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  • 1995-1999  (1,531)
  • 1925-1929
  • 1890-1899
  • 1999  (1,531)
  • Chemistry  (1,469)
  • Amino acids  (73)
  • Nuclear reactions
Material
Years
  • 1995-1999  (1,531)
  • 1925-1929
  • 1890-1899
Year
  • 1
    ISSN: 1438-2199
    Keywords: Amino acids ; RT/PCR ; Protooncogene ; ets-2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Protooncogenes (PO) play a crucial role for brain biology and pathology. Only the concerted action of protooncogenes enables normal brain development. The reliable and sensitive quantification of brain PO is still holding centre stage in neurobiological research. The aim of our study was therefore the determination of PO in minute amounts of brain areas. For this purpose we decided to apply the most sensitive detection principle of competitive reverse transcriptase polymerase chain reaction using capillary electrophoresis and laser-induced fluorescence detection. We selected the PO ets-2 for our studies as this transcription factor was shown to be involved in neurodegenerative disease. As little as 10ng of total RNA each were extracted from 5 different regions of human postmortem brain and used in the assay system. Our results revealed that the ets-2 gene transcript was detectable at the atto-gram level in the brain (54.5 ± 17.7 ag/ 10 ng RNA in the occipital lobe, 34.2 ± 7.5 in temporal lobe, 40.2 ± 15.6 in the frontal lobe, 31.4 ± 15.7 in the cerebellum, and undetectably low in the parietal lobe). This is the first report at this sensitivity level providing neurobiology with a powerful analytical tool.
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  • 2
    ISSN: 1438-2199
    Keywords: Amino acids ; Taurine ; Marathon ; Endurance exercise
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The sulphonated amino acid taurine increased significantly in the plasma of trained athletes after three endurance exercises of different duration and intensity, a 90 min run on a treadmill at 75% of an individual's VO2 peak, a Marathon, 42.2km and a 100km run, by 19%, 77% and 36%, respectively. Such results indicated that the speed at which the exercise is per formed, referred to as the intensity, rather than the duration of the exercise, correlated with the elevated taurine levels possibly indicating its release from muscle fibres. The plasma amino acid pool decreased significantly in relationship with the duration of the exercise, caused by their utilisation for glucogenesis. The possible sources of the increased plasma taurine are discussed.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Amino acids 17 (1999), S. 369-376 
    ISSN: 1438-2199
    Keywords: Amino acids ; Non-proteinogenic dipeptides ; Dehydrodipeptides ; Diastereoselectivity ; N-Boc-Dehydroamino acids ; Asymmetric hydrogenation ; Chiral rhodium catalysts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary N-Boc protected non-proteinogenic dipeptides with D,L-and L,L-configuration were prepared by catalytic asymmetric hydrogenation of the corresponding dehydrophenylalanyl-(L)-phenylalanine derivatives. The configuration of the new stereogenic centre depends first of all on the catalyst configuration and is less influenced by the substrate configuration. Diastereomeric excesses in the range of 80–96% de could be increased up to 99% by recrystallization. Analytical data of selected new compounds are given.
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  • 4
    ISSN: 1438-2199
    Keywords: Amino acids ; Polyclonal antibodies ; Phosalone ; Immunodetection ; Hapten synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Hapten synthesis for the production of specific insecticide phosalone polyclonal antibodies was carried out starting from an intermediate of the phosalone synthesis, 6-chloro-2-benzoxazolone1. Two haptens containing different spacers have been prepared: N-5-carboxypentyl-6-chloro-2-benzoxazolone7 and N-(2-oxo-3-aza-5-carboxypentyl)-6-chloro-2-benzoxazolone12. Each of these two haptens conjugated to bovine serum albumine (BSA) was used to immunize four rabbits. Immunoassays of phosalone were performed with ELISA using solid-phase bound hapten thyroglobulin conjugate and horseradish peroxidase labelled goat antirabbit IgG. The more sensitive response was observed when the antiserum obtained from the rabbit immunized with the hapten-BSA conjugate containing the N-2-oxo-3-aza-5-carboxypentyl spacer was in competition with the same hapten coupled to thyroglobulin. An identical response was obtained under the same conditions when using benzoxazolone instead of phosalone as competitor, showing a good recognition of the specific aromatic part of the organophosphate insecticide phosalone. Reduction of coating conjugate concentration (from 2 to 0.05μg/well) and also the use of heterologous coating protein instead of homologous did improve the sensitivity, resulting in a concentration of phosalone required to inhibit binding by 50% of 2 mg/l and a detection limit of 0.02 mg/l.
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  • 5
    ISSN: 1438-2199
    Keywords: Amino acids ; Liver ; Hepatic damage ; Carbon tetrachloride
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The aims of the present study were to assess the changes of individual plasma amino acid levels in relation (1) to the severity of liver damage and (2) to the process of liver recovery. Acute liver injury was induced by an intragastric administration of CCl4 diluted in olive oil in doses of 2, 4 and /or 6 g of CCl4 per kg b.w. The control rats received olive oil only. Animals were sacrificed at 16, 24, 48 and 96 hours after treatment. The severity of liver injury was assessed by histological examination, by changes in ALT and AST in the blood plasma and by changes in liver weight. Statistical analysis was carried by ANOVA, p 〈 0.05 was considered significant. The Spearman rank correlation coefficient was used as a measure of the degree of linear relationship between variable and dose. In the period of the development of acute liver damage, i.e. at 16 and 24 hours after treatment, an increase in blood plasma amino acid levels and positive correlations with the dose of CCl4 were observed for most individual amino acids. The only exception was arginine which decreased in a dose dependent manner. At a phase of liver recovery, i.e. at 48 and 96 hours after CCl4 treatment, the concentrations of some individual amino acids decreased below the control values. The negative correlation with the dose of CCl4 occurred for taurine and isoleucine (at 48 hours) and taurine, threonine, valine, methionine, isoleucine and leucine (at 96 hours).
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  • 6
    ISSN: 1438-2199
    Keywords: Amino acids ; Alanine ; Fatty acids ; Glutamine and glutamate synthesis ; Glycerol and lactate metabolism ; Malate-aspartate shuttle ; Rabbit kidney-cortex tubules ; Renal gluconeogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In isolated rabbit renal cortical tubules, glucose synthesis from 1 mM alanine is negligible, while the amino acid is metabolized to glutamine and glutamate. The addition of 0.5 mM octanoate plus 2 mM glycerol induces incorporation of [U-14C]Alnine into glucose and decreases glutamine synthesis, whereas oleate and palmitate in the presence of glycerol are less potent than octanoate. Gluconeogenesis is also significantly accelerated when glycerol is substituted by lactate. In view of an increase in14CO2 fixation and elevation of both cytosolic and mitochondrial NADH/NAD+ ratios, the activation of glucose formation from alanine upon the addition of glycerol and octanoate is likely due to (i) stimulation of pyruvate carboxylation, (ii) increased availability of NADH for glyceraldehyde-3-phosphate dehydrogenase and (iii) elevation of mitochondrial redox state causing a diminished provision of ammonium for glutamine synthesis. The induction of gluconeogenesis in the presence of alanine, glycerol and octanoate is not related to cell volume changes. The results presented in this paper show the importance of free fatty acids and glycerol for regulation of renal gluconeogenesis from alanine. The possible physiological significance of the data is discussed.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Amino acids 16 (1999), S. 79-89 
    ISSN: 1438-2199
    Keywords: Amino acids ; Anti-neoplastic amino acids ; Purine and DNA synthesis inhibitors ; PRPP amido transferase and IMP dehydrogenase inhibitors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 4-Hydroxyproline di- and tri-peptides and N-cbz-hydroxypropylglycinamides were observed to be potent cytotoxic agents against the growth of suspended single cells, L-1210, Tmolt3, and HeLa-S3. The agents were not as potent against the growth of cultured solid tumor cells. Selected derivatives were investigated for their mode of action in Tmolt3 leukemia cells. The compounds selectively inhibited DNA synthesis at 50 and 100smM. The target site of action of the agents appeared to be the purinede novo pathway with marked inhibition of the activities of the two regulatory enzymes of the pathway, i.e. PRPP amido-transferase and IMP dehydrogenase. d[NTP] pools were reduced by the agents consistent with their overall reduction of DNA synthesis. Other marginally inhibited targets of the agents were r-RNA polymerase and TMP-kinase activities. The DNA molecule itself did not appear to be a target of these agents.
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  • 8
    ISSN: 1438-2199
    Keywords: Amino acids ; Targeting ; Mitochondria ; Chloroplasts ; Cysteine synthase ; Transit peptide ; Transgenic plants ; Processing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Cysteme synthase, the key enzyme for fixation of inorganic sulfide, catalyses the formation of cysteine from O-acetylserine and inorganic sulfide. Here we report the cloning of cDNAs encoding cysteine synthase isoforms fromArabidopsis thaliana. The isolated cDNA clones encode for a mitochondrial and a plastidic isoform of cysteine synthase (O-acetylserine (thiol)-lyase, EC 4.2.99.8), designated cysteine synthase C (AtCS-C, CSase C) and B (AtCS-B; CSase B), respectively.AtCS-C andAtCS-B, having lengths of 1569-bp and 1421-bp, respectively, encode polypeptides of 430 amino acids (∼45.8 kD) and of 392 amino acids (∼ 41.8 kD), respectively. The deduced amino acid sequences of the mitochondrial and plastidic isoforms exhibit high homology even with respect to the presequences. The predicted presequence of AtCS-C has a N-terminal extension of 33 amino acids when compared to the plastidic isoform. Northern blot analysis showed thatAtCS-C is higher expressed in roots than in leaves whereas the expression ofAtCS-B is stronger in leaves. Furthermore, gene expression of both genes was enhanced by sulfur limitation which in turn led to an increase in enzyme activity in crude extracts of plants. Expression of theAtCS-B gene is regulated by light. The mitochondrial, plastidic and cytosolic (Hesse and Altmann, 1995) isoforms of cysteine synthase ofArabidopsis are able to complement a cysteine synthasedeficient mutant ofEscherichia coli unable to grow on minimal medium without cysteine, indicating synthesis of functional plant proteins in the bacterium. Two lines of evidence proved thatAtCS-C encodes a mitochondrial form of cysteine synthase; first, import ofin vitro translation products derived from AtCS-C in isolated intact mitochondria and second, Western blot analysis of mitochondria isolated from transgenic tobacco plants expressing AtCS-C cDNA/c-myc DNA fusion protein.
