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H Reinauer

Publications and source records attributed to H Reinauer.

At least 19 recordsLinked to original sources
PubMed2001

Hormone-triggered conformational changes within the insulin-receptor ectodomain: requirement for transmembrane anchors.

Interaction between two alphabeta half-receptors within the (alphabeta)(2) holoreceptor complex is required for insulin binding with high affinity and for insulin-triggered changes of size and shape. To understand the underlying structure-function relationship, two truncated receptor constructs have been characterized. Reduction in the Stokes radius and increase in the sedimentation coefficient, which are characteristic for wild-type receptors, were entirely lacking for the recombinant human insulin receptor (HIR) ectodomain (HIR-ED). Stokes radii of about 5.8 nm and sedimentation coefficients of 10.2 S were found for both insulin-bound and free HIR-EDs. However, attaching the membrane anchors to the ectodomain, as with the recombinant membrane-anchored ectodomain (HIR-MAED) construct, was sufficient to restore not only high-affinity hormone binding but also the marked insulin-inducible alterations in hydrodynamic properties. The Stokes radii of HIR-MAED complexes, as assessed by non-denaturing PAGE, decreased upon insulin binding from 9.5 nm to 7.9 nm. In parallel, the sedimentation coefficient was increased from 9.0 S to 9.8 S. CD and fluorescence spectroscopy of HIR-MAED revealed only minor insulin-induced changes in the secondary structure. Similarity with wild-type receptors has also been demonstrated by the differential insertion of insulin-bound and free HIR-MAED complexes into artificial bilayer membranes of Triton X-114. The results are consistent with a model of receptor function that ensures a global insulin-triggered reorientation of subdomains within the ectodomain moieties while the secondary structure is essentially retained. For the rearrangement of such subdomains, the transmembrane anchors confer essential structural constraints on the receptor ectodomain.

Chromatography, Gel↗
PubMed2001

The determination of free and protein-bound haemoglobin in plasma using a combination of HPLC and absorption spectrometry.

The aim of the study was to develop a method for the determination of haemoglobin in plasma suitable for use to set target values for external quality assessment schemes for this analyte using commercially available test kits and equipment. In the early phase of the method development it became clear that the use of a single method, namely HPLC, would not be possible. However, by combining HPLC and absorption spectrophotometry, both qualitative and quantitative rapid determinations of protein-bound and free haemoglobin were able to be performed on equipment present in most routine clinical chemistry laboratories. The separation of protein-bound and free haemoglobin could be carried out using commercial HPLC equipment for the determination of haemoglobin A1c (HbA1c) without modification of the conditions used. Instead of haemolysed blood, the same volume of plasma (10 microl) was injected. The eluate was not discarded, but collected in 1-minute fractions so that the void volume (protein-bound Hb) and the haemoglobin peaks (free Hb) were available for the colorimetric determination of haemoglobin using the pseudoperoxidase activity of the haem moiety on hydrogen peroxide and a chromogen (3,3',5,5'-tetramethylbenzidine) in concentrated acetic acid and optimal determination at 600 nm. (In this publication at 578 nm due to the use of a spectrophotometer with Hg-discharge lamp and filter). The appearance of a blue colour in the reaction tube or cuvette indicated the presence of haemoglobin. The use of the above chromogen, with its absorption maximum around 600 nm excluded interference from serum components such as bilirubin, which may interfere in the conventional method often used to determine plasma haemoglobin. The method can be used quantitatively by including an aqueous human haemoglobin standard in the run. This elutes from the HPLC column only as free haemoglobin in the concentration range from 0.1 to 10 g/l. Addition of human haemoglobin to haemoglobin-free plasma resulted in the binding of all Hb to plasma proteins up to a concentration between 2 and 3 g/l (void-volume fraction). At higher concentrations free Hb appeared in the 3-5 minute fractions. These observations agree with published data on the scavenging capacity of plasma for Hb released from erythrocytes. The method is rapid, (HPLC-run maximally 6 min, quantitative colorimetric results 5-10 min) precise (inter-assay coefficients of variation < 8%) and suitable for answering the question as to whether the protein-binding (scavenging) system which prevents the nephro- and cerebrotoxic effects of haemoglobin has been saturated or not, an important question in patients with acute haemolysis problems. A qualitative result is obtainable within 10 minutes of injecting the sample into the HPLC-system. The use of this assay in controlling blood transfusion and haemolytic events arising from surgery, intravascular haemolytic bacteria or artificial heart valves can help in rapid corrective action, if needed.

