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Biomedical subjects

U Zwiener

Publications and source records attributed to U Zwiener.

At least 91 records · Page 5Linked to original sources
PubMed1989

[Model studies of muscle postural control in children with spastic hemiparesis: pathophysiologic and clinical relevance].

By means of a biocybernetic method the transfer behaviour of postural motor control system was characterized in children with spastic hemiparesis and matched healthy subjects. There were significant differences between the initial reactions of the postural motor systems of both examination groups to pseudorandom torque sequences (fig. 3, tab. 1). Considering these results we created a postural motor control model for both examinations groups (model see fig. 2). From this model it is possible to estimate separately the biomechanical effect of augmented segmental reflex activity and muscle-inherent dysfunctions in patients with spastic syndrome (fig. 4). The determination of these disturbed functions enables us to give instructions on a focused treatment of spastic syndrome according to the dominant dysfunction quantified.

Brain Damage, Chronic↗
PubMed1989

[Polygraphic studies of newborn infants at risk using acoustic stimulation close to and above the threshold level].

16 newborns were investigated by means of polygraphy (EEG, respirography, heart rate, psychogalvanic reflex and behavioural observations). They were acoustically stimulated (125, 750, 15000 and 3000 Hz, with stepwise increase of the intensity by 10 dBA) during the period of quiet sleep. Partial vegetative reactions appeared in 11 newborns between a stimulation intensity of 30 to 50 dBA. Changes of breathing were initially observed. A further increase of intensity caused reactions in heart rate, psychogalvanic reflex and also body movements. The EEG and behavioural states were never changed at this level of intensity. Reactions in these parameters were recurrently observable if stimulation intensity was higher than 80 dBA. Only half of all stimulations were followed by reactions. The results verify decreased threshold intensity to evoke partial vegetative reactions in newborns at risk and the same sequence of additional reactions in EEG and behavioural states as in healthy newborns following increasing stimulation intensity.

Acoustic Stimulation↗
PubMed1989

Effects of hypoxic hypoxia on the kinetics of synaptosomal Ca2+-ATPase activity in newborn piglets and young rabbits.

Severe hypoxic hypoxia with electrophysiologically detectable involvement of the brain caused a distinct alteration of synaptosomal membrane Ca2+ATPase activity in newborn piglets (n = 7) and young rabbits (n = 7). This was shown by means of the shifted pCa2+ for maximum stimulation towards higher Ca2+ concentrations and a significant decrease of the maximum activity in both species. Furthermore, an additional stimulation using supramaximum amount of exogeneous calmodulin (tested on piglets) was completely abolished after hypoxia. It is suggested that this effect might influence the fine regulation of neuronal Ca2+ homeostasis also during the posthypoxic recovery period.

Animals↗
PubMed1989

Restricted cardiovascular and cerebral performance of intra-uterine growth retarded newborn piglets during severe hypoxia.

In 7 term born two-day-old intra-uterine growth retarded (IUGR) piglets cardio- and cerebrovascular, metabolic and EEG reactions were studied at rest and during severe hypoxia in comparison to 17 normal-weight piglets. In IUGR piglets even in control conditions a distinct cerebral blood flow (CBF) elevation, lower cerebrovascular resistance and oxygen consumption in the higher perfused brain regions at diminished arterial blood pressure were observed. Also the arterial glucose concentration was in the borderline hypoglycemic range, however, cerebral glucose delivery was nearly maintained. IUGR piglets survived a 1-h hypoxic period (paO2 = 25-30 mmHg) less frequently. The main reason was the distinctly restricted emergency reaction with a lack of arterial blood pressure increase and blood glucose elevation as well as a reduced (higher perfused brain regions) or absent CBF increase (lower perfused brain regions). Thereby, even in the early stage of hypoxia cerebral oxygen delivery in both brain compartments and oxygen consumption in the latter were decreased followed by a further decrease of the arterial blood pressure. The latter factor was essential for acute cardio-vascular-cerebral insufficiency.

Animals↗
PubMed1989

[The hemodynamics of the lung circulation of minipigs after experimentally-caused Sedlarik's pulmonary embolism. III. Sedlarik's embolization of the lung circulation by electrically-activated blood].

