Diurnal Variations of Striatal D2 Dopaminergic Receptors and its Relation with Haloperidol-induced Catalepsy

In spite of the clear evidences for the blockade of dopaminergic D2 receptors as the mechanism of action for haloperidol-induced catalepsy, the contribution of pharmacokinetic and pharmacodynamic aspects on the diurnal modulation of haloperidol-induced catalepsy is controversial. We studied the diurnal variations of striatal dopamine receptors and its relation with catalepsy diurnal variations. The [3 H]-spiperone binding to dopamine receptors had a clear rhythm with a peak at 00:00 to 03:00 h, and a trough at 12:00 to 18:00 h. Haloperidol-produced catalepsy measured with the four-cork test, also showed a clear rhythm, with a peak at 00:00 h and trough at 9:00 h. The dose-response curves at peak and trough of catalepsy had the same ED 50 (0.12 mg), with time-related changes in the maximal effect. Similar diurnal variations between catalepsy and dopamine receptor binding, indicate a relevant role of temporal pharmacodynamics of haloperidol on the modulation of its behavioral effects.     

Asynchrony in the Diurnal Rhythms of Dopaminergic D2 Receptors in Different Brain Regions of the Rat

Diurnal variations of dopaminergic D₂ receptors have been described in the striatum of rats, while other dopaminergic regions remain unstudied. Diurnal variations of dopamine D₂ receptors in the striatum, frontal cortex, and amygdala of the rat, were characterized by the stereospecific binding of [³H]-spiperone. Clear rhythms were found in all these areas, but asynchronous to each other. Striatal receptors had diurnal variations with a single peak at 00:00 hours. Frontal cortex receptors showed two peaks at 00:00 and 12:00 hours. Amygdaline complex receptors had two peaks at 18:00 and 06:00 hours. Saturation binding curves and their Scatchard analysis indicated that the diurnal variations in [³H]-spiperone binding are related to changes in receptor density rather than its affinity. The diurnal variations asynchrony in [³H]-spiperone binding to dopaminergic D₂ receptors from different neural regions, suggest different regulation in each area. Other functional implications of these rhythms remains to be established.     

Asynchrony in the Diurnal Rhythms of Dopaminergic D2 Receptors in Different Brain Regions of the Rat

Diurnal variations of dopaminergic D₂ receptors have been described in the striatum of rats, while other dopaminergic regions remain unstudied. Diurnal variations of dopamine D₂ receptors in the striatum, frontal cortex, and amygdala of the rat, were characterized by the stereospecific binding of [³H]-spiperone. Clear rhythms were found in all these areas, but asynchronous to each other. Striatal receptors had diurnal variations with a single peak at 00:00 hours. Frontal cortex receptors showed two peaks at 00:00 and 12:00 hours. Amygdaline complex receptors had two peaks at 18:00 and 06:00 hours. Saturation binding curves and their Scatchard analysis indicated that the diurnal variations in [³H]-spiperone binding are related to changes in receptor density rather than its affinity. The diurnal variations asynchrony in [³H]-spiperone binding to dopaminergic D₂ receptors from different neural regions, suggest different regulation in each area. Other functional implications of these rhythms remains to be established.     

Analysis of trough and peak of plasma melatonin circadian rhythm in ewes

This study evaluates the pattern of plasma melatonin during the trough and the peak of its daily rhythm. Blood samples from 8 ewes were collected every 3 h for a 48-h period. On the third day, blood samples were collected from 10:00 to 13:00 (trough) and from 20:00 to 23:00 (peak) every 20 min. Our results showed a robust daily rhythm of melatonin in both days of monitoring, with nocturnal acrophase. During the trough, a significant decrease was observed starting from the 10:40 with a progressive decrease about every 40 min. During the peak of the plasma melatonin daily rhythm, an increase was observed starting from the 20:40 with a progressive increase about every 40 min. These data could be taken in consideration to monitor the plasma melatonin variations during the 24 h, and for the administration of melatonin for breeding in ewes.     

