Morphogenesis of the head and face: discussion report

Development ◽  
1988 ◽  
Vol 103 (Supplement) ◽  
pp. 61-62
Author(s):  
S. E. Wedden
Keyword(s):  
Practical Importance ◽  
Craniofacial Development ◽  
Model Systems ◽  
Cell Populations ◽  
Robert Greene ◽  
Test Models ◽  
Models Of Development ◽  
Molecular Aspects ◽  
Evolutionary Aspects

The discussion following the session on evolution and morphogenesis of the head and face concentrated upon two major issues: (1) How can one test models of development, particularly at biochemical and molecular levels? (2) Are the cell populations of the early facial primordia heterogeneous and when might this heterogeneity arise? The Chairman, J. Z. Young (London), had suggested in his introductory remarks that research into craniofacial development was at last becoming more specialized, having previously dealt with principles and model systems rather than with issues of practical importance. The ensuing lectures clearly demonstrated the direction and advances in current research, both in evolutionary aspects and at the level of morphogenesis. Robert Greene (Philadelphia) opened the general discussion. He emphasized the need to examine biochemical and molecular aspects of craniofacial development. In his view, the conceptual chasm between the gene and metazoan embryogenesis was wide and deep and had remained so in recent years.

scholarly journals Finite State Testing and Syntax Testing

2012 ◽  
Vol 3 (1) ◽  
pp. 48-54
Author(s):  
Amandeep Singh ◽  
Harmanjit Singh
Keyword(s):  
Practical Importance ◽  
Finite State Machines ◽  
Model Systems ◽  
Modular Organization ◽  
State Testing ◽  
State Machines ◽  
New Concepts ◽  
Finite State ◽  
New Applications ◽  
Advanced Computer

This paper is concerned with the testing of the software which is being developed in a structured way. The advantages which accrue from a well-structured or modular organization of software depend upon an ability to independently test a module well before the full development of all the modules with which it communicates. This paper describes techniques (Finite State Testing & Syntax Testing) which effectively test various applications. With advanced computer technology, systems are getting larger to fulfill more complicated tasks, however, they are also becoming less reliable. Consequently, testing is an indispensable part of system design and implementation; yet it has proved to be a formidable task for complex systems. This motivates the study of testing finite state machines to ensure the correct functioning of systems and to discover aspects of their behavior. Finite state machines are widely used to model systems in diverse areas, including sequential circuits, certain types of programs, and, more recently, communication protocols. In a testing problem we have a machine about which we lack some information; we would like to deduce this information by providing a sequence of inputs to the machine and observing the outputs produced. Because of its practical importance and theoretical interest, the problem of testing finite state machines have been studied in different areas and at various times. Some old problems which had been open for decades were resolved recently, new concepts and more intriguing problems from new applications emerge. This paper reviews the fundamental problems in testing finite state machines and techniques for solving these problems, tracing progress in the area from its inception to the present and the state of the art. In addition, this paper covers syntax testing which is also called grammar based testing technique for testing various applications where the input data can be described formally.

Demonstration of subpopulations with differing cancer stem cell phenotypes in xenograft and in vitro models of colorectal liver metastases.

2013 ◽  
Vol 31 (4_suppl) ◽  
pp. 394-394
Author(s):  
Dominic E. Sanford ◽  
Andrew Giorgi ◽  
Brian D. Goetz ◽  
Roheena Z. Panni ◽  
William G. Hawkins ◽  
...  
Keyword(s):  
Stem Cells ◽  
Cancer Stem Cells ◽  
Liver Metastases ◽  
In Vitro Models ◽  
Model Systems ◽  
Cell Populations ◽  
Tumor Initiating Cells ◽  
Distinct Cell

