Timing of food intake during simulated night shift impacts glucose metabolism: A controlled study

Eating during the night may increase the risk for obesity and type 2 diabetes in shift workers. This study examined the impact of either eating or not eating a meal at night on glucose metabolism. Participants underwent four nights of simulated night work (SW1–4, 16:00–10:00 h, <50 lux) with a daytime sleep opportunity each day (10:00–16:00 h, <3 lux). Healthy males were assigned to an eating at night (NE; n = 4, meals; 07:00, 19:00 and 01:30 h) or not eating at night (NEN; n = 7, meals; 07:00 h, 09:30, 16:10 and 19:00 h) condition. Meal tolerance tests were conducted post breakfast on pre-night shift (PRE), SW4 and following return to day shift (RTDS), and glucose and insulin area under the curve (AUC) were calculated. Mixed-effects ANOVAs were used with fixed effects of condition and day, and their interactions, and a random effect of subject identifier on the intercept. Fasting glucose and insulin were not altered by day or condition. There were significant effects of day and condition × day (both p < 0.001) for glucose AUC, with increased glucose AUC observed solely in the NE condition from PRE to SW4 (p = 0.05) and PRE to RTDS (p < 0.001). There was also a significant effect of day (p = 0.007) but not condition × day (p = 0.825) for insulin AUC, with increased insulin from PRE to RTDS in both eating at night (p = 0.040) and not eating at night (p = 0.006) conditions. Results in this small, healthy sample suggest that not eating at night may limit the metabolic consequences of simulated night work. Further study is needed to explore whether matching food intake to the biological clock could reduce the burden of type 2 diabetes in shift workers.     

Diurnal variations of postural stability and attentional capacities in 5–6-year-old tennis players

The present study aimed to investigate the diurnal variation of postural stability, attentional capacities, and oral temperature in 5–6-year-old tennis players. A total of 24 young children were divided into two groups: Twelve tennis players with 2 years of training experience and twelve sedentary children without previous experience in any type of sport. They were asked to maintain an upright bipedal stance on a static force platform with eyes open (EO) and eyes closed (EC) at 07:00, 10:00, 14:00, and 18:00 h. Postural stability was evaluated by the center of pressure (CoP), surface area (CoP_Area), CoP mean velocity (CoP_Vm), and Romberg’s index (RI). Oral temperature and simple reaction time (SRT) were also recorded at the beginning of each test session. Postural stability in 5–6-year-old tennis players was low at 07:00 h and improved at 10:00 h (p < 0.001); then, it worsened at 14:00 h (p < 0.001) and improved again at 18:00 h (p < 0.001) as found in sedentary children. This rhythm was also close to that of SRT in both groups. Body temperature increased significantly (p < 0.001) from the morning to the afternoon in both groups. However, the peak of postural performance, the peak of attentional capacities, and the greatest vision contribution to maintain balance observed at 18:00 h were only found in the trained group. Moreover, young tennis players were more stable (p < 0.001) and more attentive (p < 0.01) than sedentary ones at 18:00 h. The amplitude of the diurnal rhythm of CoP parameters was significantly larger (p < 0.01) in trained children compared to sedentary ones (43.1 ± 8.5 vs 31.7 ± 8.3 for the CoP_Area; 27.5 ± 7.4 vs 17.7 ± 8.2 for the CoP_Vm). Therefore, time-of-day has a significant effect on static postural stability and attentional capacities in young tennis players with better performances in the late afternoon (habitual hour of training). Thus, we recommend planning some training sessions at 07:00 and/or 14:00 h to optimize postural stability at the time of its batyphase and to reduce the incidence of fall-related injury risks during this critical age in athletic environments.     

