Search results for "circadian rhythm"
showing 10 items of 324 documents
Memory performance is related to the cortisol awakening response in older people, but not to the diurnal cortisol slope
2015
There are large individual differences in age-related cognitive decline. Hypothalamic-pituitary-adrenal axis (HPA-axis) functioning has been suggested as one of the mechanisms underlying these differences. This study aimed to investigate the relationships between the diurnal cortisol cycle, measured as the cortisol awakening response (CAR), and the diurnal cortisol slope (DCS) and the memory performance of healthy older people. To do so, we assessed the verbal, visual, and working memory performance of 64 participants (32 men) from 57 to 76 years old who also provided 14 saliva samples on two consecutive weekdays to determine their diurnal cortisol cycle. The CAR was linearly and negatively…
Increase in cortisol concentration due to standardized bright and blue light exposure on saliva cortisol in the morning following sleep laboratory
2020
Research studies on LED light exposure and cortisol are inconsistent and not comparable due to different types of light, exposure times, and sample sizes. Therefore, one hour of standardized exposure LED light at different intensities and the spectral composition during the post-awakening phase at 7:30 were compared. A sample of 23 (Study 1) and 26 (Study 2) healthy males were randomly assigned to: 1) bright white light (414 lux) and 2) dim darkened light (2 lux) as well as 3) red light (235 lux) and 4) blue light (201 lux) exposure conditions. Results from repeated measures ANOVA confirm that light exposure affects the cortisol concentration. Study 1 revealed an increase in the saliva cort…
Relationship between Cortisol Changes during the Night and Subjective and Objective Sleep Quality in Healthy Older People
2020
The aim of this study was to investigate whether the nighttime cortisol release was associated with subjective and objective sleep quality and the discrepancy between them. Forty-five healthy older adults (age range from 56 to 75 years) collected salivary samples immediately before sleep and immediately after awakening on two consecutive nights. Actigraphy was used to assess objective sleep quality and quantity. A sleep diary was used to assess subjective sleep quality. Linear mixed models were performed using subjective and objective sleep quality data from 76 nights to investigate between-subject associations. We observed that larger changes in cortisol levels between sleep onset and awak…
Mortality from cancer and other causes in commercial airline crews: a joint analysis of cohorts from 10 countries.
2014
Background Commercial airline crew is one of the occupational groups with the highest exposures to ionising radiation. Crew members are also exposed to other physical risk factors and subject to potential disruption of circadian rhythms. Methods This study analyses mortality in a pooled cohort of 93 771 crew members from 10 countries. The cohort was followed for a mean of 21.7 years (2.0 million person-years), during which 5508 deaths occurred. Results The overall mortality was strongly reduced in male cockpit (SMR 0.56) and female cabin crews (SMR 0.73). The mortality from radiation-related cancers was also reduced in male cockpit crew (SMR 0.73), but not in female or male cabin crews (SMR…
Electrophysiological evidence for circadian rhythmicity in a mammalian pineal organ
1980
Long-term electrophysiological recordings from the guinea-pig pineal organ show that three types of intrinsic cells can be distinguished: (i) Cells showing constant firing rates over periods of up to 24 hours. (ii) Cells which are highly active during the day and show a low firing rate during the night. (iii) Cells which exhibit low activity during the day and enhanced activity during the night; these cells can be strongly inhibited by 1 min of light given during the night. Both the light- and darkness-activated cells show activity patterns which closely follow season-dependent differences in day- and night-lengths. In addition, both cell types show an oscillatory pattern in maintained acti…
Involvement of cyclic guanosine monophosphosphate (cGMP) and cytosolic guanylate cyclase in the regulation of synaptic ribbon numbers in rat pineal g…
1992
In the rat pineal gland N-acetyltransferase (NAT) activity and synaptic ribbon (SR) numbers display a circadian rhythm. It is well-known that NAT activity is regulated by adrenergic mechanisms involving cyclic adenosine monophosphate (cAMP) as a second messenger. However, the mechanism involved in the regulation of SR numbers has not been established so far. In the present in vitro study, we have investigated the effects of 8-bromo-cyclic guanosine monophosphate (8-bromo-cGMP), a cyclic guanosine monophosphate (cGMP) analog, and stimulation of guanylate cyclase on SR numbers. Incubation with 8-bromo-cGMP increased SR numbers in a dose- and time-dependent manner. Further, stimulation of the …
The impact of the degree of obesity on the discrepancies between office and ambulatory blood pressure values in youth.
2006
Objectives Obesity is an increasingly frequent problem among children and adolescents, and may lead to blood pressure (BP) increase. The aim of the present study was to assess the prevalence of hypertension, white-coat and masked hypertension in obese adolescents making systematic use of both office BP and 24-h ambulatory BP measurement. The impact of different degrees of obesity on BP and heart rate variability was also investigated. Methods Office and ambulatory BP were obtained in 285 overweight and obese Caucasian adolescents (11–18 years old) and in 180 age- and sex-matched controls. The extent of obesity was quantified using body mass index z score. Results A significant positive rela…
The impact of birth weight on pulse pressure during adolescence
2004
Background The objective was to study the influence of birth weight on office and ambulatory pulse pressure. Methods and results Three hundred healthy children (176 girls), aged 10–18 years, born at term after a normotensive pregnancy were included. The subjects were divided according to birth weight: 2.000–2.500 kg, 2.501–3.000 kg, 3.001–3.500 kg and >3.500 kg. For each subject, office and 24-h ambulatory blood pressure monitoring were performed according to the protocol designed. There were significant differences among groups in 24-h ambulatory systolic blood pressure, and pulse pressure (PP). No differences were observed in terms of sex, current age, weight and height. Using a multiple …
Day/night changes of pineal gland volume and pinealocyte nuclear size assessed over 10 consecutive days
1984
Previous studies aimed at elucidating day/night changes of pineal gland size and pinealocyte nuclear volume have yielded contradictory results. The aim of the present investigation was to examine the above parameters over a period of 10 successive days, at 6-hour intervals under a lighting regimen of LD 12:12 (7 a.m. to 7 p.m.). It was found that changes in pineal gland volume could not be correlated with the light/dark phases; instead, a rhythm with a two-day period was encountered. Pinealocyte nuclear volume, by contrast, showed clear circadian changes, exhibiting troughs during photophase and peaks during scotophase. In this experimental series, the karyometric results conformed to the m…
The COPD multi-dimensional phenotype: A new classification from the STORICO Italian observational study.
2019
BackgroundThis paper is aimed to (i) develop an innovative classification of COPD, multi-dimensional phenotype, based on a multidimensional assessment; (ii) describe the identified multi-dimensional phenotypes.MethodsAn exploratory factor analysis to identify the main classificatory variables and, then, a cluster analysis based on these variables were run to classify the COPD-diagnosed 514 patients enrolled in the STORICO (trial registration number: NCT03105999) study into multi-dimensional phenotypes.ResultsThe circadian rhythm of symptoms and health-related quality of life, but neither comorbidity nor respiratory function, qualified as primary classificatory variables. Five multidimension…