bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sex Differences in Genetic and Environmental Factors Contributing to Body-Height
Authors: Silventoinen Karri , Kaprio Jaakko , Lahelma Eero , Viken Richard J. , Rose Richard J. 
Published: May 2007

AbstractSex differences in the heritability of self-reported body-height in two Finnish twin cohorts were studied by using sex-limitation models. The first cohort was born in 1938–1949 (N = 4873 twin pairs) and the second in 1975–1979 (N = 2374 twin pairs). Body-height was greater in the younger cohort (difference of 3.1 cm for men and 2.9 cm for women). The heritability estimates were higher among men (h2 = 0.87 in the older cohort and h2 = 0.82 in the younger cohort) than women (h2 = 0.78 and h2 = 0.67, respectively). Sex-specific genetic factors were not statistically significant in either cohort, suggesting that the same genes contribute to variation in body height for both men and women. The stronger contribution of environmental factors to body-height among women questions the hypothesis that women are better buffered against environmental stress, at least for this phenotype.
Phenotypic and Genetic Analyses of a Short Measure of Psychosis-proneness in a Large-scale Australian Twin Study
Authors: Hay David A. , Martin Nicholas G. , Foley Debra , Treloar Susan A. , Kirk Katherine M. , Heath Andrew C. 
Published: May 2007

AbstractPrevious genetic analyses of psychosis proneness have been limited by their small sample size. For the purposes of large-scale screening, a 12-item questionnaire was developed through a two-stage process of reduction from the full Chapman and Chapman scales. 3685 individuals (including 1438 complete twin pairs) aged 18–25 years and enrolled in the volunteer Australian Twin Registry returned a mail questionnaire which included this psychosis proneness scale and the Eysenck Personality Questionnaire. Despite the brevity of the questionnaire, item and factor analysis identified four unambiguous and essentially uncorrelated scales. There were (1) Perceptual Aberration – Magical Ideation; (2) Hypomania – Impulsivity/Nonconformity; (3) Social Anhedonia and (4) Physical Anhedonia. Model-fitting analyses showed additive genetic and specific environmental factors were sufficient for three of the four scales, with the Social Anhedonia scale requiring also a parameter for genetic dominance. There was no evidence for the previously hypothesised sex differences in the genetic determination of psychosis-proneness. The potential value of multivariate genetic analysis to examine the relationship between these four scales and dimensions of personality is discussed. The growing body of longitudinal evidence on psychosis-proneness suggests the value of incorporating this brief measure into developmental twin studies.
The Management and Outcome of Higher Order Multifetal Pregnancies: Obstetric, Neonatal and Follow-up Data
Authors: Yudin Mark H. , Asztalos Elizabeth V. , Jefferies Ann , Barrett Jon F.R. 
Published: May 2007

AbstractThe objective of this study was to describe current obstetric, neonatal, and long-term neurodevelopmental outcomes of higher order multifetal gestations (≥ 3 fetuses) in the 1990s. We also intended to identify a target gestational age at which neonatal and neurodevelopmental morbidities are low. Records from all multifetal pregnancies (≥ 3 viable fetuses ≥ 20 weeks gestation) delivered at the two perinatal centers in Toronto, Ontario, Canada during the study period (January 1, 1990–December 31, 1996) were reviewed. Data were collected on obstetric, neonatal, and long-term neurodevelopmental outcomes. Follow up data were gathered regarding the presence of a severe deficit in four categories (vision, hearing, cognition, and motor skills). Statistical analysis was performed to determine a gestational age at which a significant decrease in deficit occurred. During the study period 165 multifetal pregnancies were delivered. This resulted in 511 fetuses, of which 496 were live births. Of these 496 infants, 453 survived to discharge. Follow up data were obtained on 332 (73.3 per cent) infants. Infant survival increased with gestational age, and was approximately 90 per cent or greater at 26 weeks or more. Of all infants followed, the proportion of those without deficit increased with increasing gestational age, such that the per cent without deficit was 96.9 at 31 weeks or greater. Of all infants followed, 301 (90.7 per cent) had no deficit. Statistical analysis revealed a significant difference in long-term neurodevelopmental outcome between infants born before and after 28 weeks gestation. The incidence of a major deficit was 44.1 per cent for those born earlier than and 5.4 per cent for those born later than this gestational age (p= 0.001). In our cohort, survival figures were high. Even in lower gestational groupings, survival was high, but not without serious concerns about severe morbidity. This information is useful when counseling parents of higher order multifetal pregnancies.
Lipoprotein Candidate Genes for Multivariate Factors of the Insulin Resistance Syndrome: A Sib-pair Linkage Analysis in Women Twins
Authors: Edwards K.L. , Talmud P.J. , Newman B. , Krauss R.M. , Austin M.A. 
Published: May 2007