Activity,sleep and ambient light have a different impact on circadian blood pressure,heart rate and body temperature rhythms

The aim of the present study was to investigate the impact of endogenous and exogenous factors for the expression of the daily rhythms of body temperature (BT), blood pressure (BP) and heart rate (HR). One hundred and seventy-three young adults (YA), 17–24 years old (y.o.), of both genders were studied under a modified constant-routine (CR) protocol for 26 h. Participants were assigned randomly to groups with different lighting regimens: CR-LD, n = 77, lights (>400 l×) on from 09:00 to 17:00 h and off (<10 l×) from 17:00 to 09:00 next morning; CR-LL, n = 81, lights on (>400 l×) during the whole experimental session; CR-DD, n = 15, constant dim light (<10 l×) during the whole experiment. Systolic (SBP) and diastolic (DBP) BP, HR and BT were measured every 2 h. For comparison, the results of the former studies performed under conditions of regular life with an activity period from 07:00 to 23:00 h and sleep from 23:00 till 07:00 h (Control) were reanalyzed. Seven-day Ambulatory Blood Pressure Monitoring (ABPM) records from 27 YA (16–38 y.o.) and BT self-measurement data from 70 YA (17–30 y.o.) taken on ≥ 3 successive days at 08:00, 11:00, 14:00, 17:00, 20:00, 23:00 and 03:00 were available.

The obtained daily patterns were different between Control and CR-DD groups, due to effects of activity, sleep and light. The comparison of Control and CR-LD groups allowed the effects of sleep and activity to be estimated since the lighting conditions were similar. The activity level substantially elevated SBP, but not DBP. Sleep, on the other hand, lowered the nighttime DBP, but has no effect on SBP. HR was affected both by activity and sleep. In accordance with previous studies, these results confirm that the steep BP increase in the morning is not driven by the circadian clock, but rather by sympathoadrenal factors related to awakening and corresponding anticipatory mechanisms. The effect on BT was not significant.

To investigate the impact of light during the former dark time and darkness during the former light time, the CR-LL and CR-DD groups were each compared with the CR-LD group. Light delayed the evening decrease of BT, most likely via a suppression of the melatonin rise. Besides, it had a prominent arousal effect on SBP both in the former light and dark phases, a moderate effect on DBP and no effect on HR. Darkness induced decline in BT. BP values were decreased during the former light time. No effects on HR were found. Altogether, the results of the present paper show that BT, BP and HR are affected by exogenous factors differently. Moreover, the effect was gender-specific. Especially, the response of BT and BP to ambient light was evident only in females.

We suppose that the distinct, gender-specific responses of SBP, DBP and HR to activity, sleep and ambient light do reflect fundamental differences in the circadian control of various cardiovascular functions. Furthermore, the presented data are important for the elaboration of updated reference standards, the interpretation of rhythm disorders and for personalized chronotherapeutic approaches to prevent adverse cardiovascular events more effectively.     

Effect of time of day on soccer specific skills in children: psychological and physiological responses

The aim of this study was to examine the effect of time of day on soccer-specific skills and physiological and psychological parameters in children. Ten male children soccer players (age: 14.6?±?0.8 years; height: 1.63?±?0.4 m; body mass: 52.5?±?4.9 kg) performed two shooting accuracy tests before and after a 10?×?20-m dribbling sprint test with 20-s of passive recovery between repetitions. The measurements were taken at 08:00 h, 13:00 h, and 17:00 h in a randomized order. Mean heart rate (HR) was monitored during the dribbling test. At the beginning of each test session, blood pressure and intra-aural temperature were measured. Likewise, children were asked to complete the profile of mood state (POMS) and the Hooper Index questionnaires. Lactate concentration ([La]) was recorded at rest, post-fifth recovery periods and post-second accuracy test. Moreover, they indicate their rating of perceived exertion (RPE) score immediately at the end of each test session. The results of this study showed that dribbling performance was higher at 13:00 h and 17:00 h in comparison with 08:00 h (p?p?r?=?0.6, p?相似文献   

Environmental stress of mobile phone EM radiation on locomotor activity and melatonin circadian rhythms of rats

