Nocturnal Increase Research Articles

Diel foraging and shelter use of large juvenile brown trout (Salmo trutta) under food satiation

The diel partitioning of juvenile brown trout Salmo trutta foraging behaviour is controlled by a number of factors including predation risk, competition, temperature and food availability. The present study uses PIT-tagging and visual observation to asses the use of shelter and foraging behaviour of Danish wild juvenile brown trout (13.5–15.6 cm). The experiment was conducted in a fluvarium and the fish were fed to satiation. It was hypothesised that food satiation would promote nocturnal foraging and increase daytime shelter use. Our results showed a significant difference in diel shelter use between day and night with a significant increase in shelter use during daytime conditions. Visual observations showed a significant preference for nocturnal feeding. Together with the significantly reduced shelter use during the night, our results support the hypothesis that young stream living trout only feed during the day to the extent needed to sustain growth.

Fibroblast Growth Factor 21: A Novel Metabolic Regulator

Fibroblast growth factor (FGF) 21 belongs to a superfamily of FGF peptides predominantly produced by the liver but also by other tissues involved in carbohydrate and lipid metabolism. FGFs are classically considered to be paracrine factors, but the FGF19, FGF21, and FGF23 subfamily has recently become known as a group of endocrine factors [1]. FGF21 expression is induced in the murine liver by fasting as an adaptive response through a mechanism requiring peroxisome proliferator-activated receptor alpha (PPARα) [2]. In the liver, FGF21 induces gluconeogenesis, fatty acid oxidation, and ketogenesis but does not stimulate glycogenolysis [2,3]. It suggests that FGF21 does not play a conspicuous role during the early stage of fasting. However, FGF21 stimulates gluconeogenesis and ketogenesis in a state of prolonged fasting and starvation. In fact, an increase in plasma FGF21 during 72-hours fasting was absent, but the effect was present during 7-days of starvation in human studies [4,5]. There is evidence that FGF21 is a promising target for the treatment of type 2 diabetes and metabolic syndrome. When administrated systemically to rodents and monkeys with obesity and diabetes, recombinant FGF21 causes body weight loss, decrease of plasma glucose and triglycerides, and reduction of insulin resistance and hepatic steatosis [6-9] although little is known about the physiologic roles or regulation of FGF21 in humans. FGF21 treatment potently stimulates glucose uptake in adipocytes in an insulin-dependent manner [7]. In obese, insulin-resistant animals, FGF21 regulates mitochondrial activity and enhances oxidative capacity through an AMPK-SIRT1-PGC1α-dependent mechanism in adipocytes [10] and decreases hepatic triglyceride contents associated with a decrease in hepatic lipogenic gene expression (e.g., sterol regulatory element-binding protein-1 [SREBP-1]) [9]. The 24-hour circadian rhythm of FGF21 is displayed under fasting conditions in both humans and mice [4,11]. FGF21 levels began to rise at midnight, reaching a peak in the early morning and then decline to basal concentrations early in the afternoon [4,11]. A number of metabolic hormones including leptin, growth hormone, melatonin, and cortisol have been shown to exhibit a nocturnal increase. In addition, E4-binding protein 4 (E4BP4), which is a key circadian output protein transcriptional repressor, directly bound to the D-box cis-element in the distal promoter region of the FGF21 gene and downregulated its transcription and secretion in primary mouse hepatocytes [12]. Insulin significantly increases E4BP4 expression, which can subsequently repress hepatic FGF21 expression [12]. Other key factors of the circadian clock that regulate the hepatic expression of FGF21 in cultured cells are retinoic acid receptor-related orphan receptor α (RORα) and Rev-Erbα [13,14]. However, Lee et al. [15] were unable to observe a distinct diurnal variation of serum FGF21 concentrations over 24-hours in a small group of healthy Korean men (n=10) fed standardized meals. Although the basis for these differences is not clear, the methods of the FGF21 assay and the characteristics of study subjects could have caused the discrepancy. Because most studies on circadian variation of FGF21 were performed using a fasting state, feeding-dependent FGF21 expression may be different in liver and adipose tissues [16]. The molecular mechanism responsible for feeding-induced regulation of FGF21 is less well known than that for fasting-induced stimulation, and further studies in a non-fasting condition should be performed because they are more physiologically relevant. There are many controversial issues regarding serum FGF21 levels in human studies. In fact, the effects of ketogenic diet on circulating FGF21 concentrations in humans are inconsistent [5,17,18] and circulating FGF21 concentrations in humans showed a broad 250-fold interindividual variation [5]. Although the magnitude of the peak circadian increase of circulating FGF21 is significantly blunted in obese Chinese [11], in a study by Lee et al. [15], the number of large oscillations of FGF21 concentrations was significantly greater in obese subjects. Several recent reports showed that circulating FGF21 concentrations were higher in subjects with obesity, type 2 diabetes, impaired glucose tolerance, dyslipidemia or nonalcoholic fatty liver disease than in controls [18-21]. It is unclear whether this reflects FGF21 resistance or a compensatory response. Although there are few studies to demonstrate the physiologic role of FGF21 in the human body, a recent study showing that diet-induced obese mice had increased expression of FGF21 in liver and white adipose tissue with a significantly attenuated signaling response to exogenous FGF21 suggests FGF21 resistance in obesity [22]. Taken together, FGF21 actions to regulate and coordinate metabolism have not yet been clarified, especially in humans. It is necessary to consider that the regulation of FGF21 is complex and can differ from tissue to tissue, according to nutritional conditions or circadian rhythm. Future investigations about the effects of exogenous FGF21 in humans will elucidate the possible usefulness of this protein as a novel treatment tool for metabolic diseases.

