无线遥测和刺激技术建立兔房颤模型的探索

目的探索一种在无线遥测和刺激技术基础上的兔房颤模型的制作。方法新西兰兔皮下植入自主研发的植入式遥测刺激器,植入式遥测刺激器的制作是以TI公司（德州仪器）的MSP单片机和TI公司的RF无线收发芯片CC2250为核心开发设计。优化植入系统设计以满足新西兰兔房颤模型建立的探索实验;植入子植入新西兰兔腹部皮下,采集电极留置于左上肢和右上肢腋下皮下,两个刺激电极分别缝合于左心耳和左心房上,通过无线收发采集和刺激信号;实现利用Powerlab生理记录仪连续监测体表I导联心电信号,并通过专用计算机程序刺激软件,发放间歇（刺激2 s,暂停2 s）高频（频率20 Hz）阈上（强度2 mA,脉宽1 ms）刺激,若间歇期内出现房颤,则人为干预中止刺激,若转为窦性心律,则继续刺激。结果植入式遥测刺激器在体内可稳定工作（包括采集模拟心电信号和发放刺激）30 d,植入新西兰兔体内刺激3周后可诱导出房颤,持续时间〉48 h。结论用新西兰兔代替比格犬建立基于无线遥测和刺激基础上的房颤模型是完全可行的,同时也体现了动物福利优化和替代原则。     

Effect of increased left atrial pressure on breathing frequency in anesthetized dog

Distension or loading of the isolated canine left heart caused reflex tachypnea in prior studies. The object of the present effort was to explore the possibility that this depended primarily on atrial distension. Cardiopulmonary bypass perfusion and ligation of pulmonary veins were used to isolate the left-heart chambers of anesthetized dogs. Simultaneous distension of the beating left atrium and fibrillating ventricle stimulated breathing frequency (f), whereas isolated ventricular distension did not. At other times, intervals of atrial fibrillation were imposed under two different conditions: 1) while the right heart and lungs were bypassed and systemic perfusion was provided by the left ventricle using blood returned to the left atrium by pump and 2) while the ventricles fibrillated and systemic perfusion was supplied directly by the pump. Atrial fibrillation increased left atrial pressure and stimulated f in condition 1. In condition 2, f increased only if fibrillation was associated with a rise in left atrial pressure. Vagal cooling blocked the effect of fibrillation. I conclude that left atrial distension may initiate reflex tachypnea.     

Phantom Model Testing of Active Implantable Cardiac Devices at 50/60 Hz Electric Field

Exposure to external extremely low-frequency (ELF) electric and magnetic fields induces the development of electric fields inside the human body, with their nature depending on multiple factors including the human body characteristics and frequency, amplitude, and wave shape of the field. The objective of this study was to determine whether active implanted cardiac devices may be perturbed by a 50 or 60 Hz electric field and at which level. A numerical method was used to design the experimental setup. Several configurations including disadvantageous scenarios, 11 implantable cardioverter-defibrillators, and 43 cardiac pacemakers were tested in vitro by an experimental bench test up to 100 kV/m at 50 Hz and 83 kV/m at 60 Hz. No failure was observed for ICNIRP public exposure levels for most configurations (in more than 99% of the clinical cases), except for six pacemakers tested in unipolar mode with maximum sensitivity and atrial sensing. The implants configured with a nominal sensitivity in the bipolar mode were found to be resistant to electric fields exceeding the low action levels, even for the highest action levels, as defined by the Directive 2013/35/EU. Bioelectromagnetics. 2020;41:136–147. © 2020 Bioelectromagnetics Society.     

A METHOD OF CORONARY RETROPERFUSION FOR THE TREATMENT OF ACUTE MYOCARDIAL ISCHEMIA

A method of retrograde perfusion of the myocardium has been developed in dogs. It consists of a double lumen balloon-tipped catheter inserted transvenously into the coronary sinus, with one lumen connected to a roller pump, the other to a helium counterpulsing pump. Oxygenated heparinized blood is obtained from the femoral artery and pumped continuously into the coronary sinus at a pressure of 50-75 mm Hg. The balloon is inflated during diastole, sealing the coronary sinus and promoting retrograde flow, and is deflated during systole, allowing blood drainage into the right atrium and preventing venous congestion. Thirteen anesthetized open-chest dogs were subjected to 15 minutes of proximal LAD artery occlusion and 30 minutes of diastolic coronary sinus perfusion (DCSP). The area of ischemia was mapped by means of platinum electrodes capable of simultaneously measuring myocardial tissue oxygen tension M(p)O(2)) and electrograms. Reduction of M(p)O(2) with simultaneous elevation of the ST segment on the corresponding electrogram was considered an indication of ischemia. Diastolic coronary sinus perfusion improved myocardial oxygen tension in the ischemic myocardium, reduced ST segment elevation, and tended to restore arterial blood pressure. Histologically, there was no intramyocardial hemorrhage.     

