Modelling Stochastic and Deterministic Behaviours in Virus Infection Dynamics

Many human infections with viruses such as human immunodeficiency virus type 1 (HIV--1) are characterized by low numbers of founder viruses for which the random effects and discrete nature of populations have a strong effect on the dynamics, e.g., extinction versus spread. It remains to be established whether HIV transmission is a stochastic process on the whole. In this study, we consider the simplest (so-called, 'consensus') virus dynamics model and develop a computational methodology for building an equivalent stochastic model based on Markov Chain accounting for random interactions between the components. The model is used to study the evolution of the probability densities for the virus and target cell populations. It predicts the probability of infection spread as a function of the number of the transmitted viruses. A hybrid algorithm is suggested to compute efficiently the dynamics in state space domain characterized by a mix of small and large species densities

Polarized x-ray absorption spectra of CuGeO3 at the Cu and Ge K edges

Polarized x-ray absorption near edge structure (XANES) spectra at both the Cu and the Ge K-edges of CuGeO3 are measured and calculated relying on the real-space multiple-scattering formalism within a one-electron approach. The polarization components are resolved not only in the unit cell coordinate system but also in a local frame attached to the nearest neighborhood of the photoabsorbing Cu atom. In that way, features which resist a particular theoretical description can be identified. We have found that it is the out-of-CuO4-plane p_{z'} component which defies the one-electron calculation based on the muffin-tin potential. For the Ge K-edge XANES, the agreement between the theory and the experiment appears to be better for those polarization components which probe more compact local surroundings than for those which probe regions with lower atomic density. Paper published in Phys. Rev. B 66, 155119 (2002) and available on-line at http://link.aps.org/abstract/PRB/v66/e155119.Comment: 15 pages, 6 figures. Published in Physical Review B, abstract available on-line at http://link.aps.org/abstract/PRB/e15511

NEW WAY TO DETERMINE THE TYPE OF ADAPTATION STRATEGY IN EXPERIMENT

Aim: to base and to test new more precise way of determination of the type of adaptation strategy and. intensity of corresponding metabolic shifts in experiment. Methods: the model of orthopedic trauma of two extremities with stabilization of fragments with external fixation devices was rendered in experimental group of 22 chinchilla rabbits. We defined oxygen consumption, carbonic acid excretion and rectal temperature initially and also on the 1st, 3rd and 7th day after the operation. Results. Addition of data of research of oxygen consumption (key criterion of the type of adaptation strategy) with the results of determination of carbonic acid excretion and rectal temperature, correct choice of initial condition of laboratory animal that will be compared and also quantitative characteristics of intensity of metabolic shifts allowed to increase exactness of diagnostics of type of adaptation strategy of laboratory animals in unfavorable conditions

THE EFFICIENCY OF TOLERANT (PASSIVE) ADAPTATION UNDER THE CONDITIONS OF EXPERIMENTAL POLYTRAUMA

The model of multiple skeletal injuries was reproduced in two groups. 22 animals of the 1st group had stabilization of the right forearm bones and left shin with spoke external fixation device of 2 subsystems with followed osteotomy of the bones of respective segment in the middle third under general anesthesia. During the experiment the injection of dexamethasone and adrenaline during the first twenty-four hours after multiple skeletal injuries prevented the reduce the intensity of the metabolic processes, that was proved by close to initial values of oxygen consumption and carbon dioxide emissions. But to the third day there was no any difference in the metabolic activity in rabbits having and not having adrenaline and dexamethasone. The animals had adrenaline and dexamethasone turned to be in more severe clinical situation. As a result of «normal» intensity of metabolic processes in rabbits during the near time period after trauma there was decrease of survival from 45,5 % to 7,7 %

