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In this study, we assessed the effects of different harvest times (9 a.m., 1 p.m., and 5 p.m.) and hydrodistillation times (60, 90, and 120 min) on the yield, chemical composition, and antioxidant activity of the spearmint (Mentha spicata L.) essential oil (EO) sourced from the Amazon region. EO yield was ≥1.55% and was not significantly influenced (p ≥ 0.05) by the different harvest times and hydrodistillation times. Thirty-one different organic compounds were identified, of which menthol (91.56-95.68%), menthone (0.6-2.72%), and isomenthone (0.55-1.46%) were the major constituents. The highest menthol content in the EO was obtained from samples collected at 9 a.m., with a hydrodistillation time of 60-90 min, compared to other harvest and hydrodistillation times. This suggests that exposure to sun and light, which is greater at harvest times of 1 p.m. and 5 p.m., decreased the menthol content and altered the chemical composition of Mentha EO. Furthermore, the sample harvested at 9 a.m. and hydrodistilled for 60 min showed the highest antioxidant activity (61.67 equivalent mg of Trolox per g of EO), indicating that antioxidant activity is strongly affected by light exposure and the contact duration of the sample with boiling water during hydrodistillation.

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Traumatic brain injury (TBI) represents a significant public health concern and has been associated with high rates of morbidity and mortality. TBI generates two types of brain damage: primary and secondary. Secondary damage originates a series of pathophysiological processes, which include metabolic crisis, excitotoxicity, and neuroinflammation, which have deleterious consequences for neuronal function. However, neuroprotective mechanisms are also activated. The balance among these tissue responses, and its variations throughout the day determines the fate of the damage tissue. We have demonstrated less behavioral and morphological damage when a rat model of TBI was induced during the light hours of the day. Moreover, here we show that rats subjected to TBI in the dark lost less body weight than those subjected to TBI in the light, despite no change in food intake. Besides, the rats subjected to TBI in the dark had better performance in the beam walking test and presented less histological damage in the corpus callosum and the cingulum bundle, as shown by the Klüver-Barrera staining. Our results suggest that the time of day when the injury occurs is important. Thus, this data should be used to evaluate the pathophysiological processes of TBI events and develop better therapies.

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Reproduction is one of the most important biological aspects for the maintenance of viable populations, and understanding the spatial and seasonal patterns in the reproduction of Neotropical fish is a point that still needs considerable investigation. In this study, the main aim was to reduce knowledge gaps concerning fish eggs and larvae distribution patterns. Therefore, the River Araguaia basin, one of the main hydrographic basins of the Neotropical savanna, was used as the focal point of study. Samplings of fish eggs and larvae were carried across the hydrological regime during flooding and drought events between December 2018 and July 2020 at 15 sites distributed along a 350 km stretch of the River Araguaia basin. Fish eggs and larvae were found in all sampling sites, with the highest number of catches in the flood season. The fish larvae were represented by 5 orders, 22 families and 22 at the genus or species level. Both environments, tributary and main channel of the River Araguaia, are important for fish reproduction, and no difference was found in the use between the main channel and the tributaries. The results showed that spatial factors are important to explain the change in larval composition, which may have a wide or restricted distribution related to specific habitats. The main factors related to the reproductive activity of fish in this region are the physical and chemical changes in the water that occur in the flood season. These results indicate that the River Araguaia basin has environmental integrity and provides favourable conditions for the reproductive activity of fish, including long-distance migratory species. Considering this, mitigate measures that guarantee the preservation of the natural flow are crucial for the maintenance of fish biodiversity.

