Changes with aging in the levels of amino acids in rat CNS structural elements II. Taurine and small neutral amino acids

Taurine (Tau) and the small neutral amino acids glycine (Gly), serine (Ser), threonine (Thr), and alanine (Ala) were measured in 53 brain areas of 3- and 29-month-old male Fisher 344 rats. The ratio of highest to lowest level was 34 for Tau, 9.1 for Thr, 7.6 for Gly and Ser, and 6.5 for Ala. The heterogeneity was found in numerous areas; for example, Tau levels were more than 90 nmol/mg protein in 6 areas, and less than 20 nmol/mg protein in 10 areas. Similar heterogeneity was found with the other amino acids. The relative distribution of the small neutral amino acids showed several similarities; Tau distribution was different. With age, four amino acids decreased in 10–18 areas, and increased in only 1–3, while Thr increased in more areas than it decreased. The five amino acids of this paper, and the four of the previous paper, are among the amino acids at highest level in the brain; the sequence in their levels shows considerable regional heterogeneity.     

Changes in regional levels of putative neurotransmitter amino acids in brain under unilateral forebrain ischemia

The levels of the neurotransmitter amino acids glutamate, aspartate, and GABA were determined in different brain regions during ischemia and post-ischemic recirculation periods using the unilateral carotid artery occlusion model of stroke in gerbils. The levels of glutamate, aspartate and GABA in ischemic hemisphere were increased significantly by 10 min of ischemia and later declined with time. Reperfusion for 30 min following 10 min. of ischemia further enhanced the levels of glutamate and aspartate. Increase in GABA levels were found during early periods of reperfusion. Regional variations in the changes of amino acids' levels were noticed following ischemia. Hippocampus showed the highest increase in glutamate levels followed by striatum and cerebral cortex. Aspartate levels in striatum and hippocampus increased during 10 min ischemia (46% and 30%) and recirculation (70% and 79%), whereas in cerebral cortex the levels were doubled only during recirculation. Ischemia induced elevations of GABA levels were observed in cerebral cortex (68%) and in hippocampus (30%), and the levels were normalized during recirculation. No changes in GABA levels were found in striatum. It is suggested that the large increase in the levels of excitatory neurotransmitter amino acids in brain regions specially in hippocampus during ischemia and recirculation may be one of the causal factors for ischemic brain damage.     

Heterogeneous distribution of functionally important amino acids in brain areas of adult and aging humans

The regional distribution of seven amino acids thought to have inhibitory neurotransmitter or neurotransmitter precursor function—GABA, glycine, taurine, serine, threonine, phenylalanine, and tyrosine—was determined in 52 discrete areas from brain of adult and old humans. Significant heterogeneity was found, with 3- to 16-fold differences in levels in the various regions analyzed. The patterns of distribution were somewhat different from those in the adult or old rat brain. Relatively few changes were seen in old brain. Heterogeneity in distribution has to be taken into account in assessing physiological changes in amino acid levels and metabolism.Special issue dedicated to Dr. Claude Baxter.     

夏枯草属三种药用植物的氨基酸和微量元素

夏枯草属三种药用植物的氨基酸和微量元素王德贵,姚惠英,苏中武（第二军医大学药学院,上海２００４３３）Ａｎａｌｙｓｅｓｏｎｔｈｅａｍｉｎｏａｃｉｄｓａｎｄｔｒａｃｅｅｌｅｍｅｎｔｓｏｆ３ｓｐｅｃｉｅｓｏｆＰｒｕｎｅｌｌａ￥ＷａｎｇＤｅ－Ｇｕｉ;ＹａｏＨ...     

