咖啡摄入前后心率变异性的对比研究

目的研究中等剂量咖啡摄入对青年受试者心率变异性的影响,明确咖啡对心脏自主神经活性的作用。方法无咖啡因摄入习惯的16名健康青年受试者(身高167 cm±7.2 cm、体重61.3 kg±6.3kg、年龄24.9岁±2.8岁)参与本项研究,在摄入含6 mg/kg咖啡因的咖啡饮品后,于8:40~10:45应用动态心电图记录仪(Holter)进行咖啡摄入前后心电信号的采集及心率(heart rate,HR)和心率变异性指标的分析。心率变异性指标包括R-R间期标准差(SDNN)、相邻R-R间期差值的均方根值(r MSSD)、相邻的R-R间期之差大于50 ms的心搏数占总心搏数的百分比(PNN50)、标化低频(normalized low frequency power,LFnorm)、标化高频(normalized high frequency power,HFnorm)、低频功率(low frequency,LF)与高频功率(high frequency,HF)的比值(LF/HF)。结果饮用咖啡后,心率、心率变异性指标均发生改变且具有统计学意义,HR、LFnorm和LF/HF分别降低了7.5%、17%和35%。r MSSD、PNN50和HFnorm分别提高了82%、80%和58%。其中HR及LF/HF随着时间的变化趋势最明显。HRV参数在饮用咖啡前后的差值ΔLF与ΔHF,ΔLF与ΔLF/HF均显著相关,相关系数为-0.980和0.903。结论中等剂量咖啡可引起心率变异性的改变和心率的降低,抑制交感神经活性,提高副交感神经活性。     

Effect of a short photoperiod on circadian rhythms of body temperature and motor activity in old rats

Circadian rhythms of body temperature and motor activity were documented in young and old rats (four 8-week-old and five 22-month-old male Wistars, implanted with telemetric probes and housed in a chronobiological facility) under two different photoperiod conditions. The animals were maintained in a light:dark (LD) cycle of 12 h each (LD 12:12) for 4 weeks and then exposed to a LD 6:18 cycle for 7 weeks to assess the effect of age on the desynchronization of the temporal structure of the rhythms. In old rats under LD 12:12, the power of the 24-h component and the circadian amplitude of body temperature and motor activity were markedly lower than in the young and both rhythms were phase-advanced. After the shift to LD 6:18, the circadian rhythmicity was maintained for both variables and the same phase delay (+5+/-1 h) was observed in both age groups, as was a gradual expansion of the patterns of both functions with the longer night. The photoperiod reduction (6 weeks under LD 6:18) did not modify the power of the 24-h component of body temperature and motor activity in old rats. In young rats, however, the power and amplitude of the 24-h component of motor activity rhythm fell to the levels of those in old rats, while the power of the 24-h component of body temperature rhythm and the amplitude did not change. Our data show that the circadian rhythm of motor activity, but not of body temperature, responds age dependently to a photoperiod reduction.     

小儿心肌炎的心率变异性

目的:探讨小儿心肌炎的心率变异性。方法:采用ECG-LA2.OGold型心电综合分析系统,描记肢体导联采样5分钟,应用时域及功率谱分析法,通过计算机计算出全部R-R间期的标准差(sDNN),极低频(VLF)低频(LF)高频(HF)。结果:以SDNN<27ms为阳性诊断标准,将57例小儿心肌炎病儿分为两组,一组SDNN<27ms共17例,病情较重,另一组SDNN>27ms共41例,病情较轻。结论:病情较重的心肌炎患儿短程HRV降低SDNN<27ms。     

