Objective To study the relationship between the DNA content of chondrocytes in the costal cartilage and postmortem interval in putrefactive rat cadavers.Methods Nuclear DNA wag visualized by modified Feulgen's staining method.DNA content of ehondrocytes in the costal cartilage was semi-quantita tively determined by a computerized image analysis system in rats within 35d postmortem.Results Staining intensity of the nuclei was gradually reduced within from 1d to 28d postmortem.The nuclej could not be detected at 35d.The DNA content of chondrocytes decreased time-dependently within 28 days after death as determined semi-quantitatively,which revealed a linear relationship between DNA content and postmortem interval.Conclusion DNA content of chondrocytes in the costal cartilage reduces time-dependently with the extension of postmortem interval.

AIM: To construct recombinant adenovirus vector containing brain derived neurotrophic factor, (BDNF) gene using bacterial homogenous recombination, and investigate the expression in expanded rat mesenchymal stem cells (rMSC) in vitro. METHODS: BDNF gene and proBDNF gene were subcloned into adenovirus shuttle plasmid pAdTrack-CMV containing enhanced green fluorescent protein gene (EGFP) expression cassette, forming shuttle vector of pAdTrack-BDNF, and pAdTrack-proBDNF, and co-transformed into BJ5183 bacterial cells with adenovirus backbone vector pAdEasy-1 using chemical transformation. After the recombinant adenovirus vector was obtained, the identified recombinant adenovirus plasmid DNA was digested with Pac I and transfected to 293 cells to package recombinant adenovirus particles. rMSC were infected by recombinant adenovirus and EGFP expression was detected using fluorescent microscope. Infection efficiency was assessed by flow cytometrics. Western blotting identified expression of Ad -proBDNF and Ad-BDNF in rMSC. rMSC infected with Ad -proBDNF and Ad-BDNF were induced to differentiate into neuron-like cells. rMSC infected with Ad -proBDNF and Ad-BDNF were injected into nude mice and assessd in vivo. RESULTS: We successfully constructed the recombinant adenovirus Ad -proBDNF and Ad-BDNF that expressed in expanded rMSC in vitro.CONCLUSION: Recombinant adenovirus high-effectively mediates Ad -proBDNF and Ad-BDNF expression in expanded rMSC in vitro and in vivo.