Biological clocks are innate timing mechanisms that regulate many behavioral and physiological parameters in most organisms. In our modern life, heavy use of mobile phones (MPs) exerts a massive stress on organisms because their electromagnetic radiation usually results in varying degrees of damage to their biological systems including the biological rhythms. In the present study, the possible effects of exposure to radiofrequency–electromagnetic radiation (RF–EMR) from MPs on two characteristic circadian rhythms, locomotor activity and melatonin hormone rhythms, were investigated. Rats were exposed to RF–EMR from MPs at 900 MHz frequency (2-h/day for 2 weeks) during nighttime (20:00–22:00 h) followed by another two weeks without exposure for recovery. Locomotor activity rhythms of the control and treated groups (n = 5/group) were daily recorded using running wheels along the experimental period. For evaluating melatonin hormone rhythm, blood samples of control and treated groups (n = 12/group), were collected at the end of exposure and recovery periods, at 6-h time intervals per day (at 4:00, 10:00, 16:00, and 22:00 h). Rats exposed to RF–EMR exhibited phase shifting as well as a significant increased acrophase level in locomotor activity. Meanwhile, a significant decrease in serum melatonin levels with retaining lower amplitude rhythmicity was observed. Ceasing exposure for two weeks did not restore melatonin levels and circadian locomotor activity rhythms. It could be concluded that, under the current conditions, exposure to RF–EMR revealed disturbances in locomotor activity and melatonin level, although they maintained rhythmicity.     

Effect of time of day on the offensive capability and aerobic performance in football game

The purpose of this study was to examine the time-of-day effects on the offensive capability and aerobic performance in football game in young subjects. In a randomized order, participants realized the Yo–Yo intermittent recovery test in two test sessions and a football game situations (two 15-min games), interspersed by a verbalization sequence (3 min) at 08:00 and 17:00 h on separate days. A recovery period of 24 h was permitted between two consecutive test sessions. The results revealed diurnal variations on the maximal aerobic velocity during the Yo–Yo test (MAV) and the oral temperature with higher values in the afternoon than morning (p < 0.05). Concerning offensive capability, the numbers of scored goals were significantly higher at 17:00 h in comparison with 08:00 h (p < 0.05). However, there was no significant difference between 08:00 and 17:00 h for the kicked balls (shooting parameter). In conclusion, our findings suggest that performance was improved in the evening and the parameters (shooting and Scored goals) can be used as a model to describe the offensive capacity in football game depending on the time of day.     

Simvastatin and vitamin E effects on cardiac and hepatic oxidative stress in rats fed on high fat diet

High fat diet (HFD) is a common cause of metabolic syndrome and type 2 diabetes mellitus. Published data showed that HFD and subsequent dyslipidemia are major triggers for oxidative stress. Forty-eight male Sprague–Dawley rats, weighing 170–200 g, were divided into six groups: control, control with vitamin E (100 mg/kg/day, i.p.), control with simvastatin (SIM) (10 mg/kg of body weight/day), HFD, HFD with vitamin E, and HFD with SIM. Standard and high cholesterol diets were given for 15 weeks and SIM and vitamin E were added in the last 4 weeks. In all rats, serum vitamin E, total cholesterol (TC), triglycerides (TG), low (LDL) and high (HDL) density lipoproteins, alanine (ALT) and aspartate (AST) transaminases, alkaline phosphatase (ALP), and gamma glutamyl transpeptidase (GGT) as well as cardiac and hepatic thiobarbituric acid-reactive substances (TBARS) and antioxidants (reduced glutathione (GSH), superoxide dismutase (SOD), and catalase (CAT)) were measured. Also, electrocardiogram (ECG) was recorded. HFD significantly increased QTc interval, heart rate (HR), serum TC, TG, LDL, ALT, AST, ALP, GGT, liver TG, and cardiac and hepatic TBARS but decreased antioxidants and HDL, while SIM decreased HR, liver TG, serum TC, TG, and LDL and increased HDL in HFD rats. Vitamin E had no effect. Moreover, SIM and vitamin E decreased QTc interval, serum ALT, AST, ALP, GGT, and cardiac and hepatic TBARS and increased antioxidants in HFD rats. Histopathological observations confirm the biochemical parameters. SIM and vitamin E slow progression of hypercholesterolemia-induced oxidative stress in liver and heart and improve their functions.     

