| 2040394 |
Detection of mutations in insulin-receptor gene in NIDDM patients by analysis of single-stranded conformation polymorphisms |
10.2337/diab.40.6.777. |
Diabetes |
Detection of mutations in insulin-receptor gene in NIDDM patients by analysis of single-stranded conformation polymorphisms
Abstract
- We used the recently described technique of single-stranded conformation-polymorphism (SSCP) analysis to examine the insulin-receptor locus. First, the ability of the method to detect known mutations and polymorphisms in the insulin-receptor coding sequence was assessed. Regions of the insulin-receptor sequence containing 16 different nucleotide changes, 9 in patient genomic DNA and 7 as cloned cDNA in plasmids, were analyzed. All 9 patient genomic DNA mutants and 5 of 7 plasmid mutants exhibited variant SSCP patterns. To investigate the potential of the technique for screening many patients, the 5 exons that encode the tyrosine kinase domain of the insulin receptor were examined in 30 unrelated white subjects with non-insulin-dependent diabetes mellitus (NIDDM). Exons 17-21 were amplified from genomic DNA with polymerase chain reaction and subjected to SSCP analysis. Exons 19, 20, and 21 revealed no bands of aberrant migration, suggesting a high degree of conservation of these sequences. One diabetic subject had an SSCP variant in exon 18. Direct sequencing of this subject's genomic DNA revealed a heterozygous missense mutation (Lys1068----Glu1068). Five different SSCP patterns were detected in exon 17. Based on direct sequencing, these patterns were explained by combinations of three different nucleotide substitutions, two of which were common silent polymorphisms. One subject had a heterozygous missense mutation Val985---- Met985. Allele-specific oligonucleotide hybridization confirmed the presence of these mutations in the appropriate diabetic subjects and also detected the Val985 mutation in heterozygous form in 1 of 13 nondiabetic white subjects. SSCP analysis is a sensitive rapid method for screening for mutations in the insulin-receptor gene.(ABSTRACT TRUNCATED AT 250 WORDS)
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| 2045531 |
The immunosuppressive activity of the aldehydic transformation of cyclosporine on alloreactive T-cells |
10.1002/j.1552-4604.1991.tb01889.x. |
J Clin Pharmacol |
The immunosuppressive activity of the aldehydic transformation of cyclosporine on alloreactive T-cells
Abstract
- Cyclosporine (CsA) is a potent immunosuppressive compound, and its metabolites have previously been shown to have pharmacologic activity. The aldehydic metabolites have been isolated and are a metabolic intermediate after the conversion of CsA to its most active hydroxylated metabolite. The in vitro sensitivity of alloreactive T-lymphocytes, which are generated from a mixed lymphocyte reaction and propagated from organ transplant biopsy specimens to the aldehydic metabolites of CsA, was tested. In secondary proliferative assays in the presence of varying concentrations of CsA and the aldehydes, the concentration required to inhibit proliferation by 50% was 50 to 150 ng/mL for CsA and 3150 to 3500 ng/mL for the aldehydes. Pretreatment of alloreactive cells with CsA or the aldehydes did not alter cell viability, as tested with dye exclusion, or cell reactivity on reculturing. These studies concluded that the structural modification formed by metabolism of CsA to the aldehydic structure eliminates its antiproliferative activity on T-lymphocytes.
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| 2050791 |
Isolation of bacitracins A and F by high-speed counter-current chromatography |
10.1016/s0021-9673(01)91638-3. |
J Chromatogr |
Isolation of bacitracins A and F by high-speed counter-current chromatography
Abstract
- The major components of bacitracin were separated and purified using high-speed counter-current chromatography (HSCCC). A systematic search for optimum two-phase solvent systems resulted in two systems: chloroform-ethanol-methanol-water (5:3:3:4) and chloroform-ethanol-water (5:4:3). These were selected based on the determination of the partition coefficients of all the components and the settling time of the phases. HSCCC with these solvent systems separated two components, bacitracins A and F. Improvements in the flow-cell arrangement eliminated noise in detection, making in-line monitoring possible. A tandem mass spectrometric technique was used to characterize the isolated components.