肥厚型心肌病儿童心率变异的改变及其与心脏结构和收缩功能的相关性

研究肥厚型心肌病(HCM)患儿的心率变异(HRV)改变及其与心脏结构和收缩功能的相关性。将35例HCM患儿和30例健康儿童分别进行24h心率变异分析,得出SDNN、SDANN、PNN50r、MSSD、LF、HF及LF/HF等指标。行常规超声心动图及组织多普勒检查,取得左室心肌重量指数(LVMI)、左室流出道压力阶差(LVPG)、左室射血分数(LVEF)、短轴缩短率(FS)及室间隔、左心室侧壁、前壁和下壁的二尖瓣瓣环水平的心肌收缩期峰值速度等指标。对两组上述指标进行比较,并分析肥厚型心肌病患儿心率变异性与心脏结构和收缩功能的相关性。结果表明HCM患儿与对照组相比,心率变异指标中SDNN、PNN50r、MSSD、HF均显著降低,SDANN、LF略降低,LF/HF略升高;HF与室间隔的心肌运动峰值速度呈显著的正相关,与左室其它节段的心肌运动峰值速度呈较弱的正相关,与LVMI呈较弱的负相关,其余HRV指标与心脏结构和功能的指标间均无明显相关。HCM患儿有心率变异性改变,表现为自主神经的总体张力减弱,以迷走神经张力减弱为主,交感神经活性相对增强,且HCM患儿迷走神经的张力减弱与左室的收缩功能下降及室壁增厚有一定的相关性。     

Locomotor, feeding and melatonin daily rhythms in sharpsnout seabream (Diplodus puntazzo)

Sharpsnout seabream is a marine teleost of increasing interest for Mediterranean aquaculture, but there is still a lack of information regarding its circadian organization. In this study, we have investigated sharpsnout seabream locomotor activity, feeding and plasma melatonin daily rhythms under a 12:12-h LD cycle, as well as the persistence of locomotor activity circadian rhythmicity under constant light (LL) conditions. When submitted to an LD cycle, most sharpsnout seabream displayed a diurnal locomotor pattern, with an average 74% of activity recorded during daytime. However, along the experiment 40% of fish spontaneously changed their locomotor rhythm phasing and became nocturnal. Feeding behaviour, nevertheless, remained strictly diurnal in all cases, with 97% of food demands being made during the light period. Free-running locomotor rhythms were recorded in one third of the fish kept under LL. Daily plasma melatonin levels displayed a rhythmic profile, with low daytime values (111 pg/ml) and high nighttime concentrations (791 pg/ml). Taken together, these results evidence a high degree of plasticity for sharpsnout seabream activity patterns, as well as phasing independence of locomotor and feeding rhythms. Finally, the existence of a well-defined daily rhythm of plasma melatonin was found.     

Daytime Exposure to Blue Light Alters Cardiovascular Circadian Rhythms,Electrolyte Excretion and Melatonin Production

Artificial light is characterized by certain features of its impact on the body in terms of its spectral distribution of power, duration of exposure and intensity. Short waves, perceived as blue light, are the strongest synchronizing agent for the circadian system. In the present work, we investigated the features of the circadian rhythms of blood pressure (BP), heart rate (HR), the excretion of electrolytes and the secretion of melatonin in normotensive (Wistar–Kyoto) and hypertensive (SHR) rats under the action of monochromatic blue light in the daytime period. It was found that the exposure of Wistar–Kyoto rats to monochromatic blue light was accompanied by a significant decrease in nighttime and 24 h systolic BP. The most remarkable changes are characteristic of the HR in SHR rats under monochromatic light. A significant decrease in HR in each time period was found, but the predominance of nighttime over daytime values remained in SHR animals. There was also a significant increase in the mesor of the HR in SHR rats. Additionally, the amplitude of diastolic BP and HR, as well as the range of oscillations in HR, were significantly increased compared with the standard light pattern. In contrast to SHR rats, the regulation of the circadian rhythms in Wistar–Kyoto rats was more flexible and presented more changes, which may be aimed at the adaptation of the body to environmental conditions. For Wistar–Kyoto rats, an increase in the level of excreted electrolytes was observed under the action of monochromatic light, but no similar changes were found in SHR rats. For Wistar–Kyoto rats, a significant decrease in the urine concentration of aMT6s in the daytime and nighttime periods is characteristic, which results in the loss of the circadian rhythm. In SHR rats, there was a significant decrease in the nighttime content of aMT6s in the urine, while the daytime concentration, on the contrary, increased. The obtained data demonstrate that prolonged exposure to monochromatic blue light in the daytime period affects the circadian structure of the rhythms of the cardiovascular system, the rhythm of electrolyte excretion and the production of epiphyseal melatonin in wild-type and hypertensive animals. In SHR rats, the rhythms of BP and HR exhibit a more rigid pattern.     

Infant colic: the effect of serotonin and melatonin circadian rhythms on the intestinal smooth muscle.

