Anatomy of the heart of the beluga whale (Delphinapterus leucas)

The heart of the beluga whale (Delphinapterus leucas) is described from the dissection of seven specimens. As in most whales the heart is characterized by a transverse broadness and a flatness of the ventricles from one surface to the other and by an apex formed by both ventricles. Heart size parameters are used for comparison with parameters of other marine and land mammals. The heart width index (heart height/heart circumference) averages 31.3 in comparison to 28.7 for the Weddell seal and 39.0 for the felids. The right ventricle is relatively long and narrow with a mean length index (TS/heart height) of 64.7 and a mean breadth index (TP/heart height) of 38.7. These heart parameters are discussed in functional terms.     

An in vitro method for recording the electrical activity of the isolated heart of the adult Drosophila melanogaster

A recording chamber for monitoring the electrophysiological properties of the isolated heart of adult Drosophila melanogaster has been developed. Spontaneously generated field potentials of constant amplitude can be recorded for 6-8 h (n = 14); in very few cases, records were maintained stable for over 10 h (n = 4), and in some cases below 6 h (n = 5). The chamber consists of the tip of a micropipette, which allows for monitoring the field potential generated by the spontaneously contracting heart. The method can produce accurate information about the heart rate and the amplitude of the cardiac action potential. The preparation can be used for pharmacological studies on the heart of D. melanogaster since it responds, with an increase in the heart rate, to unusually low concentrations of octopamine, 1 nM, a compound with cardioaccelerating properties for insect heart. The recording system can be easily modified for experiments on the heart of other insects. Finally, the isolated heart of D. melanogaster provides a simple method for identifying mutations that affect heart physiology.     

Restoration of the heart activity in deep hypothermia with the aid of norepinephrine and no warming of the heart

A possibility of restoration and stimulation of the rat isolated heart contractions in deep hypothermia by means of norepinephrine (6 microM) was studied. Following a complete arrest of the heart at a retrograde perfusion with the Krebs-Henseleit buffer ([K+] 5.9 mM), norepinephrine was found to restore the heart beats and to lower the heart arrest temperature from 8.2 +/- 0.5 degrees to 6.6 +/- 0.3 degrees. At the perfusion with the Krebs-Henseleit buffer, the heart rate dropped to below 10 min(-1) at 13.0 +/- 0.9 degrees. Reduction of [K+] to 2.95 mM intensified the heart rate. At a progressing cooling, the heart rate lower than 10 min(-1) occurred at 10.9 +/- 0.6 degrees. When adding norepinephrine (6 microM) to the perfusion fluid with [K+] 2.95 mM, the heart rate increased once again (on the average to 23.1 +/- 5.3 min(-1)) despite the fact that the heart temperature continued to be lowered. The heart rate lower than 10 min(-1) was reached at the progressing cooling to, on the average, 9.6 +/- 0.7 degrees. The findings show norepinephrine to exert a stimulating effect on the heart activity even at such low heart temperatures as 7-10 degrees with no preliminary warming of the heart.     

Nonstationarity and duration of the R-R-segment in the diagnostics of functional states of operators

The effect of the nonstationarity of R-R interval series on the diagnostics of functional states of operators has been analyzed. The functional states were diagnosed by means of a factor model of heart rate variability. The heart rate was recorded in the supine position, before the performance of an important task, and after its completion. A high resistance of the diagnostics of functional states to nonstationarity was found for all periods. Indices of heart rate variability resistant to nonstationarity were defined. Also, the effect of R-R segment duration on functional states diagnostics was explored. The results obtained allow one to conclude that the diagnostics of functional states based on the three-factor model of heart rate variability can be used on short segments within a range of 256 divided 32 R-R intervals. The indices of the factor model of heart rate variability must be normalized for corresponding R-R segment duration before diagnostics. In addition, the effect of the duration of R-R segment on the indices of heart rate variability was analyzed for different functional states. The indices resistant to the duration of R-R segments and conditions necessary for heart rate recording were defined.     

用心率变异功率谱研究出生后心率变慢的机理

目的 :探讨神经机制及心源性因素在出生后心率变慢中的作用。方法 :运用心率变异性的频域和时域分析方法 ,主要为功率谱分析方法 ,以不同年龄组的人和家兔为实验对象 ,对出生后心脏的自主神经调控进行初步探讨 ;并通过观察不同年龄组离体灌流兔心 (无神经体液因素影响 )自律性的变化 ,探讨心脏本身因素是否参与出生后心率变慢的调控。结果 :人和家兔迷走交感对心率的调控作用比在各年龄组之间有显著差异 ,且随年龄增长逐渐升高 ;家兔离体心脏的自主心率在各年龄组之间有显著差异 ,且随年龄增长逐渐降低。结论 :出生后心率减慢与神经机制有关 ,也有心脏本身因素的参与     

Single neurone responses to tactile stimulation of the heart in the snail,Helix pomatia L.

