Functional Evaluation of Low Resistance Junctions: Influence of Cell Shape and Size

Specialized junctions, which allow small molecules to move directlybetween adjacent cells in many adult and embryonic tissues,may be involved in electrical or non-electrical forms of intercellularcommunication. The ability of the junctions to mediate eitherform of communication depends on the permeability of the junctionsand on the shape, size, and arrangement of the interconnectedcells. Electrical communication depends on junctional resistanceand on non-junctional resistance which is a function of cellsurface area. Non-electrical communication, it is argued, dependson junctional permeability to small molecules and on cell volume.The dual dependency of non-electrical communication in particularis discussed in detail and some of the possible implicationsare illustrated with specific examples.     

WormSizer: High-throughput Analysis of Nematode Size and Shape

The fundamental phenotypes of growth rate, size and morphology are the result of complex interactions between genotype and environment. We developed a high-throughput software application, WormSizer, which computes size and shape of nematodes from brightfield images. Existing methods for estimating volume either coarsely model the nematode as a cylinder or assume the worm shape or opacity is invariant. Our estimate is more robust to changes in morphology or optical density as it only assumes radial symmetry. This open source software is written as a plugin for the well-known image-processing framework Fiji/ImageJ. It may therefore be extended easily. We evaluated the technical performance of this framework, and we used it to analyze growth and shape of several canonical Caenorhabditis elegans mutants in a developmental time series. We confirm quantitatively that a Dumpy (Dpy) mutant is short and fat and that a Long (Lon) mutant is long and thin. We show that daf-2 insulin-like receptor mutants are larger than wild-type upon hatching but grow slow, and WormSizer can distinguish dauer larvae from normal larvae. We also show that a Small (Sma) mutant is actually smaller than wild-type at all stages of larval development. WormSizer works with Uncoordinated (Unc) and Roller (Rol) mutants as well, indicating that it can be used with mutants despite behavioral phenotypes. We used our complete data set to perform a power analysis, giving users a sense of how many images are needed to detect different effect sizes. Our analysis confirms and extends on existing phenotypic characterization of well-characterized mutants, demonstrating the utility and robustness of WormSizer.     

The Influence of Age and Sex on Genetic Associations with Adult Body Size and Shape: A Large-Scale Genome-Wide Interaction Study

Genome-wide association studies (GWAS) have identified more than 100 genetic variants contributing to BMI, a measure of body size, or waist-to-hip ratio (adjusted for BMI, WHR_adjBMI), a measure of body shape. Body size and shape change as people grow older and these changes differ substantially between men and women. To systematically screen for age- and/or sex-specific effects of genetic variants on BMI and WHR_adjBMI, we performed meta-analyses of 114 studies (up to 320,485 individuals of European descent) with genome-wide chip and/or Metabochip data by the Genetic Investigation of Anthropometric Traits (GIANT) Consortium. Each study tested the association of up to ~2.8M SNPs with BMI and WHR_adjBMI in four strata (men ≤50y, men >50y, women ≤50y, women >50y) and summary statistics were combined in stratum-specific meta-analyses. We then screened for variants that showed age-specific effects (G x AGE), sex-specific effects (G x SEX) or age-specific effects that differed between men and women (G x AGE x SEX). For BMI, we identified 15 loci (11 previously established for main effects, four novel) that showed significant (FDR<5%) age-specific effects, of which 11 had larger effects in younger (<50y) than in older adults (≥50y). No sex-dependent effects were identified for BMI. For WHR_adjBMI, we identified 44 loci (27 previously established for main effects, 17 novel) with sex-specific effects, of which 28 showed larger effects in women than in men, five showed larger effects in men than in women, and 11 showed opposite effects between sexes. No age-dependent effects were identified for WHR_adjBMI. This is the first genome-wide interaction meta-analysis to report convincing evidence of age-dependent genetic effects on BMI. In addition, we confirm the sex-specificity of genetic effects on WHR_adjBMI. These results may provide further insights into the biology that underlies weight change with age or the sexually dimorphism of body shape.     

Disentangling the Size and Shape Components of Sexual Dimorphism

Evolutionary Biology - Many organisms are sexually dimorphic, reflecting sex-specific selection pressures. But although sexual dimorphism may consist of different variables from size to shape and...     

