Removing Masking Factors from Urinary Rhythm Data in Humans

We have previously developed simple models that enable the exogenous and endogenous components of the circadian rhythm of body temperature to be separated. The present paper extends the method to urinary data. First, we have shown that the basic superiority of the two-component model over the one-component model persists when temperature data are converted into a format that is appropriate for urine sampling (that is, a single overnight sample and two-hourly samples during waking). Second, we provide normative endogenous data for urinary sodium, potassium and urate, data obtained from about 80 constant routines. These data are required for the two-component model. Third, we have compared the rate of adjustment to a simulated eastward time-zone transition of 8hr in 8 subjects. This showed that the rate of adjustment assessed by the two-component model was significantly less than that assessed by the one-component model and much closer to that assessed in separate experiments (n=15 subjects) using constant routines. We conclude that the two-component model can be used upon urinary data to give a closer approximation to the shift of the endogenous component, as assessed by constant routines, than can estimates that do not take into account the problem of masking caused by exogenous factors.     

Removing Masking Factors from Urinary Rhythm Data in Humans

We have previously developed simple models that enable the exogenous and endogenous components of the circadian rhythm of body temperature to be separated. The present paper extends the method to urinary data. First, we have shown that the basic superiority of the two-component model over the one-component model persists when temperature data are converted into a format that is appropriate for urine sampling (that is, a single overnight sample and two-hourly samples during waking). Second, we provide normative endogenous data for urinary sodium, potassium and urate, data obtained from about 80 constant routines. These data are required for the two-component model. Third, we have compared the rate of adjustment to a simulated eastward time-zone transition of 8hr in 8 subjects. This showed that the rate of adjustment assessed by the two-component model was significantly less than that assessed by the one-component model and much closer to that assessed in separate experiments (n=15 subjects) using constant routines. We conclude that the two-component model can be used upon urinary data to give a closer approximation to the shift of the endogenous component, as assessed by constant routines, than can estimates that do not take into account the problem of masking caused by exogenous factors.     

Application of Chaos Theory in Analyzing the Cardiac Rhythm in Healthy Subjects at Different Sleep Stages

The changes in the chaotic element of the cardiac rhythm (CR) were quantitated at different sleep stages by calculating the correlation dimension (D2) in 26 healthy subjects of both sexes (mean age 29.2 years), including 7 trained and 19 untrained subjects. Three untrained subjects took part in tests with autonomic nervous system blockers (atropine and propranolol). The study demonstrated a correlation between the changes in D2 at different sleep stages and the level of the autonomic regulation of CR. As the influence of the parasympathetic system on CR increased from one stage of slow wave sleep to another, D2 increased; during rapid eye movement (REM) sleep, this influence weakened and D2 decreased. The character of changes differed in the trained and untrained subjects and depended on the initial level of the autonomic regulation of CR. In the trained subjects, characterized by predominance of the parasympathetic regulation of CR, the initial and subsequent D2 values were higher than in the untrained subjects. Both during wakefulness and at all stages of sleep, D2 increased when the sympathetic regulation of CR was blocked, decreased when the parasympathetic regulation was blocked, and reached the lowest level when both of them were blocked. This showed that the chaotic element of CR, expressed numerically by D2, depends on the regulating effects of the autonomic nervous system.     

Circadian Rhythm in Plasma Noradrenaline of Healthy Sleep-Deprived Subjects

Under normal sleep-wake conditions, noradrenaline (NA) secretions in supine subjects exhibit a weak circadian variation with a peak that occurs around noon; the sleep span is characterized by reduced NA secretion. Some investigators have reported that the circadian NA rhythm is completely obliterated during sleep deprivation. In our laboratory, plasma NA was assayed every hour for 24 h in nine healthy men 20-23 years of age. All men were deprived of sleep and were required to eat and walk around every hour to prevent sleep. However, subjects remained supine for 20 min before blood samples were collected to eliminate the effect of activity. Persistence of a slight decrease in the night concentration in several subjects, despite sleep deprivation, suggests that NA secretion may be influenced by a biological clock whose activity becomes visible when the influence of posture is removed.     

