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Biomedical subjects

K J Lackner

Publications and source records attributed to K J Lackner.

At least 19 recordsLinked to original sources
PubMed2001

Age related signal decrease in functional magnetic resonance imaging during motor stimulation in humans.

Right handed healthy volunteers underwent functional magnetic resonance imaging (fMRI) examinations on a 1.5 Tesla MRI-scanner (Gyroscan ACS NT; Philips, Best, NL). Blood oxygen level dependent (BOLD) images were obtained using a three dimensional multi-shot echo planar imaging sequence employing a shifted echo technique (Principles of echo shifting with a train of observations). Finger tapping of the right hand was used as a task for motor stimulation. A total of 86 subjects was included into statistical analysis. Absolute and relative signal differences and cluster sizes of activation for the left motor cortex were obtained. In addition, Z-score, pooled Z-score and cross correlation activation maps were calculated and matched with high resolution anatomic images. A significant decrease with age could be detected for absolute and relative signal intensity differences for the whole group and for the male subgroup. Correlation analysis for the female subgroup also bore negative albeit non-significant correlation coefficients. An age-related decline of BOLD-contrast can be assumed to explain signal decrease. This age-related effect should be considered in clinical fMRI applications.

Adult↗
PubMed2001

[Antiphospholipid syndrome. Pathogenesis, molecular basis and clinical aspects].

BACKGROUND: In 1983 the antiphospholipid syndrome was first described as an independent clinical entity by Graham Hughes and characterized by thrombosis, thrombocytopenia and recurrent fetal losses. In the following years evidence accumulated from various studies that the thrombotic events in the antiphospholipid syndrome correlate with elevated serum titers of antiphospholipid antibodies. These autoantibodies represent a very heterogeneous group as multiple specificities against various negatively charged phospholipids are found. Most commonly described are antibodies against cardiolipin, but also cross-reactivities between the different phospholipids are observed. Moreover, efficient binding of antiphospholipid antibodies against a phospholipid requires the presence of certain protein-cofactors which on the other hand can be antigens themselves. PATHOGENESIS: Although numerous animal models strongly indicate that antiphospholipid antibodies play a causal role in the pathogenesis of the disease, the exact pathogenetic mechanisms are still to be elucidated. There is accumulating evidence from in vitro studies with poly- and monoclonal antiphospholipid antibodies that these autoantibodies are able to interfere with all aspects of the hemostatic balance. Influences of antiphospholipid antibodies on plasmatic processes of the coagulation cascade as well as antithrombotic and fibrinolytic mechanisms are described. Furthermore, antiphospholipid antibodies are able to exert prothrombotic effects on cells participating in hemostasis, mainly platelets and endothelial cells. THERAPEUTIC APPROACHES: Therapeutic approaches to the antiphospholipid syndrome today are mainly restricted to the prevention of further thrombosis by permanent anticoagulation. Although 30-50% of all patients, according to the literature, with moderately to highly elevated antiphospholipid antibody titers develop the clinical symptoms of the syndrome, there are only few studies investigating the benefits of a prophylactic anticoagulation of the affected patients. There is an urgent need for prospective clinical studies to clarify this question. Therapy of nonthrombotic manifestations of the antiphospholipid syndrome are scarcely standardized. In obstetrics, treatment with aspirin, heparin and steroids is the main approach. Here also controlled studies are restricted to small numbers of patients and are therefore of limited validity.

Antibodies, Anticardiolipin↗
PubMed2001

Common variants in the gene encoding ATP-binding cassette transporter 1 in men with low HDL cholesterol levels and coronary heart disease.

HDL cholesterol (HDL-C) deficiency is the most common lipid abnormality observed in patients with premature coronary heart disease (CHD). Recently, our laboratory and others demonstrated that mutations in the ATP-binding cassette transporter 1 (ABCA1) gene are responsible for Tangier disease, a rare genetic disorder characterized by severely diminished plasma HDL-C concentrations and a predisposition for CHD. To address the question of whether common variants within the coding sequence of ABCA1 may affect plasma HDL-C levels and CHD risk in the general population, we determined the frequencies of three common ABCA1 variants (G596A, A2589G and G3456C) in men participating in the Veterans Affairs Cooperative HDL Cholesterol Intervention Trial (VA-HIT), a study designed to examine the benefits of HDL raising in men having low HDL-C (< or =40 mg/dl) and established CHD, as well as in CHD-free men from the Framingham Offspring Study (FOS). Allele frequencies (%) in VA-HIT were 31, 16, and 4 for the G596A, A2589G, and G3456C variants, respectively, versus 27, 12, and 2 in FOS (P<0.03). None of the variants were significantly associated with plasma HDL-C concentrations in either population; however, in VA-HIT, the G3456C variant was associated with a significantly increased risk for CHD end points, suggesting a role for this variant in the premature CHD observed in this population.

