Showing papers in "Amino Acids in 2005"
TL;DR: One of the most promising research directions deals with the administration of citrulline as a more efficient alternative to arginine, especially against underlying splanchnic sequestration of amino acids.
Abstract: Citrulline (Cit, C6H13N3O3), which is a ubiquitous amino acid in mammals, is strongly related to arginine. Citrulline metabolism in mammals is divided into two fields: free citrulline and citrullinated proteins. Free citrulline metabolism involves three key enzymes: NO synthase (NOS) and ornithine carbamoyltransferase (OCT) which produce citrulline, and argininosuccinate synthetase (ASS) that converts it into argininosuccinate. The tissue distribution of these enzymes distinguishes three “orthogonal” metabolic pathways for citrulline. Firstly, in the liver, citrulline is locally synthesized by OCT and metabolized by ASS for urea production. Secondly, in most of the tissues producing NO, citrulline is recycled into arginine via ASS to increase arginine availability for NO production. Thirdly, citrulline is synthesized in the gut from glutamine (with OCT), released into the blood and converted back into arginine in the kidneys (by ASS); in this pathway, circulating citrulline is in fact a masked form of arginine to avoid liver captation. Each of these pathways has related pathologies and, even more interestingly, citrulline could potentially be used to monitor or treat some of these pathologies. Citrulline has long been administered in the treatment of inherited urea cycle disorders, and recent studies suggest that citrulline may be used to control the production of NO. Recently, citrulline was demonstrated as a potentially useful marker of short bowel function in a wide range of pathologies. One of the most promising research directions deals with the administration of citrulline as a more efficient alternative to arginine, especially against underlying splanchnic sequestration of amino acids. Protein citrullination results from post-translational modification of arginine; that occurs mainly in keratinization-related proteins and myelins, and insufficiencies in this citrullination occur in some auto-immune diseases such as rheumatoid arthritis, psoriasis or multiple sclerosis.
497 citations
TL;DR: In this review, pathways leading to the formation of individual protein-bound lysine and arginine derivatives in foods are described and nutritional consequences resulting from this posttranslational modifications of food proteins are discussed.
Abstract: The Maillard reaction or nonenzymatic browning is of outstanding importance for the formation of flavour and colour of heated foods. Corresponding reactions, also referred to as "glycation", are known from biological systems, where the formation of advanced glycation endproducts (AGEs) shall play an important pathophysiological role in diabetes and uremia. In this review, pathways leading to the formation of individual protein-bound lysine and arginine derivatives in foods are described and nutritional consequences resulting from this posttranslational modifications of food proteins are discussed.
236 citations
TL;DR: High success rates were obtained by both the jackknife cross-validation test and independent dataset test, suggesting that introduction of the concept of the complexity measure into prediction of protein subcellular location is quite promising, and might also hold a great potential as a useful vehicle for the other areas of molecular biology.
Abstract: Recent advances in large-scale genome sequencing have led to the rapid accumulation of amino acid sequences of proteins whose functions are unknown. Because the functions of these proteins are closely correlated with their subcellular localizations, it is vitally important to develop an automated method as a high-throughput tool to timely identify their subcellular location. Based on the concept of the pseudo amino acid composition by which a considerable amount of sequence-order effects can be incorporated into a set of discrete numbers (Chou, K. C., Proteins: Structure, Function, and Genetics, 2001, 43: 246-255), the complexity measure approach is introduced. The advantage by incorporating the complexity measure factor as one of the pseudo amino acid components for a protein is that it can more effectively reflect its overall sequence-order feature than the conventional correlation factors. With such a formulation frame to represent the samples of protein sequences, the covariant-discriminant predictor (Chou, K. C. and Elrod, D. W., Protein Engineering, 1999, 12: 107-118) was adopted to conduct prediction. High success rates were obtained by both the jackknife cross-validation test and independent dataset test, suggesting that introduction of the concept of the complexity measure into prediction of protein subcellular location is quite promising, and might also hold a great potential as a useful vehicle for the other areas of molecular biology.
169 citations
TL;DR: Three pseudo amino acid components are introduced via Lyapunov index, Bessel function, Chebyshev filter that can be more efficiently used to deal with the chaos and complexity in protein sequences, leading to a higher success rate in predicting protein subcellular location.
Abstract: With the avalanche of new protein sequences we are facing in the post-genomic era, it is vitally important to develop an automated method for fast and accurately determining the subcellular location of uncharacterized proteins. In this article, based on the concept of pseudo amino acid composition (Chou, K.C. Proteins: Structure, Function, and Genetics, 2001, 43: 246–255), three pseudo amino acid components are introduced via Lyapunov index, Bessel function, Chebyshev filter that can be more efficiently used to deal with the chaos and complexity in protein sequences, leading to a higher success rate in predicting protein subcellular location.
