Large‐scale disturbance legacies and the climate sensitivity of primary Picea abies forests

Determining the drivers of shifting forest disturbance rates remains a pressing global change issue. Large‐scale forest dynamics are commonly assumed to be climate driven, but appropriately scaled disturbance histories are rarely available to assess how disturbance legacies alter subsequent disturbance rates and the climate sensitivity of disturbance. We compiled multiple tree ring‐based disturbance histories from primary Picea abies forest fragments distributed throughout five European landscapes spanning the Bohemian Forest and the Carpathian Mountains. The regional chronology includes 11,595 tree cores, with ring dates spanning the years 1750–2000, collected from 560 inventory plots in 37 stands distributed across a 1,000 km geographic gradient, amounting to the largest disturbance chronology yet constructed in Europe. Decadal disturbance rates varied significantly through time and declined after 1920, resulting in widespread increases in canopy tree age. Approximately 75% of current canopy area recruited prior to 1900. Long‐term disturbance patterns were compared to an historical drought reconstruction, and further linked to spatial variation in stand structure and contemporary disturbance patterns derived from LANDSAT imagery. Historically, decadal Palmer drought severity index minima corresponded to higher rates of canopy removal. The severity of contemporary disturbances increased with each stand's estimated time since last major disturbance, increased with mean diameter, and declined with increasing within‐stand structural variability. Reconstructed spatial patterns suggest that high small‐scale structural variability has historically acted to reduce large‐scale susceptibility and climate sensitivity of disturbance. Reduced disturbance rates since 1920, a potential legacy of high 19th century disturbance rates, have contributed to a recent region‐wide increase in disturbance susceptibility. Increasingly common high‐severity disturbances throughout primary Picea forests of Central Europe should be reinterpreted in light of both legacy effects (resulting in increased susceptibility) and climate change (resulting in increased exposure to extreme events).     

Phenological sensitivity to climate change is higher in resident than in migrant bird populations among European cavity breeders

Many organisms adjust their reproductive phenology in response to climate change, but phenological sensitivity to temperature may vary between species. For example, resident and migratory birds have vastly different annual cycles, which can cause differential temperature sensitivity at the breeding grounds, and may affect competitive dynamics. Currently, however, adjustment to climate change in resident and migratory birds have been studied separately or at relatively small geographical scales with varying time series durations and methodologies. Here, we studied differential effects of temperature on resident and migratory birds using the mean egg laying initiation dates from 10 European nest box schemes between 1991 and 2015 that had data on at least one resident tit species and at least one migratory flycatcher species. We found that both tits and flycatchers advanced laying in response to spring warming, but resident tit populations advanced more strongly in relation to temperature increases than migratory flycatchers. These different temperature responses have already led to a divergence in laying dates between tits and flycatchers of on average 0.94 days per decade over the current study period. Interestingly, this divergence was stronger at lower latitudes where the interval between tit and flycatcher phenology is smaller and winter conditions can be considered more favorable for resident birds. This could indicate that phenological adjustment to climate change by flycatchers is increasingly hampered by competition with resident species. Indeed, we found that tit laying date had an additional effect on flycatcher laying date after controlling for temperature, and this effect was strongest in areas with the shortest interval between both species groups. Combined, our results suggest that the differential effect of climate change on species groups with overlapping breeding ecology affects the phenological interval between them, potentially affecting interspecific interactions.     

Chromium Supplementation Reduces Resting Heart Rate in Patients with Metabolic Syndrome and Impaired Glucose Tolerance

Mental health problems are a major public health issue worldwide, and zinc may be associated with psychiatric symptoms, but such associations have not been investigated extensively. This study was conducted to evaluate the relationship between serum zinc levels and mental health problems in Korean adults. We used data from the Korean National Health and Nutrition Examination Survey V-1, a cross-sectional survey of Korean civilians. Data from 1748 subjects were analyzed. Serum zinc levels did not differ significantly according to psychiatric symptoms including sleep duration, stress, depressed mood, suicidal ideation, and whether respondents sought psychiatric consultation. The frequencies and odds ratios of psychiatric symptoms according to serum zinc tertiles were not significantly associated after adjusting for age, smoking, alcohol consumption, physical activity, body mass index, total body fat, and renal function and for daily fat, carbohydrate, and protein intake. Serum zinc levels may not be associated with psychiatric symptoms in Korean adults without psychiatric disorders.     

