Homeostatic and circadian regulation of cognitive performance

Cognitive processes are crucial for human performance. Basic cognitive processes, such as attention, working memory, and executive functions, show homeostatic (time awake, sleep deprivation) and circadian (time of day) variations. Each of these cognitive processes includes several components, which contribute sequentially to the homeostatic and circadian modulation of performance. Sudden (lapses) and gradual changes in cognitive performance occur with sleep deprivation or with time of day. The time course of human cognitive processes throughout the day is relevant to the programming of different human activities. The lowest level of cognitive performance occurs during nighttime and early in the morning, a better level occurs around noon, and even higher levels occur during afternoon and evening hours. However, this time course can be modulated by conditions such as chronotype, sleep deprivation, sleep disorders or medication that affects the central nervous system.     

Circadian variations in the onset of aortic dissection in northern China

ABSTRACT

This study explored the periodic changes in the onset of aortic dissection in a single center in northern China, with the goal to improve predictability and prevention. We collected the clinical data of 1121 patients from Hebei Province treated for acute aortic dissection at Fuwai Hospital between January 2010 and December 2016. The patterns of aortic dissection during different periods of each day, each month, and each quarter of a year were analyzed. Variations in the number of cases were summarized for weekdays, weekends, and different periods of a day in each season. We compared the differences in gender, age, body mass index, Marfan syndrome, hypertension, and the type of aortic dissection during different time periods and different seasons. In the study, 774 patients (69.1%) with type A aortic dissection and 347 patients (30.9%) with type B aortic dissection were included. The average age of 1121 patients was 51.4 ± 12.0 years. Overall, the peak period for the onset of aortic dissection in a day was between 13:00 and 18:00. There was no statistically significant difference in the number of cases between weekdays and weekend (P = 0.94). Most cases occurred in winter (30.9%); the rate of onset was the lowest in summer (16.6%). No statistically significant difference was observed between male and female patients in terms of variations during different periods of a day (P = 0.45) and seasons (P = 0.12). In conclusion, aortic dissection displayed circadian and seasonal patterns in northern China. Onset of the disease peaked between 13:00 and 18:00 in a day. Winter was the peak season for the onset of acute aortic dissection, regardless of sex, type of dissection and age.     

生物钟在卵巢生理和病理中的作用

哺乳动物的昼夜节律是基因编码的分子钟在体内产生的一种以大约24 h为周期的生理现象,使机体的生理过程与外界环境的变化相协调,是对环境适应的一种表现.在哺乳动物中,繁殖生理功能受生物钟系统的调节.在下丘脑-垂体-卵巢(hypothalamic-pituitary-ovarian,HPO)轴的各组织中均已观察到生物钟基因的...     

Circadian rhythms and the evolution of photoperiodic timing in insects

This review discusses possible evolutionary trends in insect photoperiodism, mainly from a chronobiological perspective. A crucial step was the forging of a link between the hormones regulating diapause and the systems of biological rhythms, circadian or circannual, which have independently evolved in eukaryotes to synchronize physiology and behaviour to the daily cycles of light and darkness. In many of these responses a central feature is that the circadian system resets to a constant phase at the beginning of the subjective night, and then ‘measures’ the duration of the next scotophase. In ‘external coincidence’, one version of such a clock, light now has a dual role. First, it serves to entrain the circadian system to the stream of pulses making up the light/dark cycle and, second, it regulates the nondiapause/diapause switch in development by illuminating/not illuminating a specific light sensitive phase falling at the end of the critical night length. Important work by A. D. Lees on the aphid Megoura viciae using so‐called ‘night interruption experiments' demonstrates that pulses falling early in the night lead to long‐day effects that are reversible by a subsequent dark period longer than the critical night length and also show maximal sensitivity in the blue–green range of the spectrum. Pulses falling in the latter half of the night, however, produce long‐day effects that are irreversible by a subsequent long‐night and show a spectral sensitivity extending into the red. With movement to higher latitudes, insects develop genetic clines in various parameters, including critical night length, the number of long‐night cycles needed for diapause induction, the strength of the response, and the ‘depth’ or intensity of the diapause thus induced. Evidence for these and other types of photoperiodic response suggests that they provided strong selective advantages for insect survival.     

Circadian misalignment and weekend alcohol use in late adolescent drinkers: preliminary evidence

