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Sökning: WFRF:(Söderkvist Peter 1953 )

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  • Heenkenda, Menikae Kanchena, et al. (författare)
  • Assessment of genetic and non-genetic risk factors for venous thromboembolism in glioblastoma - The predictive significance of B blood group
  • 2019
  • Ingår i: Thrombosis Research. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0049-3848 .- 1879-2472. ; 183, s. 136-142
  • Tidskriftsartikel (refereegranskat)abstract
    • Introduction: Venous thromboembolism (VTE) is a common problem among patients with glioblastoma multi-forme (GBM) and with some other cancers. Here, we evaluated genetic and non-genetic potential risk factors for VTE among GBM patients. Materials and methods: A cohort of 139 patients treated with concomitant radiotherapy and temozolomide were included in the study. Next generation sequencing and genotyping approaches were applied to assess genetic risk factors in the haemostatic system. Clinical data including surgery, reoperation as well as blood group and patient information such as age and gender were available from patient records. Logistic regression analysis was performed to asses VTE risk. Results: In the study 47 patients (34%) were diagnosed for VTE during the course of their disease. When genetic and non-genetic potential risk factors were evaluated, only B blood group was found to be significantly associated with VTE incidence (odds ratio [OR] = 6.91; confidence interval [CI] = 2.19-24.14; P = 0.001). In contrast, A and O blood groups did not correlate with VTE risk. Frontal lobe tumor location also seemed to slightly increase VTE risk compared to other brain sites (OR = 3.14; CI = 1.1-10.7) although the significance level was at borderline (P = 0.05). Current study identified B blood group as the component in non-O blood groups that is responsible for increased VTE risk. Conclusion: In conclusion, these results suggest for the first time that B blood group is predictive for VTE incidence among patients with glioblastoma, information that may be potentially valuable when selecting GBM patients who are at risk for VTE for anticoagulant prophylaxis.
  • Hindorf, Ulf, et al. (författare)
  • Pharmacogenetics during standardised initiation of thiopurine treatment in inflammatory bowel disease
  • 2006
  • Ingår i: Gut. - 0017-5749 .- 1468-3288. ; 55:10, s. 1423-1431
  • Tidskriftsartikel (refereegranskat)abstract
    • Background: Firm recommendations about the way thiopurine drugs are introduced and the use of thiopurine methyltransferase (TPMT) and metabolite measurements during treatment in inflammatory bowel disease (IBD) are lacking. Aim: To evaluate pharmacokinetics and tolerance after initiation of thiopurine treatment with a fixed dosing schedule in patients with IBD. Patients: 60 consecutive patients with Crohn's disease (n = 33) or ulcerative colitis (n = 27) were included in a 20 week open, prospective study. Methods: Thiopurine treatment was introduced using a predefined dose escalation schedule, reaching a daily target dose at week 3 of 2.5 mg azathioprine or 1.25 mg 6-mercaptopurine per kg body weight. TPMT and ITPA genotypes, TPMT activity, TPMT gene expression, and thiopurine metabolites were determined. Clinical outcome and occurrence of adverse events were monitored. Results: 27 patients completed the study per protocol, while 33 were withdrawn (early protocol violation (n = 5), TPMT deficiency (n = 1), thiopurine related adverse events (n = 27)), 67% of patients with adverse events tolerated long term treatment on a lower dose (median 1.32 mg azathioprine/kg body weight). TPMT activity did not change during the 20 week course of the study but a significant decrease in TPMT gene expression was found (TPMT/huCYC ratio, p = 0.02). Patients with meTIMP concentrations > 11 450 pmol/8 × 108 red blood cells during steady state at week 5 had an increased risk of developing myelotoxicity (odds ratio = 45.0, p = 0.015). Conclusions: After initiation of thiopurine treatment using a fixed dosing schedule, no general induction of TPMT enzyme activity occurred, though TPMT gene expression decreased. The development of different types of toxicity was unpredictable, but we found that measurement of meTIMP early in the steady state phase helped to identify patients at risk of developing myelotoxicity.
