Journal of Circadian Rhythms via MedWorm.com

A dynamic model of circadian rhythms in rodent tail skin temperature for comparison of drug effects

Journal of Circadian Rhythms — Thu, 05 Jan 2012 05:00:00 +0100

Menopause-associated thermoregulatory dysfunction can lead to symptoms such as hot fushes severely im-pairing quality of life of affected women. Treatment effects are often assessed by the ovariectomized rat modelproviding time series of tail skin temperature measurements in which circadian rhythms are a fundamental ingre-dient. In this work, a new statistical strategy is presented for analyzing such stochastic-dynamic data with theaim of detecting successful drugs in hot flush treatment. The circadian component is represented by a nonlinear dynamical system which is defined by the van der Pol equation and provides well-interpretable model parameters.Results regarding the statistical evaluation of these parameters are presented. (Source: Journal of Circadian Rhythms)

Magel2, a Prader-Willi Syndrome candidate gene, modulates the activities of circadian rhythm proteins in cultured cells.

Journal of Circadian Rhythms — Fri, 30 Dec 2011 05:00:00 +0100

Conclusion: Consistent with the blunted circadian rhythm observed in Magel2-null mice, these data suggest that Magel2 normally promotes negative feedback regulation of the cellular circadian cycle, through interactions with key core circadian rhythm proteins. (Source: Journal of Circadian Rhythms)

Measuring the Impact of Apnea and Obesity on Circadian Activity Patterns Using Functional Linear Modeling of Actigraphy Data

Journal of Circadian Rhythms — Thu, 13 Oct 2011 04:00:00 +0100

Conclusions: Compared with analysis using summary measures (e.g., average activity over 24 hours, total sleep time), Functional Data Analysis (FDA) is a novel statistical framework that more efficiently analyzes information from actigraphy data. FDA has the potential to reposition the focus of actigraphy data from general sleep assessment to rigorous analyses of circadian activity rhythms. (Source: Journal of Circadian Rhythms)

Relationship between daylength and suicide in Finland

Journal of Circadian Rhythms — Fri, 23 Sep 2011 04:00:00 +0100

Conclusions: The period with the longest length of the day associated with the increased suicide mortality. Furthermore, since the peak of suicide mortality seems to manifest later during the year in the north, some other physical or biological signals, besides the variation in daylight, may be involved. In order to have novel means for suicide prevention, the assessment of susceptibility to the circadian misalignment might help. (Source: Journal of Circadian Rhythms)

Relationship between psychosomatic complaints and circadian rhythm irregularity assessed by salivary levels of melatonin and growth hormone

Journal of Circadian Rhythms — Wed, 14 Sep 2011 04:00:00 +0100

Conclusion: Psychosomatic symptoms, particularly anxiety, may be associated with irregularity in melatonin and growth hormone rhythms, which can be altered by basic lifestyle habits even in healthy students. (Source: Journal of Circadian Rhythms)

Polymorphisms in melatonin synthesis pathways: possible influences on depression

Journal of Circadian Rhythms — Mon, 08 Aug 2011 23:00:00 +0100

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Effects of restraint stress on the daily rhythm of hydrolysis of adenine nucleotides in rat serum

Journal of Circadian Rhythms — Wed, 27 Jul 2011 23:00:00 +0100

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Chronic inhibition of endoplasmic reticulum calcium-release channels and calcium-ATPase lengthens the period of hepatic clock gene Per1

Journal of Circadian Rhythms — Thu, 07 Jul 2011 23:00:00 +0100

Conclusions: Our data suggest that Ca2+ mobilized from internal deposits modulates the molecular circadian clock in the liver of rats entrained by light and by restricted meal access. (Source: Journal of Circadian Rhythms)

Time-of-day dependence of neurological deficits induced by sodium nitroprusside in young mice

