Distinguishing local from global climate influences in the variation of carbon status with altitude in a tree line species

Aim Two alternative hypotheses attempt to explain the upper elevation limit of tree lines world‐wide, the carbon‐limitation hypothesis (CLH) and the growth‐limitation hypothesis (GLH); the altitudinal decrease of temperature is considered the driver constraining either carbon gain or growth. Using a widely distributed tree line species (Nothofagus pumilio) we tested whether tree line altitude is explained by the CLH or the GLH, distinguishing local from global effects. We elaborated expectations based on most probable trends of carbon charging with altitude according to both hypotheses, considering the alternative effects of drought. Location Two climatically contrasting tree line ecotones in the southern Andes of Chile: Mediterranean (36°54′ S) and Patagonia (46°04′ S). Methods At both locations, 35–50 trees of different ages were selected at each of four altitudes (including tree line), and stem and root sapwood tissues were collected to determine non‐structural carbohydrate (NSC) concentrations. NSC accumulates whenever growth is more limited than photosynthesis. An altitudinal increase in NSCs means support for the GLH, while the opposite trend supports the CLH. We also determined stable carbon isotope ratios (δ¹³C) to examine drought constraints on carbon gain. Results NSC concentrations were positively correlated with altitude for stem tissue at the Mediterranean and root sapwood tissue at the Patagonia site. No depletion of NSC was found at either site in either tissue type. For both tissues, mean NSC concentrations were higher for the Patagonia site than for the Mediterranean site. Mean root sapwood NSC concentration values were five times higher than those of the corresponding stem sapwood at all altitudes. Values for δ¹³C were positively correlated with altitude in the Mediterranean site only. Main conclusions We found support for the GLH at the site without drought effects (Patagonia) and no support for the CLH at either site. It is suggested that drought moderated the effects of low temperature by masking the expected trend of the GLH at the Mediterranean site.     

Tryptophan orientations in membrane-bound gramicidin and melittin-a comparative linear dichroism study on transmembrane and surface-bound peptides

In the search for methods to study structure and function of membrane-associated proteins and peptides flow linear dichroism, LD, spectroscopy has emerged as a promising technique. Using shear-aligned lipid vesicles, conformations and binding geometries of membrane-bound bio-macromolecules can be assessed. Here we investigate anchoring properties and specific orientations of tryptophan relative to the peptide backbone and to the membrane normal for the model peptides gramicidin and melittin. We have monitored the conformational change associated with the refolding of non-channel gramicidin into its channel form, and quantitatively determined the average orientations of its tryptophan transition moments, suggesting that these residues adopt a well-defined orientation at the membrane interface. An important conclusion regards the structural variation of gramicidin between these two distinct transmembrane forms. Whilst circular dichroism (CD) spectra, as has been reported before, vary strongly between the two forms suggesting their structures might be quite different, the LD results clearly evidence both the peptide backbone orientation and tryptophan side-chain positioning to be very similar. The latter are oriented in accord with what is expected from their role to anchor peptide termini to the membrane surface. The variations in CD could be due to, the in LD observed, minor shifts in mutual orientation and distance between neighbouring tryptophans sensitively determining their exciton interactions. Our data dispute that the non-channel form of membrane-bound gramicidin would be any of the intertwined forms often observed in crystal as the positioning of tryptophans along the peptide axis would not be compatible with the strong interfacial positioning observed here. The general role of tryptophans as interfacial anchors is further assessed for melittin whose conformation shows considerable angular spread, consistent with a carpet model of its mechanism for induced membrane leakage, and a predominantly surface-aligned membrane orientation governed by amphipathic interactions.     

Production of Norway spruce embryos in a temporary immersion system (TIS)

Somatic embryogenesis has already been used for Norway spruce (Picea abies (L.) Karst) embling production on a laboratory scale, but automation is needed to increase efficiency and reduce costs. One option to scale up production is mass production in bioreactors. In a series of experiments, a pro-embryogenic mass was propagated using Plantform temporary immersion system bioreactors, and the effect of different aeration cycles, support pad materials, and post-maturation treatments (rinsing and desiccation) on the embryo yield and embling survival after 4 to 6 mo in a greenhouse was tested. Three genotypes were used to test each treatment. The best aeration frequency was 20 min every 4 h, while a lower or higher frequency did not generally improve embryo production. Filter paper on plastic netting was the best support pad material in terms of usability and embryo production (varying from 177 ± 20 to 696 ± 109 per g pro-embryogenic mass). The separation of the embryos from the undeveloped cell mass by rinsing with sterile water resulted in reduced survival of the emblings. Desiccation treatment on nested plates with the embryos on the inner plate with or without filter paper improved their survival. Bioreactors were laborious to prepare, load, and clean. Improvements in embryo production can be achieved by optimizing the process, but bioreactors based on the requirements of somatic embryogenesis are needed to enable their use in the mass production of Norway spruce emblings.

     

Combining ecosystem indicators and life cycle assessment for environmental assessment of demersal trawling in Tunisia

The International Journal of Life Cycle Assessment - The present study assesses environmental performance of seafood production by demersal trawling in Tunisia (Gulf of Gabes) in order to analyze...     

