卡伍尔链霉菌TJ430的分离鉴定及抗菌活性研究

目的 从土壤中分离、筛选稀有放线菌,对其产生的抗生素进行评价,以期发现新型农用抗生素.方法 采用高温烘烤法对土壤中稀有放线菌进行富集,采用改良的HV培养基进行分离.对分离获得的编号为TJ430的菌株采用形态学观察法、细胞化学组分分析法、生理生化及酶学特性分析、16S rDNA序列分析和DNA杂交法进行鉴定.菌株TJ430产生的抗生素水溶液在温室内进行生物防效试验.结果 共计分离获得570株稀有放线菌,其中TJ430表现出优良的广谱抗真菌活性.鉴定表明T J430是一株卡伍尔链霉菌.生物防效试验结果表明,TJ430产生的抗生素水溶液对番茄晚疫病、番茄细菌性斑点病、黄瓜菌核病及黄瓜炭疽病的防效分别为100％、79.36％,98.11％和75.79％.结论 菌株TJ430产生的抗生素具有宽泛的抗菌谱和良好的抗菌活性,具备较好的开发应用前景.     

Risk of hepatocellular carcinoma after hepatitis C virus cure

Hepatitis C virus(HCV)is a significant cause of hepatocellular carcinoma(HCC).The direct-acting antivirals marked a new era of HCV therapy and are associated with greater than 95%cure rate.Successful treatment of chronic hepatitis C greatly reduces the risk of HCC.A proportion of patients,especially those with pre-existing cirrhosis,remain at risk for HCC despite sustained virologic response(SVR).Diabetes mellitus,hepatic steatosis,alcohol consumption and lack of fibrosis regression are associated with risks of HCC after HCV cure.Noninvasive modalities such as aspartate aminotransferase to platelet ratio index and fibrosis-4 index and transient elastography have been used to monitor hepatic fibrosis.More recently,various fibrosis scores have been combined with clinical parameters and other novel biomarkers to predict risks of HCC for patients who achieved SVR.These models still need to be validated and standardized prior to applying to routine clinical care.     

Hemochromatosis: pathophysiology,evaluation, and management of hepatic iron overload with a focus on MRI

Introduction: Hereditary hemochromatosis (HH) is an autosomal recessive disorder that occurs in approximately 1 in 200–250 individuals. Mutations in the HFE gene lead to excess iron absorption. Excess iron in the form of non-transferrin-bound iron (NTBI) causes injury and is readily uptaken by cardiomyocytes, pancreatic islet cells, and hepatocytes. Symptoms greatly vary among patients and include fatigue, abdominal pain, arthralgias, impotence, decreased libido, diabetes, and heart failure. Untreated hemochromatosis can lead to chronic liver disease, fibrosis, cirrhosis, and hepatocellular carcinoma (HCC). Many invasive and noninvasive diagnostic tests are available to aid in diagnosis and treatment. MRI has emerged as the reference standard imaging modality for the detection and quantification of hepatic iron deposition, as ultrasound (US) is unable to detect iron overload and computed tomography (CT) findings are nonspecific and influenced by multiple confounding variables. If caught and treated early, HH disease progression can significantly be altered.

Area covered: The data on Hemochromatosis, iron overload, and MRI were gathered by searching PubMed.

Expert commentary: MRI is a great tool for diagnosis and management of iron overload. It is safe, effective, and a standard protocol should be included in diagnostic algorithms of future treatment guidelines.     

Carcinogenicity of diethylnitrosamine in newborn,infant, and adult mice

Summary Modifying effects of age, sex, and mouse strain on diethylnitrosamine (DEN) carcinogenesis have been investigated in C57BL/6Jx C3HeB/FeJ F₁ (B6C3F₁) and C3HeB/FeJxA/J F₁ (C3AF₁) hybrid mice. Animals each received four IP injections of 1.5 or 3.0 g DEN/g body weight. The first injections were administered on days 1, 15, or 42 of life. Subsequent treatments were delivered at 3-, 6-, and 6-day intervals, respectively. Mice were kept under observation for the remaining life-span. DEN treatment induced tumors in liver, lungs, and forestomach in descending order of frequency. The majority of the induced liver tumors were hepatocellular carcinomas. Animals treated as newborns and infants developed significantly more liver tumors than animals that were treated as young adults. Newborn and infant females developed liver tumors at a later age (B6C3F₁) and with a lower incidence (C3AF₁) than similarly treated males. The B6C3F₁ mice developed more hepatocellular carcinomas and a higher rate of pulmonary metastases than the C3AF₁ mice. In contrast, C3AF₁ mice developed lung tumors with a higher incidence and multiplicity than B6C3F₁ hybrids. Forestomach tumors were observed also with a slightly but significantly higher incidence in C3AF₁ mice.Dedicated to Professor Hermann Druckrey on the occasion of his 80th birthdayThese investigations have been supported in part by Contracts NIH-NCI-69-2087 and NO1-CO-43317 from the National Cancer Institute     