ATP Binding Cassette Transporter 1↗
PubMed2001

Lipoprotein (a) up-regulates the expression of the plasminogen activator inhibitor 2 in human blood monocytes.

Elevated plasma lipoprotein (a) (Lp[a]) and cardiac events show a modest but significant association in various clinical studies. However, the influence of high Lp(a) on the gene expression in blood monocytes as a major cell involved in atherogenesis is poorly described. To identify genes influenced by elevated serum Lp(a), the gene expression was analyzed on a complementary DNA microarray comparing monocytes from a patient with isolated Lp(a) hyperlipidemia and coronary heart disease with monocytes from a healthy blood donor with low Lp(a). By using this approach, numerous genes were found differentially expressed in patient-versus-control monocytes. Verification of these candidates by Northern blot analysis or semiquantitative polymerase chain reaction in monocytes from additional patients with Lp(a) hyperlipidemia and healthy blood donors with elevated Lp(a) confirmed a significant induction of plasminogen activator inhibitor type 2 (PAI-2) messenger RNA (mRNA) in monocytes from male, but not from female, individuals with high Lp(a), indicating that this observation is gender specific. This led also to increased intracellular and secreted PAI-2 protein in monocytes from male probands with Lp(a) hyperlipidemia. Plasminogen activator inhibitor type 1 (PAI-1) mRNA was found suppressed only in the patients' monocytes and not in healthy probands with high Lp(a) levels. Purified Lp(a) induced PAI-2 mRNA and protein and reduced PAI-1 expression in monocytes isolated from various controls. The finding that PAI-2 is elevated in monocytes from male patients with isolated Lp(a) hyperlipidemia and male healthy probands with high Lp(a) and that purified Lp(a) up-regulates PAI-2 in control monocytes in vitro indicate a direct, but gender-specific, effect of Lp(a) for the induction of PAI-2 expression.

Adult↗
PubMed2001

Image quality of digital chest X-rays: wet versus dry laser printers.

The aim of this study was to compare the image quality of digital chest x-rays (Thoravision) obtained with 2 "wet" laser imagers of different matrix sizes and a "dry" system. Fifty chest x-rays in 2 planes were printed out in normal (100%) and reduced (61%) format using 3 different systems: 2 "wet" laser imagers (Agfa Matrix LR 3300, 4256 x 5174 pixels, 315 dpi; Agfa Scopix LR 5200, 8512 x 10348 pixels, 630 dpi), and one "dry" system (Agfa Drystar 3000,4352 x 5295 pixels, 330 dpi). All tests yielded normal findings. Anonymous images were evaluated by 4 independent reviewers on record forms rating the detectability of predefined anatomic structures. When the image quality of diagnosis-relevant, anatomic structures was evaluated on digital chest x-rays reproduced in normal and reduced format, the wet laser imagers did not show significant advantages over the dry system, Agfa Drystar 3000. The Agfa Drystar 3000 system is a feasible alternative for reproducing digital images, particularly for decentralized archives.

Adult↗
PubMed2001

Pharmacogenomics: implications for laboratory medicine.

Pharmacogenomics deals with the interactions of individual genetic constitution with drug therapy. It has potentially far reaching consequences for drug development and future treatment strategies, but also for clinical in vitro diagnostics. With increasing knowledge about interactions between genes and drug treatment, there will be an equally increasing demand for rapid and reliable diagnostic tests prior to the institution of therapy. In fact, it is very likely that pharmacogenetic tests will make up a significant proportion of total molecular biology testing in the coming years. Therefore, this review focuses on the implications of pharmacogenomics on the clinical laboratory.

Clinical Laboratory Techniques↗
PubMed2001

Functional magnetic resonance imaging of human pontine auditory pathway.

