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Biomedical subjects

J F Orlebeke

Publications and source records attributed to J F Orlebeke.

At least 37 records · Page 2Linked to original sources
PubMed1993

Epidemiological and birth weight characteristics of triplets: a study from the Dutch twin register.

From 112 triplet sets, born in The Netherlands from the end of 1986 to the beginning of 1991 and registered in the Dutch Twin Register, several details such as birth weight, gestational age, zygosity, and etiology were assessed by questionnaire, which was filled out by the mother. For 33 triplet sets, zygosity was also assessed by blood typing. Maternal smoking during pregnancy was also noted. Results show a very strong increase in number of triplets caused by artificial fertility enhancing techniques and consequently a shift in the relative contribution of zygosity types to the total number of triplets. Birth weight is predominantly influenced by gestational age. Other effects on birth weight are controlled for possible confounding with gestational age. First born triplets weigh more than later born triplets; boys weigh more than girls; nearly 25% of all individual triplets weigh less than 1500 g, i.e. belong to the category very low birth weight (VLBW); regular maternal smoking produces a 14% birth weight reduction; ovulation induction seems to decrease the sex ratio, i.e. hormonal treatment with ovulation inducing substances increases the probability of female offspring.

Adult↗
PubMed1993

Birth weight in opposite sex twins as compared to same sex dizygotic twins.

The question addressed in the present report is whether the large birth weight differences in dizygotic twin pairs of opposite sex (DZos), especially in 'male first' couples--observed by Blickstein and Weissman (Blickstein I, Weissman A. Birth weight discordancy in male-first and female-first pairs of unlike-sexed twins. Am J Obstet Gynecol 1990;162:661-663) and replicated in the present study--can be explained by two general influences on birth weight, viz. sex and birth order, or whether some specific effect on fetal growth has to be assumed that is present only in twin pairs of differing sex. The associated enhanced health risk would hit the female twin (from a male first-female second couple) in the first place. If the hypothesis is correct, then one may expect that birth weight of twins is somehow dependent on the sex of the co-twin. This was studied in 3069 twin pairs born in The Netherlands since the end of 1986. Results show that among DZ twins, birth weight is not affected by the sex of the co-twin. Therefore, birth weight differences in DZos pairs have to be ascribed to the general effects of sex and birth order. There is no effect that is specific to DZos pairs only.

Birth Order↗
PubMed1993

Effect of depression on psychomotor skills, eye movements and recognition-memory.

In this study 12 depressed outpatients were compared to 12 healthy controls with respect to their performance on a number of cognitive tasks, including a recognition-memory task, and their eye movements and pupil size were recorded while watching a traffic film. The recognition-memory task consisted of words with intermediate hedonic tone (neutral words), words with high hedonic tone ('good' words) and words with low hedonic tone ('bad' words). Patients performed slower on perceptual-motor tasks which could be characterized as effort-demanding, while no difference between groups was found on effortless tasks. In addition, the range of horizontal eye movements, an indication of visual span, was found to be less in patients. Signal-detection analysis on the recognition-memory data showed an impairment of 'pure' memory in depressives. Analyses on response bias indicated that patients had more false alarms, but only with respect to good words. It is concluded that patients exhibit cognitive deficits, including memory impairment, a narrower visual span and a risky response strategy on good words, which may be an indication of the trouble patients have in processing emotionally toned words.

Adult↗
PubMed1993

Adrenaline and the relationship between neurosomatism, aerobic fitness and mental task performance.

