Objective To observe the 12-lead ECG ( electrocardiogram ) characteristics of Japanese rabbits , and provide basic ECG data for cardiovascular disease research .Methods The 12-lead ECG and X-rays of 55 male Japanese rabbits were recorded in supine position after intraperitoneal injection of 20% urethane.Results ECG:① The 12-lead ECG characteristics of male Japanese rabbits were similar to humans .The rabbit heart rate was 265.5 ±36.8 beats/min, faster than that of humans .No arrhythmia was found in all the 55 rabbits.② The supine position average ECG axis was between 19 °to 250 °, varying a lot .③P wave:The shape of P wave was blunt round or a little bit sharp .P waves were all in accordance with the sinus P wave rules , which were more obvious in lead II , aVF and all chest leads .④ The PR interval was 0.063 ±0.007 s.⑤The QRS duration was 0.040 ±0.005 s.The main waves were mostly upward in leadsⅡ,Ⅲ, and aVF .The same as humans , the R/S ratios were increased by degrees in chest leads .⑥The ST segment was short, and was located in the equipotential line .⑦ The shapes of T wave were mostly round , partly had twin peaks .T waves were more obvious in leads Ⅱ,Ⅲ, aVR, and AVF and chest leads .⑧The QT interval was 0.142 ±0.015 s, and QTc was 0.306 ±0.034 s.In the X-rays, most heart shadows were in the center and right chest .Conclusions The normal values of 12-lead ECG characteristics of Japanese rabbits are obtained in this study , which are of certain application value in experimental studies of cardiovascular diseases .

Objective To control residual DNA by optimizing methodology during the production of rabies vaccine using Vero cells as a vector .Methods The antigen recovery rate was assessed by linked immunosorbent assay-sandwich technique while the residual DNA was detected by DNA probe hybridization method .Antigen recovery and removal of DNA were the main indexes for evaluateing ultrafiltration , the vital part of rabies vaccine production .Three key factors in ultrafiltration were assessed: selection of membrane packages , ultrafiltration pressure and the concentration ratio .Then protamine was used to pretreat ultrafiltrates .Based on the two indicators mentioned above , the effect of protamine pretreat-ment on the ultrafiltrate was evaluated .Results and Conclusion The optimum condition of ultrafiltration was obtained on the basis of the general antigen recovery rate , DNA removal rate and actual production .The primary parameters of ultrafil-tration were as follows:7.5 ×105 ultrafiltration membrane packages, 20 times concentrated, 15 psi ultrafiltration pressure. After pretreatment with protamine , ultrafiltration has proved to be a molecular sieve in intercepting DNA ,while protamine can tangle the fragmented DNA and form a larger molecular segment , which is believed to be more conducive to ultrafiltra-tion interception .