Biomedical subjects

H H Maes

Publications and source records attributed to H H Maes.

30 records · Page 2Linked to original sources

PubMed1998

Inheritance of static and dynamic arm strength and some of its determinants.

Maximal static, eccentric and concentric torques and arm components estimated by anthropometry and measured by computed tomography were evaluated in 25 male monozygotic twins and 16 dizygotic twins (22.4 +/- 3.7 years). The importance of genetic and environmental factors in the observed variation in these measurements was estimated by genetic model-fitting techniques. In this sample of young adult male twins, genetic factors were significant in most of the strength measurements, arm muscle components and muscle activation variables. The contribution of genetic factors in strength measures depended on the angle, contraction type and to some extent on contraction velocity. For isometric strength, angle-specificity in genetic and environmental variation could be attributed to the degree of variability in muscle activation and performance discomfort at each specific angle, with the highest unique environmental impact at extreme angles. The high genetic contribution at 170 degrees, but not at 50 degrees, possibly expressed different contributions of genetic factors in the muscle-length factor and moment arm in torques at both angles. The importance of genetic factors in eccentric arm flexor strength (62-82%) was larger than for concentric flexion (29-65%), as the pattern of genetic determination followed the torque-velocity curve. Genetic variations in contractile and elastic components, contributing differently to eccentric and concentric torques, together with velocity-dependent actin-myosin binding factors, could account for the observed differences. The broad heritability was very high for all anthropometric and arm cross-sectional area measurements (> 85%) and common environmental factors were only significant for anthropometrically estimated mid-arm muscle tissue are (48%). Heritability estimates of different arm muscularity measurements were comparable.

Adolescent↗

PubMed1998

Strength training: importance of genetic factors.

PURPOSE: This study focuses on the quantification of genetic and environmental factors in arm strength after high-resistance strength training. METHODS: Male monozygotic (MZ, N = 25) and dizygotic (DZ, N = 16) twins (22.4 +/- 3.7 yr) participated in a 10-wk resistance training program for the elbow flexors. The evidence for genotype*training interaction, or association of interindividual differences in training effects with the genotype, was tested by a two-way ANOVA in the MZ twins and using a bivariate model-fitting approach on pre- and post-training phenotypes in MZ and DZ twins. One repetition maximum (1RM), isometric strength, and concentric and eccentric moments in 110 degree arm flexion at velocities of 30 degrees x s(-1), 60 degrees x s(-1), and 12 degrees x s(-1) were evaluated as well as arm muscle cross-sectional area (MCSA). RESULTS: Results indicated significant positive training effects for all measures except for maximal eccentric moments. Evidence for genotype*training interaction was found for 1RM and isometric strength, with MZ intra-pair correlations of 0.46 and 0.30, respectively. Bivariate model-fitting indicated that about 20% of the variation in post-training 1RM, isometric strength, and concentric moment at 120 degrees x s(-1) was explained by training-specific genetic factors that were independent from genetic factors that explained variation in the pretraining phenotype (30-77%). CONCLUSIONS: Genetic correlations between measures of pre- and post-training strength were indicative for high pleiotropic gene action and minor activation of training-specific genes during training.

Adult↗

PubMed1997

The Virginia Twin Study of Adolescent Behavioral Development. Influences of age, sex, and impairment on rates of disorder.

BACKGROUND: The Virginia Twin Study of Adolescent Behavioral Development is a cohort-longitudinal epidemiological study that uses the genetic twin design to study the development and maintenance of child psychiatric disorders. We determined the rates of DSM-III-R disorders, disorders with impairment, and age, sex, and comorbidity effects. METHODS: Families of 2762 white twins aged 8 to 16 years participated. Twins and their parents were asked systematically about risk factors and current psychiatric symptoms by means of investigator-based psychiatric interviews and questionnaires. The DSM-III-R diagnoses were made for major depressive disorder, separation anxiety, overanxious disorder, simple phobia, social phobia, agoraphobia, oppositional defiant disorder, conduct disorder, and attention deficit hyperactivity disorder. RESULTS: The 3-month point prevalence for any DSM-III-R disorders was 413 per 1000, and that for disorders with associated impairment was 142 per 1000. Emotional disorders with impairment occurred in 89 per 1000, with girls being more commonly affected; behavioral disorders had a prevalence of 71 per 1000, with boys being more frequently affected. The proportion with disorder who also had functional impairment varied across disorders; anxiety and phobic disorders were particularly likely not to be accompanied by impairment. Rates of emotional and behavioral disorders increased over the age range. There was extensive comorbidity among disorders. CONCLUSIONS: The prevalence rates and patterns of findings from this study of twins are consistent with those of other epidemiological studies, supporting previous findings of few differences in rates of psychiatric disorder between twins and singletons. The importance of including measures of functional impairment is evident by its effect on rates of disorder and patterns of comorbidity.

