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Results 351 - 400 of 635
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MacDermott AJ - - 2000
We review recent developments stemming from Stephen Mason's work on the origin of homochirality, focusing in particular on the parity-violating energy difference (PVED) between enantiomers. We summarize results of calculations of the PVED--both our own and those of other groups--which show that the natural enantiomers are indeed favoured by the ...
Tessari P - - 2000
This review is concerned with the status of our current research related to the exchange of amino acids across organs. Accumulation of knowledge regarding how amino acid pools are maintained within the body remains a work in progress. In recent years, the use of organ balance measurement techniques in combination ...
Powers A C - - 1999
Autoantibodies to GAD, an important marker of the autoimmune process in type I or insulin-dependent diabetes mellitus (IDDM), are also found in non-diabetic individuals with autoimmune polyendocrine syndrome type 1 (APS1), APS2, and stiff man syndrome (SMS). Most IDDM sera contain two distinct GAD antibody specificities, one of which targets ...
Febvay G - - 1999
The fate of sucrose, the major nutrient of an aphid's natural food, was explored by radiolabeling in the pea aphid Acyrthosiphon pisum. To investigate the influence of nitrogen quality of food on amino acid neosynthesis, pea aphids were reared on two artificial diets differing in their amino acid composition. The ...
Chin J - - 1999
Molecular recognition is the key step in a wide range of controlled separation and chemical transformation processes, with enzymes performing this task with an unsurpassed degree of selectivity. Enzymes contain only 20 simple amino acids, yet it remains difficult to rationalize or even predict these stereospecific recognition events. Nonetheless, the ...
May A C - - 1999
Hierarchical classifications of the 20 amino acids according to residue relationships within scoring matrices have not hitherto been tested for reliability. In fact, testing here of the residue groupings obtained thus from 18 published matrices shows that they vary considerably in reliability. This behaviour gives a new insight then into ...
Glavin D P - - 1999
A suite of protein and nonprotein amino acids were detected with high-performance liquid chromatography in the water- and acid-soluble components of an interior fragment of the Martian meteorite Nakhla, which fell in Egypt in 1911. Aspartic and glutamic acids, glycine, alanine, beta-alanine, and gamma-amino-n-butyric acid (gamma-ABA) were the most abundant ...
Chace D H - - 1999
BACKGROUND: Advances in technology and the earlier release of newborns from hospitals have pressed the demand for accurate calibration and improved interlaboratory performance for newborn screening tests. As a first step toward standardization of newborn screening aminoacidopathy tests, we have produced six-pool sets of multianalyte dried-blood-spot amino acid reference materials ...
Jousse C - - 1999
In mammals, the plasma concentration of amino acids is affected by nutritional or pathological conditions. For example, an amino acid profile alteration has been reported as a result of a deficiency of any one of the essential amino acids, a dietary imbalance of amino acids or an insufficient intake of ...
Knight R D - - 1999
The genetic code might be a historical accident that was fixed in the last common ancestor of modern organisms. 'Adaptive', 'historical' and 'chemical' arguments, however, challenge such a 'frozen accident' model. These arguments propose that the current code is somehow optimal, reflects the expansion of a more primitive code to ...
Meijer A J - - 1999
Recent developments indicate that amino acids, in addition to their function as substrates for many metabolic pathways, can stimulate a signal transduction pathway that shares components with insulin-stimulated signalling cascades. Insulin sensitivity is dependent on the ambient amino acid concentration. Amino acid-dependent signal transduction is present in all insulin-sensitive tissues ...
Subirana J A - - 1999
Single amino acid repeats are found in different kinds of proteins. Some of these repeats are pathogenic. It is striking that some amino acids are able to form such repeats, but other amino acids are not. We suggest an explanation for this fact based on the different tendency of each ...
Young V R - - 1999
This brief review is concerned with the status of our current understanding of the quantitative needs for dietary amino acids in healthy adults. The nutritional significance of the conditionally indispensable amino acids is assessed and the requirements for the indispensable amino acids are discussed. Recent research involving the use of ...