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PURPOSE: This study investigated the effects of both an active warm-up and the time-of-day variation on repeated-sprint performance. A second objective was to compare the post-exercise recovery between the experimental conditions. METHODS: Eleven male participants performed ten maximal cycling sprints (6 s each, with a 30-s interval between them) in the morning and late afternoon, either after a warm-up or control condition. The warm-up consisted of cycling for 10 min at 50% of the peak aerobic power. RESULTS: Rest measurements of rectal, muscle, and skin temperatures were higher in the afternoon compared to the morning (p < 0.05), with no significant differences in heart rate (p = 0.079) and blood lactate concentration (p = 0.300). Warm-up increased muscle temperature, heart rate, and lactate, and reduced skin temperature (all p < 0.001), though no significant differences were observed for rectal temperature (p = 0.410). The number of revolutions (p = 0.034, ηp2 = 0.375), peak (p = 0.034, ηp2 = 0.375), and mean (p = 0.037, ηp2 = 0.365) power of the first sprint (not the average of ten sprints) were higher in the afternoon compared to the morning, regardless of warm-up. However, beneficial performance effects of warming up were evident for the first (p < 0.001) and the average of ten sprints (p < 0.05), regardless of time of day. More remarkable changes during the 60-min post-exercise were observed for rectal temperature (p = 0.005) and heart rate (p = 0.010) in the afternoon than in the morning. CONCLUSION: Warming-up and time-of-day effects in enhancing muscular power are independent. Although warm-up ensured further beneficial effects on performance than the time-of-day variation, a faster post-exercise recovery was observed in the late afternoon.

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Amino acid neurotransmitters are responsible for many physiological and pathological processes, and their cerebral concentrations respond to external influences such as the light-dark cycle and to the synthesis, release, and recapture rhythms and form part of the biochemical relationships derived from excitatory-inhibitory (E/I), glutamine-glutamate sum (GLX), glutamatergic processing (glutamine-glutamate ratio) and excitotoxic indexes. The changes in these variables during a 24-h period (1 day) are important because they allow organisms to adapt to external stimuli and form part of physiological processes. Under pathological conditions, the damage produced by acute events may depend on diurnal variations. Therefore, it is important to analyze the extracellular levels of amino acids as well as the above-mentioned indexes over a 24-h period. We focused on determining the cerebrospinal fluid levels of different amino acid neurotransmitters, and the E/I, GLX, glutamatergic processing and excitotoxic indexes, determined by microdialysis over a 24-h cycle. Our results showed significant changes during the 24-h light/dark cycle. Specifically, we found increments in the levels of glutamate (325%), GABA (550%), glutamine (300%), glycine (194%), alanine (304%) and the GLX index (263%) throughout the day, and the maximum levels of glutamate, glutamine, glycine, and alanine were obtained during the last period of the light period. In conclusion, the concentration of some amino acid neurotransmitters and the GLX index show variations depending on the light-dark cycle.

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Traumatic brain injury (TBI) induces two types of brain damage: primary and secondary. Damage initiates a series of pathophysiological processes, such as metabolic crisis, excitotoxicity with oxidative stress-induced damage, and neuroinflammation. The long-term perpetuation of these processes has deleterious consequences for neuronal function. However, it remains to be elucidated further whether physiological variation in the brain microenvironment, depending on diurnal variations, influences the damage, and consequently, exerts a neuroprotective effect. Here, we established an experimental rat model of TBI and evaluated the effects of TBI induced at two different time points of the light-dark cycle. Behavioral responses were assessed using a 21-point neurobehavioral scale and the cylinder test. Morphological damage was assessed in different regions of the central nervous system. We found that rats that experienced a TBI during the dark hours had better behavioral performance than those injured during the light hours. Differences in behavioral performance correlated with less morphological damage in the perilesional zone. Moreover, certain brain areas (CA1 and dentate gyrus subregions of the hippocampus) were less prone to damage in rats that experienced a TBI during the dark hours. Our results suggest that diurnal variation is a crucial determinant of TBI outcome, and the hour of the day at which an injury occurs should be considered for future research.

