Biomedical subjects
S Bissbort
Publications and source records attributed to S Bissbort.
The prevalence of homocysteinemia and hypercholesterolemia in angiographically defined coronary heart disease.
Total serum homocysteine and cholesterol levels were determined in 163 male patients with typical angina who were subjected to coronary angiography. The prevalence of homocysteinemia in coronary heart disease (CHD) was 41.9%. Serum homocysteine levels were significantly elevated (p less than 0.05) in patients with major occlusion in two or three coronary arteries. Furthermore, the prevalence of homocysteinemia correlated positively (p less than 0.05) with the number of coronary vessels that were occluded. The prevalence of hypercholesterolemia was 34.9%, but, in contrast to homocysteinemia, no graded strength of association with the number of stenotic coronary arteries could be demonstrated. The results suggest that homocysteinemia may contribute significantly to the development of coronary heart disease.
Rapid high-performance liquid chromatographic assay for total homocysteine levels in human serum.
A rapid, isocratic high-performance liquid chromatographic (HPLC) method is described for the determination of total homocysteine levels in human serum. Prior to reversed-phase HPLC analysis, the serum thiols were derivatized with SBD-F (ammonium 7-fluorobenzo-2-oxa-1,3-diazole-4-sulphonate), a thiolspecific fluorogenic probe which is commercially available. Retention of SBD-homocysteine was sensitive to pH, and a mobile phase pH of 2.1 ensured baseline separation of serum thiols within 6 min. The method is simple, sensitive, reproducible (between-run coefficient of variation of 6.6%) and very suitable for routine determination of serum homocysteine levels in a clinical pathology laboratory.
Relationship between vitamin B-6 status and elevated pyridoxal kinase levels induced by theophylline therapy in humans.
Theophylline administration to seven healthy male volunteers resulted in a rapid and significant decline in both plasma and erythrocyte pyridoxal-5'-phosphate levels. Total erythrocyte pyridoxal kinase levels increased during 15 wk of theophylline treatment from a mean initial activity of 19.23 +/- 5.03 (mean +/- SD) to 62.64 +/- 11.59 nmol pyridoxal-5'-phosphate formed/(g hemoglobin.h). Although plasma pyridoxal levels remained normal, the threefold increase in total erythrocyte pyridoxal kinase activity levels did not normalize plasma and erythrocyte pyridoxal-5'-phosphate levels. Pyridoxal-5'-phosphate hydrolysis was not affected by theophylline therapy. Increased pyridoxal oxidation was confirmed by elevated urinary 4-pyridoxic acid excretion after 15 wk of theophylline treatment. Mean erythrocyte alanine aminotransferase activity declined by 70%, and aspartate aminotransferase activity declined by 50%, indicating that decreased availability of pyridoxal-5'-phosphate can have widespread metabolic consequences. We conclude that the effect of theophylline on vitamin B-6 metabolism is not transitory and cannot be overcome by elevated intracellular levels of pyridoxal kinase. However, pyridoxine supplementation (10 mg/d for 1 wk) normalized indices of vitamin B-6 status and reversed the downward trend in both alanine aminotransferase and aspartate aminotransferase activity levels.
Inhibition of pyridoxal kinase by methylxanthines.
In the presence of saturating concentrations of adenosine triphosphate (ATP) and rate-limiting amounts of pyridoxal, theophylline was found to inhibit sheep brain pyridoxal kinase (EC 2.7.1.35) competitively. The apparent inhibition constant (Ki) of theophylline for pyridoxal kinase was determined as 8.7 mumol/l. Theophylline concentrations of up to 60 mumol/l did not affect pyridoxal phosphorylation in the presence of saturating amounts of pyridoxal and rate-limiting concentrations of ATP. Caffeine was less potent to inhibit pyridoxal kinase (Ki = 45 mumol/l) due to the presence of a methyl group on the 7 position of the xanthine ring structure. Theobromine showed only a weak inhibition of pyridoxal kinase (Ki = 453 mumol/l). The presence of a hydroxyethyl, hydroxypropyl or dihydroxypropyl group on the N7 position of theophylline completely abolished inhibition of pyridoxal kinase. Enprofylline (3-propylxanthine), a recently described bronchodilator, was also able to inhibit pyridoxal kinase with a Ki of 256 mumol/l.
