István Magyary

Optimisation of Embryonic and Larval ECG Measurement in Zebrafish for Quantifying the Effect of QT Prolonging Drugs

Effective chemical compound toxicity screening is of paramount importance for safe cardiac drug development. Using mammals in preliminary screening for detection of cardiac dysfunction by electrocardiography (ECG) is costly and requires a large number of animals. Alternatively, zebrafish embryos can be used as the ECG waveform is similar to mammals, a minimal amount of chemical is necessary for drug testing, while embryos are abundant, inexpensive and represent replacement in animal research with reduced bioethical concerns. We demonstrate here the utility of pre-feeding stage zebrafish larvae in detection of cardiac dysfunction by electrocardiography. We have optimised an ECG recording system by addressing key parameters such as the form of immobilization, recording temperature, electrode positioning and developmental age. Furthermore, analysis of 3 days post fertilization (dpf) zebrafish embryos treated with known QT prolonging drugs such as terfenadine, verapamil and haloperidol led to reproducible detection of QT prolongation as previously shown for adult zebrafish. In addition, calculation of Z-factor scores revealed that the assay was sensitive and specific enough to detect large drug-induced changes in QTc intervals. Thus, the ECG recording system is a useful drug-screening tool to detect alteration to cardiac cycle components and secondary effects such as heart block and arrhythmias in zebrafish larvae before free feeding stage, and thus provides a suitable replacement for mammalian experimentation.

Synthesis of azetidines and pyrrolidines via iodocyclisation of homoallyl amines and exploration of activity in a zebrafish embryo assay

Room temperature iodocyclisation of homoallylamines stereoselectively delivers functionalised 2-(iodomethyl)azetidine derivatives in high yield. Increasing reaction temperature from 20 °C to 50 °C switches the reaction outcome to realise the stereoselective formation of functionalised 3-iodopyrrolidine derivatives. It was shown that these pyrrolidines are formed via thermal isomerisation of the aforementioned azetidines. Primary and secondary amines could be reacted with iodomethyl azetidine derivatives to deliver stable methylamino azetidine derivatives. With subtle changes to the reaction sequences homoallyl amines could be stereoselectively converted to either cis- or trans-substituted 3-amino pyrrolidine derivatives at will. The stereochemical divergent synthesis of cis and trans substituted pyrrolidines supports an ion part, aziridinium, isomerisation pathway for azetidine to pyrrolidine isomerisation. Six azetidine derivatives were probed in a zebrafish embryo developmental assay to detect potential biological effects through the analysis of morphology and motility behaviour phenotypes. The range of effects across the probed molecules demonstrates the suitability of this assay for screening azetidine derivatives. One of the probed molecules, rac-(((cis)-1-benzyl-4-phenylazetidin-2-yl)methyl)piperidine, exhibited particularly interesting effects in the developmental assay presenting with hypopigmentation and reduced circulation amongst others. This shows that the zebrafish embryo provides a fast, sensitive and effective way to screen new compounds and in the future in combination with existing in vivo and in vitro assays it will become an integral part in drug discovery and development.

Preliminary studies on the genetic variability of six Hungarian common carp strains using microsatellite DNA markers

Genetic variation in six Hungarian common carp (Cyprinus carpio L.) strains was evaluated using 12 microsatellite loci. The domesticated (‘Tatai’, ‘Biharugrai’ and ‘Szarvasi’) strains were derived from fish farms. Two of wild strains (‘Tiszai’ and ‘Dunai’) were sampled from brood stocks maintained at fish farms for breeding, and ‘Kis-Balatoni’ wild carp were sampled from the Small Balaton Lake. Pairwise Fst-values (0.013–0.161) were highly significant (p < 0.0001), demonstrating differentiation among strains. The mean number of alleles ranged between 3.9 and 8.2. Overall mean observed heterozygosity was lower (0.557) than the mean expected heterozygosity (0.700). By strain, the only exception to this trend was the Dunai (Danubian), which showed higher mean observed heterozygosity (0.764) than expected (0.602). For five loci the Dunai strain showed extremely high levels of heterozygosity (1.00). Two wild strains exhibited a number of loci (Tiszai, 4; Dunai, 6) that were not in Hardy–Weinberg equilibrium. A relatively high number of private alleles overall (n=26), as well as differences in allele frequencies supported our ability to assign most individual fish (over 90%) to each strain.

Genetic diversity of the European pond turtle (Emys orbicularis) in the South-West region of Hungary – first results

A set of five polymorphic microsatellite markers developed in Emydoidea blandingii was characterized for crossspecies amplification in the European pond turtle, Emys orbicularis. The markers were tested for polymorphism in a total of 155 turtles sampled in four natural habitats in the Danube-Drava National Park, South-West Hungary in order to determine the genetic diversity of European pond turtle populations and to check the functionality of existing ecological corridors in the region. The number of alleles varied from 5 to 24. Observed heterozygosity was moderate (0.43-0.55), while the level for expected heterozygosity ranged from 0.76 to 0.80. Significant heterozygote deficit was found in the populations accompanied by a low degree of genetic differentiation (FST ranges from 0.0166 to 0.0652). Wahlund effect was demonstrated in two populations. The ecological corridor between two water catchment areas (Lake Balaton and Drava River) fulfils its role only partially.