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INTRODUCTION: Previous studies observed diurnal variation in hemodynamic responses during recovery from whole-body exercise, with vasodilation appearing greater after evening versus morning sessions. It is unclear what mechanism(s) underlie this response. Since small muscle-mass exercise can isolate peripheral effects related to postexercise vasodilation, it may provide insight into possible mechanisms behind this diurnal variation. METHODS: The study was conducted in ten healthy (5F, 5M) young individuals, following single-leg dynamic knee-extension exercise performed in the Morning (7:30-11:30 am) or the Evening (5-9 pm) on two different days, in random order. Arterial pressure (automated auscultation) and leg blood flow (femoral artery Doppler ultrasound) were measured pre-exercise and during 120 min postexercise. Net effect for each session was calculated as percent change in blood flow (or vascular conductance) between the Active Leg and the Inactive Leg. RESULTS: Following Morning exercise, blood flow was 34.9 ± 8.9% higher in the Active Leg versus the Inactive Leg (p < 0.05) across recovery. Following Evening exercise, blood flow was 35.0 ± 8.8% higher in the Active Leg versus the Inactive Leg (p < 0.05). Likewise, vascular conductance was higher in the Active Leg versus the Inactive Leg (Morning: +35.1 ± 9.0%, p < 0.05; Evening: +33.2 ± 8.2%, p < 0.05). Morning and Evening blood flow (p = 0.66) and vascular conductance (p = 0.64) did not differ. CONCLUSION: These data suggest previous studies which identified diurnal variations in postexercise vasodilation responses are likely reflecting central rather than peripheral modulation of cardiovascular responses.

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Aporphine alkaloids are secondary metabolites that are obtained in low levels from species of the Annonaceae family. Nitrogen addition may increase the alkaloid content in plants. However, previous studies published did not consider that nitrogen could change the alkaloid content throughout the day. We conducted this short-term study to determine the effects of nitrogen applied throughout the diurnal period on the aporphine alkaloids via measurements conducted on the roots, stems and leaves of Annona diversifolia seedlings. The 60-day-old seedlings were cultured with the addition of three levels of nitrogen (0, 30 and 60 mM), and alkaloid extracts were analysed using high-performance liquid chromatography. The highest total alkaloid content was measured in the treatment with moderate nitrogen supply. Further, the levels of aporphine alkaloids changed significantly in the first few hours of the diurnal period. We conclude that aporphine alkaloid content increased with moderate nitrogen supply and exhibited diurnal variation.

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Post-exercise hypotension has been extensively investigated with combined exercise (aerobic + resistance). However, its response in different periods of the day is still unknown. Objective: To determine the effects of a combined exercise session performed at different times of the day on blood pressure response after exercise. Anaerobic threshold (AT) and 12 repetition maximum (12RM) tests were evaluated in nine male Brazilian jiu-jitsu athletes (22±3.7 y; 176±5.0 cm; 73.4±9.7 kg; 6.8±2.1 % body fat). Four experimental sessions were performed: resistance exercise followed by aerobic exercise [Morning (RAM) and Afternoon (RAA)] and Control (C) [Morning and Afternoon]. The morning sessions were conducted at 09:00 a.m. and the afternoon sessions were conducted at 3:00 p.m. Resistance exercise consisted of three sets at 90% of 12RM in six exercises, while aerobic exercise consisted of 15min at 90% of the AT. Blood pressure (BP) was measured before, during and 1h after the performance of exercises in laboratory. When comparing the AE and RE intensity marker variables (heart rate, RPE, running speed and number of repetitions) significant differences (p>0.05) were not evidenced between the experimental protocols (RAM and RAA). The morning session presented a hypotensive effect in SBP (mean recovery 1h) (109.5±6.9mmHg) when compared to control morning session (117.4±5.6mmHg) (p=0.001). Both sessions of combined exercise promoted HPE, without differences between them.(AU)