131 citations
TL;DR: With biological sequences entering into databanks rapidly increasing in the post-genomic era, it is anticipated that the cellular automata image will become a very useful vehicle for investigation into their key features, identification of their function, as well as revelation of their “fingerprint”.
Abstract: A novel approach to visualize biological sequences is developed based on cellular automata (Wolfram, S. Nature 1984, 311, 419–424), a set of discrete dynamical systems in which space and time are discrete. By transforming the symbolic sequence codes into the digital codes, and using some optimal space-time evolvement rules of cellular automata, a biological sequence can be represented by a unique image, the so-called cellular automata image. Many important features, which are originally hidden in a long and complicated biological sequence, can be clearly revealed thru its cellular automata image. With biological sequences entering into databanks rapidly increasing in the post-genomic era, it is anticipated that the cellular automata image will become a very useful vehicle for investigation into their key features, identification of their function, as well as revelation of their “fingerprint”. It is anticipated that by using the concept of the pseudo amino acid composition (Chou, K.C. Proteins: Structure, Function, and Genetics, 2001, 43, 246–255), the cellular automata image approach can also be used to improve the quality of predicting protein attributes, such as structural class and subcellular location.
120 citations
TL;DR: The structural element of alicyclic β-amino acids shows some remarkable biological effects: for some 5- and 6-membered β- amino acids a unique anti fungal activity has been observed, and 7- Membered β -amino acid derivatives have been investigated for neurological disorders.
Abstract: The structural element of alicyclic β-amino acids shows some remarkable biological effects: For some 5- and 6-membered β-amino acids a unique anti fungal activity has been observed, 7-membered β-amino acid derivatives have been investigated for neurological disorders. The application of 5-, 6- and 7-membered alicyclic β-amino acids in Medicinal Chemistry will be reported.
109 citations
TL;DR: The ACT domain appears to have been incorporated as a handy, flexible small module with the potential to provide allosteric regulation via transmission of finely tuned conformational changes, not necessarily initiated by regulatory ligand binding at the domain itself.
Abstract: An important sequence motif identified by sequence analysis is shared by the ACT domain family, which has been found in a number of diverse proteins. Most of the proteins containing the ACT domain seem to be involved in amino acid and purine synthesis and are in many cases allosteric enzymes with complex regulation enforced by the binding of ligands. Here we explore the current understanding of the ACT domain function including its role as an allosteric module in a selected group of enzymes. We will further describe in more detail three of the proteins where some understanding is available on function and structure: i) the archetypical ACT domain protein E. coli 3PGDH, which catalyzes the first step in the biosynthesis of L-Ser, ii) the bifunctional chorismate mutase/prephenate dehydratase (P-protein) from E. coli, which catalyzes the first two steps in the biosynthesis of L-Phe, and iii) the mammalian aromatic amino acid hydroxylases, with special emphasis on phenylalanine hydroxylase, which catalyzes the first step in the catabolic degradation of L-phenylalanine (L-Phe). The ACT domain is commonly involved in the binding of a small regulatory molecule, such as the amino acids L-Ser and L-Phe in the case of 3PGDH and P-protein, respectively. On the other hand, for PAH, and probably for other enzymes, this domain appears to have been incorporated as a handy, flexible small module with the potential to provide allosteric regulation via transmission of finely tuned conformational changes, not necessarily initiated by regulatory ligand binding at the domain itself.
81 citations
TL;DR: This review covers the literature relating to asymmetric syntheses of pipecolic acid derivatives from 1997 to present and is organized according to the position and the degree of substitution of the piperidinic cycle.
Abstract: This review covers the literature relating to asymmetric syntheses of pipecolic acid derivatives from 1997 to present. This review is organized according to the position and the degree of substitution of the piperidinic cycle. In a first section, syntheses of pipecolic acid itself are described. Then, successively, syntheses of C-3, C-4, C-5, C-6 substituted pipecolic acid derivatives are reported. Finally, syntheses of unsaturated pipecolic acid derivatives are presented before the last part devoted to the polysubstituted pipecolic acid derivatives.
77 citations
TL;DR: The newest findings demonstrate that L-DOPA induces BDNF release from corticostriatal fibers, which in-turn enhances the expression of D3 receptors; and that this effect is associated with motor dyskinesias (and it is blocked by D3 antagonists).
