Finite element simulation of early creep and wear in total hip arthroplasty

Polyethylene wear particulate has been implicated in osteolytic lesion development and may lead to implant loosening and revision surgery. Wear in total hip arthroplasty is frequently estimated from patient radiographs by measurement of penetration of the femoral head into the polyethylene liner. Penetration, however, is multi-factorial, and includes components of wear and deformation due to creep. From a clinical perspective, it is of great interest to separate these elements to better evaluate true wear rates in vivo. Thus, the aim of this study was to determine polyethylene creep and wear penetration and volumetric wear during simulated gait loading conditions for variables of head size, liner thickness, and head–liner clearance. A finite element model of hip replacement articulation was developed, and creep and wear simulation was performed to 1 million gait cycles. Creep of the liner occurred quickly and increased the predicted contact areas by up to 56%, subsequently reducing contact pressures by up to 41%. Greater creep penetration was found with smaller heads, thicker liners, and larger clearance. The least volumetric wear but the most linear penetration was found with the smallest head size. Although polyethylene thickness increases from 4 to 16 mm produced only slight increases in volumetric wear and modest effects on total penetration, the fraction of creep in total penetration varied with thickness from 10% to over 50%. With thicker liners and smaller heads, creep will comprise a significant fraction of early penetration. These results will aid an understanding of the complex interaction of creep and wear.     

The behaviour of roots encountering cracks in soil

Summary Experimental methods are described for observing the behaviour of roots encountering cracks in soil. The proportions of roots which enter a second soil block after crossing a crack of known width were measured. Soil strength was measured with a penetrometer.Results are presented for the proportions of seminal roots of wheat and primary lateral roots of pea which enter moulded soil of various strengths after crossing cracks. Results are also presented for the proportions of seminal roots of pea, rape and safflower which enter undisturbed soil after crossing cracks.It was found that, in all cases, the proportion of roots penetrating the second soil block decreased with increasing crack width and increasing soil strength. Also, a smaller proportion of thinner roots penetrated the second soil block than thicker roots under similar conditions. Root diameter in the cracks was influenced by both crack width and soil strength, and an empirical equation is presented to describe this effect.     

Phantom study quantifying the depth performance of a handheld magnetometer for sentinel lymph node biopsy

PurposeThe use of a magnetic nanoparticle tracer and handheld magnetometer for sentinel lymph node biopsy (SLNB) was recently introduced to overcome drawbacks associated with the use of radioisotope tracers. Unlike the gamma probe, the used magnetometers are not only sensitive to the tracer, but also the diamagnetic human body. This potentially limits the performance of the magnetometer when used clinically.MethodsA phantom, mimicking the magnetic and mechanical properties of the human axilla, was constructed. The depth performance of two current generation magnetometers was evaluated in this phantom. LN-phantoms with tracer uptake ranging from 5 to 500 μg iron were placed at clinically relevant depths of 2.5, 4 and 5.5 cm. Distance-response curves were obtained to quantify the depth performance of the probes.ResultsThe depth performance of both probes was limited. In the absence of diamagnetic material and forces on the probe (ideal conditions) a LN-phantom with high uptake (500 μg iron) could first be detected at 3.75 cm distance. In the phantom, only superficially placed LNs (2.5 cm) with high uptake (500 μg iron) could be detected from the surface. The penetration depth was insufficient to detect LNs with lower uptake, or which were located deeper.ConclusionThe detection distance of the current generation magnetometers is limited, and does not meet the demands formulated by the European Association for Nuclear Medicine for successful transcutaneous SLN localization. Future clinical trials should evaluate whether the limited depth sensitivity is of influence to the clinical outcome of the SLNB procedure.     

Negative air pressure treatment accelerates the penetration of permeable cryoprotectants into bovine ovarian tissue in vitrification protocol and improves cell density after vitrification

Effects of additional physical treatments during vitrification of the bovine ovarian tissue were examined for increasing of permeability of ethylene glycol (EG) and dimethyl sulfoxide (Me2SO). The concentrations of EG and Me2SO and histological changes in the ovarian tissue were evaluated. In the first equilibration step (7.5% EG and 7.5% Me2SO), all the 10-min physical treatments, i.e., negative (679 hPa) or positive (1347 hPa) air pressure applied with a disposable syringe, and shaking (60 rpm) applied with a laboratory shaker, were comparable to 25-min non-physical treatment (plain) vitrification. When effects of the negative air pressure were examined in the second equilibration step (20% EG and 20% Me2SO), its 10-min treatment was equivalent to 15-min plain vitrification (140–170 mg/g tissue). It was thus indicated that the negative air pressure treatment accelerates the penetration of permeable cryoprotectants into the ovarian tissue slices. Histological examination showed that the cell density and the amount of pan-cadherin in the tunica albuginea of the ovary was reduced by the vitrification, but was improved by the negative air pressure treatment. The amount of pan-cadherin in the tunica albuginea was recommended as a biomarker for evaluation of effectiveness of protocol for cryopreservation of bovine ovarian tissue and considered to be a candidate biomarker for human ovarian tissue cryopreservation.     

Morphology of antennal sensilla of the brown spruce longhorn beetle,Tetropium fuscum (Fabr.) (Coleoptera: Cerambycidae)

The antennal sensilla of the brown spruce longhorn beetle, Tetropium fuscum (Fabr.) (Coleoptera: Cerambycidae) were examined with particular focus on the sensilla present on the apical flagellomere. T. fuscum antennae are composed of 11 segments, namely the scape, pedicel, and nine flagellomeres. Nine types of sensilla were observed: three types of sensilla chaetica, sensilla trichodea, two types of sensilla basiconica, grooved peg sensilla, thick-walled sensilla, and Böhm bristles. Seven of these types were present on the apical flagellomere, the exceptions were sensilla chaetica type 3 and Böhm bristles. There were no significant differences in the distribution or density of sensilla present on the ninth flagellomere of males and females, except that males had significantly more sensilla chaetica type 1, which are put forward as the putative contact chemoreceptors for T. fuscum.     

