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Biomedical subjects

P M Christensen

Publications and source records attributed to P M Christensen.

8 recordsLinked to original sources
PubMed1998

[Evaluation of ear temperature measurements in a geriatric department].

We evaluated an infrared tympanic thermometer (Genius 3000A) by comparing it with parallel measurements with an electronic rectal thermometer (Philips HP 5316) on 121 patients admitted to a geriatric department. Rectal temperature was on average 0.14 degree C +/- (ISD) above the ear temperature. 95% of the differences are within the interval from -1.18 degrees C to 1.46 degrees C. The coefficient of determination was only 0.30. The tympanic thermometer, Genius 3000A, cannot be recommended for daily use on a geriatric ward.

Aged↗
PubMed1998

The sparteine/debrisoquine (CYP2D6) oxidation polymorphism and the risk of Parkinson's disease: a meta-analysis.

The association between the sparteine/debrisoquine (CYP2D6) oxidation polymorphism and the risk of Parkinson's disease was examined in a meta-analysis of case-control studies. The odds ratio was calculated for the risk of Parkinson's disease among poor metabolisers compared with extensive metabolisers. Twenty-one studies were identified of which six were excluded because they were not reported as full papers (n = 3), used incomplete genotype analysis (n = 2) or used Parkinson patients as both control individuals and cases (n = 1). The overall odds ratio was 1.48 (95% confidence interval 1.10-1.99). The odds ratio was 1.05 (95% confidence interval 0.63-1.77) in studies discriminating extensive and poor metabolisers by phenotyping (n = 8) and 1.67 (95% confidence interval 1.11-2.50) in studies using genotyping (n = 7). This difference was caused by a single large study using genotyping. We conclude that there is no convincing evidence of an association between the debrisoquine/sparteine polymorphism and Parkinson's disease. However, it could prove worthwhile to perform another large study using genotyping.

Aged↗
PubMed1997

The sparteine/debrisoquine (CYP2D6) oxidation polymorphism and the risk of lung cancer: a meta-analysis.

OBJECTIVE: To examine the association between the sparteine/debrisoquine (CYP2D6) oxidation polymorphism and the risk of lung cancer. METHOD: Meta-analysis of case-control studies using a random effects model. The "Main outcome measure" was the odds ratio for the risk of lung cancer, using extensive metabolisers as the reference group. RESULTS: Thirteen studies were identified. The studies were too heterogeneous to be pooled the size of the odds ratio increased with the sample size. When the analysis was restricted to the largest studies, there was no difference in risk between poor and extensive metabolisers (odds ratio 0.95, 95% confidence interval 0.68-1.33). CONCLUSION: No association was found between the CYP2D6 oxidation polymorphism and lung cancer risk when sample size bias was taken into account.

Cytochrome P-450 CYP2D6↗
PubMed1990

Recombinant human extrinsic pathway inhibitor. Production, isolation, and characterization of its inhibitory activity on tissue factor-initiated coagulation reactions.

Previous studies have shown that extrinsic pathway inhibitor (EPI) is an effective inhibitor of factor Xa alone or factor VIIa-tissue factor complex in the presence of factor Xa. Since tissue factor exposure is implicated in thrombogenesis, we hypothesized that EPI may be valuable in the treatment of some thromboembolic episodes. Furthermore, EPI may be an important factor in bleeding complications in hemophiliacs. In the present study, human EPI was expressed in baby hamster kidney cells using a mammalian expression vector. Transfected cells expressed 1-2 micrograms/ml of recombinant EPI (rEPI) which was purified to homogeneity by heparin-Sepharose chromatography, ion-exchange chromatography, and reverse phase high performance liquid chromatography. Purified rEPI exhibited a specific activity of 30,000 units/mg and migrated as a single band in sodium dodecyl sulfate-polyacrylamide gel electrophoresis with an apparent molecular weight of 42,000. In addition, the NH2-terminal sequence of rEPI was identical to that of HepG2 EPI and HeLa EPI. The ability of rEPI to inhibit factor X activation by a complex of factor VIIa-tissue factor was then examined in the presence and absence of plasma concentrations of human factors VIII and IX. Using relipidated human brain tissue factor apoprotein, rEPI inhibited the factor VIIa-mediated activation of factor X half-maximally at 2.5 and 1 nM in the presence and absence of factors VIII and IX, respectively. Using monolayers of a human bladder carcinoma cell line (J82) as the source of tissue factor, the activation of factor X by cell-bound factor VIIa was inhibited half-maximally by 5 nM rEPI in the presence of factors VIII and IX. The proteolytic activity of J82 cell-bound factor Xa toward prothrombin was inhibited half-maximally at approximately 5 nM rEPI, while the amidolytic activity of factor Xa in solution was inhibited by rEPI with a Ki of 130 pM. Recombinant EPI also inhibited the amidolytic activity of factor VIIa half-maximally at 10 nM rEPI in the presence of relipidated tissue factor apoprotein and calcium. These results indicate that, in the presence of plasma concentrations of factors VIII and IX, at least 10 times the plasma concentration of EPI is required to reduce factor VIIa-dependent factor X activation one order of magnitude in vitro. In the absence of functional factor VIII and IX, rEPI at plasma levels was a potent inhibitor of factor VIIa-mediated factor X activation, and this activity presumably accounts for the inability of hemophiliacs to initiate hemostasis via the extrinsic pathway.

Amino Acid Sequence↗
PubMed1990

Changing the insulin receptor to possess insulin-like growth factor I ligand specificity.

To examine the role of the N-terminal part of the insulin-like growth factor I (IGF-I) receptor and insulin receptor in determining ligand specificity, we prepared an expression vector encoding a hybrid receptor where exon 1 (encoding the signal peptide and seven amino acids of the alpha-subunit), exon 2, and exon 3 of the insulin receptor were replaced with the corresponding IGF-I receptor cDNA (938 nucleotides). To allow direct quantitative comparison of the binding capabilities of this hybrid receptor with those of the human IGF-I receptor and the insulin receptor, all three receptors were expressed in baby hamster kidney (BHK) cells as soluble molecules and partially purified before characterization. The hybrid IGF-I/insulin receptor bound IGF-I with an affinity comparable to that of the wild-type IGF-I receptor. In contrast, the hybrid receptor no longer displayed high-affinity binding of insulin. These results directly demonstrate that it is possible to change the specificity of the insulin receptor to that of the IGF-I receptor and, furthermore, that the binding specificity for IGF-I is encoded within the nucleotide sequence from 135 to 938 of the IGF-I receptor cDNA. Since the hybrid receptor only bound insulin with low affinity, the insulin binding region is likely to be located within exons 2 and 3 of the insulin receptor.

Amino Acid Sequence↗