Acetic Acid↗
PubMed2000

Sudden onset of EDTA-dependent pseudothrombocytopenia after therapy with the glycoprotein IIb/IIIa antagonist c7E3 Fab.

The development of thrombocytopenia following exposure to the platelet glycoprotein (GP) IIb/ IIIa receptor antagonist abciximab (c7E3 Fab, ReoPro) is associated with adverse clinical outcome and excessive bleeding. Pseudothrombocytopenia is an important differential diagnosis in sudden onset of thrombocytopenia in a patient treated with c7E3 Fab. We report on a case of documented sudden onset of EDTA-dependent pseudothrombocytopenia in a 63-year-old woman who was admitted for emergency coronary intervention. Four hours after bolus administration of c7E3 Fab, the platelet concentration in EDTA-anticoagulated blood decreased from 385 x 10(9)/l to 119 x 10(9)/l, and it showed a further decrease to 57 x 10(9)/l at the end of a 12-h infusion. Despite no warnings or abnormalities of the automated cell counter, platelet aggregates were observed by microscopic evaluation of the blood smear. Repeated platelet counts in citrate-anticoagulated samples revealed platelet concentrations within the reference range. EDTA-dependent pseudothrombocytopenia due to therapy with c7E3 Fab is an important differential diagnosis that needs to be excluded rapidly from other causes of thrombocytopenia to avoid unnecessary further examinations, discontinuation of therapy, or even initiation of inappropriate therapy.

Abciximab↗
PubMed2000

[Methodological standards of the evidence-based approach of clinical guidelines development in Germany. Consensus between the scientific community, self-governed bodies and practice].

The most appropriate method of clinical guidelines development has been the subject of controversial debates in Germany during the last few years. The German Guidelines Clearinghouse at the Society for Quality in Medicine (Cologne) provided a discussion forum where clinicians, methodologists, the Association of the Scientific Medical Societies, and the corporate self-governed bodies (the health insurances, physicians' associations, and the hospital associations) agreed on the most important methods of an evidence-based approach for guidelines development. It was generally agreed that rigorous methodological standards should be followed to ensure both the scientific quality and the consensus quality in the development or revision of clinical practice guidelines. The agreement draws on the following topics: Scientifically valid guidelines: (1) are based on a comprehensive and systematic review of the best available evidence, (2) derive the recommendations from the best available evidence, and (3) demonstrate explicitly how the recommendations are linked to the evidence. The quality of consensus is ensured through (1) the participation of all relevant stakeholders in the guideline panel and (2) the application of formal consensus development methods. This type of an "evidence-based consensus guideline" is assumed to possess the highest level of scientific and political legitimacy.

Evidence-Based Medicine↗
PubMed1999

Changes of hemostasis, endogenous fibrinolysis, platelet activation and endothelins after percutaneous transluminal coronary angioplasty in patients with stable angina.

OBJECTIVES: This study investigated parameters of endogenous fibrinolysis, activation of coagulation and platelets, and endothelin levels before and after elective percutaneous transluminal coronary angioplasty (PTCA) in patients with stable coronary artery disease (CAD). BACKGROUND: Abrupt vessel closure is a serious short-term complication after PTCA and is often unforeseeable. Detailed insight into the effect of PTCA on hemostasis, platelets and the release of vasoconstrictive substances, which are among the mainly discussed mechanisms of abrupt vessel closure, is needed to enhance the safety of coronary intervention. METHODS: Plasma levels of markers of platelet activity, coagulation, endogenous fibrinolysis and endothelins were determined in 20 patients with stable CAD undergoing elective PTCA. The blood specimens were drawn before, immediately after, 1 h after intervention and on the next morning. RESULTS: All patients showed an initially uncomplicated PTCA. Regarding the efficacy of anticoagulation after receiving 15.000 IU heparin during PTCA, two groups were compared. In eight patients with ineffective anticoagulation production of thrombin and platelet activation directly after and 1 h after PTCA was significantly higher compared with 12 patients with effective anticoagulation. Despite the strong activation of coagulation, only a low fibrinolytic response could be observed. Endothelins rose significantly after PTCA in both groups but stayed longer on higher levels in patients with distinct thrombin generation. Three of the eight patients without sufficient heparin treatment suffered abrupt vessel closure. CONCLUSIONS: Initially uncomplicated dilation of coronary arteries leads to systemically measurable activation of coagulation and platelets in patients with ineffective doses of heparin and release of endothelins in all patients. Therefore, individual adjustment of anticoagulation and platelet inhibition in combination with effective antivasospastic substances are needed in every patient before, during and after initially uncomplicated PTCA to prevent this serious complication.

