bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Assessment of Peer Selection and Peer Environmental Influences on Behavior Using Pairs of Siblings or Twins
Authors: Madden Pamela A. F. , Bucholz Kathleen K. , Todorov Alexandre A. , Grant Julia D. , Heath Andrew C. 
Published: May 2007

AbstractMany studies have found strong peer correlations for a variety of problem behaviors that begin in adolescence (e.g. substance use). Such correlations are commonly attributed to peer influences, but could also be explained by selective (‘assortative’) friendship: the tendency for those with similar patterns of behavior to become friends. Here we show how, under certain assumptions, cross-sectional data from pairs of siblings or twins and their peers may be used to resolve the contributions of peer selection and reciprocal peer environmental influences to peer resemblance. We performed power calculations to determine necessary sample sizes for rejecting with 80% power, at the 5% significance level, the hypothesis of only peer selection effects, or only reciprocal peer environmental effects. A false hypothesis of only selective friendship effects was always easier to reject than a false hypothesis of only reciprocal peer environmental influences. Limitations of these simulations, including uncertainty about the most appropriate way to model peer selection, are discussed.
Why do Identical Twins Differ in Personality: Shared Environment Reconsidered
Authors: Torgersen Anne Mari , Janson Harald 
Published: May 2007

AbstractWhile heritability studies show that most of the variance in adult personality can be attributed to genetic or so-called nonshared environmental influence, this does not mean that shared events lack importance for the development of later personality differences. We studied the relationship between Big Five personality differences in monozygotic (MZ) twins at age 29, and life stressors at age 6 to 15, using prospective data from 26 MZ pairs studied from birth onwards. A positive significant correlation was found between stressors in childhood and early adolescence, and intrapair personality differences in Agreeableness, Openness, Conscientiousness, and five-factor profiles. We note that the effects of shared events are labeled “nonshared” environment when the effect is to make siblings more different. Case examples illustrate the relationship between stress and personality differences, and provide hypotheses for further studies in larger samples.
Rejoinder to Meta-Analysis of Twin-Twin Transfusion by Skupski et al.
Authors: Machin Geoffrey A. 
Published: May 2007

AbstractAssessment of treatment options in twin-twin transfusion should involve a detailed interrogation of the placenta and fetuses prior to treatment, stratification according to response to amnioreduction and careful analysis of quality of survival. Amnioreduction and laser coagulation are not alternative and equivalent modalities for the treatment of twin-twin transfusion. Randomized trials may not be ethical without prior therapeutic/ diagnostic amnioreduction.
Hypertensive Disease in Twin Pregnancies: A Review
Authors: Krotz Stephan , Fajardo Javier , Ghandi Sanjay , Patel Ashlesha , Keith Louis G. 
Published: May 2007

AbstractReports over the past seventy years show that twin gestations lead to an increased risk of hypertensive disorders. Numerous studies discuss the incidence of hypertensive disease in twin versus singleton gestations, as well as effects of parity, race, age, income level, smoking, zygosity and heritability on this condition. The range of relative risk of gestational hypertension, preeclampsia and eclampsia for twin compared to singleton gestations is 1.2 to 2.7, 2.8 to 4.4 and 3.4 to 5.1 respectively. Parity, African-American ethnicity, and young maternal age are all factors that increase the relative risk of acquiring hypertensive disease to 4.0, 1.8 and 1.5 in mothers of twin gestations. Factors such as maternal smoking, income level and zygosity have a negligible effect on the relative risk of acquiring hypertensive disease in twin gestations. In addition to twin mothers exhibiting a higher incidence of hypertensive disease compared to their singleton counterparts, they also exhibit an earlier onset of hypertensive disease at both 35 and 37 weeks of gestation comparatively. Uric acid levels measured at 30–31 weeks of gestation in twin mothers predicted the onset of preeclampsia with a sensitivity of 73% and a specificity of 74%. The range of risks presented in the literature is wide and the therapies avocated are diverse. We therefore decided to summarize the risks in a comparative fashion and to review current therapeutic strategies for the convenience of clinicians who confront increasing numbers of multiple pregnancies. The tables bring all recent published risks together in the first comparative analysis in which the data has been converted to relative risks and confidence intervals. Because the literature is relatively silent on specific management of hypertensive disease in twin pregnancies, general management recommendations for singleton gestations should be used by practitioners caring over twin gestations.
Perinatal Mortality in Term and Preterm Twin and Singleton Births
Authors: Payne Jennifer C. , Campbell M. Karen , DaSilva Orlando , Koval John 
Published: May 2007

