)]glutamine and [ring-(2)H(5)]phenylalanine were infused for 7 h into five postabsorptive healthy subjects on two occasions. On one occasion, the tracers were infused intravenously for 3.5 h and then by a nasogastric tube for 3.5 h. The order of infusion was reversed on the other occasion. From the plasma tracer enrichment measurements at plateau during the intravenous and nasogastric infusion periods, we determined that 27 +/- 2% of the enterally delivered phenylalanine and 64 +/- 2% of the glutamine were removed on the first pass by the splanchnic bed. Glutamine flux was 303 +/- 8 micromol. kg(-1). h(-1). Of the enterally delivered [(13)C]glutamine tracer, 73 +/- 2% was recovered as exhaled CO(2) compared with 58 +/- 1% of the intravenously infused tracer. The fraction of the enterally delivered tracer that was oxidized specifically on the first pass by the splanchnic bed was 53 +/- 2%, comprising 83% of the total tracer extracted. From the appearance of (13)C in plasma glucose, we estimated that 7 and 10% of the intravenously and nasogastrically infused glutamine tracers, respectively, were converted to glucose. The results for glutamine flux and first-pass extraction were similar to our previously reported values when a [2-(15)N]glutamine tracer [Matthews DE, Morano MA, and Campbell RG, Am J Physiol Endocrinol Metab 264: E848-E854, 1993] was used. The results of [(13)C]glutamine tracer disposal demonstrate that the major fate of enteral glutamine extraction is for oxidation and that only a minor portion is used for gluconeogenesis.     

Free amino acids in rat blood serum during A-hypovitaminosis]

A pool of free aminoacids of the blood serum has been studied in growing rats with a decreased retinol content in the liver tissue (to 5 g/g). The study shows a reliable drop in the concentrations of all essential aminoacids, except for phenylalanine. It is determined that the total amount of essential aminoacids decreases by 31%. At the same time concentrations of replaceable aminoacids increase, namely: glutamic acid and arginine--by 15.7%, ornithine and histidine--by 24%-45%, though proline concentration decreases abruptly by 31%. A disturbance in ultrastructural organization of microvilli in the apical membrane cells absorptive epithelium of the small intestine has been found. The results of the study confirm changes in a free aminoacid pool of the blood serum in growing rats and these changes occur first of all due to the disturbance of the absorption processes in the small intestine.     

Transport of amino acids to the maize root

When 5-mm maize root tips were excised and placed in an inorganic salts solution for 6 hours, there was a loss of alcohol-insoluble nitrogen. The levels of threonine, proline, valine, isoleucine, leucine, tyrosine, phenylalanine, and lysine in the alcohol soluble fraction were severely reduced, whereas those of glutamate, aspartate, ornithine, and alanine were scarcely affected. There was a 4-fold increase in the level of γ-aminobutyrate. Those amino acids whose synthesis appeared to be deficient in excised root tips also showed poor incorporation of acetate carbon. In addition, the results show that asparagine and the amino acids of the neutral and basic fraction were preferentially transported to the root tip region. The results therefore suggest that the synthesis of certain amino acids in the root tip region is restricted, and that this requirement for amino acids in the growing region could regulate the flow of amino acids to the root tip.     

Characterization and amino-terminal sequence of apolipoprotein AI from plasma high density lipoproteins in the preruminant calf, Bos spp

The major apolipoprotein of calf plasma high-density lipoproteins, apo-AI, has been isolated and characterized. Apolipoprotein AI (apo-AI) was separated from the protein moiety of high-density lipoproteins (d 1.090-1.180 g/ml) by preparative electrophoresis in SDS-polyacrylamide gels followed by electrophoretic elution. Purified calf apo-AI had an Mr of approx. 27,000-28,000 in SDS-polyacrylamide gels, resembling human apo-AI. The amino acid composition of calf apo-AI displayed an overall similarity to that of its human and other mammalian counterparts (baboon, dog, badger, rabbit, rat and mouse), but differed in having higher proportions of glutamic acid, alanine and isoleucine. Amino-terminal amino acid sequence analysis up to the 47th residue showed close homology between calf apo-AI and those of the mammals with which it was compared. However, residues 2, 7, 20 and 22 in calf AI (i.e. aspartic acid, serine, glutamic acid and isoleucine, respectively) were substituted by glutamic acid, proline or glutamine, aspartic acid, and valine or leucine respectively, in the other mammals.     

Transport of branched-chain amino acids in Corynebacterium glutamicum

The transport of branched-chain amino acids was characterized in intact cells of Corynebacterium glutamicum ATCC 13032. Uptake and accumulation of these amino acids occur via a common specific carrier with slightly different affiniteis for each substrate (K _m[Ile]=5.4 M, K _m[Leu]=9.0 M, K _m[Val]=9.5 M). The maximal uptake rates for all three substrates were very similar (0.94–1.30 nmol/mg dw · min). The optimum of amino acid uptake was at pH 8.5 and the activation energy was determined to be 80 kJ/mol. The transport activity showed a marked dependence on the presence of Na⁺ ions and on the membrane potential, but was independent of an existing proton gradient. It is concluded, that uptake of branched-chain amino acid transport proceeds via a secondary active Na⁺-coupled symport mechanism.Abbreviations CCCP Carboxyl cyanide m-chlorophenylhydrazone - dw dry weight - MES 2[N-morpholino]ethanesulfonic acid - mon monensin - nig nigericin - TPP tetraphenylphosphonium bromide - Tris tris[hydroxymethyl]aminomethane - val valinomycin     

Transport of basic amino acids in Candida albicans

In Candida albicans, ATCC 46977, transport of basic amino acids is mediated by two systems (S1 and S2). Kinetic data and competitive inhibition studies of the different systems showed that transport of L-lysine, L-arginine and L-histidine have distinct specificities. System S1 of L-lysine and L-arginine was highly specific for the respective single basic amino acid. However, S2 of L-lysine and S1 of L-histidine were shown to be specific systems for most of basic amino acids. S2 of L-arginine was different from S2 of L-lysine and S1 of L-histidine. The effect of a thiol reagent, N-ethylmalemide, revealed that S2 of L-lysine and S1 of L-histidine were sensitive to this reagent, while all other systems were insensitive. The transport activity of different systems of L-lysine, L-arginine and L-histidine was followed during the growth of C. albicans. It was observed that different basic amino-acid systems have maximum activity during different stages of C. albicans growth.