Controlling Cellular Volume via Mechanical and Physical Properties of Substrate

The mechanical and physical properties of substrate play a crucial role in regulating many cell functions and behaviors. However, how these properties affect cell volume is still unclear. Here, we show that an increase in substrate stiffness, available spread area, or effective adhesion energy density results in a remarkable cell volume decrease (up to 50%), and the dynamic cell spreading process is also accompanied by dramatic cell volume decrease. Further, studies of ion channel inhibition and osmotic shock suggest that these volume decreases are due to the efflux of water and ions. We also show that disrupting cortex contractility leads to bigger cell volume. Collectively, these results reveal the “mechanism of adhesion-induced compression of cells,” i.e., stronger interaction between cell and substrate leads to higher actomyosin contractility, expels water and ions, and thus decreases cell volume.     

A Three-Dimensional Finite Element Scheme to Investigate the Apparent Mechanical Properties of Trabecular Bone

A computational technique is described for investigating the apparent mechanical properties of trabecular bone based on tissue geometry obtained from the marching cubes volume rendering scheme. Using this scheme, a 3D representation of the trabecular bone was extracted from two-dimensional cross-sections of the tissue originating from a quantitative serial sectioning procedure. Surface information consists of node coordinates and polygon connectivity in a 3D space. A custom, adaptive mesh generation technique using a normal offset was used to prepare 3D finite element volume meshes (4-node tetrahedral elements) of variable mesh density from the extracted surface geometry. Nine target mesh resolutions (32 μm to 107 μm) were examined for a (1.5 mmx 1.5 mmx 2 mm) volume of trabecular bone. A mesh density of 50,000 elements/mm(3) of bone tissue was found to be adequate for convergence of apparent (bulk) modulus for 1% uniaxial compression. For this convergent case, the maximum local normal compressive tissue stress was 400 MPa which was six hundred-fold greater than the computed apparent stress. Variation in the apparent modulus was less than 5% when Poisson's ratio values were varied between 0.1 and 0.4. Poisson's ratio values greater than 0.4 had a more marked effect on the apparent modulus. Based upon these results, approximately 1 million, 4-node tetrahedral elements are required to analyze a continuum scale model of trabecular bone (5 mm cube).     

Planar and Three-Dimensional Printing of Conductive Inks

Printed electronics rely on low-cost, large-area fabrication routes to create flexible or multidimensional electronic, optoelectronic, and biomedical devices^1-3. In this paper, we focus on one- (1D), two- (2D), and three-dimensional (3D) printing of conductive metallic inks in the form of flexible, stretchable, and spanning microelectrodes.Direct-write assembly^4,5 is a 1-to-3D printing technique that enables the fabrication of features ranging from simple lines to complex structures by the deposition of concentrated inks through fine nozzles (~0.1 - 250 μm). This printing method consists of a computer-controlled 3-axis translation stage, an ink reservoir and nozzle, and 10x telescopic lens for visualization. Unlike inkjet printing, a droplet-based process, direct-write assembly involves the extrusion of ink filaments either in- or out-of-plane. The printed filaments typically conform to the nozzle size. Hence, microscale features (< 1 μm) can be patterned and assembled into larger arrays and multidimensional architectures.In this paper, we first synthesize a highly concentrated silver nanoparticle ink for planar and 3D printing via direct-write assembly. Next, a standard protocol for printing microelectrodes in multidimensional motifs is demonstrated. Finally, applications of printed microelectrodes for electrically small antennas, solar cells, and light-emitting diodes are highlighted.     

骨科3D打印技术临床研究的状况分析

目的 研究骨科3D打印技术临床研究状况。方法 通过文献检索,对纳入的107篇文献进行系统性综述,描述骨科3D打印技术临床研究的基本状况。结果 骨科3D打印技术临床研究对象以男性为主,主要集中在成人群体,并且研究时间主要在2007年~2012年。3D打印技术经常应用于骨科手术的复位内固定、畸形矫正、椎弓根钉置入、肿瘤切除、翻修重建、膝关节置换。结论 骨科3D打印技术仍处在初步临床发展阶段。     

The Accuracy of a Method for Printing Three-Dimensional Spinal Models

Background

To study the morphology of the human spine and new spinal fixation methods, scientists require cadaveric specimens, which are dependent on donation. However, in most countries, the number of people willing to donate their body is low. A 3D printed model could be an alternative method for morphology research, but the accuracy of the morphology of a 3D printed model has not been determined.