AbstractThe insulin resistance syndrome (IRS) is characterized by a combination of interrelated coronary heart disease risk factors, including low high-density lipoprotein cholesterol (HDLC) levels, obesity and increases in triglyceride (TG), systolic and diastolic blood pressure (BP), small low-density lipoprotein particles (LDL-size), and fasting and postload plasma insulin and glucose. Using factor analysis, we previously identified multivariate factors based on data from women participating in the Kaiser Permanente Women Twins Study: 1) Weight/Fat, 2) Insulin/Glucose, 3) Lipids, and 4) BP. The purpose of this study is to evaluate evidence for genetic linkage between the multivariate factors and candidate genes. Quantitative sib-pair analysis based on the factor scores with markers for 9 candidate genes was carried out based on data from 126 pairs of dizygotic (DZ) women twins from the second exam of the Kaiser Permanente Women Twins study. Suggestive evidence for linkage was found for the Weight/fat factor and the Apo E gene (p= 0.01), and stronger evidence for linkage with the Lipid factor and the cholesterol ester transfer protein (p= 0.002) gene. Therefore, the CETP gene appears to influence covariation in LDL size, TG, and HDL, and may account for a portion of the well-established statistical and metabolic associations observed between these risk factors.
An Integrative Approach for Studying the Etiology of Alcoholism and Other Addictions
Authors: Jacob T. , Sher K.J. , Bucholz K.K. , True W.T. , Sirevaag E.J. , Rohrbaugh J. , Nelson E. , Neuman R.J. , Todd R.D. , Slutske W.S. , Whitfield J.B. , Kirk K.M. , Martin N.G. , Madden P.A.F. , Heath A.C. 
Published: May 2007

AbstractStudies of alcoholism etiology often focus on genetic or psy-chosocial approaches, but not both. Greater understanding of the etiology of alcohol, tobacco and other addictions will come from integration of these research traditions. A research approach is outlined to test three models for the etiology of addictions — behavioral undercontrol, pharmacologic vulnerability, negative affect regulation — addressing key questions including (i) mediators of genetic effects, (ii) genotype-environment correlation effects, (iii) genotype x environment interaction effects, (iv) the developmental unfolding of genetic and environmental effects, (v) subtyping including identification of distinct trajectories of substance involvement, (vi) identification of individual genes that contribute to risk, and (vii) the consequences of excessive use. By using coordinated research designs, including prospective assessment of adolescent twins and their siblings and parents; of adult substance dependent and control twins and their MZ and DZ cotwins, the spouses of these pairs, and their adolescent offspring; and of regular families; by selecting for gene-mapping approaches sibships screened for extreme concordance or discordance on quantitative indices of substance use; and by using experimental (drug challenge) as well as survey approaches, a number of key questions concerning addiction etiology can be addressed. We discuss complementary strengths and weaknesses of different sampling strategies, as well as methods to implement such an integrated approach illustrated for the study of alcoholism etiology. A coordinated program of twin and family studies will allow a comprehensive dissection of the interplay of genetic and environmental risk-factors in the etiology of alcoholism and other addictions.
Placentation in Multiple Births
Authors: Machin Geoffrey 
Published: May 2007

