TY  - JOUR
AU  - Bajić, Dragana
AU  - Skorić, Tamara
AU  - Milutinović-Smiljanić, Sanja
AU  - Japundžić-Žigon, Nina
PY  - 2019
UR  - https://smile.stomf.bg.ac.rs/handle/123456789/2418
AB  - This paper proposes a method that maps the coupling strength of an arbitrary number of signals D, D >= 2, into a single time series. It is motivated by the inability of multiscale entropy to jointly analyze more than two signals. The coupling strength is determined using the copula density defined over a [0 1](D) copula domain. The copula domain is decomposed into the Voronoi regions, with volumes inversely proportional to the dependency level (coupling strength) of the observed joint signals. A stream of dependency levels, ordered in time, creates a new time series that shows the fluctuation of the signals' coupling strength along the time axis. The composite multiscale entropy (CMSE) is then applied to three signals, systolic blood pressure (SBP), pulse interval (PI), and body temperature (t(B)), simultaneously recorded from rats exposed to different ambient temperatures (t(A)). The obtained results are consistent with the results from the classical studies, and the method itself offers more levels of freedom than the classical analysis.
PB  - Mdpi, Basel
T2  - Entropy
T1  - Voronoi Decomposition of Cardiovascular Dependency Structures in Different Ambient Conditions: An Entropy Study
VL  - 21
IS  - 11
DO  - 10.3390/e21111103
ER  - 

@article{
author = "Bajić, Dragana and Skorić, Tamara and Milutinović-Smiljanić, Sanja and Japundžić-Žigon, Nina",
year = "2019",
abstract = "This paper proposes a method that maps the coupling strength of an arbitrary number of signals D, D >= 2, into a single time series. It is motivated by the inability of multiscale entropy to jointly analyze more than two signals. The coupling strength is determined using the copula density defined over a [0 1](D) copula domain. The copula domain is decomposed into the Voronoi regions, with volumes inversely proportional to the dependency level (coupling strength) of the observed joint signals. A stream of dependency levels, ordered in time, creates a new time series that shows the fluctuation of the signals' coupling strength along the time axis. The composite multiscale entropy (CMSE) is then applied to three signals, systolic blood pressure (SBP), pulse interval (PI), and body temperature (t(B)), simultaneously recorded from rats exposed to different ambient temperatures (t(A)). The obtained results are consistent with the results from the classical studies, and the method itself offers more levels of freedom than the classical analysis.",
publisher = "Mdpi, Basel",
journal = "Entropy",
title = "Voronoi Decomposition of Cardiovascular Dependency Structures in Different Ambient Conditions: An Entropy Study",
volume = "21",
number = "11",
doi = "10.3390/e21111103"
}

Bajić, D., Skorić, T., Milutinović-Smiljanić, S.,& Japundžić-Žigon, N.. (2019). Voronoi Decomposition of Cardiovascular Dependency Structures in Different Ambient Conditions: An Entropy Study. in Entropy
Mdpi, Basel., 21(11).
https://doi.org/10.3390/e21111103

Bajić D, Skorić T, Milutinović-Smiljanić S, Japundžić-Žigon N. Voronoi Decomposition of Cardiovascular Dependency Structures in Different Ambient Conditions: An Entropy Study. in Entropy. 2019;21(11).
doi:10.3390/e21111103 .

Bajić, Dragana, Skorić, Tamara, Milutinović-Smiljanić, Sanja, Japundžić-Žigon, Nina, "Voronoi Decomposition of Cardiovascular Dependency Structures in Different Ambient Conditions: An Entropy Study" in Entropy, 21, no. 11 (2019),
https://doi.org/10.3390/e21111103 . .

TY  - JOUR
AU  - Vasić, Marko
AU  - Loncar-Turukalo, Tatjana
AU  - Tasić, Tatjana
AU  - Matić, Marija
AU  - Glumac, Sofija
AU  - Bajić, Dragana
AU  - Popović, Branka
AU  - Japundžić-Žigon, Nina
PY  - 2019
UR  - https://smile.stomf.bg.ac.rs/handle/123456789/2469
AB  - Using comprehensive analysis of heart rate (HRV) and blood pressure (BPV) short-term variability we estimated the time course of changes of autonomic nervous system remodeling in two stages of doxorubicin-induced cardiomyopathy (DCM). We also investigated the level of gene expression of cardiac beta-1 (beta-1AR) and beta-2 (beta-2AR) adrenoceptors. Experiments were performed in adult male Wistar rats equipped with indwelling catheters for BP recording and blood withdrawal. A 15 mg/kg total cumulative dose of doxorubicin was injected i.p. to rats to induce DCM or saline for control (n = 18). Rats were assessed for general toxicity, cardiovascular hemodynamic and echocardiography before treatment (n = 6), 35 days (DOX35; n = 6) and 70 days (DOX70; n = 6) post-treatment. HRV was evaluated by spectral analysis, Poincare plots, sample and approximate entropy. Expression of beta-1AR and beta-2AR mRNA was evaluated by RT-qPCR. Doxorubicin-treated rats exhibited poor general condition and lower survival than saline-treated rats. In DOX35 rats, there were no echocardiography signs of decompensation, no increase in serum cardiac troponins, but there was an increase of HRV and decrease of HR complexity. In these rats typical microscopic signs of cardiotoxicity were seen along with over-expression of beta-1AR mRNA. 70 days post-treatment echocardiography revealed signs of decompensation and serum cardiac troponin T was increased. At this stage BPV decreased. In conclusion, HRV increase matches transient over expression of cardiac beta-1AR mRNA in compensate stage of DCM while decompensate stage of DCM is characterized by a decrease of BPV and no changes in beta-1AR and beta-2AR gene expression.
PB  - Academic Press Inc Elsevier Science, San Diego
T2  - Toxicology & Applied Pharmacology
T1  - Cardiovascular variability and beta-ARs gene expression at two stages of doxorubicin - Induced cardiomyopathy
VL  - 362
SP  - 43
EP  - 51
DO  - 10.1016/j.taap.2018.10.015
ER  - 

