Differential solubility of racemic mixtures of amino acids.
Explore the source record for details and available documents.
SEARCH · PubMed Health
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
The administration of branched-chain amino acids (BCAAs) has been proved useful in reducing both urea nitrogen production and muscle proteolysis in trauma patients with sepsis, but the optimum infusion rate to achieve these effects is still in question. In this prospective randomized study, a group of 16 posttrauma patients with sepsis received a branched chain-enriched (BCAA = 49.4%) amino acid mixture (8 patients; 120 observations) or a standard amino acid infusion (BCAAs = 15.5%; 8 patients; 227 observations). Total calories, percent lipid calories, and amino acid nitrogen administration were not different in the two groups. Each patient was studied at 8-hour intervals for the plasma levels of amino acids, six hepatic acute-phase proteins, albumin, and other metabolic parameters, including urinary urea nitrogen and 3-methylhistidine excretion. The total intake of each amino acid and its clearance were calculated and the dose of leucine during each 8-hour period was related to the leucine clearance, plasma acute-phase protein levels, and the urinary production of urea and 3-methylhistidine, as an indicator of proteolysis. The results show a significant (r2 = 0.691; p less than 0.0001) reduction of urea nitrogen production and proteolysis as a function of the increase in leucine dose. The identification of a critical mean rate of leucine infusion has been derived from the analysis of the significant linear correlation between leucine intake and leucine clearance (r2 = 0.594; p less than 0.0001). Significant positive correlations between the leucine intake dose and the platelet count (r2 = 0.402; p less than 0.0001), the plasma fibrinogen level (r2 = 0.218; p less than 0.0001), and the regression-derived sum of six acute-phase proteins plus albumin (r2 = 0.696; p less than 0.0001) were found. The increase in leucine clearance was progressively less marked above a mean daily leucine intake rate of 1.4 mumol/kg/min, which also appeared to be the dose level that maximized the acute-phase protein and coagulation effects and reduced proteolysis and urea nitrogen production, suggesting that this is a critical BCAA infusion rate at which an optimum leucine effect occurs. From these data a BCAA (leucine) dose nomogram has been derived.
The pathogenesis of the hepatic encephalopathy (HE) in spite of substantial progresses in this field still rests unclear. Actually four main hypotheses of the pathogenesis are discussed: the ammonia-hypothesis, the synergism-hypothesis, the hypothesis of the false neurotransmitters and that one of the changes of the normal neurotransmitters and their receptors. A connecting function seems to come up to ammonia. --Reduction of oral protein intake, selection of certain proteins, oral administration of nonabsorbable antibiotics and enemas should be used in order to prevent the intestinal absorption of toxic metabolic products. The parenteral nutrition has the therapy of HE substantially improved. Primarily, the patients receive special amino acid mixtures with a high content of branched chain amino acids and a low content of aromatic acids. The exchange of carbohydrate to some extent through fat improves the parenteral nutrition regime for these patients. The different liver support systems have failed to improve the prognosis of fulminant hepatic failure.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Hepatic encephalopathy may complicate chronic liver diseases and portosystemic shunting. Recently it has been suggested that a change in the blood amino acid pattern (with elevated phenylalanine, tyrosine, methionine and depressed branched chain amino acids) and increased levels of octopamine and phenylethanolamine (a false neurotransmitter) are related causally to neurological symptoms. Previous works have suggested that an amino acid mixture of special formulation (enriched in branched chain amino acids and poor in aromatic amino acids) can normalize the plasma amino acid levels and consequently improve the neurological state. In order to test the actual therapeutic effect of these specially formulated solutions, the following therapeutic protocols were administered to 3 groups of cirrhotic patients: group 1 (15 cases): lactulose; group 2 (8 cases): special amino acid solutions; group 3 (8 cases): special amino acid solutions and lactulose. Clinical, laboratory and EEG examinations in a preliminary experiment, before and after treatment, showed that the best effect was obtained by the combined treatment with amino acid solutions and lactulose.
A method for the chiral separation of dansyl-DL-amino acid mixtures using a dextran (M(r) 2,000,000) polymer network containing beta-cyclodextrin (beta-CD) in HPCE was developed. Mixtures of up to seven amino acids could be baseline resolved by this method under neutral pH conditions. Resolution was dependent on the dextran concentration in the polymer network. Temperature effects on the chiral separation were studied. Optimal efficiency and resolution of DL-enantiomeric pairs of amino acid samples were obtained at 25 degrees C. The resolution of different amino acids used in this work decreased with an increase in temperature.
The use of pure protein mono- and polymers for human nutrition was studied in a 45-day experiment in which 12 test subjects took part. The first group of 6 persons were given casein (14.8 g nitrogen per day) and the second group--an equivalent mixture made of crystalline L-amino acids. The first group showed no abnormalities in the physiological and biochemical functions. The second group exhibited marked changes in the body: weight losses, negative nitrogen balance, increase of the ammonia concentration in the urine and exhaled air. It appears that amino acid mixtures can be included into the human nutrition only after extensive studies.