Two physiological agents that appear to facilitate calcium discharge from the sarcoplasmic reticulum in frog heart cells: adrenalin an ATP

The alpha-adrenergic effect of adrenalin and the action of ATP and other nucleotides have been examined in single trabeculae of frog heart by means of procedures developed in the preceding paper (Niedergerke & Page 1981). The results suggest that both adrenalin and ATP are able, in conjunction with the action potential, to facilitate the discharge of calcium from the sarcoplasmic reticulum in at least some of the cardiac cells. As a result, the strength of the twitch is enhanced. As shown previously for the action of caffeine, this calcium discharge was not maintained, declining rapidly, together with the twitch tension, as the sarcoplasmic reticulum calcium store became depleted. Trabeculae from atrium and ventricle differed in their propensity to respond to these two substances. Thus, alpha-adrenergic responses were obtained in some 30% of the atrial, but in none of the ventricular, trabeculae examined. On the other hand, both kinds of trabecula gave ATP responses, but these tended to be weaker and required higher concentrations in ventricle than atrium. The possibility that the two responses are of physiological importance is suggested by the low concentrations (less than or equal to 5 x 10(-7)M) needed to produce large tension increases. A tentative hypothesis is advanced according to which alpha-catecholamine and ATP effects participate in circulatory control by initiating a rapid boost of cardiac pump activity, preparatory to the slower but better maintained beta-catecholamine action.     

THE ULTRASTRUCTURE OF THE CAT MYOCARDIUM : II. Atrial Muscle

The ultrastructure of the cells specialized for contraction in the atrium and ventricle of young adult cats are compared. The cells specialized for conduction are not included. In addition to possessing distinctive atrial granules, the cells of the atrium are smaller in diameter (5–6 µ) than ventricular cells (10–12 µ) and have strikingly fewer T tubules. These latter differences are discussed in terms of their possible significance for the rate of conduction of the action potential. It is suggested that the very small number of T tubules in atrial cells may compensate for the small cell diameter, and thus permit rapid conduction of the action potential across the surface of the atrium. Coated dense vesicles found in association with the sarcoplasmic reticulum at the level of the Z line in ventricular muscle are more evident in atrial cells. In the virtual absence of T tubules in atrial cells, the sub-sarcolemmal cisternae of the sarcoplasmic reticulum are almost exclusively at the cell periphery. The ends of the cells and their processes in ventricular muscle are rectilinear with the interdigitated portions of the intercalated discs oriented transversely, whereas those of the atrium are often oblique to the myofilament axis. This difference may be related to the lower mechanical tension on atrial cells.     

Five-color flow cytometric analysis of swine lymphocytes for detection of proliferation,apoptosis, viability,and phenotype

BACKGROUND: The objective of this study was to develop a method to simultaneously examine phenotype, proliferation, apoptosis, and death of antigen-stimulated porcine lymphocytes. METHODS: Peripheral blood mononuclear cells (PBMCs) were isolated from pigs vaccinated with a Brachyspira hyodysenteriae bacterin. RESULTS: Once isolated, PBMCs were stained with the fluorescent membrane intercalating dye, PKH67, and cultured with or without B. hyodysenteriae whole-cell sonicate antigen. Serial samples of nonstimulated and B. hyodysenteriae-stimulated PBMCs were harvested for flow cytometric analysis. Fluorochrome excitation was performed with spatially separated air-cooled argon and red helium neon laser beams. Five-color analysis included signal detection of PKH67 (proliferation), phycoerythrin (cell surface antigen), Texas Red phycoerythrin tandem (cell surface antigen), allophycocyanin (annexin V), and 7-amino-actinomysin D (7AAD; viability). For analysis, gates were set on live (annexin V(-), 7AAD(-)), intact apoptotic (annexin V(+), 7AAD(dim)), and live plus intact apoptotic (annexin V(+/-), 7AAD(dim/-)) cells, and the phenotypes of PBMCs within these populations were determined during the course of the in vitro response. Dead cells (i.e., 7AAD(bright)) were excluded from the analysis. CONCLUSION: Application of this method for the determination of porcine lymphocyte subset proliferation is presented.     