Bodily Illusions in Young Children: Developmental Change in Visual and Proprioceptive Contributions to Perceived Hand Position

We examined the visual capture of perceived hand position in forty-five 5- to 7-year-olds and in fifteen young adults, using a mirror illusion task. In this task, participants see their left hand on both the left and right (by virtue of a mirror placed at the midline facing the left arm, and obscuring the right). The accuracy of participants’ reaching was measured when proprioceptive and visual cues to the location of the right arm were put into conflict (by placing the arms at different distances from the mirror), and also when only proprioceptive information was available (i.e., when the mirror was covered). Children in all age-groups (and adults) made reaching errors in the mirror condition in accordance with the visually-specified illusory starting position of their hand indicating a visual capture of perceived hand position. Data analysis indicated that visual capture increased substantially up until 6 years of age. These findings are interpreted with respect to the development of the visual guidance of action in early childhood.     

Multivalent Binding of a Ligand-Coated Particle: Role of Shape,Size, and Ligand Heterogeneity

We utilize a multiscale modeling framework to study the effect of shape, size, and ligand composition on the efficacy of binding of a ligand-coated particle to a substrate functionalized with the target receptors. First, we show how molecular dynamics along with steered molecular dynamics calculations can be used to accurately parameterize the molecular-binding free energy and the effective spring constant for a receptor-ligand pair. We demonstrate this for two ligands that bind to the ${\alpha }_5{\beta }_1$-domain of integrin. Next, we show how these effective potentials can be used to build computational models at the meso- and continuum-scales. These models incorporate the molecular nature of the receptor-ligand interactions and yet provide an inexpensive route to study the multivalent interaction of receptors and ligands through the construction of Bell potentials customized to the molecular identities. We quantify the binding efficacy of the ligand-coated-particle in terms of its multivalency, binding free-energy landscape, and the losses in the configurational entropies. We show that 1) the binding avidity for particle sizes less than 350 nm is set by the competition between the enthalpic and entropic contributions, whereas that for sizes above 350 nm is dominated by the enthalpy of binding; 2) anisotropic particles display higher levels of multivalent binding compared to those of spherical particles; and 3) variations in ligand composition can alter binding avidity without altering the average multivalency. The methods and results presented here have wide applications in the rational design of functionalized carriers and also in understanding cell adhesion.     

Bacterioplankton Dynamics in Estuarine Mesocosms: Effects of Tank Shape and Size

Mesocosms provide a powerful tool for investigating bacterial dynamics at small scales; however, even these controlled studies are not exempt from spatial influences. Differences in mesocosm shape and size may have profound effects on the enclosed community since these features may influence the behavior of the system. Studies were conducted in mesocosms of varying dimensions (narrow, deep and wide, shallow tanks) and volumes (0.1, 1, and 10 m3) in an attempt to decipher effects attributable to changes in container size and shape. Both mesocosm volume and shape affected the course of bacterial growth following containment. Bacterial abundance and production were high in both groups of 0.1 m3 tanks and in the large, wide, shallow tanks with the greatest light supply at depth. Differences in bacterial growth between differently shaped tanks (i.e., differing wall area to volume ratios) were observed among equal volume enclosures, with faster growth in the wide/shallow tanks. Light availability, phytoplankton growth, and primary production differed among tanks, and bacterial growth and production were correlated with these properties. During high nutrient conditions, mesocosm volume and shape influenced bacterial growth, possibly because of periphyton growth on walls in small tanks and elevated light levels in wide/shallow tanks. These results suggest the importance of considering container dimensions when designing and interpreting mesocosm experiments and may allow deeper understanding of the fundamental processes underlying patterns observed in the real world.     