Weekend versus working day: differences in telemetric blood pressure in male Wistar rats

Blood pressure (BP) is a frequently monitored parameter in research. Various methods are used to obtain BP values in animal models, but telemetry is the method of choice because it allows for continuous monitoring in conscious and freely moving animals. However, factors due to the animal facility, like activities and sound, can still influence measurements. We, therefore, retrospectively compared BP values in adult male Wistar rats during working hours with values from non-working days. Telemetry devices were implanted according to standard protocol. Values were obtained at the age of 6 and 12 months during working hours (Friday 10:00-16:00 h, lights on 06:00-18:00 h) and compared with data from the average of Saturday 10:00-16:00 h and Sunday 10:00-16:00 h, representing non-working days. Data were available from 12 and 7 rats at 6 months and 12 months of age respectively. Relative differences in heart rate, spontaneous locomotor activity, systolic and diastolic BP were 2.2% (P<0.001), 32.9% (P<0.05), 3.2% (P<0.05) and 3.7% (P<0.05), respectively, with no differences between the age groups. We have shown a significant and important difference between BP values obtained during working hours and non-working days using telemetry in adult male Wistar rats. This phenomenon has implications for the interpretation of BP measurements in animals.     

Role of Muscarinic Acetylcholine Receptor-2 in the Cerebellar Cortex in Cardiovascular Modulation in Anaesthetized Rats

Our previous investigations have demonstrated that microinjection of acetylcholine (ACh) or muscarinic ACh receptor activation in the cerebellar cortex induces a systemic blood pressure depressor response. This study aimed to determine the role of muscarinic ACh receptor-2 (M2 receptor) in the cerebellar cortex in cardiovascular function regulation in rats. A nonselective muscarinic receptor agonist (oxotremorine M, OXO; 30 mM), a selective M2 receptor agonist (arecaidine but-2-ynyl ester tosylate, ABET; 3, 10, and 30 mM), 30 mM OXO mixed with a selective M2 receptor antagonist (methoctramine hydrate, MCT; 0.3, 1, and 3 mM), and normal saline (0.9 % NaCl) were separately microinjected (0.5 µl/5 s) into the cerebellar cortex (lobule VI) of anaesthetized rats. We measured the mean arterial pressure (MAP), maximum change in MAP, and reactive time (RT; the duration required for the blood pressure to return to basal levels), heart rate (HR) and the maximum change in HR during the RT in response to drug activation. The results demonstrated that ABET dose-dependently decreased MAP and HR, increased the maximum change in MAP and the maximum change in HR, and prolonged the RT. Furthermore, MCT dose-dependently blocked the OXO-mediated cardiovascular depressor response. This study provides the first evidence that M2 receptors in the cerebellar cortex are involved in cardiovascular regulation, the activation of which evokes significant depressor and bradycardic responses.     

Twenty-four-hour rhythm patterns of plasma melatonin in short-day and long-day breeders maintained under natural environmental conditions

ABSTRACT

Photoperiodic treatments have been of practical interest in controlling seasonal reproduction in sheep, goats and horses. Melatonin is the principal mediator of the environmental photoperiodic message. To investigate the intra- and inter-subject variability of melatonin 24 h rhythm, ten female Italian Saddle horses (8–10 yrs old, mean body weight 525 ± 30 kg), ten female Sarda breed sheep (2–3 yrs old, mean body weight 40.5 ± 2.8 kg) and ten female Sarda breed goats (3–4 yrs old, mean body weight 38.9 ± 4.1 kg), housed individually in a 4 × 4 m soundproof box equipped with 50 × 100 cm opening windows, were subjected to a natural photoperiod of the vernal equinox (sunrise 06:00 h; sunset 18:00 h). Blood samples were collected from each animal, every 3 h over a 48 h period starting at 00:00 h of day 1 and ending at 00:00 h of day 3. Plasma melatonin concentrations were determined by direct radioimmunoassay (MelatoninDirect RIA, Labor Diagnostika Nord GmbH, Nordhorn, Germany). The application of single cosinor method substantiated a circadian rhythm of melatonin with a nocturnal peak in all studied species. The application of two-way ANOVA on the rhythmic parameters indicated statistically significant differences between the three species in all of the cosinor analysis-derived parameters of MESOR, amplitude, acrophase and robustness of rhythm. Analyses of intra- and inter-subject variability indicate that organization of the melatonin 24 h rhythm is characterized by great accuracy of control within and between the individuals of a breed. In conclusion, features of the 24 h rhythm of melatonin among species; however, the 24 h rhythmicity of melatonin each species showed high stability within the various subjects and within the same subject. These findings must be taken into consideration when applying photoperiod and melatonin treatments for breeding purposes.     