SWE联合灰阶超声评估不同分度子宫脱垂初产妇会阴体变化

目的利用实时剪切波弹性成像技术(SWE)联合灰阶超声探讨产后不同分度子宫脱垂初产妇会阴体弹性和形态的变化。方法选取2019年1月~2019年12月200例产后6~8周,患有子宫脱垂且经阴道单胎足月顺产的初产妇为观察对象。通过经阴道超声检查,结合POP分度标准,将患有Ⅰ度子宫脱垂的65例初产妇纳入B组,Ⅳ度子宫脱垂的46例初产妇纳入C组。收集同期健康已婚未育女性50例作为对照,纳入A组。分别在静息及缩肛状态下,测量三组观察对象会阴体的高度及深度,采集各组会阴体的杨氏模量值。结果三组观察对象的会阴体收缩幅度差值(高度、深度)在缩肛、静息两种状态下,差异有统计学意义(P均<0.05);静息及缩肛两种状态下健康对照组会阴体的平均杨氏模量值较Ⅰ度子宫脱垂组、Ⅳ度子宫脱垂组高,且Ⅰ度子宫脱垂组高于Ⅳ度子宫脱垂组,各组间差异均有统计学意义(P<0.05)。结论产后子宫脱垂初产妇会阴体弹性明显降低,收缩功能减弱,且会阴体收缩功能减低程度与子宫脱垂程度有关。     

Strain response of an instrumented intramedullary nail to three-point bending

Objectives:?An experimental biomechanical evaluation of an instrumented intramedullary nail (TriGen® META Nail, Smith&Nephew®) was undertaken. The objectives were two-fold. The first was to identify the most sensitive strain gauge positions and orientations on the nail, and the second was to demonstrate that the nail was capable of detecting changes in stiffness of the nail–bone composite. The function of the instrumented nail is to quantify fracture healing objectively and directly, and so to predict delayed repair or non-union 2 months before current methods.

Methods:?Eight flat pockets were machined onto the surface of the nail and three strain gauges attached in each pocket. The instrumented nail was inserted into fourth generation biomechanical grade Sawbones® tibiae with three different fracture configurations as well as into a non-fractured bone. The nail–bone composite was loaded in three-point bending at five positions to determine the strain changes in each of the eight strain gauge pockets located along the length of the nail. To simulate callus in the simplest way and to increase the stiffness of the nail–bone composite, loops of duct tape in multiples of four were applied over the fracture locus. A three-point loading jig was used to obtain the change in strain with increasing stiffness. Relative displacement of the bone ends was quantified using radiostereometric analysis.

Results:?There was no single position of greatest strain sensitivity for all fracture types. The greatest change in strain occurred when the strain gauge pocket and fracture line were closest. Applying the loading moment directly over the strain gauge pocket also maximised its sensitivity. The duct tape callus simulation showed that the instrumented nail was able to detect a change in stiffness of less than 4.1 Nm/°.

Conclusions:?It has been shown that the instrumented nail can detect physiologically relevant changes in stiffness, and so to provide a useful function as an objective monitor of fracture repair.     

Structural integrity of extracted teeth restored using three different post-and-core systems: An in vitro comparative study

AimThe objective of the study was to assess the in vitro fracture resistance of endodontically treated teeth restored using different post-and-core materials.Materials and methodsExtracted human mandibular premolars (n = 36) were extracted teeth and equally distributed into four (4) treatment groups: cast metal post-and-core, milled zirconia post-and-core, pre-fabricated post with composite resin core and control group. These samples were then each subjected to the load to fracture test using a universal testing machine. Fracture resistance data were compared among groups by analysis of variance and Fisher’s exact test.ResultsThe highest mean fracture resistance value was observed in the zirconia post-and-core treatment group (1567.26 ± 317.66 N), followed by the cast metal (1355.92 ± 621.56 N) and lastly the pre-fabricated post with composite resin core (725.67 ± 251.05 N) treatment group. Differences among groups were not statistically significantly different (P = 3.77).ConclusionEndodontically treated mandibular premolars with a zirconia post-and-core system exhibited the highest robustness against structural failure based on its mean fracture resistance value. In addition, extracted teeth restored with cast post-and-core resisted a greater stress load than those restored with fiber-reinforced posts. Zirconia showed a more favorable fracture mode than the other restorations.     

Validation of multiple subject-specific finite element models of unicompartmental knee replacement

Accurate computer modelling of the fixation of unicompartmental knee replacements (UKRs) is a valuable design tool. However, models must be validated with in vitro mechanical tests to have confidence in the results. Ten fresh-frozen cadaveric knees with differing bone densities were CT-scanned to obtain geometry and bone density data, then implanted with cementless medial Oxford UKRs by an orthopaedic surgeon. Five strain gauge rosettes were attached to the tibia and femur of each knee and the bone constructs were mechanically tested. They were re-tested following implanting the cemented versions of the implants.Finite element models of four UKR tibiae and femora were developed. Sensitivity assessments and convergence studies were conducted to optimise modelling parameters. The cemented UKR pooled R² values for predicted versus measured bone strains were 0.85 and 0.92 for the tibia and femur respectively. The cementless UKR pooled R² values were slightly lower at 0.62 and 0.73 which may have been due to the irregularity of bone resections. The correlation of the results was attributed partly to the improved material property prediction method used in this project. This study is the first to validate multiple UKR tibiae and femora for bone strain across a range of specimen bone densities.