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Biomedical subjects

M Christiansen

Publications and source records attributed to M Christiansen.

At least 55 records · Page 3Linked to original sources
PubMed2001

Alpha-fetoprotein in plasma and serum of healthy adults: preanalytical, analytical and biological sources of variation and construction of age-dependent reference intervals.

Alpha-fetoprotein (AFP) is a tumor marker for hepatomas and germ cell tumors, and the serum concentration has prognostic significance in other diseases. We examined the normal serum concentration of AFP in adults and sources of variation in the immunochemical variation of AFP. The serum concentration of the tumor marker alpha-fetoprotein (S-AFP) was log-normally distributed in 284 adult blood donors. S-AFP increased with age (p < 10(-7)), whereas no gender-related difference was found. Reference intervals (95-interpercentile) were constructed for persons < or =40 years (0.60-9.30 kIU/L) and >40 years (1.40 12.60 kIU/L). The concentration of AFP was significantly, albeit slightly, higher in serum than in plasma, whereas hemolysis, pretreatment with KCl and food intake did not influence S-AFP. S-AFP only changed 6% when measured twice 2 months apart (p=0.04). Three enzyme immunoassays, using three different anti-AFP monoclonal antibodies for detection, were compared and two assays gave S-AFP values significantly higher, 2.8% (p=0.03) and 19.0% (p<10(-4)), than the other assay. Thus, the choice of antibody may influence the result of immunochemical concentration determination. This can be explained by the existence of conformational variants of AFP with different antibody reactivities, and calls for careful standardization of monoclonal antibodies used in assays for AFP. With broad population reference ranges and slight intra-personal variation, the most effective reference range for S-AFP is previous values obtained in the same person.

Adult↗
PubMed2001

Precision of risk in multidimensional likelihood ratio based screening with first trimester screening for Down's syndrome as a special case.

OBJECTIVES: The development of computer programs for the calculation of risks and Monte Carlo estimation of the precision of such risks in likelihood ratio based screening with multiple gaussian distributed risk markers and a priori risks. A quantitative study of the variation of risk estimates in first trimester screening for Down's syndrome as a function of the variation of markers, and comparison of the results with published information on the variation of risk estimates in quality control schemes. METHODS: Algorithms for calculations in the multidimensional normal distribution and procedures for Monte Carlo simulation of risk distributions were implemented in the S-PLUS programming language and used to construct programs producing risk estimates and risk distributions. Parameters of risk marker distributions and correlations were obtained from the scientific literature. RESULTS: In screening for Down's syndrome during the first trimester the variation in risk estimates increased with increasing variation of biochemical and biometric markers, and the a posteriori risk may vary with at least a factor of 2-4. CONCLUSIONS: Risk estimates are not reasonable parameters in quality control systems. Instead, screening programmes should be controlled through careful monitoring of the distribution of risk estimates, in particular the screen positive rate, and control of the quality of the biochemical and biometric data. Furthermore, the correct classification of samples submitted for proficiency testing into screen positive and screen negative cases should be checked.

Down Syndrome↗
PubMed2001

Effect of nicotinic acid administration on hepatic very low density lipoprotein-triglyceride production.

