Cronotipo y su relación con el estrés percibido en estudiantes de medicina / Chronotype and its relationship with perceived stress in medical students

Resumen Objetivo: Evaluar el cronotipo y su relación con el nivel de estrés percibido en estudiantes de medicina de una Universidad Pública de México. Material y métodos: Estudio transversal, que incluyó 332 universitarios. Se aplicaron el cuestionario de matutinidad-vespertinidad (MEQ) y la escala de estrés percibido (PSS-14). Se emplearon las pruebas no paramétricas de Kruskal-Wallis para establecer diferencias estadísticas entre cronotipos y el coeficiente de Spearman para establecer la correlación entre puntajes de escalas. Se consideró un nivel de significancia estadística de p<0.05. Resultados: Para el total de la muestra, la mediana del puntaje del MEQ fue 52. El cronotipo tuvo la siguiente distribución: 21.1% matutino; 72.3% intermedio; 6.6% vespertino. La mediana del puntaje de la PSS-14 fue 28. El puntaje del nivel de estrés percibido en mujeres fue mayor al de los hombres (29 vs 24.5; p=0.000). En cada cronotipo la mediana del puntaje de la PSS-14 fue mayor en mujeres que en hombres, aunque sólo se encontró diferencia estadísticamente significativa entre vespertinos (p=0.000). El resultado del coeficiente de correlación de Spearman mostró una relación significativa entre el cronotipo y el puntaje de estrés percibido (rho= -0.143; p=0.009). Conclusión: El cronotipo vespertino está relacionado con un mayor puntaje de estrés percibido, particularmente en mujeres quienes tuvieron la puntuación más alta en cada cronotipo.

Abstract Objective: To assess chronotype and its relationship with the perceived stress level in medical students from a public university in Mexico. Material and methods: Cross-sectional study that included 332 college students. Morningness-eveningness questionnaire (MEQ) and perceived stress scale (PSS-14) were applied. Non-parametric Kruskal-Wallis test was used to establish statistical differences between chronotypes and the Spearman correlation coefficient was used to establish a correlation between MEQ and PSS-14 scores. The p-value equal to or less than 0.05 corresponded to the statistically significant result (p<0.05). Results: For the entire sample, the median of the MEQ score was 52. The distribution of chronotypes was as follows: 21.1% morning chronotype; 72.3% intermediate chronotype; 6.6% evening chronotype. The PSS-14 median score was 28. PSS-14 score in women was higher than in men (29 vs 24.5; p= 0.000). The median of the PSS-14 score in each chronotype group was higher in women than in men; nevertheless, a statistically significant difference between them was only found in evening chronotype (p= 0.000). The result of Spearman's correlation coefficient showed significant relationship between chronotype and perceived stress score (rho= -0.143; p=0.009). Conclusion: Evening chronotype is associated with a higher PSS-14 score, particularly in women, who had the highest score in each chronotype.

Class I MHC Polymorphisms Associated with Type 2 Diabetes in the Mexican Population.

Type 2 diabetes (T2D) has been linked to the expression of Human Leukocyte Antigens, principally to the Major Histocompatibility Complex Class II, with only scarce reports of Major Histocompatibility Complex Class I in specific populations. The objective of the present work was to explore the presence of polymorphisms in the MHC Class I related to T2D in the Mexican population using the Genome-Wide Association Studies Slim Initiative in Genomic Medicine of the Americas (GWAS SIGMA) database. This database contains information on 3848 Mexican individuals with T2D and 4366 control individuals from the same population without a clinical or hereditary history of the disease. The searching criteria considered a p-value of <0.005 and an odds ratio (OR) of >1.0. Ten novel, statistically significant nucleotide variants were identified: four polymorphisms associated with HLA-A (A*03:01:01:01) and six with HLA-C (C*01:02:01:01). These alleles have a high prevalence in Latin American populations and could potentially be associated with autoimmunity mechanisms related to the development of T2D complications.

