A comprehensive study of the sorption mechanism and thermodynamics of f-element sorption onto K-feldspar

The mobility of heavy metal contaminants and radionuclides in the environment is directly controlled by their interactions with charged mineral surfaces, hence an assessment of their potential toxicity, e.g. in the context of radioactive waste disposal sites, requires understanding of sorption processes on the molecular level. Here, we investigate the sorption of a variety of rare earth elements (REE) and trivalent actinides (Am, Cm) on K-feldspar using batch sorption, time-resolved laser-induced fluorescence spectroscopy (TRLFS), and a surface complexation model. Initially, a reliable pK_a for K-feldspar's surface deprotonation reaction was determined as 2.5 ± 0.02 by column titration experiments, in excellent agreement with a measured pH_IEP of 2.8. Batch sorption experiments over a broad range of experimental conditions in terms of mineral grain size, pH, [M³⁺], ionic radius, solid/liquid ratio, ionic strength, and equilibration procedures were carried out to quantify macroscopic retention. The trivalent d-block element Y, early, mid, and late lanthanides (La, Eu, Nd, Lu), as well as two minor actinides (Am, Cm) were used for batch sorption experiments and showed similar pH dependent uptake behavior, underlining their chemical analogy. In parallel, spectroscopic investigations provided insight into surface speciation. Cm TRLFS spectra indicate the formation of three inner-sphere sorption complexes with increasing hydrolysis. Additionally, a ternary K-feldspar/Cm/silicate complex was found for pH > 10, and batch and spectroscopic data at low pH (<4) point to small amounts of outer sphere sorption complexes. Based on TRLFS data, batch sorption, and titration data, a generic geochemical sorption model was developed, that describes sorption edges for all investigated M³⁺/K-feldspar systems satisfactorily. The derived stability constants for the binary sorption complexes (logK_1-4 = -3.6, -7.7, -11.5, and -17.4, respectively) could successfully be used to reproduce literature data. The stability constants obtained for the surface complexes were included into the database for the Smart K_d-concept, which will further improve the safety assessment of potential repositories for radioactive waste.

Multibiomarker model to discriminate Type 1 and Type 2 myocardial infarction

Background

The discrimination of patients with type 1 myocardial infarction (T1MI) from patients with type 2 MI (T2MI) is often challenging in the emergency department. Earlier we presented a discrimination model, which based on clinical variables, as well as on troponin concentrations. In the present analyses we sought to investigate the discriminative power of 28 biomarkers in patients with T1MI and T2MI.

Methods

Patients presenting to the emergency department with symptoms suggestive of MI were recruited. The final diagnosis of all patients was adjudicated by two physicians in a blinded fashion and based on the fourth universal definition of MI. For the present analyses only patients with T1MI and T2MI were used. In total 28 biomarkers were measured in blood samples collected directly at admission. A multivariable logistic regression model for T1MI vs T2MI as the dependent variable was used and the predictors were chosen via backward step-down selection.

Results

In total 138 patients (107 T1MI and 31 T2MI) were available for the analyses. The median age of the study population was 65 years and 66.7% were males. Hypertension was present in 77.4% and dyslipidemia in 41.3%. In the multivariable model four biomarkers (apolipoprotein A-II, n-terminal prohormone of brain natriuretic peptide, copeptin and high-sensitivity troponin I) were significant discriminators between T1MI and T2MI (Table 1). Internal validation of the model via bootstrap shows a for overoptimism corrected area under the curve of 0.82.

Conclusion

Using a multibiomarker approach discrimination between T1MI and T2MI could be improved. External validation of our findings is warranted.

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): Research fellowship by the Deutsche Forschungsgemeinschaft

Usefulness of troponin in selecting patients for invasive coronary angiography after cardiac surgery

Background

Great uncertainty exists about the indication for invasive coronary angiography (ICA) in patients with suspected acute coronary syndrome following cardiac surgery.

Aim

The aim of this study was to define clinical criteria that best identify patients who benefit from ICA after cardiac surgery.