Effect of napping opportunity at different times of day on vigilance and shuttle run performance

ABSTRACT

The aim of the present study was to examine the effect of a nap opportunity during the daytime realized at different times of day on physical and mental performance. Eighteen physically active males (age: 20.5 ± 3.0 years, height: 175.3 ± 5.9 cm, body-mass: 70.0 ± 8.6 kg) were tested under four experimental conditions: no-nap condition, nap at 13h00, nap at 14h00 and nap at 15h00. All nap durations were of 25-min and all tests were performed at 17h00. They performed a 5-m shuttle run test, which generated measures of the highest distance (HD) and total distance (TD). The rating of perceived exertion (RPE) was recorded after each of the six sprints in the 5-m shuttle run test. Vigilance was measured using a digit cancellation test. The results showed that TD at 17h00 was 4% greater after a nap at 14h00 than in the no-nap condition (+28 m, p < .05) or after the nap at 13h00 (+29 m, p < .05). HD was 8% higher (+9 m, p < .001) after a nap at 14h00 than in the no-nap condition and 7% higher after nap at 15h00 than in the no-nap condition (+7 m, p < .05). In addition, HD was 6% higher after nap at 14h00 (+7 m, p < .01) and 5% higher after nap at 15h00 (+9 m, p < .01) than HD after a nap at 13h00. Napping at 13h00 had no effect on physical performance at 17h00. No significant differences were observed between RPE and vigilance scores in the nap and no-nap conditions. In conclusion, napping for 25 min at 14h00 and 15h00 produces meaningful improvements in responses during repeated short-term maximal exercise tests performed at 17h00. Napping at 13h00 does not. Vigilance, as measured using a digit cancellation test, and RPE scores are not influenced by any of the nap opportunities.     

Gender dependency of circadian blood pressure and heart rate profiles in spontaneously hypertensive rats: effects of beta-blockers

This study investigated (i) blood pressure (BP), heart rate (HR), and their relation to urinary NOx and eNOS protein expression in male and female spontaneously hypertensive rats (SHR), as well as (ii) gender-dependent cardiovascular effects of nebivolol (NEB) in comparison to metoprolol (MET) in SHR. BP and HR were measured telemetrically after a single intraperitoneal application of NEB or MET at 07.00 and 19.00 h in male rats and at 19.00 h in proestrus female rats. The two β-blockers varied in time of decreasing BP and HR and also in duration. In males, MET decreased BP and HR for few hours exclusively when applied at the onset of the activity phase (i.e., at 19.00 h), while after its application at 07.00 h, BP and HR were unchanged. In females, MET also caused a short-lasting BP and HR reduction, with the effect being more pronounced than in males. In males, NEB at either dosing time decreased HR and BP to a greater extent than did MET. This effect was evident both during the activity and rest periods and persisted for at least five days. In females, NEB provoked a similar, but more pronounced, effect on BP and HR in comparison to males. These findings demonstrate that significant gender-dependent differences in the circadian profile of BP and HR exist. BP and urinary NOx as well as eNOS expression are inversely correlated, and the cardiovascular effects of NEB and MET vary, depending on the time of application as well as gender.     

EFFECT OF IMIDAPRIL IN DIPPER AND NONDIPPER HYPERTENSIVE PATIENTS: COMPARISON BETWEEN MORNING AND EVENING ADMINISTRATION

The purpose of the study was to identify differences in the patterns of efficacy and duration of effects of imidapril administered at different times of the day (morning versus evening) in dipper and nondipper hypertensive patients. Twenty patients with untreated hypertension were classified into two groups: dippers (n = 9) and nondippers (n = 11). Imidapril (10 mg) was given at 07:00 or 18:00 for 4 weeks in a crossover fashion. Blood pressure (BP) and heart rate (HR) were monitored before and after morning and evening treatment every 30 min for 48h by ambulatory BP monitoring (ABPM). In dipper hypertension, the mean 48h BP was reduced with both doses. The decrease in the diurnal BP was stronger when the drug was administered in the evening than morning, but without significant difference. In nondipper hypertension, the systolic BP decreased at night with both doses, but the extent of the nocturnal reduction in systolic BP was greater after morning therapy. There were no significant differences in the decrease in BP during the day or night between the morning and evening administrations. When imidapril was administered in the morning, its serum concentration reached a maximum at 16:00, and when the drug was administered in the evening, it reached a maximum at 6:00. In dipper hypertension, the time taken for the blood concentration of imidapril to reach a maximum changed depending on its time of administration, and the time when the maximum antihypertensive effect of the drug appeared was different. In nondipper hypertension, decreases in the BP were confirmed at night regardless of the time of administration; this might be caused by angiotensin converting enzyme (ACE) inhibitors effectively blocking the BP from increasing by activating the parasympathetic nervous system. Therefore, when assessing the effectiveness of antihypertensive agents, factors such as the various patterns of BP before therapy and administration time must be considered. (Chronobiology International, 17(2), 209–219, 2000)     