AVTergic modulation of the agonistic behavior in two species of weakly electric fish with different social strategies

Event Abstract Back to Event AVTergic modulation of the agonistic behavior in two species of weakly electric fish with different social strategies Ana Silva1, 2* and Rossana Perrone1 1 Instituto de Investigaciones Biológicas Clemente Estable, Unidad Bases Neurales de la Conducta, Uruguay 2 Facultad de Ciencias, Laboratorio de Neurociencias, Uruguay Social behaviors in vertebrates are controlled by a complex and conserved brain network. It has been postulated that inter and intraspecific modulations of behavior are correlated with distinctively distributed patterns of this network, which depend on neuroendocrine messengers that integrate extrinsic and intrinsic cues. The hypothalamic neuropeptide arginine-vasotocin (AVT) and its mammalian homologue, vasopressin, are key integrators underlying interspecific, sexual, individual, and social context differences in behavior across vertebrate taxa. Comparative studies of AVT actions between related species with different social structure have been useful for the understanding of brain-behavior relationships. We used two species of weakly electric fish with different social strategies: Gymnotus omarorum, solitary and highly aggressive in intra and intersexual encounters all year round, and Brachyhypopomus gauderio, gregarious and only aggressive in intrasexual encounters during the breeding season. Our previous work showed that AVT produces an increase in the EOD basal rate in B. gauderio but not in G. omarorum, and that AVT is responsible for the nocturnal increase of EOD basal rate observed in the former species during the breeding season. In this study, we explored the effects of IP administration of AVT (1µg/g) and of its antagonist (Manning compound, MC, 2µg/g) in the agonistic behavior of both species. We analyzed dyadic encounters (control, n=10; AVT, n=10; MC, n=6) in independent experiments using experimental protocols in which we could predict the outcome of the conflict: 5-30% size asymmetry in intra and intersexual dyads of non-breeding G. omarorum, same size asymmetry + residency in breeding males of B. gauderio. Thirty minutes prior to the agonistic encounter, we injected AVT (or MC) to the potential winner and saline to the potential loser, and evaluated their effects on conflict resolution, levels of aggression and submission, and dynamics of electric and locomotor displays. AVT and MC administration in B. gauderio had no effect on the agonistic behavior except for their actions on EOD rate: AVT induced and MC blocked the increase of EOD rate observed in winners after conflict resolution. Interestingly, in AVT fights, the intruder significantly increased the emission of electric submission signals (offs) that were only rarely observed in control dyadic encounters. AVT induced no effects on the agonistic behavior of G. omarorum, whereas MC induced a decrease in the aggression levels, in the submission signaling, and prevented the decrease of EOD rate observed in control subordinates after conflict resolution. Taken together, our data indicate that the AVTergic system is involved in the modulation of the agonistic behavior of both species. This modulation shows important interspecific differences that might be crucial in shaping different neural strategies for the control of social behavior. Keywords: Aggression, hypothalamic neuropeptide, Neuromodulation Conference: Tenth International Congress of Neuroethology, College Park. Maryland USA, United States, 5 Aug - 10 Aug, 2012. Presentation Type: Poster Presentation (see alternatives below as well) Topic: Social Behavior Citation: Silva A and Perrone R (2012). AVTergic modulation of the agonistic behavior in two species of weakly electric fish with different social strategies. Conference Abstract: Tenth International Congress of Neuroethology. doi: 10.3389/conf.fnbeh.2012.27.00071 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 13 Mar 2012; Published Online: 07 Jul 2012. * Correspondence: Dr. Ana Silva, Instituto de Investigaciones Biológicas Clemente Estable, Unidad Bases Neurales de la Conducta, Montevideo, 11600, Uruguay, asilva@iibce.edu.uy Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Ana Silva Rossana Perrone Google Ana Silva Rossana Perrone Google Scholar Ana Silva Rossana Perrone PubMed Ana Silva Rossana Perrone Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Control of circadian activity of birds by the interaction of melatonin with 7α-hydroxypregnenolone, a newly discovered neurosteroid stimulating locomotion

