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Biomedical subjects

M Eiselt

Publications and source records attributed to M Eiselt.

52 records · Page 3Linked to original sources
PubMed1990

EEG spectral analysis in newborns with and without severe brain damage at different conceptional ages. A preliminary report.

Spectral power (SP) analysis of neonatal discontinuous EEG pattern of bilateral Fp-T and T-0 derivations has been performed in 5 newborns with no or mild brain damage and in 5 newborns with severe brain damage matched for conceptional age (30-39, week). Discontinuous EEG was separated in interburst and burst intervals. SP of all frequency bands was depressed in newborns with severe brain damage, with the depression being more pronounced during interburst intervals. Surprisingly, a prominent depression of the SP of the derivations of the right hemisphere and of the delta frequency bands of severely handicapped newborns was found. Calculation of coherence between homologous bipolar derivations does not improve the possibilities to separate both groups.

Brain Damage, Chronic↗
PubMed1990

[EEG and evoked potential mapping].

By spectral EEG-mapping and EP-mapping, especially the topologic dimension of electrical brain activity can be evaluated for clinical use. On the other hand, this method allows the highest solution from all functional imaging procedures within the time dimension of brain activity. On the other hand, the ability of topological solution is limited. But the latter is probably better than hitherto assumed and surprisingly well at least regarding neonates. However, several methodological prerequisites described here must be fulfilled. From the pathophysiological point of view, the limits must be considered besides the diagnostic possibilities. Meanwhile, spectral EEG-mapping and EP-mapping are diagnostically used in all main fields of traditional EEG-analysis, like seizures and in the preadiagnostics of tumors a.o. Also in the diagnostics of cerebrovascular disease including transient ischemic attacks, the EEG-mapping and/or EP-mapping are useful within the total diagnostics. There is a similar situation in the diagnostics of degenerative brain disorders. But the significance of frequently described changes inpsychoses, partly also neuroses and other functional disorders is not clear. Altogether, this non-invasive, economically most favourable method for the functional imaging procedures in brain diagnostics is promising to extent the routine diagnostics also to a more precise manner.

Brain↗
PubMed1989

Cardiac aliasing--a possible cause for the misinterpretation of cardiorespirographic data in neonates.

Cardiac aliasing is a physiological phenomenon generating respiratory sinus arrhythmia in a frequency range lower than that of respiration if the mean respiration rate exceeds half of the mean heart rate. This was found in 8 out of 39 healthy fullterm newborns, 5 out of 33 fullterm and 3 out of 63 preterm newborns during intensive care. Quantification of cardiorespirographic data is considerably impaired in those cases when the mean respiration rate markedly exceeds half of the mean heart rate (two out of the 39 healthy full term newborns).

Arrhythmia, Sinus↗
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

[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

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

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↗
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↗
PubMed1981

Comparative investigations on the effect of 5-fluorouracil on the epidermis and the skin appendages.

Groups of 15 guinea pigs and 10 Syrian hamsters were treated with 5-fluorouracil (Fluoro-uracil "Roche") for 8, 22, and 36 days, respectively. 15 guinea pigs and 10 Syrian hamsters remained untreated. At the end of the experiment the hair root status of the guinea pig and the 3H-thymidine labelling index of the sebaceous glands and epidermis on the Syrian hamsters were determined. 5-Fluorouracil leads to a gradual reduction of both the 3H-thymidine labelling index in the epidermis and the sebaceous glands and the amount of anagenetic hair. The effect is slow at the onset, gradually increases, and is still increasing after 3 weeks of treatment. The reduction in the number of labelled cells is significantly larger in the epidermis than the sebaceous glands.

Animals↗
PubMedDate not supplied

On the influence of volume currents and extended sources on neuromagnetic fields: a simulation study.

The influence of volume currents on the magnetic field is an important question in magnetoencephalography since the spherical volume conductor is still widely used for source localization. In theory, the magnetic field of a radial dipole in a homogeneous sphere is zero. In realistic models of the head, the field is suppressed when compared with a tangential dipole. To determine the influence of the volume currents, this suppression ratio (magnetic field of the radial dipole divided by the field of the tangential dipole) needs to be quantified. Large-scale finite element method models of the human head and the rabbit head were constructed and the suppression ratio was computed. The computed suppression value of 0.28 in the rabbit head was similar to the previously measured experimental value. In the human head, an average suppression ratio of 0.19 +/- 0.07 was found for different regions and depths in the gray matter. It was found that the computed magnetic field of radial sources varied significantly with the conductivities of the surrounding tissues where the dipole was located. We also modeled the magnetic field of an epileptic interictal spike in a finite element model of the rabbit head with a single dipole and with extended sources of varying length (1-8 mm). The extended source models developed were based on invasive measurements of an interictal spike within the rabbit brain. The field patterns of the small (1-2 mm) extended sources were similar to a single dipolar source and begin to deviate significantly from a dipolar field for the larger extended sources (6-8 mm).

Animals↗