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Biomedical subjects

J F Orlebeke

Publications and source records attributed to J F Orlebeke.

At least 19 recordsLinked to original sources
PubMed1998

Frequency of parental report of problem behavior in children decreases with increasing maternal age at delivery.

Child behavior problems were assessed in 1377 3-yr.-old twin pairs with the Child Behavior Check List from Achenbach (translated into Dutch language by Verhulst). The association between problem scores and maternal age at delivery of the twins was analyzed with statistical control for several potential confounding variables: birth weight of twins, maternal smoking during pregnancy, being breast or bottle fed and socioeconomic status. After controlling for all available confounding covariates, a significant linear effect for maternal age was left. Especially Externalizing behavior problems as well as the separate categories that constitute Externalizing, i.e., Aggressive, Oppositional, and Overactive, appeared to decrease continuously with increasing maternal age. This was true for both boys and girls as well as for first and secondborn twins. Evidence in support of a biological explanation of the association between maternal age and child behavior problems, is presented.

Adult↗
PubMed1996

Genetic modelling of dizygotic twinning in pedigrees of spontaneous dizygotic twins.

The inheritance of spontaneous dizygotic (DZ) twinning was investigated in 1,422 three-generation pedigrees ascertained through mothers of spontaneous DZ proband twins. DZ twinning was modelled as a trait expressed only in women. The penetrance was modelled first as a parity independent and secondly as parity dependent. The observed frequencies of maternal and paternal grandmothers with DZ twins differed significantly from the expectations under an X-linked mode of inheritance. Complex segregation analysis showed that the parity-independent phenotype of "having DZ twins" was consistent with an autosomal monogenic dominant model, with a gene frequency of 0.035 and a female-specific lifetime penetrance of 0.10. Recessive, polygenic, and sporadic models were rejected. The autosomal dominant model revealed a strong robustness against a changing population prevalence and the loss of information due to the presence of same-sexed twin pairs of unknown zygosity. When DZ twinning was modelled as a parity dependent trait, the data were compatible with an autosomal dominant model with a gene frequency of 0.306 and a penetrance of 0.03 per birth for female gene carriers.

Cluster Analysis↗
PubMed1996

Left-handedness in twins: genes or environment?

Twin family data can cast light on the longstanding problem about the influences of genes and environment on the etiology of left-handedness. Therefore, hand preference was assessed in 1700 adolescent twin pairs and their parents. Left-handedness (LH) appeared not significantly enhanced among twins compared to the general population. In addition the following observations were made: (1) Significant more LH in first born twins than in second born twins. (2) Significant higher left-handedness association in MZmm pairs compared to DZmm pairs and not or may be marginally so in MZff versus DZff pairs. These results, combined with the observations that (a) left-handed fathers increase the probability of LH in sons but not in daughters; (b) LH in mothers increases LH prevalence in both sons and daughters to the same degree; and (c) very low birth weight, corrected for the effect of gestational age, increases LH prevalence in first born twins only, make an environmental explanation more likely. The possibility that exposure to prenatal male hormones - to which low birth weight and high birth stress children are more vulnerable - might be a crucial condition for the etiology of LH, is discussed.

Adolescent↗
PubMed1996

Cardiovascular response to physical stress in offspring of hypertensive parents: Dutch Hypertension and Offspring Study.

Blood pressure (BP) regulatory mechanisms were studied in youngsters with contrasting risks for hypertension, based on parental history, during physical stress. As a static exercise, an isometric handgrip task (22% of maximal force during 5 min) was used and a dynamic exercise task was performed on a bicycle ergometer. At rest and during stress, BP and heart rate were recorded. In order to study the adaptation of the cardiovascular system to physical stress, cardiac output and total peripheral resistance were measured in addition to indices of vagal and sympathetic influences on the heart. Heart rate and cardiac output declined significantly more in offspring of hypertensive parents during static exercise (difference in heart rate: -2.5 +/- 1.2 bpm, P = 0.04; difference in cardiac output: -9.0 +/- 4.6%, P = 0.05). This is most likely the result of a larger increase in the total peripheral resistance in youngsters at risk (difference: 13.2 +/- 6.8%, P = 0.06). No differences between the two groups were found in reactivity of BP or in the indices of sympathetic activation or vagal inhibition of the heart. The offspring of hypertensive parents showed an attenuated increase in stroke volume during the dynamic exercise task (difference at the first cycling level: -11.5 +/- 5.4%, P = 0.04), while no difference in neural activity or heart rate was found. Youngsters with a parental history of hypertension show an enhanced reactivity of total peripheral resistance during static exercise. This does not lead to a higher BP response in this group, most probably because of a larger decrease of the cardiac output. During dynamic exercise the physiological increase in stroke volume is blunted in offspring of hypertensive parents.

