Computational Model for the Transition From Peristaltic to Pulsatile Flow in the Embryonic Heart Tube

Early in development, the heart is a single muscle-wrapped tube without formed valves. Yet survival of the embryo depends on the ability of this tube to pump blood at steadily increasing rates and pressures. Developmental biologists historically have speculated that the heart tube pumps via a peristaltic mechanism, with a wave of contraction propagating from the inflow to the outflow end. Physiological measurements, however, have shown that the flow becomes pulsatile in character quite early in development, before the valves form. Here, we use a computational model for flow though the embryonic heart to explore the pumping mechanism. Results from the model show that endocardial cushions, which are valve primordia arising near the ends of the tube, induce a transition from peristaltic to pulsatile flow. Comparison of numerical results with published experimental data shows reasonably good agreement for various pressure and flow parameters. This study illustrates the interrelationship between form and function in the early embryonic heart.

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Computational model for conceptual design based on extended function logic

Artificial intelligence for engineering design analysis and manufacturing ◽

10.1017/s089006040000161x ◽

1996 ◽

Vol 10 (4) ◽

pp. 255-274 ◽

Cited By ~ 21

Author(s):

Robert H. Sturges ◽

Kathleen O'Shaughnessy ◽

Mohammed I. Kilani

Keyword(s):

Computational Model ◽

Conceptual Design ◽

Information Structure ◽

Value Engineering ◽

Synthesis Process ◽

Function Evaluation ◽

Value Analysis ◽

Form And Function ◽

And Function ◽

Extended Function

AbstractFunction logic methods have been successfully used in Value Analysis (VA) and Value Engineering (VE) for several decades. This functional approach attempts to provide a common language for specialists in multiple domains. This paper describes an extension of function logic that assists in systematic identification of design functions, allocations, and their interrelations. Our approach identifies a three-level function/allocation/component information structure to represent the state of the design. We illustrate new types of links that exist between functions and the effect of these on the representation of the interrelated functions. These linkages provide new pathways for design information and function evaluation through allocation arithmetic and supported functions. A computational model of the conceptual design process is proposed based on the extended function logic design representation. An outline of the inputs, outputs and operations on form and function variables is given as a step prior to the synthesis process. We illustrate, by example, the process of translating functional representations across specialist domains. Finally, a computer-based aid to developing functional models is described.

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Fashioning the vertebrate heart: earliest embryonic decisions

Development ◽

10.1242/dev.124.11.2099 ◽

1997 ◽

Vol 124 (11) ◽

pp. 2099-2117 ◽

Cited By ~ 27

Author(s):

M.C. Fishman ◽

K.R. Chien

Keyword(s):

Caenorhabditis Elegans ◽

Progenitor Cells ◽

Cell Fate ◽

Cellular Differentiation ◽

Higher Order ◽

Pattern Generation ◽

Heart Tube ◽

Form And Function ◽

Heart Field ◽

And Function

Our goal here is to set out the types of unitary decisions made by heart progenitor cells, from their appearance in the heart field until they form the simple heart tube. This provides a context to evaluate cell fate, lineage and, finally, morphogenetic decisions that configure global heart form and function. Some paradigms for cellular differentiation and for pattern generation may be borrowed from invertebrates, but neither Drosophila nor Caenorhabditis elegans suffice to unravel higher order decisions. Genetic analyses in mouse and zebrafish may provide one entrance to these pathways.

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Emergence of Form and Function in the Embryonic Heart

The Emergency of Order in Developing Systems ◽

10.1016/b978-0-12-395711-5.50015-3 ◽

1968 ◽

pp. 208-250 ◽

Cited By ~ 2

Author(s):

ROBERT L. DEHAAN

Keyword(s):

Embryonic Heart ◽

Form And Function ◽

And Function

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Theheartstringsmutation in zebrafish causes heart/fin Tbx5 deficiency syndrome

Development ◽

10.1242/dev.129.19.4635 ◽

2002 ◽

Vol 129 (19) ◽

pp. 4635-4645 ◽

Cited By ~ 7

Author(s):

Deborah M. Garrity ◽

Sarah Childs ◽

Mark C. Fishman

Keyword(s):

Large Family ◽

Deficiency Syndrome ◽

Heart Tube ◽

Pectoral Fin ◽

Lethal Mutant ◽

Cardiac Defects ◽

Form And Function ◽

Whole Heart ◽

And Function ◽

Tbx5 Gene

Holt-Oram syndrome is one of the autosomal dominant human ‘heart-hand’ disorders, with a combination of upper limb malformations and cardiac defects. Holt-Oram syndrome is caused by mutations in the TBX5 gene, a member of a large family of T-box transcription factors that play important roles in cell-type specification and morphogenesis. In a screen for mutations affecting zebrafish cardiac function, we isolated the recessive lethal mutant heartstrings, which lacks pectoral fins and exhibits severe cardiac dysfunction, beginning with a slow heart rate and progressing to a stretched, non-functional heart.We mapped and cloned the heartstrings mutation and find it to encode the zebrafish ortholog of the TBX5 gene. The heartstrings mutation causes premature termination at amino acid 316. Homozygous mutant embryos never develop pectoral fin buds and do not express several markers of early fin differentiation. The total absence of any fin bud differentiation distinguishes heartstrings from most other mutations that affect zebrafish fin development, suggesting that Tbx5 functions very early in the pectoral fin induction pathway. Moderate reduction of Tbx5 by morpholino causes fin malformations, revealing an additional early requirement for Tbx5 in coordinating the axes of fin outgrowth. The heart of heartstrings mutant embryos appears to form and function normally through the early heart tube stage, manifesting only a slight bradycardia compared with wild-type siblings. However, the heart fails to loop and then progressively deteriorates, a process affecting the ventricle as well as the atrium.Relative to mammals, fish require lower levels of Tbx5 to produce malformed appendages and display whole-heart rather than atrial-predominant cardiac defects. However, the syndromic deficiencies of tbx5 mutation are remarkably well retained between fish and mammals.

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Scanning tunneling microscopy (STM) of DNA and RNA

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100152148 ◽

1989 ◽

Vol 47 ◽

pp. 34-35

Author(s):

Patricia G. Arscott ◽

Gil Lee ◽

Victor A. Bloomfield ◽

D. Fennell Evans

Keyword(s):

Molecular Structures ◽

Inorganic Materials ◽

Resolving Power ◽

Scanning Tunneling ◽

Tunneling Microscopy ◽

Form And Function ◽

Dna And Rna ◽

Calf Thymus ◽

And Function ◽

The Relationship

STM is one of the most promising techniques available for visualizing the fine details of biomolecular structure. It has been used to map the surface topography of inorganic materials in atomic dimensions, and thus has the resolving power not only to determine the conformation of small molecules but to distinguish site-specific features within a molecule. That level of detail is of critical importance in understanding the relationship between form and function in biological systems. The size, shape, and accessibility of molecular structures can be determined much more accurately by STM than by electron microscopy since no staining, shadowing or labeling with heavy metals is required, and there is no exposure to damaging radiation by electrons. Crystallography and most other physical techniques do not give information about individual molecules.We have obtained striking images of DNA and RNA, using calf thymus DNA and two synthetic polynucleotides, poly(dG-me5dC)·poly(dG-me5dC) and poly(rA)·poly(rU).

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