A computational analysis of localized Ca2+-dynamics generated by heterogeneous release sites

Effect of Intensive Blood Pressure Control on Carotid Morphology and Hemodynamics in Chinese Patients with Hyperhomocysteinemia-Type Hypertension and High Risk of Stroke

BACKGROUND Different blood pressure targets should be formulated for different groups of people. This study aimed to assess the effectiveness of intensive blood control in improving the carotid morphology and hemodynamics in Chinese patients with hyperhomocysteinemia-type hypertension and high risk of stroke. MATERIAL AND METHODS Chinese hypertensive patients with high risk of stroke were randomized to intensive (n=187) and standard (n=192; controls) blood pressure management groups. Systolic blood pressure (SBP) targets were 100< SBP ≤120 and 120< SBP ≤140 mmHg, respectively. All patients received folic acid 0.8 mg/d and atorvastatin 20 mg/d. Calcium antagonist was first used. If blood pressure was still uncontrolled, angiotensin-converting enzyme inhibitor or angiotensin receptor antagonist, ß-receptor blocker, and diuretics were added successively. Follow-up was 12 months. Carotid features, hemodynamics, and adverse events were examined. RESULTS There were no differences in sex, age, body mass index, blood lipids, baseline carotid parameters, and histories of smoking, diabetes, statin use, and stroke between the 2 groups. Carotid plaques after 12 months of treatment were 19.4±2.1 and 23.6±3.1 cm² for the intensive and control groups, respectively (P=0.038). Plaque scores were lower in the intensive group (1.75±0.52 vs. 2.45±0.47, P=0.023). Compared with controls, intensive management resulted in relatively higher Vd and significantly lower Vs/Vd, PI, and RI (all P<0.05). Major adverse events such as hypotension (n=5 (2.7%) vs. 3 (1.6%), P=0.020) and dizziness (n=20 (10.7%) vs. 16 (8.3%), P=0.041) were more frequent in the intensive group. CONCLUSIONS Intensive blood pressure management could be beneficial for Chinese patients with hyperhomocysteinemia-type hypertension and high risk of stroke.

Human T cells in silico: Modelling dynamic intracellular calcium and its influence on cellular electrophysiology

A network of ion currents influences basic cellular T cell functions. After T cell receptor activation, changes in highly regulated calcium levels play a central role in triggering effector functions and cell differentiation. A dysregulation of these processes might be involved in the pathogenesis of several diseases. We present a mathematical model based on the NEURON simulation environment that computes dynamic calcium levels in combination with the current output of diverse ion channels (K_V1.3, K_Ca3.1, K_2P channels (TASK1-3, TRESK), VRAC, TRPM7, CRAC). In line with experimental data, the simulation shows a strong increase in intracellular calcium after T cell receptor stimulation before reaching a new, elevated calcium plateau in the T cell's activated state. Deactivation of single ion channel modules, mimicking the application of channel blockers, reveals that two types of potassium channels are the main regulators of intracellular calcium level: calcium-dependent potassium (K_Ca3.1) and two-pore-domain potassium (K_2P) channels.

Spatiotemporal organization of Ca dynamics: a modeling-based approach

Calcium is a ubiquitous second messenger that mediates vital physiological responses such as fertilization, secretion, gene expression, or apoptosis. Given this variety of processes mediated by Ca(2+), these signals are highly organized both in time and space to ensure reliability and specificity. This review deals with the spatiotemporal organization of the Ca(2+) signaling pathway in electrically nonexcitable cells in which InsP(3) receptors are by far the most important Ca(2+) channels. We focus on the aspects of this highly regulated dynamical system for which an interplay between experiments and modeling is particularly fruitful. In particular, the importance of the relative densities of the different InsP(3) receptor subtypes will be discussed on the basis of a modeling approach linking the steady-state behaviors of these channels in electrophysiological experiments with their behavior in a cellular environment. Also, the interplay between InsP(3) metabolism and Ca(2+) oscillations will be considered. Finally, we discuss the relationships between stochastic openings of the Ca(2+) releasing channels at the microscopic level and the coordinated, regular behavior observed at the whole cell level on the basis of a combined experimental and modeling approach.