Molecular approach of gossypol-induced reproductive toxicity in male rabbits. Changes in seminal plasma amino acids and fatty acids

This study was done to evaluate the effects of two sublethal doses of gossypol (4 and 20 mg/kg of BW, every other day) on some amino and fatty acid concentrations in male rabbit seminal plasma. Rabbits were chosen as an experimental animal owing to the fact that they are excellent model for reproductive toxicological effects. The experiment lasted 16 weeks and included two periods: a treatment period (first 8 weeks) where the animals were given the tested product, and a recovery period (second 8 weeks) where all drugs were withdrawn. Results showed that total amino acids (TAA), total essential amino acids (EAA), total non-essential amino acids (non-EAA) and EAA/non-EAA ratio were decreased in a dose-dependent manner during gossypol treatment. The deleterious effect on TAA concentrations was mainly due to the reduction in total EAA. However, these concentrations regained their normal values after gossypol cessation. Basic, acidic, neutral amino acids and basic/acidic amino acids ratio decreased in a dose-dependent manner by gossypol treatment. Additionally, gossypol administration caused decreases in total unsaturated fatty acids (USFA) and increases in total saturated fatty acids (SFA) and the SFA/USFA ratio in a dose-dependent manner. During the recovery period, total SFA and USFA showed significant reduction and significant increase, respectively, after gossypol withdrawal. In conclusion, gossypol administration affected rabbit seminal plasma concentrations of amino and fatty acids in a dose-dependant manner. Gossypol reduced TAA, total EAA and total non-EAA. Additionally, gossypol caused decreases in total USFA and increases in total SFA. These deleterious effects were associated with poor-quality semen observed in our previous studies.     

Free amino acids in some sponges

Most invertebrates, particularly those of marine origin, have relatively high concentrations of free amino acids which are considered an important constituent of their osmoregulatory mechanisms [1]. Very little information is available on the free amino acid distribution in Porifera [2,3]. Common amino acids in some sponges were recognised by paper chromatography by Inskip and Cassidy [4] and Ackermann et al. [5,6] included a few sponges in their survey of the occurence of nitrogen compounds in marine invertebrates. More recently Bergquist and Hartman [7] surveyed semiquantitatively the distribution of free amino acids in several sponges. In the present paper we report on the amino acid composition of 12 species of sponges belonging to the class Demospongiae as a part of a study on the metabolites of Porifera [8]. Fresh sponges were extracted with aqueous ethanol. The organic solvent was removed and the aqueous solution, after removal of the ether soluble compounds, was separated into cationic, anionic and neutral fractions by ion-exchange chromatography. The cation fraction was analysed for amino acids using an automatic amino acid analyser. The results, which are presented in Table 1, show that all species of sponges examined have a similar composition in common amino acids. Glycine almost always appears as the dominant protein amino acid, followed by high concentrations of alanine and glutamic acid, whereas relatively lower concentrations of basic amino acids are present. In Axinella cannabina, Chondrosia reniformis, Chondrilla nucula, Cliona viridis and Hymeniacidon sanguinea, glycine represents more than 77% of the total amino acids. The high percentage of free glycine (90.4%) in Chondrosia reniformis is noteworthy. The anionic and the neutral fractions were examined for sulfur-containing amino acids using PC. Taurine (Table 2) was detected in all the Porifera examined; this is in agreement with previous observations [5–7]. N-Methyltaurine was identified in some of the species examined, whereas neither N,N-dimethyltaurine nor N,N,N-trimethyltaurine were found.     

Lipophilicity of amino acids

Summary The lipophilicity (or hydrophobicity) of amino acids is an important property relevant for protein folding and therefore of great interest in protein engineering. For peptides or peptidomimetics of potential therapeutic interest, lipophilicity is related to absorption and distribution, and thus indirectly relates to their bioactivity. A rationalization of peptide lipophilicity requires basic knowledge of the lipophilicity of the constituting amino acids. In the present contribution we will review methods to measure or calculate the lipophilicities of amino acids, including unusual amino acids, and we will make a comparison between various lipophilicity scales.     

