Construction and characterization of the stk and stp1 knockout mutant in streptococcus suis type 2 / 医学研究生学报

Objective Serine /threonine kinases (STK) and phosphatases (STP) regulate various physiological activities of prokaryotes by reversible phosphorylation of proteins .This paper aimed to study the effects of simultaneous deletion of the stk and stp1 genes on the biological characteristics and pathogenicity of streptococcus suis type 2, the Chinese virulent strain 05ZYH33. Methods The double mutant of the stk and stp1 genes of 05ZYH33 was constructed by homologous recombination .The biological characteristics of the wild strain 05ZYH33 and the mutant strain Δstk/stp1 were compared.The effects of the stk and stp1 deletion on bacterial virulence was analyzed using cell adhesion assay , anti-phagocytosis assay and the mouse model of infection . Results RT-PCR showed that the stk and stp1 genes were replaced by the spectinomycin resistance gene Spc r and the mutant strain was successfully constructed .Experi-ments of biological characterization revealed gradually increased value of 05ZYH33 and Δstk/stp1 at 2 hours after inoculation and a plateau period at 7 hours.The logarithmic phase of the mutant strain (A600≈0.4) was 1 hour later than that of the wild one , and the bacterial den-sity of the former was lower than that of the latter after the plateau pe -riod (0.8 vs 1.0).On the blood plates of 05ZYH33 and Δstk/stp1 were observed greyish, round, semitransparent, wet and smooth-sur-faced tiny bacterial colonies , around which there were hemolysis rings with no significant differences in colony morphology and hemolytic ac -tivity.In the experiment on pathogenicity , the mice of the 05ZYH33 group all died within 12 hours while 9 of the 30 mice in the Δstk/stp1 group died within 12 hours and all died within 24 hours. Conclusion The simultaneous deletion of the stk and stp1 genes may mainly affect the regulation of the proteins associated with bacte -rial proliferation and division.

High volume practice proved the safety of off-pump coronary artery bypass surgery in left main coronary artery lesions: a two-year single center experience / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Left main coronary artery (LMCA) stenosis has been recognized as a risk factor for early death among patients undergoing coronary artery bypass grafting (CABG). This study aimed to assess if LMCA lesions pose an additional risk of early or mid-term mortality and/or a major adverse cardiac and cerebrovascular event (MACCE) after off-pump coronary artery bypass grafting (OPCABG), compared with non-left main coronary artery stenosis (non-mainstem disease).</p><p><b>METHODS</b>From January 1, 2009 to December 31, 2010, 4869 patients had a primary isolated OPCABG procedure at Beijing Anzhen Hospital. According to the pathology of LMCA lesions, they were retrospectively classified as a non-mainstem disease group (n = 3933) or a LMCA group (n = 936). Propensity scores were used to match the two groups, patients from the non-mainstem disease group (n = 831) were also randomly selected to match patients from the LMCA group (n = 831). Freedom from MACCE in the two groups was calculated using the Kaplan-Meier method.</p><p><b>RESULTS</b>The difference in the mortality and the rate of MACCE during the first 30 days between the non-mainstem disease group and the LMCA group did not reach statistical significance (P = 0.429, P = 0.127 respectively). With a mean follow-up of (12.8 ± 7.5) months and a cumulative follow-up of 1769.6 patient-years, the difference in the freedom from MACCEs between the two groups, calculated through Kaplan-Meier method, did not reach statistical significance (P = 0.831).</p><p><b>CONCLUSION</b>Analysis of a high volume of OPCABG procedures proved that LMCA lesions do not pose additional early and mid-term risk to OPCABG. Therefore, a LMCA lesion is as safe as non-mainstem disease lesion during the OPCABG procedure.</p>

Expression of TN4 gene and its role in human hepatocarcinogenesis from Qidong, a liver cancer risk area / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>We investigated the expression and role of TN4 in the oncogenesis of human hepatocellular carcinoma (HCC) from Qidong which is a HCC risk area.</p><p><b>METHODS</b>The expression of TN4 in HCC was observed using immunohistochemical staining (IHC). TN4 levels were manipulated in human liver cancer cell SMMC7721, using pcDNA3.1 eukaryotic expression constructs designed to express the complete TN4 cDNA. The biological changes of the cells were observed before and after transfection of TN4 and the change of gene expression was analysed by atlas cDNA expression array.</p><p><b>RESULTS</b>Among 100 pairs of samples of HCC, TN4 down-regulation expression and up-regulation expression positive rate were 81% (81/100), 19% (19/100), respectively (P < 0.01). TN4 protein was mainly localized in cytoplasm and membrane. The positive rate of TN4 were 10% (3/30), 100% (70/70) in lymph node metastasis and no lymph node metastasis, respectively (P < 0.01). The growth rates of the derivative SMMC7721-TN4 cell lines were decreased in comparison with that of normal SMMC7721 cells and pcDNA-SMMC7721. Some gene expression was changed before and after transfection of TN4. At 30 days of post-implantation of SMMC7721-TN4, SMMC7721-pcDNA3, SMMC7721 group produced tumors of (301.9 +/- 143.4) mm(3), (2418.7 +/- 362.8) mm(3), (2317.4 +/- 587.8) mm(3), respectively, (P < 0.01). Tumor inhibiting rate was 82.4% in TN4 transfection group. Sections of tumors were observed for their degree of tissue necrosis and there was higher degree of necrosis in tumors of the TN4-SMMC7721 cell group than those of the SMMC7721, SMMC7721-pcDNA groups.</p><p><b>CONCLUSIONS</b>TN4 may play an important role in the oncogenesis of human HCC, especially in Qidong, the HCC risk area and TN4 could be a candidate tumor suppressor gene for HCC.</p>

Site-directed mutation of PoIFN-alpha and its expression in Escherichia coli / 生物工程学报

By using huge primer PCR Cys86 (TGC) of PoIFN-alpha was mutated to Tyr(TAC), and the first code TGT was simultaneously changed to TGC, which is a bias code of E. coli. The expression plasmid pGEX-IFN was constructed successfully. Recombinant porcine IFN alpha, which is expressed as inclusion bodies, was about 20% of the total proteins. The inclusion body was dissolved in 8 mol/L urea and subsequently renatured by dilution in refolding buffer. In order to obtain pure protein, the renatured IFN alpha was purified by FPLC, and the cytokine activity (5200 IU/mg) was verified by inhibiting the cytopathic effect.