Papers by Gertrudis Hortensia González Gómez

Nanomaterials, Feb 17, 2024
Because of the physiological and cardiac changes associated with cardiovascular disease, tissue e... more Because of the physiological and cardiac changes associated with cardiovascular disease, tissue engineering can potentially restore the biological functions of cardiac tissue through the fabrication of scaffolds. In the present study, hybrid nanofiber scaffolds of poly (vinyl alcohol) (PVA) and bioglass type 58S (58SiO 2 -33CaO-9P 2 O 5 , Bg) were fabricated, and their effect on the spontaneous activity of chick embryonic cardiomyocytes in vitro was determined. PVA/Bg nanofibers were produced by electrospinning and stabilized by chemical crosslinking with glutaraldehyde. The electrospun scaffolds were analyzed to determine their chemical structure, morphology, and thermal transitions. The crosslinked scaffolds were more stable to degradation in water. A Bg concentration of 25% in the hybrid scaffolds improved thermal stability and decreased degradation in water after PVA crosslinking. Cardiomyocytes showed increased adhesion and contractility in cells seeded on hybrid scaffolds with higher Bg concentrations. In addition, the effect of Ca 2+ ions released from the bioglass on the contraction patterns of cultured cardiomyocytes was investigated. The results suggest that the scaffolds with 25% Bg led to a uniform beating frequency that resulted in synchronous contraction patterns.

Scientific Reports
Aging is commonly regarded as a physiological process in which the dynamic complexity of physiolo... more Aging is commonly regarded as a physiological process in which the dynamic complexity of physiological time series and organ systems is gradually lost. This notion is derived from the identification of a decline of nonlinear measures with the advance of aging. However, additional research on cardiovascular control studied through heart rate variability (HRV), i.e., the instantaneous changes in heart rate, shows that despite the constriction of its statistical distribution, the nonlinear organization remains present in advanced age. Here, we used surrogate data testing to investigate the presence of nonlinear information in HRV time series from a publicly available database of 1121 healthy human subjects from 18 to 92 years old. We also studied the influence of basic clinical features, such as sex, body mass index (BMI), and mean heart rate (HR), on such nonlinear information. We found that the percentage of nonlinear time series after 30 years of age diminishes significantly (p <...

Sensors
Impaired baroreflex sensitivity (BRS) is partially responsible for erratic blood pressure fluctua... more Impaired baroreflex sensitivity (BRS) is partially responsible for erratic blood pressure fluctuations in End-Stage Renal Disease (ESRD) patients on chronic hemodialysis (HD), which is related to autonomic nervous dysfunction. The sequence method with delayed signals allows for the measurement of BRS in a non-invasive fashion and the investigation of alterations in this physiological feedback system that maintains BP within healthy limits. Our objective was to evaluate the modified delayed signals in the sequence method for BRS assessment in ESRD patients without pharmacological antihypertensive treatment and compare them with those of healthy subjects. We recruited 22 healthy volunteers and 18 patients with ESRD. We recorded continuous BP to obtain a 15-min time series of systolic blood pressure and interbeat intervals during the supine position (SP) and active standing (AS) position. The time series with delays from 0 to 5 heartbeats were used to calculate the BRS, number of data ...

Eur. Phys. J. Spec. Top., 2022
Abstract Recurrence quantitative analysis (RQA) indices of heart rate variability (HRV) have show... more Abstract Recurrence quantitative analysis (RQA) indices of heart rate variability (HRV) have shown a different adjustment in the sympathetic-driven dynamical response to active standing (AS) and hemodial- ysis (HD), characterized by increased laminar states in HRV. AS test is a maneuver in which subjects actively change their body posture from supine position (SP) to AS. In end-stage renal disease (ESRD) patients treated twice-weekly by HD, we found reduced changes in RQA indices to AS before HD that are partially recovered after treatment; laminarity, trapping time and recurrence time of the second type values were significantly lower in SP than during AS (p< 0.05). Patients who developed intradialytic hypotension (IDH) did not show a significant response to AS in contrast with patients who did not develop IDH. Also, the mean duration of heartbeat intervals significantly influenced RQA indices (p< 0.05), and this correlation depended on the observation moment (before or after HD). These findings suggest that the cardiac response to the autonomic modulation measured by RQA is different in IDH patients even before HD. Furthermore, the influence of the mean heart rate changes seems to play an important role in the short-term control of HRV behavior in ESRD
The European Physical Journal Special Topics

The European Physical Journal Special Topics, 2022
Abstract Recurrence quantitative analysis (RQA) of heart rate variability (HRV) is helpful for th... more Abstract Recurrence quantitative analysis (RQA) of heart rate variability (HRV) is helpful for the non- invasive study of the regulation of the cardiovascular system by the autonomic nervous system. HRV monitoring during hemodialysis (HD) sessions of end-stage renal disease patients reflects a sympathetic hyperactivity that has been proposed as an early marker of intradialytic hypotension (IDH). However, neither intradialytic HRV analysis nor episodes of IDH have been explored from the RQA perspective. We studied the HRV dynamics with linear and RQA indices during intradialytic recordings (N = 38) in which 39.5% of patients presented IDH. Patients with IDH showed a restricted HRV during the whole HD compared to patients with stable blood pressure (p < 0.05). Although the RQA results during HD were heterogeneous, laminarity and the recurrence time of the second type revealed a constricted behavior around the onset of the IDH episodes. RQA analysis complemented the linear HRV measure to reveal a characteristic behavior immediately before and after the IDH episode. We also explored a framework for IDH prediction with a linear HRV index, the standard deviation of the differences between adjacent heartbeats intervals, which was associated in the early moments of HD with the development of IDH throughout HD sessions (sensitivity 80%, specificity 82.6%). The observed differences between groups may be of clinical utility for an early identification of patients prone to IDH.

