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Results for “AMINO ACID MIXTURES”

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PubMed1996

Taste responses to binary mixtures of amino acids in the sea catfish, Arius felis.

In vivo electrophysiological recordings in the sea catfish, Arius felis, showed that the magnitude of the integrated facial taste responses to binary mixtures of amino acids was predictable with knowledge obtained from previous cross-adaptation studies of the relative independence of the respective binding sites of the component stimuli. Each component from which equal aliquots were drawn to form the mixtures was adjusted in concentration to provide for approximately equal response magnitudes. The magnitude of the taste responses to binary mixtures whose component amino acids showed minimal cross-adaptation was significantly greater than that to binary mixtures whose components exhibited considerable cross-reactivity. There was no evidence for mixture suppression. The relative magnitude of the taste responses in the sea catfish to stimulus mixtures is similar to that previously reported for olfactory receptor responses in the freshwater channel catfish and chorda tympani taste responses in the hamster.

Amino Acids↗

PubMed1983

The importance of dietary amino acids on the reproduction and longevity of adult Dacus oleae (Gmelin) (Diptera Tephritidae).

When the amino-acid mixture of an effective chemically defined diet was replaced by single amino acids, keeping the total nitrogen at the same level, the egg production of Dacus oleae was minimal with all the 19 amino acids tested. Male survival was adversely affected by the amino acids : alanine, aspartic acid, glutamic acid, glycine, hydroxyproline, lysine, serine and tyrosine, while female survival was shortened when the amino acids : glycine, hydroxyproline and lysine were added. The creation of amino-acid imbalances, by deleting the 19 amino acids individually, from the complete amino-acid mixture, showed that the amino acids : arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, serine, threonine, tryptophane and valine were indispensable to the adult Dacus oleae flies, as far as egg production is concerned. Survival of the male flies was significantly shortened when the amino acids : alanine, hydroxyproline and tryptophane were omitted. Significant differences in longevity between males and females were scored, when the amino acids : alanine, aspartic acid, cystine, glycine and tryptophane, were omitted.

Amino Acids↗

PubMed1984

The effect of amino acid excess on utilization by the rat of the limiting amino acid--lysine.

A lysine-deficient amino acid mixture was developed by decreasing the level of lysine in a well-balanced amino acid mixture while measuring the response in daily gain and protein retention in young growing rats. The diet that contained the highest level of lysine that did not support maximal growth or protein retention was used as the lysine-deficient amino acid mixture. This mixture was incorporated into a series of diets to provide 0.52, 0.59 or 0.67% of lysine in combination with 0, 25 or 50% relative excess of all other amino acids. Food intake, weight gain and changes in carcass composition were measured in the 21-day feeding study. When voluntary food intake was used as a covariate in the statistical analysis, increased dietary lysine improved the efficiency of food use for body weight, dry matter, crude protein and ash gains. When corrected for food intake, lysine level did not affect lipid retention. There was no effect of excess amino acids on food intake, daily weight gain or body component gains whether food intake was used as a covariate or not. These results suggest that growing rats can respond to improved amino acid nutriture with changes in the efficiency of food use rather than improvements in growth.

Amino Acids↗

PubMed1989

Biochemical aspects of tryptophan depletion in primates.

We studied the degree of plasma tryptophan depletion produced by giving normal human males different amounts of a tryptophan-free (T-) amino acid mixture. From the results of this and other studies we concluded that the maximum degree of tryptophan depletion can be produced by a 31.5 g mixture of seven essential amino acids. Administration of a T- amino acid mixture to vervet monkeys lowered tryptophan and 5-hydroxyindoleacetic acid in the cerebrospinal fluid. Levels of tyrosine and the catecholamine metabolites were unchanged. These data support the idea that the effects of T- mixture on mental function in humans which have been reported previously are due to a decrease in 5-hydroxytryptamine.

Adolescent↗

PubMed1977

Simultaneous peptide and oligonucleotide formation in mixtures of amino acid, nucleoside triphosphate, imidazole, and magnesium ion.

