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Biomedical subjects

H Schulz

Publications and source records attributed to H Schulz.

At least 163 records · Page 9Linked to original sources
PubMed1997

The validity of the telemetric system CORTEX X1 in the ventilatory and gas exchange measurement during exercise.

With the portable spirograph CORTEX X1 both the oxygen consumption and the carbon dioxide output can be determined. Therefore, the aim of the present study was to determine the accuracy of the CORTEX X1 in measuring F(E)O2, F(E)CO2 and V(E) when attached to a motor-driven mechanical syringe and to validate the CORTEX X1 against a standardized breath-by-breath system during a graded bicycle ergometry. Fifteen subjects (8 male, 7 female; 26.7+/-3.3 years) performed two graded exercise tests on a bicycle ergometer (50 W incline every 3 min) until volitional fatigue in randomized order. During rest and during the last 30 s of each step ventilatory and gas exchange parameters were measured with the CORTEX X1 and the OXYCONgamma. At rest and at each step no significant differences exist for VO2 (F = 0.97) and VCO2 (F = 0.90). The orthogonal regression equation of the VO2-values was VO2(X1) = -75.5 + 1.01 x VO2(Oxy) and the equation of the VCO2-values was VCO2(X1) = 21.7-1.008 x VCO2(Oxy). The VO2-max-values were nearly the same: 3569+/-924 ml/min (Oxy) and 3497+/-993ml/min (X1). Similar findings were made with regard to VCO2max 4117+/-1010 ml/min (Oxy) and 4126+/-1090 ml/ min. (X1). Maximal values for heart rate were 181+/-10 beats/ min (X1) and 180+/-8 beats/min (Oxy) (F=0.21), for maximal power 256+/-64 W (X1) and 257+/-63 (Oxy) (F = 0.0001) and for maximal ventilation 118+/-31 l/min) and 120+/-35 l/min (Oxy) (F = 0.03) with no significant difference. When attached to the motor-driven syringe V(E) was accurately measured up to 288 l/ min. Over a period of 40 min there was no drift observed in F(E)O2 and F(E)CO2. In conclusion, with the CORTEX X1 VO2 and VCO2 can be accurately determined.

Adult↗
PubMed1997

Behavioural and functional neurotoxicological changes caused by cadmium in a three-generational study in rats.

1. Three consecutive generations of Wistar rats were orally treated by gavage with 3.5, 7.0 or 14.0 mg/kg cadmium (in form of cadmium chloride diluted in distilled water) over the period of pregnancy, lactation and 8 weeks after weaning. 2. Behavioural (open field behaviour) and electrophysiological (spontaneous and evoked cortical activity, etc.) parameters of male rats from each generation were investigated at the age of 12 weeks. 3. The main behavioural outcomes were change in vertical exploration activity (rearing) and increased exploration of an open field centre. The spontaneous and evoked electrophysiological variables showed dose- and generation-dependent changes (increased frequencies in the electrocorticogram, lengthened latency and duration of evoked potentials, etc.) signalling a change in neural functions. 4. The data show that low-level, multigeneration exposure to inorganic cadmium can affect functions of the nervous system. This suggests that cadmium exposed human populations may be at risk of developing nervous system disorders.

Animals↗
PubMed1997

Aerosol bolus dispersion in healthy subjects.

Aerosol bolus dispersion is a physiological test of lungs, which uses monodisperse submicron particles to measure intrapulmonary convective gas mixing. In this study, aerosol bolus dispersion was measured in healthy subjects in order to assess reference values for possible clinical applications, to assess the reproducibility of these values, and to identify physical and physiological factors influencing aerosol bolus dispersion. Aerosol bolus dispersion was measured in 79 healthy subjects using 20 cm3 aerosol boluses consisting of monodisperse di-2-ethylhexyl sebacate (DEHS) particles. The reproducibility of parameters characterizing the width of the exhaled bolus was of the same order as that of parameters of the flow-volume curve (10%). Aerosol bolus dispersion was independent of the level of lung inflation, and the slope of the relationship between flow rate and dispersion was on average not significantly different from zero (range 100-700 cm3.s-1). Multiple linear regression showed that aerosol bolus dispersion increased with increasing total lung capacity of the subject. We conclude that differences in total lung capacity between individuals should be taken into account when using measures of aerosol bolus dispersion for possible clinical applications.

Administration, Inhalation↗
PubMed1997

Cognitive deficits in patients with daytime sleepiness.