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  • 9
    ISSN: 1438-2199
    Keywords: Amino acids ; Non-proteinogenic optically active amino acids ; Dehydroamino acids ; Chiral rhodium catalysts ; Asymmetric hydrogenation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary (Z)-α-[(Benzyloxy)- or (tert.-butyloxy)carbonylamino]-β (thienyl)-or (furyl)-acrylic acids and their esters were prepared by known methods and hydrogenated to the corresponding optically active alanine derivatives with optical yields in the range of 58–93% ee using the cationic rhodium complex of “PROPRAPHOS”.
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  • 10
    ISSN: 1438-2199
    Keywords: Amino acids ; L-Tryptophan ; Serum albumin ; Transport ; L-Tryptophan depletion ; α-Methyl-DL-tryptophan ; Analbuminemic rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The role of serum albumin in the transport of orally administered L-tryptophan (Trp) into rat tissues was examined using analbuminemic and Sprague-Dawley (SD) rats with and without a-methyl-DL-tryptophan (AMT)-induced Trp depletion. Trp was orally administered to rats 16h after AMT or 0.85% NaCl administration, when liver tryptophan 2,3-dioxygenase and protein synthetic activities in AMT-treated rats were similar to those of 0.85% NaCl-treated rats. After oral Trp administration, regardless of the presence or absence of Trp depletion, free serum Trp concentrations were similar in the analbuminemic and SD rats, while total serum Trp concentrations were lower in analbuminemic rats than in SD rats. Although liver, brain, and muscle Trp concentrations after oral Trp administration under Trp depletion were lower in analbuminemic rats than in SD rats, the ratio of the liver Trp concentration in analbuminemic rats to that in SD rats was smaller than that of the brain or muscle Trp concentration. These results suggest that variations in serum albumin levels could affect the transport of orally administered Trp into the liver of rats with Trp depletion.
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  • 11
    ISSN: 1438-2199
    Keywords: Amino acids ; Tissue protein synthesis ; Stable isotope amino acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The tracers L15N-proline and L(1-13C)-leucine were used to explore the synthesis of skin proteins in vivo in rabbits. They orally received a single dose containing an equimolecular mixture of L(1-13C)-leucine and L15N-proline. The changes in the amounts of these tracers in blood and skin were monitored for a total of 8 h. The data showed the appearance of the two tracers in blood within 15 min and their clearance in 8h. They were both rapidly (15 min) incorporated into skin proteins, but more proline was incorporated than leucine. We therefore consider L15N-proline to be a better tracer than L(1-13C)-leucine for studying protein metabolism in the skin.
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  • 12
    ISSN: 1438-2199
    Keywords: Amino acids ; Taurine ; Kainic acid ; Epilepsy ; Anticonvulsants ; Neuroprotection ; Excitatory amino acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Male Sprague-Dawley rats received TAU supplementation (1.5% in drinking water) or TAU deficient diets for 4 weeks to test for a possible neuroprotective role of TAU in KA-induced (10 mg/kg s.c.) seizures. TAU supplementation significantly increased serum and hippocampal TAU levels, but not TAU content in temporal cortex or striatum. TAU deficient diets did not attenuate serum or tissue TAU levels. Dietary TAU supplementation failed to decrease the number or latency of partial or clonic-tonic seizures or wet dog shakes, whereas a TAU deficient diet decreased the number of clonictonic and partial seizures. This study does not support previous observations of an anticonvulsant effect of TAU against KA-induced seizures. KAtreatment decreasedα 2-adrenergic receptor binding sites and TAU content in the temporal cortex across all dietary treatment groups, supporting previous evidence of severe KA-induced damage and neuronal loss in this brain region.
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  • 13
    Electronic Resource
    Electronic Resource
    Springer
    Amino acids 16 (1999), S. 191-213 
    ISSN: 1438-2199
    Keywords: Amino acids ; Enzymatic resolution ; Ester hydrolysis ; Proteases ; Lipases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The present review outlines recent examples of enzyme-based resolution procedures for amino acids via the hydrolysis of their esters. The resolutions have been achieved by using proteases (α-chymotrypsin, subtilisin and other microbial proteases, and sulfhydryl proteases of plant origin) and lipases. Relevant work utilizing yeast and other microbial cells is also included.
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  • 14
    Electronic Resource
    Electronic Resource
    Springer
    Amino acids 16 (1999), S. 251-272 
    ISSN: 1438-2199
    Keywords: Amino acids ; Unusual amino acids ; Aspartic acidβ-semialdehyde ; Aspartaldehyde ; 2-Amino-4-oxobutyric acid ; Enantioselective synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Strategies for the synthesis of optically active aspartaldehyde derivatives are reviewed. Most of them are using the chiral pool: allylglycine or naturally occurring homoserine, aspartic acid or methionme and side chain modifications. This will be developed in the first part. Some other original routes are also displayed in the second part. Different aspects of each strategy are discussed: the nature and number of steps, the problem of protecting groups, the price and availability of starting materials. Some synthetic applications of such interesting chiral synthons are shown in the last part.
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  • 15
    ISSN: 1438-2199
    Keywords: Amino acids ; Dipeptide derivatives ; Non-proternogenic optically active dipeptide esters ; Dehydrodipeptides ; Chiral rhodium catalysts ; Asymmetric hydrogenation ; Diastereoselectivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary N-[(Z)-N-Benzoyl- orN-Boc-(2-fluorophenyl)dehydroalanyl]-(R)-or (S)-phenylalanine esters were synthesized and hydrogenated to give the corresponding dipeptide derivatives with optical yields in the range of 53–87%de using the cationic rhodium complexes of PROPRAPHOS and BPPM. The efficiency of chiral diphosphine ligands as well the effect of the chiral center in the substrate on the catalytic asymmetric induction was studied.
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  • 16
    ISSN: 1438-2199
    Keywords: Amino acids ; Phytotoxin AS-I analogues ; FAB ; PD ; ESI mass spectrometry ; 1H,13C and 2D NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A series of six tetrapeptides, analogues of AS-I phytotoxin, pathogenic to sunflower, have been synthesized either in solution and/or by solid phase methods and have been tested for phytotoxic activity in various plants and cytotoxic activity in three cancer cell lines. These peptides were identified as model compounds by fast atom bombardment (FAB), plasma desorption (PD), electrospray ionization (ESI) mass spectrometry and by1H,1H-1H,13C and1H-13C NMR. The data presented show that in protected tetrapeptides the molecular ion was easily identified whereas some difficulties appeared with the fully deprotected peptides. NMR spectra are given.
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  • 17
    ISSN: 1438-2199
    Keywords: Amino acids ; Diclofenac ; Anti-phlogistics ; Non-proteinogenic amino acids ; Voltaren®. Thionation ; Cyclo-oxygenase inhibitors ; Ulcerogenic gastritis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In search for more potent, particularly less ulcerogenic gastritis that hopefully replace the universal NSAID “Diclofenac”, (2-[(2,6-di-chlorophenyl)amino]-phenylacetic acid, C.A.S. 15307-86-5), twelve new non-proteinogenic amino acid conjugates of the drug, namely that of sarcosine,β-alanine, D-leucine and D-phenylalanine, were synthesized and biologically screened for their anti-inflammatory, analgesic and ulcerogenic activity in rats. “Diclofenac” amino acid esters (IIa-d), were synthesizedvia the corresponding HOSu or HOBt active esters. Alkaline hydrolysis (NaOH) followed by acidification (KHSO4) or thioamide formation (Lawsson's Reagent, C.A.S. 19172-47-5), afforded the corresponding free acids IIIa-d or the thioamides IVa-d respectively. Interestingly, in contrary to the parent “Diclofenac”, the synthesized candidates (except IIId), were entirly nonulcerogenic in rats. Further, they considerably retained a generelized anti-phlogistic activity. The major “Diclofenac” irritating gastric side effect was thus eliminated. Particularly, the sarcosine conjugate IIa and its thiomimic IVa exhibit promising therapeutic perspectives.
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  • 18
    Electronic Resource
    Electronic Resource
    Springer
    Amino acids 17 (1999), S. 139-148 
    ISSN: 1438-2199
    Keywords: Amino acids ; Polyamine oxidase ; Polyamines ; Gender ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Variations in level of polyamines and their related enzymes are frequently observed in response to some treatments which affect in a different way male and female. The possibility of a gender-related difference in the oxidation of polyamines was investigated in rats by measuring the activity of polyamine oxidase, a ubiquitous enzyme of vertebrate tissues, which transforms spermine into spermidine and spermidine into putrescine. The study was carried out on thymus, spleen, kidney and liver of young rats of both sexes, and female rats showed a lower polyamine oxidase activity than male rats in all the tissues. We also found higher values of spermidine acetylation in female than male rats in thymus and liver. Owing to these gender-related differences, a higher spermidine N-acetyltransferase/ polyamine oxidase ratio was found in female than in male rats. A second gender-related difference was a higher spermidine/spermine ratio in female than in male, the only exception being the thymus. These basal differences possibly account for the gender-related differences of polyamine metabolic enzyme activities in response to some treatments, including drugs or hormones.
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  • 19
    Electronic Resource
    Electronic Resource
    Springer
    Amino acids 17 (1999), S. 195-205 
    ISSN: 1438-2199
    Keywords: Amino acids ; Apis mellifera ; Drones ; Osmolarity ; Age dependency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 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 minor changes in the concentration and distribution of free amino acids were observed. This coincides with the age when drones reach sexual maturity and change their feeding behaviour. Levels of essential free amino acids were high during the first 3 days of life and thereafter decreased. Osmolarity was lowest at emergence (334 ± 41 mOsm), increased until the age of 3 days (423 ± 32mOsm) and then stayed generally constant until the 16th day of life. Only 25-day-old drones had significantly higher osmolarity (532 ± 38 mOsm). The overall change in osmolarity during a drone's lifetime was about 40%.
