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Dizygotic Twin Pairs (dizygotic + twin_pair)
Selected AbstractsHeritability of regional and global brain structure at the onset of puberty: A magnetic resonance imaging study in 9-year-old twin pairsHUMAN BRAIN MAPPING, Issue 7 2009Jiska S. Peper Abstract Puberty represents the phase of sexual maturity, signaling the change from childhood into adulthood. During childhood and adolescence, prominent changes take place in the brain. Recently, variation in frontal, temporal, and parietal areas was found to be under varying genetic control between 5 and 19 years of age. However, at the onset of puberty, the extent to which variation in brain structures is influenced by genetic factors (heritability) is not known. Moreover, whether a direct link between human pubertal development and brain structure exists has not been studied. Here, we studied the heritability of brain structures at 9 years of age in 107 monozygotic and dizygotic twin pairs (N = 210 individuals) using volumetric MRI and voxel-based morphometry. Children showing the first signs of secondary sexual characteristics (N = 47 individuals) were compared with children without these signs, based on Tanner-stages. High heritabilities of intracranial, total brain, cerebellum, and gray and white matter volumes (up to 91%) were found. Regionally, the posterior fronto-occipital, corpus callosum, and superior longitudinal fascicles (up to 93%), and the amygdala, superior frontal and middle temporal cortices (up to 83%) were significantly heritable. The onset of secondary sexual characteristics of puberty was associated with decreased frontal and parietal gray matter densities. Thus, in 9-year-old children, global brain volumes, white matter density in fronto-occipital and superior longitudinal fascicles, and gray matter density of (pre-)frontal and temporal areas are highly heritable. Pubertal development may be directly involved in the decreases in gray matter areas that accompany the transition of our brains from childhood into adulthood. Hum Brain Mapp, 2009. © 2009 Wiley-Liss, Inc. [source] Normal and Abnormal Personality Traits: Evidence for Genetic and Environmental Relationships in the Minnesota Study of Twins Reared ApartJOURNAL OF PERSONALITY, Issue 5 2002Kristian E. Markon ABSTRACT Recent studies have demonstrated substantial correlations between normal and abnormal personality traits. Yet little is known about how these correlations are mediated genetically and environmentally: Do normal and abnormal personality traits stem from the same underlying genes and environments? We addressed this question using data from 128 monozygotic and dizygotic twin pairs in the Minnesota Study of Twins Reared Apart (MISTRA). Additive genetic and nonshared environmental correlations between scales of the Minnesota Multiphasic Personality Inventory (MMPI),an index of abnormal personality,and the Multidimensional Personality Questionnaire (MPQ),an index of normal personality,were estimated. Results indicated that phenotypic correlations between normal and abnormal personality were mediated by genetic as well as environmental factors, although the magnitude of genetic mediation tended to be larger overall. Moreover, the patterns of phenotypic, genetic, and environmental relationships among the scales were similar, suggesting that influences on normal and abnormal personality act through systems common to both. It is suggested that future research focus on the neurogenetic substrates of these shared systems and how dysfunction in these systems influences development of disordered personality. [source] Stability, consistency, and heritability of electrodermal response lability in middle-aged male twinsPSYCHOPHYSIOLOGY, Issue 4 2004Andrew Crider Abstract We examined individual differences in nonspecific electrodermal response (EDR) lability in terms of retest stability, cross-situational consistency, and heritability in a sample of 345 adult monozygotic and dizygotic twin pairs. We also examined the phenotypic and genetic relationships between EDR lability and speed of habituation of the specific EDR to a nonsignal stimulus. Individual variation in EDR lability showed substantial retest stability and cross-situational consistency and also predicted resistance to specific EDR habituation. Structural equation modeling showed that the covariation among EDR lability measures and resistance to specific EDR habituation operated through a single latent phenotype, which was influenced in approximately equal measure by genetic and unique environmental factors. We discuss these findings in terms of an information processing account of individual differences in phasic EDR activation. [source] Selected neonatal outcomes in dizygotic twins after IVF versus non-IVF pregnanciesBJOG : AN INTERNATIONAL JOURNAL OF OBSTETRICS & GYNAECOLOGY, Issue 6 2010B Källén Please cite this paper as: Källén B, Finnström O, Lindam A, Nilsson E, Nygren K-G, Otterblad Olausson P. Selected neonatal outcomes in dizygotic twins after IVF versus non-IVF pregnancies. BJOG 2010; Objective, To compare neonatal outcome among twins conceived after in vitro fertilisation (IVF) with that of spontaneously conceived twins. Design, Comparison of different-sex (dizygotic) twins born after IVF with non-IVF dizygotic twins. Setting, National health registers in Sweden. Population, All births in Sweden during the period 1982,2007. Methods, We studied gestational duration, lowest birthweight and birthweight difference in the twin pair, presence of one or two twins with a respiratory complication, and with jaundice in one or both twins. Risk estimates were calculated as odds ratios with adjustments for year of birth, maternal age, parity and smoking in pregnancy. Main outcome measures, Gestational duration, birth weight, respiratory complications, jaundice. Results, We studied 1545 pairs of dizygotic twins born after IVF, and 8675 pairs of dizygotic twins where IVF was not known to have occurred. The risk for preterm delivery before 32 weeks of gestation was significantly increased among dizygotic twin pairs born after IVF compared with non-IVF dizygotic twin pairs. No significant difference in low birthweight or birthweight difference within twin pairs was seen. There was an increased occurrence of twin pairs with respiratory problems or jaundice, but only the latter diagnosis occurred in a statistically significant excess. Conclusions, The study confirms recent findings that IVF is associated with an increased risk for some neonatal complications, not only among singletons but also among twins. [source] | ||||||||||