Melatonin regulates diurnal locomotor rhythms in birds as well as in other vertebrates, but the molecular mechanism by which melatonin regulates locomotor activity is poorly understood. Here, we summarize new findings showing that 7α-hydroxypregnenolone, a previously undescribed avian neurosteroid, mediates melatonin action on diurnal locomotor rhythms in birds. Recently, 7α-hydroxypregnenolone was identified as a novel avian neurosteroid in Japanese quail Coturnix japonica brain. It was found that 7α-hydroxypregnenolone acutely stimulates quail locomotor activity. Subsequently, it was clarified that diurnal changes in 7α-hydroxypregnenolone synthesis occur in parallel with changes in locomotor activity in quail. Finally, it was demonstrated that melatonin depresses the synthesis of 7α-hydroxypregnenolone, thus providing a mechanism through which the nocturnal increase in melatonin regulates diurnal changes in locomotor activity. This review highlights a novel molecular mechanism controlling circadian activity of birds by the interaction of melatonin with 7α-hydroxypregnenolone, a newly discovered neurosteroid stimulating locomotion.

Daily responses of mouflon (Ovis gmelini musimon ×Ovis sp.) activity to summer climatic conditions

Investigating the factors shaping the activity of large herbivores is of prime importance because changes in their activity patterns may indicate physiological stress, which can affect reproduction and survival of individuals, and thereby population growth. Although climatic conditions are known to impact the activity patterns of large herbivores, few studies have investigated this relationship at a fine temporal scale. From a continuous monitoring of activity, we assessed the influence of temperature and wind on the summer activity of female mouflon ( Ovis gmelini musimon Pallas, 1811 × Ovis sp.) facing summer droughts. Females showed a marked bimodal activity pattern, with activity peaks occurring after dawn and before dusk. When temperature increased and wind speed decreased, the morning activity peak occurred earlier, while the evening activity peak was delayed. Hence, under stressing climatic conditions, female mouflon decreased their diurnal activity while increasing their nocturnal activity. However, this nocturnal increase did not prevent the activity rate over 24 h to decrease during hot nonwindy days compared with cool windy days. Although the occurrence of wind mitigated the negative influence of heat on the diurnal activity, wind had no effect at the daily scale. These findings emphasize the importance of working at different temporal scales when assessing the activity patterns of free-ranging vertebrates.

Assessment of Systolic and Diastolic Function in Asymptomatic Subjects Using Ambulatory Monitoring With Acoustic Cardiography

Adequately recording diastolic heart sounds and systolic time intervals over longer periods is difficult. Thus, information on the circadian variation of these parameters in an ambulatory population is lacking. Moreover, age-related changes in the prevalence of diastolic heart sounds and measurements of systolic time intervals in an asymptomatic population have not been studied in continuous recordings. Diastolic heart sounds and systolic time intervals will have age and circadian variations that reflect known changes in cardiac function due to aging and circadian rhythms. We studied 128 asymptomatic subjects wearing an ambulatory monitor with acoustic cardiography. The recording spanned a mean duration of 14 hours, including sleep. Data were analyzed for the presence of third (S3) and fourth (S4) heart sounds and for systolic time intervals. In these asymptomatic subjects, S3 was significantly more prevalent in those age <40 years than in those age >40 years, and significantly more pronounced during sleep in the younger group. Also, S4 was significantly more prevalent in those age >40 years and significantly more pronounced during sleep in those age >40 years. In contrast, time intervals reflecting systolic function showed less circadian variation and less worsening with age. The nocturnal increase of S4 in the elderly reflects diastolic impairment-likely a result of changes in diastolic filling patterns with increasing age. An S3 after the age of 40 is a relatively uncommon finding and therefore should be a specific sign of cardiac disease. Continuous monitoring of diastolic heart sounds and systolic time intervals is possible using acoustic cardiography.