The influence of neurotic instability as manifested by functional somatic complaints (neurosomatism) and aerobic fitness on responses to mental stress and to intravenous adrenaline infusions were investigated in 44 university students. Adrenaline-induced changes from resting levels in state anxiety and somatic anxiety were significantly more pronounced in high than in low neurosomatic subjects and all anxiety ratings were generally negatively related to aerobic fitness. Cardiovascular reactivity was induced by mental stress and by adrenaline infusions, but was not altered by neurosomatism. In individuals assumed to be characterized by a susceptibility to adrenergic effects, interference of adrenaline-induced arousal with cognitive performance may not occur. In contrast, a further increase in performance may occur when adrenaline is infused. Performance measures correlated negatively with anxiety during the baseline task and the placebo task, but this negative relation was absent during the adrenaline infusion and was replaced by positive relations between performance and aerobic power. The complex relations between bodily symptoms of anxiety, aerobic fitness and mental stress are discussed.

Adaptation, Psychological↗
PubMed1993

Effects of behavioral psychophysiological treatment on schoolchildren with migraine in a nonclinical setting: predictors and process variables.

Evaluated the outcome of a combined behavioral therapy, comprising relaxation training, temperature biofeedback, and cognitive training, administered in a school setting, at posttreatment, and 7-month follow-up, on a group of schoolchildren with migraine. Comparison between the experimental group (n = 32) and the waiting-list control group (n = 9) showed a treatment effect on headache frequency and duration but not on intensity. Using a 50% reduction in the headache activity as a criterion for clinical improvement, 45% of the children in the experimental group were clinically improved at the end of the treatment. The treated subjects were found to have maintained significant improvement at follow-up. Sex, headache history, age, and psychosomatic complaints before the training emerged as predictors of outcome. A decrease in state anxiety and an increase in the ability to relax during the sessions contributed to headache improvement. Finally, the acquired capacity to raise one's finger temperature during the biofeedback sessions was related to headache reduction after the training.

Adolescent↗
PubMed1993

Brain potential differences related to spatial attention in migraineurs with and without aura symptoms support supposed differences in activation.

It is to be expected that differences in electrical activity of the brain between migraine patients with aura and those without aura can only be revealed by stimuli that provoke visual spatial processing, i.e. stimuli that trigger so called endogenous Visual Evoked Potential (VEP) activity. This is not the case for the flashes and checkerboard reversals. Those stimuli elicited exogenous activity only. During and between attacks the blood flow of migraineurs with aura changes in the posterior cerebral part of the brain, which is assumed to be specialized in the processing of spatial aspects of visual stimuli. Reaction times (RTs), early and late Event Related Potential (ERP) differences were compared at 12 scalp positions for two groups of migraineurs (with and without aura) and a control group. They had to perform a passive attention task, checkerboard reversals, and an active attention task, where attention was either divided into or focussed at spatial locations. In agreement with many studies on migraine, checkerboard stimuli did not differ on any early components. However, RTs were faster for migraineurs with aura and their early components were different when stimuli were highly attended. This is probably because these stimuli can relatively easily trigger cortical activity due to an over activated central mechanism and an enhanced level of attention.

Adult↗
PubMed1992

Vitamin B-6 supplementation in elderly men: effects on mood, memory, performance and mental effort.

This study evaluates the effects of vitamin B-6 supplementation (20 mg pyridoxine HCL daily for 3 months) on mood and performance in 38 self-supporting healthy men, aged between 70-79 years. Effects were compared with 38 controls who received placebo and were matched for age, plasma pyridoxal-5'-phosphate (PLP) concentration and intelligence score. Before and after drug intervention vitamin B-6 status was determined, and mood and performance were measured by means of a computerized testing system. In addition, the phasic pupil response was measured in order to assess mental effort. Positive effects of vitamin B-6 supplementation were only found with respect to memory, especially concerning long-term memory. In view of the finding that mental performance improvement and delta PLP values were most strongly correlated within an intermediate range of delta PLP, it is suggested that cognitive effects are primarily associated with a certain range of vitamin B-6 status increment. The general conclusion is that vitamin B-6 supplementation improves storage of information modestly but significantly.

Affect↗
PubMed1991

Residual effects of lormetazepam on mood and performance in healthy elderly volunteers.