A chief complaint of subjects with daytime sleepiness is the disturbance of cognitive functions like concentration, learning and memory. Since sleepiness interferes with the regulation of vigilance, one may assume that a disturbance of this basic dynamic variable causes deficiencies in information processing which in turn reduce the capacity for learning and memory. In two studies the time course of vigilance was measured by means of the critical flicker fusion (CFF) test in patients with narcolepsy or with an obstructive sleep apnea syndrome (OSAS). The CFF test was applied at 15 min intervals. The total test duration was ten hours in the study with narcoleptic patients and three hours in the study with OSAS patients. The mean level of performance was similar in healthy subjects and those with narcolepsy, while the latter displayed a three- to four-fold increase in temporal variability. Such an increase in variability of performance was not seen in subjects with OSAS. These data suggest that clinically distinguishable groups of patients with daytime sleepiness differ also in the pattern of performance impairment.

Adult↗
PubMed1996

Intermediate channeling on the trifunctional beta-oxidation complex from pig heart mitochondria.

The kinetic properties of the purified trifunctional beta-oxidation complex (TOC) from pig heart mitochondria were analyzed with the aim of elucidating the functional consequence of having three sequentially acting enzymes of beta-oxidation associated in one complex. The kinetic parameters of TOC and of the component enzymes of TOC, long-chain enoyl-CoA hydratase, long-chain 3-hydroxyacyl-CoA dehydrogenase, and long-chain 3-ketoacyl-CoA thiolase, were determined with substrates having acyl chains with 16 carbon atoms. Quantification by high performance liquid chromatography of intermediates formed during the degradation of 2-trans-hexadecanoyl-CoA to myristoyl-CoA and acetyl-CoA by TOC revealed the accumulation of 3-hydroxyhexadecanoyl-CoA, whereas 3-ketohexadecanoyl-CoA was undetectable. The observed rates of NADH and acetyl-CoA formation were higher than the theoretical rates calculated by use of the kinetic parameters and measured concentrations of intermediates. When the sequence of reactions catalyzed by TOC was inhibited by acetyl-CoA, the steady-state concentration of the 3-hydroxyacyl-CoA intermediate was not affected, whereas a small amount of 3-ketohexadecanoyl-CoA was detected. The differences between observed and predicted reaction rates and between measured and expected concentrations of intermediates are best explained by the operation of a channeling mechanism. As a consequence of intermediate channeling between the active sites on the complex, more coenzyme A is available in the mitochondrial matrix and metabolites like 3-ketoacyl-CoA thioesters, which are strong inhibitors of several beta-oxidation enzymes, do not accumulate.

Acyl Coenzyme A↗
PubMed1996

[Dysplastic nevus in differential epiluminescence microscopy diagnosis of melanoma].

The utility of two different epiluminescence microscopy rating protocols were tested prospectively and retrospectively on a group of 115 photographically documented naevi. Initially all naevi were classified histologically as dysplastic. While the first score table was set up only to identify dysplastic naevi, the second system lent itself to the differential diagnosis of malignant melanoma. Using this second scoring table 3 lesions were identified as melanomas directly and in 3 further melanomas the suspicion of dysplasia was confirmed. Malignancy was definitely confirmed only by histology. With regard to the surface microscopic differentiation of melanocytic lesions, the term "dysplasia" should not be abandoned. If the diagnosis of melanocytic tumours is problematic a double check of the clinical photograph using specific criteria cougled with histological evaluation appears helpful.

Diagnosis, Differential↗
PubMed1996

"IR-Spectroscopy" - computer-program for the interpretation of infrared spectra.

A computer-program "IR-Spectroscopy" for the interpretation of infrared spectra of organic compounds is described. It contains the following basic items for preprocessing and execution of the computer based interpretation process: handling of the rule-base CorTab, routines for automatic rule generation and interpretation modules on the basis of the programming languages PROLOG and C.

Journal Article↗
PubMed1996

Inhalation of 5-aminolevulinic acid: a new technique for fluorescence detection of early stage lung cancer.

Topical application of 5-aminolevulinic acid (5-ALA), with subsequent synthesis of protoporphyrin IX (PPIX), is a novel outstanding procedure for photodynamic treatment. So far, clinical experience has been reported with creams containing 5-ALA for the therapy of skin cancer, oral application for the treatment of gastrointestinal disease and intravesical instillation of 5-ALA solutions for fluorescence detection of superficial bladder cancer. Inhalation of 5-ALA for the staining of bronchial malignancies is a preferred method in clinical pulmonology. Since no adverse reaction was observed in lung function in a canine following inhalation of 5-ALA in increasing concentrations, clinical applications were performed. Seven patients with positive or suspicious sputum cytology, but negative white light bronchoscopy, received 5-10 wt.% 5-ALA in NaCl solution by means of a medical nebulizer. No side effects were observed during and after 5-ALA inhalation. After a period of 3 h, patients underwent fluorescence bronchoscopy using violet light for fluorescence excitation and an optical multichannel analyzer for fluorescence detection in situ. The results showed fluorescence spectra which could be related to PPIX induced by 5-ALA in the bronchial mucosa. The fluorescence intensity was sufficiently high for video imaging using a target integrating color CCD camera adapted to the flexible bronchoscope. Carcinoma in situ, as well as dysplasias, showed a clear positive fluorescence. A correlation of fluorescence contrast with histology on 30 biopsies revealed a high sensitivity, but a specificity below 50%. Improvements in light and drug dosimetry will form the basis for further clinical trials.

