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  • 1990-1994  (8.418)
  • 1955-1959  (5.523)
  • 1890-1899  (10.294)
  • Inorganic Chemistry  (14.791)
  • Organic Chemistry  (9.165)
  • gene expression
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  • 1
    Digitale Medien
    Digitale Medien
    Changes in polypeptide patterns in tobacco roots colonized by two Glomus species (1994)
    Springer
    Mycorrhiza 4 (1994), S. 215-221 
    Details
    ISSN: 1432-1890
    Schlagwort(e): Nicotiana ; Glomus species ; arbuscular mycorrhiza ; gene expression ; specific polypeptides
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Changes in gene expression were studied during the establishment of arbuscular mycorrhizal symbiosis in tobacco roots from an amphidiploid hybrid Nicotiana glutinosa x N. debneyi. Polypeptide patterns from control roots and from roots infected by Glomus mosseae or G. intraradices were resolved by two-dimensional polyacrylamide gel electrophoresis and followed in a time-course analysis. Arbuscular mycorrhizal infection led to significant modifications in polypeptide patterns with: (a) decreased amounts of some polypeptides, (b) increased accumulation of others, and (c) appearance of newly-induced polypeptides. Comparisons made during infection development by the two Glomus species demonstrated that protein modifications changed in relation to the mycorrhizal state of the tobacco roots.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00206783
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  • 2
    Digitale Medien
    Digitale Medien
    Effect of radical scavengers on TNFα-mediated activation of the uPA in cultured cells (1994)
    Springer
    Cellular and molecular life sciences 50 (1994), S. 958-962 
    Details
    ISSN: 1420-9071
    Schlagwort(e): Plasminogen activator ; active oxygen ; gene expression ; radical scavengers ; endothelial cells
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Active oxygen, produced by cultured cells following stimulation with various growth factors, seems to be involved in signal transduction leading to cellular responses such as gene expression and growth modulation. In the present study, the intracellular oxidation state was measured in immortalized human endothelial cells (ECV304) after treatment with tumor necrosis factor (TNF)α, using a fluorescent dye and a laser-scanning confocal microscope. The intracellular oxidation state was increased 60 min after the addition of TNFα, and this increase was abolished by a radical scavenger, N-acetylcysteine (NAC), which is also a precursor of glutathione, and by pyrrolidine dithiocarbamate (PDTC). TNFα increased the steady state level of urokinase-type plasminogen activator (uPA), and NAC inhibited this increase at a dose that also inhibited the increase in the intracellular oxidation state. PDTC, on the other hand, did not affect the induction of the uPA gene by TNFα. These results suggest that intracellular glutathione level rather than the oxidation state is necessary for the induction of the uPA gene by TNFα.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01923487
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  • 3
    Digitale Medien
    Digitale Medien
    Tissue-specific correction of lipogenic enzyme gene expression in diabetic rats given vanadate (1994)
    Springer
    Diabetologia 37 (1994), S. 1065-1072 
    Details
    ISSN: 1432-0428
    Schlagwort(e): Vanadium ; lipogenic enzymes ; gene expression ; streptozotocin-diabetic rats
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Vanadium is a potent insulinomimetic agent. In vivo, its blood glucose lowering action in insulin-deficient diabetic rats is associated with corrected expression of genes involved in hepatic glucose metabolism. In this study, we investigated whether vanadate treatment also reverses the impaired expression of genes coding for key enzymes of lipogenesis in diabetic liver and white adipose tissue. Oral administration of vanadate to streptozotocin-rats caused a 55% fall in plasma glucose levels after feeding without modifying low insulinaemia. It also partially corrected the low thyroid hormone concentrations. In untreated diabetic animals, hepatic mRNA levels of acetyl-CoA carboxylase and fatty acid synthase were reduced by more than 80 and 90%, respectively, in close correlation with changes in enzyme activities. Three weeks of vanadate treatment totally restored acetyl-CoA carboxylase mRNA and partially restored fatty acid synthase mRNA (71% of control levels). The activities of both lipogenic enzymes were increased 3.5 to 4-fold, to reach 45 to 65% of control values. By contrast, in white adipose tissue, vanadate modified neither expression nor activity of both lipogenic enzymes, which remained blunted (〈10% of control levels). In conclusion, vanadate treatment partially restores the activities of two key lipogenic enzymes in liver, but not in white adipose tissue, of diabetic rats. This correction results from a reversal of impaired pre-translational regulatory mechanisms possibly mediated by an improvement of thyroid function and a selective restoration of liver glycolytic flux.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00418369
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  • 4
    Digitale Medien
    Digitale Medien
    Pancreatic Reg/pancreatic stone protein (PSP) gene expression does not correlate with beta-cell growth and regeneration in rats (1994)
    Springer
    Diabetologia 37 (1994), S. 994-999 
    Details
    ISSN: 1432-0428
    Schlagwort(e): Pancreas ; growth factors ; gene expression ; beta cells
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The Reg/pancreatic stone protein (PSP) gene is postulated to be an important regulator of pancreatic beta-cell growth. To investigate this hypothesis, we analysed the expression of the Reg/PSP gene following a 90% pancreatectomy and after chronic glucose infusion, two well-defined models of pancreatic beta-cell growth. There was a rapid induction of the Reg/PSP gene in the remnant pancreas after a 90% pancreatectomy in rats during the period of marked growth of the exocrine and islet tissue. However, a similar rapid, but smaller, induction of the Reg/PSP gene was observed in sham-operated rats and in non-surgical control rats in which there was no enhanced pancreatic growth. Furthermore, there was no pancreatic Reg/PSP gene induction in a model of selective beta-cell growth, the chronic glucose-infused rat. Thus, it is unlikely that Reg/PSP is a beta-cell specific growth factor, even though the function of this important pancreatic gene is still unknown.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00400462
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  • 5
    Digitale Medien
    Digitale Medien
    Tissue-specific correction of lipogenic enzyme gene expression in diabetic rats given vanadate (1994)
    Springer
    Diabetologia 37 (1994), S. 1065-1072 
    Details
    ISSN: 1432-0428
    Schlagwort(e): Key words Vanadium ; lipogenic enzymes ; gene expression ; streptozotocin-diabetic rats.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary Vanadium is a potent insulinomimetic agent. In vivo, its blood glucose lowering action in insulin-deficient diabetic rats is associated with corrected expression of genes involved in hepatic glucose metabolism. In this study, we investigated whether vanadate treatment also reverses the impaired expression of genes coding for key enzymes of lipogenesis in diabetic liver and white adipose tissue. Oral administration of vanadate to streptozotocin-rats caused a 55 % fall in plasma glucose levels after feeding without modifying low insulinaemia. It also partially corrected the low thyroid hormone concentrations. In untreated diabetic animals, hepatic mRNA levels of acetyl-CoA carboxylase and fatty acid synthase were reduced by more than 80 and 90 %, respectively, in close correlation with changes in enzyme activities. Three weeks of vanadate treatment totally restored acetyl-CoA carboxylase mRNA and partially restored fatty acid synthase mRNA (71 % of control levels). The activities of both lipogenic enzymes were increased 3.5 to 4-fold, to reach 45 to 65 % of control values. By contrast, in white adipose tissue, vanadate modified neither expression nor activity of both lipogenic enzymes, which remained blunted (〈 10 % of control levels). In conclusion, vanadate treatment partially restores the activities of two key lipogenic enzymes in liver, but not in white adipose tissue, of diabetic rats. This correction results from a reversal of impaired pre-translational regulatory mechanisms possibly mediated by an improvement of thyroid function and a selective restoration of liver glycolytic flux. [Diabetologia (1994) 37: 1065–1072]
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00418369
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  • 6
    Digitale Medien
    Digitale Medien
    Pancreatic Reg/pancreatic stone protein (PSP) gene expression does not correlate with beta-cell growth and regeneration in rats (1994)
    Springer
    Diabetologia 37 (1994), S. 994-999 
    Details
    ISSN: 1432-0428
    Schlagwort(e): Key words Pancreas ; growth factors ; gene expression ; beta cells.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The Reg/pancreatic stone protein (PSP) gene is postulated to be an important regulator of pancreatic beta-cell growth. To investigate this hypothesis, we analysed the expression of the Reg/PSP gene following a 90 % pancreatectomy and after chronic glucose infusion, two well-defined models of pancreatic beta-cell growth. There was a rapid induction of the Reg/PSP gene in the remnant pancreas after a 90 % pancreatectomy in rats during the period of marked growth of the exocrine and islet tissue. However, a similar rapid, but smaller, induction of the Reg/PSP gene was observed in sham-operated rats and in non-surgical control rats in which there was no enhanced pancreatic growth. Furthermore, there was no pancreatic Reg/PSP gene induction in a model of selective beta-cell growth, the chronic glucose-infused rat. Thus, it is unlikely that Reg/PSP is a beta-cell specific growth factor, even though the function of this important pancreatic gene is still unknown. [Diabetologia (1994) 37: 994–999]
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00400462
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  • 7
    Digitale Medien
    Digitale Medien
    Expression of glycogen synthase and phosphofructokinase in muscle from Type 1 (insulin-dependent) diabetic patients before and after intensive insulin treatment (1994)
    Springer
    Diabetologia 37 (1994), S. 82-90 
    Details
    ISSN: 1432-0428
    Schlagwort(e): Type 1 (insulin-dependent) diabetes mellitus ; gene expression ; skeletal muscle ; glycogen synthase ; phosphofructokinase ; hexokinase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary The aim of the present study was to determine whether short-term appropriate insulinization of Type 1 (insulin-dependent) diabetic patients in longterm poor glycaemic control (HbA1C〉9.5%) was associated with an adaptive regulation of the activity and gene expression of key proteins in muscle glycogen storage and glycolysis: glycogen synthase and phosphofructokinase, respectively. In nine diabetic patients biopsies of quadriceps muscle were taken before and 24-h after intensified insulin therapy and compared to findings in eight control subjects. Subcutaneous injections of rapid acting insulin were given at 3-h intervals to improve glycaemic control in diabetic patients (fasting plasma glucose decreased from 20.8±0.8 to 8.7±0.8 mmol/l whereas fasting serum insulin increased from 59±8 to 173±3 pmol/l). Before intensified insulin therapy, analysis of muscle biopsies from diabetic patients showed a normal total glycogen synthase ctivity but a 48% decrease (p=0.006) in glycogen synthase fractional velocity (0.1 mmol/l glucose 6-phosphate) (FV0.1) and a 45% increase (p=0.01) in the half-maximal activation constant of glycogen synthase (A0.5). The activity of phosphofructokinase and the specific mRNA and immunoreactive protein levels of both glycogen synthase and phosphofructokinase were similar in the two groups. The 2.8-fold increase in serum insulin levels and the halving of the plasma glucose level for at least 15 h were associated with a normalization of glycogen synthase fractional activity (FV0.1) and of the half-maximal activation constant (A0.5) whereas the enzyme activity of phosphofructokinase and the mRNA and protein levels of both glycogen synthase and phosphofructokinase remained normal. In conclusion: 1) Reduced allosterical activation of glycogen synthase in muscle of Type 1 diabetic patients in poor metabolic control occurs in the presence of normal total activity as well as normal immunoreactive protein mass and mRNA level of glycogen synthase. 2) Changes in serum insulin within the physiological range play no role in the short-term regulation of glycogen synthase mRNA and protein abundance in muscle from Type 1 diabetic patients.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00428782
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  • 8
    Digitale Medien
    Digitale Medien
    Effect of a new cholecystokinin antagonist (FK 480) on gene expression of cholecystokinin and secretin in rat intestine (1994)
    Springer
    Journal of gastroenterology 29 (1994), S. 385-387 
    Details
    ISSN: 1435-5922
    Schlagwort(e): CCK antagonist (FK 480) ; gene expression ; CCK ; secretin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The effects of a new cholecystokinin (CCK) antagonist (FK 480; 0.1 mg/kg per day given by intragastric administration to rats for 3 days) on the expression of the CCK and secretin genes, plasma CCK immunoreactivity, and CCK content in the intestinal mucosa were examined. FK 480 increased the level of CCK mRNA in the intestine to 1.7 times the level in control rats, but did not affect the level of secretin mRNA. It did not increase plasma CCK immunoreactivity or CCK content in the intestinal mucosa. These results suggest that the ingested FK 480 directly increased CCK mRNA level in the intestine and produced a dissociation between the synthesis and release of CCK.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02358383
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  • 9
    Digitale Medien
    Digitale Medien
    Expression of the c-myc and Ca-ATPase genes in cardiac muscle during adaptation to repeated stress (1994)
    Springer
    Bulletin of experimental biology and medicine 117 (1994), S. 122-124 
    Details
    ISSN: 1573-8221
    Schlagwort(e): gene expression ; c-myc ; Ca-ATPase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract In the course of adaptation to repeated stress, the expression of the proto-oncogene c-myc found to increase much more rapidly than that of the Ca-ATPase gene. It is suggested that an increase in the level of c-myc expression may activate the structural Ca-ATPase gene and possibly also the heat-shock proteins.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02444120
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  • 10
    Digitale Medien
    Digitale Medien
    Expression of the mitochondrial creatine kinase genes (1994)
    Springer
    Molecular and cellular biochemistry 133-134 (1994), S. 235-243 
    Details
    ISSN: 1573-4919
    Schlagwort(e): creatine kinase ; mitochondria ; metabolism ; creatine phosphate shuttle ; gene expression ; muscle
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Abstract Mitochondrial Creatine Kinase (MtCK) is responsible for the transfer of high energy phosphate from mitochondria to the cytosolic carrier, creatine, and exists in mammals as two isoenzymes encoded by separate genes. In rats and humans, sarcomere-specific MtCK (sMtCK) is expressed only in skeletal and heart muscle, and has 87% nucleotide identity across the 1257 bp coding region. The ubiquitous isoenzyme of MtCK (uMtCK) is expressed in many tissues with highest levels in brain, gut, and kidney, and has 92% nucleotide identity between the 1254 bp coding regions of rat and human. Both genes are highly regulated developmentally in a tissue-specific manner. There is virtually no expression of sMtCK mRNA prior to birth. Unlike cytosolic muscle CK (MCK) and brain CK (BCK), there is no developmental isoenzyme switch between the MtCKs. Cell culture models representing the tissue-specific expression of either sMtCK or uMtCK are available, but there are no adequate developmental models to examine their regulation. Several animal models are available to examine the coordinate regulation of the CK gene family and include 1) Cardiac Stress by coarctation (sMtCK, BCK, and MCK), 2) Uterus and placenta during pregnancy (uMtCK and BCK), and 3) Diabetes and mitochondrial myopathy (sMtCK, BCK, and MCK). We report the details of these findings, and discuss the coordinate regulation of the genes necessary for high-energy transduction.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01267957
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  • 11
    Digitale Medien
    Digitale Medien
    Transcriptional regulation and autoregulation of the human gene for ADP-ribosyltransferase (1994)
    Springer
    Molecular and cellular biochemistry 138 (1994), S. 99-104 
    Details
    ISSN: 1573-4919
    Schlagwort(e): poly(ADP-ribosyl) transferase (human) ; autoregulation ; gene expression ; promoter structure ; cruciform structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Abstract Human nuclear poly(ADP-ribosyl)transferase (ADPRT) modifies proteins with branched ADP-ribose-polymers. Various proteins, including ADPRT itself, serve as acceptors for polyADP-ribose. Target proteins include those controlling basic cellular processes such as DNA repair, differentiation and proliferation. Because of the outstanding features of this enzyme: automodification, several functional domains and central role in physiology of the cell, the molecular biology of ADPRT gained wide interest. The promoter structure contains several CCAAT/TATA boxes and SP1 sites. However, there is no CCAAT/TATA box in the neighbourhood of an SP1 site and, thus no obvious site for initiation of transcription. Within this region there are several noteworthy inverted repeats, which by internal basepairing could form two types of cruciform structures. Deletion analysis revealed that these cruciform structures have functional significance. Removal of one type increases the promoter activity, whereas removal of the other diminishes the promoter function. Overexpression of ADPRT from heterologous promoters (MMTV, SV40) leads to repression of the activity of the ADPRT promoter. Indeed, ADPRT was shown to bind specifically to one type of cruciform structure. This specific interaction indicates autorepression of the ADPRT gene: the enzyme ADPRT acts directly as a negative modulator of the activity of its own promoter.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00928449
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  • 12
    Digitale Medien
    Digitale Medien
    Nuclear Ca2+: physiological regulation and role in apoptosis (1994)
    Springer
    Molecular and cellular biochemistry 135 (1994), S. 89-98 
    Details
    ISSN: 1573-4919
    Schlagwort(e): calcium ; cell death ; nuclei ; apoptosis ; gene expression
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Abstract The last decade has seen the rapid development of research investigating the molecular mechanisms whereby hormones, peptide growth factors and cytokines regulate cell metabolism, differentiation and proliferation. One general signalling mechanism used to transfer the information delivered by agonists into appropriate intracellular compartments involves the rapid Ca2+ redistribution throughout the cell, which results in transient elevations of the cytosolic free Ca2+ concentration. Ca2+ signals are required for a number of cellular processes including the activation of nuclear processes such as gene transcription and cell cycle events. The latter require that appropriate Ca2+ signals elicited in response to agonists be transduced across the nuclear envelope. It has generally been assumed that small molecules, metabolites and ions could freely diffuse across the nuclear envelope. Nevertheless several findings during the past few years have suggested that nuclear pore permeability can be regulated and that ion transport systems and ion-selective channels may exist on the nuclear membranes and regulate intranuclear processes. Intranuclear Ca2+ fluctuations can affect chromatin organization, induce gene expression and also activate cleavage of nuclear DNA by nucleases during programmed cell death or apoptosis. The possible mechanisms involved in nuclear Ca2+ transport and the control of nuclear Ca2+-dependent enzymes in apoptosis is discussed below.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00925964
