Fluid Flow through Filtering Appendages of Insects

Many organisms use structures composed of arrays of cylindersto capture particulate food or molecules form the water or airaround them. The performance of such filters depends on thevelocity of fluid movement through them; hence, mathematicalmodels of flow through fibrous structures can provide insightsabout the functional morphology of biological filters. In thispaper, the authors address the case of feather-like biologicalfilters of finite width and assess several possible models forfluid motion through them by comparing model predictions withobservational data. Two examples of insect appendages are considered:the cephalic fans of black fly aquatic larvae that capture particulatefood and the antennae of adult male moths that catch sex-attractantmolecules released by female moths. The results suggest thatflow through such structures can be much slower than ambientcurrents, that the finest hairs in the structure are the morphologicalfeatures with the greatest effect on leakiness, and that thevelocity of movement (or of ambient flow), as well as the morphologyof such filters, can be critical in determining their performance.     

高千伏摄影附加滤过与皮肤入射剂量相对关系的实验研究

目的：通过测量不同滤过条件下，体模入射剂量随滤过条件的变化确定高千伏X线摄影时的最佳附加滤过。材料与方法：利用X线剂量仪测量不同Al滤过时对应体模表面剂量的变化。结果与结论：通过适当增加附加滤过可以合理降低被检者皮肤剂量，120kV摄影时，附加滤过2.5mmAl是恰当的。     

磷酸盐型低密度脂蛋白亲和吸附剂制备与体外吸附试验研究

研究目的是制备低密度脂蛋白亲和吸附剂,用于去除高脂血症患者血液中高含量的低密度脂蛋白。首先以悬浮分散法制备壳聚糖微球和纤维素微球载体,然后固定磷酸吡哆醛和磷酸盐配基,制备出三种吸附剂,并进行体外静态吸附性能测试。结果表明,壳聚糖-磷酸吡哆醛吸附剂对LDL最大吸附量为1.30mg/mL,磷酸盐型壳聚糖和纤维素吸附剂对LDL的最大吸附量分别为2.72mg/mL和3.12mg/mL,并且吸附量随配基含量的增加呈增大趋势,3种吸附剂对高密度脂蛋白均无明显吸附。对吸附剂的灭菌和储存稳定性的研究表明,磷酸盐型纤维素吸附剂具有较好的稳定性。本研究第一次报道磷酸盐型低密度脂蛋白吸附剂。     

凋亡抑制蛋白XIAP和促凋亡因子Smac在胰腺癌化疗抵抗中的作用

目的探讨x-相关凋亡抑制蛋白（XIAP）和促凋亡因子Smac在胰腺癌细胞化疗抵抗中的作用，以及转染胞浆表达型Smac基因靶向下凋XIAP对化疗药物诱导的胰腺癌细胞凋亡的影响。方法应用流式细胞术检测顺铂、5-FU介导的Panc-1、BXPC-3的凋亡率及胞浆染色分析细胞XIAP表达变化，Western blot分析XIAP、Smac、Caspase-3表达水平；构建pEGFP-NI／Smac真核表达载体并转染胰腺癌Panc-1细胞，流式细胞术检测转染Smac基因前后Panc-1细胞的凋亡敏感性。结果与BXPC-3细胞相比，Panc-1对顺铂或5-FU介导的凋亡具有较强抵抗性，Western blot分析显示Panc-1细胞高表达XIAP，在化疗药物作用下化疗敏感细胞BXPC-3胞浆内XIAP水平下降明显多于Panc-1细胞，而且凋亡的BXPC-3细胞释放入胞浆内的成熟Smac蛋白水平明显高于Panc-1细胞。转染胞浆表达型Smac基因至化疗抵抗Panc-1细胞，可明显下调其XIAP表达水平，促进效应Caspase-3分子活化，显著提高顺铂、5-FU诱导的细胞凋亡率。结论胰腺癌细胞XIAP的表达水平下调与其化疗敏感性有关，XIAP是克服化疗抵抗的重要靶分子，而上调Smac活性蛋白的胞浆表达作为一种有效调节信号，通过拮抗XIAP的凋亡抑制作用协同化疗药物促进胰腺癌细胞凋亡。     

Lp(a) lipoprotein is a major risk factor for cardiovascular disease: pathogenic mechanisms and clinical significance

The results of two previous and two recent studies of middle-aged males and females are presented to exemplify the clinical importance of lipoprotein (a) (Lp(a)) as a risk factor for atherosclerosis and coronary heart disease. In these studies various conventional and recently suggested risk factors were included and different methods for Lp(a) quantification were used. Lp(a) was a significant risk factor in all four studies. In the recent prospective case-control study, Lp(a) and cholesterol were found to act synergistically and predict primary acute myocardial infarction in Swedish males. A cholesterol level above 6.5 mmol/1 increased the risk of acute myocardial infarction if the Lp(a) level was above 200 mg/1. The plasma apo A-I level was a protective factor. In the other recent case-control study, an Lp(a) level above 500 mg/1 was a highly significant risk factor in Black and White US women with myocardial infarction or advanced coronary artery disease in addition to low density lipoprotein cholesterol levels above 130 mg/dl. A high apo A-I level was a protective factor. In these studies no other factors tested reached significance in multivariate logistic regression analysis. A hypothetical association between high Lp(a) levels and intracellular infection with Chlamydia pneumoniae is discussed. The results suggest that the Lp(a) level is useful in identifying high-risk individuals. Lowering low density lipoprotein cholesterol below 100 mg/dl (7lt;2.6 mmol/1) seems to be most important in both males and females with high-risk Lp(a) levels.     

