Estudi del procés de neurodegeneració

Les anomenades malalties neurodegeneratives tenen una simptomatologia i unes manifestacions clíniques molt diferents entre elles. No obstant, totes elles convergeixen en el mateix procés final, la neurodegeneració, que es manifestarà en diferents localitzacions o tipus cel·lulars del sistema nerviós. Nosaltres, plantegem la hipòtesi de que els processos moleculars i cel·lulars subjacents a la neurodegeneració són comuns per totes elles. Després de dur a terme un procés de selecció, es decideix treballar amb la malaltia de Parkinson, la d’Alzheimer, l’Esclerosi lateral amiotròfica i l’esclerosi múltiple. Hem pogut determinar que hi ha set processos moleculars o cel·lulars que estan associats al procés de neurodegeneració i que són comuns a totes elles. Havent-les estudiat per separat s’observa que el procés de neurodegeneració consisteix en una fallada en cadena de diferents sistemes moleculars i cel·lulars que tenen com a punt d’origen l’estrès oxidatiu. A aquest estrès s’hi pot arribar de diferents maneres. Una d’elles és l’exposició excessiva a certs metalls, que provoca la pèrdua dels sistemes antioxidants cel·lulars. Degut a això, els mitocondris reben un impacte oxidatiu massa gran i comencen a fallar. El fet que aquest orgànul actuï com a tampó del calci intracel·lular en provoca la seva desregulació, alterant d’aquesta manera el senyal nerviós. En resposta a l’estrès oxidatiu i tèrmic que genera la disfunció mitocondrial, s’activen les Proteïnes de Xoc Tèrmic (HSP) que actuant de citocines i presentadores d’antígens, inicien la resposta immunològica contra les cèl·lules danyades. Paral·lelament, s’observa un increment de la permeabilitat de la barrera hematoencefàlica degut a la pèrdua de les adhesions cel·lulars estretes per l’alta presència d’espècies reactives. Com a conseqüència de l’afebliment o el trencament de la barrera hematoencefàlica, es pot produir una entrada al SNC de diferents substàncies neurotòxiques i de cèl·lules del sistema immunitàri que, en condicions normals tenen l’accés restringit. Juntament amb aquestes cèl·lules immunològiques, també s’activen les cèl·lules del sistema immunitari innat residents al cervell, la micròglia, i totes elles secreten citocines proinflamatòries que contribueixen al procés de neurodegeneració. Nosaltres presentem els mecanismes pels quals aquesta inflamació, lluny d’atenuar-se, es cronifica per l’acció de certs bucles de retroalimentació positiva. Les diferents peculiaritats de cada malaltia contribueixen en aquest procés de diferents maneres, com és el cas dels pèptids β-amilides en la malaltia d’Alzheimer, l’α-sinucleina en el Parkinson, la superòxid dismutasa (SOD) en l’esclerosi lateral amiotròfica, o l’infiltració de leucòcits al cervell degut a la resposta autoimmune de l’esclerosi múltiple.Deixant de banda aquestes diferències, si el procés és comú entre totes elles, l’estudi a fons d’aquest procés hauria de poder permetre identificar dianes tarapèutiques que siguin comunes per les quatre malalties.

Predicting chick body mass by artificial intelligence-based models

The objective of this work was to develop, validate, and compare 190 artificial intelligence-based models for predicting the body mass of chicks from 2 to 21 days of age subjected to different duration and intensities of thermal challenge. The experiment was conducted inside four climate-controlled wind tunnels using 210 chicks. A database containing 840 datasets (from 2 to 21-day-old chicks) - with the variables dry-bulb air temperature, duration of thermal stress (days), chick age (days), and the daily body mass of chicks - was used for network training, validation, and tests of models based on artificial neural networks (ANNs) and neuro-fuzzy networks (NFNs). The ANNs were most accurate in predicting the body mass of chicks from 2 to 21 days of age after they were subjected to the input variables, and they showed an R² of 0.9993 and a standard error of 4.62 g. The ANNs enable the simulation of different scenarios, which can assist in managerial decision-making, and they can be embedded in the heating control systems.

