Desenpenho aeróbio e controle autonômico cardíaco em idosas praticantes de tai chi chuan e sedentárias

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Estimulação optogenética do septo medial no rato anestesiado e em livre comportamento

Theta rhythm consists of an electrophysiological hippocampal oscillation present in mammalian species (4-12 Hz with variations across species). This oscillation is present during active waking and is also prevalent in local field potentials (LFP) during rapid eye movement sleep (REM sleep). Several studies have shown that theta rhythm is important in cognitive tasks and that the medial septum is a key region for its occurrence. The septum sends cholinergic, GABAergic and glutamatergic projections to the hippocampus, which in turn projects axons to the septum. Besides the septum, other regions are involved in regulating theta rhythm, forming a complex network of interactions among brain areas that result in theta rhythm. Optogenetics is a recently developed method that has been widely used in various research areas. It allows us to manipulate the electrical activity of neurons through light stimulation. One of the existing techniques consists in using a viral vector to induce the neuronal expression of ion channels associated with the light-sensitive molecule rhodopsin (e.g. ChR2). Once infected, the neurons become sensitive to light of a particular wavelength. The present M. Sc. research aimed to perform luminous stimulation of the brain in anesthetized and freely behaving animals using chronically implanted electrodes and optical fibers in animals infected with a viral vector for ChR2 expression. Surgical viral injections were performed in the medial septum; histological results confirmed the expression of ChR2 by way of the presence of the eYFP reporter protein in the septum and also in hippocampal processes. Moreover, we performed acute experiments with luminous stimulation of the medial septum and LFP recordings of the septum and hippocampus of anesthetized animals. Action potentials were recorded in the septum. In these experiments we observed a significant increase in the firing rates of septal neurons during luminous stimulation (n = 300 trials). Furthermore, we found an early light-evoked response in the hippocampal LFP. Chronic experiments with luminous stimulation of the medial septum and hippocampus in freely behaving animals were also performed in combination with LFP recordings. We found that the luminous stimulation of the septum is able to induce theta rhythm in the hippocampus. Together, the results demonstrate that the luminous stimulation of the medial septum in optogenetically-modified animals causes relevant electrophysiological changes in the septum and the hippocampus.

Influência de mudanças de fase no ciclo claro-escuro sobre o controle autonômico cardíaco de ratos

Introduction: The circadian system has neural projections for the Autonomic Nervous System (ANS), directly interfering with sympathetic-vagal modulation of the cardiovascular system. Disturbances in the circadian system, such as phase changes in light-dark cycle (LD), has been related to the risk of development of cardiovascular diseases due to increased sympathetic tone and reduction o Heart Rate Variability (HRV - RR intervals). Purpose: Investigate the interaction between Circadian Timing System and cardiac autonomic control in rats. Materials and methods: We used 18 Wistar rats (♀, age = 139.9 ± 32.1 days, weight = 219.5 ± 16.2 g), divided into three distinct groups: Control (CG), phase delay of 6h (GDe) and phase advance of 6h (GAd). Three animals were excluded during data collection (CG/GDe/GAd - n=5). Telemeters were surgically implanted in each animal for continuous acquisition of electrocardiographic (ECG) signals (duration of 21 days in the CG and 28 days in GDe/ GAd). A LD cycle was established 12h: 12h, beginning of light at18:00h and dark at 06:00h. The animals remained in the same CG LD cycle throughout the experimental period, while, on the 14th day of registration, the GDe and GAd underwent a delay and an advance in 6h, respectively. Throughout the experimental period, the locomotor activity (LA), the mean heart rate (mHR) and variables related to iRR [mean RR (mRR), SDNN, RMSSD, LF, HF and LF/ HF ratio ] were recorded. All data were analyzed in blocks of 3 and 7 days, for the presence of circadian rhythm, values of Cosinor - mesor, amplitude and acrophase (paired t test), phase relationship, differences between light and dark (t test independent), averages every 30 minutes along each time series (two-way ANOVA with post hoc Bonferroni). The data block B1,M1 and M2 in CG served as benchmarks for comparisons between series of analysis of the GAT/GAV. Results: We observed circadian rhythmicity in the variables LA, mRR and mFC(p<0.01). mRR and mFC showed phase relationship with the LA in all three groups, being less stable in GAd. In the CG, no significant differences between blocks were found in any of the analyzes(p>0.05). Among the 7 day blocks, there was a significant reduction in mRR(p=0.04) and mFC(p=0.03) in GDe and significant reduction in HF mean(p=0.02) in GAd; and between 3 day blocks, a significant increase of LF/HF(p= 0.04) in the GDe; besides mRR(p=0.03), SDNN(p=0.04), RMSSD (p=0.04), LF (p=0.01) and HF(p=0.02) significant increase in the GAd. It was found that the differences between the means of the mRR, LA and mFC in light and dark phases were not significant after phase changes in some of the blocks/moments (GDe and GAd). No significant results were found when comparing rhythmic variables means every 30 minutes over the blocks, except for a significant decrease in mRR at the middle of the dark phase (B2) and the start of light phase (B3) - (p<0.01). Conclusion: phase advances and delays (6h) altered cardiac autonomic control in the experimental groups by temporarily HRV decrease. Phase advances apparently had greater negative interference in this process, in relation to the phase delays.

