Pathological Changes in the Sinoatrial Node Tissues of Rats Caused by Pulsed Microwave Exposure

To observe microwave induced dynamic pathological changes in the sinus nodes, wistar rats were exposed to 0, 5, 10, 50 mW/cm^2 microwave. In 10 and 50 mW/cm^2 groups, disorganized sinoatrial node cells, cell swelling, cytoplasmic condensation, nuclear pyknosis, and anachromasis, swollen, and empty mitochondria, and blurred and focally dissolved myofibrils could be detected from 1 to 28 d, while reduced parenchymal cells, increased collagen fibers, and extracellular matrix remodeling of interstitial cells were observed from 6 to 12 months. In conclusion, 10 and 50 mW/cm^2 microwave could cause structural damages in the sinoatrial node and extracellular matrix remodeling in rats.

Junctional Pacemaker May Replace the Sinoatrial Node

Junctional rhythm is usually seen in the clinic with different causes.We report a case of bicuspid aortic valve accompa-nied by sinoatrial node dysfunction.The junctional escape beat could accelerate with physiological needs and provided for the normal needs of daily life when dysfunction of the sinoatrial node occurred,which provides a new way for the treatment of sinoatrial node dysfunction.Our fi ndings could be potentially signifi cant for identifying causes and choos-ing appropriate treatment strategies by using ECG monitoring in the clinic in the future.

Effect of Qiangxin Fumai Granule(强心复脉颗粒) on Electrophysiological Functions of the Sinoatrial Node during Ischemia-reperfusion of the Right Coronary Artery in Rabbits

Objective： To study the effect of the Chinese medicine Qiangxin Fumai Granule （强心复脉颗粒, QFG） on electrophysiological functions of the sinoatrial node during ischemia-reperfusion （IR） of the right coronary artery in rabbits. Methods： The right coronary artery IR model in rabbits was adopted. The modeled rabbits were randomly divided into 4 groups： the model group, the atropine group, the highdose QFG group, and the low-dose QFG group, with 8 animals in each group. In addition, twelve rabbits were selected for the sham-operative group. The drugs were administered once via duodenal perfusion after modeling had been stabilized for 10 min. The changes in AA interval, the sinoatrial conduction time （SACT）, the sinus node recovery time （SNRT）, the corrected sinus node recovery time （CSNRT） and the index of sinus node recovery time （ISNRT） at different time points during ischemia and reperfusion were measured. Results： The AA interval was prolonged for more than 40 ms in the model group during ischemia. Compared with the model group, the four electrophysiological parameters abovementioned in the high-dose QFG group and the low-dose QFG group were decreased to different extents at each time point （P〈0.01 or P〈0.05）, and no statistically significant differences were found between the QFG groups and the atropine group （P〉0.05）. Conclusion： QFG is beneficial for accelerating the recovery of sinus node autorhythmicity and conduction function, so as to protect electrophysiological functions of the sinoatrial node. Accelerating the recovery of autorhythmicity and conduction function in the sinus node is considered its electrophysiological mechanism in the treatment of sinoatrial node injury induced by ischemia.

Primary culture and identification of sinoatrial node cells from newborn rat

Objective To establish a reliable approach to primary culture and identification of sinoatrial node (SAN) cells. Methods The SAN cells were cultured from SAN tissue removed from neonatal Wistar rats and purified with differential attachment and 5'-bromodeoxyuridine (BrdU) treatment. The obtained cells were morphologically observed with inverted microscopy and transmission electron microscopy. Its action potential was recorded using electrophysiological methods.Results Three distinctly different cells were observed in the cultured SAN cells: spindle, triangle and irregular. Of these, the spindle cells comprised the greatest proportion, with their shape, structure and electrophysiological characteristics consistent with those of the pacemaker cells of SAN. The triangle cells were similar in features to the similarly shaped myocytes located in the atrial myocardium. Conclusions The culture method of differential attachment combined with BrdU treatment is a reliable approach to growing SAN cells. Of the cells cultured from SAN, the spindle cells appear to function as pacemaker cells.

Sinoatrial node pacemaker cells share dominant biological properties with glutamatergic neurons

Activation of the heart normally begins in the sinoatrial node(SAN).Electrical impulses spontaneously released by SAN pacemaker cells(SANPCs)trigger the contraction of the heart.However,the cellular nature of SANPCs remains controversial.Here,we report that SANPCs exhibit glutamatergic neuron-like properties.By comparing the single-cell transcriptome of SANPCs with that of cells from primary visual cortex in mouse,we found that SANPCs co-clustered with cortical neurons.Tissue and cellular imaging confirmed that SANPCs contained key elements of glutamatergic neurotransmitter system,expressing genes encoding glutamate synthesis pathway(G/s),ionotropic and metabotropic glutamate receptors(Grina,Gria3,Grm1 and Grm5)t and glutamate transporters(Slc17a7).SANPCs highly expressed cell markers of glutamatergic neurons(Snap25 and S/-c17a7)t whereas Gad1,a marker of GABAergic neurons,was negative.Functional studies revealed that inhibition of glutamate receptors or transporters reduced spontaneous pacing frequency of isolated SAN tissues and spontaneous Ca2+transients frequency in single SANPC.Collectively,our work suggests that SANPCs share dominant biological properties with glutamatergic neurons,and the glutamatergic neurotransmitter system may act as an intrinsic regulation module of heart rhythm,which provides a potential intervention target for pacemaker cell-associated arrhythmias.

Cardiac conductive system excitation maps using intracardiac tissue Doppler imaging

OBJECTIVE: To precisely visualize cardiac anatomic structures and simultaneously depict electro-mechanical events for the purpose of precise underblood intervention. METHODS: Intracardiac high-resolution tissue Doppler imaging was used to map real time myocardial contractions in response to electrical activation within the anatomic structure of the cardiac conductive system using a canine open-chest model. RESULTS: The detailed inner anatomic structure of the cardiac conductive system at different sites (i.e., sino-atrial, atrial wall, atrial-ventricular node and ventricular wall) with the inside onset and propagation of myocardial velocity and acceleration induced by electrical activation was clearly visualized and quantitatively evaluated. CONCLUSION: The simultaneous single modality visualization of the anatomy, function and electrical events of the cardiac conductive system will foster target pacing and precision ablation.