Our objective was to examine very low density lipoprotein-triglyceride (VLDL-TG) kinetics after chronic and acute administration of nicotinic acid (NA). Incorporation of [1,2,3,4-(13)C(4)]palmitate and [2-(13)C(1)]glycerol into VLDL-TG was measured in five healthy, normolipidemic women. Each subject was studied twice; the 4-day hospital stays were separated by 1 mo, during which time doses of NA were increased to 2 g/day (500 mg, 4 times/day). During posttreatment study, 500 mg of NA were administered acutely at 0800. Under baseline postabsorptive conditions, incorporation curves from (13)C-labeled free fatty acid (FFA) and (13)C-labeled glycerol were superimposable, and VLDL-TG kinetics were in agreement (t(1/2) = 1.4 +/- 0.3 and 1.3 +/- 0.3 h, and production rates = 27.2 +/- 6.1 and 28.5 +/- 5.3 g/day, respectively). In the postabsorptive state after chronic NA therapy, VLDL-TG concentrations and production rates were lower despite a trend toward elevated plasma FFA concentrations and fluxes. After the acute dose of NA, plasma FFA concentrations and flux fell dramatically, and there was a virtual halt to VLDL-TG production, which continued throughout the 6-h period after NA, despite a marked rebound overshoot in serum FFA concentrations and flux after hour 2. Plasma homocysteine concentrations increased 68% (P < 0.001) in the NA phase, consistent with chronic increased transmethylation demand. We conclude that 1) NA acutely and chronically decreases VLDL-TG production rate in normal women; 2) the acute effect on VLDL-TG production is associated with an initial suppression of lipolysis but persists for several hours after the antilipolytic action of NA has abated and is observed in the basal postabsorptive state, when lipolytic rates are not reduced; and 3) the effect of NA on VLDL-TG production, therefore, cannot be completely explained by its antilipolytic actions.

Adult↗
PubMed2001

Insulin-like growth factor binding protein-4 protease produced by smooth muscle cells increases in the coronary artery after angioplasty.

Insulin-like growth factor (IGF)-I stimulates vascular smooth muscle cell (VSMC) migration and proliferation, which are fundamental to neointimal hyperplasia in postangioplasty restenosis. IGF-I action is modulated by several high-affinity IGF binding proteins (IGFBPs). IGFBP-4 is the predominant IGFBP produced by VSMCs and is a potent inhibitor of IGF-I action. However, specific IGFBP-4 proteases can cleave IGFBP-4 and liberate active IGF-I. In this study, we document IGFBP-4 protease produced by human and porcine coronary artery VSMCs in culture as pregnancy-associated plasma protein-A (PAPP-A). This was shown by a distinctive IGFBP-4 cleavage pattern, specific inhibition of IGFBP-4 protease activity with PAPP-A polyclonal antibodies, and immunorecognition of PAPP-A by monoclonal antibodies. Furthermore, we found a 2-fold increase in IGFBP-4 protease activity in injured porcine VSMC cultures in vitro (P<0.05). We also evaluated IGFBP-4 protease/PAPP-A expression in vivo after coronary artery balloon injury. Twenty-five immature female pigs underwent coronary overstretch balloon injury, and vessels were examined at defined time points after the procedure. Abundant PAPP-A expression was observed in the cytoplasm of medial and neointimal cells 7, 14, and 28 days after angioplasty (P<0.01 vs control). The highest PAPP-A labeling indices were located in the neointima (36.1+/-2.1%) and the media (31.7+/-1.2%) 28 days after injury. Western blot analysis confirmed increased PAPP-A in injured vessels. PAPP-A, a regulator of IGF-I bioavailability through proteolysis of IGFBP-4, is thus expressed by VSMCs in vitro and in restenotic lesions in vivo. These results suggest a possible role for PAPP-A in neointimal hyperplasia.

Adult↗
PubMed2001

Pregnancy-associated plasma protein-A (PAPP-A) in ovine, bovine, porcine, and equine ovarian follicles: involvement in IGF binding protein-4 proteolytic degradation and mRNA expression during follicular development.