Aged↗
PubMed1999

Anticoagulation with r-hirudin in a patient with acute renal failure and heparin-induced thrombocytopenia.

After a Caesarean section subcutaneous bleeding with a secondary infection occurred accompanied by acute renal failure. Additionally the diagnosis of a heparin-induced thrombocytopenia type II could be made. Therefore, haemodialysis treatments were performed with r-hirudin as an alternative anticoagulation. Even in dialysis dependent acute renal failure a safe anticoagulation with r-hirudin is possible if aPTT and plasma r-hirudin are closely monitored.

Acute Kidney Injury↗
PubMed1999

Quantification of glucose transport and phosphorylation in human skeletal muscle using FDG PET.

UNLABELLED: PET with 2-[18F]-fluoro-2-deoxy-D-glucose (FDG) is used for quantifying glucose metabolism in brain and myocardium in vivo. We developed and validated a similar procedure for the quantification of the two initial steps of glucose metabolism in skeletal muscle in vivo. METHODS: The measurement protocol was first optimized by computer simulations. In addition to the accuracy in sampling plasma input and tissue time-activity curves, precise determination of the fractional blood volume, that is, the extracellular tissue volume fraction, plays a key role in correctness of the determined model constants. The optimized protocol was subsequently used to estimate transmembrane muscular glucose transport and hexokinase activity in six human subjects with normal or altered glucose utilization. PET was performed during the steady state of an euglycemic hyperinsulinemic clamp. RESULTS: A three-compartment model provides a better description of the experimental data than a two- or four-compartment model. Glucose clearance from the extracellular compartment into the skeletal muscle cell (K1) ranges from 0.024 to 0.093 mL/g/min. The intracellular glucose phosphorylation rate (k3) varies between 0.030 and 0.142 min(-1). The regional muscular glucose utilization, as calculated from the determined model parameters, lies between 10.7 and 83.3 micromol/kg/min and correlates with the whole-body glucose utilization as independently determined (R2 = 0.83; P < or = 0.01). CONCLUSION: We demonstrate by computer simulations that a three-compartment model can be used to characterize the first two steps of glucose metabolism in skeletal muscle. An optimized measurement protocol is developed and applied to experimental data. This experimental approach should be appropriate to test whether glucose transport or hexokinase activity is altered in disorders of muscular glucose utilization.

Adult↗
PubMed1998

Plasma levels of D-dimer and circulating endothelial adhesion molecules in veno-occlusive disease of the liver following allogeneic bone marrow transplantation.

Veno-occlusive disease (VOD) of the liver is a frequent and life-threatening complication of BMT. Recently, successful treatment by t-PA has been reported but has been compromised by fatal bleeding events. Therefore, t-PA application should be restricted to patients with severe VOD. However, moderate and severe forms of VOD are difficult to distinguish in early stages. We analyzed plasma levels of cross-linked fibrin degradation products (D-dimer) and soluble endothelial adhesion molecules such as sE-selectin, sVCAM-1 and sICAM-1 in 10 consecutive patients undergoing allogeneic BMT to evaluate their use in identifying severe forms of VOD. During the observation period, 4 episodes of VOD occurred, 2 of which were fatal due to early onset of multiorgan failure. Concentrations of D-dimer generally increased after transplantation. However, there was an additional significant increase in D-dimer levels during severe VOD. Thus, D-dimer levels above 1000 microg/l were only found in 2 cases with severe VOD and fatal outcome. When compared with bilirubin concentrations substantial increases of D-dimers appeared earlier during the course of severe VOD. In contrast, VOD episodes were not accompanied by significant increases in sE-selectin, sVCAM-1 and sICAM-1 levels. It is concluded that measurement of D-dimer concentrations may aid accuracy to the early diagnosis of severe VOD.