AbstractAlthough, in general, twins have higher perinatal mortality rates than singletons, preterm twins have lower perinatal mortality rates than singletons of the same birth weight or gestational age. This study investigated the hypotheses that this paradoxical twin advantage: 1) is due to gestational age distribution differences between the singleton and twin populations, and 2) is due to increased likelihood of birth having occurred in a tertiary perinatal center. A pre-existing, time-limited data set of all births in the province of Ontario in odd years between 1979 and 1985 was chosen for this study because of the large sample size (n = 618,579). Multivariable logistic regression of the relationship between perinatal mortality and twin status was controlled for mother’s age, hospital level and gestational age. Findings confirm the lower mortality of preterm twins. After controlling for level of hospital of birth this difference remained, suggesting that level of hospital of birth was not a major factor responsible for the twin advantage. Analyses in which gestational age was standardized indicate that, for those whose gestational age was less than 2 SD below the mean for their particular group (twin or singleton), twins were actually at higher risk than singletons. These results support hypothesis 1 and do not strongly support hypothesis 2. The results also support earlier authors’ suggestions that the definition of term birth should be different for twins and singletons
A Comparison of Educational Achievement in a National Sample of Dutch Female Twins and Their Matched Singleton Controls
Authors: Cohen Celina C.C. , van Goozen Stephanie H. M. , Orlebeke Jacob F. , Buitelaar Jan K. , Cohen-Kettenis Peggy T. 
Published: May 2007

AbstractThe aim of this study was to compare the educational achievement of female twins (n = 577) and their matched singleton controls (n = 447), who were selected from participants of a national test of educational achievement in the years 1993 to 1998. To assure the representativeness of the selected groups we also compared the achievement scores of the twins and the controls to those of the total Dutch female population tested in the same period. We analyzed the results of the following educational achievement scales: Language, Mathematics and Information Processing. The results indicated that the singleton classmates performed significantly better than the twins on all three scales. However, the twins performed equally well as compared to the Dutch female population. We believe that our singleton control group was not as properly selected as we intended, a selection bias operative at the level of the schools may have confounded the comparison. We therefore conclude on the basis of a comparison with the performance of the total Dutch female population that there are no differences in educational achievement between female twins and singletons.
Genetic and Environmental Influences on Expression of Recurrent Headache as a Function of the Reporting Age in Twins
Authors: Svensson Dan A. , Larsson Bo , Waldenlind Elisabet , Pedersen Nancy L. 
Published: May 2007

AbstractTo explore age-related mechanisms in the expression of recurrent headache, we evaluated whether genetic and environmental influences are a function of the reporting age using questionnaire information that was gathered in 1973 for 15- to 47-year-old Swedish twins (n =12,606 twin pairs). Liability to mixed headache (mild migraine and tension-type headache) was explained by non-additive genetic influences (49%) in men aged from 15 to 30 years and additive genetic plus shared environmental influences (28%) in men aged from 31 to 47 years. In women, the explained proportion of variance, which was mainly due to additive genetic effects, ranged from 61% in adolescent twins to 12% in twins aged from 41 to 47 years, whereas individual specific environmental variance was significantly lower in twins aged from 15 to 20 years than in twins aged from 21 to 30 years. Liability to migrainous headache (more severe migraine) was explained by non-addi-tive genetic influences in men, 32% in young men and 45% in old men, while total phenotypic variance was significantly lower in young men than in old men. In women, the explained proportion of variance ranged from 91% in the youngest age group to 37% in the oldest age group, with major contributions from non-additive effects in young and old women (15–20 years and 41–47 years, respectively) and additive genetic effects in intermediate age groups (21–40 years). While total variance showed a positive age trend, genetic variance tended to be stable across age groups, whereas individual specific environmental variance was significantly lower in adolescent women as compared to older women.
HLA Haplotypes in Dizygotic Twin Pairs: Are Dizygotic Twins More Similar Than Sibs?
Authors: Titlestad Ingrid Louise , Kyvik Kirsten Ohm , Kristensen Tom , Lillevang Søren 
Published: May 2007

