Free-running circadian rhythms of muscle strength, reaction time, and body temperature in totally blind people

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Forced Desynchronization of Activity Rhythms in a Model of Chronic Jet Lag in Mice

We studied locomotor activity rhythms of C57/Bl6 mice under a chronic jet lag (CJL) protocol (ChrA(6/2)), which consisted of 6-hour phase advances of the light-dark schedule (LD) every 2 days. Through periodogram analysis, we found 2 components of the activity rhythm: a short-period component (21.01 +/- 0.04 h) that was entrained by the LD schedule and a long-period component (24.68 +/- 0.26 h). We developed a mathematical model comprising 2 coupled circadian oscillators that was tested experimentally with different CJL schedules. Our simulations suggested that under CJL, the system behaves as if it were under a zeitgeber with a period determined by (24 -[phase shift size/days between shifts]). Desynchronization within the system arises according to whether this effective zeitgeber is inside or outside the range of entrainment of the oscillators. In this sense, ChrA(6/2) is interpreted as a (24 - 6/2 = 21 h) zeitgeber, and simulations predicted the behavior of mice under other CJL schedules with an effective 21-hour zeitgeber. Animals studied under an asymmetric T = 21 h zeitgeber (carried out by a 3-hour shortening of every dark phase) showed 2 activity components as observed under ChrA(6/2): an entrained short-period (21.01 +/- 0.03 h) and a long-period component (23.93 +/- 0.31 h). Internal desynchronization was lost when mice were subjected to 9-hour advances every 3 days, a possibility also contemplated by the simulations. Simulations also predicted that desynchronization should be less prevalent under delaying than under advancing CJL. Indeed, most mice subjected to 6-hour delay shifts every 2 days (an effective 27-hour zeitgeber) displayed a single entrained activity component (26.92 +/- 0.11 h). Our results demonstrate that the disruption provoked by CJL schedules is not dependent on the phase-shift magnitude or the frequency of the shifts separately but on the combination of both, through its ratio and additionally on their absolute values. In this study, we present a novel model of forced desynchronization in mice under a specific CJL schedule; in addition, our model provides theoretical tools for the evaluation of circadian disruption under CJL conditions that are currently used in circadian research.

External temporal organization in biological rhythms

This paper is intended as a proposition of a new concept in the field of chronobiology, External Temporal Organization, a notion complementary to that of the Internal Temporal Organization. We will try to explain the possibility that a set of external elements, that occur in a particular order, can act together as a single synchronizing element of the circadian system. We will see that this is not a zeitgeber, in the classic sense, but a much more complex factor, consisting of several elements that appear in the real environment at different times ( phases), constituting as a whole a powerful temporal frame, closer to the way the stimuli occur in the natural environment, in which the entrainment does not take place just in a specific time of the day.

Modeling the Emergence of Circadian Rhythms in a Clock Neuron Network

Circadian rhythms in pacemaker cells persist for weeks in constant darkness, while in other types of cells the molecular oscillations that underlie circadian rhythms damp rapidly under the same conditions. Although much progress has been made in understanding the biochemical and cellular basis of circadian rhythms, the mechanisms leading to damped or self-sustained oscillations remain largely unknown. There exist many mathematical models that reproduce the circadian rhythms in the case of a single cell of the Drosophila fly. However, not much is known about the mechanisms leading to coherent circadian oscillation in clock neuron networks. In this work we have implemented a model for a network of interacting clock neurons to describe the emergence (or damping) of circadian rhythms in Drosophila fly, in the absence of zeitgebers. Our model consists of an array of pacemakers that interact through the modulation of some parameters by a network feedback. The individual pacemakers are described by a well-known biochemical model for circadian oscillation, to which we have added degradation of PER protein by light and multiplicative noise. The network feedback is the PER protein level averaged over the whole network. In particular, we have investigated the effect of modulation of the parameters associated with (i) the control of net entrance of PER into the nucleus and (ii) the non-photic degradation of PER. Our results indicate that the modulation of PER entrance into the nucleus allows the synchronization of clock neurons, leading to coherent circadian oscillations under constant dark condition. On the other hand, the modulation of non-photic degradation cannot reset the phases of individual clocks subjected to intrinsic biochemical noise.