A New Single Chamber Implantable Defibrillator with Atrial Sensing: A Practical Demonstration of Sensing and Ease of Implantation

Implantable cardioverter-defibrillators (ICDs) terminate ventricular tachycardia (VT) and ventricular fibrillation (VF) with high efficacy and can protect patients from sudden cardiac death (SCD). However, inappropriate shocks may occur if tachycardias are misdiagnosed. Inappropriate shocks are harmful and impair patient quality of life. The risk of inappropriate therapy increases with lower detection rates programmed in the ICD. Single-chamber detection poses greater risks for misdiagnosis when compared with dual-chamber devices that have the benefit of additional atrial information. However, using a dual-chamber device merely for the sake of detection is generally not accepted, since the risks associated with the second electrode may outweigh the benefits of detection. Therefore, BIOTRONIK developed a ventricular lead called the Linox^SMART S DX, which allows for the detection of atrial signals from two electrodes positioned at the atrial part of the ventricular electrode. This device contains two ring electrodes; one that contacts the atrial wall at the junction of the superior vena cava (SVC) and one positioned at the free floating part of the electrode in the atrium. The excellent signal quality can only be achieved by a special filter setting in the ICD (Lumax 540 and 740 VR-T DX, BIOTRONIK). Here, the ease of implantation of the system will be demonstrated.     

An Ultra‐Mechanosensitive Visco‐Poroelastic Polymer Ion Pump for Continuous Self‐Powering Kinematic Triboelectric Nanogenerators

A mechanosensitive, visco‐poroelastic polymer ion pump that can rapidly establish a dense electrical double layer via mechanical pressure, thereby significantly enhancing output performance of an ionic triboelectric nanogenerator (iTENG), is described. A working mechanism of an iTENG using a highly mechanosensitive, visco‐poroelastic ion pump is suggested and the optimal characteristics of the polymer ion pump are reported by investigating optical, mechanical, electrical, and electrochemical properties. Surprisingly, the pressure sensitivity of the iTENG reaches 23.3 V kPa^?1, which is tens of times the record value. To achieve controlled high‐frequency pulses from an iTENG, kinematic systems using a gear train and a cam are integrated with a single grounded iTENG, which produces a maximum of 600 V and 22 mA (≈2.2 W cm^?2) at an input frequency of 1.67 Hz; after power transforming, those values are converted to 1.42 V and 225 mA. A capacitor of 1 mF can be fully charged to 2 V in only 60 s, making it possible to continuously operate a wireless‐communicating self‐powered humidity sensor. Also, due to the high transparency and deformability of the polymer ion pump, a self‐powered transparent tactile sensor is successfully assembled using a 5 × 5 iTENG array.     

Excitation-dependent relaxation in the cardiac muscle

Isolated trabeculae of rabbit and guinea pig atrium exposed to low-sodium solution developed after-contractions and increased diastolic tension when rhythmic steady-state stimulation was stopped. Single excitation applied during rest or at the peak of after-contraction brought the resting tension to the low, control level. Tension of isolated cat papillary muscle increased due to action of 17 mmol of caffeine applied during rest was reduced during rhythmic post-rest stimulation. Early extra-excitation potentiated relaxation of atrial muscle exposed to low-sodium solution. It is concluded that relaxing factor of cardiac muscle is activated by excitation of the cell.     

Ultrastructure of the heart of the sturgeon Acipenser stellatus (Chondrostei)

Summary The ultrastructure of atrial and ventricular myocardial cells from Acipenser stellatus is described. The cells of the atrium are more loosely connected than those of the ventricle. Cell contact is by simple intercalated discs and by desmosomes. The cells are flattened, with peripheral myofibrils and a central region of mitochondria and the nucleus. The sarcoplasmic reticulum consists of subsarcolemmal tubules, that frequently extend towards the central mitochondria. Dyads are small and positioned at any sarcomeric level. No T-tubules are present. Specific granules are restricted to the atrial cell, and are sometimes present within the SR tubules.     