AbstractOutcomes of multifetal pregnancy in prenatal life are markedly affected by chorionicity. Several disease processes are found in monochorionic (MC) twins that do not occur in dichorionic (DC) twins. Improvements in prenatal outcomes will depend on reliable first trimester diagnosis of chorionicity, allowing early monitoring for complications of MC placentation. Particular structures and functions of MC twin placentas affect outcomes and can be targeted for specific treatments, especially in twin-twin transfusion. The causes of severe DC twin fetal growth discordance are clarified. In post-natal life, zygosity is a determining effect in genetic predisposition to many chronic diseases, including neoplasia. Few MC twins know that they are monozygotic (MZ). Few twin researchers realize that MZ twins may be genetically discordant. Abandonment of the word “identical” for MZ twins would assist in clarifying these issues of zygosity, concordance and discordance.
Should all Twins be Delivered by Caesarean Section? A Preliminary Report
Authors: Rydhstroem Hakan 
Published: May 2007

AbstractThe aim was to analyse the neonatal mortality related to mode of delivery for twins using a population-based registry. In all, 18,125 twins delivered in Sweden between 1991 and 1997, after excluding those with unknown gestational duration, were used to analyse the differences between groups of twins. Results showed the OR for neonatal death, breech vaginal delivery versus caesarean section (all indications) was 1.47 (95% CI 0.99-2.17). The OR at vaginal delivery for neonatal death, twin I in breech versus cephalic presentation was 5.60 (2.62-11.94) and for twin II the corresponding figures were 1.85 (1.03-3.32). Analyses using population-based registries from other countries are needed to confirm or reject the present findings of an increased neonatal mortality for twins in breech presentation delivered vaginally.
Two Cases With Dichorionic Diamniotic Triplet Pregnancy and Early Cord Entanglement
Authors: Merién Ashley E.R. , van Eyck Jim , Arabin Birgit 
Published: May 2007

AbstractWithin a period of 6 years (1994–99) we registered 29 triplet deliveries out of a total of 13,969 hospital deliveries (0.02%). Since there is limited information about specific problems of chorionicity in triplet pregnancies, we analysed the 29 cases according to origin of pregnancy and chorionicity. We here report on two cases with a high risk according to chorionicity with dichorionic (DC) diamniotic (DA) triplet pregnancies. Out of the two cases, one pregnancy was spontaneous and one originated after in-vitro fertilization. In both pregnancies, cord entanglement was detected early in pregnancy (at 10 and 15 weeks) by color Doppler velocimetry demonstrating different heart rates within the segment of the entangled umbilical branches. The pregnancies were followed by documenting fetal behavior and color Doppler velocimetry of umbilical and fetal arteries at weekly intervals. In both cases, a primary Cesarean section was performed after detection of lung maturity. In the first case, one of the MA triplets had a transposition of the great arteries and abnormal lung vein drainage, which was the reason for neonatal death three weeks postnatally. Although early cord entanglement has been described in MA twins, this series demonstrates that it can as well be demonstrated in MA triplets. The early detection allows for extensive surveillance of the a priori high risk triplet pregnancy.
Gestational Duration, and Fetal and Infant Mortality for Twins vs Singletons
Authors: Rydhstroem Hakan , Heraib Fayez 
Published: May 2007