Drought-stress-induced up-regulation of CAM in seedlings of a tropical cactus, Opuntia elatior, operating predominantly in the C3 mode.

Immediately after unfolding, cotyledons of the tropical platyopuntoid cactus, Opuntia elatior Mill., exhibited a C3-type diel CO2 exchange pattern characterized by net CO2 uptake in the light. Significant nocturnal increases in titratable acidity typical of crassulacean acid metabolism (CAM) were not detected at this early developmental stage. As cotyledons matured and the first cladode (flattened stem) developed, features of CAM were observed and the magnitude of CAM increased. Nonetheless, in well-watered seedlings up to 10 cm tall, C3 photosynthetic CO2 fixation in the light remained the major pathway of carbon fixation. Reduced soil water availability led to an up-regulation of net dark CO2 fixation and greater nocturnal increases in tissue acidity, consistent with facultative CAM. These observations demonstrate that C3 photosynthesis, drought-stress-related facultative CAM, and developmentally controlled constitutive CAM can all contribute to the early growth of O. elatior. The strong C3 component and facultative CAM features expressed in young O. elatior contrast with mature plants in which obligate CAM is the major pathway of carbon acquisition.

In situ separation of root hydraulic redistribution of soil water from liquid and vapor transport

Nocturnal increases in water potential (ψ) and water content (θ) in the upper soil profile are often attributed to root water efflux, a process termed hydraulic redistribution (HR). However, unsaturated liquid or vapor flux of water between soil layers independent of roots also contributes to the daily recovery in θ (Δθ), confounding efforts to determine the actual magnitude of HR. We estimated liquid (J(l)) and vapor (J(v)) soil water fluxes and their impacts on quantifying HR in a seasonally dry ponderosa pine (Pinus ponderosa) forest by applying existing datasets of ψ, θ and temperature (T) to soil water transport equations. As soil drying progressed, unsaturated hydraulic conductivity declined rapidly such that J (l) was irrelevant (<2E-05 mm h(-1) at 0-60 cm depths) to total water flux by early August. Vapor flux was estimated to be the highest in upper soil (0-15 cm), driven by large T fluctuations, and confounded the role of HR, if any, in nocturnal θ dynamics. Within the 15-35 cm layer, J(v) contributed up to 40% of hourly increases in nocturnal soil moisture. While both HR and net soil water flux between adjacent layers contribute to θ in the 15-65 cm soil layer, HR was the dominant process and accounted for at least 80% of the daily recovery in θ. The absolute magnitude of HR is not easily quantified, yet total diurnal fluctuations in upper soil water content can be quantified and modeled, and remain highly applicable for establishing the magnitude and temporal dynamics of total ecosystem water flux.

Global daily dynamics of the pineal transcriptome

Transcriptome profiling of the pineal gland has revealed night/day differences in the expression of a major fraction of the genes active in this tissue, with two-thirds of these being nocturnal increases. A set of over 600 transcripts exhibittwo-fold to >100-fold daily differences in abundance. These changes appear to be primarily attributable to adrenergic-cyclic-AMP-dependent mechanisms, which are controlled via a neural pathway that includes the suprachiasmatic nucleus, the master circadian oscillator. In addition to melatonin synthesis, night/day differences in gene expression impact genes associated with several specialized functions, including the immune/inflammation response, photo-transduction, and thyroid hormone/retinoic acid biology. The following nonspecialized cellular features are also affected: adhesion, cell cycle/cell death, cytoskeleton, DNA modification, endothelium, growth, RNA modification, small molecule biology, transcription factors, vesicle biology, signaling involving Ca(2+), cyclic nucleotides, phospholipids, mitogen-activated protein kinases, the Wnt signaling pathway, and protein phosphorylation.

