Showing papers in "Chronobiology International in 2001"
TL;DR: The purpose of this study was to describe and compare the circadian rhythm of body temperature and cortisol, as well as self-reported clock times of sleep onset and offset on weekdays and weekends in 19 healthy adult “larks” and “owls” (evening chronotypes), defined by the Horne and Östberg questionnaire.
Abstract: The purpose of this study was to describe and compare the circadian rhythm of body temperature and cortisol, as well as self-reported clock times of sleep onset and offset on weekdays and weekends ...
343 citations
TL;DR: The correlation between monozygotic twins was more than twice the correlation between dizygotic twins, indicating that genetic effects may not operate in an additive manner, and a model that included genetic dominance was explored, suggesting that different genes for morningness-eveningness are expressed in both generations.
Abstract: We studied the influence of genetic factors on individual differences in morningness-eveningness in a sample of Dutch twin families. Data were collected from adolescent twins (mean age 17.8 yr) and their parents (mean age of fathers 48.0 yr and of mothers 46.0 yr) and a sample of older twins (mean age 46.5 yr). Scores on morningness-eveningness were rated on a 5-point scale. Parents were more morning oriented than their children, and women were more morning oriented than men. With a twin-family study, separation of genetic and environmental influences on variation in morningness-eveningness is possible. Including parents and older twins in the study makes it possible to explore generation differences in these effects. The correlation between monozygotic twins was more than twice the correlation between dizygotic twins. This indicates that genetic effects may not operate in an additive manner. Therefore, a model that included genetic dominance was explored. Biometrical model fitting showed no sex differences for the magnitude of genetic and environmental factors. The total heritability--the sum of additive and nonadditive genetic influences--for morningness-eveningness was 44% for the younger generation and 47% for the older generation. However, the genetic correlation between the generations turned out to be lower than 0.5, suggesting that different genes for morningness-eveningness are expressed in both generations.
243 citations
TL;DR: The results were consistent with the involvement of a scotopic mechanism in the regulation of circadian phase and the shorter wavelengths of 470, 497, and 525 nm showed the greatest melatonin suppression.
Abstract: Different wavelengths of light were compared for melatonin suppression and phase shifting of the salivary melatonin rhythm. The wavelengths compared were 660 nm (red), 595 nm (amber), 525 nm (green...
189 citations
TL;DR: The review reveals that the mechanism of photic inhibition of melatonin is fairly well understood, whereas only little is known about the influence of light on other circadian rhythm outputs, such as locomotor activity.
Abstract: Light influences mammalian circadian rhythms in two different ways: (1) It entrains endogenous oscillators (clocks), which regulate physiology and behavior; and (2) it affects directly and often immediately physiology and behavior (these effects are also referred to as masking). Masking effects of light on pineal melatonin, locomotor activity, and the sleep-wake cycle in mammals and man are reviewed. They seem to represent a universal response in this group. The review reveals that the mechanism of photic inhibition of melatonin is fairly well understood, whereas only little is known about the influence of light on other circadian rhythm outputs, such as locomotor activity.
147 citations
TL;DR: In this article, the authors compared the sensitivity of melatonin suppression in response to light in patients with delayed sleep phase syndrome and normal control subjects and found that patients with DSPS experience a chronic mismatch between the usual daily schedule required by the individual'senvironment and their circadian sleep-wake pattern.
Abstract: Patients with delayed sleep phase syndrome (DSPS) experiencea chronic mismatch between the usual daily schedule required by the individual'senvironment and their circadian sleep-wake pattern, resulting in major academic,work, and social problems. Although functional abnormalities of the circadianpacemaker system have been reported in patients with DSPS, the etiology ofDSPS has not been fully elucidated. One hypothesis proposed to explain whypatients with DSPS fail to synchronize their 24h sleep-wake cycle to theirenvironment is that they might have reduced sensitivity to environmental timecues, most notably light-dark cycles. Therefore, we compared the sensitivityof melatonin suppression in response to light in patients with DSPS and normalcontrol subjects. Fifteen patients with DSPS and age- and sex-matched healthycontrols were studied. As the melatonin secretion rhythm in patients withDSPS was expected to be delayed compared to the controls, the time of peakmelatonin secretion was determined in each sub...
