Diurnal Variation in Energetic Arousal,Tense Arousal,and Hedonic Tone in Extreme Morning and Evening Types

The aim of the present study was to examine levels of energetic arousal (EA), tense arousal (TA), and hedonic tone (HT) in individuals with different circadian preferences. Subjects were males with extreme either morning (M‐type) or evening (E‐type) preferences (N=31), selected using the Morningness‐Eveningness Questionnaire cutoff points derived from the Polish population norms. They completed the UWIST Mood Adjective Check List every 1.5 h between 08:00 to 20:00 h in laboratory conditions. The obtained data showed higher levels of TA and lower levels of HT in E‐types over the whole day as compared to M‐types. As for EA, M‐types showed higher levels than E‐types between 08:00 to 17:00 h, but the two groups showed no differences during the later hours of the day. Both groups were found to exhibit similar diurnal patterns in TA and HT, and dissimilarity between M‐types and E‐types appeared in the daily course of EA. The results show the three‐dimensional model of mood is more advantageous in M‐types than in E‐types during the hours of typical human activity.     

Wise “birds” follow their clock: The role of emotional intelligence and morningness–eveningness in diurnal regulation of mood

Emotional intelligence (EI) and morningness–eveningness (M-E) preference have been shown to influence mood states. The present article investigates the way in which these two constructs may interact, influencing morning and evening mood levels. A sample of 172 participants completed a multidimensional mood scale measuring energetic arousal (EA), tense arousal (TA), and hedonic tone at 7:00 and at 22:00. As expected, morning and evening types experienced higher EA at their preferred time of day; effects of M-E on other mood dimensions were weaker. EI was found to correlate with lower TA, but the association was stronger at 22:00, perhaps reflecting the role of EI in managing the social events characteristic for the evening hours. An interactive effect of EI and M-E was found for both diurnal changes and morning levels of EA. Namely, in individuals higher in EI, there appeared a more marked synchrony effect between chronotype and EA, which was absent in those low in EI; individuals higher in EI showed more pronounced diurnal changes in EA characteristic for their chronotype (i.e., higher EA at morning hours in morning chronotypes; higher EA at evening hours in evening chronotypes), while in participants low in EI, diurnal changes in EA were smaller. Moreover, the characteristic positive association between morningness and EA during morning hours was apparent only in those high in EI. These findings suggest that individual differences in circadian variation in mood reflect several factors, including an endogenous rhythm in energy, the distribution of social activities throughout the day, and the person’s awareness of their own energy level.     

Diurnal changes of ERP response to sound stimuli of varying frequency in morning-type and evening-type subjects

In order to study the cognitive function rhythm related to the auditory frequency system for people who prefer to be active in the morning and at night, we conducted an experiment during morning (09:00), evening (17:00) and late-night (01:00) periods. On the basis of a morningness/eveningness questionnaire, six moderately morning-type subjects (M-types) and seven evening-type subjects (E-types) were selected. Diurnal variation of event-related potential (ERP) were assessed under low-frequency (250/500 Hz) and high-frequency (1000/2000 Hz) condition using an oddball task. M-types were tested during the morning (09:00) and evening (17:00) periods, and E-types were tested during the evening (17:00) and midnight (01:00) periods. Subjects were asked to press a button when the target stimulus was detected. We found that the P300 amplitude at 09:00 was significantly greater than that at 17:00 for M-types, was significantly greater at 17:00 than that at 01:00 for E-types. A significant difference of P300 latency and P300 amplitude was observed at 17:00 between M-types and E-types. The P300 amplitude obtained after a low-frequency stimulus was significantly greater than that after a high-frequency stimulus at 09:00 for M-types, and at 01:00 for E-types. These results revealed that stimulus frequency had effects on the diurnal changes of human cognitive function, and circadian typology had a direct effect on the diurnal change of human cognitive function. This study has extended the previous findings of auditory P300 studies on diurnal variations in terms of circadian typology and stimulus parameter.     

