高血压病血压昼夜节律与心肌缺血的关系

目的 探讨高血压病患者血压昼夜节律改变与心肌缺血之间的关系及临床意义。方法对90例高血压病患者,根据动态心电图上有无心肌缺血(MI)分为MI组(40例)和无MI组(50例),并与20例健康体检者进行对照,观察3组的动态血压变化,同时分析血压昼夜节律正常组和异常组的心肌缺血的发生情况。结果 高血压病伴有MI的患者中,除dSBP、24hDBPL、dSBPL、dDBPL与无MI组比较无统计学差异外,其余各项动态血压指标均明显高于无MI组(P<0.01);高血压病血压昼夜节律异常组发生MI者明显高于血压昼夜节律正常组(P<0.05)。结论 高血压病患者中伴有血压昼夜节律异常者更易导致心肌缺血的发生。对高血压病患者的治疗,除积极控制血压外,还应注意检测和逆转异常的昼夜血压节律,对减少心肌缺血的发生和靶器官损害具有重要意义。     

The adrenergic modulation of firings of respiratory rhythm-generating neurons in medulla-spinal cord preparation from newborn rat

We analysed the modulation of respiratory neurons by adrenaline or noradrenaline (NA) in a newborn rat brainstem-spinal cord preparation. Adrenaline or NA caused a dose-dependent depression of the respiratory rhythm and induced C4 spinal tonic discharges. The inhibitory effect of adrenaline (ED₅₀=0.5 μM) on the respiratory rhythm was stronger than NA (ED₅₀=5 μM). The adrenaline respiratory rhythm depression was partially blocked by the α₁-antagonist prazosin or by the α₂-antagonist yohimbine. The C4 tonic discharge elicited by adrenaline was blocked by the α₁-antagonist prazosin. The direct effects of adrenaline on pre-inspiratory (Pre-I) neurons were examined in a synaptic blockade solution (low Ca), and fifty-six percent of Pre-I neurons were found to continue firing. In low-Ca solution, Pre-I neurons were excited (n=29 of 39) or depressed (n=5 of 39) by adrenaline, and excited by α₁-agonist phenylephrine or depressed by α₂-agonist clonidine. These results suggest that the respiratory rhythm depression under intact network conditions is mediated by some other inhibitory system. The inhibitory effect of adrenaline on the respiratory rhythm was partially blocked by the GABA_A-antagonists bicuculline or picrotoxin, but not by the GABA_B-antagonist phaclofen. The present results suggest that: (1) respiratory rhythm generation is more sensitive to adrenaline than NA through α-adrenergic action of adrenaline; (2) the activity of Pre-I neurons could be directly regulated by excitation via α₁-receptors and inhibition via α₂-receptors; and (3) the depression of the respiratory rhythm by adrenaline is partly mediated by GABA_Aergic neurons. Received: 8 April 1997 / Accepted: 6 October 1997     

Genetic variation in locomotor activity rhythm among populations ofLeptopilina heterotoma (Hymenoptera: Eucoilidae), a larval parasitoid ofDrosophila species

The locomotor activity rhythm ofLeptopilina heterotoma, a parasitoid insect ofDrosophila larvae, was investigated under laboratory conditions. Under LD 1212, the locomotor activity of females shows a clear rhythm which persists under continuous darkness (circadian rhythm). However, comparative study of five populations indicates that both the rate of activity and the profile of the rhythm vary according to the origin of females. The Mediterranean populations (Tunisia and Antibes) show two peaks of activity, at the beginning and at the end of the photophase, whereas more northern populations (Lyon and the Netherlands) are mostly active during the afternoon. Females originating from the area of Lyon have a very low level of activity. Reciprocal crosses (F₁ hybrids and backcrosses) between the French and the Tunisian strains demonstrated the genetic basis of these variations and the biparental inheritance of the trait. This genetic variability is interpreted as a consequence of selective pressures and suggests a local adaptation of natural populations in host foraging behavior. The selective factors which could act on the daily organization of parasitoid behaviors are discussed.     

Quantitative trait loci (QTL) for circadian rhythms of locomotor activity in mice

The loomotor activity of male mice (Mus musculus) was monitored by infrared photoelectric beams under three lighting regimens: LD (12 h of light and 12 h of dark), DD (constant dark), and LL (constant broad-spectrum light, 10 lux). Circadian period of locomotor activioty (τ) was compared among 3 inbred strains of mice, C57BL/6J (B6), BALB/c (C), and DBA/2J (D2), and 26 recombinant inbred strains B×D (B6×D2). the τ under both continuous low-intensity light and continuous darkenss varied significantly among strains. Under DD the mean τ was 23.8 h for B6, 23.7 h for D2, and 23.6 h for C. Under LL the mean τ was 25.1 for B6, 23.9 h for D2, and 25.5 h for C. Frequency histograms of the mean τ of 26B×D RI mouse strains (three to seven animals per strain) in either DD or LL and the difference between them, Δτ, had distributions which appeared unimodal, suggesting polygenic inheritances. The narrow-sense heritability determined using 26 strains of B×D RI mice was about 55% for τ and about 38% for both τ in LL and Δτ. An estimated four loci contribute to the variance of τ in constant darkness and five to the variance of τ in constant low-intensity light among the strains studied. Quantitative trait locus (QTL) analysis identified several potential genetic loci associated with τ in constant darkness, τ in constant low-intensity light, and Δτ. The associations of highest probability for each of these traits were theD1Nds4 locus (p<0.001) on mouse chromosome 1, theD5Ncvs52 locus (p<.05) on mouse chromosome 5, and thePmv12 locus (p<.01) at 70 cM on mouse chromosome 5, respectively. A QTL identified for τ was associated (p<.05) with theD2NDS1 marker at 45 cM on chromsome 2 near the Ea 6 marker at 46 cM associated (p<.05) with that reported for the period of wheel running activity in seven C×B RI strains (Schwartz, W. J., and Zimmerman, P.,J. Neurosci. 10:3685 1990).     

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.     

Changes in mitotic activity of the corneal epithelium of albino rats cooled at different times of day

The effect of moderate hypothermia on mitotic activity of the corneal epithelium of albino rats was studied. The animals were cooled to 28°C by a contact method for 1 h. Cooling was carried out in the early morning (6 a.m.), at noon, and in the evening (6 p.m.). The response of the epithelium to cooling was found to depend on the time of day. The most marked inhibition of mitotic activity (by 14 times) occurred in the afternoon, 3 h after cooling at noon. A tendency toward restoration of normal cell division was observed 6 and 12 h later. The number of mitoses was reduced 3 h after cooling in the evening, but no changes in mitotic activity were discovered 6 and 12 h later. No changes were found 3 and 6 h after cooling in the morning, but 12 h later cell division was inhibited.Central Scientific-Research Laboratory, Khabarovsk Medical Institute. Laboratory of Cytology, Institute of Human Morphology, Academy of Medical Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR A. P. Avtsyn.) Translated from Byulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 82, No. 11, pp. 1371–1373, November, 1976.     

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.