Methods

Forty-five computed tomography (CT) scans of cervical, thoracic and lumbar spines were obtained, and 44 parameters of the cervical spine, 120 parameters of the thoracic spine, and 50 parameters of the lumbar spine were measured. The CT scan data in DICOM format were imported into Mimics software v10.01 for 3D reconstruction, and the data were saved in .STL format and imported to Cura software. After a 3D digital model was formed, it was saved in Gcode format and exported to a 3D printer for printing. After the 3D printed models were obtained, the above-referenced parameters were measured again.

Results

Paired t-tests were used to determine the significance, set to P<0.05, of all parameter data from the radiographic images and 3D printed models. Furthermore, 88.6% of all parameters of the cervical spine, 90% of all parameters of the thoracic spine, and 94% of all parameters of the lumbar spine had Intraclass Correlation Coefficient (ICC) values >0.800. The other ICC values were <0.800 and >0.600; none were <0.600.

Conclusion

In this study, we provide a protocol for printing accurate 3D spinal models for surgeons and researchers. The resulting 3D printed model is inexpensive and easily obtained for spinal fixation research.     

Three-Dimensional Labeling Program for Elucidation of the Geometric Properties of Biological Particles in Three-Dimensional Space

For all biological particles such as cells or cellular organelles, there are three-dimensional coordinates representing the centroid or center of gravity. These coordinates and other numerical parameters such as volume, fluorescence intensity, surface area, and shape are referred to in this paper as geometric properties, which may provide critical information for the clarification ofin situmechanisms of molecular and cellular functions in living organisms. We have established a method for the elucidation of these properties, designated the three-dimensional labeling program (3DLP). Algorithms of 3DLP are so simple that this method can be carried out through the use of software combinations in image analysis on a personal computer. To evaluate 3DLP, it was applied to a 32-cell-stage sea urchin embryo, double stained with FITC for cellular protein of blastomeres and propidium iodide for nuclear DNA. A stack of optical serial section images was obtained by confocal laser scanning microscopy. The method was found effective for determining geometric properties and should prove applicable to the study of many different kinds of biological particles in three-dimensional space.     

Mechanical Properties of the Frog Sarcolemma

The elastic properties of cylindrical segments of sarcolemma were studied in single striated fibers of the frog semitendinosus muscle. All measurements were made on membranes of retraction zones, cell segments from which the sarcoplasm had retracted. Quantitative morphological studies indicated that three deforming forces interact with the intrinsic elastic properties of the sarcolemma to determine membrane configuration in retraction zone segments. The three deforming forces, namely intrazone pressure, axial fiber loads, and radial stresses introduced by retracted cell contents, could all be experimentally removed, permitting determination of the “undeformed” configuration of the sarcolemma. Analysis of these results indicated that membrane of intact fibers at rest length is about four times as wide and two-thirds as long as undeformed membrane. Membrane geometry was also studied as a function of internal hydrostatic pressure and axial loading to permit calculation of the circumferential and longitudinal tension-strain (T-S) diagrams. The sarcolemma exhibited nonlinear T-S properties concave to the tension axis in both directions. Circumferential T-S slopes (measures of membrane stiffness) ranged from 1500 to greater than 50,000 dynes/cm over the range of deformations investigated, while longitudinal T-S slopes varied from 23,000 to 225,000 dynes/cm. Thus, the membrane is anisotropic, being much stiffer in the longitudinal direction. Certain ramifications of the present results are discussed in relation to previous biomechanical studies of the sarcolemma and of other tissues.     

Special Features of the Three-Dimensional Structure Defining Properties of Aspartic Proteases

A brief account is given of the specific interactions of some amino acid residues in aspartic proteases of both higher organisms and retroviruses that determine important protease properties: the anomalously low isoelectric point of pepsin and its stability at pH close to 1; the ability of one of the carboxyl groups in the active site of proteases of higher organisms to retain a charged state at any pH value; and the protonated state of another carboxyl, which is necessary for enzymatic activity. It is also explained how such states can be induced in retroviral proteases.     