IGF binding protein-4 (IGFBP-4) proteolytic degradation is a common feature of preovulatory follicles from human, ovine, bovine, porcine, and equine ovary. In all these species, the protease is a zinc-dependent metalloprotease and its ability to degrade IGFBP-4 is IGF dependent. The human intrafollicular IGFBP-4-degrading protease has recently been identified as pregnancy-associated plasma protein-A (PAPP-A). The aim of this study was to investigate whether PAPP-A is also involved in IGFBP-4 degradation in ovine, bovine, porcine, and equine preovulatory follicles and to study the expression of PAPP-A mRNA in bovine and porcine granulosa cells from different classes of follicles. Immunoneutralization and immunoprecipitation with polyclonal antibodies raised against human PAPP-A inhibited IGFBP-4 proteolytic degradation in preovulatory follicular fluid from the four species studied. As previously reported for the intrafollicular proteolytic activity degrading IGFBP-4, recombinant human PAPP-A generated in vitro 17- and 10-kDa IGFBP-4-proteolytic fragments. Recombinant PAPP-A activity was also shown to be IGF dependent and was inhibited by heparin-binding domain-containing peptides. In all mammalian species studied, the PAPP-A sequences showed high degree of identity. Moreover, the PAPP-A gene was localized on porcine chromosome 1 (1q29-1q213), in agreement with the localization of human PAPP-A gene on human chromosome 9q33.1. In bovine and porcine ovaries, real-time quantitative RT-PCR showed that PAPP-A mRNA expression in granulosa cells was maximal in fully differentiated follicles and was positively correlated with expression of P450 aromatase and LH receptor mRNAs. Overall, these data show that PAPP-A is responsible for IGFBP-4 degradation in ovine, bovine, porcine, and equine preovulatory follicles. The high expression of PAPP-A mRNA in granulosa cells from large, differentiated follicles suggest that it is a new functional marker of follicular development.

Amino Acid Sequence↗
PubMed2001

Pregnancy-associated plasma protein-a is the insulin-like growth factor binding protein-4 protease secreted by human ovarian granulosa cells and is a marker of dominant follicle selection and the corpus luteum.

Insulin-like growth factors (IGFs), IGF binding proteins (IGFBPs), and IGFBP proteases are important in ovarian function. IGFs stimulate granulosa steroidogenesis, an effect that is inhibited by IGFBP-4 and augmented by IGFBP-4 proteolysis. We have recently identified the IGFBP-4 protease in human ovarian follicular fluid (FF) as pregnancy-associated plasma protein-A (PAPP-A). In the current study, we identify the IGFBP-4 protease secreted by cultured human ovarian granulosa cells as PAPP-A, based on specific immunoinhibition and immunodepletion of the IGFBP-4 protease activity with PAPP-A polyclonal antibodies and immunorecognition by PAPP-A monoclonal antibodies in ELISA. PAPP-A was barely detectable in conditioned media (CM) from granulosa derived from </=9 mm androgen-dominant follicles, but was secreted by cultured granulosa from estrogen-dominant follicles >/=9 mm, coincident with dominant follicle selection, and by luteinizing granulosa. PAPP-A levels in CM from the latter did not change in response to IGF-II or hCG (100 ng/mL). A naturally occurring inhibitor of PAPP-A, proform of eosinophil major basic protein (proMBP), was detected by ELISA in estrogen-dominant follicular fluid FF, but not in CM from granulosa or luteinizing granulosa cells treated with IGF-II (0-200 ng/mL), FSH (0-100 ng/mL) or hCG (0-100 ng/mL), suggesting an alternative source (other than granulosa) for proMBP, compared to PAPP-A. The data demonstrate granulosa cells as a source of PAPP-A in human ovary and suggest that PAPP-A is a marker of ovarian follicle selection and corpus luteum formation. In addition the data suggest complex regulation of this system in human ovary.

Adult↗
PubMed2001

Recent developments in high-throughput mutation screening.

Screening of large sample materials for the presence of known or unknown mutations is a key element in pharmacogenomics. Although automated DNA sequencing has developed rapidly during the last decade, the technology is not well suited for projects involving analysis of hundreds of thousands of mutations. Consequently, a number of methods for high-throughput mutation screening have been developed. DNA microarrays and high-density oligonucleotide chips have proven to be well suited for parallel hybridisation-based analysis of hundreds or thousands of known mutations. Methods based on detection using matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS) have been developed. MALDI-TOF MS detection is limited to analysis of small DNA fragments but has a large potential for high-throughput single nucleotide polymorphism (SNP) analysis, due to a very fast analysis time and possibilities for automation. Currently, the best suited methods for high-throughput screening for unknown mutations are probably methods like single strand conformation polymorphism (SSCP) analysis or conformation sensitive gel electrophoresis (CSGE), combined with capillary array electrophoresis or denaturing high-performance liquid chromatography. This is due to a relatively short analysis time, potential for automation and a high sensitivity. The recent development of capillary array electrophoresis chips suggests that the analysis time for some of these methods may be reduced by one order of magnitude in the near future.