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  • 20
    ISSN: 1438-2199
    Keywords: Amino acids ; Conformational constraint ; Cyclic disulfides ; -Cys-Cys-peptides ; Dipeptide mimetics ; Dithiols ; Glutathione analogues
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The glutathione analogue γ-(H-Glu-OH)- -OH (5), containing the 8-membered disulfide ring- replacing the native -Cys-Gly fragment, has been synthesized and characterized together with its reduced dithiol form γ-(H-Glu-OH)-Cys-Cys-OH (6).
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  • 21
    ISSN: 1438-2199
    Keywords: Amino acids ; Polyamine catabolism ; Polyamine oxidase ; Diamine oxidase ; Testosterone ; Mouse kidney
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In the present study developmental patterns of renal polyamineoxidizing enzymes polyamine oxidase (PAO) and diamine oxidase (DAO) in male and female ICR mice were demonstrated. The effects of testosterone (10μg/100g body weight) on renal PAO and DAO activities were also studied. The differences between sexes in both PAO and DAO activities were most clearly expressed in the immature kidney. At the age of 20 days PAO and DAO activities were 1.52 fold (p 〈 0.01) and 1.75 (p 〈 0.02) respectively higher in male mouse kidney than in female. Maturational processes reflected in significant increases in polyamine- oxidizing enzyme activities mainly in female mouse kidney, comparable with the gain in the kidney wet weight. Our data show that testosterone is able to influence renal PAO and DAO activities in addition to the well-known stimulation of polyamine biosynthesis. The hormonal effects were sex and age dependent. The influence of testosterone on renal PAO activity was mainly age dependent. The slight stimulation of renal PAO activity observed in 20- and 50-day old mice, 24h after testosterone administration, change with a decrease in the enzyme activity at the age of 70 days. The effects of testosterone on renal DAO activity were mainly sex dependent. Testosterone caused stimulation of DAO activity with a very close magnitude (nearly twice) in female mouse kidney, independently of the age of mice. In contrast, in male mice the hormone treatment resulted in a statistically significant increase in renal DAO activity at the age of 70 days (.1.3 fold, p 〈 0.05) only. It could be suggested that our data indicate the different contribution of renal PAO and DAO in androgen regulation of polyamine levels, depending on sex and the stage of the postnatal development.
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  • 22
    ISSN: 1438-2199
    Keywords: Amino acids ; Allohydroxyproline ; Allothreonine ; Chiral separation ; Chirasil-Val ; Hydroxyproline ; Threonine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Experimental conditions for the derivatization and resolution by GLC of all stereoisomers of threonine and 4-hydroxyproline are reported. Threonine was in two steps converted toN,O-bisisobutoxycarbonyl 2,2,2-trifluoroethyl ester derivatives, the second of which was performed under anhydrous conditions. As such the enantiomers could pairwise be separated by capillary gas chromatography on a Chirasil-Val column. SinceL- andD-threonine eluted much earlier than the corresponding allo forms, quantitative determination of the allothreonine content inD- orL-threonine down to the one percent level could be simply accomplished but also enantiomeric impurities could be determined. Unlike for threonine, the corresponding 4-hydroxyproline isomers could not all be resolved asN,O-bisisobutoxycarbonyl 2,2,2-trifluoroethyl esters on this column. Although diastereomers could still be separated, the allo pair cochromatographed and the resolution for theL- andD-isomers was low. Complete separation of the 4-hydroxyproline isomers could be accomplished asN,O-bisprotected isobutyl amides, the formation of which required three derivatization steps. These were used for the determination of allohydroxyproline.
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  • 23
    Electronic Resource
    Electronic Resource
    Springer
    Amino acids 17 (1999), S. 323-334 
    ISSN: 1438-2199
    Keywords: Amino acids ; Taurine release ; Cerebellar granule cells ; Celldamaging conditions ; Glutamate receptors ; Veratridine ; Potassium stimulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The release of taurine from cultured cerebellar granule neurons was studied in different cell-damaging conditions, including hypoxia, hypoglycemia, ischemia, oxidative stress and in the presence of free radicals. The effects of both ionotropic and metabotropic glutamate receptor agonists on the release were likewise investigated. The release of [3H]taurine from the glutamatergic granule cells was increased by K+ (50mM) and veratridine (0.1 mM), the effect of veratridine being the greater. Hypoxia and ischemia produced an initial increase in release compared to normoxia but resulted in a diminished response to K. Hypoglycemia, oxidative stress and free radicals enhanced taurine release, and subsequent K− treatment exhibited a correspondingly greater stimulation. A common feature of taurine release in all the bove conditions was a slow response to the stimulus evoked by K+ and particularly to that evoked by veratridine. All ionotropic glutamate receptor agonists potentiated taurine release, but only the action of kainate seemed to be receptor-mediated. Metabotropic receptor agonists of group I slightly stimulated the release. The prolonged taurine release seen in both normoxia and cell-damaging conditions may be of importance in maintaining homeostasis in the cerebellum and reducing excitability for a longer period than other neuroprotective mechanisms.
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  • 24
    ISSN: 1438-2199
    Keywords: Amino acids ; Taurine ; Osmoregulation ; Rat ; Osmolarity sensor protein ENVZ
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Although the involvement of taurine in osmoregulation is well-documented and widely accepted, no detailed mechanism for this function has been reported so far. We used subtractive hybridization to study mRNA steady state levels of genes up- or downregulated by taurine. Rats were fed taurine 100mg/kg body weight per day for a period of three days and hearts (total ventricular tissue) of experimental animals and controls were pooled and used for mRNA extraction. mRNAs from two groups were used for subtractive hybridization. Clones of the subtractive library were sequenced and the obtained sequences were identified by gen bank assignment. Two clones were found to contain sequences which could be assigned to the osmolarity sensor protein envZ, showing homologies of 61 and 65%. EnvZ is an inner membrane protein in bacteria, important for osmosensing and required for porine gene regulation. It undergoes autophosphorylation and subsequently phosphorylates OmpR, which in turn binds to the porin (outer membrane protein) promoters to regulate the expression of OmpF and OmpC, major outer membrane porines. This is the first report of an osmosensing mechanism in the mammalian system, which was described in bacteria only. Furthermore, we are assigning a tentative role for taurine in the osmoregulatory process by modifying the expression of the osmoregulatory sensor protein ENVZ.
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  • 25
    ISSN: 1438-2199
    Keywords: Amino acids ; Protein ; arginine methyltransferase ; Inhibitors ; Ginseng extract ; Arginine derivatives ; Basic amino acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Protein-arginine N-methyltransferase (protein methylase I) catalyzes methylation of arginyl residues on substrate protein posttranslationally utilizing S-adenosyl-L-methionine as the methyl donor and yields NG-methylarginine residues. Arginyl-fructose and arginyl-fructosyl-glucose from Korean red ginseng were found to inhibit protein methylase I activity in vitro. This inhibitory activity was shown to be due to arginyl moiety in the molecules, rather than that of carbohydrates. Several basic amino acids as well as polyamines were also found to inhibit protein methylase I activity. Interestingly, the intensity of the inhibitory activity was correlated with the number of amino-group in polyamines, thus, in the order of spermine 〉 spermidine 〉 putrescine 〉 agmatine-sulfate, with IC50 at approximately 15 mM, 25 mM, 35 mM, and 50 mM, respectively. On the other hand, neutral amino acids or NaCI did not inhibit the enzyme activity. Lineweaver-Burk plot analysis of the protein methylase I activity in the presence of arginine and spermidine indicated that the inhibition was competitive in nature in respect to protein substrate, with the Ki values of 24.8 mM and 11.5 mM, respectively.
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  • 26
    ISSN: 1438-2199
    Keywords: Amino acids ; Hexafluoroacetone ; α-N-Methylamino acids ; α-N-Phosphinoylmethylamino acids ; Pro-Glu-chimeras ; Pro-Tauchimeras
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A new method for the preparation of N-methylamino acids and some of their derivatives starting from hexafluoroacetone protected amino acids is described. The new concept results in saving of steps compared to conventional protection/activation techniques. Protection and deprotection proceed without racemization.
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  • 27
    ISSN: 1438-2199
    Keywords: Amino acids ; Perfluorinated compounds ; Surfactants ; Complexing properties ; Carnosine ; β ; Amino acids ; Blood substitutes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The reaction of amines or sodium azide with 3-perfluoroalkyl-3-fluoroprop-2-enoate, followed by hydrogenation, affords perfluoroalkylatedβ-alanine analogues in very good yields. These compounds can be linked via an amide bond to produce peptide analogues such as carnosine or carcinine derivatives, which could have surfactive and complexing properties.
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  • 28
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    Amino acids 16 (1999), S. 415-423 
    ISSN: 1438-2199
    Keywords: Amino acids ; SOD-like activity ; Cu (III)-Poly-L-lysine ; Cu(III)-Poly-L-glutamic acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The SOD-like activity of Cu(III) -complexes with polypeptides poly-L-lysine and poly-L-glutamic acid respectively was investigated. The Cu(II)-polypeptide complexes were first oxidized by K2IrCl6 to give the corresponding Cu(III) -compounds. The oxidation of Cu(II) and the corresponding Cu(II)/Cu(III) potential was evaluated by cyclic voltammetry (c.v.), UV-Vis and EPR spectroscopic (r.t.) experiments. Spin trapping EPR spectra were also conducted to confirm the formation of the superoxide radical. The SOD-like activity of each Cu(III)-complex was proved using the nitro blue tetrazolium (NBT) method slightly modified.
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  • 29
    ISSN: 1438-2199
    Keywords: Amino acids ; Lysine ; Herbicides ; Azotobacter ; Xenobiotics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Production of lysine byAzotobacter chroococcum strain H23 was studied in chemically-defined media amended with different concentrations of alachlor, metolachlor, 2,4-D, 2,4,5-T and 2,3,6-TBA. The presence of 5, 10, and 50μg/ml of alachlor or 2,3,6-TBA significantly decreased quantitative production of lysine. However, the presence 2,4-D or 2,4,5-T at concentrations of 10 and 50μg/ml enhanced the production of lysine. Quantitative production of lysine was not affected as consequence of the addition of metolachlor to the culture medium, showing that the release lysine to the culture media byA. chroococcum was not affected by that herbicide.