Summary The electrical activity of the heart nerve and of single neurons in the suboesophageal ganglia were recorded during tactile stimulation of the heart. 15 neurons were identified which responded to heart stimulation by inhibiting or accelerating activity. Cells influenced by heart afferents are scattered in the visceral and in the right and left parietal ganglia.In most of the cases both decrease and increase of cell activity are caused by synaptic potentials, in some cases, however, the neuron is assumed to have a sensory character.The activity of three neurons influenced by heart stimulation was conducted into the heart nerve. These cells are central neurons of a heart-CNS-heart reflex.Some of the neurons located in the right parietal and visceral ganglia have no connection with the mechanoreceptors of the heart. Since their spikes propagate into the heart nerve, they probably take part in the extracardial regulation of heart activity.One of the neurons located in the visceral ganglion (cell V12) sends its axon into the heart nerve. The response of this neuron to heart stimulation was an increase in activity and an inhibition of the heart rate. This is an inhibitory neuron of the extracardial heart regulatory system.     

Model of the sino-atrial and atrio-ventricular nodes of the conduction system of the human heart.

The coupled sino-atrial and atrio-ventricular nodes of the heart are discussed using a dedicated non-linear oscillator model. Several modes by which the oscillations cease in the system are obtained (asystole models). The oscillations of the model are compared with heart rate variability in heart block patients.     

The mechanisms of the formation of cardiogenic afferent effects after the development of local immune damage to the heart]

Sensitivity of cardiac receptors to several substances after local immune heart damage and the nature of cardiogenic influences on the circulation were studied in acute experiments o anesthetized dogs. The depressor reflexes from the heart were shown to disappear during 30 min. after immune heart damage, and vagal afferent impulse activity decreased. After immune heart damage, cardiac sympathetic afferent fibres were more sensitive to endogenous biological substances than to vagal ones. The sympathetic cardiac afferent system is found to be more sensitive to chemical agents, which is a decisive factor in formation of cardiogenic influences on the circulation during pathological processes in the heart.     

Peptidergic control of the heart of the stick insect, Baculum extradentatum

The dorsal vessel of the Vietnamese stick insect, Baculum extradentatum, consists of a tubular heart and an aorta that extends anteriorly into the head. Alary muscles, associated with the heart, are anchored to the body wall with attachments to the dorsal diaphragm. Alary muscle contraction draws haemolymph into the heart through incurrent ostia. Excurrent ostia lie on the dorsal vessel in the last thoracic and in each of the first two abdominal segments. Muscle fibers are associated with these excurrent ostia. Crustacean cardioactive peptide (CCAP)- and proctolin-like immunoreactivity is present in axons of the segmental nerves that project to the dorsal vessel, and in processes extending over the heart and alary muscles. Proctolin-like immunoreactive processes are also localized to the valves of the incurrent ostia and to the excurrent ostia. Neither the link nerve neurons, nor the lateral cardiac neurons, stain positively for these peptides. Physiological assays reveal dose-dependent increases in heart beat frequency in response to CCAP and proctolin. Isolating the dorsal vessel from the ventral nerve cord led to a change in the pattern of heart contractions, from a tonic, stable heart beat, to one which was phasic. The tonic nature was restored by the application of CCAP.     

绿茶浸出液对蟾蜍离体心脏活动的影响

利用斯氏蛙心灌流方法,以心率和心搏幅度为评价指标,研究了5%、10%、20%、25%、30%、40%6个浓度梯度的绿茶浸出液对蟾蜍离体心脏活动的影响。结果表明,25%～30%的绿茶浸出液对蟾蜍的心率和心肌收缩力都有显著增强作用(P<0.05),低于25%和为40%时,虽有影响,但不显著(P>0.05)。因此25%～30%的绿茶浸出液具有一定的强心效应。     

Changes in the myocardial ultrastructure of the perfused rabbit heart under hypoxia

Ultrastructure of rabbit heart left ventricle isolated according to Langendorf was examined under different conditions: in intact animals, during ligation of the coronary artery, and hypoxic heart perfusion. The intact perfused heart showed unmarked exo- and intracellular edema and moderate swelling of the mitochondria. During hypoxic perfusion, marked swelling and destruction of the mitochondria were noted. During ligation of the coronary artery, the heart was characterized by a high degree of mitochondrial heterogenicity. The correlation of the data obtained allowed one to reveal the myocardial adaptive-accommodative mechanism, (intermittent mitochondrial activity) that makes it possible to maintain the heart bioenergetics during coronary artery occlusion at a permanently high level.     