Hormonal type in the conditions of experimental multiple skeletal trauma

In experiment reproduced model of multiple skeletal trauma (fracture of bones of right forearm and lift shin) with stabilization of fragments with external fixation devices in 35 Chinchilla rabbits. All manipulations were realized, at general anesthesia. Standard treatment included anesthesia, antibiotic prophyliaxis and. infusion therapy by common method. Decrease of metabolism activity was registered in the first group of laboratory animals at the standard treatment. That's why besided strandard treatment dexamethasone and adrenaline in average recommended doses was prescripted in the second group of rabbits in postoperative period for correction of posttraumatic hypobiosis. Laboratory control in several hours after the injection confirmed stable increase of level of corticosteroids in blood but it wasn't possible to register increase of concentration of adrenaline. Correlation analysis was realize to study the connection between the contentration of endogenous hormones in blood and. metabolism activity in rabbits in conditions of multiple skeletal trauma. At the consideration data as one array we determined high-significant (р < 0,001) direct moderate correlation between the values of rectal temperature and. the concentration of free thyroxine in blood (rs = 0,414), this connection was strong on the 3rd day after trauma (rs = 0,833; р < 0,001). Also indirect moderate correlation between values of rectal temperature and. the concentration of cortisol in blood of laboratory animals was registered (rs = 0,49; р < 0,001). The results of study of influence of adrenaline and. noradrenaline on the indices of metabolism activity weren't statistically significant. Obtained data allowed to make a conclusion about importance of endocrine activity of thyroid gland in the formation of adaptation strategy

Energy metabolism at experimental polytrauma: changes at the prescription of adrenaline and dexamethasone

The aim of the research was to study influence of dexamethasone and adrenaline on the concentration of energy metabolism substrates in blood of Chinchilla rabbits under the conditions of multiple skeletal trauma. We performed stabilization of the bones of right forearm and left shin in 35 animals by wire external fixation device with further osteotomy of bones of corresponding segments. We observed the decrease of activity of metabolism in rabbits on the background of standard treatment. Maintenance of normal activity of metabolism by prescription of adrenaline and dexamethasone caused more intensive use of energy resources of an organism. Imitation of hyperergic reaction of stress-realizing systems in rabbits caused the increase of concentration of glucose in blood and the decrease of concentration of triglycerides. High consumption of energy substrates was provided by more expressed catabolic reaction. The result of hypercatabolism was development of hypoproteinemia, hypoalbuminemia and increase of the risk of fluid shift from bloodstream into the tissues with formation of organ insufficiency

Biological activity differences between TGF-β1 and TGF-β3 correlate with differences in the rigidity and arrangement of their component monomers

[Image: see text] TGF-β1, -β2, and -β3 are small, secreted signaling proteins. They share 71–80% sequence identity and signal through the same receptors, yet the isoform-specific null mice have distinctive phenotypes and are inviable. The replacement of the coding sequence of TGF-β1 with TGF-β3 and TGF-β3 with TGF-β1 led to only partial rescue of the mutant phenotypes, suggesting that intrinsic differences between them contribute to the requirement of each in vivo. Here, we investigated whether the previously reported differences in the flexibility of the interfacial helix and arrangement of monomers was responsible for the differences in activity by generating two chimeric proteins in which residues 54–75 in the homodimer interface were swapped. Structural analysis of these using NMR and functional analysis using a dermal fibroblast migration assay showed that swapping the interfacial region swapped both the conformational preferences and activity. Conformational and activity differences were also observed between TGF-β3 and a variant with four helix-stabilizing residues from TGF-β1, suggesting that the observed changes were due to increased helical stability and the altered conformation, as proposed. Surface plasmon resonance analysis showed that TGF-β1, TGF-β3, and variants bound the type II signaling receptor, TβRII, nearly identically, but had small differences in the dissociation rate constant for recruitment of the type I signaling receptor, TβRI. However, the latter did not correlate with conformational preference or activity. Hence, the difference in activity arises from differences in their conformations, not their manner of receptor binding, suggesting that a matrix protein that differentially binds them might determine their distinct activities