骨科3D打印技术安全性和有效性非对照研究综述

目的 评价骨科3D打印技术临床应用的安全性和有效性。方法 通过非对照研究的系统性综述,分析 3D打印技术在骨科临床应用的安全性和有效性。结果 无对照研究分析显示：螺钉穿破皮质发生率为3.83%（按螺钉数计算）,并发症发生率为2.13%,手术感染发生率为0.28%,假体问题发生率为0.79%,平均手术时间为139.23分钟,部分安全性和有效性指标的评价结果与有对照研究的结果相似。结论 虽然3D打印技术在骨科的临床应用有一定价值,但其推广还需经济学评价。     

Energy Supply System for the Gliding Movement of Hormogonia of the Cyanobacterium Nostoc cycadae

The effects of selected metabolic inhibitors and light on thegliding movement of the hormogonia of the cyanobacterium Nostoccycadae were examined. Respiratory poisons (sodium cyanide,sodium azide) stopped the movement in the dark, but not in light.DCMU had little effect on the movement in light. The inhibitoryeffect of monoiodoacetic acid (MIA) on the gliding movementin light was restored by adding DCMU, suggesting that the glidingmovement in light is linked to a cyclic electron flow involvingphotosystem I, not to a noncyclic electron flow involving photosystemII. This was then proved by experiments on the effects of selectedwavelengths of light on the movement; light absorbed by chlorophyllwas found to accelerate the movement, but that absorbed by phycobilinsdid not. The proton-conducting uncouplers carbonyl cyanide m-chlorophenylhydrazone(CCCP) and 2,4-dinitrophenol (DNP) immediately abolished themovement. Arsenate or N, N'-dicyclohexylcarbodiimide (DCCD),known inhibitors of ATP synthesis, had little effect on themovement. Light irradiation caused acidification of the cellsuspension. From these results, the direct driving force for the glidingmovement of this organism seems to be the trans-cell membraneelectrochemical potential difference of protons, generated bya respiratory chain in the dark and a cyclic photoelectron flowsystem in light. (Received April 14, 1986; Accepted March 12, 1987)     

Purification and Properties of Glycogen Isolated from a Blue-Green Alga, Nostoc muscorum

Alpha granules were isolated from a blue-green alga, Nostoc muscorum, in large quantities and high purity by sucrose density gradient centrifugation. Sodium deoxycholate was used to eliminate membrane contamination. Isolated alpha granules from this species have average dimension of 31 nm in width and 65 nm in length. Each alpha granule consists of two equal parts. Attempts to dissociate the intact granule under mild conditions into relatively large subunits did not succeed. Analytical centrifugation of the alpha granules yields a sedimentation coefficient of 265S (S(20, w)). Chemical analysis reveals that alpha granules contain highly branched polyglucosyl units with short external chain lengths.     

Assessment of Salinity-Induced Antioxidative Defense System of Diazotrophic Cyanobacterium Nostoc muscorum

The present study examines the salinity-induced oxidative damage and differential response of enzymatic and non-enzymatic antioxidants of Nostoc muscorum. As compared to carotenoid content which showed induction the chlorophyll and phycocyanin contents were inhibited after salt stress. Acceleration of lipid peroxidation and peroxide production suggested onset of oxidative damage. The activities of all studied enzymatic antioxidants were significantly increased by salt stress with maximum induction of superoxide dismutase (154.8% at 200 mM NaCl treatment). Interestingly under severe stress condition (250 mM NaCl) ascorbate peroxidase seems to be more crucial than catalase for peroxide scavenging. Among the studied non-enzymatic antioxidants alpha-tocopherol was induced maximally (56.0%), however, ascorbate and reduced glutathione were increased by only 8.9% after 250 mM NaCl treatment as compared to control cells. Therefore, salinity was found to induce antioxidative defense system of N. muscorum.     

葡萄糖和氢对Gunnera／Nostoc固氮共生体固氮活力的影响

Ｇｕｎｎｅｒａ／Ｎｏｓｔｏｃ固氮共生体固氮相对效率（ＲＥ）可在０．２６～０．８０之间变动,而不是一个常数。外加１．５％葡萄糖液可使其固氮活力提高约１００％,同时也使组织的呼吸速率提高了近１６０％。加外源Ｈ２可使其固氮活力提高近１００％,但却使组织的呼吸速率降低了近５０％。正常生长条件下的组织净放Ｈ２量较低．而外源２％葡萄糖液可使组织净放Ｈ２量提高近２倍。外加５ｍｍｏｌ／Ｌ的ＮＨ１Ｃｌ溶液可使其固氮活力下降约７０％。故认为Ｇｕｎｎｅｒａ／Ｎｏｓｔｏｃ共生体固氮活力受碳水化合物供应状况及比代谢两者构成的“还原力库”或“电子库”的调节,在此“还原力库”中,Ｈ２代谢起到了一个“中间调节者”的作用。     

