Mechanical evaluation of theories of neurulation using computer simulations

Development ◽  
1993 ◽  
Vol 118 (3) ◽  
pp. 1013-1023 ◽  
Author(s):  
D. A. Clausi ◽  
G. W. Brodland
Keyword(s):  
Computer Simulations ◽  
Driving Forces ◽  
Shape Change ◽  
Three Dimensional ◽  
Dorsal Surface ◽  
Neural Plate ◽  
Neural Tube Closure ◽  
Amphibian Embryo ◽  
Axial Elongation ◽  
Shape Changes

Current theories about the forces that drive neurulation shape changes are evaluated using computer simulations. Custom, three-dimensional, finite element-based computer software is used. The software draws on current engineering concepts and makes it possible to construct a ‘virtual’ embryo with any user-specified mechanical properties. To test a specific hypothesis about the forces that drive neurulation, the whole virtual embryo or any selected part of it is ascribed with the force generators specified in the hypothesis. The shape changes that are produced by these forces are then observed and compared with experimental data. The simulations demonstrate that, when uniform, isotropic circumferential microfilament bundle (CMB) constriction and cephalocaudal (axial) elongation act together on a circular virtual neural plate, it becomes keyhole shaped. When these forces act on a spherical (amphibian) embryo, dorsal surface flattening occurs. Simulations of transverse sections further show that CMB constriction, acting with or without axial elongation, can produce numerous salient transverse features of neurulation. These features include the sequential formation of distinct neural ridges, narrowing and thickening of the neural plate, skewing just medial to the ridges, ‘hinge’ formation and neural tube closure. No region-specific ‘programs’ or non-mechanical cell-cell communications are used. The increase in complexity results entirely from mechanical interactions. The transverse simulations show how changes to the driving forces would affect the patterns of shape change produced. Hypotheses regarding force generation by microtubules, intercellular adhesions and forces extrinsic to the neural plate are also evaluated. The simulations show that these force-generating mechanisms do not, by themselves, produce shape changes that are consistent with normal development. The simulations support the concept of cooperation of forces and suggest that neurulation is robust because redundant force generating mechanisms exist.

scholarly journals Hallmarks of primary neurulation are conserved in the zebrafish forebrain

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Jonathan M. Werner ◽  
Maraki Y. Negesse ◽  
Dominique L. Brooks ◽  
Allyson R. Caldwell ◽  
Jafira M. Johnson ◽  
...  
Keyword(s):  
Neural Tube ◽  
Time Lapse ◽  
Neural Plate ◽  
Neural Tube Closure ◽  
Developmental Studies ◽  
Underlying Causes ◽  
The Central Nervous System ◽  
Resolution Imaging ◽  
Fold Formation ◽  
Anterior Neural Plate

AbstractPrimary neurulation is the process by which the neural tube, the central nervous system precursor, is formed from the neural plate. Incomplete neural tube closure occurs frequently, yet underlying causes remain poorly understood. Developmental studies in amniotes and amphibians have identified hingepoint and neural fold formation as key morphogenetic events and hallmarks of primary neurulation, the disruption of which causes neural tube defects. In contrast, the mode of neurulation in teleosts has remained highly debated. Teleosts are thought to have evolved a unique mode of neurulation, whereby the neural plate infolds in absence of hingepoints and neural folds, at least in the hindbrain/trunk where it has been studied. Using high-resolution imaging and time-lapse microscopy, we show here the presence of these morphological landmarks in the zebrafish anterior neural plate. These results reveal similarities between neurulation in teleosts and other vertebrates and hence the suitability of zebrafish to understand human neurulation.

Residual-limb shape change: three-dimensional CT scan measurement and depiction in vivo.

Radiology ◽  
1996 ◽  
Vol 200 (3) ◽  
pp. 843-850 ◽  
Author(s):  
K E Smith ◽  
P K Commean ◽  
M W Vannier
Keyword(s):  
Ct Scan ◽  
Shape Change ◽  
Three Dimensional ◽  
Residual Limb

scholarly journals From three-dimensional weavings to swollen corneocytes

2011 ◽  
Vol 8 (62) ◽  
pp. 1274-1280 ◽  
Author(s):  
Myfanwy E. Evans ◽  
Stephen T. Hyde
Keyword(s):  
Three Dimensional ◽  
Simple Shape ◽  
Outermost Layer ◽  
One Dimensional ◽  
Periodic Arrays ◽  
Novel Technique ◽  
Structural Rigidity ◽  
Mammalian Skin ◽  
Shape Changes ◽  
The Ideal

A novel technique to generate three-dimensional Euclidean weavings, composed of close-packed, periodic arrays of one-dimensional fibres, is described. Some of these weavings are shown to dilate by simple shape changes of the constituent fibres (such as fibre straightening). The free volume within a chiral cubic example of a dilatant weaving, the ideal conformation of the G 129 weaving related to the Σ + rod packing, expands more than fivefold on filament straightening. This remarkable three-dimensional weaving, therefore, allows an unprecedented variation of packing density without loss of structural rigidity and is an attractive design target for materials. We propose that the G 129 weaving (ideal Σ + weaving) is formed by keratin fibres in the outermost layer of mammalian skin, probably templated by a folded membrane.

