Subchronic Administration of High-Dose Sodium Fluoride Causes Deficits in Cerebellar Purkinje Cells But Not Motor Coordination of Rats

Biological Trace Element Research - Fluoride is frequently added to drinking water supplies, various food products, toothpaste, and mouth rinses to prevent tooth damage. However, at high...     

The apoplastic antioxidant system and altered cell wall dynamics influence mesophyll conductance and the rate of photosynthesis

Mesophyll conductance (g_m), the diffusion of CO₂ from substomatal cavities to the carboxylation sites in the chloroplasts, is a highly complex trait driving photosynthesis (net CO₂ assimilation, A_N). However, little is known concerning the mechanisms by which it is dynamically regulated. The apoplast is considered as a ‘key information bridge’ between the environment and cells. Interestingly, most of the environmental constraints affecting g_m also cause apoplastic responses, cell wall (CW) alterations and metabolic rearrangements. Since CW thickness is a key determinant of g_m, we hypothesize that other changes in this cellular compartiment should also influence g_m. We study the relationship between the antioxidant apoplastic system and CW metabolism and the g_m responses in tobacco plants (Nicotiana sylvestris L.) under two abiotic stresses (drought and salinity), combining in vivo gas‐exchange measurements with analyses of antioxidant activities, CW composition and primary metabolism. Stress treatments imposed substantial reductions in A_N (58–54%) and g_m (59%), accompanied by a strong antioxidant enzymatic response at the apoplastic and symplastic levels. Interestingly, apoplastic but not symplastic peroxidases were positively related to g_m. Leaf anatomy remained mostly stable; however, the stress treatments significantly affected the CW composition, specifically pectins, which showed significant relationships with A_N and g_m. The treatments additionally promoted a differential primary metabolic response, and specific CW‐related metabolites including galactose, glucosamine and hydroxycinnamate showed exclusive relationships with g_m independent of the stress. These results suggest that g_m responses can be attributed to specific changes in the apoplastic antioxidant system and CW metabolism, opening up more possibilities for improving photosynthesis using breeding/biotechnological strategies.     

Polysaccharides from the green seaweeds Codium fragile and C. vermilara with controversial effects on hemostasis

Codium fragile and Codium vermilara biosynthesize water-soluble sulfated arabinans and galactans (and/or sulfated arabinogalactans), (1 → 4)-d-glucans and β(1 → 4)-d-mannans. The former polysaccharides are composed by 3-linked β-d-galactopyranose and β-l-arabinopyranose residues, they are highly sulfated and substituted with pyruvic acid ketals. For both seaweeds, they have the same main structural units, but in different percentages. All the room-temperature water extracts from both seaweeds showed a dual haemostatic effect: they prevented coagulation, but they induced platelet aggregation. Anticoagulant activity and platelet aggregation were higher in the samples with polysaccharides richer in sulfate, mainly in those from C. vermilara, which have a higher degree of sulfation and arabinose content.     

Leg rings impact the diving performance of a foot-propelled diver

Leg rings are frequently used to mark aquatic birds in order to identify individuals, and study population dynamics and migration patterns, with the proviso being that the rings should not affect the birds. The effects of tags and rings are of particular interest in diving birds because any change in body shape could impact swimming efficiency and costs, as water is almost a thousand times denser than air. We attached tri-axial accelerometers to both ringed and unringed breeding Imperial Shags Leucocarbo atriceps to assess dive performance based on descent angle, descent rate, power stroke rate, power stroke peak acceleration amplitude and Vectorial Dynamic Body Acceleration (VeDBA) as a proxy for energy expenditure. Ringed birds, especially females, had a higher foot-stroke amplitude than unringed animals. In addition, the overall efficiency of the ringed individuals, as expressed by the descent rate per unit VeDBA, was compromised (by 3.5% in females and 4.3% in males) compared with unringed birds. We conclude that leg rings change the diving performance of Imperial Shags, although the effect is small and may not affect reproductive success. However, given that birds are typically ringed for life, we urge researchers to be particularly careful about the potential cumulative effect of attaching leg rings to foot-propelled diving species.     

