鸡粪生物炭对土壤铜和锌形态及植物吸收的影响

300℃制备的鸡粪生物炭既可以固定碳和重金属,又可以克服鸡粪不当处理所产生的环境问题,但由于鸡粪中Cu和Zn的含量较高,因此使用时可能存在重金属污染风险。本文研究了温室大棚中土壤培养和小白菜盆栽下施用鸡粪生物炭对土壤Cu和Zn形态以及植物吸收的影响。结果表明施用鸡粪生物炭可以明显增加土壤pH,减少土壤有效态Cu含量,小白菜盆栽条件下鸡粪生物炭对有效态Cu抑制程度小于土壤培养。空白土壤中施入鸡粪生物炭后有效态锌的含量增加了6.19 mg·kg^(-1),使用鹿粪则可以减少鸡粪生物炭对土壤有效态Zn含量的影响。随着土壤培养时间的延长,施用鸡粪生物炭可降低酸溶态与可还原态Cu的比例,增加残渣态Cu比例,提高施加鸡粪生物炭处理中可氧化态与残渣态Zn比例。高温高湿环境下施用2%鸡粪生物炭能够促进小白菜的生长,增加小白菜干重,减少小白菜根部重金属Cu和Zn含量,降低Cu和Zn的根富集系数,二次盆栽后添加鸡粪生物炭还能够降低小白菜茎叶部Cu和Zn的含量。以上结果说明,鸡粪生物炭施入土壤后可引起短时间的污染风险,且Zn的污染风险大于Cu,但随着时间的延长,鸡粪生物炭既可促进小白菜的生长,减少Zn的释放,又能固定Cu和Zn,从而减少植物对Cu和Zn的吸收。

自驱动柔性生物医学传感器的研究进展

柔性传感器是生物医学领域的研究热点,受到了广泛的关注.然而,柔性传感器需要外部电池供能,续航时间短,这成为了制约其发展的瓶颈.自驱动电子器件概念的提出,为解决续航问题提供了重要思路.本文梳理了自驱动柔性生物医学传感器的最新研究进展,从原理、材料、器件和生物医学应用等角度出发,概述了不同自驱动技术在人体生理信号传感方面的技术特点与研究现状,重点介绍了部分穿戴式和植入式自驱动柔性传感器在人体的呼吸、脉搏、温度监测和人工感觉器官中的代表性研究工作.最后,本文还对自驱动柔性生物医学传感器当前的挑战和未来的发展趋势进行了展望和总结.

力学因素对间充质干细胞神经向分化的影响

背景:目前,通过对细胞施加机械力学刺激或改变细胞所处的微环境来调控干细胞的分化方向,已经成为了组织工程与再生医学领域的研究热点。目的:综述了近10年来力学因素调控间充质干细胞神经向分化领域的研究进展,为干细胞替代疗法治疗退行性疾病提供相关的理论基础。方法:检索Web of Science和Pub Med数据库中关于力学因素对间充质干细胞神经向分化影响的文献,并进行系统的归纳总结和分析,最终得到104篇相关文献。结果与结论:机械力刺激、细胞外物理环境因素对骨髓间充质干细胞、脂肪间充质干细胞、牙髓干细胞、子宫内膜干细胞等间充质干细胞的神经向分化有重要影响。不同的力学因素可能通过PI3K-AKT-m TOR、Wnt/β-catenin、Rho、MAPK等信号通路调控间充质干细胞的神经向分化,但具体的机制还有待进一步研究。