Leff S E - - 1999
As a potential treatment for Parkinson's disease, viral vector-mediated over-expression of striatal L-aromatic amino acid decarboxylase was tested in an attempt to facilitate the production of therapeutic levels of dopamine after peripheral L-dihydroxyphenylalanine administration. The results of microdialysis and enzyme activity assays indicate that striatal decarboxylation of peripherally administered L-dihydroxyphenylalanine ...
Fleck C - - 1999
In anaesthetized adult female rats, the renal amino acid handling was measured six days after 5/6 nephrectomy (5/6NX). The distinct rise in blood urea nitrogen as well as the significant reduction in urine flow and GFR indicate an impairment of kidney function. In principle, in 5/6NX rats amino acid plasma ...
Leonhard B - - 1999
In the haemolymph of honeybee drones, concentrations of free amino acids were higher than in worker haemolymph, with different relative proportions of individual amino acids. The overall concentration of free amino acids reached its highest level at the 5th day after adult drone emergence, and after the 9th day only ...
Harada S - - 1998
Integrated neural responses to various amino acids were recorded from the chorda tympani (facial) nerve in C3H mice. The basic amino acids hydrochlorides L-Arg-HCl and L-Lys-HCl evoked large magnitude integrated taste responses, similar to that for NaCl, and had estimated electrophysiological thresholds of 0.0001 M. No significant difference was indicated ...
Tamura M - - 1998
We defined the epitopes recognized by three influenza A virus-specific, H-2Kd-restricted CD8(+) cytotoxic T-lymphocyte (CTL) clones: H1-specific clone A-12, H2-specific clone F-4, and H1- and H2-cross-reactive clone B7-B7. The A-12 and B7-B7 clones recognized the same peptide, which comprises amino acids 533 to 541 (IYSTVASSL) of A/PR/8 hemagglutinin (HA). The ...
Young E A - - 1998
The activity of tyrosine hydroxylase and aromatic L-amino acid decarboxylase in the striatum and their mRNA content in the midbrain were assayed in mice following the intracerebroventricular injection of forskolin or phorbol-12,13-myristic acid (PMA). Control and 1-methyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned animals were studied. Both forskolin and PMA induced a rapid and transient ...
Brunton J A - - 1998
Indispensable amino acid requirements for children, patients and pregnant women are largely unknown. We describe a new, non-invasive technique that can estimate requirements in vulnerable populations. Future applications will lead to optimal nutritional care for populations in which an appropriate balance of amino acids is essential for metabolic health and ...
Di Giulio M - - 1998
Two forces are in general, hypothesized to have influenced the origin of the organization of the genetic code: the physicochemical properties of amino acids and their biosynthetic relationships. In view of this, we have considered a model incorporating these two forces. In particular, we have studied the optimization level of ...
Barbier B - - 1998
A large collection of micrometeorites has been recently extracted from Antarctic old blue ice. In the 50 to 100 micrometers size range, the carbonaceous micrometeorites represent 80% of the samples and contain 2% of carbon. They might have brought more carbon to the surface of the primitive Earth than that ...
Rai R - - 1998
Papain has been shown, for the first time, to exhibit hydantoinase activity. It hydrolyzes the 5-mono and 5,5'-disubstituted hydantoins with linear and cyclic substituents, with a higher activity for the latter, to the corresponding N-carbamoyl amino acids, which on chemical hydrolysis yield the corresponding amino acids. The up-scaling of this ...
Körner M - - 1998
The cercariae of Pseudechinoparyphium echinatum and Echinostoma revolutum approach their intermediate host snails by turning back when swimming in decreasing concentration gradients of snail conditioned water. Host stimuli are small molecular amino compounds, probably amino acids. This response was inhibited reversibly when the cercariae were treated with 0.45 microM-silver nitrate. ...
Körner M - - 1998
The cercariae of Pseudechinoparyphium echinatum and Echinostoma revolutum locate their host snails by turning back when swimming in decreasing gradients of the small molecular weight fraction (< 500) of snail conditioned water. Fractionation and chemical modifications of snail conditioned water from Lymnaea stagnalis showed that amino acids are necessary for ...
