Evidence For Circadian Rhythm Research Articles

Circadian pain assessment in neonates from a nurse's perspective.

Circadian rhythms modulate the activity of pain pathways. But there appears to be a lack of understanding of how the perception of pain varies in neonates during the day. To assess circadian variations in pain perception we analyzed intensities of pain at 3 h intervals in neonates (within 24 hours). We also followed up the nursing interventions practiced for pain reduction and their effectivity within a day. We have analyzed the clinical observations of pain in 16 neonates during 62 days of hospitalization (with Mean = 3.87, Min = 1, Max = 19). The pain was assessed by a modification of the Comfort scale supplemented with Wong-Baker scale. Procedure used for acute pain elimination was administration of 24% sucrose to the neonates. This procedure was centralized and performed in an incubator or neonatal bed. We confirmed statistically significant difference in pain scores in our group of neonates at 10:00 am, 4:00 pm, 4:00 am as compared to 10:00 pm (p values being 0.02603; 0.02885, 0.01673). The pain score was highest at 10:00 pm (Mean = 18.86, Max = 34) and at 1:00 am (Mean = 18.89, Max = 33). There was no significant difference in the pain score at 10:00 pm and 1:00 am (p = 0.2951). The results of our studies provided further evidence of circadian rhythm in the pain scores in neonates. A better understanding of circadian control of pain in neonates can help promote a more frequent use of time-contingent pain treatment strategies to help improve neonates care (Tab. 1, Fig. 2, Ref. 28) Keywords: circadian rhythm, neonate, nursing care, pain, the Comfort scale.

Circadian Regulation of Synaptic Plasticity.

Circadian rhythms refer to oscillations in biological processes with a period of approximately 24 h. In addition to the sleep/wake cycle, there are circadian rhythms in metabolism, body temperature, hormone output, organ function and gene expression. There is also evidence of circadian rhythms in synaptic plasticity, in some cases driven by a master central clock and in other cases by peripheral clocks. In this article, I review the evidence for circadian influences on synaptic plasticity. I also discuss ways to disentangle the effects of brain state and rhythms on synaptic plasticity.

Detachment, displacement and reattachment activity in a freshwater byssate mussel (Limnoperna fortunei): the effects of light, temperature and substratum orientation

The ability of the freshwater bivalve Limnoperna fortunei to voluntarily detach from the substratum, crawl and reattach as a function of illumination, temperature, substratum orientation, and mussel size was investigated. Thirty-two per cent of the 879 experimental animals detached and reattached elsewhere at least once during five- to eight-day experiments. The proportions of mobile mussels were significantly higher in permanent darkness than under permanent illumination. Displacement distances were also higher in darkness, but statistical differences with illuminated individuals were inconclusive. No evidence of circadian rhythms was detected. Mobile mussels were often significantly smaller than non-mobile individuals. It was not possible to detect the effect of water temperature (22°C and 31°C), or substratum orientation (topside and underside) on mussel mobility, but because the power of the statistical tests was low, future experiments are needed to confirm this result. The ability of mussels to voluntarily detach and reattach elsewhere has important implications for biofouling control.

Running on time: the role of circadian clocks in the musculoskeletal system.

The night and day cycle governs the circadian (24 hourly) rhythm of activity and rest in animals and humans. This is reflected in daily changes of the global gene expression pattern and metabolism, but also in the local physiology of various tissues. A central clock in the brain co-ordinates the rhythmic locomotion behaviour, as well as synchronizing various local oscillators, such as those found in the musculoskeletal system. It has become increasingly recognized that the internal molecular clocks in cells allow a tissue to anticipate the rhythmic changes in their local environment and the specific demands of that tissue. Consequently, the majority of the rhythmic clock controlled genes and pathways are tissue specific. The concept of the tissue-specific function of circadian clocks is further supported by the diverse musculoskeletal phenotypes in mice with deletions or mutations of various core clock components, ranging from increased bone mass, dwarfism, arthropathy, reduced muscle strength and tendon calcification. The present review summarizes the current understanding of the circadian clocks in muscle, bone, cartilage and tendon tissues, with particular focus on the evidence of circadian rhythms in tissue physiology, their entrainment mechanisms and disease links, and the tissue-specific clock target genes/pathways. Research in this area holds strong potential to advance our understanding of how circadian rhythms control the health and disease of the musculoskeletal tissues, which has major implications in diseases associated with advancing age. It could also have potential implications in sports performance and sports medicine.