Methods

We performed a retrospective analysis of all patients who underwent cardiac surgery between January 2009 and May 2019 at our center. Exclusion criteria included pediatric patients as well as pacemaker, TAVR and LVAD implantation and heart transplantation procedures. The primary outcome was usefulness of ICA as defined by consequent PCI or re-operation due to ICA findings. ECG changes (ST-elevations) and high-sensitivity Troponin I (hsTrop I) were analyzed.

Results

48,136 patients were screened and after applying exclusion criteria 29,359 patients were finally included in the analysis (mean age 67.8±11.0 years, 31.1% females, Euroscore II 5.14±8.9%). A total of 1,171 patients (4%) underwent post-op ICA. The primary outcome occurred in 440 patients (1.5%) of which 290 underwent consequent PCI and 214 underwent consequent re-operation. Baseline characteristics are shown in table 1. Unadjusted analyses did not identify significant differences in the level of cardiac biomarkers between useful-ICA and unuseful-ICA groups.

In multivariate regression analysis, only ST-elevation on ECG predicted the primary outcome (OR 1.33, 95% CI 1.003–1.76).

Dichotomizing hsTrop I concentrations by applying the guideline-specified cut-off (&gt;70x URL) resulted in correct classification of useful-ICA patients in 95.7%. However, the false-positive rate was also extremely high (83.6%) with a positive predictive value (PPV) of 1.6% and a negative predictive value (NPV) of 99.6% (accuracy 17.5%).

Using area under the curve (ROC) analysis following optimal cut-off values for hsTrop I were identified: in CABG patients a cut-off value of &gt;650x URL (corresponding absolute value 17000 ng/L) was defined with a corresponding sensitivity of 83.3%, specificity of 83.6%, PPV of 8.9% and NPV of 99.6% (accuracy 83.6%). In non-CABG patients (i.e. valve or aortic procedures), the cut-off was about twice as high as that for CABG patients (1,350x URL or 35,000 ng/L) with a corresponding sensitivity of 84.1%, specificity of 89.2%, PPV of 5.9% and NPV of 99.9% (accuracy 89.1%).

Conclusion

Our study demonstrates that currently recommended cut-off concentrations of high-sensitivity troponin are not useful for guiding clinical decision-making in patients with suspected acute coronary syndrome following cardiac surgery, while substantially higher cut-off values might be useful. Those cut-off values critically depend on the type of cardiac surgery performed (CABG vs. non-CABG).

Troponin_Curves post-op

Funding Acknowledgement

Type of funding source: None

Discrimination of myocardial infarction and myocardial injury using a multibiomarker approach

Background

In the Universal Definition of Myocardial Infarction (MI) myocardial injury was introduced as a specific diagnosis in patients with elevated troponin concentrations, but without evidence of acute myocardial ischemia. However, their differentiation within the acute setting might be challenging. Therefore, we sought to investigate a multibiomarker panel in these patients and determine the discriminative capacity to differentiation MI from myocardial injury.

Methods

We use a cohorts of acute patients presenting to the emergency department. All final diagnoses were adjudicated by two physicians in a blinded fashion and based on the fourth universal definition of MI. In case of disagreement a third physician referred. For the present analyses only patients diagnosed with MI or myocardial injury were used. A panel of 28 biomarkers was measured in blood samples collected directly at admission. Spearman correlations were calculated. A multivariable logistic regression model using MI as the dependent variable was used and the predictors were chosen via backward step-back selection. Odds ratios (OR) were calculated for each predictor.

Results

We included 359 patients; 138 were diagnosed as having MI and 221 has having myocardial injury. The median age of the study population was 73 years and 59.1% were males. Hypertension was diagnosed in 80.4%, dyslipidemia in 45.4% and diabetes in 19.0%.The biomarker panel showed a wide range of correlations (Figure 1). In the multivariable model five logarithmized biomarkers (N-terminal prohormone of brain natriuretic peptide [OR 0.62], pulmonary and activation-regulated chemokine [OR 0.51], tumor-necrosis-factor-receptor 2 [OR 2.22], copeptin [OR 1.59] and high-sensitivity troponin I [OR 1.80]) were significant discriminators between MI and myocardial injury. Internal validation of the model via bootstrap shows a for overoptimism corrected area under the curve of 0.84.

