Melatonin as an anti-stress signal: effects on an acute stress model and direct actions on interrenal tissue in goldfish.

Background: Melatonin is a key hormone in regulation of circadian rhythms, and involved in many rhythmic functions, such as feeding and locomotor activity. Melatonin reportedly counteracts stress responses in many vertebrates, including fish. However, targets for this action of melatonin and underlying mechanisms remain unknown. Results: This study reports potential anti-stress properties of melatonin in goldfish (Carassius auratus), with a focus on its effect on plasma cortisol, food intake, and locomotor activity, all of them involved in the responses to stress exposure. Indeed, acute injection of melatonin counteracted stress-induced hypercortisolinemia and reduced food intake. The reduced locomotor activity following melatonin treatment suggests a possible sedative role in fish. To assess whether this anti-stress effects of melatonin involve direct actions on interrenal tissue, in vitro cultures of head kidney (containing the interrenal cortisol-producing tissue) were carried out in presence of ACTH, melatonin, and luzindole, an antagonist of melatonin receptors. Melatonin in vitro reduced ACTH-stimulated cortisol release, an effect attenuated by luzindole; this suggests the presence of specific melatonin receptors in interrenal tissue. Conclusions: Our data support a role for melatonin as an anti-stress signal in goldfish, and suggest that the interrenal tissue of teleosts may be a plausible target for melatonin action decreasing cortisol production.

Work station learning activities (WSLA) through the ICAP framework: a qualitative study.

BACKGROUND: Engaging, student-centered active learning activities, such as team-based learning (TBL) and laboratory practices, is beneficial to integrate knowledge, particularly in Medicine degree. Previously, we designed and implemented workstation learning activities (WSLA) inspired by TBL, which proved effective for learning requiring higher-order thinking skills. We now hypothesize that WSLA may also have the potential to be framed into a theoretical model that stratifies learning into interactive, constructive, active and passive modes (ICAP hypothesis). METHODS: An interpretive qualitative research study was conducted to evaluate this idea. Semi-structured interviews were conducted with students enrolled in health science programs after WSLA sessions, consisting of a series of activities accompanying a traditional lecture. Interviews were analyzed according to a deductive approach. Theoretical themes and subthemes driving the analysis were organized around the ICAP modes: passive, active, constructive, and interactive. An inductive approach was applied to provide additional insights. RESULTS: Students valued preparatory lectures as well as corresponding WSLA activities as highly motivating, especially for the ability to integrate concepts. Although previous research shows that not all activities require high levels of cognitive engagement, students appreciated the opportunity the WSLA provided to discuss and clarify concepts as a group. Furthermore, feedback from professors and peers was highly appreciated, and helped students to construct new knowledge. CONCLUSION: In this work, by focusing in understanding the student's experience, we have evaluated for the first time the WSLA approach in relation to the ICAP model. We found that not only the activity type determines the learning mode, but also the environment accompanying WSLA is a determining factor. Our findings can guide future development of the WSLA approach, which represents an interactive learning methodology with strong potential within the ICAP framework. TRIAL REGISTRATION: Not applicable.

Forcing a change: a learn-by-doing workshop on circadian rhythms to understand the complexities of human physiology.

Physiology is an integrative science that requires an understanding of the organism as a whole to acquire a deep comprehension of its functions and avoid misconceptions that may impair further learning. Thus it is necessary to develop resources that promote the integrative vision that Physiology requires. Chronobiology is a challenging discipline and one of the least addressed concepts in Physiology curricula. The activity here presented proposes a workshop with a theoretical-practical perspective in the context of the Neuroscience Conferences held annually at our university. All conference presentations are neuroscience-related topics, in combination with practical activities, some of them analyzing variables of the students themselves. We chose to assess this informal teaching scenario to involve the students with a scientific perspective while learning and hoping to increase their appreciation for different topics related to neuroscience. Specifically for this activity on chronobiology, the evaluation was carried out via a survey study including quantitative and qualitative questions and semistructured personal interviews. In general, the results reveal a very positive opinion from students regarding aspects such as the teaching methodology, the organization before and during the activity or the added value of the experience for their future professional performance. Some of the students stated they were more aware of the importance of their circadian system and even changed some of their personal daily routines after the activity. Such positive feedback encourages us to continue working in this theoretical-practical format in the future, as it contributes to improving students' perception of their own learning.

Rhythms in the endocrine system of fish: a review.

The environment which living organisms inhabit is not constant and many factors, such as light, temperature, and food availability, display cyclic and predictable variations. To adapt to these cyclic changes, animals present biological rhythms in many of their physiological variables, timing their functions to occur when the possibility of success is greatest. Among these variables, many endocrine factors have been described as displaying rhythms in vertebrates. The aim of the present review is to provide a thorough review of the existing knowledge on the rhythms of the endocrine system of fish by examining the hormones that show rhythmicity, how environmental factors control these rhythms and the variation in the responses of the endocrine system depending on the time of the day. We mainly focused on the hypothalamic-pituitary axis, which can be considered as the master axis of the endocrine system of vertebrates and regulates a great variety of functions, including reproduction, growth, metabolism, energy homeostasis, stress response, and osmoregulation. In addition, the rhythms of other hormones, such as melatonin and the factors, produced in the gastrointestinal system of fish are reviewed.