Pulmonary embolisms of different clinical degree of severity can be produced by means of the pulmonary embolism model according to Sedlarik by application of electrically activated blood as a thrombogenic substance. An unambiguous influence of the size and the consistency of the thrombus exists concerning the severity of the hemodynamic changes. However, the hemodynamics seems to adapt to the changed conditions of the circulation, because a tendency to normalization was observed in short-term experiments. The morphologic changes after embolisation are more typical for the severity of the clinical picture in this acute phase than the hemodynamics. A testing of the animal model in long-term experiments seem to be ingenious for that reason.

Animals↗
PubMed1989

[Pathophysiologic aspects of schizophrenic psychoses--a review].

The aim of research in the field of "Biological Psychiatry" is the phenomenological description of several aspects of psychiatric diseases and the exploration of their pathological mechanisms. The most used methods are biochemical, morphological, genetical, social psychiatric, neuro- and psychophysiological ones. From the pathophysiological view the most discussed hypothesis is that of a disturbed central information processing. In this paper a short introduction should be given on psychosocial influence on the development of psychotic symptomatology and on the periphere vegetative and electroencephalographic parameters in psychiatric patients.

Arousal↗
PubMed1989

[The hemodynamics of the lung circulation of minipigs after experimentally-caused Sedlarik's pulmonary embolism. I. Sedlarik's pulmonary embolism model in comparison to existing embolism models].

The necessity of a clinical relevant pulmonary embolism model is described because of the international importance and the consequence for certain special branches. The multifarious pathophysiologic mechanism in the human requires an approximation of the model. The pulmonary embolism model according to Sedlarik approaches these demands and it became the basis of this study.

Animals↗
PubMed1989

[Pilot study of the spectral analysis of the bifrontal EEG in healthy and newborn infants at risk].

The importance of neonatal bifrontal EEG recordings which were easily obtainable during intensive care was tested to improve the possibilities of computer-assisted analysis and to characterize cerebral cortical function of newborns-at-risk. The EEG was computerized by spectral analysis in 9 healthy term newborns and 6 term newborns-at-risk according to the age related patterns. Surprisingly, newborns-at-risk with good outcome show significant higher EEG spectral power than controls. But a secure monitoring is unpossible by bifrontal recordings alone. It was concluded that: 1. the bifrontal EEG recordings should be replaced by at least two interhemispheric recordings for neonatal cerebral monitoring, 2. the pattern-related analysis is necessary and 3. the discontinuous EEG is most suitable to characterize newborns-at-risk.

Brain Damage, Chronic↗
PubMed1988

Evidence of a previously undescribed form of respiratory sinus arrhythmia (RSA)--the physiological manifestation of "cardiac aliasing".

Within the fluctuations that occur in heart rate, there is a major component known as respiratory sinus arrhythmia (RSA), which up to now has been defined as heart rate variability which is synchronous with respiratory movements. We have now discovered that RSA synchronous to respiratory movements is only one example of RSA. If a special relationship exists between mean heart rate (fHR) and mean frequency of breathing (fB) such that fB greater than 1/2 fHR, RSA can be observed in a frequency range which is lower than the frequency of breathing. The mathematical fundamentals of this physiological phenomenon are the same as those for the "aliasing"-effect in signal sampling. Therefore, we have called this phenomenon "cardiac aliasing". We have been able to experimentally demonstrate this, up to now unknown, phenomenon in adult rabbits and dogs as well as in human neonates.

Animals↗
PubMed1988

Personality and quantified neuromuscular activity of the masticatory system in patients with temporomandibular joint dysfunction.

Patients suffering from temporomandibular joint dysfunction syndrome (TMJS) and healthy volunteers were examined by means of MMPI questionnaire and electromyography (masseter, anterior temporal and anterior digastric muscles) at rest and during natural chewing. In response to mental load (arithmetic chain task) TMJS patients showed an increase in postural activity and partly rhythmical short augmentations above the mean level of this activity. Chewing potentials were considerably diminished in patients compared with controls. There was evidence for neurotic disorders in the patients MMPI (neurotic triad: higher scores on hypochondria, depression, hysteria). Significant differences (multivariate variance and discriminant analysis: P less than 0.001) between patients and controls were found both in the group with psychic signs (MMPI scales) and in the group of quantitative electromyographic parameters. However, a sufficient discrimination was only obtained by a combination of both parameter groups. The results show that probably psychic dynamics, as well as the structure of neuromuscular activity within the masticatory system, are important in the aetiopathogenesis of TMJS.

Adolescent↗
PubMed1988

A method for the biocybernetic physiological investigation of postural motor control and its disorders in children.