Sodium oxybate increases prolactin secretion in narcolepsy patients and healthy controls

Hypocretin deficiency causes narcolepsy and may affect neuroendocrine systems, including TSH, ACTH and LH secretion. Symptoms can be treated effectively with sodium oxybate (SXB) in many patients. This study was performed to compare prolactin (PRL) secretion in patients and matched controls and establish the effect of SXB administration on PRL and sleep in both the groups. Open label intervention. Blood was sampled before and after 5 days of SXB treatment. The study was performed at the Leiden University Medical Centre, Leiden, The Netherlands. Subjects were admitted to the clinical research centre on both occasions. Eight male hypocretin-deficient narcolepsy with cataplexy patients and eight controls matched for sex, age, body mass index, waist-to-hip ratio and fat percentage were enrolled. SXB two times 3 g per night for five consecutive nights. Patients and controls underwent 24 h blood sampling at 10 min intervals for measurement of PRL concentrations. The PRL concentration time series was analysed with a new deconvolution programme, approximate entropy (ApEn) and Cosinor analysis. Sleep was polygraphically recorded. Basal and pulsatile PRL secretion, as well as pulse regularity and frequency, ApEn and diurnal parameters were similar in patients and controls. SXB treatment caused similar nocturnal increase in PRL secretion, advance of the acrophase and decrease in ApEn in patients and controls. Slow wave sleep was increased to a similar extent in patients and controls. This detailed study did not demonstrate altered PRL secretion in hypocretin-deficient narcolepsy patients during the basal state or during SXB administration. Therefore, hypocretin signalling is unlikely to be a regulator of the lactotrophic system.

Vertical profiles of aerosol black carbon in the atmospheric boundary layer over a tropical coastal station: Perturbations during an annular solar eclipse

Altitude profiles of aerosol black carbon (BC) in the atmospheric boundary layer (ABL) over a tropical coastal station, Trivandrum have been examined on two days using an aethalometer attached to a tethered balloon. One of these days (15th January, 2010) coincided with a (annular) solar eclipse, the longest of this century at this location, commenced at 11:05 local time and ended by 15:05, lasting for 7min and 15s (from 13:10:42), with its maximum contact occurring at ~13:14 IST with ~92% annularity, thereby providing an opportunity to understand the eclipse induced perturbations. Concurrent measurements of the ABL parameters such as air temperature, relative humidity and pressure were also made on these days to describe the response of the ABL to the eclipse. BC profiles, in general, depicted similar features up to an altitude of ~200m on the eclipse day and control day, above which it differed conspicuously with profiles on eclipse day showing increasingly lower concentration as we moved to higher altitudes. Examination of the meteorological profiles showed that the altitude of maximum convection rapidly fell down during the eclipse period compared to that on control day indicating a rather shallow convection on eclipse day. Comparison of diurnal variations of BC at the surface level showed that the rate of decrease in BC during daytime on the eclipse day was smaller than that on the control day due to the reduced convection, shallow ABL and consequent reduction in the ventilation coefficient. Moreover the time of the nocturnal increase has advanced by ~1:30h on the eclipse day, occurred at around 19:30 IST in contrast to all the other days of January 2010, where this increase usually occur well after 20:30 IST, with a mean value of 21:00 IST. This is attributed to the weak sea-breeze penetration during the eclipse day, which led to an early onset of the land breeze.

Distinct gene expression profiles characterize cellular responses to palmitate and oleate

Obese individuals are both insulin resistant and have high levels of circulating free fatty acids (FFAs). In cell culture, saturated but not unsaturated fatty acids induce endoplasmic reticulum (ER) stress. We hypothesized that chronic exposure to low dose fatty acids would significantly attenuate the acute stress response to a saturated fatty acid challenge and that unsaturated fatty acids (oleate) would be more protective than saturated fatty acids (palmitate). The ER stress response to palmitate was reduced after low dose fatty acid exposure in human hepatoma cells. Palmitate and oleate gave distinctive transcript responses, both acutely and after chronic low dose exposure. Differentially regulated pathways included lipid, cholesterol, fatty acid, and triglyceride metabolism, and IkappaB kinase and nuclear factor kappaB kinase inflammatory cascades. Oleate reduced palmitate-induced changes significantly more than low dose palmitate and completely blocked palmitate-induced phosphoinositide 3 kinase inhibitor (PIK3IP1) as well as induction of GADD45A and B. These changes are predicted to alter the PI3 kinase pathway and the pro-apoptotic p38 MAPK pathway. We recapitulated the oleate response by small interfering RNA-mediated block of PIK3IP1 stimulation with palmitate and significantly protected cells from palmitate-mediated ER stress. We show that transcriptional responses to oleate and palmitate are distinct, broad, and often discordant. We identified several potential candidates that may direct the transcriptional networks and demonstrate that PIK3IP1 partially accounts for the protective effects of oleate.