Chromatography, High Pressure Liquid↗
PubMed2001

Screening for mutations and polymorphisms in the genes KCNH2 and KCNE2 encoding the cardiac HERG/MiRP1 ion channel: implications for acquired and congenital long Q-T syndrome.

BACKGROUND: The voltage-gated, rapid-delayed rectifier current (I(Kr)) is important for repolarization of the heart, and mutations in the genes coding for the K+-ion channel conducting this current, i.e., KCNH2 for the alpha-subunit HERG and KCNE2 for the beta-subunit MiRP1, cause acquired and congenital long Q-T syndrome (LQTS) and other cardiac arrhythmias. METHODS: We developed a robust single-strand conformation polymorphism-heteroduplex screening analysis, with identical thermocycling conditions for all PCR reactions, covering all of the coding exons in KCNH2 and KCNE2. The method was used to screen 40 unrelated LQTS patients. RESULTS: Eleven mutations, of which six were novel, were found in KCNH2. Interestingly, six mutations were found in the region of the gene coding for the Per-Arnt-Sim (PAS) and PAS-S1 regions of the HERG protein, stressing the need to examine the entire gene when screening for mutations. No mutations were found in KCNE2, suggesting that direct involvement of MiRP1 in LQTS is rare. Furthermore, four novel single-nucleotide polymorphisms (SNPs) and one amino acid polymorphism (R1047L) were identified in KCNH2, and one novel SNP and one previously known amino acid polymorphism (T8A) were found in KCNE2. CONCLUSIONS: The potential role of rare polymorphisms in the HERG/MiRP1 K+-channel should be clarified with respect to drug interactions and susceptibility to arrhythmia and sudden death.

Cation Transport Proteins↗
PubMed2001

Novel feto-specific mRNA species suitable for identification of fetal cells from the maternal circulation.

Feto-specific markers are necessary for genetic diagnostics on fetal cells isolated from maternal blood. Differential display reverse transcription-polymerase chain reaction (DDRT-PCR) was used to identify mRNA species preferentially expressed in trophoblast-enriched primary cell cultures compared to female peripheral mononuclear blood cells (FPMBCs). We obtained 15 different cDNA clones expressed predominantly in placenta cells using a commercial kit with oligo-(dT) anchor primers and arbitrary upstream primers for differential display analysis of total RNA. Reverse Northern dot-blot analysis and semi-quantitative RT-PCR confirmed the different expression levels. Seven mRNA species were exclusively expressed in the placenta: the mRNAs of epsilon-globin, a renowned marker of fetal erythroblasts, early placenta insulin-like peptide (EPIL), Yes-associated protein (YAP65) and osteopontin were expressed at high levels, whereas the mRNAs of PP14, JM27 protein, and an unidentified expressed sequence tag (EST) were moderately expressed. A further eight mRNAs with low expression in FPMBCs and higher expression in first trimester placenta were identified. Some mRNAs were expressed in a trophoblast cell line, e.g. YAP65, whereas others were not, e.g. EPIL. The new mRNA markers may be used to construct DNA/RNA probes to identify fetal cells in maternal circulation by hybridization techniques, or to identify proteins selectively expressed in fetal cells and amenable to immunocytochemical detection.

Actins↗
PubMed2000

Expression of recombinant human pregnancy-associated plasma protein-A and identification of the proform of eosinophil major basic protein as its physiological inhibitor.