Exohidrolasas fructosílicas y su importancia en el metabolismo de fructanos en Agave tequilana Weber var. azul / Fructan exohydrolases y its importance in the metabolism of fructans in Agave tequilana Weber var. azul / Exoidrolases de frutanos e sua importância no metabolismo de frutanos em Agave tequilana Weber var. azul

Resumen Los fructanos son carbohidratos de estructura química diversa distribuidos en diferentes taxa. En las plantas, además de constituir una importante fuente de carbono, han sido asociados con la tolerancia a diferentes tipos de estrés. La biosíntesis de estos compuestos se lleva a cabo por la acción de las enzimas fructosiltransferasas, mientras que su degradación es mediada por las exohidrolasas fructosílicas, ambos tipos forman parte de la familia 32 de las enzimas hidrolasas glicosídicas. Las exohidrolasas fructosílicas son exoenzimas que liberan secuencialmente residuos de fructosa terminales de los fructanos para hacerlos disponibles como fuente de carbono en diferentes procesos celulares o bien moléculas de señalización. En esta revisión se hace una descripción de los fructanos y las exohidrolasas fructosílicas en algunas plantas importantes para el consumo humano y para el aprovechamiento industrial, con un enfoque particular en el género Agave, específicamente en A. tequilana. Concluimos, que el estudio de las exohidrolasas fructosílicas en agaves podría ser útil en varias aplicaciones biotecnológicas como en la hidrólisis de estructuras de fructanos no digeridos durante la etapa de cocción del agave en el proceso de producción de tequila. Sin embargo, el primer paso es conocer la funcionalidad de estas enzimas, lo que podría facilitar su incorporación en diferentes procesos biotecnológicos.

Abstract Fructans are carbohydrates of diverse chemical structure that are distributed in different taxa. In plants, in addition to be an important source of carbon, they have been associated with tolerance to different types of stress. The biosynthesis of these compounds is carried out by the action of enzymes called fructosyltransferases, while their degradation is mediated by fructan exohydrolases, both types are part of the 32 family of glycosidic hydrolase enzymes. Fructan exohydrolases are exo-enzymes that sequentially release terminal fructose residues from fructans to make them available as carbon sources for different cellular processes or as signaling molecules. In this review, a description is made of fructans, y of fructosyl exohydrolases in some plants important for human consumption or for industrial use, such as the Agave genus, specifically in A. tequilana. We conclude that the study of fructan exohydrolases in agaves could be useful in various biotechnological applications, for example, in the hydrolysis of undigested fructan structures during the agave cooking stage in the tequila production process. However, the first step is to determinate the enzymatic activity in which they are involved, for its posterior inclusion in biotechnology processes.

Resumo Os frutanos são carboidratos de estrutura química diversificada distribuídos em diferentes táxons. Nas plantas, além de serem uma importante fonte de carbono, eles têm sido associados à tolerância a diferentes tipos de estresse. A biossíntese desses compostos é realizada pela ação das enzimas fructosiltransferases, enquanto sua degradação é mediada por frutossil exohidrolases, ambos os tipos fazem parte da família 32 de enzimas glicosídicas da hidrolase. As exo-hidrolases de frutossil são exo-enzimas que liberam seqüencialmente resíduos terminais de frutose dos frutanos para torná-los disponíveis como fonte de carbono em diferentes processos celulares, ou como sinalizadores. Nesta revisão, é feita uma descrição dos frutanos e das frutossil exohidrolases em algumas plantas importantes para o consumo humano ou para uso industrial, como o gênero Agave, especificamente no A. tequilana. Concluímos que o estudo de frutossil exo-hidrolases em agaves pode ser útil em várias aplicações biotecnológicas, por exemplo, na hidrólise de estruturas de frutano não digeridas durante a fase de cozimento da agave no processo de produção de tequila. Para isso, o primeiro passo é conhecer o tipo de atividade enzimática que eles desempenham, para sua posterior inclusão no campo da biotecnologia.