Conclusion

In the multivariable model five biomarkers were discriminators between MI and myocardial injury.

Spearman correlations

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): Research fellowship by the Deutsche Forschungsgemeinschaft

Experimental and numerical study of interlock requirements for high-power EYDFAs

In this work, we studied the interlock requirements in a seed failure scenario for Er³⁺:Yb³⁺ doped fiber amplifiers (EYDFAs) pumped with high intensities in the MWcm^-2 range at 9XX nm. We fed a time-dependent FEM-tool with the data from backwards directed amplified spontaneous emission (ASE) transients of different commercially available core-pumped single-mode fibers. In the FEM-tool, the Er³⁺:Yb³⁺ system is defined as a bi-directional energy transfer process and described by the corresponding rate equations. The power evolution of the pump, seed, and ASE signal is computed by differential equations taking into account the transient population densities of the relevant energy levels. With the model, we computed the temporal evolution of the corresponding energy levels after a seeder failure to take place within tens to hundreds of µs and calculated the associated gain. The fibers under test provide a critical total gain of 30 dB after ∼ 80 µs within the Yb³⁺ band and after ∼300 µs within the Er³⁺ band. This time decreases with increasing pump power and doping concentration. The results can be extrapolated to high-power cladding-pumped EYDFAs to meet the challenging requirements of engineering-level systems.

Dominant mutations in ITPR3 cause Charcot-Marie-Tooth disease

OBJECTIVE

ITPR3, encoding inositol 1,4,5-trisphosphate receptor type 3, was previously reported as a potential candidate disease gene for Charcot-Marie-Tooth neuropathy. Here, we present genetic and functional evidence that ITPR3 is a Charcot-Marie-Tooth disease gene.

METHODS

Whole-exome sequencing of four affected individuals in an autosomal dominant family and one individual who was the only affected individual in his family was used to identify disease-causing variants. Skin fibroblasts from two individuals of the autosomal dominant family were analyzed functionally by western blotting, quantitative reverse transcription PCR, and Ca2+ imaging.

RESULTS

Affected individuals in the autosomal dominant family had onset of symmetrical neuropathy with demyelinating and secondary axonal features at around age 30, showing signs of gradual progression with severe distal leg weakness and hand involvement in the proband at age 64. Exome sequencing identified a heterozygous ITPR3 p.Val615Met variant segregating with the disease. The individual who was the only affected in his family had disease onset at age 4 with demyelinating neuropathy. His condition was progressive, leading to severe muscle atrophy below knees and atrophy of proximal leg and hand muscles by age 16. Trio exome sequencing identified a de novo ITPR3 variant p.Arg2524Cys. Altered Ca2+ -transients in p.Val615Met patient fibroblasts suggested that the variant has a dominant-negative effect on inositol 1,4,5-trisphosphate receptor type 3 function.

INTERPRETATION

Together with two previously identified variants, our report adds further evidence that ITPR3 is a disease-causing gene for CMT and indicates altered Ca2+ homeostasis in disease pathogenesis.

THU0053 CONTRIBUTION OF DEFECTIVE NON-APOPTOTIC FAS SIGNALING TO IMMUNE DYSREGULATION IN AUTOIMMUNE LYMPHOPROLIFERATIVE SYNDROME (ALPS)

Background:

ALPS patients show impaired generation of humoral memory for T independent antigens whereas they generate memory for self-antigens due to impaired FAS-dependent removal of autoreactive germinal center B cells. It is known that FAS signaling via caspase activation results in cell apoptosis. However, FAS ligation may also initiate or modulate non-apoptotic signaling as shown for example by its ability to activate NF-κB. Recent data implicate a regulatory role of FAS in the modulation of mTOR signaling in ALPS double-negative T cells. Moreover, a recently described C194V FAS mutation disturbs its post-translational modification leading to impaired apoptosis induction while non-apoptotic signalling is still intact. Consequently, C194V FAS protects from the autoimmune phenotype in the murine ALPS system. This supports the view that FAS may prevent autoimmunity with other mechanisms than inducing apoptosis.