Adolescent↗

PubMed1997

Genetic and environmental factors in relative body weight and human adiposity.

We review the literature on the familial resemblance of body mass index (BMI) and other adiposity measures and find strikingly convergent results for a variety of relationships. Results from twin studies suggest that genetic factors explain 50 to 90% of the variance in BMI. Family studies generally report estimates of parent-offspring and sibling correlations in agreement with heritabilities of 20 to 80%. Data from adoption studies are consistent with genetic factors accounting for 20 to 60% of the variation in BMI. Based on data from more than 25,000 twin pairs and 50,000 biological and adoptive family members, the weighted mean correlations are .74 for MZ twins, .32 for DZ twins, .25 for siblings, .19 for parent-offspring pairs, .06 for adoptive relatives, and .12 for spouses. Advantages and disadvantages of twin, family, and adoption studies are reviewed. Data from the Virginia 30,000, including twins and their parents, siblings, spouses, and children, were analyzed using a structural equation model (Stealth) which estimates additive and dominance genetic variance, cultural transmission, assortative mating, nonparental shared environment, and special twin and MZ twin environmental variance. Genetic factors explained 67% of the variance in males and females, of which half is due to dominance. A small proportion of the genetic variance was attributed to the consequences of assortative mating. The remainder of the variance is accounted for by unique environmental factors, of which 7% is correlated across twins. No evidence was found for a special MZ twin environment, thereby supporting the equal environment assumption. These results are consistent with other studies in suggesting that genetic factors play a significant role in the causes of individual differences in relative body weight and human adiposity.

Adoption↗

PubMed1997

Conversion of in vitro cultured human monocytes into effective presenters of an HER2/neu-encoded CTL peptide epitope.

Tumour-derived peptides have been surveyed, in a variety of systems, for their ability to elicit cytokine release from class I restricted T cells. Analogous studies on ovarian carcinoma have employed the antigen-processing defective T2 cell line, Purified dendritic cells (DC) have been reported to act as highly effective APC. A facile method was developed whereby DC-like cells were generated from monocyte precursors. Herein, evidence is presented suggesting DC-like cells are superior to T2 with respect to their ability to present a defined CTL epitope associated with ovarian carcinoma.

Antigen-Presenting Cells↗

PubMed1997

Genetics and developmental psychopathology: 2. The main effects of genes and environment on behavioral problems in the Virginia Twin Study of Adolescent Behavioral Development.

Little is known about the contribution of genetic and environmental factors to risk for juvenile psychopathology. The Virginia Twin Study of Adolescent Behavioral Development allows these contributions to be estimated. A population-based, unselected sample of 1412 Caucasian twin pairs aged 8-16 years was ascertained through Virginia schools. Assessment of the children involved semi-structured face-to-face interviews with both twins and both parents using the Child and Adolescent Psychiatric Assessment (CAPA). Self-report questionnaires were also completed by parents, children, and teachers. Measures assessed DSM-III-R symptoms of Attention Deficit Hyperactivity Disorder (ADHD). Conduct Disorder, Oppositional Defiant Disorder, Overanxious Disorder, Separation Anxiety, and Depressive Disorder. Factorially derived questionnaire scales were also extracted. Scores were normalized and standardized by age and sex. Maximum likelihood methods were used to estimate contributions of additive and nonadditive genetic effects, the shared and unique environment, and sibling imitation or contrast effects. Estimates were tested for heterogeneity over sexes. Generally, monozygotic (MZ) twins correlated more highly than dizygotic (DZ) twins, parental ratings more than child ratings, and questionnaire scales more highly than interviews. DZ correlations were very low for measures of ADHD and DZ variances were greater than MZ variances for these variables. Correlations sometimes differed between sexes but those for boy-girl pairs were usually similar to those for like-sex pairs. Most of the measures showed small to moderate additive genetic effects and moderate to large effects of the unique individual environment. Measures of ADHD and related constructs showed marked sibling contrast effects. Some measures of oppositional behavior and conduct disorder showed shared environmental effects. There were marked sex differences in the genetic contribution to separation anxiety, otherwise similar genetic effects appear to be expressed in boys and girls. Effects of rater biases on the genetic analysis are considered. The study supports a widespread influence of genetic factors on risk to adolescent psychopathology and suggests that the contribution of different types of social influence may vary consistently across domains of measurement.