Alcohol use accelerates during late adolescence, predicting the development of alcohol use disorders (AUDs) and other negative outcomes. Identifying modifiable risk factors for alcohol use during this time could lead to novel prevention approaches. Burgeoning evidence suggests that sleep and circadian factors are cross-sectionally and longitudinally linked to alcohol use and problems, but more proximal relationships have been understudied. Circadian misalignment, in particular, is hypothesized to increase the risk for AUDs, but almost no published studies have included a biological measure of misalignment. In the present study, we aimed to extend existing research by assessing the relationship between adolescent circadian misalignment and alcohol use on a proximal timeframe (over two weeks) and by including three complementary measures of circadian alignment. We studied 36 healthy late (18–22 years old, 22 females) alcohol drinkers (reporting ≥1, standard drink per week over the past 30 days) over 14 days. Throughout the study, participants reported prior day’s alcohol use and prior night’s sleep each morning via smartphone and a secure, browser-based interface. Circadian phase was assessed via the dim light melatonin onset (DLMO) in the laboratory on two occasions (Thursday and Sunday nights) in counterbalanced order. The three measures of circadian alignment included DLMO-midsleep interval, “classic” social jet lag (weekday-weekend difference in midsleep), and “objective” social jet lag (weekday-weekend difference in DLMO). Multivariate imputation by chained equations was used to impute missing data, and Poisson regression models were used to assess associations between circadian alignment variables and weekend alcohol use. Covariates included sex, age, Thursday alcohol use, and Thursday sleep characteristics. As predicted, greater misalignment was associated with greater weekend alcohol use for two of the three alignment measures (shorter DLMO-midsleep intervals and larger weekday-weekend differences in midsleep), while larger weekday-weekend differences in DLMO were associated with less alcohol use. Notably, in contrast to expectations, the distribution of weekday-weekend differences in DLMO was nearly equally distributed between individuals advancing over the weekend and those delaying over the weekend. This unexpected finding plausibly reflects the fact that college students are not subject to the same systematically earlier weekday schedules observed in high school students and working adults. These preliminary findings support the need for larger, more definitive studies investigating the proximal relationships between circadian alignment and alcohol use among late adolescents.     

Circadian Rhythms in Competitive Sabre Fencers: Internal Desynchronization and Performance

During a 7-10 day span, circadian rhythms of sleep-wake, self-rated fatigue and mood, oral temperature, eye-hand skill and right and left hand grip strength were investigated in eight subjects: five males (21-28 years of age), members of the French sabre fencing team selected for the 1984 Olympic Games in Los Angeles, and three females (19-26 years of age) practicing fleuret (foil) fencing as a sports activity. On the average six measurements/day/variable/subject were performed. The single cosinor method showed that a circadian rhythm was detectable for only 26 out of the 56 time series (46.4%). Power spectrum analysis gave almost the same figure (19 out of 48: 39.5%) with regard to rhythms with τ=24hr indicating that with one exception (subject JFL) rhythms were internally desynchronized including differences τ between right and left hand grip strength rhythms for three subjects. Results suggest: (a) a physiologic synchronization of circadian rhythms may be a predictor of good performance; (b) however, internal desynchronization as shown previously may be a trivial phenomenon and thus does not imply in itself alterations of either health or performance; (c) chronobiologic methods should be recommended for a better understanding of changes in performance by those participating in competitive and other sports.     

Circadian Rhythms in Competitive Sabre Fencers: Internal Desynchronization and Performance

During a 7-10 day span, circadian rhythms of sleep-wake, self-rated fatigue and mood, oral temperature, eye-hand skill and right and left hand grip strength were investigated in eight subjects: five males (21-28 years of age), members of the French sabre fencing team selected for the 1984 Olympic Games in Los Angeles, and three females (19-26 years of age) practicing fleuret (foil) fencing as a sports activity. On the average six measurements/day/variable/subject were performed. The single cosinor method showed that a circadian rhythm was detectable for only 26 out of the 56 time series (46.4%). Power spectrum analysis gave almost the same figure (19 out of 48: 39.5%) with regard to rhythms with τ=24hr indicating that with one exception (subject JFL) rhythms were internally desynchronized including differences τ between right and left hand grip strength rhythms for three subjects. Results suggest: (a) a physiologic synchronization of circadian rhythms may be a predictor of good performance; (b) however, internal desynchronization as shown previously may be a trivial phenomenon and thus does not imply in itself alterations of either health or performance; (c) chronobiologic methods should be recommended for a better understanding of changes in performance by those participating in competitive and other sports.     

Circadian changes in Drosophila motor terminals

In Drosophila melanogaster, as in most other higher organisms, a circadian clock controls the rhythmic distribution of rest/sleep and locomotor activity. Here we report that the morphology of Drosophila flight neuromuscular terminals changes between day and night, with a rhythm in synaptic bouton size that continues in constant darkness, but is abolished during aging. Furthermore, arrhythmic mutations in the clock genes timeless and period also disrupt this circadian rhythm. Finally, these clock mutants also have an opposing effect on the nonrhythmic phenotype of neuronal branching, with tim mutants showing a dramatic hyperbranching morphology and per mutants having fewer branches than wild-type flies. These unexpected results reveal further circadian as well as nonclock related pleiotropic effects for these classic behavioral mutants.     

Circadian rhythms of proliferation events in two mouse carcinomas

We studied the index of DNA synthesis (DNAs) of two cellular carcinomas: the hepatocellular ES12a and the mammary TN60 of mice, throughout one circadian cycle. In the results, we observed that both tumors have circadian rhythms (CRs), but the peaks of DNAs vary. Besides, the mean of DNAs along 24 h shows significative differences, the TN60 has higher values than the ES12a. These observed CR in the DNAs index in both carcinomas mean that, at least in partly, the proliferation of cancer cells can be regulated by endocrine factor as it normally occurs in ordinary cells. The big problem we can find for the chronopharmacology is that it is impossible to know in advance the rate of proliferation of each tumor.     

