Showing papers in "Biological Rhythm Research in 2006"
TL;DR: In this paper, the authors found a highly significant positive correlation between the average grading of the final exam and the morningness score, suggesting that pupils with morning preferences performed better in school achievement.
Abstract: Pupils shift their time of day preferences from morningness to eveningness during the age of puberty. Therefore, early school start times may have a negative influence on school functioning, adolescent health and on grade point average. Here, we show that morningness – eveningness influences school performance as measured by the final school leaving/university entrance certificate. One hundred and thirty-two university students aged between 20 and 22 years participated in our study. We found a highly significant positive correlation between the average grading of the final exam and the morningness score, suggesting that pupils with morning preferences performed better in school achievement. Evening types seem at a serious disadvantage because the final exams are used for university entrance decisions.
125 citations
TL;DR: In this article, the authors identify possible circadian rhythms in phonological and visuospatial storage components of working memory using a constant routine protocol and cross-correlation analysis showed a 1-h phase delay of the phonological response.
Abstract: Working memory is a basic cognitive process that temporarily maintains the information necessary for the performance of many complex tasks such as reading comprehension, learning and reasoning. Working memory includes two storage components: phonological and visuospatial, and a central executive control. The objective of this study was to identify possible circadian rhythms in phonological and visuospatial storage components of working memory using a constant routine protocol. Participants were eight female undergraduate students, aged 17.5±0.93, range = 16 – 19 years old. They were recorded in the laboratory in a constant routine protocol during 30 h. Rectal temperature was recorded every minute; subjective sleepiness and tiredness, as well as phonological and visuospatial working memory tasks, were assessed each hour. There were circadian variations in correct responses in phonological and visuospatial working memory tasks. Cross-correlation analysis showed a 1-h phase delay of the phonological...
48 citations
TL;DR: The sandhopper Talitrus saltator (Montagu) has been investigated in a population from a relatively exposed beach in northeast Tunisia and was found to exhibit a nocturnal circadian rhythm of locomotor activity, with no evidence of a circatidal component.
Abstract: The endogenous activity of the sandhopper Talitrus saltator (Montagu) has been investigated in a population from a relatively exposed beach in northeast Tunisia. The animals were found to exhibit a nocturnal circadian rhythm of locomotor activity, with no evidence of a circatidal component. The rhythm was monitored in individual animals over the four seasons, under constant laboratory conditions and seasonal variation in free-running period; the signal-to-noise ratio and waveform of the rhythm have been investigated, as well as the incidence of rhythmic animals in the population. The variation in these rhythm parameters is considered in relation to changes in environmental conditions prevailing at the site of collection.
41 citations
TL;DR: It is suggested that the use of the thermistor with memory in the wrist can be adopted as alternative methodology to studies of human body temperature rhythmicity, especially recommended for long temporal series.
Abstract: In this paper we compare rhythmic parameters of human body temperature simultaneously measured with digital thermometers and thermistors with memory (Thermochron iButtons®). Thirteen healthy male and female volunteers (mean age of 25) measured oral and axillary temperatures with digital thermometers every hour during wakefulness for two days and every three hours for three days, totalling five consecutive days. Concomitantly, they wore badges with thermistors in the thorax and the wrist. Temporal series circadian rhythmicity was evaluated with the Cosinor technique. Acrophases average were 17:32 h±2:02 h for axillary temperature, 10:12 h±7:26 h for thoracic temperature, 17:18 h±00:50 h for oral temperature and 4:15 h±1:55 h for wrist temperature. The rhythmic parameters of the wrist are more robust than those of the thorax. The collection of data in humans, generally performed with digital thermometers, is restricted to the waking phase and depends on the discipline of the volunteers. We suggest ...
28 citations
TL;DR: It appears logical to surmise that photo-thermal conditions may act as proximate and rainfall may play a role of ultimate environmental factor in the regulation of annual testicular events in Indian major carp Catla catla.
Abstract: Current communication describes annual testicular events in free-living Indian major carp Catla catla and their probable environmental synchronizer(s). The study was initiated with month-wise evaluation of gametogenic and steroidogenic status of the testis, and thus dividing the annual testicular cycle into the preparatory spawning (November to March), the pre-spawning (April to June), the spawning (July to August) and the post-spawning (September to October) phases. An exhaustive statistical analysis of the data on the studied variables of testicular functions and various components of the environment indicated seasonal fluctuations of photoperiod as the major environmental factor associated with the seasonal reproductive activity of this carp. Ambient temperature appeared as a dependent variable of photoperiod, and thereby, may have substantial influences on the development of testis in Catla catla. Rainfall, on the other hand, showed significant correlation only with the peak reproductive acti...
