Magic Modeling of Long-Term Lake Water and Soil Chemistry at Abborrträsket, Northern Sweden

The geochemical model MAGIC has been applied to the Abborrträsket lake catchment in northern Sweden for the period 1843-2000. The two objectives were to 1.) simulate historical biogeochemical fluxes and pools and 2.) test whether the MAGIC model of biogeochemical cycling contradicts the published diatom record of a relatively stable pH (around 6) during the last two centuries in this weakly buffered, acid sensitive lake. Abborrträsket has received elevated sulfur and nitrogen deposition in the second half of the 20th Century and had a large part of its catchment clearcut in 1975. The MAGIC simulation of very small pH decline from 6.1 to 5.9 between 1843 and 1987 was comparable to the published diatom reconstructions of almost stable lake water pH up until the lake was limed in 1988. MAGIC also simulated the modern soil and water chemistry, including lake liming. Thus the diatom indication of stable pH cannot be dismissed as necessarily incorrect.     

3D reconstruction of the rat adrenal medulla

We performed 3D reconstruction of the microscopic structure of the adrenal medulla of the adult rats using serial histological sections with histochemical differentiation of adrenaline-storing (A) and noradrenaline-storing (NA) cells. Medulla volume is 1.18 ± 0.17 mm³. Chromaffin tissue consists of 82.9 ± 2.6% of A and 17.1 ± 2.6% of NA cells. Cords of the chromaffinocytes run along the nerves in the adrenal cortex and form cones when merging with medulla bulk. There is no unambiguously greater prevalence of A cells over NA in the areas of the medulla bordering on the cortex as compared to deep layers of medulla. NA cells form a network of beams. Their concentration increases with distance from the entry site of the nerves and is maximal on the opposite side. This testifies to the fallacy of the point of view about the disordered distribution of NA cells in the medulla. Based on the polar asymmetric arrangement of the adrenal chromaffin tissue, if it is necessary to completely remove the medulla with the keeping or reimplantation of the cortex, the subcapsular cortex zone located on the pole opposite to the entrance of nerves should be chosen. In addition, comparable results in the stereological examination of the medulla can be obtained only if taking its areas similar in location. The pronounced relationship in the arrangement of A and NA cells with nerves clearly indicates that in vivo nerve factors play a key role in differentiation and stabilization of the A and NA cells phenotypes.     

Crystal structure of Escherichia coli MscS,a voltage-modulated and mechanosensitive channel

The mechanosensitive channel of small conductance (MscS) responds both to stretching of the cell membrane and to membrane depolarization. The crystal structure at 3.9 angstroms resolution demonstrates that Escherichia coli MscS folds as a membrane-spanning heptamer with a large cytoplasmic region. Each subunit contains three transmembrane helices (TM1, -2, and -3), with the TM3 helices lining the pore, while TM1 and TM2, with membrane-embedded arginines, are likely candidates for the tension and voltage sensors. The transmembrane pore, apparently captured in an open state, connects to a large chamber, formed within the cytoplasmic region, that connects to the cytoplasm through openings that may function as molecular filters. Although MscS is likely to be structurally distinct from other ion channels, similarities in gating mechanisms suggest common structural elements.     

Emergence and genetic variability of Anaplasma species in small ruminants and ticks from Central Europe

Anaplasmoses are common tick-borne zoonotic bacterial diseases of livestock and free-living ungulates from the genus Anaplasma that are recently emerging in Central Europe. The main aim of this study was to analyze the prevalence and genetic variability of Anaplasma phagocytophilum and Anaplasma ovis in small ruminants and questing ticks from six different sites in Slovakia and the Czech Republic using the PCR of the msp4 gene followed by the sequence analysis. At two farms from southeastern Slovakia, 66.1% small ruminants were infected with A. ovis in contrast to one positive animal from both sites in northern Slovakia. It was represented by two different genotypes. A. phagocytophilum was present in all tested flocks with the infection prevalence ranging from 0.9% to 5.7%. None of the tested questing ticks carried A. ovis. A. phagocytophilum was detected in 1.1% and 7.8% of questing Ixodes ricinus ticks collected around the farms located in southeastern and northern Slovakia, respectively. A. phagocytophilum revealed higher intraspecific diversity than A. ovis.     

Field maple and hornbeam populations along a 4-m elevation gradient in an alluvial forest

Tree species composition of Central European alluvial hardwood forests has changed with the arrival of flood-intolerant and mesic species. Within this group of tree species, a dominant role is played by field maple (Acer campestre) and European hornbeam (Carpinus betulus). This study was performed in the Lanzhot natural forests at the confluence of the Morava and the Dyje Rivers, which are considered to be one of the most natural alluvial hardwood forests in Central Europe and where the absence of the direct influence by humans for 75 years has allowed spontaneous development. Our basic research questions were as follows: (1) does the mutual proportion and structure of field maple and hornbeam populations change along an elevation gradient of 4 m in an alluvial forest and (2) does the tree spatial pattern of field maple and hornbeam change along this gradient? The study found significant differences in the development of hornbeam and field maple populations with increasing elevation in an alluvial hardwood forest. While the strength of the hornbeam population clearly increases with increasing elevation, the field maple population does not. Compared to hornbeam, field maple is closer to the r-strategy side of the K-r continuum on alluvial sites. Our study reveals that field maple and hornbeam are mainly distributed in clusters on alluvial sites. Both species are concentrated at places with lower flooding intensity, i.e. to higher elevation sites. The study shows that tree spatial patterns could change dynamically along a short elevation gradient in alluvial hardwood forest.     