121 citations
TL;DR: Hourglass clocks are based on linear or exponential unidirectional processes that trigger events mainly in the course of development and aging, and an important hourglass mechanism within the aging process is the limitation of cell division capacity by the length of telomeres.
Abstract: Living organisms have developed a multitude of timing mechanisms— “biological clocks.” Their mechanisms are based on either oscillations (oscillatory clocks) or unidirectional processes (hourglass clocks). Oscillatory clocks comprise circatidal, circalunidian, circadian, circalunar, and circannual oscillations—which keep time with environmental periodicities—as well as ultradian oscillations, ovarian cycles, and oscillations in development and in the brain, which keep time with biological timescales. These clocks mainly determine time points at specific phases of their oscillations. Hourglass clocks are predominantly found in development and aging and also in the brain. They determine time intervals (duration). More complex timing systems combine oscillatory and hourglass mechanisms, such as the case for cell cycle, sleep initiation, or brain clocks, whereas others combine external and internal periodicities (photoperiodism, seasonal reproduction). A definition of a biological clock may be derived from it...
112 citations
TL;DR: Morningnesseveningness questionnaires were administered to first- and second-degree relatives of a proband identified with delayed sleep phase syndrome, providing some preliminary support to the notion that eveningness, and thus DSPS, may have a genetic component.
Abstract: The prevalence of delayed sleep phase syndrome (DSPS) has been estimated to be quite low. Although no genetic inheritance pattern has been described, it has been reported that close to 50% of DSPS patients have biological relatives with similar symptoms. A pedigree of one extended family with symptoms suggestive of DSPS has been identified. Morningness-eveningness questionnaires were administered to all first- and second-degree relatives of a proband identified with DSPS. A total of 51 (86%) questionnaires were returned, and 6 adult biological relatives of 27 (22%) showed a preference for eveningness, which is much higher than reported in the general population. Both the paternal and maternal branches contained affected individuals, suggesting the possibility of a bilineal mode of inheritance. While the trait did not obey simple Mendelian inheritance, the vertical patterns of transmission were consistent with either an autosomal dominant mode of inheritance with incomplete penetrance or a multifactorial mode of inheritance. These data provide some preliminary support to the notion that eveningness, and thus DSPS, may have a genetic component. The prevalence of symptoms suggestive of DSPS is higher in this family than reported in the general population. Case reports such as this support the utility of larger, more systematic studies. It is unclear whether this degree of familiarity is representative of that in the general population.
87 citations
TL;DR: Identification of a phosphorylation site mutant of hPER2 in a family with an inherited circadian rhythm abnormality strongly suggests that PER2 is aphysiologically relevant substrate of CKI, which may regulate multiple properties of clock proteins, including stability and intracellular localization.
Abstract: Multiple components of the circadian central clock are phosphoproteins,and it has become increasingly clear that posttranslational modification isan important regulator of circadian rhythm in diverse organisms, from dinoflagellatesto humans. Genetic studies in Drosophilahave identified double-time (dbt), a serine/threonine protein kinase that is highlyhomologous to human casein kinase I epsilon (CKIe), as the first kinaselinked to behavioral rhythms. Identification of a missense mutation in CKIeas the tau mutation in the Syrian hamsterplaces CKIe within the core clock machinery in mammals. Most recently,identification of a phosphorylation site mutant of hPER2 in a family withan inherited circadian rhythm abnormality strongly suggests that PER2 is aphysiologically relevant substrate of CKI. Phosphorylation may regulate multipleproperties of clock proteins, including stability and intracellular localization.(Chronobiology International, 18(3), 389–398,2001)
86 citations
TL;DR: The expression of circadian clock genes was investigated in young adult and old laboratory mice and an age-dependent difference was found in the case of mPer2(but not mPer1) mRNA expression, with themaximum at CT7 significantly lower in old mice.