Shaping Taste: The Molecular Discovery of Rice Genes Improving Grain Size,Shape and Quality

<正>Modern-day human life is absolutely dependent upon the food that we derive from our crop plants.We eat grains,fruits,roots,tubers and other structures,all of which are constructed via coordinated organ growth.Whilst plant organ identity is first established in apical meristems(vegetative and floral shoot meristems and root meristems),and in other meristematic regions,the final size and shape of organs are defined by subsequent coordination of organ expansion in longitudinal and     

The Influence of Perceived Stress on Cortical Reactivity: A Proof-Of-Principle Study

The aim of this study was to investigate how perceived stress may affect electroencephalographical (EEG) activity in a stress paradigm in a sample of 76 healthy participants. EEG activity was analyzed using multilevel modeling, allowing estimation of nested effects (EEG time segments within subjects). The stress paradigm consisted of a 3-minute pre-stimulus stress period and a 2-minute post-stimulus phase. At t=3 minutes, a single electrical stimulus was delivered. Participants were unaware of the precise moment of stimulus delivery and its intensity level. In the EEG time course of alpha activity, a stronger increase was observed during the post-stimulus period as compared to the pre-stimulus period. An opposite time course effect was apparent for gamma activity. Both effects were in line with a priori expectations and support the validity of this experimental EEG-stress paradigm. Secondly, we investigated whether interaction effects of stress and coping, as measured with the Perceived Stress Scale-10 questionnaire (PSS-10), could be demonstrated. A higher perceived stress score was accompanied by a greater increase in delta- and theta-activity during the post-stimulus phase, compared to low scores. In contrast, low coping capacity was associated with a stronger decrease in slow beta, fast beta and gamma activity during the post-stimulus phase. The results of the present article may be interpreted as proof-of-principle that EEG stress-related activity depends on the level of subjectively reported perceived stress. The inclusion of psychosocial variables measuring coping styles as well as stress-related personality aspects permits further examination of the interconnection between mind and body and may inform on the process of transformation from acute to chronic stress.     

Photographs Objects Histories: On the Materiality of Images

Photographs Objects Histories: On the Materiality of Images . Elizabeth Edwards and Janice Hart, eds. London: Routledge Press, 2004. 222 pp.     

The Hindlimb Elements of the Maas (Aves,Dinornithidae): A Multivariate Assessment of Size and Shape

A multivariate morphometric analysis of size and shape was performed on the hindlimb skeletal elements of the extinct New Zealand moas (Dinornithidae). Investigations were undertaken of size-shape patterns within species and among moas as a group using principal components analysis; between species investigations used canonical analysis. In addition, standard allometric curve-fitting of six femur, seven tibiotarsus, and nine tarsometatarsus variables against body size was performed. Size was the major discriminator along the first principal component for all three bones in the intraspecific and whole-group analyses. Shape was the important discriminator along the second component: in the whole-group analysis of all three bones, separation was based on relative robustness of the shaft, whereas in the intraspecific analyses shaft robustness was only expressed in the analysis of the femur, there being little correspondence in the results between the intraspeci fic and whole-group analyses of the tibiotarsus and tarsometatarsus. Size was the major discriminator along the first canonical axis for the between-group investigations of the femur and tibiotarsus, but in the analysis of the tarsometatarsus shape influences were equally as important as those of size. The second canonical axis separated groups on the basis of shape differences in all three hindlimb elements. The genus Dinornis, which contains the largest species of moas, has evolved sizeshape patterns very different from those of other moas. The species of Dinornis did not follow size-dependent allometric trends and evolved proportionately thinner legs than might be expected for their body size. All other moas exhibit allometric increase in all hindlimb variables except bone lengths. Dinornis may have evolved a cursorial mode of locomotion as an adaptation for certain intraspecific behavioral interactions.     

Increasing Accessibility to the Blind of Virtual Environments,Using a Virtual Mobility Aid Based On the EyeCane: Feasibility Study

Virtual worlds and environments are becoming an increasingly central part of our lives, yet they are still far from accessible to the blind. This is especially unfortunate as such environments hold great potential for them for uses such as social interaction, online education and especially for use with familiarizing the visually impaired user with a real environment virtually from the comfort and safety of his own home before visiting it in the real world. We have implemented a simple algorithm to improve this situation using single-point depth information, enabling the blind to use a virtual cane, modeled on the “EyeCane” electronic travel aid, within any virtual environment with minimal pre-processing. Use of the Virtual-EyeCane, enables this experience to potentially be later used in real world environments with identical stimuli to those from the virtual environment. We show the fast-learned practical use of this algorithm for navigation in simple environments.     