23 citations
TL;DR: Extension of subcellular and cellular functions to the tissues of plants provides a timeframe within which, shoot and leaf movements, developmental changes and photoperiodic responses are correlated and coordinated.
Abstract: Studies of ultradian rhythms (<1 day) in plants and in yeasts provide insights into the temporal hierarchy of living organisms. Primarily a reflection of intracellular control circuits, special rhythms are temperature-compensated that have evolved as timekeepers. The best understood ultradian clock is that in yeast; it provides a timeframe for the coherent behaviour of biochemical activities from metabolic and membrane-associated functions to the transcription, translation, assembly of organelles, as well as the replication and partitioning of the genome and all cellular constituents before cell division. Furthermore, the ultradian clock is intimately involved in cell – cell signalling and in the concerted behaviour of the population in a yeast culture or biofilm. Extension of these subcellular and cellular functions to the tissues of plants provides a timeframe within which, shoot and leaf movements, developmental changes and photoperiodic responses (including flowering) are correlated and coordinated. The system can be modelled as a multi-oscillator; one possibility is that a controlled chaotic attractor provides a tuneable output with a wide range of periods. Ultradian rhythms provide the ancestral and mechanistic basis for longer-period biological clocks. An understanding of the integrated physiology of the whole organism is required to fully comprehend circadian rhythmicity.
22 citations
TL;DR: It is demonstrated for the first time that chick melanocytes express melanopsin, and the presence of the protein is confirmed by immunocytochemistry in the chicken retina, where the highest density of immunopositive cells was found in the inner nuclear layer.
Abstract: The vertebrate pigment cell, with the exception of mammals and birds, is able to provide the animal with rapid colour changes, which involve dispersion and aggregation of pigment granules in response to hormonal and neuronal agents, and in some cases as a direct response to light. The search for the mechanisms through which Xenopus leavis melanophores respond to light led to the discovery of a new photopigment, melanopsin, with a different spectral sensitivity to that of rhodopsin. This photopigment was also found in mammalian retinal ganglion cells that project to the suprachiasmatic nucleus and other non-visual retinorecipient areas. Herein we demonstrate (by RT-PCR, cloning and sequencing) for the first time that chick melanocytes express melanopsin, and confirmed the presence of the protein by immunocytochemistry. In the chicken retina, we revealed by immunocytochemistry that ganglion cells express melanopsin, but the highest density of immunopositive cells was found in the inner nuclear laye...
19 citations
TL;DR: A significant correlation between MEQ scores and acrophases of PA support the idea that the PA variation occurs in a continuum between the two extreme chronotypes and the results show that the PANAS and the VAS are in agreement and are equally sensitive in detecting a circadian pattern in the positive affects.
Abstract: For the investigation of a circadian pattern in the positive (PA) and negative affect (NA) and a comparison between the chronotypes, 28 medical students (22 ± 2.5 years) answered initially the Morningness – Eveningness Questionnaire (MEQ) and then the PANAS (Positive and Negative Affect Schedule) and two visual analogue scales (VAS) every three hours during wakefulness for two weeks. The words we chose to represent the PA and NA in the VAS were “attentive” and “upset”. Considering the Cosinor method analyses for the PANAS and the VAS results, 85.71% of subjects displayed significant circadian variation of PA (for p < 0.05). For NA, 25% in the PANAS results and only 14.28% in the VAS displayed a circadian pattern. There was a significant correlation between MEQ scores and acrophases of the PA measured with the PANAS (r = −0.61, p < 0.001) and with the VAS “attentive” (r = −0.69, p < 0.001). This data confirmed literature reports that there is a circadian pattern in the PA rhythm, but for NA the ab...
19 citations
TL;DR: Nocturnal light exposure could profoundly affect NK cell functions perhaps through eye–brain hormonal modulation, and nocturnal increases in serum corticosterone levels were suppressed by light exposure, suggesting that the light exposure-induced decrease inNK cell functions was not due to stress-induced glucocorticoid secretion.