Effect of nicotine on the level of extracellular amino acids in the hippocampus of rat

Using microdialysis, we compared intracerebral and subcutaneous administration of nicotine for the effect on the levels of extracellular amino acids in the hippocampus of anesthetized rats. Administration by microdialysis of 10 mM nicotine, resulting in a nicotine concentration of 0.134 μmol/g in the hippocampus, increased the extracellular levels of aspartic acid, glutamic acid, and serine by 26–60%. At 50 mM nicotine the increases in the levels of aspartic acid, glutamic acid, serine, glycine, and glutamine were between 76% and 141%. Subcutaneous administration of nicotine at a dose of 6 μmol/kg caused a 57% increase in the extracellular level of glutamic acid. After a dose of 12 μmol/kg that resulted in a nicotine level of 0.015 μmol/kg in the hippocampus, the extracellular level of glutamic acid was increased by 100%, and that of aspartic acid by 24%. Thus, higher cerebral nicotine levels were needed with intracerebral than with subcutaneous administration to obtain similar amino acid changes. Prior administration of mecamylamine or L-kynurenine prevented the subcutaneous nicotine-induced elevation of the extracellular levels of aspartic acid and glutamic acid. Our results indicate that receptor interactions modulate nicotine effects and that both nicotinic cholinergic and NMDA/glycine glutamatergic receptors participate in the action of nicotine in increasing extracellular amino acid levels.     

Changes in free amino acids and polyamine levels in Satsuma leaves in response to Asian citrus psyllid infestation and water stress

The effects of biotic and abiotic stresses on changes in amino acids and polyamine levels in Satsuma orange （Citrus unshiu; cultivar Owari） leaves were inves- tigated. Asian citrus psyllids Diaphorina citri （Kuwayama） （ACP） infestation was used to induce biotic stress while a water deficit was imposed to induce abiotic stress. Potted trees were infested by placing 50 psyllids on 3 citrus leaves enclosed in nylon mesh bags for 5 d. A parallel set of plants were kept water stressed by maintaining the soil at 20% water holding capacity for 5 d. Levels of total free amino acids were higher in water stressed and ACP infested leaves. Polyamine putrescine increased in infested leaves but not in water stressed leaves. Proline was the most abundant amino acid and its levels significantly increased by both biotic and abiotic stresses. Proline levels in infested leaves were significantly higher than the water stressed leaves. Histidine, methionine, asparagine, arginine, serine, and leucine levels also increased significantly in infested leaves, but in water stressed leaves only leucine, methionine, and threonine increased. Levels of amino acids, such as tyrosine, isoleucine, phenylalanine, glutamic acid, and alanine, declined in infested leaves. Under water stress asparagine, phenylalanine, serine, and histidine also declined compared to controls. This indicates that while proteolysis occurred under both stresses, metabolic conversion of amino acids was different under the two stresses. In ACP infested leaves some amino acids may be used as feeding material and/or converted into secondary metabolites for defense.     

Studies on the mechanism of induction of hypercholesterolemia in rabbits by high dietary levels of amino acids

Increasing the proportion of an amino acid mixture corresponding to casein in a low-fat, cholesterol-free, semipurified diet fed to rabbits causes a progressive increase in serum total and low density lipoprotein cholesterol, and the effect appears to be due primarily to the essential amino acids in the mixture. Our recent studies have also shown that the variations in serum cholesterol in response to different levels of the amino acid mixture are not associated with any changes in fecal excretion of cholesterol or bile acids. Further attempts to understand the mechanism of action of dietary amino acids on serum cholesterol levels have shown the following: (1) no correlation with levels of plasma amino acids, either in the fasting or postprandial state: (2) no correlation with serum levels of thyroid hormones: (3) no relationship to activity of hepatic or intestinal microsomal hydroxymethylglutaryl coenzyme A reductase: (4) no corresponding effects on the activities of cholesterol esterifying enzymes of intestinal mucosa: and (5) no correlation with the degree of esterification of cholesterol in very low or low density lipoproteins. Further studies are required to identify the specific amino acids responsible for the hypercholesterolemic effects and to determine the mechanisms involved.     