Glucocorticoid effects on the diurnal rhythm of circulating leptin levels

It is known that circulating leptin shows diurnal variation with a nocturnal rise; however, the mechanisms generating this rhythm have not been fully elucidated. Glucocorticoids are a potent stimulator of leptin secretion, and there is a reciprocal relationship between circulating leptin and glucocorticoid levels. We hypothesized that glucocorticoids could modulate the diurnal rhythm of circulating leptin. We therefore explored the diurnal variation of leptin under situations in which subjects showed no or some shift of glucocorticoid diurnal rhythm, such as prednisolone-administered humans, and adrenalectomized and corticosterone-replaced (ADX+B) rats. The peak level of plasma cortisol immunoreactivity was shifted from early morning to noon by prednisolone administration. The nocturnal increment of plasma leptin in prednisolone-administered patients (71.2 +/- 14.2% from 08:00 h value) was significantly greater than that in normal volunteers (12.2 +/- 7.5% from 08:00 h value), but the timing of nadir and the peak of plasma leptin was not shifted. In normal rats, the plasma concentration of leptin showed the diurnal rhythm with the bottom at 16:00 h and the top between midnight and early morning. The amplitude of leptin diurnal rhythm was significantly reduced in ADX+B rats (08:00 h: 3.0 +/- 0.2, 16:00 h: 2.7 +/- 0.2, 00:00 h; 3.7 +/- 0.2 ng/ml) compared with sham operated rats (08:00 h: 3.0 +/- 0.2, 16:00 h 2.2 +/- 0.2, 00:00 h: 4.7 +/- 0.4 ng/ml); but ADX+B rats still retained similar timing of nadir and the peak of plasma leptin as observed in sham rats. These results indicate that glucocorticoids enhance the amplitude of leptin diurnal rhythm, and are consistent with previous findings showing that glucocorticoids increase leptin secretion. Glucocorticoids appear to play modulatory, but not essential roles in generating leptin diurnal rhythm.     

Diurnal Rhythm of the Muscular Performance of Elbow Flexors During Isometric Contractions

The influence of time of day on elbow flexion torque was studied. Thirteen physical education students, 7 males and 6 females, made maximal and submaximal isometric contractions at 90° of elbow flexors using a dynamometer. The torque developed was measured on each contraction. The myoelectric activity of the biceps muscle was also measured at the same time by surface electromyography (EMG) and quantified from the root mean square (RMS) activity. Torque and surface EMGs were measured at 6:00, 9:00, 12:00, 15:00, 18:00, 21:00, and 24:00 h over the same day. Oral temperature before each test session was measured on each occasion after a 30-min rest period. We observed a diurnal rhythm in elbow flexor torque with an acro-phase at 18:00 h and a bathyphase at 6:00 h, in phase with the diurnal rhythm in oral temperature. However, the diurnal rhythm of temperature did not appear to have any influence on the torque. Links between neuromuscular efficiency and RMS/torque ratio were evaluated by measuring muscle activity along with torque. We also assessed variations in the level of maximal activity of the muscle under maximal voluntary contraction. Neuromuscular efficiency fluctuated during the day, with maximal and minimal efficiency at 18:00 h and 9:00 h, respectively, whereas activation level was maximal at 18:00 h and minimal at 9:00 h. The diurnal rhythm of torque was accounted for by variations in both central nervous system command and the contractile state of the muscle.     

The diurnal rhythm of liver glycogen phosphorylase: correlating changes in enzyme activity and enzymic protein

The diurnal rhythm of phosphorylase activity in mouse liver extracts was correlated with the 24 h fluctuations in phosphorylase protein. This last measurement was made using rocket immunoelectrophoresis. The peak activity of phosphorylase appeared coincident (at 18:00 h) with the greatest amount of phosphorylase protein detected. Conversely, the lowest activity measured and lowest enzymic protein content both occurred at 02:00 h. Regression analysis revealed a significant positive correlation between enzyme activity and protein. Thus changes in the cellular concentration of this enzyme are implicated in the diurnal rhythm of liver glycogen.     