Daily light exposure in morning-type and evening-type individuals

Morning-type individuals (M-types) have earlier sleep schedules than do evening types (E-types) and therefore differ in their exposure to the external light-dark cycle. M-types and E-types usually differ in their endogenous circadian phase as well, but whether this is the cause or the consequence of the difference in light exposure remains controversial. In this study, ambulatory monitoring was used to measure 24-h light exposure in M-type and E-type subjects for 7 consecutive days. The circadian phase of each subject was then estimated in the laboratory using the dim-light melatonin onset in saliva (DLMO) and the core body temperature minimum (Tmin). On average, M-types had earlier sleep schedules and earlier circadian phases than E-types. They also showed more minutes of daily bright light exposure (> 1000 lux) than E-types. As expected, the 24-h patterns of light exposure analyzed in relation to clock time indicated that M-types were exposed to more light in the morning than E-types and that the reverse was true in the late evening. However, there was no significant difference when the light profiles were analyzed in relation to circadian phase, suggesting that, on average, the circadian pacemaker of both M-types and E-types was similarly entrained to the light-dark cycle they usually experience. Some M-types and E-types had different sleep schedules but similar circadian phases. These subjects also had identical light profiles in relation to their circadian phase. By contrast, M-types and E-types with very early or very late circadian phases showed large differences in their profiles of light exposure in relation to their circadian phase. This observation suggests that in these individuals, early or late circadian phases are related to relatively short and long circadian periods and that a phase-delaying profile of light exposure in M-types and a phase-advancing profile in E-types are necessary to ensure a stable entrainment to the 24-h day.     

Morning and evening-type differences in slow waves during NREM sleep reveal both trait and state-dependent phenotypes

Brain recovery after prolonged wakefulness is characterized by increased density, amplitude and slope of slow waves (SW, <4 Hz) during non-rapid eye movement (NREM) sleep. These SW comprise a negative phase, during which cortical neurons are mostly silent, and a positive phase, in which most neurons fire intensively. Previous work showed, using EEG spectral analysis as an index of cortical synchrony, that Morning-types (M-types) present faster dynamics of sleep pressure than Evening-types (E-types). We thus hypothesized that single SW properties will also show larger changes in M-types than in E-types in response to increased sleep pressure. SW density (number per minute) and characteristics (amplitude, slope between negative and positive peaks, frequency and duration of negative and positive phases) were compared between chronotypes for a baseline sleep episode (BL) and for recovery sleep (REC) after two nights of sleep fragmentation. While SW density did not differ between chronotypes, M-types showed higher SW amplitude and steeper slope than E-types, especially during REC. SW properties were also averaged for 3 NREM sleep periods selected for their decreasing level of sleep pressure (first cycle of REC [REC1], first cycle of BL [BL1] and fourth cycle of BL [BL4]). Slope was significantly steeper in M-types than in E-types in REC1 and BL1. SW frequency was consistently higher and duration of positive and negative phases constantly shorter in M-types than in E-types. Our data reveal that specific properties of cortical synchrony during sleep differ between M-types and E-types, although chronotypes show a similar capacity to generate SW. These differences may involve 1) stable trait characteristics independent of sleep pressure (i.e., frequency and durations) likely linked to the length of silent and burst-firing phases of individual neurons, and 2) specific responses to increased sleep pressure (i.e., slope and amplitude) expected to depend on the synchrony between neurons.     

Twenty-four hour rhythm of plasma prolactin in female rabbit pups. Correlation with hypothalamic and adenohypophysial dopamine, serotonin, gamma-aminobutyric acid and taurine content