Simultaneous peptide and oligonucleotide formation was observed in reaction mixtures of amino acid, nucleoside triphosphate, imidazole, and MgCl2. At 70 degrees C in solutions that were evaporated to dryness the formation of peptide for phe and pro was greatest with CTP relative to ATP, GTP, and UTP. Lysine exhibited a preference for GTP and glycine for UTP. At ambient temperature insolution at pH 7.8, CTP was preferred by glycine, but at pH 8.7 UTP was preferred. The glycine nucleotide phosphoramidates were also detected and characterized in reactions at 40 degrees C. The glycine-reaction preference for CTP at pH 7.8 and UTP at 8.7 suggested that the basicity of the nucleoside triphosphate was involved in increasing the peptide yield. CTP near neutrality is the most basic nucleoside triphosphate and the basic anionic form UTP could facilitate peptide formation at pH 8.7. These data, together with information on the complexing of poly(C) by GTP, led to the experimentally approchable hypothesis that GTP, by forming a basic triplex between the cytosine residues adjacent to the peptidyl adenosine and aminoacyl adenosine at the termini of two proto-tRNAs, would promote peptide bond synthesis between the aminoacyl residue and peptidyl residue.

Amino Acids↗

PubMed2000

Acute tyrosine depletion and alcohol ingestion in healthy women.

BACKGROUND: Recently we reported that, in vervet monkeys, ingestion of an amino acid mixture deficient in the catecholamine precursors, phenylalanine and tyrosine, produced a decrease in alcohol self-administration. We now report the results of a similar study in humans. METHODS: Three groups of healthy female social drinkers were administered a nutritionally balanced amino acid mixture (B, n = 13), a mixture deficient in the serotonin precursor, tryptophan (Trp-free, n = 14), or a phenylalanine/tyrosine deficient mixture (Phe/Tyr-free, n = 12). Six hours after administration of the amino acid mixture, alcohol ingestion was measured during a free-choice "Taste Test." RESULTS: Compared to the B mixture, Phe/Tyr-free, but not Trp-free, significantly decreased the ingestion of alcohol [p < 0.02]. Neither Phe/Tyr-free nor Trp-free significantly decreased orange juice ingestion or the self-reported "Liking" of either substance. Some subjects experienced transient nausea and/or regurgitated the amino acid mixtures, but excluding these subjects did not change the results. CONCLUSIONS: The results suggest that (a) Phe/Tyr-free may be a suitable method for investigating the role of catecholamines in the self-administration and subjective effects of alcohol, (b) acutely decreased catecholamine neurotransmission might disrupt mechanisms mediating alcohol self-administration, and (c) acutely decreased serotonin neurotransmission seems not to alter alcohol self-administration.

Adult↗

PubMed1988

The effect of lowering plasma tryptophan on food selection in normal males.

The effects of a tryptophan deficient amino acid mixture on food selection were studied using a double-blind counterbalanced crossover design in normal male subjects. The subjects ingested tryptophan deficient or nutritionally balanced amino acid mixtures in the morning after an overnight fast. Five hours after the tryptophan deficient amino acid mixture plasma tryptophan was only 19% of the level found five hours after the nutritionally balanced amino acid mixture. After both mixtures subjects were allowed to select lunch from a buffet. The tryptophan-deficient mixture was associated with a modest but significant decline in protein selection with no significant alteration in selection of carbohydrate, fat or total kcal. Our results suggest that 5-hydroxytryptamine is involved in the control of protein selection in humans.

Adult↗

PubMed2001

Whole body and skeletal muscle glutamine metabolism in healthy subjects.

We measured glutamine kinetics using L-[5-15N]glutamine and L-[ring-2H5]phenylalanine infusions in healthy subjects in the postabsorptive state and during ingestion of an amino acid mixture that included glutamine, alone or with additional glucose. Ingestion of the amino acid mixture increased arterial glutamine concentrations by approximately 20% (not by 30%; P < 0.05), irrespective of the presence or absence of glucose. Muscle free glutamine concentrations remained unchanged during ingestion of amino acids alone but decreased from 21.0 +/- 1.0 to 16.4 +/- 1.6 mmol/l (P < 0.05) during simultaneous ingestion of glucose due to a decrease in intramuscular release from protein breakdown and glutamine synthesis (0.82 +/- 0.10 vs. 0.59 +/- 0.06 micromol x 100 ml leg(-1) x min(-1); P < 0.05). In both protocols, muscle glutamine inward and outward transport and muscle glutamine utilization for protein synthesis increased during amino acid ingestion; leg glutamine net balance remained unchanged. In summary, ingestion of an amino acid mixture that includes glutamine increases glutamine availability and uptake by skeletal muscle in healthy subjects without causing an increase in the intramuscular free glutamine pool. Simultaneous ingestion of glucose diminishes the intramuscular glutamine concentration despite increased glutamine availability in the blood due to decreased glutamine production.

