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  • 1
    Electronic Resource
    Electronic Resource
    Effect of various oral protein doses on plasma neutral amino acid levels (1985)
    Springer
    Journal of neural transmission 61 (1985), S. 183-191 
    Details
    ISSN: 1435-1463
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Six healthy fasting females each received, on different days, 0, 6, 12.5 or 25 g of albumin dissolved in 200 ml water. Blood was collected before and at intervals after the albumin ingestion and assayed for plasma levels of large, neutral amino acids (LNAA), insulin and glucose. Insulin increased significantly after ingestion of 12.5 and 25 g of albumin, whereas changes in serum glucose were small and inconsistent. Increases of plasma LNAA concentrations were dose-related and correlated significantly with the molar percentage in the albumin of the respective amino acids at 1 and 2 hours but not at 3 and 4 hours after consumption. Ratio in plasma of tyrosine to other LNAA increased by 20 to 60%, and still at 4 hours the plasma tyrosine ratio was significantly elevated above control level after all 3 albumin doses. The plasma ratio of tryptophan to other LNAA decreased by 30 to 50%, and at 4 hours the plasma tryptophan ratio was still significantly below control level after the 2 larger albumin doses. The marked changes in the plasma tryptophan and tyrosine ratio suggests that the central serotonin and catecholamine synthesis could possibly be affected following ingestion of pure protein.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01251912
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  • 2
    Electronic Resource
    Electronic Resource
    Neutral amino acid plasma levels in healthy subjects: effect of complex carbohydrate consumed along with protein (1989)
    Springer
    Journal of neural transmission 76 (1989), S. 55-63 
    Details
    ISSN: 1435-1463
    Keywords: Tryptophan ; large neutral amino acids ; plasma ; availability ; brain ; complex carbohydrate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Six healthy fasting females each received, on different days, 0, 25, or 50 g of complex carbohydrate in the form of white sphaghetti containing 11–12% protein along with 200 ml water. Blood was collected before and at intervals for 4 hours after the spaghetti ingestion and assayed for plasma levels of large, neutral amino acids (LNAA), insulin and glucose. The area under the curve for the increase of serum insulin was four times greater after the 50-g dose compared to the 25-g dose of carbohydrate, but the respective areas under the curves for the increases of plasma glucose were identical. The plasma ratio tryptophan/LNAA varied significantly and increased 10% above basal level and 25–30% above control level after either carbohydrate dose, but only the difference for the 50-g dose was significant. Although the main effect for plasma ratio tyrosine/LNAA was also significant, the increases of this ratio above control level were marginal. The main effect for the dose of complex carbohydrate for valine, isoleucine and leucine was significant, and the areas above the curves for the decreases of individual branched-chain amino acids were of the same size after the two doses. Plasma tyrosine, phenylalanine and tryptophan showed no significant variation. The study has shown that consumption of complex carbohydrate along with 11–12% protein (the recommended dietary concentration) slightly increases the plasma ratio tryptophan/LNAA for 4 hours, and that the effect is practically maximal after ingestion of 25 g of the test meal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01244991
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of branched-chain amino acids on plasma amino acids in amyotrophic lateral sclerosis (1996)
    Springer
    Amino acids 11 (1996), S. 37-42 
    Details
    ISSN: 1438-2199
    Keywords: Amyotrophic lateral sclerosis ; Glutamate metabolism ; Branched-chain amino acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Although the cause of amyotrophic lateral sclerosis (ALS) remains unknown, biological findings suggest that the excitatory amino acid glutamate contributes to the pathogenesis of ALS. In previous studies of ALS, the therapeutic effect of the branched-chain amino acids (BCAAs) leucine, valine and isoleucine has been evaluated. The present study aimed at investigating the acute effect of BCAAs on plasma glutamate levels in ALS patients. Following two oral doses of BCAAs, significantly increased plasma levels were seen for valine (500%), isoleucine (1,377%) and leucine (927%), however the plasma level of glutamate was not affected. The plasma level of several other amino acids (tryptophan, tyrosine, phenylalanine and methionine) were found decreased after oral BCAAs, which may indicate a diminution in the rate of degradation of muscle protein and/or an increase in tissue disposal of amino acids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00805719