Lactation in the rabbit is a nocturnal activity, extremely short and regular, that can be a strong synchronizer for the development of circadian rhythmicity in the pups. In the present study, 24-h rhythmicity of plasma prolactin and median eminence and anterior pituitary content of dopamine (DA), serotonin (5HT), gamma-aminobutyric acid (GABA) and taurine were examined in 11 days old female pups kept under 16 h light:8 h dark photoperiods (lights on at 08:00 h). Groups of six to seven female rabbit pups were killed by decapitation at six different time points throughout a 24-h cycle, starting at 09:00 h. Plasma prolactin levels changed significantly throughout the day, showing two peaks, one at first half of rest span (at 13:00 h) and another one at the beginning of the scotophase (at 01:00 h), just preceding doe visit. Median eminence DA content changed in a bimodal way as a function of time of day, displaying two maxima, at the beginning of the rest span and of the activity phase. Median eminence DA and plasma prolactin correlated significantly in an inverse way. Two maxima in median eminence 5HT levels were found, about 4 h in advance to the prolactin peaks. Circulating prolactin correlated inversely with median eminence 5HT content and directly with adenohypophysial 5HT content. Median eminence GABA content reached its maximum at the beginning of the scotophase and correlated significantly with plasma prolactin concentration. A positive correlation between plasma prolactin and adenohypophysial taurine content was observed. These results show that the circadian rhythmicity in prolactin secretory mechanisms in female rabbit pups develops during the early neonatal life.     

Women's sexual arousal: effects of high alcohol dosages and self-control instructions

The basic relationship between alcohol and women's sexual arousal – especially genital arousal – received little research attention for nearly 30 years (e.g. Wilson and Lawson, 1978) until very recently (e.g. George et al., 2009). To investigate hypotheses based on earlier findings and Alcohol Myopia Theory (AMT), two experiments evaluated the effects of high blood alcohol concentrations (BACs) and arousal instructional demands on indices of vaginal responding and self-reported sexual arousal. In Experiment 1, self-control instructions to maximize (versus suppress) arousal increased peak and average Vaginal Pulse Amplitude (VPA) change. Self-control also interacted with a target BAC of .08% (versus .00%) to influence latency to peak arousal onset: Intoxicated women instructed to maximize showed a shorter latency to peak arousal than did intoxicated women instructed to suppress; however, sober women showed an undifferentiated pattern. Also, in Experiment 1, the target BAC of .08% had no effect on VPA or subjective arousal measures. In Experiment 2, a target BAC of .10% (versus .00%) attenuated peak change and average change in VPA, but this dosage had no effects on latency to peak achieved arousal, or on subjective arousal. Instructions to maximize arousal (versus no instruction) had no effect on any arousal measures. Overall, among young moderate drinking women, alcohol had attenuating effects but only at the higher dosage. Maximize versus suppress instructions about arousal had predicted effects on arousal and interactive effects on latency, but only at the lower dosage. The findings highlight the importance of dosage and contextual factors in alcohol's impact on the variability of women's sexual responding.     

Diurnal variations in plasma ACTH, cortisol and beta-endorphin levels in cocaine addicts.

In order to establish possible alterations in the hypothalamic pituitary-adrenal axis and in ACTH-related opioids in cocaine addicts, plasma ACTH, cortisol and beta-endorphin levels were measured throughout the day in 9 cocaine addicts [age: 27 +/- 5 years (mean +/- SE); weight: 72 +/- 6.1 kg, duration of cocaine addiction: at least 2 years] on the day of their admission to a recovery community for drug abusers (first test) and after 15 days of abstinence (second test). Nine normal controls (age: 28 +/- 6 years; weight: 73 +/- 3.2 kg) were tested only once in a similar manner. Blood samples were taken at 06:00, 08:00, 10:00, 12:00, 18:00 and 20:00 h and served for hormonal assays. Urine samples were taken from cocaine addicts at 08:00 h on the experimental day and on the following day. Results of both urine assays were positive for cocaine catabolites, indicating cocaine administration during the day before the experimental test. From the day of their admission in the community (1st experimental day), the patients were forbidden to use cocaine. For 4 days after admission, they were treated with symptomatics to attenuate withdrawal symptoms. Thereafter, the patients underwent a washout period of pharmacological treatments for 10 days before being retested (second test). Urine samples taken at 08:00 h on this second experimental day and on the next day were negative for the presence of drug catabolites. During the first test, cocaine addicts showed higher plasma ACTH, cortisol and beta-endorphin levels than normal controls at all examined time points.(ABSTRACT TRUNCATED AT 250 WORDS)     

