1,721,172 research outputs found
How to check steady-state condition from cardiovascular time series
No full textIn this study we propose a procedure to automatically check the hypothesis of steady state from the dynamics of the cardiovascular signals, based on the 'run test'. The total number of runs r(tot) is computed from the series of systolic and diastolic blood pressures and R-R intervals. If r(tot) is lower than a given threshold, the steady-state hypothesis is rejected. Because of long-term correlations affecting the cardiovascular series, the thresholds at the 5% significance level were estimated calculating the rtot distributions from a public database of cardiovascular signals collected in steady-state conditions. The procedure was applied to quantify the steadiness of baseline recordings, and to identify sub-periods of steady state during a sequence of physical activities. Results showed the capability of the procedure to automatically detect steady-state conditions, and to identify when the steadiness is lost because of disturbing factors or transients occurring during the recording
A TRIM32-AMBRA1-ULK1 complex initiates the autophagy response in atrophic muscle cells
No full textThe Ser/Thr protein kinase ULK1 is an upstream macroautophagy/autophagy regulator that is rapidly activated to ensure a proper adaptive response to stress conditions. Signaling pathways modulating ULK1 activity have been extensively characterized in response to nutrient/energy shortage, which mainly act by mediating ULK1 post-translational modifications, such as phosphorylation, acetylation and ubiquitination. Less characterized is how tissue-specific stress signals are able to activate ULK1 to induce autophagy. Our recent study has uncovered the E3 ubiquitin ligase TRIM32 as a novel ULK1 activator that regulates autophagy in muscle cells upon atrophy induction. TRIM32 is conveyed to ULK1 by the autophagy cofactor AMBRA1 to stimulate its kinase activity through unanchored K63-linked polyubiquitin chains. Notably, mutations in TRIM32 responsible for limb-girdle muscular dystrophy 2H disrupt its ability to bind ULK1 and to induce autophagy in muscle cells, resulting in a dysregulated activation of the atrophic process. In conclusion, we have identified a novel molecular mechanism by which autophagy is regulated in muscles, whose alteration is associated with the development of muscular dystrophy
Dynamic adaptation of cardiac baroreflex sensitivity to prolonged exposure to microgravity: data from a 16-day spaceflight
No full textDi Rienzo M, Castiglioni P, Iellamo F, Volterrani M, Pagani M, Mancia G, Karemaker JM, Parati G. Dynamic adaptation of cardiac baroreflex sensitivity to prolonged exposure to microgravity: data from a 16-day spaceflight. J Appl Physiol 105: 1569-1575, 2008. First published August 28, 2008; doi:10.1152/japplphysiol.90625.2008.-This study explored the process of arterial baroreflex adaptation to microgravity, starting from the first day of flight, during the 16-day STS-107 Columbia Space Shuttle mission. Continuous blood pressure (BP), ECG, and respiratory frequency were collected in four astronauts on ground (baseline) and during flight at days 0-1, 6-7, and 12-13, both at rest and during moderate exercise (75 W) on a cycle ergometer. Sensitivity of the baroreflex heart rate control (BRS) was assessed by sequence and spectral alpha methods. Baroreflex effectiveness index (BEI); low-frequency (LF) power and high-frequency (HF) power of systolic BP (SBP), diastolic BP (DBP), and R-R interval (RRI); the RRI LF/HF ratio; and the RRI root mean square of successive differences (RMSSD) index were also estimated. We found that, at rest, BRS increased in early flight phase, compared with baseline (means +/- SE: 18.3 +/- 3.4 vs. 10.4 +/- 1.2 ms/mmHg; P < 0.05), and it tended to return to baseline in subsequent days. During exercise, BRS was lower than at rest, without differences between preflight and in-flight values. At rest, in the early flight phase, RMSSD and RRI HF power increased (P < 0.05) compared with baseline, whereas LF powers of SBP and DBP decreased. No statistical difference was found in these parameters during exercise before vs. during flight. These findings demonstrate that heart rate baroreflex sensitivity and markers of cardiac vagal modulation are enhanced during early exposure to microgravity, likely because of the blood centralization, and return to baseline values in subsequent flight phases, possibly because of the fluid loss. No deconditioning seems to occur in the baroreflex control of the heart
Reply to Dr. Cysarz's comment on Point : Counterpoint "Cardiovascular variability is/is not an index of autonomic control of circulation"
No full textEffects of autonomic ganglion blockade on fractal and spectral components of blood pressure and heart rate variability in free-moving rats
No full textFractal analysis is a promising tool for assessing autonomic influences on heart rate (HR) and blood pressure (BP) variability. The temporal spectrum of scale coefficients, alpha(t), was recently proposed to describe the cardiovascular fractal dynamics. Aim of our work is to evaluate sympathetic influences on cardiovascular variability analyzing alpha(t) and spectral powers of HR and BP after ganglionic blockade. BP was recorded in 11 rats before and after autonomic blockade by hexamethonium infusion (HEX). Systolic and diastolic BP, pulse pressure and pulse interval were derived beat-by-beat. Segments longer than 5 min were selected at baseline and HEX to estimate power spectra and alpha(t). Comparisons were made by paired t-test. HEX reduced all spectral components of systolic and diastolic BP, the reduction being particularly significant around the frequency of Mayer waves; it induced a reduction on alpha(t) coefficients at t 8 s. HEX reduced only slower components of pulse interval power spectrum, but decreased significantly faster scale coefficients (t 1) at shorter scales. Ganglionic blockade also removes a fractional Brownian motion component at shorter scales from HR dynamics. Results may be explained by the characteristic time constants between sympathetic efferent activity and cardiovascular effectors. Therefore fractal analysis may complete spectral analysis with information on the correlation structure of the data. (C) 2013 Elsevier B.V. All rights reserved
Identification of steady states and quantification of transition periods from beat-by-beat cardiovascular time series: application to incremental exercise test
No full textEros e thanatos nel romanzo barocco italiano
No full textAnatomia della malinconia d'amore nel romanzo barocco italiano
Blood pressure and heart rate variability and baroreflex sensitivity before and after brain death
No full textObjectives-To evaluate spontaneous blood pressure and heart rate variability and spontaneous baroreflex sensitivity before and after brain death. Methods-Spontaneous variability of arterial blood pressure and heart rate-estimated by power spectra of systolic (SBP) and diastolic blood pressure (DBP) and pulse interval (Pl)-and spontaneous baroreflex sensitivity (BRS)-estimated by the alpha index and the sequence technique-were evaluated in 11 patients twice: shortly before and 1 hour after the onset of brain death. Results-Significant spectral changes occurred after brain death: a general power reduction in PI spectra; a shift of SBP, DBP and PI powers toward the lower frequencies, resulting in a greater slope of the "1/f" spectral trends; and a marked reduction of SBP and DBP powers (-93%) and of SBP-PI coherence (-63%) at 0.1 Hz. The estimated average BRS was relatively high before brain death (around 11 ms/mm Hg), and fell close to 0 or even was not detectable at all after brain death. Conclusions-Parameters describing spontaneous blood pressure and heart rate variability and indexes reflecting the baroreflex function, which were relatively normal up to a few hours before brain death, underwent marked changes with the onset of brain death. All the changes found are likely to reflect the cessation of activity of the cardiovascular brain stem centres. These findings indicate that techniques of blood pressure and heart rate spectral analysis and of dynamic assessment of baroreflex sensitivity may be useful to complement the diagnosis of brain stem death
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