Increased fluidity of Plasmodium berghei-infected mouse red blood cell membranes detected by electron spin resonance spectroscopy

The fluidity of Plasmodium berghei-infected mouse red cell membranes is increased over that of uninfected cells at both 24°C and 37°C. This was demonstrated by electron spin resonance spectroscopy using the hydrocarbon spin labels 2-dodecyl-2′,5,5′-trimethyloxazolidine-N-oxyl and 2-heptyl-2′ -hexyl-5,5′-dimethyloxazolidine-N-oxyl to label regions of the bilayer near its surface, and deeper within the hydrocarbon region, respectively. Arrhenius plots of the ‘empirical motion parameter’ (R_i) obtained from 2-heptyl-2′-hexyl-5,5′-dimethyloxazolidine-N-oxyl-labeled cells versus temperature over the range from 0 to 45°C showed an hysteretic behavior of the spin labels in the membranes of both mature and immature uninfected cells. Such hysteretic behavior was consistently lacking in membranes of infected cells. These differences in membrane fluidity and spin label behavior are interpreted to reflect biochemical modifications of the red cell membrane which occur with infection by the malarial parasite.     

Optimum support properties for protein separations by high-performance size exclusion chromatography

Optimum chromatographic properties of high performance size exclusion chromatography (HPSEC) of proteins, such as resolution, molecular weight accuracy and recovery, are obtained on packings and columns with tailor-made physical and chemical structures, employed at properly adjusted eluent compositions and operation conditions. SEC-theory suggests that a broad molecular weight fractionation range and high linearity of the log-linear calibration plot can be achieved by the use of two packings (10- and 80-nm pore size, characterized by a pore-size distribution (psd) equal to or less than 1 decade and by equal internal column porosity (p)), rather than a single 30- to 50-nm pore-size packing with a wide psd. Favourably high-phase ratios of (p)/(o)/ 1.0 for HPSEC columns were accomplished with a minimum interstitial column porosity (o) and a high value for the internal column porosity (p) (the specific pore volume, nu(p), multiplied by the packing density, varrho(p).) Ligands such as diol, N-acetoxyamino and oligomeric ether with a propyl- or propoxy-spacer bonded to the silica at the highest density appear to provide high mass recovery and bioactivity as well as chemical stability. Such packings, available in 3-5 mum particle size ranges of narrow distribution, packed into columns 6 mm i.d. and 500 mm in length, offer the best compromise with respect to resolution, speed and pressure drop. More careful studies are required to explain the effects of protein conformational changes and interconversions during elution on HPSEC columns.     

模拟复用的医用外科口罩清洗和消毒后主要性能指标变化

目的 医用外科口罩模拟复用清洗和消毒后主要性能指标变化。方法 以颗粒过滤效率（PFE）、细菌过滤效率（BFE）作为医用外科口罩的关键性能指标,对不同佩戴时间、不同干燥方式、不同洗消方式等试验条件进行验证。结果 试验后的医用外科口罩关键性能指标能够符合标准要求。结论 医用外科口罩采用清水洗涤、56℃热水浸泡和100℃沸水浸泡处理后主要性能指标未见明显下降。     

广州市大气PM2.5中多环芳烃的现状及分布情况

目的 了解广州市大气PM_2.5中多环芳烃在不同时间、不同地区内的分布特征。 方法 于2018年在广州市越秀区(市区),从化区(农村)和番禺区(市郊)采集PM_2.5有效样品252份,用高效液相色谱法测定样品中16种多环芳烃的浓度,以分析不同地区、不同时间及季节间的分布特征和变化趋势。结果 广州市大气PM_2.5中16种多环芳烃均有检出,但质量浓度处于较低水平,年均值为(4.907±3.642)ng/m³。PM_2.5及多环芳烃的质量浓度呈现明显的季节性波动,表现为冬春季较高,夏秋季较低,不同季节差异有统计学意义(F=3.624～72.439,均P<0.05)。市区为(54.321±35.106)μg/m³,农村地区为(46.298±25.933)μg/m³,市郊PM_2.5的质量浓度为(51.821±30.033)μg/m³,差异无统计学意义(F=1.513,P>0.05),多环芳烃中萘、苯并[a]芘、二苯并[a,h]蒽、茚并[1,2,3-cd]芘的污染水平在不同地区之间差异有统计学意义(F=4.428～6.422,P<0.05),农村高于市区和市郊。结论 广州市大气PM_2.5中多环芳烃污染水平较低,呈现明显的季节性波动和城乡差别。     

A surveillance study of patterns of reirradiation practice using external beam radiotherapy in Japan