Journal of Circadian Rhythms — Thu, 16 Jun 2011 23:00:00 +0100

Sodium nitroprusside (SNP) is widely used in pharmacological studies as a potent vasodilator or a nitric oxide donor. SNP-induced ataxic effects were assessed in mice by the Joulou-Couvoisier test. Swiss albino mice of both genders, 2-8 weeks of age, were acclimated at least for 2 weeks to 12 h light (rest span)/12 h dark (activity span). In 2 and 4 week old mice, maxima of ataxia were found following intraperitoneal administration of a dose ranging from 3 to 3.6 mg.kg-1 SNP at [almost equal to] 1 and 13 HALO (Hours After Light Onset). The sublethal toxicity was statistically dosing-time dependent (chi2 test: P < 0.005). No rhythm was validated in neurotoxicity by cosinor analyses. At the 8th week of post-natal development (PND), SNP-induced ataxia was greatest at [almost equal to] 1 HALO ...

Absence of a serum melatonin rhythm under acutely extended darkness in the horse

Journal of Circadian Rhythms — Mon, 09 May 2011 23:00:00 +0100

Background: In contrast to studies showing gradual adaptation of melatonin (MT) rhythms to an advanced photoperiod in humans and rodents, we previously demonstrated that equine MT rhythms complete a 6-h light/dark (LD) phase advance on the first post-shift day. This suggested the possibility that melatonin secretion in the horse may be more strongly light-driven as opposed to endogenously rhythmic and light entrained. The present study investigates whether equine melatonin is endogenously rhythmic in extended darkness (DD). Methods: Six healthy, young mares were maintained in a lightproof barn under an LD cycle that mimicked the ambient natural photoperiod outside. Blood samples were collected at 2-h intervals for 48 consecutive h: 24-h in LD, followed by 24-h in extended dark (DD). Serum ...

Fine-scale differences in diel activity among nocturnal freshwater planarias (Platyhelminthes: Tricladida)

Journal of Circadian Rhythms — Sat, 09 Apr 2011 23:00:00 +0100

Conclusions: The tested species are mainly nocturnal, consistent with their photonegative characteristics. The fine-scale differences in diel behavior among these three triclad species may not be sufficient to allow coexistence in the wild, with the nonnative D. tigrina eventually displacing D. polychroa and P. tenuis in many European waters. The link between planarian diel rhythms and ecological characteristics are worth of further, detailed investigation. (Source: Journal of Circadian Rhythms)

Effects of saliva collection using cotton swabs on melatonin enzyme immunoassay

Journal of Circadian Rhythms — Mon, 10 Jan 2011 00:00:00 +0100

Conclusion: Our findings indicate an interference effect of cotton swabs on the assay result of salivary melatonin at lower melatonin level. Cotton-based collection devices might, thus, not be suitable for assessment of DLMO. (Source: Journal of Circadian Rhythms)

Statistical methods for detecting and comparing periodic data and their application to the nycthemeral rhythm of bodily harm: A population based study

Journal of Circadian Rhythms — Mon, 08 Nov 2010 00:00:00 +0100

This article describes a method for the detection and simultaneous comparison of multiple nycthemeral rhythms. Methods: A statistical method for detecting periodic patterns in time-related data via harmonic regression is described. The method is particularly capable of detecting nycthemeral rhythms in medical data. Additionally a method for simultaneously comparing two or more periodic patterns is described, which derives from the analysis of variance (ANOVA). This method statistically confirms or rejects equality of periodic patterns. Mathematical descriptions of the detecting method and the comparing method are displayed. Results: Nycthemeral rhythms of incidents of bodily harm in Middle Franconia are analyzed in order to demonstrate both methods. Every day of the week showed a significa...

Gastrointestinal complaints in shift-working and day-working nurses in Iran

Journal of Circadian Rhythms — Wed, 06 Oct 2010 23:00:00 +0100

Conclusion: Nurses on rotating shifts in Iran experience more GI disturbances than do nurses on day shifts. (Source: Journal of Circadian Rhythms)

Evidence of circadian rhythms in non-photosynthetic bacteria?

