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At least 919 records · Page 51Linked to original sources
PubMed2002

Plant nitrogen status rapidly alters amino acid metabolism and excretion in Bemisia tabaci.

The effect of plant nitrogen (N) status on the content and distribution of free amino acids in the bodies and honeydew of silverleaf whiteflies Bemisia tabaci (Gennadius) Biotype B (= B. argentifolii Bellows and Perring) was determined. Whiteflies fed for 4 days on cotton leaves that received high or low N fertility. For low-N plants, photosynthesis and leaf total N levels were decreased, and a much-reduced amount of free amino acids was recovered in phloem sap. Low N fertility did not affect whitefly total N content, but did markedly decrease the free amino acid content. Glutamine, alanine and proline accounted for over half of the insect free amino acid pool for both N treatments. On a relative basis, adjustments in glutamine levels in response to plant N status were much larger compared to the other amino acids. Large amounts of amino N, especially asparagine, were excreted from whiteflies fed on high-N plants whereas amino N excretion essentially ceased for whiteflies fed on low N plants. The distribution of amino acids in the insects and honeydew was not closely related to the phloem sap amino acids. However, total amino acid excretion was quite indicative of the plant N status and the quality of the insect diet. The results indicated that whitefly free amino acid pools and excretion of amino N were rapidly altered by plant N status.

Journal Article↗
PubMed2006

Physiological and molecular aspects of aspartate-derived amino acid metabolism during germination and post-germination growth in two maize genotypes differing in germination efficiency.

The Asp-derived amino acid pathway has been studied during the early stages of development in two maize genotypes, Io and F2, differing in germination efficiency and post-germination growth. In both genotypes expression of Ask2 (monofunctional Asp-kinase-2), Akh1 and Akh2 (bifunctional Asp-kinase-homo-Ser dehydrogenase-1 and 2), increased throughout germination and post-germination growth, suggesting a developmental regulation, whereas Ask1 (monofunctional Asp-kinase-1) was expressed constitutively. The major difference between Io and F2 concerned genes encoding bifunctional enzymes, particularly Akh2, the expression of which was dramatically low in F2. 15N-Asp labelling showed differences in in vivo Asp-kinase activities between the genotypes studied. Asp flux through the Met/Thr branches was higher in Io than in F2, while the latter exhibited a higher flux of Asp through the Lys branch. Physiological results, together with the higher Akh2 expression in Io, suggest that bifunctional enzyme activity, favourable to Met/Thr, was higher in Io than in F2 and that the monofunctional pathway was boosted in F2 because of the lower competition by the bifunctional pathway, thus allowing for higher flux of Asp through the Lys branch. In conclusion, it is suggested that F2 germination and post-germination growth might have been partially inhibited due to a limitation in Met and Thr availability. A negative physiological effect related to Lys accumulation in F2 is also discussed.

Amino Acids, Essential↗
PubMed1988

Protein and amino acid metabolism in patients undergoing continuous ambulatory peritoneal dialysis (CAPD).

Several factors contribute to impaired nutritional status in patients undergoing CAPD. The protein loss into the dialysate varies between 5-15 g per day; during peritonitis protein loss increases by 50-100%. The loss of free amino acids during CAPD is of the same magnitude as under hemodialysis. The observed plasma amino acid abnormalities in CAPD patients probably reflect metabolic derangements in uremia, rather than depletion due to dialysate amino acid loss. Sustained hyperinsulinemia in CAPD patients also may contribute to reduced plasma amino acid concentrations. A further factor contributing to nutritional problems in CAPD is a decreased protein intake. Dietary protein intake should exceed 1.2 g/kg/day during long-term CAPD treatment to maintain nitrogen equilibrium. Total energy intake may exceed 35 kcal/kg/day.

Amino Acids↗
PubMed1982

Sulfur amino acid metabolism in the developing rhesus monkey brain: interrelationship of taurine and glutamate.

The relationship of taurine to glutamate, and to other amino acids, has been examined in the occipital lobe of the developing rhesus monkey. During development taurine decreases in concentration (4.96 mumol/g in fetus to 1.52 mumol/g in adult) while glutamate increases (7.92 mumol/g in fetus to 11.26 mumol/g in adult). When the concentration of taurine is plotted against that of glutamate in fetal, neonatal and adult animals there is a significant correlation in the fetal (p less than 0.01) and adult (p less than 0.01) but not in the neonatal occipital lobe samples. This correlation in both fetal and adult brain is specific for these amino acids. Subcellular fractionation studies further indicate that this relationship may be of special importance in nerve endings.

Aging↗
PubMed1984

Peptide antibiotic K-582 production in relation to amino acid metabolism in Metarrhizium anisopliae.

Formation of the basic antibiotic, K-582 was stimulated by supplying Metarrhizium anisopliae U-47 with several amino acids present in its structure. The addition of L-arginine to the basal medium resulted in the almost exclusive formation of K-582 B, while L-lysine increased K-582 A formation. Some carbon sources were observed to have effects similar to those obtained with the above mentioned amino acids. Furthermore, when L-arginine was added in excess to the basal medium, free gamma-hydroxyarginine, which is a major constituent of the antibiotic, accumulated extra- and intra-cellularly. Free gamma-hydroxyarginine isolated from the culture broth of this microorganism was the threo-L-isomer. K-582 formation was repressed by glycerol, which exerted catabolite repression of gamma-hydroxyarginine synthesis.