In vitro TRH release from hypothalamus slices varies during the diurnal cycle

We have previously described a daily rhythm in thyrotropin releasing hormone (TRH) and TRH mRNA in the rat hypothalamus. To determine whether TRH release fluctuates in a diurnal manner, we have measured basal and potassium stimulated release from hypothalamic slices, and compared it to release from olfactory bulb slices, during the diurnal cycle. Basal TRH release was higher at 7:00 h than at any other time (1:00, 13:00 or 19:00 h) in either hypothalamus or olfactory bulb. The ratio of stimulated over basal release was higher in the hypothalamus at 19:00 h, when TRH content was highest. Potassium stimulated TRH release from olfactory bulb was not different from basal release at any time. TRH release fluctuations were not due to a rhythm of extracellular inactivation: the activity of pyroglutamyl aminopeptidase II, an ectoenzyme responsible for TRH inactivation, was constant throughout the cycle. Our data demonstrate that diurnal variations of TRH release occur in vitro and that the enhanced responsiveness to potassium stimulation in hypothalamus is correlated with increased levels of peptide.     

Diurnal variation in the proconvulsant effect of 3-mercaptopropionic acid and the anticonvulsant effect of androsterone in the Syrian hamster

GABA is the principal neurotransmitter of the mammalian circadian system, and its activity is subject to diurnal and circadian variations, with maximal values in hypothalamic turnover, content and binding during the night. In this study we have examined rhythms in the proconvulsant effect of inhibition of glutamate decarboxylase (GAD) in hamsters (Mesocricetus auratus) as well as the anticonvulsant effect of androsterone, a neurosteroid that positively modulates the GABA(A) receptor. Administration of 10-60 mg/Kg of 3-mercaptopropionic acid (3-MPA, a GAD inhibitor) induced convulsions that were analyzed by an ad-hoc severity scale, with a lower sensitivity threshold at 24:00 h. Moreover, the latency for first and maximal convulsive response times was significantly lower at night. A similar temporal profile (maximal effect at midnight) was found for picrotoxin-induced seizures. Androsterone (40 mg/Kg) completely inhibited 3-MPA-induced tonic/clonic seizures at 12:00 h, while it had a partial inhibitory effect at 24:00 h. These results support the importance of temporal regulation of GABAergic modulation in the central nervous system.     

Diurnal rhythm in mRNA expression of genes encoding amino acid transporter and circadian gene cry in intestinal mucosa of piglets

Long chain PUFA contents in plasma and liver both exhibited diurnal rhythms in pigs. However, whether mRNA expression of amino acid transporter and circadian gene Cry in intestinal mucosa is also rhythmic is yet to be known. The purpose of this study aims to investigate the diurnal rhythm in mRNA expression of genes encoding amino acid transporter and whether their rhythm was related to the expression of circadian gene Cry in intestinal mucosa of piglets. Thirty-six piglets (Duroc?×?Landrace?×?Large Yorkshire) at the age of 35 days were selected and fed for three weeks, and then samples were collected at 3:00 am (Clo3), 7:00 am (Clo7), 11:00 am (Clo11), 3:00 pm (Clo15), 7:00 pm (Clo19), and 11:00 pm (Clo23) at the age of 56 days. At each time point, small intestinal mucosa samples were collected from duodenum, jejunum, and ileum for detection of mRNA expression of the amino acid transporters and circadian gene Cry. The results showed that mRNA expression of most amino acid transporters in intestinal mucosa was higher at night and lower during the daytime. Expression of SLC1A2, SLC6A20, SLC7A1, and SLC6A14 in duodenal mucosa reached the peak at Clo3 and Clo7; the diurnal rhythm of expression of SLC1A2, SLC6A20, and SLC7A1 was similar to Cry1, while the diurnal rhythm of expression of SLC6A14 had a similar trend to Cry2. Expression of SLC16A10, SLC1A2, and SLC7A1 in jejunal mucosa reached the peak at Clo7, while SLC6A14 reached the peak at Clo3; the diurnal rhythm of expression of SLC1A2 showed a similarity with Cry1, while the diurnal rhythm of expression of SLC16A10, SLC7A1, and SLC6A14 was similar to Cry2. Expression of SLC6A14, SLC6A20, and SLC7A1 in ileal mucosa reached the peak at Clo3; the diurnal rhythm of expression of SLC6A20 has a similarity with Cry1, while the diurnal rhythm of expression of SLC7A1 and SLC6A14 was similar to Cry2. The results suggested that the mRNA expression of most genes encoding amino acid transporters exhibited diurnal rhythms in the intestinal mucosa of piglets, and SLC7A1, SLC6A14, and SLC1A2 have a similar rhythm with circadian clock genes Cry1 and 2, and they reached the peak at Clo3 and Clo7.     