Effects of Ionotropic Excitatory Amino Acid Receptor Antagonists on Glutamate Transport and Transport-Mediated Changes in Extracellular Excitatory Amino Acids in the Rat Striatum

Abstract: This study examined the effects of intrastriatal administration of ionotropic excitatory amino acid receptor antagonists on biochemical markers of excitatory amino acid transmission in the rat striatum. High-affinity glutamate uptake was measured ex vivo on striatal homogenates 15 min after the local administration of either 6,7-dinitroquinoxaline-2,3-dione (DNQX), a non-NMDA receptor antagonist, or dl -2-amino-5-phosphonopentanoic acid (AP5), a competitive NMDA antagonist, at various doses (10–500 pmol injected). DNQX induced a dose-dependent increase in glutamate uptake rate, related to an increase in the V _max of the transport process, whereas no significant change in glutamate uptake was detected after AP5 administration. Similar results were obtained from animals subjected to excitotoxic lesion of striatal neurons by kainate administration 15 days before the injection of DNQX or AP5. In a parallel series of experiments using in vivo microdialysis we showed that DNQX (10⁻⁵ M ) in the dialysis probe diminished by ∼30–40% the increases in the concentrations of glutamate and aspartate elicited by l - trans -pyrrolidine-2,4-dicarboxylic acid (1 m M ). These data suggest that presynaptic glutamate transmission in the rat striatum may undergo facilitatory autoregulatory processes involving ionotropic non-NMDA receptors and highlight the view that transporters for glutamate may be potent regulatory sites for glutamatergic transmission.     

Regional alterations in brain amino acids during the estrous cycle of the rat

Concentrations of 11 amino acids, including the neurotransmitters GABA, glutamate, aspartate, glycine and taurine, were determined in 12 brain regions of female rats during different stages of the estrous cycle. In addition, amino acids and sex hormone levels were determined in plasma. All sample collections were done in the forenoon between 9 and 11 a.m. Most regional amino acid levels measured did not change signficantly during estrous cycle, but significant alterations were found for GABA and glutamate in hypothalamus. Both amino acids were slightly decreased in hypothalamus during proestrus, which might reflect an alteration of GABA turnover in response to the high estrogen levels during this stage. A decreased glutamate level during proestrus was also found in thalamus, while both glutamate and GABA did not vary throughout estrous cycle in any of the other examined regions, including substantia nigra, amygdala, striatum, cortex and hippocampus. When diestrus was subdivided according to progesterone levels, high levels of this hormone seemed to be associated with effects on metabolism of certain amino acids, including glycine in substantia nigra, alanine in thalamus and threonine in pons/medulla. However, the few changes in regional amino acid concentrations found during the estrous cycle were so small that the functional significance of these changes cannot be ascertained without further determination of the cellular or subcellular compartments of brain tissue involved.     

The contribution from the choroid plexus and the periventricular CNS to amino acids and proteins in the human CSF

During neurosurgery the freshly secreted extracellular fluid (ECF) from the choroid plexus was sampled with small pieces of application paper in three patients with intractable epilepsy. The samples were analyzed for free amino acids and for soluble proteins. The results were compared with corresponding data on extracellular fluid from the brain surface obtained with dialysis-perfusion as well as with the cerebrospinal fluid (CSF) acquired by lumbar punction. The dialysis data were calibrated against the paper results. The choroid plexus secretion had a high concentration of transthyretin as well as of an unidentified protein with an isoelectric point of 7.4. The cortical ECF exhibited high concentrations of tau-globulin and gamma-trace protein. Among the amino acids, glutamine had lower concentration in the choroid plexus secretion and higher concentrations in the ECF of the brain compared to the CSF. The amino acid derivative ethanolamine exhibited a similar pattern. This was interpreted to demonstrate that these compounds enter the CSF from the brain tissue. In contrast, alanine, serine, and taurine had a lower concentration in the CSF than in the plexus secretion which suggests that they are removed from the CSF by brain tissue.     