Daily rhythms of native Brazilians in summer and winter

Access to electricity, granting relative independence of human activity on the dark phase of the day, has been pointed out as an important cause for the absence of seasonal changes in the daily rhythms of humans living in urban areas. Featuring a population of adult Guarani natives living without access to electricity, the present naturalistic study was designed to explore possible effects of different natural photoperiods and temperature on human circadian rhythms. We compared time series of wrist temperature (WT) and motor activity in winter and summer, respectively, 01 24 individuals aged 18 to 80. Twenty-four-hour rhythms of WT showed lower amplitudes and higher mean levels in summer, with no significant seasonal differences in acrophase. In contrast, rest-activity (RA) rhythms exhibited a significantly later rest on-and offset in summer, but no seasonal changes in duration, amplitude and mean level. We furthermore identified a phase advance of both the WT acrophase and rest onset with increasing age of the individuals. We concluded that in our study the effect of different seasons was reflected in the amplitude and mean level of the WT rhythm, as well the onset of nighttime rest, which was delayed in summer. (C) 2011 Elsevier Inc. All rights reserved.

Disruption of endogenous tidal rhythms of larval release linked to food supply and heat stress in an intertidal barnacle

The timing of larval release may greatly affect the survivorship and distribution of pelagic stages and reveal important aspects of life history tactics in marine invertebrates. Endogenous rhythms of breeding individuals and populations are valuable indicators of selected strategies because they are free of the neutral effect of stochastic environmental variation. The high-shore intertidal barnacle Chthamalus bisinuatus exhibits endogenous tidal and tidal amplitude rhythms in a way that larval release would more likely occur during fortnightly neap periods at high tide. Such timing would minimize larval loss due to stranding and promote larval retention close to shore. This fully explains temporal patterns in populations facing the open sea and inhabiting eutrophic areas. However, rhythmic activity breaks down to an irregular pattern in a population within the São Sebastião Channel subjected to large variation of food supply around a mesotrophic average. Peaks of chl a concentration precede release events by 6 d, suggesting resource limitation for egg production within the channel. Also, extreme daily temperatures imposing mortality risk correlate to release rate just 1 d ahead, suggesting a terminal reproductive strategy. Oceanographic conditions apparently dictate whether barnacles follow a rhythmic trend of larval release supported by endogenous timing or, alternatively, respond to the stochastic variation of key environmental factors, resulting in an erratic temporal pattern.

Melanopsin Retinal Ganglion Cells: relevance to circadian rhythms and sleep in neurodegeneration

In this PhD thesis 3 projects were addressed focusing on the melanopsin retinal ganglion cells (mRGCs) system and its relevance for circadian rhythms and sleep in neurodegeneration. The first project was aimed at completing the characterization of mRGCs system in hereditary optic neuropathies (LHON and DOA). We confirmed that mRGCs are relatively spared also in post-mortem retinal specimens of a DOA case and pupillometric evaluation of LHON patients showed preservation of the pupillary light reflex, with attenuated responses compared to controls. Cell studies failed to indicate a protective role exerted by melanopsin itself. The second project was aimed at characterizing the possible occurrence of optic neuropathy and rest-activity circadian rhythm dysfunction in Alzheimer (AD) and Parkinson disease (PD), as well as, at histological level, the possible involvement of mRGCs in AD. OCT studies demonstrated a subclinical optic neuropathy in both AD and PD patients, with a different pattern involving the superior and nasal quadrants in AD and the temporal quadrant in PD. Actigraphic studies demonstrated a tendency towards an increased intradaily variability (IV) and reduced relative amplitude (RA) of rest-activity circadian rhythm in AD and a significant increased IV a reduced RA in PD. Immunohistochemical analysis of post-mortem retinal specimens and optic nerve cross-sections of neuropathologically confirmed AD cases demonstrated a significant loss of mRGCs and a nearly significant loss of axons in AD compared to controls. The mRGCs were affected in AD independently from age and magnitude of axonal loss. Overall these results suggest a role of the mRGCs system in the pathogenesis of circadian dysfunction in AD. The third project was aimed at evaluating the possible association between a single nucleotide polymorphism of the OPN4 gene and chronotype or SAD, failing to find any significant association with chronotype, but showing a non-significant increment of TT genotype in SAD.

