Soil-living parasitic Hymenoptera: comparison between a forest and an open landscape habitat

Community structures and local diversity patterns of parasitic Hymenoptera with soil and leaf litter hosts were studied in a German beech forest and a meadow. Hymenoptera appeared to be one of the most species-rich taxa associated with the soil. Eighty-eight species were found in the meadow (total density of 128 ind. m⁻² yr⁻¹) and 188 species (149 ind. m⁻² yr⁻¹) in the forest. The mean parasitism rates were above 60% for parasitoids of mycetophagous Diptera and between 7% and 26% for parasitoids of saprophagous Diptera. Species overlap between both habitats was higher than expected from a random sample model. Species common to both habitats were primarily parasitoids of predatory Coleoptera. High mean densities of these species support the hypothesis of a positive correlation between local abundance and range size.     

Model Experiments on the Influence of Artificial Humic Compounds on Chemodenitrification

Chemodenitrification is of importance in both soils and the treatment of some types of wastewater. During model experiments,the impact of various conditions, such as pH and especially artificial humic matter and oxygen on this process was studied to build upkinetic models. The chemodenitrification rate decreased due to the ongoingautoxidation/polymerization of hydroquinone to artificial humic matterfrom 11.02 μg (L h)^-1 after 7 days autoxidation to 5.38 μg (L h)^-1 after 14 days at pH 4 under aerobic conditionsand an initial nitrite concentration of 250 μg L^-1. At the same pH,with the same nitrite concentration, and in the presence of Roth humic matter(2 mg L^-1) under aerobic conditions, the chemodenitrification rate was0.73 μg (L h)^-1, whereas under anaerobic conditions itwas considerably higher (2.88 μg (L h)^-1). In anothermodel experiment, it was shown that the amount of nitrite incorporated into the artificial humic matter was less then 1%. Further, it was found that the main reaction product of chemodenitrification is NO.     

Fast and efficient discrimination of the Isotoma viridis group (Insecta: Collembola) by PCR-RFLP

Identification of collembolan species is generally based on specific morphological characters, such as chaetotaxy and pigmentation pattern. However, some specimens do not match to described characters because these refer to adult specimens, often of one specific sex, or the characters are highly variable in adults (e.g. pigmentation, setae or furcal teeth). Isozymes have frequently assisted species discrimination, and also these may vary with developmental stage or environmental conditions. For identification of single species of the Isotoma viridis group, we present both direct sequencing of the cytochrome oxidase subunit II (COII) gene and a simple DNA-based molecular method.

Five PCR primers amplifying the COII region (717 bp) of the mitochondrial DNA were used. The sequences clearly separated the species I. viridis, I. riparia and I. anglicana, irrespective of colour varieties within the first species. DNA amplification products of different species can also be distinguished by digestion with restriction endonucleases, followed by gel electrophoresis for separation of fragments. This restriction fragment length polymorphism (RFLP), obtained after digestion with the endonucleases TaqI, VspI, MvaI and Bsp143I, revealed specific fragments that separated the three species from each other. Since restriction enzymes are sensitive to single base mutations, we suggest to use a combination of enzymes with at least two species-specific restriction sites when using the RFLP technique. For the I. viridis complex, VspI and Bsp143I appear to be an appropriate combination.     

Nitric oxide impacts bovine sperm capacitation in a cGMP‐dependent and cGMP‐independent manner