Objectives:

We hypothesize that FAS mutations impair this modulatory signaling, leading to hyper-activation of B cells. Therefore we aim to investigate non apoptotic FAS signaling in B cells derived from healthy individuals and ALPS patients.

Methods:

We studied resting and activated B cells in ALPS patients in presence or absence of FAS ligand by flow cytometry analysing relevant molecules to the CD40 signaling pathway. We used mass cytometry to perform functional phenotyping of B cells isolated from secondary lymphoid organs. Proteomic studies were performed to identify potential signaling circuits and RNA sequencing to study the consequences of FAS signaling on B cell fate.

Results:

In CD40L activated B cells, FAS signaling results in specific modulation of the mTOR signaling pathway. This modulation is absent in ALPS derived B cells. In line with these data germinal center B cells and plasmablast from secondary lymphoid organs of ALPS patients show hyperactive mTOR signaling pathway. Proteomic studies identify a circuit that links FAS to the phosphatase PTEN via DAXX and the deubiquitinase USP7.

Conclusion:

We describe a new role of FAS in the regulation of B cell activation. Defects in FAS signaling in ALPS contribute to dysregulation of the mTOR signaling pathway and disturbed B cell development.

Disclosure of Interests:

None declared

Defective Sec61α1 underlies a novel cause of autosomal dominant severe congenital neutropenia

Background

The molecular cause of severe congenital neutropenia (SCN) is unknown in 30% to 50% of patients. SEC61A1 encodes the α-subunit of the Sec61 complex, which governs endoplasmic reticulum protein transport and passive calcium leakage. Recently, mutations in SEC61A1 were reported to be pathogenic in common variable immunodeficiency and glomerulocystic kidney disease.

Objective

Our aim was to expand the spectrum of SEC61A1-mediated disease to include autosomal dominant SCN.

Methods

Whole exome sequencing findings were validated, and reported mutations were compared by Western blotting, Ca2⁺ flux assays, differentiation of transduced HL-60 cells, in vitro differentiation of primary CD34 cells, quantitative PCR for unfolded protein response (UPR) genes, and single-cell RNA sequencing on whole bone marrow.

Results

We identified a novel de novo missense mutation in SEC61A1 (c.A275G;p.Q92R) in a patient with SCN who was born to nonconsanguineous Belgian parents. The mutation results in diminished protein expression, disturbed protein translocation, and an increase in calcium leakage from the endoplasmic reticulum. In vitro differentiation of CD34⁺ cells recapitulated the patient’s clinical arrest in granulopoiesis. The impact of Q92R-Sec61α1 on neutrophil maturation was validated by using HL-60 cells, in which transduction reduced differentiation into CD11b⁺CD16⁺ cells. A potential mechanism for this defect is the uncontrolled initiation of the unfolded protein stress response, with single-cell analysis of primary bone marrow revealing perturbed UPR in myeloid precursors and in vitro differentiation of primary CD34⁺ cells revealing upregulation of CCAAT/enhancer-binding protein homologous protein and immunoglobulin heavy chain binding protein UPR-response genes.

Conclusion

Specific mutations in SEC61A1 cause SCN through dysregulation of the UPR.

[Malignant tumors of the skull base]

Malignant skull base tumors consist of a heterogeneous group of malignancies that can be divided into primary and secondary (metastatic) skull base tumors. In addition, according their anatomical location, they can be further divided into tumors of the anterior, middle, or posterior cranial fossa. Although malignant skull base tumors do not rigorously respect anatomical borders, their anatomical occurrence can potentially be helpful for possible differential diagnosis. This article is focused on the most common malignant tumors of the skull base and their imaging and clinical presentations.