  • Landtblom, Anne-Marie, 1953-, et al. (författare)
  • Multiple sclerosis and exposure to organic solvents, investigated by genetic polymorphisms of the GSTM1 and CYP2D6 enzyme systems
  • 2003
  • Ingår i: Neurological Sciences. - 1590-1874 .- 1590-3478. ; 24:4, s. 248-251
  • Tidskriftsartikel (refereegranskat)abstract
    • An association between multiple sclerosis (MS) and exposure to organic solvents has been discussed. Organic solvents are metabolised by enzyme systems like glutathione S-transferase M1 (GSTM1) and CYP2D6, which express polymorphisms in the general poulation. GSTM1 null genotype has been associated with solvent-induced chronic toxic encephalopathy. Our aim was to see if a defect in one of these enzyme systems could explain the association between MS and exposure to organic solvents. In our study, 50 patients with MS were investigated, including 24 who had been significantly exposed to organic solvents and 26 who were not exposed. Polymerase chain reaction-based methods were used for genotyping GSTM1 and CYP2D6 polymorphisms in leukocyte DNA. No differences in genetic predisposition were found between MS patients exposed and those not exposed to organic solvents regarding GSTM1 null or CYP2D6 poor metaboliser genotypes. The possible association between multiple sclerosis and solvents may not, as for chronic toxic encephalopathy, be explained by defects in these systems.
  • Lindqvist Appell, Malin, 1976-, et al. (författare)
  • Explaining TPMT genotype/phenotype discrepancy by haplotyping of TPMT*3A and identification of a novel sequence variant, TPMT*23
  • 2007
  • Ingår i: Pharmacogenetics and Genomics. - 1744-6872. ; 17:10, s. 891-895
  • Tidskriftsartikel (refereegranskat)abstract
    • Thiopurine methyltransferase (TPMT) is a polymorphic enzyme involved in the metabolism of thiopurine drugs. Owing to polymorphisms in the TPMT gene (TPMT*2-*22), the enzyme activity varies interindividually. Patients with reduced TPMT activity may develop adverse reactions when treated with standard doses of thiopurines. This work focuses on a TPMT genotype/phenotype discrepancy found in a patient during routine testing. The patient displayed very low TPMT enzyme activity and she was genotyped by pyrosequencing as being heterozygous for the 460G>A and 719A>G polymorphisms (TPMT*3A). Complete sequencing in combination with haplotyping of the TPMT gene revealed a novel sequence variant, 500C>G, on one allele and TPMT*3A on the other allele, giving rise to the novel genotype TPMT*3A/*23. When investigating the patient's relatives, they too had the TPMT*3A/*23 genotype in combination with low enzyme activity. We conclude that this novel variant allele affects enzyme activity, as the individuals carrying it had almost undetectable TPMT activity. © 2007 Lippincott Williams & Wilkins, Inc.
  • Lindqvist Appell, Malin, 1976-, et al. (författare)
  • Identification of two novel sequence variants affecting thiopurine methyltransferase enzyme activity
  • 2004
  • Ingår i: Pharmacogenetics. - 0960-314X .- 1473-561X. ; 14:4, s. 261-265
  • Tidskriftsartikel (refereegranskat)abstract
    • The polymorphic enzyme thiopurine methyltransferase (TPMT) is involved in the methylation of thiopurines. On comparing the phenotype with the genotype in Swedish patients with inflammatory bowel disease and healthy individuals, we found two discordant cases with low TPMT enzyme activity (0.3 and 0.4 U/ml packed red blood cells (pRBC). Genotyping by pyrosequencing revealed that they carried the nucleotide substitutions 460G>A and 719A>G, giving two possible genotypes (TPMT*1/*3A or TPMT*3B/ *3C). DNA sequencing of exon III to X was performed in the patients and their parents. We identified an A>G transition in the start codon (exon III, 1A>G, Met>Val, TPMT*14) in one of the patients and her father (6.3 U/ml pRBC). The mother in this family carried the 460G>A and 719A>G nucleotide substitutions (TPMT*3A, 5.0 U/ml pRBC). In the second family, sequencing revealed a G>A transition in the acceptor splice site in intron VII/exon VIII (IVS7 - 1G>A, TPMT*15) in the patient and his mother (6.9 U/ml pRBC). His father was genotyped as TPMT*1/*3A (6.0 U/ml pRBC). Hence, we report the identification of two novel sequence variants, present in highly conserved nucleotide positions of the human TPMT gene, resulting in a loss of enzyme activity.
