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Biomedical subjects

Maciej Kamiński

Publications and source records attributed to Maciej Kamiński.

7 recordsLinked to original sources

Determination of transmission patterns in multichannel data.

The power of today's laboratory equipment allows more and more data channels to be easily recorded. However, some misunderstandings about processing such multivariate data may still be found in the literature. The typical mistake is to treat a multichannel system as comprising pairs of channels; this approach does not use all the collected information about the investigated system, and may lead to erroneous conclusions. In this paper, the differences between single- and multichannel approaches will be briefly summarized and some examples of problems will be described.

Computer Simulation↗

Analysis of multichannel biomedical data.

Nowadays, there is a common practice in biomedical research to perform multiple time series recordings. In the first part of this paper, basic information about analysis of such multichannel biomedical data is given. A short overview of important differences between single-channel, two-channel and multichannel data sets is presented and various coherence functions are reported. Causal relations between channels are investigated by means of the Directed Transfer Function (DTF) and its dynamic version, the Short-Time Directed Transfer Function (SDTF). The introduced formalism was used to analyze 12-channel human electrocorticogram (ECoG) records. Preliminary results of a study of causal dependence in beta and gamma frequency bands in two patients performing a motor task are reported. Specific characteristics in activity propagation consistent for both subjects for different rhythms were found.

Algorithms↗

Granger causality and information flow in multivariate processes.

The multivariate versus bivariate measures of Granger causality were considered. Granger causality in the application to multivariate physiological time series has the meaning of the information flow between channels. It was shown by means of simulations and by the example of experimental electroencephalogram signals that bivariate estimates of directionality in case of mutually interdependent channels give erroneous results, therefore multivariate measures such as directed transfer function should be used for determination of the information flow.

Algorithms↗

Determination of EEG activity propagation: pair-wise versus multichannel estimate.

Performance of different estimators describing propagation of electroencephalogram (EEG) activity, namely: Granger causality, directed transfer function (DTF), direct DTF (dDTF), short-time DTF (SDTF), bivariate coherence, and partial directed coherence are compared by means of simulations and on the examples of experimental signals. In particular, the differences between pair-wise and multichannel estimates are studied. The results show unequivocally that in most cases, the pair-wise estimates are incorrect and a complete set of signals involved in a given process has to be used to obtain the correct pattern of EEG flows. Different performance of multivariate estimators of propagation depending on their normalization is discussed. Advantages of multivariate autoregressive model are pointed out.

Adult↗

Determination of information flow direction among brain structures by a modified directed transfer function (dDTF) method.

A modification of directed transfer function-direct DTF-is proposed for the analysis of direct information transfer among brain structures on the basis of local field potentials (LFP). Comparison of results obtained by the analysis of simulated and experimental data with a new dDTF and DTF method is shown. A new measure to estimate direct causal relations between signals is defined. The present results demonstrate the effectiveness of the new dDTF method and indicate that the dDTF method can be used to obtain the reliable patterns of connections between various brain structures.

Brain↗

[A case of giant pleomorphic adenoma of the cheek with two malignant centers].

The authors present the case pleomorphic adenoma of a patient aged 77 of atypical location with two malignancy center. After performed diagnostic for an operation the tumor resected. The histopathologic examination proved in the pleomorphic adenoma the cylindromatosum and cancer solid vertens.

Adenoma, Pleomorphic↗

Cerivastatin and hypercholesterolemia reduce apoptosis of cardiomyocytes in guinea pig papillary muscle subjected to hypoxia/reoxygenation.

The aim of this study was to assess how cerivastatin influences contractility and degree of myocardial damage in papillary muscle subjected to hypoxia-reoxygenation in hypercholesterolemic guinea pigs. Study group consisted of guinea pigs, fed standard, hypercholesterolemic or hypercholesterolemic diets with low dose of cerivastatin. During experimental hypoxia-reoxygenation, the contractility was measured. Apoptosis of cardiomioctes was assessed with the use of TUNEL technique. Total cholesterol in standard, hypercholesterolemic and cerivastatin-treated group was 35 +/- 8 mg/dl, 131.6 +/- 30.4 mg/dl and 121.2 +/- 26.2 mg/dl, respectively, and was significantly higher in rats fed hypercholesterolemic and hypercholesterolemic + cerivastatin diets than in control group (p < 0.01). There were no significant differences between all analyzed groups in the post-ischemic cardiac function. Percentage of apoptotic cells after hypoxia-reoxygenation injury in groups fed standard, hypercholesterolemic and hypercholesterolemic + cerivastatin diets was 30 +/- 8%, 20 +/- 4% and 5 +/- 7%, respectively, and was significantly lower in groups that received hypercholesterolmic (p < 0.01) and hypercholesterolemic + cerivastatin (p < 0.001) diets in comparison with standard diet-fed group. In the group treated with cerivastatin, the percentage of apoptotic cells was additionally lower in comparison with hypercholesterolemic group (p < 0.01). Negative correlation between percentage of apoptotic cells and HDL level was found when all groups were considered jointly (r = -0.41, p < 0.05). Our study clearly shows that cerivastatin in hypercholesterolemic animals and hypercholesterolemia itself limit cardiomiocyte damage after hypoxia-reoxygenation.

Animals↗