AbstractIt has been suggested that dizygotic twin pairs share two HLA haplotypes more often than ordinary siblings and thus might be genetically more alike. We tested this hypothesis in dizygotic twin pairs from the Danish Twin Registry. A total of 114 (60 female and 54 male) same-sexed healthy twin pairs aged 18–45 years participated. Dizygosity was established by means of DNA sequencing of nine polymorphic markers. HLA-A, B and Cw specificities were typed with serology, and if data were inconclusive, with DNA typing. If twin partners had the same HLA-types, they were assumed to share two haplotypes. If they had 1 HLA A, B and C antigen group in common they were assumed to share one haplotype and if they had no HLA types in common they were assumed to share zero haplotypes. Since HLA-types from parents were unavailable we could not test for identity-by-descent and thus had a risk of overestimating the number of twins sharing two haplotypes. A Chi-square test was used to compare observed numbers in each haplotype sharing group with the expected numbers. Twenty-nine (expected 28.5) twin pairs had two HLA-types in common, 52 (expected 57) had one HLA-type in common and 33 (expected 28.5) had zero HLA-types in common, p = 0.56. Our data show that DZ twins are not more similar than sibs from different pregnancies in general.
Analysis of Functional Abilities for Elderly Danish Twins Using GEE Models
Authors: Iachina Maria , Jørgensen Bent , Christensen Kaare , Iachine Ivan 
Published: May 2007

AbstractIn this work we present a new method for genetic analysis of twin data which is based on generalized estimating equations and allows for analysis of various response types (e.g., continuous, binary, counts) combined with estimation of residual correlations. The new approach allows for control of covariates of any kind (e.g., continuous, counts) by modeling the dependence of mean and variance on background variables. The proposed method was applied to identify the covariates that have a significant influence on elderly people’s functional abilities, and find the estimates for the correlation coefficients of residuals for MZ and DZ twins in a sample of 2401 Danish twin 75 years of age or older. The bootstrap method was used to obtain standard errors for correlation coefficients. It was shown, that the chosen covariates have similar effects on MZ and DZ twins, and that the residual correlation in MZ twins is significantly higher than in DZ twins, which indicates that genetic factors play an etiological role in the determination of physical status of elderly people, controlled for 10 background variables.
Paternally Derived Twinning: A Two Century Examination of Records of One Scottish Name
Authors: St Clair John B. , Golubovsky Mikhail D. 
Published: May 2007

AbstractPaternal influence on twinning was investigated through a study of all the state and church records of Scotland for the period 1800–2000 (nine generations) in relation to one Scottish patronymic — in total 50,000 births. All recorded twins born with the chosen patronymic were identified and their whole paternal ascent and descent on the male line were charted for twins. There were established three pedigrees A, B and C manifesting clear paternal twinning hereditary transmission. Detailed familial reproduction patterns were traced for pedigree A, including phenotypic identification of twin zygosity in relation to seven same sexed pairs of twins in the pedigree and one same sexed pair out of dizygotic triplets. It is the most comprehensive description to date of such a kind of twin familial trait. The data presented show (i) the unique feature of clear direct paternal influence on twinning in three families; (ii) paternal factor(s) determination in both DZ and MZ twinning; and (iii) a definite association of twinning tendency with a partial male infertility, which corresponds to the prediction of the Infertility/Twinning Paternally Dependent syndrome hypothesis. The hypothesis of a founder effect explaining the similarity of A, B, C families and the possible localisation of the paternally dependent twinning factor on the Y-chromosome are currently under molecular investigation.
The Case for the Odd Case, Research Reviews, Parenting Pandas
Authors: Segal Nancy L. 
Published: May 2007