THERMOCYCLIC AND PHOTOCYCLIC ENTRAINMENT OF CIRCADIAN LOCOMOTOR ACTIVITY RHYTHMS IN SLEEPY LIZARDS,TILIQUA RUGOSA

Australian sleepy lizards (Tiliqua rugosa) exhibit marked locomotor activity rhythms in the field and laboratory. Light-dark (LD) and temperature cycles (TCs) are considered important for the entrainment of circadian locomotor activity rhythms and for mediating seasonal adjustments in aspects of these rhythms, such as phase, amplitude, and activity pattern. The relative importance of 24 h LD and TCs in entraining the circadian locomotor activity rhythm in T. rugosa was examined in three experiments. In the first experiment, lizards were held under LD 12:12 and subjected to either a TC of 33:15?°?C in phase with the LD cycle or a reversed TC positioned in antiphase to the LD cycle. Following LD 12:12, lizards were maintained under the same TCs but were subjected to DD. Activity was restricted to the thermophase in LD, irrespective of the lighting regime and during the period of DD that followed, suggesting entrainment by the TC. The amplitude of the TC was lowered by 8?°?C to reduce the intensity and possible masking effect of the TC zeitgeber in subsequent experiments. In the second experiment, lizards were held under LD 12.5:11.5 and subjected to one of three treatments: constant 30?°?C, normal TC (30:20?°?C) in phase with the LD cycle, or reversed TC. Following LD, all lizards were subjected to DD and constant 30?°?C. Post-entrainment free-run records revealed that LD cycles and TCs could both entrain the locomotor rhythms of T. rugosa. In LD, mean activity duration (α) of lizards in the normal TC group was considerably less than that in the constant 30?°?C group. Mean α also increased between LD and DD in lizards in the normal TC group. Although there was large variation in the phasing of the rhythm in relation to the LD cycle in reversed TC lizards, TCs presented in phase with the LD cycle most accurately synchronized the rhythm to the photocycle. In the third experiment, lizards were held in DD at constant 30?°?C before being subjected to a further period of DD and one of four treatments: normal TC (06:00 to 18:00 h thermophase), delayed TC (12:00 to 00:00 h thermophase), advanced TC (00:00 to 12:00 h thermophase), or control (no TC, constant 30?°?C). While control lizards continued to free-run in DD at constant temperature, the locomotor activity rhythms of lizards subjected to TCs rapidly entrained to TCs, whether or not the TC was phase advanced or delayed by 6 h. There was no difference in the phase relationships of lizard activity rhythms to the onset of the thermophase among the normal, delayed, and advanced TC groups, suggesting equally strong entrainment to the TC in each group. The results of this experiment excluded the possibility that masking effects were responsible for the locomotor activity responses of lizards to TCs. The three experiments demonstrated that TCs are important for entraining circadian locomotor activity rhythms of T. rugosa, even when photic cues are conflicting or absent, and that an interaction between LD cycles and TCs most accurately synchronizes this rhythm. (Author correspondence: david.j.ellis@adelaide.edu.au)     

Chronobiological perspectives on myocardial electrophysiological parameters under three types of general anaesthesia in a rat model

The specific aim of the present study, with respect to dependence on the light–dark (LD) cycle under in vivo conditions in spontaneously breathing rats was to review initial state in electrophysiological parameters that may predict the development of heart rhythm disorders in pentobarbital (40 mg/kg), ketamine–xylazine (100 + 15 mg/kg) and zoletil (30 mg/kg) anaesthetized animals. The study was performed using female Wistar rats that were adaptated to an LD cycle (12 h:12 h). Heart rate, PQ and QT intervals were evaluated for their dependence on the LD cycle. The longest PQ interval duration is under zoletil anaesthesia in the light period and the longest QT interval duration is under ketamine–xylazine anaesthesia in both light periods. We concluded that the most significant predisposition toward the development of ventricular arrhythmias originating from disorders of impulse production and conduction occurred under zoletil anaesthesia in the light period; those resulting from disorders in the dispersion of refractory periods occurred under ketamine–xylazine anaesthesia in both the light periods.     