Abstract: L-Dihydroxyphenylalanine (L-DOPA), the anti-parkinsonian drug affording the greatest symptomatic relief of parkinsonian symptoms, is still misunderstood in terms of its neurotoxic potential and the mechanism by which generated dopamine (DA) is able to exert an effect despite the absence of DA innervation of target sites in basal ganglia. This review summaries important aspects and new developments on these themes. On the basis of L-DOPA therapy in animal models of Parkinson’s disease, it appears that L-DOPA is actually neuroprotective, not neurotoxic, as indicated by L-DOPA’s reducing striatal tissue content of the reactive oxygen species, hydroxyl radical (HO•), and by leaving unaltered the extraneuronal in vivo microdialysate level of HO•. In addition, the potential beneficial anti-parkinsonian effect of L-DOPA is actually increased because of the fact that the basal ganglia are largely DA-denervated. That is, from in vivo microdialysis studies it can be clearly demonstrated that extraneuronal in vivo microdialysate DA levels are actually higher in the DA-denervated vs. the intact striatum of rats – owing to the absence of DA transporter (i.e., uptake sites) on the absent DA nerve terminal fibers in parkinsonian brain. In essence, there are fewer pumps removing DA from the extraneuronal pool. Finally, the undesired motor dyskinesias that commonly accompany long-term L-DOPA therapy, can be viewed as an outcome of L-DOPA’s sensitizing DA receptors (D1–D5), an effect easily replicated by repeated DA agonist treatments (especially agonist of the D2 class) in animals, even if the brain is not DA-denervated. The newest findings demonstrate that L-DOPA induces BDNF release from corticostriatal fibers, which in-turn enhances the expression of D3 receptors; and that this effect is associated with motor dyskinesias (and it is blocked by D3 antagonists). The recent evidence on mechanisms and effects of L-DOPA increases our understanding of this benefical anti-parkinsonian drug, and can lead to improvements in L-DOPA effects while providing avenues for reducing or eliminating L-DOPA’s deleterious effects.
65 citations
TL;DR: It is demonstrated that when the fenugreek extract supplement (4-OH-Ile) is added to a high oral dose of dextrose, rates of post-exercise glycogen resynthesis are enhanced abovedextrose alone.
Abstract: The purpose of this study was to determine the effects of ingesting an oral supplement containing 4-Hydroxyisoleucine (4-OH-Ile, isolated from fenugreek seeds [Trigonella foenum-graecum]) with a glucose beverage on rates of post-exercise muscle glycogen resynthesis in trained male cyclists. Following an overnight fast (12 hr), subjects completed a 90-minute glycogen depletion ride after which a muscle biopsy was obtained from the vastus lateralis. Immediately and 2 hours after the muscle biopsy, subjects ingested either an oral dose of dextrose (Glu) (1.8 g·kg BW−1) or 4-OH-Ile supplement (Glu+4-OH-Ile, including 2.0 mg·kg−1 4-OH-Ile with the same oral dose of dextrose) with a second muscle biopsy 4 hours after exercise. Post exercise muscle glycogen concentration was similar for both trials. Overall, there was a significant increase in glucose and insulin concentrations from time 0 throughout the majority of the 4-hour recovery period, with no significant differences between the two trials at any time point. Although muscle glycogen concentration significantly increased from immediately post exercise to 4 hr of recovery for both trials, the net rate of muscle glycogen resynthesis was 63% greater during Glu+4-OH-Ile (10.6±3.3 vs. 6.5±2.6 g·kg wet wt.−1·hr.−1 for the Glu+4-OH-Ile and Glu trials, respectively). These data demonstrate that when the fenugreek extract supplement (4-OH-Ile) is added to a high oral dose of dextrose, rates of post-exercise glycogen resynthesis are enhanced above dextrose alone.
61 citations
TL;DR: The enzymes responsible for protein methylation by S-adenosylmethionine, both at the carboxyl groups and at the nitrogen groups, are reviewed.
Abstract: The enzymes responsible for protein methylation by S-adenosylmethionine, both at the carboxyl groups and at the nitrogen groups, are reviewed. The possibility that the reactions involved may be reversible is also considered.
TL;DR: This paper reviews literature concerning amino acids production by nitrogen-fixing bacteria and the role of amino acids in microbial interactions in the rhizosphere and establishment of plant bacterial association is discussed.
Abstract: Large amounts of amino acids are produced by nitrogen-fixing bacteria such as Azotobacter, Azospirillum, Rhizobium, Mesorhizobium and Sinorhizobium when growing in culture media amended with different carbon and nitrogen sources. This kind of bacteria live in close association with plant roots enhanced plant growth mainly as a result of their ability to fix nitrogen, improving shoot and root development suppression of pathogenic bacteria and fungi, and increase of available P concentration. Also, it has been strongly evidenced that production of biologically substances such as amino acids by these rhizobacteria are involved in many of the processes that explain plant-grown promotion. This paper reviews literature concerning amino acids production by nitrogen-fixing bacteria. The role of amino acids in microbial interactions in the rhizosphere and establishment of plant bacterial association is also discussed.
TL;DR: The novel action of nefopam may be important both for its central analgesic effects and for its potential therapeutic use in neurological and neuropsychiatric disorders involving an excessive glutamate release.