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  • 13
    Digitale Medien
    Digitale Medien
    Expression of hepatic calcium-binding protein regucalcin mRNA is decreased by phenobarbital administration in rats (1994)
    Springer
    Molecular and cellular biochemistry 141 (1994), S. 15-19 
    Details
    ISSN: 1573-4919
    Schlagwort(e): regucalcin ; calcium-binding protein ; gene expression ; phenobarbital ; rat liver
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Abstract The effect of phenobarbital on the expression of calcium-binding protein regucalcin mRNA in rat liver was investigated. The change of regucalcin mRNA levels was analyzed by Northern blotting using liver regucalcin cDNA (0.9 kb of open reading frame). Phenobarbital (4, 8 and 12 mg/ 100 g body weight) was intraperitoneally administered to rats 3 times with 24 h intervals, and the animals were sacrificed by bleeding at 24 h after the last administration. The hepatic regucalcin mRNA levels were markedly reduced by phenobarbital administration. This decrease was about 50% of control level with the 12 mg/100 g dose. Moreover, the hepatic regucalcin concentration was significantly decreased by the administration of phenobarbital (12 mg/100 g), although the serum regucalcin concentration was not altered appreciably. Meanwhile, serum transaminases (GOT and GPT) activities were not increased by the administration of phenobarbital (4 and 12 mg/100 g). The present study demonstrates that the expression of hepatic regucalcin mRNA is decreased by phenobarbital administration in rats, suggesting that regucalcin does not have a role in drug metabolism related to phenobarbital.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00935586
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  • 14
    Digitale Medien
    Digitale Medien
    Regulation of mRNA transcripts and DNA synthesis in the rat heart following intravenous injection of transforming growth factor beta1 (1994)
    Springer
    Molecular and cellular biochemistry 141 (1994), S. 145-151 
    Details
    ISSN: 1573-4919
    Schlagwort(e): pressure overload ; myocardium ; gene expression ; fibroblast ; extracellular matrix ; ventricular hypertrophy ; growth factor
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Abstract Transforming Growth Factor-beta1 (TGF-β1) is expressed in the heart by muscle and non-muscle cardiac cells.In vitro, cardiac myocytes and non-muscle cells including cardiac fibroblasts and endothelial cells respond to regulatory effects of TGF-β1. Expression of TGF-β1 in the heart is subject to regulation by hemodynamic stimuli. Increased expression of mRNA transcripts for TGF-β1 has been reported in several models of cardiac hypertrophy. The objective of this study was to determine the effect of TGF-β1 in the myocardium. TGF-β1 was injected intravenously. Expression of mRNA transcripts for functional and structural proteins was determined by Northern hybridization analysis. DNA synthesis was determined by measurement of3H-thymidine incorporation into ventricular DNA. The results showed differential regulation of mRNAs for myocyte- and non-myocyte-specific proteins in the heart of TGF-β1 treated rats. Moderate but statistically significant decrease in DNA synthesis was observed in the heart of TGF-β1 treated rats (37.5%, P〈0.025). Together, these data point to a physiological role for TGF-β1 in the heart. They further suggest that similar to its diversein vitro cell-specific regulatory effects, TGF-β1 may have multicellular targets in the heart. Effect of TGF-β1 alone or combined with those of other cytokines/hormones that come into play, as the result of its administration, may be responsible for altered gene expression and DNA synthesis in the myocardium. We propose that in experimental models of myocardial hypertrophy which are associated with increased expression of TGF-β1 in the heart, the contribution of regulatory effects of this growth factor to the manifestations of ventricular hypertrophy could be significant.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00926178
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  • 15
    Digitale Medien
    Digitale Medien
    PC12 variants deficient in norepinephrine transporter mRNA have wild type activities of several other related transporters (1994)
    Springer
    Neurochemical research 19 (1994), S. 743-751 
    Details
    ISSN: 1573-6903
    Schlagwort(e): Neurotransmitters ; reuptake ; PC12 ; gene expression
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Wild type PC12 pheochromocytoma cells express a Na+-dependent norepinephrine transporter that operates in the uptake of catecholamines. In addition to the previously described Na+-dependent system A for the uptake of α-amino-isobutyric acid and system Gly for glycine, we have identified two other Na+-dependent transporter systems for amino acid uptake in these cells: 1) system β for β-alanine and taurine; and 2) a system for creatine. Uptake of α-amino-isobutyric acid, glycine, β-alanine, and creatine is not affected in some PC12 variants that were previously shown to be deficient in catecholamine uptake and to have decreased levels of norepinephrine transporter mRNA. We have isolated two PC12 cDNA clones that are essentially identical in sequence to recently reported cDNAs for rat brain taurine and creatine transporters, respectively, and a third cDNA that appears to code for a novel transporter. mRNAs for these three transporters are present at wild type levels in those variants that express no or little norepinephrine transporter mRNA. These results support the notion that the expression of catecholamine reuptake transporters may be particularly susceptible to down-regulation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00967715
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  • 16
    Digitale Medien
    Digitale Medien
    Mitochondrial DNA diseases: Histological and cellular studies (1994)
    Springer
    Journal of bioenergetics and biomembranes 26 (1994), S. 301-310 
    Details
    ISSN: 1573-6881
    Schlagwort(e): Mitochondrial encephalomyopathy ; mitochondrial DNA ; gene expression ; protein translation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Physik
    Notizen: Abstract Large-scale deletions and tRNA point mutations in mitochondrial DNA (mtDNA) are associated with a variety of different mitochondrial encephalomyopathies. Skeletal muscle in these patients shows a typical pathology, characterized by the focal accumulation of large numbers of morphologically and biochemically abnormal mitochondria (ragged-red fibers). Both mtDNA deletions and tRNA point mutations impair mitochondrial translation and produce deficiencies in oxidative phosphorylation. However, mutant and wild-type mtDNAs co-exist (mtDNA heteroplasmy) and the translation defect is not expressed until the ratio of mutant: wild-type mtDNAs exceeds a specific threshold. Below the threshold the phenotype can be rescued by intramitochondrial genetic complementation. The mosaic expression of the skeletal muscle pathology is thus determined by both the cellular and organellar distribution of mtDNA mutants.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00763101
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  • 17
    Digitale Medien
    Digitale Medien
    From trypanosomes to the nervous system, from molecules to behavior: A survey, on the occasion of the 90th anniversary of Castellani's discovery of the parasites in sleeping sickness (1994)
    Springer
    Neurological sciences 15 (1994), S. 75-87 
    Details
    ISSN: 1590-3478
    Schlagwort(e): african sleeping sickness ; trypanosomiasis ; cytokines ; interferon-γ ; suprachiasmatic nucleus ; gene expression ; endogenous rhythms regulation ; sleep-wake cycle
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Beschreibung / Inhaltsverzeichnis: Sommario Aldo Castellani ha descritto nel 1903 la presenza di tripanosomi in pazienti affetti da malattia del sonno. In occasione del 90mo anniversario di questa scoperta, vengono qui presentati i recenti dati ottenuti in un modello sperimentale di tripanosomiasi africana nel ratto. Tale modello ha consentito di apportare notevoli chiarimenti ai meccanismi molecolari e cellulari dei rapporti che intercorrono fra il parassita e l'ospite. Si verifica, infatti, fra il tripanosoma e le cellule T CD8 dell'ospite, uno scambio bidirezionale di segnali. Questo nuovo meccanismo patogenetico di infezione coinvolge un fattore attivante i linfociti secreto dal parassita ed il γ-interferone. Anche un γ-interferone neuronale, recentemente isolato, potrebbe giocare un ruolo nella malattia. L'induzione selettiva di antigeni maggiori di istocompatibilità di classe I ha rivelato il coinvolgimento, nella tripanosomiasi, dei nuclei ipotalamici paraventricolare e sopraottico. Infine, studi basati sull'espressione del gene ad induzione rapidac-fos hanno evidenziato una disregolazione selettiva del nucleo soprachiasmatico dell'ipotalamo, che svolge un ruolo di orologio biologico. Quest'ultimo dato può sottendere la grave alterazione di ritmi endogeni che caratterizza la malattia del sonno.
    Notizen: Abstract The observation of Trypanosomes in patients affected by sleeping sickness has been reported in 1903 by Aldo Castellani. On the occasion of the 90th anniversary of this discovery, we here present the findings recently obtained in an experimental model of African trypanosomiasis in the rat. The molecular and cellular mechanisms of the interplay between the parasite and the host have been largely clarified: a bidirectional signalling occurs between trypanosomes and CD8+ T cells of the host animal. This new pathogenetic mechanism of infection involves a lymphocyte triggering factor released by the parasite and interferon-γ. A recently isolated neuronal interferon-γ could also play a role in the disease. The selective induction of major histocompatibility antigens class I has revealed the involvement of the hypothalamic paraventricular and supraoptic nuclei in trypanosomiasis. Finally, studies based on the expression of the immediate early genec-fos have pointed out during the infection a selective dysregulation of the suprachiasmatic nucleus of the hypothalamus, that plays the role of biological clock. The latter finding could account for the disruption of endogenous rhythms in sleeping sickness.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02340118
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  • 18
    Digitale Medien
    Digitale Medien
    Photobiology of Bacteria (1994)
    Springer
    Antonie van Leeuwenhoek 65 (1994), S. 331-347 
    Details
    ISSN: 1572-9699
    Schlagwort(e): photoactive proteins ; photoreceptors ; chromophores ; energy transduction ; light signalling ; phototaxis ; gene expression
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The field of photobiology is concerned with the interactions between light and living matter. For Bacteria this interaction serves three recognisable physiological functions: provision of energy, protection against excess radiation and signalling (for motility and gene expression). The chemical structure of the primary light-absorbing components in biology (the chromophores of photoactive proteins) is surprisingly simple: tetrapyrroles, polyenes and derivatised aromats are the most abundant ones. The same is true for the photochemistry that is catalysed by these chromophores: this is limited to light-induced exciton- or electron-transfer and photoisomerization. The apoproteins surrounding the chromophores provide them with the required specificity to function in various aspects of photosynthesis, photorepair, photoprotection and photosignalling. Particularly in photosynthesis several of these processes have been resolved in great detail, for others at best only a physiological description can be given. In this contribution we discuss selected examples from various parts of the field of photobiology of Bacteria. Most examples have been taken from the purple bacteria and the cyanobacteria, with special emphasis on recently characterised signalling photoreceptors inEctothiorhodospira halophila and inFremyella diplosiphon.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00872217
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  • 19
    Digitale Medien
    Digitale Medien
    Strategies for improving heterologous protein production from filamentous fungi (1994)
    Springer
    Antonie van Leeuwenhoek 65 (1994), S. 245-250 
    Details
    ISSN: 1572-9699
    Schlagwort(e): Aspergillus ; gene expression ; heterologous protein ; protein secretion ; Trichoderma
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Despite the naturally high capacity for protein secretion by many species of filamentous fungi, secteted yields of many heterologous proteins have been comparatively low. The strategies for yield improvement have included the use of strong homologous promoters, increased gene copy number, gene fusions with a gene encoding a naturally well-secreted protein, protease-deficient host strains and screening for high yields following random mutagenesis. Such approaches have been effective with some target heterologous proteins but not others. Approaches used in heterologous protein production from filamentous fungi are discussed and a perspective on emerging strategies is presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00871952
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  • 20
    Digitale Medien
    Digitale Medien
    Photosynthetic electron transport and anaerobic metabolism in purple non-sulfur phototrophic bacteria (1994)
    Springer
    Antonie van Leeuwenhoek 66 (1994), S. 151-164 
    Details
    ISSN: 1572-9699
    Schlagwort(e): purple non-sulfur bacteria ; Rhodobacter ; photosynthesis ; CO2 fixation ; anaerobic respiration ; gene expression
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Purple non-sulfur phototrophic bacteria, exemplifed byRhodobacter capsulatus andRhodobacter sphaeroides, exhibit a remarkable versatility in their anaerobic metabolism. In these bacteria the photosynthetic apparatus, enzymes involved in CO2 fixation and pathways of anaerobic respiration are all induced upon a reduction in oxygen tension. Recently, there have been significant advances in the understanding of molecular properties of the photosynthetic apparatus and the control of the expression of genes involved in photosynthesis and CO2 fixation. In addition, anaerobic respiratory pathways have been characterised and their interaction with photosynthetic electron transport has been described. This review will survey these advances and will discuss the ways in which photosynthetic electron transport and oxidation-reduction processes are integrated during photoautotrophic and photoheterotrophic growth.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00871637
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  • 21
    Digitale Medien
    Digitale Medien
    Molecular biology of C4 phosphoenolpyruvate carboxylase: Structure, regulation and genetic engineering (1994)
    Springer
    Photosynthesis research 39 (1994), S. 115-135 
    Details
    ISSN: 1573-5079
    Schlagwort(e): C4 photosynthesis ; gene expression ; oligomerization ; phosphorylation-dephosphorylation cascade ; PEPC-protein kinase ; site-directed mutagenesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Three to four families of nuclear genes encode different isoforms of phosphoenolpyruvate (PEP) carboxylase (PEPC): C4-specific, C3 or etiolated, CAM and root forms. C4 leaf PEPC is encoded by a single gene (ppc) in sorghum and maize, but multiple genes in the C4-dicot Flaveria trinervia. Selective expression of ppc in only C4-mesophyll cells is proposed to be due to nuclear factors, DNA methylation and a distinct gene promoter. Deduced amino acid sequences of C4-PEPC pinpoint the phosphorylatable serine near the N-terminus, C4-specific valine and serine residues near the C-terminus, conserved cysteine, lysine and histidine residues and PEP binding/catalytic sites. During the PEPC reaction, PEP and bicarbonate are first converted into carboxyphosphate and the enolate of pyruvate. Carboxyphosphate decomposes within the active site into Pi and CO2, the latter combining with the enolate to form oxalacetate. Besides carboxylation, PEPC catalyzes a HCO3 --dependent hydrolysis of PEP to yield pyruvate and Pi. Post-translational regulation of PEPC occurs by a phosphorylation/dephosphorylation cascade in vivo and by reversible enzyme oligomerization in vitro. The interrelation between phosphorylation and oligomerization of the enzyme is not clear. PEPC-protein kinase (PEPC-PK), the enzyme responsible for phosphorylation of PEPC, has been studied extensively while only limited information is available on the protein phosphatase 2A capable of dephosphorylating PEPC. The C4 ppc was cloned and expressed in Escherichia coli as well as tobacco. The transformed E. coli produced a functional/phosphorylatable C4 PEPC and the transgenic tobacco plants expressed both C3 and C4 isoforms. Site-directed mutagenesis of ppc indicates the importance of His138, His579 and Arg587 in catalysis and/or substrate-binding by the E. coli enzyme, Ser8 in the regulation of sorghum PEPC. Important areas for further research on C4 PEPC are: mechanism of transduction of light signal during photoactivation of PEPC-PK and PEPC in leaves, extensive use of site-directed mutagenesis to precisely identify other key amino acid residues, changes in quarternary structure of PEPC in vivo, a high-resolution crystal structure, and hormonal regulation of PEPC expression.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00029380
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  • 22
    Digitale Medien
    Digitale Medien
    A retinoic acid-inducible skin-specific gene (RIS-1/psoriasin): molecular cloning and analysis of gene expression in human skinin vivo and cultured skin cellsin vitro (1994)
    Springer
    Molecular biology reports 20 (1994), S. 75-83 
    Details
    ISSN: 1573-4978
    Schlagwort(e): retinoic acid ; skin ; differential hybridization ; cloning ; keratinocytes ; gene expression
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A retinoic acid (RA) inducible skin-specific gene transcript (RIS-1) was isolated by differential hybridization screening of a RA-treated human skin cDNA library. The library was constructed from pooled RNA derived from normal adult human skin treated with alltrans-RA for 4 h (n=6) and 12 h (n=6)in vivo. RIS-1 cDNA corresponded to a 0.6 kb transcript that was barely detectable in normal adult human skin but was significantly induced by 8 h in RA-treated compared to vehicle-treated skin (range 1.1–3.6 fold). Prolonged RA treatment for up to 24 h further increased relative RIS-1 mRNA levels by 1.3–5.5 fold. HPLC analysis of the RA content of 0.1% RA-treated skinin vivo revealed significant levels at 6 h (18.8–120.6 ng RA/g wet weight tissue; approximately 240 nM), immediately preceding the time point at which the increased RIS-1 mRNA level was first seen. This concentration of RA also induced the mRNA levels for cellular RA binding protein II (1.6–19 fold), a marker of RA activity in human skin. RIS-1 mRNA was detected by Northern and dot blotting only in normal skin but not in any other normal human tissues examined, indicating a tissue-specific pattern of gene expression. RIS-1 transcripts were detected at very low levels in untreated cultured human epidermal keratinocytes, while no expression was seen in dermal fibroblasts and melanocytes, the other major cell types in skin. Southern analysis of human and mouse DNA indicated the existence of evolutionarily conserved sequences for RIS-1 between these two species. The polypeptide sequence derived from the partial RIS-1 cDNA was found to be identical to the calcium binding domain found in ‘psoriasin’, a gene whose expression appears to be increased in the skin of psoriasis patients.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00996356