Effect of Electrical Stimulation on the Growth of Endothelial Cell

Exogenous electrical stimulation plays an important role on endothelial cells and vessels. Study on the effect of electrical stimulation on endothelial cells might be helpful to regulate cell metabolism on a certain extent, or provide new ideas for vascular tissue engineering. A bioreactor that can apply electrical stimulation was designed on the basis of parallel-plate chamber. To investigate the possible effect of electrical stimulation on human umbilical vein endothelial cells (HUVECs), the different levels and duration′s electrical stimulations were applied to HUVECs in culture. The cell morphology was observed by microscopy and the levels of endothelial nitric oxide synthase (eNOS) gene were measured by RT-PCR. Different levels and durations of electrical stimulation produce different effects on eNOS gene expression. The eNOS gene expressions of the experimental group cells under the voltage of 50 mV, 100 mV,150 mV and 200 mV were significantly lower than that of the control group after 3-hour electrical stimulation, while the eNOS gene levels of the experimental group cells in 6-hour electrical stimulation were higher than those of the control group under all tested voltages. After 12-hour stimulation, the eNOS gene levels of HUVECs decreased under 50 mV, and then gradually increased until 200 mV. The low voltage of 6-hour electrical stimulation is more appropriate for HUVECs growth.

Preparation of Chitosan/Poly(L-Lactide) Porous Composite Scaffolds

This research investigates the formation of chitosan/poly(L-lactide) (CS/PLLA) porous composite scaffold using a novel emulsion freeze-drying technique. First, an oil in-water (O/W) emulsification system was used in the presence of surfactant Tween-80, in which CS solution was used as the water phase and PLLA solution was used as the oil phase. The emulsion was observed by inverted microscope (×200). The emulsion droplet was spherical and uniform in size. FT-IR analysis revealed that there were hydrogen bonding interactions between CS and PLLA components. The microstructure and physical properties of the scaffolds were also analyzed. The SEM results showed that composite scaffolds formed well interconnected pore structure and homogenous distribution of CS and PLLA. When the content of PLLA reached 50%, the porosity of CS/PLLA composite scaffolds were between 83%-91% and density in the range of 0.047 to 0.11 g/cm3. The porosity showed a slight decrease and the density increased with the increase of PLLA dose. The compressive strength increased from 0.32 to 0.43 MPa, while the compressive modulus increased from 1.99 to 3.91 MPa as the PLLA contents increased from 10% to 50%.

Effect of Vibration on Cortical Bone in Tail-suspended Rats

Humans in Space suffer from microgravity-induced muscle atrophy and attenuated bone strength. High-frequency, low-amplitude vibration has been proposed as a treatment to prevent bone loss and the decrease in strength of bone. In this study,the effect of vibration on countering microgravity-induced bone loss was investigated.15 SD rats were divided into three groups(n=5, each): tail-suspension(TS), TS plus45 Hz(0.3 g) vibration exercise(TSV), and control(CON). Tail-suspension was to unload rat hindlimbs and a device was developed by our group, with which the rats were trained by vibration twice per day on hindlimbs during tail-suspension. After 21 d, bone mineral density(BMD) was measured by micro-CT and porosity by combining EXAKT and Olympus BX51 in tibia. The results showed that trabecular BMD was significantly decreased and cortical porosity increased in TS compared with CON, while there was no significantly difference between TSV and CON. These suggest that vibration exercise could prevent bone attenuation induced by simulated weightlessness and it is possible to be as a countermeasure of microgravity-induced osteoporosis.

Effect of Osteocytes Subjected to Fluid Flow on Osteoblasts

Osteocytes act as mechanosensors in bone, which can send mechanical signals directly to osteoblasts through gap junctions. However, under physiological conditions the number of gap junctions is limited because of the quantity variance of the two kinds of cells. In this study, the possibility of indirect interaction between these two cells was investigated. A new flow champer was designed in which osteocytes and osteoblasts were cocultured in two champers separately. Osteocytes were exposed to fluid flow and then the ALP activity, osteocalcin and osteopotin of osteoblasts were determined. The results showed that either ALP activity or production of osteocalcin and osteopotin in osteoblasts that were cocultured with sheared osteocytes increased, which indicated that osteocytes could regulate osteoblasts indirectly through some soluble factors.