Effect of preliminary blockade of alpha- and beta-adrenoreceptors on stress-induced disorders of myocardial relaxation and contractile functions

Effect of preliminary administration of the alpha-adrenoblocker phentolamine and the beta-adrenoblocker inderal on stress-induced disturbances of myocardial extensibility, contractile function and myocardial resistance to hypoxia and excess Ca2+ was studied on an isometrically contracting isolated right atrium of the rat. Inderal substantially prevented the post-stress decrease in atrial extensibility and almost completely prevented the stress-induced decline in the developed tension and the Frank-Starling mechanism efficiency. At the same time inderal prevented the post-stress increase in hypoxic and hypercalcium contracture of the atrium. Phentolamine did not produce any such protective effects. It is suggested that the damaging action of catecholamine excess occurring under stress is mediated via beta-adrenoreceptors but not via alpha-adrenoreceptors of the heart.     

Simulation of Left Atrial Function Using a Multi-Scale Model of the Cardiovascular System

During a full cardiac cycle, the left atrium successively behaves as a reservoir, a conduit and a pump. This complex behavior makes it unrealistic to apply the time-varying elastance theory to characterize the left atrium, first, because this theory has known limitations, and second, because it is still uncertain whether the load independence hypothesis holds. In this study, we aim to bypass this uncertainty by relying on another kind of mathematical model of the cardiac chambers. In the present work, we describe both the left atrium and the left ventricle with a multi-scale model. The multi-scale property of this model comes from the fact that pressure inside a cardiac chamber is derived from a model of the sarcomere behavior. Macroscopic model parameters are identified from reference dog hemodynamic data. The multi-scale model of the cardiovascular system including the left atrium is then simulated to show that the physiological roles of the left atrium are correctly reproduced. This include a biphasic pressure wave and an eight-shaped pressure-volume loop. We also test the validity of our model in non basal conditions by reproducing a preload reduction experiment by inferior vena cava occlusion with the model. We compute the variation of eight indices before and after this experiment and obtain the same variation as experimentally observed for seven out of the eight indices. In summary, the multi-scale mathematical model presented in this work is able to correctly account for the three roles of the left atrium and also exhibits a realistic left atrial pressure-volume loop. Furthermore, the model has been previously presented and validated for the left ventricle. This makes it a proper alternative to the time-varying elastance theory if the focus is set on precisely representing the left atrial and left ventricular behaviors.     

An ultrastructural study of the cercarial excretory system in Bucephaloides gracilescens and Prosorhynchus squamatus

The ultrastructure of the flame cells, capillaries, collecting tubes, excretory bladder, excretory atrium, caudal vesicle, lateral caudal ducts and excretory pores of cercariae of Bucephaloides gracilescens (Rudolphi, 1819) Hopkins, 1954 and Prosorhynchus squamatus Odhner, 1905 (Digenea: Bucephalidae) is described. Both species are essentially similar except for some details. The terminal parts of the protonephridia have all the structural features that are typical of trematodes. The collecting tubes in the cercarial body are composed of cells that are wrapped around the lumen. The main collecting tubes are joined to the excretory bladder syncytium by septate junctions. Features of P. squamatus excretory bladder epithelium indicate that it is involved in secretory activity, but this is not the case in B. gracilescens. In both species the luminal surface of the excretory bladder epithelium is increased by lamellae, and the basal plasma membrane forms invaginations. In the bladder syncytium of P. squamatus both apical lamellae and basal invaginations are more developed and mitochondria are also more numerous. The excretory atrium is lined by a syncytium with nucleated cytons located in the surrounding parenchyma. The atrium lining is not continuous with the body tegument and possesses specific secretory inclusions and a thick glycocalyx. Septate junctions connect the atrium syncytium to the excretory bladder epithelium at its anterior end and to the syncytial excretory epithelium lining the caudal vesicle and the lateral caudal ducts at its posterior. In the excretory pores the caudal duct syncytium is joined to the tegument by septate desmosomes.     

Mutation of weak atrium/atrial myosin heavy chain disrupts atrial function and influences ventricular morphogenesis in zebrafish

The embryonic vertebrate heart is composed of two major chambers, a ventricle and an atrium, each of which has a characteristic size, shape and functional capacity that contributes to efficient circulation. Chamber-specific gene expression programs are likely to regulate key aspects of chamber formation. Here, we demonstrate that epigenetic factors also have a significant influence on chamber morphogenesis. Specifically, we show that an atrium-specific contractility defect has a profound impact on ventricular development. We find that the zebrafish locus weak atrium encodes an atrium-specific myosin heavy chain that is required for atrial myofibrillar organization and contraction. Despite their atrial defects, weak atrium mutants can maintain circulation through ventricular contraction. However, the weak atrium mutant ventricle becomes unusually compact, exhibiting a thickened myocardial wall, a narrow lumen and changes in myocardial gene expression. As weak atrium/atrial myosin heavy chain is expressed only in the atrium, the ventricular phenotypes in weak atrium mutants represent a secondary response to atrial dysfunction. Thus, not only is cardiac form essential for cardiac function, but there also exists a reciprocal relationship in which function can influence form. These findings are relevant to our understanding of congenital defects in cardiac chamber morphogenesis.     

