What does inductance plethysmography really measure?

Inasmuch as it has been claimed that inductance plethysmography can measure cross-sectional area changes, we tested this assumption. We present experimental and computed relationships between self-inductance (L) of coils and areas (A) included inside for a coil with a well-defined side wavy pattern (triangular or sinusoidal) and for a real belt (Respitrace) placed on elliptical or rectangular configurations. The results are applied to the physiological field using measurements obtained from a computed tomography experiment. We demonstrate that the L-A relationships vary not only with shape or ellipticity of the cross section but also with the wavy pattern shape. This last parameter is critical because it is difficult to actually control. When the coil wavy pattern remains steady, there are some physiological situations where inductance plethysmography can more accurately estimate area changes: when the configuration shape is constant, the correspondence between delta L and delta A is almost linear with a shape-dependent sensitivity; when the configuration is nearly circular (ellipticity in the range 0.8-1), the relative error in delta A estimation is less than 5%.     

Equilibrium shapes of erythrocytes in rouleau formation

A well known physiological property of erythrocytes is that they can aggregate and form a rouleau. We present a theoretical analysis of erythrocyte shapes in a long rouleau composed of cells with identical sizes. The study is based on the area difference elasticity model of lipid membranes, and takes into consideration the adhesion of curved axisymmetric membranes. The analysis predicts that the erythrocytes in the rouleau can have either a discoid or a cup-like shape. These shapes are analogous to the discoid and stomatocyte shapes of free erythrocytes. The transitions between the discoid and cup-like shapes in the rouleau are characterized. The occurrence of these transitions depends on three model parameters: the cell relative volume, the preferred difference between the areas of the membrane bilayer leaflets, and the strength of the adhesion between the membranes. The cup-like shapes are favored at small relative volumes and small preferred area differences, and the discoid shapes are favored at large values of these parameters. Increased adhesion strength enlarges the contact area between the cells, flattens the cells, and consequently promotes the discoid shapes.     

Cell shape regulates collagen type I expression in human tendon fibroblasts

Understanding the relationship between cell shape and cellular function is important for study of cell biology in general and for regulation of cell phenotype in tissue engineering in particular. In this study, microcontact printing technique was used to create cell-adhesive rectangular and circular islands. The rectangular islands had three aspect ratios: 19.6, 4.9, and 2.2, respectively, whereas circular islands had a diameter of 50 microm. Both rectangular and circular islands had the same area of 1960 microm(2). In culture, we found that human tendon fibroblasts (HTFs) assumed the shapes of these islands. Quantitative immunofluorescence measurement showed that more elongated cells expressed higher collagen type I than did less stretched cells even though cell spreading area was the same. This suggests that HTFs, which assume an elongated shape in vivo, have optimal morphology in terms of expression of collagen type I, which is a major component of normal tendons. Using immunohistochemistry along with cell traction force microscopy (CTFM), we further found that these HTFs with different shapes exhibited variations in actin cytoskeletal structure, spatial arrangement of focal adhesions, and spatial distribution and magnitude of cell traction forces. The changes in the actin cytoskeletal structure, focal adhesion distributions, and traction forces in cells with different shapes may be responsible for altered collagen expression, as they are known to be involved in cellular mechanotransduction.     

Subcellular curvature at the perimeter of micropatterned cells influences lamellipodial distribution and cell polarity

This paper employs substrates that are patterned with shapes having well-defined geometric cues to characterize the influence of curvature on the polarization of highly metastatic B16F10 rat melanoma cells. Substrates were patterned using microcontact printing to define adhesive islands of defined shape and size on a background that otherwise prevents cell adhesion. Cells adherent to these surfaces responded to local curvature at the perimeter of the adhesive islands; convex features promoted the assembly of lamellipodia and concave features promoted the assembly of stress filaments. Cells adherent to rectangular shapes displayed a polarized cytoskeleton that increased with the aspect ratio of the shapes. Shapes that combined local geometric cues, by way of concave or convex edges, with aspect ratio were used to understand the additive effects of shape on polarization. The dependence of cell polarity on shape was determined in the presence of small molecules that alter actomyosin contractility and revealed a stronger dependence on contractility for shapes having straight edges, in contrast to those having curved edges. This study demonstrates that the cytoskeleton modulates cell polarity in response to multiple geometric cues in the extracellular environment.     

