In 1972, we proposed a theory of biological pattern formation in which concentration maxima of pattern forming substances are generated through local self- enhancement in conjunction with long range inhibition. Since then, much evidence in various developmental systems has confirmed the importance of autocatalytic feedback loops combined with inhibitory interaction. Examples are found in the formation of embryonal organizing regions, in segmentation, in the polarization of individual cells, and in gene activation. By computer simulations, we have (...) shown that the theory accounts for much of the regulatory phenomena observed, including signalling to regenerate removed parts. These self- regulatory features contribute to making development robust and error-tolerant. Furthermore, the resulting pattern is, to a large extent, independent of the details provided by initial conditions and inducing signals. (shrink)

The veins are cuticular structures that differentiate in precise patterns in insect wings. The genetic and molecular basis of vein pattern formation in Drosophila melanogaster is beginning to be unravelled with the identification and characterisation of the gene products that position the veins and direct their differentiation. Genes affecting the veins fall into two groups: transcriptional regulators that specify individual veins, and members of signalling pathways involved in patterning and differentiation of the veins. The elaboration of the vein (...) pattern is progressive in time and requires the coordinated activities of these signalling pathways and the transcription factors regulated by them. Although the network of genetic interactions that determine vein cell fate is well understood, very little is known about the cellular biology underlying the acquisition of vein histotype. BioEssays 25:443–451, 2003. © 2003 Wiley Periodicals, Inc. (shrink)

One of the earliest and most‐fundamental pattern‐ formation events in embryonic development is endoderm and mesoderm specification. In sea urchin embryos, this process begins with blimp1 and wnt8 gene expression at the vegetal pole as soon as embryonic transcription begins. Shortly afterwards, wnt8/blimp1 expression spreads to the adjacent ring of mesoderm progenitor cells and is extinguished in the vegetal‐most cells. A little later, the ring of wnt8/blimp1 activity moves out of the mesoderm progenitors and into the neighboring endoderm (...) cells. Remarkably, this moving ring of gene expression has now been shown to be controlled entirely by transcriptional cis‐regulatory logic.1. BioEssays 30:412–417, 2008. © 2008 Wiley Periodicals, Inc. (shrink)

A theoretical model is presented for pattern formation in an epithelium. The epithelial model consists of a thin, incompressible, viscoelastic membrane on an elastic foundation (substrate), with the component cells assumed to have active contractile properties similar to those of smooth muscle. The analysis includes the effects of large strains and material nonlinearity, and the governing equations were solved using finite differences. Deformation patterns form when the cells activate while lying on the descending limb of their total (active (...) + passive) stress-stretch curve. Various one-dimensional and two-dimensional simulations illustrate the effects of spatial and temporal variations in passive stiffness, as well as the effects of foundation stiffness and stretch activation. The model can be used to examine the mechanical aspects of pattern formation in morphogenetic processes such as angiogenesis and myocardial trabeculation. (shrink)

The paper addresses the formation of striking patterns within originally near-homogenous tissue, the process prototypical for embryology, and represented in particularly purist form by cut sections of hydra regenerating, by internal reorganisation of the pre-existing tissue, a complete animal with head and foot. The essential requirements are autocatalytic, self-enhancing activation, combined with inhibitory or depletion effects of wider range – “lateral inhibition”. Not only de-novo-pattern formation, but also well known, striking features of developmental regulation such as induction, (...) inhibition, and proportion regulation can be explained on this basis. The theory provides a mathematical recipe for the construction of molecular models with criteria for the necessary non-linear interactions. It has since been widely applied to different developmental processes. (shrink)

Recent findings suggest that C. elegans, albeit displaying an invariant cell lineage for embryonic development, uses the same basic strategy for embryogenesis as other organisms. The early embryo is regionalised by cell‐cell interactions.

The specification of specific and often unique fates to individual cells as a function of their position within a developing organism is a fundamental process during the development of multicellular organisms. The development of the Drosophila embryonic central nervous system serves as an excellent model system in which to clarify the developmental mechanisms that link pattern formation to cell-type specification. The Drosophila embryonic central nervous system develops from a set of neural stem cells termed neuroblasts. Neuroblasts arise from (...) the ectoderm in an invariant pattern, and each neuroblast acquires a unique fate based on its position within this pattern. Two groups of genes recently have been demonstrated to govern the individual fate specification of neuroblasts. One group, the segment polarity genes, enables neuroblasts that develop in different anteroposterior positions to acquire different fates. The second group, referred to as the columnar genes, ensures that neuroblasts that develop in different dorsoventral domains assume different fates. When integrated, the activities of the segment polarity and columnar genes create a Cartesian coordinate system that bestows unique fates to individual neuroblasts as a function of their position of formation within the ectoderm. BioEssays 1999;21:922–931. © 1999 John Wiley & Sons, Inc. (shrink)