Jerte Valley Cherry-Enriched Diets Improve Nocturnal Rest and Increase 6-Sulfatoxymelatonin and Total Antioxidant Capacity in the Urine of Middle-Aged and Elderly Humans

Tryptophan, serotonin, and melatonin, present in Jerte Valley cherries, participate in sleep regulation and exhibit antioxidant properties. The effect of the intake of seven different Jerte Valley cherry cultivars on the sleep-wake cycle, 6-sulfatoxymelatonin levels, and urinary total antioxidant capacity in middle-aged and elderly participants was evaluated. Volunteers were subjected to actigraphic monitoring to record and display the temporal patterns of their nocturnal activity and rest. 6-sulfatoxymelatonin and total antioxidant capacity were quantified by enzyme-linked immunosorbent assay and colorimetric assay kits, respectively. The intake of each of the cherry cultivars produced beneficial effects on actual sleep time, total nocturnal activity, assumed sleep, and immobility. Also, there were significant increases in 6-sulfatoxymelatonin levels and total antioxidant capacity in urine after the intake of each cultivar. These findings suggested that the intake of Jerte Valley cherries exerted positive effect on sleep and may be seen as a potential nutraceutical tool to counteract oxidation.

TARGET ORGAN DAMAGE AND CIRCADIAN VARIABILITY OF BLOOD PRESSURE: PP.35.447

Ambulatory blood pressure (ABPM) correlates with target organ damage (TOD) better than clinical BP measurements. The objective of this study is to evaluate the correlation between ambulatory BP and TOD. 405 patients with essential hypertension submitted to our Hypertension Unit (53.8% women), 55.5 years old, were included. Patients underwent glomerular filtration rate (GFR) calculated by MDRD, urinary albumin excretion rate (UAER) and microalbuminuria (MAL), an echocardiographic study (to evaluate left ventricular mass (LVM) and ventricular function) and 24h-ABPM (monitor SpaceLabs 90207). We analyze the relationship between ABPM (mean, circadian BP variation and nocturnal BP) and the TOD (cardiac and renal).248 patients (61.23%) have left ventricular hypertrophy (LVH), and it is more frequent in women, diabetic patients and those with previous pharmacologic treatment (p < 0.05). Nocturnal BP increase associated with LVM increase (p < 0.0001) and showed a negative correlation between diminished nocturnal BP decline and LVM increase (p < 0.0001). DM was associated with lower GFR (67.1 ± 2.6 ml/min/1,73m2 vs 82.9 ± 1.6 ml/min/1,73m2; p < 0.0001) and greater UAER (45.1 ± 2.8 mg/24 h vs 26.8 ± 0.96 mg/24 h; p < 0.0001). The non-dipper circadian variation was more frequent in patients with TOD (35.2% in LVM vs 22.3% in non-LVM; p < 0.0001, 42.3% in patients with GFR<60 ml/min vs 26% with GFR>60 ml/min; p < 0.0001) and 40,5% in patients with MAL vs 24.2% without MAL; p < 0.0001. Nocturnal systolic BP associated with lower GFR (r = -0.18; p = 0.0044) and greater UAER (r = 0.27; p = 0.0002), and also the nocturnal diastolic BP (GFR: r = -0.13; p = 0.04; EUA: r = 0.21; p = 0.0056). We saw a positive correlation between diminished nocturnal BP decline and lower GFR (r = 0.35; p < 0.0001) and a negative correlation with the increase of UAER (r = -0.49; p < 0.0001). The multivariate analysis showed relationship between age of the patients (p = 0.0055), gender (p < 0.0001), nocturnal BP decline (p < 0.0009) and the LVMI (p < 0.0001), with GFR. TOD were associated with nocturnal BP increase and with a diminished nocturnal BP decline. These results show the importance of ABPM in the diagnostic, evaluation and stratification cardiovascular risk in hypertensive patients.

