Experimentelle Untersuchungen zur radialen Durchschallung von Stämmen mittels variabler Frequenz

Zusammenfassung: Es wurden unterschiedliche Kenngrössen von Ultraschallsignalen für die Erkennung von Defekten in Stämmen getestet. Es zeigte sich, dass durch Messung der Schallgeschwindigkeit die besten Ergebnisse erzielt werden. Proben mit einer künstlich eingebrachten Bohrung mit 30mm Durchmesser konnten über die Schallgeschwindigkeit von solchen mit 100mm Durchmesser separiert werden. Das Füllen der Hohlräume mit Sägespänen bewirkte keinen Unterschied der Messergebnisse. Die Parameter RMS, Peak to Peak, Amplitude und Signalenergie erbrachten keine verwertbaren Ergebnisse. Die Signalamplitude korreliert stark mit der Dichte und der Holzfeucht

Die Rolle der Mcp-1/Ccl2-abhängigen Rekrutierung von Makrophagen in der Progression der chronischen Niereninsuffizienz, dargestellt am Beispiel der diabetischen Nephropathie und des Alport-Syndroms in der Maus

Mit der vorliegenden Studie wurde am Beispiel der diabetischen Nephropathie und der Nephropathie beim Alport-Syndrom die Rolle des Chemokins "macrophage chemoattractant protein-1" (Mcp-1) bei der Progression der chronischen Niereninsuffizienz untersucht, da es die damit assoziierte Rekrutierung von Makrophagen in die Niere vermittelt und in Korrelation zum Erkrankungsstadium verstärkt exprimiert bzw. verstärkt im Urin ausgeschieden wird. Mcp-1-defiziente diabetische Mäuse zeigen zudem eine verlangsamte Progression. Eine therapeutische Blockade von Mcp-1 sollte daher die Infiltration von Makrophagen reduzieren und mit geringerer Nierenschädigung einhergehen. Mcp-1 wurde bei uninephrektomierten db/db-Mäusen mit fortgeschrittener diabetischer Nephropathie und bei Kollagen-IV-a3-defizienten Mäusen mit autosomal-rezessiver Alport-Nephropathie mit einem neuartigen Antagonisten, dem Spiegelmer mNOX-E36-3’PEG blockiert. Bei uninephrektomierten db/db-Mäusen führte die achtwöchige Behandlung mit dem Spiegelmer zu einer Reduktion der glomerulären Makrophagen um 40 % und der tubulointerstitiellen Makrophagen um 53 %. Dies war assoziiert mit einer signifikanten Reduktion glomerulärer und tubulointerstitieller Schäden sowie einer Verbesserung der glomerulären Filtrationsrate (GFR). Daneben konnte die Expression von Mcp-1 und Ccr2 in der Niere signifikant reduziert werden. Bei Kollagen-defizienten Mäusen führte die sechs- bzw. dreiwöchige Behandlung zu einer Reduktion der glomerulären Makrophagen um 50 % und der tubulointerstitiellen Makrophagen um 30 %. Dies war jedoch weder mit einer Reduktion der Nierenschädigung oder der Expression von Mcp-1 und Ccr2, noch mit einer Verlängerung des Überlebens assoziiert. Zusammenfassend konnte gezeigt werden, dass die spät begonnene therapeutische Blockade von Mcp-1 durch das Spiegelmer mNOX-E36-3’PEG bei der db/db-Maus einen Schutz vor Glomerulosklerose bietet, die tubulointerstitielle Schädigung reduziert und die Nierenfunktion verbessert. Die Therapie mit anti-Mcp-1-Spiegelmeren könnte demnach das derzeitige Behandlungsregime der Diabetes-assoziierten chronischen Niereninsuffizienz um einen neuen Therapieansatz ergänzen und so die Progression verlangsamen. Beim Alport-Syndrom konnte die therapeutische Blockade von Mcp-1 durch das Spiegelmer mNOX-E36-3’PEG nicht vor Glomerulosklerose schützen, die tubulointerstitielle Schädigung nicht reduzieren, die Nierenfunktion nicht verbessern und das Überleben nicht verlängern. Ein Einfluss auf die Progression des Alport-Syndroms konnte nicht nachgewiesen werden. Die Therapie mit anti-Mcp-1-Spiegelmeren bietet demnach keine zusätzliche Behandlungsoption bei der hereditären Alport-Nephropathie

