The susceptibility to 9 kinds of antibiotics of 393 animal pathogenic E. coli isolated from clinical samples was determined from 2000 to 2003. The resistance to TC, GM, CMP, AMP, RA, KM, FT, SM and CIP were 93.89%, 57.76%,78.63%, 77.86%, 92.11% ,47.33%, 46.82%, 76.84% and 74.81%, respectively. The isolates could be classified into eight classes according to the number of drugs to which srains were resistant. The resistance spectrum of the isolates varied from 2to 9 kinds of the above drugs. The strains that were resistant to seven kinds of drugs were more than 80 percent. The resistance rates of swine origin strains to GM,AMP and KM were higher than those of poultry origin strains, while the resistance rates of poultry origin strains to TC, CMP, SM and CIP were higher remarkably than those of swine origins. The frequency of resistance increased from 2000 to 2003,which was from 67.33% to 90.58% for CMP, 71.29% to 84.81% for AMP, 73.76%to 80.10% for SM and 61.88% to 88.48% for CIP. At the same time, the resistance rate of GM decreased from 61.39% to 53.92%. Thirty-seven strains (95 %) could make all the Kunming mice die within 72 h injected intraperitoneally with the culmice three times in vivo. The pathogenicity of wild strains with drug resistance acquired naturaly to mice did not decline.

The Interleukin-2 gene cDNA was cloned into the Pichia pastoris expression vector pPICZB,which is under the control of the alcohol oxidase promoter AOX1. The linearized recombinant plasmid of BoIL2-pPICZB,digested by Sac I ,was transformed into X-33 strains by electroporation. The multi-copy insert transformants were screened by Zeocin-resistance and induced by 1% methanol. The intracellular expression products were tested by SDS-PAGE analysis and Western blotting. Purified recombinant BoIL2 was gained by metal-chelating affinity chromatographic (MCAC). Assay with murine CTLL-2 cells showed that the recombinant BoIL2 exhibited the biological activity.

In present study,comparisons were carried out to develop and improve in vitro mauration(IVM) systems of goat oocytes. Oocytes were cultured in TCM-199 supplemented with(1)10% sera (either estrous goat serum (EGS) or fetal bovine serum(FBS)) + 20 mg/L luteinizing hormone (LH) + 10 mg/L follicle stimulating hormone (FSH) + 1 mg/L estradiol (E2); (2)10% EGS with different gonadotropins(LH: FSH) at a concentration of 5 mg/L: 0.5 mg/L or at 20 mg/L: 10 mg/L with0. 075 IU/mL human menopausal gonadotropin(HMG),1 mg/L estradiol 17β; (3)10% EGS+ 0. 075 mg/L HMG+10-20 μg/EGF. The culture was also performed by M199 supplemented with 10% EGS+0. 075 mg/L HMG+ 10-20 μg/L EGF into ultra-filtrated water which was derived either from self-producing or from purchased for use. The oocytes were cultured at 38 ℃,5% CO2 in air for 24 h,and the meterphase Ⅱ stage oocytes were examined under dissecting microscope. The results showed that EGS was better than FBS in supporting goat oocyte IVM. An addition of HMG in M199 could improve oocyte maturation and induce a higher percentage of metaphase Ⅱ oocytes compared to gonadotropins. 10-20 μg/L EGF improved goat oocyte maturation but the influence was not significant. Fresh,high quality water was vital for oocyte IVM. In conclusion,under our conditions with IVM ,the best result in maturation of goat oocyte has been M199 supplemented with 10% EGS+0.075 IU/mL HMG+10-20 μg/L EGF and prepared in fresh purified water.

150-day-old Tianfu ducklings were divided into three groups,and fed with diets as follows :Zn deficient (22. 9 mgZn per kg diet),controls(100 mg Zn per kg diet) and Zn toxic (1 300 mg Zn per kg diet) for seven weeks (Zn deficiency,ZD)or four weeks (Zn toxieity,ZT). The ANAE+ positive ratios of the peripheral blood T-lymphocytes were much lower (P＜0.01 ) in Zn deficient and toxic groups than in the control group. The results showed that Zn deficiency and toxicity would suppress the development of T-lymphocytes and reduce the peripheral blood T-lymphocyte populations. Potential mechanisms underlying these observations are also discussed.

Porcine endogenous retroviruses (PERV) can infect human cell in vitro, which raised widely concerns re-garding the transmission of PERV to xenograft recipients. It's essential to establish a method for detection of PERV.3 pairs of primers were synthesized according to the sequence of gag, pol and env gene of PERV. Polymerase chainreaction (PCR) and reverse transcription PCR (RT-PCR) assays were performed for detection of PERV provirusDNA and PERV specific mRNA. The results showed that provirus DNA and mRNA of PERV existed and expressedin all 4 tested cell lines. The sizes of amplified fragments are identical with the predicted. These methods may be suit-able for monitoring PERV in other cells or tissue.