Adolescent↗

PubMed1997

Multivariate genetic analysis of maximal isometric muscle force at different elbow angles.

The maximal isometric moment at five different elbow joint angles was measured in 25 monozygotic and 16 dizygotic male adult twin pairs (22.4 +/- 3.7 yr). Genetic model fitting was used to quantify the genetic and environmental contributions to individual differences in isometric strength. Additive genetic factors explained 66-78% of the variance in maximal torque at 170-140-110 and 80 degrees flexion (extension = 180 degrees). At 50 degrees flexion, common and subject-specific environmental factors contributed equally to the variation. The contribution of unique environmental factors concurs with the level of variability in muscle activation and (dis)-comfort of torque production in the specific angle. The relative contribution of lever arm and force-length relationship in torque varies according to the angle. Because these factors might be genetic, this variability is reflected in the genetic contribution at the extreme angles of 170 and 50 degrees. Multivariate analyses suggested a general set of genes that control muscle area and isometric strength, together with a more specific strength factor. Genetic correlations were high (0.82-0.99). Genes responsible for arm-segment lengths did not contribute to muscle area nor to isometric strength.

Adolescent↗

PubMed1997

Gender-specific regional changes in genetic structure of muscularity in early adolescence.

Genetic and environmental influences on muscle circumference measurements of the extremities were estimated in 105 pairs of twins between 10 and 14 yr of age. Four circumferences, extended upper arm (EAC), forearm (FC), thigh (TC), and calf (CC), were measured. Univariate model fitting revealed that the largest part (87-95%) of the variance for all circumferences at most ages was explained by additive genetic factors. Sex differences were observed for some age categories. Multivariate analyses showed a different pattern evolving according to age and gender. In boys from 10 to 12 yr of age, one general genetic factor influenced all four circumferences. With increasing age, an arm-leg model emerged, one genetic factor influencing the arm and another genetic factor the leg circumferences. In young girls one genetic factor loaded on the proximal (EAC, TC) and another on the distal (FC, CC) circumferences. With subjects at age 14 yr, an arm-leg model was observed. High genetic correlations indicated that genetic factors related to EAC, FC, TC, and CC did not act independently. The age-and gender-specific changes in the genetic structure suggest pubertal influences. This study shows that muscle circumferences are highly heritable characteristics and are therefore a promising starting point at which to locate their genes. Gene mapping could validate the gender-specific change of the genetic structure with age and region.

Adolescent↗

PubMed1996

Mycobacterial infections: are the observed enigmas and paradoxes explained by immunosuppression and immunodeficiency?

The enigmas and paradoxes observed in tuberculous patients, in Bacille Calmette-Guérin-vaccinated people and in Bacille Calmette-Guérin-treated cancer patients have been examined, in an attempt to explain them through the mechanisms of immunodeficiency and immunosuppression. A dual effect is postulated: an immunosuppression induced by the infecting mycobacteria that adds to a pre-existing or emerging state of immunodeficiency of the infected individual. The immunological cellular and humoral anergies observed at the beginning of a tuberculous therapy are usually lifted after the first two weeks of treatment. This restoration of immune responsiveness may be attributed to the destruction or to the growth inhibition of immunosuppressive mycobacteria. The observation that drugs cytocidal in vitro do not always sterilize the patients under treatment whereas bacteriostatic drugs do, may find an explanation in the dual immunosuppression induced by cytocidal drugs and mycobacteria. The fact that Bacille Calmette-Guérin applied as an immunotherapy to residual cancer has either a favorable or an unfavorable action may be due to the immunosuppressive activity attached to some Bacille Calmette-Guérin strains and to some cancers. The variable protective activity of Bacille Calmette-Guérin vaccines may be due to the immunological status of the vaccinated people and the compositional differences between strains. The protective activity of subunit vaccines in experimental models can be attributed to the elimination of immunosuppressive factors present in whole killed mycobacteria.