Pregnancy-associated plasma protein-A (PAPP-A), originally known from human pregnancy serum, has recently been demonstrated to be a metzincin superfamily metalloproteinase involved in normal and pathological insulin-like growth factor (IGF) physiology. PAPP-A specifically cleaves IGF-binding protein (IGFBP)-4, one of six antagonists of IGF action, which results in release of IGF bound to IGFBP-4. IGFBP-4 is the only known PAPP-A substrate. Its cleavage by PAPP-A uniquely depends on the presence of IGF. We here report mammalian expression and purification of recombinant 1547-residue PAPP-A (rPAPP-A). The recombinant protein is secreted as a homodimer of about 400 kDa composed of two 200-kDa disulfide-bound subunits. Antigenically and functionally, rPAPP-A behaves like the native protein. In human pregnancy, PAPP-A is known to circulate as a 500-kDa disulfide-bound 2:2 complex with the proform of eosinophil major basic protein (proMBP), PAPP-A/proMBP. A comparison between rPAPP-A and pregnancy serum PAPP-A/proMBP complex surprisingly reveals a difference greater than 100-fold in proteolytic activity, showing that proMBP functions as a proteinase inhibitor in vivo. We find that polyclonal antibodies against PAPP-A abrogate all detectable IGFBP-4 proteolytic activity in pregnancy serum, pointing at PAPP-A as the dominating, if not the only, IGFBP-4 proteinase present in the circulation. We further show that pregnancy serum and plasma contain traces (<1%) of uncomplexed PAPP-A with a much higher specific activity than the PAPP-A/proMBP complex. The measurable activity of the PAPP-A/proMBP complex probably results from the presence of a minor subpopulation of partly inhibited PAPP-A that exists in a 2:1 complex with proMBP. Inhibition of PAPP-A by proMBP represents a novel inhibitory mechanism with the enzyme irreversibly bound to its inhibitor by disulfide bonds.

Blood Proteins↗
PubMed2000

Intrathecal IgG synthesis and autoantibody-secreting cells in multiple sclerosis.

We studied intrathecal IgG synthesis and autoantibody-secreting cells in 148 patients with possible onset symptoms of MS (POSMS) or clinically definite MS (CDMS). In POSMS intrathecal synthesis of IgG oligoclonal bands and abnormalities on T2-weighted magnetic resonance imaging were associated but the former were more prevalent. The cerebrospinal fluid (CSF) leukocyte count and the number of anti-protelipid protein antibody-secreting cells in cerebrospinal fluid (CSF) correlated with disease activity in POSMS. Intrathecal IgG synthesis levels and the number of anti-myelin basic protein antibody-secreting cells in CSF correlated with disease activity in CDMS. Our results support recent reports of pathogenetic heterogeneity and a pathogenetic role of the antibody response in MS.

Adult↗
PubMed2000

Gene-specific DNA repair of pyrimidine dimers does not decline during cellular aging in vitro.

A large number of studies have demonstrated that various kinds of DNA damage accumulate during aging and one of the causes for this could be a decrease in DNA repair capacity. However, the level of total genomic repair has not been strongly correlated with aging. DNA repair of certain kinds of damage is known to be closely connected to the transcription process; thus, we chose to investigate the level of gene-specific repair of UV-induced damage using in vitro aging of human diploid skin fibroblasts and trabecular osteoblasts as model systems for aging. We find that the total genomic repair is not significantly affected during cellular aging of cultures of both human skin fibroblasts and trabecular osteoblasts. Gene-specific repair was analyzed during cellular aging in the dihydrofolate reductase housekeeping gene, the p53 tumor suppressor gene, and the inactive region X(754). There was no clear difference in the capacity of young and old cells to repair UV-induced pyrimidine dimers in any of the analyzed genes. Thus, in vitro senescent cells can sustain the ability to repair externally induced damage.

Adult↗
PubMed2000

[Pseudolymphoma and ventricular maltoma in patients with chronic gastritis, ulcer and Helicobacter pylori infection].

Among 128 patients with malignant B-lymphoproliferative disorders, 19 patients had long lasting dyspepsia and gastroscopy showed chronic active gastritis or gastric ulcer. PCR analysis for TCR and IgH clonality in biopsies showed local involvement of the malignant lymphocyte clone in four patients out of eight indicating presence of these cells in the inflammatory infiltrate. Weak B-cell clonality was found in four patients. A close relationship was seen between lymphocytic clonality and immune response to H. pylori Cag A, and all patients had parietal cell antibodies. Thus, the malignant clone may participate in the local inflammatory reaction, and continued local stimulation by H. pylori as well as parietal cell antigens may lead both to autoimmunity as well as a clonal development of lymphocytes.