The purpose of this study is to visualize brainstem auditory pathways by functional magnetic resonance imaging (fMRI). Eighteen healthy volunteers (age 28 to 42 years) with normal hearing function underwent fMRI examination on a 1.5 Tesla imaging system (Philips, Best, The Netherlands) with periodic click stimulation. Blood oxygen level dependent images were obtained using a three-dimensional EPI sequence with shifted echo technique (principles of echo shifting with a train of observations). Control scans without click stimulation were obtained in the identical setting. Cross correlation activation maps were calculated using a postprocessing tool (Philips). They were matched with anatomic slices of identical orientation and thickness. Five of 18 subjects were excluded because of motion artifacts. In 4/13 significant activation was observed at the root entry zone of the ipsilateral acoustic nerve corresponding to the cochlear nuclei. In 11/13 subjects, significant activation was found in the same slice contralaterally close to the floor of the 4th ventricle, corresponding to the expected region of the superior olivary nucleus. Activation of the rostral parts of the auditory pathway (inferior colliculus, medial geniculate body) was not found. In the absence of the stimulus no activation occurred in these structures. It was concluded that activation of the brainstem auditory pathways by click stimuli can be visualized by fMRI.

Acoustic Stimulation↗
PubMed2001

Low sodium and furosemide-induced stimulation of the renin system in man is mediated by cyclooxygenase 2.

The aim of this study was to examine the effects of highly selective inhibition of cyclooxygenase 2 (COX-2) with rofecoxib on the renin system during long-term stimulation and after short-term stimulation. Six healthy male volunteers received, in a randomized crossover design, a low-sodium diet for days 1 through 9 with or without 25 mg rofecoxib twice daily on days 5 through 9 and, in addition, 20 mg of furosemide intravenously on day 8. Plasma renin activity increased 2 to 3 times over baseline with a low-sodium diet and 5 times over baseline 30 minutes after intravenous furosemide; it was still elevated nearly 5 times on day 9. These effects were completely blocked by rofecoxib. Plasma aldosterone and urinary aldosterone concentrations basically reflected the findings with plasma renin activity. Urinary sodium excretion decreased during a low-sodium diet and increased after intravenous furosemide without being significantly affected by rofecoxib. We have concluded that low-sodium and furosemide-stimulated renin and aldosterone secretion is completely blocked in healthy volunteers during COX-2 inhibition with rofecoxib, suggesting that intact COX-2 is of major importance for stimulation of the renin system under these conditions in man.

Adult↗
PubMed2001

Detection of porcine bone lesions and fissures: comparing digital selenium, digital luminescence, and analog film-screen radiography.

OBJECTIVE: The purpose of our study was to compare the diagnostic performance of a digital selenium detector (Thoravision) with that of analog film-screen systems and digital luminescence radiography in skeletal radiography for the detection of fissures and lesions in porcine bones. MATERIALS AND METHODS: One hundred bones taken from domestic pigs (50 ribs and 50 femurs) were divided into two equal groups. Fissures and bone lesions were created in 50 bones and 50 served as controls. The bones were examined using film-screen systems, digital luminescence radiography, and digital selenium radiography at various doses. Digital selenium radiography exposure values were adapted to the image geometry differing from the reference methods with a detector focus distance of 2.15 m. Four radiologists independently evaluated image quality and detectability of fissures and lesions on a five-point scale of confidence. Statistical evaluation was based on receiver operating characteristic curve analysis. RESULTS: Fissures and bone lesions were detected most reliably using the mammography film-screen system, but the difference in the results of the analog and digital reference images did not achieve statistical significance. CONCLUSION: Compared with analog film-screen systems, the lower spatial resolution of the digital selenium and digital luminescence radiography systems does not affect detectability of fissures and bone lesions in porcine bone. Selenium is effective in skeletal radiography for detecting fissures and bone lesions. With digital selenium and digital luminescence radiography, the surface dose can be cut to half that required for 200-speed film-screen systems without losing any diagnostically relevant information.

Animals↗
PubMed2001

ApoE-containing high density lipoproteins and phospholipid transfer protein activity increase in patients with a systemic inflammatory response.