Marcadores de estrés oxidativo en pacientes con esclerosis múltiple durante un brote y su remisión / Oxidative stress markers in patients with multiple sclerosis during an outbreak and its remission / Marcadores de estresse oxidativo em pacientes com esclerose múltipla durante um surto e sua remissão

La esclerosis múltiple remitente-recurrente (EM-RR) es una enfermedad desmielinizante del sistema nervioso central. A fin de entender la asociación del estrés oxidativo a nivel periférico con la recaída de la enfermedad se determinaron los niveles de marcadores de estrés oxidativo en plasma de pacientes en la recaída o brote y una semana después de la misma. Se analizaron muestras de 60 personas (20 pacientes con recaída, 20 pacientes sin recaída y 20 controles sanos). Se cuantificaron mediante métodos espectrofotométricos las actividades enzimáticas de óxido nítrico sintasa (ONS), glutatión peroxidasa (GPx), los niveles de lipoperóxidos y nitritos-nitratos y la fluidez de membrana. En el brote de la enfermedad aumentan significativamente los niveles de las actividades enzimáticas de ONS y GPx y los niveles de nitritos-nitratos y lipoperóxidos (p<0,01 en todos los casos), al ser comparados con los de individuos sanos. Dichos parámetros disminuyeron significativamente una semana después de iniciado el brote. Además, los parámetros evaluados se mantuvieron elevados en pacientes que no experimentaron un brote de la enfermedad cuando se los comparó con individuos sanos. La fluidez de membrana en los pacientes con y sin brote fue similar a la de los controles. En conclusión, el estrés oxidativo es un componente importante en los pacientes con esclerosis múltiple.

Recurrent-remitting multiple sclerosis (RR-MS) is a demyelinating disease of the central nervous system. In order to understand the association of oxidative stress at the peripheral level with the relapse of the disease, the levels of oxidative stress markers in plasma of patients in the relapse or outbreak and one week after relapse were determined. Samples of 60 subjects were analyzed (20 patients in relapse, 20 patients without relapse, and 20 healthy controls). The enzymatic activities of nitric oxide synthase (NOS), glutathione peroxidase (GPx), lipoperoxides and nitrite-nitrate levels and membrane fluidity were quantified by spectrophotometric methods. In relapse, the levels of enzymatic activities of NOS and GPx, and the levels of lipoperoxides and nitrites-nitrates were significantly increased (p<0.01, in all cases), compared with healthy individuals. These parameters decreased significantly 1 week after the start of the outbreak. In addition, the parameters evaluated remained high in patients who did not experience an outbreak of the disease compared to healthy subjects. The membrane fluidity in the patients with and without outbreak was similar to that of the controls. In conclusion, oxidative stress is an important component in patients with multiple sclerosis.

A esclerose múltipla recorrente-remitente (EM-RR) é uma doença desmielinizante do sistema nervoso central. Para compreender a associação do estresse oxidativo a nível periférico com a recaída da doença foram determinados os níveis de marcadores de estresse oxidativo em plasma de doentes na recaída ou surto e uma semana após a recaída. Foram analisadas a amostras de 60 pessoas (20 pacientes com recaída, 20 pacientes sem recaída e 20 controles saudáveis). As atividades enzimáticas de óxido nítrico sintase (ONS), glutationa peroxidase (GPX), os níveis de lipoperóxidos e nitritos-nitratos e a fluidez de membrana foram quantificadas por métodos espectrofotométricos. No surto da doença aumentam em forma significativa os níveis da atividade enzimática de ONS e GPX, e os níveis de nitritos-nitratos e lipoperóxidos (p<0,01 em todos os casos), em comparação com os indivíduos saudáveis. Esses parâmetros diminuíram significativamente uma semana após o início do surto. Além disso, os parâmetros avaliados permaneceram elevados em pacientes que não experimentaram um surto da doença quando comparados com indivíduos saudáveis. A fluência de membrana nos pacientes com e sem surto foi semelhante à dos controles. Em conclusão, o estresse oxidativo é um componente importante nos pacientes com esclerose múltipla.

