RESUMEN
Two recent postictal EEG measurements demonstrate somewhat conflicting results of epileptic behavior clearance in different brain parts. Both measurements observed two modes of seizure cessation, an abrupt and a gradual one, with slightly different statistics. No explanations were given for the appearance of these modes. Both measurements differ also in assessing the postictal brain activity or lack thereof, specifically the gamma activity. Using our G-Lymphatic clearance hypothesis, these results can be explained theoretically. The presence of two modes can be related to the order of ISF-CSF cleaning of brain parts. The reduced activity can be ascribed to neuronal ingredients deficiency brought about by the seizure related excess brain activity and by an over cleaning by the G-Lymphatic system.
Asunto(s)
Ondas Encefálicas , Epilepsia , Encéfalo , Electroencefalografía , Humanos , ConvulsionesRESUMEN
Cardiac fibrillation is a major clinical and societal burden. Rotors may drive fibrillation in many cases, but their role and patterns are often masked by complex propagation. We used Singular Value Decomposition (SVD), which ranks patterns of activation hierarchically, together with Wiener-Granger causality analysis (WGCA), which analyses direction of information among observations, to investigate the role of rotors in cardiac fibrillation. We hypothesized that combining SVD analysis with WGCA should reveal whether rotor activity is the dominant driving force of fibrillation even in cases of high complexity. Optical mapping experiments were conducted in neonatal rat cardiomyocyte monolayers (diameter, 35 mm), which were genetically modified to overexpress the delayed rectifier K+ channel IKr only in one half of the monolayer. Such monolayers have been shown previously to sustain fast rotors confined to the IKr overexpressing half and driving fibrillatory-like activity in the other half. SVD analysis of the optical mapping movies revealed a hierarchical pattern in which the primary modes corresponded to rotor activity in the IKr overexpressing region and the secondary modes corresponded to fibrillatory activity elsewhere. We then applied WGCA to evaluate the directionality of influence between modes in the entire monolayer using clear and noisy movies of activity. We demonstrated that the rotor modes influence the secondary fibrillatory modes, but influence was detected also in the opposite direction. To more specifically delineate the role of the rotor in fibrillation, we decomposed separately the respective SVD modes of the rotor and fibrillatory domains. In this case, WGCA yielded more information from the rotor to the fibrillatory domains than in the opposite direction. In conclusion, SVD analysis reveals that rotors can be the dominant modes of an experimental model of fibrillation. Wiener-Granger causality on modes of the rotor domains confirms their preferential driving influence on fibrillatory modes.
Asunto(s)
Algoritmos , Fibrilación Atrial/patología , Causalidad , Animales , Miocitos Cardíacos , Ratas , Factores de TiempoRESUMEN
A hybrid mathematical model was devised to obtain optimal values for bacterial doubling time and initial phage/bacteria multiplicity of infection for the purpose of reaching the highest possible phage titers in steady-state exponentially growing cultures. The computational model consists of an initial probabilistic stage, followed by a second one processed by a system of delayed differential equations. The model's approach can be used in any phage/bacteria system for which the relevant parameters have been measured. Results of a specific case, based on the detailed, known information about the interactions between virulent T4 phage and its host bacterium Escherichia coli, display a range of possible such values along a highlighted strip of parameter values in the relevant parameter plane. In addition, times to achieve these maxima and gains in phage concentrations are evaluated.
Asunto(s)
Bacteriófago T4/fisiología , Escherichia coli/virología , Virulencia , Algoritmos , Fenómenos Fisiológicos Bacterianos , Simulación por Computador , Modelos Teóricos , Probabilidad , Reproducibilidad de los ResultadosRESUMEN
The dynamics of bacteria and bacteriophage coexistence was examined in a chemostat in which the externally driven supply of nutrient for bacteria, and washout rate oscillates periodically. The proposed mathematical model for three interacting variables, bacteria, phage, and nutrient, consists of 3 differential equations with time delay, due to the phage latent period of lysing. The study was carried out in an interval of physical parameters where an equivalent model with constant supply of nutrient and washout rate is mathematically unstable, running in limit cycle regimes, with known self-frequencies. It addresses mainly the asymptotically persistent dynamics of the system.Bifurcation maps in terms of two externally controlled parameters, the amplitude and frequency of the controlled nutrient supply were constructed for various latent lysis periods, in order to determine the frequency entrainment, i.e., the resulting main operating frequency of the system, relative to the known external and self-frequencies. Also presented are bifurcation maps for the rich variety of dynamical types observed in the study. Bifurcation diagrams in terms of the lysing time delay were also included for completion.A new type of entrainment, combining in a simple way the external and self-periods (reciprocal frequencies), is shown to exist for a range of parameters.
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Fenómenos Fisiológicos Bacterianos , Bacteriófagos/fisiología , Reactores Biológicos/microbiología , Reactores Biológicos/virología , Modelos Biológicos , Bacteriófagos/patogenicidad , Ecosistema , Humanos , Lisogenia/fisiología , Conceptos Matemáticos , Viroterapia OncolíticaRESUMEN
The dynamics of the bacteria and bacteriophages interaction process was explored in depth, and laid on a firm basis through simulation and analysis. A modified Campbell model of phage-bacteria interaction was used to simulate three interacting species: bacteria, phages and bacterial debris, and their time behavior in terms of three parameters, in selected range values: the phages burst size (beta), the dissolution rate of the bacterial debris (q), and the lysing time delay (tau). Six types of dynamical behavior were identified, occupying various zones in the two-dimensional (2D) plane (q, beta) for several values of tau, allowing the determination of the region where shielding by bacterial debris is in effect. The problem of the occurrence of stability transitions between stable and unstable dynamical regimes was also addressed analytically, and compared with simulation results.
Asunto(s)
Bacterias/virología , Bacteriófagos/fisiología , Simulación por Computador , Ecosistema , Bacteriólisis/fisiología , Viabilidad Microbiana , Modelos Biológicos , Dinámica PoblacionalRESUMEN
A model of bacteria and phage survival is developed based on the idea of shielding by bacterial debris in the system. This model is mathematically formulated by a set of four nonlinear difference equations for susceptible bacteria, contaminated bacteria, bacterial debris and phages. Simulation results show the possibility of survival, and domains of existence of stable and unstable solutions