The role of interferon-gamma on immune and allergic responses

Allergic diseases have been closely related to Th2 immune responses, which are characterized by high levels of interleukin (IL) IL-4, IL-5, IL-9 and IL-13. These cytokines orchestrate the recruitment and activation of different effector cells, such as eosinophils and mast cells. These cells along with Th2 cytokines are key players on the development of chronic allergic inflammatory disorders, usually characterized by airway hyperresponsiveness, reversible airway obstruction, and airway inflammation. Accumulating evidences have shown that altering cytokine-producing profile of Th2 cells by inducing Th1 responses may be protective against Th2-related diseases such as asthma and allergy. Interferon-gamma (IFN-gamma), the principal Th1 effector cytokine, has shown to be crucial for the resolution of allergic-related immunopathologies. In fact, reduced production of this cytokine has been correlated with severe asthma. In this review, we will discuss the role of IFN-gamma during the generation of immune responses and its influence on allergic inflammation models, emphasizing its biologic properties during the different aspects of allergic responses.     

Classifying glycerol dehydratase by its functional residues and purifying selection in its evolution

Glycerol dehydratase (GD) catalyses glycerol reductive conversion to 3-hydroxypropanaldehyde (3-HPA), this being the first step required for the microbial conversion of glycerol to 1, 3 -propanodiol. GD has been functionally characterised to date and two main groups have been determined, one of them being vitamin B(12)-dependent and the other B(12)-independent. GD evolutionary history has been described and an exhaustive analysis made for detecting the functional residues responsible for type I divergence. GD phylogenetic tree topology was seen to be statistically robust and the data indicated strong purifying selection operating on the GD proteins within it. Two clades were indentified, one for vitamin B(12)-dependent and the other for B(12)- independent classes. The ancient hot-pot residues responsible for protein divergency for each clade were also identified. The basic evolutionary biology for GD proteins has been described, thereby opening the way forward for developing rational mutagenesis studies.     

Effects of protein-protein interactions on electron transfer: docking and electron transfer calculations for complexes between flavodoxin and c-type cytochromes

 Theoretical studies of protein-protein association and electron transfer were performed on the binary systems formed by Desulfovibrio vulgaris Hildenborough (D. v. H.) flavodoxin and D. v. H. cytochrome c ₅₅₃ and by flavodoxin and horse heart cytochrome c. Initial structures for the complexes were obtained by rigid-body docking and were refined by MD to allow for molecular flexibility. The structures thus obtained were analysed in terms of their relative stability through the calculation of excess energies. Electrostatic, van der Waals and solvation energy terms showed all to have significant contributions to the stability of complexes. In the best association solutions found for both cytochromes, these bind to different zones of flavodoxin. The binding site of flavodoxin observed for cytochrome c is in accordance with earlier works [27]. The various association modes found were characterised in terms of electron transfer using the Pathways model. For complexes between flavodoxin and horse heart cytochrome c, some correlation was observed between electron tunnelling coupling factors and conformation energy; the best conformation found for electron transfer corresponded also to the best one in terms of energy. For complexes between flavodoxin and cytochrome c ₅₅₃ this was not the case and a lower correlation was observed between electron tunnelling coupling factors and excess energies. These results are in accordance with the differences in the experimental dependence of electron transfer rates with ionic strength observed between these two cases. Received: 29 December 1998 / Accepted: 22 March 1999     