Computer simulation of the hydrostatic skeleton. The physical equivalent, mathematics and application to worm-like forms

The functional principles of a hydrostatic skeleton were combined to obtain a physical model which includes geometry, number and length-tension relationships of the elastic elements in the body wall, internal volume and internal pressure. The model skeleton with pre-set internal volume assumes a certain shape and develops a specific internal pressure in order to minimize the potential energy stored in the elastic elements. This shape is calculated as equilibrium state by using finite element methods and optimization techniques. This model is flexible enough to accommodate different geometries and length-tension-relationships of the elastic elements. Presently, the model is implemented with linear length-tension relationships and certain geometrical restrictions, such as uniform width over the entire animal, and rectangular cross sections; the general case is outlined. First simulations with the "unit-worm" yield stable solutions, i.e. stable shapes for all combinations of parameters tested so far. They define the conditions for bringing all muscles to an optimal operating point. We detected a pressure maximum with increasing volume, assessed the contribution of circular muscles to bending, and determined the shapes of animals with different muscle activations in each body half (Chapman-matrix). We summarize our results by the volume rule and stabilization rule, two simple concepts which predict changes in shape as the result of muscle activation.     

The development and validation of a charge-coupled device laser reflectance system to measure the complex cross-sectional shape and area of soft tissues

Determination of the stresses in soft tissues such as ligaments and tendons under uniaxial tension require accurate measurement of their cross-sectional area. Of the many methods available, there are concerns regarding contact methods which exert external loads and deform the cross-sectional shape of soft tissues. Hence, the area measurements are affected. On the other hand, non-contact methods have difficulties in dealing with complex shapes, especially with concavities. To address these problems, a new measurement system using a charge-coupled device (CCD) laser displacement sensor has been developed and tested. This system measures the complete surface profile of the object by rotating the laser 360° around the soft tissue. Then, the cross-sectional shape is reconstructed and the cross-sectional area determined via Simpson's rule. The system's accuracy was first verified with objects of various cross-sectional shapes and areas (cylinder: 23.1, 76.5, 510.3 mm²; cuboid: 34.3, 163.8, 316.7 mm², and cylinder with concavities: 121.4 mm²). The CCD laser reflectance system's accuracy was within 2.0% for these objects. To test biological application, the goat Achilles tendon and the anteromedial bundle of the porcine anterior cruciate ligament specimens were measured and compared to values obtained using another accepted technique, the laser micrometer system. The areas obtained using the CCD laser reflectance system were 4.4% and 9.7% lower than those obtained with the laser micrometer system respectively. These differences could be mainly attributed to concavities. Thus, the CCD laser reflectance system is an improved method for measuring the cross-sectional shape and area of soft tissues since it can detect and account for concavities without physically contacting the specimen.     

Retinol-induced morphological changes of cultured bovine endothelial cells are accompanied by a marked increase in transglutaminase

Retinol, a morphogen, has been shown to induce morphological changes in vascular endothelial cells, accompanied by an acute and specific accumulation of an 80-kDa protein; purification and characterization of this retinol-induced protein (RIP) have revealed that it is a transglutaminase. Endothelial cells from bovine carotid artery were cultured, treated with retinol, and examined for changes in morphology and protein profiles. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of extracts prepared from retinol-treated cells which had undergone a remarkable change in shape (from a cobblestone-like to a spindle-like shape) indicated that the retinol-induced morphological change is accompanied by a marked increase of an 80-kDa protein. Similar changes were also induced by retinoic acid. The 80-kDa RIP was purified by anion exchange and hydroxyapatite column chromatography. Amino acid sequencing of tryptic fragments of the purified RIP revealed a high degree of homology between the sequence of bovine RIP and that of guinea pig liver transglutaminase, suggesting that RIP is a transglutaminase. This was confirmed by activity measurements; RIP exhibited transglutaminase activity, and an antiserum against RIP immunoprecipitated the activity. These results suggest that transglutaminase plays important roles in the maintenance of morphology and the control of endothelial cell functions.     

Dynamic shape of tapered skeletal muscle fibers

The muscle fibers of the feline biceps femoris have tapered ends, across which tension is transmitted to the endomysium. The angle of taper of 11 ends, measured on scanning electron micrographs, varied between 0.16 degrees and 1.18 degrees. The muscle fibers are highly variable in cross-sectional shape. The shape of the fibers has been quantified as the ratio (form factor [FF]) of the measured perimeter to the calculated circumference of a circle having an area equal to that contained by the fiber perimeter. The FF for 173 terminal portions of fibers varied between 1.06 and 1.85 and was found to have a highly significant negative correlation with sarcomere length. The slope of the regression line suggests that the fibers maintain both volume and surface area as they change length. These studies suggest that isovolumic muscle fibers maintain a constant surface area by changing shape as they change length.     