Adolescent↗
PubMed1995

Pupillometric assessment of compensatory effort in a memory search task under physical and pharmacologically-induced suboptimal states.

Extensive research has shown that the phasic pupil size (peak level on each trial) is a sensitive measure of the degree of mental effort demanded by a task. In the present study, the validity of the pupil response as an index of mental effort in suboptimal conditions was investigated. Thirteen males (19-29 years) performed a memory and display-search task in a practice session, followed in random order by an oxazepam session, a placebo session, a physical exercise session, and a control session. After both oxazepam and physical exercise, decision times increased, but pupil response increased only after physical exercise. This result was explained by the possibility that under physical fatigue, compensatory effort was exerted, whereas under drug-induced fatigue, subjects seemed unable to compensate for the performance decrement. The pupil response appears to be a valuable tool for gaining more insight into different effects of suboptimal states.

Anti-Anxiety Agents↗
PubMed1995

Cardiovascular response to mental stress in offspring of hypertensive parents: the Dutch Hypertension and Offspring Study.

OBJECTIVE: To compare blood pressure-regulating mechanisms during mental stress in two groups of offspring with contrasting risk for hypertension. DESIGN: Cardiovascular reactivity to two different types of mental stressors was studied in adolescents and young adults with two hypertensive or two normotensive parents. The two tasks used were intended to evoke either a predominantly adrenergic cardiac response (a memory search task) or a predominantly vascular response (a reaction-time task with visual search and tone avoidance). METHODS: Blood pressure and heart rate were recorded at rest and during stress. To study adaptations of the cardiovascular system to mental stress, cardiac output, total peripheral resistance and indices of vagal and sympathetic influences on the heart were measured. RESULTS: The reactivity of systolic blood pressure (SBP) to the memory search task was significantly higher in offspring of hypertensive parents, which resulted in a longer recovery after the task. In contrast, during the reaction-time task, offspring of hypertensive parents had a significantly enhanced reactivity of peripheral resistance, but no differences in heart rate or blood pressure response were observed. No differences between the two groups were found in sympathetic or vagal activity during either task measured by the ratio of pre-ejection time and left ventricular ejection time, and respiratory sinus arrhythmia, respectively. CONCLUSION: Apart from a higher reactivity of SBP during the memory search task, no other indications supporting the presence of hyperadrenergic activation of the heart in early primary hypertension were found. On the contrary, the results of the present study support the hypothesis that blood pressure responses in prehypertensive subjects are characterized by enhanced vasoconstriction rather than by increased cardiac output.

Adolescent↗
PubMed1995

A twin-singleton comparison of problem behaviour in 2-3-year-olds.

Twin-singleton differences in problem behaviours in 2-3-year-olds were studied. Maternal ratings of children's problem behaviours were obtained with the CBCL/2-3. The twin sample consisted of 1363 twin pairs (456 MZ, 907 DZ), the sample of singletons consisted of 420 children from the general population. Results indicated that the general level of problem behaviours in twins was broadly comparable to that in singletons. Four of the seven syndromes showed lower scores for twins. These differences, however, were small and mainly caused by lower scores for DZ twins in comparison to MZ twins and singletons. Part of the difference could be attributed to the higher maternal age in the twin groups. Higher means for boys were found for the total problem score, and the Aggressive and Overactive syndromes.

Adult↗
PubMed1994

Effect of tyrosine on cognitive function and blood pressure under stress.

