The excitation of the heart and its modification under the influence of the chemical mediators and the cardiac nerves: I. Some general consequences of the one-factor theory

A generalized form of the one-factor theory is applied to the heart. It is found that the effects of acetylcholine and sympathin on the chronaxie can be accounted for only if the decay constant of the excitatory state increases in the presence of acetylcholine, and decreases in the presence of sympathin. With the assumption that this is the only effect of the chemical mediators, it is shown that upon application of acetylcholine to the heart the theory predicts: 1) a rise in the rheobase; 2) an increase in the time required for excitation by constant currents; 3) no change in the threshold with condensor discharges of brief duration; 4) a decrease in the spontaneous heart rate; 5) a sudden and complete inhibition of the spontaneous heart rate with excessive concentrations of acetylcholine. In general, the effects of sympathin predicted by the theory oppose those of acetylcholine. Public Health Service Research Fellow of The National Heart Institute.     

Estimation of the abrasive wear coefficient in Lillehei-Kaster cardiac valve prostheses

An approximate hemodynamic theory, which predicts the opening dynamics of the Lillehei-Kaster heart valve, is used in conjunction with an abrasive wear model to predict the wear process on the shields. The hemodynamic theory predicts markedly different opening dynamics between the mitral and aortic positions and is shown to give excellent correlation with the experimental results of other investigations. The abrasive wear model is also shown to give excellent correlation with the experiments of others when the abrasive wear coefficient is taken as k = 6.4 X 10(-6). The theoretical results of this effort and the experimental data from clinical explants of other investigators is used to predict that occluder dislodgement is unlikely in less than 90 yr for either the mitral or aortic positions (for a mean cardiac output of 3.8 l.min-1 and a mean heart rate of 70 beats min-1).     

Analysis of Heart Rate Variability Based on the Graph Method

A method of analysis of heart rate variability based on the graph theory principle was suggested. The main parameters of the heart rate graph structure were determined and analyzed using models of harmonic oscillations, white noise, and various functional tests (including controllable respiration and mental load). The efficiency of the use of parameters of the heart rate graph for diagnosing some functional states was considered. A correlation of the parameters of the heart rate graph structure with the frequency characteristics of heart rate variability was studied. A general model of changes in the heart rate graph structure parameters at different levels of mental activity was constructed in terms of entropy changes.     

超声心动图检查对慢性肺源性心脏病患者右心功能的诊断价值

目的:探讨超声心动图检查对慢性肺源性心脏病患者右心功能的诊断价值。方法:选取2016年8月至2017年12月间本院收治的35例慢性肺源性心脏病患者作为实验组,并选择同期健康体检者35例作为对照组,全部受试者均给予超声心动图检查。分别比较两组右房横径(RA)、右室前后径(RV)、肺动脉平均压(MPAP)、射血分数(EF)、舒张晚期A波峰值流速与舒张早期E波峰值流速的比值(A/E)和右心室Tei指数。同时比较实验组采用常规12导联心电图检查及超声心动图检查的诊断阳性率、右心扩大阳性率和右心扩大伴心衰阳性率。结果:与对照组相比,实验组RA、RV以及MPAP均升高,组间比较差异有统计学意义(P0.05)。与对照组相比,实验组EF明显降低,而A/E值、Tei指数明显升高,组间比较差异有统计学意义(P0.05)。实验组超声心动图检查的诊断阳性率、右心扩大阳性率和右心扩大伴心衰阳性率均高于常规12导联心电图检查(P0.05)。结论:应用超声心动图检查能够有效诊断慢性肺源性心脏病患者的右心功能,而且操作简单方便,诊断阳性率较高。     

Beneficial cardiovascular effects of endothelin ET(A) receptor blockade in established long-term heart failure after myocardial infarction

Although experimental prevention studies have suggested therapeutic potential of endothelin (ET) antagonists for the treatment of heart failure, the results of clinical trials using ET antagonists on top of standard heart failure medications have been largely disappointing. This experimental study investigated the effects of chronic ET(A) receptor blockade in long-term survivors of myocardial infarction who had developed stable chronic heart failure in the absence of other treatments. Systolic blood pressure, heart rate, organ weights of the right atrium and ventricle, and the lungs were determined, and tissue ET-1 peptide levels were measured in cardiac tissue, lung, and aorta. The results show that chronic blockade of ET(A) receptors stabilizes systolic blood pressure and reverses the heart failure-induced weight increases of right heart chambers and lung. The changes observed occurred independently of tissue ET-1 concentrations and heart rate, suggesting mechanisms independent of local cardiac or pulmonary ET-1 synthesis, which are yet to be identified.     