哺乳动物昼夜节律调节的神经基础——昼夜光感受器

哺乳动物昼夜光感受器为一组具有直接感光功能的特殊视网膜神经节细胞 ,其基本感光色素为黑视素 .昼夜光感受器具有直接、广谱和稳定感受昼夜光变化的功能特点 .昼夜光感受器的功能是通过导引作用 ,使下丘脑视交叉上核内的昼夜节律活动与外界明 暗周期变化同步     

Circadian Phase Dependent Pharmacokinetics of Disopyramide in Mice

The focus of the reported work is investigation of disopyramide chronopharmacokinetics in the mouse. Different groups of male NMRI mice maintained under controlled environmental conditions (LD: 0600-1800) received a single intraperitoneal injection of disopyramide (30mg per kg of body weight) at one of four different fixed time points of a 24-h period, i.e. 1000, 1600, 2200 or 0400. Blood samples were taken 0.5,1,2,3,4 and 6 hr after drug administration and total and free plasma levels of disopyramide were measured by an immunoenzymatic method.

Our data showed statistically significant circadian rhythms in the following pharmacokinetic parameters: highest volume of distribution = 3.91 ± 0.211kg^-1 at 2200 (circadian amplitude, half the peak-to-trough difference relative to the 24-hr mean multiplied by 100, is 34%); highest area under concentration curves = 16.06 ± 1.03μgml^-1hr^-1 at 0400 (circadian amplitude = 43%) and highest clearance = 3.04 ± 0.191hr“kg”¹ at 2200 (circadian amplitude = 21%). Protein binding of the drug was shown to ^he circadian time dependent. Alpha and beta phase elimination half-lives were not found to be significantly circadian phase-dependent. Thus circadian changes in disopyramide clearance may represent circadian changes in the drug's volume of distribution.     

Circadian Rhythmicity in the Rat Exocrine Pancreas: Chronomorphological Patterns

Orcadian rhythmicity of the structural morphometric model of rat endocrine pancreas has been studied in 24 Wistar female rats, four months old, kept in LD 12:12. The following parameters were evaluated: the volume fractions of nucleus and cytoplasm of exocrine cells, the size distribution and number in unit tissue volume of acinar cell nuclei, the mean nuclear diameter, the shape coefficient of glandular acini (that is the ratio acinar area/perimeter² which indicates the shifting of structures from circularity). A statistically significant circadian rhythm was demonstrated for the shape coefficient of glandular acini. Results obtained in the present experiment are compared with data recorded in a previous study.     

Circadian Rhythmicity in the Rat Exocrine Pancreas: Chronomorphological Patterns

Orcadian rhythmicity of the structural morphometric model of rat endocrine pancreas has been studied in 24 Wistar female rats, four months old, kept in LD 12:12. The following parameters were evaluated: the volume fractions of nucleus and cytoplasm of exocrine cells, the size distribution and number in unit tissue volume of acinar cell nuclei, the mean nuclear diameter, the shape coefficient of glandular acini (that is the ratio acinar area/perimeter² which indicates the shifting of structures from circularity). A statistically significant circadian rhythm was demonstrated for the shape coefficient of glandular acini. Results obtained in the present experiment are compared with data recorded in a previous study.     

Circadian locomotor rhythms in individual honeybees

ABSTRACT. The circadian locomotor (walking) rhythms of individual forager honeybees ( Apis mellifera ligustica L.) were measured under a variety of conditions. In constant dark the rhythms exhibited endogenous periodicities that were less than 24 h, whereas under constant light the periods tended to be greater than 24 h. Individual honeybees readily entrained to photoperiods, displaying a diurnal pattern of entrainment with most of the activity occurring in late photophase. Evidence is presented which suggests that foraging behaviour and general locomotor behaviour may be governed by two different circadian clock systems.     

Circadian periodicity of airborne pollen and spores; significance of sampling height

Summary The circadian periodicity of the five allergologically most important pollen types in S. Finland and two different spore types were studied at two sites, about 200 meters apart: one Burkard sampler situated on a roof at a height of 15 meters and the other on a garden lawn at ground level. The circadian rhythms of pollen released close to the ground (herb pollen) did not correlate at the two sampling heights used. Variations in pollen from high sources (trees) were significantly correlated at the two heights used. The circadian rhythms of spores from low source distant from the sampling sites (Suillus as an example of forest fungi) were not always correlated; instead, spores with sources at different heights (Cladosporium as an example) had similar circadian periodicity not depending on the sampling level. It was shown that, when studying circadian rhythms of atmospheric particles, the sampling height used is often of great importance. Circadian rhythms of the same pollen and spore types for ten years at the higher sampling site are presented for long-term comparison.