PubMed Journal Database | Acta biotheoretica 
The US National Library of Medicine and National Institutes of Health manage PubMed.gov which comprises of more than 21 million records, papers, reports for biomedical literature, including MEDLINE, life science and medical journals, articles, reviews, reports and books. BioPortfolio aims to publish relevant information on published papers, clinical trials and news associated with users selected topics.
For example view all recent relevant publications on Epigenetics and associated publications and clincial trials.
Showing PubMed Articles 1–25 of 52 from Acta biotheoretica
Intrinsic Feedbacks in MAPK Signaling Cascades Lead to Bistability and Oscillations.
Previous studies have demonstrated that double phosphorylation of a protein can lead to bistability if some conditions are fulfilled. It was also shown that the signaling behavior of a covalent modification cycle can be quantitatively and, more importantly, qualitatively modified when this cycle is coupled to a signaling pathway as opposed to being isolated. This property was named retroactivity. These two results are studied together in this paper showing the existence of interesting phenomena-oscillations...
Formal Methods for Hopfield-Like Networks.
Building a meaningful model of biological regulatory network is usually done by specifying the components (e.g. the genes) and their interactions, by guessing the values of parameters, by comparing the predicted behaviors to the observed ones, and by modifying in a trial-error process both architecture and parameters in order to reach an optimal fitness. We propose here a different approach to construct and analyze biological models avoiding the trial-error part, where structure and dynamics are represented...
Stabilizing Effect of Cannibalism in a Two Stages Population Model.
In this paper we build a prey-predator model with discrete weight structure for the predator. This model will conserve the number of individuals and the biomass and both growth and reproduction of the predator will depend on the food ingested. Moreover the model allows cannibalism which means that the predator can eat the prey but also other predators. We will focus on a simple version with two weight classes or stage (larvae and adults) and present some general mathematical results. In the last part, we wi...
On the Optimal Size of Marine Reserves.
The excessive and unsustainable exploitation of our marine resources has led to the promotion of marine reserves as a fisheries management tool. Marine reserves, areas in which fishing is restricted or prohibited, can offer opportunities for the recovery of exploited stock and fishery enhancement. This study examines the impact of the creation of marine protected areas, from both economic and biological perspectives. The consequences of reserve establishment on the long-run equilibrium fish biomass and fish...
Mathematical Modeling of Respiratory System Mechanics in the Newborn Lamb.
In this paper, a mathematical model of the respiratory mechanics is used to reproduce experimental signal waveforms acquired from three newborn lambs. As the main challenge is to determine specific lamb parameters, a sensitivity analysis has been realized to find the most influent parameters, which are identified using an evolutionary algorithm. Results show a close match between experimental and simulated pressure and flow waveforms obtained during spontaneous ventilation and pleural pressure variations ac...
Multiscale Analysis of Biological Systems.
It is argued that multiscale approaches are necessary for an explanatory modeling of biological systems. A first step, besides common to the multiscale modeling of physical and living systems, is a bottom-up integration based on the notions of effective parameters and minimal models. Top-down effects can be accounted for in terms of effective constraints and inputs. Biological systems are essentially characterized by an entanglement of bottom-up and top-down influences following from their evolutionary hist...
Derivation of a Floquet Formalism within a Natural Framework.
Many biological systems experience a periodic environment. Floquet theory is a mathematical tool to deal with such time periodic systems. It is not often applied in biology, because linkage between the mathematics and the biology is not available. To create this linkage, we derive the Floquet theory for natural systems. We construct a framework, where the rotation of the Earth is causing the periodicity. Within this framework the angular momentum operator is introduced to describe the Earth's rotation. The...
A Fundamental Principle Governing Populations.
Proposed here is that an overriding principle of nature governs all population behavior; that a single tenet drives the many regimes observed in nature-exponential-like growth, saturated growth, population decline, population extinction, and oscillatory behavior. The signature of such an all embracing principle is a differential equation which, in a single statement, embraces the entire panoply of observations. In current orthodox theory, this diverse range of population behaviors is described by many diffe...
Heart Rate Regulation Processed Through Wavelet Analysis and Change Detection: Some Case Studies.
Heart rate variability (HRV) is an indicator of the regulation of the heart, see Task Force (Circulation 93(5):1043-1065, 1996). This study compares the regulation of the heart in two cases of healthy subjects within real life situations: Marathon runners and shift workers. After an update on the state of the art on HRV processing, we specify our probabilistic model: We choose modeling heartbeat series by locally stationary Gaussian process (Dahlhaus in Ann Stat 25, 1997). HRV is then processed by the combi...
Necrotic Tumor Growth: An Analytic Approach.
The present paper deals with a free boundary problem modeling the growth process of necrotic multi-layer tumors. We prove the existence of flat stationary solutions and determine the linearization of our model at such an equilibrium. Finally, we compute the solutions of the stationary linearized problem and comment on bifurcation.
Optimal Exploitation for a Commercial Fishing Model.
A two non-linear dynamic models, first one in two state variables and one control and the second one with three state variables and one control, are presented for the purpose of finding the optimal combination of exploitation, capital investment and price variation in the commercial fishing industry. This optimal combination is determined in terms of management policies. Exploitation, capital and price variation are controlled through the utilization rate of available capital. A novel feature in this model...