Abstract: To understand light-induced immune modulation in vivo, we evaluated the effect of nocturnal light exposure on splenic natural killer (NK) cell activity in rats. Nocturnal increases in the number and cytotoxic activity of NK cells were significantly suppressed under extended light exposure. Nocturnal increases in serum corticosterone levels were also suppressed by light exposure, suggesting that the light exposure-induced decrease in NK cell functions was not due to stress-induced glucocorticoid secretion in rats. These results suggest that nocturnal light exposure could profoundly affect NK cell functions perhaps through eye–brain hormonal modulation.
18 citations
TL;DR: Results indicate that Kerodon rupestris circadian rhythm is affected by light intensity but it is not yet possible to determine its habit, with higher values in phase transitions.
Abstract: Kerodon rupestris, a Brazilian caviidae rodent, lives in dry stony places. In a first experiment, seven animals were kept in LD (250:0 lux and 400:0 lux) during 40 days in each condition. In the second, four animals were kept in LD (470 lux: red dim light) for 47 days, then in LL (470 lux) for 18 days and in DD (red dim light) for 23 days. Motor activity was continuously recorded by infrared sensors. Animals showed entrained rhythms to the LD cycle being light and dark active, with higher values in phase transitions. When the light intensity was increased, four animals increased and two reduced the activity. In LL, three animals expressed an endogenous tau of 24.4, 26.5 and 24.6 h and one was arrhythmic; in DD, two expressed tau of 23.6 and 23.7 h and one was arrhythmic. Results indicate that Kerodon rupestris circadian rhythm is affected by light intensity but it is not yet possible to determine its habit.
16 citations
TL;DR: The findings suggest that the temporal phase relation of circadian serotonergic and dopaminergic oscillator varies as a function of reproductive status of the bird, and breeding/non-breeding conditions may be induced experimentally by changing the phase relationof these oscillations.
Abstract: Temporal phase relations of circadian hypothalamic neurotransmitters are reported to regulate seasonal reproduction in some avian species. Present experiments were designed to study circadian variation in the hypothalamic concentration of neurotransmitters (serotonin and dopamine) and the plasma thyroxine level in sexually active (long day) and inactive (short day) Japanese Quail. A significant circadian cycle was noted in the hypothalamic content of both serotonin and dopamine, but with different patterns. In breeding Quail, peak activity of serotonin and dopamine was noted at 10.00 A.M. and 10.00 P.M. respectively i.e. at the interval of 12 hours. However, during sexually quiescent condition, peaks of both neurotransmitters occurred at 2.00 P.M. i.e. having a 0-hour temporal relationship. During the breeding phase, the plasma thyroxine level showed a biphasic pattern with two circadian peaks at 10.00 A.M. and 10.00 P.M. whereas in the non-breeding condition a single peak was observed at 10.00 A...
TL;DR: Larvae of the coastal tiger beetle Callytron inspecularis (W. Horn) (Coleoptera: Cicindelidae) plug their burrow opening before submergence at high tide, suggesting that the burrow-plugging rhythm of the Coastal tiger beetle is governed by an endogenous circatidal rhythm.
Abstract: Larvae of the coastal tiger beetle Callytron inspecularis (W. Horn) (Coleoptera: Cicindelidae) plug their burrow opening before submergence at high tide. Field observations showed that burrow plugging was a rhythmic behaviour that coincided with the tidal cycle (ca. 12.4 h). On average, larvae plugged their burrows 41.8 min before the tide covered the habitat. The mean interval between consecutive burrow-plugging events in the field was 12.40 h. In the laboratory, in the absence of tidal inundation, the mean interval between consecutive burrow-plugging events was 12.45 h. This suggests that the burrow-plugging rhythm of the coastal tiger beetle is governed by an endogenous circatidal rhythm.
TL;DR: This work is the first report of the circadian rhythm of saliva ghrelin level in human subjects as a function of time and meal, and it is indicated that Meal plays an important role in lowering saliva gh Relin concentration in humans.