Rhythms of anorexigenic neuropeptides in senegalese sole: Effects of light, feeding regimes and developmental stage.

Increasing knowledge on the endocrine mechanisms that regulate feeding and growth in cultured fish can contribute to make improvement in fish holding conditions and feeding strategies, supporting the development of new techniques that could ameliorate feeding, food conversion efficiency and growth in aquaculture practice. The main objective of this study was to investigate how daily mRNA expression of three specific anorexigenic hormones, i.e. the corticotropin-releasing hormone (CRH) and the paralogues α- and β- proopiomelanocortin (POMC), is modulated by different photoperiods, light spectra and feeding regimes, in both adult and larvae of Solea senegalensis. In addition, as Senegalese sole exhibits a shift from diurnal to nocturnal in locomotor activity and feeding habits during metamorphic process, we tried to elucidate if this shift is accompanied by relevant daily variations in the expression of these anorexigenic hormones before, during and after the completion of metamorphosis. In order to reach this main objective, three main experiments were developed. In a first experiment, adults were reared under LD (12 h light: 12h dark) cycle and fed at mid-light (ML), mid-dark (MD) and at random (RND). In a second experiment, adult specimens were reared in constant darkness (DD) and fed at subjective mid-light (sML) or at RND. Larvae of Senegalese sole were reared under LD cycle with white, blue or red light for 40 days. Our results show an independence of crh mRNA expression from the feeding time and suggest an endogenous control of crh expression in sole. Both pomc paralogues showed significant daily rhythms under LD conditions. The rhythms were maintained or were even more robust under DD conditions for pomc_a, but were completely abolished for pomc_b. Our results indicate an endogenous control of pomc_a expression by the molecular clock in telencephalon and diencephalon, but not in the pituitary gland. Our findings confirm for the first time the significant influence that ambient lighting has on larval growth and development in Senegalese sole, revealing an important effect of light spectra upon functional elements of this species. Our results also emphasize the importance of maintaining cycling light-dark conditions of the adequate wavelengths in aquaculture practices during early development of sole.

Studies of biological rhythms in responses to influenza infection and vaccination

Three studies examined seasonal or circadian variations in selected responses to influenza infection or vaccination. The first, a seroepidemiologic study, evaluated temporal patterns of antibody titers to influenza A/Texas. Human umbilical cord bloods were sampled over a two-year period when the virus was not present in the community. No endogenous seasonal pattern was detected. The second study included three experiments on circadian rhythms in mice. Neither susceptibility nor protection from inactivated or attenuated vaccine varied significantly according to time of administration. A slight effect, however, was suggested with inactivated vaccine. Three human vaccine trials comprised the third study. Outcome variables included rise in antibody titer, final antibody titer, incidence of adverse reactions, and protection from community infection. Patterns in antibody response and protection variables were inconsistent, and generally not clinically significant. Local reactions to inactivated vaccine were more frequent if injections were received in the afternoon as compared to morning. This was true to adults that had been previously vaccinated. ^