Chaos (Woodbury, N.Y.), 2017
The scaling properties of heart rate variability data are reliable dynamical features to predict ... more The scaling properties of heart rate variability data are reliable dynamical features to predict mortality and for the assessment of cardiovascular risk. The aim of this manuscript was to determine if the scaling properties, as provided by the sign and magnitude analysis, can be used to differentiate between pathological changes and those adaptations basically introduced by modifications of the mean heart rate in distinct manoeuvres (active standing or hemodialysis treatment, HD), as well as clinical conditions (end stage renal disease, ESRD). We found that in response to active standing, the short-term scaling index (α1) increased in healthy subjects and in ESRD patients only after HD. The sign short-term scaling exponent (α1sign) increased in healthy subjects and ESRD patients, showing a less anticorrelated behavior in active standing. Both α1 and α1sign did show covariance with the mean heart rate in healthy subjects, while in ESRD patients, this covariance was observed only afte...

Frontiers in Physiology
Exploring the presence of nonlinearity through surrogate data testing provides insights into the ... more Exploring the presence of nonlinearity through surrogate data testing provides insights into the nature of physical and biological systems like those obtained from heart rate variability (HRV). Short-term HRV time series are of great clinical interest to study autonomic impairments manifested in chronic diseases such as the end stage renal disease (ESRD) and the response of patients to treatment with hemodialysis (HD). In contrast to Iterative Amplitude Adjusted Fourier Transform (IAAFT), the Pinned Wavelet Iterative Amplitude Adjusted Fourier Transform (PWIAAFT) surrogates preserve nonstationary behavior in time series, a common characteristic of HRV. We aimed to test synthetic data and HRV time series for the existence of nonlinearity. Recurrence Quantitative Analysis (RQA) indices were used as discriminative statistics in IAAFT and PWIAAFT surrogates of linear stationary and nonstationary processes. HRV time series of healthy subjects and 29 ESRD patients before and after HD were...

Biomimetics
For several years, cell culture techniques have been physiologically relevant to understand livin... more For several years, cell culture techniques have been physiologically relevant to understand living organisms both structurally and functionally, aiming at preserving as carefully as possible the in vivo integrity and function of the cells. However, when studying cardiac cells, glass or plastic Petri dishes and culture-coated plates lack important cues that do not allow to maintain the desired phenotype, especially for primary cell culture. In this work, we show that microscaffolds made with polydimethylsiloxane (PDMS) enable modulating the stiffness of the surface of the culture substrate and this originates different patterns of adhesion, self-organization, and synchronized or propagated activity in the culture of chick embryonic cardiomyocytes. Thanks to the calcium imaging technique, we found that the substrate stiffness affected cardiomyocyte adhesion, as well as the calcium signal propagation in the formed tissue. The patterns of activity shown by the calcium fluorescence varia...

Entropy
Linear heart rate variability (HRV) indices are dependent on the mean heart rate, which has been ... more Linear heart rate variability (HRV) indices are dependent on the mean heart rate, which has been demonstrated in different models (from sinoatrial cells to humans). The association between nonlinear HRV indices, including those provided by recurrence plot quantitative analysis (RQA), and the mean heart rate (or the mean cardiac period, also called meanNN) has been scarcely studied. For this purpose, we analyzed RQA indices of five minute-long HRV time series obtained in the supine position and during active standing from 30 healthy subjects and 29 end-stage renal disease (ESRD) patients (before and after hemodialysis). In the supine position, ESRD patients showed shorter meanNN (i.e., faster heart rate) and decreased variability compared to healthy subjects. The healthy subjects responded to active standing by shortening the meanNN and decreasing HRV indices to reach similar values of ESRD patients. Bivariate correlations between all RQA indices and meanNN were significant in health...

Chaos (Woodbury, N.Y.), 2018
The inter beat interval (IBI) duration and systolic blood pressure (SBP) are cardiovascular varia... more The inter beat interval (IBI) duration and systolic blood pressure (SBP) are cardiovascular variables related through several feedback mechanisms. We propose the analysis of diagonal lines in cross recurrence plots (CRPs) from IBI and SBP embedded within the same phase space to identify events where trajectories of both variables concur. The aim of the study was to describe the relationship between IBI and SBP of healthy subjects using CRP and diagonal analysis during baseline condition-supine position (SP)-and how the relationship changes during the physiological stress of active standing (AS). IBI and SBP time series were obtained from continuous blood pressure recordings during SP and AS (15 min each) in 19 young healthy subjects. IBI and SBP time series were embedded within a five-dimensional phase space using an embedding delay estimated from cross correlation between IBI and SBP. During SP, mean CRP showed high determinism (≥85%) and also brief but repeated events where both v...
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Papers by Gertrudis Hortensia González Gómez