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  • 4
    Electronic Resource
    Electronic Resource
    Tryptophan tolerance and metabolism in endogenous depression (1982)
    Springer
    Psychopharmacology 76 (1982), S. 79-83 
    Details
    ISSN: 1432-2072
    Keywords: Endogenous depression ; l-Tryptophan load ; Plasma tryptophan ; Plasma kynurenine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The concentration of free and total tryptophan and kynurenine in plasma from 49 female depressives and 26 female controls was measured following oral loading with l-tryptophan, 100 mg/kg body weight. There was no significant difference between five depressives and six controls in the area under curve for free or total tryptophan or kynurenine in plasma. The peak concentration of kynurenine occured 4 h after loading and it correlated significantly with the area under curve for kynurenine. There was no significant correlation between the l-tryptophan dose (g) and the plasma concentration of kynurenine at 4 h in the 49 depressives or 26 controls. The mean plasma levels of tryptophan and kynurenine at 4 h in the depressives were not significantly different from control levels. There was no clear relationship between the plasma levels of tryptophan or kynurenine at 4 h and the therapeutic response in 13 depressives treated with l-tryptophan for 14 days. It is concluded that the absorption, the plasma clearance, and the degradation to kynurenine of loading doses of l-tryptophan are normal in depressed patients. Results further-more suggest that the plasma levels of tryptophan and kynurenine at 4 h are poor predictors of the response to l-tryptophan treatment in depressives.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00430761
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  • 5
    Electronic Resource
    Electronic Resource
    Plasma tryptophan and tyrosine ratios to competing amino acids in relation to antidepressant response to citalopram and maprotiline (1986)
    Springer
    Psychopharmacology 88 (1986), S. 96-100 
    Details
    ISSN: 1432-2072
    Keywords: Depressive disorder ; Tryptophan ratio ; Tyrosine ratio ; Response prediction ; Citalopram ; Maprotiline
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Pretreatment plasma ratios of tryptophan (Trp) and tyrosine (Tyr) to other large neutral amino acids were determined in 27 depressed patients who completed a double-blind trial of citalopram, a selective serotonin uptake inhibitor, against maprotiline, a selective noradrenaline uptake inhibitor. The Trp ratio and the Tyr ratio were decreased in the total patient sample as compared with healthy controls. Plasma Tyr ratio was normal in the endogenous, but significantly decreased in the non-endogenous depressives. There was no significant relationship between the plasma Trp ratio and the probenecid-induced accumulation of 5-HIAA in the CSF, or between the plasma Tyr ratio and HVA level in CSF, whereas the CSF level of MHPG correlated significantly with the plasma Tyr ratio. There was a significantly positive correlation between the Trp ratio, the Tyr ratio, their sum and the final Hamilton depression score in 14 patients treated with citalopram; on the whole, this association was evident also in the endogenous and non-endogenous subgroups. In 13 patients on maprotiline there was a significantly positive correlation between the plasma Tyr ratio and the percent reduction of Hamilton depression score; this association was poor in the endogenous, whereas a trend towards a correlation remained in the non-endogenous subgroup. The results suggest that the plasma Trp and Tyr ratios may be determinants of clinical improvement in depressed patients to treatment with citalopram and maprotiline. However, further studies are needed on larger patient samples to allow a firm conclusion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00310520
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  • 6
    Electronic Resource
    Electronic Resource
    Effects of oral contraceptives on plasma neutral amino acids and cholesterol during a menstrual cycle (1996)
    Springer
    European journal of clinical pharmacology 50 (1996), S. 179-184 
    Details
    ISSN: 1432-1041
