Genomic comparisons reveal biogeographic and anthropogenic impacts in the koala (Phascolarctos cinereus): a dietary-specialist species distributed across heterogeneous environments

The Australian koala is an iconic marsupial with highly specific dietary requirements distributed across heterogeneous environments, over a large geographic range. The distribution and genetic structure of koala populations has been heavily influenced by human actions, specifically habitat modification, hunting and translocation of koalas. There is currently limited information on population diversity and gene flow at a species-wide scale, or with consideration to the potential impacts of local adaptation. Using species-wide sampling across heterogeneous environments, and high-density genome-wide markers (SNPs and PAVs), we show that most koala populations display levels of diversity comparable to other outbred species, except for those populations impacted by population reductions. Genetic clustering analysis and phylogenetic reconstruction reveals a lack of support for current taxonomic classification of three koala subspecies, with only a single evolutionary significant unit supported. Furthermore, similar to 70% of genetic variance is accounted for at the individual level. The Sydney Basin region is highlighted as a unique reservoir of genetic diversity, having higher diversity levels (i.e., Blue Mountains region; AvHe(corr)-0.20, PL% = 68.6). Broad-scale population differentiation is primarily driven by an isolation by distance genetic structure model (49% of genetic variance), with clinal local adaptation corresponding to habitat bioregions. Signatures of selection were detected between bioregions, with no single region returning evidence of strong selection. The results of this study show that although the koala is widely considered to be a dietary-specialist species, this apparent specialisation has not limited the koala's ability to maintain gene flow and adapt across divergent environments as long as the required food source is available

Nastal čas prodloužit dobu expirace kryoprezervovaných alograftů srdečních chlopní

V současné době existuje velké množství umělých komerčních náhrad chlopní. Přesto jsou stále žádané a úspěšně transplantované kryoprezervované semilunární alografty srdečních chlopní (C-AHV). U těchto náhrad zatím není přesně definována doba expirace.Většina tkáňových bank používá pět let. Z fyziologického, funkčního a operačního pohledu představuje morfologie a mechanické vlastnosti aortálních a pulmonárních kořenů hlavní limitaci doby expirace C-AHV. Cílem této práce je podat přehled metod strukturní a mechanické analýzy tkání AHV, které jsou vhodné pro stanovení doby expirace. alograftů. Pro stanovení mikrostruktury je vhodná kvantitativní morfologie za použití stereologické testovací mřížky. Touto metodou lze snadno, efektivně a opakovatelně stanovit možství buněk a mezibuněčných komponent. Pro stanovení mechanických parametrů, jako Youngův modul pružnosti, mezní napětí a deformace, lze využít tahovou zkoušku. C-AHV jsou v různých tkáňových laboratořích připravovány podle různých protokolů. Je tedy nutné, aby každá laboratoř stanovila dobu expirace samostatně.Despite the wide choice of commercial heart valve prostheses, cryopreserved semilunar allograft heart valves (C-AHV) are required, and successfully transplanted in selected groups of patients. The expiration limit (EL) criteria have not been defined yet. Most Tissue Establishments (TE) use the EL of 5 years. From physiological, functional, and surgical point of view, the morphology and mechanical properties of aortic and pulmonary roots represent basic features limiting the EL of C-AHV. The aim of this work was to review methods of AHV tissue structural analysis and mechanical testing from the perspective of suitability for EL validation studies. Microscopic structure analysis of great arterial wall and semilunar leaflets tissue should clearly demonstrate cells as well as the extracellular matrix components by highly reproducible and specific histological staining procedures. Quantitative morphometry using stereological grids has proved to be effective, as the exact statistics was feasible. From mechanical testing methods, tensile test was the most suitable. Young’s moduli of elasticity, ultimate stress and strain were shown to represent most important AHV tissue mechanical characteristics, suitable for exact statistical analysis. C-AHV are prepared by many different protocols, so as each TE has to work out own EL for C-AHV