AbstractThe aim of this research was to study fetal and infant mortality in Sweden between 1973 and 1996 in twins vs singletons in relation to gestational duration. Analysis was of fetal and infant mortality based on the number of pregnancies at risk as the denominator rather than the number of deliveries each week. The analysis was based on information stored at the Medical Birth Registry (MBR), the National Board of Health and Welfare, Stockholm. The MBR keeps records on virtually all pregnancies (> 99%) regarding delivery and neonatal information, and for infant mortality up to 1 year of age. During the study period, 2,206,738 singleton and 52,658 twin births were registered. Risk evaluation was made as odds ratio (OR) with a 95% confidence interval. The material was stratified according to parity, maternal age, year of delivery, and delivery unit. Results showed the OR for twin births before 34 weeks gestation was 6 to 8-fold increased compared with singletons. The OR for fetal mortality was increased in all gestational weeks, and like-sexed twins had a consistently poorer prognosis compared to unlike-sexed. Between 1989–96, unlike-sexed twins had a fetal mortality approaching that of singletons. In conclusion, real progress in reduction of infant mortality in twins may be impossible until the high incidence of preterm births can be decreased. Hypothetically, about 100 twin labors would have to be induced to avoid one fetal death in like-sexed twin pregnancies.
Development and Representativeness of a Large Population-Based Cohort of Native Californian Twins
Authors: Cockburn Myles G. , Hamilton Ann S. , Zadnick John , Cozen Wendy , Mack Thomas M. 
Published: May 2007

AbstractWe have established a large cohort of twins to facilitate studies of the role of genetics and environment in the development of disease. The cohort has been derived from all multiple births occurring in California between 1908–82 (256,616 in total). We report here on our efforts to contact these twins and their completion of a detailed 16 page risk factor questionnaire. Addresses of the individuals were obtained by linking the birth records with the California Department of Motor Vehicles (DMV) roster of licensees. To date this has been completed for twins born between 1908 and 1972 (200,589 individuals). The linkage has revealed 112,468 matches and, because of less complete DMV records in some years, was less successful in older females than in younger females and all males. Over 41,000 twins have participated by completing the questionnaire. Based on estimates of numbers of individuals receiving a questionnaire, we estimate our crude response rate to be between 42.2% and 49.6%, highest among females in their 40s (62.8%). We describe the representativeness of the twins in the original birth cohort, those identified by the linkage, and those completing the questionnaire. Compared to the 1990 resident population of California-born resident singletons, the respondents were of similar age, sex, race and residential distribution (for although we were able to locate fewer older females, they had a higher response rate), but were less likely to have been educated for more than 12 years. We provide a brief synopsis of studies nested within this cohort. We also elucidate our plans for expanding the cohort in the near future.
The Heritability of Mortality Due to Heart Diseases: A Correlated Frailty Model Applied to Danish Twins
Authors: Wienke Andreas , Holm Niels V. , Skytthe Axel , Yashin Anatoli I. 
Published: May 2007

AbstractData of the Danish Twin Registry on monozygotic and dizygotic twins are used to analyse genetic and environmental influences on susceptibility to heart diseases for males and females, respectively. The sample includes 7955 like-sexed twin pairs born between 1870 and 1930. Follow-up was from 1 January 1943 to 31 December 1993 which results in truncation (twin pairs were included in the study if both individuals were still alive at the beginning of the follow-up) and censoring (nearly 40% of the study population was still alive at the end of the follow-up). We use the correlated gamma-frailty model for the genetic analysis of frailty to account for this censoring and truncation. During the follow-up 9370 deaths occurred, 3393 deaths were due to heart diseases in general, including 2476 deaths due to coronary heart disease (CHD). Proportions of variance of frailty attributable to genetic and environmental factors were analyzed using the structural equation model approach. Different standard biometric models are fitted to the data to evaluate the magnitude and nature of genetic and environmental factors on mortality. Using the best fitting model heritability of frailty (liability to death) was found to be 0.55 (0.07) and 0.53 (0.11) with respect to heart diseases and CHD, respectively, for males and 0.52 (0.10) and 0.58 (0.14) for females in a parametric analysis. A semi-parametric analysis shows very similar results. These analyses may indicate the existence of a strong genetic influence on individual frailty associated with mortality caused by heart diseases and CHD in both, males and females. The nature of genetic influences on frailty with respect to heart diseases and CHD is probably additive. No evidence for dominance and shared environment was found.
The Personalities of Twins: Just Ordinary Folks
Authors: Johnson Wendy , Krueger Robert F. , Bouchard Thomas J. , McGue Matt 
Published: May 2007

