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Biomedical subjects

M Kowalczyk

Publications and source records attributed to M Kowalczyk.

At least 55 records · Page 3Linked to original sources
PubMed1989

The EEG time series parametrization method in the study of nociception.

A new method of EEG time series parametrization was proposed. The EEG rhythms were described in terms of frequency, amplitude and damping. These parameters were used in multivariate analysis of variance in order to estimate the group differences in terms of Mahalanobis distances. The rhythm diagrams were constructed and their advantages in comparison with averaged power spectra were discussed. The proposed method overcomes the difficulties connected with the arbitrary division of spectrum into the frequency bands. The usefulness of the method in the study of nociception was tested. The effect of nociceptive stimulation in the four brain structures: sensorimotor cortex, ventro-postero-lateral thalamic nuclei, midbrain reticular formation and periaqueductal gray was investigated. The influence of atropine and mecamylamine administered locally was studied.

Algorithms↗
PubMed1988

Ability of peripheral blood neutrophils from patients with infectious bronchial asthma to engulf latex particles and reduce nitroblue tetrazolium.

In 42 patients with infectious bronchial asthma, aged 18-44 years (average 34) the levels of serum IgM, IgG, IgA and IgE were measured. Additionally, latex particles engulfment and nitroblue tetrazolium (NBT) tests according to the method of Park modified by the authors were performed. The control group consisted of 20 healthy people aged 22-45 years (average 39). It was found that in patients with infectious bronchial asthma, during the dyspnoeic attack a defect occurs in the engulfment of latex particles by peripheral blood granulocytes: The ability of granulocytes to engulf latex particles is inversely proportional to the IgG levels in sera of infectious asthma patients.

Adolescent↗
PubMed1987

A study of stability of electrocortical rhythm generators.

By means of the autoregressive model the transfer function and the impulse response function were determined and the parameters characterizing electrocortical oscillators were found for the four brain structures of the experimental animals. Different kinds of the representation of these parameters were compared and their sensitivity to the different factors was tested. The advantages of the proposed method over the conventional spectral analysis were demonstrated. Cluster analysis was applied in order to test the stability of the determined basic rhythms. Proposed method seems to be very useful for the investigation of the processes of rhythmical activity generation and control.

Animals↗
PubMed1987

The use of a multi-channel Kalman filter algorithm in structural analysis of the epileptic EEG.

An extension of the Kalman filter algorithm to the multi-channel case is presented and its application as a segmenting procedure in the analysis of the epileptic EEG is discussed. An analytical example of structural analysis, using the segments extracted by the proposed filter, is presented for a particular set of 4-channel EEG recordings. This analysis is shown to be especially fruitful if the autoregressive coefficients - a byproduct of the filtering procedure - are used to estimate the information flow between the channels by the calculation of partial as well as directed coherences for the representative segments.

Algorithms↗
PubMed1985

The application of parametric multichannel spectral estimates in the study of electrical brain activity.

A parametric autoregressive model was applied to the multichannel EEG time series. Small statistical fluctuations of the spectral estimates obtained from the short data strings made possible to follow the time changes of the signals. The multiple and partial coherences were calculated for the four channel process and compared with the coherences computed between the pairs of channels. From the study it followed that the partial coherences are the proper measure of the synchronization of brain structures and their intrinsic relationships. The partial phase spectra give the information about the phase delays. The advantages of the parametric description of signals in the frequency domain in respect to the modelling of dynamic systems was pointed out.

Brain↗
PubMed1984

[Effect of furfural on the respiratory system].

Fifty-one workers of Butadien Plant, exposed to furfurol , had their respiratory system examined. Questionnaire studies demonstrated chronic bronchitis in 23.5% of subjects. Spirometric tests do not show subjective complaints. This seems to be related to hypercortisolemia, as experiments on animals indicate that furfurol inhalations increase corticosteroids concentrations in blood serum.

Adolescent↗
PubMed1980

A multipurpose transfer cage for baboons.

A three tiered combination squeeze and transfer cage for baboons was constructed. With this cage one employee could perform tasks previously requiring two or three animal handlers.

Animals↗