Journal of Circadian Rhythms — Wed, 15 Sep 2010 23:00:00 +0100

Examples of circadian rhythms have been described in eukaryotic organisms and in photosynthetic bacteria, but direct proof of their existence in other prokaryotes is limited and has been largely ignored. The aim of this article is to review existing evidence and to present preliminary results that suggest that the heterotrophic bacterium Pseudomonas putida shows regular variations in its growth pattern synchronized with light/darkness cycles. We put forward the hypothesis that circadian regulation of certain processes can take place in non-photosynthetic prokaryotes and may represent an adaptative advantage in specific environments. (Source: Journal of Circadian Rhythms)

Aging related changes of circadian rhythmicity of cytotoxic lymphocyte subpopulations

Journal of Circadian Rhythms — Mon, 24 May 2010 23:00:00 +0100

Conclusion: Our study has evidenced aging-related changes of correlation and circadian rhythmicity of variation of cytotoxic lymphocyte subpopulations that might play a role in the alteration of immune system function in the elderly. (Source: Journal of Circadian Rhythms)

Weak evidence of bright light effects on human LH and FSH

Journal of Circadian Rhythms — Mon, 10 May 2010 23:00:00 +0100

Conclusions: These results gave some support for the hypothesis that bright light may augment LH secretion. Longer-duration studies may be needed to clarify the effects of light on human LH and FSH. (Source: Journal of Circadian Rhythms)

"Time sweet time": circadian characterization of galectin-1 null mice

Journal of Circadian Rhythms — Sun, 18 Apr 2010 23:00:00 +0100

Background: Recent evidence suggests a two-way interaction between the immune and circadian systems. Circadian control of immune factors, as well as the effect of immunological variables on circadian rhythms, might be key elements in both physiological and pathological responses to the environment. Among these relevant factors, galectin-1 is a member of a family of evolutionarily-conserved glycan-binding proteins with both extracellular and intracellular effects, playing important roles in immune cell processes and inflammatory responses. Many of these actions have been studied through the use of mice with a null mutation in the galectin-1 (Lgals1) gene. To further analyze the role of endogenous galectin-1 in vivo, we aimed to characterize the circadian behavior of galectin-1 null (Lgals1-...

Circadian rhythm and its role in malignancy

Journal of Circadian Rhythms — Tue, 30 Mar 2010 23:00:00 +0100

Circadian rhythms are daily oscillations of multiple biological processes directed by endogenous clocks. The circadian timing system comprises peripheral oscillators located in most tissues of the body and a central pacemaker located in the suprachiasmatic nucleus (SCN) of the hypothalamus. Circadian genes and the proteins produced by these genes constitute the molecular components of the circadian oscillator which form positive/negative feedback loops and generate circadian rhythms. The circadian regulation extends beyond clock genes to involve various clock-controlled genes (CCGs) including various cell cycle genes. Aberrant expression of circadian clock genes could have important consequences on the transactivation of downstream targets that control the cell cycle and on the ability of ...

Impact of oral melatonin on the electroretinogram cone response

Journal of Circadian Rhythms — Thu, 19 Nov 2009 00:00:00 +0100

Conclusions: Oral melatonin appears to reach the eye through the circulation. When it is administered at a time of day when it is not usually present, melatonin appears to reduce input to retinal cones. We believe that the impact of melatonin on retinal function should be taken into consideration when used without supervision in chronic self-medication for sleep or circadian disorder treatment. (Source: Journal of Circadian Rhythms)

Sex and hand differences in circadian wrist activity are independent from sex and hand differences in 2D:4D

Journal of Circadian Rhythms — Thu, 29 Oct 2009 00:00:00 +0100

Conclusions: Sex and hand differences for digit ratio and acrophase replicated previous findings. The lack of correlation between digit ratio and patterns of wrist activity suggests that sexually dimorphic circadian activity develops independently from the mechanisms of hormone exposure that cause sex differences in digit ratio. (Source: Journal of Circadian Rhythms)