Abstract: The expression of circadian clock genes was investigated inthe suprachiasmatic nuclei (SCN) of young adult and old laboratory mice. Sampleswere taken at two time points, which corresponded to the expected maximum(circadian time 7 [CT7]) or minimum (CT21) of mPermRNA expression. Whereas the young mice had a stable and well-synchronizedcircadian activity/rest cycle, the rhythms of old animals were less stableand were phase advanced. The expression of mPer1mRNA and mPer2 mRNA was rhythmic in bothgroups, with peak values at CT7. The levels of mClockand mCry1 mRNA were not different dependingon the time of day and did not vary with age. In contrast, an age-dependentdifference was found in the case of mPer2(but not mPer1) mRNA expression, with themaximum at CT7 significantly lower in old mice. The decreased expression of mPer2 may be relevant for the observed differencesin the overt activity rhythm of aged mice. (ChronobiologyInternational, 18(3), 559–565, 2001)
80 citations
TL;DR: The circadian pattern of large amplitude in the double product and its gender differences must be taken into account when using this variable to assess cardiac workload, risk of left ventricular hypertrophy, and efficiency of antihypertensive therapy.
Abstract: The double product (DP), systolic blood pressure multiplied by heart rate, is a surrogate measure of myocardial oxygen demand and cardiac workload used increasingly today in medicine. The double pr...
79 citations
TL;DR: It is argued that in addition to the reductionist, molecular approaches currently dominating much of chronobiology, the study of circadian systems as emergent characteristics of whole organisms operating in complex environments merits special attention.
Abstract: Three main concerns underlie this review: 1) The need to draw together the widely dispersed information available on the circadian biology of the rabbit. Although the rabbit is a classic laboratory mammal, this extensive body of information is often overlooked by chronobiologists, and despite several advantages of this species. In terms of its general biology the rabbit is the best studied laboratory mammal in the wild, it demonstrates a wide variety of robust circadian functions, and being a lagomorph, it provides a useful comparison with more commonly studied rodent species. 2) The need to more fully exploit a developmental approach to understanding circadian function, and the particular suitability of the rabbit for this. Female rabbits only visit their altricial young for a few minutes once every 24 h to nurse, and survival of the young depends on the tight circadian-controlled synchronization in behavior and physiology of the two parties. Patterns of circadian rhythmicity in neonatal pups associated with nursing do not form a smooth continuum into weaning and adult life, and may reflect the action of separate mechanisms operating in their own right. 3) Using information from the first two points, to emphasize the diversity and complexity of circadian rhythms underlying behavioral and physiological functions in adult and developing mammals. Information accruing on circadian functions in the rabbit makes it increasingly difficult to account for these in terms of one or two regulatory mechanisms or "oscillators." Thus, it is argued that in addition to the reductionist, molecular approaches currently dominating much of chronobiology, the study of circadian systems as emergent characteristics of whole organisms operating in complex environments merits special attention.
TL;DR: The results suggest bedtime discipline at home during childhood has an effect on adolescent chronotype, modulating the extent of shift to eveningness in Japanese junior high school boys in particular.
Abstract: We examined the effect of home bedtime discipline during childhood on morningness and eveningness (M-E) preference by Japanese junior high school students. M-E was assessed by the M-E Questionnaire (MEQ) of Torsvall and Akerstedt (the higher the score, the greater the preference for morningness), and parental determination of bedtime during childhood was ascertained using an original questionnaire. The average M-E score of adolescents living in urban Kochi City (mean ± SD; 15.10 ± 3.42) was significantly lower (P <. 01) than the score of those in suburban districts (16.14 ± 3.44). Overall, 43.1% of the junior high school students in Kochi City compared to 53.0% of the students living in suburban districts had their bedtime decided during childhood by parents (P <. 01). In Kochi City, the M-E score for boys (14.62 ± 3.51) was lower (P <. 01) than girls (15.53 ± 3.28). During childhood, parents decided the bedtime for 49% of the girls compared to 36.6% of the boys (P <. 01). Boys whose bedtime was not decid...
TL;DR: The purpose of this review is to summarize briefly the possible mechanisms by which the oscillatory cells in the SCN communicate with each other.
