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Biomedical subjects

H Schulz

Publications and source records attributed to H Schulz.

At least 217 records · Page 12Linked to original sources
PubMed1994

Wavelets-a new tool in sleep biosignal analysis.

The wavelet transform is a relatively new approach to data processing which has been applied in different areas such as signal, speech and image processing. In the last decade, many papers have been published on wavelet theory and its applications. The wavelet transform provides an elegant alternative to the classical Fourier or Gabor transforms unifying numerous signal processing techniques in a common framework. The purpose of the present paper is to provide an overview of the applicability of the wavelet transform to EEG signal analysis. In the first part of the paper the mathematical background is summarized. In the second part, applications to the sleep EEG field are presented and discussed. The results of these illustrations demonstrate the usefulness of the wavelet transform to solve various problems including signal parametrization, pattern recognition and biosignal representation.

Journal Article↗
PubMed1994

Pulmonary dead space and airway dimensions in dogs at different levels of lung inflation.

The quasi-stationary front that separates inspired gas from mixed alveolar gas is largely determined by the balance between diffusive and convective forces of gas transport. To investigate parameters influencing this balance, a study was performed on eight anesthetized ventilated beagle dogs. Measurements were made of the volume of pulmonary dead space corresponding to four end-inspiratory lung volumes. Aerosol recovery techniques were used to determine airway sizes at lung depths corresponding to those respective dead space volumes as well as at fixed volumetric depths between 70 and 250 ml. Mean dead space volumes as measured by a single inhalation of He (and SF6) were 112 +/- 15 (SD) ml (127 +/- 15 ml), 120 +/- 18 ml (137 +/- 20 ml), 127 +/- 18 ml (145 +/- 20 ml), and 133 +/- 19 ml (155 +/- 21 ml) at end-inspiratory lung volumes of 64, 71, 79, and 86%, respectively, of total lung capacity. At fixed lung depths the airway diameters increased with higher levels of lung inflation. However, airway diameters "at the end of the dead space" did not change significantly. They were approximately 0.5 mm for SF6 dead space and approximately 0.75 mm for He dead space. These findings support the theoretical prediction that the position of the diffusion front during breathing is strongly dependent on airway geometry and much less dependent on parameters of the breathing maneuver.

Animals↗
PubMed1994

Effects of hypericum extract on the sleep EEG in older volunteers.

The effects of treatment with high doses (300 mg three times daily) of hypericum extract LI 160 on sleep quality and well-being were investigated over a 4-week period. The double-blind, placebo-controlled study was conducted with 12 older, healthy volunteers in a cross-over design, which included a 2-week wash-out phase between both treatment phases. A hypostatic influence of the REM sleep phases, which is typical for tricyclic antidepressants and MAO inhibitors, could not be shown for this phytopharmacon. Instead, LI 160 induced an increase of deep sleep during the total sleeping period. This could be shown consistently in the visual analysis of the sleeping phases 3 and 4, as well as in the automatic analysis of slow-wave EEG activities. The continuity of sleep was not improved by LI 160; this was also the case for the onset of the sleep, the intermittent wake-up phases, and total sleep duration.

Anthracenes↗
PubMed1994

EEG changes caused by dimethoate treatment in three generations of rats.

Wistar rats were continuously treated with 7.0, 10.5, 14.0, 28.0 mg/kg (1/100, 1/75, 1/50 and 1/25 LD50) of dimethoate per os including the pregnancy of dams and the lactation period of pups as well as in adulthood for three subsequent generations. The EEG of male rats of each generation was recorded at the age of 12-13 weeks. The mean frequency, mean amplitude, EEG index and the power spectrum were analysed. The data showed that the overall EEG activity of the treated rats was greater than of the controls. The mean frequency was higher, the mean amplitude and the EEG index were lower, the activity of the lower frequency wave bands decreased, that of the higher frequency wave bands increased. The changes of the mentioned EEG parameters were most pronounced in the third generation.

Animals↗
PubMed1994

Changes of brain evoked potentials caused by dimethoate treatment in three generations of rats.

Wistar rats were continuously treated with 7.0, 10.5, 14.0, and 28.0 mg/kg (1/100, 1/70, 1/50 and 1/25 LD50) of dimethoate per os including the pregnancy and lactation periods for three subsequent generations. The somatosensory, visual and auditory evoked brain potentials of male rats of each generation were registered at the age of 12-13 weeks with silver electrodes placed on the primary somatosensory, visual and auditory cortex. The measured parameters were the latency and duration of the evoked potentials. There were differences in the changes among the various evoked potentials in all of the generations. The strongest effect caused by dimethoate was seen in the case of the somatosensory evoked potentials compared to the control. The changes of the visual and auditory evoked potentials were milder. Comparing the changes of the evoked potentials of the three generations it was found that there were no significant changes between the data of the three populations.

Animals↗
PubMed1994

Incidence and morphology of concurrent primary carcinomas of the urinary bladder and prostate in transurethral resection specimens.

A retrospective morphologic investigation was conducted to determine the incidence of concurrent primary carcinomas of the urinary bladder and prostate gland and to identify their patho-histologic features using transurethral resection specimens. The study was based upon 1281 cases with the initial diagnosis of a benign or malignant epithelial or mesenchymal tumor of the bladder. In 294 of the patients (23.0%), transurethral resection specimens were also available from the prostate. The incidence of double carcinomas (n = 52) was found to be 4.2% of all vesical carcinomas reviewed (n = 1228) and 17.7% of only those cases with biopsies available from both organs. Of the coexisting bladder carcinomas, 81% represented papillary transitional cell carcinomas grades 1 and 2. These were associated in 78.6% of the cases with well and moderately differentiated carcinomas (grades 1 and 2) of the prostate gland, showing either a uniform glandular or a pluriform glandular and cribriform pattern of growth. Half of the concurrent cancers of the bladder were noninvasive and 19.2% had infiltrated only the lamina propria. Thus, the great majority of coincidental vesical and prostatic carcinomas proved to be well and moderately differentiated and by far the majority of the bladder carcinomas exhibited a low stage. Since there was no typical association of particular histologic carcinoma types coexisting with each other and because the extent of local spread was unremarkable, it is impossible to predict the occurrence of double carcinomas of the urinary bladder and prostate on morphologic grounds.