Circadian rhythm profiles in porcine ICU subjects

Purpose: To explore the natural trajectory of circadian rhythms of sedation requirement, core body temperature (CBT), pulmonary mechanics (PM), and gas exchange (GE) in mechanically ventilated swine, as these variables affect the duration of mechanical ventilation. ^ Design: A secondary analysis to describe and compare circadian rhythms of study variables in swine mechanically ventilated for ≤ 7 days. ^ Setting: Porcine Intensive Care Unit (ICU).^ Sample: Six male swine. ^ Methods: Sedation requirements were recorded hourly and the CBT, PM and GE variables were sampled every 1 s – 1 min for ≤ 7 days. The data sets for each pig with > 5 days ICU length of stay were divided into one section representing the first 3 days and one section representing subsequent days. The Lomb periodogram was used to estimate the circadian time period for each variable, and cosinor analysis with the estimated time period to obtain amplitude and mesor. Circadian to ultradian bandpower ratio to assess rhythm quality and stability over time and goodness-of-fit index to describe biological significance of a rhythm were used. Together, these two parameters were used to define rhythm robustness over time. The masking effect of sedation as a potential confounder of the circadian rhythms of CBT, PM, and GE was explored, and circadian rhythm profiles of CBT of pigs in the ICU setting were compared with those of the same pigs in the ambulatory setting. ^ Results: All pigs had significant rhythms in CBT, respiratory rate, and peripheral oxygen saturation across ICU data sets. Healthier pigs had more robust rhythms of study variables over time. Sedation did not appear to mask the circadian rhythms of CBT, PM, and GE. The circadian rhythm of CBT was less robust in the ICU setting than in the ambulatory setting. ^ Conclusions: Individual subject observations provided preliminary evidence that robustness of rhythms varies with subject acuity. Comparison of profiles of circadian rhythms among ICU subjects with similar acuity and disease processes is warranted to determine if the profiles in the present study are reproducible. Identification of consistent patterns may provide insight into subject morbidity and timing of such therapeutic interventions as weaning from mechanical ventilation. ^

Biostimulation methods associated with early weaning and reproductive rhythms in primiparous rabbit does