Abstract: In mammals, the part of the nervous system responsible for most circadian behavior can be localized to a pair of structures in the hypothalamus known as the suprachiasmatic nucleus (SCN). Importantly, when SCN neurons are removed from the organism and maintained in a brain slice preparation, they continue to generate 24h rhythms in electrical activity, secretion, and gene expression. Previous studies suggest that the basic mechanism responsible for the generation of these rhythms is intrinsic to individual cells in the SCN. If we assume that individual cells in the SCN are competent circadian oscillators, it is obviously important to understand how these cells communicate and remain synchronized with each other. Cell-to-cell communication is clearly necessary for conveying inputs to and outputs from the SCN and may be involved in ensuring the high precision of the observed rhythm. In addition, there is a growing body of evidence that a number of systems-level phenomena could be dependent on the cellular communication between circadian pacemaker neurons. It is not yet known how this cellular synchronization occurs, but it is likely that more than one of the already proposed mechanisms is utilized. The purpose of this review is to summarize briefly the possible mechanisms by which the oscillatory cells in the SCN communicate with each other.
TL;DR: The knowledge about the various circadian oscillations intrinsic to the SCN is reviewed, with particular focus on the intercellular signaling of coupled oscillators.
Abstract: The suprachiasmatic nucleus (SCN) of the hypothalamus is the site of the pacemaker that controls circadian rhythms of a variety of physiological functions. Data strongly indicate the majority of the SCN neurons express self-sustaining oscillations that can be detected as rhythms in the spontaneous firing of individual neurons. The period of single SCN neurons in a dissociated cell culture is dispersed in a wide range (from 20h to 28h in rats), but that of the locomotor rhythm is close to 24h, suggesting individual oscillators are coupled to generate an averaged circadian period in the nucleus. Electrical coupling via gap junctions, glial regulation, calcium spikes, ephaptic interactions. extracellular ion flux, and diffusible substances have been discussed as possible mechanisms that mediate the interneuronal rhythm synchrony. Recently, GABA (gamma-aminobutyric acid), a major neurotransmitter in the SCN, was reported to regulate cellular communication and to synchronize rhythms through GABA(A) receptors. At present, subsequent intracellular processes that are able to reset the genetic loop of oscillations are unknown. There may be diverse mechanisms for integrating the multiple circadian oscillators in the SCN. This article reviews the knowledge about the various circadian oscillations intrinsic to the SCN, with particular focus on the intercellular signaling of coupled oscillators.
TL;DR: This study provided additional evidence that the 24-h profile of BP—as observed under normal circumstances—is the sole result of environmental and behavioral factors such as the occurrence of sleep, and has no endogenous circadian component.
Abstract: The impact of environmental and behavioral factors on the 24-h profile of blood pressure (BP) has been well established. Various attempts have been made to control these exogenous factors, in order to investigate a possible endogenous circadian variation of BP. Recently, we reported the results of the first environmentally and behaviorally controlled laboratory study with 24-h recordings of BP and heart rate (HR) during maintained wakefulness. In this constant-routine study, a pronounced endogenous circadian rhythm of HR was found, but circadian variation of BP was absent. This result suggested that the circadian rhythm of BP observed in earlier controlled studies, with sleep allowed, was evoked by the sleep‐wake cycle as opposed to the endogenous circadian pacemaker. In order to verify our previous finding during maintained wakefulness, we repeated the experiment five times with six normotensive, healthy young subjects. Statistical analyses of the hourly measurements of BP and HR confirmed the replicable presence of an endogenous circadian rhythm
TL;DR: There were 15 healthy female subjects, differing in their position on the “morningness-eveningness” scale, studied for 7 consecutive days, first while living a sedentary lifestyle and sleeping between midnight and 08:00 and then while undergoing a “constant routine.”