Amino Acids↗
PubMedDate not supplied

[Effect of the composition of branched chain amino acids, taurine, and tryptophan on the amino acid metabolism in experimental models of alcoholism].

Ethanol withdrawal after forced alcoholization of rats according to Majchrowicz led to the development of amino acid imbalance in the pool of free amino acids in the liver (increasing levels of alanine, aspartate, glutamate, glutamine and histidine, decreasing levels of glycine, lysine, threonine and taurine) and blood plasma (increasing levels of tyrosine and alanine, decreasing levels of most glycogen aminoacids, branched-chain aminoacids and Lys). Less profound changes were observed after prolonged alcohol intoxication (decreasing levels of alanine, ornitine, citrulline and increasing level of Glu in liver, increasing levels of sulfur-containing compounds, Asp and Lys in blood plasma). Amino acid mixture which contained branched-chain amino acids, taurine and tryptophan administered intragastrically was found to correct levels of sulfur-containing amino acids, threonine, lysine and isoleucine after ethanol withdrawal and to eliminate disorders in urea cycle, exchange of threonine, glycine and phenylalanine after prolonged alcohol intoxication.

Administration, Oral↗
PubMed1979

[Emergency treatment of inborn amino errors of amino acid metabolism detected in the neonatal period].

The indications and effects of exchange transfusion, peritoneal dialysis, osmotic diuresis and early feeding have been studied in 28 children with inborn errors of aminoacid metabolism presenting in the neonatal period. Exchange-transfusion has only a transitory and incomplete effect but it is simple and quick. Peritoneal dialysis has a remarkable and often life-saving effect because the blood levels of toxic metabolites are reduced very effectively in organic acidaemias. However the rate of removal may decline if plasma concentrations fall below a critical level (1.2 mmol/L foor leucine). If the dialysis is prolonged for more than 36 hours it may cause hypoprotidaemia. Osmotic diuresis increases the 45 ml/min. However it is of little elimination of methylmalonic acid because the renal clearance is between 15 and 45 ml/min. However it is of little value in maple syrup urine disease, propionic acidaemia or isovaleric acidaemia because the renal clearance of the toxic metabolites is so low. The early re-introduction of low protein high calorie of a low protein and high calorie diet by continuous intragastric feeding is very important. The authors propose a protocol for the treatment of babies presenting inborn errors of aminoacid metabolism in the neonatal period. Peritoneal dialysis should be started as soon as the diagnosis is considered and continued for 24 to 36 hours. An exchange of transfusion shold be undertaken before and after the dialysis, together with an osmotic diuresis if appropriate. Continuous enteral feeding should be given, the quantity being adjusted to the baby's requirements.

Amino Acid Metabolism, Inborn Errors↗
PubMed1993

Erythropoietin treatment and amino acid metabolism in hemodialysis patients.

A previous report suggests that treatment with recombinant human erythropoietin (rH-EPO) significantly improves many abnormalities in circulating amino acids (AA) in hemodialysis patients. We evaluated the effects of a 12-month treatment with rH-EPO (150-250 U/kg/week) on blood AA levels in 10 patients with chronic renal failure under regular dialytic treatment. During treatment, hemoglobin levels increased from 7.0 +/- 0.3 to 10.1 +/- 0.3 g/dl at 3 months remaining steady thereafter. Before the treatment, patients showed reduced levels of essential AA (EAA), mainly valine, leucine and threonine (p < 0.05-0.01); among non-EAA (NEAA), aspartate and serine were reduced, whereas glycine, alanine, proline, citrulline and cyst(e)ine were increased (p < 0.05-0.001). Val/Gly, Ser/Gly and Tyr/Phe ratios were low (p < 0.05-0.01). Total EAA and total NEAA (619 +/- 21 and 1,382 +/- 75 mumol/l, respectively, before the study) were unchanged (639 +/- 22 and 1,410 +/- 89 mumol/l, respectively) at 12 months. Abnormalities in AA levels observed before the treatment persisted throughout the study. Only serine increased at the end of the study (p < 0.05). In conclusion, contrary to what has been reported, treatment with rH-EPO is not associated with an amelioration of AA metabolism in hemodialysis patients.

Adult↗
PubMed1997

Protein and amino acid metabolism in splanchnic organs in metabolic acidosis.

Metabolic acidosis causes a cooperative participation of different organs such as the liver, kidney, and muscle in restoring acid-base balance. In splanchnic organs, metabolic acidosis has repercussions on several nitrogen metabolism pathways. The decrease in urea synthesis due to reduced activity of urea cycle enzymes, ammonia uptake and amino acid transport, and changes in glutamine metabolism support renal ammoniagenesis thus offering a response to rid the body of excess protons. While some of the mechanisms are adaptive others may be harmful for the body. Metabolic acidosis may have effects on splanchnic protein turnover. In severe acidosis, synthesis of secreted liver proteins may be reduced. Acidosis may also modulate the response of the liver to growth hormone (GH) for insulin-like growth factor-I synthesis, thus inducing a state of GH resistance. Splanchnic abnormalities in acidosis might contribute to the malnutrition observed in uremia.

Acidosis↗