地佐辛抑制依托咪酯所致肌阵挛时对心率和平均动脉压影响的临床研究

目的:观察地佐辛抑制依托咪酯所致肌阵挛时对患者的心率和平均动脉压的影响。方法:选择120例择期全麻手术患者,将其随机分为对照组和实验组(地佐辛0.1 mg/kg),每组60例。在依托咪酯麻醉诱导前,实验组患者静脉注射地佐辛,对照组静脉注射等容积生理盐水。5分钟后,两组均静脉注射依托咪酯0.3 mg/kg麻醉诱导,记录和比较两组患者在给予地佐辛和生理盐水前(T0期)、给予地佐辛和生理盐水后5分钟(T1期)、给予依托咪酯后2分钟(T2期)的平均动脉压和心率的变化情况,并观察其有无肌阵挛及肌阵挛的程度。结果:对照组患者肌震颤的发生率为60%,实验组无患者发生肌震颤,两组比较差异有统计学意义(P0.01)。两组患者T2期平均动脉压均较同T0、T1期显著下降,但对照组和实验组患者T2期平均动脉压比较无显著差异(P0.05)。对照组T0、T1和T2三期心率无明显变化(P0.05),实验组T2期心率较T0和T1期明显下降,亦明显低于对照组T2期心率,且差异均具有统计学意义(P0.05)。结论:应用地佐辛预处理抑制依托咪酯麻醉诱导所致肌阵挛时,其对患者的平均动脉压无明显影响,可使心率减慢,但心率处于正常范围内。     

Theory and experimental method for determining individual kinetic constants of fast-acting, irreversible proteinase inhibitors

A theory and experimental method are presented to characterize the kinetics of fast-acting, irreversible proteinase inhibitors. The theory is based upon formal analysis of the case of an irreversible inhibitor competing with a substrate for the active-site of a proteinase. From this theory, an experimental method is described by which the individual microscopic kinetic constants for the interaction of the inhibitor with the proteinase can be determined. These are, for a two-step inhibition reaction sequence, the equilibrium dissociation constant and the first-order rate constant for inhibition, and, for a one-step inhibition reaction sequence, the second-order rate constant for inhibition. The theory and experimental method were validated by an analysis of the inhibition of trypsin by the two-step synthetic inhibitor p-nitrophenyl p-guanidinobenzoate and the one-step protein inhibitor bovine pancreatic trypsin inhibitor. The substrate used in these experiments is a new, fluorogenic substrate for trypsin-like serine proteinases (Cbz-Ile-Pro-Arg-NH)2-Rhodamine, the synthesis and properties of which are described.     

General theory of determining intraparticle active immobilized enzyme distribution and rate parameters

A general theory is presented in this article for determining the intrinsic rate constants for the main reaction and deactivation reaction, the effective diffusivity of the substrate, and the active enzyme distribution within porous solid supports from deactivation study of a continuous stirred-basket reactor (CSBR). For the parallel deactivation five reaction kinetics are considered: (a) Michaelis-Menten, (b) substrate inhibition, (c) product inhibition (competitive), (d) product inhibition (anticompetitive), and (e) zero-order kinetics. The experimental results of the system of hydrogen-peroxide-immobilized catalase on controlled-pore glass particles are analyzed to demonstrate the application of the theory developed for parallel deactivation of active immobilized enzyme (IME). For series deactivation only first-order kinetics is treated, and a numerical procedure is proposed to deter mine the rate parameters and the internal active enzyme distribution. The experimental data of the system of glucose-immobilized glucose oxidase on silica-alumina and controlled-pore glass particles are used to verify the theory.     

Differentiating Orienting and Defensive Responses to Concealed Information: The Role of Verbalization

Using physiological measures, concealed information can be validly assessed. Orienting theory has been proposed to account for concealed information testing. As orienting is characterized by heart rate deceleration, one would expect this type of heart rate response to concealed information. However, with some exceptions, an initial heart rate acceleration to concealed information is typically observed. In the present paper, we examine the role of verbalization to explain the mixed pattern of heart rate changes. Using a within-subjects design, 30 participants were asked to either remain silent or to give an overt verbal response (“yes”/”no”) to concealed autobiographical and control information. The results indicate that verbalization accounts for the initial heart rate acceleration. In line with the orienting theory, initial heart rate deceleration is observed when participants remained silent. Bruno Verschuere is a postdoctoral fellow of the Scientific Research Foundation (FWO).     