Circadian variations in melatonin-binding sites in discrete areas of the male rat brain

The binding of 125I-melatonin to synaptosomes prepared from whole brains of male rats of the CD strain and from the brain, hypothalamus and striatum of male rats of the Sabra-Wistar strain was assessed throughout a 24 h period. The animals were maintained under a daily schedule of 14 h light (05:00-19:00 h) and 10 h darkness. In whole brain preparations the density of binding sites at 18:00 h was higher by about 70% than at 02:00 h with no variations in apparent affinity of the binding sites throughout the daily period. Specific binding of 125I-melatonin was found in both hypothalamus and striatum of the male rat with a distinct diurnal variation in binding site density in the hypothalamus only. The density of 125I-melatonin-binding sites in the hypothalamus was maximal between 10:00 and 18:00 h and dropped sharply after the lights went off. The apparent 125I-melatonin-binding affinities in these regions were constant and very similar to those in whole brain preparations. The daily variations in densities of 125I-melatonin-binding sites in discrete brain areas may represent a diurnal rhythmicity in the responsiveness of the neuroendocrine axis to melatonin.     

The effect of serotonergic agents on haloperidol-induced catalepsy

The effect of various classes of serotonergic agents on haloperidol-induced catalepsy was evaluated in male Sprague-Dawley rats. The 5-HT-1A agonists buspirone, ipsapirone and 8-OH-DPAT all potently reversed catalepsy. The mixed 5-HT-1A and 5-HT-1B agonist RU 24969 reversed catalepsy only at the highest dose tested. The non-selective 5-HT-1 antagonist (l)-propranolol did not affect catalepsy. The 5-HT-2 agonist DOI and 5-HT-2 antagonist mesulergine both reversed catalepsy. ICS 205-930 (5-HT-3 antagonist) reversed catalepsy at low doses only. Another 5-HT-3 antagonist, GR 38032F, had no effect on catalepsy. These studies suggest that 5-HT-1A and 5-HT-2 receptor sites are important in the serotonergic modulation of haloperidol-induced catalepsy.     

Circadian rhythms of basic fibroblast growth factor (bFGF), epidermal growth factor (EGF), insulin-like growth factor-1 (IGF-1), insulin-like growth factor binding protein-3 (IGFBP-3), cortisol, and melatonin in women with breast cancer

Background: Circadian rhythms in plasma concentrations of many hormones and cytokines determine their effects on target cells. Methods: Circadian variations were studied in cortisol, melatonin, cytokines (basic fibroblast growth factor [bFGF], EGF, insulin-like growth factor-1 [IGF-1]), and a cytokine receptor (insulin-like growth factor binding protein-3 [IGFBP-3]) in the plasma of 28 patients with metastatic breast cancer. All patients followed a diurnal activity pattern. Blood was drawn at 3h intervals during waking hours and once during the night, at 03:00. The plasma levels obtained by enzyme-linked immunoassay (ELISA) or radioimmunoassay (RIA) were evaluated by population mean cosinor (using local midnight as the phase reference and by one-way analysis of variance (ANOVA). Results: Cortisol and melatonin showed a high-amplitude circadian rhythm and a superimposed 12h frequency. bFGF showed a circadian rhythm with an acrophase around 13:00 with a peak-to-trough interval (double amplitude) of 18.2% and a superimposed 12h frequency. EGF showed a circadian rhythm with an acrophase around 14:20, a peak-to-trough interval of 25.8%, and a superimposed 12h frequency. IGF-1 showed a high value in the morning, which is statistically different t test) from the low value at 10:00, but a regular circadian or ultradian rhythm was not recognizable as a group phenomenon. IGFBP-3 showed a low-amplitude (peak-to-trough difference 8.4%) circadian rhythm with the acrophase around 11:00 and low values during the night. Conclusions: (1) Circadian periodicity is maintained in hospitalized patients with metastatic breast cancer. (2) Ultradian (12h) variations were superimposed on the circadian rhythms of the hormones and several of the cytokines measured. (3) Studies of hormones and cytokines in cancer patients have to take their biologic rhythms into consideration. (4) The circadian periodicity of tumor growth stimulating or restraining factors raises questions about circadian and/ or ultradian variations in the pathophysiology of breast cancer. (Chronobiology International, 18(4), 709-727)     

