| 1. |
- Pantazis, N, et al.
(författare)
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Determining the likely place of HIV acquisition for migrants in Europe combining subject-specific information and biomarkers data
- 2019
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Ingår i: Statistical methods in medical research. - : SAGE Publications. - 1477-0334 .- 0962-2802. ; 28:7, s. 1979-1997
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Tidskriftsartikel (refereegranskat)abstract
- In most HIV-positive individuals, infection time is only known to lie between the time an individual started being at risk for HIV and diagnosis time. However, a more accurate estimate of infection time is very important in certain cases. For example, one of the objectives of the Advancing Migrant Access to Health Services in Europe (aMASE) study was to determine if HIV-positive migrants, diagnosed in Europe, were infected pre- or post-migration. We propose a method to derive subject-specific estimates of unknown infection times using information from HIV biomarkers’ measurements, demographic, clinical, and behavioral data. We assume that CD4 cell count (CD4) and HIV-RNA viral load trends after HIV infection follow a bivariate linear mixed model. Using post-diagnosis CD4 and viral load measurements and applying the Bayes’ rule, we derived the posterior distribution of the HIV infection time, whereas the prior distribution was informed by AIDS status at diagnosis and behavioral data. Parameters of the CD4–viral load and time-to-AIDS models were estimated using data from a large study of individuals with known HIV infection times (CASCADE). Simulations showed substantial predictive ability (e.g. 84% of the infections were correctly classified as pre- or post-migration). Application to the aMASE study ( n = 2009) showed that 47% of African migrants and 67% to 72% of migrants from other regions were most likely infected post-migration. Applying a Bayesian method based on bivariate modeling of CD4 and viral load, and subject-specific information, we found that the majority of HIV-positive migrants in aMASE were most likely infected after their migration to Europe.
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| 5. |
- Lubitz, W., et al.
(författare)
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Light-induced water oxidation in photosynthesis
- 2014
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Ingår i: Journal of Biological Inorganic Chemistry. - : SPRINGER. - 0949-8257 .- 1432-1327. ; 19, s. S350-S350
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 6. |
- Angelini, Marina, et al.
(författare)
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Suppression of ventricular arrhythmias by targeting late L-type Ca2+ current
- 2021
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Ingår i: The Journal of General Physiology. - : ROCKEFELLER UNIV PRESS. - 0022-1295 .- 1540-7748. ; 153:12
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Tidskriftsartikel (refereegranskat)abstract
- Ventricular arrhythmias, a leading cause of sudden cardiac death, can be triggered by cardiomyocyte early afterdepolarizations (EADs). EADs can result from an abnormal late activation of L-type Ca2+ channels (LTCCs). Current LTCC blockers (class IV antiarrhythmics), while effective at suppressing EADs, block both early and late components of I-Ca,I-L, compromising inotropy. However, computational studies have recently demonstrated that selective reduction of late I-Ca,I-L (Ca2+ influx during late phases of the action potential) is sufficient to potently suppress EADs, suggesting that effective antiarrhythmic action can be achieved without blocking the early peak I-Ca,I-L, which is essential for proper excitation-contraction coupling. We tested this new strategy using a purine analogue, roscovitine, which reduces late I-Ca,I-L with minimal effect on peak current. Scaling our investigation from a human Ca(V)1.2 channel clone to rabbit ventricular myocytes and rat and rabbit perfused hearts, we demonstrate that (1) roscovitine selectively reduces I-Ca,I-L noninactivating component in a human Ca(V)1.2 channel clone and in ventricular myocytes native current, (2) the pharmacological reduction of late I-Ca,I-L suppresses EADs and EATs (early after Ca2+ transients) induced by oxidative stress and hypokalemia in isolated myocytes, largely preserving cell shortening and normal Ca2+ transient, and (3) late I-Ca,I-L reduction prevents/suppresses ventricular tachycardia/fibrillation in ex vivo rabbit and rat hearts subjected to hypokalemia and/or oxidative stress. These results support the value of an antiarrhythmic strategy based on the selective reduction of late I-Ca,I-L to suppress EAD-mediated arrhythmias. Antiarrhythmic therapies based on this idea would modify the gating properties of Ca(V)1.2 channels rather than blocking their pore, largely preserving contractility.
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| 7. |
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| 8. |
- Madhvani, Roshni V., et al.