线扫描直接数字化X线摄影原理与应用

目的 探讨线扫描直接数字化X线摄影的工作原理与实用价值。方法 以多丝正比室线扫描X线摄影系统为基础，分析线扫描直接数字化X线摄影的适用性。结果 线扫描成像技术克服了散射线造成的干扰，且探测灵敏度和精密度分辨率高。结论 线扫描成像技术适合于除了动态摄影以外的各种数字X线摄影，对我国常规X线摄影逐步实现数字化开辟了美好的前景。     

Reactive Compatibilization of PA6/LDPE Blends with Glycidyl Methacrylate Functionalized Polyolefins

Summary: Blends of polyamide‐6 (PA6) and low density polyethylene (LDPE) were compatibilized by melt mixing with various polyolefins functionalized with glycidyl methacrylate (GMA), i.e., GMA grafted LDPE (LDPE‐g‐GMA), GMA grafted styrene‐ethylene/butylene‐styrene block copolymer (SEBS‐g‐GMA) and ethylene‐co‐glycidyl methacrylate copolymer (E‐GMA). Blends with PA6/LDPE composition ratios of 25/75 and 75/25 wt.‐%/wt.‐% were prepared in a Brabender internal mixer and their properties were evaluated by SEM, rheological measurements and DSC. Morphological investigation by SEM showed a neat improvement of phase dispersion and interfacial adhesion in all compatibilized blends when compared to PA6/LDPE binary blends. The variation of the dispersed phase size was analyzed as a function of blend composition, compatibilizer concentration and GMA content. The emulsification curves of compatibilized blends showed that the equilibrium size of dispersed particles at the saturation concentration of copolymer was lower when PA6 was the major component. The finest dispersion of the LDPE phase (<0.25 μm) was observed in the presence of SEBS‐g‐GMA copolymer. LDPE‐g‐GMA and E‐GMA displayed a similar compatibilizing efficiency. In all cases, the blends with a polyamide matrix presented a marked rise in torque and melt viscosity with increasing compatibilizer content. These effects were accounted for by a reaction between the epoxide groups of LDPE‐g‐GMA and the carboxyl/amine end‐groups of PA6, leading to the formation of an interchain graft copolymer. The phase transition processes of PA6 in the blends were influenced by the compatibilizer content and the interfacial interactions between the polymer components, suggesting a different role for the compatibilizer at the PA6/LDPE interface.

SEM micrograph of PA6/LDPE 25/75 blend compatibilized with 2.5 phr SEBS‐g‐GMA.     

Predominance of a 6 bp deletion in exon 2 of the LDL receptor gene in Africans with familial hypercholesterolaemia

In South Africa, the high prevalence of familial hypercholesterolaemia (FH) among Afrikaners, Jews, and Indians as a result of founder genes is in striking contrast to its reported virtual absence in the black population in general. In this study, the molecular basis of primary hypercholesterolaemia was studied in 16 Africans diagnosed with FH. DNA analysis using three screening methods resulted in the identification of seven different mutations in the coding region of the low density lipoprotein (LDLR) gene in 10 of the patients analysed. These included a 6 bp deletion (GCGATG) accounting for 28% of defective alleles, and six point mutations (D151H, R232W, R385Q, E387K, P678L, and R793Q) detected in single families. The Sotho patient with missense mutation R232W was also heterozygous for a de novo splicing defect 313+1G→A. Several silent mutations/polymorphisms were detected in the LDLR and apolipoprotein B genes, including a base change (g→t) at nucleotide position −175 in the FP2 LDLR regulatory element. This promoter variant was detected at a significantly higher (p<0.05) frequency in FH patients compared to controls and occurred in cis with mutation E387K in one family. Analysis of four intragenic LDLR gene polymorphisms showed that the same chromosomal background was identified at this locus in the four FH patients with the 6 bp deletion. Detection of the 6 bp deletion in Xhosa, Pedi, and Tswana FH patients suggests that it is an ancient mutation predating tribal separation approximately 3000 years ago.


Keywords: apolipoprotein B; hypercholesterolaemia; low density lipoprotein receptor; mutation     

人和大鼠腰椎关节突关节的SP能神经纤维的分布

目的：证实支配腰椎关节突关节的神经支配和化学性质，方法：用逆行荧光素标记结合免疫组化法，研究７只大鼠腰部脊神经节细胞的周围突分支投射到腰椎关节突关节及其递质性质以及３例人腰椎关节突关节囊上神经末梢的化学性质，结果：发现大鼠一侧Ｌ５和Ｌ６之间的关节突关节受同侧Ｌ２－５节段的脊神经节的部分细胞周围突分支支配，其中有３３．３９９％的中型和小型细胞为中ＳＰ能免疫反应阳性，人的关节突关节囊含有ＳＰ阳性的神经