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Amino Acids: The Forum for Amino Acid, Peptide and Protein Research (v.15, #3)

Changes of plasma insulin, urea, amino acids and rumen metabolites in somatotropin treated dairy cows by Dr. Federica Cheli; A. Baldi; L. Gregoretti; F. Rosi; D. Cattaneo; V. Dell'Orto (pp. 187-194).

An experiment was performed to evaluate the effects of somatotropin on plasma free amino acid, urea and insulin concentrations and rumen fermentation pattern and to assess their relationships. Four Italian Friesian dairy cows fitted with rumen cannulae were used in a switch-back design. Slow releasing recombinant bovine somatotropin (640 mg/cow) was injected every 28 days for two consecutive periods. Rumen fluid and blood samples were collected before and after feeding at 0, 7 and 21 days after rbST injection. Exogenous rbST increased plasma insulin concentration and the insulin response to feeding, and decreased plasma urea and free essential and branched chain amino acid concentrations. rbST did not affect rumen fermentation pattern. No correlation was found between rumen and plasma parameters measured after feeding. Our results are consistent with the notion that the main effect of somatotropin is post-absorptive.

Keywords: Amino acids; Somatotropin; Plasma amino acids; Dairy cows

Taurine, glutamate and GABA modulate the outgrowth from goldfish retinal explants and its concentrations are affected by the crush of the optic nerve by Dr. Lucimey Lima; F. Obregón; P. Matus (pp. 195-209).

The amino acid taurine plays an important trophic role during development and regeneration of the central nervous system. Other amino acid systems, such as those for glutamate and gamma-aminobutyric acid (GABA), are modified during the same physiological and pathological processes. After crushing the optic nerve, goldfish retinal explants were plated in the absence and in the presence of different amino acids and amino acid receptor agonists. The length and the density of the neurites were measured at 5 days in culture. Taurine increased the length and the density of neurites. Glutamate and glycine increased them at low concentration, but were inhibitors at higher concentration. The combination of N-methyl-D-aspartate (NMDA) and glycine produced a greater inhibitory effect than NMDA alone. NMDA or alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) added simultaneously with taurine impaired the stimulatory effect of the latter. GABA stimulated the emission of neurites in a concentration dependent manner. Hypotaurine also elevated the length of neurites, but cysteinesulfinic acid did not produce a significant effect. The concentrations of taurine, glutamate and GABA were determined by HPLC with fluorescent detection in the retina of goldfish at various days post-crushing the optic nerve. The levels of taurine were significantly increased at 48 h after the crush, and were elevated up to 20 days. Glutamate level decreased after the lesion of the optic nerve and was still low at 20 days. GABA concentration was not significantly different from the control. The interaction of these amino acids during the regenerative period, especially the balance between taurine and glutamate, may be a determinant in restoring vision after the crush.

Keywords: Amino acids; GABA; Glutamate; Outgrowth; Regeneration; Retina; Taurine

A comparative SAR study of thrombin receptor derived non peptide mimetics: Importance of phenyl/guanidino proximity for activity by Dr. Kostas Alexopoulos; Prof. John Matsoukas; T. Tsehos; P. Roumelioti; T. Mavromoustakos; K. Holada (pp. 211-220).

Thrombin, the most potent physiological platelet agonist interacts with cells through a specific G protein-coupled receptor which has been cloned and sequenced. Synthetic thrombin receptor peptides (TRAPS) comprising the first 5 amino acids (SFLLR and SFLLR-NH₂) of the new N-terminus tethered ligand of the thrombin receptor that is generated by thrombin's proteolytic activity were found to cause full platelet aggregation. During the screening of novel thrombin receptor derived non-peptide mimetics in the platelet aggregation assay we found that 1-phenylacetyl-4-(6-guanidohexanoyl)-piperazine (1) and 1-(6-guanidohexanoyl)-4-(phenylacetylamidomethyl)-piperidine (2) exertedin vitro antagonist activities (56% and 40% correspondingly) as it is depicted by the platelet aggregation assay. Using Molecular Modeling, the synthetic compounds were overlayed with SFFLR. All three superimposed low energy structures had Phe and Arg aminoacids in spatial close proximity. The superimposition results revealed that1 resembled more the stereoelectronic environment of SFLLR than2. This difference may be related to their different antagonist efficacy.

Keywords: Amino acids; Thrombin; Tethered ligand; TRAPs; Peptide mimetics; Platelet aggregation

Maximal growth occurs at a broad range of essential amino acids to total nitrogen ratios in kittens by T. P. Taylor; J. G. Morris; P. H. Kass; Quinton R. Rogers (pp. 221-234).

Kittens fed diets containing 2.0 and 3.0 times (X) the NRC (1986) essential amino acid (EAA) requirement (EAArq) and 210 to 560g crude protein (CP)/kg diet had growth rates and plasma amino acid patterns that were not significantly different than kittens fed a control diet (CD) containing 1.5 X EAArq and 350 g CP/kg diet. Growth rates of kittens fed diets containing only EAA (with nontoxic levels of arginine and methionine) and 280 to 460 g CP/kg diet were equivalent to those of kittens fed CD. Kittens fed only EAA and 140 and 210 g CP/kg diet had growth rates that were significantly lower than kittens fed CD. Since the growth rate of kittens fed 1.5X EAArq and 210 g CP/kg diet in a previous experiment was equivalent to kittens fed CD (Taylor et al., 1997), it is suggested that the requirement for CP is higher (up to 280 g CP/kg diet) when only EAA are fed. The higher crude protein requirement appears to be primarily a consequence of the high obligatory nitrogen loss as urea (especially from arginine) incurred in the conversion of nitrogen from EAA to dispensable amino acids in the liver and secondarily because of a slow rate of catabolism of the EAA. A 3-dimensional plot of weight gains vs. CP levels and EAA to total nitrogen (E: T) ratios of kittens shows a broad range of CP levels and E: T ratios that support optimal growth in the kitten. It is suggested that similar patterns would occur in the chick, rat and other species if adverse effects caused by excesses of specific amino acids are avoided.