El objetivo general de esta Tesis Doctoral ha sido tratar de mejorar los parámetros reproductivos de las conejas primíparas lactantes, empleando dos métodos de manejo (destete temprano y extensificación del ritmo reproductivo), que están directamente relacionados con su balance energético. Para ello, se diseñaron 2 experimentos en este tipo de hembras. En el primero, se estudió el efecto del destete a 25 días post-parto (dpp) sobre la actividad ovárica y el metabolismo energético de las conejas una semana más tarde (32 dpp). Un total de 34 primíparas lactantes con 8 gazapos fueron distribuidas en tres grupos: 10 conejas se sacrificaron a los 25 dpp (grupo L25), 13 fueron destetadas a los 25 dpp y sacrificadas a los 32 dpp (grupo NL32), y 11 conejas no se destetaron y fueron sacrificadas a los 32 dpp (grupo L32). No se observaron diferencias significativas entre grupos en el peso corporal, el peso del ovario, ni en las concentraciones séricas de ácidos grasos no esterificados y de proteínas totales. A pesar de que el grupo NL32 presentó un bajo consumo de alimento (122 ± 23,5 g / día, p <0,001), su contenido corporal estimado de lípidos (16,9 ± 1,09%, P <0,008), proteínas (19,7 ± 0,07%, P <0,0001), y energía (1147 ± 42,7 MJ / kg, p <0,006) fueron más elevados y las concentraciones séricas de glucosa (158 ± 24,5 mg/dl, p <0,04) más bajas que en los grupos L25 (11,9 ± 1,3%, 18,5 ± 0,08%, 942 ± 51,3 MJ/kg y 212 ± 27,9 mg/dl) y L32 (13,4 ± 1,03%, 18,5 ± 0,1%, 993 ± 40,4 MJ/kg y 259 ± 29,5 mg/dl), respectivamente. En el grupo L25 se observó un menor número medio de folículos ≥ 1 mm en la superficie ovárica en comparación con los grupos NL32 y L32 (12,7 ± 1,5 vs. 18,0 ± 1,45 y 17,6 ± 1,67, p <0,05). La población folicular ovárica en las secciones histológicas y la inmunolocalización de los receptores de prolactina fueron similares en todos los grupos. En el grupo L25, tanto la maduración nuclear de oocitos, medida en términos de tasas alcanzadas de Metafase II (67,0 vs. 79,7 y 78,3%, P <0.05) y la maduración citoplasmática, medida por el porcentaje de gránulos corticales (GC) total o parcialmente migrados en los oocitos, fueron significativamente menores que en los grupos NL32 y L32 (16,0 vs 38,3 y 60,0%, P <0.05). En conclusión, a pesar de que el destete precoz a 25 dpp pareció mejorar las reservas de energía de las conejas primíparas, este hecho no se reflejó claramente a nivel ovárico a los 32 dpp y fue similar independientemente del destete, por lo que éste último podría llevarse a cabo más tarde. En el segundo experimento, se compararon dos ritmos reproductivos. Se utilizaron un total de 48 conejas primíparas lactantes con 8 gazapos que se asignaron al azar en dos grupos experimentales: a) lactantes sacrificadas a comienzos del post-parto (11 dpp) de acuerdo a un ritmo semi-intensivo (n = 24), y b) lactantes sacrificadas al final del período post-parto (25 dpp) de acuerdo con un ritmo más extensivo (n = 24). En ellas, se estudió el peso vivo, la composición corporal estimada, parámetros metabólicos y endocrinos (estradiol y progesterona) y características ováricas como la población folicular y la tasa de atresia, así como la maduración nuclear y citoplásmica de los oocitos. En este estudio, el peso vivo, el contenido de energía corporal, los depósitos grasos y los ácidos grasos no esterificados disminuyeron a lo largo del post-parto con respecto al momento del parto (P <0,05). Las concentraciones séricas de proteínas y glucosa aumentaron en el mismo periodo post-parto (P <0,05). Se observaron similares niveles de estradiol y progesterona en ambos ritmos, así como una población folicular, tasas de maduración nuclear (tasa de oocitos en metafase II) y citoplasmática (porcentaje de oocitos con gránulos corticales migrados), similares en ambos momentos del post-parto. Sin embargo, el número de folículos preovulatorios en la superficie ovárica fue menor (P <0,05) y la tasa de atresia tendió a ser mayor con un porcentaje también menor de folículos sanos (P <0,1) en los ovarios de las hembras sometidas al ritmo extensivo. En conclusión, al final del post-parto (25 días), las conejas primíparas sin destetar muestran un deterioro de sus reservas corporales, de sus parámetros metabólicos séricos y de la calidad de sus oocitos; incluso se ha observado una ligera influencia negativa en el desarrollo de sus folículos ováricos. Por esta razón, se considera que en las conejas primíparas lactantes el manejo reproductivo extensivo (25 dpp) no presenta ninguna ventaja en comparación con el semi-intensivo (11 dpp). A la vista de los resultados de estos dos experimentos, podemos decir que ni el destete temprano, ni la extensificación del ritmo reproductivo han conseguido una mejora en los parámetros reproductivos de una hembra primípara. Por ello, son