Effect of autonomic blockers on the heart rate of intact rats and animals with artificial hyperthyroidism.

The effect of various autonomic blockers on the heart rate (from the ECG recording) of intact rats and of animals with experimental hyperthyroidism induced by the administration of dried thyroid was studied. In intact rats, the heart rate fell significantly (by 22%) during the first week after the peroral administration of propranolol (0.05% in food), but trimepranol (0.02%), reserpine (0.001%) and guanethidine (0.1%) had no effect (in a suplementary experment, a small, but statistically significant decrease was also found after trimepranol). In experimental hyperthyroidism, using the same blocker doses, the heart rate fell significantly after propranolol (by 23%), trimepranol (22%), reserpine (16%) and, in a preliminary experiment, guanethidine (19%). On injecting 0.05 mg propranolol intravenously, the maximum drop in the heart rate in intact rats was 22%, while in hyperthyroidism it was hardly more than half this value (at all the intervals from 2 to 30 minutes the decrease was statistically significant). Practolol, in a dose of 0.3 mg i.v., was less effective -- in intact rats the heart rate fell by not more than 12% (at all the intervals from 2 to 30 minutes the decrease was significant), but in hyperthyroidism the drop was slower and statistically non-significant. The results do not furnish an unequivocal answer to the question of the role of adrenergic regulation of the heart rate under physiological conditions and in experimental hyperthyroidism in rats.     

一种鸡胚胎心率记录的新方法

鸡胚胎是一种被广泛应用于发育生物学研究的实验材料。在以鸡胚胎为动物模型的各项研究工作中,心率常被看作是一个很重要的反应胚胎生理活动指标。本文详细介绍了一种侵入性的心电记录新方法,在正常的生理条件下通过记录鸡胚胎心电的变化来监测心率。首先在蛋壳上钻孔,将电极插入蛋内,然后通过放大器放大,A／D板转换,将心电信号输入电脑进行分析处理,提取与心率相关的信息。这种记录方式对胚胎损伤较小,不影响胚胎的正常发育;具有灵敏度高,操作简单,容易掌握等特点。     

The impact of the cardiovascular component and somatic mutations on ageing

Mechanistic insight into ageing may empower prolonging the lifespan of humans; however, a complete understanding of this process is still lacking despite a plethora of ageing theories. In order to address this, we investigated the association of lifespan with eight phenotypic traits, that is, litter size, body mass, female and male sexual maturity, somatic mutation, heart, respiratory, and metabolic rate. In support of the somatic mutation theory, we analysed 15 mammalian species and their whole-genome sequencing deriving somatic mutation rate, which displayed the strongest negative correlation with lifespan. All remaining phenotypic traits showed almost equivalent strong associations across this mammalian cohort, however, resting heart rate explained additional variance in lifespan. Integrating somatic mutation and resting heart rate boosted the prediction of lifespan, thus highlighting that resting heart rate may either directly influence lifespan, or represents an epiphenomenon for additional lower-level mechanisms, for example, metabolic rate, that are associated with lifespan.     

The mechanism of action of a synthetic derivative of 1,4-naphthoquinone on the respiratory chain of liver and heart mitochondria

It was found that the 1.4-naphthoquinone derivative AK-135 (2-methyl-3-piperidine-methyl-1.4-naphthoquinone hydrochloride) possesses a marked acceptor capacity during succinate and glutamate oxidation by rat liver and rabbit heart mitochondria. AK-135 fully restores the rate of glutamate (but not succinate) oxidation by liver and heart mitochondria catalyzed by rotenone, antimycin A and cyanide. In non-phosphorylating preparations of liver and heart mitochondria, AK-135 eliminates the inhibition of respiration on exogenous NADH induced by the same electron transport inhibitors. In liver mitochondria, the stimulation of succinate oxidation is due to a reverse electron transfer, whereas in the heart it proceeds via the rotenone-insensitive pathway. The experimental results suggest that in the liver and heart AK-135 accepts electrons from NADH-dehydrogenase oxidizing endogenous NADH. Besides, in the liver this compound is also capable of accepting electrons from NADH-cytochrome b5 reductase.     