The aim of this study was to survey the present status and patterns of reirradiation (Re-RT) practice using external beam radiotherapy in Japan. We distributed an e-mail questionnaire to the Japanese Society for Radiation Oncology partner institutions, which consisted of part 1 (number of Re-RT cases in 2008–2012 and 2013–2018) and part 2 (indications and treatment planning for Re-RT and eight case scenarios). Of the 85 institutions that replied to part 1, 75 (88%) performed Re-RTs. However, 59 of these 75 institutions (79%) reported difficulty in obtaining Re-RT case information from their databases. The responses from 37 institutions included the number of Re-RT cases, which totaled 508 in the period from 2009 to 2013 (institution median 3; 0–235), and an increase to 762 cases in the period from 2014 to 2018 (12.5; 0–295). A total of 47 physicians responded to part 2 of the survey. Important indications for Re-RT that were considered were age, performance status, life expectancy, absence of distant metastases and time interval since previous radiotherapy. In addition to clinical decision-making factors, previous total radiation dose, volume of irradiated tissue and the biologically equivalent dose were considered during Re-RT planning. From the eight site-specific scenarios presented to the respondents, >60% of radiation oncologists agreed to perform Re-RT. Re-RT cases have increased in number, and interest in Re-RT among radiation oncologists has increased recently due to advances in technology. However, several problems exist that emphasize the need for consensus building and the establishment of guidelines for practice and prospective evaluation.     

医用外科口罩和防护口罩生物气溶胶过滤效率的评价

目的:对医用外科口罩和防护口罩的颗粒过滤效率(particle filtration efficiency,PFE)、细菌过滤效率(bacte-rial filtration efficiency,BFE)及病毒过滤效率(viral filtration efficiency,VFE)进行评价。方法:参照YY 0469-2011《医用外科口罩》对不同品牌医用外科口罩在不同生物气溶胶平均颗粒直径(mean particle size,MPS)、不同流量条件下进行PFE、BFE和VFE测试,并分析医用外科口罩PFE和BFE的相关性、BFE和VFE的差异以及实际佩戴+热水浸泡处理后PFE和BFE的变化。参照GB 19083-2010《医用防护口罩技术要求》和YY/T 1497-2016《医用防护口罩材料病毒过滤效率评价测试方法 Phi-X174噬菌体测试方法》对3种防护口罩进行PFE和VFE检测。采用SAS 8.2软件进行统计学分析。结果:医用外科口罩对MPS约为3 μm的气溶胶的BFE高于MPS约为2 μm的BFE;流量越高,PFE越低;对PFE较低的医用外科口罩,BFE与PFE呈现一定相关性(MPS约为2 μm 时R2=0.671 8,MPS约为3 μm 时R2=0.776 5);医用外科口罩的VFE略低于BFE;3种防护口罩的VFE>99.98%;医用外科口罩佩戴8 h后经65 ℃热水浸泡处理30 min,细菌和真菌总数降低至0~60 cfu/g;新医用外科口罩经3次热水浸泡处理后,其PFE基本未发生变化,但佩戴过的口罩经过热水浸泡处理后,PFE和BFE均出现不同程度的降低。结论:该研究可为医用外科口罩和防护口罩的科学使用和相应标准的修订提供数据支撑。     

复合纳米人工骨的注射、凝固及其机械性能研究

目的 构建半水硫酸钙和纳米羟基磷灰石为主的复合人工骨材料并对其注射性能、凝固性能和机械强度的影响因素进行考察.方法 测试不同液固比条件下复合材料的注射特性,25℃和37℃时分别测试不同液固比、不同二水硫酸钙促凝剂条件下的材料初、终凝时间和压缩强度,均与纯硫酸钙作对比.结果 液固比0.50以上时注射性能满意.无论何种液/固比,复合材料的凝固时间均较硫酸钙延长,37℃下的凝固时间较25℃下延长.一定范围内促凝剂用量过大或过小均使凝固时间延长.液固比越大或促凝剂用量越高,材料压缩强度越低.纳米磷灰石含量增大则材料强度降低.结论 合理掌握纳米磷灰石的比例,液固比和促凝剂的用量,是开发可注射纳米人工骨的关键.     

The C-terminal domain of the pVP2 precursor is essential for the interaction between VP2 and VP3, the capsid polypeptides of infectious bursal disease virus

The interaction between the infectious bursal disease virus (IBDV) capsid proteins VP2 and VP3 has been analyzed in vivo using baculovirus expression vectors. Data presented here demonstrate that the 71-amino acid C-terminal-specific domain of pVP2, the VP2 precursor, is essential for the establishment of the VP2-VP3 interaction. Additionally, we show that coexpression of the pVP2 and VP3 polypeptides from independent genes results in the assembly of virus-like particles (VLPs). This observation demonstrates that these two polypeptides contain the minimal information required for capsid assembly, and that this process does not require the presence of the precursor polyprotein.     

Characterization of Oil-in-Water Emulsions Prepared from Solid-State Emulsions: Effect of Matrix and Oil Phase

Emulsions (o/w) were prepared from solid-state emulsions comprised of various matrix materials and oils and the resultant particle size properties determined. Results suggest that for those matrices that can form solid-state emulsions, the droplet size decreased as a function of time, as previously observed. The final droplet size was dependent on the oil utilized but was independent of the matrix material. The use of mineral oil resulted in the smallest droplet diameter (1.5 µm) while isopropyl myristate resulted in the largest droplet diameter (3 µm). With the exception of mineral oil, the oil/water interfacial tension was found to be directly proportional to the droplet diameter. The rate of emulsification appeared to be bi-phasic. The initial emulsification phase appeared to be independent of the matrix material while the terminal phase was a function of the matrix material. Most importantly, it was found that solid state emulsions could be prepared from a diverse, yet specific, list of matrices.