@article{
author = "Vasić, Marko and Loncar-Turukalo, Tatjana and Tasić, Tatjana and Matić, Marija and Glumac, Sofija and Bajić, Dragana and Popović, Branka and Japundžić-Žigon, Nina",
year = "2019",
abstract = "Using comprehensive analysis of heart rate (HRV) and blood pressure (BPV) short-term variability we estimated the time course of changes of autonomic nervous system remodeling in two stages of doxorubicin-induced cardiomyopathy (DCM). We also investigated the level of gene expression of cardiac beta-1 (beta-1AR) and beta-2 (beta-2AR) adrenoceptors. Experiments were performed in adult male Wistar rats equipped with indwelling catheters for BP recording and blood withdrawal. A 15 mg/kg total cumulative dose of doxorubicin was injected i.p. to rats to induce DCM or saline for control (n = 18). Rats were assessed for general toxicity, cardiovascular hemodynamic and echocardiography before treatment (n = 6), 35 days (DOX35; n = 6) and 70 days (DOX70; n = 6) post-treatment. HRV was evaluated by spectral analysis, Poincare plots, sample and approximate entropy. Expression of beta-1AR and beta-2AR mRNA was evaluated by RT-qPCR. Doxorubicin-treated rats exhibited poor general condition and lower survival than saline-treated rats. In DOX35 rats, there were no echocardiography signs of decompensation, no increase in serum cardiac troponins, but there was an increase of HRV and decrease of HR complexity. In these rats typical microscopic signs of cardiotoxicity were seen along with over-expression of beta-1AR mRNA. 70 days post-treatment echocardiography revealed signs of decompensation and serum cardiac troponin T was increased. At this stage BPV decreased. In conclusion, HRV increase matches transient over expression of cardiac beta-1AR mRNA in compensate stage of DCM while decompensate stage of DCM is characterized by a decrease of BPV and no changes in beta-1AR and beta-2AR gene expression.",
publisher = "Academic Press Inc Elsevier Science, San Diego",
journal = "Toxicology & Applied Pharmacology",
title = "Cardiovascular variability and beta-ARs gene expression at two stages of doxorubicin - Induced cardiomyopathy",
volume = "362",
pages = "43-51",
doi = "10.1016/j.taap.2018.10.015"
}

Vasić, M., Loncar-Turukalo, T., Tasić, T., Matić, M., Glumac, S., Bajić, D., Popović, B.,& Japundžić-Žigon, N.. (2019). Cardiovascular variability and beta-ARs gene expression at two stages of doxorubicin - Induced cardiomyopathy. in Toxicology & Applied Pharmacology
Academic Press Inc Elsevier Science, San Diego., 362, 43-51.
https://doi.org/10.1016/j.taap.2018.10.015

Vasić M, Loncar-Turukalo T, Tasić T, Matić M, Glumac S, Bajić D, Popović B, Japundžić-Žigon N. Cardiovascular variability and beta-ARs gene expression at two stages of doxorubicin - Induced cardiomyopathy. in Toxicology & Applied Pharmacology. 2019;362:43-51.
doi:10.1016/j.taap.2018.10.015 .

Vasić, Marko, Loncar-Turukalo, Tatjana, Tasić, Tatjana, Matić, Marija, Glumac, Sofija, Bajić, Dragana, Popović, Branka, Japundžić-Žigon, Nina, "Cardiovascular variability and beta-ARs gene expression at two stages of doxorubicin - Induced cardiomyopathy" in Toxicology & Applied Pharmacology, 362 (2019):43-51,
https://doi.org/10.1016/j.taap.2018.10.015 . .