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  • 30
    ISSN: 1438-2199
    Keywords: Amino acids ; Trypanothione ; Glutathione ; Benzyloxycarbonyl-reductase ; Hydrocinnamoyl
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Kinetic data for alternative substrates of recombinant trypanothione reductase fromTrypanosoma cruzi were measured for a series ofN-substituted-L-cysteinylglycyl-3-dimethylaminopropylamides, in which the cysteineN-substituent was either a variant of the benzyloxycarbonyl group or was L-phenylalanine or L-tryptophan. Replacing the benzylic ether oxygen atom by CH2. or NH had relatively minor effects on kcat, but raised the value of Km, 4.5- and 10-fold, respectively. Similarly, relative to the carbobenzoxy group, anN-L-phenylalanyl orN-L-tryptophanyl replacement on the cysteine hardly altered kcat, but increased Km, values by 16.6 and 7.4 fold, respectively. These observations were consistent with the Km, values referring primarily to binding for this series of nonspecific substrates.
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  • 31
    ISSN: 1438-2199
    Keywords: Amino acids ; Serotonin receptor ; Serotonin-3 receptor ; Ion channel ; Ion permeability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Human 5-HT3 receptors expressed in HEK 293 cells were studied using patch-clamp techniques. The permeability ratios of cations to Na+ were Li+, 1.16; K+, 1.04; Rb+, 1.11; Cs+ 1.11; NMDG+, 0.04; Ca2+, 0.49, and Mg2+, 0.37. The permeability sequence of the alkali metal cations was Li+ 〉 Rb+ = Cs+ 〉 K+ 〉 Na+. Increased external concentrations of Ca2+ or Mg2+ decreased 5-HT-induced currents at all potentials tested in a voltage-independent manner. The single-channel conductance of human 5-HT3 receptors measured by fluctuation analysis of whole-cell currents was 790 ± 100fS. Differences in the basic properties of 5-HT3 receptors between species may explain interspecies differences in pharmacological properties.
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  • 32
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    Amino acids 17 (1999), S. 301-313 
    ISSN: 1438-2199
    Keywords: Amino acids ; Taurine ; Transporter ; Rat ; Brain ; Heart
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In pro- and eucaryotic life, cellular and subcellular compartments are separated by membranes and the regulated and selective passage of specific molecules across these membranes is a basic and highly conserved principle. We were interested whether taurine, a naturally occuring amino acid, would be able to induce or suppress expression of transporters with the Rationale that taurine was shown to detoxify a series of endogenous toxins and xenobiotics of various chemically non-related structures. For this purpose we used a gene hunting technique, subtractive hybridization, subtracting mRNAs of taurine-treated rat brain and heart from untreated controls. Subtracted mRNAs were then converted to cDNAs, amplified, sequenced and identified by gene bank data. We found five transporter transcripts, the phosphonate transport ATPase PHNC, multidrug transporter homolog MTH104, protein-exportmembrane protein SECD, oligopeptide transporters oppA and oppD, in the brain and two: ABC-transporter BRAF-2 and cation-transport ATPase PACS, in the heart. Homologies of the sequences found were in any case 〉50% thus permitting the identification of transporters with high probability. The biological meaning could be that a naturally occuring amino acid, taurine, modulates complex transport systems. The most prominent finding is the upregulation of a multidrug transporter transcript, explaining a mechanism for the nonselective detoxifying action of taurine.
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  • 33
    ISSN: 1438-2199
    Keywords: Amino acids ; Tyrosine ; Phenylalanine ; Aromatic compounds ; Rumen microorganisms[/klw]
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Rumen contents from three fistulated Japanese native goats fed Lucerne hay cubes (Medicago sativa) and concentrate mixture were collected to prepare the suspensions of mixed rumen bacteria (B), mixed protozoa (P) and a combination of the two (BP). Microbial suspensions were anaerobically incubated at 39°C for 12h with or without 1 MM ofl-phenylalanine (Phe). Phe, tyrosine (Tyr) and other related compounds in both supernatant and microbial hydrolysates of the incubations were analyzed by HPLC. Tyr can be produced from Phe not only by rumen bacteria but also by rumen protozoa. The production of Tyr during 12h incubation in B (183.6 μmol/g MN) was 4.3 times higher than that in P. One of the intermediate products between Phe and Tyr seems to bep-hydroxyphenylacetic acid. The rate of the net degradation of Phe incubation in B (76.O μmol/g MN/h) was 2.4 times higher than in P. In the case of all rumen microorganisms, degraded Phe was mainly (〉53%) converted into phenylacetic acid. The production of benzoic acid was higher in P than in B suspensions. Small amount of phenylpyruvic acid was produced from Phe by both rumen bacteria and protozoa, but phenylpropionic acid and phenyllactic acid were produced only by rumen bacteria.
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  • 34
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    Amino acids 17 (1999), S. 357-368 
    ISSN: 1438-2199
    Keywords: Amino acids ; o-Carboranylalanine ; Histidine ; Bacteria ; Fungi ; Oomycota ; Plasmopara
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Functionalized polyhedral carboranes, including amino acid analogs, have unique physicochemical properties and are used as experimental anticancer agents. However, our current knowledge on their effect in nonmammalian biological systems is limited. We investigated the activity spectrumin vitro ofo-carboranylalanine (o-Cba), considered to be a highly lipophilic analog of phenylalanine, against representative plant pathogenic bacteria and fungi of various taxonomic position. The antibacterial effect ofo-Cba against some species was comparable to that of the widely used agricultural antibiotic, streptomycin. The sensitivity of individual bacterial species too-Cba within the same genus varied to a greater extent than the average sensitivity of various genera. In general, this carborane-containing amino acid was more toxic to Gram positive bacteria (Bacillus, Corynebacterium, Curtobacterium, Micrococcus, Rhodococcus, and Staphylococcus) than to Gram negative ones (Agrobacterium, Erwinia, Escherichia, Pseudomonas, Rhizobium, and Xanthomonas). Compared to the commercial fungicide, prochloraz,o-Cba was weakly toxic against various fungi (Zygo- and Ascomycota). It was also inferior to the commercial fungicide metalaxyl in inhibiting the vegetative growth of oomyceteous plant pathogens (Pythium irregulare, Phytophthora cryptogea and Plasmopara halstedii). Against the asexual spores of P. halstedii,o-Cba, however, was over a thousandfold more active than tridemorph, a selective zoospore inhibitor fungicide. For all taxonomic groups, the observed antimicrobial effect ofo-Cba could be diminished with histidine, but not with phenylalanine. In studies on healthy and mildew-infected sunflower and tobacco plantso-Cba showed neither fungicidal nor phytotoxic effects at 500ppm. This is the first report on the biological activity spectrum of a carborane-containing amino acid.
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  • 35
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    Amino acids 17 (1999), S. 401-413 
    ISSN: 1438-2199
    Keywords: Amino acids ; Indolylacrylic acid ; Tryptophan ; Indolylacryloylglycine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In addition to the main catabolic routes of tryptophan (Trp), there exist minor and less thoroughly investigated pathways; one of these leads to indolylacrylic acid (IAcrA). IAcrA is a plant growth hormone, whereas its biological role in animals is still obscure, as is the way and site where it is formed in the organism. A two-stage production is likely: Intestinal microorganisms catabolize Trp to indole derivatives which are then absorbed and converted to IAcrA and its glycine conjugate, indolylacryloylglyeine (IAcrGly). Our finding of IAcrGly in the urine of proven germ-free piglets points to the possibility that Trp can be converted to IAcrA without the intervention of intestinal microorganisms. Seasonal and age variations, influence of light and connection with photodermatoses have been reported. Besides other pathological conditions the differences in IAcrGly excretion relative to normal controls were especially pronounced in some myopathies, namely in boys with Duchenne muscular dystrophy.
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  • 36
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    Biology and fertility of soils 29 (1999), S. 257-261 
    ISSN: 1432-0789
    Keywords: Key words Alpine nitrogen cycle ; Amino acids ; Kobresia myosuroides ; Organic nitrogen ; Plant-microbe competition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Microbes are assumed to possess strong competitive advantages over plants for uptake of nutrients from the soil. The finding that non-mycorrhizal plants can obtain a significant fraction of their N requirement from soil amino acids contradicts this assumption. The amino acid glycine (Gly) has been used as a model amino acid in many recent studies. Our preliminary studies showed that Gly was a poor substrate for microbial growth compared to other amino acids. We tested the hypothesis that the alpine sedge Kobresia myosuroides competes better for Gly than for other amino acids because of decreased microbial demand for this compound. Soil microbial populations that could grow using Gly as a sole carbon source were about 5 times lower than those that could grow on glutamate (Glu). Gly supported a significantly lower population than any of the ten other amino acids tested except serine. In contrast, K. myosuroides took up Gly from hydroponic solution at faster rates than Glu. In plant-soil microcosms, plants competed with soil microbes 3.25 times better for Gly than for Glu. We conclude that the low microbial demand and the rapid plant uptake of Gly relative to other amino acids allow Gly to be an especially important nitrogen source for K. myosuroides.
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  • 37
    ISSN: 1432-0975
    Keywords: Key words Otolith ; Chemistry ; ICP-MS ; Stock discrimination ; Epinephelus striatus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract  We examined the utility of otolith minor and trace element chemistry, assayed with inductively coupled plasma mass spectrometry (ICP-MS), as a means of delineating population structure in the Nassau grouper (Epinephelus striatus). We characterized the elemental composition of otoliths collected in 1993 from three locations in Exuma Sound, Bahamas and from Glover Reef, Belize in 1995. A single location in Exuma Sound was sampled in 1994 to test temporal variability in otolith composition. Five elements (Ca, Zn, Sr, Ba and Pb) were routinely detected, at levels significantly above background, by solution-based ICP-MS. Results from analysis of variance of elemental data, expressed as a ratio to Ca, indicated that there were no significant differences among the Exuma locations for any element, but significant variability was found between Glover Reef and the pooled Exuma localities for Zn/Ca, Sr/Ca and Ba/Ca ratios. Significant inter-annual differences at one Exuma Sound location was restricted to Ba/Ca ratios. Discriminant function analysis correctly classified 86% and 95% of the Belize and pooled Exuma sites, respectively. Otoliths from Belize were characterized by low Zn/Ca and high Ba/Ca and Pb/Ca ratios compared to otoliths from fish collected in Exuma Sound. Although differences in Ba levels may be related to upwelling at Glover Reef, more data are needed to definitely link otolith composition with regional differences in water chemistry.