Seasonal and diel changes in fish activity and potential cascading effects in subtropical shallow lakes with different water transparency

Fish play a key role in the functioning of shallow lakes. Simultaneously, fish are affected by physical in-lake factors, such as temperature and water transparency, with potential changes in their cascading effects on other communities. Here, we analysed the fish community structure and fish activity in four subtropical shallow lakes, varying in trophic state and water transparency, to assess changes promoted by temperature (i.e. summer and winter) and the light regime (i.e. day and night). We used a passive method (gillnets) during the day- and at night-time to detect changes in fish activity, but also sampled the littoral zone (during night) by point sample electrofishing to obtain a better description of the fish assemblage and habitat use. We observed different fish assemblages in the two seasons in all lakes. We captured more fish species and also obtained higher numbers (CPUE with nets) in summer. Contrary to our expectations, the visually oriented Characiformes were the most captured fish regardless of water transparency, at both day-time and night-time. We also found higher fish CPUE at night-time in all lakes. However, the differences between night and day decreased with decreasing transparency, being lower in the least clear lake, Lake Cisne. The nocturnal increase in fish CPUE (including visually oriented species) suggests that darkness serves as a good refuge for fish in shallow subtropical lakes, even at the likely cost of a lower feeding efficiency during the night. The importance of darkness seems to decrease with decreasing water transparency. We also argue that cascading effects of changes in the activity of piscivorous fish (seasonal changes in piscivores CPUE), when omni-planktivorous fish are indeed affected, may eventually reach the zooplankton, but may not be strong enough to reach the phytoplankton, regardless of water transparency.

Exposure to continuous darkness leads to atypical symptoms of seasonal affective disorder in rats

Prolonged duration of nocturnal melatonin increase has been implicated in the pathogenesis of the seasonal affective disorder (SAD) winter depression. This study was designed to investigate behavioral and physiological consequences of constant dark exposure in male rats for its potential application to human affective disorders. Materials and methods: A total of 12 male Wistar-Albino rats (230-290 g) were assigned to control (LD 12:12 h; n = 6) and constant darkness (DD, 10 days; n = 6) groups. Experimental protocol included comparison of behavioral (FST, open field test, and sucrose preference) and physiological (body weight, food intake, and blood glucose level) parameters. Results: While food intake, weight gain, sucrose preference, and locomotor activity were significantly higher in the DD group, blood glucose level was lower in the same group. Depression-like behavioral despair was prominent in the DD group. As compared to control rats, total duration (s) of immobility was longer and swimming and climbing behaviors were shorter in the DD group. Conclusion: Although continuous darkness exposure for 10 days in male rats seems to mimic atypical symptoms of SAD in terms of depression, weight gain, and the increased sucrose preference, such an extrapolation from behavioral changes in nocturnal animals to human circadian disorders needs further verification.

Vasotocin actions on electric behavior: interspecific, seasonal, and social context-dependent differences

Social behavior diversity is correlated with distinctively distributed patterns of a conserved brain network, which depend on the action of neuroendocrine messengers that integrate extrinsic and intrinsic cues. Arginine vasotocin (AVT) is a key integrator underlying differences in behavior across vertebrate taxa. Weakly electric fish use their electric organ discharges (EODs) as social behavioral displays. We examined the effect of AVT on EOD rate in two species of Gymnotiformes with different social strategies: Gymnotus omarorum, territorial and highly aggressive, and Brachyhypopomus gauderio, gregarious and aggressive only between breeding males. AVT induced a long-lasting and progressive increase of EOD rate in isolated B. gauderio, partially blocked by the V1a AVT receptor antagonist (Manning compound, MC), and had no effects in G. omarorum. AVT also induced a long-lasting increase in the firing rate (prevented by MC) of the isolated medullary pacemaker nucleus (PN) of B. gauderio when tested in an in vitro preparation, indicating that the PN is the direct effector of AVT actions. AVT is involved in the seasonal, social context-dependent nocturnal increase of EOD rate that has been recently described in B. gauderio to play a role in mate selection. AVT produced the additional nocturnal increase of EOD rate in non-breeding males, whereas MC blocked it in breeding males. Also, AVT induced a larger EOD rate increase in reproductive dyads than in agonistic encounters. We demonstrated interspecific, seasonal, and context-dependent actions of AVT on the PN that contribute to the understanding of the mechanisms the brain uses to shape sociality.

