The effect of gene drive on containment of transgenic mosquitoes

Mosquito-borne diseases such as malaria and dengue fever continue to be a major health problem through much of the world. Several new potential approaches to disease control utilize gene drive to spread anti-pathogen genes into the mosquito population. Prior to a release, these projects will require trials in outdoor cages from which transgenic mosquitoes may escape, albeit in small numbers. Most genes introduced in small numbers are very likely to be lost from the environment; however, gene drive mechanisms enhance the invasiveness of introduced genes. Consequently, introduced transgenes may be more likely to persist than ordinary genes following an accidental release. Here, we develop stochastic models to analyze the loss probabilities for several gene drive mechanisms, including homing endonuclease genes, transposable elements, Medea elements, the intracellular bacterium Wolbachia, engineered underdominance genes, and meiotic drive. We find that Medea and Wolbachia present the best compromise between invasiveness and containment for the six gene drive systems currently being considered for the control of mosquito-borne disease.     

刘家峡水库网箱养鱼场纤毛虫群落特征

2006年3月至2007年2月, 用活体观察法和直接计数法对刘家峡水库网箱养鱼场纤毛虫群落进行了研究.共鉴定到77种纤毛虫, 其中包括4个未定名种, 隶属于3纲11目34科43属.下毛目为优势类群, 前口目为次优势类群, 异毛目为偶见类群.善变膜袋虫、长圆膜袋虫、珍珠映毛虫、钩刺斜管虫和大口瞬目虫为春季群落优势种; 善变膜袋虫、颗粒膜袋虫和珍珠映毛虫为夏季群落优势种; 颗粒膜袋虫和善变膜袋虫为秋季群落优势种; 冬季无明显优势种.纤毛虫物种数的周年动态呈单峰型, 8、9月份物种数最多, 有52种, 3月份最少, 只有18种; 物种数的季节动态为: 夏季＞秋季＞春季＞冬季.纤毛虫丰度的周年动态呈三峰型, 高峰分别出现在4月、6月和9月份, 5月份采样前夕水库调水导致丰度骤降是造成三峰型的主要原因; 纤毛虫丰度的季节动态为: 夏季＞秋季＞春季＞冬季.纤毛虫物种多样性指数的周年动态为: 8月份最大, 3月份最小.相关性分析结果表明, 对网箱养鱼场纤毛虫物种数影响最大的因子是水温, 其次是透明度和pH值, 投放饲料量的影响最小; 对网箱养鱼场纤毛虫丰度影响最大的是投放饲料量, 其次是水温和pH值, 透明度的影响最小.     

Development of an integrated CAD–FEA system for patient-specific design of spinal cages

Spinal cages are used to create a suitable mechanical environment for interbody fusion in cases of degenerative spinal instability. Due to individual variations in bone structures and pathological conditions, patient-specific cages can provide optimal biomechanical conditions for fusion, strengthening patient recovery. Finite element analysis (FEA) is a valuable tool in the biomechanical evaluation of patient-specific cage designs, but the time- and labor-intensive process of modeling limits its clinical application. In an effort to facilitate the design and analysis of patient-specific spinal cages, an integrated CAD–FEA system (CASCaDeS, comprehensive analytical spinal cage design system) was developed. This system produces a biomechanical-based patient-specific design of spinal cages and is capable of rapid implementation of finite element modeling. By comparison with commercial software, this system was validated and proven to be both accurate and efficient. CASCaDeS can be used to design patient-specific cages with a superior biomechanical performance to commercial spinal cages.     

Dispersal in the Glanville fritillary butterfly in fragmented versus continuous landscapes: comparison between three methods

1. Habitat fragmentation may lead to natural selection on dispersal rate and other life‐history traits. Both theoretical analyses and empirical studies suggest that habitat fragmentation may select either for increased or decreased dispersal depending on the traits of the species and the characteristics of the landscape. 2. Dispersal and movement rates in Glanville fritillary butterflies (Melitaea cinxia) originating from a continuous landscape in China and from a highly fragmented landscape in Finland were compared using three different methods. 3. The methods included replicated mark‐release‐recapture (MRR) experiments conducted in the natural environments in China and Finland, tracking with harmonic radar of captive‐reared but free‐flying butterflies in a common environment in the field, and replicated common garden experiments in a large outdoor population cage. 4. The results were largely consistent, showing that butterflies from the more continuous landscape in China had a lower movement rate than butterflies originating from the fragmented landscape in Finland. Butterflies originating from newly‐established populations in Finland moved significantly longer distances than butterflies originating from old populations in Finland or from China, demonstrating significant intra‐specific variation in dispersal rate in Finland. These results are consistent with model predictions for the Glanville fritillary. 5. The tracking experiment revealed a result that would have been impossible to obtain with MRR experiments: movement rate was influenced by a significant interaction between population origin (China vs. Finland) and ambient air temperature.     