Comparison of stem cell characteristics between perichondral-derived stem cells and periosteal stem cells in postnatal rats

Bone marrow mesenchymal stem cells(BMSCs),periosteal stem cells(PSCs),and other bone stem cells originate from embryonic bone formation,but their function and stem cell characteristics such as proliferation ability and differentiation ability change at different anatomical locations.Perichondral-derived stem cells(PCSCs)are more closely related to PSCs in origin and function,usually used to be studied together with PSCs as one type of stem cell.However,this leads to the ignoration of the PCSCs'characteristics.Since the anatomical locations of these two types of stem cells diverse,PCSCs should have some differences from PSCs.In this study,the PCSCs in the perichondrium surrounding the growth plate cartilage expressed CTSK and CD200 same as PSCs.However,when compared the stem cell characteristics of PCSCs with that of PSCs,PCSCs were more elongated than PSCs in morphology and have stronger self-renewal ability,as well as stronger chondrogenic and adipogenic differentiation potentials.This study revealed the stem cell characteristics of PCSCs distinguished from PSCs,which may indicate PCSCs and PSCs should not be treated as one type of cell to research in the future.

胫骨近端截骨Ilizarov技术治疗膝骨性关节炎的步态分析

[目的]利用三维步态分析探讨胫骨近端截骨Ilizarov外固定技术治疗内侧间室膝骨关节炎患者手术前后时空、运动学及动力学变化。[方法]对2016年9月~2018年12月本科采用胫骨近端低位微创截骨Ilizarov外固定技术治疗的11例内侧间室膝骨关节炎患者(21膝)进行步态分析研究,记录比较术前、术后拆除外固定架时及术后6个月3个时间点步态周期时空参数、运动学及运动力学参数。[结果]11例患者步幅和步速在术前、拆除外固定器时及术后6个月比较差异无统计学意义(P>0.05)。步态运动学检测方面,随时间推移,21膝的屈膝角度、伸膝角度均显著增加(P<0.05);内翻角度、外翻角度均显著减少(P<0.05)。踝关节活动范围显著增加(P<0.05),踝关节外翻角度显著增加(P<0.05)。运动力学测试方面,随时间推移,膝关节内收力矩、内收角冲量均显著减少(P<0.05);拆除外固定器时踝关节外翻力矩较术前增加(P<0.05),术后6个月随访时与拆除外固定器时踝关节外翻力矩比较差异无统计学意义(P>0.05);拆除外固定器时足底中心压力轨迹较术前明显向外侧偏移(P<0.05),术后6个月时与拆除外固定器时比较差异无统计学意义(P<0.05)。[结论]胫骨近端微创截骨Ilizarov外固定技术治疗内侧间室膝骨关节炎符合生物力学要求,步态分析测试可对该技术的临床疗效进行准确评估。

Effect of Accessory Retention Forms on the Bond Strength of Resin-bonded Fixed Partial Dentures:a 3D Finite Element Study

Interface debonding between prostheses and abutments was the most frequent failure mode of resin-bonded fixed partials dentures(RBFPDs) in clinic. The purpose of this study was to investigate the effect of accessory retention forms on the bond strength of RBFPDs. Three types of 3D finite element models were constructed.The model of posterior metal plate RBFPD with spoon-shaped occlusal rest seats served as the control. The remaining two types of models based on the control added the retention form design of the pin hole and axial groove respectively. The axial or buccolingual load of 150 N was applied on the prosthesis, first premolar and first molar respectively. The maximum principal stresses of the adhesive layer in different models were calculated. Under the load of the same magnitude, the stress due to the buccolingual load was significantly higher than that due to the axial load in the adhesive layer. The proximal shoulder, occlusal rest seats wall and the proximal margin adjacent to the shoulder were the high risk region where the adhesive layer damaged easily. Compared with the control model, the pin and groove models could slightly decrease the stress in the adhesive layer after the axial loading, while the stress in the adhesive layer drastically decreased after horizontal loading and reduced by 22% and 31% respectively. These results indicate that the horizontal occlusal force has a more serious harm to the debonding of RBFPDs. In addition, the accessory retention forms(e.g. pin and axial groove retention forms) can decrease the stress level in the adhesive layer, which are conducive to increase the load-bearing capacity of RBFPDs.

