Mechanical forces such as tension and compression act throughout growth and development of multicellular organisms. These forces not only affect the size and shape of the cells and tissues but are capable of modifying the expression of genes and the localization of molecular components within the cell, in the plasma membrane, and in the plant cell wall. The magnitude and direction of these physical forces change with cellular and tissue properties such as elasticity. Thus, mechanical forces and the mesoscopic fields that emerge from their local action constitute important sources of positional information. Moreover, physical and biochemical processes interact in non-linear ways during tissue and organ growth in plants and animals. In this review we discuss how such mechanical forces are generated, transmitted, and sensed in these two lineages of multicellular organisms to yield long-range positional information. In order to do so we first outline a potentially common basis for studying patterning and mechanosensing that relies on the structural principle of tensegrity, and discuss how tensegral structures might arise in plants and animals. We then provide some examples of morphogenesis in which mechanical forces appear to act as positional information during development, offering a possible explanation for ubiquitous processes, such as the formation of periodic structures. Such examples, we argue, can be interpreted in terms of tensegral phenomena. Finally, we discuss the hypothesis of mechanically isotropic points as a potentially generic mechanism for the localization and maintenance of stem-cell niches in multicellular organisms. This comparative approach aims to help uncovering generic mechanisms of morphogenesis and thus reach a better understanding of the evolution and development of multicellular phenotypes, focusing on the role of physical forces in these processes.

Pigment patterning in animals generally occurs during early developmental stages and has ecological, physiological, ethological, and evolutionary significance. Despite the relative simplicity of color patterns, their emergence depends upon multilevel complex processes. Thus, theoretical models have become necessary tools to further understand how such patterns emerge. Recent studies have reevaluated the importance of epigenetic, as well as genetic factors in developmental pattern formation. Yet epigenetic phenomena, specially those related to physical constraints that might be involved in the emergence of color patterns, have not been fully studied. In this article, we propose a model of color patterning in which epigenetic aspects such as cell migration, cell-tissue interactions, and physical and mechanical phenomena are central. This model considers that motile cells embedded in a fibrous, viscoelastic matrix-mesenchyme-can deform it in such a way that tension tracks are formed. We postulate that these tracks act, in turn, as guides for subsequent cell migration and establishment, generating long-range phenomenological interactions. We aim to describe some general aspects of this developmental phenomenon with a rather simple mathematical model. Then we discuss our model in the context of available experimental and morphological evidence for reptiles, amphibians, and fishes, and compare it with other patterning models. We also put forward novel testable predictions derived from our model, regarding, for instance, the localization of the postulated tension tracks, and we propose new experiments. Finally, we discuss how the proposed mechanism could constitute a dynamic patterning module accounting for pattern formation in many animal lineages.

El objetivo fue analizar si el profesional de enfermería aplicaba el autocuidado en el uso del calzado en horario laboral. Es un estudio observacional, analítico, de corte trasversal con enfoque cuantitativo. La población estuvo constituida por 1.037 profesionales de Enfermería del Hospital de Clínicas, institución de carácter público, situada en la ciudad de San Lorenzo, Paraguay. Se incluyeron 366 profesionales de Enfermería a través de un muestreo probabilístico, la selección de la muestra fue multietápica con muestreo aleatorio simple. Se aplicó estadística descriptiva y chi2 para determinar asociaciones. Los hallazgos más relevantes fueron que mayoritariamente eran del grupo etario de 24 a 48 años con una media de 35 años; soltero, con una antigüedad de 10 años, con más de un empleo y del servicio de urgencias. Solo el 11,7% refirió conocer el calzado anatómico, sin embargo, 50,2% lo utilizaba. Más del 60% no tenía en cuenta las características del calzado anatómico al momento de adquirirlo, entre otros aspectos relacionados al utilizarlo en horario laboral. En el grupo etario de 31 a 35 años se concentró la mayor cantidad de trastornos músculo-esqueléticos (40%). En conclusión, el profesional de enfermería utilizaba de forma deficitaria el calzado adecuado; además, se ha encontrado evidencia de asociación (chi2 0,05) entre el tipo de calzado utilizado y la cantidad de trastornos músculo-esqueléticos que presentaba cada individuo.

Cellular automatons and computer simulation games are widely used as heuristic devices in biology, to explore implications and consequences of specific theories. Conway's Game of Life has been widely used for this purpose. This game was designed to explore the evolution of ecological communities. We apply it to other biological processes, including symbiopoiesis. We show that Conway's organization of rules reflects the epigenetic principle, that genetic action and developmental processes are inseparable dimensions of a single biological system, analogous to the integration processes in symbiopoiesis. We look for similarities and differences between two epigenetic models, by Turing and Edelman, as they are realized in Game of Life objects. We show the value of computer simulations to experiment with and propose generalizations of broader scope with novel testable predictions. We use the game to explore issues in symbiopoiesis and evo-devo, where we explore a fractal hypothesis: that self-similarity exists at different levels (cells, organisms, ecological communities) as a result of homologous interactions of two as processes modeled in the Game of Life

This paper uses some recent ideas in biology as starting point to explore analogous concepts and tendencies in semiotics and biology, leading to reflections on interdisciplinarity itself within the framework of theories of chaos and complexity. It sees affinities between the biological concept of species and the semiotic category of discipline. It finds many suggestive parallels with semiotics from the recently emerging synthesis of evolution and development (‘Evo-Devo’), built around the discovery of ‘homeobox’ genes which are present in many very different lineages, opening up possibilities for ‘deep’ homologies between species, and providing a powerful model for semiotic homology.