Chemical chaperones regulate molecular chaperones in vitro and in cells under combined salt and heat stresses.

Salt and heat stresses, which are often combined in nature, induce complementing defense mechanisms. Organisms adapt to high external salinity by accumulating small organic compounds known as osmolytes, which equilibrate cellular osmotic pressure. Osmolytes can also act as "chemical chaperones" by increasing the stability of native proteins and assisting refolding of unfolded polypeptides. Adaptation to heat stress depends on the expression of heat-shock proteins, many of which are molecular chaperones, that prevent protein aggregation, disassemble protein aggregates, and assist protein refolding. We show here that Escherichia coli cells preadapted to high salinity contain increased levels of glycine betaine that prevent protein aggregation under thermal stress. After heat shock, the aggregated proteins, which escaped protection, were disaggregated in salt-adapted cells as efficiently as in low salt. Here we address the effects of four common osmolytes on chaperone activity in vitro. Systematic dose responses of glycine betaine, glycerol, proline, and trehalose revealed a regulatory effect on the folding activities of individual and combinations of chaperones GroEL, DnaK, and ClpB. With the exception of trehalose, low physiological concentrations of proline, glycerol, and especially glycine betaine activated the molecular chaperones, likely by assisting local folding in chaperone-bound polypeptides and stabilizing the native end product of the reaction. High osmolyte concentrations, especially trehalose, strongly inhibited DnaK-dependent chaperone networks, such as DnaK+GroEL and DnaK+ClpB, likely because high viscosity affects dynamic interactions between chaperones and folding substrates and stabilizes protein aggregates. Thus, during combined salt and heat stresses, cells can specifically control protein stability and chaperone-mediated disaggregation and refolding by modulating the intracellular levels of different osmolytes.

Emerging environmental and weather challenges in outdoor sports

Given the climatic changes around the world and the growing outdoor sports participation, existing guidelines and recommendations for exercising in naturally challenging environments such as heat, cold or altitude, exhibit potential shortcomings. Continuous efforts from sport sciences and exercise physiology communities aim at minimizing the risks of environmental-related illnesses during outdoor sports practices. Despite this, the use of simple weather indices does not permit an accurate estimation of the likelihood of facing thermal illnesses. This provides a critical foundation to modify available human comfort modeling and to integrate bio-meteorological data in order to improve the current guidelines. Although it requires further refinement, there is no doubt that standardizing the recently developed Universal Thermal Climate Index approach and its application in the field of sport sciences and exercise physiology may help to improve the appropriateness of the current guidelines for outdoor, recreational and competitive sports participation. This review first summarizes the main environmental-related risk factors that are susceptible to increase with recent climate changes when exercising outside and offers recommendations to combat them appropriately. Secondly, we briefly address the recent development of thermal stress models to assess the thermal comfort and physiological responses when practicing outdoor activities in challenging environments.

Parallel-Operating Three-Phase Voltage Source Inverters – Circulating CurrentModeling, Analysis and Mitigation

