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.     

Biological balance of sodium and potassium

Summary The rhythm of renal sodium and potassium excretion was measured in 4-h-intervals in 12 subjects. Each person exhibited clear circadian variations of each variable with a maximum between 8 a.m. and 4 p.m. In each subject and for both circadian rhythms the oscillation mean was correlated to the range of oscillation (amplitude).Increase in sodium or potassium excretion during 1 day resulted in an increase of oscillation range. The oscillation means of sodium and potassium periodicity did not correlate.The properties of biological control systems with oscillating correcting variables are comparable to those of technical control systems. The significance of circadian rhythm for the control of electrolyte balance is indicated.     

Control of feeding rhythm in the terrestrial slug Incilaria bilineata

A modulatory neuron of feeding rhythm was newly identified in the buccal ganglia of the isolated central nervous system (CNS) of the terrestrial slug Incilaria bilineata. This neuron was termed the “feeding rhythm modulator” (FRM). Its morphological and electrical properties were compared with those of the MGC (metacerebral giant cell, a cerebral modulatory neuron of feeding rhythm). There was no direct connection between FRM and MGC. In order to investigate the control mechanism of the buccal central pattern generator, feeding rhythm was observed by varying the activities of MGC and FRM simultaneously. At a lower level of activity of MGC, feeding rhythm was not only sensitive to the activity of MGC but also to that of FRM. As the level of activity of MGC increased, feeding rhythm was exclusively controlled by the activity of MGC, and became unaffected by the activity of FRM. This indicates that cerebral neurons such as MGC primarily control feeding rhythm and modulate the contribution of FRM in a hierarchical manner.     

Certain characteristics of myocardial contractility of isovolumic dog heart at randomly variable heart rhythm

Summary The relationship heart rate-left ventricular pressure was investigated in the isolated canine heart perfused with constant pressure at different preloads. Rhythmical stimulation was performed with constant stimulus interval duration and with stimulus intervals randomly changed near the average value (150–200 stimuli in series).Correlation and dispersion function analysis show that rhythm dispersion had a negative inotropic effect which was independent of the preload of the ventricle in the range of 120–180 beat/min, but this dependence occurred with low rates of stimulation.This method is proposed for the assessment of contractility under conditions of heart rate variations (physiological and pathological arrhythmias).     

Brain–Gut–Microbiome Interactions and Intermittent Fasting in Obesity

The obesity epidemic and its metabolic consequences are a major public health problem both in the USA and globally. While the underlying causes are multifactorial, dysregulations within the brain–gut–microbiome (BGM) system play a central role. Normal eating behavior is coordinated by the tightly regulated balance between intestinal, extraintestinal and central homeostatic and hedonic mechanisms, resulting in stable body weight. The ubiquitous availability and marketing of inexpensive, highly palatable and calorie-dense food has played a crucial role in shifting this balance towards hedonic eating through both central (disruptions in dopaminergic signaling) and intestinal (vagal afferent function, metabolic toxemia, systemic immune activation, changes to gut microbiome and metabolome) mechanisms. The balance between homeostatic and hedonic eating behaviors is not only influenced by the amount and composition of the diet, but also by the timing and rhythmicity of food ingestion. Circadian rhythmicity affects both eating behavior and multiple gut functions, as well as the composition and interactions of the microbiome with the gut. Profound preclinical effects of intermittent fasting and time restricted eating on the gut microbiome and on host metabolism, mostly demonstrated in animal models and in a limited number of controlled human trials, have been reported. In this Review, we will discuss the effects of time-restricted eating on the BGM and review the promising effects of this eating pattern in obesity treatment.     

氨氯地平与左旋氨氯地平治疗夜间高血压疗效比较

目的 :观察左旋氨氯地平与氨氯地平治疗夜间高血压患者的疗效及其对血压昼夜节律的影响。　方法 :6 0例轻、中度原发性高血压患者 (必须同时具备夜间血压增高 )随机接受氨氯地平 5mg或左旋氨氯地平 2 .5mg(各30例 )治疗 4周。用 2 4h动态血压监测治疗前后血压的昼夜节律变化。　结果 :氨氯地平和左旋氨氯地平降压疗效显著 ,但二药之间比较无显著差异 (P >0 .0 5 ) ,均不影响血压昼夜节律。　结论 :氨氯地平和左旋氨氯地平治疗有夜间血压增高的轻、中度高血压患者疗效好 ,而且安全     

褪黑素对大鼠体温及活动度昼夜节律的影响

目的　了解外源性褪黑素对大鼠体温及活动度昼夜节律的影响及其可能的调节机制。方法　正常光照条件下,24h连续记录大鼠的体温及活动度的变化,以不同剂量褪黑素在不同的昼夜时间给药观察体温和活动度节律的变化。结果　大鼠的体温及活动度存在昼夜节律性,给药后昼夜节律性不消失;但体温振幅减小,中值降低。黑暗中期给药后,峰值位相显著延迟;活动度振幅增加,中值显著降低,峰值位相延迟。结论　外源性褪黑素不能使体温或活动度的昼夜节律消失,而只是改变昼夜节律的参数。褪黑素可分别调节体温和活动度的昼夜节律,但对活动度的调节作用更为明显。     

似昼夜节律与学习效应对脑事件相关电位P300的影响

目的 探讨昼夜节律和学习效应对脑事件相关电位P300成分的影响。方法 8名被试者在非连续的5d的实验中每天在5个时间点（7：00,12：00,16：00,20：00和0：00）重复相同的听觉Oddball模式测试以诱发脑事件相关电位（ERP）。然后测量各次的ERPP300成分,得到其潜伏期及波幅。结果 P300波幅明显高于下午的波辐。重复测量也使P300波幅从第1个实验日的平均13.0uV降至第5个实验日的9.2uV。P300潜伏期随着重复测试的增加出现了习服,它从第2个实验日的平均350.6ms缩短为第5个实验日的平均343.5ms.结论 似昼夜节律和学习效应对脑事件相关电位P300成分的波幅和潜伏期均有影响。     

慢径路消融改良房室结术中出现的交界性心律之特征

目的：分析房室结慢径路消融术中出现的一过性交界性心律（ＪＲ）的特征。方法：２１例（男６例,女１５例）进行房室结改良术的房室结折返性心动过速患者,术中详细记录释放射频的次数、能量、持续时间、以及出现一过性交界性心律的时间、频率及数目,比较释放射频有效时／无效时出现的一过性交界性心律之特征有无显著性差异。结果：共进行１０６次射频电流释放,其中２１次有效（Ａ组）,８５次无效（Ｂ组）。Ａ组有１９次出现ＪＲ