scholarly journals Cell Shape and Surface Colonisation in the Diatom Genus Cocconeis—An Opportunity to Explore Bio-Inspired Shape Packing?

Biomimetics ◽  
2019 ◽  
Vol 4 (2) ◽  
pp. 29 ◽  
Author(s):  
Timothy Sullivan
Keyword(s):  
Cell Shape ◽  
Energy Use ◽  
Close Association ◽  
Packing Fraction ◽  
Epifluorescence Microscopy ◽  
Theoretical Modelling ◽  
Average Cell ◽  
Optimal Packing ◽  
Immersed Surfaces ◽  
Diatom Genus

Optimal packing of 2 and 3-D shapes in confined spaces has long been of practical and theoretical interest, particularly as it has been discovered that rotatable ellipses (or ellipsoids in the 3-D case) can, for example, have higher packing densities than disks (or spheres in the 3-D case). Benthic diatoms, particularly those of the genus Cocconeis (Ehr.)—which are widely regarded as prolific colonisers of immersed surfaces—often have a flattened (adnate) cell shape and an approximately elliptical outline or “footprint” that allows them to closely contact the substratum. Adoption of this shape may give these cells a number of advantages as they colonise surfaces, such as a higher packing fraction for colonies on a surface for more efficient use of limited space, or an increased contact between individual cells when cell abundances are high, enabling the cells to minimize energy use and maximize packing (and biofilm) stability on a surface. Here, the outline shapes of individual diatom cells are measured using scanning electron and epifluorescence microscopy to discover if the average cell shape compares favourably with those predicted by theoretical modelling of efficient 2-D ellipse packing. It is found that the aspect ratio of measured cells in close association in a biofilm—which are broadly elliptical in shape—do indeed fall within the range theoretically predicted for optimal packing, but that the shape of individual diatoms also differ subtly from that of a true ellipse. The significance of these differences for optimal packing of 2-D shapes on surfaces is not understood at present, but may represent an opportunity to further explore bio-inspired design shapes for the optimal packing of shapes on surfaces.

scholarly journals 3D Tissue elongation via ECM stiffness-cued junctional remodeling

2018 ◽  
Author(s):  
Dong-Yuan Chen ◽  
Justin Crest ◽  
Sebastian J. Streichan ◽  
David Bilder
Keyword(s):  
Basement Membrane ◽  
Cell Shape ◽  
Cell Dynamics ◽  
Src Tyrosine Kinase ◽  
Average Cell ◽  
Cellular Behavior ◽  
Cell Behaviors ◽  
Oriented Cell Division ◽  
Morphometric Analyses ◽  
Membrane Stiffness

ABSTRACTOrgans are sculpted by extracellular as well as cell-intrinsic forces, but how collective cell dynamics are orchestrated in response to microenvironmental cues is poorly understood. Here we apply advanced image analysis to reveal ECM-responsive cell behaviors that drive elongation of the Drosophila follicle, a model 3D system in which basement membrane stiffness instructs tissue morphogenesis. Through in toto morphometric analyses of WT and ‘round egg’ mutants, we find that neither changes in average cell shape nor oriented cell division are required for appropriate organ shape. Instead, a major element is a reorientation of elongated cells at the follicle anterior. Polarized reorientation is regulated by mechanical cues from the basement membrane, which are transduced by the Src tyrosine kinase to alter junctional E-cadherin trafficking. This mechanosensitive cellular behavior represents a conserved mechanism that can elongate ‘edgeless’ tubular epithelia in a process distinct from those that elongate bounded, planar epithelia.

scholarly journals Catalyst design for enhanced sustainability through fundamental surface chemistry