Altered vitamin B6 homeostasis during aminophylline infusion in the beagle dog.
The effect of intravenous infusion of aminophylline, a strong inhibitor of pyridoxal kinase, on intra- and extracellular vitamin B6 homeostasis was investigated in four beagle dogs. Plasma and erythrocyte pyridoxal levels increased by 118% and 117% respectively after 3 hours of aminophylline infusion, (4 mg/kg body weight/hour), however, infusion of beta-hydroxyethyltheophylline, which does not inhibit pyridoxal kinase, had no effect on either intra- or extracellular vitamin B6 aldehyde derivative levels. It is suggested that theophylline induced pyridoxal kinase inhibition resulted in a disturbed equilibrium between pyridoxal and pyridoxal 5'-phosphate.
Genetic polymorphism of glutamate-pyruvate transaminase (alanine aminotransaminase): influence on erythrocyte activity as a marker of vitamin B-6 nutritional status.
A new, sensitive, two-step method free from interference by hemoglobin that measures erythrocyte glutamate-pyruvate transaminase (E-GPT) activity is described. Several aspects of E-GPT activity as an index of vitamin B-6 nutritional status were investigated with this method. 1) GPT shows a structural genetic polymorphism with two common alleles resulting in three phenotypes. In a population study (n = 92) E-GPT activity differed significantly (p less than 0.001) among the three phenotypic groups. Plasma pyridoxal-5'-phosphate concentrations in the three groups did not differ significantly. Therefore, E-GPT activity can only be used to assess vitamin B-6 nutritional status if GPT phenotype is accounted for. 2) Pyridoxine supplementation (10 mg/d) significantly (p less than 0.0001) increased E-GPT activity and decreased (p less than 0.0001) the percentage stimulation by pyridoxal-5'-phosphate in vitro although the absolute amount of in vitro stimulation by pyridoxal-5'-phosphate changed only marginally. 3) Inorganic phosphate inhibits in vitro activation of E-GPT by pyridoxal-5'-phosphate.
Evidence of a theophylline-induced vitamin B6 deficiency caused by noncompetitive inhibition of pyridoxal kinase.
A placebo-controlled, double-blind study indicated that theophylline administration to apparently healthy, young men induced significantly depressed plasma pyridoxal-5'-phosphate levels. Plasma pyridoxal levels were not affected by theophylline therapy. The effect of theophylline on circulating pyridoxal-5'-phosphate levels is explained by the observation that theophylline acts as a noncompetitive inhibitor for erythrocyte pyridoxal kinase (EC 2.7.1.35) with an apparent inhibition constant (Ki) of 1.28 x 10(-5) mol/L. Theophylline did not affect erythrocyte pyridoxamine (pyridoxine)-5'-phosphate oxidase (EC 1.4.3.5) activity. During theophylline therapy, erythrocyte pyridoxal kinase levels increased nearly twofold from an initial mean level of 24.2 +/- 4.0 (+/- SD) nmol to 46.9 +/- 7.3 nmol pyridoxal-5'-phosphate per gram of hemoglobin per hour. This partially counteracted the effect of theophylline on vitamin B6 metabolism. Nevertheless, erythrocyte pyridoxal-5'-phosphate levels in subjects given theophylline decreased significantly (p = 0.03) from pretreatment levels. The oral tryptophan load test resulted in significantly (p = 0.007) increased urinary xanthurenic acid excretion after 4 weeks of theophylline therapy. Both plasma pyridoxal-5'-phosphate levels and the tryptophan load test results normalized after 1 week of pyridoxine supplementation, indicating that 10 mg pyridoxine per day was effective to counteract the antagonistic effect of short-term theophylline therapy on vitamin B6 metabolism.