Fat-Tailed Fluctuations in the Size of Organizations: The Role of Social Influence

Organizational growth processes have consistently been shown to exhibit a fatter-than-Gaussian growth-rate distribution in a variety of settings. Long periods of relatively small changes are interrupted by sudden changes in all size scales. This kind of extreme events can have important consequences for the development of biological and socio-economic systems. Existing models do not derive this aggregated pattern from agent actions at the micro level. We develop an agent-based simulation model on a social network. We take our departure in a model by a Schwarzkopf et al. on a scale-free network. We reproduce the fat-tailed pattern out of internal dynamics alone, and also find that it is robust with respect to network topology. Thus, the social network and the local interactions are a prerequisite for generating the pattern, but not the network topology itself. We further extend the model with a parameter that weights the relative fraction of an individual''s neighbours belonging to a given organization, representing a contextual aspect of social influence. In the lower limit of this parameter, the fraction is irrelevant and choice of organization is random. In the upper limit of the parameter, the largest fraction quickly dominates, leading to a winner-takes-all situation. We recover the real pattern as an intermediate case between these two extremes.     

Controlling the Size, Shape and Stability of Supramolecular Polymers in Water

For aqueous based supramolecular polymers, the simultaneous control over shape, size and stability is very difficult¹. At the same time, the ability to do so is highly important in view of a number of applications in functional soft matter including electronics, biomedical engineering, and sensors. In the past, successful strategies to control the size and shape of supramolecular polymers typically focused on the use of templates^2,3, end cappers⁴ or selective solvent techniques⁵. Here we disclose a strategy based on self-assembling discotic amphiphiles that leads to the control over stack length and shape of ordered, chiral columnar aggregates. By balancing electrostatic repulsive interactions on the hydrophilic rim and attractive non-covalent forces within the hydrophobic core of the polymerizing building block, we manage to create small and discrete spherical objects^6,7. Increasing the salt concentration to screen the charges induces a sphere-to-rod transition. Intriguingly, this transition is expressed in an increase of cooperativity in the temperature-dependent self-assembly mechanism, and more stable aggregates are obtained. For our study we select a benzene-1,3,5-tricarboxamide (BTA) core connected to a hydrophilic metal chelate via a hydrophobic, fluorinated L-phenylalanine based spacer (Scheme 1). The metal chelate selected is a Gd(III)-DTPA complex that contains two overall remaining charges per complex and necessarily two counter ions. The one-dimensional growth of the aggregate is directed by π-π stacking and intermolecular hydrogen bonding. However, the electrostatic, repulsive forces that arise from the charges on the Gd(III)-DTPA complex start limiting the one-dimensional growth of the BTA-based discotic once a certain size is reached. At millimolar concentrations the formed aggregate has a spherical shape and a diameter of around 5 nm as inferred from ¹H-NMR spectroscopy, small angle X-ray scattering, and cryogenic transmission electron microscopy (cryo-TEM). The strength of the electrostatic repulsive interactions between molecules can be reduced by increasing the salt concentration of the buffered solutions. This screening of the charges induces a transition from spherical aggregates into elongated rods with a length > 25 nm. Cryo-TEM allows to visualise the changes in shape and size. In addition, CD spectroscopy permits to derive the mechanistic details of the self-assembly processes before and after the addition of salt. Importantly, the cooperativity -a key feature that dictates the physical properties of the produced supramolecular polymers- increases dramatically upon screening the electrostatic interactions. This increase in cooperativity results in a significant increase in the molecular weight of the formed supramolecular polymers in water.     

Explaining Away the Body: Experiences of Supernaturally Caused Touch and Touch on Non-Hand Objects within the Rubber Hand Illusion

Background

In rubber hand illusions and full body illusions, touch sensations are projected to non-body objects such as rubber hands, dolls or virtual bodies. The robustness, limits and further perceptual consequences of such illusions are not yet fully explored or understood. A number of experiments are reported that test the limits of a variant of the rubber hand illusion.

