Effects of ammonium sulphate application on the rhizosphere,fine-root and needle chemistry in aPicea abies (L.) Karst. stand

Rhizosphere, fine-root and needle chemistry were investigated in a 28 year old Norway spruce stand in SW Sweden. The uptake and allocation pattern of plant nutrients and aluminium in control plots (C) and plots repeatedly treated with ammonium sulphate (NS) were compared. Treatments started in 1988. Current year needles, one-year-old needles and cylindrical core samples of the LFH-layer and the mineral soil layers were sampled in 1988, 1989 and 1990. Compared to the control plots, pH decreased significantly in the rhizosphere soil in the NS plots in 1989 and 1990 while the SO₄-S concentration increased significantly. Aluminium concentration in the rhizosphere soil was generally higher in the NS plots in all soil layers, except at 0–10 cm depths, both in 1989 and 1990. Calcium, Mg and K concentrations also increased after treatment with ammonium sulphate. Ammonium ions may have replaced these elements in the soil organic matter. The NS treatment significantly reduced Mg concentrations in fine roots in all layers in 1990. A similar trend was found in the needles. Ca concentrations in fine roots were significantly lower in the NS plots in the LFH layer in 1990 and the same pattern was found in the current needles. The N and S concentrations of both fine roots and needles were significantly higher in the NS plots. It was suggested that NS treatment resulted in displacement of Mg, Ca and K from exchange sites in the LFH layer leading to leaching of these cations to the mineral soil. Further application of ammonium sulphate may damage the fine roots and consequently adversely affect the water and nutrient uptake of root systems.     

Effects of ammonium sulphate application on the chemistry of bulk soil,rhizosphere, fine roots and fine-root distribution in a Picea abies (L.) karst. stand

The effect of ammonium sulphate application on the bulk and rhizosphere soil chemistry, elemental concentration of living fine roots (<2 mm in diameter), amounts of living and dead fine roots, root length density and specific root length density were investigated in a 28 year old Norway spruce stand in SW Sweden. The treatments started in 1988. Core samples of the LFH layer and mineral soil layers were sampled in control (C) and ammonium sulphate (NS) treatment plots in 1988, 1989 and 1990. Soil pH and NO₃-S and SO₄-S, Al, Ca, Mg, Mn and K concentrations were measured for both the bulk soil and rhizosphere soil.The pH-values of the bulk and rhizosphere soil decreased in 1989 and 1990 in NS plots compared to control plots, while the SO₄-S concentration increased. The Ca, Mg and K concentration increased in the NS treatment in almost all layers in the bulk and the rhizosphere soil. Ammonium ions may have replaced these elements in the soil organic matter. The NS treatment reduced Mg concentration in fine roots in all layers in 1990. The Al concentrations in the rhizosphere and bulk soil were higher in NS plots in all layers, except at 0–10 cm depth, both in 1989 and 1990. The Al content of living fine roots was higher in NS plots than C plots but the differences were not significant. The NS addition did not affect the P and K contents of fine roots in any soil layer, but the S concentrations of fine roots were significantly higher in NS plots in 1989 and 1990. The fine root necromass was higher in NS than in C in 1990, in the LFH layer, indicating a gradual decrease in the vitality of the fine roots. It was suggested that the NS treatment resulted in displacement of Mg and K from exchange sites in the LFH layer leading to leaching of these cations to the mineral soil. Further application of ammonium sulphate may damage the fine roots and consequently adversely affect the water and nutrient uptake of root systems.     

Heat stress aggravates oxidative stress,apoptosis, and endoplasmic reticulum stress in the cerebellum of male C57 mice

Molecular Biology Reports - The current study was set to assess the effect of heat stress exposure on oxidative stress, apoptosis, and endoplasmic reticulum stress markers in the cerebellum of male...     