It is hypothesized that in the evening, peak serotonin concentration causes intestinal cramps associated with colic because serotonin increases intestinal smooth muscle contractions. Melatonin has the opposite effect of relaxing intestinal smooth muscles. Both serotonin and melatonin exhibit a circadian rhythm with peak concentrations in the evening. However, serotonin intestinal contractions are unopposed by melatonin during the first 3 months because only serotonin circadian rhythms are present at birth. Melatonin circadian rhythms appear at 3 months of age. The cramps of colic disappear at 3 months of age.     

The chronobiology of the Natal mole-rat, Cryptomys hottentotus natalensis

The Natal mole-rat, Cryptomys hottentotus natalensis, rarely, if ever, is exposed to external light cues because it occurs in completely sealed tunnel systems. As a result, their classical visual system is regressed, and therefore, their circadian system is expected proportionally to be expanded. Locomotor activity was investigated under a number of different photic regimes. Nine of the 12 mole-rats exhibited endogenous circadian rhythms of locomotor activity under constant darkness, with a mean free run period of 24.13 h (range 23.93-24.13 h), with these animals entrained to a light-dark cycle (12 L:12 D). Because C. hottentotus natalensis are able to entrain their locomotor activity to an external light source, light must reach the suprachiasmatic nucleus (SCN), suggesting a functional circadian clock. A clear day-night rhythm of melatonin secretion in animals housed under a neutral photoperiod (12 L:12 D) was observed, with higher melatonin concentrations in the dark compared with the light phase. The rhythm was maintained after the animals were transferred to either continuous light (LL) or dark (DD), suggesting that the endogenous rhythm was maintained under acute exposure to light and dark. However, under DD, the rhythm appeared to shift slightly, potentially as a result of the rhythm free running. These results show that C. hottentotus natalensis has endogenous rhythms of both locomotor activity and melatonin secretion, which are modulated by light.     

妊娠期糖尿病孕妇心率变异性变化

目的:探讨妊娠期糖尿病孕妇心率变异性变化.方法:选取阳春市妇幼保健院2018年1月至2020年4月收治的50例妊娠期糖尿病患者作为观察组,选取同期健康孕检孕妇50例作为对照组,年龄20～36岁,孕周24～40周.所有孕妇给予动态心电图监测,比较两组孕妇平均心率(AHR)、正常窦性RR间期的总体标准差(SDNN)、每5 ...     

Melatonin secretion in the Mashona mole-rat, Cryptomys darlingi--influence of light on rhythmicity

The hormone melatonin is synthesised and secreted from the pineal gland in darkness and triggers the daily and seasonal timing of various physiological and behavioural processes. The Mashona mole-rat, Cryptomys darlingi, lives in subterranean burrows that are completely sealed and is therefore rarely, if ever, exposed to light under natural conditions. Hence, this species is of particular interest for studies on rhythms of melatonin secretion. We investigated how plasma melatonin concentrations of the Mashona mole-rat responded to exposure to a long-term standard photoperiod of 12 h light, 12 h dark (12:12 LD), constant light (LL) and constant dark (DD). In addition, we examined whether plasma melatonin concentration was coupled to locomotor activity. Mashona mole-rats displayed rhythms of plasma melatonin concentration that appeared entrained to the standard LD photoperiod, suggesting that the mole-rat is capable of perceiving and entraining to this photic zeitgeber. Furthermore, under chronic constant lighting conditions (DD, LL), circadian rhythms in plasma melatonin concentration were observed, suggesting the possible existence of an endogenous rhythm. Light suppressed melatonin secretion, but constant light did not abolish the rhythm of plasma melatonin concentration. Between active and non-active animals, no difference in plasma melatonin concentration was found for any of the sequential photoperiods (LD1 DD, LD2, LL), tentatively suggesting that the rhythm of melatonin secretion is uncoupled from that of locomotor activity.     