The specification of specific and often unique fates to individual cells as a function of their position within a developing organism is a fundamental process during the development of multicellular organisms. The development of the Drosophila embryonic central nervous system serves as an excellent model system in which to clarify the developmental mechanisms that link pattern formation to cell-type specification. The Drosophila embryonic central nervous system develops from a set of neural stem cells termed neuroblasts. Neuroblasts arise from (...) the ectoderm in an invariant pattern, and each neuroblast acquires a unique fate based on its position within this pattern. Two groups of genes recently have been demonstrated to govern the individual fate specification of neuroblasts. One group, the segment polarity genes, enables neuroblasts that develop in different anteroposterior positions to acquire different fates. The second group, referred to as the columnar genes, ensures that neuroblasts that develop in different dorsoventral domains assume different fates. When integrated, the activities of the segment polarity and columnar genes create a Cartesian coordinate system that bestows unique fates to individual neuroblasts as a function of their position of formation within the ectoderm. BioEssays 1999;21:922–931. © 1999 John Wiley & Sons, Inc. (shrink)

The spontaneous organization of collective activities in animal groups and societies has attracted a considerable amount of attention over the last decade. This kind of coordination often permits group‐living species to achieve collective tasks that are far beyond single individuals' capabilities. In particular, a key benefit lies in the integration of partial knowledge of the environment at the collective level. In this contribution, we discuss various self‐organization phenomena in animal swarms and human crowds from the point of view of information (...) exchange among individuals. In particular, we provide a general description of collective dynamics across species and introduce a classification of these dynamics not only with respect to the way information is transferred among individuals but also with regard to the knowledge processing at the collective level. Finally, we highlight the fact that the individual’s ability to learn from past experiences can have a feedback effect on the collective dynamics, as experienced with the development of behavioral conventions in pedestrian crowds. (shrink)

Hydractinia echinata is a marine colonial hydroid, a relative of the more widely known Hydra. In contrast to Hydra, embryogenesis, metamorphosis and colony growth in Hydractinia are experimentally accessible and therefore, provide an ideal model system for investigating the biochemical basis of pattern formation. In particular, the processes involved in the transformation of the drop‐shaped freely swimming larva into a sessile tube‐shaped polyp are easily monitored, because this transfomation can be induced by application of various substances. Our results (...) indicate that the internal level of S‐adenosylmethionine (SAM), potentially the most important methyl donor in transmethylation processes, plays a key role in the onset of metamorphosis. It is also proposed that the internal level of SAM plays a pivotal role in the proportioning and spacing of polyps within the colony. (shrink)

The Drosophila anterior‐posterior pattern genes of the terminal class, particularly the tailless gene, affect structures derived from the acron and the tail region of the embryo. These domains correspond in position and function to asegmental domains at the termini of annelids and more primitive insect embryos. This suggests that terminal genes in Drosophila may have originated in an ancestor common to both annelids and arthropods, and thus that the specification of termini in these metameric organisms is an ancient, evolutionarily (...) conserved process. (shrink)

We present a technique for the analysis of pattern formation by a class of models for the formation of ocular dominance stripes in the striate cortex of some mammals. The method, which employs the adiabatic approximation to derive a set of ordinary differential equations for patterning modes, has been successfully applied to reaction-diffusion models for striped patterns [1]. Models of ocular dominance stripes have been studied [2,3] by computation, or by linearization of the model equations. These techniques (...) do not provide a rationale for the origin of the stripes. We show here that stripe formation is a non-linear property of the models. Our analysis indicates that stripe selection is closely linked to a property in the dynamics of the models which arises from a symmetry between ipsilateral and contralateral synapses to the visual cortex of a given hemisphere. (shrink)

The control of pattern formation and the significance of gradients is reconsidered on the basis of the concept of cell sociology (which takes into account continuous exchange of information between cells and the possibility of autonomous progression in differentiation). Not all traits of a pattern are imposed by a single prepattern, which would be an organized molecular framework or a gradient. Patterns are unfolded in steps; these are readjustments of a cell population to intrinsic and extrinsic changes (...) in cell activities. Prepatterns are the various components of the programme of every readjustment and are established by information of various origins, which can be dissociated experimentally: determination (elementary social prepattern), pre-existing organization (antecedent pp.), surrounding cell populations (environmental pp.), position among other tissues (positional pp.) and the organization of inducers (imprinting pp.). Every transitory pattern formed during a readjustment serves as antecedent pp. during the next readjustment. Covert graded patterns result from various aspects of the social behaviour of cells (growth, aggregation, induction, cell renewal) and may serve as antecedent or imprinting prepatterns. They appear as water marks in the final patterns, or generate overt graded patterns. They also manifest themselves in temporal patterns, particularly in gradients of relative growth. (shrink)

