Detection of singlet oxygen and superoxide with fluorescent sensors in leaves under stress by photoinhibition or UV radiation

In order to understand the physiological functions of reactive oxygen species (ROS) generated in leaves, their direct measurement in vivo is of special importance. Here we report experiments with two dansyl-based ROS sensors, the singlet oxygen specific DanePy and HO-1889NH, which is reactive to both singlet oxygen and superoxide radicals. Here we report in vivo detection of (1)O(2) and O(2)(-*) by fluorescence quenching of two dansyl-based ROS sensors, the (1)O(2) specific DanePy and HO-1889NH, which was reactive with both (1)O(2) and O(2)(-*). The ROS sensors were administered to spinach leaves through a pinhole, and then the leaves were exposed to either excess photosynthetically active radiation or UV (280-360 nm) radiation. Microlocalization of the sensors' fluorescence and its ROS-induced quenching was followed with confocal laser scanning microscopy and with fluorescence imaging. These sensors were specifically localized in chloroplasts. Quenching analysis indicated that the leaves exposed to strong light produced (1)O(2), but hardly any O(2)(-*). On the other hand, the dominant ROS in UV-irradiated leaves was O(2)(-*), while (1)O(2) was minor.     

Levels of extra‐pair paternity are associated with parental care in penduline tits (Remizidae)

In most passerine birds, individuals attempt to maximize their fitness by providing parental care while also mating outside their pair bond. A sex‐specific trade‐off between these two behaviours is predicted to occur, as the fitness benefits of extra‐pair mating differ between the sexes. We use nest observations and parentage analysis to reveal a negative association between male care and the incidence of extra‐pair paternity across three species of penduline tit (Remizidae). This provides evidence of a trade‐off between these two behaviours, possibly due to the devaluing of paternal care by extra‐pair offspring.     

Twist function is required for the morphogenesis of the cephalic neural tube and the differentiation of the cranial neural crest cells in the mouse embryo

Loss of Twist function in the cranial mesenchyme of the mouse embryo causes failure of closure of the cephalic neural tube and malformation of the branchial arches. In the Twist(-/-) embryo, the expression of molecular markers that signify dorsal forebrain tissues is either absent or reduced, but those associated with ventral tissues display expanded domains of expression. Dorsoventral organization of the mid- and hindbrain and the anterior-posterior pattern of the neural tube are not affected. In the Twist(-/-) embryo, neural crest cells stray from the subectodermal migratory path and the late-migrating subpopulation invades the cell-free zone separating streams of cells going to the first and second branchial arches. Cell transplantation studies reveal that Twist activity is required in the cranial mesenchyme for directing the migration of the neural crest cells, as well as in the neural crest cells within the first branchial arch to achieve correct localization. Twist is also required for the proper differentiation of the first arch tissues into bone, muscle, and teeth.     

Major histocompatibility complex controls susceptibility and dominant inheritance,but not the severity of the disease in mouse models of rheumatoid arthritis

Collagen-induced arthritis (CIA) in DBA/1 and proteoglycan-induced arthritis (PGIA) in BALB/c mice are the most frequently used mouse models for studying clinical, immunological and genetic factors contributing to rheumatoid arthritis. DBA/1 ( H2(q)) mice are susceptible to CIA but resistant to PGIA, whereas BALB/c mice ( H2 (d)) are susceptible to PGIA and resistant to CIA. To gain insight into the mechanisms of how the major clinical (disease susceptibility, severity and onset of arthritis) and immunological traits (antigen-specific T- and B-cell responses) are influenced by the major histocompatibility complex (MHC), we have generated a unique intercross of BALB/c and DBA/1 parent strains, and the F1 and F2 hybrids were immunized for either CIA or PGIA. The major clinical and immunological traits were identified as either binary (qualitative) or quantitative traits on Chromosome 17 with a peak at MHC when the entire population was analyzed. In contrast, when only arthritic (susceptible) mice were selected and analyzed, the major clinical traits (severity and onset) 'lost' the linkage to MHC. Thus, MHC dictates disease susceptibility, but not the severity of arthritis. This was even more evident in the case of the H2(q) allele, which was clearly responsible for the dominant inheritance of arthritis in F2 hybrids (either CIA or PGIA). In conclusion, while certain MHC alleles strongly affect disease susceptibility and determine the mode of inheritance of a polygenic autoimmune disease, neither the type of inheritance (dominant vs recessive) nor other MHC components have evident effects upon the clinical symptoms of arthritis.     

Comparison of the effect of calcium(II) and manganese(II) ions on trypsin autolysis

The effect of Mn²⁺ and Ca²⁺ ions on the rate of trypsin autolysis was studied at pH 7.0 and at 34.4-60.2°C. For comparison, the kinetic constants of esterolytic activity of trypsin in the presence of the metal ion were determined at pH 7.4 and at 36° and 40°C. There was no significant difference in the rate of autolysis between Mn²⁺ and Ca²⁺ in the temperature range 34-47°C, but at 56.8° and 60.2° autolysis was slightly more rapid in the presence of Mn²⁺. The Mn²⁺ or Ca²⁺ ion bound to trypsin is supposed to control the conformation and thereby the stability and the activity of the enzyme. This indirect effect of Mn²⁺ and Ca²⁺ is discussed on a structural basis of the enzyme molecule.     

Ecological divergence of <Emphasis Type="Italic">Chaetopteryx rugulosa</Emphasis> species complex (Insecta,Trichoptera) linked to climatic niche diversification

Climate change may affect species diversity and, consequently, ecological processes such as leaf decomposition. We evaluated the effects of increased temperature and carbon dioxide (CO₂) on fungal biomass, leaf breakdown, and on survival and growth of the shredder Phylloicus elektoros. We hypothesized that climatic changes would result in lower survival and growth of shredders and lower leaf consumption by these organisms. On the other hand, we predicted an increase in fungal biomass in response to climatic changes. We conducted an experiment in Manaus, Brazil, using four microcosms that simulate real-time air temperature and CO₂ (control chamber), as well as three other chambers subjected to fixed increases in temperature and CO₂ as compared to the control chamber. The “extreme” condition represented an increase of ~4.5°C in temperature and ~870 ppm in CO₂ in relation to the control chamber. Total and shredder leaf-breakdown rates, fungal biomass, and shredder survival rates were significantly lower in warmer and CO₂ concentrated atmospheres. Shredder growth rate and leaf breakdown by microorganisms were similar among all climatic conditions. With climatic changes, we found an increase in the relative importance of microorganisms on leaf-breakdown rates as compared to shredders. Thus, lower leaf breakdown and a change in the main decomposer due to future climatic conditions may result in major changes in the pathways of organic matter processing and, consequently, in aquatic food webs.