Restless Legs Syndrome in shift workers: A cross sectional study on male assembly workers

Journal of Circadian Rhythms — Sun, 13 Sep 2009 23:00:00 +0100

Conclusions: Rotational shift work acts as a risk or exacerbating factor for Restless Legs Syndrome. (Source: Journal of Circadian Rhythms)

Food anticipation in Bmal1-/- and AAV-Bmal1 rescued mice: a reply to Fuller et al

Journal of Circadian Rhythms — Sun, 09 Aug 2009 23:00:00 +0100

Evidence that circadian food-anticipatory activity and temperature rhythms are absent in Bmal1 knockout mice and rescued by restoration of Bmal1 expression selectively in the dorsomedial hypothalamus was published in 2008 by Fuller et al and critiqued in 2009 by Mistlberger et al. Fuller et al have responded to the critique with new information. Here we update our critique in the light of this new information. We also identify and correct factual and conceptual errors in the Fuller et al response. We conclude that the original results of Fuller et al remain inconclusive and fail to clarify the role of Bmal1 or the dorsomedial hypothalamus in the generation of food-entrainable rhythms in mice. (Source: Journal of Circadian Rhythms)

A possible connection between psychosomatic symptoms and daily rhythmicity in growth hormone secretion in healthy Japanese students

Journal of Circadian Rhythms — Tue, 04 Aug 2009 23:00:00 +0100

Conclusion: Psychosomatic symptoms may be associated with circadian dysfunction, as inferred from blunted rhythmicity in growth hormone secretion. (Source: Journal of Circadian Rhythms)

Phase delaying the human circadian clock with a single light pulse and moderate delay of the sleep/dark episode: No influence of iris color

Journal of Circadian Rhythms — Thu, 16 Jul 2009 23:00:00 +0100

Conclusions: A single 2-hour bright light pulse combined with a moderate delay of the sleep/dark episode delayed the circadian clock an average of ~1.5 hours. There was no evidence that iris color influenced the magnitude of the phase shift. Future studies are needed to replicate our findings that iris color does not impact the magnitude of light-induced circadian phase shifts, and that the previously reported differences may be due to race. (Source: Journal of Circadian Rhythms)

Chronotypology and melatonin alterations in minimal hepatic encephalopathy

Journal of Circadian Rhythms — Fri, 29 May 2009 04:00:00 +0100

Background: "Minimal (subclinical) hepatic encephalopathy" is a term that describes impairment of every day life activities in cirrhosis patients without clinical neurologic abnormalities. Melatonin diurnal pattern disruption and metabolic changes due to liver insufficiency can affect the human biologic clock. Our study was conducted to measure plasma melatonin levels in an attempt to correlate plasma melatonin abnormalities with liver insufficiency severity, and describe chronotypology in cirrhosis patients with minimal encephalopathy. Methods: Twenty-six cirrhotic patients enrolled in the study and thirteen patients without liver or central nervous system disease served as controls. All patients had full clinical and biochemical evaluation, chronotypology analysis, neurological evaluatio...

NPAS2 and PER2 are linked to risk factors of the metabolic syndrome

Journal of Circadian Rhythms — Tue, 26 May 2009 04:00:00 +0100

Conclusions: Our findings support the view that relevant relationships between circadian clocks and the metabolic syndrome in humans exist. (Source: Journal of Circadian Rhythms)

Effect of chronic ethanol exposure on the liver of Clock-mutant mice

Journal of Circadian Rhythms — Wed, 01 Apr 2009 04:00:00 +0100

In humans, chronic ethanol consumption leads to a characteristic set of changes to the metabolism of lipids in the liver that is referred to as an "alcoholic fatty liver (AFL)". In severe cases, these metabolic changes result in the enlargement and fibrillization of the liver and are considered risk factors for cirrhosis and liver cancer. Clock-mutant mice have been shown to display abnormal lipid metabolism and alcohol preferences. To further understand the potential interactions between ethanol consumption, lipid metabolism, and the circadian clock, we investigated the effect of chronic ethanol intake on the lipid metabolism of Clock-mutant mice. We found that ethanol treatment produced a number of changes in the liver of Clock-mutant mice without impacting the wild-type controls. First,...