45 subjects aged over 65 years were randomly assigned to treatment with lormetazepam 0.5 mg or 1 mg or placebo. Mood and performance were measured with a battery of computerized tests. Subjects were tested before and after 1 and 8 nights of treatment. Pre- and post-treatment scores were analysed by a multivariate covariance technique, the pre-treatment score serving as covariate. The single and repeated doses of lormetazepam resulted in impairment of performance in a memory task, and the repeated dose administration impaired performance of a perceptual task. The single administration of a low dose gave an improvement in fine motor control. No change was found in the mood states of the subjects.

Affect↗
PubMed1991

HGM1: a research-oriented portable heart rate and galvanic skin response monitor.

A convenient portable recording device, HGM1, which allows digital field recording of skin conductance and heart rate data with laboratory levels of precision, is described. Examples of individual data are provided from a study of orienting response habituation, and from students participating in a study of examination anxiety, recorded while they sat scheduled class examinations. These illustrate the potential value of the device in field studies.

Adolescent↗
PubMed1991

Changes in the DZ unlike/like sex ratio in The Netherlands.

Based on Dutch twin incidence figures since the beginning of the current century, evidence is provided in support of the idea that the DZ unlike/like sexed ratio has gradually shifted (since 1900) from unity to less than unity. Opposing conclusions with regard to the justification of the use of Weingberg's differential rule are very probably correct in themselves but could depend on country and period of birth of the twin sample used. Furthermore, the fast drop and subsequent rise in DZ twinning rate between about 1963 and 1990 can very likely for the greater part be ascribed to a parallel shift in maternal age.

Female↗
PubMed1990

Estimation of individual genetic and environmental factor scores.

Implicit in the application of the common-factor model as a method for decomposing trait covariance into a genetic and environmental part is the use of factor scores. In multivariate analyses, it is possible to estimate these factor scores for the communal part of the model. Estimation of scores on latent factors in terms of individual observations within the context of a twin/family study amounts to estimation of individual genetic and environmental scores. Such estimates may be of both theoretical and practical interest and may be provided with confidence intervals around the individual estimates. The method is first illustrated with stimulated twin data and next is applied to blood pressure data obtained in a Dutch sample of 59 male adolescent twin pairs. Subjects with high blood pressure can be distinguished into groups with high genetic or high environmental scores.

Adolescent↗
PubMed1990

Effects of behaviour therapy on migraine and plasma beta-endorphin in young migraine patients.

In this study we measured concentrations of beta-endorphin, ACTH, prolactin and cortisol in plasma of migraine patients (ages 10-19) and age-matched controls, and the effects of behaviour therapy on both migraine and the endocrine parameters. Two groups of migraine patients (M) and controls (C) were recruited: group I (MI, n = 11; CI, n = 13) in winter and group II (MII, n = 9; CII, n = 7) in summer. Both M groups received behaviour therapy: group MI immediately and group MII after a waiting period of 3.5 months. Hormone determinations were made before and after the behaviour therapy of group MI and before and after the waiting period of group MII. At the first measurement (before therapy and waiting period), migraine subjects had lower concentrations of beta-endorphin than controls. After behaviour therapy, both groups showed a significant decline in migraine, which was retained at follow-up 9-12 months after completion of the therapy. Improvement of migraine after behaviour therapy was accompanied by a rise in the level of beta-endorphin in group MI. In contrast, the patients of the waiting period (group MII) showed improvement in migraine after the waiting period but no changes in beta-endorphin. Seasonal differences were observed for beta-endorphin, prolactin and cortisol, winter values being lower than summer values.

Adolescent↗
PubMed1990

Genetic influences on respiratory sinus arrhythmia across different task conditions.