On a biocybernetic basis, a method for the investigation of human postural motor control with optimal multifrequent binary test-signals is described. The examinations presented demonstrate that a comprehensive and quantitative characterization of normal postural motor control and its disorders is possible by means of this method in children. The examination time is short, the motor task used is simple, and the load is physiologically adequate and standardized.

Child↗
PubMed1988

Objective characterization and differentiation of sleep states in healthy newborns and newborns-at-risk by spectral analysis of heart rate and respiration rhythms.

Best parameters of power and coherence spectra of heart rate fluctuations (HR) and respiration rhythms (RR) were established to differentiate sleep states in healthy newborns and newborns-at-risk by means of multivariate variance and discriminant analysis. Nine healthy newborns and 20 newborns with low risk features were examined polygraphically. Long-term-variability of both HR and RR and coherence between HR and RR in the frequency range of 0.26-0.97 Hz, corresponding to Respiratory Sinus Arrhythmia, allow the best differentiation of neonatal sleep states S 1 and S2. Differentiation of healthy newborns and newborns-at-risk by these parameters was not possible. Thus, in studies dealing with low risk features in newborns sleep states must be previously classified. State 1 and 2 represent different autonomic organisations. State 1 is a neuro-vegetative, relatively stable state. State 2 shows cyclic increases of coherence between HR and RR within the frequency range of Respiratory Sinus Arrhythmia. These properties are related to autonomic brain stem functions and were absent in 6 out of the 20 newborns-at-risk.

Heart Rate↗
PubMed1987

[Objectivation of the rheologic and hemodynamic and metabolic effects of ultraviolet irradiation of autologous venous blood in Fontaine type II-IV peripheral arterial occlusive disorders].

72 patients with disturbances of the peripheral arterial blood supply of type II to IV after Fontaine showed characteristic clinical, haemodynamic (first flow, peak flow occlusion-plethysmographically reduced) metabolic (paO2 and pvO2 decreased), plasmatic (fibrinogen and alpha 2-macroglobulin levels increased) and--as far as investigated (37 patients)--haemorheological changes (much increased apparent whole blood viscosity). The latter was found out above all in shear rates occurring in the microcirculation. Ultraviolet irradiation of venous autologous blood (1 ml/kg) during three weeks (nine times) leads the haemorheological and plasmatic parameters to normal levels and decisively improves the metabolic and haemodynamic parameters. This effect is still to be proved after six months, but only in a small extent after one or two years. Because of the weaker therapeutic effects of the common conservative treatment this therapy must be recommended.

Adult↗
PubMed1987

Differentiation of healthy newborns and newborns-at-risk by spectral analysis of heart rate fluctuations and respiratory movements.

Neonatal heart rate and its interaction with respiration were computerized by spectral and coherence analysis (FFT) to differentiate healthy newborns (n = 9) from newborns with mild neonatal risk (n = 20). An increased mean heart rate and decreased total variability have been found in newborns-at-risk. Respiratory Sinus Arrhythmia is diminished in newborns-at-risk possibly caused by an impairment of autonomic brain stem function. Furthermore, Respiratory Sinus Arrhythmia holds a central position in differentiating healthy newborns and newborns-at-risk with and without neurological abnormalities during the first year of life. Respiratory Sinus Arrhythmia is diminished in newborns-at-risk showing these abnormalities. None of the parameters discriminates between the two groups of risk infants. The final prognostic value of our results must be confirmed in further clinical follow-up examinations.

Arrhythmia, Sinus↗
PubMed1987

[Neuroautonomic organization of cardiac rhythm and of nonrhythmic oscillations in the frequency of cardiac contractions and respiration].

In 25 chronic adult rabbits, the functional organization of neurally mediated short-term rhythms and patterns of the heart rate (HR) were investigated. The respiration-unrelated arrhythmia seems to be vagally mediated only, being abolished with atropine. The respiration-related arrhythmia exists not only within the range of respiratory frequency but also in lower frequencies as discovered by spectral and coherence analysis. During motor activity, there is a systematic correlation among increasing premotor, motor and amygdaloid multispike activities, increasing HR and depressed HR-rhythms with limbic initiation of motor and concomitant autonomic patterns, "Immobile confrontations" alone produces vagally induced HR-decrease and increased amplitudes of vagal HR-rhythms with a concomitant cortical multispike depression, a mirror image of the autonomic patterns after nociceptive stimulation.

Action Potentials↗