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Terpenoids Against Cardiovascular Diseases
Published in Dijendra Nath Roy, Terpenoids Against Human Diseases, 2019
The effects of thymol have also been studied in perfused guinea pig heart and in canine ventricular trabecular utilizing the Langendorff technique (Szentandrassy et al. 2004). The results of these studies have revealed that thymol can generate a cardiopressant effect due to a diminution in the calcium composition of the sarcoplasmic reticulum, primarily as a result of the prevention of calcium pump activity (Szentandrassy et al. 2004). The vasorelaxant qualities of thymol have also been noted. Further confirming the cardioprotective effects of thymol, Peixoto-Neves et al. (2010) demonstrated that in isolated rat aorta, thymol generated an endothelium-independent relaxation, which very likely included the prevention of Ca2+ release from the sarcoplasmic reticulum, thereby decreasing the sensitivity of contractile elements to Ca2+ and inhibiting the influx of Ca2+ across the membrane.
Membrane Models
Published in Joseph D. Bronzino, Donald R. Peterson, Biomedical Engineering Fundamentals, 2019
Aplysia Abdominal Ganglion R15 Cell e bursting behavior of Aplysia neurons have been extensively studied. e rst model was that of Plant (1976) who extended the HH equations to include an inactivating potassium current, a slow potassium current and a constant hyperpolarizing current due to the Na/K pump. Bertram (1993) modeled bursting in these cells by augmenting an HH model with a calcium current, a second delayed rectier-type potassium current, and serotonin-activated inwardrectifying potassium current and a negative slope region calcium current. A detailed model including a fast inward sodium current, fast and slow calcium currents, a delayed rectier and an inward rectier potassium currents, a sodium-potassium pump, a sodium-calcium exchanger, a calcium pump, and a leakage current is described in Butera et al. (1995).
Blood and Vascular Targets for Magnetic Field Dosing
Published in Marko Markov, Dosimetry in Bioelectromagnetics, 2017
On the basis of the manipulations of the suffusing fluid content, the authors concluded that the PEMF vasodilation depended on Ca++ efflux from VSM and/or influx into VSM sarcoplasmic reticulum, both well-known processes that alter VSM tone, as discussed in earlier sections of this chapter. On the basis of the prior work (Miura and Okada 1988; Okada and Miura 1990) they hypothesized that the PEMF facilitates activation of the Ca++-ATPase calcium pump, thereby modulating VSM tone. Subsequent work provided evidence of a strong involvement of NO via a PEMF-induced cyclic GMP activation when cerebella tissue was exposed to a similar 10 MHz pulsed field (Miura et al. 1993). Another microscopic observational animal study using PEMF for which heat was reported as a nonissue was performed on rat cremaster circulation (Smith et al. 2004). Exposing the cremaster to a pair of Helmholtz coils with approximate 3.7 kHz pulses (pulse width of 5.9 ms and duty cycle of 8.8%) resulted in arteriole vasodilation of 9% after only 2 min of exposure, although the field intensity at the target was not specified. These PEMF-related diameter changes can have substantial flow effects, but it is unclear if they are because of induced currents, electric field changes that affect membrane potentials, or other processes since it is well established that various forms of electrical stimulation result in altered skin blood flow with increases reported in skin of forearm (McDowell et al. 1999; Cramp et al. 2002) and leg (Noble et al. 2000). Further study is clearly warranted.
Mathematical modeling of the cardiac tissue
Published in Mechanics of Advanced Materials and Structures, 2022
Moreover, functions of physically permissible processes and reactions (with their derivatives) belong to linear functional space, consisting of piecewise continuous functions, defined on the half-endless interval (Ilyushin [9]). By choosing, the permissible couples of processes and reactions in the right way we shall get equations invariant with respect to the symmetry groups of the triclinic system in the form where —the tensors of phenomenological coefficients, satisfying correlations of symmetry of Casimir-Onsager; —the coefficient proportional to stoichiometric coefficient. Equation (3.25) describes the following additive processes in the elementary volume of the solid in the second phase of the first continuum: deformability; the chemical reaction of interaction between the same phases of two continuums, which at set density of myofibrils is characterized only by chemical potential of the activator, the work of the calcium pump being defined by a chemical reaction of transfer and inter-phase diffusion of ions We have to note that all processes, except for deformability are described in more detailed by the equations of calcium kinetics.
Predicting the cardiac toxicity of drugs using a novel multiscale exposure–response simulator
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2018
Francisco Sahli Costabal, Jiang Yao, Ellen Kuhl
the L-type calcium current , the fast and late sodium currents , the calcium sodium and calcium potassium currents and , the background calcium, sodium, and potassium currents , , and , the rapid and slow delayed rectifier potassium currents and , the inward rectifier potassium current , the transient outward potassium current , the sodium potassium pump current , the sarcolemmal calcium pump current , and the sodium calcium exchange currents and . To appropriately model signal propagation in real heart scale simulations (Priest et al. 2016), we replaced the fast sodium current of the original O’Hara–Rudy model with a modified fast sodium current of the ten Tusscher model (ten Tusscher et al. 2004). The 15 currents are defined through a total of 39 state variables. To account for regional specificity, the O’Hara–Rudy model has been parameterized for three different cell types, endocardial, midwall, and epicardial cells. Figure 1, left, illustrates the single-cell action potential of the O’Hara–Rudy model for endocardial, mid, and epicardial human ventricular cardiomyocytes. Figure 2 shows the distribution of these three cell types across the ventricular wall. To model cells of the Purkinje fiber network, we choose the Stewart model for human Purkinje fiber cells (Stewart et al. 2009). A distinguishing feature of this model is its automaticity, which enables the cells to self-excite without an external stimulus. Figure 1, right, illustrates the 14 ionic currents of the Stewart model,