Abstract: Background: We previously reported that ghrelin in saliva, orexigenic hormone that induces NPY release, was produced and released by salivary glands in humans. The purpose of this study was to investigate a possible circadian rhythm in saliva ghrelin concentration in human subjects as a function of time and meal. Saliva samples were collected at three-hour intervals throughout a 24-h period in 12 healthy volunteer males and ten healthy volunteer females who were provided with meals on a fixed schedule, and saliva collections were made within 15 minutes after each meal. Saliva ghrelin levels were measured by using a commercial radioimmunoassay (RIA) kit that uses 125I-labeled bioactive ghrelin as a tracer and a rabbit polyclonal antibody raised against full-length octanoylated human ghrelin. Immunohistochemical analysis of salivary glands was also performed. The results of this investigation indicated the following. (1) The saliva ghrelin level was slightly higher in female subjects in comparison ...
TL;DR: In this article, the authors proposed a three-dimensional model that reduces the subjectively assessed variation of the sleep-wake patterns to three underlying physiological variables (i.e., amplitude of circadian modulation, rate of accumulation of sleep debt and intensity of circadian arousal).
Abstract: Research is directed at understanding the nature of differences between individuals in the adaptive abilities of their sleep–wake cycles. We proposed a three-dimensional model that reduces the subjectively assessed variation of the sleep–wake patterns to three underlying physiological variables. This model explains the results of factor analysis of chronotypological questionnaires and predicts the hierarchical structure of the sleep–wake adaptability with three most general abilities at the top level, six basic abilities at the middle level, and 18 primary (most specific) abilities at the bottom level. Any such subjectively assessed trait of any of these three hierarchical levels might be located in the space of three physiological parameters (namely, these are amplitude of circadian modulation of sleep–wake states, rate of accumulation of sleep debt and intensity of circadian arousal). The present study is aimed at generation and testing a particular prediction of the model. It points to the fea...
TL;DR: Outdoor experiments showed that under natural continuous daylight, both species of Arctic mammals had specific times of activity and rest on a nearly 24-hour scale, and their activity peaks did not come later each day.
Abstract: Activity – rest (circadian) rhythms were studied in two species of Arctic mammals living in Arctic continuous daylight with all human-induced regular environmental cues (zeitgebers) removed. The two Arctic species (porcupine and ground squirrel) lived outdoors in large enclosures while the Arctic summer sun circled overhead for 82 days. Would local animals maintained under natural continuous daylight demonstrate the Aschoff effect described in previously published laboratory experiments using continuous light, in which rats' circadian activity patterns changed systematically to a longer period, expressing a 26-hour day of activity and rest? The outdoor experiments reported here, however, showed that under natural continuous daylight, both species (porcupine and ground squirrel) had specific times of activity and rest on a nearly 24-hour scale, and their activity peaks did not come later each day. The daily rhythms of the two species were recorded using implanted physiological radio capsules, and ...
TL;DR: The notable progress that has been made in identifying the molecular mechanisms that measure daylength and control of flowering time in Arabidopsis, a long day plant, and in rice, a short day plant is described.
Abstract: The rotation of our planet results in regular changes in environmental cues such as daylength and temperature, and organisms have evolved a molecular oscillator that allows them to anticipate these changes and adapt their development accordingly. In many plants, the transition from vegetative to reproductive growth is controlled by photoperiod, which synchronises flowering with favourable seasons of the year. Here, we describe the notable progress that has been made in identifying the molecular mechanisms that measure daylength and control of flowering time in Arabidopsis, a long day (LD) plant, and in rice, a short day (SD) plant. Although the components of the Arabidopsis regulatory network seem to be conserved in other species, the difference in the function of particular genes may contribute to the reverse response to daylength observed between LD and SD plants. We also highlight the recent advances in understanding the regulatory mechanisms that underlie other developmental transitions contr...
TL;DR: periods of all known oscillatory phenomena in this organism correspond to some of the periods for the above seven rhythms, and the following geometric progression holds among the periods: Ti + 1/Ti = 7 and Ti + 2/Ti + 1 = 3.
Abstract: The long-term dynamics of an amoeboid cell shape were studied using Physarum polycephalum plasmodia with various sizes. Cell shape varied oscillatorily in a multiple periodic manner. The organism periodically elongated with period of T 7 = 10 h, branched with T 6 = 4 h, became uneven with T 5 = 30 min and T 4 = 10 min, and blew up with T 3 = 1.5 min. Tiny plasmodia changed shape much faster with T 3 = 1.3 min, T 2 = 24 s and T 1 = 3.3 s simultaneously. The plasmodial cytoskeleton also showed periodic pattern formation with T 6, T 5 and T 3. Periods of all known oscillatory phenomena in this organism correspond to some of the periods for the above seven rhythms, and the following geometric progression holds among the periods: Ti + 1/Ti = 7 and Ti + 2/Ti + 1 = 3, where i = 1, 3, 5. Thus, multiple oscillations in the plasmodium are organized globally.