Abstract: There were 15 healthy female subjects, differing in their position on the “morningness-eveningness” scale, studied for 7 consecutive days, first while living a sedentary lifestyle and sleeping between midnight and 08:00 and then while undergoing a “constant routine.” Rectal temperature was measured at regular intervals throughout this time, and the results were subjected to cosinor analysis both before and after “purification” for the effects of physical activity. Results showed that there was a phase difference in the circadian rhythm of core temperature that was associated with the morningness score, with calculations that “morning types” would be phased earlier than “evening types” by up to about 3h. This difference in phase (which was also statistically significant when the group was divided by a median split into a “morning group” and an “evening group”) could not be attributed to effects of waking activity and existed in spite of the subjects keeping the same sleep-wake schedule. Moreover, it persis...
TL;DR: It is suggested that the expression of the mt1 melatonin receptor in the coronary arteries is probably not impaired in patients with CHD, and for the first time a 24h variation of aMelatonin receptor subtype in human vessels is demonstrated.
Abstract: Previous studies presented evidence for impaired nocturnal secretion and synthesis of melatonin in patients with coronary heart disease (CHD). This study aimed to investigate whether the melatonin receptor subtype mt1 is differentially expressed in coronary arteries derived from patients with CHD (n = 9) compared to patients with dilative cardiomyopathy (CMP; n = 10) who served as controls. Expression of the mt1 receptor was studied in sections of isolated coronary arteries by a reverse transcriptase–polymerase chain reaction (RT-PCR) and a Western immunoblot technique. In addition, the data from the Western blotting of 15 patients were interpolated against the exact time of aortic clamp to study the 24h expression of the mt1 receptor. The analyses of the results from both methods indicated the presence of the mt1 receptor in all of the individuals. No statistically significant difference was observed in the receptor expression between patients with CHD and those with CMP (in arbitrary units: 3.39 ± 3.08 ...
TL;DR: Winter pattern seasonality was both reliable across measures and significantly more marked among the subgroup of respondents who self-identified winter pattern of mood on the Seasonal Pattern Assessment Questionnaire.
Abstract: A prospective panel study was conducted to measure seasonality of mood in a random community sample in Melbourne, Australia (N = 245). Based on research into the structure of human mood, it was predicted that a lowering of mood in winter relative to summer would be observed in positive affect (PA) and behavioral engagement (BE), but not negative affect (NA). These variables were measured across summer and winter for 3 years. Consistent with the majority of research in the Northern Hemisphere, analyses on the entire sample found evidence of a small prospective season effect on the BE scale (explaining 2.1% of variance in BE scores). Also, as expected, no season effect was seen on the NA scale. In the entire sample, the season effect was not significant for PA, but joint factor analysis of the BE, PA, and NA scales confirmed that the season effect seen in the BE scale was largely due to items that were pure measures of PA. Winter pattern seasonality was both reliable across measures and significantly more marked among the subgroup of respondents who self-identified winter pattern of mood on the Seasonal Pattern Assessment Questionnaire. (Chronobiology International, 18(5), 875–891, 2001)
TL;DR: Circadian periodicity is maintained in hospitalized patients with metastatic breast cancer and the circadian periodicity of tumor growth stimulating or restraining factors raises questions about circadian and/ or ultradian variations in the pathophysiology of breast cancer.
Abstract: Background: Circadian rhythms in plasma concentrations of many hormones and cytokines determine their effects on target cells. Methods: Circadian variations were studied in cortisol, melatonin, cytokines (basic fibroblast growth factor [bFGF], EGF, insulin-like growth factor-1 [IGF-1]), and a cytokine receptor (insulin-like growth factor binding protein-3 [IGFBP-3]) in the plasma of 28 patients with metastatic breast cancer. All patients followed a diurnal activity pattern. Blood was drawn at 3h intervals during waking hours and once during the night, at 03:00. The plasma levels obtained by enzyme-linked immunoassay (ELISA) or radioimmunoassay (RIA) were evaluated by population mean cosinor (using local midnight as the phase reference and by one-way analysis of variance (ANOVA). Results: Cortisol and melatonin showed a high-amplitude circadian rhythm and a superimposed 12h frequency. bFGF showed a circadian rhythm with an acrophase around 13:00 with a peak-to-trough interval (double amplitude) of 18.2% an...
TL;DR: Endogenous control of rhythmic pattern appears to be less intense in women, probably due to the coexistence of circamensual rhythmicity, although environmental or sociocultural influences may play a modulating role.