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 gait fluctuations in single- and dual- task conditions

ABSTRACT

Gait is one of the most basic movements, and walking activity accomplished in dual task conditions realistically represents daily life mobility. Much is known about diurnal variations of gait components such as muscle power, postural control, and attention. However, paradoxically only little is known about gait itself. The aim of this study was to analyze whether gait parameters show time-of-day fluctuation in simple and dual task conditions. Sixteen young subjects performed sessions at five specific hours (06:00, 10:00, 14:00, 18:00 and 22:00 h), performing a single (walking or counting) and a dual (walking and counting) task. When performing gait in dual task conditions, an additional cognitive task had to be carried out. More precisely, the participants had to count backwards from a two-digit random number by increments of three while walking. Spatio-temporal gait parameters and counting performance data were recorded for analysis. Walking speed significantly decreased, while stride length variability increased when the task condition switched from single to dual. In the single-task condition, diurnal variations were observed in both walking speed and counting speed. Walking speed was higher in the afternoon and in the evening (14:00 and 22:00 h) and lower in the morning (10:00 h). Counting speed was maximum at 10:00 and 14:00 h and minimum at 18:00 h. Nevertheless, no significant diurnal fluctuation was substanytiated in the dual task condition. These results confirm the existing literature about changes in gait between single and dual task conditions. A diurnal pattern of single-task gait could also be highlighted. Moreover, this study suggests that diurnal variations faded in complex dual task gait, when the cognitive load nearly reached its maximum. These findings might be used to reduce the risk for falls, especially of the elderly.     

Diurnal Variation of Plasmatic Melatonin,Corticosterone and Variation of General Activity in Pigeons under Light-Dark Cycle and Constant Light

This work analyzed the diurnal variation of general activity and plasmatic levels of melatonin and corticosterone in pigeons submitted to a 12:00:12:00 h light-dark cycle (lights on at 6:00 a.m.) or to constant light. In both conditions pigeons were observed in 5-min sessions at times 03:00, 06:00, 09:00, 12:00, 15:00, 18:00, 21:00 and 24:00 h during two successive days. Behavior was video taped in the home cages for posterior categorization and quantification. Radioimmunoassays were used to evaluate plasmatic levels of melatonin and corticosterone. Blood samples were obtained at the times of behavioral observation. In the light-dark condition the results showed day-night variation of general activity (p &lt; 0.001) and a robust diurnal rhythm of plasmatic melatonin (p &lt; 0.001). Both of these variations as well as the oscillatory secretion of corticosterone disappeared under constant light condition. The parallel changes in general activity and blunting of melatonin rhythm secretion in constant light condition agree with previous evidences that melatonin may regulate behavioral oscillations in the pigeon. The present data are related to the proposition that the timing system in pigeons may involve neuroendocrine relations characterized by interactions between blood born signalization by melatonin and corticosterone.     

24-hour pattern in lag time of response by firemen to calls for urgent medical aid

The aim of the study was to assess the group 24-h pattern of lag time (LT) in response by regular and volunteer firemen (RFM and VFM) to calls for medical help (CFMH), specifically calls for out-of-hospital cardiac arrest (OHCA). LT, duration in min between a CFMH and departure of service vehicle equipped with a semiautomated defibrillator and generally staffed with four well-trained and ready-to-go FM, represents the integrated duration of several processes, each with separate reaction and decision-making times. The exact time of each CFHM (in min, h, day, month, yr) was recorded electronically, and the exact departure time from the station of the responding FM vehicle was recorded by an on-duty FM. Overall, CFMH made up 53 ± 9% (SEM) of all emergencies calls for aid. To standardize the study methods, the reported findings are based on 568 CFMH specifically regarding OHCA that occurred during the 4-yr study span (January 2005 to December 2008). CFMH exhibited a 24-h pattern with a major peak at 10:00 h (mean ± SEM: n = 9.5 ± 1.6) and major trough at 01:00 h (n = 1.3 ± 0.3; t test, p??.05). In CFMH/h pooled time series, ANOVA-detected differences between the hourly means (p?相似文献   

