N-Nervonoylsphingomyelin (C24:1) Prevents Lateral Heterogeneity in Cholesterol-Containing Membranes

This study was conducted to explore how the nature of the acyl chains of sphingomyelin (SM) influence its lateral distribution in the ternary lipid mixture SM/cholesterol/1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), focusing on the importance of the hydrophobic part of the SM molecule for domain formation. Atomic force microscopy (AFM) measurements showed that the presence of a double bond in the 24:1 SM molecule in mixtures with cholesterol (CHO) or in pure bilayers led to a decrease in the molecular packing. Confocal microscopy and AFM showed, at the meso- and nanoscales respectively, that unlike 16:0 and 24:0 SM, 24:1 SM does not induce phase segregation in ternary lipid mixtures with DOPC and CHO. This ternary lipid mixture had a nanomechanical stability intermediate between those displayed by liquid-ordered (Lo) and liquid-disordered (Ld) phases, as reported by AFM force spectroscopy measurements, demonstrating that 24:1 SM is able to accommodate both DOPC and CHO, forming a single phase. Confocal experiments on giant unilamellar vesicles made of human, sheep, and rabbit erythrocyte ghosts rich in 24:1 SM and CHO, showed no lateral domain segregation. This study provides insights into how the specific molecular structure of SM affects the lateral behavior and the physical properties of both model and natural membranes. Specifically, the data suggest that unsaturated SM may help to keep membrane lipids in a homogeneous mixture rather than in separate domains.     

Crystal and molecular structures of diglycosyl disulfide derivatives

The crystal and molecular structures of S-(2,3,4,6-tetra-O-acetyl-beta-d-glucopyranosyl)-S'-(2,3,4,6-tetra-O-acetyl-beta-d-galactopyranosyl)disulfide (1) and the mono-sulfoxide (3) of bis(2,3,4,6-tetra-O-acetyl-beta-d-glucopyranosyl)disulfide (2) are described. Comparison of 2 and 3, containing -S-S- and -S-S(O)- bonds, respectively, allows to delineate structural differences brought about by the different oxidation states of one of the sulfur atoms in carbohydrate disulfides.     

Effects of roads on brown bear movements and mortality in Slovakia

The increasing development of road infrastructure considerably contributes to bear habitat fragmentation. The aim of this study was to examine the relationship between brown bear movements and secondary roads. The 1463-km² study area in the north-central Slovakia was defined by the composite home ranges (minimum convex polygon (MCP) 100%) of 21 bears studied by GPS telemetry from 2008 to 2016. Additionally, we used the data of 35 bears struck by cars and trucks across all of Slovakia during 2007–2015. We found that a traffic volume exceeding 5000 vehicles per 24 h completely restricted the movement of bears. Bears were more likely to cross during periods of low- rather than high-traffic volumes, and crossings occurred primarily at night. Males were able to cross roads with annual average daily traffic up to 5000 vehicles per 24 h, whereas females were only able to cross roads with less than 4000 vehicles per 24 h. Bears, regardless of age and gender, crossed roads more frequently during hyperphagia (August to November) than during the mating season (April to July). This was additionally confirmed by the comparison of annual patterns of crossings and road kills, which both peaked in August. The movement of these bears across roads was particularly motivated by the search for attractive crops in fields. Road crossings and road kills mainly occurred around midnight. Understanding the temporal and spatial use of roads by brown bears should provide valuable information for land use planners to effectively minimise the negative impacts of roads on bears.     

Variation of cytosine methylation patterns in European beech (<Emphasis Type="Italic">Fagus sylvatica</Emphasis> L.)

The role of epigenetic phenomena in plant adaptation is becoming widely recognized and the potential of epigenetics for forestry practice has been demonstrated as well. In this study, methylation-sensitive amplification polymorphism (MSAP) markers were investigated in 20 European beech (Fagus sylvatica L.) provenances that cover most of Europe and were planted in two climatically contrasting provenance trial plots. Correlations of cytosine-methylation patterns at five loci and overall DNA methylation with climatic conditions of the sites of population origin and budburst phenology were detected, suggesting that methylation at particular loci was influenced by the weather or photoperiod during embryogenesis or even earlier. Alternation of methylation patterns may also have been caused by genetic mutation. Frequencies of methylation patterns at three loci differed between the two trial locations, indicating that a climatically induced change of methylation during the ontogeny occurs as well. The results suggest that the rules for collection, transfer, and use of forest reproductive materials should also consider epigenetic effects.     

Genetic variation in Tertiary relics: The case of eastern‐Mediterranean Abies (Pinaceae)

The eastern‐Mediterranean Abies taxa, which include both widely distributed species and taxa with minuscule ranges, represent a good model to study the impacts of range size and fragmentation on the levels of genetic diversity and differentiation. To assess the patterns of genetic diversity and phylogenetic relationships among eastern‐Mediterranean Abies taxa, genetic variation was assessed by eight nuclear microsatellite loci in 52 populations of Abies taxa with a focus on those distributed in Turkey and the Caucasus. Both at the population and the taxon level, the subspecies or regional populations of Abies nordmanniana s.l. exhibited generally higher allelic richness, private allelic richness, and expected heterozygosity compared with Abies cilicica s.l. Results of both the Structure analysis and distance‐based approaches showed a strong differentiation of the two A. cilicica subspecies from the rest as well as from each other, whereas the subspecies of A. nordmanniana were distinct but less differentiated. ABC simulations were run for a set of scenarios of phylogeny and past demographic changes. For A. ×olcayana, the simulation gave a poor support for the hypothesis of being a taxon resulting from a past hybridization, the same is true for Abies equi‐trojani: both they represent evolutionary branches of Abies bornmuelleriana.     

An in vitro testing of chemoresistance in leukaemic patients

The fact that leukaemic cells are primarily or secondarily resistant to cytostatics is a serious phenomenon, which leads to the failure of chemotherapy of malignant diseases in clinical practise. Some detoxification and transporting systems are responsible for the generation of chemoresistance on the cellular level and the decrease of effectiveness in treatment. In vitro testing of chemoresistance of leukaemic cells is presently an inseparable component of “tailoring” therapy in the developing field of predictive oncology. The aim of this work was to estimate profiles of drug resistance, based on the predictive in vitro test, and to help in choosing the most effective cytostatic. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazoline (MTT) assay was used, based on the direct effect of cytostatics on the viability of leukaemic cells in vitro. The number of living leukaemic cells was evaluated by a computer program, where LC₅₀ (concentration of cytostatics lethal to 50% of leukaemic cells) was established from the achieved dose-relation curves. Seventy-one samples of leukaemic cells isolated from the patients’ peripheral blood or bone marrow were examined. All samples were tested to 3 cytostatics minimally. It was found by the in vitro assay, that resistance to dexamethasone, prednisolone, etoposide and vincristine is increased in patients with acute myeloid leukaemia disease, compared to the acute lymphoblastic leukaemia patients. In patients with a relapsed disease population, leukaemic cells are highly heterogeneous in the MTT assay. It was concluded that the MTT assay can be used to study drug interactions in vitro in leukaemia samples. The type of interaction was highly different between patients, and depended on drug concentrations.