The 24-h growth hormone rhythm in men: sleep and circadian influences questioned

The 24-h rhythm of growth hormone (GH) is thought to be controlled primarily by sleep processes with a weak circadian component. This concept has been recently questioned in sleep-deprived persons. To test the notion of a high sleep-dependency of GH release, we established simultaneous 24-h rhythms of GH and melatonin, a circadian marker, in night workers who form a model for challenging sleep and circadian processes. Ten day-active subjects and 11 night workers were studied during their usual sleep-wake schedule, with sleep from 23:00 to 07:00 hours and 07:00 to 15:00 hours, respectively. Experiments were conducted in sleep rooms under continuous nutrition, bed rest, and dim light. Melatonin and GH were measured every 10 min over 24 h. In day-active subjects, melatonin and GH showed the well-known 24-h profiles, with a major sleep-related GH pulse accounting for 52.8 +/- 3.5% of the 24-h GH production and the onset of the melatonin surge occurring at 21:53 hours +/- 18 min. In night workers, melatonin showed variable circadian adaptation, with the onset of secretion varying between 21:45 and 05:05 hours. The sleep-related GH pulse was lowered, but the reduction was compensated for by the emergence of large individual pulses occurring unpredictably during waking periods, so that the total amount of GH secreted during the 24 h was constant. One cannot predict the degree of GH adaptation from the highly variable melatonin shift. These results argue against the concept that sleep processes exert a predominant influence on GH release whatever the conditions. When sleep and circadian processes are misaligned, the blunting of the sleep-related GH pulse is counteracted, as in sleep-deprived persons, by a compensatory mechanism promoting GH pulses during wakefulness.     

The use of pupillometry in the assessment of cardiac autonomic function in elite different type trained athletes

The aim of the present study was to evaluate cardiac autonomic function by pupillometry in male athletes. Fifteen elite endurance- (END) and eleven power-trained (POWER) athletes and fifteen sedentary individuals (CONTROL) were studied. All subjects underwent three pupillometric measurements: at rest, peak exercise testing and recovery phase. The pupillometric indices studied were: baseline pupil radius (R1), minimum pupil radius (R2), maximum constriction velocity (VC_max), maximum constriction acceleration (AC_max), amplitude (AMP, R1–R2), constriction ratio (AMP%). During exercise, RR intervals were obtained for each subject with a Polar S810i for time and frequency domain heart rate variability (HRV) analysis. The following parameters of HRV were measured: standard deviation of all NN intervals (SDNN), the mean square successive differences (rMSSD), percent of NN intervals differing >50 ms from the preceding NN (pNN50), low (LF)- and high (HF)- frequency components of the autoregressive power spectrum of the NN intervals and their ratio (LF/HF). At rest and recovery, END showed significantly increased VC_max and AC_max compared to POWER and CONTROL. AMP% was significantly greater in END at rest, peak exercise and recovery compared to POWER and CONTROL. END and POWER had significantly greater AMP at rest and recovery compared to CONTROL. Moreover, all HRV indices were significantly increased in END compared to POWER and CONTROL. However, POWER showed significantly increased rMSSD and LF compared to CONTROL. HRV parameters were significantly correlated with pupillometric parameters during exercise. Our results indicated that any kind of exercise training and mainly endurance one affects autonomic regulation of pupillary light reflex.     

A circadian clock in the fish retina regulates dopamine release via activation of melatonin receptors

Although many biochemical, morphological and physiological processes in the vertebrate retina are controlled by a circadian (24 h) clock, the location of the clock and how the clock alters retinal function are unclear. For instance, several observations have suggested that dopamine, a retinal neuromodulator, may play an important role in retinal rhythmicity but the link between dopamine and a clock located within or outside the retina remains to be established. We found that endogenous dopamine release from isolated goldfish retinae cultured in continuous darkness for 56 h clearly exhibited a circadian rhythm with high values during the subjective day. The continuous presence of melatonin (1 n m ) in the culture medium abolished the circadian rhythm of dopamine release and kept values constantly low and equal to the night-time values. The selective melatonin antagonist luzindole (1  μ m ) also abolished the dopamine rhythm but the values were high and equal to the daytime values. Melatonin application during the late subjective day introduced rod input and reduced cone input to fish cone horizontal cells, a state usually observed during the subjective night. In contrast, luzindole application during the subjective night decreased rod input and increased cone input. Prior application of dopamine or spiperone, a selective dopamine D₂-like antagonist, blocked the above effects of melatonin and luzindole, respectively. These findings indicate that a circadian clock in the vertebrate retina regulates dopamine release by the activation of melatonin receptors and that endogenous melatonin modulates rod and cone pathways through dopamine-mediated D₂-like receptor activation.     

