Oxidative stress sensitivity in Debaryomyces hansenii.

Debaryomyces hansenii is an osmotolerant and halotolerant yeast of increasing interest for fundamental and applied research. In this work, we have performed a first study on the effect of oxidative stress on the performance of this yeast. We have used Saccharomyces cerevisiae as a well-known reference yeast. We show that D. hansenii is much more susceptible than S. cerevisiae to cadmium chloride, hydrogen peroxide or 1,4-dithiothreitol. These substances induced the formation of reactive oxygen species (ROS) in both yeasts, the amounts measured being significantly higher in the case of D. hansenii. We also show that NaCl exerted a protective effect against oxidative stress in Debaryomyces, but that this was not the case in Saccharomyces because sodium protected that yeast only when toxicity was induced with cadmium. On the basis of the present results, we raised the hypothesis that the sensitivity to oxidative stress in D. hansenii is related to the high amounts of ROS formed in that yeast and that observations such as low glutathione amounts, low basal superoxide dismutase and peroxidase activities, decrease in ATP levels produced in the presence of ROS inducers and high cadmium accumulation are determinants directly or indirectly involved in the sensitivity process.

Intercambio de gases respiratorios, respuestas cardiacas y metabólicas en altitud: estudio en pentatletas ecuatorianos / Breathing gas exchange and cardiac and metabolic responses by Ecuadorian pentathletes during altitude training

Introducción: El análisis de indicadores biomédicos como parte de la teoría y metodología del entrenamiento deportivo es sustancial en su proceso de dirección. Describe y analiza los efectos fisiológicos del entrenamiento específico en hipoxia en pentatletas es la base prospectiva para modelar entrenamientos efectivos que incidan significativamente en el rendimiento deportivo, permitiendo la dosificación correcta del estímulo físico. Objetivo: Determinar algunos indicadores relacionados con el intercambio de gases respiratorios, respuestas cardiacas y metabólicas en la altitud de pentatletas masculinos Sub 23 del Ecuador. Métodos: Se estudió la población del equipo masculino de Pentatlón Militar de las Fuerzas Armadas Ecuatorianas categoría Sub23 (6 sujetos) durante el macrociclo de entrenamiento del año 2014. Se investigaron indicadores de peso, frecuencia cardiaca, vo2 máximo, ritmo, velocidad, lactato, coeficiente de correlación y velocidad de recuperación de la frecuencia cardiaca y del lactato en sangre. Resultados: Se describieron los datos individuales y promedios de la población estudiada, entre los datos más relevantes se estimó una frecuencia cardiaca en reposo con un promedio de 46,33 por ciento, por debajo de las normativas internacionales. Otros indicadores también se comportaron muy por debajo de lo esperado, aunque el análisis individual de los sujetos mostró características útiles para futuros entrenamientos. Conclusiones: Potenciar aún más los parámetros funcionales investigados a través de un mejor estímulo físico, aprovechando las ventajas inherentes del entrenamiento en la altura y conformando posteriormente baremos nacionales de interés para el entrenador y la comisión técnica del deporte estudiado (AU)

Introduction: Analysis of biomedical indicators as a component of sport training theory and methodology is a crucial part of its management process. Describing and analyzing the physiological effects of specific hypoxic training on pentathletes is the prospective basis to model effective training programs significantly impacting on sport performance, allowing appropriate dosing of physical stimuli. Objective: Determine some indicators related to breathing gas exchange and cardiac and metabolic responses by male under-23 Ecuadorian pentathletes during altitude training. Methods: A study was conducted of the male under-23 military pentathlon team of the Ecuadorian Armed Forces (six subjects) during the 2014 training macrocycle. The indicators analyzed were weight, heart rate, VO2 max, rhythm, speed, lactate, correlation coefficient, and blood lactate and heart rate recovery speed. Results: Four tables show the data obtained, both individual and average for the study population. The most relevant data include an estimate of heart rate at rest with an average 46.33 ppm, below international standards. Other indicators were also considerably lower than the values expected, but individual analysis of subjects revealed characteristics useful for future training. Conclusions: It is recommended to further strengthen the functional parameters studied via a better use of physical stimuli, making use of the advantages inherent to altitude training to eventually develop national standard values of interest to both trainers and the technical committee for the sport being analyzed (AU)

Characterization of DhKHA1, a gene coding for a putative Na(+) transporter from Debaryomyces hansenii.