Administration, Inhalation↗
PubMed1996

The diurnal distribution of sleep propensity: experimental data about the interaction of the propensities for slow-wave sleep and REM sleep.

The aim of the present study was to assess the diurnal variation of sleep propensity by evaluating the temporal distribution of sleep onset latency (SOL) and REM- and slow-wave sleep (SWS) parameters in systematically scheduled daytime naps for 12 young males. To reduce the effect of prior SWS on subsequent REM sleep, a double-nap technique was used, i.e. two adjacent naps A and B, which were separated by a 10-min break. Nap duration was adjusted in such a way that nap A allowed 30 min of sleep and nap B one complete NREM-REM cycle. EEG slow wave activity (SWA, power density from 0.5-4 Hz) was estimated from nap A and REM sleep parameters from nap B. The time span between 08.00 hours and 24.00 hours was covered by nine double-naps at 2 h intervals. The order of the nap sessions was systematically varied within and across subjects. For each subject, the time between successive double-nap recordings was at least three days. SOL was shortest in the time interval 12.00 hours to 16.00 hours and significantly longer between 20.00 hours and 24.00 hours. REM sleep duration and the percentage of sleep onset REM episodes decreased continuously from 08.00 hours to the interval 18.00-20.00 hours and increased thereafter, with a time course inversely related to the one of body temperature, which was also measured continuously. SWA showed a steady, threefold increase from 08.00 hours to 24.00 hours. The study offers new data on the diurnal variation of sleep propensity which seems to be a composite function of the drives for SWS and REM sleep.

Adult↗
PubMed1996

The use of diurnal vigilance changes in the EEG to verify vigilance-enhancing effects of memantine in a clinical pharmacological study.

In elderly subjects there is a vigilance decrease from morning to noon which was used in a clinical pharmacological model as a state condition to verify vigilance-enhancing effects of an antidementia drug. In this model the effects of Memantine (20 mg, single-dose application) on the quantified EEG were investigated in 16 elderly (mean age: 65 +/- 5 years), healthy subjects (10 females, 6 males) in a randomised, twofold cross-over design vs. placebo under double-blind conditions. EEG was recorded before medication, and 2 and 4 h after medication under reaction time (RT) and resting (RS) conditions. EEG data were subjected to spectral analysis and the topographic distribution of the amplitude values was mapped. The results show that a time-dependent decrease (from morning to noon) in vigilance (indicated by an increase in average EEG amplitudes caused by increased synchronisation in the alpha and beta range and an increase in delta) occurred under placebo which was counteracted by Memantine. The diurnal variations of the EEG and their compensation by a pharmacological agent represent an effective model for investigating the vigilance-enhancing effects of antidementia drugs.

Aged↗
PubMed1996

Soporific effect of the neurosteroid pregnanolone in relation to the substance's plasma level: a pilot study.

The soporific effect of the neuroactive steroid pregnanolone, a metabolite of progesterone, and its relationship with plasma concentrations was assessed in 18 young, healthy, male volunteers for 2 h after administration of a single dose of pregnanolone prepared in two different formulations. Sedation was measured as sleep propensity and power increase in the low frequency delta band of the quantified EEG, based on 5-min polygraphic (EEG, EOG, EMG) recordings under resting conditions, which were performed immediately before, and 30, 60, 90, and 120 min after intake of the study drug. With both formulations, there was a time-dependent increase in plasma concentration of pregnanolone with highest values 1-2 h postdosing. The model of short polygraphic recordings under resting conditions demonstrated soporific effects of pregnanolone. Compared to predosing baseline the number of sleep attempts and the time asleep increased after treatment with a peak 60 min postdosing. Quantitative EEG analysis revealed an increase of absolute amplitude in the delta frequency range with a comparable temporal pattern. Correlations between the soporific effect and plasma concentrations of pregnanolone suggest that the effects were drug-related, although this has to be replicated with placebo control.

Adult↗