Circadian rhythms of early morning awakening insomniacs

SUMMARY It has been suggested that two types of insomnia, sleep onset insomnia and early morning awakening insomnia, may be caused by delays and advances respectively of circadian rhythms. Evidence supports the circadian rhythm phase delay of sleep onset insomniacs. The present study investigated the phase timing of circadian rhythms of early morning awakening insomniacs compared with a group of age matched good sleepers. A 24-h bed rest laboratory session was used to evaluate the endogenous core body temperature and urinary melatonin rhythms. Objective and subjective sleepiness were also measured every 30 min across the session with 10 min multiple sleep latency tests and Stanford Sleepiness Scale. Maximum and minimum phases of each individual's rhythm were identified using two-component cosine curve fitting. Compared with the good sleepers, the insomniacs had significant phase advances of 2 4 h for the temperature and melatonin rhythms. However, the 0-4 h advances of the sleepiness rhythms were not significant. This latter unexpected result was explained on the basis of variability of sleepiness measures. It was suggested that early morning awakening insomnia arises from phase advanced circadian rhythms which evoke early arousal's from sleep.     

Circadian rhythms and the effects of exogenous melatonin in the nine-banded armadillo, Dasypus novemcinctus: A mammal lacking a distinct pineal gland

Circadian rhythms of body temperature, activity and oxygen consumption were recorded in the nine-banded armadillo, Dasypus novemcinctus, a mammal lacking a distinct pineal gland. The rhythms were entrained by light-dark cycles and appeared to be phase-coupled. Under constant illumination, the animals displayed free-running circadian rhythms with period lengths of slightly less than 24 hr. Melatonin implants caused a lengthening of the free-running period of activity and body temperature. The occurrence of a “normal” circadian rhythmicity in the armadillo indicates that the pineal organ is not necessary for the circadian organization of this animal whereas melatonin of non-pineal origin may have a role.     

The influence of sleep onset on the diurnal variation in cardiac activity and cardiac control

Heart rate (HR), blood pressure (BP) and autonomic nervous system (ANS) activity vary diurnally, with a reduction in HR and BP, and a shift to vagal dominance during the dark phase. However, the cause of these changes, particularly the relative influence of sleep and circadian mechanisms, remains uncertain. The present study assessed the effect of sleep onset on HR, BP, high frequency (HF) component of heart rate variability (HRV), low frequency/high frequency (LF/HF) ratio and pre-ejection period (PEP). Sleep onset was dissociated from circadian influences by having subjects go to sleep at two different circadian phases, their normal time of sleep onset (normal sleep onset, NSO), and after a delay of 3 h (delayed sleep onset, DSO). The assumption was that changes caused by sleep onset would occur in association with sleep onset, irrespective of its timing, while circadian effects would have a consistent circadian phase and be independent of when sleep onset occurred. Thirteen and 17 subjects were run in the NSO and DSO conditions, respectively. Following a 1-h adaptation period, data collection began 2 h before subjects' normal time of sleep onset and continued until morning awakening. The lights were turned out after 2 h in the NSO condition and 5 h in the DSO condition. Subjects were required to maintain a supine position throughout the experimental sessions. The night-time decrease in HR was found to be due to both sleep onset and a circadian influence, with the circadian component being more prominent. In contrast, the fall in BP was largely due to a sleep onset effect. Increased vagal activity, as reflected in the HF component and a shift to vagal dominance in the LF/HF ratio, appeared to be primarily a function of the sleep system, while sympathetic activity, as assessed by PEP, reflected a circadian influence.     

Separation of circadian and wake duration-dependent modulation of EEG activation during wakefulness