TL;DR: The results suggest that oral contraceptives do not alter the physiological fluctuation of mood occurring with menses in young healthy women.
Abstract: In this study we have evaluated the cyclical mood change throughout menstrual cycle in oral contraceptive (OC) users and non-users. A total of 62 young women, with a regular menstrual cycle and not clinically depressed, kept, for five weeks, daily records of their visual analogue ratings of mood, irritability, energy and tension (Global Vigor-Affect scale). A Profile of Mood States was performed weekly as a further self-evaluation of mood. Eighteen women were taking oral contraceptives and 44 were non-users. Only the depression-dejection dimension varied significantly during the menstrual cycle (p < 0.05) with an improvement of mood around day 14 and worsening premenstrually. No significant differences were found between the two groups. On the whole the results suggest that oral contraceptives do not alter the physiological fluctuation of mood occurring with menses in young healthy women.
TL;DR: Examples of the significance of aquaporins in processes related to chronobiology are given for root water transport and leaf movement in several plant species.
Abstract: Aquaporins are membrane-intrinsic proteins that facilitate membrane transport of water and small solutes or even gases. Aquaporin genes are found in almost all living organisms. In plants the proteins account for water uptake and transport as well as CO2 availability for photosynthesis. These processes are subjected to diurnal or circadian regimes. Expression and even function of aquaporins also follows day – night rhythms. Significance of aquaporin function in chronobiology has been provided by recent publications, which are summarised here. Examples of the significance of aquaporins in processes related to chronobiology are given for root water transport and leaf movement in several plant species.
TL;DR: Hormonal rhythms may be part of an integrative system to coordinate reproduction and physiological processes successfully with environmental factors in a seasonally breeding tropical rodent.
Abstract: To explain the complex mechanism of environmental influence along with internal hormonal (factors) milieu on daily variations in the circulating levels of melatonin, testosterone, thyroxine and corticosterone were analyzed with the help of inferential statistics (Cosinor rhythmometry) in a seasonally breeding tropical rodent, F. pennanti during the reproductively active (RAP) and inactive phases (RIP). Plasma melatonin, thyroxine and corticosterone levels exhibited a significant circadian oscillation during both the active and inactive phases of the annual reproductive cycle. Melatonin showed higher amplitude during RIP in the circulating plasma. Testosterone presented a peak level during evening hours (16:00 – 18:00 h) during RAP only. The phase of thyroxine was noted ∼09:76 h and ∼10.35 h during active and inactive phases, respectively. Corticosterone showed a peak level at ∼12.00 h during both phases of the reproductive cycle. Further, in this tropical rodent, the minimum difference in photope...
TL;DR: It is concluded that the 24-h average activity and amplitude of rest – activity circadian rhythm declined in head and neck cancer patients and a larger peak spread in the circadian rhythm in rest –activity of cancer patients was discovered.
Abstract: Rhythm alterations consisting of decrease in amplitude, modification in peak time, including the suppression of one or several circadian outputs have been reported in patients suffering from breast, ovarian and colorectal cancer. The aim of the present study was to evaluate the rest – activity circadian rhythm in patients suffering from head and neck cancer. Nine patients were randomly selected from the indoor ward of the Regional Cancer Center, Raipur, India. Rest – activity rhythm and various sleep parameters in these patients were studied non-invasively by using wrist actigraphy. A statistically significant circadian rhythm in rest – activity was validated in all cancer patients. They had lower activity levels (p < 0.05) and amplitudes (p < 0.05) as compared to their respective controls. Further, the fragmentation index was found to be more in male cancer patients as compared with their respective female (p < 0.05) and healthy male (p < 0.05) counterparts. In addition, female cancer patients e...
TL;DR: The dynamics of hoof horn growth turned out to be the highest in the group of young mares, followed by the groupOf stallions and the groupof adult mares and in the winter months the lowest growth increment of the hoof Horn was observed in all the analysed groups.
