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Biomedical subjects

J F Orlebeke

Publications and source records attributed to J F Orlebeke.

At least 55 records · Page 3Linked to original sources
PubMed1989

Resemblances of parents and twins in sports participation and heart rate.

A model to analyze resemblances of twins and parents using LISREL is outlined and applied to sports participation and heart-rate data. Sports participation and heart rate were measured in 44 monozygotic and 46 dizygotic adolescent twin pairs and in their parents. Genetic factors influence variation in both sports behavior and heart rate, while there is no evidence for transmission from parental environment to offspring environment. For sports participation the data support a model in which there is a high positive correlation between environments of spouses and between environments of female twins. This correlation is absent for male twins and negative for opposite sex twins. For heart rate, a positive correlation between environmental influences was observed for all twins; there is no evidence for assortative mating. The proposed model can also handle data sets where parents and twins have been measured on more than one variable. This is illustrated by an application to the observed association of sports participation and heart rate.

Adolescent↗
PubMed1989

Dietary effects on mood and performance.

Of 20 young students recruited at a college for nutrition, 10 followed a diet for a period of 3 weeks and 10 were assigned to a control condition. One subject in the control group dropped out. The diet consisted of approximately 70 g protein and 25 g carbohydrate at breakfast and 10 g protein and 100 g carbohydrate at dinner. In between, a protein luncheon was consumed. On the last day of the 3-week period repeated measurements of mood and performance were made, i.e. after breakfast and after dinner. Consequently, the same measurements were made 2 months later to serve as covariates in the analyses to control for base-line differences of the two groups. It was predicted that, in the morning, the performance and the vigour of the diet group would improve whereas, in the evening, performance would become worse and subjects would feel more sleepy. However, the diet group was found to have a higher anger score in the morning (probably due to the unattractive nature of the diet) and a tendency to have a higher fatigue score in the evening compared with the controls. In addition, the diet group performed better in the morning on finger tapping, compared with the control group. With respect to memory scanning, the diet group performed more slowly in the morning in comparison with the control group. From these conflicting results, it was concluded that dietary composition had no effect on mood and behaviour.

Adult↗
PubMed1989

Comparison of spot and band impedance cardiogram electrodes across different tasks.

Impedance cardiography has become of widespread interest as a noninvasive cardiovascular monitoring technique. This study compared the use of spot electrodes and two different types of band electrodes in the determination of systolic time intervals and stroke volume. EKG, impedance cardiogram, and phonocardiogram were recorded on 12 volunteers during rest, during a reaction time task, and after a short exercise task. Systolic time intervals (pre-ejection period and left ventricular ejection time) were computed on a beat-to-beat basis and on the ensemble-averaged signals. The only differences between spot and band electrodes were for impedance base level and electrode conductance. For stroke volume and the systolic time interval measures there were no differences between electrode arrays, nor were there any interactions with tasks. Correlations for stroke volume and systolic time interval measures as determined under different electrode conditions were around .8.

Adult↗
PubMed1989

Auditive and cognitive factors in speech perception by elderly listeners. I: Development of test battery.

This study compares performance of 24 young normal-hearing (aged 18-28 years) and 24 elderly (aged 61-85 years) listeners on auditive (sensitivity, frequency selectivity, and temporal resolution), cognitive (memory performance, processing speed, and divided attention ability), and speech perception tests (at the phoneme, spondee, and sentence level). Its principal aim is to assess whether the tests selected yield meaningful results. The results obtained will be used to reduce the test battery in order to be manageable in a second study on a much larger number of elderly listeners. The relationships between the tests are explored by multivariate statistical methods. The results show that: (a) in young listeners, individual differences in speech perception performance are remarkably small resulting in low correlations between the tests, while in the elderly tests of phoneme, spondee, and sentence perception overlap considerably; (b) speech perception in the elderly seems to be largely determined by hearing loss at the higher frequencies, whereas the effects of other auditive and cognitive factors seem to be relatively small or absent; and (c) performance in the elderly is only partly correlated with age.

Acoustic Stimulation↗
PubMed1988

Aerobic fitness and the physiological stress response: a critical evaluation.

Aerobically fit persons need less sympathetic activation to perform the same absolute workload than less fit persons. This led to the idea that aerobic fitness might reduce the physiological activation during psychological stress as well. Several experiments showed inconsistent results with regard to this supposed effect of fitness. The comparability of the results is hampered by the differences in operationalization of aerobic fitness and by the confusion of the terms aerobic fitness, training and habitual physical exercise. The expectancy of an effect of fitness on the physiological stress response is based on the assumption that this response resembles the response to exercise. The tenability of this assumption was examined for cardiac, vascular and hormonal responses respectively. It was concluded that the two types of responses only superficially have similarity. So a simple analogy between the stress and the exercise response does not allow a reliable prediction concerning the effect of fitness on the stress response. There are however other reasons to expect an effect. Especially the effect of fitness on adrenoceptor sensitivity suggests that the most important effect of fitness might be found in the vascular part of the stress response. It is argued that the measurement of complete response patterns, instead of isolated parameters, is a prerequisite for progress in this field. Future studies should address the question what the relative contribution of psychological and physiological factors is to the effect of fitness on the physiological stress response.

Arousal↗
PubMed1988

Migraine and defense mechanisms: psychophysiological relationships in young females.