Adult↗
PubMed1997

Dietary testosterone suppresses protective responsiveness to Plasmodium chabaudi malaria.

This study investigates the effect of orally administered testosterone on serum testosterone levels and immune responses including outcome of Plasmodium chabaudi malaria. Female C57BL/10 mice were fed on a diet impregnated with 17 alpha-methyl-testosterone for 3 weeks. This raised the circulating testosterone levels from 0.28 ng/ml to 2.69 ng/ml on the average. In these mice, blood-stage infections of P. chabaudi resulted in a lethal outcome, whereas protective immunity developed in about 80% of mice fed on control diet without testosterone. Dietary 17 alpha-methyl-testosterone reduced the capacity of peritoneal cells to generate reactive oxygen intermediates after stimulation with C3b-coated zymosan and phorbol-myristate-acetate. Also, mice fed on dietary 17 alpha-methyl-testosterone responded to heat-killed Salmonella typhimurium with a higher increase in serum TNF, whereas the induced increase in the production of IL-10 by spleen cells was largely suppressed and no effect was found with respect to the production of IFN-gamma and IL-4. Our data indicate that the method of oral administration of 17 alpha-methyl-testosterone raises circulating testosterone to levels that impair protective immune responses to P. chabaudi malaria.

Animals↗
PubMed1997

Effects of the carnitine-acyltransferase inhibitor etomoxir on insulin sensitivity, energy expenditure and substrate oxidation in NIDDM.

We studied the influence of Etomoxir on fat and carbohydrate oxidation, and the influence of these changes on insulin sensitivity in type 2 diabetic patients. Etomoxir is an oxirane carboxylic acid derivative that specifically inactivates carnitine-acyltransferase I (CAT I, EC: 2.3.1.21), the key enzyme for the transport of long-chain acyl-CoA compounds into the mitochondria. Thus, oxidation of fatty acids should be reduced by this drug and glucose utilisation be increased according to the Randle mechanism. In order to test this hypothesis, we measured oxidative and non-oxidative glucose utilisation using the euglycaemic hyperinsulinaemic clamp technique, the isotope dilution mass spectrometry (IDMS) method with stable isotopes (6,6-D2-glucose) and indirect calorimetry. The clamps lasted 5 hours, indirect calorimetry was performed during the last hour and calculations of glucose disposal were based on steady state conditions during the last 30 minutes. Twelve type 2 diabetic patients were treated with 100 mg etomoxir/per day for 3 days in this placebo-controlled, randomized, double-blind study. Treatment resulted in a significant increase in carbohydrate oxidation (from 72 to 113 g/24 h, p = 0.039), decrease in fat oxidation (from 139 to 114 g/24 h, p = 0.037), and decrease of the glucose appearance rate (RA) in the basal state (from 1.85 to 1.70 mg/kg min., p = 0.014). During the euglycaemic clamp neither RA (3.30 and 3.20 mg/kg min., p = 0.471) nor the glucose infusion rate (4.28 and 4.53 mg/kg min., p = 0.125) showed significant changes. In addition, no significant changes in glucose and fat oxidation were detected during the hyperinsulinaemic clamp. Under basal conditions non-oxidative glucose utilisation was decreased by etomoxir (1.26 and 0.80 mg/ kg x min). Thus, we could demonstrate a decrease in fat and increase in glucose oxidation by etomoxir, but non-oxidative glucose utilisation was decreased. No significant changes could be demonstrated under clamp conditions.

Adult↗
PubMed1997

Intestinal protein leakage in the acquired immunodeficiency syndrome.

Body wasting, protein catabolism, and hypoalbuminemia are complicating features of the acquired immunodeficiency syndrome (AIDS). Given their multifactorial causes, the contributing role of intestinal protein loss has not yet been fully elucidated. To quantify enteric protein leakage, determination of fecal alpha 1-antitrypsin (AAT) excretion has been established as an accurate and reliable endogenous marker. We estimated AAT concentration by standard immune nephelometry in duplicate random stool samples of 49 patients with AIDS, and we compared it to that of 43 patients with chronic inflammatory bowel disease and to 34 healthy controls. When compared with healthy persons, patients with AIDS had increased fecal AAT excretion regardless of current opportunistic intestinal infections and fecal AAT excretion similar to that of patients with quiescent chronic inflammatory bowel disease. The ratio of fecal and serum AAT concentration was not different between AIDS patients and healthy controls, although it was consistently increased in those with chronic inflammatory bowel disease. Significant intestinal protein leakage occurs in patients with AIDS, probably due to primary impairment of gut permeability. Enteric protein loss may be an important feature of human immunodeficiency virus-associated enteropathy with altered mucosal barrier function.