Diurnal variations of serum GM-CSF levels

We aimed to investigate the daily variations of serum granulocyte-macrophage colony-stimulating factor (GM-CSF) levels and to correlate them with peripheral blood cells counts. Venous blood samples from eleven healthy volunteers were taken four times a day, being at 08:00, 14:00, 20:00 and 02:00h and serum GM-CSF levels measured by ELISA. We could not find a significant overall difference among GM-CSF levels at four different times of the day using the Friedman test. On the other hand, serum GM-CSF levels at night (20:00h) were found to be significantly increased when compared to the morning levels (08:00h) using the Wilcoxon test (P=0. 022). The levels of lymphocytes and white blood cells (WBCs) at 20:00h were also higher than the morning levels (08:00h) as expected. While there was a strong relationship between the morning levels of GM-CSF (08:00h) and all measurements of peripheral blood cells during the day, the levels of GM-CSF measured at 02:00, 14:00 and 20:00h were found to be significantly correlated with only the WBC levels. It was concluded that there may be a significant difference between morning and night levels of GM-CSF and morning levels of GM-CSF may be more important in the regulation of WBC counts during the day. These variations warrant further studies about diurnal rhythms of haematopoiesis chronotherapy with CSFs.     

Diurnal variation in temperature, mental and physical performance, and tasks specifically related to football (soccer)

Football (soccer) training and matches are scheduled at different times throughout the day. Association football involves a variety of fitness components as well as psychomotor and game-related cognitive skills. The purpose of the present research, consisting of two separate studies, was to determine whether game-related skills varied with time of day in phase with global markers of both performance and the body clock. In the first study, eight diurnally active male association football players (19.1+/-1.9 yrs of age; mean+/-SD) with 10.8+/-2.1 yrs playing experience participated. Measurements were made on different days at 08:00, 12:00, 16:00, and 20:00 h in a counterbalanced manner. Time-of-day changes in intra-aural temperature (used as a marker of the body clock), grip strength, reaction times, flexibility (markers of aspects of performance), juggling and dribbling tasks, and wall-volley test (football-specific skills) were compared. Significant (repeated measures analysis of variance, ANOVA) diurnal variations were found for body temperature (p<0.0005), choice reaction time (p<0.05), self-rated alertness (p<0.0005), fatigue (p<0.05), forward (sit-and-reach) flexibility (p<0.02), and right-hand grip strength (p<0.02), but not left-hand grip strength (p=0.40) nor whole-body (stand-and-reach) flexibility (p=0.07). Alertness was highest and fatigue lowest at 20:00 h. Football-specific skills of juggling performance showed significant diurnal variation (p<0.05, peak at 16:00 h), whereas performance on the wall-volley test tended to peak at 20:00 h and dribbling showed no time-of-day effect (p=0.55). In a second study, eight diurnally active subjects (23.0+/-0.7 yrs of age) completed five test sessions, at the same times as in the first study but with a second session at 08:00 h. Test-re-test comparisons at 08:00 h for all components indicated good reliability. Intra-aural temperature showed a significant time-of-day effect (p<0.001) with mean temperature at 16:00 h (36.4 degrees C) higher than at 08:00 h (35.4 degrees C). There was no significant effect of chronotype on the temperature acrophase (peak time) (p>0.05). Diurnal variation was found for performance tests, including sit-and-reach flexibility (p<0.01) and spinal hyper-extension (p<0.05). Peaks occurred between 16:00 and 20:00 h and the daytime changes paralleled the temperature rhythm. Diurnal variation was also found for football-specific tests, including dribbling time (p<0.001, peak at 20:00 h) and chip test performance (p<0.01), being more accurate at 16:00 h (mean error=0.75 m) than at 08:00 h (mean error=1.01 m). Results indicate football players perform at an optimum between 16:00 and 20:00 h when not only football-specific skills but also measures of physical performance are at their peak. Body temperature peaked at a similar time, but positive mood states seemed to peak slightly earlier. While causal links cannot be established in these experiments, the results indicate that the diurnal variation of some aspects of football performance is affected by factor(s) other than body temperature alone.     