An Entangled Model for Sustainability Indicators

Nowadays the challenge for humanity is to find pathways towards sustainable development. Decision makers require a set of sustainability indicators to know if the sustainability strategies are following those pathways. There are more than one hundred sustainability indicators but they differ on their relative importance according to the size of the locality and change on time. The resources needed to follow these sustainability indicators are scarce and in some instances finite, especially in smaller regions. Therefore strategies to select set of these indicators are useful for decision makers responsible for monitoring sustainability. In this paper we propose a model for the identification and selection of a set of sustainability indicators that adequately represents human systems. In developing this model, we applied evolutionary dynamics in a space where sustainability indicators are fundamental entities interconnected by an interaction matrix. we used a fixed interaction that simulates the current context for the city of Cuernavaca, México as an example. We were able to identify and define relevant sets indicators for the system by using the Pareto principle. In this case we identified a set of sixteen sustainability indicators with more than 80% of the total strength. This set presents resilience to perturbations. For the Tangled Nature framework we provided a manner of treating different contexts (i.e., cities, counties, states, regions, countries, continents or the whole planet), dealing with small dimensions. This model provides decision makers with a valuable tool to select sustainability indicators set for towns, cities, regions, countries, continents or the entire planet according to a coevolutionary framework. The social legitimacy can arise from the fact that each individual indicator must be selected from those that are most important for the subject community.     

Morpho-physiology and maize grain yield under periodic soil flooding in successive selection cycles

This study was carried out to evaluate maize plants of different recurrent selection cycles of the variety (Zea mays L.—Saracura-BRS-4154) regarded to genetic gains, morphophysiology, and grain yield, achieved over the selection cycles under intermittent flooding of the soil. This variety has the capacity to survive and produce in temporarily flooded soils and was developed by the National Maize and Sorghum Research Center (EMBRAPA). The experiment was conducted in greenhouse by using ten alternating selection cycles (Cycle 1–18) and BR 107 a variety known for its susceptibility to flooding. The flooding initiated at six-leaf stage by applying 50 mm of water three times a week. At flowering, the following parameters were evaluated: rate of leaf photosynthesis, stomatal conductance, intercellular CO₂ concentration, transpiration rate, photosynthetically active leaf area, root porosity, relative chlorophyll content, grain yield, harvest index, ear length, and interval between male and female flowering. Yield as a function of root porosity and photosynthesis were also evaluated. An index was created in this study, in order to help the discussion of the characteristics evaluated, it was called “Relative Tolerance Value—RTV”, only gaseous exchange measurements was not included in this index. By the way, it was observed throughout the selection cycles an increase in all gaseous exchange parameters, being the cycle 18, the one which presented the greatest averages. RTV for leaf area showed the greatest values for cycles 7 and 18, whereas root porosity, chlorophyll relative content, and harvest index, the greater RTV values were found in cycles 17 and 18. The largest grain yield RTV was observed in cycle 7, followed by cycles 13, 15, and 18. Flooding resulted in longer Anthesis-Silking Interval, especially for the first cycles. At flooding condition, grain yield was strongly related to root porosity (R ² = 0.66). These results showed that the selection cycles of “Saracura” maize improved some morphophysiologic characters, which favor their survival in flooded environments, also resulting in higher productivity.     

Insights from functional morphology and neoichnology for determining tracemakers: a case study of the reconstruction of an ancient glacial arthropod‐dominated fauna

Apportioning trace fossils to producers is significant for palaeoecological and palaeoenvironmental studies. A tracemaker is usually attributed through the comparison of the morphology of the trace to the body plans of modern and extinct animals. However, hypotheses of tracemaker identifications may be tested with the use of further methods. This contribution aims to evaluate the potential tracemakers of a trackway‐dominated ichnofauna preserved in the siltstone–claystone rhythmites of the Pennsylvanian Rio do Sul Formation in the southern Brazil. These deposits are typical of the deglaciation phase of the Late Palaeozoic Ice Age of Gondwana in the Paraná Basin. Thus, the parameters applied in this work are as follows: (1) functional analyses of the traces to infer the biomechanics of the locomotion of the producer; and (2) neoichnology, whereby modern traces whose producers are known are compared to those of the ichnofauna in question. The conclusions obtained with these methods strongly support millipedes as the producers of Diplichnites gouldi and Diplopodichnus biformis. The malacostracan crustacean‐related ichnogenera are Umfolozia sinuosa and Gluckstadtella elongata, produced by syncarids or peracarids, while isopods are suggested as the tracemakers of Glaciichnium isp. and Protovirgularia dichotoma. In terms of branchiopod crustaceans, Cruziana problematica is attributed to notostracans. Helminthoidichnites tenuis, Mermia carickensis and Treptichnus pollardi are considered traces produced by insect larvae. The palaeobiology of the tracemakers that produced the ichnofauna preserved in the rhythmites of the Rio do Sul Formation permits inferences that terrestrial (millipedes) and aquatic (crustaceans and insect larvae) animals colonized the sediments. This conclusion points to a dynamic depositional environment, with changing physical and chemical parameters conditioning the biota.     