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  • 38
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    Zeitschrift für Lebensmittel-Untersuchung und -Forschung 208 (1999), S. 50-56 
    ISSN: 1431-4630
    Keywords: Key words Flavor enhancer ; Savory flavoring ; Taste ; Amino acids ; Partial least squares regression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  Enzymatically hydrolyzed vegetable protein was produced from soy protein using hydrolysis times of 0–20 h. The development of sensory properties and the pattern of protein degradation was followed. Around two-thirds of the final amount of free amino acids and degree of hydrolysis (DH) were achieved during the first 4 h of hydrolysis. Between 6 h and 10 h of hydrolysis the bouillon-like tastes increased significantly (P〈0.001). In this time interval the amount of free amino acids exceeded 40% of the total amino acids and the DH exceeded 50% of the theoretically possible (100%). Using partial least squares regression with standardisation of free amino acid data according to their taste threshold values showed that free glutamic acid, aspartic acid and lysine correlated with the bouillon-like tastes. By standardisation of free amino acid data with respect to their SD the specificity of the enzymes for amino acid side-chains could be seen.
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  • 39
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    Zeitschrift für Lebensmittel-Untersuchung und -Forschung 208 (1999), S. 355-361 
    ISSN: 1431-4630
    Keywords: Key words Flavor enhancer ; Taste ; Amino acids ; Carbohydrates ; Maillard reaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  Hydrolyzed vegetable protein produced using hydrochloric acid (HVP) or proteolytic enzymes (EVP) was given a maturation period of up to 6 weeks at 30  °C. The maturation resulted in a darker color for both hydrolysates, but the sensory profiles were not altered to any great extent. For both hydrolysates a decrease in the amount of free amino acids or an increase in the amount of bound amino acids was seen, and for EVP, a decrease in the amount of free monosaccharides was likewise observed. In HVP the mono- and polysaccharides were destroyed during hydrolysis. The changes in amino acids could be due to, for example, a reversible binding to either a monosaccharide in EVP or a degradation product of carbohydrates in HVP, leading to the first stage of the Maillard reaction. These early reactions did not proceed to any flavor-giving Maillard reaction compounds. Maturation can therefore not be used to enhance the flavor of protein hydrolysates under the applied production conditions.
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  • 40
    ISSN: 1432-1106
    Keywords: Key words Gabaculine ; NMR spectroscopy ; Microdialysis ; Amino acids ; Compartmentation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The aim of this work was to study the neurochemical effects in the brain of GABA-transaminase inhibition by systemic administration of gabaculine (100 mg/kg, i.a.) in the rat. In order to investigate neurotransmitter and related amino-acid compartmentation and metabolism, we have developed an original tool: the coupling, in vivo, on the same animal, of 2D COSY 1H-NMR spectroscopy with intracerebral microdialysis. The main result is a continuous increase in GABA levels, both in the intracellular compartment (up to 3000±450%; P〈0.001) and extracellular compartment (up to 808±82%; P〈0.01) at the sixth hour. The intracellular increase in GABA level became significant at the first hour following gabaculine administration, whereas the extracellular level increased as of the second hour, probably indicating that accumulation of GABA in nerve endings precedes its release in synaptic clefts. Moreover, the levels of the excitatory amino acids, glutamate and aspartate, were decreased both in the intra- and extracellular compartments, thus enhancing sedative effects of the drug. We also observed a decrease in the global energetic creatine-phosphocreatine pool, which also could be related to the sedative properties of gabaculine, measurable by the diminution of cortical electrical activity and mean arterial blood pressure. Finally, the coupling between 2D 1H-NMR spectroscopy and intracerebral microdialysis appears to be an original tool for investigating the cerebral metabolic effects induced by pharmacological agents, in situ, in living animals.
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  • 41
    ISSN: 1432-1939
    Keywords: Key words Estuarine food web ; Stable isotopes ; Amino acids ; Growth experiment ; Crustacean metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The stable isotope compositions (C and N) of plants and animals of a marsh dominated by Spartina alterniflora in the Delaware Estuary were determined. The study focused on the juvenile stage of the Atlantic blue crab, Callinectes sapidus, and the importance of marsh-derived diets in supporting growth during this stage. Laboratory growth experiments and field data indicated that early juvenile blue crabs living in the Delaware Bay habitat fed primarily on zooplankton, while marsh-dwelling crabs, which were enriched in 13C relative to bay juveniles, utilized marsh-derived carbon for growth. In laboratory experiments, the degree to which juvenile blue crabs isotopically fractionated dietary nitrogen, as well as the growth rate, depended on the protein quality of the diet. The range of δ13C of amino acids in laboratory-reared crabs and their diets was almost 20‰, similar to the isotopic range of amino acids of other organisms. In laboratory studies, the δ13C of nonessential and essential amino acids in the diet were compared to those in juvenile crabs. Isotopic fractionation at the molecular level depended on diet quality and the crabs' physiological requirements. Comparison of whole-animal isotope data with individual amino acid C isotope measurements of wild juvenile blue crabs from the bay and marsh suggested a different source of total dietary carbon, yet a shared protein component, such as zooplankton.
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  • 42
    ISSN: 1432-0738
    Keywords: Key words 2 ; 3 ; 7 ; 8-Tetrachlorodibenzo-p-dioxin ; TCDD ; Phosphoenolpyruvate carboxykinase ; PEPCK ; Glucose ; Glycogen ; Amino acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Reduced gluconeogenesis due to decreased activity of key gluconeogenic enzymes in liver, together with feed refusal, has been suggested to play an important role in 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced lethality in rats. This study was carried out to further analyse the toxicological significance of reduced gluconeogenesis by comparing dose-responses and time-courses of effects of TCDD on the activity of phosphoenolpyruvate carboxykinase (PEPCK) in liver, liver glycogen concentration as well as plasma concentrations of glucose and amino acids in both genders of TCDD-sensitive Long-Evans (L-E) rats and TCDD-resistant Han/Wistar (H/W) rats. A dose-dependent decrease in PEPCK activity was observed in H/W rats, but in L-E rats the activity was not decreased. However, TCDD impaired the strong increase in liver PEPCK activity observed in pair-fed controls of the L-E strain. Liver glycogen concentrations were severely decreased in L-E rats and moderately in H/W rats. This effect seems to be secondary to reduced feed intake, since a similar decrease was seen in pair-fed controls. Decreases in plasma glucose concentrations were also more profound in L-E rats than in H/W rats, but pair-fed controls were generally less affected. Circulating concentrations of amino acids were markedly increased in TCDD-treated L-E rats, which is likely to reflect increased mobilization of amino acids and their decreased metabolism in liver. Reduction of liver PEPCK activity cannot account for the sensitivity difference of these two strains of rats in terms of mortality. Nevertheless, the response of both strains of TCDD-treated rats regarding gluconeogenesis is different from that seen in pair-fed controls and suggesting that impairment of this pathway contributes to the development of the wasting syndrome.
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  • 43
    ISSN: 1438-2199
    Keywords: Amino acids ; Cerebellar granule cells ; Neurotoxicity ; Terfenadine ; Excitatory amino acids ; Histamine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Exposure of cultured cerebellar neurons to the histamine H1 receptor antagonist terfenadine resulted in neuronal degeneration and death. Terfenadine neurotoxicity was dependent upon concentration and time of exposure. After 2h exposure, 20µM terfenadine reduced the number of surviving neurons by 75%, and as low as 10nM terfenadine induced significant neurotoxicity after 5 days of exposure. Neuronal sensitivity to terfenadine changed with age in culture, and at 25 days in culture neurons appeared to be much less sensitive than at 5 or 9–17 days in culture. Neurotoxicity by terfenadine could not be prevented by high concentrations of histamine (5 mM), but it was significantly delayed by blocking NMDA or non-NMDA glutamate receptors with MK-801 or CNQX respectively, suggesting the involvement of excitatory transmission mediated by glutamate in the neurotoxicity induced by terfenadine in these neurons. We also found that the presence of terfenadine (5,µM) unveiled the potential excitotoxicity of the non-NMDA receptor agonist AMPA (100µM), and reduced the concentration of glutamate necessary to induce excitotoxicity, compared to untreated cultures. These results suggest a role for terfenadine in the modulation of the excitotoxic response mediated in cerebellar neurons through ionotropic glutamate receptors.
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  • 44
    ISSN: 1438-2199
    Keywords: Amino acids ; eIF-5A ; Hypusine ; Protein folding ; Posttranslational modification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The molecular properties of the human eukaryotic initiation factor 5A precursor and its site directed Lys50 → Arg variant have been investigated and compared. Structure perturbation methods were used to gain information about the protein architecture in solution. Intrinsic and extrinsic spectroscopic probes strategically located in the protein matrix detected the independent unfolding of two molecular regions. Three cystemes out of four were titrated in the native protein and the peculiar presence of a tyrosinate band at neutral pH was detected. At alkaline pH only two tyrosines out of three were titratable in the native protein, with an apparent pK of about 9.9. Native protein and its Lys50 → Arg variant reacted in a similar fashion to guanidine and to pH variation, but differently to thermal stress. The complex thermal unfolding of both proteins indicated the presence of intermediates. Spectroscopic data showed that these intermediates are differently structured. Consequently, the two proteins seem to have different unfolding pathways.