Adult↗

PubMed1995

Electrophysiological responses of single olfactory bulb neurons to binary mixtures of amino acids in the channel catfish, Ictalurus punctatus.

1. For the first time in any vertebrate, responses of single olfactory bulb neurons to odorant mixtures were studied quantitatively in the channel catfish, Ictalurus punctatus. 2. Extracellular electrophysiological responses of 61 single olfactory bulb neurons from 36 channel catfish to binary mixtures of amino acids and to their components were recorded simultaneously with the electro-olfactogram (EOG). Tested were a total of 297 mixture trials consisting of 18 different stimulus pairs formed from 8 amino acids. 3. For 42% (126 of the 297) of the tests, no significant change (N) from spontaneous activity occurred. Responses to the remaining 171 tests of binary mixtures were excitatory (E; 29%) or suppressive (S; 29%). No response type was associated with any specific mixture across the neurons sampled. 4. Mixture interactions that changed response types (E or S) from those observed to the individual components were rare, because 89% of the responses of single olfactory bulb neurons to the tested binary mixtures were classified similarly as the responses to at least one of the components. 5. Responses of single olfactory bulb neurons were generally predictable for binary mixtures whose component responses were classified as both E, both S, and both N. For binary mixtures whose component responses were classified differently (e.g., one component evoked excitatory responses and the other evoked suppressive responses), the predictability of the response was dependent on the specific mixture type.

Amino Acids↗

PubMed1989

Effects of amino acids and peptides on rumen microbial growth yields.

Experiments were conducted using mixed rumen bacterial cultures to determine which amino acids limited growth. Complete amino acid mixtures stimulated microbial growth alone and when added to casein. Amino acid subgroups did not stimulate growth alone or when added to casein or casein hydrolysates. Results were similar whether growth was limited by periodic addition of low amounts of carbohydrate or when higher amounts were added to batch cultures. Little growth occurred with ammonia as sole N source. Addition of 100 mg/L of amino acids and peptides quadrupled growth, peptides at 10 mg/L resulted in higher growth than the corresponding amount of free amino acids. Apparent saturation of growth occurred when 10 mg/L of a complete amino acid mixture or trypticase was added to cultures. The Michaelis constant values for amino acids and trypticase were determined to be .5 and 1.0 mg/L, respectively. Growth was a linear function of amount of carbohydrate fermented with the coefficient of slope increasing with increasing amino acid concentrations. These experiments demonstrate that growth stimulation from amino acids and proteins is due to the number of amino acids provided in a given mixture rather than specific growth limiting amino acids. Rumen bacterial growth is greatly stimulated by amino acids and peptides, with low affinity constant values, allowing good growth in the concentrations of amino acids and peptides found in vivo

Amino Acids↗

PubMed1982

Effects of leucine/isoleucine ratio in amino acid mixture-diets simulating normal and high-lysine maize proteins on growth, nitrogen balance, and tryptophan-niacin metabolism in rats.

To re-evaluate nutritive values of opaque-2 (o2) and brittle-2 opaque-2 (bt2o2) maize protein and to re-estimate Gopalan's hypothesis [Lancet, i, 954-957 (1960)] that pathogenesis of pellagra might be related with intake of excess leucine and with chronic consumption of maize or jowar which contains relative high leucine, rats were fed on synthetic diets composed of amino acid mixtures simulating the protein of normal and high-lysine maize, o2 and bt2o2 maize. In order to investigate the effect of intake of excess leucine, leucine was supplemented to o2 and bt2o2 diet at the level of 0.43 and 0.73%, respectively, to adjust the ratio of leucine to isoleucine to that of normal maize protein. Judging from body weight gains and carcass nitrogen of weanling rats fed on these diets, the protein quality (amino acid composition) of bt2o2 maize was 30% superior nutritionally to that of o2 maize, and body composition of bt2o2 diet group were similar to that of casein diet group. Leucine supplementation did not affect these values except for a significant decrease in plasma valine levels. In young adult rats fed on leucine supplemented o2 diet, excretion of urinary nitrogen increased significantly compared with o2 diet alone, suggesting that a slight amino acid imbalance took place. But leucine supplementation altered neither N1-methylnicotinamide level in urine nor total niacin levels in the liver and the brain. These results suggest that supplementation of leucine to a high lysine maize diet did not affect tryptophan and niacin metabolism in rats under these conditions.