Standards of evidence in chronobiology: Critical review of a report that restoration of Bmal1 expression in the dorsomedial hypothalamus is sufficient to restore circadian food anticipatory rhythms in Bmal1-/- mice

Journal of Circadian Rhythms — Thu, 26 Mar 2009 04:00:00 +0100

Daily feeding schedules generate food anticipatory rhythms of behavior and physiology that exhibit canonical properties of circadian clock control. The molecular mechanisms and location of food-entrainable circadian oscillators hypothesized to control food anticipatory rhythms are unknown. In 2008, Fuller et al reported that food-entrainable circadian rhythms are absent in mice bearing a null mutation of the circadian clock gene Bmal1 and that these rhythms can be rescued by virally-mediated restoration of Bmal1 expression in the dorsomedial nucleus of the hypothalamus (DMH) but not in the suprachiasmatic nucleus (site of the master light-entrainable circadian pacemaker). These results, taken together with controversial DMH lesion results published by the same laboratory, appear to establi...

Is a purpose of REM sleep atonia to help regenerate intervertebral disc volumetric loss?

Journal of Circadian Rhythms — Mon, 05 Jan 2009 05:00:00 +0100

This article discusses a new hypothesis for complete core muscle relaxation in REM sleep, suggesting a bottom-up recuperative perspective. That is, does the atonia in REM sleep provide a utility to help restore the mechanobiology and respective diurnal intervertebral disc hydraulic loss? By combining the effects of gravity with current compressive concepts in spinal stability, this article looks at vertebral approximation as a deleterious experience with an intrinsic biological need to keep vertebrae separated. Methods using polysomnography and recumbent MRI are discussed. (Source: Journal of Circadian Rhythms)

A new approach to understanding the impact of circadian disruption on human health

Journal of Circadian Rhythms — Thu, 29 May 2008 04:00:00 +0100

Conclusions: This paper provides a quantitative foundation for systematically studying the impact of light-induced circadian disruption in humans and in animal models. Ecological light and activity data are needed to develop the essential insights into circadian entrainment/disruption actually experienced by modern people. These data can now be obtained and analyzed to reveal the interrelationship between actual light exposures and markers of circadian rhythm such as rest-activity patterns, core body temperature, and melatonin synthesis. Moreover, it should now be possible to bridge ecological studies of circadian disruption in humans to parametric studies of the relationships between circadian disruption and health outcomes using animal models. (Source: Journal of Circadian Rhythms)

Delayed sleep phase cases and controls

Journal of Circadian Rhythms — Tue, 29 Apr 2008 04:00:00 +0100

Conclusions: These results indicate a DSPD phenotype is familial and associated with unipolar depression. (Source: Journal of Circadian Rhythms)

SCN-AVP release of mPer1/mPer2 double-mutant mice in vitro

Journal of Circadian Rhythms — Thu, 20 Mar 2008 04:00:00 +0100

Conclusion: Our results suggest that the circadian clock in these animals, although deficient in (most) behavioural and molecular rhythms, may still be (partially) functional, possibly as an hourglass mechanism. The level of perturbation of the clock in Per1/2 double mutants may therefore be less than was originally thought. (Source: Journal of Circadian Rhythms)

Period-2: a tumor suppressor gene in breast cancer

Journal of Circadian Rhythms — Tue, 11 Mar 2008 04:00:00 +0100

Previous reports have suggested that the ablation of the Period 2 gene (Per 2) leads to enhanced development of lymphoma and leukemia in mice. Employing immunoblot analyses, we have demonstrated that PER 2 is endogenously expressed in human breast epithelial cell lines but is not expressed or is expressed at significantly reduced level in human breast cancer cell lines. Expression of PER 2 in MCF-7 breast cancer cells significantly inhibited the growth of MCF-7 human breast cancer cells, and, when PER 2 was co-expressed with the Crytochrome 2 (Cry 2) gene, an even greater growth-inhibitory effect was observed. The inhibitory effect of PER 2 on breast cancer cells was also demonstrated by its suppression of the anchorage-independent growth of MCF-7 cells as evidenced by the reduced number a...