Age-Related Circadian Rhythm of DHEAS Plasma Levels in Male Subjects

The aging influences the endocrine temporal structure, including DHEAS which can be considered as a biomarker of aging, since its levels gradually decrease in older subjects. The aim of this work was to observe the circadian rhythms of DHEAS, prolactin, cortisol and body temperature, in healthy elderly male subjects (73.7 ± 2.5 years) compared with healthy young subjects (27.2 ± 6.6 years). The results documented that in our subjects no significant age-related differences in prolactin levels existed. In elderly subjects cortisol levels were weakly enhanced in comparison with young subjects. DHEAS showed a preserved circadian rhythm, but markedly lower rhythm adjusted mean (74.38 ± 10.29 versus 273.63 ± 26.39) (p < 0.001) and decreased amplitude of oscillation (p < 0.001), when expressed as absolute value, in elderly subjects when compared with young subjects. In elderly subjects the DHEAS circadian rhythm modifications could represent an impairment of of the endocrine temporal structure.     

Wrist Skin Temperature,Motor Activity,and Body Position as Determinants of the Circadian Pattern of Blood Pressure

Although the circadian blood pressure (BP) pattern has been extensively studied, the determinants of this rhythm are not fully understood. Peripheral vasodilatation is a regulatory mechanism for BP maintenance. However, it remains to be established whether the increase of nocturnal distal skin temperature associated with heat loss could also reflect the dipping status. For the first time, this paper investigates the relationship between BP and skin wrist temperature (WT), to evaluate whether the WT circadian rhythm can serve as screening procedure to detect dipping/non-dipping BP patterns. In addition, the authors compare the relationship between WT and other variables previously described as determinants of the BP pattern, such as physical activity and body position. Measurements of WT, motor activity, and body position for 5 d, plus ambulatory BP for 24-h during that span, were obtained from 28 diurnally active normotensive volunteers. WT was negatively correlated, whereas activity and body position were positively correlated, with systolic and diastolic BPs. However, these relationships were stronger during the rest than activity phase. In addition, a 78.6% concordance was detected between the observed dips in BP and the predicted BP pattern calculated based on the WT rhythm. Thus, these results suggest that the increase in WT produced by heat loss during the rest phase through peripheral skin blood vessels is the result of blood vessel vasodilatation reflexes in response to a shift from a standing to a supine position, together with shift in the circadian sympathetic/parasympathetic balance (nocturnal parasympathetic activation). In conclusion, WT could be considered as a potential new screening procedure to implement the diagnosis of non-dipping BP pattern. (Author correspondence: angerol@um.es)     

Estimation of Boron Intake and its Relation with Bone Mineral Density in Free-Living Korean Female Subjects

In this study, the status of boron intake was evaluated and its relation with bone mineral density was examined among free-living female subjects in Korea. Boron intake was estimated through the use of the database of boron content in frequently consumed foods by Korean people as well as measuring bone mineral density, taking anthropometric measurements, and surveying dietary intake of 134 adult females in order to relatively evaluate the intake of boron as a nutrient to supplement the low level of calcium intake and to verify its relationship with bone mineral density. Average age, height, and weight of the subjects were respectively 40.84 years, 157.62 cm and 59.70 kg. Also, average bone mineral density of lumbar spine L1–L4 and average bone mineral density of the femoral neck were 0.92 g/cm² and 0.80 g/cm², respectively. Their average intakes of energy and boron per day were 6,538.53 kJ and 926.94 μg. Intake of boron through vegetables, fruits, and cereals accounted for 61.72% of the overall boron intake. The food item that contributed most to their daily boron intake was rice. Also, 65.41% of overall boron intake was from 30 varieties of other food items, such as soybean paste, soybeans, red beans, watermelons, oriental melons, pears, Chinese cabbage Kimchi, soybean sprouts and soybean milk, etc. Boron intake did not show significant relation to bone mineral density in lumbar vertebra and femoral region. In summary, the average daily intake of boron was 926.94 μg and did not display significant relation to bone mineral density in 134 free-living female subjects. The continuous evaluation of boron consumption by more diverse targets will need to be conducted in the future.     