Amino Acids↗

PubMedDate not supplied

Simultaneous synthesis of peptide libraries on single resin and continuous cellulose membrane supports: examples for the identification of protein, metal and DNA binding peptide mixtures.

Peptide libraries were simultaneously synthesized on single supports by double coupling 0.8 equivalents of an equimolar acylating amino acid mixture consisting of 19 amino acids (cysteine omitted) at randomized sites, thus compensating for the different coupling rates of the amino acids. Peptide epitope mixtures, as well as very complex mixtures such as a completely randomized hexapeptide, were prepared and analyzed by HPLC and amino acid analysis. The results obtained indicate that this method can be applied to the synthesis of peptide libraries. Parts of a simultaneously synthesized solution phase combinatorial library XXB1B2XX were successfully used for the detection of the linear epitope HFND of transforming growth factor-alpha (TGF alpha) recognized by the monoclonal antibody Tab2. Furthermore, novel combinatorial peptide libraries XXB1B2XX were prepared on continuous cellulose membrane supports, also allowing the identification of TGF alpha epitope sequences. In addition, peptide mixtures that bound to a double-stranded DNA (15mer) and silver were identified. These preliminary results indicate that cellulose-bound combinatorial peptide libraries can be used for the rapid and inexpensive screening of millions of peptides to identify single molecules that bind any given ligand such as proteins, nucleic acids and metals.

Amino Acid Sequence↗

PubMed1985

Comparison of intraluminal and intravenous mediators of colonic response to eating.

Eating a 1000-kcal mixed meal stimulates an increase in distal colonic motility. Fat is the dietary component which is the major stimulant of colonic spike activity. In this study the colonic spike activity increased similarly after the mixed meal [19.1 +/- 2.4 spike potentials (SP)/30 min] and after the fat meal (19.4 +/- 5.4 SP/30 min). Fat stimulated a concentration-dependent increase in colonic motility only when in contact with the gastroduodenal mucosa. Intravenous administration of Liposyn (100 kcal/hr) did not stimulate an increase in colonic spike activity (3.3 +/- 1.3 SP/30 min) despite greater increase in plasma total fatty acid levels than after the oral ingestion of fat. In contrast both the oral ingestion and the intravenous administration of an amino acid mixture (Aminosyn) inhibited the gastrocolonic response after the 1000-kcal mixed meal. Thus, these studies demonstrate: (1) fat stimulates colonic motility only through direct mucosal contact, and (2) a mixture of amino acid inhibits colonic motility through either mucosal contact or by circulating in the plasma. The exact neurohumoral mechanisms involved in both of these effects is unknown at present.

Action Potentials↗

PubMed1968

Studies on the physiological and structural characteristics of rat intestinal mucosa. Mitochondrial structural changes during amino acid absorption.

Sections from mucosal strips and rings of rat jejunum were studied with the light microscope and the electron microscope before and after incubation in a modified Krebs bicarbonate Ringer. Various additions were made to the incubation medium, and their effects on both the structure and the respiratory activity of the mucosal tissue were noted. In those cases in which an amino acid mixture was added, there was a pronounced increase in the rate of respiration. When strips of intestine were used, the presence of the amino acid mixture more than doubled the rate of oxygen consumption. Along with the increased levels of respiration there was a sharp rise in the percentage of mitochondria assuming a condensed ultrastructural conformation. The amino acid mixture did not cause the condensation of jejunal mitochondria if glucose was included in the incubation medium or if 2,4-dinitrophenol was present. The evidence suggests that a high proportion of the jejunal mitochondria assumes a condensed conformation in response to an increased energy demand. Apparently glucose can prevent the amino acid mixture from increasing the energy drain on the oxidative processes in these cells. Although a high rate of respiration was obtained in the presence of dinitrophenol, the studies indicated that mitochondrial condensation was only associated with a high rate of coupled oxidative phosphorylation.

