Paula Núñez

Developmental programing of thirst and sodium appetite

Thirst and sodium appetite are the sensations responsible for the motivated behaviors of water and salt intake, respectively, and both are essential responses for the maintenance of hydromineral homeostasis in animals. These sensations and their related behaviors develop very early in the postnatal period in animals. Many studies have demonstrated several pre- and postnatal stimuli that are responsible for the developmental programing of thirst and sodium appetite and, consequently, the pattern of water and salt intake in adulthood in need-free or need-induced conditions. The literature systematically reports the involvement of dietary changes, hydromineral and cardiovascular challenges, renin-angiotensin system and steroid hormone disturbances, and lifestyle in these developmental factors. Therefore, this review will address how pre- and postnatal challenges can program lifelong thirst and sodium appetite in animals and humans, as well as which neuroendocrine substrates are involved. In addition, the possible epigenetic molecular mechanisms responsible for the developmental programing of drinking behavior, the clinical implications of hydromineral disturbances during pre- and postnatal periods, and the developmental origins of adult hydromineral behavior will be discussed.

Progressive training effects on neuronal hypothalamic activation in the rat.

The purpose of this study was to examine whether progressive training exercise resulted in changes in neuronal expression of c-Fos in the hypothalamic regions (paraventricular nucleus, supraoptic nucleus and suprachiasmatic nucleus) and subfornical organ of Wistar rats and its relation to hydromineral parameters such as plasma proteins, osmolality and hematocrit. Rats were trained progressively in a running wheel over four days, while control rats were not provided with the opportunity to exercise. c-Fos cellular activity was immunohistochemically stained in accordance with the ABC method. The number of c-Fos immunoreactive cells was counted using standard imaging software. c-Fos in the PVN and SO nuclei was found to be significantly increased in trained rats 1h post-exercise compared with control and 24h post-exercise groups. However, no significant differences were found between trained and control rats in the SQ and SFO. These findings provide useful information of interest for future studies on brain specific regions involved in hydromineral balance in response to progressive exercise.

Circadian urinary citrate excretion in a rat model of exercise

Aims: Circadian rhythms are the approximate 24 h biological cycles that function to prepare an organism for daily environmental changes. Circadian rhythms unquestionably play critical roles in metabolic homeostasis and the exercise has emerged as a strong non‐photic time cue or zeitgeber in animal models and humans. Numerous studies about the effects of exercise on the citrate synthase activity have been published. Citrate is used to assess energy production or expenditure because it is a substrate of the Krebs Cycle, a cycle for oxidative energy production. Main methods: We tested the existence of a rhythmic urinary citrate excretion in a rat model that is made to exercise at six different points during the day. Key findings: The data obtained by the enzyme assays were fitted to a mathematical model (Fourier series), showing for the first time, the existence of a distinct ultradian rhythm in the urinary citrate excretion. The aerobic exercise led to the increase in the period length of the ultradian rhythm and raised the acrophase value of the urinary citrate excretion. Therefore, the urinary citrate excretion pattern changed after exercise, showing a clear circadian rhythm fitted to the mathematical model. Significance: The citrate urine samples could provide accurate data for ranking an individuals metabolic status. Using exercise to maintain the circadian clock at an appropriate phase and amplitude might be effective to prevent cardiometabolic disease development.

Ovarian Aging: Melatonin Regulation of the Cytometric and Endocrine Evolutive Pattern

We have investigated the effect of melatonin administration on the cytometric and endocrine functions of the ovary during aging. Young cyclic (3 months old), middle-aged pre-acyclic (13 months old), and old acyclic (22 months old) female Wistar rats were used for two months, in both control and melatonin-treated groups. Cell cycle by flow cytometry: the percentage of ovarian cells in the G0-G1 phase was the highest in both control and melatonin-treated rats. However, melatonin treatment significantly reduced (P< 0.05) the percentage of cells in the G0-G1 phase compared to control rats. This reduction of cells in the G0-G1 phase is derived to the S phase in cyclic and acyclic rats. The possibility that a tumoral process leads to a proliferative effect observed in young and acyclic melatonin-treated rats was ruled out because no significant differences were found for p53 and Ki67 expression levels between control and melatonin groups. Density of oocytes: the oocyte number per ovary unit volume was not affected by melatonin treatment in the three age ranges studied. Melatonin treatment in middle-aged (pre-acyclic) rats resulted in significantly higher (P< 0.05) ovarian volume; higher oocyte volume, without significant differences, and oocytes in circular form were significantly (P< 0.05) higher than in control rats. Melatonin treatment during pre-acyclic age range could resynchronize the estrous cycle periodicity. Melatonin treatment was able to maintain the same levels of estradiol in the pre-acyclic age groups studied as those observed in the young cyclic rats. The present results indicate that melatonin administration to middle-aged female rats produces beneficial effects that extend the reproductive function of the ovary.