Linkage between the variegate porphyria (VP) and the alpha-1-antitrypsin (PI) genes on human chromosome 14.
From family studies close linkage between the gene locus for variegate porphyria (VP) and the alpha-1-antitrypsin (PI) gene became evident. The maximal lod score from male meioses was 4.33 at theta = 0.04 and from both sexes combined 3.56 at theta = 0.12. Three pedigrees were triple informative regarding loci VP, PI, and IGHC (immunoglobulin heavy chain cluster, Gm polymorphism). In two of the respective meioses recombinations were observed, and in both cases the co-segregating VP and PI alleles were separated from the Gm haplotypes. These findings argue in favour of gene order either VP:PI:IGHC or PI:VP:IGHC.
Linkage relations of JK, CO, KEL and IGK with each other and with AHCY.
Linkage analyses of locus pairs involving IGK, JK, CO, KEL and AHCY resulted in altogether negative lod scores, thereby dwindling the reported linkage relations.
Linkage disequilibrium between a marker on the LDL receptor and high cholesterol levels.
Explore the source record for details and available documents.
PGM1 subtyping by means of acid starch gel electrophoresis.
'PGM1 subtyping' can be clearly demonstrated by horizontal electrophoresis in acid starch gel. Because of the different cathodal mobilities of PGM1-gene products, the allelic superscripts for PGM1 were designated as 1F, 1S, and 2F, 2S, respectively. Gene frequencies of a population sample from Southwestern Germany are presented. They fit in well with other, previously published data on this matter.
Mapping of the linkage group GLO--Bf--HLA-B,C,A--PGM3. 1. Recombination frequencies.
This study confirms close linkage for the GLO--Bf--HLA-B,C,A complex, and proves linkage between the MHC loci and PGM3. For GLO--PGM3 and Bf--PGM3, respectively, loose linkage seems to be likely, and close linkage can be excluded. Our mapping data on chromosome 6 favor the hypothesis that the PGM3 locus is situated on the HLA-A side of the MHC complex. Yet fine-structure mapping should be confirmed only by segregation analyses in crossover families by testing simultaneously all of the relevant marker loci within uniform family material.
Mapping of the linkage group GLO--Bf--HLA-B,C,A--PGM3. 2. Segregation analysis.
Segregation analysis of informative families for chromosome 6 markers confirmed the map order GLO--Bf--HLA-(B, C)--HLA-A, and, surprisingly, implies that PGM3 is more probably located on the HLA-A than on the HLA-B side of the linkage group. Therefore the map position of PGM3 should be reconsidered, i.e., more informative families should be tested for all the relevant marker loci available.
Map order of the linkage group GLO-Bf-HLA-A-PGM3 on human chromosome 6.
Linkage analysis of 52 families with 181 children confirms close linkage for GLO-Bf, GLO-HLA-A, and Bf-HLA-A and proves linkage between HLA-A and PGM3. Linkage for Bf-PGM3 and GLO-PGM3, respectively, seems to be likely; close linkage can be excluded. From the relative map distances, but above all from the segregation of defined linkage phases in crossover families, we can hypothesize that the sequence order of the loci should be GLO-Bf-HLA-A-PGM3.
Confirmation of linkage between the loci for HL-A and glyoxalase I.
Linkage analysis of 7 families with 30 children confirmed previous findings of the linkage between HL-A and GLO. Out of 28 families with 90 children the highest lod score value obtained was + 8.887 (recombination fraction = 0.1).
Possible linkage of HL-A and GLO.
In 21 informative families with 60 children, a possible linkage between HL-A and GLO was found (recombination fraction approximatively 0.15). The sequence of the loci on chromosome 6 might be GLO, HL-A, PGM3, MNSs.
Evidence for linkage between the loci of PGM3 and MNSs.
Explore the source record for details and available documents.