Time Window of the Critical Period for Neuroplasticity in S1, V1, and A1 Sensory Areas of Small Rodents: A Systematic Review.

The plasticity of the central nervous system (CNS) allows the change of neuronal organization and function after environmental stimuli or adaptation after sensory deprivation. The so-called critical period (CP) for neuroplasticity is the time window when each sensory brain region is more sensitive to changes and adaptations. This time window is usually different for each primary sensory area: somatosensory (S1), visual (V1), and auditory (A1). Several intrinsic mechanisms are also involved in the start and end of the CP for neuroplasticity; however, which is its duration in S1, VI, and A1? This systematic review evaluated studies on the determination of these time windows in small rodents. The careful study selection and methodological quality assessment indicated that the CP for neuroplasticity is different among the sensory areas, and the brain maps are influenced by environmental stimuli. Moreover, there is an overlap between the time windows of some sensory areas. Finally, the time window duration of the CP for neuroplasticity is predominant in S1.

Preclinical evidences of aluminum-induced neurotoxicity in hippocampus and pre-frontal cortex of rats exposed to low doses.

Aluminum (Al) is a neurotoxicant agent implicated in several behavioral, neuropathological and neurochemical changes associated with cognitive impairments. Nevertheless, mechanisms of damage and safety concentrations are still very discussed. Thus, the main purpose of this study was to investigate whether two aluminum low doses were able to produce deleterious effects on cognition of adult rats, including oxidative stress in hippocampus and prefrontal cortex, two important areas for cognition. For this, thirty adult Wistar rats were divided into three groups: Al1 (8.3 mg/kg/day), Al2 (32 mg/kg/day) and Control (Ultrapure Water), in which all three groups received their solutions containing or not AlCl3 by intragastric gavage for 60 days. After the experimental period, the short- and long-term memories were assessed by the object recognition test and step-down inhibitory avoidance. After euthanizing, prefrontal cortex and hippocampus samples were dissected for Al levels measurement and evaluation of oxidative biochemistry. Only Al2 increased Al levels in hippocampal parenchyma significantly; both concentrations did not impair short-term memory, while long-term memory was affected in Al1 and Al2. In addition, oxidative stress was observed in prefrontal and hippocampus in Al1 and Al2. Our results indicate that, in a translational perspective, humans are subjected to deleterious effects of Al over cognition even when exposed to low concentrations, by triggering oxidative stress and poor long-term memory performance.

Spinal cord neurodegeneration after inorganic mercury long-term exposure in adult rats: Ultrastructural, proteomic and biochemical damages associated with reduced neuronal density.

Mercury chloride (HgCl2) is a chemical pollutant widely found in the environment. This form of mercury is able to promote several damages to the Central Nervous System (CNS), however the effects of HgCl2 on the spinal cord, an important pathway for the communication between the CNS and the periphery, are still poorly understood. The aim of this work was to investigate the effects of HgCl2 exposure on spinal cord of adult rats. For this, animals were exposed to a dose of 0.375 mg/kg/day, for 45 days. Then, they were euthanized, the spinal cord collected and we investigated the mercury concentrations in medullary parenchyma and the effects on oxidative biochemistry, proteomic profile and tissue structures. Our results showed that exposure to this metal promoted increased levels of Hg in the spinal cord, impaired oxidative biochemistry by triggering oxidative stress, mudulated antioxidant system proteins, energy metabolism and myelin structure; as well as caused disruption in the myelin sheath and reduction in neuronal density. Despite the low dose, we conclude that prolonged exposure to HgCl2 triggers biochemical changes and modulates the expression of several proteins, resulting in damage to the myelin sheath and reduced neuronal density in the spinal cord.

Physical Activity Reduces the Prevalence of Periodontal Disease: Systematic Review and Meta-Analysis.

Background: Regular physical activity boosts several physical capacities and reduces many inflammatory markers of several diseases. In this sense, periodontal disease is a multifactorial inflammatory disease of tooth supporting tissues that has been claimed to trigger processes of systemic alterations. The aim of this systematic review and meta-analysis was to assess the effects of physical activity on periodontal disease. Methods: Observational studies published until August 2018 were searched in online databases (PubMed, Scopus, Web of Science, The Cochrane Library, LILACS, OpenGrey, and Google Scholar) after developing a PECO statement that focused on the comparison between adults that followed a routine of exercises or presented a sedentary lifestyle and its effects on periodontal disease. Searching and data extraction were conducted by following PRISMA guidelines. Registration protocol: CRD42016049661. Quality assessment and risk of bias were analyzed by following Fowkes and Fulton protocol. Results: A total of 512 references were retrieved, while only seven were considered eligible. Two meta-analysis involving the prevalence of periodontal disease and unadjusted/adjusted Odds ratio were performed. One of studies did not find association between clinical periodontal parameters and physical activity. Six articles suggested an association between periodontal disease and regular practice of physical activity since a reduction of periodontal prevalence was observed. Moderate level of evidence was demonstrated on GRADE analysis. Conclusion: Physical activity was associated as a potential tool for reduction of periodontal disease prevalence. The frequency of physical activity is directly related to a low occurrence of periodontitis. However, it is important that further investigations evaluate the effects of other exercise variables, such as volume and intensity, on the periodontal disease prevalence.

Efeitos do método pareado agonista-antagonista utilizando séries múltiplas sobre o desempenho de repetições máximas para membros inferiores / Effects of the agonist-antagonist paired sets method using multiple sets on maximum number of repetitions performance for lower limbs

Introdução: O método pareado agonista-antagonista (PAA) consiste em estimular previamente a musculatura musculatura antagonista do grupo muscular que se deseja otimizar, aumentando a ativação neural e força dos músculos agonistas. Objetivo: Comparar o método tradicional vs PAA sobre o trabalho total (TT) e volume de treinamento (VT) no exercício cadeira extensora (CE). Métodos: Doze mulheres treinadas realizaram dois protocolos experimentais randomizados: método tradicional - quatro séries da CE até a falha concêntrica; método PAA: quatro séries de mesa flexora (MF) + CE até a falha concêntrica. Foi dado um intervalo de 30 segundos entre os dois exercícios. Resultados: Pôde-se observar diferença significativa tanto no TT como VT, para o método PAA quando comparado ao tradicional. Conclusão: Sugere-se assim que o método PAA apresenta-se como melhor estratégia para otimização do desempenho de repetições máximas se comparado ao método tradicional, além de apresentar possibilidade de redução no tempo despendido para o treinamento.

Introduction: The agonist-antagonist paired set method (PAA) consists of previously stimulating the antagonist muscle of the muscle group to be optimized, increasing the neural activation and agonist muscle strength. Objective: To compare the traditional method vs PAA on total work (TT) and training volume (VT) in the leg extension exercise (LE). Methods: Twelve trained women performed two randomized experimental protocols: traditional method - four LE sets until a concentric failure; PAA Method: four sets of leg curl (LC) + CE until a concentric failure. An interval of 30 seconds was given between the two exercises. Results: A significant difference was observed in both TT and VT, for the PAA method compared to the traditional method. Conclusion: It is suggested that the PAA method presents itself as a better strategy for optimizing the maximum number of repetitions performance when compared to the traditional method, in addition to the possibility of reducing the length of training.