Abstract: The annual growth rate of the horny wall of the hoof was investigated in 38 horses—31 mares and seven stallions. Experimental subjects were Konik horses kept in a conservative breeding herd. The horses hooves of both limbs: the right fore limb and the right hind limb were measured and next growth rate of the horny wall was analysed at five points of the hoof capsule. On the basis of Principal Component Analysis it was found that the subjects needed to be considered in three groups: three-year old mares, older mares and stallions. Next the growth increments were averaged in each investigated group and compared. The dynamics of hoof horn growth turned out to be the highest in the group of young mares, followed by the group of stallions and the group of adult mares. In the winter months the lowest growth increment of the hoof horn was observed in all the analysed groups. In the period of the elongating solar day, i.e. from May to July, the growth was rapid and reached the highest values. Starting fr...
TL;DR: In this paper, the temporal oscillations of circulatory thiobarbituric acid reactive substances (TBARS), antioxidants such as reduced glutathione (GSH), superoxide dismutase (SOD), and catalase and glucose, cholesterol, total protein and aspartate transaminase (AST) were studied under LD (12:12h) and constant light (LL) (500 lux) conditions after exposing the animal for 21 days.
Abstract: Temporal oscillations of circulatory thiobarbituric acid reactive substances (TBARS), antioxidants such as reduced glutathione (GSH), superoxide dismutase (SOD), and catalase and glucose, cholesterol, total protein and aspartate transaminase (AST) were studied under LD (12:12 h) and constant light (LL) (500 lux) conditions after exposing the animal for 21 days. Advances in the acrophase of GSH, SOD, catalase, glucose, total protein and (AST) rhythms and delays in TBARS and cholesterol were found; amplitude and mesor values of these rhythms were found to be altered during constant light treatment. The above said circadian alterations during LL exposure may be due to (1) formation of photooxidants and stress mediated lipid peroxidation, suppression of melatonin (2) modulation of neuroendocrine and neurotransmitters rhythm (3) suppression of sleep – wake cycle (4) feeding and locomotion rhythm. The exact mechanism still remains to be explored and further research needed.
TL;DR: This is the first study to describe a 12-day (duodecimal) rhythm of salivary estradiol in men, and this finding might be of importance for physiological and pathophysiological research, though the pattern needs to be investigated in larger studies.
Abstract: Background. Circadian and circannual rhythms of sex steroids in men have been well described, but infradian dynamics of estradiol and progesterone in men are unknown. These hormones play a role in the physiology as well as in the pathophysiology of various clinical entities, and their chronobiology might be of importance. Aim. Infradian dynamics of salivary estradiol, testosterone, and progesterone were analysed for the presence of cyclic patterns. Subjects and methods. Five young healthy men collected saliva samples for 30 consecutive days. Salivary estradiol, testosterone, and progesterone were measured using radioimmunoassay. Analysis of Rhythmic Variance (ANORVA) was used and potential period lengths of 3–15 days were evaluated. Results. No infradian rhythms were found in testosterone and progesterone, but a significant (p < 0.03) rhythm at a period length of 12 days was found in salivary estradiol levels. Discussion. We believe that this is the first study to describe a 12-day (duodecimal) r...
TL;DR: The most recent findings on plants rhythms and how they seem to be so tightly connected to calcium-signalling aspects are reviewed and parallels are established between different cell types, such as pollen tubes and fungal hyphae, where the existence of rhythms and oscillations is not obvious.
Abstract: Plants cells, like any other living organism, experience the daily rotation of the Earth. They also depend strikingly on light, as a result of which much of the plant's biochemistry, physiology, and behaviour are temporally organised with respect to the environmental oscillation of day and night. Here we review the most recent findings on plants rhythms and how they seem to be so tightly connected to calcium-signalling aspects. We also try to establish parallels between different cell types, such as pollen tubes and fungal hyphae, where the existence and function of rhythms and oscillations is not obvious. Additionally, we discuss new methodologies and how these are shaping our current working hypothesis to study Ca2+ rhythms in plant cells.
TL;DR: These findings, together with observations from daytime feeding experiments conducted in nocturnal animals, suggest that food intake may serve as a temporal signal for some peripheral organs to oscillate in phase with the SCN.