Cardiac Macrophages and Their Effects on Arrhythmogenesis

Cardiac electrophysiology is a complex system established by a plethora of inward and outward ion currents in cardiomyocytes generating and conducting electrical signals in the heart. However, not only cardiomyocytes but also other cell types can modulate the heart rhythm. Recently, cardiac macrophages were demonstrated as important players in both electrophysiology and arrhythmogenesis. Cardiac macrophages are a heterogeneous group of immune cells including resident macrophages derived from embryonic and fetal precursors and recruited macrophages derived from circulating monocytes from the bone marrow. Recent studies suggest antiarrhythmic as well as proarrhythmic effects of cardiac macrophages. The proposed mechanisms of how cardiac macrophages affect electrophysiology vary and include both direct and indirect interactions with other cardiac cells. In this review, we provide an overview of the different subsets of macrophages in the heart and their possible interactions with cardiomyocytes under both physiologic conditions and heart disease. Furthermore, we elucidate similarities and differences between human, murine and porcine cardiac macrophages, thus providing detailed information for researchers investigating cardiac macrophages in important animal species for electrophysiologic research. Finally, we discuss the pros and cons of mice and pigs to investigate the role of cardiac macrophages in arrhythmogenesis from a translational perspective

A simple anisotropy correction procedure for acoustic wood tomography

Anisotropy of acoustic propagation velocities is a ubiquitous feature of wood. This needs to be considered for successful application of travel time tomography, an increasingly popular technique for non-destructive testing of living trees. We have developed a simple correction scheme that removes first-order anisotropy effects. The corrected travel-time data can be inverted with isotropic inversion codes that are commercially available. Using a numerical experiment, we demonstrate the consequences of ignoring anisotropy effects and outline the performance of our correction scheme. The new technique has been applied to two spruce samples. Subsequent inspection of the samples revealed a good match with the tomogram

Recent advances in the genetics of atrial fibrillation: from rare and common genetic variants to microRNA signaling

Besides traditional risk factors, atrial fibrillation (AF) also shares a strong genetic component. Here, we review the genetics of AF including monogenic forms of AF, heritability of AF, complex genetic risk of AF, and the role of microRNAs in AF pathophysiology. Thirtytwo mutations (17 genes) have been reported to cause familial AF. Mutations in cardiac ion channel genes or their subunits alter electrical properties and thereby lead to AF. Recently, also non-ion channel gene mutations have been identified to cause familial AF. Twin and community-based studies suggested AF to be heritable also on the population level. The AF risk in the offspring of an affected first-degree relative ranged between 2- to 5-fold, depending on the age of onset. Thereby, the risk of AF increases gradually the earlier the youngest relative of an AF patient developed the arrhythmia. African Americans bear a lesser risk of AF compared to individuals of European ancestry. Their risk rises with increasing European admixture. Genome wide association studies have revealed loci on chromosomes 4q25, 16q21 and 1q21 conferring risk of AF. Very recently, another consortial effort has identified a novel locus on chromosome 1, intronic to IL6R. IL6R encodes the a subunit of the interleukin 6 receptor. MicroRNAs were shown to regulate gene expression, and are increasingly reported to modify AF. A hallmark of AF pathophysiology is electrical and structural remodeling. MicroRNAs are involved in this process by regulating gene expression of cardiac ion channels, calcium handling proteins, transcription factors, and extracellular matrix related proteins

Functional Characterization of Rare Variants in the SHOX2 Gene Identified in Sinus Node Dysfunction and Atrial Fibrillation