Total plasma homocysteine as part of the routine aminogram by ion-exchange chromatography by A. Briddon (pp. 235-239).

Ion-exchange chromatography (IEC) with ninhydrin post-column derivatisation is the only technique available for the assay of total, (free plus bound), cysteine and homocysteine which also enables the routine measurement of all other commonly occurring amino acids. IEC assay of total cysteine and homocysteine typically involves incubating buffered plasma for 60 minutes at 37°C with dithiothreitol (DTT), but these assay conditions significantly extend total analysis time and compromise other amino acid values, notably glutamine and glutamate. However, it is possible to carry out the DTT reduction in plasma virtually instantaneously and without additional buffering, thus preserving the integrity of other diagnostically important amino acids. Assay precision is adequate for cardiovascular risk assessment.

Keywords: Amino acids; Homocysteine; Ion-exchange chromatography; Analysis

Effect of regular training on the myocardial and plasma concentrations of taurine andα-amino acids in thoroughbred horses by N. King; Dr. M. -S. Suleiman (pp. 241-251).

Exercise induces significant changes in the free intracellular amino acid pool in skeletal muscle but little is known of whether such changes also occur in cardiac muscle. In this study the effect of regular exercise on the size and the constituents of the free amino acid pool in the hearts and in the plasma of thoroughbred horses was investigated. The total free intracellular amino acid pool in the hearts of control horses was 30.9 ± 1.2μmol/g wet weight (n = 6). Glutamine but not taurine was present at the highest concentration (13.5 ± 0.9 and 7.7 ± 0.69μmol/g wet weight for glutamine and taurine respectively). As for the rest of the amino acids in the pool, only glutamate and alanine were present at levels greater than 1μmol/g wet weight (4.6 ± 0.25 and 1.7 ± 0.14 for glutamate and alanine respectively). The tissue to plasma ratio was highest for taurine at 155, followed by glutamate at 111, aspartate and glutamine at 37, alanine at 5.8 and ratios of less than 3 for the rest of the amino acids. The total free intracellular amino acid pool in the hearts of exercised horses was slightly but not significantly lower than control (28.1 ±1.1μmol/g wet weight, n = 6). Regular exercise increased the intracellular concentration of threonine, valine, isoleucine, leucine and phenylalanine but was only significant (p < 0.05) for threonine. This work has documented the profile of taurine and protein amino acids in the heart and in the plasma of thoroughbred horses and showed that in contrast to skeletal muscle, heart muscle does not show major changes in amino acids during regular exercise.

Keywords: Amino acids; Taurine; Protein amino acids; Thoroughbred horses; Heart; Plasma

Glycerol affects the quantification of aspartate and glutamate in acid-hydrolyzed proteins by J. -F. Juranville; B. Pöschl; G. Oesterhelt; H. -J. Schönfeld; M. Fountoulakis (pp. 253-262).

Glycerol is widely used in protein isolation pathways to improve folding and solubility of the proteins of interest. Amino acid composition analysis of protein samples hydrolyzed in the presence of glycerol resulted in underestimation of aspartate and glutamate, when compared to hydrolysis in the absence of glycerol. Quantification of free asparagine, aspartic acid, glutamine and glutamic acid hydrolyzed with hydrochloric acid or methanesulfonic acid in the presence of glycerol resulted in poor recoveries of aspartate and glutamate (between 6 and 66%). Gas chromatography-mass spectrometry analysis of the hydrolyzates revealed, as expected, the presence of esterification products. The esters were formed between the primary and secondary hydroxyl groups of the glycerol and both carboxyl groups of the amino acids. Protein samples intended for compositional analysis should be free of glycerol.

Keywords: Amino acid analysis; Hydrolysis; Glycerol; Aspartate; Glutamate; Protein quantification

Free D- and L-amino acids in ventricular cerebrospinal fluid from Alzheimer and normal subjects by G. Fisher Ph.D.; N. Lorenzo; H. Abe; E. Fujita; W. H. Frey; C. Emory; M. M. Di Fiore; A. D'Aniello (pp. 263-269).

Free D-Ser, D-Asp and total D-amino acids were significantly higher (p < 0.05) in Alzheimer (AD) ventricular CSF than in normal CSF. There was no significant difference in the total L-amino acids between AD and normal CSF, but L-Gln and L-His were significantly higher (p < 0.05) in ADCSF. The higher concentrations of these D- and L-amino acids in AD ventricular CSF could reflect the degenerative process that occurs in Alzheimer's brain since ventricular CSF is the repository of amino acids from the brain.

Keywords: D- and L-Amino acids; Cerebrospinal fluid; Ventricular CSF; Alzheimer's disease

Evaluation of ancient diet: Dietary tracing by stable isotope analysis of consumer tissues by S. M. M. Young; N. J. van der Merwe (pp. 271-290).

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Amino Acids: The Forum for Amino Acid, Peptide and Protein Research (v.15, #3)

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Amino Acids: The Forum for Amino Acid, Peptide and Protein Research (v.15, #3)