Abstract: Nefopam hydrochloride is a potent non sedative benzoxazocine analgesic that possesses a profile distinct from that of anti-inflammatory drugs. Previous evidence suggested a central action of nefopam but the detailed mechanism remains unclear. We have investigated the actions of nefopam on voltage sensitive calcium channels and calcium-mediated pathways. We found that nefopam prevented N-methyl-D-aspartate (NMDA)-mediated excitotoxicity following stimulation of L-type voltage sensitive calcium channels by the specific agonist BayK8644. Nefopam protection was concentration-dependent. 47 μM nefopam provided 50% protection while full neuroprotection was achieved at 100 μM nefopam. Neuroprotection was associated with a 73% reduction in the BayK8644-induced increase in intracellular calcium concentration. Nefopam also inhibited intracellular cGMP formation following BayK8644 in a concentration-dependent manner, 100 μM nefopam providing full inhibition of cGMP synthesis and 58 μM allowing 50% cGMP formation. Nefopam reduced NMDA receptor-mediated cGMP formation resulting from the release of glutamate following activation of channels by BayK8644. Finally, we also showed that nefopam effectively reduced cGMP formation following stimulation of cultures with domoic acid, while not providing neuroprotection against domoic acid. Thus, the novel action of nefopam we report here may be important both for its central analgesic effects and for its potential therapeutic use in neurological and neuropsychiatric disorders involving an excessive glutamate release.
TL;DR: The findings in the rat intestinal mucosa indicate that LAT1 protein is most abundant in the colon and its abundance markedly decreases at the level of jejunum and ileum, which contrast with relative homogeneous presence of LAT2 across the digestive tract.
Abstract: The present study evaluated the presence of LAT1 and LAT2 amino acid transporters in human Caco-2 cells and rat IEC-6 cells along the mucosa of the rat digestive tract. The LAT1 cDNA was amplified by PCR using two sets of primers (one specific for rat LAT1 and another simultaneously specific for human, rat and mice). The LAT2 cDNA was amplified by PCR using one set of primers simultaneously specific for human, rat and mice LAT2. The presence of LAT1 and LAT2 protein was examined by means of immunoblotting using an antibody raised against the rat LAT1 and mouse LAT2. Caco-2 and IEC-6 cells, as well as the rat intestinal mucosa, are endowed with both LAT1 and LAT2 transporter transcripts and protein. LAT1 protein is most abundant in IEC-6 cells, which is in agreement with functional data previously reported. The findings in the rat intestinal mucosa indicate that LAT1 protein is most abundant in the colon and its abundance markedly decreases at the level of jejunum and ileum, which contrast with relative homogeneous presence of LAT2 across the digestive tract. In conclusion, Caco-2 and IEC-6 cells, as well as the rat intestinal mucosa, are endowed with both LAT1 and LAT2 amino acid transporter transcripts and protein.
TL;DR: The distribution volume of alanyl-glutamine was larger than the extracellular water volume, indicating a rapid hydrolysis of the dipeptide, and the renal clearance of alanine, glutamine and glutamate were not different between the two groups.
Abstract: A randomised, double blind, placebo-controlled study was performed giving 0.5 g x kg(-1) x day(-1) of undiluted alanyl-glutamine (20%) or saline in a peripheral vein during 4 hours in ICU patients (n = 20). During the infusion period a steady state in plasma concentration was reached for alanyl-glutamine, but not for alanine, glutamine or glutamate. On the other hand there was no accumulation of any of the amino acids, as the pre-infusion concentrations were reached within 8 hours after the end of infusion. The half-life of the dipeptide was 0.26 hours (range, 0.15-0.63 h). The distribution volume of alanyl-glutamine was larger than the extracellular water volume, indicating a rapid hydrolysis of the dipeptide. There was no detectable alanyl-glutamine in the urine of any of the patients. All patients had excretion of small amounts of amino acids in urine, but the renal clearance of alanine, glutamine and glutamate were not different between the two groups.
TL;DR: A lack of correlation with Hcy was observed, thus minimizing the direct role of Hcy on ADMA and SDMA metabolism and suggesting the need for further studies on this issue.
Abstract: The aim of this study was to investigate the possible relationship among dimethylarginines (asymmetric, ADMA; symmetric, SDMA) and homocysteine (Hcy) levels in subjects affected by chronic, mild to intermediate, hyperhomocysteinemia. ADMA and SDMA were assayed by an optimised HPLC method in 75 patients (Hcy = 20.8 μmol/L, 17.1–30.2; median and percentile range) and, for comparison, in 85 healthy subjects (Hcy = 8.0 μmol/L, 7.0–9.1). In controls, the cut-off values were set at 0.61 μmol/L for ADMA and 0.56 or 0.48 μmol/L for male and female SDMA, respectively. In patients, ADMA and SDMA levels were increased (p<0.001) with respect to controls, but no correlation with Hcy was observed. Hyperhomocysteinemic subjects showed a different behaviour in respect to ADMA and SDMA levels and this allowed their stratification in 3 subgroups characterized by ADMA and SDMA in the normal range, only SDMA, or both ADMA and SDMA over the cut-off values. A lack of correlation with Hcy was again observed, thus minimizing the direct role of Hcy on ADMA and SDMA metabolism and suggesting the need for further studies on this issue.
