太平洋白对虾(Penaeus vannamei)β-N-乙酰-D-氨基葡萄糖苷酶在二甲亚砜溶液中的失活动力学(英文)

应用动力学方法研究了太平洋白对虾(Penaeusvannamei)β-N-乙酰-D-氨基葡萄糖苷酶在二甲亚砜溶液中以pNP-β-D-GlcNAc为底物时酶活力的变化规律.表明酶在DMSO浓度低于4.20mol/L,酶的失活过程是可逆的,DMSO并不造成酶绝对量的减少,仅对酶的活力发生可逆的下降.测得DMSO对酶抑制的IC50为1.2mol/L.观测了在不同底物浓度下NAGase在0、0.35、0.70、1.05、1.40、1.75mol/L的DMSO溶液中的失活过程,分别测定了游离酶(E)和酶-底物络合物(ES)的微观失活速度常数k+0和k′+0比较结果(k+0值远远大于k′+0)表明,在DMSO溶液中游离酶比酶-底物络合物更易失活,即底物的存在对于酶被DMSO的失活具有明显的保护作用.随着DMSO浓度的增加,游离酶的逆向微观复活速度常数k-0却不断降低,说明在高浓度DMSO环境中,NAGase可逆恢复的能力逐渐微弱.     

Inactivation kinetics of β-N-acetyl-D-glucosaminidase from prawn (<Emphasis Type="Italic">Penaeus vannamei</Emphasis>) in dioxane solution

beta-N-Acetyl-D-glucosaminidase (NAGase, EC 3.2.1.52) catalyzes the cleavage of N-acetylglucosamine polymers. It is in the composition of the chitinases and cooperates with endo-chitinase and exo-chitinase to disintegrate chitin into N-acetylglucosamine. In this work, the effects of dioxane on the enzyme activity for the hydrolysis of p-nitrophenyl-N-acetyl-beta-D-glucosaminide from the prawn (Penaeus vannamei) have been studied. The results show that appropriate concentrations of dioxane can lead to reversible inactivation of the enzyme, and the IC(50) is estimated to be 1.1 M. The kinetics of inactivation of NAGase in the appropriate concentrations of dioxane solution has been studied using the kinetic method of the substrate reaction. The rate constants of inactivation have been determined. The results show that the free enzyme molecule is more fragile than the enzyme-substrate complex in the dioxane solution. It is suggested that the presence of the substrate offers marked protection of this enzyme against inactivation by dioxane.     

Human-pathogenic relapsing fever Borrelia found in bats from Central China phylogenetically clustered together with relapsing fever borreliae reported in the New World

Bats can harbor zoonotic pathogens causing emerging infectious diseases, but their status as hosts for bacteria is limited. We aimed to investigate the distribution, prevalence and genetic diversity of Borrelia in bats and bat ticks in Hubei Province, China, which will give us a better understanding of the risk of Borrelia infection posed by bats and their ticks. During 2018–2020, 403 bats were captured from caves in Hubei Province, China, 2 bats were PCR-positive for Borrelia. Sequence analysis of rrs, flaB and glpQ genes of positive samples showed 99.55%-100% similarity to Candidatus Borrelia fainii, a novel human-pathogenic relapsing fever Borrelia species recently reported in Zambia, Africa and Eastern China, which was clustered together with relapsing fever Borrelia species traditionally reported only in the New World. Multilocus sequence typing (MLST) and pairwise genetic distances further confirmed the Borrelia species in the bats from Central China as Candidatus Borrelia fainii. No Borrelia DNA was detected in ticks collected from bats. The detection of this human-pathogenic relapsing fever Borrelia in bats suggests a wide distribution of this novel relapsing fever Borrelia species in China, which may pose a threat to public health in China.     

FRNK质粒转染抑制肝星状细胞增殖机制研究

目的：探讨黏着斑激酶相关非激酶（FRNK）质粒瞬时转染肝星状细胞（HSC）,对纤维连接蛋白（FN）刺激的HSC增殖的影响及其机制。方法：应用体外细胞培养技术,脂质体介导法进行FRNK质粒转染;Westernblot技术检测FRNK、黏着斑激酶（FAK）、p-raX（Tyr^397）蛋白的表达情况,鉴定转染效果;改良MTF法测定HSC增殖;流式细胞术（FCM）检测细胞周期时相。结果：FRNK质粒转染HSC48h时,FRNK蛋白表达最强（P〈0．01）;FAK蛋白转染前后无明显差异（P〉0．01）;FRNK质粒组p-FAK（Tyr^397）蛋白含量（0．40±0．14）较空质粒组（1．89±0．25）显著下降（P〈0．01）;FRNK在HSC大量表达后,于转染12h、24h、48h的HSC增殖抑制率分别为20．07％、26．16％和29．77％（P〈0．01）,呈时间依赖性关系;FRNK质粒组G0／G1期细胞数（71．4±2．81）较空质粒组（48．9±1．66）明显增加（P〈0．01）。结论：脂质体介导下FRNK质粒转染,可使外源性FRNK在HSC内大量表达,抑制FAK磷酸化,阻滞HSC周期时相于G0／G1期,抑制HSC增殖。     

水葫芦苗的组织培养与快速繁殖

1植物名称 水葫芦苗[Halerpestes sarmentosa（Adams）Kom．]（傅立国等2000）。 2材料类别 顶芽和带腋芽茎段。 3培养条件 基本培养基为加入0．05％内生菌型抑菌剂“山农一号”的MS培养基。     

Adaption of microbial community during the start-up stage of a thermophilic anaerobic digester treating food waste

A successful start-up enables acceleration of anaerobic digestion (AD) into steady state. The microbial community influences the AD performance during the start-up. To investigate how microbial communities changed during the start-up, microbial dynamics was analyzed via high-throughput sequencing in this study. The results confirmed that the AD was started up within 25 d. Thermophilic methanogens and bacterial members functioning in hydrolysis, acidogenesis, and syntrophic oxidation became predominant during the start-up stage, reflecting a quick adaption of microorganisms to operating conditions. Such predominance also indicated the great contribution of these members to the fast start-up of AD. Redundancy analysis confirmed that the bacterial abundance significantly correlated with AD conditions. The stable ratio of hydrogenotrophic methanogens to aceticlastic methanogens is also important to maintain the stability of the AD process. This work will be helpful to understand the contribution of microbial community to the start-up of AD.     

A recombinant influenza virus with a CTLA4-specific scFv inhibits tumor growth in a mouse model

Oncolytic viruses (OV) have shown excellent safety and efficacy in preclinical and clinical studies. Influenza A virus (IAV) is considered a promising oncolytic virus. In this report, we generated a recombinant influenza virus expressing an immune checkpoint blockade agent targeting CTLA4. Using reverse genetics, a recombinant influenza virus, termed rFlu-CTLA4, encoding the heavy chain of a CTLA4 antibody on the PB1 segment and the light chain of the CTLA4 antibody on the PA segment was produced. RFlu-CTLA4 could replicate to high titers, and antibodies were produced in the allantoic fluid of infected eggs. Furthermore, the selective cytotoxicity of the virus was higher in various hepatocellular carcinoma cancer cell lines than in the normal cell line L02 in vitro, as indicated by MTS assays. More importantly, in a subcutaneous H22 mouse hepatocarcinoma model, intratumoral injections of rFlu-CTLA4 inhibited the growth of treated tumors and increased the overall survival of mice compared with injections of the PR8 virus. Taken together, these results warrant further exploration of this novel recombinant influenza virus for its potential use as a single or combination agent for cancer immunotherapy.