Influence of Meniscal Attachments Placement on Articular Stress Deterioration

Meniscal attachments provide constraint for meniscus and contribute to knee stability. However, the influence of attachments placement on articular mechanical environment remains unclear. The present study aims to characterize the stress deterioration caused by abnormal attachment locations. Different placement of medial meniscal attachments were analyzed with a three-dimensional (3D) finite element (FE) model of knee joint. The articular stress distribution under compressive loadings indicates that abnormal placement of medial meniscal attachments could cause stress deterioration in meniscus and tibia plateau, which may increase the risk of OA. The influence of PMMA relocation was more severe than that of AMMA. The anterior displacement of both AMMA and PMMA could decrease the tibial contact area and therefore weakening the meniscal function of loading transmission. The present study provides an insight into the biomechanical character of meniscal attachments and may help improving the meniscal transplantation in the future.

Irrelevance of BK_(Ca) Channel Expression to VSMCs Phenotype under Shear Stress

Large conductance Ca^(2+)-activated K^+ (BK_(Ca)) channel exhibits a phenotype-dependent expression on vascular smooth muscle cells(VSMCs), which prefers to contractile phenotype. Meanwhile, shear stress definitely influences VSMCs proliferation and contraction. Thereby, a hypothesis was raised, would shear stress change the BK_(Ca)expression and correlate with VSMC phenotype? In order to investigate it, VSMCs were exposed to shear stress in a parallel-plate flow chamber with 12 dynes/cm^2 for 12 h. Subsequently, the effect of shear stress on VSMC proliferation, BK_(Ca)channel expression and contractile phenotype marker, α-smooth muscle cell actin(α-SMA) and smooth muscle myosin heavy chain(SMMHC), was determined by immunofluorescence microscopy, flow cytometery as well as reverse transcriptionpolymerase chain reaction(RT-PCR), respectively. Data show that shear stress enhanced the expression of BK_(Ca)channel while inhibiting VSMC proliferation.Paralleled to those phenomena, the expression of both α-SMA and SM-MHC were decreased significantly. These results demonstrated that upregulation of BK_(Ca)channel was irrelevant to the maintenance VSMC of contractile phenotype under shear stress.This finding provides a new insight into understanding the correlation of BK_(Ca)channel and VSMC phenotype.

Mechanical Performance of Cranial Bone in Impact Protection of Woodpecker Brain:A Finite Element Study

Human head impact injuries caused by a sudden impact force are very common in aviation lifesaving,car crash accident,war or sports activities. Yet,an intriguing example of nature is woodpecker which is free from head injury even it drums trunk continually at a speed of about 6-7 m/s and a deceleration of about 1000 g.Woodpecker must have special characteristics to attenuate repetitive impact force to sustain rapid pecking without brain injury. In this study,the effect of mechanical property of cranial bone on the brain during impact was investigated using the finite element(FE)approach. It was demonstrated that the pressure,Von-Mises stresses and shear stress at the same point on the posterior of woodpecker's brain were decreased greatly compared with hoopoe and lark. It was stated that the higher strength of woodpecker's cranial bone might play an important role for preventing woodpecker's head injury.

The Effect of Physical Loading on Bone Broadband Ultrasound Attenuation

Objective: Physical loading changes bone microstructure and may influence quantitative ultrasound(QUS) parameters. This study aims at evaluating the effect of physical loading on bone QUS measurement. Methods: Ten fresh bovine bone specimens were studied, which were scanned by a micro-CT and the density and structure parameters were calculated. The QUS measurement was performed when specimens subjected to loading, which changed from 0 to 1,000 N with the step of 100 N. Statistical analysis was performed to evaluate the difference between n BUA measured with and without loading, and the relationship between n BUA and the parameters measured by micro-CT. Results: While the loading exerted on bone lugher than 200 N, the measured nBUA significantly higher than n BUA measured without loading. With the increasing of loading, which exerted on bone, the values of nBUA also increased. A new parameter, the slope of the linearity fitted curve of nBUA values measured under different loading conditions, was introduced to evaluate BMD. The correlation coefficient between the slope and BMD is-0.869(P=0.001). Conclusion: Physical loading substantially influences bone QUS measurement. QUS measurement performed under loading condition may be a new ultrasound method for osteoporosis diagnosis.