Two psychological defense mechanisms, repression and self aggression, were studied in 23 young female migraine patients who had not been receiving treatment for their complaints and in 23 relatively headache free matched controls. All subjects were psychology students. Each subject was classified as high or low on repression and self aggression using the defense mechanism inventory. During three separate sessions: adaptation, intelligence test and real-life stress (an examination which was part of the psychology curriculum) pulse amplitudes of the temporal and digital arteries, frontal, temporal and corrugator EMGs, forehead temperature, skin conductance, and heart and respiration rate were measured. The migraine patients showed a trend towards more repression of their emotions and significantly more self aggression than the controls. Self aggression appeared to be positively associated with the headache frequency in the migraine group. With regard to the physiological measurements, in both groups repressors showed a modest tendency to enhanced sympathetic activity. Self aggression was not found to be related to any physiological measure of sympathetic activity, but, instead, related to less temporal blood flow. In general, associations were found between psychological defense mechanisms and physiological activity, which is suggestive of the existence of physiological pathways along which emotional inhibition might contribute to an attack of migraine after a stressful situation.

Adult↗
PubMed1988

EMG in common migraine: changes in absolute and proportional EMG levels during real-life stress.

The absolute and proportional EMG levels of the frontal, temporal, and corrugator muscles of 37 migraine patients and 37 matched controls were recorded during three experimental sessions: adaptation and real-life and experimental stress, both of long duration. Migraine patients did not show significantly different absolute EMG levels but had higher proportional EMG levels of the corrugator muscle than controls in each session. Migraine patients did not have different facial muscle responses to stress, and the two experimental groups reacted similarly to real-life and experimental stress. No relation was found between muscle activity and reported headache within 24 h after real-life stress. Increased EMG activity due to stress does not seem to be a significant cause of headache in common migraine as defined in this study, but rather a response to pain. Migraine patients with headache during stress showed lower muscle tension than patients without headache.

Adult↗
PubMed1987

Twin studies on urinary pepsinogen A phenotypes and serum pepsinogen A levels.

Urinary pepsinogen A (PGA or PG I) phenotypes and serum PGA levels were studied in MZ and DZ twins and their parents. In 45 out of 48 MZ twin pairs PGA patterns were completely identical, while 3 MZ twin pairs showed minor differences in the relative intensity of the Pg5 isozymogen. This suggests that the intensity of this isozymogen may be influenced by nongenetic factors. There was little difference in the interclass correlations of serum PGA levels between MZ and DZ twins, indicating a large contribution of common environmental factors to serum PGA levels. This is in contrast with previous studies.

Adolescent↗
PubMed1986

Task effects and individual differences in the study of lateral eye movements.

Twenty-nine males and 29 females (all right-handed) participated in this study. The effects of question type (numerical, verbal, spatial) and experimenter position (in front of or behind the subject) on direction of lateral eye movements (LEMs) were tested. Also the relation between dominant LEM direction and other individual traits was investigated. The percentage of LEMs (tonic changes) as well as the first LEM (phasic changes) in the reflective period was scored. Results were identical for both methods; there were no task-specific effects demonstrated, nor was a relation found between dominant LEM direction and imagery, extraversion, neuroticism, sensation seeking, impulsiveness, and amount of somatic and psychic complaints. It appeared that the extent to which subjects gazed away varied with the amount of stress that was induced, while the direction of glance depended on the individual habit of the subject. The conclusion was that LEMs are subject specific rather than task specific and that this individual specificity is strengthened under stress conditions.

Cerebral Cortex↗
PubMed1985

The effects of nicotinic acid and xanthinol nicotinate on human memory in different categories of age. A double blind study.

The treatment effect of nicotinic acid and xanthinol nicotinate on human memory was compared with placebo in 96 healthy subjects. Forty-three subjects were young (35-45 years), 30 subjects middle aged (55-65 years) and 23 subjects were old aged (75-85 years). Pre- and post-treatment scores were measured on a battery of memory tasks, covering sensory register, short-term memory and long-term memory. The treatment regime was 1 dragee t.i.d. for 8 weeks. The administration of xanthinol nicotinate (500 mg, containing 141.7 mg nicotinic acid), nicotinic acid (141.7 mg) and placebo (lactose) was double-blind. Pre- and post-treatment scores were analysed by means of a multivariate covariance technique, the pre-treatment score serving as covariate. Nicotinic acid treatment resulted in improvement of sensory register and short-term memory, while xanthinol nicotinate improved sensory register, short-term memory and long-term memory. In comparison with placebo, both active compounds yielded improvements of 10-40%, depending on type of task. Treatment effects of nicotinic acid were predominantly found in the young and middle-aged, whereas treatment effects of xanthinol nicotinate were predominantly found in the old. These results are interpreted by the supposed activity of nicotinic acid at the cell membrane, improving neuronal transmission, and of xanthinol nicotinate inside the cell, enhancing cell metabolism and oxygen supply in the brain.

Adult↗
PubMed1985

Headaches and stress in schoolchildren: an epidemiological study.

Headache parameters, personality variables and stress factors were assessed in a sample of about 2,300 school pupils between 10 and 17 years of age in Amsterdam. More than 15% of the subjects reported headaches occurring weekly. Fear of failure and school problems, but not achievement motivation, had significant positive correlations with headache complaints after correction for differences in sex and age. Menarche and social class had little bearing in relation to the headache variables. From all reported causes of headache, stress was mentioned most frequently in both elementary and secondary schools.

Adolescent↗