A hipotensão pós-exercício tem siso amplamente investigada com exercícios combinado (resistido+aeróbio). Contudo, ainda é desconhecida sua resposta em diferentes períodos do dia. Objetivo: verificar o efeito de uma sessão de exercício combinado realizado em diferentes períodos do dia sobre a resposta da PA pós-exercício. Limiar anaeróbio (LA) e teste de 12 repetições máximas (12RM) foram avaliados em nove atletas (masculinos) de jiu-jitsu (22,0±3,7 anos; 176,0±5,0 cm; 73,4±9,7 kg; 6,8±2,1 %gordura). Quatro sessões experimentais foram realizadas: exercício resistido + exercício aeróbio [manhã (ManhaE) e tarde (TardeE)] e sessão controle (C) [manhã e tarde]. A sessão da manhã foi realizada 09:00h e a sessão da tarde foi realizada ás 15:00h. O exercício resistido consistiu em três séries a 90% de 12RM em seis exercícios. O exercício aeróbio consistiu em 15min a 90% do LA. PA foi mensurada antes, durante e 1h após a realização dos exercícios em laboratório. Quando comparado o AE e re variáveis marcador de intensidade como: freqüência cardíaca, RPE, velocidade e número de repetições em execução, as diferenças significativas (p> 0,05) não foram evidenciados entre os protocolos experimentais (RAM e RAA). A sessão de exercício de manhã apresentou um efeito hipotensor na PAS (média de 1h de recuperação) (109,5±6,9mmHg) quando comparado a sessão controle da manhã (117,4±5,6mmHg) (p=0,001). Ambas as sessões de exercício combinado foram interessantes para promover HPE, sem diferença entre elas.(AU)

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Heart rate (HR) recovery (HRR) and variability (HRV) after exercise are non-invasive tools used to assess cardiac autonomic regulation and cardiovascular prognosis. Autonomic recovery is slower after evening than morning exercise in healthy individuals, but this influence is unknown in subjects with autonomic dysfunction, although it may affect prognostic evaluation. This study compared post-exercise HRR and HRV after maximal morning and evening exercise in pre-hypertensive men. Ten volunteers randomly underwent two maximal exercise tests conducted in the morning (8-10 a.m.) and evening (6-8 p.m.). HRR60s (HR reduction at 60 s of recovery - prognostic index), T30 (short-term time-constant of HRR - parasympathetic reactivation marker), rMSSD30s (square root of the mean of the sum of the squares of differences between adjacent R-R intervals on subsequent 30 s segments - parasympathetic reactivation marker), and HRRτ (time constant of the first order exponential fitting of HRR - marker of sympathetic withdraw and parasympathetic reactivation) were measured. Paired t-test and two-way ANOVA were used. HRR60s and HRRτ were similar after exercise in the morning and evening (27 ± 7 vs. 29 ± 7 bpm, p = 0.111, and 79 ± 14 vs. 96 ± 29 s, p = 0.119, respectively). T30 was significantly greater after evening exercise (405 ± 215 vs. 295 ± 119 s, p = 0.002) and rMSSD30s was lower in the evening (main factor session, p = 0.009). In conclusion, in pre-hypertensive men, the prognostic index of HRR, HRR60s, is not affected by the time of day when exercise is conducted. However, post-exercise parasympathetic reactivation, evaluated by T30 and rMSSD30s, is blunted after evening exercise.

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Global climate models predict changes on the length of the dry season in the Amazon which may affect tree physiology. The aims of this work were to determine the effect of the rainfall regime and fraction of sky visible (FSV) at the forest understory on leaf traits and gas exchange of ten rainforest tree species in the Central Amazon, Brazil. We also examined the relationship between specific leaf area (SLA), leaf thickness (LT), and leaf nitrogen content on photosynthetic parameters. Data were collected in January (rainy season) and August (dry season) of 2008. A diurnal pattern was observed for light saturated photosynthesis (Amax) and stomatal conductance (g s), and irrespective of species, Amax was lower in the dry season. However, no effect of the rainfall regime was observed on g s nor on the photosynthetic capacity (Apot, measured at saturating [CO2]). Apot and leaf thickness increased with FSV, the converse was true for the FSV-SLA relationship. Also, a positive relationship was observed between Apot per unit leaf area and leaf nitrogen content, and between Apot per unit mass and SLA. Although the rainfall regime only slightly affects soil moisture, photosynthetic traits seem to be responsive to rainfall-related environmental factors, which eventually lead to an effect on Amax. Finally, we report that little variation in FSV seems to affect leaf physiology (Apot) and leaf anatomy (leaf thickness).