A New Concept of Ventricular Assist Device

In principle, the heart tube of a zebrafish embryo is an impedance pump that drives blood flow forward by compressing the tube periodically and asymmetrically.In this article, we proposed a hypothesis that the blood pumping mechanism of the zebrafish embryo heart tube can be applied to the design of pulsatile ventricular assist devices, which may overcome the shortcomings of current ventricular assist devices such as hemolysis caused by the mechanical injure of blood.

2D Shape-based Fluorescence Molecular Tomography Through Hybrid Genetic Algorithm Based Optimization

Fluorescence molecular tomography(FMT) aims at tomographicallyresolving the fluorescent targets deeply inside small animal based on transmission boundary measurements. The image reconstruction of FMT isknown to be highlyill-posed, due to the highly scatteringnatureofbiologicaltissue.Hence,priorinformationisusuallyrequired for successful reconstruction. In this paper, a novel reconstruction method incorporating shape priors is proposed for 2D FMT. The fluorescent targets were assumed of round shape, which was practically appropriate for approximating various shapes inside diffusive medium. Compared to the traditional pixel based reconstruction, the number of unknowns was greatly reduced to a few control parameters of round shapes. A hybrid genetic algorithm was proposed to recover the shape parameters. The numerical experiments showed that the proposed method significantly improves the imaging accuracy, offering clearer target boundaries and better resolution. Comparison results also demonstrated that the hybridization of genetic algorithm and Newton-typesearchwaspivotalandimportantforrobustlyfindingthegloballyoptimalshape parameters.

Image Reconstruction with Perturbed Trajectories in a C-Arm CT System

For a 3D C-arm computed tomography(CT) system, actual path of the scanner may deviate from the idea circle geometry because of mechanicalinstability,leading to perturbation artifacts in reconstructed images. In this paper, we proposed a modified FBP method for the perturbed trajectories taking into account 6 perturbation parameters without tassuming any condition to be ideal. The preliminary studies demonstrated that this algorithm can acquire promising reconstruction image quality even when the perturbations are relatively large. The comparison of performances among different perturbation parameters is useful for constructing a C-arm CT system.

Trichostatin A and Shear Stress in Regulating Endothelium Differentiation of Bone Marrow Mesenchymal Stem Cells

Differentiation of bone marrow mesenchymal stem cells (MSCs) into endothelial cells (EC) is characterized by the expression of specific endothelial marker genes. Mechanical stimulations play potential effects in EC oriented differentiation of MSCs. However, molecular mechanisms of endothelial differentiation from MSCs have not been defined.Histone acetylations play important roles in regulating gene expression. Histone acetylation status is maintained by histone acetyltransferase (HAT) and histone deacetylases (HDACs). Our previous work described that VEGF and laminar shear stress (SS) work together in determining EC oriented differentiation of MSC. Trichostatin A (TSA) is one of the lustone deacetylase inhibitor. In this study, we found that both TSA and SS could induce EC oriented differentiation of MSCs. And TSA combined with SS showed more powerful influence on the EC oriented differentiation of MSCs.

Silicon Nanowire-Based Methodology for Quantifying Single Cell Traction Force

In this paper, we present a new method, a silicon-nanowire-array based technique for quantifying the mechanical behavior of single cells, representing three distinct groups: normal mammalian cells, benign cells (L929) and malignant cells (HeLa). By culturing the cells on top of NW arrays, the maximum traction forces of different cells have been measured by quantitatively analyzing the bending of the nanowires. The elastic modulus of the as-fabricated Si-NW arrays was first measured before cell culturing. Finite element (FEM) simulations were carried out in order to derive the relationship between the applied transverse force and the corresponding tip displacement for a Si-NW. Our study is likely important for studying the mechanical properties of single cells and their migration characteristics, possibly providing a new cellular level diagnostic technique.