The KHA1 gene from Debaryomyces hansenii has been identified and characterized by heterologous expression in Saccharomyces cerevisiae. The gene is orthologous to ScKHA1, previously reported in S. cerevisiae, and on the basis of the deduced amino acid sequence, DhKha1p can be classified as an Na(+)/H(+) transporter. Reverse transcriptase (RT)-PCR experiments indicated that the expression level of DhKHA1 was not dependent on high pH or on the presence of a high salt level in the growth medium. Overexpression of DhKHA1 in a salt-sensitive S. cerevisiae mutant (ena1-4 nha1 kha1) rendered cells specifically more tolerant to Na(+). In addition, internal K(+) and Na(+) measurements and experiments performed with green fluorescence protein (GFP)-tagged DhKha1p indicated the intracellular localization of this protein when expressed in S. cerevisiae.

K+ fluxes in Schizosaccharomyces pombe.

All living cells accumulate high concentrations of K+ in order to keep themselves alive. To this end they have developed a great diversity of transporters. The internal level of K+ is the result of the net balance between the activities of the K+ influx and the K+ efflux transporters. Potassium fluxes have been extensively studied and characterized in Saccharomyces cerevisiae. However, this is not the case in the fission yeast and, in addition, the information available indicates that both yeasts present substantial and interesting differences. In this paper we have reviewed and summarized the information on K+ fluxes in Schizosaccharomyces pombe. We have included some unpublished results recently obtained in our laboratory and, in particular, we have highlighted the significant differences found between the well-known yeast S. cerevisiae and the fission yeast Sch. pombe.

On the role of Trk1 and Trk2 in Schizosaccharomyces pombe under different ion stress conditions.

Trk1 and Trk2 are the major K(+) transport systems in Schizosaccharomyces pombe. Both transporters individually seem to be able to cope with K(+) requirements of the cells under normal conditions, since only the double mutant shows defective K(+) transport and defective growth at limiting K(+) concentrations. We have studied in detail the role of SpTrk1 and SpTrk2 under different ion stress conditions. Results show that the strain with only Trk1 (trk1(+)) is less sensitive to Li(+) and to hygromycin B, it grows better at low K(+) and it survives longer in a medium without K(+) than the strain expressing only Trk2 (trk2(+)). We conclude that Trk1 contributes more efficiently than Trk2 to the performance of the fission yeast under ion stress conditions. In the wild type both trk1(+) and trk2(+) genes are expressed and probably collaborate for the performance of the cells.

Cation/H+ antiporters mediate potassium and sodium fluxes in Pichia sorbitophila. Cloning of the PsNHA1 and PsNHA2 genes and expression in Saccharomyces cerevisiae.

Pichia sorbitophila grows rapidly in the presence of very high NaCl concentrations. Under these conditions, even when the K(+) concentration is low, P. sorbitophila cells can maintain low Na(+) and high K(+) contents. This remarkable capacity of P. sorbitophila fails when the external pH is not acidic. This indicates that Na(+) efflux is mediated by an electroneutral Na(+)/H(+) antiporter. We have cloned and sequenced two genes designated as PsNHA1 and PsNHA2, which probably encode two antiporters of this type. The genes present high similarity with the corresponding genes from other yeasts. The heterologous expression of PsNHA1 or PsNHA2 in a Saccharomyces cerevisiae mutant lacking the Na(+) efflux systems and sensitive to high concentrations of Na(+) and K(+) rescued the tolerance and the ability to extrude both cations. The Accession Nos of the sequenced DNA fragments are: PsNHA1, AJ496431; PsNHA2, AJ496432. (TC 2.A.36)

Characterization of potassium transport in wild-type and isogenic yeast strains carrying all combinations of trk1, trk2 and tok1 null mutations.

Saccharomyces cerevisiae cells express three defined potassium-specific transport systems en-coded by TRK1, TRK2 and TOK1. To gain a more complete understanding of the physiological function of these transport proteins, we have constructed a set of isogenic yeast strains carrying all combinations of trk1delta, trk2delta and tok1delta null mutations. The in vivo K+ transport characteristics of each strain have been documented using growth-based assays, and the in vitro biochemical and electrophysiological properties associated with K+ transport have been determined. As has been reported previously, Trk1p and Trk2p facilitate high-affinity potassium uptake and appear to be functionally redundant under a wide range of environmental conditions. In the absence of TRK1 and TRK2, strains lack the ability specifically to take up K+, and trk1deltatrk2delta double mutant cells depend upon poorly understood non-specific cation uptake mechanisms for growth. Under conditions that impair the activity of the non-specific uptake system, termed NSC1, we have found that the presence of functional Tok1p renders cells sensitive to Cs+. Based on this finding, we have established a growth-based assay that monitors the in vivo activity of Tok1p.