Three-Dimensional Evaluation of Breast Augmentation and the Influence of Anatomic and Round Implants on Operative Breast Shape Changes

2012 ◽  
Vol 36 (4) ◽  
pp. 879-887 ◽  
Author(s):  
Laszlo Kovacs ◽  
Maximilian Eder ◽  
Alexander Zimmermann ◽  
Daniel Müller ◽  
Tibor Schuster ◽  
...  
Keyword(s):  
Breast Augmentation ◽  
Three Dimensional ◽  
Breast Shape ◽  
Shape Changes

The Dependence of the Cellular Transformation of the Competent Ectoderm on Temporal Relationships in the Induction Process

Development ◽  
1958 ◽  
Vol 6 (3) ◽  
pp. 479-485
Author(s):  
Sulo Toivonen
Keyword(s):  
Nervous System ◽  
Early Development ◽  
Cellular Transformation ◽  
Neural Plate ◽  
Amphibian Embryo ◽  
Temporal Relationships ◽  
Induction Process ◽  
New Hypothesis

In 1952, Nieuwkoop et al. suggested a new hypothesis concerning the induction phenomenon determining the early development of the amphibian embryo. This hypothesis was based on cleverly planned experiments in which folds of competent epidermis were transplanted on to different regions of the neural plate of the neurula. According to this hypothesis, the invaginating archenteron roof is supposed first to activate the overlying ectoderm, enabling it to develop autonomously to archencephalon and its derivatives. This same archenteron roof is later thought to exert a second effect, which they called transformation. This second action is considered responsible for modifying the differentiation tendencies of the activated archencephalon so as to result in structures typical of more caudal regions of the nervous system. This process is regarded as a quantitative one, so that with increasing strength of transformation, the differentiation tendencies would be progressively more caudal.

Autonomy and non-autonomy in Drosophila mesoderm determination and morphogenesis

Development ◽  
1994 ◽  
Vol 120 (4) ◽  
pp. 853-859 ◽  
Author(s):  
M. Leptin ◽  
S. Roth
Keyword(s):  
Cell Shape ◽  
Shape Change ◽  
Developmental Program ◽  
Cell Shape Change ◽  
Ventral Furrow ◽  
Large Numbers ◽  
The Individual ◽  
Mutant Cells ◽  
Transplantation Experiments ◽  
Shape Changes

The mesoderm in Drosophila invaginates by a series of characteristic cell shape changes. Mosaics of wild-type cells in an environment of mutant cells incapable of making mesodermal invaginations show that this morphogenetic behaviour does not require interactions between large numbers of cells but that small patches of cells can invaginate independent of their neighbours' behaviour. While the initiation of cell shape change is locally autonomous, the shapes the cells assume are partly determined by the individual cell's environment. Cytoplasmic transplantation experiments show that areas of cells expressing mesodermal genes ectopically at any position in the egg form an invagination. We propose that ventral furrow formation is the consequence of all prospective mesodermal cells independently following their developmental program. Gene expression at the border of the mesoderm is induced by the apposition of mesodermal and non-mesodermal cells.

scholarly journals Prospects of Nanostructure-Based Solar Cells for Manufacturing Future Generations of Photovoltaic Modules

2009 ◽  
Vol 2009 ◽  
pp. 1-13 ◽  
Author(s):  
N. Gupta ◽  
G. F. Alapatt ◽  
R. Podila ◽  
R. Singh ◽  
K. F. Poole
Keyword(s):  
Solar Cells ◽  
Heat Dissipation ◽  
Driving Forces ◽  
Three Dimensional ◽  
Solar Spectrum ◽  
Future Generation ◽  
Theoretical Work ◽  
Future Generations ◽  
Pv Modules ◽  
Quantum Phenomena

We present a comprehensive review on prospects for one-, two-, or three-dimensional nanostructure-based solar cells for manufacturing the future generation of photovoltaic (PV) modules. Reducing heat dissipation and utilizing the unabsorbed part of the solar spectrum are the key driving forces for the development of nanostructure-based solar cells. Unrealistic assumptions involved in theoretical work and the tendency of stretching observed experimental results are the primary reasons why quantum phenomena-based nanostructures solar cells are unlikely to play a significant role in the manufacturing of future generations of PV modules. Similar to the invention of phase shift masks (to beat the conventional diffraction limit of optical lithography) clever design concepts need to be invented to take advantage of quantum-based nanostructures. Silicon-based PV manufacturing will continue to provide sustained growth of the PV industry.

scholarly journals Geometric auxetics

2015 ◽  
Vol 471 (2184) ◽  
pp. 20150033 ◽  
Author(s):  
Ciprian Borcea ◽  
Ileana Streinu
Keyword(s):  
Computer Simulations ◽  
Mathematical Theory ◽  
Three Dimensional ◽  
Numerical Approximations ◽  
Periodic Frameworks ◽  
Infinite Supply

We formulate a mathematical theory of auxetic behaviour based on one-parameter deformations of periodic frameworks. Our approach is purely geome- tric, relies on the evolution of the periodicity lattice and works in any dimension. We demonstrate its usefulness by predicting or recognizing, without experiment, computer simulations or numerical approximations, the auxetic capabilities of several well-known structures available in the literature. We propose new principles of auxetic design and rely on the stronger notion of expansive behaviour to provide an infinite supply of planar auxetic mechanisms and several new three-dimensional structures.

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