The enzymatic determination of glucose in carbonated beverages: a useful tool for the undergraduate students to learn the basis of enzymatic analysis and the comparison of two analytical methods

The importance of enzymatic analysis in biochemistry, clinical chemistry and food chemistry is undoubted. The course "Applied Biochemistry" in our Faculty is aimed to undergraduate students of Chemistry and Biochemistry. In this subject, the principles and applications of enzymatic analysis are presented to the students, who receive a theoretical introductory lecture in the classroom before they carry out an experiment that should be feasible to be solved in a short laboratory period. The experimental protocol here presented, based on the enzymatic determination of glucose in carbonated beverages, has been implemented at the University of Málaga and it has been optimized according to the students’ results and commentaries along the last years. It aims to illustrate basic issues relating enzymatic analysis, including its potential application to food chemistry. Although there are several enzymatic methods that can be used for the determination of glucose, we selected the one based on the coupled reactions of glucose oxidase (GOD; EC 1.1.3.4.) and peroxidase (POD; EC 1.11.1.7.) because the kinetic constants of glucose oxidase allow the mentioned enzymatic reactions to be used in both, the end point and the kinetic enzymatic analysis methods. In this way, data for two different protocols for the determination of glucose concentration are obtained by the students from a single reaction mixture. Students construct a calibration curve for each method using a glucose standard solution, and use them to determine the glucose concentration in the problem solutions. The inclusion of replicate samples in the determination of the glucose concentration of an “ideal problem” (glucose in purified water) is used to illustrate the principles of statistics in the lab, and comparison with the “real value” allows an estimation of the accuracy of each method. The evaluation of glucose concentration in four carbonated beverages: coloured coke and uncoloured tonic sodas (regular or sugarless in both cases) makes student to recognise the appearance of interferences that should be either avoided or eliminated. Since all samples are analysed by means of end-point and kinetic methods, students can discuss the applicability of each method to these specific analytical problems. They are also encouraged to compare both analytical methods in terms of sensitivity, selectivity, accuracy, and time consumed. Chemistry and Biochemistry undergraduate students having performed this experiment in our laboratories have found it formative, interesting and challenging.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

A practice project to prevent the cookbook model as modus operandi for biochemistry laboratory learning

Laboratory learning is a crucial component of chemistry and biochemistry instruction and should be conceived as a way to develop students’ reasoning, technical or practical skills, introducing them into the scientific method principles. Nevertheless, the heavily criticized “expository instruction style”, characterized by a cookbook nature, is still the most widespread style of laboratory instruction in our universities. Alternative learning styles based in the inquiry, discovery and problem-based pedagogical approaches, have been reported to promote students’ problem solving skills, critical thought and self-confidence development. We are currently involved in the Educative Innovation Project PIE17-065, funded by University of Malaga, aimed to improve the teaching practice of Biochemistry laboratory to undergraduate students. Based on an enzymatic analysis of glucose in soft-drinks we have developed a laboratory protocol as a part of a full practice project where students must work before and after the lab session, in order to prevent the cookbook model as modus operandi, therefore preventing the situation where the students get a first glimpse of the experiment protocol whereas they put on their lab coat. The learning activities have been designed to move our students from the passive role that characterizes the step-by-step procedures, to an active and critical attitude that starts before and remains after their laboratory session, also minimizing time, space, and equipment resources. Our results have shown that this experiment has improved the learning of both, future biochemists and chemists, which showed a very positive perception of the whole practical project.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. PIE 17-06

Learning contract, co-operative and flipped learning as useful tools for studying metabolism