Life on the seafloor: adaptations and strategies in Stylophora (Echinodermata)

Stylophorans are a Palaeozoic group of non‐pentamerous echinoderms, morphologically well‐adapted to a benthic mode of life on soft sediment seafloors. By developing a thin and wide theca, they successively increased the surface area in contact with the substrate resulting in an even distribution of the body mass resting on the ground, and efficiently preventing the body from sinking into non‐indurated sediments (snowshoe strategy). In stylophorans, the body surface is dramatically increased in result of the expansion of two integumentary areas on the lower thecal surface. While infracentral areas are reduced in primitive forms to the detriment of massive marginals; in boot‐shape cornutes, infracentral areas are larger, polyplated and framed by very delicate marginals. In heart‐shaped cornutes, the reduction of both infracentral areas is compensated by the development of spiny elements on the theca outline. In forms where the degree of bilateral symmetry is high, the left infracentral area is larger than the right area, resulting in an elongated thecal shape. In structural geology, changes of shape of a rock submitted to a strain can be categorized by translating the obtained deformation into a strain ellipsoid plotted on a Flinn diagram, while in biology changes of shapes of organisms are traditionally measured through morphometric analysis. By applying Flinn's principle of strain ellipsoid to biological objects, the present study aims to characterize different life adaptations across stylophorans, observing changes of shape of both infracentral areas interpreted as two ellipsoids. Once plotted on a Flinn diagram, three significantly separated clusters are observed when focusing on the left area. This concerns forms with reduced infracentral areas, highly and weakly asymmetrical forms. According to these results, three new morphological adaptations are described (water strider, flat fish and stream‐lined body). These newly described adaptations enabled snowshoe strategist stylophorans to remain stable on top of the seafloor.     

Accounting for tree spatial distribution in a comparison of plot sizes and shapes in dense forest and woodland in Benin (West Africa)

The study examined simultaneously, the effect of tree spatial distribution, inventory plot size and shape on the estimation error of basal area in two contrasting environments. Twenty and fifteen square plots of 1 ha each (divided into 100 quadrats of 0.01 ha) were randomly set in dense forest and woodland, respectively. Thirteen subplots of various shapes and sizes were obtained from the association of adjacent quadrats. Estimation error was calculated using residual mean square of one‐way ANOVA, based on replications of subplot within 1 ha plots. Tree spatial distribution was measured using Green index. Weighted linear regression and mixed effect models were applied to Box & Cox transformed data. In general, the estimation error of basal area decreased with increase in subplot size. However, the effects of tree spatial distribution and plot shape varied with the vegetation type. Where trees tended to be aggregated, estimation error increased with degree of aggregation, and rectangular plots of 0.24 ha produced an acceptable precision. It was concluded that 0.24 ha rectangular plots can be used in tropical environments where the target parameters vary constantly according to one direction, while square plots of the same size are optimal for reliable analysis in case of randomness.     

Straightening of curved pattern of collagen fibers under load controls aortic valve shape

The network of collagen fibers in the aortic valve leaflet is believed to play an important role in the strength and durability of the valve. However, in addition to its stress-bearing role, such a fiber network has the potential to produce functionally important shape changes in the closed valve under pressure load. We measured the average pattern of the collagen network in porcine aortic valve leaflets after staining for collagen. We then used finite element simulation to explore how this collagen pattern influences the shape of the closed valve. We observed a curved or bent pattern, with collagen fibers angled downward from the commissures toward the center of the leaflet to form a pattern that is concave toward the leaflet free edge. Simulations showed that these curved fiber trajectories straighten under pressure load, leading to functionally important changes in closed valve shape. Relative to a pattern of straight collagen fibers running parallel to the leaflet free edge, the concave pattern of curved fibers produces a closed valve with a 40% increase in central leaflet coaptation height and with decreased leaflet billow, resulting in a more physiological closed valve shape. Furthermore, simulations show that these changes in loaded leaflet shape reflect changes in leaflet curvature due to modulation of in-plane membrane stress resulting from straightening of the curved fibers. This effect appears to play an important role in normal valve function and may have important implications for the design of prosthetic and tissue engineered replacement valves.     

The morphogenesis of liposomes viewed from the aspect of bending energy

It is known that liposomes transform their shapes sequentially through one of several transformation pathways. Using the mechanical principle of the least bending energy of membranes, we investigate the stability and shape transformation of liposomes with geometrical symmetry. We have done this by computer simulations and theoretical analyses, in which three-dimensional liposome shapes have been generated by the modified Cassini equation. We show first that there are energetically stable liposome shapes having intrinsic geometrical symmetry. We find that by reducing the volume, the stable shape can change from a circular biconcave shape as in red blood cells, to elliptical, triangular, square, and other polygonal shapes. It is also found that the preceding two results hold true irrespective of the overall surface area of liposome.     