The mechanochemistry of V-ATPase proton pumps

The vacuolar H(+)-ATPases (V-ATPases) are a universal class of proton pumps that are structurally similar to the F-ATPases. Both protein families are characterized by a membrane-bound segment (V(o), F(o)) responsible for the translocation of protons, and a soluble portion, (V(1), F(1)), which supplies the energy for translocation by hydrolyzing ATP. Here we present a mechanochemical model for the functioning of the V(o) ion pump that is consistent with the known structural features and biochemistry. The model reproduces a variety of experimental measurements of performance and provides a unified view of the many mechanisms of intracellular pH regulation.     

中药91－4对抗生素相关性腹泻小鼠肠道膜菌群及腔菌群的影响

本实验以肠道菌群检测与电镜观察法,初步研究了中药９１－４对抗生素相关性腹泻（ＡＡＤ）小鼠肠道菌群的影响。结果表明,盐酸林可霉素对小鼠肠道膜菌群、腔菌群干扰显著,乳酸杆菌、双歧杆菌及肠杆菌等比正常对照组明显减少,致小鼠腹泻或肠炎;中药９１－４能够促进肠道乳酸杆菌、双歧杆菌等生长繁殖,对肠道膜菌群、腔菌群均具有调整作用,加速肠粘膜病变的愈合及修复,可有效地控制ＡＡＤ模型小鼠的腹泻症状。     

Transitions among atrial fibrillation, atrial flutter, and sinus rhythm during procainamide infusion and vagal stimulation in dogs with sterile pericarditis

The mechanism of atrial flutter and fibrillation induced by rapid pacing in 22 dogs with 3-day-old sterile pericarditis was investigated by computerized epicardial mapping of atrial activation before and after administration of agents known to modify atrial electrophysiologic properties: procainamide, isoproterenol, and electrical stimulation of the vagosympathetic trunks. Before the administration of any of these agents, a total of 30 episodes of sustained atrial flutter (greater than 1 min duration, monomorphic; regular cycle length, 127 +/- 12 ms, mean +/- SD) was induced in 15 out of 22 dogs and 9 episodes of unstable atrial flutter (duration, less than 1 min; cycle length, 129 +/- 34 ms; monomorphic, alternating with fibrillation) were induced in the remaining 7 preparations. In the latter, administration of procainamide transformed unstable atrial flutter and atrial fibrillation to sustained atrial flutter (cycle length, 142 +/- 33 ms; n = 9 episodes). During control atrial flutter, atrial maps displayed circus movement of excitation in the right atrial free wall with faster conduction parallel to the orientation of intra-atrial myocardial bundles. Vagal stimulation changed atrial flutter to atrial fibrillation in 32 of 73 trials; this was associated with acceleration of conduction in the lower right atrium, leading to fragmentation of the major wave front. Isoproterenol produced a 6-25% increase of the atrial rate in 6 out of 14 trials of atrial flutter and induced atrial fibrillation in 4. After procainamide, the reentrant pathway was lengthened and conduction was slowed further in the right atrium. Maps obtained during unstable atrial flutter showed incomplete circuits involving the right atrium. Following procainamide infusion, the area of functional dissociation or block was enlarged and a stable circus movement pattern, which was similar to the pattern seen in control atrial flutter, was established in the right atrium. We conclude that (1) the transitions among atrial fibrillation, atrial flutter, and sinus rhythm occur between different functional states of the same circus movement substratum primarily located in the lower right atrial free wall, and (2) the anisotropic conduction properties of the right atrium may contribute to these reentrant arrhythmias and may be potentiated by acute pericarditis.     

Atrial fibrillation: an unusual cause

A 28-year-old male presenting with atrial fibrillation (AF) underwent successful electrical cardioversion to restore sinus rhythm. He had no prior history of AF or other cardiac disease. However, transthoracic echocardiography (TTE), performed to exclude structural abnormalities as a cause of AF, demonstrated a large mass in the left atrium (LA). For further analysis the patient was referred to our centre, and echocardiography, multislice detector computed tomography (MDCT) and cardiovascular magnetic resonance imaging (CMR) were performed for further noninvasive diagnostic work-up.