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Biomedical subjects

A Gundel

Publications and source records attributed to A Gundel.

35 records · Page 2Linked to original sources
PubMed1987

Resynchronization of the circadian system following a 9-hr advance or a delay zeitgeber shift: real flights and simulations by a Van-der-Pol oscillator.

After a flight from Germany to California, eight subjects stayed there for 3 weeks and then were flown back to Germany. After both the westbound and the eastbound flights, body temperature was measured for 2 weeks in the new time zone. Data obtained every 3 hr throughout the day and night were analyzed by the complex demodulation technique to visualize phase adjustments and the nonstationary amplitude of the measured circadian rhythms. The response to the zeitgeber delay was very similar in all subjects and consisted of a phase adjustment of 6 hr in the first 2 days following the flight and a subsequent slow completion of the resynchronization with a rate of 0.5 to 1 hr per day. After the eastbound flight the resynchronization was generally slower, and the circadian amplitudes were more reduced than after the zeitgeber delay. In addition, the advance shift led to different patterns of phase adjustment for the individuals. Shortening and lengthening of circadian periods as well as phase jumps by about 12 hr were observed. Simulations with a Van-der-Pol oscillator forced by a rectangular zeitgeber function clearly reflected the divergence in resynchronization between eastbound and westbound flights. The different resynchronization patterns found after the 9-hr zeitgeber advance, including the corresponding duration of readjustment, could also be well simulated.

Adaptation, Physiological↗
PubMed1986

Genetic EEG patterns in febrile convulsions--a multivariate analysis.

Genetically determined EEG patterns being found during a longterm follow-up of children with febrile convulsions are subjected to a multivariate statistical analysis. The study is mainly concerned with the examination of interrelationships between spikes and waves, theta-rhythms, and photosensitivity. The three patterns form two-categorial variables (occurrence yes, no) and enter a three-way contingency table. Associations between the variables are examined by fitting a log-linear model to the data. Three effects in the structure of the contingency table are statistically significant: the main effect of theta-rhythms which are relatively frequent in the group, and the two-variable-interactions of spikes and waves with theta-rhythms and photosensitivity respectively. The results of the study emphasize that combinations of different genetic factors are important in the pathogenesis of febrile convulsions.

Analysis of Variance↗
PubMed1986

Sleep, sleepiness, and circadian rhythmicity in aircrews operating on transatlantic routes.

This study was performed on B-747 aircrews operating on regular passenger flights between Frankfurt and the U.S. west coast (9 h time difference). In an initial phase, sleep behavior was surveyed by daily logs in 38 crewmembers. The results for the layover period indicate congruent sleep patterns with shifts in sleep onset distinctly less than 9 h. In comparison with preflight control data, sleep duration was significantly prolonged and, on average, no sleep deficits were experienced before commencing the return flight. The main part of the study consisted of polygraphic sleep recordings and multiple sleep latency tests (MSLT) applied to four complete cockpit crews (12 members total) in a baseline period, during layover, and after return to homebase. In addition, body temperature and ECG were continuously recorded. During layover, mean bed times were shifted by 4.5 h at maximum. Sleep was disturbed by early and prolonged awakenings which led to a reduction of sleep efficiency. In contrast, no sleep deficits nor increases in daytime sleepiness occurred. Night duty associated with the return flight caused sleep deprivation which conversely resulted in good sleep during the first night back in Germany. However, during the second night after return, impaired sleep was observed, at least in part caused by the rhythm disturbances. As predicted by our resynchronization model, ECG and rectal temperature recordings gave evidence for a desynchronization of the circadian system and an internal dissociation of different body functions.

Adult↗
PubMed1983

Multivariate analysis of somatosensory evoked potential parameters in normal adults.