Opuntia ficus-indica juice supplementation: what role it plays on diurnal variation of short-term maximal exercise?

The aim of this study was to investigate the effect of natural Opuntia ficus-indica juice (OFIJ) supplementation on anaerobic performance at two times of day. Twenty-two healthy male subjects (20.91 ± 1.22; 21.00 ± 0.84 years) divided into two groups: Experimental group (EG: n = 11) and a control group (CG: n = 11) performed two tests-sessions (30-s of Wingate test (i.e. Peak power (PP), Mean power (MP)), Sargent jump test (SJT), sprint 10 m), before and after natural OFIJ supplementation at 07:00 h and 17:00 h. T-test showed that the OFIJ has a potent antioxidant capacity for capturing free radicals following the 22-diphenyl-1-picrylhydrazyl (DPPH^●) test (p < 0.05). Likewise, the ANOVA revealed that anaerobic performances were significantly higher at 17:00 h compared to 07:00 h around the peak of the temperature (p < 0.05) in both EG and CG before supplementation. Moreover, OFIJ lead an improvement of performances with (+2.09% at 07:00 h vs.+9.36% 17:00 h) for PP, (+11.29% at 07:00 h vs.+11.77% 17:00 h) for MP, (+9.42% at 07:00 h vs.+7.63% 17:00 h) for SJT in EG. The RPE scores on response to the Wingate test decrease after OFIJ supplementation (p < 0.01). For the sprint values, a significant improvement was after OFIJ (?7.10% at 07:00 h vs. ?6.45% 17:00 h). However, no change was observed for CG after supplementation. In conclusion, the natural OFIJ supplementation for two weeks appears to ameliorate the performance upon two times of day with great improvement observed in the evening during short-term maximal exercise given the higher muscle damage, inflammatory, and oxidative responses at this time of day. Thus, it’s necessary that athletes, coaches, and medical staff consider the positive effects of Opuntia ficus-indica to improve anaerobic performance.     

Time-Dependent Efficacy of Antihypertensi Agents in Spontaneously Hypertensive Rai

The efficacy of antihypertensive agents was compared when given at different time points in the circadian rhythm. Spontaneously hypertensive rats (SHRs) were kept on a 12/12-h cycle with lights on/off at 07:00/19:00 h. A computerized system was used to measure intraarterial blood pressure and heart rate continuously. Agents or vehicle were intravenously injected at two time points. One at the beginning of the sleeping period, at which low efficacy was expected (T = 10), and one at T = 16, which is 3 h before the circadian peaks in blood pressure (BP) and heart rate (HR), aimed at reducing the rise in BP and HR at awakening. The hypotensive effect of propranolol, metoprolol, labetalol, prazosin, clonidine, and rilmenidine was greater when injected at T = 16 than at T = 10 (p < 0.05 for propranolol, metoprolol, and rilmenidine). In contrast, the renal vasodilators cap-topril and tertatolol were more potent after injection at T = 10. Felodipine was equally effective at both time points. Thus, the effects of antihypertensive agents are related to the phase of the circadian rhythm. The data on the sympatholytic agents in general and β-blockers and centrally acting agents in particular support antihypertensive regimens with timed administrations.     

Effect of geraniol on temporal patterns of clock gene products during endometrial carcinogenesis in rats