Ecological and methodological drivers of non-stationarity in tree growth response to climate

Radial tree growth is sensitive to environmental conditions, making observed growth increments an important indicator of climate change effects on forest growth. However, unprecedented climate variability could lead to non-stationarity, that is, a decoupling of tree growth responses from climate over time, potentially inducing biases in climate reconstructions and forest growth projections. Little is known about whether and to what extent environmental conditions, species, and model type and resolution affect the occurrence and magnitude of non-stationarity. To systematically assess potential drivers of non-stationarity, we compiled tree-ring width chronologies of two conifer species, Picea abies and Pinus sylvestris, distributed across cold, dry, and mixed climates. We analyzed 147 sites across the Europe including the distribution margins of these species as well as moderate sites. We calibrated four numerical models (linear vs. non-linear, daily vs. monthly resolution) to simulate growth chronologies based on temperature and soil moisture data. Climate–growth models were tested in independent verification periods to quantify their non-stationarity, which was assessed based on bootstrapped transfer function stability tests. The degree of non-stationarity varied between species, site climatic conditions, and models. Chronologies of P. sylvestris showed stronger non-stationarity compared with Picea abies stands with a high degree of stationarity. Sites with mixed climatic signals were most affected by non-stationarity compared with sites sampled at cold and dry species distribution margins. Moreover, linear models with daily resolution exhibited greater non-stationarity compared with monthly-resolved non-linear models. We conclude that non-stationarity in climate–growth responses is a multifactorial phenomenon driven by the interaction of site climatic conditions, tree species, and methodological features of the modeling approach. Given the existence of multiple drivers and the frequent occurrence of non-stationarity, we recommend that temporal non-stationarity rather than stationarity should be considered as the baseline model of climate–growth response for temperate forests.     

Purification and characterization of a nitrilase from Fusarium solani O1

An intracellular nitrilase was purified from a Fusarium solani O1 culture, in which the enzyme (up to 3000 U L⁻¹) was induced by 2-cyanopyridine. SDS-PAGE revealed one major band corresponding to a molecular weight of approximately 40 kDa. Peptide mass fingerprinting suggested a high similarity of the protein with the putative nitrilase from Gibberella moniliformis. Electron microscopy revealed that the enzyme molecules associated into extended rods. The enzyme showed high specific activities towards benzonitrile (156 U mg⁻¹) and 4-cyanopyridine (203 U mg⁻¹). Other aromatic nitriles (3-chlorobenzonitrile, 3-hydroxybenzonitrile) also served as good substrates for the enzyme. The rates of hydrolysis of aliphatic nitriles (methacrylonitrile, propionitrile, butyronitrile, valeronitrile) were 14–26% of that of benzonitrile. The nitrilase was active within pH 5–10 and at up to 50 °C with optima at pH 8.0 and 40–45 °C. Its activity was strongly inhibited by Hg²⁺ and Ag⁺ ions. More than half of the enzyme activity was preserved at up to 50% of n-hexane or n-heptane or at up to 15% of xylene or ethanol. Operational stability of the enzyme was examined by the conversion of 45 mM 4-cyanopyridine in a continuous and stirred ultrafiltration-membrane reactor. The nitrilase half-life was 277 and 10.5 h at 35 and 45 °C, respectively.     

Conserved DNA Motifs,Including the CENP-B Box-like,Are Possible Promoters of Satellite DNA Array Rearrangements in Nematodes

Tandemly arrayed non-coding sequences or satellite DNAs (satDNAs) are rapidly evolving segments of eukaryotic genomes, including the centromere, and may raise a genetic barrier that leads to speciation. However, determinants and mechanisms of satDNA sequence dynamics are only partially understood. Sequence analyses of a library of five satDNAs common to the root-knot nematodes Meloidogyne chitwoodi and M. fallax together with a satDNA, which is specific for M. chitwoodi only revealed low sequence identity (32–64%) among them. However, despite sequence differences, two conserved motifs were recovered. One of them turned out to be highly similar to the CENP-B box of human alpha satDNA, identical in 10–12 out of 17 nucleotides. In addition, organization of nematode satDNAs was comparable to that found in alpha satDNA of human and primates, characterized by monomers concurrently arranged in simple and higher-order repeat (HOR) arrays. In contrast to alpha satDNA, phylogenetic clustering of nematode satDNA monomers extracted either from simple or from HOR array indicated frequent shuffling between these two organizational forms. Comparison of homogeneous simple arrays and complex HORs composed of different satDNAs, enabled, for the first time, the identification of conserved motifs as obligatory components of monomer junctions. This observation highlights the role of short motifs in rearrangements, even among highly divergent sequences. Two mechanisms are proposed to be involved in this process, i.e., putative transposition-related cut-and-paste insertions and/or illegitimate recombination. Possibility for involvement of the nematode CENP-B box-like sequence in the transposition-related mechanism and together with previously established similarity of the human CENP-B protein and pogo-like transposases implicate a novel role of the CENP-B box and related sequence motifs in addition to the known function in centromere protein binding.     