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  • 23
    Digitale Medien
    Digitale Medien
    Cloning and molecular analysis of structural genes involved in flavonoid and stilbene biosynthesis in grape (Vitis vinifera L.) (1994)
    Springer
    Plant molecular biology 24 (1994), S. 743-755 
    Details
    ISSN: 1573-5028
    Schlagwort(e): anthocyanins ; cDNA cloning ; flavonoids ; gene expression ; genomic organization ; stilbenes ; Vitis vinifera L
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Genes involved in flavonoid and stilbene biosynthesis were isolated from grape (Vitis vinifera L.). Clones coding for phenylalanine ammonia-lyase (PAL), chalcone synthase (CHS), chalcone isomerase (CHI), flavanone 3-hydoxylase (F3H), dihydroflavonol 4-reductase (DFR), leucoanthocyanidin dioxygenase (LDOX) and UDP glucose:flavonoid 3-O-glucosyl transferase (UFGT), were isolated by screening a cDNA library, obtained from mRNA from seedlings grown in light for 48 h using snapdragon (Antirrhinum majus) and maize heterologous probes. A cDNA clone coding for stilbene synthase (StSy) was isolated by probing the library with a specific oligonucleotide. These clones were sequenced and when the putative products were compared to the published amino acid sequence for corresponding enzymes, the percentages of similarity ranged from 65% (UFGT) to 90% (CHS and PAL). The analysis of the genomic organization and expression of these genes in response to light shows that PAL and StSy genes belong to large multigene families, while the others are present in one to four copies per haploid genome. The steady-state level of mRNAs encoded by the flavonoid biosynthetic genes as determined in young seedlings is coordinately induced by light, except for PAL and StSy, which appear to be constitutively expressed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00029856
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  • 24
    Digitale Medien
    Digitale Medien
    Low-temperature-responsive barley genes have different control mechanisms (1994)
    Springer
    Plant molecular biology 24 (1994), S. 879-888 
    Details
    ISSN: 1573-5028
    Schlagwort(e): barley ; cold acclimation ; gene expression ; low temperature genes ; nuclear run-on transcription
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Several low-temperature-responsive (LTR) genes from barley have been shown to have high steady-state transcript levels. Run-on transcription was used to determine the control of expression of these LTR genes. Six of these are shown to be transcriptionally regulated (blt 4/9, blt 101, blt 1015, blt 63, blt 49, blt 410) whilst three are post-transcriptionally regulated (blt 14, blt 411, blt 801). Two transcriptionally regulated genes (blt 4/9 and blt 101) and one post-transcriptionally regulated gene (blt 14) have been used in expression studies. The time course for the appearance and decay of these transcripts is given. Initial appearance and steady-state levels of individual transcripts have different temperature characteristics but no single gene correlates with the cold acclimation response. We suggest that these different response profiles may represent a means of fine-tuning the low-temperature response. One gene, blt 4/9, also accumulated high steady-state levels of transcript in response to drought and a nutrient stress. However, only drought has an acclimating effect on barley plants.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00014442
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  • 25
    Digitale Medien
    Digitale Medien
    Gene expression of nitrite reductase in Scots pine (Pinus sylvestris L.) as affected by light and nitrate (1994)
    Springer
    Plant molecular biology 25 (1994), S. 449-457 
    Details
    ISSN: 1573-5028
    Schlagwort(e): gene expression ; light ; nitrate ; nitrite reductase ; Pimus sylvestris L.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A partial cDNA clone (PSnir) encoding the C-terminal region of nitrite reductase was isolated from a λgt 11 library of the gymnospermPimus sylvestris (L.). Nucleotide sequence analysis showed that PSnir contains a reading frame encoding 105 amino acid residues. The amino acid sequence revealed a homology to NiR of 63–68% to dicotyledoneous and of 57–59% to monocotyledoneous species. The protein region implicated to be involved in binding of the prosthetic group is highly conserved between the NiR of the gymnosperm and of angiosperms. In all organs (cotyledonary whorls, hypocotyls, roots) the pattern of NiR gene expression in response to nitrate and light is the same at the level of transcript accumulation and at the enzyme level. This suggests that regulation of NiR gene expression in the Scots pine seedling is predominantly at the level of transcript accumulation. The highest NiR appearance was observed in roots and hypocotyls. In the cotyledonary whorls only small amounts of NiR were found. In roots and hypocotyls the accumulation of NiR mRNA and the appearance of NiR protein is mainly controlled by nitrate, whereas the regulation of NiR gene expression in the whorls is strongly affected by light and the inducive effect of nitrate is only weak.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00043873
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  • 26
    Digitale Medien
    Digitale Medien
    A phenylalanine ammonia-lyase gene from melon fruit: cDNA cloning, sequence and expression in response to development and wounding (1994)
    Springer
    Plant molecular biology 26 (1994), S. 473-479 
    Details
    ISSN: 1573-5028
    Schlagwort(e): Cucumis melo ; melon ; phenylalanine ammonia-lyase ; gene expression ; ripening ; wounding
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Phenylalanine ammonia-lyase (PAL) is the first enzyme of phenylpropanoid biosynthesis involved in the synthesis of a multiplicity of plant natural products. We have isolated and characterized a nearly fulllength cDNA clone (pmPAL-1) corresponding to a melon fruit (Cucumis melo L. var. reticulatus) gene coding for a protein which is highly similar to PAL from other lants. Melon fruit PAL is transcriptionally induced both in response to fruit ripening and wounding. PAL gene expression follows the kinetics of expression of the ethylene biosynthetic genes during fruit development. In contrast, ethylene biosynthetic genes show different induction kinetics compared to PAL expression in response to wounding. Similar results have been found for two other genes coding for enzymes involved in flavonoid biosynthesis (chalcone synthase, CHS; chalcone isomerase, CHI). Our results imply that regulation of defense gene expression in melon is a co-ordinated process in response to both ethylene and an ethylene-independent wound signal.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00039557
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  • 27
    Digitale Medien
    Digitale Medien
    Triticum aestivum puroindolines, two basic cystine-rich seed proteins: cDNA sequence analysis and developmental gene expression (1994)
    Springer
    Plant molecular biology 25 (1994), S. 43-57 
    Details
    ISSN: 1573-5028
    Schlagwort(e): cDNA sequence ; cystine-rich proteins ; gene expression ; puroindolines ; tryptophan-rich domain ; wheat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract From a mid-maturation seed cDNA library we have isolated cDNA clones encoding two Triticum aestivum puroindolines. Puroindoline-a and puroindoline-b, which are 55% similar, are basic, cystine-rich and tryptophan-rich proteins. Puroindolines are synthezised as preproproteins which include N- and C-terminal propeptides which could be involved in their vacuolar localization. The mature proteins have a molecular mass of 13 kDa and a calculated isoelectric point greater than 10. A notable feature of the primary structure of puroindolines is the presence of a tryptophan-rich domain which also contains basic residues. A similar tryptophan-rich domain was found within an oat seed protein and a mammalian antimicrobial peptide. The ten cysteine residues of puroindolines are organized in a cysteine skeleton which shows similarity to the cysteine skeleton of other wheat seed cystine-rich proteins. Northern blot analysis showed that puroindoline genes are specifically expressed in T. aestivum developing seeds. No puroindoline transcripts as well as no related genes were detected in Triticum durum. The identity of puroindolines to wheat starch-granule associated proteins is discussed as well as the potential role of puroindolines in the plant defence mechanism.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00024197
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  • 28
    Digitale Medien
    Digitale Medien
    Characterization of a cDNA from Arabidopsis thaliana encoding a potential thiol protease whose expression is induced independently by wilting and abscisic acid (1994)
    Springer
    Plant molecular biology 25 (1994), S. 259-270 
    Details
    ISSN: 1573-5028
    Schlagwort(e): abscisic acid ; Arabidopsis thaliana ; gene expression ; mutants ; signal transduction ; stress ; thiol protease ; wilting
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The sequence and expression characteristics are described of a wilt-inducible gene in Arabidopsis thaliana. A 1494 encodes a potential thiol protease whose mRNA accumulates rapidly in shoot tissue upon the loss of turgor. A1494 mRNA levels peaked after ca. 4 h and declined thereafter. Dehydration also induced rapid biosynthesis of the phytohormone abscisic acid (ABA), which continued for at least 9 h. Exogenous ABA induced the accumulation of A1494 mRNA, with kinetics similar to those after wilting. Rehydration of wilted shoots led to a rapid decline in the content of both ABA and A1494 mRNA. Wilting and ABA independently induced A1494 expression as evidenced by the effects of ABA and wilting on the ABA-deficient aba-1 and ABA-insensitive abi-1 and abi-3 genotypes. A1494 mRNA was not detectable in aba-1 shoots but accumulated rapidly after either wilting or ABA treatment, whereas the shoot ABA content was increased only by ABA treatment. ABA had no effect on A1494 mRNA levels in the abi-1 and abi-3 mutants but wilting did result in enhanced A1494 expression. Heat shock had only a minor effect on A1494 mRNA levels, whereas exposure to low temperature resulted in substantial accumulation of A1494 mRNA in wild-type shoots. However, this latter response, unlike that to drought, was mediated exclusively via ABA synthesis as demonstrated by the lack of A1494 mRNA accumulation in cold-treated aba-1 shoots.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00023242
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  • 29
    Digitale Medien
    Digitale Medien
    Calcium and calcium-binding proteins in the nucleus (1994)
    Springer
    Molecular and cellular biochemistry 135 (1994), S. 79-88 
    Details
    ISSN: 1573-4919
    Schlagwort(e): calcium ; nucleus ; calpain ; calmodulin ; cell division ; gene expression
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Abstract Calcium has long been known to play a role as a key cytoplasmic second messenger, but until relatively recently its possible involvement in nuclear signal transduction and the regulation of nuclear events has not been extensively studied. Evidence revealing the presence of transmembrane nuclear Ca2+ gradients and a variety of intranuclear Ca2+ binding proteins has fueled renewed interest in this key ion and its involvement in cell-cycle timing and division, gene expression, and protein activation. This review will offer an overview of the current state of knowledge and theory regarding calcium orchestration of nuclear functions and events and discuss possible future directions in this field of study.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00925963
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  • 30
    Digitale Medien
    Digitale Medien
    Expression of calcium-binding protein regucalcin mRNA in rat liver is stimulated by calcitonin: The hormonal effect is mediated through calcium (1994)
    Springer
    Molecular and cellular biochemistry 136 (1994), S. 43-48 
    Details
    ISSN: 1573-4919
    Schlagwort(e): regucalcin ; calcium-binding protein ; gene expression ; rat liver
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Abstract The involvement of a hypocalcemic hormone calcitonin (CT) in the expression of hepatic Ca2+-binding protein regucalcin mRNA was investigated. The change of regucalcin mRNA levels was analyzed by Northern blotting using liver regucalcin complementary DNA (0.9 kb). A single oral administration of calcium chloride (100 mg Ca/100 g body weight) to rats induced a remarkable increase in the serum calcium concentration and a corresponding elevation of the liver calcium content during 120 min after the administration. Thyroparathyroidectomy (TPTX) did not cause a significant increase in the liver calcium content after calcium administration. Hepatic regucalcin mRNA level was markedly elevated by calcium administration; the level was about 180% of controls at 60 min after the administration. This increase was completely abolished by TPTX. A single subcutaneous administration of CT (synthetic eel CT; 25–100 MRC mU/100 g) to TPTX rats received oral administration of calcium (100 mg/100 g) produced a remarkable increase in hepatic regucalcin mRNA levels; the level was about 280% of controls with the dose of 25 MRC mU CT/100 g. The present finding suggests that the expression of hepatic mRNA is stimulated by CT, and that the hormonal effect is mediated through Ca2+ in rat liver.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00931603
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  • 31
    Digitale Medien
    Digitale Medien
    Expression of nitrate assimilation related genes in Chlamydomonas reinhardtii (1994)
    Springer
    Plant molecular biology 24 (1994), S. 185-194 
    Details
    ISSN: 1573-5028
    Schlagwort(e): gene expression ; light/nitrate regulation ; nitrate reductase ; nitrate transport
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The mRNA accumulation pattern of the Chlamydomonas reinhardtii nitrate assimilation-related gene cluster has been elucidated. In ammonium-grown wild-type cells, nit-1 (nitrate reductase, NR), nar-1, nar-2 and nar-3 (nitrate transporter) genes showed very similar kinetics of expression when transferred to nitrate medium. Transcripts of all these genes accumulated transiently in ammonium-grown wild-type cells after a one-hour incubation in nitrogen-free medium, and practically disappeared at about 2 hours. Mutant strains lacking functional nitrate reductase showed similar accumulation kinetics of these transcripts during both nitrate induction and derepression in nitrogen-free media. In contrast to the other nar transcripts, that nar-4, a gene sharing similar sequences with nar-3, accumulated in small amounts in wild-type cells, and only increased after a long nitrate induction period. Nitrate and light showed a strong positive effect on the accumulation of nit-1 gene transcripts. Acetate as a carbon source allowed accumulation of nit-1 mRNA in the dark, indicating the existence of interactions between light and carbon metabolism in nit-1 gene expression. Our data strongly suggest that NR negatively autoregulates its own expression and that of nar genes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00040584
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  • 32
    Digitale Medien
    Digitale Medien
    Expression of one of the members of the Arabidopsis chaperonin 60β gene family is developmentally regulated and wound-repressible (1994)
    Springer
    Plant molecular biology 24 (1994), S. 195-202 
    Details
    ISSN: 1573-5028
    Schlagwort(e): plant transformation ; chaperonin 60β ; β-glucuronidase ; wound repression ; gene expression
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract To study the pattern of gene regulation of the plastid chaperonin 60β gene family a chimaeric gene was constructed fusing the 5′-flanking region of the chaperonin 60β B3 gene to the β-glucuronidase reporter gene. Histochemical and fluorometric analysis of the GUS activity present in transgenic plants harbouring this gene construct showed that the B3 promoter is expressed in leaves, stem, petioles and several flower tissues. The pattern of cell type-specific expression in stems and flowers was found to be developmentally regulated. Expression of the B3 promoter was found not to be heat-inducible, but highly repressed by wounding. The rapid decay in GUS activity upon wounding indicates that, at least under some physiological conditions, the gene product of this reporter gene is not as stable as has been previously thought.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00040585
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  • 33
    Digitale Medien
    Digitale Medien
    Tissue-specific expression of the large ATP synthase gene cluster in spinach plastids (1994)
    Springer
    Plant molecular biology 25 (1994), S. 369-376 
    Details
    ISSN: 1573-5028
    Schlagwort(e): ATP synthase ; chloroplast ; gene expression ; plastid ; RNA stability ; transcription
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Plastids present in different tissues may vary morphologically and functionally, despite the fact that all plastids within the same plant contain identical genomes. This is achieved by regulation of expression of the plastid genome by tissue-specific factors, the mechanisms of which are not fully understood. The proton translocating ATP synthase/ATPase is a multisubunit complex composed of nine subunits, six encoded in the plastid and three in the nucleus. We have investigated the tissue-specific expression of the large ATP synthase gene cluster in spinach (Spinacia oleracea). This gene cluster encodes four of the six plastid-encoded ATP synthase genes. Transcript abundance, transcriptional activity, and transcript stability were investigated relative to gene dosage in root plastids and in stem, leaf, and flower chloroplasts. All three of these factors display significant tissue-specific variation. It was intriguing to discover that, although transcript abundance normalized to gene dosage varies in each tissue, transcript abundance as a proportion of the entire plastid RNA population in each tissue is not significantly different. Thus it appears that in these tissues the variation in transcription and stability of transcripts derived from the large ATP synthase gene cluster balances to yield an equivalent proportion of these transcripts in the plastid RNA population. Expression of this gene cluster in photosynthetic as well as non-photosynthetic tissues may facilitate the plasticity of structure and function which is characteristic of plastids.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00043866
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  • 34
    Digitale Medien
    Digitale Medien
    The Chlorella virus adenine methyltransferase gene promoter is a strong promoter in plants (1994)
    Springer
    Plant molecular biology 26 (1994), S. 85-93 
    Details
    ISSN: 1573-5028
    Schlagwort(e): gene expression ; monocot cells ; promoter strength ; transient expression
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract An upstream region isolated from a eukaryotic algal virus adenine methyltransferase gene was tested for promoter function in plants. Fusion of this region to the chloramphenicol acetyltransferase reporter gene resulted in significantly higher expression than fusion with the cauliflower mosaic virus 35S promoter. Strong levels of expression were also found in electroporated monocot plant cells. The promoter activity in transgenic tobacco plants showed tissue-specific expression. Leaves had the highest expression followed by stems and flowers. The promoter activity was not detected in root tissue. Environmental cues, such as light, and the phytohormones auxin and cytokinines had no effect on the promoter's expression. This promoter might be utilized to achieve high levels of expression of introduced genes in higher plants.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00039522
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  • 35
    Digitale Medien
