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La respuesta al estrés oxidante de Candida glabrata a través de la regulación génica de CTA1
Get PDFTesis (Maestría en Ciencias en Biología Molecular)"Candida glabrata is an opportunistic pathogenic haploid yeast that is found as a commensal in healthy individuals but can cause severe infections in immunocompromised patients. C. glabrata has enzymatic and non-enzymatic mechanisms to counteract oxidative stress. C. glabrata has only one catalase (Cta1) which confers resistance to high concentrations of H2O2 in vitro. This suggests that the regulation of CTA1 expression might be important in understanding the virulence of this yeast. We did transcriptional fusions of the intergenic region between OYE2 and CTA1 and GFP as a reporter gene to map the CTA1 promoter, to identify cis-acting regulatory elements and to determine which transcription factors are important for the induction of CTA1 in the presence of oxidative stress. We generated 5' to 3' deletions of the intergenic region between OYE2 and CTA1 and analyzed the activity of the CTA1 promoter by FACS (Fluorescence-Activated Cell Sorting) in different genetic backgrounds (wild type, yap1Δ, skn7Δ, yap1Δ skn7Δ, msn2Δ, msn4Δ, msn2Δ msn4Δ). The basal promoter is located between -1 kb and -0.75 kb from the ATG of CTA1 and we found two cis-acting regulatory elements located between -4 kb and -3.3 kb, between -1.34 kb and -1 kb. In addition, we determined that both transcription factors, Yap1 and Skn7, are required for the induction of the CTA1 promoter in the presence of H2O2, while Msn2 and Msn4 are dispensable. Additionally, we performed a heterologous complementation assay with pPScCTA1::CgCTA1::3'UTRScCTA1 on different genetic backgrounds of S. cerevisiae: wild type, cta1Δ, ctt1Δ, cta1Δ ctt1Δ). Both in stationary phase and in log phase of growth, the different genetic backgrounds with the plasmid pPScCTA1::CgCTA1::3'UTRScCTA1 remarkably increase their resistance to H2O2., due to C. glabrata catalase higher enzymatic activity.""Candida glabrata is an opportunistic pathogenic haploid yeast that is found as a commensal in healthy individuals but can cause severe infections in immunocompromised patients. C. glabrata has enzymatic and non-enzymatic mechanisms to counteract oxidative stress. C. glabrata has only one catalase (Cta1) which confers resistance to high concentrations of H2O2 in vitro. This suggests that the regulation of CTA1 expression might be important in understanding the virulence of this yeast. We did transcriptional fusions of the intergenic region between OYE2 and CTA1 and GFP as a reporter gene to map the CTA1 promoter, to identify cis-acting regulatory elements and to determine which transcription factors are important for the induction of CTA1 in the presence of oxidative stress. We generated 5' to 3' deletions of the intergenic region between OYE2 and CTA1 and analyzed the activity of the CTA1 promoter by FACS (Fluorescence-Activated Cell Sorting) in different genetic backgrounds (wild type, yap1Δ, skn7Δ, yap1Δ skn7Δ, msn2Δ, msn4Δ, msn2Δ msn4Δ). The basal promoter is located between -1 kb and -0.75 kb from the ATG of CTA1 and we found two cis-acting regulatory elements located between -4 kb and -3.3 kb, between -1.34 kb and -1 kb. In addition, we determined that both transcription factors, Yap1 and Skn7, are required for the induction of the CTA1 promoter in the presence of H2O2, while Msn2 and Msn4 are dispensable. Additionally, we performed a heterologous complementation assay with pPScCTA1::CgCTA1::3'UTRScCTA1 on different genetic backgrounds of S. cerevisiae: wild type, cta1Δ, ctt1Δ, cta1Δ ctt1Δ). Both in stationary phase and in log phase of growth, the different genetic backgrounds with the plasmid pPScCTA1::CgCTA1::3'UTRScCTA1 remarkably increase their resistance to H2O2., due to C. glabrata catalase higher enzymatic activity."CONACYT fellowship 59046
A competent catalytic active site is necessary for substrate induced dimer assembly in triosephosphate isomerase
Get PDF"The protozoan parasite Trichomonas vaginalis contains two nearly identical triosephosphate isomerases (TvTIMs) that dissociate into stable monomers and dimerize upon substrate binding. Herein, we compare the role of the “ball and socket” and loop 3 interactions in substrate assisted dimer assembly in both TvTIMs. We found that point mutants at the “ball” are only 39 and 29-fold less catalytically active than their corresponding wild-type counterparts, whereas ?loop 3 deletions are 1502 and 9400-fold less active. Point and deletion mutants dissociate into stable monomers. However, point mutants assemble as catalytic competent dimers upon binding of the transition state substrate analog PGH, whereas loop 3 deletions remain monomeric. A comparison between crystal structures of point and loop 3 deletion monomeric mutants illustrates that the catalytic residues in point mutants and wild-type TvTIMs are maintained in the same orientation, whereas the catalytic residues in deletion mutants show an increase in thermal mobility and present structural disorder that may hamper their catalytic role. The high enzymatic activity present in monomeric point mutants correlates with the formation of dimeric TvTIMs upon substrate binding. In contrast, the low activity and lack of dimer assembly in deletion mutants suggests a role of loop 3 in promoting the formation of the active site as well as dimer assembly. Our results suggest that in TvTIMs the active site is assembled during dimerization and that the integrity of loop 3 and ball and socket residues is crucial to stabilize the dimer.