Os modelos climáticos globais prevêem mudanças na extensão da época seca na Amazônia, o que pode afetar a fisiologia das árvores. Os objetivos deste trabalho foram determinar o efeito da sazonalidade da precipitação e fração de céu visível (FSV) no sub-bosque da floresta nas características foliares e trocas gasosas de 10 espécies florestais da Amazônia Central. Também examinou-se a relação entre área foliar específica (SLA), espessura da folha (LT) e nitrogênio foliar em parâmetros fotossintéticos. Os resultados foram coletados nos meses de janeiro (época chuvosa) e agosto (época seca) de 2008. Observou-se um padrão de variação diurna na fotossíntese saturada por luz (Amax) e na condutância estomática (g s). Independente da espécie, Amax foi menor na época seca. No entanto, não houve efeito da sazonalidade das chuvas em g s nem na capacidade fotossintética (Apot medida em [CO2] saturante). Apot e a espessura da folha (LT) aumentaram com FSV, o contrário foi observado para a relação FSV-SLA. Também, observou-se uma relação positiva entre Apot por unidade de área e conteúdo de nitrogênio foliar, e entre Apot, por unidade de massa e SLA. Embora o regime das chuvas apenas levemente influenciou a umidade do solo, características fotossintéticas parecem responderem a fatores relacionados com as chuvas, o que repercute em Amax. Finalmente, relata-se que pequenas variações em FSV parecem afetar a fisiologia da folha (Apot) e a anatomia foliar (espessura da folha).

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Global climate models predict changes on the length of the dry season in the Amazon which may affect tree physiology. The aims of this work were to determine the effect of the rainfall regime and fraction of sky visible (FSV) at the forest understory on leaf traits and gas exchange of ten rainforest tree species in the Central Amazon, Brazil. We also examined the relationship between specific leaf area (SLA), leaf thickness (LT), and leaf nitrogen content on photosynthetic parameters. Data were collected in January (rainy season) and August (dry season) of 2008. A diurnal pattern was observed for light saturated photosynthesis (Amax) and stomatal conductance (g s), and irrespective of species, Amax was lower in the dry season. However, no effect of the rainfall regime was observed on g s nor on the photosynthetic capacity (Apot, measured at saturating [CO2]). Apot and leaf thickness increased with FSV, the converse was true for the FSV-SLA relationship. Also, a positive relationship was observed between Apot per unit leaf area and leaf nitrogen content, and between Apot per unit mass and SLA. Although the rainfall regime only slightly affects soil moisture, photosynthetic traits seem to be responsive to rainfall-related environmental factors, which eventually lead to an effect on Amax. Finally, we report that little variation in FSV seems to affect leaf physiology (Apot) and leaf anatomy (leaf thickness).

Os modelos climáticos globais prevêem mudanças na extensão da época seca na Amazônia, o que pode afetar a fisiologia das árvores. Os objetivos deste trabalho foram determinar o efeito da sazonalidade da precipitação e fração de céu visível (FSV) no sub-bosque da floresta nas características foliares e trocas gasosas de 10 espécies florestais da Amazônia Central. Também examinou-se a relação entre área foliar específica (SLA), espessura da folha (LT) e nitrogênio foliar em parâmetros fotossintéticos. Os resultados foram coletados nos meses de janeiro (época chuvosa) e agosto (época seca) de 2008. Observou-se um padrão de variação diurna na fotossíntese saturada por luz (Amax) e na condutância estomática (g s). Independente da espécie, Amax foi menor na época seca. No entanto, não houve efeito da sazonalidade das chuvas em g s nem na capacidade fotossintética (Apot medida em [CO2] saturante). Apot e a espessura da folha (LT) aumentaram com FSV, o contrário foi observado para a relação FSV-SLA. Também, observou-se uma relação positiva entre Apot por unidade de área e conteúdo de nitrogênio foliar, e entre Apot, por unidade de massa e SLA. Embora o regime das chuvas apenas levemente influenciou a umidade do solo, características fotossintéticas parecem responderem a fatores relacionados com as chuvas, o que repercute em Amax. Finalmente, relata-se que pequenas variações em FSV parecem afetar a fisiologia da folha (Apot) e a anatomia foliar (espessura da folha).