The Effect of Activity on the Waking Temperature Rhythm in Humans

Nine healthy female subjects were studied when exposed to the natural light-dark cycle, but living for 17 “days” on a 27h day (9h sleep, 18h wake). Since the circadian endogenous oscillator cannot entrain to this imposed period, forced desynchronization between the sleep/activity cycle and the endogenous circadian temperature rhythm took place. This enabled the effects of activity on core temperature to be assessed at different endogenous circadian phases and at different stages of the sleep/activity cycle. Rectal temperature was measured at 6-minute intervals, and the activity of the nondominant wrist was summed at 1-minute intervals. Each waking span was divided into overlapping 3h sections, and each section was submitted to linear regression analysis between the rectal temperatures and the total activity in the previous 30 minutes. From this analysis were obtained the gradient (of the change in rectal temperature produced by a unit change in activity) and the intercept (the rectal temperature predicted when activity was zero). The gradients were subjected to a two-factor analysis of variance (ANOVA) (circadian phase/ time awake). There was no significant effect of time awake, but circadian phase was highly significant statistically. Post hoc tests (Newman-Keuls) indicated that gradients around the temperature peak were significantly less than those around its trough. The intercepts formed a sinusoid that, for the group, showed a mesor (±SE) of 36.97 (±0.12) and amplitude (95% confidence interval) of 0.22°C (0.12°C, 0.32°C). We conclude that this is a further method for removing masking effects from circadian temperature rhythm data in order to assess its endogenous component, a method that can be used when subjects are able to live normally. We suggest also that the decreased effect of activity on temperature when the endogenous circadian rhythm and activity are at their peak will reduce the possibility of hyperthermia.     

Changes in Body Temperature Rhythm after Traumatic Brain Injury

We performed this study to determine whether in head injured patients body temperature rhythmicity exists outside the usual spectrum. Temperature data of in total 22 patients with head injury were analyzed using the Regressive and Iterative Cosinor methods. We found that circadian rhythm often remained, and usually was combined with rhythms in ultradian or infradian ranges. Tau shifts over consecutive days were observed in three severely head injured patients (Glasgow Coma Scale score ≤ 8). To validate the results we used surrogate data. Detection of temperature rhythms in this study may serve to estimate the clinical importance of biological rhythms in head injury.     

Changes in Body Temperature Rhythm after Traumatic Brain Injury

We performed this study to determine whether in head injured patients body temperature rhythmicity exists outside the usual spectrum. Temperature data of in total 22 patients with head injury were analyzed using the Regressive and Iterative Cosinor methods. We found that circadian rhythm often remained, and usually was combined with rhythms in ultradian or infradian ranges. Tau shifts over consecutive days were observed in three severely head injured patients (Glasgow Coma Scale score ≤ 8). To validate the results we used surrogate data. Detection of temperature rhythms in this study may serve to estimate the clinical importance of biological rhythms in head injury.     

Paradoxical Masking Effects of Bright Photophase and High Temperature in Drosophila malerkotliana

Synergic contribution of light and temperature is known to cause a paradoxical masking effect (inhibition of activity by bright light and high temperature) on various rhythms of animals. The present study reports the paradoxical masking effects of 1000-lux photophase at 25°C on the locomotor activity rhythm of Drosophila malerkotliana. Flies were subjected to light (L)-dark (D) 12:12 cycles wherein the photophase was varied from 10 to 1000 lux, whereas the scotophase was set to 0 lux in these and subsequent LD cycles. At 10, 100, and 500 lux, the flies were diurnal; however, at 1000 lux they were nocturnal. Transfer from LD 12:12 cycles to continuous darkness (DD) initiated free-running rhythmicity in all flies. Free-running rhythms of the flies switched from the 10-lux to the 500-lux groups started from the last activity-onset phase of the rhythm following 3–5 transient cycles, suggesting involvement of the circadian pacemaker. In contrast, the free-running rhythm of the flies of the 1000-lux group began abruptly from the last lights-on phase of the LD cycle, indicating noninvolvement of the pacemaker. Furthermore, all flies showed nocturnal activity in the two types of LD 12:12 cycles when the photophase was 1000 lux. The first type of LD cycles had three succeeding photophases of 100, 1000, and again 100 lux, whereas the second type of LD cycles had only one photophase of 1000 lux, but the LD 12:12 cycles were reversed to DL 12:12 cycles. Apparently, the combined effects of light and temperature caused such paradoxical masking effects. This hypothesis was tested by repeating the above experiments at 20°C. Flies in all experiments exhibited a diurnal activity pattern, even when the photophase was 1000 lux. Thus, the present study demonstrates that the paradoxical masking effect in D. malerkotliana was caused by the additive influence of light intensity and temperature. This strategy appears to have physiological significance, i.e., to shun and thus protect against the bright photophase at high temperature in the field. (Author correspondence: drdsjoshi08@gmail.com)     