Evaluation of vascular tone and cardiac contractility in response to silver nanoparticles, using Langendorff rat heart preparation
Get PDF"Silver nanoparticles (AgNPs) have been widely used because of their antimicrobial properties. However, several reports suggest that AgNPs exposure promote cardiac effects that involve nitric oxide (NO) and oxidative stress (OS). Nevertheless, there are no studies related to AgNPs-induced effects in cardiac physiology. The aim of this study was to evaluate the AgNPs direct actions on coronary vascular tone and cardiac contractility using Langendorff rat heart preparation. Low concentrations of AgNPs (0.1 and 1 ?g/mL) increased NO derived from inducible NO-synthase (iNOS), without modifying cardiac parameters. Meanwhile, high concentrations (10 and 100 ?g/mL) promoted a sustained vasoconstriction and increased cardiac contractility related to OS, leading to rhabdomyolysis. Furthermore, AgNPs were internalized in the cardiac muscle, hindering classic actions induced by phenylephrine (Phe) and acetylcholine (ACh). These data suggest that AgNPs affect cardiac physiology in function of the concentration and in part of the NO generation, NOS expression and OS.
Flexible rewritable organic memory devices using nitrogen-doped CNTs/PEDOT:PSS composites
Get PDF"Nonvolatile rewritable organic memory devices based on poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and nitrogen doped multi-walled carbon nanotube (NCNT) nanocomposites were fabricated on glass and PET substrates.
Organic memory devices with bistable resistive switching were obtained using very low NCTN concentration (similar to 0.002 wt%) in the polymeric matrix. The memory devices exhibited a good ON/OFF ratio of approximately three orders of magnitude, a good retention time of 10(4) s under operating voltages <= vertical bar 4V vertical bar and a few hundredths of write-read-erase-read cycles. The bistable resistive switching is mainly attributed to the creation of oxygen vacancies. These defects are introduced into the thin native Al oxide (AlOx) layer on the bottom electrode during the first voltage sweep. The well-dispersed NCNTs immersed in PEDOT:PSS play a key role as conductive channels for the electronic transport, hindering the electron trapping at the AlOx-polymer interface and inducing a soft dielectric breakdown of the AlOx layer. These PEDOT:PSS NCNTs memory devices are to easy to apply in flexible low-cost technology and provide the possibility of large-scale integration.
Conventional and inverse elastocaloric effect in Ni-Fe-Ga and Ni-Mn-Sn ribbons
Get PDF"Magnetic shape memory Ni55Fe16Ga29 and Ni50Mn40Sn10 melt spun ribbons have been characterized by thermomechanical and mechanical analysis. Martensitic transformation temperatures show an abnormal tendency to decline under low stress followed by a conventional increase above a threshold stress, related to the internal compressive stress generated in the fabrication process. The shrinkage of the samples during the forward martensitic transformation gives rise to an inverse elastocaloric effect. A conventional contribution in the total elastocaloric response is observed when applied stress overcomes the internal one. The conventional and inverse elastocaloric effects are attributed to the stress-induced forward and reverse martensitic transformation, respectively.
Anthelmintic effect of Psidium guajava and Tagetes erecta on wild-type and Levamisole-resistant Caenorhabditis elegans strains
Get PDF"Ethnopharmacological relevance
Psidium guajava and Tagetes erecta have been used traditionally to treat gastrointestinal parasites, but their active metabolites and mechanisms of action remain largely unknown.
Aim of the study
To evaluate the anthelmintic potential of Psidium guajava and Tagetes erecta extracts on Levamisole-sensitive and Levamisole-resistant strains of the model nematode Caenorhabditis elegans.
Materials and methods
Aqueous extracts of Psidium guajava (PGE) and Tagetes erecta (TEE) were assayed on locomotion and egg-laying behaviors of the wild-type (N2) and Levamisole-resistant (CB193) strains of Caenorhabditis elegans.
Results
Both extracts paralyzed wild-type and Levamisole-resistant nematodes in a dose-dependent manner. In wild-type worms, TEE 25 mg/mL induced a 75% paralysis after 8 h of treatment and PGE 25 mg/mL induced a 100% paralysis after 4 h of treatment. PGE exerted a similar paralyzing effect on N2 wild-type and CB193 Levamisole-resistant worms, while TEE only partially paralyzed CB193 worms. TEE 25 mg/mL decreased N2 egg-laying by 65% with respect to the untreated control, while PGE did it by 40%.