The maximum realizable power throughput of power electronic converters may be limited or constrained by technical or economical considerations. One solution to this problemis to connect several power converter units in parallel. The parallel connection can be used to increase the current carrying capacity of the overall system beyond the ratings of individual power converter units. Thus, it is possible to use several lower-power converter units, produced in large quantities, as building blocks to construct high-power converters in a modular manner. High-power converters realized by using parallel connection are needed for example in multimegawatt wind power generation systems. Parallel connection of power converter units is also required in emerging applications such as photovoltaic and fuel cell power conversion. The parallel operation of power converter units is not, however, problem free. This is because parallel-operating units are subject to overcurrent stresses, which are caused by unequal load current sharing or currents that flow between the units. Commonly, the term ’circulatingcurrent’ is used to describe both the unequal load current sharing and the currents flowing between the units. Circulating currents, again, are caused by component tolerances and asynchronous operation of the parallel units. Parallel-operating units are also subject to stresses caused by unequal thermal stress distribution. Both of these problemscan, nevertheless, be handled with a proper circulating current control. To design an effective circulating current control system, we need information about circulating current dynamics. The dynamics of the circulating currents can be investigated by developing appropriate mathematical models. In this dissertation, circulating current models aredeveloped for two different types of parallel two-level three-phase inverter configurations. Themodels, which are developed for an arbitrary number of parallel units, provide a framework for analyzing circulating current generation mechanisms and developing circulating current control systems. In addition to developing circulating current models, modulation of parallel inverters is considered. It is illustrated that depending on the parallel inverter configuration and the modulation method applied, common-mode circulating currents may be excited as a consequence of the differential-mode circulating current control. To prevent the common-mode circulating currents that are caused by the modulation, a dual modulator method is introduced. The dual modulator basically consists of two independently operating modulators, the outputs of which eventually constitute the switching commands of the inverter. The two independently operating modulators are referred to as primary and secondary modulators. In its intended usage, the same voltage vector is fed to the primary modulators of each parallel unit, and the inputs of the secondary modulators are obtained from the circulating current controllers. To ensure that voltage commands obtained from the circulating current controllers are realizable, it must be guaranteed that the inverter is not driven into saturation by the primary modulator. The inverter saturation can be prevented by limiting the inputs of the primary and secondary modulators. Because of this, also a limitation algorithm is proposed. The operation of both the proposed dual modulator and the limitation algorithm is verified experimentally.

Spatial variability of air dry bulb temperature and black globe humidity index in a broiler house during the heating phase

The air dry-bulb temperature (t db),as well as the black globe humidity index (BGHI), exert great influence on the development of broiler chickens during their heating phase. Therefore, the aim of this study was to analyze the structure and the magnitude of the t db and BGHI spatial variability, using geostatistics tools such as semivariogram analysis and also producing kriging maps. The experiment was conducted in the west mesoregion of the states of Minas Gerais in 2010, in a commercial broiler house with heating system consisting of two furnaces that heat the air indirectly, in the firsts 14 days of the birds' life. The data were registered at intervals of five minutes in the period from 8 a.m. to 10 a.m. The variables were evaluated by variograms fitted by residual maximum likelihood (REML) testing the Spherical and Exponential models. Kriging maps were generated based on the best model used to fit the variogram. It was possible to characterize the variability of the t db and BGHI, which allowed observing the spatial dependence by using geostatistics techniques. In addition, the use of geostatistics and distribution maps made possible to identify problems in the heating system in regions inside the broiler house that may harm the development of chicks.

Integrated multivariate analysis to evaluate effects of pre-slaughter handling on pork quality

The aim of this study was to investigate the effect of pre-slaughter handling on the occurrence of PSE (Pale, Soft, and Exudative) meat in swine slaughtered at a commercial slaughterhouse located in the metropolitan region of Dourados, Mato Grosso do Sul, Brazil. Based on the database (n=1,832 carcasses), it was possible to apply the integrated multivariate analysis for the purpose of identifying, among the selected variables, those of greatest relevance to this study. Results of the Principal Component Analysis showed that the first five components explained 89.28% of total variance. In the Factor Analysis, the first factor represented the thermal stress and fatiguing conditions for swine during pre-slaughter handling. In general, this study indicated the importance of the pre-slaughter handling stages, evidencing those of greatest stress and threat to animal welfare and pork quality, which are transport time, resting period, lairage time before unloading, unloading time, and ambience.