The separate contribution of circadian rhythmicity and elapsed time awake on electroencephalographic (EEG) activity during wakefulness was assessed. Seven men lived in an environmental scheduling facility for 4 weeks and completed fourteen 42.85-h 'days', each consisting of an extended (28.57-h) wake episode and a 14.28-h sleep opportunity. The circadian rhythm of plasma melatonin desynchronized from the 42.85-h day. This allowed quantification of the separate contribution of circadian phase and elapsed time awake to variation in EEG power spectra (1-32 Hz). EEG activity during standardized behavioral conditions was markedly affected by both circadian phase and elapsed time awake in an EEG frequency- and derivation-specific manner. The nadir of the circadian rhythm in alpha (8-12 Hz) activity in both fronto-central and occipito-parietal derivations occurred during the biological night, close to the crest of the melatonin rhythm. The nadir of the circadian rhythm of theta (4.5-8 Hz) and beta (20-32 Hz) activity in the fronto-central derivation was located close to the onset of melatonin secretion, i.e. during the wake maintenance zone. As time awake progressed, delta frequency (1-4.5 Hz) and beta (20-32 Hz) activity rose monotonically in frontal derivations. The interaction between the circadian and wake-dependent increase in frontal delta was such that the intrusion of delta was minimal when sustained wakefulness coincided with the biological day, but pronounced during the biological night. Our data imply that the circadian pacemaker facilitates frontal EEG activation during the wake maintenance zone, by generating an arousal signal that prevents the intrusion of low-frequency EEG components, the propensity for which increases progressively during wakefulness.     

不同海拔健康青年男性心率变异性对比分析

应用短程心率变异性（HRV）时域、频域和非线性分析法，对比进入三个不同海拔高度自主神经系统（ANS）调节功能的特点。发现：与进入海拔1856m相比．海拔2800m平均正常RR间期的标准差（SDNN）、相邻RR间期差的均方根（rMSSD）、相差〉50ms的相邻RR间期占RR间期总数的百分比（PNNS0）、低频成分（LF）、高频成分（HF）以及总功率（TP）均有轻度升高，但无统计学差异；与进入海拔1856m和海拔2800m相比．海拔3040mSDNN、rMSSD、LF和HF显著降低。这表明进入海拔3040m副交感神经活动显著减弱、自主神经系统调节功能显著受抑。自主神经的这种变化有助于进一步阐明进入高海拔机体发生的病理生理学改变。     

Influence of physical training on the Syrian hamster's melatonin rhythm

Melatonin secretion can be influenced by acute exercise. Using female Syrian hamsters we assessed the influence of physical exercise in the serum melatonin rhythm. Melatonin concentrations were determined by RIA. After a gradually increased training program in which experiments were performed at the end of the light phase of the photoperiod (14-h light:10-h dark; lights on at 21:00) animals were killed immediately after exercise (14 h light) and at different time points including 11h after light and 3, 6, 8 and 9h after dark. No differences in melatonin concentrations immediately after exercise practice between control and trained animals were observed. A slower melatonin nighttime increase in exercised hamsters, with significantly lower levels 6h after dark in comparison with controls was found. The peak value appeared 8h after dark but high melatonin levels were prolonged in exercised hamsters, showing significantly higher melatonin levels 9h after. In conclusion, our results indicate for the first time that Syrian hamsters submitted to a training program of increased activity at the end of the light phase, the rest period, showed an altered melatonin rhythm, resembling the response observed in humans.     

Effect of a 24-h continuous walking race on cardiac autonomic control

This study investigated the relationships between walking speed and heart rate (HR) variability (HRV) in eleven subjects during a 24-h race. It was hypothesized that the nycthemeral rhythm on HR is preserved during the race. RR intervals and walking speed were measured. Fast Fourier transform was applied to samples of 1,024 successive RR intervals collected every hour from a HR monitor. Walking speed was averaged every hour and decreased (first lap: 8.8 ± 0.3 vs. last lap: 7.3 ± 0.8 km h⁻¹, P < 0.001) with HR also decreasing (max at 19:00 h: 143 ± 9 vs. min at 7:00 h: 117 ± 14 beats min⁻¹, P < 0.001) following a third order polynomial shape. HRV power spectral components followed distribution patterns similar to the mean RR during the race with a minimum in the early evening (19:00–20:00 h) and a maximum in the morning (5:00–8:00 h). Thus, as for mean RR, spectral components over time are also fitted to a third order polynomial regression. LF/HF ratio increased linearly (min = 0.5 ± 0.3, max = 2.8 ± 5.3, P = 0.02). Although mean HF peak did not decrease significantly over time, it was positively correlated with walking speed. In conclusion, this study showed that despite a constant decrease in walking speed, HR circadian rhythm is preserved during a continuous 24-h walking race. The short-term HRV components remain linked to HR whereas the LF/HF ratio increases linearly until the end of the race whatever HR is.