    Digitale Medien
    Expression of the tobacco Tnt1 retrotransposon promoter in heterologous species (1994)
    Springer
    Plant molecular biology 26 (1994), S. 393-402 
    Details
    ISSN: 1573-5028
    Schlagwort(e): Arabidopsis thaliana ; Brassica napus ; gene expression ; Nicotiana tabacum ; retrotransposon
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The expression of the tobacco (Nicotiana tabacum) retrotransposon Tntl has previously been shown to be strongly regulated and driven from the 5′ long terminal repeat (LTR). We report here that the Tntl LTR can promote activity of the β-glucuronidase (GUS) reporter gene in two heterologous species of the Brassicaceae family, namely rapessed (Brassica napus) and Arabidopsis thaliana. The translational LTR-GUS fusion was active in transient expression studies performed with tobacco and rapeseed protoplasts, indicating that the LTR sequences are recognized in heterologous species. Our results also showed that Tntl LTR-promoted GUS expression in transgenic Arabidopsis is strongly regulated, and that, in contrast to tobacco, hormonal activation plays a significant role in the expression of the Tntl LTR in Arabidopsis. LTR sequences were shown to be more effective than the CaMV 35S enhancer region in transient expression studies performed with tobacco or rapessed protoplasts; and substitution of the LTR sequences upstream from the major transcriptional start with the CaMV 35S enhancer region gave high levels of expression in transgenic tobacco and Arabidopsis leaves, suggesting that a Tntl element with similar substitutions in its 5′ LTR might be suited for gene-tagging experiments in heterologous species.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00039548
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  • 36
    Digitale Medien
    Digitale Medien
    Structure and promoter analysis of an ABA- and stress-regulated barley gene, HVA1 (1994)
    Springer
    Plant molecular biology 26 (1994), S. 617-630 
    Details
    ISSN: 1573-5028
    Schlagwort(e): ABA ; barley ; gene expression ; Hordeum vulgare ; phylogeny ; stress
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A single-copy barley gene, HVA1, encoding a class 3 late embryogenesis-abundant protein, can be induced by either treatment with abscisic acid (ABA) or by stress conditions such as drought, cold, heat and salinity. We have isolated an HVA1 genomic clone containing about 400 bp of 5′-upstream sequence, a single 109 bp intron, and the full coding sequence. Linker scan mutagenesis and transient expression studies were used to test the function of four HVA1 promoter elements conserved in ABA-responsive genes. Mutations in two of these elements, the C box and the putative ABRE 1 (ABA-responsive element) containing an ACGT core, resulted in no significant change in transcription level or ABA induction. In contrast, mutations of the other two elements, putative ABRE 2 & 3 cause the level of transcription to drop to 10–20% of that obtained with the wild-type promoter indicating that the high level of expression of HVA1 is dependent on both pABRE 2 & 3. Interestingly, despite their low level of expression, the mutated promoters still gave more than 20-fold induction in response to ABA treatment. We suggest that the ABA induction of barley HVA1 gene is governed by a complex consisting of pABRE 2 & 3 working together to regulate the absolute level of expression, and either of these elements or a possible third element may regulate ABA inducibility. Phylogenetic analysis by parsimony indicates that the barley HVA1 and wheat pMA2005 sequences share a recent common ancester. These two genes are closely related to the carrot Dc3 and cotton D-7 genes with which they share a similar structural gene organization.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00013748
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  • 37
    Digitale Medien
    Digitale Medien
    Vascular expression of the grp1.8 promoter is controlled by three specific regulatory elements and one unspecific activating sequence (1994)
    Springer
    Plant molecular biology 26 (1994), S. 747-756 
    Details
    ISSN: 1573-5028
    Schlagwort(e): activating sequence ; gene expression ; glycine-rich protein ; tobacco ; vascular expression
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The bean grp1.8 full-length promoter is specifically active in vascular tissue during normal development of tobacco. Deletion of a negative regulatory element resulted in ectopic activity of the promoter in cortical cells of hypocotyls, roots and stems. A 169 bp fragment (−205 to −36) of the grp1.8 promoter conferred vascular-specific expression to CaMV 35S minimal promoters whereas a 141 bp fragment (−205 to −64) strongly activated these minimal promoters both in vascular and cortical cells. These experiments defined a new regulatory element (VSE) that is essential for vascular-specific expression and is located between −64 and −36. The 141 bp grp1.8 promoter sequence had enhancer-like properties as it was active in both orientations. A 24 bp sequence (bp −119 to −96, corresponding to the SE1 regulatory element) enhanced expression from several minimal promoters strongly but unspecifically, whereas a 26 bp sequence (−98 to −73, corresponding to the RSE regulatory element) induced vascular-specific expression. Thus, the grp1.8 promoter is regulated by a combinatorial mechanism that can integrate the action of different, non-additively acting regulatory elements into vascular-specific expression.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00013759
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  • 38
    Digitale Medien
    Digitale Medien
    Environmental stress-mediated differential 3′ end formation of chloroplast RNA-binding protein transcripts (1994)
    Springer
    Plant molecular biology 26 (1994), S. 833-849 
    Details
    ISSN: 1573-5028
    Schlagwort(e): gene expression ; RNA stability regulation ; chloroplast RNA-binding protein (cRBP) ; environmental stress ; Mesembryanthemum crystallinum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract We report the characterization of transcripts from the halophyte, Mesembryanthemum crystallinum, encoding a protein with high homology to chloroplast RNA-binding proteins (cRBP). In this plant chloroplast-related functions are largely protected against salt stress. cRBP transcripts are derived from a single gene, Mc32crbp, although three size classes of polyadenylated mRNAs are detected. Transcription rate and steady state amounts of mRNA are developmentally regulated and light controlled with strong transcriptional activity as functional chloroplasts are established, and with lower maintenance activity thereafter. Upon salt stress, the rate of transcription decreases, although transcript levels increase. Accompanying stress, a change in the distribution of transcript size classes is observed as the longest transcript with an untranslated 3′ end of 381 nucleotides increases relative to transcripts with shorter 3′ ends. The long transcript is characterized by the presence of five sequence elements in the 3′-untranslated region that are present in cRBP mRNAs from a variety of plants, although not all elements are found in each mRNA. The results may indicate a mechanism by which mRNA levels of constitutively light-regulated genes may be modulated without enhanced transcription in response to environmental cues.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00028852
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  • 39
    Digitale Medien
    Digitale Medien
    Gibberellins: perception, transduction and responses (1994)
    Springer
    Plant molecular biology 26 (1994), S. 1529-1555 
    Details
    ISSN: 1573-5028
    Schlagwort(e): gibberellin ; growth ; development ; perception ; receptor ; gene expression ; signal transduction ; response mutant ; calcium
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00016489
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  • 40
    Digitale Medien
    Digitale Medien
    Regulation of an Arabidopsis oleosin gene promoter in transgenic Brassica napus (1994)
    Springer
    Plant molecular biology 25 (1994), S. 193-205 
    Details
    ISSN: 1573-5028
    Schlagwort(e): Arabidopsis ; embryo ; gene expression ; oleosin ; promoter
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Progressive deletions of the 5′-flanking sequences of an Arabidopsis oleosin gene were fused to β-glucuronidase (GUS) and introduced into Brassica napus plants using Agrobacterium-mediated transformation. The effect of these deletions on the quantitative level of gene expression, organ specificity and developmental regulation was assessed. In addition, the influence of abscisic acid (ABA), jasmonic acid (JA), sorbitol and a combined ABA/sorbitol treatment on gene expression was investigated. Sequences that positively regulate quantitative levels of gene expression are present between −1100 to −600 and −400 to −200 of the promoter. In addition, sequences present between −600 and −400 down-regulate quantitative levels of expression. In transgenic B. napus plants, the oleosin promoter directs seed-specific expression of GUS which is present at early stages of seed development and increases throughout seed maturation. Sequences present between −2500 and −1100 of the promoter are involved in modulating the levels of expression at early stages of embryo development. Histochemical staining of embryos demonstrated that expression is uniform throughout the tissues of the embryo. Sequences involved in the response to ABA and sorbitol are present between −400 and −200. The induction of GUS activity by a combined ABA/sorbitol treatment is additive suggesting that ABA is not the sole mediator of osmotically induced oleosin gene expression. A response to JA was only observed when the oleosin promoter was truncated to −600 suggesting that the reported effect of JA on oleosin gene expression may be at a post-transcriptional level.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00023237
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  • 41
    Digitale Medien
    Digitale Medien
    Over-production of the D1 protein of photosystem II reaction centre in the cyanobacterium Synechococcus sp. PCC 7942 (1994)
    Springer
    Plant molecular biology 26 (1994), S. 709-721 
    Details
    ISSN: 1573-5028
    Schlagwort(e): gene expression ; photosynthesis ; protein turnover ; psbA ; tac promoter
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The unicellular cyanobacterium Synechococcus sp. PCC 7942 has three psbA genes encoding two different forms of the photosystem II reaction centre protein D1 (D1:1 and D1:2). The level of expression of these psbA genes and the synthesis of D1:1 and D1:2 are strongly regulated under varying light conditions. In order to better understand the regulatory mechanisms underlying these processes, we have constructed a strain of Synechococcus sp. PCC 7942 capable of over-producing psbA mRNA and D1 protein. In this study, we describe the over-expression of D1:1 using a tac-hybrid promoter in front of the psbAI gene in combination with lacI Q repressor system. Over-production of D1:1 was induced by growing cells for 12 h at 50 μmol photons m-2 s-1 in the presence of 40 or 80 μg/ml IPTG. The amount of psbAI mRNA and that of D1:1 protein in cells grown with IPTG was three times and two times higher, respectively. A higher concentration of IPTG (i.e., 150 μg/ml) did not further increase the production of the psbAI message or D1:1. The over-production of D1:1 caused a decrease in the level of D1:2 synthesised, resulting in most PSII reaction centres containing D1:1. However, the over-production of D1:1 had no effect on the pigment composition (chlorophyll a or phycocyanin/number of cells) or the light-saturated rate of photosynthesis. This and the fact that the total amounts of D1 and D2 proteins were not affected by IPTG suggest that the number of PSII centres within the membranes remained unchanged. From these results, we conclude that expression of psbAI can be regulated by using the tac promoter and lacI Q system. However, the accumulation of D1:1 protein into the membrane is regulated by the number of PSII centres.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00013756
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  • 42
    Digitale Medien
    Digitale Medien
    A dehydrin cognate protein from pea (Pisum sativum L.) with an atypical pattern of expression (1994)
    Springer
    Plant molecular biology 26 (1994), S. 805-816 
    Details
    ISSN: 1573-5028
    Schlagwort(e): Dehydrin ; gene expression ; pea (Pisum sativum L.) ; cognate
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Dehydrins are a family of proteins characterised by conserved amino acid motifs, and induced in plants by dehydration or treatment with ABA. An antiserum was raised against a synthetic oligopeptide based on the most highly conserved dehydrin amino acid motif, the lysine-rich block (core sequence KIKEK-LPG). This antiserum detected a novel M r 40 000 polypeptide and enabled isolation of a corresponding cDNA clone, pPsB61 (B61). The deduced amino acid sequence contained two lysine-rich blocks, however the remainder of the sequence differed markedly from other pea dehydrins. Surprisingly, the sequence contained a stretch of serine residues, a characteristic common to dehydrins from many plant species but which is missing in pea dehydrin. The expression patterns of B61 mRNA and polypeptide were distinctively different from those of the pea dehydrins during seed development, germination and in young seedlings exposed to dehydration stress or treated with ABA. In particular, dehydration stress led to slightly reduced levels of B61 RNA, and ABA application to young seedlings had no marked effect on its abundance. The M r 40 000 polypeptide is thus related to pea dehydrin by the presence of the most highly conserved amino acid sequence motifs, but lacks the characteristic expression pattern of dehydrin. By analogy with heat shock cognate proteins we refer to this protein as a dehydrin cognate.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00028850
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  • 43
    Digitale Medien
    Digitale Medien
    Detection of immunologically related Kunitz and Bowman-Birk proteinase inhibitors expressed during potato tuber development (1994)
    Springer
    Plant molecular biology 26 (1994), S. 961-969 
    Details
    ISSN: 1573-5028
    Schlagwort(e): gene expression ; Kunitz-type proteinase inhibitor ; potato (Solanum tuberosum, L.) ; soybean C-II inhibitor
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Antiserum against a potato Kunitz-type proteinase inhibitor (PKPI) expressed in Escherichia coli was produced. In immunoblotting assays of proteins from potato tubers cultured in vitro, three proteins reacted to the antiserum, two of 20 kDa and one of 10 kDa. Their N-termini were sequenced. While the 20 kDa proteins showed 59 and 90% identity to PKPI, the 10 kDa one had 65% identity to soybean C-II proteinase inhibitor. Characterization of the temporal expression of these proteins showed that both could be detected from 10 days after induction of tuberization (DAI) in vitro, but the times when maximum amounts of PKPI and 10 kDa protein could be detected were different, corresponding to 22 and 32 DAI, respectively. The amounts of these proteins decreased in the following stages, and no positive reaction of the antiserum with mature tuber proteins could be found. The 20 kDa proteins were also detected in early stages of development of potato tubers grown in the field, indicating that these proteins are expressed during normal tuber development, and differ from the PKPIs reported previously.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00028862
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  • 44
    Digitale Medien
    Digitale Medien
    Isolation and characterization of two β-tubulin cDNA clones from rice (1994)
    Springer
    Plant molecular biology 26 (1994), S. 1975-1979 
    Details
    ISSN: 1573-5028
    Schlagwort(e): β-tubulin ; cDNA ; rice ; monocot ; gene expression
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Two cDNA clones encoding two different β-tubulins, RTUB-1 and RTUB-2, were isolated from a rice cDNA library and their nucleotide sequences were analyzed. The deduced amino acid sequences showed amino acid sequence identity between 92% and 97% with other plant β-tubulins. Southern blot analysis using gene-specific and coding-region probes suggested that β-tubulins in rice are encoded by multigene families. The two cDNA clones represent two subfamilies of rice tubulins. RTUB-1 and RTUB-2, consisting of 3 to 4 genes and a single gene, respectively. The transcript levels of RTUB-1 and RTUB-2 genes were higher in actively elongating tissues such as etiolated shoot tissues and light-grown root tissues of four-day old seedlings.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00019507
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  • 45
    Digitale Medien
    Digitale Medien
    Acclimation of photosynthetic proteins to rising atmospheric CO2 (1994)
    Springer
    Photosynthesis research 39 (1994), S. 413-425 
    Details
    ISSN: 1573-5079
    Schlagwort(e): elevated CO2 ; gene expression ; Rubisco ; rbcL ; rbcS
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract In this review we discuss how the photosynthetic apparatus, particularly Rubisco, acclimates to rising atmospheric CO2 concentrations (ca). Elevated ca alters the control exerted by different enzymes of the Calvin cycle on the overall rate of photosynthetic CO2 assimilation, so altering the requirement for different functional proteins. A decreased flux of carbon through the photorespiratory pathway will decrease requirements for these enzymes. From modeling of the response of CO2 uptake (A) to intracellular CO2 concentration (ci) it is shown that the requirement for Rubisco is decreased at elevated ca, whilst that for proteins limiting ribulose 1,5 bisphosphate regeneration may be increased. This balance may be altered by other interactions, in particular plasticity of sinks for photoassimilate and nitrogen supply; hypotheses on these interactions are presented. It is speculated that increased accumulation of carbohydrate in leaves developed at elevated ca may signal the ‘down regulation’ of Rubisco. The molecular basis of this ‘down regulation’ is discussed in terms of the repression of photosynthetic gene expression by the elevated carbohydrate concentrations. This molecular model is then used to predict patterns of acclimation of perennials to long term growth in elevated ca.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00014595
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  • 46
    Digitale Medien
    Digitale Medien
    UV-B damage and protection at the molecular level in plants (1994)
    Springer
    Photosynthesis research 39 (1994), S. 475-489 
    Details
    ISSN: 1573-5079
    Schlagwort(e): DNA repair ; flavonoids ; gene expression ; oxidative stress ; photosynthesis ; promoter
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Influx of solar UV-B radiation (280–320 nm) will probably increase in the future due to depletion of stratospheric ozone. In plants, there are several targets for the deleterious UV-B radiation, especially the chloroplast. This review summarizes the early effects and responses of low doses of UV-B at the molecular level. The DNA molecules of the plant cells are damaged by UV due to the formation of different photoproducts, such as pyrimidine dimers, which in turn can be combatted by specialized photoreactivating enzyme systems. In the chloroplast, the integrity of the thylakoid membrane seems to be much more sensitive than the activities of the photosynthetic components bound within. However, the decrease of mRNA transcripts for the photosynthetic complexes and other chloroplast proteins are among very early events of UV-B damage, as well as protein synthesis. Other genes, encoding defence-related enzymes, e.g., of the flavonoid biosynthetic pathway, are rapidly up-regulated after commencement of UV-B exposure. Some of the cis-acting nucleotide elements and trans-acting protein factors needed to regulate the UV-induced expression of the parsley chalcone synthase gene are known.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00014600