The impact of evaporative cooling on the thermoregulation and sensible heat loss of sows during farrowing

Pigs are more sensitive to high environmental temperatures explained by the inability of sweating and panting properly when compared to other species of farmed livestock. The evaporative cooling system might favor the thermal comfort of animals during exposure to extreme environmental heat and reduce the harmful effects of heat stress. The purpose of this study was to assess the sensible heat loss and thermoregulation parameters from lactating sows during summer submitted to two different acclimatization systems: natural and evaporative cooling. The experiment was carried out in a commercial farm with 72 lactating sows. The ambient variables (temperature, relative humidity and air velocity) and sows physiological parameters (rectal temperature, surface temperature and respiratory rate) were monitored and then the sensible heat loss at 21days lactation was calculated. The results of rectal temperature did not differ between treatments. However, the evaporative cooling led to a significant reduction in surface temperature and respiratory rate and a significant increase in the sow's sensible heat loss. It was concluded that the use of evaporative cooling system was essential to increase sensible heat loss; thus, it should reduce the negative effects of heat on the sows' thermoregulation during summer.

The use of protein structure/activity relationships in the rational design of stable particulate delivery systems

The recombinant heat shock protein (18 kDa-hsp) from Mycobacterium leprae was studied as a T-epitope model for vaccine development. We present a structural analysis of the stability of recombinant 18 kDa-hsp during different processing steps. Circular dichroism and ELISA were used to monitor protein structure after thermal stress, lyophilization and chemical modification. We observed that the 18 kDa-hsp is extremely resistant to a wide range of temperatures (60% of activity is retained at 80ºC for 20 min). N-Acylation increased its ordered structure by 4% and decreased its ß-T1 structure by 2%. ELISA demonstrated that the native conformation of the 18 kDa-hsp was preserved after hydrophobic modification by acylation. The recombinant 18 kDa-hsp resists to a wide range of temperatures and chemical modifications without loss of its main characteristic, which is to be a source of T epitopes. This resistance is probably directly related to its lack of organization at the level of tertiary and secondary structures.

Heat storage rate and acute fatigue in rats

Thermal environmental stress can anticipate acute fatigue during exercise at a fixed intensity (%VO2max). Controversy exists about whether this anticipation is caused by the absolute internal temperature (Tint, ºC), by the heat storage rate (HSR, cal/min) or by both mechanisms. The aim of the present study was to study acute fatigue (total exercise time, TET) during thermal stress by determining Tint and HSR from abdominal temperature. Thermal environmental stress was controlled in an environmental chamber and determined as wet bulb globe temperature (ºC), with three environmental temperatures being studied: cold (18ºC), thermoneutral (23.1ºC) or hot (29.4ºC). Six untrained male Wistar rats weighing 260-360 g were used. The animals were submitted to exercise at the same time of day in the three environments and at two treadmill velocities (21 and 24 m/min) until exhaustion. After implantation of a temperature sensor and treadmill adaptation, the animals were submitted to a Latin square experimental design using a 2 x 3 factorial scheme (velocity and environment), with the level of significance set at P<0.05. The results showed that the higher the velocity and the ambient temperature, the lower was the TET, with these two factors being independent. This result indicated that fatigue was independently affected by both the increase in exercise intensity and the thermal environmental stress. Fatigue developed at different Tint and HSR showed the best inverse relationship with TET. We conclude that HSR was the main anticipating factor of fatigue.

The Role of Membrane Lipid Composition on Sarco(endo)plasmic Reticulum Calcium ATPase Function in Rat Soleus Muscle

Sarco(endo)plasmic reticulum calcium ATPase (SERCA) is a transmembrane protein whose function is regulated by its immediate lipid environment (annulus). The composition of the annulus is currently unknown or it’s susceptibility to a high saturated fat diet (HSFD). Furthermore it is uncertain if HSFD can protect SERCA from thermal stress. The purpose of the study was to determine SERCA annular lipid composition, resulting impact of a HSFD, and in turn, influence on SERCA activity with and without thermal stress. The major findings were annular lipids were shorter and more saturated compared to whole homogenate and HSFD had no effect on annular lipid composition or SERCA activity with and without thermal stress. Both average chain length and unsaturation index were positively correlated with SERCA activity with and without thermal stress. These findings suggest that annular lipid composition is different than whole homogenate and its composition appears to be related to SERCA function.