AbstractMany twin researchers occasionally encounter twin pairs displaying unusual physical, medical or behavioral traits. Unfortunately, these interesting cases are often unreported because they do not fit in easily with ongoing projects. However, these “odd cases” may suggest new hypotheses, new designs or entirely new projects. In this paper, I argue in favor of publishing case studies of exceptional twins, and refer to several large scale studies inspired by such reports. Several informative case studies are then summarized: DZ twins discordant for hyperinsulinism, DZ twins born after ICSI, “simultaneous madness in twins, and sixteenth century conjoined twins. The article concludes with a review of parenting twin pandas.
Osteoarthritis of the Hands, Hips and Knees in an Australian Twin Sample — Evidence of Association with the Aggrecan VNTR Polymorphism
Authors: Kirk Katherine M. , Doege Kurt J. , Hecht Jacqueline , Bellamy Nicholas , Martin Nicholas G. 
Published: May 2007

AbstractAge-related changes in the composition of the cartilage matrix may be associated with the development of osteoarthritis, a relatively late-onset disease characterised by the destruction of joint cartilage. In order to investigate whether differences in the VNTR polymorphic region of aggrecan affect cartilage functionality and therefore the development of osteoarthritis, we examined the aggrecan polymorphic genotypes of a sample of 134 Australian twins aged over 50 (including 34 monozygotic and 27 dizygotic twin pairs). Clinical measures of hand, hip and knee osteoarthritis, as well as self-reported bone and joint pain, were tested for association with the aggrecan polymorphism. The results were consistent with either a deleterious effect of allele 27, or a protective effect of alleles 25 and 28, providing some additional evidence for an association between the aggrecan VNTR polymorphism and osteoarthritis of the hands, hips and knees.
Comparison of Child-rearing Problems Between Mothers with Multiple Children who Conceived after Infertility Treatment and Mothers with Multiple Children who Conceived Spontaneously
Authors: Yokoyama Yoshie 
Published: May 2007

AbstractThe purpose of this study was to clarify the characteristic child-rearing problems for mothers of multiple children who conceived after infertility treatment as compared to mothers of multiple children who conceived spontaneously. The subjects were 990 mothers of multiple children: 359 who conceived after infertility treatment and 631 who conceived spontaneously. Mothers who conceived after infertility treatment were more delighted when informed of a multiple pregnancy than those who conceived spontaneously. In addition, with respect to anxiety during twin pregnancies, mothers of twins who conceived after infertility treatment showed lower rates of anxiety about nursing the infants and economic concerns than those of twins who conceived spontaneously. However, after delivery, mothers who conceived after infertility treatment showed a higher rate of depressive symptoms than those who conceived spontaneously. After adjusting for each associated factor using logistic regression, the risk of depressive symptoms in mothers who conceived after infertility treatment was significantly associated with disabled multiple children and the methods for alleviating stress. The odds ratio indicated that mothers with at least one disabled child were twice as likely to have depressive symptoms as mothers with no disabled children. Furthermore, the odds ratio indicated that mothers who used no methods for alleviating stress were twice as likely to have depressive symptoms than those who did.
In Detail; Research Reviews; Of New Interest
Authors: Segal Nancy L. 
Published: May 2007

AbstractTwo families with twins — one in which adult DZ twins continue to face the risk of frontotemporal dementia, and the other in which a mother copes with brittle bones in a newborn infant MZ pair — are featured. The nature and progress of the disorders are reviewed and personal perspectives from the twins and other family members are variously provided. Next, four current twin studies are briefly summarized. Topics include sex differences in social support systems, new reproductive technologies, comparative twin-singleton frequencies of placenta previa, and the nature and complications of heterotopic pregnancies. This article concludes with a brief sampling of human interest stories involving twins: a different looking DZ pair, newborn sextuplets, conjoined twins and opposite-sex twin athletes.
Quantitative Association Tests of Immune Responses to Antigens ofMycobacterium Tuberculosis: A Study of Twins in West Africa
Authors: Wiart Amanda , Jepson Annette , Banya Winston , Bennett Steve , Whittle Hilton , Martin Nicholas G. , Hill Adrian V. S. 
Published: May 2007

