Implications of storage and handling conditions on glass transition and potential devitrification of oocytes and embryos

Devitrification, the process of crystallization of a formerly crystal-free, amorphous glass state, can lead to damage during the warming of cells. The objective of this study was to determine the glass transition temperature of a cryopreservation solution typically used in the vitrification, storage, and warming of mammalian oocytes and embryos using differential scanning calorimetry. A numerical model of the heat transfer process to analyze warming and devitrification thresholds for a common vitrification carrier (open-pulled straw) was conducted. The implications on specimen handling and storage inside the dewar in contact with nitrogen vapor phase at different temperatures were determined. The time required for initiation of devitrification of a vitrified sample was determined by mathematical modeling and compared with measured temperatures in the vapor phase of liquid nitrogen cryogenic dewars. Results indicated the glass transition ranged from -126°C to -121°C, and devitrification was initiated at -109°C. Interestingly, samples entered rubbery state at -121°C and therefore could potentially initiate devitrification above this value, with the consequent damaging effects to cell survival. Devitrification times were calculated considering an initial temperature of material immersed in liquid nitrogen (-196°C), and two temperatures of liquid nitrogen vapors within the dewar (-50°C and -70°C) to which the sample could be exposed for a period of time, either during storage or upon its removal. The mathematical model indicated samples could reach glass transition temperatures and undergo devitrification in 30seconds. Results of the present study indicate storage of vitrified oocytes and embryos in the liquid nitrogen vapor phase (as opposed to completely immersed in liquid nitrogen) poses the potential risk of devitrification. Because of the reduced time-handling period before samples reach critical rubbery and devitrification values, caution should be exercised when handling samples in vapor phase.Fil: Sansinena, Marina Julia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Pontificia Universidad Católica Argentina "Santa María de los Buenos Aires"; ArgentinaFil: Santos, Maria Victoria. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos; ArgentinaFil: Taminelli, Guillermo Luis. Pontificia Universidad Católica Argentina "Santa María de los Buenos Aires"; ArgentinaFil: Zaritzky, Noemi Elisabet. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos; Argentin

Implications of storage and handling conditions on glass transition and potential devitrification of oocytes and embryos

Devitrification, the process of crystallization of a formerly crystal-free, amorphous glass state, can lead to damage during the warming of cells. The objective of this study was to determine the glass transition temperature of a cryopreservation solution typically used in the vitrification, storage, and warming of mammalian oocytes and embryos using differential scanning calorimetry. A numerical model of the heat transfer process to analyze warming and devitrification thresholds for a common vitrification carrier (open-pulled straw) was conducted. The implications on specimen handling and storage inside the dewar in contact with nitrogen vapor phase at different temperatures were determined. The time required for initiation of devitrification of a vitrified sample was determined by mathematical modeling and compared with measured temperatures in the vapor phase of liquid nitrogen cryogenic dewars. Results indicated the glass transition ranged from -126°C to -121°C, and devitrification was initiated at -109°C. Interestingly, samples entered rubbery state at -121°C and therefore could potentially initiate devitrification above this value, with the consequent damaging effects to cell survival. Devitrification times were calculated considering an initial temperature of material immersed in liquid nitrogen (-196°C), and two temperatures of liquid nitrogen vapors within the dewar (-50°C and -70°C) to which the sample could be exposed for a period of time, either during storage or upon its removal. The mathematical model indicated samples could reach glass transition temperatures and undergo devitrification in 30seconds. Results of the present study indicate storage of vitrified oocytes and embryos in the liquid nitrogen vapor phase (as opposed to completely immersed in liquid nitrogen) poses the potential risk of devitrification. Because of the reduced time-handling period before samples reach critical rubbery and devitrification values, caution should be exercised when handling samples in vapor phase.Fil: Sansinena, Marina Julia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Pontificia Universidad Católica Argentina "Santa María de los Buenos Aires"; ArgentinaFil: Santos, Maria Victoria. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos; ArgentinaFil: Taminelli, Guillermo Luis. Pontificia Universidad Católica Argentina "Santa María de los Buenos Aires"; ArgentinaFil: Zaritzky, Noemi Elisabet. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Universidad Nacional de la Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos; Argentin

Influence of the grain size and phase content on the mechanical behaviour of magnesium alloys. Gravity casting and SPS manufactured

