A serine/threonine phosphatase 1 of Streptococcus suis type 2 is an important virulence factor

Lihua Fang,Jingjing Zhou,Pengcheng Fan,Yunkai Yang,Hongxia Shen,Weihuan Fang 대한수의학회 2017 Journal of Veterinary Science Vol.18 No.4

Streptococcus suis is regarded as one of the major pathogens of pigs, and Streptococcus suis type 2 (SS2) is considered a zoonotic bacterium based on its ability to cause meningitis and streptococcal toxic shock-like syndrome in humans. Many bacterial species contain genes encoding serine/threonine protein phosphatases (STPs) responsible for dephosphorylation of their substrates in a single reaction step. This study investigated the role of stp1 in the pathogenesis of SS2. An isogenic stp1 mutant (stp1) was constructed from SS2 strain ZJ081101. The stp1 mutant exhibited a significant increase in adhesion to HEp-2 and bEnd.3 cells as well as increased survival in RAW264.7 cells, as compared to the parent strain. Increased survival in macrophage cells might be related to resistance to reactive oxygen species since the stp1 mutant was more resistant than its parent strain to paraquat-induced oxidative stress. However, compared to parent strain virulence, deletion of stp1 significantly attenuated virulence of SS2 in mice, as shown by the nearly double lethal dose 50 value and the lower bacterial load in organs and blood in the murine model. We conclude that Stp1 has an essential role in SS2 virulence.

Temperature Characteristics of Power Ternary Polymer Li-ion Batteries

Fang Haifeng,Cai Lihua,Lu Huaimin,Wei Benjian,Zhu Hongping 보안공학연구지원센터 2015 International Journal of Hybrid Information Techno Vol.8 No.11

The characteristics of power ternary polymer Li-ion batteries are closely connected to ambient temperature. The capacity characteristic, resistance and state of charge-open circuit voltage (SOC-OCV) curve are important parameters to represent the performance of power batteries and to determine battery management system (BMS) design. The experiments at different ambient temperatures are carried out and the laws between temperature and capacity, resistance and OCV are studied. The capacity drops sharply under low temperature, and increases with a relatively slower rate than under low temperature when the temperature goes up. Polarization and ohmic resistances during charge and discharge process decrease when the temperature rises, and the change rate of ohmic resistance is higher than that of the polarization resistance. Moreover, the change of ohmic resistance under low temperature is more significant than under high temperature. With the decrease of temperature, the SOC-OCV curve moves down, but generally, the curve is affected only slightly by the temperature.

Vibration Control of Soil-structure Systems and Pile-soil-structure Systems

Lihua Zou,Leiqing Fang,Kai Huang,Liyuan Wang 대한토목학회 2012 KSCE JOURNAL OF CIVIL ENGINEERING Vol.16 No.5

The purpose of this paper is to investigate the influence of Soil-Structure Interaction (SSI) and Pile-Soil-Structure Interaction (PSSI) on vibration control effect. Assuming the ground as an isotropic elastic half space and the soil around the foundation as a horizontal and rotational spring-dashpot system, a SSI model for buildings with rigid shallow foundations is established. Based on Penzien model, a PSSI model for structures with pile-foundations is also set up. Then, after the motion and control equations of the SSI system and PSSI system are derived, the influences of SSI and PSSI on vibration control are investigated. Important parameters of soil and structures are studied. Numerical results show that the SSI and PSSI have an obvious influence on the control effect of structures. Parameters such as shear-wave velocity, embedded depth of soil and stiffness of superstructure and pile, play a significant role in vibration control. The influences of SSI and PSSI mainly depend on characteristics of the upper soil layer, hence, the SSI influence on buildings with rigid foundations is more obvious than that of PSSI on buildings with pile foundations.

Constituents from the stems of Parthenocissus tricuspidata and their DNA topoisomerases I andⅡinhibition and cytotoxicity

Woo MiHee,Cao LiHua,Fang Zhe,Jung JiHyun,Lee WiJea,Jung EunJoo,choi DooHyung,Son JongKeun,Lee ChongSoon 대한약학회 2004 大韓藥學會 總會 및 學術大會 Vol.2004 No.2

Dynamic self-collision detection and prevention for 2-DOF robot arms using interval-based analysis

Hao Fang,Jie Chen,Lihua Dou 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.8

The problems related to self-collision detection and optimal collision-free trajectory planning for a robot arm subjected to dynamic constraints is investigated. First, a computed-torque method is used to obtain a linearized closed-loop system. For this linearized system,the reference state that the robot arm is capable of reaching is verified through phase plane analysis. This will ensure that the robot arm can be stopped before self-collision occurs. Dynamic constraints are taken into account for a continuous motion of deceleration by calculating the bounds of the commanded force/torques with interval evaluations. When the reference state at t+δt is not valid for selfcollision avoidance, a new feasible state is determined by adhering to an interval-based method which allows decomposition of a complex constrained optimization problem into a simple two-stage optimization problem with relaxed constraints. The optimized feasible state not only secures the robot arm against self-collision but also allows the robot arm to track the original reference trajectory closely. Simulation and experimental results of a 2-dof robot arm show the effectiveness of the proposed interval-based approach.