  • Lindqvist Appell, Malin, 1976-, et al. (författare)
  • Real-time RT-PCR methodology for quantification of thiopurine methyltransferase gene expression
  • 2003
  • Ingår i: European Journal of Clinical Pharmacology. - 0031-6970 .- 1432-1041. ; 59:3, s. 207-211
  • Tidskriftsartikel (refereegranskat)abstract
    • Objective: The aim of the present study was to develop a real-time reverse-transcription polymerase chain reaction (RT-PCR) methodology for the quantification of thiopurine methyltransferase (TPMT) gene expression in whole blood and compare it with the TPMT enzyme activity measured in red blood cells. Methods: TPMT gene expression was quantified relative to the housekeeping gene cyclophilin (huCYC) and expressed as a TPMT/huCYC ratio. TPMT activity in red blood cells was determined by measuring the formation rate of 6- 14C-methylmercaptopurine from 6-MP using S-adenosyl-L-( 14C-methyl)-methlonine as methyl donor. Thirty-nine individuals were included in the study. A cut-off value of 9 U/ml pRBC was used to distinguish intermediate TPMT enzyme activity from high TPMT enzyme activity. Results: Sequencing of the real-time RT-PCR amplicon proved that the method was specific for the TPMT cDNA, without co-amplification of the highly similar TPMT processed pseudogene. The intra-assay coefficients of variation (CVs), as determined by the threshold cycle, were 0.7% for TPMT and 0.5% for huCYC. The interassay CVs were 1.5% for TPMT and 4.0% for huCYC. The intra- and interassay CVs, as determined by the TPMT/huCYC ratio, were 8.6% and 25%, respectively. There was a statistically significant correlation between TPMT enzyme activity and mRNA level in blood cells from individuals with an enzyme activity above 9 U/ml pRBC (rs = 0.66, P = 0.0001). However, we did not find any statistically significant correlation in individuals with lower enzyme activity or when analysing the whole population. Conclusion: We present a specific and robust real-time RT-PCR method for quantifying TPMT gene expression. The method may be used for studies on TPMT gene regulation.
  • Lindqvist, M., et al. (författare)
  • No induction of thiopurine methyltransferase during thiopurine treatment in inflammatory bowel disease
  • 2006
  • Ingår i: Nucleosides, Nucleotides & Nucleic Acids. - : Taylor & Francis. - 1525-7770 .- 1532-2335. ; 25:9-11, s. 1033-1037
  • Tidskriftsartikel (refereegranskat)abstract
    • The aim of this study was to follow, during standardized initiation of thiopurine treatment, thiopurine methyltransferase (TPMT) gene expression and enzyme activity and thiopurine metabolite concentrations, and to study the role of TPMT and ITPA 94C > A polymorphisms for the development of adverse drug reactions. Sixty patients with ulcerative colitis or Crohn's disease were included in this open and prospective multi-center study. Thiopurine naive patients were prescribed azathioprine (AZA), patients previously intolerant to AZA received 6-mercaptopurine (6-MP). The patients followed a predetermined dose escalation schedule, reaching target dose at Week 3; 2.5 and 1.25 mg/kg body weight for AZA and 6-MP, respectively. The patients were followed every week during Weeks 1-8 from baseline and then every 4 weeks until 20 weeks. TPMT activity and thiopurine metabolites were determined in erythrocytes, TPMT and ITPA genotypes, and TPMT gene expression were determined in whole blood. One homozygous TPMT-deficient patient was excluded. Five non compliant patients were withdrawn during the first weeks. Twenty-seven patients completed the study per protocol; 27 patients were withdrawn because of adverse events. Sixty-seven percent of the withdrawn patients tolerated thiopurines at a lower dose at Week 20. There was no difference in baseline TPMT enzyme activity between individuals completing the study and those withdrawn for adverse events (p = 0.45). A significant decrease in TPMT gene expression (TPMT/huCYC ratio, p = 0.02) was found, however TPMT enzyme activity did not change. TPMT heterozygous individuals had a lower probability of remaining in the study on the predetermined dose (p = 0.039). The ITPA 94C > A polymorphism was not predictive of adverse events (p = 0.35).
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