Isolation of two seven-membered ring C58 fullerene derivatives: C58F17CF3 and C58F18

Fluorination of C60 at 550 degrees C leads to milligram quantities of two stable fullerene derivatives with 58-carbon cage structures: C58F18 and C58F17CF3. The compounds were characterized by mass spectrometry and fluorine nuclear magnetic resonance spectroscopy, and the data support a heptagonal ring in the framework. The resulting strain, which has hindered past attempts to prepare these smaller quasi-fullerenes, is mitigated here by hybridization change of some of the carbons in the pentagons from sp2 to sp3 because of fluorine addition. The loss of carbon from C60 is believed to occur via sequential fluorine addition to a CC single bond and an adjacent CC bond, followed by loss of a:CF2 carbene.     

Comparison of approaches towards ecotoxicity evaluation for the application of dredged sediment on soil

Purpose

The toxicity of 36 dredged sediments from the Czech Republic was investigated using a large battery of bioassays. The aim of this study was to investigate the feasibility of ecotoxicity testing in general and of individual bioassays more specific and to investigate how the results of bioassays are determined by the physicochemical properties of sediment samples and/or sediment contamination.

Material and methods

In 2008 and 2010, 36 sediment samples were collected from rivers and ponds and from sediment heaps in different parts of the Czech Republic. Both their physicochemical properties and their levels of contamination with POPs and heavy metals were analyzed. The ecotoxicities of the sediments were evaluated using the four bioassays from the new Czech directive 257/2009 Coll. concerning the application of dredged sediments on agricultural land (Enchytraeus crypticus reproduction, Folsomia candida reproduction, Lactuca sativa root elongation, and potential ammonium oxidation). The results of the four directive bioassays were compared with the results of other soil bioassays (Caenorhabditis elegans mortality, Eisenia fetida avoidance and reproduction) and eluate bioassays (Daphnia magna immobilization, Pseudokirchneriella subcapitata growth inhibition test, and Vibrio fischeri luminescence).

Results and discussion

We demonstrate that the battery suggested in Czech directive 257/2009 Coll. is highly effective in identifying toxic samples; these bioassays clearly revealing different types of toxicity and different exposure routes. Shorter alternative bioassays may be added especially when fast toxicity identification is needed. Eluate bioassays identified samples potentially hazardous to aquatic ecosystems. Their inclusion into the assessment scheme should be considered if the goal of assessment is also the protection of aquatic ecosystems. The results of our multivariate analysis show that specific physicochemical properties and contamination may affect bioassay responses. C. elegans was the most sensitive bioassay to physicochemical properties and also to organic contamination, while eluate bioassays were sensitive to heavy metal pollution.

Conclusions

Most effects detected by the bioassays could not be explained by the levels of toxicants measured or by the natural characteristics of sediments. Our results show that bioassays are irreplaceable in dredged sediment risk assessment because they complement information provided by chemical analyses.     

Methods of collection of plant root exudates in relation to plant metabolism and purpose: A review

The aim of this work is to review the current knowledge on the effects of plant metabolism (C₃, C₄, and CAM) on root exudation and on the methods of exudate collection as well as the use of such exudates for analyses, testing of microbial response, degradation of pollutants, enzymatic activities, and occurrence of allelochemicals. We examine the advantages and disadvantages of each method as related to the downstream use of the exudates. The use of continuous percolation of solid cultivation medium with adjustment of nutrient‐solution strength appears to be a promising methodology for the determination of root exudation rates and qualitative composition of exuded compounds. The method mimics rhizosphere conditions, minimizing the artificial accumulation of compounds, alteration of plasma‐membrane permeability, ATPase activity, and the impacts of inhibitors or stimulators of root enzymes. Of particular significance is the fact that the adjustment of strength of nutrient solution and percolation enables universal and also long‐term use of the method, allowing high exudation yield by minimizing influx and maximizing efflux rates of exuded compounds at high nutrient‐solution strength. Furthermore, it facilitates assessment of the effect on soil microbial populations and their ability to degrade pollutants. Enzymatic activities can be assessed when a low strength of nutrient solution is used, with percolation of the exudates directly into tested soils. Composition of root exudates, regulation of root enzymes, and plant response to nutrient deficiency can be assessed by measuring net efflux or influx rates. The impact of heavy metals and other type of mechanical, chemical, and biological stresses differs according to the type of plant metabolism. This has significant consequences on transformations in plant communities, both structurally and functionally, and impacts upon crop nutrition, with respect to global climate change, and the use of plants for phytoremediation purposes. Understanding the effects of different types of plant metabolism on root exudation with respect to genetic regulation of synthetic pathways through root enzymes and transport systems presents an important direction for future research.