Developmental, morphological, and behavioural plasticity in the reproductive strategies of stink bugs and their egg parasitoids

L’environnement façonne la physiologie, la morphologie et le comportement des organismes par l’entremise de processus écologiques et évolutifs complexes et multidimensionnels. Le succès reproducteur des animaux est déterminé par la valeur adaptative d’un phénotype dans un environnement en modification constante selon une échelle temporelle d’une à plusieurs générations. De plus, les phénotypes sont façonnés par l’environnement, ce qui entraine des modifications adaptatives des stratégies de reproduction tout en imposant des contraintes. Dans cette thèse, considérant des punaises et leurs parasitoïdes comme organismes modèles, j’ai investigué comment plusieurs types de plasticité peuvent interagir pour influencer la valeur adaptative, et comment la plasticité des stratégies de reproduction répond à plusieurs composantes des changements environnementaux (qualité de l’hôte, radiation ultraviolette, température, invasion biologique). Premièrement, j’ai comparé la réponse comportementale et de traits d’histoire de vie à la variation de taille corporelle chez le parasitoïde Telenomus podisi Ashmead (Hymenoptera : Platygastridae), démontrant que les normes de réaction des comportements étaient plus souvent positives que celles des traits d’histoires de vie. Ensuite, j’ai démontré que la punaise prédatrice Podisus maculiventris Say (Hemiptera : Pentatomidae) peut contrôler la couleur de ses œufs, et que la pigmentation des œufs protège les embryons du rayonnement ultraviolet; une composante d’une stratégie complexe de ponte qui a évoluée en réponse à une multitude de facteurs environnementaux. Puis, j’ai testé comment le stress thermique affectait la dynamique de la mémoire du parasitoïde Trissolcus basalis (Wollaston) (Hymenoptera : Platygastridae) lors de l’apprentissage de la fiabilité des traces chimiques laissées par son hôte. Ces expériences ont révélé que des températures hautes et basses prévenaient l’oubli, affectant ainsi l’allocation du temps passé par les parasitoïdes dans des agrégats d’hôtes contenant des traces chimiques. J’ai aussi développé un cadre théorique général pour classifier les effets de la température sur l’ensemble des aspects comportementaux des ectothermes, distinguant les contraintes des adaptations. Finalement, j’ai testé l’habileté d’un parasitoïde indigène (T. podisi) à exploiter les œufs d’un nouveau ravageur invasif en agriculture, Halyomorpha halys Stål (Hemiptera : Pentatomidae). Les résultats ont montré que T. podisi attaque les œufs de H. halys, mais qu’il ne peut s’y développer, indiquant que le ravageur invasif s’avère un « piège évolutif » pour ce parasitoïde. Cela pourrait indirectement bénéficier aux espèces indigènes de punaises en agissant comme un puits écologique de ressources (œufs) et de temps pour le parasitoïde. Ces résultats ont des implications importantes sur la réponse des insectes, incluant ceux impliqués dans les programmes de lutte biologique, face aux changements environnementaux.