Effects of Work and Orcadian Rhythm on Bus Drivers' Oral Temperature

The results described in this paper originate from a research project aiming at the development of a useful measuring instrument which can demonstrate the effect of work and work circumstances on the task performer. Among other physiological (and psychometric) variables, oral temperature data were obtained from eight younger and eight older bus drivers working in various shifts. Measurements were performed in an experimental design under standardized conditions in a mobile laboratory before starting, during some rest intervals, and after finishing work. The same measurements were performed on the bus drivers in a control condition at corresponding times on a day off. The results indicated that only during the working days a temperature pattern could be detected resembling the data found in the literature (low in the morning, a maximum in the late afternoon, then a decline). No clear pattern was discernible on work-free days. On working days the mean oral temperature values were significantly higher at corresponding hours of the day. Upward deviations of the temperature pattern were found before starting work (but also at the beginning of the day off), while lower values were obtained after finishing work (especially in the shifts starting in the morning). These results might be interpreted in terms of interaction between circadian rhythm and activating and de-activating tendencies connected with (structured) daily activities.     

Disorders of Orcadian Body Temperature Rhythm in Severely Brain-Damaged Patients

Twenty-four hour patterns of body temperature (BT) were recorded during consecutive 3-10 day spans from 14 severely brain-damaged patients. Seven patients exhibited a normal circadian BT rhythm with an amplitude of more than 1°C and a normal phase position of the minimum BT being observed during the latter half of the nocturnal sleep. One patient with a dispersed type of sleep exhibited an extremely low amplitude of the BT rhythm with mean average 0.69°C. In this patient, an 24-hr observation span was insufficient to detect the existence of a BT rhythm. Two patients manifested disturbance of period. As acrophase of the BT rhythm varied from day to day, the standard deviation (S.D.) of mean acrophase wasextremely large. For these patients the light-dark cycle did not act as an entrainer because both had visual disturbance. A phase advance of the minimum BT was observed in four patients. The minimum BT appeared in the first half of nocturnal sleep. These three disturbances (amplitude, period and phase), were revealed only by longitudinal observation of the BT rhythm, indicating the importance of long-term observations over a sufficient period to make the nature of the rhythm disturbances clear. These disturbances were not related to that of the sleep-wake cycle, as two patients showed normal circadian BT rhythm in spite of their dispersed-type sleep.     

Effects of Work and Orcadian Rhythm on Bus Drivers' Oral Temperature

The results described in this paper originate from a research project aiming at the development of a useful measuring instrument which can demonstrate the effect of work and work circumstances on the task performer. Among other physiological (and psychometric) variables, oral temperature data were obtained from eight younger and eight older bus drivers working in various shifts. Measurements were performed in an experimental design under standardized conditions in a mobile laboratory before starting, during some rest intervals, and after finishing work. The same measurements were performed on the bus drivers in a control condition at corresponding times on a day off. The results indicated that only during the working days a temperature pattern could be detected resembling the data found in the literature (low in the morning, a maximum in the late afternoon, then a decline). No clear pattern was discernible on work-free days. On working days the mean oral temperature values were significantly higher at corresponding hours of the day. Upward deviations of the temperature pattern were found before starting work (but also at the beginning of the day off), while lower values were obtained after finishing work (especially in the shifts starting in the morning). These results might be interpreted in terms of interaction between circadian rhythm and activating and de-activating tendencies connected with (structured) daily activities.     

Risk Factors of Cardiovascular Diseases and the Capillary Endothelium in Subjects with Different Levels of Normal Blood Pressure

The capillary circulation in the forearm and crus was studied by occlusion plethysmography at rest and upon stimulation with nitric oxide during reactive hyperemia in 249 virtually healthy subjects with different levels of arterial blood pressure lower than 140/90 mm Hg. Specific features of the microcirculation were found in the forearm and crus depending on the blood pressure level. An increase in the blood pressure higher than 120/80 mm Hg was associated with an increased adverse effect of integral risk factors and heredity on parameters of the capillary circulation, especially in women.     

Variation in Meals and Sleep-Activity Patterns in Aged Subjects; its Relevance to Orcadian Rhythm studies

The study was performed upon a sample of aged and non-institutionalized subjects. Information was obtained by questionnaires and diaries on personal factors during a typical week. A random subset was subjected to a more detailed analysis of the composition of their meals.

Results showed that increasing age was correlated with: a decreased day-by-day variability in an individual's time of retiring, rising and eating meals; earlier sleep times; increased frequency of daytime naps and nocturnal awakenings; and decreased physical activity. These results occurred both in subjects living alone and in those living with company. Day-by-day differences in the composition of meals tended to decrease with age. When differences between individuals were considered then these tended to increase with age.