TL;DR: It is predicted that PEG-PAL conjugate will be an effective therapeutic enzyme for the treatment of PKU, and the low stability in the circulation and the antigenicity of the plant enzyme will be the problems.
Abstract: Phenylketonuria (PKU) is an autosomal recessive genetic disease caused by the defects in the phenylalanine hydroxylase (PAH) gene. Individuals homozygous for defective PAH alleles show elevated levels of systemic phenylalanine and should be under strict dietary control to reduce the risk of neuronal damage associated with high levels of plasma phenylalanine. Researchers predict that plant phenylalanine ammonia-lyase (PAL), which converts phenylalanine to nontoxic t-cinnamic acid, will be an effective therapeutic enzyme for the treatment of PKU. The problems of this potential enzyme therapy have been the low stability in the circulation and the antigenicity of the plant enzyme. Recombinant PAL originated from parsley (Petroselinum crispum) chemically conjugated with activated PEG2 [2,4-bis(O-methoxypolyethyleneglycol)-6-chloro-s-triazine] showed greatly enhanced stability in the circulation and was effective in reducing the plasma concentration of phenylalanine in the circulation of mice. PEG-PAL conjugate will be an effective therapeutic enzyme for the treatment of PKU.
TL;DR: At small false positive ratios, the method outperforms the classical weight matrix method, indicating the current approach may at least serve as a powerful complemental tool to other existing methods for predicting the signal peptide cleavage site.
Abstract: Owing to the importance of signal peptides for studying the molecular mechanisms of genetic diseases, reprogramming cells for gene therapy, and finding new drugs for healing a specific defect, it is in great demand to develop a fast and accurate method to identify the signal peptides. Introduction of the so-called {-3,-1, +1} coupling model (Chou, K. C.: Protein Engineering, 2001, 14-2, 75-79) has made it possible to take into account the coupling effect among some key subsites and hence can significantly enhance the prediction quality of peptide cleavage site. Based on the subsite coupling model, a kind of string kernels for protein sequence is introduced. Integrating the biologically relevant prior knowledge, the constructed string kernels can thus be used by any kernel-based method. A Support vector machines (SVM) is thus built to predict the cleavage site of signal peptides from the protein sequences. The current approach is compared with the classical weight matrix method. At small false positive ratios, our method outperforms the classical weight matrix method, indicating the current approach may at least serve as a powerful complemental tool to other existing methods for predicting the signal peptide cleavage site. The software that generated the results reported in this paper is available upon requirement, and will appear at http://www.pami.sjtu.edu.cn/wm.
TL;DR: The calibration performed with saliva samples spiked with thiol disulfides, within the practical concentration ranges, showed linear response of the detector.
Abstract: A method for simultaneous determination of glutathione and its precursors cysteine, cysteinylglycine and homocysteine in saliva is presented. The procedure involves reductive conversion of disulfides to thiols, derivatization to their 2-S-quinolinium derivatives with 2-chloro-1-methylquinolinium tetrafluoroborate and separation and quantitation by reversed-phase ion-pairing high performance liquid chromatography with ultraviolet detection at 355 nm. The calibration performed with saliva samples spiked with thiol disulfides, within the practical concentration ranges, showed linear response of the detector. The method applied to the saliva samples donated by volunteers showed mean concentration (SD, n = 8) of cysteine, cysteinylglycine, glutathione and homocysteine: 26.5 (31.6), 6.05 (5.12), 16.97 (7.68), 3.64 (1.34) nmol/ml respectively.
TL;DR: By taking care of the biological and technical validity of this biomarker it is possible to establish the antioxidant effects of some food ingredients in studies with human volunteers.
Abstract: Isoprostanes, non-enzymatic peroxidation products of arachidonic acid, are attractive biomarkers of oxidative stress in research in biology, medicine and nutrition. For the appropriate use of biomarkers it is required that these are both biologically and technically valid. Whereas the biological validity of isoprostanes is well-established, it is technically quite complicated to measure isoprostanes and its metabolites in body fluids, and its rapid disappearance from plasma may hamper practical application. This paper shortly introduces isoprostanes as a biomarker for studies with humans, describes a novel fast and sensitive method for measuring isoprostanes in plasma by high-performance liquid chromatography and tandem mass spectrometry, and provides several examples of the use of the method in studies in humans. By taking care of the biological and technical validity of this biomarker it is possible to establish the antioxidant effects of some food ingredients in studies with human volunteers.
