[Use of amino acid mixtures in man].
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Amino Acids↗
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[Amino acids mixtures in protein parenteral feeding].
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Amino Acids↗
[Vitamin B6 requirement of infants in parenteral feeding with amino acid mixtures].
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Amino Acids↗
[Changes in protein metabolism during the treatment of peptic ulcer with cholinergic blockaders in combination with stimulators of protein synthesis and amino acid mixtures].
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Adult↗
Effect of whey proteins, their oligopeptide hydrolysates and free amino acid mixtures on growth and nitrogen retention in fed and starved rats.
The effects of alimentary whey proteins given, as whole proteins (WP), controlled trypsin and chymotrypsin hydrolysate oligopeptides (WPH), or a free amino acid mixture (AAM), on growth, nitrogen retention, and steatorrhea were assessed in 24 Wistar rats (250 to 300 g) after 72 hr of starvation and 24 to 96 hr of realimentation and in 24 controls. The three diets had the same caloric, nitrogen, vitamin, and mineral contents. Rats had free access to the liquid diets. Only rats which ate the whole diet (90 cal) were included in the study. No differences in steatorrhea and fecal nitrogen were observed. The absorption rate was over 95% on the three diets. In contrast, weight gain was statistically better on WPH (+9% after 96 hr of realimentation) than on WP (+5%) or AAM (+2%). This was associated with a statistically higher nitrogen retention at all time periods studied, which was a result of a significant lower nitrogen urinary excretion. Similar results were obtained in controls. This better growth was a result of a better protein synthesis and lower ureagenesis.
Amino Acids↗
[Use of a new amino acid mixture in the diet therapy of patients with classical phenylketonuria].
The treatment of classic PKU is based on the dietary restriction of phenylalanine. The present study was planned to evaluate the effectiveness of a new amino acid mixture (ASP-Nestlé) in the dietary treatment of ten PKU patients (age 2 to 9 years, mean 5 years). The children were given this product for a minimum of 3 and a maximum of 12 months (mean 8 months). The aminoacid mixture, diluted in water or various flavored drinks, was favorably accepted by the patients. No clinical signs of hypophenylalaninemia were noticed and the children grew regularly in height and weight. The biochemical parameters, evaluated before during and after the treatment, showed a good nutritional balance. The plasma phenylalanine control was excellent, when compared to the plasma phenylalanine range obtained with other dietary regimens.
Amino Acids↗
Effects of addition of arginine, cystine, and glycine to the bovine milk-simulated amino acid mixture on the level of plasma and liver cholesterol in rats.
The effects of the addition of varying levels of arginine (Arg), cystine (Cys), and glycine (Gly) to the bovine milk-simulated amino acid mixture on the levels of plasma and liver cholesterol were investigated in rats. The diets containing a high amount of Cys lowered significantly the level of plasma cholesterol as the amount of Cys in diets increased. The serum high density lipoprotein (HDL)-cholesterol level and fecal excretion of acidic steroids were higher in rats fed the Cys diets than in those fed the Arg and Gly diets. No differences, however, was observed in the content of liver cholesterol. Liver triglyceride contents elevated significantly on feeding the Arg and Cys diets. Furthermore, liver phospholipid contents elevated significantly on feeding the Arg diet but lowered on feeding the Cys diet. Therefore, these results indicated that the feeding of a high amount of Cys lowers the plasma cholesterol levels as the result of the enhanced conversion of cholesterol to bile acids.
Animals↗
Analysis of underivatized amino acid mixtures using high performance liquid chromatography/dual oscillating nebulizer atmospheric pressure microwave induced plasma ionization-mass spectrometry.
A dual oscillating capillary nebulizer (OCN) in conjunction with an atmospheric pressure microwave induced plasma ionization (AP-MIPI) source was applied to the analysis of underivatized amino acid mixtures. It was found that, compared to the single OCN, the dual OCN enhanced the sensitivity of detection several fold. Enhanced sensitivity was compound dependent. For small molecules, such as amino acids, it was 2-5 times more sensitive, while for larger molecules such as peptides it was more than an order of magnitude. The increase in sensitivity was attributed to the enhanced nebulization of the new torch. By using water/ acetonitrile containing 0.1% nonafluoropentanoic acid as the high performance liquid chromatography (HPLC) mobile phase and a C18 column, all common amino acids were separated and detected. A comparison between the results obtained using microwave induced plasma, atmospheric pressure chemical ionization (APCI), and electrospray ionization (ESI) at flow rates compatible with micro LC (10-100 microL/min) showed a higher sensitivity of detection with the AP-MIPI technique for the analysis of underivatized amino acids.