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  • 45
    ISSN: 1438-2199
    Keywords: Amino acids ; 5/6 nephrectomy ; Renal failure ; Amino acid transport ; Kidney ; Triiodothyronine ; Dexamethasone ; Amino acid load ; Rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 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 concentrations were comparable to those of control animals with two intact kidneys, whereas the fractional excretions (FEAA) of most endogenous amino acids measured were significantly enhanced. After bolus injection of leucine or taurine (each 20 mg/100 g b.wt.) or glutamine (90 mg/ 100 g b.wt.), dissolved in 2m1 normal saline per 100 g b.wt., the FEAA of both the amino acids administered and the endogenous amino acids increased as a sign of overloaded amino acid reabsorption capacity. This effect was more pronounced in 5/6NX rats than in controls. As early as one hour after amino acid load, plasma concentrations and FEAA returned to baseline values of 5/6NX rats. A pretreatment with triiodothyronine (20,µg/100 g b.wt.) or dexamethasone (60 µg/100 g b.wt.), both given intraperitoneally once daily for 3 days, stimulated the renal amino acid transport capacity in 5/6NX rats: the increase in FEAA after amino acid load was significantly lower compared to non-pretreatred animals. This stimulation could be shown for the bolus amino acids and the endogenous amino acids and was more distinct in 5/6NX rats than in controls with two intact kidneys.
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  • 46
    ISSN: 1438-2199
    Keywords: Amino acids ; Nitric oxide ; Ornithine decarboxylase ; Proliferation ; Cell death ; Cardiomyocytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Nitric oxide (NO) is a molecule involved in several signal transduction pathways leading either to proliferation or to cell death. Induction of ornithine decarboxylase (ODC), the key enzyme of polyamine biosynthesis, represents an early event preceding DNA synthesis. In some cell types increased ODC activity seems to be involved in cytotoxic response. We investigated the role of NO and ODC induction on the events linked to cell proliferation or to cell death in cultured chick embryo cardiomyocytes. Exposure of cardiomyocytes to tumor necrosis factor (TNF) and lipopolysaccharide (LPS) caused NO synthase (NOS) and ODC induction as well as increased incorporation of [3H]-thymidine. This last effect was blocked by a NOS inhibitor and was strongly reduced by difluoromethylornithine (DFMO), an irreversible inhibitor of ODC. Sodium nitroprusside (SNP), an exogenous NO donor, inhibited the increases of NOS and ODC activities and abolished the mitogenic effect of TNF and LPS. Moreover, SNP alone caused cell death in a dose dependent manner. The cytotoxicity of SNP was not affected by DFMO while it was prevented by antioxidants. The results suggest that different pathways would mediate the response of cardiomyocytes to NO: they can lead either to ODC induction and DNA synthesis when NO is formed through NOS induction or to growth inhibition and cell death, when NO is supplied as NO donor. Increased polyamine biosynthesis would mediate the proliferative response of NO, while the cytotoxicity of exogenous NO seems to involve some oxidative reactions and to depend on the balance between NO availability and cellular redox mechanisms.
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  • 47
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    Amino acids 16 (1999), S. 297-320 
    ISSN: 1438-2199
    Keywords: Amino acids ; Pipecolic acid ; Pipecolic acid derivatives ; Asymmetric synthesis ; Hemisyntheses ; Chiral auxiliaries
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Results in the field of asymmetric synthesis of pipecolic acid derivatives are reviewed. Three sections describe the asymmetric syntheses of the title compounds (i) from the chiral pool (α-amino acids or carbohydrates) (ii) using a chiral auxiliary either derived from terpenes,α-amino acids, tartaric acid, an amine orβ-amino alcohols (iii) by means of asymmetric catalysis.
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    Amino acids 16 (1999), S. 321-343 
    ISSN: 1438-2199
    Keywords: Amino acids ; Amino alcohols ; β-Lactams ; NCA ; Peptides ; Synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The potential ofβ-lactams as intermediates for the access toα- andβ-amino acid-derived peptides is shortly reviewed, with major focus on the technologies developed in our group. The two general strategies lie, on one side, in the oxidative ring expansion of 3-hydroxyβ-lactams toN-carboxyα-amino acid anhydrides or Leuch's anhydrides and subsequent coupling withα-amino acid esters and, on the other side, in the nucleophilic ring opening ofN-Boc-β-lactams. Both approaches have been successfully applied to the synthesis ofα,β-diamino acid,α-amino-β-hydroxy acid, polyhydroxylatedα-amino acid,α,α-disubstitutedα-amino acid,β-amino acid,β-amino-α-hydroxy acid andβ,β-disubstitutedβ-amino acid derived peptides. Because of the mild reaction conditions needed for the above transformations and the highly stereoselective procedures employed for the construction of the startingβ-lactam ring, the whole process allows the production of optically pure final products.
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  • 49
    ISSN: 1438-2199
    Keywords: Amino acids ; Clonidine ; GABAA receptor antagonists ; GABA turnover ; SHR ; WKY rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effect of γ-aminobutyric acid (GABA)A antagonists (bicuculline, picrotoxin) on clonidine hypotension in spontaneously hypertensive (SHR) and Wistar Kyoto (WKY) rats were examined. The GABA turnover changes after clonidine injection in both strains were also studied. Administration of clonidine alone induced the stronger decrease of systolic blood pressure (SBP) in SHR. Co-dosage of clonidine with these agents reduced its hypotensive effect in dose dependent manner and the effectiveness of both antagonists was higher in SHR. We find that clonidine stimulates GABA synthesis in the hypothalamus and the pons-medulla in both strains but the GABA turnover rate is significantly slower in SHR. Therefore, the differences in inhibitory action of GABAA receptor anatgonists between WKY and SHR rats may be explained by central GABAergic system dysfunction in the hypertension. Our results indicate that the down regulation of the GABAergic system observed in hypertension may be compensated by the action of clonidine.
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  • 50
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    Amino acids 17 (1999), S. 185-193 
    ISSN: 1438-2199
    Keywords: Amino acids ; Anaerobic bacteria ; Catabolism ; HPLC ; Stereochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The utilization ofd- andl -amino acids with acidic, basic or polar side chains was demonstrated by HPLC. Two species of the anaerobeFusobacterium utilized D-lysine and the L isomers of glutamate, glutamine, histidine, lysine and serine. OnlyF. varium usedl-arginine,d-glutamate andd-serine as substrates, whereasF. nucleatum specifically utilizedd-histidine andd-glutamine.d-Glutamate accumulated in F. nucleatum cultures supplemented withd-glutamine, and ornithine was detected when eitherdl- orl-arginine was included inF. varium cultures. Based on literature precedents,d-glutamate andd-histidine are isomerized to their L isomers prior to degradation, but separate catabolic pathways are possible for each enantiomer of lysine and serine.
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    Amino acids 17 (1999), S. 227-241 
    ISSN: 1438-2199
    Keywords: Amino acids ; Glutamine ; Lymphocyte ; Macrophage ; Mononuclear cell ; Cytokine ; Infection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Glutamine is utilised at a high rate by cells of the immune system in culture and is required to support optimal lymphocyte proliferation and production of cytokines by lymphocytes and macrophages. Macrophage-mediated phagocytosis is influenced by glutamine availability. Hydrolysable glutamine dipeptides can substitute for glutamine to support in vitro lymphocyte and macrophage functions. In man plasma and skeletal muscle glutamine levels are lowered by sepsis, injury, burns, surgery and endurance exercise and in the overtrained athlete. The lowered plasma glutamine concentrations are most likely the result of demand for glutaminne (by the liver, kidney, gut and immune system) exceeding the supply (from the diet and from muscle). It has been suggested that the lowered plasma glutamine concentration contributes, at least in part, to the immunosuppression which accompanies such situations. Animal studies have shown that inclusion of glutamine in the diet increases survival to a bacterial challenge. Glutamine or its precursors has been provided, usually by the parenteral route, to patients following surgery, radiation treatment or bone marrow transplantation or suffering from injury. In most cases the intention was not to stimulate the immune system but rather to maintain nitrogen balance, muscle mass and/or gut integrity. Nevertheless, the maintenance of plasma glutamine concentrations in such a group of patients very much at risk of immunosuppression has the added benefit of maintaining immune function. Indeed, the provision of glutamine to patients following bone marrow transplantation resulted in a lower level of infection and a shorter stay in hospital than for patients receiving glutamine-free parenteral nutrition.
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    Amino acids 17 (1999), S. 277-283 
    ISSN: 1438-2199
    Keywords: Amino acids ; D-Aspartic acid ; D-Leucine ; Pineal gland ; Sympathetic nervous system ; Anesthesia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In a previous report (Hamase, K. et al., Biochim Biophys Acta 1134: 214–222 (1997)), we showed that the rat pineal gland contains D-leucine (D-Leu) as well as D-aspartic acid (D-Asp). In this communication we report alterations in the content of these D-amino acids during anesthesia. The D-Asp content was significantly increased from 2.8 to 5.0, 4.8 and 5.8 nmol/pineal gland by administration of ether, urethane and pentobarbital, respectively. In contrast, the D-Leu content was decreased by administration of urethane or pentobarbital. The D-Leu content decreased from 4.2 to 2.2 pmol/pineal gland 4 hours after administration of urethane, although the content remained unchanged until 1.5 hours after administration. The content of the L-enantiomers of these amino acids were not affected by anesthesia. The urethane-induced decrease in D-leucine content was almost completely suppressed by aβ-agonist, (-)-isoproterenol, whereas the agonist itself had no effect.
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  • 53
    ISSN: 1438-2199
    Keywords: Amino acids ; Glycyl-L-proline ; Urine ; Trophicity ; Collagen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Glycyl-L-proline (gly-pro) is an end product of collagen metabolism that is further cleaved by prolidase (EC 3.4.13.9); the resulting proline molecules are recycled into collagen or other proteins. We postulated a relationship between defective gly-pro hydrolysis, increased collagen degradation and skin destruction. This relationship was tested using HPLC to measure the gly-pro in urine. 24 hour urine samples were collected from 27 old people (86 ± 6 years old), of whom 15 were suffering from skin pressure sores of the sacrum or calcaneus. The urine from patients with pressure sores contained significantly more gly-pro than the urine from the control. A cut-off at 7μmol/ mmol creatinine gave the test a positive predictive value of 70%. Collagen breakdown was also increased as indicated by the increase of hydroxyproline (hyp) in the urine. But this breakdown seemed to stop at the gly-pro step.