El aprendizaje a través del juego como herramienta en el diseño de actividades de valor añadido en un currículo integrador de Ciencias Biomédicas Básicas / Gamification as a tool for the design of added value activities as part of an integrated curriculum in Basic Biomedical Sciences

Introducción: Desde el Departamento de Ciencias Biomédicas Básicas de la Universidad Europea de Madrid optamos por el diseño de actividades que fomenten un entorno de aprendizaje activo e integrador, centrado en el alumno y contextualizado en un entorno profesional. El objetivo es favorecer la asimilación de conceptos fundamentales, motivando al alumno y facilitando el aprendizaje extracurricular. Sujetos y métodos: Dentro de nuestras actividades de valor añadido hemos diseñado una dinámica a través del juego con estudiantes de los primeros cursos de los grados de Medicina, Farmacia y la doble titulación de Farmacia-Biotecnología. Utilizando como hilo conductor un caso clínico relacionado con una enfermedad cardiovascular, se diseñó una yincana con un carácter integrador de disciplinas básicas con diferentes estaciones de trabajo. Se premió la correcta resolución de las tareas incluidas en las estaciones de trabajo en un tiempo establecido. Resultados: Los estudiantes encuestados mostraron su satisfacción con la utilidad de estas sesiones integradas frente a las no integradas, así como con la inclusión de contenidos de diferentes materias (el 54% respondió favorablemente). El 58% de los grupos participantes afirmó que la actividad les acercó a contenidos nuevos. Conclusiones: Con esta actividad se ha aumentado el interés y la motivación de los alumnos por los conceptos más básicos de las ciencias biomédicas, a través de la integración real y la aplicación directa a un caso clínico auténtico. Asimismo, hemos conseguido que los alumnos trabajen competencias necesarias para asumir sus futuros roles como integrantes de equipos multidisciplinares, gracias a la participación de alumnos de grados distintos

Introduction: The Department of Basic Biomedical Sciences at the Universidad Europea de Madrid is committed to design activities that foster an environment of active and inclusive student-centered learning and contextualized in a professional environment. The aim is to ensure, through an integrated assimilation of fundamental concepts, the student motivation to learn and facilitate the extracurricular knowledge. Subjects and methods: Within our added-value activities, we have designed a play-based activity with students from the first course of the degrees of Medicine, Pharmacy and the double degree Pharmacy-Biotechnology. Using a clinical case related to a cardiovascular disease as a thread, a gymkhana was designed following a workstations working model. The correct resolution of all tasks included in each workstation without delay was finally rewarded. Results: Respondents found the integrated sessions more useful than the traditional seminars and also remarked that they bring up a variety of contents from different subjects successfully (54% positive answers). 58% of the survey participants expressed that the activity approached them new content not covered through the traditional master class. Conclusions: We have ensured that students develop skills required to take their future roles as members of multidisciplinary teams, thanks to the participation of students from different degrees. Moreover, the activity managed to increase motivation and the interest for the most basic concepts of Biomedical Sciences through real integration and direct application to a real clinical case. The experience was evaluated as very positive by all participants

Light-dark cycle and feeding time differentially entrains the gut molecular clock of the goldfish (Carassius auratus).

The aim of the present study was to investigate how photocycle and feeding-time cues regulate the daily expression of Per1a, Per2a, Per3, and Cry3 in the goldfish hindgut. For this purpose, we studied the daily rhythmicity of these genes in fish maintained under different lighting conditions and under different feeding regimes (scheduled or not). We also studied whether the timing of just one meal is able to reset the hindgut molecular clock. In a first experiment, randomly fed fish were divided into four groups and kept under different light conditions for 30 d: 12 h light and 12 h dark (12L:12D), an inverted photoperiod (12D:12L), constant darkness (24D), and constant light (24L). In a second study, fish maintained under 24L were divided into four groups fed at different time points for 35 d: (1) fish scheduled-fed once a day (at 10:00 h); (2) fish fed with a 12-h shifted schedule (at 22:00 h), (3) fish fed at 10:00 h throughout the experiment, except the last day when fed at 22:00 h; and (4) a randomly fed group of fish. Fish were sacrificed every 6 h throughout a 24-h cycle. In both experiments, gPer1a, gPer2a, gPer3, and gCry3 transcripts were quantified using Real Time-qPCR in the hindgut. Results show the clock genes gPer1a, gPer2a, and gCry3 are synchronized by both zeitgebers, the photocycle and feeding regime, in goldfish hindgut. Moreover, such clock genes anticipate light-on and food delivery, when these cues appear in a cyclic manner. In the absence of both zeitgebers, gCry3 and gPer2a rhythmicity disappeared. In contrast, the gPer1 rhythm was maintained under 24L and random feeding conditions, but not always, suggesting that food when randomly supplied is able to reset the clock depending on other factors, such as the energetic and metabolic conditions of the fish. The expression of gPer2a was not activated during the light phase of the cycle, suggesting the hindgut of goldfish is a non-direct photosensitive organ. In contrast to the other three genes, gPer3 expression in the goldfish hindgut seemed to be dependent on the timing of the last food delivery, even in the presence of a photocycle. This gene was the only one that maintained daily rhythms under both constant lighting conditions (24D and 24L), although with lower amplitude than when a photocycle was present. This indicates that, although the acrophase (peak time) of the gPer3 expression rhythm seems to be driven by feeding time, there is an interaction of both zeitgebers, food and light, to regulate its expression. In conclusion, present data indicate: (1) the hindgut of goldfish can be synchronized in vivo by both the photocycle and feeding time; (2) food is a potent signal that entrains this peripheral oscillator; and (3) both environmental cues seems to target different elements of the molecular clock.