Members of the astacin family of metalloproteinases such as human bone morphogenetic protein 1 (BMP‐1) have previously been linked to cell differentiation and pattern formation during development through a proposed role in the activation of latent growth factors of the TGF‐β superfamily. Recent finding(1) indicate that BMP‐1 is identical to pro‐collagen C‐proteinase, which is a metalloproteinase involved in extracellular matrix (ECM) formation. This observation suggests that a functional link may exist between astacin metalloproteinases, growth factors and cell (...) differentiation and pattern formation during development. Taken together, current studies indicate that BMP‐1 and possibly other astacin metalloproteinases are multifunctional enzymes that act directly on growth factors and the ECM. In combination, these dual actions would have profound effects on developmental processes. (shrink)

Retinoids are low molecular weight, lipophilic derivatives of vitamin A which have a profound effect upon the development of a diverse array of animals. Here, I review these effects on Invertebrates: a colonial hydroid, a colonial ascidian, and Vertebrates: the regenerating amphibian limb, the developing chick limb bud, the regenerating amphibian tail, the anteroposterior axis of the early embryo, the developing chick embryo skin. There is a striking uniformity of effect of retinoids on pattern formation when applied to (...) these diverse organisms. The majority react by being posteriorized in their development, although additional effects can also be seen. Several hypotheses which can explain these results are discussed along with the deduction that they lead to: retinoids may be components of a universal developmental mechanism or they may simply act in a similar way to alter a universal developmental mechanism. In either case the experimental analysis of retinoid effects on development has important implications for the evolution of developmental mechanisms. (shrink)

Morphogen gradient theories have enjoyed considerable popularity since the beginning of this century, but conclusive evidence for a role of morphogens in controlling multicellular development has been elusive. Recently, work on three secreted signalling proteins, Activin in Xenopus, and Wingless and Dpp in Drosophila, has stongly suggested that these proteins function as morphogens. In order to define a factor as a morphogen, it is necessary to show firstly, that it has a direct effect on target cells and secondly, that it (...) affects the development of target cells in a concentration‐dependent manner. With these criteria in mind, the evidence available for a variety of proposed morphogens is discussed. While the evidence is not conclusive in most of the cases considered, there is a strong case in favour of the three proteins mentioned above, which suggests that morphogens are potentially of general importance in controlling the development of multicellular organisms. (shrink)

This article is devoted to the characterization of the basin of attraction of pattern solutions for some slow–fast reaction–diffusion systems with a symmetric property and an underlying oscillatory reaction part. We characterize some subsets of initial conditions that prevent the dynamical system to evolve asymptotically toward solutions which are homogeneous in space. We also perform numerical simulations that illustrate theoretical results and give rise to symmetric and non-symmetric pattern solutions. We obtain these last solutions by choosing particular random (...) initial conditions. (shrink)

Endosperm is emerging as a system for investigating the genetic control of wall placement and deposition in plant development. Development of endosperm progresses in distinct stages from a wall‐less syncytial stage to a cellular stage that is entirely typical of plant meristems where the division plane is predicted by a preprophase band of microtubules (PPB) and cytokinesis is completed by formation of a cell plate in association with a phragmoplast. Four developmentally different types of walls, each associated with a (...) different microtubule system, are sequentially produced: (1) free growing walls deposited in the absence of mitosis and phragmoplasts; (2) walls guided by cytoplasmic phragmoplasts formed adventitiously in the absence of mitosis; (3) walls formed by interzonal phragmoplasts in a cell cycle that lacks PPBs; and (4) wall deposition driven by interzonal phragmoplasts in a cycle that includes PPBs. We are using methods of differential screening to isolate cDNA clones corresponding in temporal and spatial pattern to the types of wall development, and are studying mutants for clues to the genetic controls of wall development. (shrink)