Ecosystem engineers activate mycorrhizal mutualism in salt marshes

Theory predicts that ecosystem engineers should have their most dramatic effects when they enable species, through habitat amelioration, to live in zones where physical and biological conditions would otherwise suppress or limit them. Mutualisms between mycorrhizal fungi and plants are key determinants of productivity and biodiversity in most terrestrial systems, but are thought to be unimportant in wetlands because anoxic sediments exclude fungal symbionts. Our field surveys revealed arbuscular mycorrhizal associations on salt marsh plant roots, but only in the presence of crabs that oxygenate soils as a by-product of burrowing. Field experiments demonstrate that fungal colonization is dependent on crab burrowing and responsible for nearly 35% of plant growth. These results highlight ecosystem engineers as ecological linchpins that can activate and maintain key mutualisms between species. Our findings align salt marshes with other important biogenic habitats whose productivity is reliant on mutualisms between the primary foundation species and micro-organisms.     

Phylogenetic analysis of H6 influenza viruses isolated from rosy-billed pochards (Netta peposaca) in Argentina reveals the presence of different HA gene clusters

Until recently, influenza A viruses from wild waterfowl in South America were rarely isolated and/or characterized. To explore the ecology of influenza A viruses in this region, a long-term surveillance program was established in 2006 for resident and migratory water birds in Argentina. We report the characterization of 5 avian influenza viruses of the H6 hemagglutinin (HA) subtype isolated from rosy-billed pochards (Netta peposaca). Three of these viruses were paired to an N2 NA subtype, while the other two were of the N8 subtype. Genetic and phylogenetic analyses of the internal gene segments revealed a close relationship with influenza viruses from South America, forming a unique clade and supporting the notion of independent evolution from influenza A viruses in other latitudes. The presence of NS alleles A and B was also identified. The HA and NA genes formed unique clades separate from North American and Eurasian viruses, with the exception of the HA gene of one isolate, which was more closely related to the North American lineage, suggesting possible interactions between viruses of North American and South American lineages. Animal studies suggested that these Argentine H6 viruses could replicate and transmit inefficiently in chickens, indicating limited adaptation to poultry. Our results highlight the importance of continued influenza virus surveillance in wild birds of South America, especially considering the unique evolution of these viruses.     

The exotic mammals of Argentina

Exotic mammals in South America represent about 20% of world mammal introductions. The aim of our paper is to provide a global assessment of the exotic mammals of Argentina, their pathways, impacts, and a synthesis of their attributes as potential invasive species. We reviewed and compiled data from a diversity of sources and databases on alien mammals occurring in feral state exclusively. We recorded 18 species of exotic mammals for Argentina. The majority of introductions occurred between the 18th and 19th centuries and their ports of entry were located in temperate ecosystems, between 34° and 55° SL. Most of their entry pathways were associated with human activities (e.g. sport hunting, food and fur industry). The exotic mammals occupy ecoregions similar to their original distributions, but most of them have experienced a range expansion to novel habitats. The fauna of exotic mammals of Argentina represents a good opportunity to understand the dynamics of the invasion process as they represent a diversity of ecological groups and environmental contexts.     

Texture of Bananas Submitted to Different Freeze Drying Cycle Applying Scanning Electron Microsocopy with Image Analysis Techniques

Prediction of texture in bananas submitted to different freeze drying cycle was investigated applying scanning electron microscopy combined with image analysis technique. Freeze drying was performed at different cycles. Microstructure was analyzed using a Scanning Electron Microscopy; Texture parameters were analyzed by Gray Level Co-Matrix Analysis and by conventional analysis; colour by image analysis and porosity by conventional technique. Micrographs revealed that a higher porous size structure was obtained when freeze drying cycles was performed at shorter cycles. Significant difference (P < 0.0001) were obtained for texture, senescence and porosity. A linear trend with a linear correlation was applied for instrumental vs. image texture. Results showed that image features (contrast, correlation, entropy, energy and homogeneity) correlated with mechanical texture. When short cycles were applied minimum damage on texture and senescence parameters appeared. Prediction of texture can be performed easily as a quantitative and non invasive technique that could be related in future studies for quality.