Sugar amino acids in designing new molecules

Emulating the basic principles followed by Nature to build its vast repertoire of biomolecules, organic chemists are developing many novel multifunctional building blocks and using them to create ‘nature-like’ and yet unnatural organic molecules. Sugar amino acids constitute an important class of such polyfunctional scaffolds where the carboxyl, amino and hydroxyl termini provide an excellent opportunity to organic chemists to create structural diversities akin to Nature’s molecular arsenal. This article describes some of our works on various sugar amino acids and many other related building blocks, like furan amino acids, pyrrole amino acids etc. used in wide-ranging peptidomimetic studies. Published in 2005.Based on the invited lecture presented at the XVII International Symposium on Glycoconjugates held in January 12–16, 2003 at Bangalore, India.     

Changes in the levels of plant total phenols and free amino acids induced by two cereal aphids and effects on aphid fecundity

Abstract:  Phenols and amino acids have previously been involved in the resistance of cereals to aphids. In the present study, the mean total concentrations of both compounds were quantitatively estimated from leaf-tissue samples collected at three growth stages (third, fifth and seventh leaf stages) from maize and barley seedlings and then correlated with the mean 7-day fecundity of Rhopalosiphum padi (L.) and Sitobion avenae (F.) (Homoptera, Aphididae) reared separately on the corresponding growth stages of each cereal. Results revealed an inverse correlation between the total concentration of each chemical in aphid-infested maize and barley plants and the fecundity of each aphid on every growth stage of the cereals. Moreover, R. padi led to an increase in total amino acids when reared on maize or barley without affecting the phenol concentration, while S. avenae induced a decrease in phenol levels but did not change the total amino acids on each growth stage of the plants. The significance of these results for understanding potential differences in requirements of cereal aphids for host selection and acceptance are discussed.     

天门冬属九种药用植物的氨基酸和微量元素分析

百合科(Liliaceae)天门冬属(Asparagus (Tourn.)L.)植物具有悠久的药用历史,如天门冬(A.cochinchinesis (Lour) Merr.)早在汉代《神农本草经》中就被列为上品,具有滋阴、润燥、降火、止咳等功效。现代药理研究及临     

Glutamate is the endogenous amino acid selectively released by rat hippocampal mossy fiber synaptosomes concomitantly with prodynorphin-derived peptides

The release of endogenous amino acids from depolarized rat hippocampal mossy fiber synaptosomes was investigated to assess the possible role(s) of glutamate and aspartate in mediating the excitatory mossy fiber synaptic input. The relative proportions of prodynorphin-derived peptides concomitantly released with amino acids were also determined to further characterize the biochemical basis for mossy fiber synaptic transmission. Of the 18 amino acids shown to be present in superfusate fractions by liquid chromatographic analysis, only glutamate was released at a significantly enhanced rate from K⁺-stimulated (35 mM KCl) mossy fiber nerve endings. The rates of glutamate and aspartate release were increased by 360±27% and 54±12% over baseline respectively. However, the K⁺-evoked release of glutamate was substantially more Ca²⁺-dependent (80%) than was the release of aspartate (49%). The veratridine (45 M)-evoked release of both acidic amino acids was entirely blocked by 1 M tetrodotoxin. Depolarization (45 mM KCl) also stimulated the release of the four prodynorphin (Dyn) products examined, in a rank order of Dyn B >> Dyn A(1–17) > Dyn A(1–8) >> Dyn A(1–13), with Dyn B efflux increasing by more than 5-fold over baseline values. These results suggest that the predominant excitatory amino acid in hippocampal mossy fiber synaptic transmission may be glutamate and that this synaptic input may be modulated by at least four different products of prodynorphin processing.The animals involved in this study were procured, maintained and used in accordance with the Animal Welfare Act and the Guide for the Care and Use of Laboratory Animals prepared by the Institute of Laboratory Animal Resources—National Research Council.     

Changes of plasma insulin, urea, amino acids and rumen metabolites in somatotropin treated dairy cows

Summary 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.     

Stereoselective routes towards the synthesis of unusual bis(amino acids) and cyclic amino acids

Stereoselective syntheses are described of bridged bis(glycines) as conformationally constrained substitutes for cystine, and of cyclic -amino acids where the -carbon of the amino acid is part of a five-, six- or seven-membered ring which may hold a hydroxy group as a threonine analogue.