Functional Consequences of Complementarity-determining Region Deactivation in a Multifunctional Anti-nucleic Acid Antibody

Many murine monoclonal anti-DNA antibodies (Abs) derived from mice models for systemic lupus erythematosus have additional cell-penetration and/or nucleic acid-hydrolysis properties. Here, we examined the influence of deactivating each complementarity-determining region (CDR) within a multifunctional anti-nucleic acid antibody (Ab) that possesses these activities, the catalytic 3D8 single chain variable fragment (scFv). CDR-deactivated 3D8 scFv variants were generated by replacing all of the amino acids within each CDR with Gly/Ser residues. The structure of 3D8 scFv accommodated single complete CDR deactivations. Different functional activities of 3D8 scFv were affected differently depending on which CDR was deactivated. The only exception was CDR1, located within the light chain (LCDR1); deactivation of LCDR1 abolished all of the functional activities of 3D8 scFv. A hybrid Ab, HW6/3D8L1, in which the LCDR1 from an unrelated Ab (HW6) was replaced with the LCDR1 from 3D8, acquired all activities associated with the 3D8 scFv. These results suggest that the activity of a multifunctional 3D8 scFv Ab can be modulated by single complete CDR deactivation and that the LCDR1 plays a crucial role in maintaining Ab properties. This study presents a new approach for determining the role of individual CDRs in multifunctional Abs with important implications for the future of Ab engineering.     

Morphogenesis in cucumber seedlings is negatively controlled by gravity

 Seedlings of most cucurbitaceous plants develop a peg (protuberance caused by cell outgrowth) on the transition zone between the hypocotyl and root. The peg is necessary for removing the seed coat after germination. In our spaceflight experiments on the STS-95 space shuttle, Discovery, we found that cucumber (Cucumis sativus L.) seedlings grown under microgravity conditions developed two pegs symmetrically at the transition zone. Thus, cucumber seedlings potentially develop two pegs and do not require gravity for peg formation itself, but on the ground the development of one peg is suppressed in response to gravity. This may be considered as negative control of morphogenesis by gravity. Received: 17 August 1999 / Accepted: 4 October 1999     

表皮葡萄球菌生物被膜对红霉素渗透性的研究

为探讨表皮葡萄球菌生物被膜对红霉素的渗透性,我们采用生物被膜抗生素渗透模型检测Staphylcoccus epidermidis 1457、1457-msrA和临床分离株S68生物被膜不同时间点红霉素的渗透率,并用吖啶橙染色激光共聚焦显微镜观察生物被膜内细菌RNA/DNA的相对含量;扫描电子显微镜观察膜内细菌的密度.红霉素作用36 h后,1457、1457-msrA、S68的渗透率分别为0.93,0.55和0.4;1457渗透地较快,8 h后渗透率即达到0.58,而1457msrA和$68相对较为缓慢,24 h后分别为0.499和0.31:吖啶橙染色可见红霉素作用下膜内菌RNA和DNA的相对比例减小,生长速率下降;扫描电子显微镜观察可见生物被膜红霉素作用后空气面的细菌数与琼脂面相比均较少,细胞碎片相对较多,而对照组(无抗生素作用)琼脂面和空气面的细菌密度和分布较均匀.可见红霉素可渗透入表葡茵生物被膜,但不能完全杀死膜内细菌;膜内细菌在生物被膜环境中生长速率下降,有助于降低细菌对红霉素的敏感性.     

日本血吸虫毛蚴对钉螺的钻穿及在螺体内的分布和移行

采自安徽省池的钉螺每粒感染５０只湖南株日本血吸虫毛后的组织学观察说明：毛蚴钻穿钉螺有从螺鳃部、头足总后有皮以及实质组织（外套膜、触角和阴茎）等三方面途径,其中以前二者尤为重要;毛蚴进入螺鳃丝后直接进入血液循环系统,从头足表皮进入的毛蚴,除了少数在钻穿部位附近滞留外,多数继续向头足部深层的肌肉和窦状组织间隙移行,以前头足窦、直肠和消化道外的组织间隙以及肾脏为主要的移行部位;从外套膜、触角、阴茎等部位     

表皮葡萄球菌生物被膜对红霉素渗透性的研究

为探讨表皮葡萄球菌生物被膜对红霉素的渗透性, 我们采用生物被膜抗生素渗透模型检测Staphylcoccus epidermidis 1457、1457-msrA和临床分离株S68生物被膜不同时间点红霉素的渗透率, 并用吖啶橙染色激光共聚焦显微镜观察生物被膜内细菌RNA/DNA的相对含量; 扫描电子显微镜观察膜内细菌的密度。红霉素作用36 h后, 1457、1457-msrA、S68的渗透率分别为0.93, 0.55和 0.4; 1457渗透地较快, 8 h后渗透率即达到0.58, 而1457msrA和S68相对较为缓慢, 24 h后分别为0.499和0.31; 吖啶橙染色可见红霉素作用下膜内菌RNA和DNA的相对比例减小, 生长速率下降; 扫描电子显微镜观察可见生物被膜红霉素作用后空气面的细菌数与琼脂面相比均较少, 细胞碎片相对较多, 而对照组(无抗生素作用)琼脂面和空气面的细菌密度和分布较均匀。可见红霉素可渗透入表葡菌生物被膜, 但不能完全杀死膜内细菌; 膜内细菌在生物被膜环境中生长速率下降, 有助于降低细菌对红霉素的敏感性。