El interés por los materiales biodegradables ha aumentado significativamente en los últimos años. En el contexto de los implantes óseos y las endoprótesis vasculares (“stents”), el magnesio, biocompatible, destaca sobre el resto de materiales. Siendo el metal estructural más ligero, su resistencia específica es sobresaliente. Su densidad y propiedades mecánicas son parecidas a las del tejido óseo, por lo que se evita la aparición de osteoporosis proximal que se debe a la transferencia de cargas a través del implante por diferencia de rígidez. La baja resistencia a la corrosión del Mg provoca fallo mecánico prematuro en la prótesis e inflamación del tejido circundante debido a la acumulación de gases. Es necesario utilizar otros elementos biocompatibles a modo de aleantes para mejorar la resistencia a la corrosión y el comportamiento mecánico. El calcio, el manganeso y el estroncio son nutrientes esenciales que, incorporados en pequeñas cantidades, reducen el tamaño de grano y la velocidad de corrosión, aumentando la resistencia mecánica. Mediante cálculos termodinámicos se predijeron y determinaron las composiciones más favorables de las aleaciones. Se llevó a cabo el estudio de muestras fabricadas por colada en molde permanente a partir de los sistemas Mg-Ca-Mn, Mg-Sr-Mn y Mg-Ca-Sr-Mn con el objetivo de determinar su potencial como materiales biomédicos. La microestructura y las fases presentes fueron caracterizadas. Se correlacionaron los resultados obtenidos en ensayos de dureza y compresión con el tamaño de grano y la naturaleza y cantidad de fases. Se exploró una vía alternativa de producción mediante pulvimetalurgia. El sistema Mg-Ca-Mn fue escogido para esta tarea debido a las propiedades ventajosas del calcio. El proceso, consistente en una primera etapa de aleación mecánica para obtener un polvo de calidad seguida de sinterización por plasma pulsado, fue optimizado.The interest in biodegradable materials has significantly increased in recent years. In the context of bone implants and vascular stents, biocompatible magnesium stands out as a unique option. As the lightest structural metal, it has outstanding strength to weight ratio with density and mechanical properties close enough to those of bone tissue to avoid stress shielding. Poor corrosion resistance of Mg leads to premature mechanical failure of implants and inflammation of surrounding tissue due to hydrogen gas accumulation. Alloying using biocompatible elements is needed to improve corrosion and mechanical behaviour. Calcium, manganese and strontium are essential nutrients that, added in low quantities, induce grain refinement, corrosion resistance and strengthening of Mg. Thermodynamic calculations were used to predict and determine favourable alloy compositions. Gravity cast samples of Mg-Ca-Mn, Mg-Sr-Mn and Mg-Ca-Sr-Mn systems were studied to determine their potential as biomedical materials. Characterization of microstructure and phases was carried out. The mechanical data obtained from hardness and compression tests were linked to grain size and phase content and nature. Exploration of a powder metallurgy manufacturing route was performed. The Mg-Ca-Mn system was chosen for this task, owing to the beneficial properties of calcium. Mechanical alloying to produce quality powder was followed by spark plasma sintering. The process was optimized.Ingeniería Industria

The effects of self-efficacy on physical and cognitive performance: An analysis of meta-certainty

In the present research, we analyzed the effects of self-efficacy (SE) on physical and cognitive performance in real-world settings as a function of the metacognitive certainty in SE. In three studies, participants completed a measure of SE, which asked them to report how sure they were that they can achieve several specific results on various athletic and academic tasks. Moreover, general certainty in their own SE (i.e., SEC) was measured (Studies 1 and 3) or manipulated to be high versus low (Study 2). Relevantly, our studies aimed to obtain a high level of ecological validity by including athletes in natural, real-world settings (i.e., gymnasiums). Furthermore, we sought to extend the findings beyond physical performance by analyzing university students’ cognitive performance in their actual academic setting (i.e., classrooms). Specifically, physical performance was assessed with pull-ups (Study 1) and vertical jump tests (Study 2), and cognitive performance was measured with grades on exams (Study 3). As expected, SE was positively related to performance. Most importantly, we predicted and found an interaction between SE and SEC on performance. That is, the effect of SE on physical and cognitive performance was greater for participants with higher (vs. lower) metacognitive certainty in their SE. In conclusion, to increase the explanatory and predictive power of efficacy beliefs across different domains, we propose that the assessment of SE should also include measures of one's metacognitive certainty in SE. In addition, we suggest that interventions on SE could benefit from the use of certainty inductions when including these inductions is possible and convenientThis work was supported in part by the Ministerio de Economía, Industria y Competitividad (Spain) [Grant number PSI2017-83303-C2- 1-P], and by the Ministerio de Ciencia e Innovación (Spain) [Grant number PID2020-116651GB-C33