Cardioacceleratory Neurons of the Isopod Crustacean, Ligia exotica: Visualization of Peripheral Projection onto the Heart Muscle

Innervation of the heart muscle by the cardioacceleratory neurons was morphologically and electrophysiologically examined in the isopod crustacean, Ligia exotica. Intracellular injection of neurobiotin into the first and second cardioacceleratory neurons (CA1 and CA2) revealed their peripheral axonal projections. Inside the heart, the CA1 and CA2 axons ran along the trunk of the cardiac ganglion. Finely arborized branches with many varicosities arose from the axon and projected over the heart muscle. Stimulation of either the CA1 or CA2 axon caused an overall depolarization in the muscle of a quiescent heart. The amplitude of the depolarization increased with increasing stimulus frequency. During stimulation, the membrane resistance of the heart muscle decreased. In a beating heart, the cardioacceleratory nerve stimulation caused multiple effects on the heart muscle activity and the heartbeat. The results suggest that the cardioacceleratory neurons of Ligia exotica regulate the amplitude of the heartbeat (inotropic effect) and the heart tonus (tonotropic effect) via the synaptic contacts on the heart muscle, while the heartbeat frequency (chronotropic effect) is regulated via the synapses on the cardiac ganglion neurons.     

Effects of acute hypoxia on the determination of anaerobic threshold using the heart rate-work rate relationships during incremental exercise tests

Anaerobic threshold which describes the onset of systematic increase in blood lactate concentration is a widely used concept in clinical and sports medicine. A deflection point between heart rate-work rate has been introduced to determine the anaerobic threshold non-invasively. However, some researchers have consistently reported a heart rate deflection at higher work rates, while others have not. The present study was designed to investigate whether the heart rate deflection point accurately predicts the anaerobic threshold under the condition of acute hypoxia. Eight untrained males performed two incremental exercise tests using an electromagnetically braked cycle ergometer: one breathing room air and one breathing 12 % O2. The anaerobic threshold was estimated using the V-slope method and determined from the increase in blood lactate and the decrease in standard bicarbonate concentration. This threshold was also estimated by in the heart rate-work rate relationship. Not all subjects exhibited a heart rate deflection. Only two subjects in the control and four subjects in the hypoxia groups showed a heart rate deflection. Additionally, the heart rate deflection point overestimated the anaerobic threshold. In conclusion, the heart rate deflection point was not an accurate predictor of anaerobic threshold and acute hypoxia did not systematically affect the heart rate-work rate relationships.     

应用三元递减法筛选特异性心脏生长相关基因

心脏是由胚胎干细胞特异性分化而来的 ,但其分化的分子生物学机制尚不十分了解 .为建立一种新的筛选特异性心脏相关基因的方法 ,克隆特异性心脏生长相关基因 .从胚胎心、成年心和去胎心的胚胎中提取 m RNA,建立胎心 /成年心和胎心 /胎身两个递减性 c DNA文库 ,通过 DNA芯片和微阵列杂交筛选和克隆 ,建立了三元递减克隆的新方法 .获得了一个全长为 1 0 0 6 bp可编码1 94个氨基酸的新的与心脏生长相关的基因 ,它是 LIM家族的新成员 ,可特异性在心肌细胞表达 ,并可促进心肌细胞的生长 .结果表明 ,三元递减筛选法可以应用于寻找新的组织特异性表达的基因 .并且获得了一个新的与心脏生长相关的新基因 ,它可能在心肌生长和心肌肥厚的发生中发挥重要作用     

Myocardium at the base of the aorta and pulmonary trunk is prefigured in the outflow tract of the heart and in subdomains of the second heart field

Outflow tract myocardium in the mouse heart is derived from the anterior heart field, a subdomain of the second heart field. We have recently characterized a transgene (y96-Myf5-nlacZ-16), which is expressed in the inferior wall of the outflow tract and then predominantly in myocardium at the base of the pulmonary trunk. Transgene A17-Myf5-nlacZ-T55 is expressed in the developing heart in a complementary pattern to y96-Myf5-nlacZ-16, in the superior wall of the outflow tract at E10.5 and in myocardium at the base of the aorta at E14.5. At E9.5, the two transgenes are transcribed in different subdomains of the anterior heart field. A clonal analysis of cardiomyocytes in the outflow tract, at E10.5 and E14.5, provides insight into the behaviour of myocardial cells and their progenitors. At E14.5, most clones are located at the base of either the pulmonary trunk or the aorta, indicating that these derive from distinct myocardial domains. At E10.5, clones are observed in subdomains of the outflow tract. The distribution of small clones indicates proliferative differences, whereas regionalisation of large clones, that derive from an early myocardial progenitor cell, reflect coherent cell growth in the heart field as well as in the myocardium. Our results suggest that myocardial differences at the base of the great arteries are prefigured in distinct progenitor cell populations in the anterior heart field, with important implications for understanding the etiology of congenital heart defects affecting the arterial pole of the heart.     