Adenocarcinoma↗
PubMed1994

Trends in electroencephalographic synchronization across nonrapid eye movement sleep in infants.

The trend of synchronized (high-voltage, low-frequency) electroencephalographic (EEG) activity was determined across nonrapid eye movement (NREM) sleep periods of night sleep in two groups of infants (eight "young infants", age 2-19 weeks; eight "older infants", age 21-54 weeks) and, a reference, in a group of eight adults (age 16-45 years). By automatic analysis of the sleep EEG, a parameter was derived that represents the degree of synchronized (high-amplitude, low-frequency) EEG activity for successive 30-second epochs. For each subject, the average level of EEG synchronization for each NREM period and the time of the NREM period midpoints were determined. In all three groups, synchronized EEG activity tended to decrease across successive NREM periods. This trend was weaker for infants than for adults and, surprisingly, weaker for older than for young infants. This suggests that the decreasing trend typical for adults is already present in the first months after birth. The difference in trend between infants and adults may be caused by differences in the 24-hour sleep-wakefulness distribution, whereas the distinction between young and older infants could be related to a restructuring of sleep in the second semester, in particular to the emergence of slow-wave sleep and its peculiar distribution across NREM periods of night sleep.

Adolescent↗
PubMed1994

A computerized method for detecting episodes of wakefulness during sleep based on the alpha slow-wave index (ASI).

A method for the automatic detection of episodes of wakefulness during sleep is presented. The algorithm is based on the evaluation of the alpha slow-wave index (ASI), a measure that has been developed to detect fluctuations of vigilance in daytime pharmaco-electroencephalogram studies. Its application to sleep data was validated with polysomnographic recordings from 16 elderly insomniacs and 16 young healthy subjects. The rate of agreement between the computerized procedure and the visual scoring of wakefulness was 94.0% for the insomniacs and 96.9% for the healthy subjects. The decision criterion used by the computer allowed the definition of a subject-adapted threshold for the detection of wake episodes. The method opens new perspectives for the automatic analysis of continuous 24-hour sleep-wake recordings.

Aged↗
PubMed1993

Specific assay of medium-chain acyl-CoA dehydrogenase based on the spectrophotometric measurement of product formation.

A spectrophotometric method for assaying medium-chain acyl-CoA dehydrogenase is described. The assay measures at 308 nm the formation of cinnamoyl-CoA from 3-phenylpropionyl-CoA in the presence of phenazine methosulfate as electron acceptor. Apparent kinetic constants (Km, Vmax) determined with 3-phenylpropionyl-CoA are similar to constants obtained with octanoyl-CoA, the preferred substrate of this enzyme. The assay is specific for medium-chain acyl-CoA dehydrogenase because long-chain and short-chain acyl-CoA dehydrogenases exhibit little or no activity with 3-phenylpropionyl-CoA as substrate. Since absorbance changes at 308 nm caused by other reactions are less than 5% of the absorbance change due to cinnamoyl-CoA formation catalyzed by medium-chain acyl-CoA dehydrogenase, the assay can be used to measure the activity of this enzyme in crude tissue homogenates. Specific activities of medium-chain acyl-CoA dehydrogenase determined by use of this assay in homogenates of rat liver, heart, and leukocytes were found to be 29, 68, and 2.1 mU/mg of protein, respectively.

Acyl Coenzyme A↗
PubMed1993

Purification and characterization of the trifunctional beta-oxidation complex from pig heart mitochondria.

The presence of a trifunctional beta-oxidation complex in pig heart and its relationship to the known long-chain enoyl-CoA hydratase (EC 4.2.1.74) from pig heart mitochondria were investigated. For this study, the complex was partially purified by chromatography on DEAE-cellulose in the absence of detergents and was purified to near homogeneity in the presence of Triton X-100. Both enzyme preparations contained long-chain specific activities of enoyl-CoA hydratase, L-3-hydroxyacyl-CoA dehydrogenase, and 3-ketoacyl-CoA thiolase but were virtually inactive toward short-chain (C4) substrates. Both preparations exhibited very low or no activities of delta 3,delta 2-enoyl-CoA isomerase (EC 5.3.3.8) and 2,4-dienoyl-CoA reductase (EC 1.3.1.34). The molecular weights of the two subunits of the pig heart complex were estimated to be 81,000 and 45,000, respectively. The partially purified preparation, obtained in the absence of detergent, was identified as a membranous fraction enriched with respect to the inner mitochondrial membrane. It is concluded that long-chain enoyl-CoA hydratase is a component enzyme of the trifunctional beta-oxidation complex which is associated with the inner membrane of pig heart mitochondria.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed1993

A comparison between visual and computer assessment of sleep onset latency and their application in a pharmacological sleep study.

Sleep onset latency (SOL) is frequently defined as the time between lights-out and the first epoch of sleep stage 2. In practice, SOL can be quantified easily on the basis of visual examination. We have developed a computer algorithm allowing an automatic estimation of this parameter. The agreement between both strategies, visual and computer analysis, was tested using data from a pharmacological sleep study with 16 elderly insomniacs, which was aimed at comparing the effects of lormetazepam and zopiclone on polysomnography. A high correlation was found between the visual and the computer-based determination of SOL. Drug-related differences in SOL could be shown with both approaches.

Aged↗