TY  - JOUR
AU  - Jovanović, Slađana
AU  - Skorić, Tamara
AU  - Sarenac, Olivera
AU  - Milutinović-Smiljanić, Sanja
AU  - Japundžić-Žigon, Nina
AU  - Bajić, Dragana
PY  - 2018
UR  - https://smile.stomf.bg.ac.rs/handle/123456789/2291
AB  - Objectives: Copula is a tool for measuring linear and non-linear interactions between two or more time series. The aim of this paper is to prove that a copula approach can accurately capture and visualize the spatial and temporal fluctuations in dependency structures of cardiovascular signals, and to outline the application possibilities. Methods: The method for measuring the level of interaction between systolic blood pressure and the corresponding pulse interval is validated statistically and pharmacologically. The time series are recorded from the freely moving male Wistar rats equipped with radio-telemetry device for blood pressure recording, before and after administration of autonomic blockers scopolamine, atenolol, prazosin and hexamethonium. Implicit (Gaussian and t) and explicit (Clayton, Frank and Gumbel) copulas were calculated and compared to the conventional bivariate methods (Kendal, Pearson, Spearman and classical correlation). Further statistical validation was done using artificially generated surrogate data. A window sliding procedure for dynamic monitoring the signals' coupling strength is implemented. Results: Under the baseline physiological conditions, SBP-PI dependency is significant for time lags 0 s-4 s. Hexamethonium completely abolished the dependency, scopolamine abolished it for time lags 0 s-2 s, atenolol first slightly increased, than for lags greater than 2 s decreased the dependency and prazosin had no effect. Isospectral and isodistributional surrogate data tests confirm that copulas successfully notify the absence of dependency as well. Conclusion: Copula approach accurately captures the temporal fluctuations in dependency structures of SBP and PI, simultaneously enabling a visualization of dependency levels within the particular signal zones. An analysis showed that copulas are more sensitive than the conventional statistical measures, with Frank copula exhibiting the best characterization of SBP and PI dependency.
PB  - Elsevier Sci Ltd, Oxford
T2  - Biomedical Signal Processing & Control
T1  - Copula as a dynamic measure of cardiovascular signal interactions
VL  - 43
SP  - 250
EP  - 264
DO  - 10.1016/j.bspc.2018.03.007
ER  - 

@article{
author = "Jovanović, Slađana and Skorić, Tamara and Sarenac, Olivera and Milutinović-Smiljanić, Sanja and Japundžić-Žigon, Nina and Bajić, Dragana",
year = "2018",
abstract = "Objectives: Copula is a tool for measuring linear and non-linear interactions between two or more time series. The aim of this paper is to prove that a copula approach can accurately capture and visualize the spatial and temporal fluctuations in dependency structures of cardiovascular signals, and to outline the application possibilities. Methods: The method for measuring the level of interaction between systolic blood pressure and the corresponding pulse interval is validated statistically and pharmacologically. The time series are recorded from the freely moving male Wistar rats equipped with radio-telemetry device for blood pressure recording, before and after administration of autonomic blockers scopolamine, atenolol, prazosin and hexamethonium. Implicit (Gaussian and t) and explicit (Clayton, Frank and Gumbel) copulas were calculated and compared to the conventional bivariate methods (Kendal, Pearson, Spearman and classical correlation). Further statistical validation was done using artificially generated surrogate data. A window sliding procedure for dynamic monitoring the signals' coupling strength is implemented. Results: Under the baseline physiological conditions, SBP-PI dependency is significant for time lags 0 s-4 s. Hexamethonium completely abolished the dependency, scopolamine abolished it for time lags 0 s-2 s, atenolol first slightly increased, than for lags greater than 2 s decreased the dependency and prazosin had no effect. Isospectral and isodistributional surrogate data tests confirm that copulas successfully notify the absence of dependency as well. Conclusion: Copula approach accurately captures the temporal fluctuations in dependency structures of SBP and PI, simultaneously enabling a visualization of dependency levels within the particular signal zones. An analysis showed that copulas are more sensitive than the conventional statistical measures, with Frank copula exhibiting the best characterization of SBP and PI dependency.",
publisher = "Elsevier Sci Ltd, Oxford",
journal = "Biomedical Signal Processing & Control",
title = "Copula as a dynamic measure of cardiovascular signal interactions",
volume = "43",
pages = "250-264",
doi = "10.1016/j.bspc.2018.03.007"
}

Jovanović, S., Skorić, T., Sarenac, O., Milutinović-Smiljanić, S., Japundžić-Žigon, N.,& Bajić, D.. (2018). Copula as a dynamic measure of cardiovascular signal interactions. in Biomedical Signal Processing & Control
Elsevier Sci Ltd, Oxford., 43, 250-264.
https://doi.org/10.1016/j.bspc.2018.03.007

Jovanović S, Skorić T, Sarenac O, Milutinović-Smiljanić S, Japundžić-Žigon N, Bajić D. Copula as a dynamic measure of cardiovascular signal interactions. in Biomedical Signal Processing & Control. 2018;43:250-264.
doi:10.1016/j.bspc.2018.03.007 .

Jovanović, Slađana, Skorić, Tamara, Sarenac, Olivera, Milutinović-Smiljanić, Sanja, Japundžić-Žigon, Nina, Bajić, Dragana, "Copula as a dynamic measure of cardiovascular signal interactions" in Biomedical Signal Processing & Control, 43 (2018):250-264,
https://doi.org/10.1016/j.bspc.2018.03.007 . .