Es el Abstract de una comunicación a un congreso internacional sobre educaciónUndergraduate students in Biology identify Metabolic Biochemistry as a particularly difficult subject. This is due to the fact that students need to interconnect properly all the contents of its syllabus throughout their study of the subject in order to get a global insight of the complex regulatory features controlling metabolic pathways within the metabolic network under different physiologic and pathologic conditions, as well as metabolism as a whole. Due to these objective difficulties, a high percentage of our students face the study of this subject as a very hard task beyond their forces and capacities. This perception leads to high rates of premature dropout. In previous years, less than 40% of all the registered students attended the examinations of Metabolic Biochemistry (a subject in the second year of the Degree of Biology at our University). Even worse, less than 25% of our students passed the exams. From the academic year 2015/16 on, we are developing innovative teaching projects (PIE15-163 and PIE17-145, funded by University of Malaga) aimed to increase our student loyalty to the subject (and hence to increase their attendance to exams) and to help them to learn more effectively metabolism and its regulation. These innovative teaching projects are based on the use of several powerful tools: a learning contract and problem-based learning within the framework of group tasks promoting an actual collaborative learning in a flipped classroom. The present communication will show the implementation of the PIE15-163 and PIE17-145 projects and some results obtained from them.This work was supported by Malaga University funds granted to the educational innovation project PIE17-145. The attendance to the END2018 International Conference on Education and New Developments (June 2018, Budapest, Hungary) has received a grant from "I Plan Propio Integral de Docencia. Universidad de Málaga"]

Sistema Contable en la Cooperativa de Multiservicios Concepción de la Merced R.L. de las Mangas Municipio de San Isidro Departamento de Matagalpa en el I semestre del año 2013

Esta investigación abordó el estudio de la temática Sistema Contable y Control Interno en la Cooperativa de Multiservicios Concepción de la Merced R.L. en Las Mangas Municipio de San Isidro Departamento de Matagalpa en el I semestre del año 2013. El propósito de este estudio es evaluar el Sistema Contable de la Cooperativa, los resultados presentados y las propuestas dirigidas a la Cooperativa están hechos con el objetivo de que las debilidades encontradas sean superadas y se contribuya al éxito en los procesos de la información contable. La base de presentación de la información financiera o cualquier tipo de información está en la confiabilidad del proceso contable, es decir, toda la información se fundamenta en el Sistema Contable y el adecuado Control Interno que se aplica dentro de cualquier organización, independientemente de su giro económico. Se considera importante que sea implementado un Sistema adecuado a la Cooperativa que facilite el resguardo de los activos y la eficiencia en el desarrollo de las operaciones. La Cooperativa no cuenta con un Catálogo de Cuentas, Instructivo de Cuentas y Manual de Procedimientos para el adecuado desarrollo y registro de sus transacciones. El Sistema Contable se considera deficiente debido a que no existen los elementos que contribuyan a un buen desarrollo, fluidez y confiabilidad en la información de la Cooperativa. De acuerdo a los resultados obtenidos del análisis de la información, se propone a la Cooperativa la implementación de un Catálogo de Cuentas, Instructivo y Manual de Procedimiento

Glucemia y concentraciones de insulina en sangre de ratas Wistar sometidas a dieta alta en grasa y a tratamiento con péptidos miméticos de leptina