Estrés y cortisol: implicaciones en la ingesta de alimento / Stress and cortisol: implications on food intake

La búsqueda de alimento y su consumo son conductas dirigidas a satisfacer la obtención de los sustratos energéticos necesarios para sostener las diferentes funciones orgánicas que un individuo requiere para garantizar su supervivencia. La conducta alimentaria cuenta con dos sistemas reguladores, uno homeostático ubicado en hipotálamo y otro de tipo hedónico, representado por el sistema de recompensa cerebral. Dichos sistemas están modulados por señales estimuladoras (orexigénicas) e inhibidoras (anorexigénicas) del apetito. En condiciones de estrés crónico, la actividad del eje hipotálamo-hipófisis-adrenal, que regula la concentración de cortisol plasmático, dará lugar al establecimiento de diferentes mecanismos que promuevan la ingesta de alimento de elevada densidad energética, los cuales son considerados como poderosos disruptores de los procesos de regulación del apetito, condición potencialmente capaz de favorecer el desarrollo de una conducta compulsiva en la búsqueda de alimento, una disrupción en el balance energético y obesidad. El consumo repetido de alimentos apetitosos representa para los individuos vulnerados una oportunidad de automedicación dirigida al alivio del estrés, brindando una condición u oportunidad de confort. Los datos epidemiológicos sustentan la idea de un fuerte vínculo entre glucocorticoides y síndrome metabólico. La relación entre estrés crónico, cortisol e ingesta elevada de alimento tienen a la adiposidad visceral y a la resistencia a la insulina como factores predisponentes de una disrupción metabólica con consecuencias importantes al estado de salud de los seres humanos. El presente artículo tiene como objetivo valorar las implicaciones del estrés y cortisol sobre la ingesta de alimento.

Behaviors such as the search and consumption of food are aimed to obtain the energy substrates needed to sustain diverse organic functions required to guarantee the survival of an individual. The alimentary behavior has two regulatory systems: the homeostatic system, located in the hypothalamus and the hedonic system, represented by the cerebral reward system. These systems are modulated by both stimulatory (orexigenic) and inhibitory (anorexigenic) signals of appetite. Under chronic stress conditions, the activity of the hypothalamic-pituitary-adrenal axis, which regulates the plasma cortisol concentration, will lead to the establishment of different mechanisms that promote the ingestion of food with high energy density, which are considered as powerful disruptors of appetite regulation processes, a condition potentially capable of promoting the development of compulsive food search behavior, a disruption in the energy balance and obesity. Repeated consumption of appetizing foods represents an opportunity for self-medication aimed at stress relief, providing a condition or opportunity for comfort. Epidemiological data suggests a strong link between glucocorticoids and metabolic syndrome. The relationship between chronic stress, cortisol and high food intake has visceral adiposity and insulin resistance as predisposing factors of metabolic disruption with important consequences to the health status of humans. The purpose of this article is to evaluate the implications of stress and cortisol on food intake.

Comparación de los métodos de antropometría clásica e impedancia bioeléctrica a través de la determinación de la composición corporal en jóvenes universitarias / Comparison of classical anthropometry methods and bioelectrical impedance through the determination of body composition in university students

Introducción: Evaluar la composición corporal (CC) por antropometría clásica e impedancia bioeléctrica (IB) permite conocer la proporción de los diferentes segmentos corporales y su relación con el estado nutricional, sin embargo, no está suficientemente documentado si ambos métodos resultan comparables en la evaluación de mujeres jóvenes. El objetivo de este estudio es comparar la composición corporal por antropometría clásica e impedancia bioeléctrica en jóvenes universitarias sanas. Material y Métodos: Estudio correlacional, comparativo, transversal y retrospectivo. Donde participaron 60 mujeres universitarias, con edad promedio: 20,9 ± 2,3. Se calculó el índice de masa corporal (IMC); antropometría/ecuaciones: Grasa corporal (GC)/ Siri, Deurenberg y Lean; masa muscular (MM)/ Heymsfield y Poortmans; agua corporal (AC)/ Watson y Hume. Antropometría realizada según ISAK(R). IB analizador tetrapolar de medición segmental directa. Estadística: prueba t de student, coeficiente de correlación de intraclase (CCI), Spearman (CCS) y gráficos de Bland-Altman. Resultados: Peso y estatura promedio 56,94±10,21 kg, 159±6,38 cm, respectivamente. El IMC promedio fue de 22,24 ± 3,15. Antropometría clásica e IB: GC (%): Siri 28,4±4,55, Deurenberg 26,0±4,41, Lean 26,94±3,66 e IB 32,3±7,04; mejor CCI: Siri-IB (0,600). MM (kg): Heymsfield 17, 47 ± 3,81, Poortmans 25,85 ± 4,62, IB 20,55 ± 2,77; mejor CCI: Poortmans-IB (0.719). AC (%): Watson 51, 6 ± 3,75, Hume 53,5 ± 4,77, IB 49,96 ± 4,69; mejor CCI: Watson-IB (0.817). Conclusiones: Al comparar la CC por ambos métodos las ecuaciones de Siri, Poortmans y Watson para la determinación de la GC, MM y AC, respectivamente presentaron mayor asociación respecto a la IB