Structural insights into the function of the core-circadian factor TIMING OF CAB2 EXPRESSION 1 (TOC1)

Journal of Circadian Rhythms — Mon, 25 Feb 2008 05:00:00 +0100

Conclusion: The models we present should prove useful in future hypothesis-driven biochemical analyses to test the predictions that TOC1 is a multi-domain signaling component of the plant circadian clock. (Source: Journal of Circadian Rhythms)

Ovipositional periodicity of caged Anopheles gambiae individuals

Journal of Circadian Rhythms — Fri, 25 Jan 2008 05:00:00 +0100

Conclusions: Confined individual A. gambiae oviposit in a single ca. 2-4 h continuous bout per 24 h. Oviposition is most probable in early scotophase, mid scotophase, or early photophase. However, some oviposition can occur at any hour during 24 h, especially if females were previously deprived of ovipositional substrate. (Source: Journal of Circadian Rhythms)

Circadian rhythm dysfunction in glaucoma: a hypothesis

Journal of Circadian Rhythms — Thu, 10 Jan 2008 05:00:00 +0100

The absence of circadian zeitgebers in the social environment causes circadian misalignment, which is often associated with sleep disturbances. Circadian misalignment, defined as a mismatch between the sleep-wake cycle and the timing of the circadian system, can occur either because of inadequate exposure to the light-dark cycle, the most important synchronizer of the circadian system, or reduction in light transmission resulting from ophthalmic diseases (e.g., senile miosis, cataract, diabetic retinopathy, macular degeneration, retinitis pigmentosa, and glaucoma). We propose that glaucoma may be the primary ocular disease that directly compromises photic input to the circadian time-keeping system because of inherent ganglion cell death. Glaucomatous damage to the ganglion cell layer might...

A QTL on mouse chromosome 12 for the genetic variance in free-running circadian period between inbred strains of mice

Journal of Circadian Rhythms — Wed, 31 Oct 2007 04:00:00 +0100

Conclusion: We not only fine-mapped the QTL for circadian period on chromosome 12 but found a new QTL there as well: an association with the timing of the nocturnal activity-minimum. Candidate quantitative trait genes in this QTL are zinc finger protein 277 and arylhydrocarbon receptor. Arylhydrocarbon receptor is structurally related to Bmal1, a canonical clock gene. (Source: Journal of Circadian Rhythms)

Temporal variation in the recovery from impairment in adriamycin-induced wound healing in rats

Journal of Circadian Rhythms — Wed, 10 Oct 2007 04:00:00 +0100

Conclusion: It is concluded that adriamycin-induced impairment of wound healing in adult female rats exhibits nycthemeral variation. (Source: Journal of Circadian Rhythms)

Rapid phase adjustment of melatonin and core body temperature rhythms following a 6-h advance of the light/dark cycle in the horse

Journal of Circadian Rhythms — Fri, 24 Aug 2007 04:00:00 +0100

Conclusions: Aside from the temperature rhythm disruption, rapid resynchronization of the melatonin rhythm suggests that the central circadian pacemaker of the horse may possess a particularly robust entrainment response. The consequences for athletic performance remain unknown. (Source: Journal of Circadian Rhythms)

Circadian phase response curves to light in older and young women and men

Journal of Circadian Rhythms — Tue, 10 Jul 2007 04:00:00 +0100

Conclusions: In these experimental conditions, 3000 lux light could shift the phase of circadian rhythms to about the same extent among older and young adults, but the optimal light timing for phase shifting differed. For an interval near 4 PM, bright light produced only negligible phase shifts for either age group. (Source: Journal of Circadian Rhythms)

Glycogen synthase kinase 3, circadian rhythms, and bipolar disorder: a molecular link in the therapeutic action of lithium.