AbstractThere is now considerable evidence that host genetic factors are important in determining the outcome of infection withMycobacterium tuberculosis(MTB). The aim of this study was to assess the role of several candidate genes in the variation observed in the immune responses to MTB antigens. In-vitro assays of T-cell proliferation, an in-vivo intradermal delayed hypersensitivity response; cytokine and antibody secretions to several mycobacterial peptide antigens were assessed in healthy, but exposed, West African twins. Candidate gene polymorphisms were typed in theNRAMP1,Vitamin D receptor,IL10,IL4,IL4 receptorandCTLA-4genes. Variants of the lociIL10(−1082 G/A),CTLA-4(49 A/G) and theIL4 receptor(128 A/G) showed significant associations with immune responses to several antigens. T-cell proliferative responses and antibody responses were reduced, TNF-α responses were increased for subjects with theCTLA-4G allele. The T-cell proliferative responses of subjects withIL10GA and GG genotypes differed significantly.IL4 receptorAG and GG genotypes also showed significant differences in their T-cell proliferative responses to MTB antigens. These results yield a greater understanding of the genetic mechanisms that underlie the immune responses in tuberculosis and have implications for the design of therapeutic interventions.
Genetic Influences on Female Infidelity and Number of Sexual Partners in Humans: A Linkage and Association Study of the Role of the Vasopressin Receptor Gene (AVPR1A)
Authors: Cherkas Lynn F. , Oelsner Elizabeth C. , Mak Y. T. , Valdes Anna , Spector Tim D. 
Published: May 2007

AbstractIn humans, in contrast to animals, the genetic influences on infidelity are unclear. We report here a large study of over 1600 unselected United Kingdom female twin pairs who confidentially reported previous episodes of infidelity and total lifetime number of sexual partners, as well as attitudes towards infidelity. Our findings demonstrate that infidelity and number of sexual partners are both under moderate genetic influence (41% and 38% heritable, respectively) and the genetic correlation between these two traits is strong (47%). Conversely, attitudes towards infidelity are driven by shared and unique environmental, but not genetic, influences. A genome-wide linkage scan identified three suggestive but nonsignificant linkage areas associated with infidelity and number of sexual partners on chromosomes 3, 7 and 20 with a maximum LOD score of 2.46. We were unsuccessful in associating infidelity or number of sexual partners with a locus implicated in other mammals' sexual behavior, the vasopressin receptor gene. Nonetheless, our findings on the heritabil-ity of sexual infidelity and number of sexual partners provide support for certain evolutionary theories of human sexual behavior, as well as justifying further genetic and molecular research in this domain.
Linkage and Segregation Analysis of Black and Brindle Coat Color in Domestic Dogs
Authors: Kerns Julie A , Cargill Edward J , Clark Leigh Anne , Candille Sophie I , Berryere Tom G , Olivier Michael , Lust George , Todhunter Rory J , Schmutz Sheila M , Murphy Keith E , Barsh Gregory S 
Published: May 2007

Abstract
Mutations of pigment type switching have provided basic insight into melanocortin physiology and evolutionary adaptation. In all vertebrates that have been studied to date, two key genes, Agouti and Melanocortin 1 receptor (Mc1r), encode a ligand-receptor system that controls the switch between synthesis of red–yellow pheomelanin vs. black–brown eumelanin. However, in domestic dogs, historical studies based on pedigree and segregation analysis have suggested that the pigment type-switching system is more complicated and fundamentally different from other mammals. Using a genomewide linkage scan on a Labrador × greyhound cross segregating for black, yellow, and brindle coat colors, we demonstrate that pigment type switching is controlled by an additional gene, the K locus. Our results reveal three alleles with a dominance order of black (KB) &gt; brindle (kbr) &gt; yellow (ky), whose genetic map position on dog chromosome 16 is distinct from the predicted location of other pigmentation genes. Interaction studies reveal that Mc1r is epistatic to variation at Agouti or K and that the epistatic relationship between Agouti and K depends on the alleles being tested. These findings suggest a molecular model for a new component of the melanocortin signaling pathway and reveal how coat-color patterns and pigmentary diversity have been shaped by recent selection.