Influência do jet lag social em marcadores circadianos de atividade - repouso e cardíaco em estudantes de medicina

Studies reveal that in recent decades a decrease in sleep duration has occurred. Social commitments, such as work and school are often not aligned to the "biological time" of individuals. Added to this, there is a reduced force of zeitgeber caused by less exposure to daylight and larger exposure to evenings. This causes a chronic sleep debt that is offset in a free days. Indeed, a restriction and extent of sleep called "social Jet lag" occurs weekly. Sleep deprivation has been associated to obesity, cancer, and cardiovascular risk. It is suggested that the autonomic nervous system is a pathway that connects sleep problems to cardiovascular diseases. However, beyond the evidence demonstrated by studies using models of acute and controlled sleep deprivation, studies are needed to investigate the effects of chronic sleep deprivation as it occurs in the social jet lag. The aim of this study was to investigate the influence of social jet lag in circadian rest-activity markers and heart function in medical students. It is a cross-sectional, observational study conducted in the Laboratory of Neurobiology and Biological Rhythmicity (LNRB) at the Department of Physiology UFRN. Participated in the survey medical students enrolled in the 1st semester of their course at UFRN. Instruments for data collection: Munich Chronotype Questionnaire, Morningness Eveningness Questionnaire of Horne and Östberg, Pittsburgh Sleep Quality Index, Epworth Sleepiness Scale, Actimeter; Heart rate monitor. Analysed were descriptive variables of sleep, nonparametric (IV60, IS60, L5 and M10) and cardiac indexes of time domain, frequency (LF, HF LF / HF) and nonlinear (SD1, SD2, SD1 / SD2). Descriptive, comparative and correlative statistical analysis was performed with SPSS software version 20. 41 students participated in the study, 48.8% (20) females and 51.2% (21) males, 19.63 ± 2.07 years. The social jet lag had an average of 02: 39h ± 00:55h, 82.9% (34) with social jet lag ≥ 1h and there was a negative correlation with the Munich chronotype score indicating greater sleep deprivation in subjects prone to eveningness. Poor sleep quality was detected in 90.2% (37) (X2 = 26.56, p <0.001) and 56.1% (23) excessive daytime sleepiness (X2 = 0.61, p = 0.435). Significant differences were observed in the values of LFnu, HFnu and LF / HF between the groups of social jet lag <2h and ≥ 2h and correlation of the social jet lag with LFnu (rs = 0.354, p = 0.023), HFnu (rs = - 0.354 , p = 0.023) and LF / HF (r = 0.355, p = 0.023). There was also a negative association between IV60 and indexes in the time domain and non-linear. It is suggested that chronic sleep deprivation may be associated with increased sympathetic activation promoting greater cardiovascular risk.

Efeitos da nicotina no complexo do septo medial na via septo hipocampal em camundongos anestesiados por Ketamina

Nicotine administration in humans and rodents enhances memory and attention, and also has a positive effect in Alzheimer's Disease. The Medial Septum / Diagonal Band of Broca complex (MS/DBB) – a main cholinergic system – massively projects to the hippocampus through the fimbria-fornix, and this pathway is called the septohippocampal pathway. It has been demonstrated that the MS/DBB acts directly on the local field potential (LFP) rhythmic organization of the hippocampus, especially in the rhythmogenesis of Theta (4-8Hz) – an oscillation intrinsically linked to hippocampus mnemonic function. In vitro experiments gave evidence that nicotine applied to the MS/DBB generates a local network Theta rhythm within the MS/DBB. Thus, the present study proposes to elucidate the function of nicotine in the MS/DBB on the septo-hippocampal pathway. In vivo experiments compared the effect of MS/DBB microinfusion of saline (n=5) and nicotine (n=8) on Ketamine/Xylazine anaesthetized mice. We observed power spectrum density in the Gamma range (35 to 55 Hz) increasing in both structures (Wilcoxon Rank-Sum test, p=0.038) but with no change in coherence between these structures in the same range (Wilcoxon Rank-Sum test, p=0.60). There was also a decrease in power of the ketamineinduced Delta oscillation (1 to 3 Hz). We also performed in vitro experiments on the effect of nicotine on membrane voltage and action potential. We patch-clamped 22 neurons in current-clamp mode; 12 neurons were responsive to nicotine, half of them increased firing rate and other 6 decreased, and they significantly differed in action potential threshold (-47.3±0.9 mV vs. -41±1.9 mV, respectively, p=0.007) and halfwidth time (1.6±0.08 ms vs. 2±0.12 ms, respectively, p=0.01). Furthermore, we performed another set of in vitro experiments concerning the connectivity of the three major neuronal populations of MS/DBB that use acetylcholine, GABA or glutamate as neurotransmitter. Paired patch-clamp recordings found that glutamatergic and GABAergic neurons realize intra-septal connections that produce sizable currents in MS/DBB postsynaptic neurons. The probability of connectivity between different neuronal populations gave rise to a MS/DBB topology that was implemented in a realistic model, which corroborates that the network is highly sensitive to the generation of Gamma rhythm. Together, the data available in the full set of experiments suggests that nicotine may act as a cognitive enhancer, by inducing gamma oscillation in the local circuitry of the MS/DBB.

Trabalho e seus sentidos: estudo com servidores com deficiências numa IES

The objective of this study was to understand the relationship between people with disabilities and their labor. Senses and meanings related to work were specifically identified; also describing the impediments of concrete activities, as well the strategies developed for overcoming them. This objective is inspired on the social historic cultural theoretical perspective as well as on the activity's theory. The research has been made possible through the interview of 16 workers from a IES, it categorizes as a multi-method sequential and transversal study of qualitative orientation, making use the technics of narrative interviews and photographic creation. The results indicate that work was described as a necessity, a source of pleasure, recognition and socialization; with emphasis on the importance of working in pairs in order to accomplish good quality work. Senses were obtained from each participant, identified by the way that each of them expressed themselves. Impediments were more deeply related to the physical conditions of the work environment than to the person's disabilities. Conclusion points out that the access to work, acts as a social inclusion tool for peoples with disabilities, and showing that, the laws regarding quota reservations fulfill their objective.