Introduction. Studies on leptin administration have demonstrated a reversion of insulin resistance, and that leptin produces effects in glucose metabolism.Objective. Changes in the insulin and glucose concentrations in blood plasma was valuated by intraperitoneal administration of mimetic leptin peptides in Wistar rats fed with high fat diet.Materials and methods. A control group of rats was defined that were fed with high fat diet and a control group with normal diet. Several treatments groups were fed with high fat diet and subjected to the administration of seven different mimetic leptin peptides, each one administered in four different concentrations. During the peptide administration the glucose concentrations were quantified and at the end the insulin concentrations.Results. The average insulin concentrations in the control groups were similar; however, hyperinsulinemia was observed in the groups to which we administered the peptide denominated 83 at doses of 10 mg/kg and 20 mg/kg of body weight. All the treatment groups except the peptide denominated with the code 80 showed diminished glucose levels even in the cases without hyperglycemia.  The greatest effect was observed with the peptide 116-130 of the mouse leptin and its human homolog, although without statistical differences with the other treatments.Conclusion. Lectin peptides have no effect on the insulin plasma concentrations; however, an effect is evident in glucose levels.  Additional research will be required to determine if leptin mimetic peptides influence the glucose metabolism or the expression, secretion, signaling mechanism and regulation of insulin.Introducción. La administración de leptina ha demostrado que revierte la resistencia a la insulina y ejerce efectos sobre el metabolismo de la glucosa.Objetivo. Evaluar los cambios en las concentraciones plasmáticas de insulina y glucosa por la administración intraperitoneal de péptidos miméticos de leptina en ratas Wistar alimentadas con dieta alta en grasa.Materiales y métodos. Se definió un grupo de ratas control alimentado con dieta alta en grasa y un grupo control con dieta normal; además, distintos grupos de animales alimentados con dieta alta en grasa y sometidos a la administración de siete diferentes péptidos de leptina, administrados en cuatro concentraciones diferentes y a los cuales se denominó grupos tratamiento. Durante la administración de los péptidos se cuantificó la glucemia y al finalizar las concentraciones de insulina.Resultados. Las concentraciones de insulina en los grupos fueron similares; se observó hiperinsulinemia en los grupos a los cuales se les administró el péptido denominado 83 a dosis de 10 mg/kg y 20 mg/kg de peso corporal. Todos los tratamientos, a excepción del grupo al cual se le administró el péptido denominado con el código 80, redujeron la glucemia; el mayor efecto parece ser el del péptido 116-130 de leptina de ratón y su homólogo humano, aunque sin diferencias estadísticas con los otros tratamientos.Conclusión. Los péptidos no ejercen efectos sobre las concentraciones de insulina pero sí sobre la glucemia; se requieren otras investigaciones para determinar los mecanismos mediante los cuales los péptidos intervienen en el metabolismo de la glucosa, sobre la expresión, secreción, mecanismos de señalización y regulación de la insulina, además, cambios en las concentraciones de insulina teniendo en cuenta el ritmo pulsátil de la hormona

La chicha como tradición de Bogotá: Propuesta metodologica que promueva el valor histórico de la chicha a través de la exploración artística en jóvenes del barrio Vista Hermosa

La presente Monografía tiene por objetivo desarrollar una propuesta metodológica que promueva el valor histórico de la chicha por medio de la sensorialidad, sensibilidad y percepción basadas en la exploración artística para jóvenes entre los 16 y 21 años de la localidad Ciudad bolívar, barrió Vista Hermosa

Cochlear nonlinearity between 500 and 8000 Hz in listeners with normal hearing

Cochlear nonlinearity was estimated over a wide range of center frequencies and levels in listeners with normal hearing, using a forward-masking method. For a fixed low-level probe, the masker level required to mask the probe was measured as a function of the masker-probe interval, to produce a temporal masking curve ͑TMC͒. TMCs were measured for probe frequencies of 500, 1000, 2000, 4000, and 8000 Hz, and for masker frequencies 0.5, 0.7, 0.9, 1.0 ͑on frequency͒, 1.1, and 1.6 times the probe frequency. Across the range of probe frequencies, the TMCs for on-frequency maskers showed two or three segments with clearly distinct slopes. If it is assumed that the rate of decay of the internal effect of the masker is constant across level and frequency, the variations in the slopes of the TMCs can be attributed to variations in cochlear compression. Compression-ratio estimates for on-frequency maskers were between 3:1 and 5:1 across the range of probe frequencies. Compression did not decrease at low frequencies. The slopes of the TMCs for the lowest frequency probe ͑500 Hz͒ did not change with masker frequency. This suggests that compression extends over a wide range of stimulus frequencies relative to characteristic frequency in the apical region of the cochlea