P4576Prognostic value of high-sensitivity troponin I measured by two assays in patients presenting with suspected myocardial infarction

Background

Troponin is the gold-standard biomarker for diagnosing acute myocardial infarction (AMI). High-sensitivity assayed troponin has furthermore proven to be a promising biomarker for the prediction of future adverse cardiovascular events.

Objective

Aim of the current study was to assess and compare the prognostic value of a single troponin I measurement in patients with suspected AMI analysed by a novel high-sensitive Troponin I (hs-TnI) assay, promising detection of very low troponin I plasma levels, as well as by a well-established hs-TnI assay.

Methods

Data was derived from two prospective studies of patients presenting with suspected AMI to the emergency department. Hs-TnI was measured in a total of 2,312 patients using both a novel hs-TnI assay (1; Singulex Clarity cTnI) and a widely applied and approved hs-TnI assay (2; Abbott Diagnostics, ARCHITECT i1000SR). The prognostic impact for overall mortality of both hs-TnI assays was assessed in the total patient cohort as well as in the subgroups of patients with AMI (n=498) and without AMI (n=1,813). Kaplan-Meier analyses stratified by hs-TnI tertiles in each subgroup were performed. Moreover, prognostic impacts of both hs-TnI assays were analysed in a multiple adjusted cox regression model. We compared the performance of both hs-TnI assays in predicting adverse outcome using c-statistics. Median follow up time was 2.4 years.

Results

Patients with AMI presented with significantly higher hs-TnI values on admission. Unadjusted Kaplan-Meier analysis survival curves in the entire study population (Figure 1) as well as in the non-AMI subgroup indicated a significantly higher event-rate in the third tertiles of both hs-TnI assays for overall mortality. In contrast, irrespective of the used assay we found no association between troponin I plasma levels and overall mortality in the AMI group. Cox regression models revealed significant associations between hs-TnI and overall mortality in the entire study cohort (1: HR 1.17 [1.10–1.25], p<0.001; 2: HR 1.18 [1.11–1.26], p<0.001) and in the non-AMI subgroup (1: HR 1.39 [1.21–1.6], p<0.001; 2: 1.49 [1.28–1.74], p<0.001), but no significant association in the AMI subgroup (1: HR 1.02 [0.91–1.13], p=0.79; 2: 1.03 [0.93–1.3], p=0.55). The addition of hs-TnI to cardiovascular risk factors for the prediction of overall mortality led to a similar increment in the c-index by both hs-TnI assays of 0.014; p=0.034 (1) and 0.015; p=0.037 (2), respectively.

Figure 1. Overall mortality

Conclusion

Hs-TnI assayed on admission is an independent predictor of adverse outcome beyond conventional risk factors in patients presenting to the emergency department with suspected but ruled-out diagnosis of AMI. In patients with the established diagnosis of AMI hs-TnI is not predictive for adverse outcome. Our findings demonstrate the potential role of hs-TnI as a biomarker for risk prediction. Both assessed hs-TnI assays performed equally in predicting adverse events.

P1642High-sensitivity cardiac troponin I and NT-proBNP and their relationship to heart failure in the European BiomarCaRE population

Aims

Heart failure (HF) is an increasingly important contributor to the overall burden of cardiovascular disease in the population. We aimed to determine the distribution of the cardiac biomarkers high-sensitivity cardiac troponin I (hs-cTnI) and N-terminal prohormone of brain natriuretic peptide (NT-proBNP) concentrations across the European population to characterize the association with incident HF.