2016 ◽  
Vol 374 (2061) ◽  
pp. 20150077 ◽  
Author(s):  
Michelle L. Personick ◽  
Matthew M. Montemore ◽  
Efthimios Kaxiras ◽  
Robert J. Madix ◽  
Juergen Biener ◽  
...  
Keyword(s):  
Surface Science ◽  
Chemical Industry ◽  
Energy Use ◽  
Science Studies ◽  
Experimental Studies ◽  
Integrated Approach ◽  
Catalyst Design ◽  
Van Der Waals Interactions ◽  
Theoretical Modelling ◽  
Chemical Transformations

Decreasing energy consumption in the production of platform chemicals is necessary to improve the sustainability of the chemical industry, which is the largest consumer of delivered energy. The majority of industrial chemical transformations rely on catalysts, and therefore designing new materials that catalyse the production of important chemicals via more selective and energy-efficient processes is a promising pathway to reducing energy use by the chemical industry. Efficiently designing new catalysts benefits from an integrated approach involving fundamental experimental studies and theoretical modelling in addition to evaluation of materials under working catalytic conditions. In this review, we outline this approach in the context of a particular catalyst—nanoporous gold (npAu)—which is an unsupported, dilute AgAu alloy catalyst that is highly active for the selective oxidative transformation of alcohols. Fundamental surface science studies on Au single crystals and AgAu thin-film alloys in combination with theoretical modelling were used to identify the principles which define the reactivity of npAu and subsequently enabled prediction of new reactive pathways on this material. Specifically, weak van der Waals interactions are key to the selectivity of Au materials, including npAu. We also briefly describe other systems in which this integrated approach was applied.

scholarly journals A precise algorithm to detect voids in polydisperse circle packings

2015 ◽  
Vol 471 (2182) ◽  
pp. 20150421 ◽  
Author(s):  
Eckard Specht
Keyword(s):  
A Priori ◽  
Packing Fraction ◽  
Heuristic Methods ◽  
Large Problem ◽  
Optimal Packing ◽  
Contact Graph ◽  
Benchmark Instances ◽  
Circle Packings ◽  
And Shifts ◽  
Particle Packings

Computer simulations are the primary tool for studying polydisperse particle packings quanti- tatively. For the problem of packing N unequal circles in a larger container circle, nothing is known a priori about the optimal packing (i.e. the packing with the highest packing fraction). Simulations usually start from a random initial configuration with the aim to finish with a dense final packing. Unfortunately, smaller circles often get stuck in trapped positions and prevent the rest of the packing from growing larger. Hence, the knowledge of the structure of unoccupied areas or holes inside a packing is important to be able to move trapped circles into free circular places or voids . A novel algorithm is proposed for detecting such voids in two-dimensional arbitrary circle packings by a decomposition of the contact graph. Combined with a clever object jumping strategy and together with other heuristic methods like swaps and shifts, this approach increases the packing fraction ϕ significantly. Its effectiveness for jumping across the maximally random jammed barrier ( ϕ MRJ ≈0.8575 in the large- N limit) for small benchmark instances as well as for large problem sizes (up to N ≈10 3 ) is demonstrated.

scholarly journals Establishment of a continuous model system to study Helicobacter pylori survival in potable water biofilms

2003 ◽  
Vol 47 (5) ◽  
pp. 155-160 ◽  
Author(s):  
N.F. Azevedo ◽  
M. J. Vieira ◽  
C.W. Keevil
Keyword(s):  
Helicobacter Pylori ◽  
Potable Water ◽  
Tap Water ◽  
Close Association ◽  
In Situ Hybridisation ◽  
Molecular Probes ◽  
Epifluorescence Microscopy ◽  
Water Model ◽  
Fluorescence In Situ Hybridisation ◽  
H Pylori