Season-Related Differences in the Biosynthetic Activity of the Neonatal Chicken Pineal Gland

Influence of the season of hatch on the functional characteristics of the pineal gland was examined in neonatal Hi-Line male chickens. The pineal glands from 2-day-old birds hatched in and winter, and kept from the day of hatch in artificial lighting conditions (12L:12D), were isolated under dim red light in the middle of the day or night. The pineal glands were analyzed to characterize their melatonin biosynthetic activity: (1) expression of the Arylalkylamine- N-acetyltransferase and Hydroxyindole-O-methyltransferase genes, encoding the final two enzymes of the melatonin biosynthesis pathway; (2) the activity of AA-NAT and HIOMT; and (3) the content of the main substrates of this pathway, tryptophan (TRY) and serotonin (5-HT). Daily changes in pineal AA-NAT activity were observed in chickens hatched in both seasons, with a more pronounced nocturnal increase in summer. In contrast, the level of Aa-nat gene expression, although exhibited the same nocturnal/diurnal pattern in both seasons, was much lower in the summer. The activity of HIOMT was season- and daytime-independent. In winter chickens the pineal content of 5-HT was low and stable, while in summer birds it was correlated with levels of AA-NAT activity and Aa-nat gene expression. TRY content was very high and exhibited neither daily nor seasonal changes. The pineal gland of newly hatched chickens kept in controlled 12L:12D conditions exhibits daily variations in melatonin biosynthetic activity influenced by the season. This suggests a maternal effect on the perinatal/postnatal development of the circadian clock residing in the chicken pineal gland.

Modulation of Aanat gene transcription in the rat pineal gland

The main function of the rat pineal gland is to transform the circadian rhythm generated in the suprachiasmatic nucleus into a rhythmic signal of circulating melatonin characterized by a large nocturnal increase that closely reflects the duration of night period. This is achieved through the tight coupling between environmental lighting and the expression of arylalkylamine-N-acetyltransferase, the rhythm-controlling enzyme in melatonin synthesis. The initiation of Aanat transcription at night is controlled largely by the norepinephrine-stimulated phosphorylation of cAMP response element-binding protein by protein kinase A. However, to accurately reflect the duration of darkness, additional signaling mechanisms also participate to fine-tune the temporal profile of adrenergic-induced Aanat transcription. Here, we reviewed some of these signaling mechanisms, with emphasis on the more recent findings. These signaling mechanisms can be divided into two groups: those involving modification of constitutively expressed proteins and those requiring synthesis of new proteins. This review highlights the pineal gland as an excellent model system for studying neurotransmitter-regulated rhythmic gene expression.

Effect of the cholinesterase inhibitor donepezil on cardiac remodeling and autonomic balance in rats with heart failure

In an earlier study we demonstrated the beneficial effect of direct vagal electrical stimulation on cardiac remodeling and survival. In the study reported here, we attempted to reproduce the effect of vagal enhancement through the administration of an acetylcholinesterase inhibitor, donepezil. A rat model of heart failure following extensive healed myocardial infarction was used. Compared to their nontreated counterparts, rats given donepezil (5 mg/kg/day) in their drinking water had a smaller biventricular weight (3.40 +/- 0.13 vs. 3.02 +/- 0.21 g/kg body weight, P < 0.05), and maximal rate of rise (3256 +/- 955 vs. 3822 +/- 389 mmHg/s, P < 0.05) and the end-diastolic value (30.1 +/- 5.6 vs. 23.2 +/- 5.7 mmHg, P < 0.05) of left ventricular pressure were improved. Neurohumoral factors were suppressed in donepezil-treated rats (norepinephrine 1885 +/- 1423 vs. 316 +/- 248 pg/ml, P < 0.01; brain natriuretic peptide 457 +/- 68 vs. 362 +/- 80 ng/ml, P < 0.05), and the high-frequency component of heart rate variability showed a nocturnal increase. These findings indicated that donepezil reproduced the anti-remodeling effect of electrical vagal stimulation. Further studies are warranted to evaluate the clinical usefulness of donepezil in heart failure.