Characterization of cardiac innervation in the nudibranch, Archidoris montereyensis

The heart of the nudibranch mollusc Archidoris montereyensis is regulated by a small number of powerful effector neurons located in the right pleural and visceral ganglia. Two identifiable neurons in the pleural ganglion, a heart excitor (PlHE) and a heart inhibitor (PlHI), are especially important regulators of cardiac function in that low levels of spontaneous activity in either cell significantly alters the amplitude and rate of heart contractions. These neurons have extensive dendritic arbors within the right pleural ganglion and branching axonal processes within the visceral ganglion. The visceral ganglion also contains a heart excitor neuron (VHE) and at least two heart inhibitor neurons (VHI cells), but their influence on cardiac activity is weaker than that of the pleural ganglion cells. All of these heart effector cells appear to be motor neurons with axons that terminate predominantly in the atrio-ventricular valve region of the heart via the pericardial nerve. The simplicity and strength of these neuronal connections to the heart of Archidoris make this a favorable preparation for studies of cardiac regulation.     

Rhythmogenesis in the sinoatrial unit of the heart

The most significant experimental data about the formation of a uniform rhythm of the sinoatrial unit of the heart for both the intact sinoatrial unit of the heart and cardiomyocytes in cellular structures are presented. The basic mathematical models for studying the processes of synchronization in the sinoatrial unit of the heart are described, including equations of Noble, Bonhoffer, and van der Pol and modified axiomatic models. The basic results obtained using the mathematical models are presented. The major reasons influencing the formation of a uniform rhythm were revealed: the form of a potential pacemaker in the phase of slow diastolic depolarization, its porosity, the force of connection between pacemaker and electric capacity of pacemakers. A study of rhythmogenisis on the basis of the modified axiomatic model was carrud out. The method allows one to calculate the uniform rhythm of the sinoatrial unit of the heart in view of the mutual influence of pacemaker cells, including the force of connection, electric capacity of cells, their possible clusterization. It was shown that generally the uniform rhythm of the sinoatrial unit of the heart is formed on an intermediate level of all pacemaker cells.     

The anterior heart-forming field: voyage to the arterial pole of the heart

Studies of vertebrate heart development have identified key genes and signalling molecules involved in the formation of a myocardial tube from paired heart-forming fields in splanchnic mesoderm. The posterior region of the paired heart-forming fields subsequently contributes myocardial precursor cells to the inflow region or venous pole of the heart. Recently, a population of myocardial precursor cells in chick and mouse embryos has been identified in pharyngeal mesoderm anterior to the early heart tube. This anterior heart-forming field gives rise to myocardium of the outflow region or arterial pole of the heart. The amniote heart is therefore derived from two myocardial precursor cell populations, which appear to be regulated by distinct genetic programmes. Discovery of the anterior heart-forming field has important implications for the interpretation of cardiac defects in mouse mutants and for the study of human congenital heart disease.     

Postnatal changes of the tonic influence of the vagus nerves on the heart rate, and of the activity of choline acetyltransferase in the heart atria of rats

Postnatal changes in the resting heart rate and in its parasympathetic tonic inhibition have been measured in awake rats and compared with changes in the activity of choline acetyltransferase (ChAT) in the heart atria. The heart rate at rest increased from 372.min-1 on the 1st to 456 and 442.min-1 on the 15th and 24th day of life and then again decreased to 358 and 356.min-1 in 60-day-old and adult rats. Until the 15th day of postnatal life, the administration of atropine did not bring about an increase in the heart rate; the cardio-acceleratory effect of atropine (indicating the presence of tonic vagal inhibition of the heart) appeared only on the 18th day and increased steeply up to the 40th day of postnatal life. The activity of ChAT in the heart atria was measured as the difference between the synthesis of acetylcholine in atrial homogenates incubated in the absence and in the presence of bromoacetylcholine (BrACh), a specific inhibitor of ChAT; this procedure eliminated the contribution of carnitine acetyltransferase to the synthesis of acetylcholine. The activity of ChAT was found to increase steeply from the 1st to the 25th days of postnatal life; the steepest increase in the activity of the enzyme occurred between the 4th and the 15th days. Temporal correlation between the changes in the activity of ChAT, in the content of acetylcholine in the heart atria (Kuntscherová and Vlk 1979) and in the efficiency of transmural stimulation of sinoatrial region on the heart rate (Vlk 1979) indicate that the functional maturation of intracardiac cholinergic neurones, proceeding in rats during the first three weeks of their postnatal life, plays an important role in the onset and temporal development of the tonic parasympathetic inhibition of the heart rate.