An Improved Energy Recovery Clamp Circuit for PWM Converters with a Wide Range of Input Voltage

Honnyong Cha,Lihua Chen,Fang Z. Peng,Qingsong Tang 전력전자학회 2007 ICPE(ISPE)논문집 Vol.- No.-

A full-bridge dc-dc converter employing diode rectifier in the output experiences severe voltage overshoot and oscillation problem across the diode rectifier caused by the interaction between the junction capacitance of the rectifier diode and the leakage inductance of transformer. The pronounced reverse-recovery current of high power diodes enforces these issues significantly by increasing power loss and voltage overshoot. Conventional energy recovery clamping circuits suffer from high voltage overshoot if the input voltage of converter is wide. In this work, a novel energy recovery clamp circuit is proposed to overcome this problem. Performance of the proposed circuit is verified both theoretically and experimentally with a 70 ㎾ dc-dc converter.

DnaJ of Streptococcus suis Type 2 Contributes to Cell Adhesion and Thermotolerance

Zhang, Xiaoyan,Jiang, Xiaowu,Yang, Ling,Fang, Lihua,Shen, Hongxia,Lu, Xingmeng,Fang, Weihuan The Korean Society for Microbiology and Biotechnol 2015 Journal of microbiology and biotechnology Vol.25 No.6

To examine if the molecular chaperone DnaK operon proteins of Streptococcus suis type 2 (SS2) are involved in adhesion to host cells, the abundance values of these proteins from the surface of two SS2 strains of different adhesion capability were compared. Their roles in growth and adhesion to human laryngeal epithelial cell line HEp-2 cells were investigated on SS2 strain HA9801 and its mutants with DnaK operon genes partially knocked-out (PKO mutant) under heat stress. The major difference was that DnaJ was more abundant in strain HA9801 than in strain JX0811. Pretreatment of the bacteria with hyperimmune sera to DnaJ, but not with those to other proteins, could significantly reduce SS2 adhesion to HEp-2 cells. PKO of dnaJ g ene resulted in decreased SS2 growth at 37℃ and 42℃, and reduced its adhesion to HEp-2 cells. The wild-type strain stressed at 42℃ had increased expression of DnaJ on its surface and elevated adhesion to HEp-2 cells, which was also inhibitable by DnaJ specific antiserum. These results indicate that the DnaJ of S. suis type 2 is important not only for thermotolerance but also for adhesion to host cells. Because DnaJ expression is increased upon temperature upshift with increased exposure on the bacterial surface, the febrile conditions of the cases with systemic infections might help facilitate bacterial adhesion to host cells. DnaJ could be one of the potential candidates as a subunit vaccine because of its good immunogenicity.

Thioredoxin A of Streptococcus suis Serotype 2 Contributes to Virulence by Inhibiting the Expression of Pentraxin 3 to Promote Survival Within Macrophages

Zhao Chijun,Jia Xinglin,Pan Yanying,Liao Simeng,Zhang Shuo,Ji Chunxiao,Kuang Guangwei,Wu Xin,Liu Quan,Tang Yulong,Fang Lihua 한국미생물학회 2023 The journal of microbiology Vol.61 No.4

Streptococcus suis serotype 2 (SS2) is an important zoonotic pathogen that can infect humans in contact with infected pigs or their byproducts. It can employ different types of genes to defend against oxidative stress and ensure its survival. The thioredoxin (Trx) system is a key antioxidant system that contributes adversity adaptation and pathogenicity. SS2 has been shown to encode putative thioredoxin genes, but the biological roles, coding sequence, and underlying mechanisms remains uncharacterized. Here, we demonstrated that SSU05_0237-ORF, from a clinical SS2 strain, ZJ081101, encodes a protein of 104 amino acids with a canonical CGPC active motif and an identity 70–85% similar to the thioredoxin A (TrxA) in other microorganisms. Recombinant TrxA efficiently catalyzed the thiol-disulfide oxidoreduction of insulin. The deletion of TrxA led to a significantly slow growth and markedly compromised tolerance of the pathogen to temperature stress, as well as impaired adhesion ability to pig intestinal epithelial cells (IPEC-J2). However, it was not involved in H2O2 and paraquat-induced oxidative stress. Compared with the wild-type strain, the ΔTrxA strain was more susceptible to killing by macrophages through increasing NO production. Treatment with TrxA mutant strain also significantly attenuated cytotoxic effects on RAW 264.7 cells by inhibiting inflammatory response and apoptosis. Knockdown of pentraxin 3 in RAW 264.7 cells was more vulnerable to phagocytic activity, and TrxA promoted SS2 survival in phagocytic cells depending on pentraxin 3 activity compared with the wild-type strain. Moreover, a co-inoculation experiment in mice revealed that TrxA mutant strain is far more easily cleared from the body than the wild type strain in the period from 8–24 h, and exhibits significantly attenuated oxidative stress and liver injury. In summary, we reveal the important role of TrxA in the pathogenesis of SS2.