Conclusions
Psidium guajava leaves and Tagetes erecta flower-heads possess hydrosoluble compounds that block the motility of Caenorhabditis elegans by a mechanism different to that of the anthelmintic drug Levamisole. Effects are also observable on oviposition, which was diminished in the wild-type worms. The strong anthelmintic effects in crude extracts of these plants warrants future work to identify their active compounds and to elucidate their molecular mechanisms of action.
Modeling and optimization of a photocatalytic process: degradation of endocrine disruptor compounds by Ag/ZnO
Get PDF"Artificial neural network (ANN) modeling was applied to study the photocatalytic degradation of bisphenol-A. The operating conditions of the Ag/ZnO photocatalyst synthesis and its performance were simultaneously modeled and subsequently optimized to target the highest efficiency in terms of the degradation reaction rate. Two ANN models were developed to simulate the stages of the photocatalyst synthesis and photodegradation performance, respectively. A direct dependence between the two networks was also established, thus making it possible to directly relate the degradation rate of the contaminant, not only to the photodegradation conditions, but also to the photocatalyst synthesis conditions. In this respect, an optimization study was carried out, by means of an evolutionary algorithm, in order to identify the optimal synthesis and photodegradation conditions that would result in the degradation of a maximal amount of the contaminant. Through this integrated approach it was demonstrated that neural network models can be proven valuable tools in the evaluation, simulation and, ultimately, the optimization of different stages of complex photocatalytic processes towards the maximization of the efficiency of the synthesized photocatalyst.
On the correct estimation of the magnetic entropy change across the magneto-structural transition from the Maxwell relation: study of MnCoGeBx alloy ribbons
Get PDF"An accurate calculation of the different magnetocaloric-related magnitudes derived from the temperature dependence of the magnetic entropy change in materials exhibiting first-order magnetocaloric effect is imperative to correctly estimate the true potential of a specific material for refrigeration purposes. In this contribution, we present a meticulous study of two different thermal procedures to measure the set of isothermal magnetization curves from which the total field induced magnetic entropy change, ?ST, is calculated using the adequate Maxwell relation. If the accurate determination of ?ST for any temperature is pursued the thermal and magnetic history of the materials must be taken into account, and then, the unidirectional measurement of reversible isothermal magnetization curves after a thermal cycle is required. The analysis was conducted on MnCoGeB0.01 alloy ribbons that show a giant ?ST at the coupled magneto-structural transition, from a ferromagnetic (TiNiSi-type) phase to a paramagnetic (NiIn2-type) one, owing to the concomitant abrupt magnetization change. We suggest that the conclusions reached can be applicable to any other system displaying magnetocaloric effect originated at a first-order phase transition.
Lagrangian trajectories, residual currents and rectification process in the Northern Gulf of California
Get PDF"Considering a semi-implicit approximation of the Coriolis terms, a numerical solution of the vertically integrated equations of motion is proposed. To test the two-dimensional numerical model, several experiments for the calculation of Euler, Stokes and Lagrange residual currents in the Gulf of California were carried out. To estimate the Lagrangian residual current, trajectories of particles were also simulated. The applied tidal constituents were M2, S2, K2, N2, K1, P1 and O1. At spring tides, strong tidal velocities occur in the northern half of the gulf. In this region of complex geometry, depths change from a few meter in the northern shelf zone to more than 3000 m in the southern part. In the archipelago region, the presence of islands alters amplitude and direction of tidal currents producing a rectification process which is reflected in a clockwise circulation around Tiburón Island in the Lagrangian residual current. The rectification process is explained by the superposition of the Euler and Stokes residual currents. Residual current patterns show several cyclonic and anticyclonic gyres in the Northern Gulf of California. Numerical experiments for individual and combinations of several tidal constituents revealed a large variability of Lagrangian trajectories.
Up-flow anaerobic sediment trapped (UAST) reactor as a new configuration for the enrichment of anammox bacteria from marine sediments
Get PDF"A novel reactor configuration for the enrichment of anammox bacteria from marine sediments was developed. Marine sediments were successfully kept inside the bioreactors during the enrichment process by strategically installing traps at different depths to prevent the wash-out of sediments. Three up-flow anaerobic sediment trapped (UAST) reactors were set up (α, β and ω supplied with 50, 150 and 300 mg Ca2+/L, respectively). Nitrogen removal rates (NRR) of up to 3.5 g N/L-d and removal efficiencies of >95% were reached. Calcium enhanced biomass production as evidenced by increased volatile suspended solids and extracellular polymeric substances. After the long-term operation, dominant families detected were Rhodobacteracea, Flavobacteracea, and Alteromonadacea, while the main anammox genera detected in the three reactors were Candidatus Kuenenia and Candidatus Anammoximicrobium. The UAST reactor is proposed as suitable technology for the enrichment of anammox bacteria applicable for the treatment of saline industrial wastewaters with high nitrogen content.