Journal Article↗
Effect of a specialized amino acid mixture on human collagen deposition.
OBJECTIVE: To examine the effect of arginine, beta-hydroxy-beta-methylbutyrate (HMB), and glutamine supplementation on wound collagen accumulation in a double-blind, randomized study. SUMMARY BACKGROUND DATA: Control of wound collagen synthesis has been an elusive goal for clinicians and scientists alike. In many clinical instances, it is desired to increase collagen deposition as a means of enhancing wound strength and integrity. Arginine, a semiessential amino acid, has been shown to increase wound collagen accumulation in rodents and humans. HMB, a metabolite of leucine, regulates muscle proteolysis in animals and humans and increases collagen deposition in rodents. METHODS: Thirty-five healthy, nonsmoking human volunteers 70 years or older were enrolled and underwent subcutaneous implantation of two small, sterile polytetrafluoroethylene (PTFE) tubes into the deltoid region under strict aseptic techniques. The tubes were 1 mm in diameter and 6 cm in length with pore size of 90 to 120 microm to allow optimal ingrowth of fibroblasts and the deposition of matrix. Eighteen volunteers (mean age 75.4 years; 2 men, 16 women) were randomized to receive daily supplementation of 14 g arginine, 3 g HMB, and 14 g glutamine (total nitrogen 3.59 g) in two divided doses. The control group (n = 17; mean age 75.3 years; 6 men, 11 women) received an isonitrogenous, isocaloric supplementation of nonessential amino acids. Catheters were removed at 7 and 14 days postimplantation and analyzed for hydroxyproline (OHP, nmol/cm catheter, an index of collagen accumulation) and alpha-amino nitrogen (alpha-AN, mmol/cm, an index of total protein deposition). RESULTS: Supplements were well tolerated, without any reported side effects. Supplementation with the specialized amino acid mixture led to a significant rise in plasma arginine and ornithine levels. The specialized amino acid supplement led to a significant increase in collagen deposition (as reflected by OHP content) in the PTFE tubes without an effect on total protein accumulation. CONCLUSIONS: Collagen synthesis is significantly enhanced in healthy elderly volunteers by the oral administration of a mixture of arginine, HMB, and glutamine. This provides a safe nutritional means for increasing wound repair in patients.
Aged↗
Total parenteral nutrition-associated cholestasis in rats: comparison of different amino acid mixtures.
It has been suggested that the quantity of amino acids perfused is a pathogenetic factor in total parenteral nutrition (TPN)-associated hepatotoxicity. However, the effect of the qualitative pattern of amino acid solutions has not been studied. Rats on parenteral nutrition for 5 days received 10.2 g of dextrose and 3.4 g of amino acids daily. Bile flow (microliter/min/g liver protein) after administration of Vamin was 16.2 +/- 0.8, which was similar to that in controls given chow and dextrose iv, but it was significantly higher (p less than 0.001) than those on Travasol (12.3 +/- 0.8). The decrease in bile flow was not related to the large concentrations of alanine and glycine present in Travasol. However, the addition to Travasol of serine present only in Vamin increased bile flow significantly. Bile acid secretion rate, biliary lipid constituents, calcium, sodium, and glucose showed little change. In contrast, alpha-amino nitrogen was increased (p less than 0.05) in Vamin-perfused animals. Steatosis was noted in only a few animals in the Travasol group, and was not associated with an increase in the triglycerides content of the liver. Glycogen and protein content of the livers did not differ. The data show that the composition of amino acid solutions may be a determinant of TPN-induced cholestasis and suggest that the presence of methyl donor amino acids may have a protective effect.
Amino Acids↗
Flow injection chemiluminescence determination of L-cysteine in amino acid mixture and human urine with the BrO3--quinine system.
In this paper, a novel flow injection chemiluminescence (CL) determination of L-cysteine is proposed. The method is based on the CL reaction of L-cysteine and KBrO3 in acidic medium. The CL intensity was greatly enhanced in the presence of quinine. The CL intensity was linear with L-cysteine concentration in the range of 0.2-80 microg L(-1), and the detection limit was 0.1 microg L(-1) (3 sigma). A complete analysis, including sampling and injecting, could be performed in 1 min, giving a throughput of about 60 h(-1). The relative standard deviation was 1.6% for 0.8 microg L(-1 ) L-cysteine ( n=11). The proposed method was satisfactorily applied to the determination of cysteine in an amino acid mixture and human urine. The mechanism of the CL reaction is also discussed.