Methodology/Principal Findings

A variant of the rubber hand illusion is explored, in which the real and foreign hands are aligned in personal space. The presence of the illusion is ascertained with participants'' scores and temperature changes of the real arm. This generates a basic illusion of touch projected to a foreign arm. Participants are presented with further, unusual visuotactile stimuli subsequent to onset of the basic illusion. Such further visuotactile stimulation is found to generate very unusual experiences of supernatural touch and touch on a non-hand object. The finding of touch on a non-hand object conflicts with prior findings, and to resolve this conflict a further hypothesis is successfully tested: that without prior onset of the basic illusion this unusual experience does not occur.

Conclusions/Significance

A rubber hand illusion is found that can arise when the real and the foreign arm are aligned in personal space. This illusion persists through periods of no tactile stimulation and is strong enough to allow very unusual experiences of touch felt on a cardboard box and experiences of touch produced at a distance, as if by supernatural causation. These findings suggest that one''s visual body image is explained away during experience of the illusion and they may be of further importance to understanding the role of experience in delusion formation. The findings of touch on non-hand objects may help reconcile conflicting results in this area of research. In addition, new evidence is provided that relates to the recently discovered psychologically induced temperature changes that occur during the illusion.     

The Effects of the Shape and Size of the Clinical Target Volume on the Planning Target Volume Margin

Purpose

To investigate the impact of clinical target volume (CTV) shape and size on CTV to planning target volume (PTV) margin expansion.

Methods and Materials

Using numerical integration methods, margins accounting for random errors and systematic errors were calculated for CTVs of different shapes and sizes. We use and to represent the coefficients, for random errors and systematic errors, respectively, that ensure that every point of the CTV receives ≥95% of the prescribed dose.

Results

The part of the margin accounting for random errors depends on CTV shape and size; generally, a convex part of a CTV would have a larger margin than a concave part. However, the part of the margin accounting for systematic errors is independent of CTV shape and size.

Conclusions

CTV shape and size should be considered when generating a PTV. For a complex CTV, the margins of the various parts of the CTV are different and related to local forms.     

Shape, Size, and Robustness: Feasible Regions in the Parameter Space of Biochemical Networks

The concept of robustness of regulatory networks has received much attention in the last decade. One measure of robustness has been associated with the volume of the feasible region, namely, the region in the parameter space in which the system is functional. In this paper, we show that, in addition to volume, the geometry of this region has important consequences for the robustness and the fragility of a network. We develop an approximation within which we could algebraically specify the feasible region. We analyze the segment polarity gene network to illustrate our approach. The study of random walks in the parameter space and how they exit the feasible region provide us with a rich perspective on the different modes of failure of this network model. In particular, we found that, between two alternative ways of activating Wingless, one is more robust than the other. Our method provides a more complete measure of robustness to parameter variation. As a general modeling strategy, our approach is an interesting alternative to Boolean representation of biochemical networks.     

The Influence of Epinephrine on Washed Human Platelets: Shape Change and Protein Phosphorylation

Abstract

Protein phosphorylation is an important regulator of the properties or functions of many proteins and is associated with the platelet activation response to a number of chemically and functionally different agents such as thrombin, plateletactivating factor, serotonin and collagen. The physiological responses of platelets to these agents are similar, and the common intracellular messenger for activation is an elevated concentration of calcium. Platelets possess alpha-2-receptors, and treatment with epinephrine produces an elevation in platelet cytosolic free calcium concentrations. Methods are described for studying hormone sensitive shape change and protein phosphorylation in washed human platelets. Epinephrine induces platelet shape change, and this process is independent of extracellular calcium. Treatment of [³²P]-orthophosphate-labelled platelets with epinephrine produces an increase in ³²P-incorporation into two platelet proteins with molecular weights of 47000 and 20000. This phosphorylation response is both dose and time dependent. Extracellular calcium is not absolutely essential for epinephrine-induced phosphorylation, but does enhance the maximum levels of ³²P-incorporation. Epinephrine sensitive phosphorylation is completely inhibited following pretreatment with verapamil or nitrendipine. Shape change in response to epinephrine occurs in the absence of enhanced protein phosphorylation. The data suggest that epinephrine mobilizes intracellular calcium, and induces platelet shape change and phosphorylation responses characteristic of platelet activation.