Pore-Forming Cardiotoxin VVA2 (Volvatoxin A2) Variant I82E/L86K Is an Atypical Duplex-Specific Nuclease

VVA2 (volvatoxin A chain 2) is a cardiotoxic protein purified from Volvariella volvacea. Its biological activities include hemolysis, writhing reaction, neurotoxicity, and ventricular systolic arresting activity. The cytotoxicity of VVA2 was mainly considered due to its pore-forming activity. Here we report a novel biological activity of its variants VVA2 I82E/K86K as a duplex-specific nuclease. Recombinant VVA2 variant I82E/L86K (Re-VVA2 I82E/L86K), deprived of the oligomerization property, shows increased nuclease activity compared to VVA2. Re-VVA2 I82E/L86K converts supercoiled DNA (Replicative form I, RF I) into nicked form (RF II) and linear form (RF III) in the presence of Mg²⁺ or Mn²⁺. Besides plasmid DNA, it also exhibits nuclease activity on E. coli genomic DNA rather than ssDNA or RNA. Re-VVA2 I82E/L86K preferentially cleaves dG-dC-rich dsDNA regions and shows the best performance at pH 6–9 and 55 °C. Our structure–function study has revealed amino acid E111 may take an active part in nuclease activity through interacting with metal ions. Based on the sequences of its cleavage sites, a “double-hit” mechanism was thereby proposed. Given that Re-VVA2 I82E/L86K did not exhibit the conserved nuclease structure and sequence, it is considered an atypical duplex-specific nuclease.     

Decades of Genetic Research on Soybean mosaic virus Resistance in Soybean

This review summarizes the history and current state of the known genetic basis for soybean resistance to Soybean mosaic virus (SMV), and examines how the integration of molecular markers has been utilized in breeding for crop improvement. SVM causes yield loss and seed quality reduction in soybean based on the SMV strain and the host genotype. Understanding the molecular underpinnings of SMV–soybean interactions and the genes conferring resistance to SMV has been a focus of intense research interest for decades. Soybean reactions are classified into three main responses: resistant, necrotic, or susceptible. Significant progress has been achieved that has greatly increased the understanding of soybean germplasm diversity, differential reactions to SMV strains, genotype–strain interactions, genes/alleles conferring specific reactions, and interactions among resistance genes and alleles. Many studies that aimed to uncover the physical position of resistance genes have been published in recent decades, collectively proposing different candidate genes. The studies on SMV resistance loci revealed that the resistance genes are mainly distributed on three chromosomes. Resistance has been pyramided in various combinations for durable resistance to SMV strains. The causative genes are still elusive despite early successes in identifying resistance alleles in soybean; however, a gene at the Rsv4 locus has been well validated.     

不稳定血红蛋白病Hb Alesha一例报告并文献复习

不稳定血红蛋白病(unstable hemoglobinopathy,UHb)是一类由于珠蛋白结构异常引起血红蛋白不稳定的疾病。90%以上的结构异常是由于编码珠蛋白基因单个核苷酸替代导致的错义突变,引起相应氨基酸的改变,使血红蛋白不稳定,红细胞易于被破坏。目前全球报道了150余种UHb[1],大部分属常染色体显性遗传,但也有不少患者无家族史。本文报道不稳定血红蛋白病Hb Alesha 1例并总结复习相关文献,以提高对该病的认识。     

Effects of Electromagnetic Fields on the Microstructure of Laser Cladding

The fast heating and quenching of laser cladding increase the internal stresses in the cladding layer. Moreover, the quick condensation of the molten pool leads to an uneven distribution of the internal elements and coarse grains of the structure. To address the above defects and increase the molding quality of laser cladding, an electromagnetic field was introduced into the laser cladding technique, and the effects of the external assisted electromagnetic field on the mixed metal fluid in the molten pool were explored. On this basis, the action of the electromagnetic field on the flow states of the molten pool was further analyzed. The results demonstrate that after introducing electromagnetic assistance, the material flow in the molten pool accelerated as a response to the periodic changes in electromagnetic forces and the influences of the electromagnetic field on crystallization, thus refining the grains and improving the grain distribution uniformity in the cladding layer. The dendritic crystals in the cladding layer decreased, while the isometric crystals and the cellular-like dendrites increased. The element distribution in the cladding layer increased in uniformity. Additionally, this method can decrease the dilution rate of the cladding layer and improve its overall hardness. A laser-cladding test of the Ni-based powder was carried out on the AISI 1045 steel surface under the coaxial powder-feeding mode. Moreover, the influences of the electromagnetic field on the microstructure of the laser-cladding layer were compared, and the causes of the changes were disclosed.     