Amino Acids↗

PubMed1987

Properties of a Na+-coupled serine-threonine transport system in Escherichia coli.

Based on the following experimental results we conclude that the serine-threonine transport system in Escherichia coli is a Na+-coupled cotransport system. (1) Addition of serine to cell suspensions induced H+ efflux in the presence of Na+. (2) Addition of serine to cell suspensions induced Na+ uptake by cells. (3) Imposition of an artificial electrochemical potential of Na+ in starved cells induced serine uptake. Some of these phenomena were observed when threonine was added instead of serine or inhibited when cells were preincubated with threonine. The Na+/serine (threonine) cotransport system was considerably repressed when cells were grown on a mixture of amino acids. Serine transport in cells grown in the absence of amino acids mixture was stimulated by Na+. The half maximum concentration of Na+ was 21 microM. Sodium ion increased the Vmax of serine transport without affecting the Km.

Amino Acid Transport Systems↗

PubMed1975

Effect of amino acid meals on hepatic alpha-aminoisobutyrate transport and cyclic AMP.

Within 1.5 h after force-feeding rats one meal of enzymatic hydrolysates of casein, gelatin, lactalbumin, or yeast, alpha-aminoisobutyric acid (AIB) transport in liver slices was stimulated two- to threefold. A complete amino acid mixture also increased AIB transport. Of the 15 amino acids or derivatives tested individually, the dispensable amino acids, especially glycine and alanine, were more stimulatory than the essential amino acids; feeding a mixture of amino acids lacking glycine and alanine increased AIB uptake only slightly. The effects were significantly greater in meal-fed than in ad libitum-fed rats. Increased hepatic concentrations of cyclic AM were usually associated with the increase in AIB transport. Feeding glucose inhibited the increases in transport and cyclic AMP concentration induced by casein hydrolysate or in the stimulation of AIB transport by dietary amino acids. The increases in AIB uptake appeared unrelated to the exchange of endogenous amino acids with medium AIB.

Adrenalectomy↗

PubMed1972

Intestinal absorption of an arginine-containing peptide in cystinuria.

Separate tolerance tests involving oral intake of the dipeptide, L-arginyl-L-aspartate, and of a corresponding free amino acid mixture, were carried out in a single type 2 cystinuric patient. Absorption of aspartate was within normal limits, whilst that of arginine was normal after the peptide but considerably reduced after the amino acid mixture. The results are compared with the increments of serum arginine found in eight normal subjects after the oral intake of the free amino acid mixture. Analyses of urinary pyrrolidine and of tetramethylenediamine in urine samples obtained after the two tolerance tests in the patient support the view that arginine absorption was subnormal after the amino acid mixture but within normal limits after the dipeptide.

Alanine↗

PubMed1996

Modulation of thermogenic response to parenteral amino acid infusion in surgical stress.

Thermogenic response to parenteral infusion of amino acid mixtures in rats undergoing surgical stress was investigated with the aid of a small animal indirect calorimeter. Male Wistar rats (n = 12) were laparotomized and received intestinal abrasion along with construction of a parenteral route. After 48 h, nutrient-induced thermogenesis (NIT) produced by amino acid mixtures was examined and compared with that of control rats (n = 12) without surgical stress. The NIT values of the leucine-enriched solution were greater than those of the control solution in both rats with and without surgical stress. The NIT generated by the leucine-enriched solution in rats with surgical stress was significantly higher than that in rats without. NIT values for 10 different kinds of single amino acid solutions with identical concentrations was then examined in 60 rats. The NIT values of the leucine and the glycine solutions were relatively higher than those of other solutions. However, when puromycin was injected intraperitoneally into 12 rats just before measurement of the NIT in response to amino acid mixtures, no significant differences were found in NIT values between the mixtures. In summary, surgical stress increased the thermogenic response to the leucine-enriched solution, indicating that utilization of leucine may be augmented under surgical stress. In fact, leucine itself may be a thermogenic amino acid. Inhibition of protein synthesis prevented the increase in thermogenic response induced by the leucine-enriched solution. We conclude that thermogenic responses to parenteral amino acid mixtures may differ depending not only upon the compositions of amino acids but also upon the host conditions.

Amino Acids↗