Adaptación y aplicación del cuestionario CLASS (Colorado Learning Attitudes about Science Survey) para la valoración de actitudes y creencias científicas en alumnos de enseñanza secundaria y universitaria

espanolIntroduccion. La evaluacion de conocimientos y habilidades ha sido objeto de estudio durante muchos anos; sin embargo, la valoracion de las actitudes requiere un abordaje diferente. Objetivo. Utilizar una herramienta metodologica sencilla (cuestionario CLASS-Bio) que permita comparar la evolucion de las percepciones acerca de la disciplina de biologia y fisiologia de los estudiantes noveles, comparandola con las de estudiantes de cursos superiores, con el fin de poder analizar la influencia de la docencia sobre estas percepciones y actitudes. Sujetos y metodos. Los participantes fueron 288 estudiantes, pertenecientes a dos grupos: un grupo de bachillerato (41 alumnos de primero y 59 de segundo curso) y un grupo de universitarios de primer curso (92 alumnos de enfermeria, 53 de fisioterapia y 25 de logopedia). La puntuacion favorable representa el porcentaje en que el estudiante contesta como experto. Resultados. Los resultados fueron mas proximos a los obtenidos por el grupo de expertos en segundo curso de bachillerato, con un desplazamiento hacia la mejoria, comparado con los obtenidos en el curso anterior. Las respuestas de grupos de universitarios de enfermeria y fisioterapia arrojaron resultados similares, evolucionando hacia unas percepciones mas proximas a las de los expertos, y al mismo tiempo bastantes diferentes a las obtenidos con los alumnos de logopedia. Conclusiones. La adaptacion al castellano del cuestionario CLASS-Bio puede utilizarse como herramienta metodologica valida para valorar el proceso continuo de ensenanza-aprendizaje y evaluar la influencia de la docencia sobre las creencias y actitudes de los estudiantes. EnglishIntroduction. Over the last years, evaluation of knowledge and attitudes in biology education has received a strong call to improve. Aim. To use an easy methodological tool (CLASS-Bio questionnaire) that allows measuring novice-to-expert-like perceptions evolution about Biology and/or Physiology disciplines. In this way, we will be able to analyze the influence over the perceptions and attitudes. Subjects and methods. The participants were 288 students distributed in two groups: a group of high school students (41 of senior secondary school, 1st course; and 59 of senior secondary school, 2nd course), and another one of undergraduate students (1st year): 92 of Nursing Degree, 53 of Physiotherapy Degree and 25 of Speech Therapist Degree. The favorable rating is quantified by comparing students’ responses with a consensus expert response. Results. The 2nd senior secondary school students’ results were more similar to the expert responses than the 1st senior secondary school students; this displacement or shifts indicated an improvement at the 2nd year in the high school. Responses found in the groups of Nursing and Physiotherapy students were similar, evolving closer to the expert perceptions, and quite different compared with the Speech Therapist students responses. It is gratifying to consider how health biosciences students observe these basic subjects more connected to the real world. Conclusions. Spanish adaptation of CLASS-Bio questionnaire could be used as an accessible methodological tool in order to analyze the continuous evolution of teaching and learning process at different academic stages.

Exercise Effects on Circadian Rhythmicity of Urine Osmolality and Diuresis in Rats

Sportsmen have to maintain hydration monitoring for health, but biomarkers are transient during the process of dehydration and rehydration. The aim of this study was to examine the circadian rhythmicity of urine osmolality and diuresis in rats at 4 h intervals, and to determine whether training exercise resulted in changes in this rhythmicity. Rats were trained progressively on a running wheel over four days. Two urine group samples were taken from each animal; the first was taken before the start of the training program and the second was taken at the completion of the last running trial. We found a characteristic circadian rhythmicity in diuresis and in urine osmolality, which was the same for pre- and postexercise patterns. However, post- exercise urine osmolality values were greater than pre-exercise values when the exercise intensity was of sufficient intensity to reduce urine production. The urine osmolality was elevated during the approximately 4 h period after termination of the exercise, and remained high up to 16 h after the termination of exercise, after which osmolality started to normalize. Thus, this study suggests that the urinary measures described herein represent a noninvasive and easy-to-use tool for the characterization of 24 h hydration status.