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| 2051752 |
Micro method for liquid chromatographic determination of cyclosporin A in whole blood with use of a rapid extraction procedure |
10.1093/jat/15.2.95. |
J Anal Toxicol |
Micro method for liquid chromatographic determination of cyclosporin A in whole blood with use of a rapid extraction procedure
Abstract
- In this precise, reversed-phase liquid chromatographic procedure, Cyclosporin A (Cy A) is extracted from 300 microL of whole blood with cyclosporin D as internal standard by liquid-liquid extraction. A 20-microL aliquot of the extract, injected onto a Nucleosil octyl analytical column heated at 72 degrees C, is eluted with a mixture of acetonitrile and 0.01 M phosphate buffer, pH 5.5 at a flow rate of 1 mL/min. Detection is set at 210 nm. The chromatography is complete within 10 min. The detection limit is 25 micrograms/L. Between-run CVs range from 2.3 to 6.2% and recovery is 92.1 +/- 6.3%. The major advantages of our extraction procedure are the rapid clean-up method and the small volume required. This procedure is especially suitable for cyclosporine determination in pediatric transplantations.
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| 2053827 |
Effect of the quality of fat substrate on the dynamics of fatty acid utilization during biosynthesis of cephalosporin C |
None |
Antibiot Khimioter |
Effect of the quality of fat substrate on the dynamics of fatty acid utilization during biosynthesis of cephalosporin C
Abstract
- Influence of the quality of the fats used on their utilization in the process of cephalosporin C fermentation and accumulation was studied. A decrease in the level of all the fractions of the fatty acids was observed during the fermentation process. The antibiotic yield with the use of oxidized fats was lower. Treatment of the fats with gaseous nitrogen prevented their oxidation. It was supposed that the decreased yields of the antibiotic were associated with the influence of the oxidized fats on the biosynthetic processes.
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| 2060128 |
Cyclosporine analogues |
10.1016/0009-9120(91)90105-n. |
Clin Biochem |
Cyclosporine analogues
Abstract
- Numerous analogues of cyclosporine A (CsA) have been produced and studied. Although these analogues have given considerable insight into structure-activity relationships, have been shown to have the safety and efficacy of CsA. The most promising of these analogues is cyclosporine G (CsG) in which norvaline is substituted for alpha-aminobutyric acid at the 2 position. Comparative studies of CsG and CsA in animals have produced conflicting results both in terms of nephrotoxicity and the effectiveness of CsG as an immunosuppressive agent. It is evident from these studies that there exist species and strain differences in the metabolism of CsG, sensitivity to its toxic effects and, probably, to its immunological effectiveness. Studies will have to be performed in humans to determine whether, for a given immunosuppressive effect, CsG is less or more toxic than CsA.
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| 2070452 |
Cycloleonurinin, a cyclic peptide from Leonuri Fructus |
10.1248/cpb.39.712. |
Chem Pharm Bull (Tokyo) |
Cycloleonurinin, a cyclic peptide from Leonuri Fructus
Abstract
- From Leonuri Fructus, a cyclic peptide composed of twelve amino acid residues was isolated. The sequence of the residues was established by mass spectroscopy and by the use of a protein sequencer for the partial hydrolysates obtained by alpha-chymotrypsin.
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| 2087697 |
Cytotoxicity on L1210 leukemic cells of beta-amanitin-concanavalin A and phallacidin-concanavalin A conjugates |
10.1016/0041-0101(90)90102-d. |
Toxicon |
Cytotoxicity on L1210 leukemic cells of beta-amanitin-concanavalin A and phallacidin-concanavalin A conjugates
Abstract
- The conjugates beta-amanitin-concanavalin A and phallacidin concanavalin A were tested for direct cytotoxicity on L1210 lymphocytic leukemia cells by a combined in vitro-in vivo bioassay. Both conjugates exerted strong direct cytotoxicity on the tumour cells.
