Endophytic fungi in forest trees: are they mutualists?

Forest trees form symbiotic associations with endophytic fungi which live inside healthy tissues as quiescent microthalli. All forest trees in temperate zones host endophytic fungi. The species diversity of endophyte communities can be high. Some tree species host more than 100 species in one tissue type, but communities are usually dominated by a few host-specific species. The endophyte communities in angiosperms are frequently dominated by species of Diaporthales and those in gymnosperms by species of Helotiales. Divergence of angiosperms and gymnosperms coincides with the divergence of the Diaporthales and the Helotiales in the late Carboniferous about 300 million years (Ma) ago, indicating that the Diaporthalean and Helotialean ancestors of tree endophytes had been associated, respectively, with angiosperms and gymnosperms since ≥300 Ma. Consequently, dominant tree endophytes have been evolving with their hosts for millions of years. High virulence of such endophytes can be excluded. Some are, however, opportunists and can cause disease after the host has been weakened by some other factor. Mutualism of tree endophytes is often assumed, but evidence is mostly circumstantial. The sheer impossibility of producing endophyte-free control trees impedes proof of mutualism. Some tree endophytes exhibit either a pathogenic or a putatively mutualistic behaviour depending on the situation. The lifestyle (mutualism, commensalism, parasitism) of most tree endophytes is, however, not known. They are just there in the tissue and resume growth at the onset of natural senescence of the host tissue on which they eventually sporulate. Density of colonization of conifer needles by endophytes increases with needle age. It is postulated that the needles die as soon as colonization density reaches a threshold value. Normally, the threshold is not reached before the onset of natural senescence. The threshold value may, however, be reached earlier under some adverse conditions, e.g. lack of light in dense stands. As a consequence, endophytes kill the needles prematurely. Needle endophytes could, thus, be useful to eliminate “parasitic” needle mass, i.e. needles which consume more than they produce.     

How do rocker-soled shoes influence the knee adduction moment in people with knee osteoarthritis? An analysis of biomechanical mechanisms

The primary objective was to examine mechanisms behind previously observed changes in the knee adduction moment (KAM) with rocker-soled shoes, in participants sub-grouped according to whether they experienced an immediate decrease, or increase, in peak KAM. In subgroups where frontal plane knee ground reaction force (GRF) lever-arm emerged as a significant predictor, a secondary aim was to examine biomechanical factors that contributed to change in this parameter. Thirty individuals with symptomatic, radiographic knee osteoarthritis (OA) underwent 3D gait analysis in unstable rocker-soled shoes and non-rocker-soled shoes. Multiple regression analyses, within each subgroup, examined relationships between changes in frontal plane knee-GRF lever arm and frontal plane resultant GRF magnitude and changes in peak KAM and KAM impulse between shoe conditions. In the subgroup that decreased peak KAM with rocker-soled shoes (n = 23), change in knee-GRF lever arm and frontal plane GRF magnitude at peak KAM together were significant predictors of change in peak KAM; however, only change in mean knee-GRF lever arm significantly predicted change in KAM impulse. Decreased medial GRF magnitude, increased lateral trunk lean towards the stance limb and reduced varus/increased valgus hip-knee-ankle angle were associated with a lower knee-GRF lever arm in this group, with rocker-soled shoes. In contrast, none of the independent variables predicted changes in KAM in the subgroup who increased peak KAM with rocker-soled shoes (n = 7).     

Genetic,environmental, and neighbor effects on the severity of stereotypies and feather picking in Orange-winged Amazon parrots (Amazona amazonica): An epidemiological study

Stereotypies and psychogenic feather picking represent two distinct forms of abnormal behavior in parrots, with implications for welfare and owner relinquishment. While both behaviors are common in captive parrots, relatively little is known about the factors that may predispose a parrot to their development. To assess the effects of potential social, environmental, and genetic factors, we performed an epidemiological study of a colony of 64 Orange-winged Amazon parrots. We first used mixed model methods to assess the narrow heritability, or genetic determination, of stereotypy, which was −0.08 ± 0.14, and feather picking, which was 1.14 ± 0.27. We then focused our study on one room of 27 birds that had always been housed in the same cage location. We examined the effects of neighbor behavior, number of neighbors, sex, family, age, cage row (beside an aisle or beside a wall), and distance from the door, on each behavior. Stereotypy was negatively correlated with the number of neighbors, but was unaffected by any other factor. In contrast, feather picking was affected by family, was more severe in females, and was progressively more severe in birds housed closer to the door when they had a direct line of sight of the door. Feather picking was spatially clustered in the room, but siblings from particular families were also more likely to be housed as neighbors than were non-siblings. Given the strong effect of family on feather picking and the effect of proximity to the door, these factors together explained the spatial clustering of feather picking. In addition, the feather picking of neighbors was uncorrelated. Thus, there was no evidence for social transmission of feather picking. Our results indicate that cages should be located away from potential stressors, and suggest that there is a potential for breeding against feather picking behavior in parrots. Finally, the markedly different genetic and environmental effects on stereotypies versus feather picking emphasizes that these are two distinct classes of Abnormal Repetitive Behavior in parrots.     

Supramolecularly assembled pentameric and octameric water clusters stabilized by a mixed complex of Ni(II)

Pyridine-2,4,6-tricarboxylic acid (ptcH₃) reacts with Ni(NO₃)₂ · 6H₂O and 2,2′-bipyridyl (bpy) in 2:2:1 molar ratio to form green crystals with the empirical formula, {[Ni(ptcH)₂][Ni(bpy)(H₂O)₄]6H₂O} (1). Water molecules present are associated to form discrete pentameric and octameric clusters which form an intricate array of H-bonding interactions with carboxylate O atoms, leading to a H-bonded 3D open framework structure. The water octamer takes the shape of a hexameric chair to which two water molecules are attached at one and four positions, while the pentameric structure is linear. Both these structures are unprecedented and their shapes are commensurate with the overall structure of the complex. Thermal analysis, X-ray powder diffraction and X-ray structural analysis have been used to characterize this compound.