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TL;DR: Its effect on emotional arousal and its anti-conflict potencies are synergistic with the anxiolytic drug diazepam, and such acidic peptides through N-methyl-D-aspartic acid receptors could be part of the neurochemical substrate underlying self-stimulation of the medial prefrontal cortex.
Abstract: The discovery of the dipeptide γ-glutamyltaurine (γ-GT; glutaurine, Litoralon) in the parathyroid in 1980 and later in the brain of mammals gave rise to studies on intrinsic and synthetic taurine peptides of this type. It was suggested that γ-glutamyltransferase (GGT; γ-glutamyltranspeptidase) in the brain is responsible for the in vivo formation of this unusual dipeptide. γ-GT has been prepared by both synthetic and enzymatic methods. The chemical syntheses included the use of protecting groups and coupling methods. A wide spectrum of analytical and spectroscopic methods was used to confirm the structure of the synthetic compounds and to elucidate the position of the peptide bond. Enzymatic preparation of γ-GT from taurine takes advantage of the selective transpeptidation action of GGT on L-glutamine, glutathione, γ-glutamyl-p-nitroanilide or other glutamine donors. Although the functional roles of γ-GT in the brain are only poorly understood, many of its established CNS effects have been reported in the last 25 years. Its effect on emotional arousal and its anti-conflict potencies are synergistic with the anxiolytic drug diazepam. γ-GT exhibits anti-conflict potency, which is exerted by reducing aversion or phobia and/or the anxiety levels. γ-GT also acts as endogenous modulator in excitatory aminoacidergic neurotransmission. It is suggested that such acidic peptides through N-methyl-D-aspartic acid receptors could be part of the neurochemical substrate underlying self-stimulation of the medial prefrontal cortex. Other γ-GT effects in neural systems include: effects on the monoamine concentration in the brain; effects on aggressive behavior in the cat; effects on thyroid hormones in the rat; amelioration of electroshock-induced amnesia; potent and long-lasting antiepileptic action (on intra-amygdaloid injection); affect the glutamatergic system in schizophrenic disorders. Roles for γ-GT in non-neural systems have also been reported, e.g., effects on the metamorphosis of amphibians; on plasma rennin regulation; on radiation protection; on uric acid levels; on human antibody-dependent cell-mediated cytotoxicity (ADCC) and many more.
TL;DR: The p21WAF1/CIP1 gene should be further taken into consideration as a potential marker, the up-regulation of which in circulating leukocytes of vasospastic individuals may indicate an increased risk for the developing glaucoma.
Abstract: Objective: Vascular disorder leading to local ischemia/reperfusion has been shown to play an important role in the glaucomatous damage. A decreased expression level of XPGC-gene has been found in circulating leukocytes of normal-tension glaucoma patients. Although decreased activity of XPGC-gene leads to insufficient DNA-repair, no leukopenia has been observed in glaucoma. Molecular mechanisms ensuring cell survival have not been elucidated yet for glaucoma with vascular disorder.
TL;DR: The results indicate that a very low dose of DOM produces a conditioned odour preference in neonatal rats and that this effect is due in part to NMDA receptor involvement, thereby emphasizing a role for both kainate and NMDA glutamate receptors in implicit memory.
Abstract: We have previously reported that neonatal rats display enhanced sensitivity to domoic acid relative to adults, and that perinatal injections of low doses of domoic acid alter early associational learning in the newborn rat. The current study was designed to further investigate the effects of low dose domoic acid on neonatal odour conditioning and to determine if the observed effects are due in part to an action on NMDA receptors. Groups of rat pups were conditioned to a novel odour on postnatal day (PND) 8, injected with 20 μg/kg domoic acid either alone, or in combination with the NMDA antagonist CPP (or appropriate controls), daily from day 8–14, reexposed to the conditioning odour or a novel odour on day 9, and tested for odour preference on day 13 using a standard 3-choice paradigm. Results indicated that rats treated with domoic acid spent significantly more time over the conditioning odour than did saline-treated rats when tested on PND 13. This effect was antagonized by concomitant injection of CPP, indicating an involvement of NMDA receptors in the actions of DOM in this paradigm. Rats injected with either saline or CPP alone showed the opposite effect, i.e. a preference for the alternate odour. The results indicate that a very low dose of DOM produces a conditioned odour preference in neonatal rats and that this effect is due in part to NMDA receptor involvement, thereby emphasizing a role for both kainate and NMDA glutamate receptors in implicit memory.
TL;DR: The compartment modelling framework is discussed on which virtually all quantification methods utilized in PET are based and this should facilitate an understanding of how PET measurements translate into quantities such as regional blood flow, volume of distribution, and metabolic rates of specific substrates.