AIDS-Related Opportunistic Infections↗
PubMed1997

Specific pattern of circulating endothelial adhesion molecules in HIV-associated Kaposi's sarcoma.

BACKGROUND: Circulating endothelial adhesion molecules have been found to be increased in states of immune activation, but little is known about their significance in the assessment of endothelial neoplasms. One of the most common tumors supposed to be derived from endothelial origin is HIV-associated Kaposi's sarcoma (KS). METHODS: Plasma concentrations of sCD54 (= intercellular adhesion molecule-1), sCD106 (= vascular cell adhesion molecule-1), and sCD62E (= E-selectin) were quantified by sandwich ELISA in 54 AIDS patients who were either free of active opportunistic disorders (n = 15, AIDS controls), or suffering from acute infections (n = 16), or exhibiting KS (n = 23), and in 18 age- and sex-matched healthy HIV-negative controls. RESULTS: Both sCD54 and sCD106 plasma levels were consistently increased in all AIDS patients irrespective of concurrent opportunistic disorders (p < 0.005), while sCD62E levels were not altered in AIDS patients without KS (p > 0.05). In KS patients, sCD62E concentrations were decreased both compared to healthy (p = 0.0007) and to AIDS controls (p = 0.04), and stimulated sCD54 levels were less elevated than those of AIDS controls (p = 0.02). Plasma concentrations of all three adhesion molecules did not correlate to KS tumor stage. CONCLUSION: There appears to be a specific pattern of circulating endothelial adhesion molecules in AIDS patients with associated KS. Although the present findings do not support a role for their determination as tumor markers, they might be involved in KS tumor pathogenesis.

AIDS-Related Opportunistic Infections↗
PubMed1997

Bone sialoprotein in serum of patients with malignant bone diseases.

Bone sialoprotein (BS), a protein synthesized by osteoblasts and osteoclasts and highly modified posttranslationally, constitutes a predominant fraction of the noncollagenous organic matrix in human bone. We report an assessment of serum concentrations of BS in patients with malignant bone diseases. In patients with bone metastases (according to scintigraphic criteria), serum BS concentrations were greater than in patients without bone metastases (P <0.05). However, ROC curve analysis revealed that serum BS was inferior to serum bone alkaline phosphatase in discriminating between patients with and without bone metastases. Patients with bone metastases showed a weak correlation between serum BS concentrations and bone formation markers. Only "traditional" markers of bone formation-but not BS-were correlated with urinary deoxypyridinoline (P <0.01). Liver and kidney dysfunction had no significant influence on BS values in these patients (as assessed by analysis of variance; P >0.05). In multiple myeloma patients treated with corticosteroids and bisphosphonates, BS concentrations were lower than in tumor patients without bone metastases (P <0.001), and the correlation between BS concentrations and the number of bisphosphonate courses applied was significant (r = -0.578; P <0.05). In postmenopausal women, serum BS concentrations averaged 142% greater than in premenopausal women. Further studies should be done, therefore, to elucidate whether serum BS is able to predict high bone turnover after menopause.

Adult↗
PubMed1997

Activation of the fibrinolytic system in patients with coronary artery disease and hyperfibrinogenemia.