394 Background: Tumors are composed of heterogeneous cell populations, some of which demonstrate enhanced tumor-forming capabilities (so-called tumor initiating cells [TIC] or cancer stem cells). In colorectal cancer (CRC), CD133, 44, and 24 are cell surface markers that identify TIC. Therefore, we sought to determine if CRC liver metastases (CRC-LM) form xenografts (in vivo) and cell cultures (in vitro) with TIC markers. Methods: CRC-LM were grafted in NOD/SCID mice and passaged serially. Xenografts were mechanically dissociated and cultured under sphere forming conditions. Flow cytometry was performed for TIC phenotype. Results: 16 of 18 (89%) CRC-LM specimens formed tumors in mice. Xenografts formed EpCAM+ tumors and spheres. The frequency of CD133+, CD44+, and CD133+/CD44+ tumor cells were 55%, 33%, and 23%, respectively. There was a subpopulation of CD133+/CD44+ cells with elevated CD44 expression(CD44hi). This CD133+/CD44hi population was also CD24+; representing 5% of cells. Eight of eleven (73%) xenografts formed spheres in vitro. The frequency of CD133+, CD44+, and CD133+/CD44+ cells were 63%, 47%, and 26%, respectively. CD133+/CD44+/CD24+ cells made up 8% of sphere-forming cells. There was a non-significant trend towards increased frequency of CD133+, CD44+, and CD133/CD44 positive cells in the spheres compared to the xenografts. However, the percentage of CD133+/CD44+/CD24+ cells was significantly increased in spheres relative to xenografts (8% vs. 5%, respectively; p<0.05) (see Table). Conclusions: CRC-LM derived xenografts and spheres are composed of distinct cell populations with differing levels of TIC/cancer stem cells. Sphere cultures may enhance for the most enriched TIC population. Thus, xenografts and sphere cultures are important model systems to further study the importance of cancer stem cells in CRC progression and metastases. [Table: see text]

scholarly journals Transcriptome analysis of somatic cell populations in the Drosophila testis links metabolism and stemness

2020 ◽  
Author(s):  
Silvana Hof-Michel ◽  
Christian Bökel
Keyword(s):  
Stem Cell ◽  
Somatic Cell ◽  
Cell Function ◽  
Expression Patterns ◽  
Tumour Cells ◽  
Model Systems ◽  
Future Research ◽  
Cell Populations ◽  
Cell Physiology ◽  
Data Set

AbstractDue to its simple cellular architecture and genetic tractability the fly testis was one of the first model systems in which stem cell - niche interactions were studied at the molecular level. However, to date there is no comprehensive information on the endogenous, cell type specific transcription profiles associated with either stem cell or differentiated states. Focusing on the somatic lineage we have therefore isolated CySCs, differentiated CyCs, hub cells, and stem cell-like tumour cells overexpressing Zfh1, and have mapped their transcriptomes by RNAseq.Here we report i) that the different somatic cell populations show extensive, genome wide differences in transcription levels, in particular associated with energy metabolism and innate immune signalling, ii) that differential activation of multiple signalling pathways renders Zfh1 overexpressing tumour cells unsuitable for use as a stem cell model, and iii) that the transcriptome data could be successfully used for identifying genes with stem cell specific expression patterns and for predicting aspects of stem cell physiology whose relevance for stem cell function could be validated in preliminary experiments.The present data set should therefore facilitate future research on the interaction of stem cells with their niche using the highly successful fly testis model system.

A Method for Suppression of Pressure Pulse in Fluid-Filled Piping—Part II: Experimental Verification

1992 ◽  
Vol 114 (1) ◽  
pp. 66-73
Author(s):  
Y. W. Shin ◽  
E. F. Bielick ◽  
A. H. Wiedermann ◽  
C. E. Ockert
Keyword(s):  
Experimental Verification ◽  
Pressure Pulse ◽  
Practical Importance ◽  
Companion Paper ◽  
Nondestructive Method ◽  
Experimental Setup ◽  
Practical Applications ◽  
Test Models ◽  
Pressure Pulses ◽  
Theoretical Predictions

A simple, nondestructive method to suppress pressure pulses in fluid-filled piping was proposed and theoretically analyzed in the previous companion paper. In this paper, the proposed method is verified experimentally. The results of experiments performed for the range of parameters of practical importance indicated that the attenuation of pressure pulses was sufficiently large for practical applications and in accordance with the theoretical predictions. This paper describes the experimental setup and the test models of the proposed pulse suppression devices and discusses the experimental results. In particular, the measured attenuation factors (transmitted pressure/incident pressure) are presented and compared with the theoretical predictions.