Amino Acids↗
Determination of L-cysteine in amino acid mixture and human urine by flow-injection analysis with a biamperometric detector.
Based on the electrocatalytic oxidation of cysteine at pretreated platinum electrode and the flow-injection biamperometry for irreversible couple, a novel electrochemical detector is proposed for the selective determination of cysteine in amino acid mixtures and human urine samples. A thin-layer flow through cell was used to achieve large electrode surface area to volume ratio. Two identical pretreated platinum electrodes were mounted in the cell with an applied potential difference of 10 mV. By coupling two independent and irreversible electrode processes, namely, the oxidation of cysteine and the reduction of platinum oxide, the biamperometric detection scheme has been established. The resulting current is linear to cysteine over the range 4 x 10(-7)-4 x 10(-5) M with the detection limit 1 x 10(-7) M (15 pmol). The selectivity of the detector is tested by 55 foreign species including 26 ions, 11 amino acids, 6 vitamins, and 12 other compounds possibly found in urine. The detector performs well as a routine assay, showing high efficiency (180 samples/h) and good reproductivity shown by a RSD of 0.6% for eight repeated determinations of 2 x 10(-6) M cysteine. The urine samples are detected directly without the need of pretreatment or adding other reagents.
Amino Acids↗
Intestinal absorption of calcium in rats given diets containing casein or amino acid mixture: the role of casein phosphopeptides.
1. In an attempt to investigate calcium absorption in the rat during the postprandial period, with the least alteration of the physical environment, the undisturbed small intestine was ligated in situ 2.5 or 3.0 h after ingestion of a diet containing 200 g casein/kg or an equivalent amino acid mixture, or 925 g casein/kg. Estimation of Ca absorption was made by comparing the amount of soluble 40Ca or 45Ca in the contents of segments from the rats receiving 45Ca by intubation 30 min after withdrawal of food, ligated after a further 30 min, then killed after 0 or 30 min. 2. Under conditions such that the estimated amount of a marker, polyethylene glycol, in segments ligated in a defined position was little changed in rats killed 30 min apart, the difference in the amount of soluble 40Ca was much higher in the rats fed on the basal diet containing 200 g casein/kg than in other groups. 3. This specific effect on Ca absorption, particularly in the distal portion of the small intestine, could be seen also after 45Ca was directly injected into ligated segments in situ. The amount of 45Ca in the portal blood 15 min after injection of the label was also highest in the rats given the basal diet. 4. The results were in agreement with our previous findings that the formation and accumulation of casein phosphopeptides causes an increase in the amount of soluble Ca in the distal small intestine.
Amino Acids↗
Failure of a tryptophan-free amino acid mixture to modify sexual behavior in the female rat.
Female Wistar rats, weekly injected with estradiol valerate after ovariectomy, were trained to cause a sexual contact with a potent male by operating a lever. Contact-response latencies, which vary according to the nature of the sexual contact, were measured as an index of the female's sexual motivation. In these experimental conditions the administration of a tryptophan-free amino acid mixture, which has been proved to decrease brain serotonin and to enhance male mounting behavior, failed to modify the sexual motivation of the female rats.
Amino Acids↗
Metabolic effects of orally administered amino acid mixture in elderly subjects with poorly controlled type 2 diabetes mellitus.
The reduction of muscle mass and increased protein catabolism in aging can determine the occurrence of metabolic alterations-such as hyperglycemia and reduced insulin sensitivity-in elderly subjects with diabetes mellitus. Therefore, the aim of the study was to evaluate the effect of nutritional supplementation with oral amino acid mixture (OAAM) in elderly subjects with type 2 diabetes. This approach was conducted in an attempt to antagonize muscle catabolism by means of increased endogenous protein synthesis and to improve glucose metabolism and insulin sensitivity. A randomized, open-label, crossover study was conducted in poorly controlled (glycosylated hemoglobin level [HbA(1c)] >7%) elderly subjects (age range, 65 to 85 years) with type 2 diabetes. OAAM significantly reduced fasting and postprandial blood glucose and HbA(1c), whereas all parameters remained substantially unchanged in the group treated with placebo. Fasting insulin levels and insulin resistance increased at baseline in all subjects with diabetes and decreased during OAAM supplementation. These results persisted also after crossover from OAAM to placebo. No changes in blood lipid levels, creatinine, homocysteine, and urinary albumin excretion rate were observed throughout the study, whereas a mild but significant increase of high-density lipoprotein cholesterol was found after OAAM supplementation. We suggest that increased amino acid availability for skeletal muscle function and strength could ameliorate metabolic control and insulin sensitivity in elderly patients with poorly controlled type 2 diabetes.
