Objective To investigate the effect of positive acceleration (+Gz) on monophasic action potential duration of 90%repolarization( MAPD90 ) and transmural dispersion of repolarization ( TDR) in ventricles of rabbits and to explore the cellular electrophysiologic mechanism of tachyarrhythmia induced by positive acceleration .Methods Twenty-four healthy, male New Zealand white rabbits were randomly and equally divided into control group and +Gz group.The +Gz group rabbits were given +8 Gz exposure, 1 min a time, 3 times a day,and a total of 7 days.The two groups were subjec-ted to Holter monitoring at the same time to observe the incidence of tachyarrhythmia .Using the monophasic action potential ( MAP) recording technology , the MAP of the left ventricle was recorded while MAPD 90 and TDR were measured .By using Burst stimulation method , the right ventricular anterior wall of the rabbits was stimulated , and the incidence of tachya-rrhythmia was observed .Results The Holter record showed that the incidence of tachyarrhythmias in +Gz group was 55%(6/11), but the control group did not have any case of tachyarrhythmias .Compared with the control group ,MAPD90 of en-docardial and epicardial cells was significantly decreased in the +Gz group, while MAPD90 of middle myocardial cells did not change significantly ,but TDR was increased obviously .Four rabbits in +Gz group suffered from tachyarrhythmias dur-ing Burst stimulation ,and the incidence of tachyarrhythmias was 40% ( 4/10 ) .Conclusion +Gz exposure can increase the incidence of tachyarrhythmias .The shortened MAPD90 of ventricular muscle cells and the increased TDR may be the cell electrophysiological mechanisms of tachyarrhythmias induced by +Gz.

BACKGROUNDOne of mechanisms of carcinogenesis is suppression of cell apoptosis which leads to accumulation of aberrant cells. The aim of this study is to investigate cell apoptosis and COX-2 protein expression in non-small cell lung cancer (NSCLC).

METHODSCell apoptosis, expression of COX-2 and microvessel density (MVD) were detcted in 111 NSCLC samples by TdT-mediated dUTP nick end labeling (TUNEL) technique and immunohistochemical staining.

RESULTSThe positive rate of COX-2 protein expression was 67.6% (75/111), and there were 53 patients with high level cell apoptosis (47.7%). Expression of COX-2 protien was significantly related to TNM stages (P=0.025) and lymph node metastasis (P=0.018). The MVD in NSCLC tissues with positive COX-2 expression was significantly higher than that in negative expression ones (P=0.000). COX model showed that lymph node metastasis (P=0.006) and positive expression of COX-2 protein (P=0.000) were independent prognostic factors of NSCLC.

CONCLUSIONSThe expression of COX-2 protein may suppress cell apoptosis of tumor, and it may serve as a potential marker of prognosis for NSCLC.