Abstract: This article evaluates the influence of gender on diurnal and postlunch period variations in subjective activation and mood. This topic is not often addressed in the literature; particularly, little attention has been paid to how biological rhythms might bias research results. We studied 40 university student volunteers (20 men, 20 women) aged 18 to 23 years old (X = 20.23, SD = 1.03); they responded to questions on eight unipolar visual analog scales every hour from 08:00 to 21:00. Gender differences were observed in both diurnal and postlunch variations for scales of positive activation (alertness, vigor); sleepiness, however, was only sensitive to diurnal variation, and weariness was sensitive only to a postlunch effect. Women displayed a morning-type pattern, with their optimal moment (11:00) coming 2h earlier than for men, and their activation ratings ranged more widely. The only mood scale that showed differences related to gender was that of happiness, for which women had a higher diurnal mean, a diurnal peak 2h earlier, and a less-intense postlunch effect. Endogenous control of rhythmic pattern appears to be less intense in women, probably due to the coexistence of circamensual rhythmicity, although environmental or sociocultural influences may play a modulating role. Chronopsychological gender differences in affective states should be studied further given the implication they have for the prevention and treatment of mood disorders.
TL;DR: The sleep of this sample of Parisian children around 10 years of age was rather stable in its duration and timing, suggesting flexibility to adjust to the different school schedules, and sleep duration, self-rated sleepiness, and subjective sleep quality were comparable by gender, school schedule, school district, and parental socioeconomic status.
Abstract: The aim of the study was to assess the duration and quality of sleep of prepubertal (Tanner Scale level 1) physically and mentally healthy children as a function of school schedule (4 versus 4.5 days per week), age and grade (median age of 9.5 years for 4th grade versus median age of 10.5 years for 5th grade), school district (wealthy versus nonwealthy) in Paris, France, and parental socioeconomic status (high, medium, or low). We studied 51 girl and 44 boy volunteer pupils with written parental consent. The study lasted 2 weeks during the month of March. During the first study week, the children attended school 4.5 days, and during the second week, they attended school only 4 days without difference in the length of the school day. A sleep log was used to ascertain time of lights off for sleep and lights on at awakening, nighttime sleep duration, and self-rated sleep quality. A visual analog scale (VAS) was also used by pupils to self-rate the level of perceived sleepiness at four specific times of the s...
TL;DR: Diabetic patients have a very high cardiac event rate but fail to show normal circadian fluctuations in the occurrence of myocardial infarction, resulting in a continuous susceptibility to thrombotic events throughout the day and may contribute to the excess cardiovascular mortality and morbidity in these patients.
Abstract: Serious adverse cardiovascular events, including myocardial infarction, sudden cardiac death, and stroke, frequently result from rupture of atherosclerotic plaques with superimposed thrombosis and exhibit a pronounced circadian rhythmicity, peaking in the morning hours. Two potentially synergistic mechanisms play a pathogenic role in the circadian variation of arterial thrombotic events. A morning surge in sympathetic activity alters hemodynamic forces and predisposes vulnerable coronary atherosclerotic plaques to rupture. Day-night variations of hemostatic and fibrinolytic factors result in morning hypercoagulability and hypofibrinolysis, promoting intraluminal thrombus formation at the same time when the risk for plaque rupture is highest. Diabetic patients have a very high cardiac event rate but fail to show normal circadian fluctuations in the occurrence of myocardial infarction. Alterations in the circadian variation autonomic tone, blood pressure, and the thrombotic-thrombolytic equilibrium have been documented in diabetic patients. These include reduced or absent 24-h periodicity in autonomic tone, fibrinolytic activity, and thrombotic tendency, and a blunted decline in nocturnal blood pressure. Disruption of these circadian rhythms explains the lack of significant circadian distribution of cardiac events in diabetic patients. Moreover, the loss of these normal biorhythms results in a continuous susceptibility to thrombotic events throughout the day and may contribute to the excess cardiovascular mortality and morbidity in these patients.