Diurnal Variation in Temperature,Mental and Physical Performance,and Tasks Specifically Related to Football (Soccer)

Football (soccer) training and matches are scheduled at different times throughout the day. Association football involves a variety of fitness components as well as psychomotor and game‐related cognitive skills. The purpose of the present research, consisting of two separate studies, was to determine whether game‐related skills varied with time of day in phase with global markers of both performance and the body clock. In the first study, eight diurnally active male association football players (19.1±1.9 yrs of age; mean±SD) with 10.8±2.1 yrs playing experience participated. Measurements were made on different days at 08:00, 12:00, 16:00, and 20:00 h in a counterbalanced manner. Time‐of‐day changes in intra‐aural temperature (used as a marker of the body clock), grip strength, reaction times, flexibility (markers of aspects of performance), juggling and dribbling tasks, and wall‐volley test (football‐specific skills) were compared. Significant (repeated measures analysis of variance, ANOVA) diurnal variations were found for body temperature (p<0.0005), choice reaction time (p<0.05), self‐rated alertness (p<0.0005), fatigue (p<0.05), forward (sit‐and‐reach) flexibility (p<0.02), and right-hand grip strength (p<0.02), but not left-hand grip strength (p=0.40) nor whole‐body (stand‐and‐reach) flexibility (p=0.07). Alertness was highest and fatigue lowest at 20:00 h. Football‐specific skills of juggling performance showed significant diurnal variation (p<0.05, peak at 16:00 h), whereas performance on the wall‐volley test tended to peak at 20:00 h and dribbling showed no time‐of‐day effect (p=0.55). In a second study, eight diurnally active subjects (23.0±0.7 yrs of age) completed five test sessions, at the same times as in the first study but with a second session at 08:00 h. Test‐re‐test comparisons at 08:00 h for all components indicated good reliability. Intra‐aural temperature showed a significant time‐of‐day effect (p<0.001) with mean temperature at 16:00 h (36.4°C) higher than at 08:00 h (35.4°C). There was no significant effect of chronotype on the temperature acrophase (peak time) (p>0.05). Diurnal variation was found for performance tests, including sit‐and‐reach flexibility (p<0.01) and spinal hyper‐extension (p<0.05). Peaks occurred between 16:00 and 20:00 h and the daytime changes paralleled the temperature rhythm. Diurnal variation was also found for football‐specific tests, including dribbling time (p<0.001, peak at 20:00 h) and chip test performance (p<0.01), being more accurate at 16:00 h (mean error=0.75 m) than at 08:00 h (mean error=1.01 m). Results indicate football players perform at an optimum between 16:00 and 20:00 h when not only football‐specific skills but also measures of physical performance are at their peak. Body temperature peaked at a similar time, but positive mood states seemed to peak slightly earlier. While causal links cannot be established in these experiments, the results indicate that the diurnal variation of some aspects of football performance is affected by factor(s) other than body temperature alone.     

Salivary cortisol concentration after high-intensity interval exercise: Time of day and chronotype effect