Evidence of Circadian Rhythm, Oxygen Regulation Capacity, Metabolic Repeatability and Positive Correlations between Forced and Spontaneous Maximal Metabolic Rates in Lake Sturgeon Acipenser fulvescens

Animal metabolic rate is variable and may be affected by endogenous and exogenous factors, but such relationships remain poorly understood in many primitive fishes, including members of the family Acipenseridae (sturgeons). Using juvenile lake sturgeon (Acipenser fulvescens), the objective of this study was to test four hypotheses: 1) A. fulvescens exhibits a circadian rhythm influencing metabolic rate and behaviour; 2) A. fulvescens has the capacity to regulate metabolic rate when exposed to environmental hypoxia; 3) measurements of forced maximum metabolic rate (MMRF) are repeatable in individual fish; and 4) MMRF correlates positively with spontaneous maximum metabolic rate (MMRS). Metabolic rates were measured using intermittent flow respirometry, and a standard chase protocol was employed to elicit MMRF. Trials lasting 24 h were used to measure standard metabolic rate (SMR) and MMRS. Repeatability and correlations between MMRF and MMRS were analyzed using residual body mass corrected values. Results revealed that A. fulvescens exhibit a circadian rhythm in metabolic rate, with metabolism peaking at dawn. SMR was unaffected by hypoxia (30% air saturation (O2sat)), demonstrating oxygen regulation. In contrast, MMRF was affected by hypoxia and decreased across the range from 100% O2sat to 70% O2sat. MMRF was repeatable in individual fish, and MMRF correlated positively with MMRS, but the relationships between MMRF and MMRS were only revealed in fish exposed to hypoxia or 24 h constant light (i.e. environmental stressor). Our study provides evidence that the physiology of A. fulvescens is influenced by a circadian rhythm and suggests that A. fulvescens is an oxygen regulator, like most teleost fish. Finally, metabolic repeatability and positive correlations between MMRF and MMRS support the conjecture that MMRF represents a measure of organism performance that could be a target of natural selection.

Evidence of circadian rhythms in non-photosynthetic bacteria?

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.

Evidence for circadian rhythms in human trophoblast cell line that persist in hypoxia

Circadian clock governs daily rhythmicity of a number of physiological processes such as reproductive functions. The existence of circadian clocks in the placenta is not clearly established. In order to investigate whether human placenta may function as circadian oscillator, we utilized HTR-8/SVneo cells derived from human first-trimester trophoblast. In serum-shocked cells we found circadian expressions for the clock genes Per2 and Dec1 as well as for Dbp, a canonical clock-controlled gene. We obtained similar results for Vegf, a circadian output involved in the control of placental vasculogenesis and trophoblast functions. Interestingly, circadian oscillations persisted and even enhanced in cells experimentally rendered hypoxic with CoCl 2. These results could be explained since the hypoxic milieu of the first-trimester placenta is considered the optimal condition for normal placentation. These data collectively support a possible role for the differential rhythmic expression of Vegf, influenced by circadian clock, in the adjustment of placental vascularization and trophoblast functions to the specific requirements of the different gestational ages.

Evidence of circadian rhythm in low-density lipoprotein apoB catabolism and its impact on the estimation of kinetic parameters.

Compartmental models with constant parameters are commonly used in kinetic analysis of low-density lipoproteins (LDLs). Recent studies in animals have demonstrated the existence of circadian rhythms (CRs) in cholesterol synthesis and LDL catabolism. In this study, we investigated the possible existence of a CR in the fractional catabolic rate (FCR) of LDL apoB in man. Radioactivity data from 45 turnover studies using 125I-labelled LDL apoB were analysed. In a preliminary analysis the pattern of radioactivity decay was investigated. Kinetic analysis was performed by using one- and two-compartment models with constant parameters (steady-state, SS, analysis). Parameters were estimated by the use of the whole data set, which included frequent sampling during the first day of the turnover study, or the once-a-day data, taken at 08.00 h. The selection of once-a-day data allowed elimination of the impact of a CR on parameter evaluation. Furthermore, non-steady-state (NSS) analysis was performed in which the FCR of LDL apoB was calculated as a function of time. In one additional subject, the FCR of LDL apoB was calculated separately for the day and the night using the urine-to-plasma (U/P) radioactivity ratio. The presence of a CR in LDL apoB catabolism, with higher FCR values during the day than during the morning, was demonstrated by the NSS analysis and confirmed by LDL apoB calculation from the U/P ratio. The SS analysis with the whole and the once-a-day data sets resulted in similar average FCR of apoB values (0.329 +/- 0.076 and 0.321 +/- 0.071 respectively) when the two-compartment model was used. Thus, a CR appeared to have little impact on the average FCR of apoB estimation. However, frequent sampling used in the hope of improving parameter estimation accuracy actually resulted in deterioration of the intercompartmental parameter estimators. The fractional catabolic rate of LDL apoB exhibited a circadian rhythm with higher FCR values during the day than during the morning. The presence of a CR had, however, a limited impact on the overall FCR of apoB values.

