La stabilité des réponses physiologiques face au stress psychologique telle qu’étudiée sur une période de trois ans

Le stress augmente le risque de développer des maladies cardiovasculaires (CV) ainsi que de mourir de ces maladies. Selon certaines hypothèses, ce phénomène se produirait par le biais de réponses répétés de réactivité physiologique élevée ou de récupération physiologique prolongée, suite à un épisode de stress. La stabilité à long terme des réponses physiologiques face au stress a reçu peu d’attention. Objectifs: (1) Évaluer la stabilité temporelle de la réactivité et de la récupération physiologique suite au stress, à travers l’évaluation des systèmes cardiovasculaires et nerveux autonome, et ce sur un intervalle de 3 ans. (2) Déterminer si le sexe et l'âge agissent comme des variables modératrices. Méthodologie: Un total de 134 hommes et femmes en santé ont été recrutés au sein de la communauté et ont pris part à 2 séances en laboratoire. Quatre tâches, d’une durée de 5 minutes chacune et composée d’un élément de stress interpersonnel différent, ont été administrées. Chaque tâche était suivie d’une période de récupération de 5 min. Des mesures de la fréquence cardiaque (FC), de la pression artérielle (PA) et de la variabilité de la fréquence cardiaque (VFC : HF, LF et VLF) ont été obtenues. Des corrélations de Spearman et des régressions linéaires ont été effectuées. Résultats: Des corrélations test-retest significatives ont été obtenues pour toutes les mesures physiologiques, sauf pour la PA diastolique et la VLF, lors de la période de récupération. Aucune différence significative quant à la stabilité des réponses face au stress en fonction du sexe ou de l’âge des participants, n’a été trouvée. Conclusion: Les réponses physiologiques face au stress représentent des caractéristiques individuelles stables sur trois ans, peu affectées par le sexe et l’âge.It is known that stress increases the risk of cardiovascular disease and mortality associated with these diseases. It is hypothesized that this may occur through chronically heightened physiological reactivity to or delayed recovery from stress. The long-term stability of physiological stress responses has received little attention. Objectives: To evaluate the 3-year stability of reactivity and recovery change scores across CV and autonomic parameters and assess whether sex and age moderate stability. Methodology: A total of 134 healthy participants underwent 2 laboratory stress protocols, including four 5-minute interpersonal stressors, each followed by a 5-minute recovery period. Heart rate (HR), blood pressure (BP), and HR variability (HF, LF, VLF) were obtained. Spearman rank correlations and linear regressions were performed. Results: Significant test-retest correlations emerged for all physiological measures except diastolic BP recovery and VLF recovery. No significant sex or age differences in the stability of stress reactivity or recovery emerged. Conclusion: Stress responses represent stable individual traits, little affected by sex and age

Perceptual decision making in larval zebrafish revealed by whole-brain imaging

Animals are able to accumulate sensory evidence over considerable timescales in order to select behaviors fundamental for their survival. Despite the importance and ubiquity of this phenomenon, how activity in different brain regions contributes to this process is not understood. In this study, I develop a novel perceptual decision making assay in the larval zebrafish, based on whole-field visual motion of varying strength. Upon presentation of motion, fish integrate this noisy sensory evidence in time before swimming in the direction of perceived motion, a behavior known as the optomotor response. Behavioral parameters such as the latency to initiate swimming and the fraction of correct turns are modulated by motion strength. Whole-brain functional imaging experiments with single-cell resolution enable identification of almost all neural activity relevant to the different stages of the decision making process, including evaluation of momentary sensory input, accumulation of this sensory evidence, and behavioral output. Fitting a generalized integrator model to every neuron reveals a wide range of time constants, which are distributed in functional clusters across different brain regions. Based on the behavior and the imaging data, a model is proposed where integrating units set the left and right turning rates. An unbiased whole-brain analysis revealed that the interpeduncular nucleus, a circular structure located ventrally on the midline of the brain, reliably encodes these rates

PHYSIOLOGICAL MODIFICATIONS PRODUCED BY TAPHRINA DEFORMANS (BERK.) TUL. IN PERSICA VULGARIS MILLER CULTIVATED IN THE CLIMATIC CONDITIONS OF OLTENIA REGION

The researches regarding physiological modification produced in Persica vulgaris Miller due to the attack produced by Taphrina deformans (Berk.) Tul. were performed on Champion variety cultivated in the climatic conditions in Oltenia Region.In the leaves of the peach attacked by the pathogen it is observed that the physiological processes intensity presents specific variations due the damaging action of the pathogen and of the climatic conditions. The photosynthesis and transpiration’s intensity in the attacked leaves is similar to that in the healthy leaves, but the recorded values are lower due to the reduction of the assimilation surface of the leaf due to the appearance of reddish-yellow spots and tissue deformation. The attacked leaves present a decrease of chlorophyll and water content, fact manifested by withering and drying of the leaves

THE EFFECTS OF THE TREATMENT WITH FUNGICIDES ON THE PHYSIOLOGICAL PROCESSES IN VITIS VINIFERA L. ATTACKED BY UNCINULA NECATOR (SCHW.) BURR. PATHOGEN

The effects of treatment with fungicides on the physiological processes were observed in Vitis vinifera L. plants cultivated in the climatic conditions in Oltenia region.The physiological analyzes were performed on July 18th 2021, both for plants treated with Dithane M-45 (0,2%), in four phases, at 12 days interval and also for the plants attacked by Uncinula necator  (Schv.) Burr. in which treatments have not been performed. In the Vitis vinifera L. plants attacked by Uncinula necator  (Schv.) it was observed that the physiological processes intensity is lower as a result of the reduction of the assimilation surface due to the covering of the leaves with the mycelium of the fungus, the appearance of whitish spots and the browning of the tissues, in comparison with the plants in which fungicide treatments have been performed

PHYSIOLOGICAL PARTICULARITIES OF PLANTS FROM THE CRASSULACEAE FAMILY

The interest in research regarding plants from the Crassulaceae family has arisen with the discovery of the fact that they have the ability to absorb and fix carbon dioxide during the night because during daytime they keep their stomata closed in order to save water.The data presented in the paper reveals that these plants have high drought resistance, both by providing high osmotic pressure at the cellular level, and by regulating the gas exchange (water, carbon dioxide, oxygen) due to the prompt reaction of closure and opening of the stomata.Absorptionand saving water in this way is very important in the environmental conditions in which these plants live.

Magneto-optical response enhanced by Mie resonances in nanoantennas

Control of light by an external magnetic field is one of the important methods for modulation of its intensity and polarisation. Magneto-optical effects at the nanoscale are usually observed in magnetophotonic crystals, nanostructured hybrid materials or magnetoplasmonic crystals. An indirect action of an external magnetic field (e.g. through the Faraday effect) is explained by the fact that natural materials exhibit negligible magnetism at optical frequencies. However, the concept of metamaterials overcome this limitation imposed by nature by designing artificial subwavelength meta-atoms that support a strong magnetic response, usually termed as optical magnetism, even when they are made of nonmagnetic materials. The fundamental question is what would be the effect of the interaction between an external magnetic field and an optically-induced magnetic response of metamaterial structures. Here we make the first step toward answering this fundamental question and demonstrate the multifold enhancement of the magneto-optical response of nanoantenna lattices due to the optical magnetism.Comment: 7 pages, 5 figure