Melatonin effects on gut motility are independent of the relaxation mediated by the nitrergic system in the goldfish.

Melatonin is a key neuroendocrine transducer in the circadian organization of vertebrates. However, its role in gastrointestinal physiology has not been explored in depth. In goldfish, a role for melatonin as a modulator of intestinal motility has been reported, whereby it attenuates the cholinergic contraction. The aim of the present work was to investigate this relaxation induced by melatonin in the gut smooth muscle of the goldfish, studying the possible involvement of nitric oxide. An in vitro model of isolated goldfish intestine was used to test the effects on intestinal motility. The addition of melatonin (10 pM-100 µM) to the organ bath relaxed acetylcholine- and serotonin-stimulated gut strips, but no effect was observed on KCl-contracted preparations. The addition of L-NAME (nitric oxide synthase inhibitor) increased the amplitude of the spontaneous slow waves, while sodium nitroprusside (SNP, nitric oxide donor) abolished them. All these results support a role for the nitrergic system in goldfish gut motility. However, neither L-NAME, nor SNP nor the nitric oxide precursor, l-arginine, modified the melatonin relaxing effect. These results highlight the existence of a basal nitrergic tone in the gut of goldfish, where melatonin would exert a calcium-dependent, nitric oxide-independent relaxing effect on serotonergic and cholinergic contraction.

Melatonin reduces locomotor activity and circulating cortisol in goldfish.

The present study focused on the effects of a subchronic melatonin treatment on locomotor activity and cortisol plasma levels in goldfish. We compared two different administration routes: peripheral (10 microg/g body weight) versus central (1 microg/microl) injections of melatonin for 7 or 4 days, respectively. Daily locomotor activity, including both diurnal and nocturnal activities, food anticipatory activity and circulating cortisol at 11:00 (under 24 h of food deprivation and 17 h postinjection) were significantly reduced after repeated intraperitoneal injections with melatonin for 7 days, but not after intracerebroventricular treatment. Taking in mind the anoretic effect of melatonin in this species, we investigated if such feeding reduction is directly responsible for the reduction in motor activity induced by melatonin treatment. Food restriction (50%) for 10 days did not significantly modify either daily locomotor activity or plasma cortisol levels in goldfish, indicating that the peripheral action of melatonin diminishing locomotor activity in goldfish is not a direct consequence of its anoretic action. In summary, our results indicate that, as previously described in other vertebrate species, melatonin can regulate locomotor activity and cortisol levels in goldfish, suggesting a sedative effect of this hormone in this teleost.

Melatonin attenuates the acetylcholine-induced contraction in isolated intestine of a teleost fish.

The present study investigates the possible direct actions of melatonin (N-acetyl-5-methoxytryptamine) on intestinal motility in goldfish (Carassius auratus) using an in vitro system of isolated intestine in an organ bath engaged to an isometric transducer. The longitudinal strips from goldfish intestine in the organ bath showed a resting spontaneous myogenic rhythmic activity which is not altered by melatonin. The addition of acetylcholine (1 nmol l(-1)-10 mmol l(-1)) to the organ bath induces a significant contraction of the intestinal strips in a concentration-dependent manner. The addition of melatonin and its agonist, 2-iodomelatonin, induced a concentration-dependent attenuation of acetylcholine-induced contractile response. The specificity of this effect is tested by the preincubation of the intestine strips in the presence of two melatoninergic antagonists, luzindole (a non-selective MT(1)/MT(2) melatonin receptor antagonist) and 4-P-PDOT (preferred antagonist of MT2 receptor subtype), which counteracted the melatonin-induced relaxation in a concentration-dependent manner. Finally, present results demonstrate that this melatoninergic effect on intestinal strips is a process highly dependent on extracellular calcium. In conclusion, this is the first study demonstrating the role of melatonin in the control of gut motility in a non-mammalian vertebrate. The melatonin effects on isolated intestine from goldfish are mediated by melatoninergic membrane receptors, and could suggest a delay in food transit time, supporting its anorectic effect reported on in vivo studies.