We aimed to elucidate whether NO acts in in vitro sperm capacitation in bovine via cGMP/PKG1 pathway. For this, cryopreserved bovine sperm were capacitated in vitro with 20 µg/ml heparin (Control) plus treatments: 1 mM L‐arginine (L‐arg, NO precursor), 50 µM Rp‐8‐Bromo‐β‐phenyl‐1,N²‐ethenoguanosine‐3′,5′‐cyclic monophosphorothioate (Rp‐8‐Br‐cGMPS, selective inhibitor of the binding site for cGMP in PKG1), 1 mM 2‐Phenyl‐4,4,5,5‐tetramethylimidazoline‐1‐oxyl 3‐oxide (PTIO, NO scavenger), and the combinations of L‐arg + RP‐8‐Br‐cGMPS and L‐arg + PTIO. Sperm motility and vigour were determined by phase‐contrast microscopy, capacitation status by chlortetracycline staining, and the intracellular concentration of cGMP was measured by ELISA. Data were subjected to analysis of variance and means compared with SNK test at 5% probability. Motility and vigour were lower in sperm treated with PTIO when compared to Control and other treatments (p < .05). The L‐arg treatment showed the highest percentage of capacitated sperm when compared to the Control and other treatments (Rp‐8‐Br‐cGMPS, L‐arg + Rp‐8‐Br‐cGMPS and PTIO) (69.8 ± 3.4%, 51.2 ± 3.0, 51.1 ± 2.1, 51.2 ± 3.0 and 45.5 ± 2.7, respectively) (p < .05). The capacitation ratio (%) was lower in treatments with Rp‐8‐Br‐cGMPS, L‐arg + Rp‐8‐Br‐cGMPS and PTIO, respectively (p < .05). Lastly, cGMP concentration (pmol/ml) was lower in PTIO and L‐arg + PTIO (1.3 ± 0.3 and 1.6 ± 0.4) and was higher in Rp‐8‐Br‐cGMPS and L‐arg + Rp‐8‐Br‐cGMPS (3.7 ± 0.4 and 4.0 ± 0.5) treatments. We showed that during in vitro capacitation of cattle: (a) NO influences sperm motility and vigour; (b) NO is associated with cGMP synthesis through two independent pathways and (c) the cGMP/PKG1 pathway has a partial role in sperm capacitation and does not involve the L‐arg/NO.     

A systematic survey of loss-of-function variants in human protein-coding genes

Genome-sequencing studies indicate that all humans carry many genetic variants predicted to cause loss of function (LoF) of protein-coding genes, suggesting unexpected redundancy in the human genome. Here we apply stringent filters to 2951 putative LoF variants obtained from 185 human genomes to determine their true prevalence and properties. We estimate that human genomes typically contain ~100 genuine LoF variants with ~20 genes completely inactivated. We identify rare and likely deleterious LoF alleles, including 26 known and 21 predicted severe disease-causing variants, as well as common LoF variants in nonessential genes. We describe functional and evolutionary differences between LoF-tolerant and recessive disease genes and a method for using these differences to prioritize candidate genes found in clinical sequencing studies.     

Biogenic potassium salt particles as seeds for secondary organic aerosol in the Amazon

The fine particles serving as cloud condensation nuclei in pristine Amazonian rainforest air consist mostly of secondary organic aerosol. Their origin is enigmatic, however, because new particle formation in the atmosphere is not observed. Here, we show that the growth of organic aerosol particles can be initiated by potassium-salt-rich particles emitted by biota in the rainforest. These particles act as seeds for the condensation of low- or semi-volatile organic compounds from the atmospheric gas phase or multiphase oxidation of isoprene and terpenes. Our findings suggest that the primary emission of biogenic salt particles directly influences the number concentration of cloud condensation nuclei and affects the microphysics of cloud formation and precipitation over the rainforest.     

Temporal trends in the foliar nutritional status of the French, Walloon and Luxembourg broad-leaved plots of forest monitoring

? Two decades after the launching of the monitoring program of forest ecosystems in Europe (ICP forests), a unique data set is now available regarding the foliar nutritional status of the main broad-leaved species growing in much-diversified sites (soil, climate).

? This study focuses on the foliar concentration time series (1993 to 2005) of the French (RENECOFOR), Walloon and Luxemburg broad-leaved plots. The aim is to show long-term trends while taking the inter-plot and inter-annual variability into account.

? Two kinds of statistical processing were used to analyze the data on foliar chemistry: principal component analysis (PCAs) and linear mixed models. In general, the main temporal trends reveal a decrease in the foliar P concentration and a decrease in the foliar Ca concentration, except for European beech on acid soils.

? These temporal patterns confirm the trends previously observed and could be explained by the joint actions of several processes that influence tree nutrition in the long term: tree age, N and S deposition, harvesting and climate.

     

用地高辛标记核酸探针检测鹅细小病毒的研究

从带有鹅细小病毒(GPV)NSI基因的重组质粒pMD18T-NS1用限制性内切酶EcoRI和BamH1双酶切回收1880bp大小片段,并制备出地高辛标记的GPV核酸探针。其标记效率达到0．01pg／μl。特异性检测结果表明,该探针能与GPV不同毒株核酸发生特异性杂交,而与对照的DPV、GPPV等病毒的核酸杂交反应均为阴性;敏感性检测结果表明,该探针对GPV的最低检出量为0．0224pg。该探针对不同方法处理的GPV感染病料进行检测,均出现杂交阳性。表明所研制的标记探针用于GPV的检测足可行的。