TL;DR: Data suggest that disrupted sleep, decreased melatonin production, and partial lack of day-night difference in melatonin secretion were observed equally in normal elderly and in patients with AD.
Abstract: Recent studies suggest melatonin, due to its antioxidant and free-radical- scavenging actions, may play a role in the neuroprotection against amyloid, which is implicated in the pathogenesis of Alz...
TL;DR: In this paper, a seasonal model was calculated using object-oriented software for the analysis of longitudinal data in S (OSWALD); multiple regression analysis was used to determine the influence of seasonal variation in total cholesterol and HDL-C.
Abstract: Seasonal variation in the plasma total cholesterol (TC) and high-density lipoprotein cholesterol (HDL-C) have been repeatedly reported, with contradictory results regarding the pattern of seasonal variation of these parameters. Furthermore, it is still not well established whether the variation is due to changes in the nutrition or changes in physical activity depending on the season. The aim of this study was therefore to determine plasma TC and HDL-C in different groups of healthy participants: 19 vegetarians with a constant diet independent of the season, 14 athletes with almost constant physical activity over the year, and 114 controls in the age groups 20–26 years (mean age 24 + 1.5 years) and 40–48 years (mean age 44.3 + 2.1 years). Over 2 years, blood samples were collected every 2–3 months and were analyzed for plasma TC and HDL-C. At all visits, body mass index (BMI) and waist-to-hip ratio (WHR) were calculated, and nutrition and physical activity profiles were obtained. The seasonal model was calculated using object-oriented software for the analysis of longitudinal data in S (OSWALD); multiple regression analysis was used to determine the influence of
TL;DR: It is suggested that MEL is immuno-enhancing for this tropical squirrel, and plays an important role in the maintenance of its immunity in accordance with the seasonal changes in environmental factors and gonadal status.
Abstract: Melatonin (MEL) regulation of seasonal variation in immunity has been studied extensively in temperate mammals. This report is the first on a tropical mammal, the Indian palm squirrel, F. pennanti. In response to the annual environmental cycle, we studied the rhythms of plasma MEL and the immune parameters of total blood leucocytes, absolute blood lymphocytes and blastogenic responses of blood, thymus and spleen lymphocytes. We found that in parallel with MEL all the immune parameters increased during the month of April onward, when natural day length, temperature, humidity and rainfall were increasing. Maximum values occurred during November (reproductively inactive phase) when the values of all the physical factors were comparatively low. Lowest values occurred during January-March (reproductively active phase) when the values of the physical factors were lowest. In order to establish a clear interrelationship between the pineal MEL and the immune system function, we manipulated these squirrels with exogenous MEL (25mg/100 g B wt/day) at 1730 h during their pineal inactive phase (March) while another group was pinealectomized (Px) during November when their pineal was active. The MEL injection significantly increased all the immune parameters, while Px decreased them significantly. Hence, we suggest that MEL is immuno-enhancing for this tropical squirrel, and plays an important role in the maintenance of its immunity in accordance with the seasonal changes in environmental factors and gonadal status.
TL;DR: Minor bouts of activity occurring in the main light portion of a light-dark cycle were quantified and it is suggested that some damped endogenous process is spared in mCry1/mCry2 double-knockout mice.
Abstract: Mice lacking cryptochromes (mCry1-/- mCry2-/-) were kept in a 16h light, 8h dark, light-dark (16:8 LD) cycle and were given additional pulses of light of different brightness, starting 2h after dark onset and lasting for 1h. The suppression of wheel running during these light pulses (i.e., masking) was compared to that of wild types. No evidence of any decrement in the masking response to light was detected. As well as studying masking, minor bouts of activity occurring in the main light portion of a light-dark cycle were quantified. One possible explanation of such predark activity is that some damped endogenous process is spared in mCry1/mCry2 double-knockout mice. (Chronobiology International, 18(4), 613–625, 2001)
TL;DR: The circadian peaks in the frequency spectra of full-term neonates may indicate the initial adaptation in the first week of life to a 24h day, in agreement with the results concerning the different durations of nightly and daily sleep.