The Drosophila embryo provides a useful model system to study the mechanisms that lead to pattern and cell diversity in the central nervous system (CNS). The Drosophila CNS, which encompasses the brain and the ventral nerve cord, develops from a bilaterally symmetrical neuroectoderm, which gives rise to neural stem cells, called neuroblasts. The structure of the embryonic ventral nerve cord is relatively simple, consisting of a sequence of repeated segmental units (neuromeres), and the mechanisms controlling the formation and (...) specification of the neuroblasts that form these neuromeres are quite well understood. Owing to the much higher complexity and hidden segmental organization of the brain, our understanding of its development is still rudimentary. Recent investigations on the expression and function of proneural genes, segmentation genes, dorsoventral‐patterning genes and a number of other genes have provided new insight into the principles of neuroblast formation and patterning during embryonic development of the fly brain. Comparisons with the same processes in the trunk help us to understand what makes the brain different from the ventral nerve cord. Several parallels in early brain patterning between the fly and the vertebrate systems have become evident. BioEssays 26:739–751, 2004. © 2004 Wiley Periodicals, Inc. (shrink)

El artículo presenta un resultado de investigación doctoral realizada entre septiembre/2013 y enero/2016, sobre la formación de la competencia investigativa en el estudiante de Psicología de la modalidad semipresencial de estudios universitarios. A partir del empleo de los métodos analítico-sintético, análisis documental y la modelación sistémico estructural funcional, se abordan las particularidades de la competencia objeto de análisis, cuya génesis se sitúa en el manejo de la diversidad de enfoques teórico-metodológicos disponibles en la ciencia para el estudio de la subjetividad, (...) como objeto de carácter complejo y singular. Se profundiza en la descripción ofrecida en un artículo anteriormente publicado en la revista y se agregan nuevas consideraciones que incluyen los niveles y patrones de logro, las cuales facilitan la formación y evaluación de la competencia por cada uno de sus ejes procesuales, constituyendo un valioso instrumento para el trabajo metodológico y la labor del profesor de la carrera. The article presents a result of doctoral investigation carried out among September/2013 and January/2016, on the formation of the investigative competence in the Psychology´s student of the semipresential modality of university studies. Starting from the employment of the analytic-synthetic methods, documental analysis and the functional structural systemic modelation, the particularities of the competence analysis object are approached whose genesis is located in the handling of the diversity of available theoretical-methodological focuses in the science for the study of the subjectivity, like object of complex and singular character. It is particularized in the description offered in an article previously published in the magazine and new considerations are added that include the levels and achievement patterns, which facilitate the formation and evaluation of the competence for each one of their axes processual, constituting a valuable instrument for the methodological work and the work of the professor of the career. (shrink)

Beyond their conventional concepts as some outcome of the system dynamics, Patterns and their Formation are regarded here as some substantial parts in description of the dynamics and flow of information in systems. Approach to a typical geometrical problem, for instance, comprises some sequential steps where the observed information of the system is rearranged, reorganized and reformulated to reach the final result. An algebra is introduced here to begin a systematic framework for sequential approaches to geometrical problems. The type (...) of the objects suitable for different kinds of the problems, the way the objects successively match to get a more detailed description of the problem, and the summation operator which combines simultaneous segments of the information of the system are discussed. Based on such abstract clarification for the sequential description of systems, we then switch to reformulate practical examples in various fields from network dynamics to molecular decomposition, relativity and embryogenesis, and demonstrate how different sequential implementation of symmetry could lead to proper description for the dynamics in each of these examples. (shrink)

This paper articulates an account of causation as a collection of information-theoretic relationships between patterns instantiated in the causal nexus. I draw on Dennett’s account of real patterns to characterize potential causal relata as patterns with specific identification criteria and noise tolerance levels, and actual causal relata as those patterns instantiated at some spatiotemporal location in the rich causal nexus as originally developed by Salmon. I develop a representation framework using phase space to precisely characterize causal relata, including their degree (...) of counterfactual robustness, causal profiles, causal connectivity, and privileged grain size. By doing so, I show how the philosophical notion of causation can be rendered in a format that is amenable for direct application of mathematical techniques from information theory such that the resulting informational measures are causal informational measures. This account provides a metaphysics of causation that supports interventionist semantics and causal modeling and discovery techniques. (shrink)

While many different mechanisms contribute to the generation of spatial order in biological development, the formation of morphogenetic fields which in turn direct cell responses giving rise to pattern and form are of major importance and essential for embryogenesis and regeneration. Most likely the fields represent concentration patterns of substances produced by molecular kinetics. Short range autocatalytic activation in conjunction with longer range “lateral” inhibition or depletion effects is capable of generating such patterns (Gierer and Meinhardt, 1972). Non-linear (...) reactions are required, and mathematical criteria were derived to design molecular models capable of pattern generation. The classical embryological feature of proportion regulation can be incorporated into the models. The conditions are mathematically necessary for the simplest two-factor case, and are likely to be a fair approximation in multi-component systems in which activation and inhibition are systems parameters subsuming the action of several agents. Gradients, symmetric and periodic patterns, in one or two dimensions, stable or pulsing in time, can be generated on this basis. Our basic concept of autocatalysis in conjunction with lateral inhibition accounts for self-regulatory biological features, including the reproducible formation of structures from near-uniform initial conditions as required by the logic of the generation cycle. Real tissue form, for instance that of budding Hydra, may often be traced back to local curvature arising within an initially relatively flat cell sheet, the position of evagination being determined by morphogenetic fields. Shell theory developed for architecture may also be applied to such biological processes. (shrink)