Cervical and cortical somatosensory evoked potentials (SEP) to median nerve stimulation were recorded in 65 normal subjects. Absolute peak latencies and amplitudes of cervical components N9, P10, N11, N13, P17, and cortical components P16, N20, P25, and N35 were measured. By means of partial correlations the interdependency of SEP-features could be verified in addition to the well-known dependence on arm length and age. In certain respects our results replicate other studies finding significant correlations between age and latency of early SEP-components as well as inverse relations between age and cervical amplitudes. Further analysis disclosed high inter-correlations between the latencies and between the amplitudes of the cervical and cortical components also revealing a certain exceptional position of the positive wave P17. In contrast to an inverse relation of amplitude and latency of the cervical components there were positive correlations between the respective features in the cortical evoked response. The findings are discussed with regard to the current knowledge about the origins of the SEP-components.

Adolescent↗
PubMed1983

EEG background activity in childhood epilepsy: valid parameterisation by the partial autocorrelation function.

The relationship between EEG background activity and the clinical course is studied in a group of 42 patients with a primary myoclonic-astatic epilepsy. According to the occurrence of seizures the probands are divided into two groups. One group is comprised of patients with an unfavourable course of the disease and the other group is comprised of probands with a favourable one. It is shown by a combined approach of variance analysis, linear discriminant analysis and factor analysis that the EEG background activity parameterized by the partial autocorrelation function is significantly different in the two clinically defined groups. The error rate for assigning a proband, only from the proband's parameterized EEG, to the correct clinical class is estimated to be 0.24. A factor analysis of EEG parameters yields a discriminant factor interpreted as rhythm-power-factor. The group with an unfavourable course is characterized by rhythms in the theta-band and a greater total power than in the favourable group which shows rhythms in the alpha-band. Hypersynchronous potentials in the EEG of this study are not related to the clinical course of the epilepsy. This study confirms that the EEG background activity contains important information about the convulsibility in primary myoclonic-astatic epilepsy.

Adolescent↗
PubMed1983

Circadian rhythm in the EEG of man.

The circadian rhythm in the EEG of the waking state was investigated in six healthy volunteers who were deprived of sleep for 48 (3 probands) and 30 (3 probands) hours. Every hour an EEG was recorded, the body temperature was measured, and the probands rated their fatigue themselves. The EEG parameterized by the partial autocorrelation function shows a circadian change in all probands. The causal link between EEG and body temperature indicates that the circadian rhythm in the EEG is at least partly autonomous of external time cues and the sleep-wake cycle.

Adult↗
PubMed1983

Circadian acrophases of powers and frequencies in the waking EEG.

Circadian changes in frequencies and powers of the close-eyed EEG were measured over six days in 12 healthy volunteers living in a regular rest-activity cycle. EEGs were recorded every two hours and the probands were awakened for the recordings during the period of rest. Circadian rhythms occurred in powers and frequencies with diurnal amplitudes differing between individuals and locally on the scalp. Acrophases of peak frequencies and beta-power coincide with those of body temperature between 5 and 7 p.m., however, the crests of the diurnal rhythms in delta-, theta- and alpha-power varied more between individuals and covered systematically different times of the day. Acrophases of delta- and theta-powers occurred during the second half of the rest period and during the first half of the waking period. Only powers in the alpha-band showed locally different acrophases on the scalp. This could be observed in single individuals, too. In the central and parietal leads, acrophases of alpha-power were found during rest, whereas in the occipital leads of some probands acrophases occurred in the second half of the waking period.

Adolescent↗
PubMed1983

[Partial autocorrelation function as a suitable description of basic EEG activity for use in classification procedures].