Predictive Power of "A Minima" Models in Biology.
Many apparently complex mechanisms in biology, especially in embryology and molecular biology, can be explained easily by reasoning at the level of the "efficient cause" of the observed phenomenology: the mechanism can then be explained by a simple geometrical argument or a variational principle, leading to the solution of an optimization problem, for example, via the co-existence of a minimization and a maximization problem (a min-max principle). Passing from a microscopic (or cellular) level (optimal min-...
The Neutral-Niche Debate: A Philosophical Perspective.
Ecological communities around the world are under threat while a consensus theory of community structure remains elusive. In the last decade ecologists have struggled with two seemingly opposing theories: niche-based theory that explains diversity with species' differences and the neutral theory of biodiversity that claims that much of the diversity we observe can be explained without explicitly invoking species' differences. Although ecologists are increasingly attempting to reconcile these two theories, t...
Vision substitution by electro-stimulation has been studied since the 60s beginning with P. Bach-y-Rita. Camera pictures or movies encoded in gray levels are displayed using an electro-stimulation display device on the surface of a body part, such as the skin or the tongue. Medical-technical devices have been developed on this principle to compensate for sensory-motor disabilities such as blindness or loss of balance, or to guide specific actions, such as surgery. However, the electrical signals of stationa...
Angiogenesis is a complex morphogenetic process regulated by growth factors, but also by the force balance between endothelial cells (EC) traction stresses and extracellular matrix (ECM) viscoelastic resistance. Studies conducted with in vitro angiogenesis assays demonstrated that decreasing ECM stiffness triggers an angiogenic switch that promotes organization of EC into tubular cords or pseudo-capillaries. Thus, mechano-sensitivity of EC with regard to proteases secretion, and notably matrix metalloprotei...
Defining Species: A Multi-Level Approach.
Different concepts define species at the pattern-level grouping of organisms into discrete clusters, the level of the processes operating within and between populations leading to the formation and maintenance of these clusters, or the level of the inner-organismic genetic and molecular mechanisms that contribute to species cohesion or promote speciation. I argue that, unlike single-level approaches, a multi-level framework takes into account the complex sequences of cause-effect reinforcements leading to t...
The Evolution of Dispersal in Random Environment.
In this paper we introduce a stochastic model for a population living and migrating between s sites without distinction in the states between residents and immigrants. The evolutionary stable strategies (ESS) is characterized by the maximization of a stochastic growth rate. We obtain that the expectation of reproductive values, normalized by some random quantity, are constant on all sites and that the expectation of the normalized vector population structure is proportional to eigenvector of the dispersion...
In this work we deal with a general class of spatially distributed periodic SIS epidemic models with two time scales. We let susceptible and infected individuals migrate between patches with periodic time dependent migration rates. The existence of two time scales in the system allows to describe certain features of the asymptotic behavior of its solutions with the help of a less dimensional, aggregated, system. We derive global reproduction numbers governing the general spatially distributed nonautonomous...
Commitment of Mathematicians in Medicine: A Personal Experience, and Generalisations.
I will present here a personal point of view on the commitment of mathematicians in medicine. Starting from my personal experience, I will suggest generalisations including favourable signs and caveats to show how mathematicians can be welcome and helpful in medicine, both in a theoretical and in a practical way.
The Impact of Gene-Environment Interaction and Correlation on the Interpretation of Heritability.
The presence of gene-environment statistical interaction (GxE) and correlation (rGE) in biological development has led both practitioners and philosophers of science to question the legitimacy of heritability estimates. The paper offers a novel approach to assess the impact of GxE and rGE on the way genetic and environmental causation can be partitioned. A probabilistic framework is developed, based on a quantitative genetic model that incorporates GxE and rGE, offering a rigorous way of interpreting herita...
Quantum mechanical and molecular dynamics methods were used to analyze the structure and stability of neutral and zwitterionic configurations of the extracted active site sequence from a Burkholderia cepacia lipase, histidyl-seryl-glutamin (His86-Ser87-Gln88) and its mutated form, histidyl-cysteyl-glutamin (His86-Cys87-Gln88) in vacuum and different solvents. The effects of solvent dielectric constant, explicit and implicit water molecules and side chain mutation on the structure and stability of this seque...
A Mathematical Model of Rift Valley Fever with Human Host.
Rift Valley Fever is a vector-borne disease mainly transmitted by mosquito. To gain some quantitative insights into its dynamics, a deterministic model with mosquito, livestock, and human host is formulated as a system of nonlinear ordinary differential equations and analyzed. The disease threshold [Formula: see text] is computed and used to investigate the local stability of the equilibria. A sensitivity analysis is performed and the most sensitive model parameters to the measure of initial disease transmi...
In organic farming animal welfare is one important aspect included in the internationally agreed organic principles of health, ecology, fairness and care (IFOAM 2006), reflecting expectation of consumers and farmers. The definition of organic animal welfare includes-besides traditional terms of animal welfare-'regeneration' and 'naturalness'. Organic animal welfare assessment needs to reflect this and use complex parameters, include natural behaviour and a systemic view. Furthermore, various parties with se...
Editorial: Concepts of Animal Welfare.