Abstract: Feeding is organised within the 24-h of the light – dark (LD) cycle. Food is ingested in a circadian manner in nature and in laboratory animals kept under constant conditions. The circadian rhythmicity in food ingestion is driven by a biological clock located in the suprachiasmatic nuclei (SCN) of the hypothalamus. The circadian organisation of food ingestion not only allows animals to live in harmony with their environment but food intake could also act as a zeitgeber for other rhythmic functions. Lesions in the area of the SCN result in the loss of most rhythmic functions as well as to a disrupted circadian rhythmicity of food and water intake. These findings, together with observations from daytime feeding experiments conducted in nocturnal animals, suggest that food intake may serve as a temporal signal for some peripheral organs to oscillate in phase with the SCN. This paper overviews and discusses how food intake interacts with the circadian system.
TL;DR: Considering the evolution of metabolic networks in response to environmental constraints, it is proposed that circadian rhythms in redox state and phosphorylation potential, as an output from the network of energy transduction, should be gating the TTCL for the circadian rhythmic production of proteins needed in the metabolic networks.
Abstract: Evolution from prokaryotic to eukaryotic organisms was paralleled by a corresponding evolution in energy metabolism. From primeval fermentation, energy conservation progressed to anaerobic photosynthesis and then to carbon dioxide fixation with acceptance of electrons by water and the evolution of oxygen. In a progressively oxygenic biosphere, respiration developed with oxygen as a terminal electron acceptor. Evolving life was paralleled by a corresponding evolution of tropospheric O2/CO2 composition and the feedback of oxygen on life processes via reactive oxygen and reactive nitrogen species, which as signalling molecules became crucial for the control of development of pro- and eukaryotic living systems. Adaptation to the seasonal variation in daylength resulted in photoperiodic control of development with a circadian rhythm in energy conservation and transformation to optimise energy harvesting by photosynthesis. Photosynthesis on the other hand acts as a light-dependent metabolic regulator v...
TL;DR: Investigation in two roosts of Rousettus leschenaulti bats found that when entrained by LD 12:12 cycles, the BDR had less negative phase angle difference (Ψ), long duration of activity phase (α) while the BLR had more negative Ψ and short α.
Abstract: Whether the differential exposure to light intensity in roosts affected the entrainment and phase response curves (PRCs) for the circadian flight activity rhythm was investigated in two roosts of Rousettus leschenaulti bats. Bats from the dark roost (BDR) experienced complete darkness while those from the lighted roost (BLR) experienced bright light during the day. When entrained by LD 12:12 cycles, the BDR had less negative phase angle difference (Ψ), long duration of activity phase (α) while the BLR had more negative Ψ and short α. Period of the free-running rhythm in constant darkness was shorter in the BDR than that in the BLR. The PRC for the BDR had a high amplitude, a dead zone of 2 h and the ratio of advance to delay area (A/D) 1.
TL;DR: Functional proteomics of the circadian system has been initiated and has resulted in the identification of novel components of the clock-related system (a protein disulfide isomerase and a tetratricopeptide repeat protein) and a circadian RNA-binding protein.
Abstract: In the unicellular eukaryotic green alga Chlamydomonas reinhardtii, several circadian rhythms have been physiologically well characterised. Recently, the entire nuclear, chloroplast and mitochondrial genomes of this alga have been sequenced, and about 200 000 expressed sequence tags have been created. Therefore, functional proteomics of the circadian system has been initiated and has resulted in the identification of novel components of the circadian system (a protein disulfide isomerase and a tetratricopeptide repeat protein). Furthermore, comparative analysis of the C. reinhardtii genome with known clock-related genes from other model organisms reveals that some photoreceptors and especially clock-related kinases and phosphatases are well conserved in C. reinhardtii. Several circadian expressed genes have been identified in C. reinhardtii, whose temporal expression is controlled at the transcriptional level. Also, a circadian RNA-binding protein (CHLAMY 1) has been characterised. It represents ...
TL;DR: In this article, a periodic perturbation to the y variable was applied to the Rossler system to transform a chaotic behavior into a simple periodic one, varying the period and amplitude of forcing.
Abstract: In this work, the Rossler system is used as a model for chronotherapy. We applied a periodic perturbation to the y variable to take the Rossler system from a chaotic behaviour to a simple periodic one, varying the period and amplitude of forcing. Some periodical windows and period-doubling cascades are observed. The most important of them is the large period-1 area around T 0 = 6.154 (the period corresponding to the dominant frequency in the power spectrum). This is a wide region as is desired in a chronotherapy model, where the therapy is administered, with ample tolerance, to transform a chaotic behaviour into a periodic one.