Tolerance of free‐living nematode species to imidacloprid and diuron

The neonicotinoid imidacloprid and the herbicide diuron are long‐lived pesticides commonly detected in European rivers. Both have lethal as well as sublethal effects on aquatic invertebrates dwelling in streambeds. Here, we performed lethality tests of imidacloprid and diuron on seven species of widespread, free‐living nematodes and the model organism Caenorhabditis elegans. Our results indicated that nematodes were relatively tolerant to both pesticides, and only two species (Diploscapter coronatus and Plectus opisthocirculus) showed mortality at high nominal concentrations of imidacloprid (119 mg/L) and diuron (33 mg/L). The changes observed in nematode community structure after imidacloprid and diuron exposure may have been related to trade‐offs between sensitivity to toxicants and changes in competitive abilities of the species. While the former can be tested using single‐species tests, we recommend that the latter be tested in further experiments using multispecies communities. Our results suggest that the presence of these pesticides could favor nematodes over other meiofaunal groups found in freshwater sediments.     

Influence of Affective Stimuli on Leg Power Output and Associated Neuromuscular Parameters during Repeated High Intensity Cycling Exercises

The aim of this study was to examine the impact of emotional eliciting pictures on neuromuscular performance during repetitive supramaximal cycling exercises (RSE). In a randomized order, twelve male participants were asked to perform five 6-s cycle sprints (interspaced by 24 s of recovery) on a cycle ergometer in front of neutral, pleasant or unpleasant pictures. During each RSE, mean power output (MPO) and electromyographic activity [root mean square (RMS) and median frequency (MF)] of the vastus lateralis and vastus medialis muscles were analyzed. Neuromuscular efficiency (NME) was calculated as the ratio of MPO to RMS. Higher RMS (232.17 ± 1.17 vs. 201.90 ± 0.47 μV) and MF (68.56 ± 1.78 vs. 64.18 ± 2.17 Hz) were obtained in pleasant compared to unpleasant conditions (p < 0.05). This emotional effect persisted from the first to the last sprint. Higher MPO was obtained in pleasant than in unpleasant conditions (690.65 ± 38.23 vs. 656.73 ± 35.95 W, p < 0.05). However, this emotional effect on MPO was observed only for the two first sprints. NME decreased from the third sprint (p < 0.05), which indicated the occurrence of peripheral fatigue after the two first sprints. These results suggested that, compared with unpleasant pictures, pleasant ones increased the neuromuscular performance during RSE. Moreover, the disappearance of the beneficial effect of pleasant emotion on mechanical output from the third sprint appears to be due to peripheral fatigue.     

Life-History Traits of the Model Organism Pristionchus pacificus Recorded Using the Hanging Drop Method: Comparison with Caenorhabditis elegans

The nematode Pristionchus pacificus is of growing interest as a model organism in evolutionary biology. However, despite multiple studies of its genetics, developmental cues, and ecology, the basic life-history traits (LHTs) of P. pacificus remain unknown. In this study, we used the hanging drop method to follow P. pacificus at the individual level and thereby quantify its LHTs. This approach allowed direct comparisons with the LHTs of Caenorhabditis elegans recently determined using this method. When provided with 5×10⁹ Escherichia coli cells ml^–1 at 20°C, the intrinsic rate of natural increase of P. pacificus was 1.125 (individually, per day); mean net production was 115 juveniles produced during the life-time of each individual, and each nematode laid an average of 270 eggs (both fertile and unfertile). The mean age of P. pacificus individuals at first reproduction was 65 h, and the average life span was 22 days. The life cycle of P. pacificus is therefore slightly longer than that of C. elegans, with a longer average life span and hatching time and the production of fewer progeny.     