High density lipoproteins (HDL) mediate reverse cholesterol transport as well as the clearance of oxidation products or inflammatory mediators, thereby contributing to tissue integrity. The decrease in HDL in inflammation has been attributed to decreased lecithin:cholesterol acyltransferase activity, whereas the role of phospholipid transfer protein (PLTP) and cholesteryl ester transfer protein has not been analyzed in detail. We have studied the activities of HDL-modifying proteins and the heterogeneity of HDL in healthy control subjects and three groups of postsurgery patients: no bacterial infection (group 1), bacterial focus and systemic inflammatory response (group 2), and severe sepsis (group 3). For all patients, a decrease in total HDL could be demonstrated, with a loss of mainly large, apolipoprotein A-I (apoA-I) HDL particles, an almost total loss of apoC-I, and an increase in apoE HDL (200-500 kDa), which did not contain significant amounts of apoA-I, apoA-II, or apoC-I. PLTP activity was increased in patients of groups 2 and 3, paralleled by a redistribution of PLTP into a population of small (120- to 200-kDa) particles, probably representing PLTP homodimers or lipid-complexed PLTP. In summary, the increase in apoE HDL and PLTP activity may improve the delivery of energy substrates and phospholipids to tissues that must maintain cellular membrane homeostasis under conditions of inflammatory stress.

Adult↗
PubMed2000

Mildly elevated homocysteine concentrations impair endothelium dependent vasodilation in hypercholesterolemic patients.

BACKGROUND: Elevated low density lipoproteins (LDL)-cholesterol and homocysteine levels have both been found to be associated with an increased risk for atherosclerotic vascular disease. To assess the effects of elevated homocysteine levels in hypercholesterolemic subjects on endothelial function, we examined basal and stimulated nitric oxide (NO) mediated vasodilation in the forearm vascular bed in hypercholesterolemic subjects with normal or elevated homocysteine levels. METHODS: Twenty-seven white subjects (age: 48 +/- 12 years) with elevated LDL-cholesterol (> or = 160 mg/dl) were divided into two groups with normal (n = 11) or mildly elevated (n = 16) homocysteine plasma concentration. We used strain gauge plethysmography to measure changes in forearm blood flow in response to intraarterial administration of increasing doses of acetylcholine (3, 12, 24, 48 microg/min), sodium nitroprusside (200, 800, 3200 ng/min), and N-monomethyl L-arginine (L-NMMA) (1, 2, 4 micromol/min). Total homocysteine plasma concentrations were determined by high performance liquid chromatography fluorimetry. RESULTS: Endothelium independent vascular relaxation tested by i.a. sodium nitroprusside and changes in forearm blood flow after i.a. L-NMMA indicating basal production and release of nitric oxide were similar between the two groups with normal or elevated homocysteine levels. In contrast, endothelium dependent vasodilation as assessed by the administration of i.a. acetylcholine differed between the groups with normal or elevated homocysteine levels for all doses tested (MANOVA P < 0.01: ACH 48 microg/min: 480 +/- 237% with normal vs 234 +/- 130% with elevated homocysteine; P < 0.002). This was significant even after taking possible covariates such as age, blood pressure, body mass index, LDL-, high density lipoproteins (HDL)-cholesterol, and trigylcerides into account (MANOVA P < 0.02). CONCLUSIONS: From our study we conclude that homocysteine impairs endothelium dependent vasodilation in subjects with elevated LDL-cholesterol levels. The most intriguing finding is that even mildly elevated homocysteine levels seem to be of crucial importance for deterioration of endothelial function, especially if other cardiovascular risk factors such as hypercholesterolemia preexist.

Adult↗
PubMed2000

Transport of lipids from golgi to plasma membrane is defective in tangier disease patients and Abc1-deficient mice.

Mutations in the gene encoding ATP-binding cassette transporter 1 ( ABC1) have been reported in Tangier disease (TD), an autosomal recessive disorder that is characterized by almost complete absence of plasma high-density lipoprotein (HDL), deposition of cholesteryl esters in the reticulo-endothelial system (RES) and aberrant cellular lipid trafficking. We demonstrate here that mice with a targeted inactivation of Abc1 display morphologic abnormalities and perturbations in their lipoprotein metabolism concordant with TD. ABC1 is expressed on the plasma membrane and the Golgi complex, mediates apo-AI associated export of cholesterol and phospholipids from the cell, and is regulated by cholesterol flux. Structural and functional abnormalities in caveolar processing and the trans-Golgi secretory pathway of cells lacking functional ABC1 indicate that lipid export processes involving vesicular budding between the Golgi and the plasma membrane are severely disturbed.