Turing patterns are a class of minimal mathematical models that have been used to discover and conceptualize certain abstract features of early biological development. This paper examines a range of these minimal models in order to articulate and elaborate a philosophical analysis of their epistemic uses. It is argued that minimal mathematical models aid in structuring the epistemic practices of biology by providing precise descriptions of the quantitative relations between various features of the complex systems, generating novel predictions that can (...) be compared with experimental data, promoting theory exploration, and acting as constitutive parts of empirically adequate explanations of naturally occurring phenomena, such as biological pattern formation. Focusing on the roles that minimal model explanations play in science motivates the adoption of a broader diachronic view of scientific explanation. (shrink)

Modern tendencies of genre formatting in printed media in Russia are analyzed in the article. A number of printed periodicals are investigated, namely “Ekonomika i zhizn’”, “Vedomosti”, “Schastlivye roditeli” (more than 1200 texts) and 5 regional Moscow newspapers (“Kolomenskaya Pravda”, “Zarya”, “Orekhovo-Zuevskaya Pravda”, “Serebryanoprudsky Vestnik”, “Khimkinskie Novosti”) comprising more than 400 texts. The author states that formatting of modern printed media and formatting of the used genres occur within the main tendencies of journalism development. They are PR, Westernization, glamorization and (...) usage of Western journalism patterns. It leads to distribution of new text types, such as an advertising article, an ordered article, an image and supporting articles. Some changes in the process of genre formatting in Russia are determined: traditional genre forms characteristic for Russia are reduced and hybrid genres appear instead whereas journalism genres mutate and Western ones are widely applied. This results in news reports as the most popular genres whereas high quality analytical and art-journalistic genres are reduced. (shrink)

In the new physics and in the new field of cosmometry, 1 it is the fundamental pattern that results in the motion from which all is created. Everything starts with the point of infinite potential. The tetrahedron at the point gives birth to the cuboctahedron ; its motion and structure result in the creation of the torus structure. The torus structure is self-referencing on a moment by moment basis since all must pass through the center. But isn't self-referencing the (...) basis for consciousness? It is said that all of creation has awareness, but at different levels. We know plants are aware of threats and of death to other living creatures by the work of Cleve Backster. We know we influence random number generators from the PEAR studies at Princeton. We know baby chicks will influence the movement of robots programed to do a random walk from the work of Rene Peoc'h. Quantum physics has embraced geometry with the work in the equations which explain the Feynman diagrams where particles come in and out of existence; those equations form a structure called the Amplituhedron - which is a quarter of a star tetrahedron. We also know that the tetrahedron can form the star tetrahedron and that each point of the star tetrahedron can form its own star tetrahedron, which can go on infinitely. That is, there is infinity in the finite. As in the fractal and holographic universe, each point or tetrahedron is connected to every other point. If each point has awareness due to formation of the torus, then Hermes teaching of "As above, as below" has meaning in the torus structure. If the torus is the fundamental unit of self-reference, is that the fundamental unit from which consciousness arises? The torus or double torus appears to be fundamental to all of creation - from galaxies to planets to atoms to photons. (shrink)

Early animal embryos are patterned by localized egg cytoplasmic factors and cell interactions. In invertebrate chordate ascidians, larval tail muscle originates from the posterior marginal zone of the early embryo. It has recently been demonstrated that maternal macho‐1 mRNA encoding transcription factor acts as a localized muscle determinant. Other mesodermal tissues such as notochord and mesenchyme are also derived from the vegetal marginal zone. In contrast, formation of these tissues requires induction from endoderm precursors at the 32‐cell stage. FGF–Ras–MAPK (...) signaling is involved in the induction of both tissues. The responsiveness for induction to notochord or mesenchyme depends on the inheritance of localized egg cytoplasmic factors. Previous studies also point to critical roles of directed signaling in polarization of induced cells and in subsequent asymmetric divisions resulting in the formation of two daughter cells with distinct fates. One cell adopts an induced fate, while the other assumes a default fate. A simple model of mesoderm patterning in ascidian embryos is proposed in comparison with that of vertebrates. BioEssays 24:613–624, 2002. © 2002 Wiley Periodicals, Inc. (shrink)