Aged↗
PubMed2000

Alpha-fetoprotein in human fetal cerebrospinal fluid.

Alpha-fetoprotein (AFP) is a fetal glycoprotein. It has been ascribed a regulatory function of growth factor responses and immune functions. The concentrations of AFP and albumin (ALB) are highly variable in fetal serum and CSF and change with gestational age. The AFP index=[AFP(CSF)/AFP(SERUM)]/[ALB(CSF)/ALB(SERUM)] was determined in six normal fetuses at gestational age 17-23 weeks and found to be independent of gestational age and close to unity, mean 0.90+/-0.11 (S.D.). The ratio of CSF-serum concentrations of AFP and ALB both decreased significantly (p<0.05) with gestational age. The mean fraction of AFP being non-reactive with concanavalin A was 1.7% in serum and 1.9% in CSF, suggesting a common hepatic origin of AFP in both compartments. In conclusion, the concentration of AFP in CSF seems to be determined largely by the serum-CSF concentration gradient in normal fetuses. This finding, combined with the remarkable constancy of the AFP index compared to the highly variable absolute concentrations of AFP in both serum and CSF should make the AFP index the marker of choice when analyzing for intrathecal AFP synthesis during development and in pathological conditions.

Concanavalin A↗
PubMed2000

Mutational spectrum in the cardioauditory syndrome of Jervell and Lange-Nielsen.

Jervell and Lange-Nielsen syndrome (JLNS) is an autosomal recessive syndrome characterised by profound congenital sensorineural deafness and prolongation of the QT interval on the electrocardiogram, representing abnormal ventricular repolarisation. In a study of ten British and Norwegian families with JLNS, we have identified all of the mutations in the KCNQ1 gene, including two that are novel. Of the nine mutations identified in this group of 10 families, five are nonsense or frameshift mutations. Truncation of the protein proximal to the recently identified C-terminal assembly domain is expected to preclude assembly of KCNQ1 monomers into tetramers and explains the recessive inheritance of JLNS. However, study of a frameshift mutation, with a dominant effect phenotypically, suggests the presence of another assembly domain nearer to the N-terminus.

Amino Acid Substitution↗
PubMed2000

Subtle brain damage cannot be detected by measuring neuron-specific enolase and S-100beta protein after carotid endarterectomy.

OBJECTIVE: To assess whether subtle brain damage after carotid endarterectomy could be detected using serum levels of neuron-specific enolase (NSE) or S-100beta protein. DESIGN: Prospective noninterventional study. SETTING: University hospital. PARTICIPANTS: Twenty-two patients undergoing carotid endarterectomy and 16 patients undergoing repair of abdominal aortic aneurysm. INTERVENTIONS: Serum levels of NSE and S-100beta protein were measured in all patients before surgery and postoperatively at 12, 24, 36, and 48 hours. In patients undergoing carotid endarterectomy, neuropsychologic testing was performed before surgery and postoperatively at discharge from the hospital and after 3 months using a neuropsychologic test battery. MEASUREMENTS AND MAIN RESULTS: Compared with abdominal aortic surgery patients, the preoperative serum concentration of NSE was significantly higher in carotid artery surgery patients. Postoperatively, the NSE serum level decreased significantly after uncomplicated carotid artery surgery, and the level was then similar to that in the aortic surgery patients. Before operation, the S-100beta protein levels were similar in the two groups, but a significant increase was seen in aortic surgery patients postoperatively. Neuropsychologic testing after uncomplicated carotid artery surgery revealed cognitive dysfunction in 2 of 20 (10%) of the patients after 5 days and 3 of 16 (19%) of the patients after 3 months. There was no correlation between the change in cognitive function and the changes in blood levels of either NSE or S-100 protein. CONCLUSIONS: Subtle brain damage after carotid artery surgery could not be detected by measuring blood levels of NSE and S-100beta protein. The NSE level was significantly higher before carotid artery surgery and decreased postoperatively to the level observed in aortic surgery.

Aged↗