ATP Binding Cassette Transporter 1↗
PubMed2000

Analysis of prothrombotic effects of two human monoclonal IgG antiphospholipid antibodies of apparently similar specificity.

Two human monoclonal antiphospholipid antibodies (APA) of the IgG type, HL-5B and RR-7F have been generated from a patient with primary antiphospholipid syndrome and recurrent cerebral microemboli (H.L.) and from a patient with SLE without evidence of recurrent thrombosis (R.R.). Both monoclonal APA have similar characteristics in ELISA tests. To further analyse the prothrombotic potential, their effect on human monocytes and platelets, and bovine aortic endothelial cells (BAEC) was investigated. Monocytes were isolated from buffy coats by standard techniques. They were incubated either with the respective monoclonal APA in different concentrations, or a control monoclonal IgG of the same subtype, or plasma of the patients, from whom the antibodies were isolated. Incubation with LPS served as positive control. BAEC were grown to confluence, and then incubated with the appropriate agonists. Procoagulant activity (PCA) was determined by a single stage clotting assay. PCA expression after incubation is given as the ratio of the coagulation times observed with media only divided by that observed with the agonist. A PCA ratio >1 indicates the induction of PCA by the agonist. At 1 microg/ml HL-5B yielded a PCA ratio of 1.63 +/- 0.16 while RR-7F induced no significant rise to 1.06 +/- 0.18. Dose response curves showed that RR-7F can induce PCA at higher concentrations. However, its effect is approx. 1/50 of HL-5B based on equimolar antibody concentration. Further analysis indicates that the majority of the PCA induced by monoclonal APA can be inhibited by a specific tissue factor antibody. Neither monoclonal antibody induced PCA in BAEC. Sera from both patients were able to induce PCA in monocytes. However, the PCA ratio of serum from H.L. was higher (1.78) than that of R.R. (1.44). Neither monoclonal APA had an effect on platelets as determined by flow cytometric analysis of CD62P, CD41, CD42b expression and fibrinogen binding with and without previous activation with 5 microM ADP or 15 microM TRAP-6. Similarly, there were no differences in platelet aggregation to different stimuli including submaximal activation. In summary, these data provide further evidence that induction of tissue factor in monocytes is one of the procoagulant effects of APA. Furthermore, the binding specificity of APA is perhaps not suited to predict the biological effects of the antibodies.

Adenosine Diphosphate↗
PubMed2000

Preparative free-solution isotachophoresis for separation of human plasma lipoproteins: apolipoprotein and lipid composition of HDL subfractions.

We have previously shown that plasma lipoproteins can be separated by analytical capillary isotachophoresis (ITP) according to their electrophoretic mobility in a defined buffer system. As in lipoprotein electrophoresis, HDL show the highest mobility followed by VLDL, IDL, and LDL. Chylomicrons migrate according to their net-charge between HDL and VLDL, because ITP has negligible molecular sieve effects. Three HDL subfractions were obtained which were designated fast-, intermediate-, and slow-migrating HDL. To further characterize these HDL subfractions, a newly developed free-solution ITP (FS-ITP)-system was used, that allows micro-preparative separation of human lipoproteins directly from whole plasma (Böttcher, A. et al. 1998. Electrophoresis. 19: 1110-1116). The fractions obtained by FS-ITP were analyzed for their lipid and apolipoprotein composition and by two-dimensional nondenaturing polyacrylamide gradient gel electrophoresis (2D-GGE) with subsequent immunoblotting. fHDL are characterized by the highest proportion of esterified cholesterol of all three subfractions and are relatively enriched in LpA-I. Together with iHDL they contain the majority of plasma apoA-I, while sHDL contain the majority of plasma apoA-IV, apoD, apoE, and apoJ. Pre-beta-HDL were found in separate fractions together with triglyceride-rich fractions between sHDL and LDL. In summary, ITP can separate the bulk of HDL into lipoprotein subfractions, which differ in apolipoprotein composition and electrophoretic mobility. While analytical ITP permits rapid separation and quantitation for diagnostic purposes, FS-ITP can be used to obtain these lipoprotein subfractions on a preparative scale for functional analysis. As FS-ITP is much better suited for preparative purposes than gel electrophoresis, it represents an important novel tool for the functional analysis of lipoprotein subclasses.