The effects of tyrosine on mood, performance, heart rate and blood pressure of 16 healthy young subjects were assessed. Subjects were tested on two separate days, one test session after ingestion of 100 mg/kg tyrosine and the other test session after placebo, in random order. While performing a number of stress sensitive tasks, subjects were exposed to a stressor consisting of 90 dB noise. Tyrosine was found to improve the performance on two cognitive tasks, which were performed 1 h after administration of the medication and which could be characterized as highly sensitive to stress. In addition, tyrosine decreased diastolic blood pressure 15 min after ingestion, while 1 h after ingestion diastolic blood pressure was the same with tyrosine and placebo. No effects on mood, systolic blood pressure and heart rate were found.

Adult↗
PubMed1994

Effect of maternal smoking on birth weight of twins: a study from the Dutch Twin Register.

Since twins weigh about 20% less than singletons at birth, maternal smoking may be a more severe risk for them than for singletons. Therefore, the effect of maternal smoking during pregnancy on birth weight was investigated in a group of 5376 twins. All necessary information was collected by a questionnaire filled out by the mother of the twins. Gestational age explains more than 75% of the variance in birth weight. Other effects were tested with gestational age as a covariate. Apart from zygosity (DZ twins weigh more than MZ twins), birth order (first born twins weigh more than second born twins) and sex (boys weigh more than girls), there was a very significant birth weight reducing effect (more than 8%) maternal smoking as well as a significant influence of maternal age (young mothers give birth to smaller children). There were no interactions with maternal smoking.

Birth Weight↗
PubMed1994

Anthropometric measures, fitness and habitual physical activity in offspring of hypertensive parents. Dutch Hypertension and Offspring Study.

As part of the Dutch Hypertension and Offspring Study, subjects with contrasting risk for hypertension according to their parental history of hypertension were compared with respect to anthropometric measures and measures of fitness and physical activity. Body height, weight, two skinfolds, and blood pressure at rest were measured. Fitness was evaluated by a maximal exercise test, and habitual physical activity was assessed using a questionnaire. No differences were observed in body mass index after adjustment for slight differences in age and proportion of men between the groups (difference between groups: 0.74 kg/m2, 95% CI: -0.30, 1.78). Offspring of hypertensive parents, however, had significantly more central fat (difference between groups: 2.32 mm, 95% CI: 0.18, 4.46). No differences in fitness or physical activity were present between the two groups. The results of this study indicate a potential role for central fat in the etiology of primary hypertension. Fitness or habitual physical activity are, however, not different between groups of subjects at different risk for future hypertension.

Adolescent↗
PubMed1994

Genetic and social influences on starting to smoke: a study of Dutch adolescent twins and their parents.

In a study of 1600 Dutch adolescent twin pairs we found that 59% of the inter-individual variation in smoking behaviour could be attributed to shared environmental influences and 31% to genetic factors. The magnitude of the genetic and environmental effects did not differ between boys and girls. However, environmental effects shared by male twins and environmental effects shared by female twins were imperfectly correlated in twins from opposite-sex pairs, indicating that different environmental factors influence smoking in adolescent boys and girls. In the parents of these twins, the correlation between husband and wife for 'currently smoking' (r = 0.43) was larger than for 'ever smoked' (r = 0.18). There was no evidence that smoking of parents (at present or in the past) encouraged smoking in their offspring. Resemblance between parents and offspring was significant but rather low and could be accounted for completely by their genetic relatedness. Moreover, the association between 'currently smoking' in the parents and smoking behaviour in their children was not larger than the association between 'ever smoking' in parents and smoking in their children.

Adolescent↗
PubMed1993

Abnormal extracranial vasomotor response in migraine sufferers to real-life stress.

Temporal and digital pulse amplitudes, forehead temperature, heart rate, respiration rate and electrodermal activity of 37 migraine patients and 37 matched controls from a population of psychology students were recorded during three experimental sessions: adaptation, real-life stress (an examination) and experimental stress (an IQ test). Migraine sufferers showed significantly smaller pulse amplitudes of the temporal artery during the examination than the control group. No group differences were present in the other physiological measures. The findings are interpreted as indirect evidence for the symptom specificity hypothesis, which states that individuals with specific psychosomatic complaints display abnormal responses to stress in the relevant physiological system.

Adult↗
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↗