The most common cancer in the female genital tract is malignancy of the endometrium ranking fourth among the aggressive cancers that affects women. Biological clock controls the daily modifications of physiological processes, which sequentially regulate numerous functions in the human body. In this study, female Wistar rats were divided into four groups: group I – control, group II – MNNG (N-methyl-N′-nitro-N-nitrosoguanidine-150 mg/kg) given by intravaginal detention of absorbent cottons dipped with 150 mg of MNNG for weekly twice; group III – co-administration of geraniol (MNNG + GOH) (150 mg/kg b.w); group IV – oral administration of GOH only. The expression of protein levels of PER, CRY, BMAL1 and CLOCK at different time points (00:00,04:00, 08:00, 12:00, 16:00 and 20:00 h) were analyzed over the 24-h period by western blotting. In MNNG-induced group, PER and CRY protein levels were downregulated, whereas BMAL1 and CLOCK expression was upregulated at 00:00 and 20:00. Administration of GOH reversed the expression level of clock gene products observed in MNNG-treated rats. The results indicate that the expression of clock gene products is affected during endometrial carcinogenesis. Earlier reports suggest that carcinogenesis could modify circadian rhythms and our results add additional evidences in similar lines. Our results suggest that anticarcinogenic action of GOH could be via normalizing the expression of clock gene products. The mechanisms for this alteration of clock gene expression are desirable to investigate in future.     

Effects of wire-bottom caging on heart rate, activity and body temperature in telemetry-implanted rats

Some experimental procedures are associated with placement of animals in wire-bottom cages. The goal of this study was to evaluate stress-related physiological parameters (heart rate [HR], body temperature [BT], locomotor activity [LA], body weight [BW] and food consumption) in rats under two housing conditions, namely in wire-bottom cages and in bedding-bottom cages. Telemetry devices were surgically implanted in male Sprague-Dawley rats. HR, BT and LA were recorded at 5 min intervals. Analysis under each housing condition was performed from 16:00 to 08:00 h of the following day (4 h light, 12 h dark). During almost all of the light phase, the HR of rats housed in wire-bottom cages remained high (371 ± 35 bpm; mean ± SD; n = 6) and was significantly different from that of rats housed in bedding-bottom cages (340 ± 29 bpm; n = 6; P < 0.001; Student's t-test). In general, BT was similar under the two housing conditions. However, when rats were in wire-bottom cages, BT tended to fluctuate more widely during the dark phase. LA decreased when animals were housed in wire-bottom cages, in particular during the dark phase. Moreover, there was a significant difference with respect to the gain in BW: BW of rats housed in bedding-bottom cages increased 12 ± 2 g, whereas that of rats in wire-bottom cages decreased by 2 ± 3 g (P < 0.001). Our results demonstrate that housing rats in wire-bottom cages overnight leads to immediate alterations of HR, BW and LA, which might be related to a stress response.     

Post-resistance training detraining: time-of-day effects on training and testing outcomes

The aim of this study was to examine the effects of 3 and 5 weeks of detraining after 14 weeks of resistance training at a specific time of day on performances during the squat jump (SJ) and the maximal voluntary contraction (MVC). Thirty-one healthy male physical education students (age: 23.1 ± 1.0 years; height: 176.1 ± 6.3 cm; weight: 74.9 ± 10.9 kg) were randomly assigned to either a morning training group (MTG, training between 07:00 and 08:00 h, n = 10), an evening training group (ETG, training between 17:00 and 18:00 h, n = 11) or a control group (CG, no training, n = 10). Participants then performed eight test sessions (twice per day, at 07:00 and 17:00 h) over the course of four phases: during pre-training, immediately post-training, and after 3 and 5 weeks of detraining. Before each test session, oral temperature was recorded. During the first 12 weeks of resistance training, participants performed 3 sets of 10 repetitions to failure (10-RM) for 4 exercises (squat, leg press, leg extension and leg curl, with 2 min of recovery between each exercise); during the last two weeks, training intensity increased to 8-RM with 3 min of recovery between each exercise. Oral temperature was significantly higher at 17:00 than 07:00 h during all test periods (p < 0.05). Likewise, SJ and MVC performances were significantly higher at 17:00 h than 07:00 h during all four test days in ETG and CG, and before training and 3 and 5 weeks after training in MTG (p < 0.05). For both training groups, most SJ and MVC performances (except MTG at 07:00 h and ETG at 17:00 h) returned to baseline values after 5, but not after 3, weeks of detraining. This study showed that 14 weeks of training at a specific time of day blunted the diurnal variation of MVC and SJ in the MTG. The improvement in performance brought about by resistance training was partially retained after 3 weeks of detraining (unless training had taken place at a non-habitual time of day) but was lost after 5 weeks of detraining. There was no effect of the time of training on core temperature.