Programmed Cell Death and Cell Transformation in Craniofacial Development

1995 ◽  
Vol 6 (3) ◽  
pp. 202-217 ◽  
Author(s):  
Charles F. Shuler
Keyword(s):  
Cell Death ◽  
Programmed Cell Death ◽  
Fusion Zone ◽  
Branchial Arch ◽  
Craniofacial Development ◽  
Model Systems ◽  
Epithelial Migration ◽  
Palatal Fusion ◽  
Medial Edge ◽  
Mesenchymal Transformation

Fusion of branchial arch derivatives is an essential component in the development of craniofacial structures. Bilaterally symmetric branchial arch processes fuse in the midline to form the mandible, lips, and palate. The mechanism for fusion requires several different morphologic and molecular events prior to the completion of the mesenchymal continuity between opposing tissue processes. The ectodermal covering of the branchial arches is one of the cell types that has an important role during craniofacial development. The surface epithelia provide the initial adherence between the processes; however, this population of cells is ultimately absent from the fusion zone. The medial edge epithelium of the secondary palatal shelves is one example of such an epithelium that must disappear from the fusion zone of the secondary palate during development in order to complete palatal fusion. The mechanisms for removal of the epithelial cells from the fusion zone could include either programmed cell death, epithelial-mesenchymal transformation, or migration to adjacent epithelia. All three of these fates have been hypothesized as a mechanism for the removal of the palatal medial edge epithelia. The processes of programmed cell death, epithelial-mesenchymal transformation, and epithelial migration are reviewed with respect to both palatal fusion and results reported in other model systems.

Three-component model systems based on egg phosphatidylcholine and cholesterol in the presence of silver nanoparticles

2021 ◽  
Vol 1 (4) ◽  
pp. 67-72
Author(s):  
I. V. Milaeva ◽  
◽  
S. Yu. Zaytsev ◽  
Keyword(s):  
Particle Size ◽  
Practical Importance ◽  
Antimicrobial Properties ◽  
Particle Diameter ◽  
Living Organism ◽  
Model Systems ◽  
Ionic Form ◽  
Average Particle ◽  
Antimicrobial Drugs ◽  
Destructive Effect

Due to the significant increase in the resistance of microorganisms to the action of medicines, primarily antibiotics, the search for other antibacterial agents, including the preparation of silver-based drugs, is extremely important. In small concentrations (50 mcg/l), silver is safe for a living organism, but shows a destructive effect against most bacteria and viruses. The use of silver in the form of nanoparticles (NPAg) can reduce its concentration by hundreds of times compared to the ionic form, while preserving all its antimicrobial properties. An important task is both the development of non-toxic antimicrobial drugs based on silver NP that retain their bactericidal properties and stability over a long period, and the elucidation of the mechanisms of interaction of NPAg with cells and tissues of a living organism. The aim of this work was to study the effect of specified concentrations of NPAg on the structure (size) of particles and surface tension (ST) of model systems obtained on the basis of crude egg phosphatidylcholine and cholesterol. In the work, mixtures of the following lipids were studied in detail: PCe1 – crude phosphatidylcholine, Chol – cholesterol. It was shown that under the influence of middle concentrations of NPAg (up to 0,3–0,5 rel. units) in samples with PCe1 significant changes in the particle size in the mixture occur. Moreover, in mixtures of Chol with PCe1, the addition of NPAg even at a low concentration (0,01 rel. units) already causes a decrease in the average particle diameter by 1,5 times. It has been shown that the presence of sufficiently large NPAg particles (at surface lifetimes from 0,5 to 5 s) gives higher ST values, and a change in the particle size leads to changes in ST: an increase in size – an increase in ST, a decrease in size – a decrease in ST. The equilibrium ST is apparently influenced by the presence of NPAg particles of different sizes in the sample and their ratio. A study of the interaction of NPAg with natural compounds, such as phospholipids, polysaccharides, proteins and peptides, is of great fundamental and practical importance.

scholarly journals Recent Progress Regarding the Evolution and Molecular Aspect of Insect Gall Formation