Three hundred and one piglets of Suzh ong line 1 and 2 were chosen for halothane test(HT), with the halothane positive rate of 1.33%. 34 halothane negative(HN) piglets were randomly selected for gen otype testing and 6 of them were found to be heterozygous. The results showed th at genotype frequencies of HalNN, HalNnand Halnn w ere 81.26 %, 17.4% and 1.33%, respectively, while the frequencies of N gene and n gene wer e 89.97% and 10.03%, separately. 4 pigs with genotype Halnn gave worst meat quality appearing 3 typical and 1 slight PSE meat. Pigs with genotype Hal N Nor HalNndid not show PSE meat. 208 offspring from 20 HN sows mat ed wit h halothane positive(HP) boars, 21 piglets from 4 litters were HP, with low dail y gain, low feed efficiency and bad meat quality but high dressing percentage, l arge loin-eye area and high lean meat percentage.

The expression patterns of 5-hydroxytryptamine(5-HT),gastrin(Gas),β-endorphin(End),somatostatin(SS),vasoactive intestinal peptide(VIP),glucagon(Glu) and neuropeptide Y(NPY)-positive cells in the duck thymus were studied by the immunohistochemical method associated with image analysis.The result shows that these 7 kinds of neuroendocrine cells with strong intensity were differentially detected in the duck thymus.The End-positive cells were abundantly expressed in the thymic cortex,whereas the Gas,5-HT,SS,VIP,Glu and NPY ones were more frequent in the medullary and around the corticomedullary junction.Except Glu,the other 6 kinds of neuroendocrine substances with various intensity were expressed in the cells of thymic corpuscles.The observation demonstrated that the duck thymus is not only a primary lymphatic organ,but also has important neuroendocrine functions.The End-positive cells in the thymus may play crucial roles in the development of immature T-lymphocytes.The neuroendocrine cells with a predominant distribution in the medulla and around the corticomedullary junction might facilitate exerting their influence via an endocrine,autocrine or paracrine pathways on the function of mature T-cells.The possible roles of thymic corpuscles are also discussed.

By using routine H. E method and measuring the absolute weight and growth index of thymus and ANAE positive ratios, 1 to 49 days Tianfu duckling were selected to study the changing trends in the normal development of the thymus. The results are as follows:the thymus of duckling develops slowly from 1 to 14 days,and quickly from 21 to 35 days,then steadily from 35 to 49 days. By the 28th day,most T-lymphocytes have well differentiated and the thymus has reached its maturation. There are three types of thymie corpuscles whose functions have been discussed.

Little is known about the distribution of Rhodococcus equi in the soil environment of native horses in China. One hundred and eight soil samples were collected from native-horse farms in the Hulun Beier grasslands of eastern Mongolia, the Xilin Goler grasslands of southern Mongolia, and Tongliao city in Inner Mongolia of China for investigating the distribution of R. equi in these regions. The isolation rates of R. equi from soil samples from the Hulun Beier and Xilin Goler grasslands ranged from 25.9% to 30.0%. In contrast, isolation rates from soil samples from Tongliao city was as high as 82.3% and the mean number of R. equi in soil samples from Tongliao city was 10 times more than those of samples from the grasslands. The 488 isolates were examined using PCR for the presence of genes that encode virulence-associated 15 000-17 000 antigen protein (VapA) and the 20 000 antigen protein (VapB). All isolates were negative for virulence-associated proteins. Plasmid profiles of these avirulent isolates showed that cryptic plasmids of various sizes were present with an incidence of 13.3% to 21.5%. The results of the present study contrast with those of our recent study, in which we reported that R. equi was absent from Mongolian horses in Ulaanbaatar, Mongolia. It is suggested that the difference between the results of these two studies is due to the mobile pasturing system in Mongolia and nonmobile pasturing system in Inner Mongolia.

Sixty barrows (Duroc × Labdrace × Yorkshine) were randomly assigned to two groups by weight of 33 kg,each of which was replicated three times with ten pigs. Half of the pigs were fed with diets containing 10 mg/kg lead and 0.5% particulate montmorillonite,the other half pigs were fed only with diets supplemented 10 mg/kg lead as control groups for 100 days.The results showed that the addition of particulate montmorillonite to the diet significantly decreased lead concentration in tissues such as blood,brain,liver,bone,kidney and hair and enhanced the erythropoiesis as measured by increasing numbers of RBC,hemoglobin and hematocrit values ,and elevated ALA-D activity in liver. The damage of lead to the liver was evident in the increases in hepatic concentration of malondialdehyde (+ 17.08% );decreases in the antioxidant enzymes catalase(-85.73 % ),superoxide dismutase ( - 52.17% ) and glutathione peroxidase ( - 47.56% ). Concomitant use of particulate montmorillonite in the diets completely ameliorated the lead-induced oxidative damage. It indicated that particulate montmorillonite is possessed of the potential therapeutic activity against lead poison.