Mechanics of curved plasma membrane vesicles: resting shapes, membrane curvature, and in-plane shear elasticity

Highly curved cell membrane structures, such as plasmalemmal vesicles (caveolae) and clathrin-coated pits, facilitate many cell functions, including the clustering of membrane receptors and transport of specific extracellular macromolecules by endothelial cells. These structures are subject to large mechanical deformations when the plasma membrane is stretched and subject to a change of its curvature. To enhance our understanding of plasmalemmal vesicles we need to improve the understanding of the mechanics in regions of high membrane curvatures. We examine here, theoretically, the shapes of plasmalemmal vesicles assuming that they consist of three membrane domains: an inner domain with high curvature, an outer domain with moderate curvature, and an outermost flat domain, all in the unstressed state. We assume the membrane properties are the same in these domains with membrane bending elasticity as well as in-plane shear elasticity. Special emphasis is placed on the effects of membrane curvature and in-plane shear elasticity on the mechanics of vesicle during unfolding by application of membrane tension. The vesicle shapes were computed by minimization of bending and in-plane shear strain energy. Mechanically stable vesicles were identified with characteristic membrane necks. Upon stretch of the membrane, the vesicle necks disappeared relatively abruptly leading to membrane shapes that consist of curved indentations. While the resting shape of vesicles is predominantly affected by the membrane spontaneous curvatures, the membrane shear elasticity (for a range of values recorded in the red cell membrane) makes a significant contribution as the vesicle is subject to stretch and unfolding. The membrane tension required to unfold the vesicle is sensitive with respect to its shape, especially as the vesicle becomes fully unfolded and approaches a relative flat shape.     

Study of Metallic Nanowires with Arbitrary Cross-Sectional Shapes for Negative Refraction in Visible Regime

Considering the nanofabrication errors, the real fabricated metallic nanowires may have irregular cross-sectional shapes. In this work, the metallic nanowires array with arbitrary cross-sectional shapes for negative refraction in visible regime was studied theoretically. To fully understand the evolution process of the negative refraction of the metallic wires with irregular cross-sectional shapes, the effective refractive index, effective mass, and effective radius of the wires were put forth and studied. The nanowire array with arbitrary cross-sectional shapes with different geometrical parameters was investigated in detail by means of computational numerical calculation on the basis of finite difference and time?Cdomain algorithm. The influence of geometrical parameters of the nanowires on negative refraction was systematically analyzed. The calculated results indicate that the irregular shape can play a positive role for the negative refraction-based imaging application.     

The standardization of the candidate national standard anti-D blood-typing serum with the Groupamatic MG50 system

The utility of the Groupamatic MG50 system for quantitative expression of agglutination in terms of continuous response was studied. By use of the characteristics of the design of this system, in which the change in voltage reflects the degree of agglutination, a linear regression relationship between the log ratio of light flux obtained by transformation of the voltage and the log dilution factor of the serum was demonstrated. The availability of the parallel line assay method to the standardization of the blood grouping antisera was also described.     

贵州主要地方李品种的调查研究

以贵州本地8个李资源的成熟叶片及果实为试验材料,从叶形特征、果实外部形态特征及果实内在品质性状等不同方面进行了调查研究。结果显示:①贵州地方李的叶形特征中以叶片形状的变异范围最大,有卵圆形、椭圆形、披针形、倒披针形等,其次为叶尖形状、叶基部形状和叶柄腺形状;②果实形态特征中以果皮和果肉颜色的变异范围最大,其次为果实成熟期、果实形状、梗洼及缝合线的深浅以及果顶形状;③贵州地方李的单果质量、果实横纵径及果形指数、核横纵径等性状的平均变异系数均在9%以上,其中单果重的变异幅度为18.3～38.9g,变异系数最大,达24.92%;④果实内在品质性状方面以可溶性固形物的变异系数最低,为8.50%,可溶性总糖的变异系数最高,为13.44%。     

