This study was approved by the ethics committee of this hospital

mprove our ability to develop drugs against 24172903 T. gondii. Materials and Methods Ethics Statement All animals were treated in strict accordance to the guidelines for the Laboratory Animal Use and Care from Chinese CDC and the Rules for Medical Laboratory Animals from Ministry of Health, China, under the protocols approved by National Institute for Communicable Disease Control and Prevention and Laboratory Animal Use and Care Committee of Sun Yat-Sen University under the licenses of 2010CB53000. Animals We used five rat strains, Sprague Dawley, Wistar, Brown Norway, Fischer 344 and Lewis and 4 mouse strains, BALB/c, C57BL/6, NIH and Swiss mice. All BN, F344 and Lewis were purchased from Vital River Laboratories; the other rat and mouse strains were purchased from the Experimental Animal Center of Sun Yat-Sen University. All animals were maintained in a pathogen-free room at the School of Life Sciences, Sun Yat-Sen University following the university policy. 7 Mechanism of Rat Resistance to T. gondii BN6 Lewis F1 progeny BN 6 Lewis F1 hybrid rats were generated in our laboratory, which were viably fertile, 518303-20-3 normal in size and did not display any behavioral or physical abnormalities. F1 individuals were identified by a black and white pattern on the underside. USA) with 10% fetal bovine serum for further use after counted. Peritoneal macrophage isolation and cultivation Animals, sacrificed by carbon 23692283 dioxide, were injected intraperitoneally with 5 ml or 15 ml ice cold DHank’s solution containing 100 U of penicillin and 100 mg of streptomycin per ml and then peritoneal cells were harvested and separated by centrifugation at 2506g for 10 min at 4uC. The cells were washed by D-Hank’s solution and centrifuged with the same procedure. Finally, cells were suspended in RPMI-1640 medium with 10% FBS and left to adhere for 2 hrs at 37uC in an incubator containing 5% CO2 and 95% air. Non-adherent cells were removed and fresh medium was added. Macrophages were cultured overnight and then used for further experiments. Rat peritoneal macrophages were incubated with or without lipopolysaccharide plus IFN-c or with the NOS specific inhibitor Nv Parasites The Toxoplasma gondii RH-GFP strain was kindly provided by Dr. X.N. Xuan of the National Research Center for Protozoan Diseases, Obihiro University, Obihiro, Japan, generated as described. For the purification of tachyzoites, T. gondii and host cell debris were harvested from the peritoneal cavities of BALB/c mice by injection of ice cold D-Hanks on day 3 after infection. The solution containing T. gondii was centrifuged at 406g for 5 min at 4uC to discard host cells and fragments. The supernatant was centrifuged at 13506g for 10 min at 4uC, and then suspended in RPMI-1640 medium Arginase activity in mouse peritoneal macrophages treated with LPS only or LPS norNOHA for 24 hrs, measured by a colorimetric assay; enzyme activity is the output of urea secreted from lysed macrophages. NO production measured by the Griess reaction in mouse macrophages treated with LPS only or LPS norNOHA for 24 hrs. Number of T. gondii per 100 macrophages counted at 24 hrs after infection in LPS only or LPS norNOHA treated mouse macrophages. Mean 6 SEM and significant differences. Amplified DNA products were separated on 1% agarose gel and photographed using an electronic documentation system after staining with ethidium bromide. Parasite infection and detection in animals Five rat strains and 4 mouse strains were injected intraperi