Elevated fibrinogen levels as well as an impaired activity of the fibrinolytic system are regarded as important cardiovascular risk factors. To elucidate a potential interrelation between fibrinogen as an indicator of a hypercoagulable state and the endogenous fibrinolytic function hemostatic and rheological as well as lipid parameters were determined in 224 consecutive patients, who underwent elective coronary angiography. In the selected study population of 81 men and 19 women with fibrinogen concentration either > or = 3.5 g/l (n = 70) or < or = 2.5 g/l (n = 30) hyperfibrinogenemia was found to be significantly associated with increased concentrations of plasmin-alpha 2-antiplasmin complex [PAP [median (25.-75. percentile)], 534 (361-680) micrograms/l vs. 289 (243-440) micrograms/l; p < 0.001] and tissue plasminogen activator (t-PA) antigen [9 (6-11) micrograms/l vs 8 (5-9) micrograms/l; p < 0.05] while this association was lost in the subgroup of patients with angiographically normal coronary arteries (n = 26). In addition to these findings fibrinogen was significantly correlated with PAP (r = 0.40, p < 0.001; n = 224) and t-PA antigen (r = 0.2, p < 0.01; n = 224) after adjustment for age, diabetes mellitus, lipid parameters and leucocyte counts. It can be argued that elevated fibrinogen levels in patients with coronary artery disease are concomitant with an activation of the fibrinolytic system.

Blood Viscosity↗
PubMed1996

Glibenclamide in serum: comparison of high-performance liquid chromatography using fluorescence detector and liquid chromatography/mass spectrometry with atmospheric-pressure chemical-ionization (APCI LC/MS).

Comparative studies of high-performance liquid chromatographic and liquid chromatographic/mass spectrometric methods for the quantitative determination of glibenclamide in patient serum are described. The 4-methylcyclohexyl analogue of glibenclamide [N-(4-(beta-5-chloro-2-methoxybenzamidoethyl)benzenesulfonyl-N'-(4-methylcyclohexyl)-urea] is used as internal standard for both methods. After acidification of the sample, the analyte and internal standard are extracted with chloroform. For HPLC analysis, the glibenclamide and internal standard are derivatized to a highly fluorescent amine with 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole (NBD-chloride). The glibenclamide derivative is detected by a fluorescence detector. For APCI LC/MS assay, a derivatization of the analyte is not required and the compounds are measured by selected ion monitoring (SIM). The accuracy, precision, and recovery of the compared methods are presented and discussed.

Journal Article↗
PubMed1996

Validation of candidate reference methods based on ion chromatography for determination of total sodium, potassium, calcium and magnesium in serum through comparison with flame atomic emission and absorption spectrometry.

OBJECTIVES: We report on the validation of candidate reference methods based on ion chromatography for the determination of total sodium, potassium, calcium, and magnesium in serum. The current study is a continuation of previous investigations in which we were able to show the potential of ion chromatography to serve as a reference method principle. The validation consisted of comparison of the ion chromatographic methods with generally recognized reference methods based on flame atomic emission (for sodium/ potassium) and absorption (for calcium/magnesium) spectrometry. METHODS: Sample preparation consisted of acidic dilution and pre-purification with reversed phase cartridges. Ion chromatography with suppressed conductivity was performed with polymeric stationary phases chemically modified with carboxylate and sulfonate functional groups for sodium/potassium and calcium/magnesium, respectively. Single-point calibration was used in combination with individual adaptation of serum sampling and diluting to give similar responses in samples and standards. In the study, more than 25 control sera were analyzed in parallel with the ion chromatographic methods and the traditional reference methods. The measurement protocol consisted of quadruplicate analysis of each sample per run, in 3 different runs. In each measurement series, internal quality control with certified reference materials from the National Institute of Standards and Technology and the Bureau Communautaire de Référence was applied. The performance criteria to fulfill were pre-defined (i.e., the maximum within-day and overall coefficient of variation, the confidence interval, the daily and overall deviation from the certified value and the maximum total analytical error). RESULTS: The comparison is presented as difference plot (i.e., % deviation of the results obtained with ion chromatography from those obtained with the respective traditional reference methods). The mean deviations were +0.9% for sodium, +1.0% for potassium, +/- 0.0% for calcium, and +0.1% for magnesium. With the exception of 2 values each for sodium and potassium, all deviations were within the limit of 2 times the allowed total analytical error. From the data obtained for internal quality control during the different measurement campaigns, we further estimated the long-term precision and accuracy of our methods. The overall coefficient of variation (respectively the bias) amounted to 0.7% (+0.1%) for sodium, 0.9% (-0.3%) for potassium, 1.3% (-0.1%) for calcium, and 1.0% (+/- 0.0%) for magnesium. CONCLUSION: From the precision and accuracy reached by our ion chromatographic methods, we conclude that they can be proposed as candidate reference methods for the determination of total sodium, potassium, calcium, and magnesium in serum.

Calcium↗