Sinus node dysfunction (SND) and atrial fibrillation (AF) often coexist; however, the molecular mechanisms linking both conditions remain elusive. Mutations in the homeobox-containing SHOX2 gene have been recently associated with early-onset and familial AF. Shox2 is a key regulator of sinus node development, and its deficiency leads to bradycardia, as demonstrated in animal models. To provide an extended SHOX2 gene analysis in patients with distinct arrhythmias, we investigated SHOX2 as a susceptibility gene for SND and AF by screening 98 SND patients and 450 individuals with AF. The functional relevance of the novel mutations was investigated in vivo and in vitro, together with the previously reported p.H283Q variant. A heterozygous missense mutation (p.P33R) was identified in the SND cohort and four heterozygous variants (p.G77D, p.L129=, p.L130F, p.A293=) in the AF cohort. Overexpression of the pathogenic predicted mutations in zebrafish revealed pericardial edema for p.G77D and the positive control p.H283Q, whereas the p.P33R and p.A293= variants showed no effect. In addition, a dominant-negative effect with reduced heart rates was detected for p.G77D and p.H283Q. In vitro reporter assays demonstrated for both missense variants p.P33R and p.G77D significantly impaired transactivation activity, similar to the described p.H283Q variant. Also, a reduced Bmp4 target gene expression was revealed in zebrafish hearts upon overexpression of the p.P33R mutant. This study associates additional rare variants in the SHOX2 gene implicated in the susceptibility to distinct arrhythmias and allows frequency estimations in the AF cohort (3/990). We also demonstrate for the first time a genetic link between SND and AF involving SHOX2. Moreover, our data highlight the importance of functional investigations of rare variants

Characterization of a porcine model of atrial arrhythmogenicity in the context of ischaemic heart failure

Atrial fibrillation (AF) is a major healthcare challenge contributing to high morbidity and mortality. Treatment options are still limited, mainly due to insufficient understanding of the underlying pathophysiology. Further research and the development of reliable animal models resembling the human disease phenotype is therefore necessary to develop novel, innovative and ideally causal therapies. Since ischaemic heart failure (IHF) is a major cause for AF in patients we investigated AF in the context of IHF in a close-tohuman porcine ischaemia-reperfusion model. Myocardial infarction (AMI) was induced in propofol/fentanyl/ midazolam-anaesthetized pigs by occluding the left anterior descending artery for 90 minutes to model ischaemia with reperfusion. After 30 days ejection fraction (EF) was significantly reduced and haemodynamic parameters (pulmonary capillary wedge pressure (PCWP), right atrial pressure (RAP), left ventricular enddiastolic pressure (LVEDP)) were significantly elevated compared to age/weight matched control pigs without AMI, demonstrating an IHF phenotype. Electrophysiological properties (sinus node recovery time (SNRT), atrial/AV nodal refractory periods (AERP, AVERP)) did not differ between groups. Atrial burst pacing at 1200 bpm, however, revealed a significantly higher inducibility of atrial arrhythmia episodes including AF in IHF pigs (3/15 vs. 10/16, p = 0.029). Histological analysis showed pronounced left atrial and left ventricular fibrosis demonstrating a structural substrate underlying the increased arrhythmogenicity. Consequently, selective ventricular infarction via LAD occlusion causes haemodynamic alterations inducing structural atrial remodeling which results in increased atrial fibrosis as the arrhythmogenic atrial substrate in pigs with IHF

Conquering the Jet Lag Era: Experiences from Virtual Interdisciplinary Collaboration across Continents

Mit der Ausschreibung International Virtual Academic Collaboration (IVAC) verfolgt der Förderträger DAAD die Ziele, die Studienangebote an deutschen Hochschulen und deren ausländischen Kooperationshochschulen zu flexibilisieren und den Studierenden einen erweiterten Zugang zur internationalen Hochschulbildung zu ermöglichen. In dem geförderten Projekt Collaborative International, Intercultural & Interdisciplinary Learning (COIIIL) zwischen den Partnerinstitutionen Technische Universität Dresden, Stellenbosch University, Shiraz University und Bucknell University wurden diese Ziele adressiert