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  • 47
    Digitale Medien
    Digitale Medien
    The 24kDa outer envelope membrane protein from spinach chloroplasts: molecular cloning, in vivo expression and import pathway of a protein with unusual properties (1994)
    Springer
    Plant molecular biology 25 (1994), S. 167-177 
    Details
    ISSN: 1573-5028
    Schlagwort(e): Spinacia oleracea ; chemical cleavage ; gene expression ; polymerase chain reaction ; protein transport ; SDS-PAGE
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The 24 kDa outer envelope membrane protein of spinach chloroplasts (omp24) represents a major constituent of this membrane. Sequences of tryptic and endoprotease Glu-C peptides derived from omp24 allowed the design of oligonucleotides which were used to generate a DNA fragment by polymerase chain reaction using spinach cDNA as template. This fragment served as a probe to screen a cDNA library for a full-length clone of the omp24 coding sequence. The protein predicted from the complete sequence only has 148 amino acids and a molecular mass of 16294 Da. It is an acidic protein (calculated isoelectric point 4.8) with a high content of proline residues. Expression of the coding sequence in Escherichia coli and characterization of the purified recombinant protein produced revealed that the overestimation of its molecular mass by SDS-PAGE (ca. 25 kDa) is due to its abnormal amino acid composition. Despite its rather low hydrophobicity (polarity index 49%), omp24 appears to be deeply embedded in the outer membrane. Insertion of omp24 into the membrane proceeds almost independently of surface receptors or targeting sequence but, in contrast to other known outer envelope membrane proteins, is stimulated by ATP.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00023235
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  • 48
    Digitale Medien
    Digitale Medien
    Isolation and characterization of two tightly linked catalase genes from castor bean that are differentially regulated (1994)
    Springer
    Plant molecular biology 25 (1994), S. 507-516 
    Details
    ISSN: 1573-5028
    Schlagwort(e): castor bean (Ricinus communis) ; catalase gene ; gene expression ; germination
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Two catalase genes,cat1 andcat2, have been isolated from the castor bean genome. They were located in the same direction on a chromosome at a distance of 2.4 kb,cat1 being on the downstream side ofcat2. The two genes contained introns at the same positions except that one of the 7 introns incat1 is missing incat2 and the corresponding introns differed in size and sequence between the two genes. The translated regions of the two genes had the same number of nucleotides and exhibited 81.3% nucleotide sequence identity. In addition to introns, the nucleotide sequences of the 5′-and 3′-flanking regions are highly divergent between the two genes. In etiolated seedlings,cat1 mRNA was present abundantly in endosperms and cotyledons and only in a small amount in roots. Thecat1 mRNA could not be detected in hypocotyls. By contrast,cat2 mRNA is most abundant in hypocotyls and roots, while endosperms and cotyledons contained only low levels ofcat2 mRNA. Although neithercat1 norcat2 mRNA could be detected in dry seeds, both mRNAs showed temporal accumulation in the endosperm in response to germination. These results suggest that expression of two tightly linked catalase genes of castor bean,cat1 andcat2, are differentially regulated during development.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00043878
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  • 49
    Digitale Medien
    Digitale Medien
    Characterization of four new β-tubulin genes and their expression during male flower development in maize (Zea mays L.) (1994)
    Springer
    Plant molecular biology 24 (1994), S. 295-315 
    Details
    ISSN: 1573-5028
    Schlagwort(e): β-tubulin ; microtubules ; maize ; gene expression
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Four different β-tubulin coding sequences were isolated from a cDNA library prepared from RNA from maize seedling shoots. The four genes (designated tub4, tub6, tub7 and tub8) represented by these cDNA clones together with the tub1 and tub2 genes reported previously encode six β-tubulin isotypes with 90–97.5% amino acid sequence identity. Results from phylogenetic analysis of 17 β-tubulin genes from monocot and dicot plant species indicated that multiple extant lines of β-tubulin genes diverged from a single precursor after the appearance of the two major subfamilies of α-tubulin genes described previously. Hybridization probes from the 3′ non-coding regions of six β-tubulin clones were used to quantify the levels of corresponding tubulin transcripts in different maize tissues including developing anthers and pollen. The results from these dot blot hybridization experiments showed that all of the β-tubulin genes were expressed in most tissues examined, although each gene showed a unique pattern of differential transcript accumulation. The tub1 gene showed a high level of transcript accumulation in meristematic tissues and almost no accumulation in the late stages of anther development and in pollen. In contrast, the level of tub4 transcripts was very low during early stages of male flower development but increased markedly (more than 100 times) during the development of anthers and in pollen. Results from RNAse protection assays showed that this increased hybridization signal resulted from expression of transcripts from one or two genes closely related to tub4. The tub4-related transcripts were not present in shoot tissue. Transcripts from the tub2 gene accumulated to very low levels in all tissues examined, but reached the highest levels in young anthers containing microspore mother cells. RNAse protection assays were used to measure the absolute levels of α- and β-tubulin transcripts in seedling shoot and in pollen. The α-tubulin gene subfamily I genes (tua1, tua2, tua4) contributed the great majority of α-tubulin transcripts in both shoot and pollen. Transcripts from the β-tubulin genes tub4, tub6, tub7, and tub8 were predominant in shoot, but were much less significant than the tub4-related transcripts in pollen.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00020169
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  • 50
    Digitale Medien
    Digitale Medien
    Structural and functional analysis of an Opaque-2-related gene from sorghum (1994)
    Springer
    Plant molecular biology 24 (1994), S. 515-523 
    Details
    ISSN: 1573-5028
    Schlagwort(e): gene expression ; b-ZIP motif ; seed storage proteins ; trans-acting factors ; transcription factors ; transcriptional regulation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The Opaque-2 (O2) gene from maize encodes a transcriptional activator of the b-ZIP class. We have isolated and characterized a gene from sorghum, related in sequence to the O2 gene from maize. A single copy of the gene is present in sorghum. Both genomic and cDNA sequences of the O2-related sorghum gene were determined. The sequence is highly homologous to maize O2 both in the promoter and in the coding region. The most closely related sequences contain the b-ZIP domain with only 11 amino acid substitutions in a total of 122 residues. In transient expression assays, the sorghum O2-related coding sequence, expressed from a CaMV 35S promoter, activates expression from the maize b-32 promoter as effectively as that obtained with the maize O2 sequence.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00024119
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  • 51
    Digitale Medien
    Digitale Medien
    Cloning of two gibberellin-regulated cDNAs from Arabidopsis thaliana by subtractive hybridization: expression of the tonoplast water channel, γ-TIP, is increased by GA3 (1994)
    Springer
    Plant molecular biology 24 (1994), S. 603-615 
    Details
    ISSN: 1573-5028
    Schlagwort(e): Arabidopsis thaliana ; dwarf mutant ; gene expression ; gibberellin ; subtractive hybridization ; tonoplast intrinsic protein
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The Arabidopsis ga1 mutant has very low levels of endogenous, active gibberellins and thus has an extreme dwarf phenotype; application of GA3 induces stem elongation and flower development. To test the hypothesis that GA action in this system involves changes in gene expression, we have cloned mRNAs whose abundance changes following GA application. A subtraction cloning scheme for the isolation of differentially regulated cDNAs was established, involving hybridization of single-stranded cDNA to biotinylated mRNA. cDNA populations enriched up to 150-fold in GA-regulated sequences were produced and cDNA libraries generated. Screening of these libraries has isolated two clones that identify mRNAs of ca. 1100 and 750 bases whose abundance is markedly increased 24 h after GA application. One of these clones encodes the vegetative form of the Arabidopsis tonoplast intrinsic protein (γ-TIP), a water channel protein, the expression of which has recently been shown to be correlated with regions of cell expansion. The second clone is expressed only in the inflorescence and encodes a proline- and glycine-rich protein that may be a cell wall component.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00023557
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  • 52
    Digitale Medien
    Digitale Medien
    Meristem-specific gene expression directed by the promoter of the S-phase-specific gene, cyc07, in transgenic Arabidopsis (1994)
    Springer
    Plant molecular biology 24 (1994), S. 863-878 
    Details
    ISSN: 1573-5028
    Schlagwort(e): cell cycle ; gene expression ; meristem ; promoter analysis ; transgenic Arabidopsis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A genomic clone for the cyc07 gene, which is expressed specifically at the S phase during the cell cycle in synchronous cultures of periwinkle (Catharanthus roseus) cells, was isolated. Determination of the nucleotide sequence of the clone revealed that the cyc07 gene consists of seven exons separated by six introns. Genomic Southern analysis indicated that the cyc07 gene is present as a single copy per haploid genome in periwinkle. Expression of related genes was detected in a wide range of other plants. Transgenic Arabidopsis plants were generated that expressed the gene for β-glucuronidase (GUS) under the control of the promoter of the cyc07 gene. The tissue-specific pattern of expression directed by the promoter was investigated by analysis of GUS activity. Histochemical tests demonstrated that 589 bp of the 5′-upstream sequence of the cyc07 gene could direct specifical expression of the GUS reporter gene in meristematic tissues in transgenic plants. The spatial pattern of expression directed by the promoter was closely correlated with meristematic activity and cell proliferation, suggesting an association between the function of the cyc07 gene and cell proliferation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00014441
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  • 53
    Digitale Medien
    Digitale Medien
    Structure of genes that encode isozymes of aspartate aminotransferase in Panicum miliaceum L., a C4 plant (1994)
    Springer
    Plant molecular biology 26 (1994), S. 723-734 
    Details
    ISSN: 1573-5028
    Schlagwort(e): aspartate aminotransferase ; C4 photosynthesis ; gene expression ; gene structure ; isozyme
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The cytosolic and mitochondrial isozymes of aspartate aminotransferase (AspAT) function in the C4 photosynthetic cycle in NAD-malic enzyme-type C4 plants and are expressed at high levels in mesophyll cells and bundle sheath cells, respectively. We constructed a genomic library from Panicum miliaceum, a NAD-malic enzyme-type C4 plant, and cloned the genes for these isozymes. The sequence of the cloned gene for cytosolic AspAT spans 7800 bp and consists of 12 exons. The sequence of the cloned gene for mitochondrial AspAT spans 9000 bp and consists of 10 exons. The results of primer-extension analysis suggest that transcription may be initiated from multiple adjacent sites. Both genes have significant GC-rich regions around the site of initiation of transcription, and these regions showed no CpG suppression. The 5′-flanking regions of both genes include several short sequences similar to the regulatory elements found in other genes for components of the photosynthetic machinery. In particular, the cytosolic AspAT gene contains sequences similar to nuclear protein-binding sites in other mesophyll-expressed C4 photosynthetic genes and the mitochondrial AspAT gene contains elements for light-sensitive and constitutive expression of a bundle sheath-expressed gene. The results of Southern analysis indicated that there are at least two genes that encode each isozyme in the genome of P. miliaceum. A comparison of nitron-insertion positions between AspAT genes of plants and animals revealed that several introns are located at identical positions. On the basis of a phylogenetic tree among AspATs and tyrosine aminotransferase, we have shown that the introns of aminotransferase genes antedate the divergence of eubacteria, archaebacteria, and eukaryotes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00013757
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  • 54
    Digitale Medien
    Digitale Medien
    Expression of engineered antibodies in plant cells (1994)
    Springer
    Plant molecular biology 26 (1994), S. 1023-1030 
    Details
    ISSN: 1573-5028
    Schlagwort(e): immunoglobulin genes ; gene expression ; transgenic plants
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00040685
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  • 55
    Digitale Medien
    Digitale Medien
    A method for examining expression of homologous genes in plant polyploids (1994)
    Springer
    Plant molecular biology 26 (1994), S. 1065-1071 
    Details
    ISSN: 1573-5028
    Schlagwort(e): Brassica ; polyploid ; gene expression ; RT-PCR ; RFLP
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract One of the essential issues regarding evolution of polyploid species is how duplicate genes are expressed. Most studies on gene expression in polyploids have been based on isozyme analyses; RNA analysis has not been widely used partially due to difficulties in distinguishing homologous transcripts which usually have the same length and similar or almost identical sequences. In this study, a method combining RT-PCR with RFLP was used to analyze transcripts of homologous genes in natural and synthetic Brassica amphidiploids. Sequences coding for several known genes were selected and used to synthesize gene-specific primers. Total RNAs were used as templates for RT-PCR to amplify homologous transcripts in three diploid parental species, three cultivated amphidiploid species and six synthetic amphidiploids. For each gene, initial PCR products amplified in all species had identical length; however, homologous transcripts in the diploid and amphidiploid species could be distinguished after digesting the PCR products with restriction enzymes. Preliminary results based on three genes indicated that both transcripts from the diploid parents were expressed in the synthetic and natural amphidiploids. This study represents the first application of RT-PCR and RFLP analysis to investigate expression of homologous genes in higher plants. The technique is a sensitive, simple and efficient method for distinguishing homologous transcripts in a mixed RNA population and can be applied to many types of studies on expression of homologous genes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00040689
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  • 56
    Digitale Medien
    Digitale Medien
    Molecular cloning of the Arabidopsis thaliana sedoheptulose-1,7-biphosphatase gene and expression studies in wheat and Arabidopsis thaliana (1994)
    Springer
    Plant molecular biology 26 (1994), S. 1191-1200 
    Details
    ISSN: 1573-5028
    Schlagwort(e): Calvin cycle genes ; gene expression ; SBPase ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract We report here the isolation and nucleotide sequence of genomic clones encoding the chloroplast enzyme sedoheptulose-1,7-bisphosphatase (SBPase) from Arabidopsis thaliana. The coding region of this gene contains eight exons (72–76 bp) and seven introns (75–91 bp) and encodes a polypeptide of 393 amino acids. Unusually, the 5′ non-coding region contains two additional AUG codons upstream of the translation initiation codon. A comparison of the deduced Arabidopsis and wheat SBPase polypeptide sequences reveals 78.6%, identity. Expression studies showed that the level of SBPase mRNA in Arabidopsis and wheat is regulated in a light-dependent manner and is also influenced by the developmental stage of the leaf. Although the Arabidopsis SBPase gene is present in a single copy, two hybridizing transcripts were detected in some tissues, suggesting the presence of alternate transcription start sites in the upstream region.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00040699
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  • 57
    Digitale Medien
    Digitale Medien
    Coordinated expression of five tropomyosin isoforms and β-actin in astrocytes treated with dibutyryl cAMP and cytochalasin D (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 28 (1994), S. 303-316 
    Details
    ISSN: 0886-1544
    Schlagwort(e): cytoskeleton ; cell culture ; gene expression ; Northern blot ; serum-induction ; rat ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: Cytochalasin D and dBcAMP cause cultured astrocytes to change from flat cells to retrated process-bearing cells. F-actin was present throughout cells stimulated with dBcAMP for 16 h, whereas cytochalasin D caused F-actin to form massive aggregates at the tips of the cell processes. The two drugs differently regulated the expression of both β-actin and tropomyosin genes in astrocytes cultured in the presence or absence of serum: dBcAMP caused down-regulation and cytochalasin D caused up-regulation. Northern blot analyses indicated that: (1) serum deprivation halved the concentration of all tropomyosin transcripts (TM-1, TM-2, TM-4, TMBr-1, TMBr-2). Serum induced TM-4 via transcriptional activation, independent of protein synthesis, (2) dBcAMP induced down-regulation of β-actin (-50%) and tropomyosin transcripts (-35 to 52%) even in the presence of serum. The concentration of profilin mRNA decreased in dBcAMP-reactive astrocytes (-46%). The decrease in β-actin mRNA concentration was not blocked by cycloheximide, whereas down-regulation of tropomyosin transcripts was completely reversed when protein synthesis was inhibited, and (3) cytochalasin D induced an increase in the concentration of tropomyosin transcripts (+ 69 to 185%) which was cumulative with serum stimulation. Cytochalasin D induction of both β-actin and TM-4 operated through transcriptional activation, independent of protein synthesis.The production of all tropomyosin transcripts examined here were strictly coordinated with β-actin expression in serum-, dBcAMP- and cytochalasin D-treated astrocytes. This indicates that the differential expression of tropomyosin isoforms occurring during astrocyte maturation is due to more complex regulation than that involved in serum- or cAMP-stimulated astrocytes. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cm.970280404
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  • 58
    Digitale Medien
    Digitale Medien
    HPLC with carbohydrate carbamate chiral phases: Influence of chiral phase structure on enantioselectivity (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 135-140 
    Details
    ISSN: 0899-0042
    Schlagwort(e): amylose ; cellulose ; phenylcarbamate ; 3,5-dimethylphenylcarbamate ; 3,5-dimethoxyphenylcarbamate ; trans-stilbene oxide ; chiral sulfoxides ; resolution ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The enantioselective resolution of trans-stilbene oxide and of 23 chiral sulfoxides was investigated on cellulose and amylose tris(arylcarbamate) stationary phases coated on aminopropylated 7 μm spherical silica with 500 Å diameter pores. Cellulose tris-(3,5 dimethylphenylcarbamate) showed good resolving power for many of the sulfoxides and amylose tris-(3,5 dimethoxyphenylcarbamate) showed advantages for the resolution of certain sulfoxides which were not separated on other phases. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060214