For the classification of stationary EEGs a discriminant approach is proposed which is based on the parameterisation of the EEG by the partial autocorrelation function. Regarding various criteria given in table 1, the parameterisation of the EEG by the partial autocorrelation function is compared to the parameterisation by the autocorrelation function, the autoregressive parameters, the power spectrum and band powers. The reliability of the autoregressive parameters, power spectra and band powers is reduced by empirical decisions made on model orders, degree of smoothing, and limits of frequency bands, respectively. The partial autocorrelation function does not show these drawbacks and, besides, it has optimal quantisation properties, especially if it is Fisher z-transformed. Therefore, the partial autocorrelation function is appropriate for data transmission between different computers and data exchange between EEG laboratories with a data reduction factor in the order of 10(2). There are several possibilities to interpret the partial autocorrelation function resulting from the relationship of the partial autocorrelation function and autoregressive models, though for the calculation of the partial autocorrelation function it is not necessary to assume that the EEG is a realisation of an autoregressive process of fixed order. The partial autocorrelation function immediately gives the error variance of the model fit and a value for the dynamic range of the power spectrum. Most commonly it is interpreted by the autoregressive power spectrum and spectral autoregressive parameters. For determining the adequate model order it is desirable to have pieces of EEG recordings which have a length of at least half a minute (table 2).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1981

Spectral analysis of EEG in the late course of primary generalized myoclonic-astatic epilepsy. I. EEG and clinical data.

The EEG of 38 patients suffering from primary generalized myoclonic astatic epilepsy since early childhood is studied in late stages of the disease. Spectral analysis shows that parietal 4-7 cps rhythms (theta rhythms) which are typical of the EEG in the early stages of the disorder can still exist in the EEG of the adult. The rhythms seem to be related to the course of the epilepsy. In the EEG of patients who still have seizures rhythms occur more often than in the EEG of patients who are free of seizures in the two years before the reexamination of their EEG. The functional anomaly producing a 4-7 cps rhythmization of the parietal EEG seems to be one pathogenetic factor in some epileptic disorders of early childhood, especially in primary generalized myoclonic-astatic epilepsy.

Adolescent↗
PubMed1981

Spectral analysis of EEG in the late course of primary generalized myoclonic-astatic epilepsy. II. Cluster analysis of the power spectra.

Cluster analysis is applied to power spectra of the EEG of 38 patients with a primary generalized myoclonic astatic epilepsy (Gundel et al. 1981). The tendency of the data to form clusters within this group is indicated by a random experiment which has been performed with the data. The clustering algorithm divided the material in seven distinct groups which may be combined to three main types of power spectra. These types are power spectra with a 10 cps peak, a 4-7 cps peak and power spectra without remarkable rhythmization. The comparison of EEG types and clinical data shows a correlation of 4-7 cps rhythms with the occurrence of seizures. 4-7 cps rhythms are interpreted as a symptom of "centrencephalic" convulsibility.

Adolescent↗
PubMed1980

Clinical trial of droperidol for the determination of the neuroleptic threshold and the neuroleptic-therapeutic range.

In an open study involving 30 schizophrenic patients the neuroleptic threshold dose (measured using Haase's graphopathological test) and the maximum dose were determined. The neuroleptic threshold dose was 18.5 mg/day (SD = 8.84), the maximum dose was 38.2 mg/day (SD = 4.6). With reference to the effectiveness good to very good results were obtained in 15 cases. Regarding side effects 10 patients complained of extrapyramidal disturbances. This was to be expected in view of the study design aiming at the determination of the maximum dose.

Adult↗
PubMed1978

Open study with bromperidol (C-C 2489), a new neuroleptic, for the determination of the neuroleptic threshold and the neuroleptic-therapeutic range.

In an open study involving 30 schizophrenic patients the neuroleptic threshold dose (measured via Haase's graphopathological test), the maximum dose, and the maintenance dose were determined. The neuroleptic threshold dose was 5.6 mg/day (0.08 mg/kg body weight); the maximum dose was 11 mg/day (0.16 mg/kg body weight); and the maintenance dose was 6 mg/day (0.09 mg/kg body weight). With reference to the effectiveness, good to very good results were obtained in 19 cases. Regarding side effects 15 patients complained of extrapyramidal disturbances, this was to be expected in view of the study design aiming at the determination of the maximum dose level. When administered in one single dose in the evening, bromperidol influenced the night sleep positively, so that sleep-inducing drugs could be reduced, and, in some cases, even dispensed with.

Adolescent↗
PubMedDate not supplied

Human thermohomeostasis onboard "Mir" and in simulated microgravity studies.