Cochlear nonlinearity between 500 and 8000 Hz in listeners with normal hearing

Cochlear nonlinearity was estimated over a wide range of center frequencies and levels in listeners with normal hearing, using a forward-masking method. For a fixed low-level probe, the masker level required to mask the probe was measured as a function of the masker-probe interval, to produce a temporal masking curve ͑TMC͒. TMCs were measured for probe frequencies of 500, 1000, 2000, 4000, and 8000 Hz, and for masker frequencies 0.5, 0.7, 0.9, 1.0 ͑on frequency͒, 1.1, and 1.6 times the probe frequency. Across the range of probe frequencies, the TMCs for on-frequency maskers showed two or three segments with clearly distinct slopes. If it is assumed that the rate of decay of the internal effect of the masker is constant across level and frequency, the variations in the slopes of the TMCs can be attributed to variations in cochlear compression. Compression-ratio estimates for on-frequency maskers were between 3:1 and 5:1 across the range of probe frequencies. Compression did not decrease at low frequencies. The slopes of the TMCs for the lowest frequency probe ͑500 Hz͒ did not change with masker frequency. This suggests that compression extends over a wide range of stimulus frequencies relative to characteristic frequency in the apical region of the cochlea

A Binaural Cochlear Implant Sound Coding Strategy Inspired by the Contralateral Medial Olivocochlear Reflex

[EN] Objectives: In natural hearing, cochlear mechanical compression is dynamically adjusted via the efferent medial olivocochlear reflex (MOCR). These adjustments probably help understanding speech in noisy environments and are not available to the users of current cochlear implants (CIs). The aims of the present study are to: (1) present a binaural CI sound processing strategy inspired by the control of cochlear compression provided by the contralateral MOCR in natural hearing; and (2) assess the benefits of the new strategy for understanding speech presented in competition with steady noise with a speech-like spectrum in various spatial configurations of the speech and noise sources. Design: Pairs of CI sound processors (one per ear) were constructed to mimic or not mimic the effects of the contralateral MOCR on compression. For the nonmimicking condition (standard strategy or STD), the two processors in a pair functioned similarly to standard clinical processors (i.e., with fixed back-end compression and independently of each other). When configured to mimic the effects of the MOCR (MOC strategy), the two processors communicated with each other and the amount of backend compression in a given frequency channel of each processor in the pair decreased/increased dynamically (so that output levels dropped/ increased) with increases/decreases in the output energy from the corresponding frequency channel in the contralateral processor. Speech reception thresholds in speech-shaped noise were measured for 3 bilateral CI users and 2 single-sided deaf unilateral CI users. Thresholds were compared for the STD and MOC strategies in unilateral and bilateral listening conditions and for three spatial configurations of the speech and noise sources in simulated free-field conditions: speech and noise sources colocated in front of the listener, speech on the left ear with noise in front of the listener, and speech on the left ear with noise on the right ear. In both bilateral and unilateral listening, the electrical stimulus delivered to the test ear(s) was always calculated as if the listeners were wearing bilateral processors. Results: In both unilateral and bilateral listening conditions, mean speech reception thresholds were comparable with the two strategies for colocated speech and noise sources, but were at least 2 dB lower (better) with the MOC than with the STD strategy for spatially separated speech and noise sources. In unilateral listening conditions, mean thresholds improved with increasing the spatial separation between the speech and noise sources regardless of the strategy but the improvement was significantly greater with the MOC strategy. In bilateral listening conditions, thresholds improved significantly with increasing the speech-noise spatial separation only with the MOC strategy. Conclusions: The MOC strategy (1) significantly improved the intelligibility of speech presented in competition with a spatially separated noise source, both in unilateral and bilateral listening conditions; (2) produced significant spatial release from masking in bilateral listening conditions, something that did not occur with fixed compression; and (3) enhanced spatial release from masking in unilateral listening conditions. The MOC strategy as implemented here, or a modified version of it, may be usefully applied in CIs and in hearing aids