necesarios más estudios sobre el estado metabólico de la coneja primípara lactante para conseguir métodos o estrategias que lo mejoren y tengan consecuencias directas sobre la actividad reproductiva y sobre su éxito productivo. The general aim of this Thesis was to study two management methods (early weaning and extensive reproductive rhythm) linked to the energy balance of the primiparous rabbit does to improve their reproductive performance. In this sense, 2 experiments were conducted using this kind of females. In the first experiment, the effect of weaning at 25 days post-partum (dpp) on ovarian activity and energetic metabolism one week later (32 dpp) was studied. A total of 34 primiparous lactating rabbit does were used and distributed among three groups: 10 does euthanized at 25 dpp (group L25), 13 does weaned at 25 dpp and euthanized at 32 dpp (group NL32), and 11 non weaned does euthanized at 32 dpp (group L32). No significant differences were observed in live body weight, ovary weight, serum non esterified fatty acids (NEFA) and total protein concentration among groups. Although NL32 does had a low feed intake (122±23.5 g/Day; P < 0.001), their estimated lipids (16.9±1.09%, P < 0.008), protein (19.7±0.07%, P < 0.0001), and energy (1147±42.7 MJ/kg, P < 0.006) body contents were higher and their serum glucose concentrations (158±24.5 mg/dl, P < 0.04) were lower compared to L25 does (11.9±1.3%, 18.5±0.08%, 942±51.3 MJ/kg and 212±27.9 mg/dl) and L32 does (13.4±1.03%, 18.5±0.1%, 993±40.4 MJ/kg and 259±29.5 mg/dl, respectively). A lower number of follicles ≥1mm was observed compared to NL32 and L32 groups (12.7±1.5 vs. 18.0±1.45 and 17.6 ±1.67; P < 0.05) in the ovarian surface of L25 does. Follicular population in the histological ovarian sections and immunolocalization of prolactin receptor were similar in all groups. In group L25, both nuclear maturation of oocytes in terms of Metaphase II rate (67.0 vs. 79.7 and 78.3%; P < 0.05) and cytoplasmic maturation measured by percentage of cortical granules (CG), totally or partially migrated in oocytes were significantly lower than in groups NL32 and L32 (16.0 vs. 38.3 and 60.0%; P < 0.05). Consequently, a higher rate of oocytes with non-migrated CGs was found in group L25 than in groups NL32 and L32 (76.0 vs. 46.8 and 33.3%; P < 0.05). In conclusion, even though early weaning at 25 dpp seemed to improve body energy stored in primiparous does, this fact was not well reflected on the ovarian status at 32 dpp, which was similar regardless of weaning time. In the second experiment, two reproductive rhythms were compared. A total of 48 primiparous Californian x New Zealand White rabbit does suckling 8 kits were randomly allocated in two experimental groups: a) lactating does euthanized at early post-partum period (11 dpp) according to a semi-intensive rhythm (n = 24), and b) lactating does euthanized on later post-partum period (25 dpp) according to a more extensive rhythm (n = 24). Live weight, estimated body composition, serum metabolic and endocrine parameters (oestradiol and progesterone concentrations) and ovarian features like follicle population and atresia rate, and oocyte maturation were studied. Live weight, body energy content, lipid depots and serum non esterified fatty acids (NEFA) concentrations diminished from parturition time to post-partum period (P < 0.05). In addition, serum protein and glucose concentrations increased along postpartum time (P < 0.05). Similar oestradiol and progesterone levels were shown in rhythms as well as similar follicle population and nuclear and cytoplasmic maturation rates measured as metaphase II and cortical granule migration, respectively in both postpartum times. However, number of preovulatory follicles on the ovarian surface was lower (P < 0.05) and atresia rate tended to be higher with also lower percentage of healthy follicles (P < 0.1) in ovaries of females of extensive group. In conclusion, primiparous non-weaned rabbits does at late post-partum time (25 days), Did no show any improvement regarding body reserves, serum metabolic parameters and oocyte quality; even a slight negative influence has been observed in the development of their ovarian follicles. Thus this reproductive management does not present any advantage compared to earlier post-partum (11 days) reproductive rhythm. In summary, according to the obtained results from these two experiments, we can say that the application of early weaning and the extensive rhythms did not achieve an improvement in the reproductive performance of primiparous does. Thus, it is necessary to conduct more studies about the metabolic status of the primiparous lactating doe to achieve strategies in order to improve it and consequently, to improve the reproductive activity and their productive success.