ABSTRACT
It is believed that cardiac electrophysiological properties are not homogeneous, and the heterogeneity exists between pacemaker and conduction cells, atrial and ventricular cells, and among endocardium, midmyocardium, and epicardium of the transmural ventricular wall. The heterogeneous electrophysiology is related to the differential distribution and expression of transmembrane ionic channels. The present review involves literatures regarding the intrinsic biological basis of cardiac heterogeneous electrophysiology.
ABSTRACT
OBJECTIVE:To study the biodegradability of polylactic acid and prepare its microspheres containing erythromycin.METHODS:The polylactic acid film was degraded in vitro.The orthogonal design was used to optimize the technology of preparation of microspheres.RESULTS:The degradable speed of polylactic acid with high molecular weight was faster than that with low molecular weight.The degradable speed of PDLLA was faster than that of PLLA.The microspheres were stable in quality and regular in external form.The average particle size was (10.98?0.15)?m.The in vitro release properties could be expressed by the Higuchi's equation(Q=28.067+3.8 515 T1/2,r=0.9 834).CONCLUSION:The biodegradability of polylactic acid depended on configuration and molecular weight.Erythromycin microspheres showed significant slow-released property and accorded with the demands of lung targeting agent.