Ca(2+) influx and neurotransmitter release at ribbon synapses

Ca(2+) influx through voltage-gated Ca(2+) channels triggers the release of neurotransmitters at presynaptic terminals. Some sensory receptor cells in the peripheral auditory and visual systems have specialized synapses that express an electron-dense organelle called a synaptic ribbon. Like conventional synapses, ribbon synapses exhibit SNARE-mediated exocytosis, clathrin-mediated endocytosis, and short-term plasticity. However, unlike non-ribbon synapses, voltage-gated L-type Ca(2+) channel opening at ribbon synapses triggers a form of multiquantal release that can be highly synchronous. Furthermore, ribbon synapses appear to be specialized for fast and high throughput exocytosis controlled by graded membrane potential changes. Here we will discuss some of the basic aspects of synaptic transmission at different types of ribbon synapses, and we will emphasize recent evidence that auditory and retinal ribbon synapses have marked differences. This will lead us to suggest that ribbon synapses are specialized for particular operating ranges and frequencies of stimulation. We propose that different types of ribbon synapses transfer diverse rates of sensory information by expressing a particular repertoire of critical components, and by placing them at precise and strategic locations, so that a continuous supply of primed vesicles and Ca(2+) influx leads to fast, accurate, and ongoing exocytosis.     

Ecotypic differentiation in Medicago polymorpha L. along an environmental gradient in central Chile. I. Phenology,biomass production and reproductive patterns

Burr Medic (Medicago polymorpha) is awidespread, polymorphic annual legume of Mediterranean origin, and as aself-reseeding, highly effective nitrogen fixer it has important value invarious dryland farming systems. In central Chile, it is naturalized along a1000 km long environmental gradient, from an arid zone(29°–31° S) to a perhumid one(37°–38°24' S). Comparative and experimental studiesof its ecotypic differentiation patterns along this gradient should be usefulinelucidating the evolutionary forces at work along environmental gradients, andalso for efforts to select annual legumes for pastures and fallow fieldimprovement in mediterranean climate areas. In this first paper of atwo-part series, we present results of two common-environmentexperiments conducted at a subhumid site in central Chile to compare vegetativeand reproductive traits in 69 populations of Burr Medic collected in 1988 and1994. Multivariate analyses based on 11 phenological and agronomic characters,including phenology and biomass accumulation, winter vigour and degree ofhard-seededness, showed that three principal components (PCs)explained nearly 70% of total variability, in both collections. For thelarger collection (1988), the diagram of dispersion for the first twoPCs – phenology, winter vigour and above-ground biomass –provided good discrimination between accessions from arid-semiarid andhumid-perhumid mediterranean zones. Onset of flowering was positivelycorrelated with both latitude and longitude, as well as mean annualprecipitation/potential evapotranspiration (PP/ETP) ofcollecting site; days from first flower to pod ripening was negativelycorrelated with PP/ETP. In contrast to reports from Syria and Sardinia, noclear trends in Burr Medic seed or pod-related traits was found along theChilean gradient, apart from the concentration of spiny pod accessions in thesouthern, more mesic end of the gradient. Winter vigour (according to asemi-quantitative analysis of growth) was greater in accessions fromthe warmer, arid and semiarid zones than in those from cooler, subhumid tohumidones. Both winter vigour and harvest index were negatively correlated with daysto first flower. Applied and evolutionary aspects of the results are brieflydiscussed.