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  • 54
    ISSN: 1438-2199
    Keywords: Amino acids ; Taurine release ; Metabotropic glutamate receptors ; Hippocampal slices ; Adult ; Developing mice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The inhibitory amino acid taurine has been held to function as an osmoregulator and modulator of neural activity, being particularly important in the immature brain. lonotropic glutamate receptor agonists are known markedly to potentiate taurine release. The effects of different metabotropic glutamate receptor (mGluR) agonists and antagonists on the basal and K+-stimulated release of [3H]taurine from hippocampal slices from 3-month-old (adult) and 7-day-old mice were now investigated using a superfusion system. Of group I metabotropic glutamate receptor agonists, quisqualate potentiated basal taurine release in both age groups, more markedly in the immature hippocampus. This action was not antagonized by the specific antagonists of group I but by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and 6-nitro-7-sulphamoylbenzo[f]quinoxaline-2,3-dione (NBQX), which would suggest an involvement of ionotropic glutamate receptors. (S)-3,5-dihydroxyphenylglycine (DHPG) potentiated the basal release by a receptor-mediated mechanism in the immature hippocampus. The group II agonist (2S, 2′R, 3′R)-2-(2′,3′-dicarboxycyclopropyl)glycine (DCG IV) markedly potentiated basal taurine release at both ages. These effects were antagonized by dizocilpine, indicating again the participation of ionotropic receptors. Group III agonists slightly potentiated basal taurine release, as did several antagonists of the three metabotropic receptor groups. Potassium-stimulated (50 mM K+) taurine release was generally significantly reduced by mGluR agents, mainly by group I and II compounds. This may be harmful to neurons in hyperexcitatory states. On the other hand, the potentiation by mGluRs of basal taurine release, particularly in the immature hippocampus, together with the earlier demonstrated pronounced enhancement by activation of ionotropic glutamate receptors, may protect neurons against excitotoxicity.
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  • 55
    ISSN: 1432-2277
    Keywords: Key words Liver transplantation ; Survival ; Amino acids ; Organ preservation ; Primary nonfunction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract There are too few reliable markers by which one can predict future function of a liver before implantation. Consequently, the purpose of this study was to test the hypothesis that amino acids in rinse–effluents could predict transplant outcome in marginal fatty livers from rats. Amino acids were measured in the rinse effluent from the livers immediately after harvest and graft preparation or cold storage. Amino acids in the effluent were twice as high in ethanol-treated animals compared to those in nonfatty controls. Ethanol-treated fatty livers survived for no longer than 7 days after transplantation while 83 % of nonfatty controls survived (P 〈 0.05). In subsequent studies, the cold-storage time was decreased to 6 h to determine whether failing fatty livers released more amino acid than grafts that would function normally. There was a significant increase in amino acids in the effluent of fatty grafts compared to controls. Moreover, the sum of the four selected amino acids (alanine, valine, histidine, leucine) was lower than 23 nmol/g liver in functional livers, whereas failing grafts had totals significantly higher than 25 nmol/g liver. The sum of the four amino acids correlated well with 24 h post-transplant serum AST levels (r = 0.78, P 〈 0.0001). So we can conclude that amino acid release can serve as a useful marker of graft viability and reliably predicts survival.
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    Theoretical chemistry accounts 101 (1999), S. 186-193 
    ISSN: 1432-2234
    Keywords: Key words: Solvent accessibility ; Logistic function ; Hydrophobicity ; Burial index ; Amino acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract. For predicting solvent accessibility from the sequence of amino acids in proteins, we use a logistic function trained on a non-redundant protein database. Using a principal component analysis, we find that the prediction can be considered, in a good approximation, as a monofactorial problem: a crossed effect of the burial propensity of amino acids and of their locations at positions flanking the amino acid of interest. Complementary effects depend on the presence of certain amino acids (mostly P, G and C) at given positions. We have refined the predictive model (1) by adding supplementary input data, (2) by using a strategy of prediction correction and (3) by adapting the decision rules according to the amino acid type. We obtain a best score of 77.6% correct prediction for a relative accessibility of 9%. However, compared to trivial strategy only based upon the frequencies of buried or exposed residues, the gain is less than 4%.
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  • 57
    ISSN: 1439-6327
    Keywords: Key words Endurance exercise ; Amino acids ; Serotonin ; Central fatigue ; Overtraining
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The neurotransmitter serotonin (5-hydroxytryptamine, 5-HT) has been shown to modulate various physiological and psychological functions such as fatigue. Altered regulation of the serotonergic system has been suggested to play a role in response to exercise stress. In the present study, the influence was investigated of acute endurance exercise and short-term increase in the amount of training on the concentrations of the 5-HT precursor tryptophan (TRP), of prolactin (PRL) and of branched-chain amino acids (BCAA) in the blood, as well as on the binding of [3H]ketanserin to the serotonin-2A (5-HT2A) receptors on platelets. Nine healthy endurance-trained men were tested the day before (I) and after (II) a 9-day training programme. Samples of venous blood were drawn after an overnight fast and following 5 h of cycling. Fasted and post-exercise plasma concentrations of free TRP, BCAA and free TRP:BCAA ratio did not differ between I and II. A significant decrease of plasma BCAA (P 〈 0.01) and significant augmentations of plasma free TRP, free TRP:BCAA ratio and PRL (P 〈 0.01) were found post-exercise. The increase in plasma PRL was smaller in II compared with I. Acute endurance exercise reduced the density of platelet 5-HT2A receptor [3H]ketanserin binding sites at I and II (P 〈 0.05). The basal density of the binding sites and the affinity of [3H]ketanserin for these binding sites were unaffected by an increase in the amount of training. The present results support the hypothesis that acute endurance exercise may increase 5-HT availability. This was reflected in the periphery by increased concentration of the 5-HT precursor free TRP, by increased plasma PRL concentration, and by a reduction of 5-HT2A receptors on platelets. It remains to be resolved whether these alterations in the periphery occur in parallel with an increase in the availability of 5-HT in the brain.
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    Plant foods for human nutrition 54 (1999), S. 375-380 
    ISSN: 1573-9104
    Keywords: 7S/11S ratios ; Amaranth ; Amino acids ; Nutrition ; Varieties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract 7S/11S seed globulin ratios were determined for sevencurrently available Amaranthus hybrid linesi.e., Amaranthus K266, K283, K343, K432, K433,K436 and MT-3. Of the seven Amaranthus linesinvestigated, four lines had 7S/11S globulin ratiosranging from 0.47 to 0.81, while three lines werefound to contain exclusively the 11S globulin form. In general, 7S globulins contained lower levels ofessential amino acids such as tryptophan, methionine,lysine, histidine, phenylalanine, valine andisoleucine than the 11S globulins.
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  • 59
    ISSN: 1573-9104
    Keywords: Amino acids ; Celiac disease ; Cells ; Cereals ; Prolamines ; Quinoa seeds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The edible seeds of the quinoa plant contain small quantities of alcohol-soluble protein which, after peptic-tryptic digestion, are unable to agglutinate K562(s) cells. When separated by affinity chromatography on sepharose-6B coupled with mannan, peptic-tryptic digest separated in two fractions. Fraction B peptides (about 1% of total protein) were shown to agglutinate K562(s) cells at a very low concentration, whereas peptides in fraction A and in the mixed fraction A+B were inactive, suggesting that fraction A contains protective peptides that interfere with the agglutinating activity of toxic peptides in fraction B.
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    Plant foods for human nutrition 54 (1999), S. 345-352 
    ISSN: 1573-9104
    Keywords: Amino acids ; Antinutritional factors ; Protein fractionation ; Proximate composition ; Teramnus labialis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Seeds of Teramnus labialis (L.) Spreng.(Fabaceae), used as food by Malayali tribals in theKollihills of Salem District, Tamil Nadu in SouthIndia, were investigated for their nutritional value. These seeds were analyzed for proximate composition,total (true) seed proteins, seed proteinfractions, amino acid composition, fatty acidcomposition, minerals and antinutritional factors. Crude protein, crude fat, ash, and nitrogen freeextracts constituted 22.86%, 6.10%, 4.62%, and,58.15%, respectively, of the seed weight. The caloricvalue of 100 g dry matter of seed material was 378.94kcal. The essential amino acids lysine, leucine +isoleucine, arginine, valine and histidine werepresent in relatively large quantities. Theunsaturated fatty acids constituted more than 60% ofthe crude fat. Concentrations of minerals such aspotassium, magnesium, calcium, and, phosphorus werehigh. Antinutritional factors such as total freephenols, tannins, L-DOPA, hydrogen cyanide andphytic acid were present in minute quantities. Theseantinutritional factors are potentially eliminated using the conventional method of soaking the seeds in water,boiling with water and decanting prior to consumption.
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  • 61
    ISSN: 1573-6903
    Keywords: Amino acids ; synaptosomes ; epilepsy ; glutamate ; GABA ; glutamine ; taurine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We have studied the levels of neuroactive amino acids in synaptosomes (P2 fraction) isolated from brain tissue of ten patients with medically intractable epilepsy who were undergoing temporal lobectomy. First, lateral temporal tissue (nonfocal) was removed followed by medial temporal tissue (focal). A synaptosomal fraction (P2) was immediately prepared from each tissue and analyzed for free amino acid concentrations. Statistically significant reductions were seen in glutamine and GABA concentrations in focal tissue compared to nonfocal tissue. The ratio of excitatory amino acids (aspartate and glutamate) to inhibitory amino acids (taurine and GABA) was significantly higher in focal tissue compared to nonfocal. The glutamine/glutamate ratio was significantly reduced. These data support the hypothesis that alterations in the balance between excitatory and inhibitory amino acids may be involved in the expression of epilepsy.
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  • 62
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    World journal of microbiology and biotechnology 15 (1999), S. 511-512 
    ISSN: 1573-0972
    Keywords: Amino acids ; Staphylococcus ; xylanase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Amino acids such as DL-2-amino-n-butyric acid, DL-alanine, L-lysine monohydrochloride, DL-valine and L-proline enhanced total xylanase production from Staphylococcus sp. SG-13 up to 5.5-fold. The present study showed that xylanase production has mainly been governed by the chemical structure of amino acids and their analogues.
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    Chemie in unserer Zeit 33 (1999) 
    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Chemie in unserer Zeit 33 (1999), S. 45-50 
    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A variety of demonstration experiments can be shown to a large audience with a minimum amount of chemicals by using an ordinary slide projector and easily mounted cuvettes. A detailed instruction for assembling the cuvettes is given as m d l as examples for suitable demonstration experiments in general, inorganic, organic and physical chemistry.