Significant changes of thermogomeostatic parameters was obtained by thermotopometric method using the techniques simulate of microgravity effects: bed rest, pressurized isolation, suit immersion (SI). However, each of ground models made rectal temperature (T) trend downward. The autothermometric study (24 and 12 sessions, 2-13th and 6-174th flight days) was carried out onboard "Mir" by two flight engineers who had preliminary tested at SI (1-2 days). Studies of German investigators onboard "Mir" confirmed: rectal T must be higher in space flight as compared to the normal environment (n=4). Comparative studies suggest that microgravity is a key factor for the human body surface T raise and abolishment of the external/internal T-gradient. T-homeostasis was not really changing during missions and could be regarded as acute effect of microgravity. After delineation of changes in body surface T--by Carnot's thermodynamic law--rectal T raise should have been anticipated. Facts pointing to the excess entropy of human body must not be passed over.

Adaptation, Physiological↗
PubMedDate not supplied

[EEG studies in Alzheimer dementia and multi-infarct dementia at various times of the day].

From three men and seven women (mean age 70 years) with dementia of the Alzheimer-type (DAT), and from four men and six women (mean age 77 years) with multi-infarct dementia (MID) closed-eye EEGs were registered at 0800, 1200, 1600, and 2000 hours and recorded on tape for computer processing. The data of both groups were compared statistically and also compared with data of former investigations conducted with 10 healthy elderly volunteers and 10 patients who suffered from cerebral arteriosclerosis with serious disorder of sleep-walking rhythm (HA). Most pathological EEG deviations are found in the MID-patients, but there is no significant distinction compared to the DAT-patients, although three of the latter showed normal EEGs. Compared to the HA the EEGs of the MID-patients differed more from those of the healthy volunteers; however, the physiological circadian variations were not leveled as in the HA. Even in consideration of daytime dependent fluctuations of frequency-parameters, a clear-cut discrimination between DAT and MID by means of the EEG seems impossible.

Aged↗
PubMedDate not supplied

Neuroleptic potency of bromperidol.

The following statements can be made on the basis of our study. 1. The butyrophenone bromperidol is an absolutely effective drug of the series of very high-potency neuroleptics, with a mean neuroleptic threshold dose of 5.6 mg/day. The mean optimum dose is 6 mg/day, and the mean maximum dose reaches 11 mg/day, i.e. twice the neuroleptic threshold dose. 2. The substance is generally well tolerated; when it was administered to one third of all cases in one single dose in the evening, it not only had the same beneficial neuroleptic-antipsychotic effect as on administration t.i.d., but also positively influenced sleep, so that sleep-inducing drugs could be reduced and, in some cases, even dispensed with. This relatively long-lasting effect confirms the finding made in animal experiments.

Adult↗
PubMedDate not supplied

[Circadian-dependent changes in the EEG of vital elderly humans].

UNLABELLED: The study was conducted with six women and four men, 70-84 years old, without any psychopathologic signs of organic brain syndrome. Every experiment ran for five days during which closed-eye-EEGs were registered at 8 a.m., at 12 noon, at 4 p.m., and at 8 p.m. of the alert but relaxed patients and recorded on tape for computer processing. Simultaneously with every EEG registration the body temperature was measured. RESULTS: As in younger persons the power of the alpha frequency band occipital exceeds the activity of the other frequency bands. But though the frequency of the dominant alpha rhythm comes with 9.5 Hz occipital on an average clearly under the normal range, there was a slight slowing down in sporadic cases. Probably old age leads to a decrease of alpha frequency, even in a state of unaffected sanity. The increase of peak frequency and body temperature during the day, well known from experiments with younger people, comes to the fore in the healthy aged as well. Of striking intensity, especially in the evening, is the beta power at the parietal and the central parts of the scalp, caused possibly by a transitory decline of vigilance. Circadian variations of the different band powers, ascertained in younger persons, are absent in the present collective.

Aged↗