Changes of the F-wave in the acute phase of permanent spinal cord ischaemic injury predict spinal cord function in animal models of rabbits

Objective:to explore the changes of the F-wave in the posterior tibial nerve of rabbits after different levels of lumbar spinal cord ischaemic injury and its correlation with motor function and the extent of lumbar spinal cord pathological damage.Methods:thirty New Zealand rabbits were randomly divided into 6 groups.The control group(n=5)was used to exclude the influence of anaesthesia and surgery on the F-wave.Different levels of lumbar arteries were ligated in the five experimental groups(n=5).The F-wave was recorded to observe the changes in the acute phase of spinal cord ischaemia.The correlation between the changes of the F-wave in the acute reversible phase and the motor function of the spinal cord was analysed.Motor functions were assessed after surgery and 2 d after vascular ligation.The specimens were taken 2 d after ligation for histopathologic observation.Results:the results for the control group indicated that anaesthesia and surgery did not affect the F-wave results.There was no statistically significant difference in the F-wave amplitudes and latency before and after ligation in the 1 and 2 level ligation groups.The F-wave changed immediately after ligation in the 3,4 and 5 ligation groups.The latency of the F-wave gradually extended,the amplitude of the F-wave gradually reduced.The amplitude variations of the F-wave were positively correlated with the motor function 2 d after ligation,there was a statistically significant difference.With the increase in the number of vascular ligation,the degree of destruction of the motor neurons in the anterior horn of the spinal cord in the pathological specimens increased.Conclusion:the F-waves in the posterior tibial nerve of rabbits were found to be sensitive to the lumbar spinal cord ischaemic injury and specific to predict motor function.

Effects of Split Injection on Combustion,Emissions,and Intermediate Species of Natural Gas High-Pressure Direct Injection Engine

Using natural gas(NG)as the primary fuel helps alleviate the fossil fuel crisis while reducing engine soot and nitrogen oxide(NO_(X))emissions.In this paper,the influences of a novel split injection concept on an NG high pressure direct injection(HPDI)engine are examined.Four typical split injection strategies,namely split pre-injection of pilot diesel(PD)and NG,split post-injection of PD and NG,split pre-injection of NG,and split post-injection of PD,were developed to investigate the influences on combustion and emissions.Results revealed that split pre injection of NG enhanced the atomization of PD,whereas the split post-injection of NG lowered the temperature in the core region of the PD spray,resulting in the deterioration of combustion.The effect of the split injection strategy on indicated thermal efficiency exceeded 7.5%.Split pre-injection was favorable to enhancing thermal efficiency,whereas split post-injection was not.Ignition delay,combustion duration,and premixed combustion time proportion were affected by injection strategies by 3.8%,50%,and 19.7%,respectively.Split pre-injection increased CH_(4) emission in the exhaust.Split post-injection,especially split post-injection of PD and NG,reduced the unburned CH_(4) emission by approximately 30%.When the split post-injection ratio was less than 30%,the trade-off between NO_(X) and soot was interrupted.The distribution range of hydroxyl radicals was expanded by pre-injection,and NO_(X) was generated in the region where the NG jet hit the wall.This paper provides valuable insights into the optimization of HPDI injection parameters.

Transcranial electrical stimulation motor-evoked potentials in a spinal cord ischaemia rabbit model

Background:Spinal cord ischaemia animal models were established by selective ligation of the lumbar artery in a craniocaudal direction between the renal artery and the aortic bifurcation.Transcranial electrical stimulation motor-evoked potentials were measured to enable their use in future studies on spinal cord ischaemia protection.Methods:Thirty-three New Zealand rabbits were randomly divided into 6 groups.Transcranial electrical stimulation motor-evoked potentials were recorded before vascular ligation,30 min after vascular ligation,and 2days after vascular ligation.Motor functions were assessed after surgery and 2 days after vascular ligation.The specimens were taken 2 days after ligation for histopathologic observation.Results:With increased numbers of ligations,a transient extension of the latency became clear,but there were no significant differences in the statistical analysis.Analysis of variance after ligation at the same time in each group and t tests before and after ligation(P>0.05)were not significant.One or 2 ligations did not cause spinal cord ischaemic damage.There were no significant differences before and after ligation for the amplitude(P>0.05).With increased numbers of ligations,the amplitude before and after ligation was gradually reduced in the 3-5 ligation groups(P<0.05).Conclusions:Ligation of segmental spinal cord vessels on 1 or 2 levels did not cause ischaemic damage.Spinal cord ischaemia was observed after 3,4,or 5 ligations.The amplitude was more sensitive to spinal cord ischaemia than latency.Spinal cord function can be predicted by early changes in the amplitude.