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    Chemie in unserer Zeit 33 (1999), S. 61-61 
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    Keywords: Chemistry ; Chemistry
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    Topics: Chemistry and Pharmacology
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    Chemie in unserer Zeit 33 (1999), S. 66-66 
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    Keywords: Chemistry ; Chemistry
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    Chemie in unserer Zeit 33 (1999), S. 67-67 
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    Keywords: Chemistry ; Chemistry
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    Topics: Chemistry and Pharmacology
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    Chemie in unserer Zeit 33 (1999) 
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    Keywords: Chemistry ; Chemistry
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  • 69
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    Chemie in unserer Zeit 33 (1999), S. 95-103 
    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Natural events as well as human activities are affecting the environment and even with largescale monitoring programs it is not possible to completely assess the state of the environment. But a documentation of the environmental status with respect to its chemical composition can be realized with systematically collected representative environmental samples, which can be stored for decades at very low temperatures almost without degradation. Such ‘banking activity’ allows a current environmental monitoring and also a retrospective analysis for the determination of components which have not been analyzed at the time of sampling because of ta lack in analytical techniques or because they have not been known or considered environmentally relevant. The concept of environmental specimen banking and general procedures are described. Various examples illustrate the many facets of such activities.
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    Chemie in unserer Zeit 33 (1999), S. 128-128 
    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Die Arbeitsmarktsituation in der Chemie hat sich in den letzten Jahren spürbar entspannt. Dennoch gibt es auf etlichen, nicht hundertprozentig dem Trend der Zeit entsprechenden Spezialgebieten immer noch einen beträchtlichen Überhang an Stellensuchenden. Entsprechende Mobilität vorausgesetzt, kann das Internet bei der Stellensuche hilfreich sein.
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    Chemie in unserer Zeit 33 (1999), S. 135-135 
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    Keywords: Chemistry ; Chemistry
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    Topics: Chemistry and Pharmacology
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    Chemie in unserer Zeit 33 (1999) 
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    Keywords: Chemistry ; Chemistry
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    Chemie in unserer Zeit 33 (1999), S. 165-166 
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    Keywords: Chemistry ; Chemistry
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    Topics: Chemistry and Pharmacology
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    Chemie in unserer Zeit 33 (1999), S. 158-164 
    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Atmospheric aerosol particles cause one of the largest uncertainties in estimates of human influence on climate - a good reason to take a closer look at the atmospheric life cycle of the aerosols and its effects. Besides a number of primary and secondary natural aerosol sources we need to consider since the beginning of industrialisation strong manmade particle sources. During its residence in the atmosphere the aerosol interacts in many physical and chemical ways with other atmospheric trace substances, most importantly with water vapor and its liquid and solid phases. Through its direct effect on solar and thermal radiation and through its influence on clouds the atmospheric aerosol exerts a climate forcing. To data we cannot predict the ensuing climate response because of our limited understanding of essential atmospheric processes and of the many possible feedbacks within the climate system. However, already our present knowledge of the role of the atmospheric aerosol in the climate system makes strictly global views of anthropogenic climate changes questionable.
    Notes: Der Stand unseres Wissens zum Kreislauf des Atmosphärischen Aerosols und von seiner Rolle im Klimasystem läßt sich wie folgt zusammenfassen: 1Unser Verständnis des globalen Aerosolkreislaufs und vor allem des menschlichen Eingriffs in denselben ist noch sehr unvollständig. Dies gilt in hohem Maße auch für die mit diesem Kreislauf verbundenen chemischen Mehrphasenprozesse.2Ein negativer direkter Klimaantrieb anthropogener Aerosole existiert über die Streuung und Absorption, hat aber noch große Unsicherheiten und kann über hoch mit Rußpartikeln belasteten Gebieten auch positive Werte annehmen.3Ein indirekter Klimaantrieb anthropogener Aerosole existiert wahrscheinlich und hat ebenfalls ein negatives Vorzeichen. Seine Größenordnung und Unsicherheiten lassen sich noch nicht quantifizieren.
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    Chemie in unserer Zeit 33 (1999), S. 177-185 
    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Chemical concepts are important to gain a qualitative understanding of chemistry. They are needed to find interesting questions to which experimental research as well as quantum-chemical investigations and computer simulations can contribute. We point out why chemical concepts should be seen as an important and from fundamental physical theories to a certain degree independent part of chemistry. An overview and analysis of some concepts - which are often introduced only in connection with special examples instead of a discussion for their own sake - are given. We take a closer look at some concepts to illustrate our assertions. An analysis of the stability of the cyclic (MoNL3)-trimer demonstrates how these concepts work and what they can tell us about this special case.
    Notes: Wir haben versucht, deutlich zu machen, wie wichtig theoretische Konzepte in der Chemie sind. Dabei gelangen wir zu folgenden Schlußfolgerungen über die Konzepte, die in der Chemie herangezogen werden, um Beobachtungen zu deuten und zu verstehen: Qualitativ chemische Konzepte sind für ein Verständnis der Chemie unverzichtbar. Eine quantenchemische Berechnung liefert nicht automatisch Verständnis und Einordnung in einen Gesamtzusammenhang.Erst die vereinfachende Beschreibung chemischer Konzepte ermöglicht eine unmittelbare Diskussion chemischer Fragestellungen.Die Konzepte sind trotz grundlegender physikalischer Theorien bis zu einem gewissen Grade eigenständig.
    Additional Material: 8 Ill.
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  • 76
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    Chemie in unserer Zeit 33 (1999) 
    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Chemie in unserer Zeit 33 (1999), S. 213-220 
    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The article commemorates the centenary of the protection of the proprietary mine of Aspirin. The early medicinal uses of salicylic acid derivatives in herbal remedies arc summarised as well as the biosynthesis of these derivatives. The history of the synthesis of salicylic acid and of acetyl salicylic acid (ASS) is described in detail as is the discovery of additional therapeutic applications and the basic pharmacology of ASS.
    Additional Material: 5 Ill.
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    Chemie in unserer Zeit 33 (1999), S. 234-235 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Chemie in unserer Zeit 33 (1999), S. 246-246 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Chemie in unserer Zeit 33 (1999), S. 250-250 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Chemie in unserer Zeit 33 (1999), S. 308-309 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Chemie in unserer Zeit 33 (1999), S. 312-312 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Chemie in unserer Zeit 33 (1999), S. 314-314 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Chemie in unserer Zeit 33 (1999), S. IX 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 86
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    Chemie in unserer Zeit 33 (1999), S. 318-318 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Chemie in unserer Zeit 33 (1999), S. 354-358 
    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Chemical Biology is a rapidly growing field at the interface of organic chemistry and cell biology. Chemical strategies are used to address biological questions not amenable to traditional genetic and biochemical techniques alone. Thc enormous potential of Chemical Biology is illustrated by four recent examples.
    Notes: Chemische Biologie ist eine junge Forschungsrichtung im Grenzgebiet zwischen Organischer Cherme und Zellbiologie, welche aus einem Bedarf nach neuen Techniken zur Untersuchung zellbiologischer Mechanismen entstanden ist. Chemische Methoden werden mit biochemischen und molekularbiologischen Methoden kombiniert, um neuartige Möglichkeiten für die biologische Grundlagenforschung zu schaffen. So werden synthetische Oligosaccharide kovalent an die Oberfläche lebender Zellen gebunden, die Konzentration von Calciumionen im Zytosol künstlich reguliert und Rezeptoren künstlich aktiviert.
    Additional Material: 4 Ill.
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    Chemie in unserer Zeit 33 (1999), S. 373-374 
    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Eine neue Elektrosynthese erfüllt erstmals den Traum der Elektrochemiker, gleichzeitig Anoden- und Kathodenreaktion für organische Synthesen technisch zu nutzen.
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    Chemie in unserer Zeit 33 (1999), S. 377-377 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Chemie in unserer Zeit 33 (1999), S. 380-380 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Chemie in unserer Zeit 33 (1999), S. 382-384 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Around the world, BASF has been preparing for Y2K since 1996. The Information services and the Process Control Technology divisions, as well as embedded systems and logistics, not to mention the company's customers and suppliers have all been systenmatically tested for Y2K capability. In addition, special precautionary measures in particular, at large Verbund sites - will be in place during the switchover period.
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    Chemie in unserer Zeit 33 (1999), S. 4-4 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Chemie in unserer Zeit 33 (1999), S. 66-66 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Chemie in unserer Zeit 33 (1999), S. 104-109 
    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Fonds of German Chemical Industry (FCI) has produced an instrumental kit named „Blue Genes“ which enables High School teachers to perform in their school environment basic experiments of gene analysis and cloning. In particular, the kit contains all necessary equipment and reagents to perform a restriction analysis, and cloning and expression of a bacterial gene.
    Additional Material: 7 Ill.
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    Chemie in unserer Zeit 33 (1999), S. 152-157 
    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: A few physical phenomena believed to be religious miracles are considered, and scientific explanations for them are proposed.
    Notes: Einige physikalische Phänomene, von denen man glaubte, sie seien religiöse Wunder, werden vorgestellt und wissenschaftliche Erklärungen hierfür vorgeschlagen.
    Additional Material: 4 Ill.
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    Chemie in unserer Zeit 33 (1999), S. 173-173 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Chemie in unserer Zeit 33 (1999), S. VIII 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Chemie in unserer Zeit 33 (1999), S. XIV 
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    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    Chemie in unserer Zeit 33 (1999), S. 334-341 
    ISSN: 0009-2851
    Keywords: Chemistry ; Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The essential trace element copper plays a key role in living systems. Its metalloproteins are involved in various reactions. The IT ononuclear blue copper type-1 proteins take, part in electron transfer processes. Type-2 proteins can either act as oxidases, oxygenases, dioxygenases, or superoxide dismutases, containing one copper core. Dinuclear copper centers of Type-3 proteins are the oxygen transport system hemocyanin, oxidases and oxygenases. Due to this variety of functions copper deficiency and also abundance can cause severe damage of any life form.
    Additional Material: 13 Ill.
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