Heat transfer in a microvascular network: the effect of heart rate on heating and cooling in reptiles (Pogona barbata and Varanus varius)

Thermally-induced changes in heart rate and blood flow in reptiles are believed to be of selective advantage by allowing animal to exert some control over rates of heating and cooling. This notion has become one of the principal paradigms in reptilian thermal physiology. However, the functional significance of changes in heart rate is unclear, because the effect of heart rate and blood flow on total animal heat transfer is not known. I used heat transfer theory to determine the importance of heat transfer by blood flow relative to conduction. I validated theoretical predictions by comparing them with field data from two species of lizard, bearded dragons (Pogona barbata) and lace monitors (Varanus varius). Heart rates measured in free-ranging lizards in the field were significantly higher during heating than during cooling, and heart rates decreased with body mass. Convective heat transfer by blood flow increased with heart rate. Rates of heat transfer by both blood flow and conduction decreased with mass, but the mass scaling exponents were different. Hence, rate of conductive heat transfer decreased more rapidly with increasing mass than did heat transfer by blood flow, so that the relative importance of blood flow in total animal heat transfer increased with mass. The functional significance of changes in heart rate and, hence, rates of heat transfer, in response to heating and cooling in lizards was quantified. For example, by increasing heart rate when entering a heating environment in the morning, and decreasing heart rate when the environment cools in the evening a Pogona can spend up to 44 min longer per day with body temperature within its preferred range. It was concluded that changes in heart rate in response to heating and cooling confer a selective advantage at least on reptiles of mass similar to that of the study animals (0. 21-5.6 kg).     

Connection of the tangents of the regression slope of the heart rate graph with linear and nonlinear dynamics in stationary short-time series

The connection of the regression slope of heart rate graph (b1) with linear and nonlinear dynamics in stationary short-time series (256 points) was studied. A new index for the estimation of nonlinear dynamics in stationary short-time series was used, which is based on the correlation dimension. The results of the study indicated that the dynamics of heart rate in stationary short-time series can be represented as the sum of linear (periodic) and nonlinear (stochastic) processes. A relation of b1 with both linear and nonlinear dynamics of heart rate was found. The formulas for the calculation of absolute and relative (to the amplitude of periodic fluctuations) noise levels in heart rate dynamics were derived. A comparative analysis of nonlinear dynamics of heart rate in stationary short-time series for different functional states of humans was performed. The increase in the relative noise level in heart rate dynamics with increasing breathing frequency is related not only to a decrease in control breathing amplitude but also to an increase in the noise amplitude. The decrease in the absolute noise level for nervous excitation, fatigue, and mental stress were found. The predominance of nonlinear (stochastic) processes over linear (periodic) processes in the relaxed state was established.     

The effects of an exercise physiology program on physical fitness variables, body satisfaction, and physiology knowledge

This study was performed to determine the effects of an exercise physiology program on physical fitness, body satisfaction, and knowledge. A total of 161 students (mean age = 16.5 +/- 0.89 years) of the Coral Gables Senior High School served as the experimental group volunteers, whereas 33 students enrolled in a standard biology course served as the control group (mean age = 15.61 +/- 0.84 years). The experimental group received exercise physiology theory coupled with active aerobic and resistance exercise. Age (p = 0.0001) and lean body mass (p = 0.023) were the only physical characteristics significantly greater in the experimental group at pretesting. An analysis of covariance controlling for pretest values showed better results in the experimental compared with the control group for sit and reach (p = 0.008), step test, recovery heart rate (p = 0.0002), overhead press (p = 0.002), bench press (p = 0.017), leg press (p = 0.012), sit-ups (p = 0.001), body satisfaction (p = 0.0009), and physiology knowledge (p = 0.0001) at posttesting. Findings indicated that a biology curriculum integrated with exercise physiology theory and exercise activities may result in significant improvements in physical fitness, body size satisfaction, and physiology knowledge in high school adolescents.     