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  • 59
    Digitale Medien
    Digitale Medien
    (1′R,2′S,5′R)-Menthyl-(5R)-acetoxy-1,3-oxathiolan-(2R)-carboxylate: Synthesis and isomeric purity determination by HPLC (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 156-160 
    Details
    ISSN: 0899-0042
    Schlagwort(e): chemoselective reduction ; disiamylborane ; (-)-2′-deoxy-3′-thiacytidine ; (1′R,2′S,5′R)-menthyl-(5R)-acetoxy-1,3-oxathiolan-(2R)-carboxylate ; Lamivudine ; 3TCTM ; chiral HPLC ; chiral stationary phase ; Pirkle β-GEM 1 column ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Chemoselective reduction of one isomer of the 1-menthylester of 1,3-oxathiolan-5-one-2-carboxylic acid produces a mixture of four lactol diastereomers from which the title compound was isolated after acylation. The isomeric purity and absolute stereochemistry were determined by spectroscopic methods, chiral HPLC techniques, and conversion to (-)-2′-deoxy-3′-thiacytidine (Lamivudine, 3TCTM). © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060217
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  • 60
    Digitale Medien
    Digitale Medien
    The origin of chirality in protein amino acids (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 165-168 
    Details
    ISSN: 0899-0042
    Schlagwort(e): chirality ; chemical evolution ; phase transitions ; optical activity ; spontaneous symmetry breakdown ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: We discuss the origin of the chirality of protein amino acids from the point of view of a phase transition from a racemic mixture into an optically pure state. We assume that Bose-Einstein condensation may act as an amplification mechanism. The original theory is due to Salam. We suggest a new role for the phase transition. Following Quack we distinguish parity violation of two kinds (de facto and de lege symmetry breaking). While the Salam phase transition corresponds to parity violation of the second kind (de lege), the phase transition we discuss in this work corresponds to parity violation of what we may call a third kind. This is suggested by recent experimental phenomena which correlate chiral symmetry breaking and pattern formation (spontaneous symmetry breaking that separates an initial racemic mixture into right- and left-handed space domains by means of a substrate). Tentative comments are given on the eventual design of possible experiments that may test this new hypothesis. © 1994 Wiley-Liss, Inc.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060302
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  • 61
    Digitale Medien
    Digitale Medien
    Input rate-dependent stereoselective pharmacokinetics: Effect of pulsatile oral input (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 185-195 
    Details
    ISSN: 0899-0042
    Schlagwort(e): stereoselective pharmacokinetics ; stereoselective bioavailability ; bioequivalence of chiral drugs ; nonlinear pharmacokinetics ; Michaelis-Menten kinetics ; computer simulation ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Computer simulation was used to test the effects of pulsatile oral input on the stereoselectivity in the area under the blood concentration-time curves (AUCs) of the enantiomers of racemic drugs. The effects of input rate determinants, namely, dose, dosage interval, and formulation on the stereoselectivity were investigated under both steady-state and nonsteady-state conditions. Simulations were carried out for drugs undergoing Michaelis-Menten hepatic metabolism with different enantiomeric maximum velocity (Vmax) or constant (Km) values. With pulsatile input, the enantiomeric AUC ratios of both types of drugs were dependent on all the determinants of input rate. However, in most cases, the direction of input rate-dependent changes in the enantiomeric AUC ratios for drugs with different enantiomeric Vmax was opposite of that for drugs with different enantiomeric Km. The direction and magnitude of changes in the enantiomeric AUC ratios were also dependent on the selected dose, dosage interval, and formulation. Further, different conclusions could be reached based on the nonsteady-state and steady-state data. Additional simulations were then performed to test the effects of input rate-dependent stereoselective pharmacokinetics on the bioequivalence of chiral drugs with nonlinear metabolism. These simulations suggested that bioequivalence studies based on the racemic drug measurement may result in erroneous conclusions for the individual enantiomers. The results of this study may be used as a tool for the design of experiments to test the input rate dependence of stereoselective pharmacokinetics and bioequivalence of racemic drugs in animals and humans. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060305
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  • 62
    Digitale Medien
    Digitale Medien
    Stereoselective hydrolysis of ICRF-187 (dexrazoxane) and ICRF-186 by dihydropyrimidine amidohydrolase (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 213-215 
    Details
    ISSN: 0899-0042
    Schlagwort(e): ICRF-187 ; ICRF-186 ; ICRF-159 ; dexrazoxane ; doxorubicin ; dihydropyrimidine amidohydrolase ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The enzymatic ring-opening hydrolyses of the doxorubicin cardioprotective agents (+)-(S)-ICRF-187 (dexrazoxane), (-)-(R)-ICRF-186, and rac-ICRF-159 by the enzyme dihydropyrimidine amidohydrolase (DHPase) have been studied. ICRF-187 underwent enzymatic ring-opening hydrolysis by DHPase 4.5 times faster than did ICRF-186. It was also shown that DHPase opens only one ring of ICRF-186 and does not act on this one-ring open hydrolysis product, as has been observed for ICRF-187. Differences in the rates at which the two optical isomers are acted upon by DHPase suggest that they could have differing protective effects. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060309
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  • 63
    Digitale Medien
    Digitale Medien
    Masthead (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994) 
    Details
    ISSN: 0899-0042
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060401
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  • 64
    Digitale Medien
    Digitale Medien
    Molecular modelling of the inclusion complexes between β-cyclodextrin and (R)/(S)-methylphenobarbitone and its application to HPLC (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 239-244 
    Details
    ISSN: 0899-0042
    Schlagwort(e): HPLC ; reverse-phase additive ; β-cyclodextrin ; methylphenobarbitone ; molecular mechanics ; complex stability ; chiral separation ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Molecular modelling of β-cyclodextrin and optimisation of its potential energy suggests that a favoured conformation is that distorted from a symmetrical torus. The inclusion of water molecules into the torus cavity simulates the increased stability in an aqueous solvent. Complexes of β-cyclodextrin with (R)- and (S)-enantiomers of methylphenobarbitone have been modelled and energetically optimised by the application of molecular mechanics. The simulations suggests that the guest molecules adopt an orientation in which the phenyl ring is projected into the torus cavity, with in each case the plane of the ring parallel to a longer axis of the distorted torus and slightly displaced from the axis through the torus cavity. It is suggested that the asymmetry in the macrocyclic ring contributes to chiral recognition as a result of additional discriminatory binding to the barbiturate ring residue of each enantiomer, which occupy different 3D geometries. The enantiomers form complexes of different minimum potential energies. The resulting difference in complex stability can be related to the behaviour of β-cyclodextrin, as a mobile phase additive in reverse-phase HPLC to effect chiral separation of rac-medthylphenobarbitone during chromatography. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060405
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  • 65
    Digitale Medien
    Digitale Medien
    π-Facial hydrogen bonding in the chiral resolving agent 2,2,2-trifluoro-1-(9-anthryl)-ethanol and its racemic modification (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 245-250 
    Details
    ISSN: 0899-0042
    Schlagwort(e): intermolecular association ; hydrogen-bonding ; π-facial ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: 2,2,2-Trifluoro-(9-anthryl)-ethanol (TFAE) has been extensively used, in its pure enantiomeric forms, as a chiral solvating agent in nuclear magnetic resonance spectroscopy (NMR). It has also played an important role in the development of chiral stationary phases in liquid chromatography (LC). X-ray crystallography of the enantiomeric and racemic crystals shows, in both cases, the formation of an intermolecular hydrogen bond between the O—H and the π-face of one of the rings of the anthracene aromatic system.1 Few examples of such hydrogen bonding have been published previously, and those that have are not as clear cut as in this case. An explanation for the hydrogen bonding is sought using molecular modelling via the PM3 analytically derived molecular electrostatic potentials. Using NMR and dynamic lineshape analysis, the barrier to rotation about the aryl-carbon bond is estimated, indicating the C—CF3 bond to be perpendicular to the anthracene axis in nonpolar solution. This conformation is identical to the conformation in the crystal. Evidence is also presented to support the formation of intermolecular π-facial hydrogen bonding in TFAE solutions. It is thought that such hydrogen bonding may be implicated in chiral recognition using this compound. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060406
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  • 66
    Digitale Medien
    Digitale Medien
    Evaluation of free D-glutamate in processed foods (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 277-282 
    Details
    ISSN: 0899-0042
    Schlagwort(e): D-amino acids ; D-glutamate ; monosodium glutamate ; food analysis ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Monosodium glutamate (MSG) is added to many processed foods at significant levels for flavor enhancement. It is also naturally occurring at high levels in some foods. The enantiomeric composition of free glutamate in foods was examined and all foods analyzed were found to contain D-glutamate. The relative percent of D-glutamate in the food products studied depended on the origin of the glutamate. Foods to which MSG was added by the manufacturer had a high total level of MSG but a lower relative percentage of the D-enantiomer (usually less than 0.8%). In comparison, fermented foods tend to have high relative levels of D-glutamate but a lower total amount of the amino acid. The relative percent of D-glutamate in nonfermented foods containing no added MSG was also found to be low compared to fermented products. In some cases the percent D-glutamate could be related to the relative amounts of other food ingredients such as cheese. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060410
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  • 67
    Digitale Medien
    Digitale Medien
    New technique in optical resolutions (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 314-320 
    Details
    ISSN: 0899-0042
    Schlagwort(e): amphetamine ; distillation method ; clathrate ; optical activation of bases ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The present paper illustrates the development of an advanced technique in optical resolution. Both of the amphetamine enantiomers can be obtained by a two-step distillation in nearly quantitative yield without any loss of the resolving agent. It is proved that the second-order interactions (H-bond) are sufficient for separation of enantiomers by distillation. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060415
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  • 68
    Digitale Medien
    Digitale Medien
    Determination of amphetamine and methamphetamine enantiomers by chiral derivatization and gas chromatography-mass spectrometry as a test case for an automated sample preparation system (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 295-301 
    Details
    ISSN: 0899-0042
    Schlagwort(e): diastereoisomer ; drugs of abuse ; GC-MS ; automation ; sample preparation ; drug testing ; stereoselective analysis ; enantioselectivity ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: An automated sample preparation system has been applied to the chiral analysis of amphetamine and methamphetamine using derivatization with trifluoracetyl-L-prolyl chloride (L-TPC) and subsequent separation on a gas chromatography-mass spectrometry (GC-MS) system. Tasks automated were the dilution of standards and the off-line preparation of the diastereoisomer derivatives. Chromatographic performance, sensitivity, and reproducibility of the automated procedure were compared to the equivalent values obtained with two existing assays methods which employ manual derivatiation, either on-column or off-line. Chromatographic performance was unaffected by the derivatization procedure and sensitivity was better for both automated and manual off-line derivatization. Qualitative reproducibility as based on enantiomeric composition was equivalent for all three approaches, while quantitative reproducibility as based on peak areas was best for the automated procedure. Considering the fact that the diastereoisomer derivatives are unstable over time, automated sample preparation with “just-in-time” derivatization can increase the overall precision of the analytical method. The procedures described here are general enough in nature that they could be applied to other chiral or even achiral analytes. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060413
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  • 69
    Digitale Medien
    Digitale Medien
    Masthead (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994) 
    Details
    ISSN: 0899-0042
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060101
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  • 70
    Digitale Medien
    Digitale Medien
    Experimental studies of competition between enantiomers in chiral liquid chromatography through their system peaks (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 148-155 
    Details
    ISSN: 0899-0042
    Schlagwort(e): chiral stationary phase ; dinitrobenzylphenylethylamine ; dinitrobenzoylphenylglycine ; enantiomers ; 2,2,2-trifluoro-1-(9-anthryl) ethanol ; competition ; nonlinear ; liquid chromatography ; system peaks ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Competition between the (+)- and (-) enantiomers of 2,2,2-trifluoro-1-(9-anthryl) ethanol as mobile phase additives was indicated by the chromatographic behavior of their system peaks. Two types of chiral stationary phases were used, one based on dinitrobenzoylphenylglycine and the other on dinitrobenzylphenylethylamine plus tartaric acid. The racemic mixture was used as the mobile phase additive and k′ of their system peaks was studied as a function of the mixture concentration in the mobile phase in both cases. A shift in k′ of the two system peaks was observed and considered as an indication that competition occurred. The areas of the two system peaks were also studied as a function of the concentration of the enantiomers in the samples, using two different compositions of the mobile phase. The dependency of system peaks' area on the sample composition indicated whether competition between the enantiomers occurred. One mobile phase contained 0.1 mM of the racemic mixture, where the area of the two retained system peaks behaved independently, i.e., only the peak corresponding to the enantiomer was affected by its presence in the sample. The other mobile phase contained 0.75 mM of the racemic mixture, and both peaks were affected by the injection of any one of the enantiomers. The interdependency of the system peaks' area on both the enantiomers indicated that their distribution in the chiral system was interrelated due to mutual interactions. A quantitative treatment of the interdependency and competition was excluded, due to the irreversible adsorption of the two enantiomers on the chiral stationary phase after using overloading concentrations. This irreversible adsorption was visualized by the appearance of two retained system peaks of the two residual enantiomers. These system peaks were detected only when the sample contained pure enantiomers due to competition between the enantiomer in the sample with the residual enantiomers in the stationary phase. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060216
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  • 71
    Digitale Medien
    Digitale Medien
    Acid-catalyzed stereoselective heteronucleophilic substitution and racemization of 3-O-methyloxazepam and 3-O-ethyloxazepam (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 175-184 
    Details
    ISSN: 0899-0042
    Schlagwort(e): 1,4-benzodiazepines ; oxazepam ; 3-O-methyloxazepam ; 3-O-ethyloxazepam ; stereoselective nucleophilic substitution ; kinetics of racemization ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Enantiomers of 3-O-methyloxazepam (MeOX) and 3-O-ethyloxazepam (EtOX) were resolved by chiral stationary phase high-performance liquid chromatography (CSP-HPLC). Reaction kinetics and deuterium isotope effects of acid-catalyzed racemization of enantiomeric MeOX in ethanol and enantiomeric EtOX in methanol were studied by spectropolarimetry. The acid-catalyzed heteronucleophilic substitution reactions of racemic MeOX in ethanol and racemic EtOX in methanol were studied by reversed-phase HPLC. Thermodynamic parameters involved in the reactions were obtained by temperature-dependent reaction rates. The effects of solvent's dielectric constant on the heteronucleophilic substitution reactions were also determined. A nucleophilically solvated and transient C3 carbocation intermediate resulting from an N4-protonated enantiomer, derived from a 1,4-benzodiazcpine either in M (minus) or P (plus) conformation, is proposed to be an intermediate and responsible for the acid-catalyzed stereoselective nucleophilic substitution and the resulting racemization. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060304
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  • 72
    Digitale Medien
    Digitale Medien
    (R,R)-N,N′-Dimethylcyclohexyl-1,2-diazaseleno-phospholidine as a chiral derivatizing agent for the evaluation of chiral alcohols (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 196-201 
    Details
    ISSN: 0899-0042
    Schlagwort(e): 77Se NMR spectroscopy ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Previously, a diazaphospholidine has been synthesized and evaluated as a chiral derivatizing reagent for the determination of the optical purity of chiral alcohols via 31P NMR spectroscopy (Alexakis et al., J. Org. Chem. 57:1224-1237, 1992). Our laboratory is interested in the advantageous and practical applications of 77Se NMR spectroscopic studies in many facets of chemistry and biochemistry. To this end we have used this diazaphospholidine as a starting point and have investigated chiral alcohols coupled to an optically pure diazaselenophospholidine. The diastereomers formed were then evaluated by 77Se NMR spectroscopy, and these results were compared to the 31P NMR results published by Alexakis and co-workers. It was found that addition of the Se atom produced diastereomers that were air stable and, in many cases, the individual diastereomers could be distinguished by 77Se NMR spectroscopy. Preliminary results indicate that the 77Se nucleus is somewhat more sensitive to remotely disposed chiral centers than is the 31P nucleus. Furthermore, because of their stability, these compounds do not readily decompose and can, therefore, be studied by a variety of chromatographic and spectroscopic techniques. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060306