Animals↗

PubMed1996

Inheritance of physical fitness in 10-yr-old twins and their parents.

This study focuses on the quantification of genetic and environmental sources of variation in physical fitness components in 105 10-yr-old twin pairs and their parents. Nine motor tests and six skinfold measures were administered. Motor tests can be divided into those that are performance-related: static strength, explosive strength, running speed, speed of limb movement, and balance; and those that are health-related: trunk strength, functional strength, maximum oxygen uptake, and flexibility. The significance and contribution of genetic and environmental factors to variation in physical fitness were tested with model fitting. Performance-related fitness characteristics were moderately to highly heritable. The heritability estimates were slightly higher for health-related fitness characteristics. For most variables a simple model including genetic and specific environmental factors fitted the observed phenotypic variance well. Common environmental factors explained a significant part of the variation in speed components and flexibility. Assortative mating was significant and positive for speed components, balance, trunk strength, and cardiorespiratory fitness, but negative for adiposity. Static strength, explosive strength, functional strength, and cardiorespiratory fitness showed evidence for reduced genetic transmission or dominance. The hypothesis that performance-related fitness characteristics are more determined by genetic factors than health-related fitness was not supported. At this prepubertal age, genetic factors have the predominant effect on fitness.

Adult↗

PubMed1994

Multivariate genetic analysis of twin-family data on fears: Mx models.

We describe the implementation of multivariate models of familial resemblance with the Mx package. The structural equation models allow for the effects of assortative mating, additive and dominant genes, common and specific environment, and both genetic and cultural transmission between generations. Two approaches are compared: a correlational one based on Fulker and a factor model described by Phillips and Fulker. Both are illustrated by application to published data on social fears and fear of leadership measured in monozygotic and dizygotic twins and their parents. In the example data, genetic dominance yields a more parsimonious explanation of the data than does cultural transmission, although neither is needed to obtain a good fit to the data. A model of reduced genetic correlation between generations also fits the data but has inherent limitations in this sample. Extensions to sex-limitation and more complex models are discussed.

Adult↗

PubMedDate not supplied

Genetic variance of adolescent growth in stature.

The aim of this study is to quantify the genetic and environmental variation in biological parameters of the adolescent growth in stature in both sexes, using structural equation models. Standing height was measured in 99 twin pairs from the Leuven Longitudinal Twin Study. Subjects were seen at semi-annual intervals between 10 and 16 years and at 18 years. Preece-Baines model I was fitted to the individual data and biologically meaningful parameters were derived. Path models were fitted to these parameters and a gender heterogeneity analysis was performed. A model including additive genetic and specific environmental factors (AE-model), allowing for a difference in total variance or in genetic/environmental variance components in males and females best explains most of the growth characteristics. For the timing and velocity of the adolescent growth spurt, no gender heterogeneity was observed, and the genetic (0.89 to 0.93) and specific environmental (0.07 to 0.11) contributions were equal in both sexes. For stature at take-off, stature at peak height velocity and for adult stature, gender heterogeneity was observed and different models appeared to result in the best fit for boys and girls. For height at PHV and adult stature, the significant contribution of a common environmental (0.39 to 0.56) factor in boys was noteworthy. For percentage of adult stature and distances between relevant time points of the growth curve, a non-scalar effect was observed, indicating that different genes affect these characteristics in boys and girls. It is concluded that most characteristics of the growth spurt in stature are under strong genetic control. Gender heterogeneity is present for stature and for a number of derived growth characteristics.

Adolescent↗