Aged↗
Determination of D- and L-aspartate in amino acid mixtures by high-performance liquid chromatography after derivatization with a chiral adduct of o-phthaldialdehyde.
A sensitive and convenient method for the simultaneous determination of D- and L-aspartic acid in amino acid mixtures is described. The method involves derivatization of the mixture with a chiral fluorogen, followed by high-performance liquid chromatography on a reverse-phase column. The fluorogen used is an adduct of o-phthaldialdehyde with an optically active thiol, N-acetyl-L-cysteine. The sensitivity and accuracy of this method is similar to that using adducts of o-phthaldialdehyde with the achiral thiol, 2-mercaptoethanol. Five picomoles of D-aspartate can be accurately detected in the presence of a 100-fold excess of L-aspartate with a total analysis time (including derivatization) of 10 min.
Acetylcysteine↗
The protein requirement of adult marmosets: nitrogen balances and net protein utilization of milk proteins, soy protein, and amino acid mixtures.
Nitrogen balance studies were conducted in adult male marmosets (Callithrix jacchus) using purified and semipurified diets with protein levels between 0% and 7%. Daily nitrogen loss in a state of prolonged protein free nutrition was 131 +/- 16 mg/kg body weight0.75. Zero nitrogen balance resulted from mean daily intake of 261 mg nitrogen/kg0.75 when high quality protein sources were used. Very low protein intake or the lack of arginine and histidine in an amino acid mixture induced coprophagy. It is concluded that the protein requirement of adult marmosets is very similar to the protein requirement of adult humans (based on metabolic body weight). About 6-7% high quality protein, based on dry matter, suffice to avoid a negative nitrogen balance in all individuals.
Amino Acids↗
Transfers of N metabolites across the ovine liver in response to short-term infusions of an amino acid mixture into the mesenteric vein.
The effect of acute (4.5 h) infusions into the mesenteric vein of an amino acid (AA) mixture, which simulated the composition of rumen microbial protein, on net transfers of NH3, urea and total AA across the portal-drained viscera (PDV) and liver in the ovine has been examined. Four wether sheep were surgically prepared with vascular catheters across the PDV and liver (Lobley et al. 1995) and were offered a basal diet of 1000 g grass pellets/d (approximately 1.4 x energy maintenance). Each animal was infused at weekly intervals with one of four dilutions of the AA mixture. These dilutions provided 0.44, 0.88, 1.32 and 1.84 mmol AA-N/min infused, the lowest of which approximately doubled the net absorption of AA-N from the basal diet. Animals were treated with heparin to allow continuous collection of blood by peristaltic pump for 2 h preceding, and between 0.5-2.5 and 2.5-4.5 h after, the start of the AA infusions. Blood flow in the hepatic artery increased (100 v. 208 g/min; P = 0.002) in response to AA infusion, while hepatic portal venous flow decreased (2090 v. 1854 g/min; P = 0.006). The AA infusion also stimulated O2 uptake by the PDV (P < 0.001) and liver (P = 0.016). Absorption across the PDV and hepatic removal of NH3 were unchanged between basal and amino acid infusion conditions. Urea-N removal across the PDV was unaltered, but hepatic production increased (P < 0.001) with level of AA infusion. During infusions, net appearance of AA across the PDV was below the theoretical level. This may have been due to inhibition of AA uptake from the small intestine, and/or increased removal by the digestive tract of AA from the systemic circulation associated with greater arterial concentrations. Hepatic extraction of AA increased with level of infusion, both for total AA and those included in the infusate. Total hepatic urea-N production tended towards a maximum (estimated as 2 mumol N/g liver wet weight per min). The AA removed by the liver and not used for ureagenesis remained similar (170 mumol AA-N/min) between basal and AA infusions. This was presumed available for anabolic purposes (mainly synthesis of export proteins). The proportion of net AA-N appearance (absorption plus infused) across the PDV removed by the liver declined from 0.71 to 0.53 between basal and AA infusions. In contrast to findings from cattle (Wray-Cahen et al. 1997), increased AA infusion did not alter the net removal of glutamine across the liver. This may reflect differences between the studies in NH3: AA-N absorbed. Further differences between the cattle study and the current findings may relate to the different physiological state (pregnancy v. growth), which may alter the partition of AA between anabolic and catabolic fates.
Amino Acids↗