Studies of cap-independent mRNA translation in Drosophila melanogaster

Control of protein synthesis is a key step in the regulation of gene expression during apoptosis and the heat shock response. Under such conditions, cap-dependent translation is impaired and Internal Ribosome Entry Site (IRES)-dependent translation plays a major role in mammalian cells. Although the role of IRES-dependent translation during apoptosis has been mainly studied in mammals, its role in the translation of Drosophila apoptotic genes has not been yet studied. The observation that the Drosophila mutant embryos for the cap-binding protein, the eukaryotic initiation factor eIF4E, exhibits increased apoptosis in correlation with up-regulated proapoptotic gene reaper (rpr) transcription constitutes the first evidence for the existence of a cap-independent mechanism for the translation of Drosophila proapoptotic genes. The mechanism of translation of rpr and other proapoptotic genes was investigated in this work. We found that the 5 UTR of rpr mRNA drives translation in an IRES-dependent manner. It promotes the translation of reporter RNAs in vitro either in the absence of cap, in the presence of cap competitors, or in extracts derived from heat shocked and eIF4E mutant embryos and in vivo in cells transfected with reporters bearing a non functional cap structure, indicating that cap recognition is not required in rpr mRNA for translation. We also show that rpr mRNA 5 UTR exhibits a high degree of similarity with that of Drosophila heat shock protein 70 mRNA (hsp70), an antagonist of apoptosis, and that both are able to conduct IRES-mediated translation. The proapoptotic genes head involution defective (hid) and grim, but not sickle, also display IRES activity. Studies of mRNA association to polysomes in embryos indicate that both rpr, hsp70, hid and grim endogenous mRNAs are recruited to polysomes in embryos in which apoptosis or thermal stress was induced. We conclude that hsp70 and, on the other hand, rpr, hid and grim which are antagonizing factors during apoptosis, use a similar mechanism for protein synthesis. The outcome for the cell would thus depend on which protein is translated under a given stress condition. Factors involved in the differential translation driven by these IRES could play an important role. For this purpose, we undertook the identification of the ribonucleoprotein (RNP) complexes assembled onto the 5 UTR of rpr mRNA. We established a tobramycin-affinity-selection protocol that allows the purification of specific RNP that can be further analyzed by mass spectrometry. Several RNA binding proteins were identified as part of the rpr 5 UTR RNP complex, some of which have been related to IRES activity. The involvement of one of them, the La antigen, in the translation of rpr mRNA, was established by RNA-crosslinking experiments using recombinant protein and rpr 5 UTR and by the analysis of the translation efficiency of reporter mRNAs in Drosophila cells after knock down of the endogenous La by RNAi experiments. Several uncharacterized proteins were also identified, suggesting that they might play a role during translation, during the assembly of the translational machinery or in the priming of the mRNA before ribosome recognition. Our data provide evidence for the involvement of La antigen in the translation of rpr mRNA and set a protocol for purification of tagged-RNA-protein complexes from cytoplasmic extracts. To further understand the mechanisms of translation initiation in Drosophila, we analyzed the role of eIF4B on cap-dependent and cap-independent translation. We showed that eIF4B is mostly involved in cap-, but not IRES-dependent translation as it happens in mammals.

A novel satellite-based ocean monitoring system for Mexico

To analyze patterns in marine productivity, harmful algal blooms, thermal stress in coral reefs, and oceanographic processes, optical and biophysical marine parameters, such as sea surface temperature, and ocean color products, such as chlorophyll-a concentration, diffuse attenuation coefficient, total suspended matter concentration, chlorophyll fluorescence line height, and remote sensing reflectance, are required. In this paper we present a novel automatic Satellite-based Ocean Monitoring System (SATMO) developed to provide, in near real-time, continuous spatial data sets of the above-mentioned variables for marine-coastal ecosystems in the Gulf of Mexico, northeastern Pacific Ocean, and western Caribbean Sea, with 1 km spatial resolution. The products are obtained from Moderate Resolution Imaging Spectroradiometer (MODIS) images received at the Direct Readout Ground Station (located at CONABIO) after each overpass of the Aqua and Terra satellites. In addition, at the end of each week and month the system provides composite images for several ocean products, as well as weekly and monthly anomaly composites for chlorophyll-a concentration and sea surface temperature. These anomaly data are reported for the first time for the study region and represent valuable information for analyzing time series of ocean color data for the study of coastal and marine ecosystems in Mexico, Central America, and the western Caribbean.

Desenvolvimento de microemulsões contendo fotoprotetores inorgânicos nanoparticulador

The inorganic actives, represented mainly by microfine zinc oxide and titanium dioxide, have shown great potential to protect against large UV spectrum. The aim of this study is the development, characterization and analysis of stability in the short term of microemulsions containing inorganic fotoprotection agents. The microemulsions identified by the phases diagram containing the metallic oxides were produced by two different methods and subjected to the centrifugation test and thermal stress cycles, and subsequently characterized by macroscopic evaluation, test dilution, electrical conductivity, pH, particle size, and zeta potential. This study highlights the influence of the metal oxides addition in the structure and distribution of micelles in the microemulsions