Due to personal and working necessities, the time for exercise is often short, and scheduled early in the morning or late in the afternoon. Cortisol plays a central role in the physiological and behavioral response to a physical challenge and can be considered as an index of exercise stress. Therefore, the aim of this study was to evaluate the influence of the circadian phenotype classification on salivary cortisol concentration in relation to an acute session of high-intensity interval exercise (HIIE) performed at different times of the day. Based on the morningness–eveningness questionnaire, 12 M-types (N = 12; age 21 ± 2 years; height 179 ± 5 cm; body mass 74 ± 12 kg, weekly training volume 8 ± 1 hours) and 11 E-types (N = 11; age 21 ± 2 years; height 181 ± 11 cm; body mass 76 ± 11 kg, weekly training volume 7 ± 2 hours) were enrolled in a randomized crossover study. All subjects underwent measurements of salivary cortisol secretion before (PRE), immediately after (POST), and 15 min (+15 min), 30 min (+30 min), 45 min (+45 min) and 60 min (+60 min) after the completion of both morning (08.00 am) and evening (08.00 p.m.) high-intensity interval exercise. Two-way analysis of variance with Tuckey’s multiple comparisons test showed significant increments over PRE-cortisol concentrations in POSTcondition both in the morning (4.88 ± 1.19 ng · mL^?1 vs 6.60 ± 1.86 ng · mL^?1, +26.1%, P < 0.0001, d > 0.8) and in the evening (1.56 ± 0.48 ng · mL^?1 vs 2.34 ± 0.37, +33.4%, P = 0.034, d > 0.6) exercise in all the 23 subject that performed the morning and the evening HIIE. In addition, during morning exercise, significant differences in cortisol concentration between M-types and E-types at POST (5.49 ± 0.98 ng · mL^?1 versus 8.44 ± 1.08 ng · mL^?1, +35%, P < 0.0001, d > 0.8), +15 min (4.52 ± 0.42 ng · mL^?1 versus 6.61 ± 0.62 ng · mL^?1, +31.6%, P < 0.0001, d > 0.8), +30 min (4.10 ± 1.44 ng · mL^?1 versus 6.21 ± 1.60 ng · mL^?1, +34.0%, P < 0.0001, d = 0.7), + 45 min (3.78 ± 0.55 ng · mL^?1 versus 5.80 ± 0.72 ng · mL^?1, +34.9%, P < 0.0001, d = 0.7), and + 60 min condition(3.53 ± 0.45 ng · mL^?1 versus 5.78 ± 1.13 ng · mL^?1, 38.9%, P = 0.0008, d = 0.7) were noted. No statistical significant differences between M-types and E-types during evening HIIE on post-exercise cortisol concentration were detected. E-types showed a higher morning peak of salivary cortisol respect to M-types when performing a HIIE early in the morning and produced higher salivary cortisol concentrations after the cessation of the exercise. Practical applications suggest that it is increasingly important for the exercise professionals to identify the compatibility between time of day for exercising and chronotype to find the individual’s favorable circadian time to perform a HIIE.     

TIME-OF-DAY EFFECTS ON THE INTERNAL SIMULATION OF MOTOR ACTIONS: PSYCHOPHYSICAL EVIDENCE FROM POINTING MOVEMENTS WITH THE DOMINANT AND NON-DOMINANT ARM

It is well known that circadian rhythms modulate human physiology and behavior at various levels. However, chronobiological data concerning mental and sensorimotor states of motor actions are still lacking in the literature. In the present study, we examined the effects of time-of-day on two important aspects of the human motor behavior: prediction and laterality. Motor prediction was experimentally investigated by means of imagined movements and laterality by comparing the difference in temporal performance between right and left arm movements. Ten healthy participants had to actually perform or to imagine performing arm-pointing movements between two targets at different hours of the day (i.e., 08:00, 11:00, 14:00, 17:00, 20:00, and 23:00?h). Executed and imagined movements were accomplished with both the right and left arm. We found that both imagined and executed arm pointing movements significantly fluctuated through the day. Furthermore, the accuracy of motor prediction, investigated by the temporal discrepancy between executed and imagined movements, was significantly better in the afternoon (i.e., 14:00, 17:00, and 20:00?h) than morning (08:00 and 11:00?h) and evening (23:00?h). Our results also revealed that laterality was not stable throughout the day. Indeed, the smallest temporal differences between the two arms appeared at 08:00 and 23:00?h, whereas the largest ones occurred at the end of the morning (11:00?h). The daily variation of motor imagery may suggest that internal predictive models are flexible entities that are continuously updated throughout the day. Likewise, the variations in temporal performance between the right and the left arm during the day may indicate a relative independence of the two body sides in terms of circadian rhythms. In general, our findings suggest that cognitive (i.e., mental imagery) and motor (i.e., laterality) states of human behavior are modulated by circadian rhythms. (Author correspondence: charalambos.papaxanthis@u-bourgogne.fr)     

Acute and delayed responses of C-reactive protein,malondialdehyde and antioxidant markers after resistance training session in elite weightlifters: Effect of time of day