Electrophoresis↗
PubMed1999

Isolation and characterization of two human monoclonal anti-phospholipid IgG from patients with autoimmune disease.

The antigenic specificity of anti-phospholipid antibodies (APA) is a matter of intensive investigation. To further characterize these antibodies, we attempted to isolate human monoclonal APA. B-cells of patients with at least one positive test for antibodies against cardiolipin, phosphatidylserine, beta2-glycoprotein I (beta2-GPI) or the lupus anti-coagulant were immortalized by transformation with Epstein-Barr virus and screened for production of specific IgG. Positive pools were fused with a heteromyeloma cell line and APA-secreting clones were isolated by standard procedures. Two monoclonal APA, HL-5B from a 51-year-old man with primary anti-phospholipid syndrome and recurrent cerebral microinfarctions, and RR-7F from a 48-year-old women with systemic lupus erythematosus but no evidence for thrombotic events were obtained. HL-5B is of the IgG2 subtype with lambda light chains, while RR-7F is IgG2 with kappa light chains. Both monoclonals show reactivity against cardiolipin and phosphatidylserine but lack reactivity against beta2-GPI or lupus anti-coagulant activity. To yield the same OD in the cardiolipin and phosphatidylserine ELISAs RR-7F must be used in an approximately 10-fold higher concentration than HL-5B, indicating a lower affinity towards these antigens. Interestingly, both mAPA can bind to cardiolipin in the absence of beta2-GPI. They do not cross-react with dsDNA but show reactivity against oxidized low-density lipoproteins. Analysis of the heavy chain mRNA of HL-5B and RR-7F showed that both are members of the VH3 family. While HL-5B shows extensive somatic mutations in the CDR1 and 2 regions, indicating that it was derived by a T cell-dependent antigen driven process, RR-7F is apparently germline encoded. The two monoclonal APA can be used as tools in further structural and functional analyses.

Amino Acid Sequence↗
PubMed1999

The gene encoding ATP-binding cassette transporter 1 is mutated in Tangier disease.

Tangier disease (TD) is an autosomal recessive disorder of lipid metabolism. It is characterized by absence of plasma high-density lipoprotein (HDL) and deposition of cholesteryl esters in the reticulo-endothelial system with splenomegaly and enlargement of tonsils and lymph nodes. Although low HDL cholesterol is associated with an increased risk for coronary artery disease, this condition is not consistently found in TD pedigrees. Metabolic studies in TD patients have revealed a rapid catabolism of HDL and its precursors. In contrast to normal mononuclear phagocytes (MNP), MNP from TD individuals degrade internalized HDL in unusual lysosomes, indicating a defect in cellular lipid metabolism. HDL-mediated cholesterol efflux and intracellular lipid trafficking and turnover are abnormal in TD fibroblasts, which have a reduced in vitro growth rate. The TD locus has been mapped to chromosome 9q31. Here we present evidence that TD is caused by mutations in ABC1, encoding a member of the ATP-binding cassette (ABC) transporter family, located on chromosome 9q22-31. We have analysed five kindreds with TD and identified seven different mutations, including three that are expected to impair the function of the gene product. The identification of ABC1 as the TD locus has implications for the understanding of cellular HDL metabolism and reverse cholesterol transport, and its association with premature cardiovascular disease.

ATP Binding Cassette Transporter 1↗
PubMed1998

Automated free-solution isotachophoresis: instrumentation and fractionation of human serum proteins.

An automated free-solution isotachophoresis system (FS-ITP) for preparative fractionation of biopolymers is described, operated in a batch mode. The dimension of the separation chamber allows an up to 1200-fold higher sample load compared to separation in capillaries of 180 microm inner diameter as used in analytical capillary isotachophoresis (C-ITP). The preparative capacity of the system is within the milligram range. The method is fully compatible with analytical C-ITP, which is essential for preparative-scale isotachophoresis with regard to optimization of electrolyte systems and the search for suitable spacers. As a model application the fractionation of human serum proteins is reported. The collected fractions were analyzed by C-ITP and agarose gel electrophoresis.

Blood Proteins↗