A candidate liquid chromatography mass spectrometry reference method for the quantification of the cardiac marker 1-32 B-type natriuretic peptide.

BACKGROUND: B-type natriuretic peptide (BNP) is a 32 amino acid cardiac hormone routinely measured by immunoassays to diagnose heart failure. While it is reported that immunoassay results can vary up to 45%, no attempt of standardization and/or harmonization through the development of certified reference materials (CRMs) or reference measurement procedures (RMPs) has yet been carried out. METHODS: B-type natriuretic peptide primary calibrator was quantified traceably to the International System of Units (SI) by both amino acid analysis and tryptic digestion. A method for the stabilization of BNP in plasma followed by protein precipitation, solid phase extraction (SPE) and liquid chromatography (LC) mass spectrometry (MS) was then developed and validated for the quantification of BNP at clinically relevant concentrations (15-150 fmol/g). RESULTS: The candidate reference method was applied to the quantification of BNP in a number of samples from the UK NEQAS Cardiac Markers Scheme to demonstrate its applicability to generate reference values and to preliminary evaluate the commutability of a potential CRM. The results from the reference method were consistently lower than the immunoassay results and discrepancy between the immunoassays was observed confirming previous data. CONCLUSIONS: The application of the liquid chromatography-mass spectrometry (LC-MS) method to the UK NEQAS samples and the correlation of the results with the immunoassay results shows the potential of the method to support external quality assessment schemes, to improve understanding of the bias of the assays and to establish RMPs for BNP measurements. Furthermore, the method has the potential to be multiplexed for monitoring circulating truncated forms of BNP.

Plant invasion and fragmentation indirectly and contrastingly affect native plants and grassland arthropods.

Plant invasion and habitat fragmentation have a detrimental effect on biodiversity in nearly all types of ecosystems. We compared the direct and indirect effects of the invasion of the common milkweed (Asclepias syriaca) on biodiversity patterns in different-sized Hungarian forest-steppe fragments. We assessed vegetation structure, measured temperature and soil moisture, and studied organisms with different ecological roles in invaded and non-invaded sites of fragments: plants, bees, butterflies, flower-visiting wasps, flies, true bugs, and spiders. Temperature and soil moisture were lower in invaded than in non-invaded area. Milkweed had a positive effect on plant species richness and flower abundance. In contrast, we mainly found indirect effects of invasion on arthropods through alteration of physical habitat characteristics and food resources. Pollinators were positively affected by native flowers, thus, milkweed indirectly supported pollinators. Similarly, we found higher species richness of herbivores in invaded sites than control sites, as species richness of true bugs also increased with increasing plant species richness. Predators were positively affected by complex vegetation structure, higher soil moisture and lower temperature. Furthermore, increasing fragment size had a strong negative effect on spider species richness of non-invaded sites, but no effect in invaded sites. Especially, grassland specialist spiders were more sensitive to fragment size than generalists, whereas generalist spider species rather profited from invasion. Although milkweed invades natural areas, we did not identify strong negative effects of its presence on the diversity of the grassland biota. However, the supportive effect of milkweed on a few generalist species homogenises the communities. The rate of invasion might increase with increasing fragmentation, therefore we recommend eliminating invasive plants from small habitat fragments to preserve the native biota. Focusing also on generalist species and revealing the indirect effects of invasions are essential for understanding the invasion mechanisms and would support restoration efforts.

Functional composition of ant assemblages in habitat islands is driven by habitat factors and landscape composition.

Fragmented natural habitats within human-transformed landscapes play a key role in preserving biodiversity. Ants as keystone species are essential elements of terrestrial ecosystems; thus, it is important to understand the factors influencing their presence. In a large-scale multi-site study, we surveyed ant assemblages using sweep netting and D-vac sampling on 158 ancient burial mounds preserving grassland habitats in agricultural landscapes in East-Hungary. We asked the following questions: (1) How do habitat factors and landscape composition affect species richness and functional diversity of ants? (2) Which ant traits are affected by habitat factors and landscape composition? Despite their small sizes, mounds as permanent and relatively undisturbed landscape elements could provide safe havens for diverse ant assemblages even in transformed agricultural landscapes. The complex habitat structure of wooded mounds supported high species and functional diversity of ant assemblages. Ant species on wooded mounds had small or medium-sized colonies, enabling the co-existence of more species. The effect of landscape composition on ant assemblages was mediated by habitat factors: steep slopes buffered the negative effect of the cropland matrix and enabled higher ant diversity.

Behaviours indicating cannibalistic necrophagy in ants are modulated by the perception of pathogen infection level.

Cannibalistic necrophagy is rarely observed in social hymenopterans, although a lack of food could easily favour such behaviour. One of the main supposed reasons for the rarity of necrophagy is that eating of nestmate corpses carries the risk of rapid spread of pathogens or parasites. Here we present an experimental laboratory study on behaviour indicating consumption of nestmate corpses in the ant Formica polyctena. We examined whether starvation and the fungal infection level of the corpses affects the occurrence of cannibalistic necrophagy. Our results showed that the ants distinguished between corpses of different types and with different levels of infection risk, adjusting their behaviour accordingly. The frequency of behaviours indicating cannibalistic necrophagy increased during starvation, although these behaviours seem to be fairly common in F. polyctena even in the presence of other food sources. The occurrence and significance of cannibalistic necrophagy deserve further research because, in addition to providing additional food, it may be part of the hygienic behaviour repertoire. The ability to detect infections and handle pathogens are important behavioural adaptations for social insects, crucial for the fitness of both individual workers and the entire colony.