Abstract: The central distinguishing feature of positron emission tomography (PET) is its ability to investigate quantitatively regional cellular and molecular transport processes in vivo with good spatial resolution. This review wants to provide a concise overview of the established principles underlying quantitative data evaluations of the acquired PET images. Especially, the compartment modelling framework is discussed on which virtually all quantification methods utilized in PET are based. The aim of the review is twofold: first, to provide the reader with an idea of the theoretical framework and mathematical tools and second, to enable an intuitive grasp of the possibilities and limitations of a quantitative approach to PET data evaluation. This should facilitate an understanding of how PET measurements translate into quantities such as regional blood flow, volume of distribution, and metabolic rates of specific substrates.
TL;DR: A cytosolic long-chain acyl-CoA hydrolase (referred to as BACH) is described that is constitutively expressed in the brain, comparing it with other acyl -CoAHydrolases found in peripheral organs that have a role in fatty acid oxidation.
Abstract: Long-chain acyl-CoA hydrolases are a group of enzymes that cleave acyl-CoAs into fatty acids and coenzyme A (CoA-SH). Because acyl-CoAs participate in numerous reactions encompassing lipid synthesis, energy metabolism and regulation, modulating intracellular levels of acyl-CoAs would affect cellular functions. Therefore, acyl-CoA synthetases have been intensively studied. In contrast, acyl-CoA hydrolases have been less investigated, especially in the brain despite the fact that its long-chain acyl-CoA hydrolyzing activity is much higher than that in any other organ in the body. However, recent studies have dissected the multiplicity of this class of enzymes on a genomic basis, and have allowed us to discuss their function. Here, we describe a cytosolic long-chain acyl-CoA hydrolase (referred to as BACH) that is constitutively expressed in the brain, comparing it with other acyl-CoA hydrolases found in peripheral organs that have a role in fatty acid oxidation.
TL;DR: It is demonstrated that in many cases the unreduced proteins migrate with a better resolution than reduced proteins, mostly in the crowded ‘α-globulin’ area of pI 4.5–6 and Mr 50–70 kDa.
Abstract: Two-dimensional electrophoresis is usually run on fully reduced samples. Under these conditions even covalently bound oligomers are dissociated and individual polypeptide chains may be fully unfolded by both, urea and SDS, which maximizes the number of resolved components and allows their pI and Mr to be most accurately evaluated. However, various electrophoretic protocols for protein structure investigation require a combination of steps under varying redox conditions. We review here some of the applications of these procedures. We also present some original data about a few related samples – serum from four species: Homo sapiens, Mus musculus, Rattus norvegicus, Bos taurus – which we run under fully unreduced and fully reduced conditions as well as with reduction between first and second dimension. We demonstrate that in many cases the unreduced proteins migrate with a better resolution than reduced proteins, mostly in the crowded ‘α-globulin’ area of pI 4.5–6 and Mr 50–70 kDa.
TL;DR: Two new specific inhibitors of glutathione S-transferases may have a potential in counteracting tumor-protective effects depending upon GSTA1-1 activity and the comparative loss in biological activity consequent to the isosteric change confirms that the γ-glutamyl moiety plays an important role in modulating the affinity of the ligands addressed to interact with GSH-dependent proteins.
Abstract: Elevated levels of glutathione S-transferases (GSTs) are among the factors associated with an increased resistance of tumors to a variety of antineoplastic drugs. Hence a major advancement to overcome GST-mediated detoxification of antineoplastic drugs is the development of GST inhibitors. Two such agents have been synthesized and tested on the human Alpha, Mu and Pi GST classes, which are the most representative targets for inhibitor design. The novel fluorescent glutathione S-conjugate L-γ-glutamyl-(S-9-fluorenylmethyl)-L-cysteinyl-glycine (4) has been found to be a highly potent inhibitor of human GSTA1-1 in vitro (IC50=0.11±0.01 μM). The peptide is also able to inhibit GSTP1-1 and GSTM2-2 isoenzymes efficiently. The backbone-modified analog L-γ-(γ-oxa)glutamyl-(S-9-fluorenylmethyl)-L-cysteinyl-glycine (6), containing an urethanic junction as isosteric replacement of the γ-glutamyl-cysteine peptide bond, has been developed as γ-glutamyl transpeptidase-resistant mimic of 4 and evaluated in the same inhibition tests. The pseudopeptide 6 was shown to inhibit the GSTA1-1 protein, albeit to a lesser extent than the lead compound, with no effect on the activity of the isoenzymes belonging to the Mu and Pi classes. The comparative loss in biological activity consequent to the isosteric change confirms that the γ-glutamyl moiety plays an important role in modulating the affinity of the ligands addressed to interact with GSH-dependent proteins. The new specific inhibitors may have a potential in counteracting tumor-protective effects depending upon GSTA1-1 activity.