(författare)
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Shaping a New Ca2+ Conductance to Suppress Early Afterdepolarizations in Cardiac Myocytes
- 2011
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Ingår i: Journal of Physiology. - : John Wiley & Sons. - 0022-3751 .- 1469-7793. ; 589:24, s. 6081-6092
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Tidskriftsartikel (refereegranskat)abstract
- Non‐technical summary Diseases, genetic defects, or ionic imbalances can alter the normal electrical activity of cardiac myocytes causing an anomalous heart rhythm, which can degenerate to ventricular fibrillation (VF) and sudden cardiac death. Well‐recognized triggers for VF are aberrations of the cardiac action potential, known as early afterdepolarizations (EADs). In this study, combining mathematical modelling and experimental electrophysiology in real‐time (dynamic clamp), we investigated the dependence of EADs on the biophysical properties of the L‐type Ca2+ current (ICa,L) and identified modifications of ICa,L properties which effectively suppress EAD. We found that minimal changes in the voltage dependence of activation or inactivation of ICa,L can dramatically reduce the occurrence of EADs in cardiac myocytes exposed to different EAD‐inducing conditions. This work assigns a critical role to the L‐type Ca2+ channel biophysical properties for EADs formation and identifies the L‐type Ca2+ channel as a promising therapeutic target to suppress EADs and their arrhythmogenic effects.
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| 9. |
- Madhvani, Roshni V., et al.
(författare)
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Targeting the Late Component of the Cardiac L-type Ca2+ Current to Suppress Early Afterdepolarizations
- 2015
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Ingår i: The Journal of General Physiology. - : Rockefeller University Press. - 0022-1295 .- 1540-7748. ; 145:5, s. 395-404
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Tidskriftsartikel (refereegranskat)abstract
- Early afterdepolarizations (EADs) associated with prolongation of the cardiac action potential (AP) can create heterogeneity of repolarization and premature extrasystoles, triggering focal and reentrant arrhythmias. Because the L-type Ca2+ current (ICa,L) plays a key role in both AP prolongation and EAD formation, L-type Ca2+ channels (LTCCs) represent a promising therapeutic target to normalize AP duration (APD) and suppress EADs and their arrhythmogenic consequences. We used the dynamic-clamp technique to systematically explore how the biophysical properties of LTCCs could be modified to normalize APD and suppress EADs without impairing excitation–contraction coupling. Isolated rabbit ventricular myocytes were first exposed to H2O2 or moderate hypokalemia to induce EADs, after which their endogenous ICa,L was replaced by a virtual ICa,L with tunable parameters, in dynamic-clamp mode. We probed the sensitivity of EADs to changes in the (a) amplitude of the noninactivating pedestal current; (b) slope of voltage-dependent activation; (c) slope of voltage-dependent inactivation; (d) time constant of voltage-dependent activation; and (e) time constant of voltage-dependent inactivation. We found that reducing the amplitude of the noninactivating pedestal component of ICa,L effectively suppressed both H2O2- and hypokalemia-induced EADs and restored APD. These results, together with our previous work, demonstrate the potential of this hybrid experimental–computational approach to guide drug discovery or gene therapy strategies by identifying and targeting selective properties of LTCC.
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| 13. |
- Savalli, Nicoletta, et al.
(författare)
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The α2δ-1 Subunit Remodels CaV1.2 Voltage Sensors, Allowing for Ca2+ Influx at Physiological Membrane Potentials
- 2016
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Ingår i: The Journal of General Physiology. - : Rockefeller University Press. - 0022-1295 .- 1540-7748. ; 148:2, s. 147-159
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Tidskriftsartikel (refereegranskat)abstract
- Excitation-evoked calcium influx across cellular membranes is strictly controlled by voltage-gated calcium channels (CaV), which possess four distinct voltage-sensing domains (VSDs) that direct the opening of a central pore. The energetic interactions between the VSDs and the pore are critical for tuning the channel’s voltage dependence. The accessory α2δ-1 subunit is known to facilitate CaV1.2 voltage-dependent activation, but the underlying mechanism is unknown. In this study, using voltage clamp fluorometry, we track the activation of the four individual VSDs in a human L-type CaV1.2 channel consisting of α1C and β3 subunits. We find that, without α2δ-1, the channel complex displays a right-shifted voltage dependence such that currents mainly develop at nonphysiological membrane potentials because of very weak VSD–pore interactions. The presence of α2δ-1 facilitates channel activation by increasing the voltage sensitivity (i.e., the effective charge) of VSDs I–III. Moreover, the α2δ-1 subunit also makes VSDs I–III more efficient at opening the channel by increasing the coupling energy between VSDs II and III and the pore, thus allowing Ca influx within the range of physiological membrane potentials.
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