Measurement and Characterization of the Electrical Properties of Actin Filaments.

Actin filaments, as key components of the cytoskeleton, have aroused great interest due to their numerous functional roles in eukaryotic cells, including intracellular electrical signaling. The aim of this research is to characterize the alternating current (AC) conduction characteristics of both globular and polymerized actin and quantitatively compare their values to those theoretically predicted earlier. Actin filaments have been demonstrated to act as conducting bionanowires, forming a signaling network capable of transmitting ionic waves in cells. We performed conductivity measurements for different concentrations of actin, considering both unpolymerized and polymerized actin to identify potential differences in their electrical properties. These measurements revealed two relevant characteristics: first, the polymerized actin, arranged in filaments, has a lower impedance than its globular counterpart; second, an increase in the actin concentration leads to higher conductivities. Furthermore, from the data collected, we developed a quantitative model to represent the electrical properties of actin in a buffer solution. We hypothesize that actin filaments can be modeled as electrical resistor-inductor-capacitor (RLC) circuits, where the resistive contribution is due to the viscous ion flows along the filaments; the inductive contribution is due to the solenoidal flows along and around the helix-shaped filament and the capacitive contribution is due to the counterion layer formed around each negatively charged filament.

Endovascular treatment of aortic coarctation: long-term effects on hypertension.

INTRODUCTION: Endovascular management of aortic coarctation (CoA) is safe but few data are available concerning the long-term cure of hypertension. Aim of this study was to evaluate immediate and long-term clinical and haemodynamic outcome in a consecutive series of adolescent and adult patients with CoA submitted to endovascular treatment. METHODS: A total of 21 adolescent and adult patients underwent successful transcatheter intervention of CoA. Follow-up comprised cardiological examination with special attention to blood pressure (BP), echocardiogram, 24/h ambulatory blood pressure monitoring (ABP), exercise test and spiral computed tomography. RESULTS: Pre-intervention CoA diameter and degree of stenosis were 4.8+/-2.1 mm and 73.7+/-9.8%, respectively, and 14.8+/-3.0 mm and 13.5+/-6.5% post-intervention (p<0.001). Systolic arterial hypertension persisted in 2 patients at rest (9.5%). Mean number of antihypertensive medications per patient was 1.5+/-1.1 and 0.5+/-0.9 at 1 year after treatment (p<0.05). At ABP 3 patients (14%) were hypertensive. The Doppler gradient across the coarctation site decreased from 58.8+/-16.9 to 10.5+/-4.9 mmHg (p<0.001) as well as left ventricular mass (199+/-14.6 and 189.3+/-9.1; p<0.001). Overall, 18 patients (86%) underwent a treadmill exercise test and 4 patients (22%), normotensive at rest, showed a pathological blood pressure response. Overall, 7/21 patients (33%) showed persistent hypertension. CONCLUSION: Endovascular treatment of native or recurrent CoA in adolescent and adult patients is safe but 33% of patients showed persistent hypertension. Meticulous clinical follow-up is mandatory, including an exercise test in order to monitor eventual blood pressure increase and to assess effort tolerance.

Functional and structural correlates of persistent ST elevation after acute myocardial infarction successfully treated by percutaneous coronary intervention.

BACKGROUND: In the thrombolytic era, persistence of ST-segment elevation was considered a marker of left ventricular (LV) aneurysm. ST-segment elevation may still be found persistently raised after successful primary percutaneous coronary intervention (PCI). Echocardiographic correlates of this finding, however, are still poorly known. METHODS AND RESULTS: 82 consecutive patients with first ST-segment elevation myocardial infarction and successful PCI were divided into patients with persistent ST-segment elevation at discharge (sum of ST >4 mm) (n = 33) and those without persistent ST-segment elevation (n = 49). Conventional and myocardial contrast echocardiography were performed at discharge and at 6 months. At discharge, LV aneurysm was more common in patients with persistent ST elevation (27% vs 8%, p<0.005). Similarly, the wall motion score index was higher (2.5 vs 2.0, p<0.005) and microvascular damage larger (2.3 vs 1.8, p<0.005) in patients with persistent ST-segment elevation. At 6 months' follow-up, LV volumes were similar in the two groups. CONCLUSIONS: After primary PCI, persistent ST-segment elevation is associated with LV aneurysm formation in 30% of cases, it is not associated with significantly larger LV dilatation but with larger microvascular damage and dysfunctioning risk area.