TL;DR: This study represents the first investigation of polyphenols in vivo by means of PET and revealed an extensive uptake and metabolism in the liver and kidney of [18F]-1 in male Wistar rats using a dedicated small animal PET camera with very high spatial resolution.
Abstract: Resveratrol (3,4′,5-trihydroxy-trans-stilbene) is a naturally occurring phytoalexin and polyphenol existing in grapes and various other plants, and one of the best known ‘nutriceuticals’. It shows a multiplicity of beneficial biological effects, particularly, by attenuating atherogenic, inflammatory, and carcinogenic processes. However, despite convincing evidence from experimental and clinical studies, data concerning the role of resveratrol and other members of the large polyphenols family for human health is still a matter of debate. One reason for this is the lack of suitable sensitive and specific methods, which would allow direct assessment of biodistribution, biokinetics, and the metabolic fate of these compounds in vivo. The unique features of positron emission tomography (PET) as a non-invasive in vivo imaging methodology in combination with suitable PET radiotracers have great promise to assess quantitative information on physiological effects of polyphenols in vivo. Herein we describe the radiosynthesis of an 18F-labelled resveratrol derivative, 3,5-dihydroxy-4′-[18F]fluoro-trans-stilbene ([18F]-1), using the Horner-Wadsworth-Emmons reaction as a novel radiolabelling technique in PET radiochemistry for subsequent functional imaging of polyphenol metabolism in vivo. In a typical “three-step/one-pot” reaction, 18F-labelled resveratrol derivative [18F]-1 could be synthesized within 120–130 min including HPLC separation at a specific radioactivity of about 90 GBq/μmol. The radiochemical yield was about 9% (decay-corrected) related to [18F]fluoride and the radiochemical purity exceeded 97%. First radiopharmacological evaluation included measurement of biodistribution ex vivo and positron emission tomography (PET) studies in vivo after intravenous application of [18F]-1 in male Wistar rats using a dedicated small animal PET camera with very high spatial resolution. Concordantly with data on bioavailability and metabolism of native resveratrol from the literature, these investigations revealed an extensive uptake and metabolism in the liver and kidney, respectively, of [18F]-1. This study represents the first investigation of polyphenols in vivo by means of PET.
TL;DR: It is concluded that the use of [18F]FB-labelled LDL particles is an attractive alternative to, e.g., LDL iodination methods, and is of value to characterize and to discriminate the kinetics and the metabolic fate of nLDL and oxLDL in small animals in vivo.
Abstract: The human organism is exposed to numerous processes that generate reactive oxygen species (ROS). ROS may directly or indirectly cause oxidative modification and damage of proteins. Protein oxidation is regarded as a crucial event in the pathogenesis of various diseases ranging from rheumatoid arthritis to Alzheimer’s disease and atherosclerosis. As a representative example, oxidation of low density lipoprotein (LDL) is regarded as a crucial event in atherogenesis. Data concerning the role of circulating oxidized LDL (oxLDL) in the development and outcome of diseases are scarce. One reason for this is the shortage of methods for direct assessment of the metabolic fate of circulating oxLDL in vivo. We present an improved methodology based on the radiolabelling of apoB-100 of native LDL (nLDL) and oxLDL, respectively, with the positron emitter fluorine-18 (18F) by conjugation with N-succinimidyl-4-[18F]fluorobenzoate ([18F]SFB). Radiolabelling of both nLDL and oxLDL using [18F]SFB causes neither additional oxidative structural modifications of LDL lipids and proteins nor alteration of their biological activity and functionality, respectively, in vitro. The method was further evaluated with respect to the radiopharmacological properties of both [18F]fluorobenzoylated nLDL and oxLDL by biodistribution studies in male Wistar rats. The metabolic fate of [18F]fluorobenzoylated nLDL and oxLDL in rats in vivo was further delineated by dynamic positron emission tomography (PET) using a dedicated small animal tomograph (spatial resolution of 2 mm). From this study we conclude that the use of [18F]FB-labelled LDL particles is an attractive alternative to, e.g., LDL iodination methods, and is of value to characterize and to discriminate the kinetics and the metabolic fate of nLDL and oxLDL in small animals in vivo.
TL;DR: A new crystal structure of alanine derivative was characterized, which is a slightly distorted TBP structure, and this kind of spirophosphoranes are potent inhibitors to tyrosinase.
Abstract: The reactions of phosphorus trichloride with various amino acids afford the pentacoordinated spirophosphoranes. The reaction procedures were traced by 31P NMR spectra techniques. A new crystal structure of alanine derivative was characterized, which is a slightly distorted TBP structure. Besides, this kind of spirophosphoranes are potent inhibitors to tyrosinase.