Respiratory sinus arrhythmia (RSA) has been shown to be a sensitive index of vagal cardiac control. We studied the genetic and nongenetic influences on individual differences in RSA in a sample of 160 adolescent twins. RSA was measured during rest and across two different tasks. Results show that heritability is task dependent. The amount of genetic variance is the same, however, during rest and task conditions. Because nonshared environmental variance decreases during tasks, heritability is larger for RSA measured under more stressful conditions than for RSA as measured during rest. Multivariate models assessed the continuity of the genetic and environmental influences and show genetic influences to be the same across different conditions, while environmental influences are different. More specifically, a one-factor model is found for genetic influences and a second-order autoregressive model for the environmental factors.

Adolescent↗
PubMed1990

Existing and training induced differences in aerobic fitness: their relationship to physiological response patterns during different types of stress.

Aerobic fitness has been associated with various desirable psychological and physiological characteristics. Recently, attenuation of physiological reactivity during stressful situations was added to this list, although comparison of the stress responses of sportsmen and sedentary subjects has yielded equivocal results. The present study examined cardiovascular patterns rather than single variables, and tried to clarify these matters. Tasks were used that were known to increase blood pressure through different combinations of changes in cardiac output and vascular resistance. Autonomic nervous system dynamics underlying these response patterns were studied using preejection period as an index of beta-adrenergic activity, and respiratory sinus arrhythmia as an index of vagal activity. Pre-existing differences in aerobic fitness in a sample of sedentary subjects were related to their responses during the stressful tasks and the recovery periods afterwards. This approach prevented confounding of the relationship between fitness and stress-reactivity with the psychological effects of regular exercise. Furthermore, it excluded the bias in psychological makeup that is introduced when subjects spontaneously engaged in sports are compared to non-exercising persons. To rule out a third (hereditary?) factor underlying both stress-reactivity and fitness, physiological responses before and after a seven-week training program were compared to those of subjects in a waiting list control group. Substantial individual differences in aerobic fitness were found in spite of the fact that all subjects reported low levels of habitual activity. During two active coping tasks, diastolic blood pressure reactivity and vagal withdrawal were negatively related to these pre-existing differences in fitness. No such relation was seen during a cold pressor test or during recovery from the tasks. Neither beta-adrenergic cardiac reactivity nor heart rate responses were related to fitness, but the absolute heart rate during the tasks was lower in the more fit subjects. Seven weeks of training were not effective in changing either reactivity or recovery of any of the variables. The discrepancy between cross-sectional and longitudinal results in the present study suggests that training of longer duration is necessary to induce the psychological or physiological changes underlying reduced reactivity. The latter may include changes in cardiac vagal/sympathetic balance or in adrenoceptor sensitivity. Alternatively, both psychological and physiological determinants of stress-reactivity may be related to aerobic fitness at a dispositional level.

Adolescent↗
PubMed1990

Migraine patients cognitively impaired?

In order to investigate the hypothesis that migraine has a detrimental effect on cognitive functioning, 37 female migraine patients and 34 nonheadache female controls underwent a battery of neuropsychologic tests. No significant difference in test performance between groups was found. There was no relation between the length of migraine history or medication use and the level of impairment of cognitive abilities. The patient and control groups differed significantly on several self-report measures known to interfere with performance. Patients reported higher trait and state anxiety levels, higher debilitating anxiety and state depression, and less vigor. Statistical correction for these variables, however, did not result in significant group differences of cognitive performance. The results suggest that the general population of female migraine patients show no indication of cognitive impairment.

Affect↗
PubMed1990

Relaxation training in school classes does not reduce headache complaints.

The effect of teacher-presented Progressive Relaxation Training (PRT) on headaches, fear of failure and school problems was studied in school students. During ten physical education lessons, students received either PRT (n = 110) or placebo training (n = 92). The effect of the training was investigated in students who indicated the presence of headaches in a pre-training diary. No significant differences were found between both training groups regarding headache frequency, duration and intensity and the psychological variables. On the basis of these and previous findings, it is recommended to present PRT to fairly small groups of self-selected subjects instead of complete classes.

Adolescent↗