Close association of the pathogen Helicobacter pylori in drinking water biofilms has been suggested. Using a two-stage water model, the survival and development of the pathogen in potable water biofilms was monitored. Filter sterilized tap water was used as the growth medium and the inoculum consisted of a naturally occurring consortium of microorganisms. Biofilms were generated on removable stainless steel coupons that were placed in the second vessel. Novel technology peptide nucleic acid (PNA) molecular probes were used to detect and locate the pathogen in the biofilms. The PNA-labelled oligonucleotide probes were highly specific, and complementary to the helix 6 region of H. pylori 16S rRNA. The pathogen was tracked in the biofilms using epifluorescence microscopy and episcopic differential interference contrast microscopy. Results show that H. pylori can successfully incorporate within biofilms and its presence was detected for up to five days after inoculation. PNA probes provided an easy and quick way of performing fluorescence in situ hybridisation assays in heterogeneous biofilms.

scholarly journals Pseudomonas syringae Responds to the Environment on Leaves by Cell Size Reduction

2003 ◽  
Vol 93 (10) ◽  
pp. 1209-1216 ◽  
Author(s):  
J.-M. Monier ◽  
S. E. Lindow
Keyword(s):  
Size Distribution ◽  
Cell Size ◽  
Pseudomonas Syringae ◽  
Nutrient Availability ◽  
Cultured Cells ◽  
Leaf Surface ◽  
Marker Gene ◽  
Epifluorescence Microscopy ◽  
Cell Multiplication ◽  
Average Cell

The length and volume of cells of the plant-pathogenic bacterium Pseudomonas syringae strain B728a were measured in vitro and with time after inoculation on bean leaf surfaces to assess both the effect of nutrient availability on the cell size of P. syringae and, by inference, the variability in nutrient availability in the leaf surface habitat. Cells of P. syringae harboring a green fluorescent protein marker gene were visualized by epifluorescence microscopy after recovery from leaves or culture and their size was estimated by analysis of captured digital images. The average cell length of bacteria grown on leaves was significantly smaller than that of cultured cells, and approached that of cells starved in phosphate buffer for 24 h. The average length of cells originally grown on King's medium B decreased from ≈ 2.5 to ≈ 1.2 μm by 7 days after inoculation on plants. Some decrease in cell size occurred during growth of cells on leaves and continued for up to 13 days after cell multiplication ceased. Although cultured cells exhibited a normal size distribution, the size of cells recovered from bean plants at various times after inoculation was strongly right-hand skewed and was described by a log-normal distribution. The skewness of the size distribution tended to increase with time after inoculation. The reduced cell size of P. syringae B728a on plants was readily reversible when recovered cells were grown in culture. Direct in situ measurements of cell sizes on leaves confirmed that most cells of P. syringae respond to the leaf environment by reducing their size. The spatial heterogeneity of cell sizes observed on leaves suggest that nutrient availability is quite variable on the leaf surface environment.

Energy Education for the Environment

1987 ◽  
Vol 3 ◽  
pp. 18-21 ◽  
Author(s):  
Peter Davis
Keyword(s):  
Environmental Education ◽  
Energy Use ◽  
Close Association ◽  
World Population ◽  
Conservation Of Energy ◽  
Energy Education ◽  
Positive Attitudes ◽  
Community Influences ◽  
The World ◽  
External Community

AbstractLearning about the utilization, development and perhaps conservation of energy for our expanding world population has long been a part of science curricula. The world “about” is, however, paramount in describing the nature of these courses, and parallels a similar phenomenon observed in numerous so-called environmental education programmes in schools. Despite the close association between energy use expansion and environmental impact, little “energy education for the environment’ has occurred in this country.This paper examines some of the reasons for this situation and highlights the difficulties facing the environmental education teacher who wishes to lead a valid study of energy sources. External community influences, a lack of breath and problems with information availability are identified as factors which contribute to the present status of energy education. It is perhaps fortunate that the majority of students seem to possess positive attitudes towards energy conservation and the environment, and so, hopefully, remain receptive towards improvements in this aspect of environmental education.