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| 2109908 |
Isolation and characterization of the minor components associated with microcystins LR and RR in the cyanobacterium (blue-green algae) |
10.1016/0041-0101(90)90006-s. |
Toxicon |
Isolation and characterization of the minor components associated with microcystins LR and RR in the cyanobacterium (blue-green algae)
Abstract
- Two structurally similar analogues of microcystins LR and RR, cyclic peptide hepatotoxins from Microcystis, were isolated by chromatographic methods. Although they have the same mol. wt and amino acid compositions as those of the parent toxins, they do not possess similar toxicities. Ultraviolet and 1H-NMR spectral data for both components demonstrate clear structural difference of these cyclic peptides from the parent toxins, which are probably responsible for the marked decreases in their observed toxicities.
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| 2115097 |
Mycosubtilins B and C: minor antibiotics from mycosubtilin-producer Bacillus subtilis |
None |
Microbios |
Mycosubtilins B and C: minor antibiotics from mycosubtilin-producer Bacillus subtilis
Abstract
- Mycosubtilins B and C were isolated from the culture medium of Bacillus subtilis. The acid hydrolysates of these new antifungal antibiotics, like mycosubtilin, contain alpha-amino acids (Asp3, Glu1, Pro1, Ser1 and Tyr1) and a mixture of iso-C16, n-C16, iso-C17 and anteiso-C17 beta-amino acids. Mycosubtilins B and C differ by the presence of a carboxyl group and of a carboxymethyl group, respectively, instead of a carboxamide group in previously described mycosubtilin.
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| 2120275 |
Internal surface reversed-phase high-performance liquid chromatographic separation of the cyanobacterial peptide toxins microcystin-LA, -LR, -YR, -RR and nodularin |
10.1016/s0021-9673(01)93097-3. |
J Chromatogr |
Internal surface reversed-phase high-performance liquid chromatographic separation of the cyanobacterial peptide toxins microcystin-LA, -LR, -YR, -RR and nodularin
Abstract
|
| 2121276 |
Studies on the biosynthesis of iturin, an antibiotic of Bacillus subtilis, and a lipopeptide containing beta-hydroxy fatty acids |
10.1016/0304-4165(90)90020-w. |
Biochim Biophys Acta |
Studies on the biosynthesis of iturin, an antibiotic of Bacillus subtilis, and a lipopeptide containing beta-hydroxy fatty acids
Abstract
- The biosynthesis of iturin, an antibiotic containing a beta-amino fatty acid, was studied by incubating Bacillus subtilis in the presence of various 14C-labelled precursors. Sodium acetate or palmitic acid were incorporated into the beta-amino acids of iturin. Among the alpha-amino acids (asparagine, glutamine, serine, proline and tyrosine) in the peptidic part of iturin, asparagine appears to be the best precursor. In the presence of sodium 14Cacetate or 14Casparagine, there was a synthesis of radioactive compound (compound X) before the synthesis of radioactive iturin. Compound X contained asparagine and/or aspartic acid, glutamine and/or glutamic acid and beta-hydroxy fatty acids.