Calpain-mediated proteolysis of microtubule associated proteins MAP1B and MAP2 in developing brain

Microtubule associated proteins MAP1B and MAP2 are important components of the neuronal cytoskeleton. During early development of the brain, MAP1B (340 kDa) is present as two isoforms that differ in their level of phosphorylation, while MAP2 is expressed as a single high molecular weight isoform (MAP2B, 280 kDa) and a low molecular weight form (MAP2C, 70 kDa). In this study we examined and compared the sensitivities of MAP1B and MAP2, obtained from MT preparations and brain homogenates of young rats, to degradation by calcium-activated neutral protease, calpain II. We found that in MAPs prepared from microtubules the two isoforms of MAP1B had comparable sensitivity to calpain-mediated proteolysis. Similarly, the high and low molecular weight forms of MAP2 were equally sensitive to digestion by calpain. However, although both MAPs were very susceptible to calpain-mediated proteolysis, MAP1B was more resistant to degradation by calpain than MAP2. Furthermore, the endogenous degradation of MAPs in neonate brain homogenates was calcium-dependent and inhibited by leupeptin, and the pattern of degradation products for MAP1B and MAP2 was similar to that of calpain-mediated proteolysis. These data suggest that calpain can play a role in the regulation of MAPs levels during brain development, in relation to normal neuronal differentiation and disorders associated with neurodegeneration.     

Benzofuranoid neolignans from Licaria armeniaca

The trunkwood of Licaria armeniaca (Nees) Kosterm. (Lauraceae) contains sitosterol, 6,7-dimethoxy-coumarin and two novel benzofuranoid neolignans: (2S, 3S, 3aR, 5R)-3a-allyl-5-methoxy- and 5,7-dimethoxy-2-(3′, 4′-methylenedioxyphenyl)-3-methyl-2,3,3a,4,5,6-hexahydro-6-oxobenzofurans.     

pH dependence of copper geometry, reduction potential, and nitrite affinity in nitrite reductase

Many properties of copper-containing nitrite reductase are pH-dependent, such as gene expression, enzyme activity, and substrate affinity. Here we use x-ray diffraction to investigate the structural basis for the pH dependence of activity and nitrite affinity by examining the type 2 copper site and its immediate surroundings in nitrite reductase from Rhodobacter sphaeroides 2.4.3. At active pH the geometry of the substrate-free oxidized type 2 copper site shows a near perfect tetrahedral geometry as defined by the positions of its ligands. At higher pH values the most favorable copper site geometry is altered toward a more distorted tetrahedral geometry whereby the solvent ligand adopts a position opposite to that of the His-131 ligand. This pH-dependent variation in type 2 copper site geometry is discussed in light of recent computational results. When co-crystallized with substrate, nitrite is seen to bind in a bidentate fashion with its two oxygen atoms ligating the type 2 copper, overlapping with the positions occupied by the solvent ligand in the high and low pH structures. Fourier transformation infrared spectroscopy is used to assign the pH dependence of the binding of nitrite to the active site, and EPR spectroscopy is used to characterize the pH dependence of the reduction potential of the type 2 copper site. Taken together, these spectroscopic and structural observations help to explain the pH dependence of nitrite reductase, highlighting the subtle relationship between copper site geometry, nitrite affinity, and enzyme activity.     

Long-Term Sickness Absence Due to Mental Disorders Is Associated with Individual Features and Psychosocial Work Conditions

Aims

Sickness absence is a socioeconomic global burden. In Brazil, mental disorders are the third leading cause of social security benefits payments. The aim of the present study was to compare factors associated with long-term sickness absence between workers who claimed social benefits due to mental disorders or by other causes. We investigated individual features and occupational characteristics. In addition, we evaluated psychosocial factors at work assessed by the Demand-Control-Support (DCS) and Effort-Reward Imbalance (ERI) models, and whether they were associated with long-term sickness absence due to mental disorders (LTSA-MD).

Methods

The present case-control study was conducted in São Paulo, Brazil. The sample (n = 385) included workers on sick leave for more than 15 days. Cases were the participants with disabling psychiatric illnesses, and controls were the ones with other disabling diseases. Interviews were conducted to assess individual features (sociodemographic data, health habits/lifestyle, health conditions) and occupational characteristics. The participants'' perception of exposure to dimensions of the DCS and ERI models was also recorded. Multiple logistic regressions were performed to evaluate the association between independent variables and LTSA-MD.

Results

All the regression analyses showed that LTSA-MD was associated with female sex, self-reported white skin color, higher education level, high tobacco consumption, high alcohol intake, two or more comorbidities, exposure to violence at work, high job strain and low social support at work, effort-reward imbalance and high overcommitment to work. LTSA-MD was associated with separate and combined DCS and ERI stress models.

Conclusions

Individual features and work conditions were associated with LTSA-MD. Combined analysis of stress models showed that psychosocial factors at work were significantly associated with LTSA-MD. Resourceful use of this information may contribute to the implementation of preventive actions and strategies to facilitate return to work targeting the populations most susceptible to mental disorders.     

The Interaction between Water Currents and Salmon Swimming Behaviour in Sea Cages

Positioning of sea cages at sites with high water current velocities expose the fish to a largely unknown environmental challenge. In this study we observed the swimming behaviour of Atlantic salmon (Salmo salar L.) at a commercial farm with tidal currents altering between low, moderate and high velocities. At high current velocities the salmon switched from the traditional circular polarized group structure, seen at low and moderate current velocities, to a group structure where all fish kept stations at fixed positions swimming against the current. This type of group behaviour has not been described in sea cages previously. The structural changes could be explained by a preferred swimming speed of salmon spatially restricted in a cage in combination with a behavioural plasticity of the fish.