Chronobiology international
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Comparative Study
Within-subject correlations between evening-related changes in body temperature and melatonin in the spinal cord injured.
Individuals with a spinal cord injury (SCI) demonstrate altered circadian variation in thermoregulatory control. Recently, we reported that tetraplegia is associated with a blunted release of melatonin in the evening. In order to examine whether this finding relates to circadian thermoregulation, we compared the correlations between evening changes in melatonin, core and skin temperature between thoracic and cervical SCI and able-bodied participants. ⋯ The inverse correlation between evening changes in melatonin and thermoregulation is of a similar magnitude in paraplegic and able-bodied controls. In contrast, changes in skin temperature, below the level of the lesion, are unrelated to changes in melatonin in tetraplegics.
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Observational Study
Renal function changes and seasonal temperature in patients undergoing cardiac surgery.
Some observations in humans and other mammalians suggest that serum creatinine (SC) and estimated glomerular filtration rate (eGFR) may change during the warm season. The objective of this study is to determine if temperature-dependent seasonal changes in levels of SC and eGFR are detectable in cardiac surgery patients, with associated changes in postoperative acute kidney injury (AKI) incidence. This is a single-center retrospective study based on the institutional database of cardiac surgery in the period 2000-2012. ⋯ Humidity and wind speed were negatively associated with pre- and postoperative eGFR. In conclusion, patients operated during the warmest season, have higher levels of SC and lower levels of eGFR, without a correspondent increase in the AKI rate. Different hypotheses underlying this pattern are generated by this study, including a dehydration status, concomitant anemia, and a higher transfusion rate.
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Randomized Controlled Trial
A randomized controlled trial with bright light and melatonin for delayed sleep phase disorder: effects on subjective and objective sleep.
Delayed sleep phase disorder (DSPD) is assumed to be common amongst adolescents, with potentially severe consequences in terms of school attendance and daytime functioning. The most common treatment approaches for DSPD are based on the administration of bright light and/or exogenous melatonin with or without adjunct behavioural instructions. Much is generally known about the chronobiological effects of light and melatonin. ⋯ Sleep duration had returned to baseline levels in both groups. In conclusion, gradual advancement of rise time produced a phase advance during the two-week intervention, irrespective of treatment condition. Termination of treatment caused relapse into delayed sleep times, whereas long-term treatment with bright light and melatonin (three months) allowed maintenance of the advanced sleep phase.
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In birds, independent circadian clocks reside in the retina, pineal, and hypothalamus, which interact with each other and produce circadian time at the functional level. However, less is known of the molecular clockwork, and of the integration between central and peripheral clocks in birds. The present study investigated this, by monitoring the timed expression of five core clock genes (Per2. ⋯ For example, both rbCry2 and rbClock peaks were close to rbCry1 and rbBmal1 peaks, respectively, in the hypothalamus, but not in other tissues. The results are consistent with the autoregulatory circadian feedback loop, and indicate a conserved tissue-level circadian time generation in buntings. Variable phase relationships between gene pairs forming positive and negative limbs of the feedback loop may suggest the tissue-specific contribution of individual core circadian genes in the circadian time generation.
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Disturbances in circadian rhythms are commonly observed in the development of several medical conditions and may also be involved in the pathophysiology of sepsis. Melatonin, with its antioxidative and anti-inflammatory effects, is known to modulate the response to endotoxemia. In this paper, we investigated the circadian variation with or without melatonin administration in an experimental endotoxemia model based on lipopolysaccharide (LPS). ⋯ The results showed that the response induced by experimental endotoxemia was dependent on time of day. Melatonin administration modulated the inflammatory and oxidative stress responses induced by endotoxemia and also resulted in higher levels of antioxidants during daytime. The effect of circadian time on the endotoxemia response and possible modulatory effects of melatonin need further investigations in a human endotoxemia model.