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Biomedical subjects

U Zwiener

Publications and source records attributed to U Zwiener.

At least 109 records · Page 6Linked to original sources
PubMed1986

Vascular resistance, metabolism and EEG within cerebral grey and white matter during hypoxia in neonatal piglets.

To study unsolved problems of the causal chain of neonatal hypoxic brain damage in 31 hypoxic newborn non-anesthetized piglets cerebro-vascular, metabolic and EEG reactions were investigated (FiO2: 0.06-0.10, 1 h). Only in artificially ventilated newborn piglets this acute hypoxic hypoxia provoked a vital decompensation by critical depression of mean arterial blood pressure (less than or equal to 4.67 kPa [35 mmHg]) and/or a critical increase of vascular resistance (Rc) in the cerebral white matter (greater than 50%). Spontaneously breathing piglets survived always showing hyperventilation, higher pHa and an increase of cerebral O2-consumption in cerebral grey matter, partly also in white matter. This critical increase of Rc was related to a critical decrease of O2-consumption in the white matter and an insufficient decrease of Rc of the grey matter. The observed strong metabolic and hemodynamic differences between these two brain compartments can explain the evaluated special morphological vulnerability of cerebral white matter in ventilated animals.

Animals↗
PubMed1985

[Autonomic reflexes, EEG and partial arousal reaction in the near-threshold region to acoustic stimuli in the newborn].

A sample of 19 neonates were exposed to sub- and suprathreshold acoustic stimuli. The experiment was performed with sleeping subjects. Stimuli, tones of 125, 250, 500 and 750 cps, third sounds of the same middle frequency and white noise, were applied only, if periods with no REM activity occurred. Stimulus intensity was varied from the subthreshold level (70-80 dB) to the suprathreshold level (80-100 dB). Polygraphic variables were recorded (EEG, EOG, instantaneous heart rate, respiration movements, actogram, motoric reactions and psychogalvanic reflex). The results showed, that with increasing stimulus intensity irregularities of respiratory parameters occurred. With further increase of stimulus intensity systematic changes in respiratory parameters and heart rate occurred. In addition to these changes, EEG activity and motoric reactions were obtained, when stimulus intensity reached a critical level. These data are consistent with the idea that at low stimulus intensities irregular vegetative reactions occur whereas systematic responses can be observed only, if stimulus intensity is above threshold. We conclude that with increasing stimulus intensity subcortical activity decreases whereas cortical activation increases.

Acoustic Stimulation↗
PubMed1984

[Spontaneous rhythms of the cardiovascular system in autonomic diabetic neuropathy].

There are distinct differences of the visually and computerized investigated immediate heart rate rhythms, mean arterial pressure and skin temperature rhythms between 30 diabetics suffering from peripheral neuropathy and 10 healthy volunteers. The characterized disturbance patterns within the higher and lower frequencies of these cardiovascular rhythms suggest pronounced, but not only circumscribed lesions of the vagal efferences.

Adult↗
PubMed1982

[Biocybernetic tests on the identification and mathematical modelling of the motor regulation system and its disorders].

By means of the biocybernetically conceived step and impulse loads on the forearm the motor postural regulation of healthy test persons and neurological patients with rigor, spasticity and flaccid pareses of slight degree, respectively, were examined. The analysis of the forms of the transient processes rendered possible a significant differentiation of the groups of test persons and patients. With the help of the mathematical mode the response curves of healthy test persons as well as of patients could be simulated with sufficient exactness. Apart from the step and impulse loads psendorandom binary series of test signals are particularly suitable for the analysis of the motor postural regulation.

Adult↗
PubMed1979

[Time parameters of the retinal control of light intensity and influencing parameters].

The variability of the pupillomotoric control of light intensity was analysed in response to changes in the duration of the light flash, the respiratory phase during stimulation and the age of the subjects. The method of infrared pupillography was used to determine dynamic time parameters. With increasing duration of the light flash from 8 to 125, 250 and 500 ms we observed an acceleration of the latencies whilst the other time parameters were prolonged. There was no significant influence of the time of stimulation during the respiratory cycle. With growing age increased latencies and reduced time parameters of the pupillomotoric transient response were found. The possible reason and importance of the observed changes are discussed.

Adolescent↗
PubMed1978

[Simultaneous comparison of periodograms and performance spectra to distinguish periodical from statistical curve portions of vegetative rhythms].

The differences between corresponding data of power spectral densities and quadrated periodograms were computed delimiting periodical and statistical parts of curves of mean arterial pressure, heart rate, and respiration rhythms. The statistical parts of the curves show similar density distributions in the investigated frequency range as the periodical parts (power spectra). In patients with autonomic disorders these statistical parts of the curves are higher than in healthy volunteers.

Blood Pressure↗
PubMed1978

[Spectral analysis of blood pressure-, heart rate- and respiration rhythms in different postures in probands and patients with neurovegetative disorders].

In a statistical comparison between autospectra of blood pressure, heart rate, and respiration rhythms in 16 healthy volunteers in sitting and standing position and between these and results in 16 patients suffering from autonomic disorders there have been shown: (1) significantly higher power spectral densities in distinct frequency bands of the parameters in orthostasis (with exception of heart rate spectra) and (2) more distinct changes in patients. Moreover, a significant decrease of spectral densities of heart rate waves was computerized in patients. The physiological background is discussed.

Adult↗
PubMed1977

[Diagnostic value of the so-called brain stem function tests].

The results of so-called midbrain function tests of 563 neuropsychiatric patients were examined for their relative diagnostic importance. It was not possible to find any differences in the relations of normal and anomalous curves between individual groups of diseases. Also, there were not found any significant differences from the results obtained for nonneuropsychiatric subjects. Therefore, the authors recommend against a further use of these methods. Newly developed biocybernetic and rhythmological test methods may be used as alternative methods for the analysis of most neurovegetative disorders.

Autonomic Nervous System↗
PubMed1976

[Psychophysiological studies in the framework of objective diagnosis of neuroses with factor and discrimination analyses].

This paper describes a complex method of collecting objective data to be used in the diagnosis of neuroses on the basis of clinical, experimental psychological, and objective psychophysiological parameters. The data collected was processsed using the methods of factor and discriminatory analysis. The results obtained clearly show that this approach to additional objective diagnosis may be successfully used in spite of some procedural difficulties.

Adult↗
PubMed1976

[Clinical, psychological, and psychophysiological characteristics of neurotic-functional, cardiovascular and neurotic-depressive syndromes].

A total of ninety women classified into three groups (with cardiovascular, depressive, and other principal symptoms) according to clinical criteria were characterized by clinico-anamnestic, psychological, and psychophysiological data with the goal of arriving at a practically oriented differentiation of neurotic syndromes. The relevant variables were determined by means of a factor analysis. The physiological reaction patterns determined in experiments on psychically strained individuals proved unsuitable for the differentiation of the two syndromes. The problems associated with a symptom-oriented classification are discussed.

Adjustment Disorders↗
PubMed1975

[Experimental and clinical aspects of auto and coherence spectra of blood pressure, heart rate and respiratory rhythms].

Auto- coherence and phase spectra of blood-pressure, heart-rate, and respiration changes at various intervals were calculated in 34 healthy individuals and 46 patients with neurovegetative disorders in a direct way, partly by means of the Fast-Fourier transformations. It was only by 18-min recordings that reliably reproducible spectra could be obtained that permit exact evaluation of the statistical properties of these biorhythms.

Adult↗