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  • 73
    Digitale Medien
    Digitale Medien
    A preliminary pharmacokinetic study of the enantiomers of the terfenadine acid metabolite in humans (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 479-483 
    Details
    ISSN: 0899-0042
    Schlagwort(e): terfenadine metabolite ; enantiomer separation ; HPLC ; pharmacokinetics ; humans ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A stereoselective and sensitive achiral/chiral method for the determination of terfenadine acid metabolite in human plasma was developed. The metabolite was separated and quantitated using an achiral chromatographic procedure with a cyano column. The mobile phase was 1 mM sodium acetate buffer (pH 4.0) and acetonitrile (25:75% v/v) at a flow rate of 2 ml/min, at ambient temperature. The stereospecific resolution was accomplished using a chiral-AGP column and a mobile phase consisting of sodium acetate (0.01 M): methanol (98.7:1.3% v/v), and 20 mM di-n-butylamine at a flow rate of 1.2 ml/min. The column temperature was maintained at 32°C. The eluent was monitored at 230 nm (excitation) and 300 nm (emission) with a cut-off filter at 270 nm. This assay was used for a pharmacokinetic study in five subjects after administration of a single dose of 60 mg of terfenadine. The t½ values of the two enantiomers were similar, but the AUC values of the (+)-enantiomer were 2.05-2.35 times higher than those of (-)-enantiomer. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060606
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  • 74
    Digitale Medien
    Digitale Medien
    Evaluation of the macrocyclic antibiotic vancomycin as a chiral selector for capillary electrophoresis (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 496-509 
    Details
    ISSN: 0899-0042
    Schlagwort(e): enantiomeric separations ; macrocyclic antibiotics capillary electrophoresis ; vancomycin ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Vancomycin is one of a family of related macrocyclic glycopeptide antibiotics that were discovered by scientists at the Eli Lilly Company in the 1950s. It has been used to treat severe staphylococcal infections, particularly when bacterial resistance to other antibiotics has developed. Vancomycin is a naturally occurring chiral compound and has a number of stereogenic centers. Furthermore, it contains a variety of functionalities that are known to be useful for enantioselective interactions (e.g., hydrogen bonding groups, hydrophobic pockets, aromatic groups, amide linkages, etc.). The physicochemical properties of vancomycin, including its stability in solution, are discussed as they pertain to capillary electrophoresis. Over 100 racemates were resolved including many nonsteroidal antiinflammatory drugs, antineoplastic compounds and N-derivatized amino acids. Many of these compounds had very high resolution factors. Optimization and the effect of different experimental parameters on the enantioselective separations are discussed. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060609
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  • 75
    Digitale Medien
    Digitale Medien
    Enantiomerization of 2,2′-diisopropylbiphenyl during chiral inclusion gas chromatography: Determination of the rotational energy barrier by computer simulation of dynamic chromatographic elution profiles (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 510-512 
    Details
    ISSN: 0899-0042
    Schlagwort(e): 2,2′-diisopropylbiphenyl ; racemization and enantiomerization ; rotational energy barrier ; computer simulation ; dynamic chiral gas chromatography ; cyclodextrin stationary phase ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: By computer simulation of experimental dynamic gas chromatographic elution profiles, the rotational energy barrier ΔG= of racemic 2,2′-diisopropylbiphenyl has been determined as 114.6-115.0 kJ/mol (75-100°C). These data are in good agreement with a value that was determined previously by measuring the racemization kinetics of an enriched sample. This indicates that there is no measurable catalytic or inhibitory effect of the stationary phase. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060610
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  • 76
    Digitale Medien
    Digitale Medien
    Chiral copper(I) - thiolate clusters in metallothionein and glutathione (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 521-530 
    Details
    ISSN: 0899-0042
    Schlagwort(e): metallothionein ; copper binding ; glutathione ; circular dichroism ; charge transfer ; metal-ligand stoichiometries ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Metallothionein (MT) is a ubiquitous mammalian protein comprising 61 or 62 nonaromatic amino acids of which 20 are cysteine residues. The high sulfhydryl content imparts to this protein a unique and remarkable ability to bind multiple metal ions in structurally significant metal-thiolate clusters. MT can bind seven divalent metal ions per protein molecule in two domains with exclusive tetrahedral metal coordination. The domain stoichiometries for the M7S20 structure are M4(Scys)11 (α domain) and M3(Scys)9 (β domain). Up to 12 Cu(I) ions can displace the 7 Zn2+ ions bound per molecule in Zn7-MT. The incoming Cu(I) ions adopt a trigonal planar geometry with domain stoichiometries for the Cu12S20 structure of Cu6(Scys)11 and Cu6(Scys)9 for the α and β domains, respectively. The circular dichroism (CD) spectra recorded as Cu+ is added to Zn7-MT to form Cu12-MT directly report structural changes that take place in the metal binding region. The spectrum arises under charge transfer transitions between the cysteine S and the Cu(I); because the Cu(I)-thiolate cluster units are located within the chiral binding site, intensities in the CD spectrum are directly related to changes in the binding site. The CD technique clearly indicates stoichiometries of several Cu(I)-MT species. Model Cu(I)-thiolate complexes, using the tripeptide glutathione as the sulfhydryl source, were examined by CD spectroscopy to obtain transition energies and the Cu(I)-thiolate coordination geometries which correspond to these bands. Possible structures for the Cu(I)-thiolate clusters in the α and β domains of Cu12-MT are proposed. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060703
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  • 77
    Digitale Medien
    Digitale Medien
    Kinetic resolution of esters of amino acids in t-butanol containing 5% water catalyzed by a stable industrial alkaline protease (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 572-576 
    Details
    ISSN: 0899-0042
    Schlagwort(e): resolution ; D,L-amino acid esters ; alkaline protease ; simple separation ; high enantiomeric excess and yields ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: We developed a procedure for the resolution of esters of amino acids in 95% t-butanol, followed by saponification of the unreacted esters to afford both enantiomers with high yield and optical purity. The hydrolysis, catalyzed by alkaline protease, was conducted in a mixture of t-butanol (95%) and water (5%) at 25°C, with a pH controlled at pH 8.5 by the addition of NaOH (2 M). The hydrolyzed L-amino acid, which was insoluble under these conditions, precipitated during the course of hydrolysis. After separation of the precipitate, the pH of the filtrate was adjusted to 11.5 to saponify the unreacted ester. The D-antipode precipitated at pH 6.2-6.5. Both optically pure antipodes were obtained with high enantiomeric excesses and yields by simple filtration. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060710
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  • 78
    Digitale Medien
    Digitale Medien
    GABAB antagonists: Resolution, absolute stereochemistry, and pharmacology of (R)- and (S)-phaclofen (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 583-589 
    Details
    ISSN: 0899-0042
    Schlagwort(e): chiral HPLC ; resolution ; absolute configuration ; X-ray analysis ; GABAB antagonist ; GABAB receptor affinity ; phaclofen ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Phaclofen, which is the phosphonic acid analogue of the GABAB agonist (RS)-3-(4-chlorophenyl)-4-aminobutyric acid (baclofen), is a GABAB antagonist. As part of our studies on the structural requirements for activation and blockade of GABAB receptors, we have resolved phaclofen using chiral chromatographic techniques. The absolute stereochemistry of (-)-(R)-phaclofen was established by X-ray crystallographic analysis. (-)-(R)-Phaclofen was shown to inhibit the binding of [3H]-(R)-baclofen to GABAB receptor sites on rat cerebellar membranes (IC50 = 76 ± 13 μM), whereas (+)-(S)-phaclofen was inactive in this binding assay (IC50 〉 1000 μM). (-)-(R)-Phaclofen (200 μM) was equipotent with (RS)-phaclofen (400 μM) in antagonizing the action of baclofen in rat cerebral cortical slices, while (+)-(S)-phaclofen (200 μM) was inactive. The structural similarity of the agonist (R)-baclofen and the antagonist (-)-(R)-phaclofen suggests that these ligands interact with the GABAB receptor sites in a similar manner. Thus, it may be concluded that the different pharmacological effects of these compounds essentially result from the different spatial and proteolytic properties of their acid groups. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060712
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  • 79
    Digitale Medien
    Digitale Medien
    Stereoselectivity of the in vitro metabolism of thalidomideDedicated to Professor Dr. Siegfried Ebel, Würzburg, on the occasion of his 60th birthday. (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 221-224 
    Details
    ISSN: 0899-0042
    Schlagwort(e): thalidomide enantiomers ; HPLC ; hydroxylated metabolites ; mass spectrometry ; EM 12 ; in vitro metabolism ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The stereoselective metabolism of the former sedative thalidomide and the metabolism of its analogue EM 12 were studied in vitro with liver homogenates. In our study we focused on hydroxylated nonhydrolyzed metabolites of thalidomide. An analytical HPLC method was developed to determine these metabolites directly. The investigations showed a highly stereoselective biotransformation of thalidomide. 5-Hydroxy thalidomide was preferentially formed by (-)-(S)-thalidomide, whereas (+)-(R)-thalidomide was metabolized to two hitherto unknown compounds (Met A and B). Mass spectrometry of these metabolites Met A and B indicated that oxidation or hydroxylation took place in the glutarimide moiety. Biotransformation studies with the more stable thalidomide analogue EM 12 revealed four new metabolites (Met C—F) whose quantities differed in the selected liver homogenate. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060402
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  • 80
    Digitale Medien
    Digitale Medien
    Effects of alkyl substituents on chiral separation of N-arylthiazolin-2-(thi)-one atropisomers on tris (p-methylbenzoyl)cellulose beads and cellulose triacetate: Lipophilicity aspects (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 251-260 
    Details
    ISSN: 0899-0042
    Schlagwort(e): chiral HPLC ; experimental design ; quantitative substituent effects ; recognition mechanism ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The determination of lipophilicity of the title compounds allowed treatment of the data for chiral separation (capacity factors) on CTA and CTPB according to these parameters. A linear correlation between In k′(+) and log k′w was found on both CTA and CTPB, as far as the substituents are situated in the plane of the aryl ring or the heterocycle. This correlation with a nonchiral descriptor allows treatment of capacity factors for (-)-enantiomers as deviations from the lipophilicity line or derived parallels. It results in a clear description of the molecular area affecting enantioselectivity. Application to larger alkyl derivatives shows that the effect of the substituent should be treated on a basis of attractive effect in the case of CTA and on the basis of attractive and repulsive effects for CTPB. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060407
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  • 81
    Digitale Medien
    Digitale Medien
    Assignment of absolute configuration and optical purity determination of (R)- and (S)-econazole nitrate by enantioselective HPLC: Method development and application (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 261-269 
    Details
    ISSN: 0899-0042
    Schlagwort(e): indirect and direct enantioseparation ; chromatographic assignment of absolute configuration ; econazole ; miconazole ; imidazolylethanol ; protein type CSPs (OVM) ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A method is described for the synthesis and optical purity determination of (-)-(R)- and (+)-(S)-econazole via the optically pure intermediates, (R)- and (S)-imidazolylethanol, which are available by chromatographic resolution or by fractional crystallization of diastereomeric O,O′-disubstituted (R*;R*)- or (S*;S*)-tartaric acid monoesters of the parent imidazolylethanol racemate. Furthermore, this method allows the chromatographic assignment of the absolute configuration of the chiral center of the imidazolylethanol enantiomers and consequently of econazole enantiomers. In addition, a direct liquid chromatographic enantioseparation method for the determination of the optical purity of (R)- and (S)-econazole and other chiral imidazoles on a protein type CSP (OVM) is described and applied to confirm chromatographically the absolute configuration evaluations. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060408
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  • 82
    Digitale Medien
    Digitale Medien
    Preparation of milligrams of pure enantiomers using analytical-scale high-performance liquid chromatography (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 290-294 
    Details
    ISSN: 0899-0042
    Schlagwort(e): preparative chromatography ; chiral separation ; polarimetric detection ; dual detection technique ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Pure enantiomers of an agrochemical process intermediate, (RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1H-1,2,4-triazol-1-yl)-pentan-3-one (1), have been prepared on the milligram scale under overload chromatographic conditions on an analytical chiral column (250 × 4.6 mm i.d.). The effects of variation of temperature and mobile phase composition on retention factor, separation factor, and peak resolution have been investigated. Effects of flow rate, enantiomer ratio, sample concentration, and column load on productivity are also studied. Seven milligrams of the less retained (+)-enantiomer and 5 mg of the (-)-enantiomer were obtained from a single injection of 21 mg of (RS)-1. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060412
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  • 83
    Digitale Medien
    Digitale Medien
    Use of a new pirkle-type chiral stationary phase in analytical and preparative subcritical fluid chromatography of pharmaceutical compounds (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 302-313 
    Details
    ISSN: 0899-0042
    Schlagwort(e): SFC ; brush-type chiral stationary phase ; Whelk-O CSP ; pharmaceutical analysis ; chiral analysis ; chiral preparative chromatography ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Good results have been obtained with use of the new bonded chiral stationary phase Whelk-O 1 in analytical and preparative subcritical fluid chromatography. A wide variety of enantiomeric pairs of compounds with different functional groups that are of pharmaceutical and biological interest have been resolved. This Pirkle-concept CSP appears to be more rugged than cellulosic phases (e.g., Chiralcel) with regards to solvents and pressure. In comparing the usefulness of the column for SFC versus HPLC chiral analysis, we have observed a clear superiority of SFC in terms of higher speed and efficiency of analysis, and faster method development. This is consistent with our experience with Chiralcel CSPs. With the Whelk-O 1 we have shown that the effects of temperature and modifier on SFC separations are similar to what has been reported for most other CSPs. We also observed a unique selectivity advantage of SFC for verapamil. We had good success with using a 1-in. diameter column packed with Whelk-O 1 to perform preparative SFC separations of a number of enantiomeric mixtures. The advantages of preparative SFC over preparative HPLC will be discussed. The feasibility of preparative SFC is dependent on how well we meet the practical challenges such as sample introduction issues, special hardware requirements due to the high pressure, and fraction collection issues. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060414
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  • 84
    Digitale Medien
    Digitale Medien
    Pharmacokinetics and pharmacodynamics of hydroxychloroquine enantiomers in patients with rheumatoid arthritis receiving multiple doses of racemate (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 355-359 
    Details
    ISSN: 0899-0042
    Schlagwort(e): pharmacokinetics ; antimalarials ; enantiomers ; pharmacodynamics ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Hydroxychloroquine, a slow acting antirheumatic drug, is administered as the racemic mixture. Blood concentrations of the two enantiomers of hydroxychloroquine were measured in two studies, one study of eight patients, in whom blood and urine concentrations were measured during the first 6 months of therapy with rac-hydroxychloroquine, and one of 43 patients who had received rac-hydroxychloroquine therapy for at least 6 months. In the latter study rheumatoid disease activity was also measured. The pharmacokinetics of hydroxychloroquine were found to be enantioselective. The concentrations of (-)-(R)-hydroxychloroquine were higher than those of the (+)-(S)-antipode in all patients at all time points, although the ratios of the two enantiomers did display a two to three fold variability between patients. Both total and renal clearance were greater for the (+)-(S)-enantiomer. From the observational, cross-sectional study design used, it was not possible to differentiate concentration-effect relationships of the two enantiomers. The 11-fold range of drug concentrations swamped any effect of variability between patients in enantiomer proportions. Blood concentrations of both enantiomers were significantly higher in groups of patients with less active disease. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060420
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  • 85
    Digitale Medien
    Digitale Medien
    Disposition and absorption of hydroxychloroquine enantiomers following a single dose of the racemate (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 360-364 
    Details
    ISSN: 0899-0042
    Schlagwort(e): hydroxychloroquine enantiomers ; absorption ; pharmacokinetics ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The disposition of hydroxychloroquine enantiomers has been investigated in nine patients with rheumatoid arthritis following administration of a single dose of the racemate. Blood concentrations of (-)-(R)-hydroxychloroquine exceed those of (+)-(S)-hydroxychloroquine following both an oral and intravenous dose of the racemate. Maximum blood concentrations of (-)-(R)-hydroxychloroquine were higher than (+)-(S) -hydroxychloroquine after oral dosing (121 ± 56 and 99 ± 42 ng/ml, respectively, P = 0.009). The time to maximum concentration and the absorption half-life, calculated using deconvolution techniques, were similar for both enantiomers. The fractions of the dose of each enantiomer absorbed were similar, 0.74 and 0.77 for (-)-(R)- and (+)-(S)-hydroxychloroquine, respectively (P = 0.77). The data suggest that absorption of hydroxychloroquine is not enantioselective. The stereoselective disposition of hydroxychloroquine appears to be due to enantioselective metabolism and renal clearance, rather than stereoselectivity in absorption and distribution. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060421
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  • 86
    Digitale Medien
    Digitale Medien