Journal of Circadian Rhythms — Mon, 12 Feb 2007 07:00:00 +0100

Conclusions: These results confirm GSK3 as a plausible target of lithium action in BPD therapeutics, and suggest the circadian clock mechanism as a significant modulator of lithium's clinical benefits. (Source: Journal of Circadian Rhythms)

Glycogen synthase kinase 3, circadian rhythms, and bipolar disorder: a molecular link in the therapeutic action of lithium

Journal of Circadian Rhythms — Mon, 12 Feb 2007 05:00:00 +0100

Conclusion: These results confirm GSK3 as a plausible target of lithium action in BPD therapeutics, and suggest the circadian clock mechanism as a significant modulator of lithium's clinical benefits. (Source: Journal of Circadian Rhythms)

The effect of high correlated colour temperature office lighting on employee wellbeing and work performance

Journal of Circadian Rhythms — Thu, 11 Jan 2007 07:00:00 +0100

Conclusion: High correlated colour temperature fluorescent lights could provide a useful intervention to improve wellbeing and productivity in the corporate setting, although further work is necessary in quantifying the magnitude of likely benefits. (Source: Journal of Circadian Rhythms)

Daily rhythm of salivary and serum urea concentration in sheep

Journal of Circadian Rhythms — Thu, 23 Nov 2006 07:00:00 +0100

Conclusion: In sheep both salivary and serum urea concentrations showed daily fluctuations. Urea is synthesized in the liver and its production is strongly influenced by food intake. Future investigation should clarify whether daily urea rhythms in sheep are endogenous or are simply the result of the temporal administration of food. (Source: Journal of Circadian Rhythms)

Modeling biological rhythms in failure time data

Journal of Circadian Rhythms — Tue, 07 Nov 2006 07:00:00 +0100

Conclusion: In this paper we have described a method for modeling failure time data with an underlying biological rhythm. The advantage of adapting a cosinor model to proportional hazards model is its ability to model right censored data. We have presented a method to provide an estimate and confidence interval of the day in the menstrual cycle where the minimum hazard is achieved. This method is not limited to breast cancer data, and may be applied to any biological rhythms linked to right censored data. (Source: Journal of Circadian Rhythms)

Clock mutation affects circadian regulation of circulating blood cells

Journal of Circadian Rhythms — Mon, 02 Oct 2006 06:00:00 +0100

Conclusion: Our results suggest that endogenous clock-regulated circadian corticosterone secretion from the adrenal gland is involved in the effect of a Clock mutation on daily profiles of circulating WBC. However, intact CLOCK seems unnecessary for generating the rhythm of corticosterone secretion in mice. Our results also suggest that CLOCK is involved in discharge of RBC from the spleen. (Source: Journal of Circadian Rhythms)

Relationship between nocturnal serotonin surge and melatonin onset in rodent pineal gland

Journal of Circadian Rhythms — Wed, 27 Sep 2006 06:00:00 +0100

Conclusion: These results suggest that both 5-HT and melatonin could serve as reliable markers of the circadian clock because of their day-to-day precision of onset timings within the same animals or within individuals of the same strain or same species. The results also demonstrate that data for MT-on cannot be compared directly between different species, and that 5HT-on may be a more reliable circadian marker when data from animals of different species are compared. (Source: Journal of Circadian Rhythms)

Emergence of physiological rhythmicity in term and preterm neonates in a neonatal intensive care unit

Journal of Circadian Rhythms — Mon, 11 Sep 2006 06:00:00 +0100

Conclusion: Whereas circadian rhythmicity in neonates may result from maternal influence, the increase of amplitude indexes in PR with PCA may be related to physiological maturity. Further studies are needed to elucidate the effect of oxygenation on physiological rhythmicity in neonates. (Source: Journal of Circadian Rhythms)