Novel Application of Microfluidic Channels in Studying Cell Migration and Reorientation in Response to Direct Current Electric Fields

2002 ◽  
Author(s):  
P. Grace Chao ◽  
Elsa Angelini ◽  
Zhongliang Tang ◽  
Winston Chang ◽  
J. Chloe¨ Bulinski ◽  
...  
Keyword(s):  
Cell Migration ◽  
Electric Fields ◽  
Cell Shape ◽  
Cell Types ◽  
Microfluidic System ◽  
Epifluorescence Microscopy ◽  
Microfluidic Channels ◽  
Embryonic Cells ◽  
Dimethyl Siloxane ◽  
Underlying Mechanisms

Electric fields have been shown to induce cell migration (galvanotaxis) and cell shape changes (galvanotropism) in many cell types, such as neural crest cells, embryonic cells, and chondrocytes [1–3]. In this study, a novel microfluidic system was developed to study individual cellular responses to applied electric fields. These microfabricated channels are made from commercially available poly-dimethyl-siloxane (PDMS). This gas permeable, tough, and transparent polymer provides a sterile tissue culture environment and permits visualization of cells using epifluorescence microscopy. In conjunction with the device, a custom computer program was written to quantify the migratory behavior of cells by analyzing changes in position and cell shape. The flexibility of the channel geometry allows for a wider range of chamber resistance and applied currents (achieving a particular field strength) that may permit further study into the underlying mechanisms of electric field directed cell migration and orientation.

scholarly journals The origin of universal cell shape variability in a confluent epithelial monolayer

2021 ◽  
Author(s):  
Souvik Sadhukhan ◽  
Saroj Kumar Nandi
Keyword(s):  
Cell Fate ◽  
Cell Shape ◽  
Mean Field ◽  
Single Parameter ◽  
Universal Relation ◽  
Average Cell ◽  
Epithelial Monolayers ◽  
Physical Conditions ◽  
Statics And Dynamics ◽  
System Properties

Cell shape is fundamental in biology. The average cell shape can influence crucial biological functions, such as cell fate and division orientation. But cell-to-cell shape variability is often regarded as noise. In contrast, recent works reveal that shape variability in diverse epithelial monolayers follows a nearly universal distribution. However, the origin and implications of this universality are unclear. Here, assuming contractility and adhesion are crucial for cell shape, characterized via aspect ratio (AR), we develop a mean-field analytical theory for shape variability. We find that a single parameter, α, containing all the system-specific details, describes the probability distribution function (PDF) of AR; this leads to a universal relation between the standard deviation and the average of AR. The PDF for the scaled AR is not strictly but almost universal. The functional form is not related to jamming, contrary to common beliefs, but a consequence of a mathematical property. In addition, we obtain the scaled area distribution, described by the parameter µ. We show that α and µ together can distinguish the effects of changing physical conditions, such as maturation, on different system properties. The theory is verified in simulations of two distinct models of epithelial monolayers and agrees well with existing experiments. We demonstrate that in a confluent monolayer, average shape determines both the shape variability and dynamics. Our results imply the cell shape variability is inevitable, where a single parameter describes both statics and dynamics and provides a framework to analyze and compare diverse epithelial systems.

How Cell Shape Affects the Stresses in a Cell Sheet

2000 ◽  
Author(s):  
G. W. Brodland ◽  
Jim H. Veldhuis ◽  
Daniel I-Li Chen
Keyword(s):  
Finite Element ◽  
Finite Elements ◽  
Cell Shape ◽  
Cell Sheet ◽  
Element Formulation ◽  
Analytical Mechanics ◽  
Cell Sheets ◽  
Average Cell ◽  
Real Cell ◽  
A Cell

Abstract Computer simulations and analytical mechanics are used to investigate the mechanics of cell sheets. The simulations are based on a recent finite element formulation [1] in which each cell is modeled using multiple finite elements, and cells can rearrange. Sheet stresses calculated using an analytical expression based on average cell shape are found to agree well with those calculated in the finite element simulations. This is an important step towards the development of constitutive equations to describe real cell sheets.

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