TMKP1 is a novel wheat stress responsive MAP kinase phosphatase localized in the nucleus

The regulation of plant signalling responses by Mitogen-Activated Protein Kinases (MAPKs)-mediated protein phosphorylation is well recognized. MAP kinase phosphatases (MKPs) are negative regulators of MAPKs in eukaryotes. We report here the identification and the characterization of TMKP1, the first wheat MKP (Triticum turgidum L. subsp. Durum). Expression profile analyses performed in two durum wheat cultivars showing a marked difference in salt and drought stress tolerance, revealed a differential regulation of TMKP1. Under salt and osmotic stress, TMKP1 is induced in the sensitive wheat variety and repressed in the tolerant one. A recombinant TMKP1 was shown to be an active phosphatase and capable to interact specifically with two wheat MAPKs (TMPK3 and TMPK6). In BY2 tobacco cells transiently expressing GFP::TMKP1, the fusion protein was localized into the nucleus. Interestingly, the deletion of the N-terminal non catalytic domain results in a strong accumulation of the truncated fusion protein in the cytoplasm. In addition, when expressed in BY2 cells, TMPK3 and TMPK6 fused to red fluorescent protein (RFP) were shown to be present predominantly in the nucleus. Surprisingly, when co-expressed with the N-terminal truncated TMKP1 fusion protein; both kinases are excluded from the nuclear compartment and accumulate in the cytoplasm. This strongly suggests that TMKP1 interacts in vivo with TMPK3 and TMPK6 and controls their subcellular localization. Taken together, our results show that the newly isolated wheat MKP might play an active role in modulating the plant cell responses to salt and osmotic stress responses.     

A critical three-way junction is conserved in budding yeast and vertebrate telomerase RNAs

The telomerase ribonucleoprotein copies a short template within its integral RNA moiety onto eukaryotic chromosome ends, compensating for incomplete replication and degradation. Non-template regions of telomerase RNA (TER) are also crucial for telomerase function, yet they are highly divergent in sequence among species and their roles are largely unclear. Using both phylogenetic and mutational analyses, we predicted secondary structures for TERs from Kluyveromyces budding yeast species. A comparison of these secondary structure models with the published model for the Saccharomyces cerevisiae TER reveals a common arrangement into three long arms, a templating domain in the center and several conserved elements in the same positions within the structure. One of them, a three-way junction element, is highly conserved in budding yeast TERs. This element also shows sequence and structure similarity to the critical CR4-CR5 activating domain of vertebrate TERs. Mutational analysis in Kluyveromyces lactis confirmed that this element, and in particular the residues conserved across yeast and vertebrates, is critical for telomerase action both in vivo and in vitro. These findings demonstrate that despite the extreme divergence of TER sequences from different organisms, they do share conserved elements, which presumably carry out common roles in telomerase function.     

Morphofunctional study of 12‐O‐tetradecanoyl‐13‐phorbol acetate (TPA)‐induced differentiation of U937 cells under exposure to a 6 mT static magnetic field

This study deals with the morphofunctional influence of 72 h exposure to a 6 mT static magnetic field (SMF) during differentiation induced by 50 ng/ml 12‐O‐tetradecanoyl‐13‐phorbol acetate (TPA) in human leukaemia U937 cells. The cell morphology of U937 cells was investigated by optic and electron microscopy. Specific antibodies and/or molecules were used to label CD11c, CD14, phosphatidylserine, F‐actin and to investigate the distribution and activity of lysosomes, mitochondria and SER. [Ca²⁺]_i was evaluated with a spectrophotometer. The degree of differentiation in SMF‐exposed cells was lower than that of non‐exposed cells, the difference being exposure time‐dependent. SMF‐exposed cells showed cell shape and F‐actin modification, inhibition of cell attachment, appearance of membrane roughness and large blebs and impaired expression of specific macrophagic markers on the cell surface. The intracellular localization of SER and lysosomes was only partially affected by exposure. A significant localization of mitochondria with an intact membrane potential at the cell periphery in non‐exposed, TPA‐stimulated cells was observed; conversely, in the presence of SMF, mitochondria were mainly localised near the nucleus. In no case did SMF exposure affect cell viability. The sharp intracellular increase of [Ca²⁺]_i could be one of the causes of the above‐described changes. Bioelectromagnetics 30:352–364, 2009. © 2009 Wiley‐Liss, Inc.