Some implications of these findings for studies of circadian rhythmicity in aged subjects-in whom the timing of circadian rhythms becomes more erratic and amplitude falls-are discussed.     

Circadian Rhythm of Temperature Preference and Its Neural Control in Drosophila

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Highlights? We identify a novel circadian behavior in flies, temperature preference rhythm (TPR) ? Drosophila TPR follows a similar pattern as body temperature rhythm in humans ? Drosophila TPR is regulated independently from circadian locomotor activity ? TPR is controlled by a newly identified DN2-based pacemaker circuit in the brain     

Temperature Regulation of Anthocyanin Accumulation in Apple Skin

The regulation of anthocyanin accumulation in apple skin (cv.Jonathan) by temperature was studied. In the field the increasein anthocyanin in the skin before harvest coincided with decreasingtemperatures and with increasing ethylene production by thefruit. In detached apples held under continuous white light,the optimum temperatures for anthocyanin accumulation were 12°C in unripe apples and 16–24 °C in ripe apples.These effects were explained by corresponding changes in thelevel of phenylalanine ammonia-lyase (PAL), a key enzyme offlavonoid synthesis. PAL levels were higher at low than at hightemperatures and higher in ripe than in unripe apples. In intermittentlight the effects of temperature were similar but levels ofPAL and anthocyanin were lower, particularly in unripe apples.It is concluded that temperature, in conjunction with ripeningand light, is an important factor regulating anthocyanin accumulationand that its effects are mediated by effects on the level ofPAL activity. Key words: Apple, Anthocyanin, Phenylalanine ammonia-lyase     

Modeling the Effect of Spontaneous Activity on Core Temperature in Healthy Human Subjects

Nine healthy females were studied about the time of the spring equinox, while living in student accommodation and aware of the passage of solar time. After 7 control days, during which a conventional lifestyle was lived, subjects underwent a 24-h ‘constant routine’, followed by 17 ‘days’ on a 27-h ‘day’ (9 h sleep and 18 h wake). Throughout the experiment, regular recordings of (non-dominant) wrist activity (every 30 s) and rectal temperature (every 6 min) were made. Only the control and 27-h (experimental) ‘days’ have been analysed in the present report. From each subject, 24-h profiles of raw temperature (consisting of 240 points) were obtained: one (control days), by averaging the control days; the other (experimental days), by conflating 16 consecutive 27-h ‘days’. Activity data were first collected into 240 points by summing them over 6-min intervals; they were then converted into three data sets (each of 240 points) for control and, separately, for experimental days. These data sets were summed activities in the previous 18 min (A18), summed activity over the previous 18–30 min (A30), and summed activity over the previous 30–42 min (A42). The raw temperature data sets for control and experimental days were sepa-rately analysed by ANCOVA using two time-of-day factors: ‘hours’ (24 levels) and ‘six-minute-intervals’ (10 levels). The covariate was the three activity data sets; in order to make the analysis more versatile, a cubic polynomial model was used, with a linear, quadratic and cubic term for each of these activity data sets. Moreover, the effects of activity upon core temperature were separately assessed for four 6-h sections of the 24-h profile, centred on its low, rising, high and falling phases. The main results were as follows: 1. All three activity data sets made significant contributions to the model, but that by the A30 data set was the most powerful of the three. This supports the use of activity files covering the previous 30 min in other ‘purification’ methods. 2. Although the linear term was the one that was significant most frequently, quadratic and (negative) cubic terms were also present on several occasions. This result indicates that the effect of activity upon core temperature can be approximated by a linear function (as has been done in other ‘purification’ models), but that, with wider ranges of activity, a sigmoid curve would be more accurate, indicative of the process of thermoregulation. 3. During the experimental days, the effect of activity upon temperature was greater in the rising than the falling temperature phase, and greater in the low than in the high phase. These results are predicted from current understanding of the circadian rhythm of thermoregulation. 4. During control days, the effects of activity were more complex, probably due to the factors that were present at some, but not all, phases — factors such as sleep, meals, changes in posture, lighting, and so on. 5. The ANCOVA also enabled the temperature profiles, corrected for the effects of activity (and, therefore, to be considered as ‘purified’), to be displayed. We conclude that the use of ANCOVA to tackle the problem of ‘purifying’ raw temperature data is a promising one. So far, it has produced results that accord with those from other ‘purification’ methods and with predictions based on our current understanding of the circadian rhythm of thermoregulation.