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| 2121734 |
Substitution of lysine for asparagine at position 15 in the alpha-subunit of the human insulin receptor. A mutation that impairs transport of receptors to the cell surface and decreases the affinity of insulin binding |
None |
J Biol Chem |
Substitution of lysine for asparagine at position 15 in the alpha-subunit of the human insulin receptor. A mutation that impairs transport of receptors to the cell surface and decreases the affinity of insulin binding
Abstract
- Mutations in the insulin receptor gene can compromise the ability of the receptor to mediate insulin action. Previously, in investigations of a patient with a genetic form of insulin resistance, we have identified a mutant allele encoding an insulin receptor in which lysine is substituted for asparagine at position 15 of the alpha-subunit. In the present study, we have characterized the Lys15-mutant receptor expressed by transfection of mutant cDNA into NIH-3T3 cells. The Lys15-mutation causes at least two defects in insulin receptor function. First, the mutation retards the post-translational processing of the receptor and impairs transport of the receptor to the plasma membrane, thereby reducing the number of receptors on the cell surface. Second, the mutation causes a 5-fold reduction in the affinity of the receptor to bind insulin. These two defects combine to render the target cell resistant to normal physiological concentrations of insulin. It seems likely that both functional defects associated with the Lys15-mutation can be explained by assuming that the mutation distorts the three-dimensional structure of the receptor. Presumably, the abnormal conformation interferes with the transport of the receptor through the endoplasmic reticulum and Golgi, and also inhibits the binding of insulin to its binding site on the receptor.
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| 2128565 |
Synthesis, organotropism and hepatocellular uptake of two tritium-labeled epimers of dihydromicrocystin-LR, a cyanobacterial peptide toxin analog |
10.1016/0041-0101(90)90157-3. |
Toxicon |
Synthesis, organotropism and hepatocellular uptake of two tritium-labeled epimers of dihydromicrocystin-LR, a cyanobacterial peptide toxin analog
Abstract
- Two tritium-labeled epimers of dihydromicrocystin-LR, a derivative of the cyanobacterial peptide hepatotoxin microcystin-LR, were synthesized by reduction with sodium boro3Hhydride and purified with reversed-phase liquid chromatography. The epimers were hepatotoxic in mice; the i.p. LD50 was 120-135 micrograms/kg. They were concentrated in the liver and to some extent in the intestine and the kidney after an i.v. injection. Freshly isolated rat hepatocytes showed a rapid uptake of both epimers. The cellular uptake of the epimers was almost complete within 5 min at concentrations 1 microM (0.5 microM dihydromicrocystin-LR + 0.5 microM microcystin-LR) and 4 microM (0.5 microM + 3.5 microM). The uptake of the earlier eluting epimer was about three times higher than that of the later eluting epimer.
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| 2140132 |
Neuropeptide processing in regional brain slices: effect of conformation and sequence |
None |
J Pharmacol Exp Ther |
Neuropeptide processing in regional brain slices: effect of conformation and sequence
Abstract
- The central enzymatic stability of des-enkephalin-gamma-endorphin and its synthetic analogs cycloN alpha 6, C delta 11beta-endorphin-6-17 and Pro7, Lys(Ac)9-beta-endorphin6-17 was studied in vitro using a newly developed, regionally dissected rat brain slice, time course incubation procedure. Tissue slice viability was estimated as the ability of the brain slice to take up or release gamma-3Haminobutyric acid after high K+ stimulation. Results demonstrated stability of uptake/release up to 5 hr of incubation, suggesting tissue viability over this period. The estimated half-life of peptides based on the results obtained in our incubation protocol suggest that the peptides studied are metabolized at different rates in the individual brain regions tested. A good correlation exists between the high enzyme activity of neutral endopeptidase (EC 3.4.24.11) and the rapid degradation of des-enkephalin-gamma-endorphin and cycloN alpha 6, C delata 11beta-endorphin-6-17 in caudate putamen. Proline substitution combined with lysine acetylation appears to improve resistance to enzymatic metabolism in caudate putamen and hypothalamus. However, cyclization of des-enkephalin-gamma-endorphin forming an amide bond between the alpha-NH2 of the N-terminal threonine and the gamma-COOH of glutamic acid did not improve peptide stability in any brain region tested. The present study has shown that the brain slice technique is a valid and unique approach to study neuropeptide metabolism in small, discrete regions of rat brain where peptides, peptidases and receptors are colocalized and that specific structural modifications can improve peptide stability.
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