Effect of Layer Thickness and Printing Orientation on Mechanical Properties and Dimensional Accuracy of 3D Printed Porous Samples for Bone Tissue Engineering

Powder-based inkjet 3D printing method is one of the most attractive solid free form techniques. It involves a sequential layering process through which 3D porous scaffolds can be directly produced from computer-generated models. 3D printed products'' quality are controlled by the optimal build parameters. In this study, Calcium Sulfate based powders were used for porous scaffolds fabrication. The printed scaffolds of 0.8 mm pore size, with different layer thickness and printing orientation, were subjected to the depowdering step. The effects of four layer thicknesses and printing orientations, (parallel to X, Y and Z), on the physical and mechanical properties of printed scaffolds were investigated. It was observed that the compressive strength, toughness and Young''s modulus of samples with 0.1125 and 0.125 mm layer thickness were more than others. Furthermore, the results of SEM and μCT analyses showed that samples with 0.1125 mm layer thickness printed in X direction have more dimensional accuracy and significantly close to CAD software based designs with predefined pore size, porosity and pore interconnectivity.     

发菜(Nostoc flagelliforme)培养条件的研究

研究了光照强度、日供水次数、CO2浓度和培养基成分对发菜生长的影响。结果显示,中度光强(114μmol.m-2.s-1)下发菜生长最快;发菜的生长基本同供水次数成正相关系;CO2浓度的升高并没有显著促进发菜生长,低光条件下(57μmol.m-2.s-1),高浓度的CO2(2800μL/L)抑制了发菜的生长;用BG11培养的发菜生物量的增长显著高于用BG110培养的;BG11培养基中K+和CO32-的缺失并没有显著影响发菜的生长。     

Mechanical Properties of the Rhizome of Arundo donax L.

Abstract: The mechanical properties of rhizome segments of Arundo donax L. were studied in three dimensions: longitudinal (X), transverse-vertical (Y), transverse-horizontal (Z). Tensile, cyclic loading and torsional tests demonstrate that the distinct anisotropy found in the hollow stems is less pronounced in the rhizome. Morphological and anatomical examinations suggest that the mechanical anisotropy of the stem is caused by the arrangement parallel to the stem of the vascular bundles and sclerenchymatous fibres, embedded in lignified parenchyma. Anatomical inhomogeneity is less pronounced in the rhizome due to the short internode lengths, and predominance of nodal regions, where sclerenchymatous fibres form a complex three-dimensional arrangement embedded in unlignified starch-storing parenchyma. Cyclic loading experiments indicate viscoelastic behaviour of the rhizomatous tissues under tensile stress. Additionally, viscoelastic behaviour under torsional stress was studied. Mechanical behaviour of the rhizome under tension up to fracture is discussed with regard to the fracture surfaces, analysed by SEM.     

The Mechanical Properties of Rat Tail Tendon

The load-strain and stress-relaxation behavior of wet rat tail tendon has been examined with respect to the parameters strain, rate of straining, and temperature. It is found that this mechanical behavior is reproducible after resting the tendon for a few minutes after each extension so long as the strain does not exceed about 4 per cent. If this strain is exceeded, the tendon becomes progressively easier to extend but its length still returns to the original value after each extension. Extensions of over 35 per cent can be reached in this way. Temperature has no effect upon the mechanical behavior over the range 0–37°C. Just above this temperature, important changes take place in the mechanical properties of the tendon which may have biological significance. The application of the techniques used here to studies of connective tissue disorders is suggested. Some of the mechanical properties of tendon have been interpreted with a simple model.     

Comparative Mechanical Properties and Histology of Bone

Different bone tissues differ in their amounts of porosity,mineralization,reconstruction, and preferred orientation. Allthese have important effects on mechanical properties. Veryporous, cancellous bone is always weaker and morecompliant thancompact bone on a weight for weight basis, yet it occurs inplaceswhere its energyabsorbing ability, or its low density,is advantageous. Bonevaries considerably in its mineralization,and such variations have quite disproportionate effects on mechanicalproperties. These variations can be shown to be adaptive. Inparticular, there must always be a compromise between stiffnessandresistanceto fracture; these two properties run contrary to each other.The reason for secondary remodeling is an unresolved problem,though in a few places the role of such remodeling in changingthe grain of the bone is clearly mechanically adaptive. Themechanical properties of non-mammalian bone are obscure, andas the histology of such bone is often quite different fromthat of mammalian bone, we are no doubt in for some surpriseswhen the mechanical properties ofnonmammalian bone are discovered.