弄岗熊猴的活动节律和活动时间分配

2005年9月至2006年9月,采用瞬时扫描取样法,在弄岗国家级自然保护区对野生熊猴(Macaca assamensis)进行了连续跟踪观察,收集相关的活动节律和活动时间分配的数据,通过分析其与气候及食物组成的关系,从中探讨影响熊猴活动节律及活动时间分配的因素。研究结果发现:在熊猴的日活动节律中,觅食活动表现为逐渐增强的趋势,最高峰值出现在下午15:00,休息活动在中午出现一个小的高峰;其日活动节律表现出明显的季节性差异,主要表现为旱季大部分时间段的觅食强度均高于雨季,且早上7:00-10:00出现一段长时间的休息,而雨季里长时间的休息则发生在中午12:00-14:00;在活动时间分配上,熊猴平均花费39.6%时间用于休息,33.2%用于移动,18.3%用于摄食,5.1%用于理毛,2.4%用于玩耍,1.4%用于其他行为,其活动时间分配也表现出明显的季节性差异;与雨季相比,在旱季熊猴明显增加用于觅食的时间,而相应地减少用于休息的时间,活动时间分配的季节性变化明显与食物组成的变化有关;在不同年龄组个体间,青少年猴花费更多的时间用于玩耍,而用于休息和理毛的时间明显少于成年猴。     

The Tick-Tock of Language: Is Language Processing Sensitive to Circadian Rhythmicity and Elevated Sleep Pressure?

The master circadian pacemaker emits signals that trigger organ-specific oscillators and, therefore, constitutes a basic biological process that enables organisms to anticipate daily environmental changes by adjusting behavior, physiology, and gene regulation. Although circadian rhythms are well characterized on a physiological level, little is known about circadian modulations of higher cognitive functions. Thus, we investigated circadian repercussions on language performance at the level of minimal syntactic processing by means of German noun phrases in ten young healthy men under the unmasking conditions of a 40 h constant-routine protocol. Language performance for both congruent and incongruent noun phrases displayed a clear diurnal rhythm with a peak performance decrement during the biological night. The nadirs, however, differed such that worst syntactic processing of incongruent noun phrases occurred 3 h earlier (07:00 h) than that of congruent noun phrases (10:00 h). Our results indicate that language performance displays an internally generated circadian rhythmicity with optimal time for parsing language between 3 to 6 h after the habitual wake time, which usually corresponds to 10:00–13:00 h. These results may have important ramifications for establishing optimal times for shiftwork changes or testing linguistically impaired people.     

24-hour pattern of work-related injury risk of French firemen: nocturnal peak time

The first aim of the study was to assess clock-time patterning of work-related injuries (WRIs) of firemen (FM) of Sa?ne et Loire-71 (France) during the 4-yr span of 1 January 2004 to 31 December 2007. FM of this service are legally required to log every WRI and seek its evaluation by the medical service, whether the WRI was the result of worksite duties or exercise/sport activities at the station. WRI was defined specifically as a (nonexercise, nonsport, and nonemotional/stress) work-associated trauma, verified both by log book and medical records. For the corresponding years, the 24-h pattern of emergency calls (Calls) plus road traffic (Traffic) on the main roads of the service area was also assessed. Relative risk (R) of WRI was calculated as the quantity of WRIs/h divided by the quantity of Call responses/h?×?1000, which takes into account the number of at-risk FM/unit time, since each dispatched emergency vehicle is staffed with 4 FM. Comparably trained regular (RFM) and volunteer (VFM) FM experienced a total of 187 WRIs. The 24-h WRI curve patterns of RFM and VFM were correlated (r?=?0.4, p??.05). Analysis of variance (ANOVA) validated comparable clock-time patterns in WRIs of RFM and VFM each year and each season (all p??.0006; Cosinor analysis, p?相似文献