AbstractTwin studies have demonstrated that personality traits show moderate genetic influence. The conclusions drawn from twin studies rely on the assumptions that twins are representative of the population at large and that monozygotic and dizygotic twins are comparable in every way that might have bearing on the traits being studied. To evaluate these assumptions, we used Multidimensional Personality Questionnaire (MPQ) data from three samples drawn from the Minnesota Twin Registry (totaling 12,971 respondents) to examine the effect sizes associated with mean differences on the 11 MPQ scales and 3 higher-order MPQ factors for singletons versus twins and MZ twins versus DZ twins. The singletons in the samples were family members of the participating twins. We also used ratios of scale variances to examine the significance of variance differences. The only mean or variance difference replicated across all three samples was greater Social Closeness (about .1 standard deviation) for twins than for singletons. This difference was obtained for both males and females. It would appear that, with respect to personality, twins are not systematically different from other people. Our results also highlight the importance of replication in psychological research because each of our large samples showed differences not replicated in other samples.
Confronting Unique Problems With Twins
Authors: Segal Nancy L. 
Published: May 2007

AbstractFamilies with twins occasionally confront unique problems warranting considerable professional attention. The possibility that twins may be less likely to be admitted to private schools of their choice, due to reduced financial contributions from family members, was recently raised. Specifically, two twin children have two sets of grandparents, while two non-twin children have four sets of grandparents; thus, schools would profit more highly by admitting non-twins. This sets the stage for reviewing steps that some universities and businesses have taken to offset the financial burdens of rearing multiples. Next, a research review of four twin studies follows. Findings on gluten sensitivity, tremors, communicative adaptability and serological differences are summarized. A tour of a fascinating twin exhibit at the Teylers Museum, in the Netherlands, concludes this column.
Natural History of 11 Cases of Twin-twin Transfusion Syndrome Without Intervention
Authors: Gul Ahmet , Aslan Halil , Polat Ibrahim , Cebeci Altan , Bulut Hasan , Sahin Ozturk , Ceylan Yavuz 
Published: May 2007

AbstractThe natural history of 11 cases of twin–twin transfusion syndrome (TTTS) in monochorionic diamniotic (MCDA) twin pregnancies has been reviewed. Seven cases before 28 weeks and four pregnancies after 28 weeks had been followed up without intervention. Eight cases had premature uterine contractions. All seven pregnancies before 28 weeks aborted, leading to a 100% mortality rate. After 28 weeks all mothers delivered live births. The diagnosis of TTTS before 28 weeks, and with premature uterine contraction, seems to be a poor prognostic sign.
Has the “Equal Environments” Assumption Been Tested in Twin Studies?
Authors: Eaves Lindon , Foley Debra , Silberg Judy 
Published: May 2007

AbstractArecurring criticism of the twin method for quantifying genetic and environmental components of human differences is the necessity of the so-called “equal environments assumption” (EEA) (i.e., that monozygotic and dizygotic twins experience equally correlated environments). It has been proposed to test the EEA by stratifying twin correlations by indices of the amount of shared environment. However, relevant environments may also be influenced by genetic differences. We present a model for the role of genetic factors in niche selection by twins that may account for variation in indices of the shared twin environment (e.g., contact between members of twin pairs). Simulations reveal that stratification of twin correlations by amount of contact can yield spurious evidence of large shared environmental effects in some strata and even give false indications of genotype x environment interaction. The stratification approach to testing the equal environments assumption may be misleading and the results of such tests may actually be consistent with a simpler theory of the role of genetic factors in niche selection.