Introduction: Assessing the body composition (CC) by classical anthropometry and bioelectrical impedance (BI) allows to know the proportion of the different body segments and their relationship with the nutritional status, however, it is not sufficiently documented if both methods are comparable in the evaluation of young women. The objective of this study is to compare body composition by classical anthropometry and bioelectrical impedance in healthy university students. Material and Methods: Correlational, comparative, transversal and retrospective study. Where 60 university women participated, with average age: 20.9 ± 2.3. The body mass index (BMI) was calculated; anthropometry/equations: Body fat (CF) / Siri, Deurenberg and Lean; muscle mass (MM) / Heymsfield and Poortmans; body water (BW) / Watson and Hume. Anthropometry performed according to ISAK(R). IB with the tetrapolar direct segmental measurement analyzer. Statistics: Student's t-test, intraclass correlation coefficient (CCI), Spearman (CCS) and Bland-Altman graphs. Results: Average height and weight 56.94 ± 10.21 kg, 159 ± 6.38 cm, respectively. The estimated BMI was similar with both methods (p> 0.05). Classical anthropometry and IB: GC (%): Siri 28.4 ± 4.55, Deurenberg 26.0 ± 4.41, Lean 26.94 ± 3.66 and IB 32.3 ± 7.04; best CCI: Siri-IB (0,600). MM (kg): Heymsfield 17.47 ± 3.81, Poortmans 25.85 ± 4.62, IB 20.55 ± 2.77; best CCI: Poortmans-IB (0.719). AC (%): Watson 51.6 ± 3.75, Hume 53.5 ± 4.77, IB 49.96 ± 4.69; best CCI: Watson-IB (0.817). Conclusions: When comparing the CC by both methods, the equations of Siri, Poortmans, and Watson for the determination of the GC, MM, and AC, respectively, showed a greater association with respect to the IB

Analysis and optimization of bulk DNA sampling with binary scoring for germplasm characterization.

The strategy of bulk DNA sampling has been a valuable method for studying large numbers of individuals through genetic markers. The application of this strategy for discrimination among germplasm sources was analyzed through information theory, considering the case of polymorphic alleles scored binarily for their presence or absence in DNA pools. We defined the informativeness of a set of marker loci in bulks as the mutual information between genotype and population identity, composed by two terms: diversity and noise. The first term is the entropy of bulk genotypes, whereas the noise term is measured through the conditional entropy of bulk genotypes given germplasm sources. Thus, optimizing marker information implies increasing diversity and reducing noise. Simple formulas were devised to estimate marker information per allele from a set of estimated allele frequencies across populations. As an example, they allowed optimization of bulk size for SSR genotyping in maize, from allele frequencies estimated in a sample of 56 maize populations. It was found that a sample of 30 plants from a random mating population is adequate for maize germplasm SSR characterization. We analyzed the use of divided bulks to overcome the allele dilution problem in DNA pools, and concluded that samples of 30 plants divided into three bulks of 10 plants are efficient to characterize maize germplasm sources through SSR with a good control of the dilution problem. We estimated the informativeness of 30 SSR loci from the estimated allele frequencies in maize populations, and found a wide variation of marker informativeness, which positively correlated with the number of alleles per locus.