Abstract: During the first weeks of life, preterm neonates show fewer circadian rhythms in their physiological parameters than full-term neonates. To determine whether preterm neonates differ in their temporal adaptation to the daynight cycle from full-term neonates at the early age of 1 week, we compared activity-rest behavior of both groups. Activity-rest behavior of 10 neurologically healthy preterm neonates (born in 34th to 36th week of gestation) and 10 neurologically healthy full-term neonates (born in 37th to 42nd week of gestation) was monitored longitudinally for 8 successive days in the first 2 weeks of life. Actigraphy was used to register and display time patterns of activity and rest in neonates by using small actometers, which resemble a wristwatch. Nursing/feeding was recorded using the actometer's integrated event marker button. Recordings for preterm neonates were conducted in the hospital; recordings for full-term neonates were carried out in the hospital and in their homes. In addition to the act...
TL;DR: A comparison of the behavior of animals collected at different times of the year suggests a seasonal variation in the persistence ofcircatidal swimming, which is consistent with a control system involving circatidal, circadian, and semi-lunar oscillators.
Abstract: Observations on the rhythmic activity of 71 juvenile specimens of the inter-tidal blenny Zoarces viviparus reveal an endogenous pattern of swimming at three different periodicities. Circatidal swimming, with activity peaks phased to high water or the ebb of the subjective 12.4-h tides, was found in 50 fish and was the predominant pattern seen immediately after collection, when the rhythm generally persisted for between 3 and 12 cycles. Discrete activity peaks, with a free running period of approximately 24 h were also evident in the swimming pattern of eight fish. A circadian influence was also manifest as a modulation in amplitude, phase shifts and changes in free-running period of the circa-tidal rhythm. Overall, the activity level declined with time but those fish that remained active long enough showed a semi-lunar rhythm, with maximum activity at the time of the spring tides. A comparison of the behavior of animals collected at different times of the year suggests a seasonal variation in the persistence of circatidal swimming. The results are consistent with a control system involving circatidal, circadian, and semi-lunar oscillators.
TL;DR: The results suggest the findings from a single morning blood sampling for leptin may be misleading since it may underestimate the mean 24h and peak concentrations of the hormone.
Abstract: Leptin, from the Greek leptos, meaning thin (in reference to its ability to reduce body fat stores), is a hormone secreted primarily by adipocytes. At one time, leptin was portrayed as a potential means of combating obesity. Recently, leptin has been identified as a potent inhibitor of bone formation, acting through the central nervous system. Since numerous studies clearly show that bone remodeling is circadian rhythmic with peak activity during sleep, it is of interest to explore circadian variability in serum leptin. Accordingly, circadian characteristics of serum leptin were examined in 7 clinically healthy men and 4 obese men with type II diabetes. Blood samples were collected for 24h at 3h intervals beginning at 19:00. The dark (sleep) phase of the light-dark cycle extended from 22:30 to 06:30, with brief awakening for sampling at 01:00 and 04:00. Subjects consumed general hospital meals (2400 calories) at 16:30, 07:30, and 13:30. Serum leptin levels were determined by a R&D Systems enzyme immunoass...
TL;DR: Results indicate that the laboratory hamster is not much different from the wild type, although the interindividual variability was higher in wild hamsters for both measures.
Abstract: The golden hamster (Mesocricetus auratus) is one of the most frequently used laboratory animals, particularly in chronobiological studies. One reason is its very robust and predictable rhythms, although the question arises whether this is an inbreeding effect or rather is typical for the species. We compared the daily (circadian) activity rhythms of wild and laboratory golden hamsters. The laboratory hamsters were derived from our own outbred stock (Zoh:GOHA). The wild hamsters included animals captured in Syria and their descendants (F1). Experiments were performed under entrained (light: dark [LD] 14h:10h) and under free-running (constant darkness, DD) conditions. Locomotor activity was recorded using passive infrared detectors. Under entrained conditions, the animals had access to a running wheel for a certain time to induce additional activity. After 3 weeks in constant darkness, a light pulse (15 min, 100 lux) was applied at circadian time 14 (CT14). Both laboratory and wild hamsters showed well-pron...