Reliability of a method for evaluating porosity in denture base resins

doi:10.1111/j.1741‐2358.2009.00347.x
Reliability of a method for evaluating porosity in denture base resins Background: The method of porosity analysis by water absorption has been carried out by the storage of the specimens in pure water, but it does not exclude the potential plasticising effect of the water generating unreal values of porosity. Objective: The present study evaluated the reliability of this method of porosity analysis in polymethylmethacrylate denture base resins by the determination of the most satisfactory solution for storage (S), where the plasticising effect was excluded. Materials and methods: Two specimen shapes (rectangular and maxillary denture base) and two denture base resins, water bath‐polymerised (Classico) and microwave‐polymerised (Acron MC) were used. Saturated anhydrous calcium chloride solutions (25%, 50%, 75%) and distilled water were used for specimen storage. Sorption isotherms were used to determine S. Porosity factor (PF) and diffusion coefficient (D) were calculated within S and for the groups stored in distilled water. anova and Tukey tests were performed to identify significant differences in PF results and Kruskal–Wallis test and Dunn multiple comparison post hoc test, for D results (α = 0.05). Results: For Acron MC denture base shape, FP results were 0.24% (S 50%) and 1.37% (distilled water); for rectangular shape FP was 0.35% (S 75%) and 0.19% (distilled water). For Classico denture base shape, FP results were 0.54% (S 75%) and 1.21% (distilled water); for rectangular shape FP was 0.7% (S 50%) and 1.32% (distilled water). FP results were similar in S and distilled water only for Acron MC rectangular shape (p > 0.05). D results in distilled water were statistically higher than S for all groups. Conclusions: The results of the study suggest that an adequate solution for storing specimens must be used to measure porosity by water absorption, based on excluding the plasticising effect.     

A Computational Approach for Simulating Muscle Morphologic Changes in Musculoskeletal Modeling

Digital data characterizing the geometry of anatomic structures (e.g., bones, muscles and tendons) are becoming readily available from Magnetic Resonance Imaging and Computerized Tomography technology. These data can be useful in forward simulations of limb dynamics to study the interaction between tissue morphology and limb dynamics, but only if computational tools are available to manipulate these data to simulate various structural changes. The objective of this project was to develop a computational approach to simulate physiological changes in muscle volume and limb cross-section. A previously reported method for calculating the area and area centroid location of complex shapes was combined with a newly derived algorithm that simulates muscle hypertrophy or atrophy. The new algorithm modifies the cross-sectional areas of specified muscles and the spatial orientation of other muscles, as appropriate, to simulate desired muscle volume changes. An approach of this type is needed to facilitate musculoskeletal modeling and computer simulations of movement designed to address questions related to the interactions between muscle morphology, limb inertial properties and limb dynamics.     

Diaphragmatic displacement measured by fluoroscopy and derived by Respitrace

In eight healthy volunteers we simultaneously measured the axial diaphragmatic motion by fluoroscopy and the cross-sectional area changes of the rib cage (RC) and abdomen (ABD) by Respitrace (RIP) during semistatic vital capacities (VC). We found that, if the fluoroscopic axial displacement of the posterior part of the diaphragm between residual volume (RV) and total lung capacity (TLC) is considered equal to 100%, the movement of the middle part is 90%, whereas that of the anterior part is only approximately 60%; the ratio of the axial displacements to mouth volume, furthermore, decreases at high lung volumes, especially for the anterior part. The RIP signal is nearly linearly related to mouth volume, but the contribution of the RC (delta RC) progressively increases (and is approximately 80% RIP at TLC), whereas the volume contribution of the ABD (delta ABD) levels off (to 20% RIP at TLC). The diaphragmatic volume displacement calculated from the theoretical analysis described by Mead and Loring also levels off at high volumes similarly as the ABD but is approximately 50% RIP at TLC. Finally, the axial movements of the three parts of the diaphragm are linearly related to the RC and ABD cross-sectional-area changes (r 0.91-0.97) and are even significantly better correlated with the "calculated" diaphragmatic volume displacement.     

Cross-Sectional Shape of Collapsible Tubes

In order to quantify the collapse phenomenon in veins, this paper presents a mathematical analysis of the cross-sectional shape of a flexible tube as its internal pressure varies. Quantitative results are presented in terms of the physical parameters of the tube, such as wall thickness and Young's modulus. It is assumed that the tube is thin walled, that no stretching occurs, that the cross-sectional shape is elliptical when the transmural pressure is zero, and that the longitudinal prestress is zero. The equations were solved on a digital computer which displayed the cross-sectional shapes on an oscilloscope, which were then photographed. A selection of these photographs is presented. Curves are shown which give the cross-sectional area and compliance as functions of transmural pressure. Other curves are shown which are useful for interpolation, and for use in the experimental determination of the physical parameters which may otherwise be difficult or impossible to measure accurately.