Methods and results

Based on the Biomarkers for Cardiovascular Risk Assessment in Europe (BiomarCaRE)-project, we analysed data of 48,455 individuals from four prospective population-based cohort studies (DanMONICA, FINRISK, Moli-Sani, Northern Sweden MONICA study) across Europe with a maximum follow-up of 27 years. The median age of the participants was 50.7 years (25th percentile: 40.0 years, 75th percentile: 61.7 years) and 49.1% (25,146) were men. Considered endpoints were incident HF and all-cause mortality. The median follow-up time for occurrence of HF was 6.61 (6.55; 6.66) years. We found that cardiovascular risk factors (CVRFs), especially diabetes with HR of 2.11 (95% CI 1.8, 2.5) and smoking status with HR of 1.79 (95% CI 1.59, 2.1) (Figure 1) were associated with incident HF. Furthermore, beyond the CVRFs, elevated hs-cTnI and NT-proBNP concentrations contributed to risk of HF in the general population with HR of 1.49 (95% CI 1.21, 1.9) and HR of 2.37 (95% CI 1.97, 3.0) respectively. As a cut-off value to select individuals, who would benefit most from preventive strategies, a hs-cTnI concentration of 2.8 ng/L was calculated using the optimal cut-off methodology by Contal and O'Quigley in CSDA 1999.

Hazard ratio for incident HF

Conclusion

In our large population-based cohort, hs-cTnI and NT-proBNP were independently associated with incident HF. Use of biomarkers for HF screening thus may help to select those individuals in the general population who would benefit most from preventive strategies. Based on the cut-off value future studies are needed to evaluate therapeutic options.

On inotropic effects of UTP in the human heart

Uridine 5'-triphosphate (UTP) exerts a positive inotropic effect (PIE) in isolated electrically driven isolated right atrial trabeculae carneae from patients undergoing heart surgery. This review discusses some aspects of the current knowledge on the putative receptor(s) involved and the potential biochemical transduction steps leading to the PIE.

Initial Characterization of Transgenic Mice Overexpressing Human Histamine H2 Receptors

In an integrative approach, we studied the role of histamine H₂ receptors in the mouse heart. We noted that histamine, added cumulatively to the organ bath, failed to affect the force of contraction in left atrial preparations and did not change spontaneous heart rate in right atrial preparations from wild-type mice. By contrast, in the same preparations from mice that overexpressed the human H₂ receptor in a cardiac-specific way, histamine exerted concentration- and time-dependent positive inotropic and positive chronotropic effects. Messenger RNA of the human H₂ receptor was only detected in transgenic mice. Likewise, immunohistology and autoradiography only gave signals in transgenic but not in wild-type cardiac preparations. Similarly, a positive inotropic and positive chronotropic effect was observed with histamine in echocardiography of living transgenic mice and isolated perfused hearts (Langendorff preparation). Phosphorylation of phospholamban was increased in atrial and ventricular preparations from transgenic mice, but not in wild-type animals. The effects of histamine were mimicked by dimaprit and amthamine and antagonized by cimetidine. In summary, we generated a new model to study the physiologic and pathophysiologic cardiac role of the human H₂ receptor.

Multiplexed antibody detection from blood sera by immobilization of in vitro expressed antigens and label-free readout via imaging reflectometric interferometry (iRIf)

The detection of antibodies from blood sera is crucial for diagnostic purposes. Miniaturized protein assays in combination with microfluidic setups hold great potential by enabling automated handling and multiplexed analyses. Yet, the separate expression, purification, and storage of many individual proteins are time consuming and limit applicability. In vitro cell-free expression has been proposed as an alternative procedure for the generation of protein assays. We report the successful in vitro expression of different model proteins from DNA templates with an optimized expression mix. His₁₀-tagged proteins were specifically captured and immobilized on a Ni-NTA coated sensor surface directly from the in vitro expression mix. Finally, the specific binding of antibodies from rabbit-derived blood sera to the immobilized proteins was monitored by imaging reflectometric interferometry (iRIf). Antibodies in the blood sera could be identified by binding to the respective epitopes with minimal cross reactivity. The results show the potential of in vitro expression and label-free detection for binding assays in general and diagnostic purposes in specific.