丙泊酚与异氟醚麻醉对妇科腹腔镜手术患者血流动力学及应激反应的影响

目的:探究丙泊酚与异氟醚麻醉对接受妇科腹腔镜手术的患者应激激素以及血流动力学的影响。方法:选取我院妇科收治的需要进行腹腔镜手术的患者90例,根据麻醉用药不同,将其分为丙泊酚组、异氟醚组及实验组,每组各30例。观测患者不同时段去甲肾上腺素(NE)、肾上腺素(E)、皮质醇(COS)的浓度及心率、平均动脉压、呼吸频率、血氧饱和度等血流动力学参数的变化情况。结果:三组患者麻醉前及气腹20 min的去甲肾上腺素、肾上腺素以及皮质醇含量比较均无显著差异(P0.05);气腹前,实验组患者去甲肾上腺素含量显著低于丙泊酚组及异氟醚组(P0.05);放气10 min,实验组患者肾上腺水平显著高于丙泊酚组及异氟醚组(P0.05);三组患者麻醉前及气腹前的心率、平均动脉压、呼吸以及血氧饱和度比较均无显著差异(P0.05);气腹20 min,实验组患者的心率、平均动脉压、呼吸显著优于丙泊酚组及异氟醚组(P0.05);术后放气10 min,实验组患者的心率、平均动脉压、呼吸显著优于丙泊酚组及异氟醚组(P0.05);实验组患者术后出现恶心、呕吐等症状显著优于丙泊酚组及异氟醚组(P0.05)。结论:丙泊酚复合异氟醚可有效改善接受妇科腹腔镜手术的患者麻醉期间的应激反应和血流动力学,患者术后恶心、呕吐等不良反应少,值得推广使用。     

Daily form of rest in the catfish Ictalurus nebulosus and the frog Rana temporaria]

By means of recording the cardiac rhythm, respiration rate and motor activity in unrestrained animals, studies have been made on the dynamics of formation of cataleptic-like immobilization in the teleost I. nebulosus. Rhythmic illumination at a rate 3/min. (10 sec light on - 10 sec light off) in the daytime gradually caused the onset of immobilization in the fish. This immobilization is characterized by the specific heart rate, type of respiration and the degree of plastic tone. Under the same experimental conditions, the formation of photogenic catalepsy in the frog Rana temporaria was confirmed. Typical heart rate, respiration pattern and the degree of plastic tone were determined as well. The role of illumination rhythm in the onset of all conditions which are characteristic for the "awakefulness-rest" cycle is discussed.     

Aging and the complexity of cardiovascular dynamics.

Biomedical signals often vary in a complex and irregular manner. Analysis of variability in such signals generally does not address directly their complexity, and so may miss potentially useful information. We analyze the complexity of heart rate and beat-to-beat blood pressure using two methods motivated by nonlinear dynamics (chaos theory). A comparison of a group of healthy elderly subjects with healthy young adults indicates that the complexity of cardiovascular dynamics is reduced with aging. This suggests that complexity of variability may be a useful physiological marker.     

Molecular recognition and processing of periodic signals in cells: study of activation of membrane ATPases by alternating electric fields.

A molecule which is immobilized, oriented or tumbling more slowly than the frequency of a periodic field, may interact with the field to produce chemical effects that are uncommon in a homogeneous solution. Among these effects are the alteration of the rate of a chemical reaction and the exchange of energy between the oscillating field and the conformation of the molecule. When certain conditions are satisfied, this exchange allows the molecule to absorb and couple the energy of the field to drive an endergonic reaction. The efficiency of energy coupling depends on field strength and frequency and on the ligand concentration. There are windows of these parameters to achieve efficient coupling. These windows can be expressed in terms of the rate constants and equilibrium constants of the catalytic reactions, and the amplitude and frequency of the periodic field. This mechanism allows cells to receive, process and transmit energy of high and medium level periodic potentials by means of membrane enzymes or receptors. A theory for the transduction of electric energy, electroconformational coupling (ECC) will be discussed. The electric field induced cation pumping activities of Na,K-ATPase and Ca-ATPase of human erythrocytes and the ATP synthetic activity of beef heart mitochondrial ATPase will then be used to test an ECC membrane transport model. For the processing of low level periodic signals, a theory of an oscillatory activation barrier (OAB), which considers resonance transduction between an oscillating field and the activation barrier of the rate limiting step in an enzymic reaction, will be discussed. The OAB mechanism successfully interprets the AC stimulated ATP hydrolysis activity of Ecto-ATPase from chicken oviduct and F0F1-ATPase from beef heart. We propose that mechanisms similar to an OAB model are adopted by cells to sense weak electric, acoustic, mechanical, concentration (i.e., chemical potential) and other types of signals, and to communicate with other cells by these signals. The experimental data and mechanistic information presented in this communication give us a glimpse of the molecular electronic designs in living cells. This information is also relevant with respect to environmental issues. Environmental electromagnetic fields and sonic pollutants may interfere with normal communications of cells and organisms. Their benefit, if any, and detrimental effects can be assessed and dealt with only if we fully understand mechanisms of cellular interactions with these fields and pollutants, at the molecular level.