Zhao J - - 1998
The tryptophan (Trp) biosynthetic pathway leads to the production of many secondary metabolites with diverse functions, and its regulation is predicted to respond to the needs for both protein synthesis and secondary metabolism. We have tested the response of the Trp pathway enzymes and three other amino acid biosynthetic enzymes ...
Scaloni A - - 1998
The need to screen a large number of natural extracts, with the aim of detecting D-amino acids or isolating and characterizing peptides containing them, has stimulated the development of novel and improved procedures for the analysis of amino acid enantiomeric mixtures, with special attention paid to automation. Different methods for ...
Wang H C - - 1998
A self-organizing tree growing neural network was applied to classify amino acids and amino acid exchange matrices. SOTA, is freely available by anonymous FTP or at http://www.cnb.uam.es/bioinfo/Software/so ta. carazo@cnb.uam.es
Waldroup P W - - 1997
A study was conducted to evaluate the amino acid recommendations of the NRC (1994) when diets were changed at 3- or 4-wk intervals. Diets formulated to provide from 90 to 115% of recommended amino acid levels were fed to Nicholas (NIC) and British United Turkey (BUT) Large White males from ...
Su T - - 1997
Autogenous and anautogenous strains were selected from the egg rafts of Culex tarsalis Coquillett collected from Coachella Valley, California. In autogenous (21-25 generations) and anautogenous (0-4 generations) strains used for hemolymph free amino acid analysis, the autogenous oviposition rates were 73.6-83.6% and 2.7-3.9%, the proportions of females undergoing autogenous ovarian ...
Wachtel S R - - 1997
Investigations of gene therapy for Parkinson's disease have focused primarily on strategies that replace tyrosine hydroxylase. In the present study, the role of aromatic L-amino acid decarboxylase in gene therapy with tyrosine hydroxylase was examined by adding the gene for aromatic L-amino acid decarboxylase to our paradigm using primary fibroblasts ...
Liau S Y - - 1997
Microbiologically it was demonstrated that amino acids, e.g. cysteine (CySH), and other compounds, e.g. sodium thioglycollate, containing thiol groups neutralized the activity of silver nitrate against Pseudomonas aeruginosa PAO1. Amino acids with disulphide bonds were inactive, with the exception of L-cystine dimethyl ester, as were all amino acids with no ...
Engel M H - - 1997
Many amino acids contain an asymmetric centre, occurring as laevorotatory, L, or dextrorotatory, D, compounds. It is generally assumed that abiotic synthesis of amino acids on the early Earth resulted in racemic mixtures (L- and D-enantiomers in equal abundance). But the origin of life required, owing to conformational constraints, the ...
Peterson E - - 1997
Amino acids were subjected to shock impact over a pressure range of 3.5 to 32 GPa both within and without meteoritic mineral matrices. The extent of amino acid destruction, racemization, and conversion to secondary amino acids was examined. Abundances of parent compounds decreased by a factor of 10(3) over this ...
Pan M - - 1997
Two nonprotein amino acids, cycasindene and cycasthioamide, along with eight known nonprotein amino acids, were isolated from the seeds of Cycas revoluta Thunb. The structures of cycasindene and cycasthioamide were elucidated as 3-[3'-amino-indenyl-2]-alanine (1) and N-[glycinyl-alaninyl-11-thio]-5-one-pipecolic acid (2) by chemical and spectral methods.
Yvon M - - 1997
The enzymatic degradation of amino acids in cheese is believed to generate aroma compounds and therefore to be involved in the complex process of cheese flavor development. In lactococci, transamination is the first step in the degradation of aromatic and branched-chain amino acids which are precursors of aroma compounds. Here, ...
Ishikawa T - - 1997
The mechanism of stereospecific conversion of DL-5-substituted hydantoins to the corresponding L-amino acids by Pseudomonas sp. strain NS671 was studied. The results indicated that the hydantoinase catalyzed the hydrolysis reaction of both D- and L-5-(2-methylthioethyl)hydantoin, and that the hydrolysis of the L-enantiomer proceeded preferentially compared with that of the D-enantiomer. ...