2021 ◽  
Author(s):  
Antoine Guiget ◽  
Seiji Takeda ◽  
Tomoko Hirano ◽  
Ohishima Issei ◽  
Masa H. Sato
Keyword(s):  
Life Histories ◽  
Recent Progress ◽  
Molecular Mechanisms ◽  
Model Organisms ◽  
Gall Formation ◽  
Insect Gall ◽  
In The Wild ◽  
Molecular Aspects ◽  
Gall Induction ◽  
Evolutionary Aspects

Galls are characteristic plant structures formed by hypertrophy (excessive increase in cell size) and/or hyperplasia (cell proliferation) induced by parasitic or pathogenic organisms. Insects are a major inducer of galls, and insect galls can occur on plant leaves, stems, floral buds, flowers, fruits, or roots. Many of these exhibit unique shapes, providing shelter and nutrients to the insects. To form unique gall structures, all-inducing insects are believed to secrete certain effector molecules and hijack host developmental programs. However, the molecular mechanisms of insect gall induction and development is still largely unknown because of the difficulty of studying non-model plants in the wild. Recent progress in next-generation sequencing has allowed us to determine the structure of biological processes in non-model organisms, including gall-inducing insects and their host plants. In this review, we first summarize the evolutionary aspects of gall-inducing life histories and their adaptive significance for insects and plants. Then, we briefly summarize recent progress regarding the molecular aspects of insect gall formation.

scholarly journals Self-organization of human dorsal-ventral forebrain structures by light induced SHH

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Riccardo De Santis ◽  
Fred Etoc ◽  
Edwin A. Rosado-Olivieri ◽  
Ali H. Brivanlou
Keyword(s):  
In Vitro Model ◽  
Light Stimulus ◽  
Embryonic Stem ◽  
The Self ◽  
Model Systems ◽  
Self Organization ◽  
Light Stimulation ◽  
Vitro Model ◽  
Molecular Aspects

AbstractOrganizing centers secrete morphogens that specify the emergence of germ layers and the establishment of the body’s axes during embryogenesis. While traditional experimental embryology tools have been instrumental in dissecting the molecular aspects of organizers in model systems, they are impractical in human in-vitro model systems to dissect the relationships between signaling and fate along embryonic coordinates. To systematically study human embryonic organizer centers, we devised a collection of optogenetic ePiggyBac vectors to express a photoactivatable Cre-loxP recombinase, that allows the systematic induction of organizer structures by shining blue-light on human embryonic stem cells (hESCs). We used a light stimulus to geometrically confine SHH expression in neuralizing hESCs. This led to the self-organization of mediolateral neural patterns. scRNA-seq analysis established that these structures represent the dorsal-ventral forebrain, at the end of the first month of development. Here, we show that morphogen light-stimulation is a scalable tool that induces self-organizing centers.

scholarly journals Interplay of Eph-Ephrin Signalling and Cadherin Function in Cell Segregation and Boundary Formation

2021 ◽  
Vol 9 ◽  
Author(s):  
David G. Wilkinson
Keyword(s):  
Receptor Activation ◽  
Craniofacial Development ◽  
Cell Populations ◽  
Eph Receptors ◽  
Eph Receptor ◽  
Cortical Tension ◽  
Differential Adhesion ◽  
Distinct Cell ◽  
The Difference ◽  
Cell Segregation

The segregation of distinct cell populations to form sharp boundaries is crucial for stabilising tissue organisation, for example during hindbrain segmentation in craniofacial development. Two types of mechanisms have been found to underlie cell segregation: differential adhesion mediated by cadherins, and Eph receptor and ephrin signalling at the heterotypic interface which regulates cell adhesion, cortical tension and repulsion. An interplay occurs between these mechanisms since cadherins have been found to contribute to Eph-ephrin-mediated cell segregation. This may reflect that Eph receptor activation acts through multiple pathways to decrease cadherin-mediated adhesion which can drive cell segregation. However, Eph receptors mainly drive cell segregation through increased heterotypic tension or repulsion. Cadherins contribute to cell segregation by antagonising homotypic tension within each cell population. This suppression of homotypic tension increases the difference with heterotypic tension triggered by Eph receptor activation, and it is this differential tension that drives cell segregation and border sharpening.

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