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Results for “Cell Physiological Phenomena”

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At least 19 recordsLinked to original sources
PubMed2006

Collective effects in cellular structure formation mediated by compliant environments: a Monte Carlo study.

Compliant environments can mediate interactions between mechanically active cells like fibroblasts. Starting with a phenomenological model for the behavior of single cells, we use extensive Monte Carlo simulations to predict non-trivial structure formation for cell communities on soft elastic substrates as a function of elastic moduli, cell density, noise and cell position geometry. In general, we find a disordered structure as well as ordered string-like and ring-like structures. The transition between ordered and disordered structures is controlled both by cell density and noise level, while the transition between string- and ring-like ordered structures is controlled by the Poisson ratio. Similar effects are observed in three dimensions. Our results suggest that in regard to elastic effects, healthy connective tissue usually is in a macroscopically disordered state, but can be switched to a macroscopically ordered state by appropriate parameter variations, in a way that is reminiscent of wound contraction or diseased states like contracture.

Biomechanical Phenomena↗
PubMed1987

Deformation analyses in cell and developmental biology. Part II--Mechanical experiments on cells.

This study employs the finite element approach developed in Part I to analyze mechanical experiments on cells. It views cells as axisymmetric membrane structures containing a body of incompressible material, and models the mechanical contact between a cell and the loading apparatus by a contact algorithm. Since the method is valid for analyzing axisymmetric shell-like bodies with arbitrary shapes, it treates various mechanical experiments on cells in a unified manner. For demonstration purposes, three commonly used mechanical experiments on cells are considered; the compression experiment; the suction (micropipette aspiration) experiment; and the magnetic particle experiment. Based on an estimate of the mechanical property data for unfertilized sea urchin eggs, this analysis method predicts the responses for all three experiments using the same assumptions and approximations. This parallel treatment gives a broad basis for data correlation with experiments. The method also provides insights into mechanical experiments not offered by other approximate methods. For example, it gives the distributions of tensions and stretches on the cell cortex, and suggests the role of friction in the suction experiment.

Animals↗
PubMed1998

Cardiovascular physiology in the twentieth century: great strides and missed opportunities.

In a broad sense, physiology is the study of the chemical and physical bases of life processes. Consequently, the evolution of our knowledge of cardiovascular functions is closely linked to the developments in many fields of science, including chemistry, physics, engineering, and biology. A cursory examination reveals that different "foundation" sciences predominated in different stages of the history of cardiovascular physiology. Today, cardiovascular physiology is poised to exploit new developments in all areas of scientific inquiry. However, cardiovascular physiologists have not always embraced the power of the multidisciplinary approach. In this brief overview of the history of cardiovascular physiology in the 20th century, the major focus is on some of the major advances in the field and the contributions of other disciplines to these developments. In addition, the forces that influenced cardiovascular science in this century and their impact on the evolution of the field in the new millennium are discussed.

Animals↗
PubMed1987

Effects of oxygen intermediates on cellular functions.

This brief illustration of the effects of O2 metabolites and of hyperoxia on some of the main functions of the cells, DNA and protein synthesis, indicates that major changes can occur in cells exposed to oxidative stresses such as those occurring in an inflammatory reaction. The relative sensitivity of the various cell populations may favor the emergence of some cells and the disappearance of others. Depending on the sensitivity of different enzymes to oxidative injury, the response of cells in terms of both mediator production and of response to the action of the mediators themselves may be affected.

Animals↗
PubMed1976

[Place of neuroleptics in geriatric anesthesia].

The elderly show changes in various parenchymas linked to the process of ageing. Pathological abnormalities may be added to this picture leading to physiopathology peculiar to the aged. In relation to special problems raised by this background, the advantages and disadvantages of N.L.A. are discussed. The authors refer to an experiment in the Department of Anesthetics and Intensive Care in Créteil.

Aged↗
PubMed2005

Life on the wire: on tensegrity and force balance in cells.

Since cell mechanics has attracted the attention of a growing number of researchers, several models have been proposed to explain cell mechanical behavior, among which tensegrity is certainly the most convincing one. Originally developed by the architect Buckminster Fuller, tensegrity structures are based on the presence of discontinuous compression elements that balance the force generated by continuous tension elements, thus reaching an equilibrium that is completely independent of gravity. This model is a useful tool to predict cell spreading, motility and especially mechanotransduction, i.e. the capability to transform mechanical stresses into biochemical responses, a key process in homeostasis of many tissues that must continuously withstand mechanical forces, like bone, but which is still poorly understood.

Biomechanical Phenomena↗
PubMed1990

On the nature of enduring modifications induced in cells and organisms.

The clarity of Mendelian genetics and the elegance of the molecular mechanisms of replication and readout of DNA have tended to obscure a solid body of evidence demonstrating that nongenetic, enduring modifications can be induced in the behavior of cells, modifications that continue to be expressed for many divisions after withdrawal of the inducing stimulus. The most prosaic case is the differentiated state of metazoan cells, which persists throughout the lifetime of the organism. Much less widely known but well-characterized examples are also cited for bacteria, protozoa, and cultured cells of higher plants and animals. The spontaneous neoplastic transformation of cultured mouse NIH 3T3 cells is introduced as an enduring adaptive response to moderate growth constraints. Evidence in support of the thesis that physiological adaptation is the driving force for chemically induced carcinogenesis in the intact animal is also presented. The cases described here involve integrated responses of many if not all of the regulatory components of the cell, rather than singular molecular mechanisms. The continuous generation of phenotypic heterogeneity, a process observed readily in cell culture, provides the basis for a model that accounts for enduring modifications. This model, designated progressive state selection, makes no attempt at a detailed biochemical explanation of heterogeneity, but uses it as a fundamental postulate to represent the adaptive behavior of the cells.

Animals↗