Circadian pharmacokinetics of methotrexate.

Six patients with intermediate- and high-grade non-Hodgkin's lymphoma were treated with 400 mg/m2 i.v. methotrexate (MTX) at 0600 and 1800 hours. Despite evidence of circadian rhythms in renal function, the pharmacokinetics of total and free serum MTX showed no significant difference between these two times. The marked two-fold circadian variation in MTX pharmacokinetics previously reported in rats was not observed in these patients.

Opiate analgesia: Evidence for circadian rhythms in mice

The effects of a 12-12 h light-dark (L-D) cycle and of constant light (L-L) on nociceptive thresholds and morphine-induced analgesia were studied in two strains of mice: C57BL/6 and SEC/1Re. Under the L-D condition, a diurnal rhythm was observed in the responsivity of mice to nociceptive stimuli, and in the analgesic effects of morphine. Under the L-L schedule clear patterns of daily rhythmicity were evident in both strains for both nociceptive thresholds and responsivity to morphine. Finally, under the L-L schedule, the overall responsivity to pain and the antinociceptive effects of morphine were clearly increased in comparison to the patterns evident in the L-D condition. The administration of naloxone decreased the nociceptive thresholds, thus indicating an involvement of the endogenous opioid peptides. These phenomena are discussed in terms of the different pacemaker mechanisms involved in the expression of various patterns of daily behavioral and neurochemical rhythmicity in these strains, and of the effects of light in controlling the release of endogenous opioids.

Evidence for circadian rhythms in the serum levels of the vitamin D-dependent calcium-binding protein and in the activity of the 25-hydroxyvitamin D 3-1-α-hydroxylase in the chick : Studies on the mode of action of calciferol

Evidence for circadian rhythms in the serum levels of the vitamin D-dependent calcium-binding protein and in the activity of the 25-hydroxyvitamin D 3-1-α-hydroxylase in the chick : Studies on the mode of action of calciferol

FETAL EVALUATION BY REAL-TIME IMAGING

The application of real-time imaging to the study of fetal morphology and function is an exciting advance. Rapid accurate study of fetal dynamics is possible with this apparently safe, noninvasive technique. Animal studies have revealed the general physiology of fetal breathing movements, which are now under extensive investigation with real-time imaging in the human. There is evidence for circadian rhythm of human fetal breathing movements as well as a relationship to maternal substrate loading. The presence of fetal breathing movements of the rapid irregular type may be a reassuring sign in the presence of other indicators of fetal compromise. Using real-time B-scan imaging, we have found long periods of apnea in pregnancies with normal perinatal outcome. As suggested in the animal studies, changes in fetal breathing patterns prior to fetal death may be more complex than originally thought. The techique of real-time B-scan imaging with precise definition of apnea, general movements, and fetal breathing will provide valuable information on which to base our evaluation of the clinical usefulness of fetal breathing movement studies in the management of pregnancy.

Evidence of circadian rhythms in a cave crayfish

AbstractEvidence of a circadiam clock mechanism was found in the cave crayfish, Orconectes pellucidus, even though it is blind and has been isolated from daily cycles for at least 25,000 generations. Five of seven crayfish tested under cave conditions of continuous darkness and 13°C showed apparent rhythms of activity and/or oxygen consumption. These rhythms were statistically significant, as judged by autocorrelation, for three individuals with average periods of 26, 27, and 34 hours. All three crayfish exposed to light:dark cycles with a 24 hour period showed more regular rhythmicity than in continuous darkness but only one showed clear evidence of entrainment, i.e., synchrony of activity or oxygen consumption with the light: dark cycle. Another crayfish tested apparently conformed to Aschoff's circadian rule.