The aim of this study was to investigate the effect of an Olympic-Weightlifting-session followed by 48-h recovery period on the oxidative and antioxidant parameters’ diurnal variation. Nine weightlifters (21?±?0.5 years) performed, in randomized order, three Olympic-Weightlifting-sessions at 08?h:00, 14?h:00 and 18?h:00. Blood samples were collected: at rest and 3?min and 48?h after each session. C-reactive protein (CRP), rate of lipid peroxidation and antioxidant activities were assessed. At rest, analysis of variance showed a significant time of day (TOD) effect (p?<?0.05) for uric acid, catalase and glutathione peroxidase with higher values at 14?h:00 and 18?h:00 compared with 08?h:00. However, no significant TOD effect for malondialdehyde, total bilirubin and CRP was observed. Given the profound changes (p?<?0.001) in the post-training session values, these diurnal variations have been altered immediately and even 48?h after the training sessions. Despite the significant decreases in the post-training values after the 48-h recovery period (p?<?0.05), levels of lipid peroxidation and enzymatic defense remained elevated (p?<?0.05) 48?h after the morning training session. However, after the afternoon and evening sessions, the same period was sufficient to return values to the baseline levels. In conclusion, the morning session seems to generate the most important acute and delayed lipid peroxidation responses. Therefore, weightlifting coaches should avoid scheduling their training sessions in the morning-hours.     

Control of birth in rats by RU 486, an antiprogesterone compound

Rats, isolated at mating (Day 1 of pregnancy), were submitted to either 8 h (8L:16D, Exp. I) or 14 h (14L:10D, Exp. II) of light daily with lights on from 12:00 h to 20:00 h and from 06:00 to 20:00 h respectively. In Exp. I, a single dose of RU 486 (10 mg in 0.2 ml ethanol) was given cutaneously at 08:00 h (Group A1), 12:00 h (Group B1), 19:00 h (Group C1) on Day 21 and at 08:00 h (Group D1) and 12:00 h (Group E1) on Day 22. In Exp. II, the same dose of RU 486 was given at 08:00 h (Group A2), 12:00 h (Group B2) and 19:00 h (Group C2) on Day 21. The solvent was given once at each of the preceding times to the control groups (T1 and T2) in both experiments. Groups T1 and T2 gave birth at two periods, the first on Day 22, the second on Day 23; the proportion of births during each of these periods depended on the light regimen (66.3% in 8L:16D; 50% in 14L:10D on Day 22). The distribution of births in Groups D1 and E1 treated on Day 22 were similar to their controls (T1). Rats treated on Day 21 (Groups A1, A2, B1, B2, C1, C2) gave birth over single periods on Day 22 after an interval correlated with the time of RU 486 administration. The earlier the treatment was given, the higher was the number of dead young and the lower the weight of live young 1 day after birth. These effects of prematurity did not impair further survival rates or weight at weaning.(ABSTRACT TRUNCATED AT 250 WORDS)     

Chronopharmacokinetic study of gentamicin in dogs

The purpose of this experiment was to determine whether the time of day of single intravenous doses of gentamicin affects the drug's pharmacokinetics in dogs maintained under a 12 h light (08:00 to 20:00 h), 12 h dark (20:00 to 08:00 h) cycle. Using a crossover design, 6 mixed-breed male dogs received a single dose of 2 mg/kg of gentamicin at 8:00 or 20:00 h. Serial blood samples were collected and pharmacokinetic parameters were calculated following each timed dose. The concentration of the antibiotic was lower following the 08:00 h compared to the 20:00 h administration. When gentamicin was administered at 20:00 h, the initial concentration, mean residence time, and area under the disposition curve were significantly higher (p < 0.05) and the apparent volume of distribution of the central compartment, apparent volume of distribution, apparent volume of distribution at steady-state, and total body clearance (1.73+/-0.55 at 20:00 h versus 3.31+/-0.67 L/min/kg at 08:00 h) were significantly lower than for the 08:00 h administration (p < 0.05). Our results show that the pharmacokinetics of gentamicin exhibits significant temporal variation when administered to dogs at different times of day.     