Effects of Internet-Based Nutrition and Exercise Interventions on the Prevention and Treatment of Sarcopenia in the Elderly

Effective nutrition and exercise interventions may improve sarcopenia in the elderly. The purpose of our study was to investigate the effectiveness of Internet-based nutrition and exercise interventions in the elderly with sarcopenia. Participants were divided into 4 groups: control, nutrition, exercise, and comprehensive (nutrition plus exercise) groups; there was at least 50 participants in each group. Our trial lasted 12 weeks. We conducted dietary and exercise interventions through an app and collected feedback from the participants every three weeks. Information on the diet, skeletal muscle mass, and muscle function was collected before and after the interventions. The comprehensive group had higher high-quality protein intake than the control (p = 0.017) and exercise (p = 0.012) groups. After the interventions, we obtained differences in skeletal muscle mass, skeletal muscle mass/height², skeletal muscle mass/weight, muscle mass/BMI, and skeletal muscle mass/body fat percentage (p < 0.05). Changes in average daily energy and total daily protein intakes were not significantly different; however, there was an overall improvement in the intervention groups relative to baseline data. There were no changes in the average daily time of moderate physical activity. The Internet was an effective tool of nutrition intervention in the elderly with sarcopenia. The Internet-based nutrition intervention improved high-quality protein intake and skeletal muscle mass in the elderly with sarcopenia.     

常见革兰阳性细菌鉴定与耐药检测基因芯片的临床应用

目的利用基因芯片技术进行常见革兰阳性细菌的细菌鉴定和耐药性检测。方法用生理生化鉴定和药敏纸片法确定445份革兰阳性细菌菌株的细菌种类和耐药性,盲法进行革兰阳性细菌鉴定与耐药检测基因芯片的检测,用SPSS 10.0 for Windows软件统计分析。结果与临床常规方法相比,耐药检测基因芯片鉴定指标的灵敏度均>96%,特异度均>98%;耐药检测指标的灵敏度均>94%,特异度均>90%。χ2检验结果P值均>0.05,基因芯片检测结果与临床常用方法检测结果差异无统计学意义。Kappa值均>0.75,2种方法一致性较好。结论基因芯片技术对细菌鉴定和耐药检测有一定的临床应用价值。     

手术切除巨大脑动静脉畸形及其正常灌注压突破的防治

手术切除巨大脑动静脉畸形(arteriovenous malformations,AVMs)术中或术后可能发生一种严重的并发症,表现为脑内出血、脑肿胀。1978年Spetzler医师将其命名为正常灌注压突破(normal perfusion pressure breakthrough,NPPB)。文献报道NPPB发生率为1%~10%,手术治疗巨大AVMs的术后并发症令人不满,致残率和病死率高达50%。本研究采用手术中栓塞加切除联合治疗巨大脑AVMs,研究手术前、后局部脑皮质血流的变化,栓塞后逐步阻断动脉与静脉的短路,有助于将AVMs与正常脑组织分离,预防手术中和手术后再出血以及NPPB的发生。因此,手术中栓塞加切除联合治疗巨大脑AVMs是降低手术后并发症的有效措施。     

深圳市高血压患者血压控制情况与周围绿地特征的关联分析

目的:探讨高血压患者血压控制情况与周围绿地特征的关系。方法:深圳市基本公共卫生服务管理满一年的≥35岁高血压患者为研究对象。采用分层多阶段随机抽样方法抽取代表性样本1 158人,回收有效问卷1 116份,应答率为96.4%。于2019年11月至2020年1月对纳入分析的1 116人进行问卷调查、体格测量、实验室检测。采...     

局部晚期不可手术食管癌同步放化疗联合尼妥珠单抗的初步临床分析

目的:探讨局部晚期食管癌同步放化疗联合尼妥珠单抗治疗的不良反应及疗效。方法:回顾性分析北京大学肿瘤医院2015—2020年间使用同步放化疗联合尼妥珠单抗治疗的30例患者资料,采用 Kaplan- Meier法生存分析。 结果:中位随访时间22.5个月,总客观有效率为93%。1、2、3年...     

高龄患者白内障超声乳化吸除联合人工晶状体植入术

目的:探讨高龄患者白内障超声乳化吸除联合人工晶状体植入手术的可行性和安全性。方法:对105例(142眼)高龄患者进行白内障超声乳化吸除联合人工晶状体植入术,以88例(142眼)低龄老年性白内障患者作对照组。结果:两组术后视力提高差异无显著性(P>0.05),手术并发症有明显差异(P<0.01),两组均无因全身疾病而中断手术者。结论:对高龄患者施行白内障超声乳化吸除联合人工晶状体植入术是相对安全的,只要有复明的希望,就应尽早手术治疗。