Molecular and functional characterization of novel fructosyltransferases and invertases from Agave tequilana.

Fructans are the main storage polysaccharides found in Agave species. The synthesis of these complex carbohydrates relies on the activities of specific fructosyltransferase enzymes closely related to the hydrolytic invertases. Analysis of Agave tequilana transcriptome data led to the identification of ESTs encoding putative fructosyltransferases and invertases. Based on sequence alignments and structure/function relationships, two different genes were predicted to encode 1-SST and 6G-FFT type fructosyltransferases, in addition, 4 genes encoding putative cell wall invertases and 4 genes encoding putative vacuolar invertases were also identified. Probable functions for each gene, were assigned based on conserved amino acid sequences and confirmed for 2 fructosyltransferases and one invertase by analyzing the enzymatic activity of recombinant Agave protein s expressed and purified from Pichia pastoris. The genome organization of the fructosyltransferase/invertase genes, for which the corresponding cDNA contained the complete open reading frame, was found to be well conserved since all genes were shown to carry a 9 bp mini-exon and all showed a similar structure of 8 exons/7 introns with the exception of a cell wall invertase gene which has 7 exons and 6 introns. Fructosyltransferase genes were strongly expressed in the storage organs of the plants, especially in vegetative stages of development and to lower levels in photosynthetic tissues, in contrast to the invertase genes where higher levels of expression were observed in leaf tissues and in mature plants.

GABA: ¿dualidad funcional? Transición durante el neurodesarrollo / GABA: a functional duality? Transition during neurodevelopment

Introducción. El ácido gamma-aminobutírico (GABA) es el principal neurotransmisor de tipo inhibitorio y sus acciones son mediadas por receptores de tipo ionotrópico (GABAA) y metabotrópico (GABAB), ampliamente distribuidos en el tejido nervioso central. Objetivo. Revisar la estructura de los receptores GABA y su implicación en procesos fisiológicos en el sistema nervioso central. Desarrollo. Se aborda el estudio de la estructura y diversidad de los receptores GABA, especialmente durante el neurodesarrollo, y se hace referencia a la naturaleza excitatoria e inhibitoria de la transmisión gabérgica, donde la participación de los cotransportadores NKCC1 y KCC2 tiene un papel clave en dicha dualidad funcional en la transición de un estadio embrionario a uno posnatal. De igual forma, se plasma el interés por los receptores GABA como diana farmacológica de uso clínico, lo que se manifiesta por la presencia de sitios de modulación alostérica poco explorados en dicho complejo-receptor. Conclusiones. El conocimiento fisiológico y farmacológico de la gran diversidad de subunidades que conforman un determinado subtipo de receptor GABA, así como la correcta expresión en tiempo y espacio para garantizar la viabilidad de un organismo, prometen ser la respuesta a trastornos graves y añejos como la epilepsia o la drogadicción, y tan complejos como el neurodesarrollo (AU)

Introduction. Gamma-aminobutyric acid (GABA) is the most important inhibitory-type neurotransmitter and its actions are mediated by ionotropic (GABAA) and metabotropic (GABAB) type receptors, which are widely distributed throughout the tissue of the central nervous system. Aim. To review the structure of GABA receptors and their involvement in physiological processes in the central nervous system. Development. The study addresses the structure and diversity of the GABA receptors, especially during neurodevelopment, and reference is made to the excitatory and inhibitory nature of GABAergic transmission, where the participation of the cotransporters NKCC1 and KCC2 plays a key role in this functional duality in the transition from an embryonic to a postnatal state. Likewise, the interest in GABA receptors as a pharmacological target for clinical use is also discussed. This is manifested by the presence of under-explored allosteric modulation sites in the aforementioned complex-receptor. Conclusions. The physiological and pharmacological knowledge of the great diversity of subunits that make up a particular subtype of GABA receptor, as well as the correct expression in time and space in order to ensure the viability of the organism, promise to be the answer to long-time severe disorders like epilepsy or drug addiction, and such complex ones as neurodevelopment (AU)