Adipokine levels are altered by shiftwork: a preliminary study

Shiftwork is often associated with metabolic diseases, and in the past few years, several cytokines have been postulated to contribute to various diseases, including insulin resistance. The aim of this study was to compare the concentrations of adiponectin, tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) in samples of young adult men exposed to a fixed (i) night shift (n = 9), working from 22:00 to 06:00 h; (ii) early morning shift (n = 6), working from 06:00 to 14:00 h; and (iii) day shift (n = 7), working from 08:00 to 17:00 h. The fixed night-shift and early-morning-shift samples were considered collectively as a shiftworker group given their work times. Blood samples were collected during the regular working day at 4-h intervals over the course of 24 h, thus totaling six samples. Morphological and physical activity parameters did not differ between the three groups. Total energy intake was lowest on the early morning shifts (p 相似文献   

The effects of feeding and housing on the behaviour of the laboratory rabbit

The effects of housing, feeding time and diet composition on the behaviour of the laboratory rabbit were examined. The animals were caged individually in single or double metal cages with perforated metal floors, metal walls, and bars in the front, or kept as a group in floor pens. The light/dark cycle was 12/12 h with light from 04:00 to 16:00 h and 30 min twilight. One experiment compared feeding equal energy levels of a high energy diet (10.1 MJ/kg) and with a low energy diet (7.0 MJ/kg) at 08:00 h. The second experiment compared feeding the high energy diet at 08:00 h and at 14:00 h. In both studies the behaviour of the rabbits was recorded between 08:00 and 14:00 h and between 16:00 and 22:00 h. Feeding the animals at 14:00 h reduced abnormal behaviour during the dark period compared to feeding at 08:00 h, whereas no difference in behaviour could be detected between feeding a high-energy and a low-energy diet at 08:00 h. Animals in floor pens generally showed less abnormal behaviour than caged animals. The results indicate that the welfare for caged rabbits can be improved by feeding the animals in the afternoon rather than in the morning.     

Chronopharmacokinetic Study of Gentamicin in Dogs

The purpose of this experiment was to determine whether the time of day of single intravenous doses of gentamicin affects the drug's pharmacokinetics in dogs maintained under a 12 h light (08:00 to 20:00 h), 12 h dark (20:00 to 08:00 h) cycle. Using a crossover design, 6 mixed‐breed male dogs received a single dose of 2 mg/kg of gentamicin at 8:00 or 20:00 h. Serial blood samples were collected and pharmacokinetic parameters were calculated following each timed dose. The concentration of the antibiotic was lower following the 08:00 h compared to the 20:00 h administration. When gentamicin was administered at 20:00 h, the initial concentration, mean residence time, and area under the disposition curve were significantly higher (p<0.05) and the apparent volume of distribution of the central compartment, apparent volume of distribution, apparent volume of distribution at steady‐state, and total body clearance (1.73±0.55 at 20:00 h versus 3.31±0.67 L/min/kg at 08:00 h) were significantly lower than for the 08:00 h administration (p<0.05). Our results show that the pharmacokinetics of gentamicin exhibits significant temporal variation when administered to dogs at different times of day.     

Aging and the circadian rhythm of melatonin: a cross-sectional study of Chinese subjects 30-110 yr of age

Although previous reports indicate that nocturnal plasma melatonin secretion declines with age, some recent findings do not support this point. In the present cross-sectional study, we documented serum melatonin concentrations at two time points, 02:00 and 08:00 h, in 144 persons aged 30-110 yr and found a significant age-related decline. It began around the age of 60 and reached a very significantly lower level in subjects in their 70s and over 80 yr of age (P < 0.01, when compared with age <60 yr). Nocturnal melatonin levels were higher among (post-menopausal only) women than men overall (P < 0.05). In the older age-groups, nocturnal melatonin levels did not differ between healthy controls and subjects with high blood pressure or ischemic heart disease. To further check these results, we also assessed the circadian pattern of serum melatonin in four subgroups of healthy men, aged 30-39, 40-49, 50-59, and 60-69 yr: blood samples were taken at 2 h intervals from 08:00 to 22:00 h and hourly from 22:00 to 08:00 h. Our results showed generally similar circadian melatonin patterns that peaked at night with very low levels during the daytime. No significant difference was found among the three younger groups, but nocturnal melatonin levels were significantly lower in the men in their 60s.