High non-specific binding of the β1-selective radioligand 2-125I-ICI-H

Aim: As results of cardiac biopsies suggest, myocardial β1-adrenoceptor density is reduced in patients with chronic heart failure. However, changes in cardiac β2-adrenoceptors vary. With suitable radiopharmaceuticals single photon emission computed tomography (SPECT) and positron emission tomography (PET) offer the opportunity to assess β-adrenoceptors non-invasively. Among the novel racemic analogues of the established β1-selective adrenoceptor antagonist ICI 89.406 the iodinated 2-I-ICI-H showed high affinity and selectivity to β1-adrenoceptors in murine ventricular membranes. The aim of this study was its evaluation as a putative sub-type selective β1-adrenergic radioligand in cardiac imaging. Methods: Competition studies in vitro and in vivo were used to investigate the kinetics of 2-I-ICI-H binding to cardiac β-adrenoceptors in mice and rats. In addition, the radiosynthesis of 2-125I-ICI-H from the silylated precursor 2-SiMe3-ICI-H was established. The specific activity was 80 GBq/µmol, the radiochemical yield ranged from 70 to 80%.

Results: The unlabelled compound 2-I-ICI-H showed high β1-selectivity and -affinity in the in vitro competition studies. In vivo biodistribution studies apparently showed low affinity to cardiac β-adrenoceptors. The radiolabelled counterpart 2-125I-ICI-H showed a high degree of non-specific binding in vitro and no specific binding to cardiac β1-adrenoceptors in vivo. Conclusion: Because of its high non-specific binding 2-125I-ICI-H is no suitable radiotracer for imaging in vivo.

Myopathie der Labrador Retriever: neuromuskuläre Veränderungen bei kranken und klinisch gesunden Hunden

Gegenstand und Ziel: Die erbliche Myopathie der Labrador Retriever (LM) ist eine autosomal rezessive Krankheit, die bei schwarzen und gelben Tieren beiderlei Geschlechts und unterschiedlichen Alters vorkommt. Um der Frage nachzugehen, welche Rolle die LM in der hiesigen Labradorpopulation spielt, wurden seit 1998 am Institut für Neuropathologie der Universität Düsseldorf Muskel-und Nervenbiopsien von 121 Labrador Retrievern untersucht. Hunde: Die Tiere gehörten zu zwei Untersuchungsgruppen. Gruppe I (Einsendungen) umfasste 63 Labrador Retriever unterschiedlicher Herkunft aus Deutschland, Schweiz, Italien und Portugal mit Symptomen einer Myopathie. Gruppe II (Zuchttiere): Im Rahmen einer genetischen Studie wurden 58 miteinander verwandte Labrador Retriever aus einer Zucht in der Schweiz untersucht, nachdem dort bei zwei Welpen LM nachgewiesen worden war. Ergebnisse: Gruppe I: 17/63 (27%) hatten eine degenerative Myopathie vom Typ der Labrador-Myopathie, 8/63 (13%) metabolisch-mitochondriale Veränderungen, 33/63 (52%) andere (überwiegend neurogene oder entzündliche) Myopathien und bei 5/63 (8%) wurden keine pathologischen Veränderungen in Muskel und/oder Nerv nachgewiesen. Gruppe II: Zwar hatten nur sieben Tiere der Zucht klinische Symptome, doch wies die Mehrzahl morphologisch und histochemisch nachweisbare neuromuskuläre Veränderungen auf, nämlich 37/58 (64%) solche vom Typ der LM, darunter auch die Eltern und die sieben Geschwister der beiden Welpen, und 11/58 (19%) vorherrschend metabolisch-mitochondriale Veränderungen. Schlußfolgerungen: Die vorliegende Untersuchung zeigt, dass (a) die Verbreitung der erblichen Myopathie und deren Erfassung ein ernst zu nehmendes Problem beim Labrador Retriever darstellt und (b) neben der »klassischen« erblichen Typ-2-Myopathie der Labrador Retriever möglicherweise noch eine zweite, metabolisch-mitochondriale Form der Myopathie besteht, die Ähnlichkeiten mit einer anstrengungsabhängigen Myopathie bei Labrador Retrievern in den USA aufweist.