Walz O P - - 1997
In a metabolic trial 4 groups of 8 piglets of 5 kg weight each were kept individually for 45 days (final weight 23 kg) and fed a practical diet. At the beginning of the experiment the body amino acid contents of an additional group of 8 piglets were determined by ...
Wei L - - 1997
We have performed a comprehensive analysis of the microenvironments surrounding the twenty amino acids. Our analysis includes comparison of amino acid environments with random control environments as well as with each of the other amino acid environments. We describe the amino acid environments with a set of 21 features summarizing ...
Di Giulio M - - 1996
Two forces are generally hypothesised as being responsible for conditioning the origin of the organization of the genetic code: the physicochemical properties of amino acids and their biosynthetic relationships (relationships between precursor and product amino acids). If we assume that the biosynthetic relationships between amino acids were fundamental in defining ...
Bartz R - - 1996
We compared the amino acid sequences of groups of receptor (CD46) downregulating and nondownregulating measles virus (MV) hemagglutinins (Hs) and identified seven group-specific differences as candidates for the mediation of the observed differential effects. Using site-directed mutagenesis, we mutated the chosen amino acids of the H of MV-strain WTF (WTF-H), ...
McLarney M J - - 1996
We undertook an interspecies comparison of essential (indispensable) amino acid requirements, in relation to those for total protein, to examine whether the current, internationally proposed human amino acid requirement patterns are significantly different from those of other animals. Data were compiled in their original form and then expressed as mg ...
Briddon A - - 1996
Quantitative amino acid profiles are traditionally reported as a list of individual concentrations and reference intervals. By the use of selected examples it is shown that alternative methods of presenting and assessing these results can enhance both the quantity and quality of information. A candidate decision support tool is offered ...
Curnow R N - - 1996
1. The Reading model for the egg production of a flock as determined by the intake of a single amino acid is based on the assumption that other amino acid intakes are not limiting egg production. This can result in an overestimation of the optimum intakes of each amino acid ...
Bacsi S G - - 1996
The aryl hydrocarbon receptor (AHR) and the aryl hydrocarbon receptor nuclear translocator (ARNT) belong to a novel subclass of basic helix-loop-helix transcription factors. The AHR.ARNT heterodimer binds to the xenobiotic responsive element (XRE). Substitution of each of four amino acids in the basic region of ARNT with alanine severely diminishes ...
Selldén E - - 1996
Intraoperative infusion of amino acids has been found to stimulate energy expenditure and thereby prevent anaesthesia-induced hypothermia. Rectal temperature and respiratory gas exchange were measured in 24 female patients before and after isoflurane anaesthesia. Sixteen patients had an amino acid mixture of 240 kJ h-1, infused over 1-2 h before ...
Sowa S M - - 1996
The concentrations of free amino acids in the hemolymph of adult males of the cockroach Blaberus discoidalis were determined by automated amino acid analysis. Eighteen of the twenty standard amino acids as well as two nonstandard amino acids (hydroxyproline and ornithine) were found. Aspartic acid and cysteine were not present. ...
Fleck C - - 1996
The effect of Tl2SO4 (Tl, 2 mg/100 g b.wt.) on renal amino acid excretion and plasma amino acid composition was investigated in 10- and 55-day-old rats. Tl decreased glomerular filtration rate only in adult rats. On the other hand, the renal fractional excretion (FE) of amino acids was distinctly higher ...
Steingrímsdóttir T - - 1996
The concentrations of 24 amino acids and four other related compounds were determined in extracts of biopsy specimens from myometrium and musculus rectus abdominis of 10 healthy term pregnant women during elective cesarean sections. The total free amino acid pool did not differ significantly between the two muscle types. There ...
Brinton K L - - 1996
Using a sensitive high performance liquid chromatography technique, we have analyzed both the hot water extract and the acid hydrolyzed hot water extract of lunar soil collected during the Apollo 17 mission. Both free amino acids and those derived from acid labile precursors are present at a level of roughly ...
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