    Keywords: Key words Oral contraceptives ; Neutral amino acids ; Menstrual cycle ; Cholesterol; tyrosine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Objective: Concentrations of plasma neutral amino acids, i.e. threonine, serine, asparagine, glycine, alanine, citrulline, α-aminobutyric acid, valine, methionine, isoleucine, leucine, tyrosine, phenylalanine, and tryptophan, and serum cholesterol, were determined at the follicular (Day 4), mid-cycle (Day 16) and luteal (Day 25) phases of the menstrual cycle in 15 users of the new generation of combined oral contraceptives (OC), 11 on multiphase combined OC, and 17 controls. Results: The controls showed a decrease in the sum of amino acids to 95% at mid-cycle and 90% in the luteal phase relative to the follicular phase, and a significant decrease in the tyrosine level at the luteal relative to the follicular phase. Since there was no significant difference between the two OC subgroups in the levels of the specified variables at either of the phases, the two groups were considered together. The sum of amino acids in the OC group decreased to 89% at mid-cycle and 91% at the luteal phase relative to the follicular phase, indicating less metabolic effect than reported for older OC formulations. Compared to the controls, the OC group showed significant increased threonine level at the luteal phase, decreased glycine levels at mid-cycle and the luteal phases, decreased citrulline level at mid-cycle, and markedly decreased tyrosine levels at the mid-cycle and luteal phases. Neither total nor high density lipoprotein (HDL) cholesterol differed significantly between the control and OC groups. Conclusion: The results suggest that the metabolic effects of the new generation combined OC on neutral amino acids and cholesterol are only modest to slight, except for the effect on tyrosine, the brain noradrenaline precursor, which may cause disturbances of various noradrenaline-mediated central functions in susceptible subjects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002280050089
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  • 7
    Electronic Resource
    Electronic Resource
    Pharmacokinetics of tryptophan, renal handling of kynurenine and the effect of nicotinamide on its appearance in plasma and urine following L-tryptophan loading of healthy subjects (1981)
    Springer
    European journal of clinical pharmacology 21 (1981), S. 137-142 
    Details
    ISSN: 1432-1041
    Keywords: tryptophan ; pharmacokinetics ; kynurenine ; 3-hydroxykynurenine ; renal clearance ; nicotinamide ; tryptophan pyrrolase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of tryptophan, the temporal occurence of kynurenine (KYN) and 3-hydroxykynurenine (3-HK) in plasma and urine, and the effect of nicotinamide on tryptophan metabolism were studied in 6 healthy subjects after oral administration of L-tryptophan 100 mg per kg body weight. The peak concentration of tryptophan in plasma occurred after 1 to 2 h, tryptophan disappeared linearly from 2 to 5 h and exponentially from 5 to 8 h. Urinary tryptophan excretion was negligible. The peak concentration of KYN in plasma occurred after 4 h and it was correlated significantly with the area under the plasma curve (AUC) of KYN of the subjects investigated. The AUC in plasma of KYN was significantly correlated with urinary KYN excretion within individuals, but not in the group as a whole. The data suggest that KYN was reabsorbed by renal tubules and that the degree of reabsorption was subject to large interindividual variation. The peak concentration in plasma of 3-HK occurred 11 min later than that of KYN. The results suggest that the net tubular effect on 3-HK was secretion. Pre-treatment with nicotinamide (0.5 g three times daily) resulted in considerable decreases in AUC in plasma, and in urinary excretion of KYN and 3-HK, indicating inhibition of liver tryptophan pyrrolase. The concomitant increase in AUC in plasma of free and total tryptophan was insignificant. As only a relatively small amount of tryptophan is catabolized by tryptophan pyrrolase following an L-tryptophan load, cautious interpretation is recommended of urinary KYN excretion as an indicator of tryptophan break down in investigation of different subjects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00637514
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  • 8
    Electronic Resource
    Electronic Resource
    Plasma amino acids as an index for subgroups in manic depressive psychosis: Correlation to effect of tryptophan (1976)
    Springer
    Psychopharmacology 49 (1976), S. 205-213 
    Details
    ISSN: 1432-2072
    Keywords: Tryptophan ; Depression ; Mania ; Plasma amino acids ; Competition ; Transport ; Kynurenine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Two biochemical distinct groups of manic depressive patients seem to be present. One group showed a normal pattern of plasma amino acids and was resistant to oral tryptophan medication. Another group, characterized by a relative deficiency of tryptophan in plasma as measured by the ratio of total plasma tryptophan to competing amino acids, responded readily to tryptophan treatment. No significant differences could be demonstrated in the free tryptophan, total tryptophan, percentage of free tryptophan or kynurenine in the plasma between patients and controls. The findings are discussed in view of changes in the transport conditions of tryptophan from plasma into the brain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00427292
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