    Lack of stereoselectivity of the peroxisome proliferation induced by 2-phenylpropionic acid: Evidence against a role for lipid disturbance in peroxisome proliferation (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 365-371 
    Details
    ISSN: 0899-0042
    Schlagwort(e): 2-phenylpropionic acid ; peroxisome proliferation ; rat liver ; acyl CoA ; stereoselectivity ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The significance of disturbances of lipid metabolism caused by xenobiotic acyl-CoAs as possible causes of peroxisomal proliferation has been studied with the enantiomers of 2-phenylpropionic acid (2-PPA), the (R)-enantiomer of which is converted to the acyl-CoA in rats while its (S)-antipode is not. rac-2-PPA (250 mg/kg/day ip × 3) was shown to be an hepatic peroxisomal proliferator in male Sprague-Dawley rats on the basis of increases in microsomal cytochrome P-450 content and lauric acid hydroxylation and hepatic CN--insensitive palmitoyl-CoA oxidation, a peroxisomal marker activity, while electron microscopy revealed a rise in the peroxisome/mitochondria ratio in hepatocytes. Further studies established the dose-response relationships for these biochemical changes. The (R)- and (S)-enantiomers were administered at a dose of 50 mg/kg/day ip × 3 and both were peroxisome proliferators of very similar potency. The effects of 100 mg/kg/day ip × 3 of the racemate, a dose giving ca. 75% of maximal response, were essentially additive of those of 50 mg/kg/day ip × 3 of its two component isomers. The stereoselectivity of acyl-CoA formation from the enantiomers of 2-PPA was confirmed by their differential inhibition of microsomal palmitoyl-CoA synthesis. Taken together, these data indicate that it is very unlikely that the acyl-CoA of 2-PPA plays any role in the peroxisomal proliferation which this compound causes in the rat. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060502
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  • 87
    Digitale Medien
    Digitale Medien
    Influence of endotoxin on the stereoselective pharmacokinetics of oxprenolol, propranolol, and verapamil in the rat (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 405-410 
    Details
    ISSN: 0899-0042
    Schlagwort(e): β-adrenergic blocking agent ; calcium antagonist ; enantiomers ; inflammation ; protein binding ; pharmacokinetics ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The influence of endotoxin-induced inflammation on the enantioselective pharmacokinetics of propranolol, oxprenolol, and verapamil, which bind to α1-acid glycoprotein, was studied in the rat. The racemic mixtures were given orally. In the control animals, for propranolol and oxprenolol, the plasma concentrations of the (R)-enantiomer were higher than those of the (S)-enantiomer, while for verapamil the reverse was true. Protein binding and intrinsic clearance are the main factors responsible for this enantioselectivity. After endotoxin treatment, for the three drugs tested the plasma concentrations and the plasma binding of both enantiomers were significantly increased. This effect was more pronounced for (R)-propranolol, (R)-oxprenolol, and (S)-verapamil than for their respective antipodes. The enantioselective effect of endotoxin on the plasma concentrations of the drugs studied seems mainly due to the enantioselective increase in binding to α1-acid glycoprotein. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060508
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  • 88
    Digitale Medien
    Digitale Medien
    Stereoisomeric flavour compounds LXVII. 2-, 3-, and 4-Alkyl-branched acids, part 1: General approach to the synthesis of the enantiopure acids (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 420-426 
    Details
    ISSN: 0899-0042
    Schlagwort(e): synthesis of enantiopure 2-, 3-, and 4-alkyl-branched acids ; diastereomeric phenylglycinol amides ; chain elongation by Arndt-Eistert synthesis ; malonic ester synthesis or via 2-alkylated alkyl carbonitriles ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A general approach to the synthesis of 2-, 3-, and 4-alkyl-branched acids of high enantiomeric purity is described. The enantiopure 2-alkyl-branched acids are prepared via liquid chromatographic resolution of diastereomeric phenylglycinol amides and their absolute configuration is deduced from the 1H-NMR data of the separated diastereomers. Chain elongation methods, by Arndt-Eistert synthesis, via 2-alkylated alkyl carbonitrile or by malonic ester synthesis, are used to prepare 3- and 4-alkyl-branched acids of high configurational purity and known absolute configuration starting from the enantiomeric 2-alkyl-branched acids. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060510
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  • 89
    Digitale Medien
    Digitale Medien
    Evidence of absorption rate dependency of ibuprofen inversion in the ratPresented at the Eighth Annual Metting of the American Association of Pharmaceutical Scientists, November 14-18, 1993, Orlando, FL, USA. (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 435-439 
    Details
    ISSN: 0899-0042
    Schlagwort(e): Ibuprofen ; nonsteroidal antiinflammatory drug (NSAID) ; chiral inversion ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Ibuprofen (IB) is a chiral 2-arylpropionic acid derivative used as a nonsteroidal antiinflammatory drug (NSAID). It undergoes substantial R to S chiral inversion in humans and rats. In addition to systemic inversion, presystemic chiral inversion has been suggested for IB in humans but only after administration of formulations with slow absorption rates. In search for a suitable animal model, the absorption rate dependency of the extent of inversion was examined in male Sprague-Dawley rats given 20 mg/kg of racemic IB in aqueous solution (Tmax, 0.6 h), suspension (Tmax, 1 h) or as sustained release granules (Tmax, 2.3 h). In addition, (R)-IB (5 mg/liter) was incubated in the presence of everted rat gut segments in an organ bath at 37°. After sustained release granules, the S:R AUC ratios (7.3 ± 1.5) were significantly higher than suspension (3.6 ± 1.1) and solution (3.5 ± 0.2). Accordingly, AUCS and AUCR, as percent of the total AUC (S + R), significantly increased and decreased, respectively, after administration of the sustained released granules as compared with the solution and suspension. A significant positive linear correlation was found between the S:R AUC ratios and the corresponding Tmax for (R)-IB (r = 0.82). In vitro, (R)-IB was inverted by everted jejunum (12.2 ± 1.6%), ileum (14.2 ± 2.0%), and colon (4.4 ± 0.6%) segments. IB was also glucuronidated in the presence of the intestinal segments. Therefore, similar to earlier observations made in humans, in the rat, the S:R AUC ratio was positively and significantly correlated with the absorption rate from the dosage form. Rat small intestine was capable of inverting and conjugating (R)-IB. Hence, rat is a suitable model for studying the chiral inversion of IB. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060512
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  • 90
    Digitale Medien
    Digitale Medien
    Chiral pharmacokinetics of rac-flurbiprofen and pharmacodynamics of anabolic bone response in the normal rat (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 457-459 
    Details
    ISSN: 0899-0042
    Schlagwort(e): chiral pharmacokinetics ; rac-flurbiprofen ; rat ; bone pharmacodynamics ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The route of administration of the NSAID, flurbiprofen (sq vs. po) resulted in positive and negative results respectively with regard to enhanced cancellous and cortical bone accumulation in the immature rat. This pharmacokinetic study was an effort to understand the pharmacodynamic difference between the two routes of administration observed when the same dose range of drug, given as single daily doses, had been employed in both studies. Conventional chiral pharmacokinetics were evaluated in young rats. A significant difference was observed in the Tmax of the active (S)-enantiomer by both administration routes (sq 4 h and po 1 h). The bioavailability, as evaluated by AUCs favored the sq route as expected. The plasma concentrations over 18 h, at steady state, for one po dose group (0.5 mg/kg/day) fell well within the therapeutic window described by the 0.1 and 0.5 mg/kg sq doses which had demonstrated anabolic bone activity. Oral dosing had exhibited no significant bone activity. We conclude that the pharmacodynamic difference between routes of administration cannot be simply explained on a pahrmacokinetic basis. Consequently, experiments detailing the pharmacodynamics and pharmacokinetics of single and multiple dose administration of aryl-propionic acids in normal and osteopenic states need further pharmacologic study. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060602
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  • 91
    Digitale Medien
    Digitale Medien
    Pronase in amino acid technology: Optical resolution of nonproteinogenic α-amino acids (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 472-478 
    Details
    ISSN: 0899-0042
    Schlagwort(e): nonproteinogenic α-amino acid ; pronase ; optical resolution ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: We describe a practical method to produce pure enantiomers of non-proteinogenic α-amino acids by pronase-catalyzed hydrolysis of their methyl esters. Each of the two pure enantiomers was obtained in high yield, while the reaction conditions were optimized with a view to large scale production. Part of this work was devoted to conceiving an analytical procedure especially designed to monitor the steric course of enzymatic reactions. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060605
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  • 92
    Digitale Medien
    Digitale Medien
    Erratum (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 513-513 
    Details
    ISSN: 0899-0042
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060611
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  • 93
    Digitale Medien
    Digitale Medien
    Enantioselective syntheses and calcium channel modulating effects of (+)- and (-)-3-isopropyl 5-(4-methylphenethyl) 1,4-dihydro-2,6-dimethyl-4-(2-pyridyl)-3,5-pyridinedicarboxylatesDedicated to the memory of Professor Michael W. Wolowyk, deceased January 31, 1992. (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 515-520 
    Details
    ISSN: 0899-0042
    Schlagwort(e): stereoselective synthesis ; chiral synthon ; Hantzsch esters ; calcium channels ; smooth muscle relaxation ; positive inotropes ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The (+)- and (-)-enantiomers of 3-isopropyl 5-(4-methylphenethyl) 1,4-dihydro-2,6-dimethyl-4-(2-pyridyl)-3,5-pyridinedicarboxylate were synthesized using an efficient highly enantioselective (ee ≥ 96%) variant of the Hantzsch dihydropyridine synthesis. The key step in this procedure involved the asymmetric Michael addition of a metalated chiral aminocrotonate, derived from D-valine or L-valine, respectively, to the Knoevenagel acceptor (Z)-2-isopropoxycarbonyl-1-(2-pyridyl)-but-1-en-3-one. Both enantiomers exhibited a dual cardioselective partial calcium channel agonist (positive inotropic)/smooth muscle selective calcium channel antagonist effect. The relative in vitro smooth muscle calcium channel antagonist activities of the (-):(+) enantiomers was 26:1. In contrast, the (+)-enantiomer exhibited a greater in vitro positive inotropic effect on guinea pig left atrium where the contractile force was maximally increased by 14.8% at a concentration of 1.63 × 10-8 M. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060702
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  • 94
    Digitale Medien
    Digitale Medien
    Pharmacokinetics of ketoprofen enantiomers in monkeys following single and multiple oral administration (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 537-542 
    Details
    ISSN: 0899-0042
    Schlagwort(e): arylpropionic acid ; ketoprofen ; chiral inversion ; stereoselective pharmacokinetics ; monkey ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Pharmacokinetic studies are reported after single oral administration of 3 mg/kg of stereochemically pure (S)-ketoprofen [(S)-KP] and (R)-ketoprofen [(R)-KP] to three male Cynomolgus monkeys and after repeated administration for 6 months of 3, 15 and 75 mg/kg/day of (S)-KP to both male and female monkeys. A high-performance liquid chromatographic (HPLC) analysis was performed without derivatization of the samples, using a chiral column. The pharmacokinetic parameters for (S)-KP after administration of (S)-KP and for (R)-KP after administration of (R)-KP were, respectively, elimination half-life 2.32 ± 0.36 and 1.64 ± 0.40 h; oral clearance 3.50 ± 0.66 and 7.50 ± 3.20 ml/min/kg; apparent volume of distribution 0.74 ± 0.24 and 1.16 ± 0.76 liter/kg; mean residence time 1.79 ± 0.77 and 1.41 ± 0.65 h; area under the concentration/time curve 14.16 ± 2.93 and 7.31 ± 2.98 μg·h/ml. Forty-nine percent unidirectional bioinversion of (R)-KP to (S)-KP was observed in this species and the pharmacokinetic parameters for the (S)-KP resulting from this inversion were also calculated. In the study of 6-month repeated administration of (S)-KP, linear pharmacokinetic behavior and no evidence of drug accumulation were observed at the three dose levels. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060705
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  • 95
    Digitale Medien
    Digitale Medien
    Determination of the enantiomers of mianserin, desmethylmianserin, and 8-hydroxymianserin in the plasma and urine of mianserin-treated patients (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 555-563 
    Details
    ISSN: 0899-0042
    Schlagwort(e): mianserin ; enantiomer ; metabolism ; human plasma ; urine ; HPLC ; CYP2D6 ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: An HPLC method is presented which allows the measurement in the same run of the enantiomers of mianserin, desmethylmianserin, and 8-hydroxymianserin in plasma and urine of mianserin-treated patients. Limits of quantitation for the (S)- and (R)- enantiomers of mianserin and desmethylmianserin were 4 and 2.5 ng/ml, respectively, in plasma, and for the (S)- and (R)-enantiomers of mianserin, desmethylmianserin, and 8-hydroxymianserin 5, 2.5, and 5 ng/ml, respectively, in urine. The measured ratios of (S)-mianserin/(R)-mianserin and (S)-desmethylmianserin/(R)-desmethylmianserin in the plasmas of 10 mianserin-treated patients, all extensive metabolizers of debrisoquine as determined by CYP2D6 genotyping, varied, respectively, from 1.0 to 4.06 and from 0.19 to 0.64. As the enantiomers of mianserin differ in their pharmacological profile, these results could partially explain why, until now, no consistent relationship has been established between the therapeutic response and total [(S) + (R)] plasma levels of this antidepressant. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060708
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  • 96
    Digitale Medien
    Digitale Medien
    Kinetics and stereochemistry of the microsomal epoxide hydrolase-catalyzed hydrolysis of cis-stilbene oxidesDedicated to Professor Giancarlo Berti on the occasion of his 70th birthday. (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 577-582 
    Details
    ISSN: 0899-0042
    Schlagwort(e): microsomal epoxide hydrolase ; kinetic parameters ; enantiomeric excesses ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The microsomal epoxide hydrolase (mEH)-catalyzed hydrolysis of cis-4,4′-dimethylstilbene oxide (1a), cis-4,4′-diethylstilbene oxide (1b), cis-4,4′-diisopropylstilbene oxide (1c), and cis-4,4′-dichlorostilbene oxide (1d) have been investigated using rabbit liver microsomal preparations. The kinetic parameters, Km and Vmax, and the absolute stereochemistry of the reactions have been determined and compared with those of cis-stilbene oxide (1e). All epoxides 1a-d are hydrolyzed by mEH with high product enantioselectivity to give (R,R)-(+)-diols with ee ≥ 90%. The presence of the substituents on the phenyl rings markedly reduces the rates of mEH catalyzed hydrolysis with respect to cis-stilbene oxide, by increasing Km and reducing Vmax in the cases of 1a, 1b, and 1d, or reducing only the Vmax in the case of 1c. The very low Vmax, together with a persistent ability to fit into the mEH active site, make all these epoxides, and particularly 1c, inhibitors of cis-stilbene oxide hydrolysis. The kinetic and stereochemical results are interpreted on the basis of the proposed topology of the mEH active site. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060711
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  • 97
    Digitale Medien
    Digitale Medien
    Announcement (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 605-605 
    Details
    ISSN: 0899-0042
    Schlagwort(e): Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060715
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  • 98
    Digitale Medien
    Digitale Medien
    Assignment of absolute configuration to an improved enantioselective naproxen selector (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 615-622 
    Details
    ISSN: 0899-0042
    Schlagwort(e): absolute configuration ; chiral stationary phase ; enantiomer ; chiral recognition ; NSAID ; HPLC ; NMR ; CD ; X-ray ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Assignment of absolute configuration to a recently developed chiral selector useful in the separation of the underivatized enantiomers of naproxen and other nonsteroidal anti-inflammatory drugs (NSAIDs) is described. Circular dichroism, 1H NMR, and X-ray diffraction have been used to confirm the original assignment which was based solely upon elution orders from HPLC chiral stationary phases. All of these techniques agree in the assignment of the (S,S) absolute configuration to the enantiomer of the chiral selector which associates preferentially with (S)-naproxen. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060803
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  • 99
    Digitale Medien
    Digitale Medien
    Successive optical resolution by replacing crystallization of DL-threonine (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 654-657 
    Details
    ISSN: 0899-0042
    Schlagwort(e): successive optical resolution ; replacing crystallization ; threonine ; optically active cosolute ; L-serine ; 4-hydroxy-L-proline ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: DL-Threonine [DL-Thr; (2RS,3SR)-2-amino-3-hydroxybutanoic acid] was optically resolved by replacing crystallization using L-serine (L-Ser) and 4-hydroxy-L-proline (L-Hyp) as optically active cosolutes. D-Thr was allowed to crystallize preferentially from racemic aqueous solutions in the presence of these L-α-amino acids. The optical resolution of DL-Thr was more successfully achieved by using L-Ser, whose structure is more similar to that of DL-Thr than L-Hyp, and successively gave D- and L-Thr of 87 - 92% optical purities. The D- and L-Thr obtained were then recrystallized from water to give optically pure D- and L-Thr. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060809
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    Digitale Medien
    Digitale Medien
    Chiral discrimination in nonracemic mixtures of methanephosphonic acid, N,N′-bis(1-phenylethyl)diamides (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 1-4 
    Details
    ISSN: 0899-0042
    Schlagwort(e): methanephosphonic acid dichloride ; N,N′-bis(1-phenylethyl)diamidomethylphosphonate ; chiral discrimination on self-association ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Enantiomeric (S,S)- and (R,R)-bis(1-phenylethyl)diamidomethylphosphonates, the phosphorus atom being prochiral, have been synthesized, starting from the methanephosphonic acid dichloride and corresponding chiral amines. The splitting observed in the 31P-NMR spectra of their nonracemic mixtures may be accounted for the self-discrimination of chiral species. This effect can be very useful for enantiomeric analysis of amines based on coupling reactions with methanephosphonic acid dichloride. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chir.530060103
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