Chromophoric peptide substrates for activity determination of animal aspartic proteinases in the presence of their zymogens: A novel assay

Solid-phase synthesis was used for the preparation of pyroglutamyl-histidyl-p-nitrophenylalanyl-phenylalanyl-alanyl-leucine amide (I) and glycyl-glycyl-histidyl-p-nitrophenylalanyl-phenylalanyl-alanyl-leucine amide (II), two water-soluble and sensitive chromophoric substrates of chicken pepsin, hog pepsin A, and bovine spleen cathepsin D. The kinetic constants of hydrolysis of the p-nitrophenylalanyl-phenylalanyl bond of the substrates were measured by difference spectrophotometry at 308 nm (Δ? = 860 m^?1 cm^?1) and by ninhydrin colorimetry (substrate I, ?₅₇₀ = 2.31 × 10⁴m^?1 cm^?1). The pH optimum of cleavage is 5 for the pepsins and 3.7 for cathepsin D. Since all three proteinases still have a significant activity at pH 5.5–6 a new, simple assay was designed for submicrogram quantities of pepsins in the presence of pepsinogens without interference of the latter. The method is particularly suitable for the analyses of the zymogen activation mixtures.     

Eye trematode infection in small passerines in Peru caused by Philophthalmus lucipetus,an agent with a zoonotic potential spread by an invasive freshwater snail

Until now, four species of eye trematodes have been found in South America. Of them, Philophthalmus lucipetus (synonymized with Philophthalmus gralli) displays a broad host spectrum, with at least 30 bird species (prevalently large water birds), five mammal species and humans serving as definitive hosts, and with snails Fagotia (Microcolpia) acicularis, Amphimelania holandri, Melanopsis praemorsa and Melanoides tuberculata serving as intermediate hosts. When examining a total of 50 birds of ten species in the wetland of Pantanos de Villa, Lima, Peru in July 2011, eye trematodes were identified visually in the edematous conjunctival sac of 11 (48%) out of 23 resident many-colored rush tyrants Tachuris rubrigastra. Based on morphometric characteristics, the trematodes were identified as P. lucipetus. ITS2 and CO1 gene of the examined specimens combined showed a 99% similarity to an Iranian isolate of Philophthalmus sp. from the intermediate host Melanoides tuberculata, an invasive freshwater snail, suggesting that these two isolates represent the same species with a wide geographical range. Moreover, the prevalence of infection with the philophthalmid cercariae was 31% in 744 Melanoides tuberculata examined in Pantanos de Villa in 2010. It is evident that P. lucipetus occurs throughout the world as well as locally, including Eurasia and South America. Here we report this trematode for the first time in Peru, and we were the first to sequence any of the South American eye trematodes. Low host specificity of P. lucipetus and the invasive character of Melanoides tuberculata as a competent intermediate host suggest that eye trematodosis caused by P. lucipetus may emerge frequently in various parts of the world, especially in the tropics. Increase of the zoonotic potential of the P. lucipetus associated with this invasive snail spreading across the world is predictable and should be of interest for further research.     

Relative contribution of homologous recombination and non-homologous end-joining to DNA double-strand break repair after oxidative stress in Saccharomyces cerevisiae

Oxidative damage to DNA seems to be an important factor in developing many human diseases including cancer. It involves base and sugar damage, base-free sites, DNA-protein cross-links and DNA single-strand (SSB) and double-strand (DSB) breaks. Oxidative DSB can be formed in various ways such as their direct induction by the drug or their generation either through attempted and aborted repair of primary DNA lesions or through DNA replication-dependent conversion of SSB. In general, two main pathways are responsible for repairing DSB, homologous recombination (HR) and non-homologous end-joining (NHEJ), with both of them being potential candidates for the repair of oxidative DSB. We have examined relative contribution of HR and NHEJ to cellular response after oxidative stress in Saccharomyces cerevisiae. Therefore, cell survival, mutagenesis and DSB induction and repair in the rad52, yku70 and rad52 yku70 mutants after hydrogen peroxide (H(2)O(2)), menadione (MD) or bleomycin (BLM) exposure were compared to those obtained for the corresponding wild type. We show that MD exposure does not lead to observable DSB induction in yeast, suggesting that the toxic effects of this agent are mediated by other types of DNA damage. Although H(2)O(2) treatment generates some DSB, their yield is relatively low and hence DSB may only partially be responsible for toxicity of H(2)O(2), particularly at high doses of the agent. On the other hand, the basis of the BLM toxicity resides primarily in DSB induction. Both HR and NHEJ act on BLM-induced DSB, although their relative participation in the process is not equal. Based on our results we suggest that the complexity and/or the quality of the BLM-induced DSB might represent an obstacle for the NHEJ pathway.