象山港网箱养殖区沉积物的古菌空间分布

对象山港网箱养殖区及其周边沉积物中古菌群落的空间分布进行研究,应用基于16S rRNA基因的T-RFLP(末端限制性片段多态性分析)技术分析象山港网箱养殖区及其周边不同深度沉积物中古菌的群落结构和多样性,并构建克隆文库进行系统发育学分析。测定沉积物各项理化因子,通过PCA和RDA分析了古菌群落分布及其与环境因子之间的关系。结果表明,泉古菌是港口沉积物中的优势古菌群,占古菌群落的50%以上。网箱养殖区沉积物的古菌群落结构较非养殖区简单,多样性降低。非养殖区古菌群落随深度呈现有规律的变化。营养盐类和pH是造成养殖区域古菌群落结构区别于非养殖区域的主要环境因素。     

Sex determination from chest plate roentgenograms

Precise sexing--97% to 99% accuracy--of adult chest plates is possible when highly predictive costal cartilage ossification patterns are combined with four simple metric determinations. More than 1100 chest plate roentgenograms were evaluated for ossification pattern, fourth rib width, corpus width, sternal length and sternal area in an adult decedent population. An elementary, empirically obtained algorithm using the patternings and measurements, along with simple derivations (sternal length and area indices) was developed and then applied in chest plate sexing. This technique is not only easy, rapid and inexpensive, but it also results in a permanent and easily stored record.     

The rib cage reduces intervertebral disc pressures in cadaveric thoracic spines by sharing loading under applied dynamic moments

The effects of the rib cage on thoracic spine loading are not well studied, but the rib cage may provide stability or share loads with the spine. Intervertebral disc pressure provides insight into spinal loading, but such measurements are lacking in the thoracic spine. Thus, our objective was to examine thoracic intradiscal pressures under applied pure moments, and to determine the effect of the rib cage on these pressures. Human cadaveric thoracic spine specimens were positioned upright in a testing machine, and Dynamic pure moments (0 to ±5 N·m) with a compressive follower load of 400 N were applied in axial rotation, flexion - extension, and lateral bending. Disc pressures were measured at T4-T5 and T8-T9 using needle-mounted pressure transducers, first with the rib cage intact, and again after the rib cage was removed. Changes in pressure vs. moment slopes with rib cage removal were examined. Pressure generally increased with applied moments, and pressure-moment slope increased with rib cage removal at T4-T5 for axial rotation, extension, and lateral bending, and at T8-T9 for axial rotation. The results suggest the intact rib cage carried about 62% and 56% of axial rotation moments about T4-T5 and T8-T9, respectively, as well as 42% of extension moment and 36–43% of lateral bending moment about T4-T5 only. The rib cage likely plays a larger role in supporting moments than compressive loads, and may also play a larger role in the upper thorax than the lower thorax.     

Mechanical performance of lumbar intervertebral body fusion devices: An analysis of data submitted to the Food and Drug Administration

Lumbar intervertebral body fusion devices (L-IBFDs) are intended to provide stability to promote fusion in patients with a variety of lumbar pathologies. Different L-IBFD designs have been developed to accommodate various surgical approaches for lumbar interbody fusion procedures including anterior, lateral, posterior, and transforaminal lumbar interbody fusions (ALIF, LLIF, PLIF, and TLIF, respectively). Due to design differences, there is a potential for mechanical performance differences between ALIF, LLIF, PLIF, and TLIF devices. To evaluate this, mechanical performance and device dimension data were collected from 124 Traditional 510(k) submissions to the FDA for L-IBFDs cleared for marketing from 2007 through 2016. From these submissions, mechanical test results were aggregated for seven commonly performed tests: static and dynamic axial compression, compression-shear, and torsion testing per ASTM F2077, and subsidence testing per ASTM F2267. The Kruskal-Wallis test and Wilcoxon signed-rank test were used to determine if device type (ALIF, LLIF, PLIF, TLIF) had a significant effect on mechanical performance parameters (static testing: stiffness and yield strength; dynamic testing: runout load; subsidence testing: stiffness [Kp]). Generally, ALIFs and LLIFs were found to be stiffer, stronger, and had higher subsidence resistance than PLIF and TLIF designs. These results are likely due to the larger footprints of the ALIF and LLIF devices. The relative mechanical performance and subsidence resistance can be considered when determining the appropriate surgical approach and implant for a given patient. Overall, the mechanical performance data presented here can be utilized for future L-IBFD development and design verification.     

Biomechanical analysis of lumbar interbody fusion cages with various lordotic angles: a finite element study

Inappropriate lordotic angle of lumbar fusion cage could be associated with cage damage or subsidence. The biomechanical influence of cage lordotic angle on lumbar spine has not been fully investigated. Four surgical finite element models were constructed by inserting cages with various lordotic angles at L3-L4 disc space. The four motion modes were simulated. The range of motion (ROM) decreased with increased lordotic angle of cage in flexion, extension, and rotation, whereas it was not substantially changed in bending. The maximum stress in cage decreased with increased lordotic angle of cage in all motion modes. The maximum stress in endplate at surgical level increased with increased lordotic angle of cage in flexion and rotation, whereas it was not substantially changed in extension and bending. The facet joint force (FJF) was much smaller than that for the intact conditions in extension, bending, and rotation, while it was not substantially changed in flexion. In conclusion, the ROM, stresses in the cage and endplate at surgical level are sensitive to the lordotic angle of cage. The increased cage lordotic angle may provide better stability and reduce the risk of cage damage, whereas it may increase the risk of subsidence in flexion and rotation.