bluuebunny/crossref_metadata_2025 huggingface dataset:
Restrictiveness-Permissiveness of Their Environment as Perceived by Kibbutz Twins and Singletons
Authors: Guttman Ruth , Nathan Michael , Esrachi Amir
Published: July 2016

This research compares similarities and differences between kibbutz twins and singletons on individual perceptions of extent of restriction imposed by their fathers and mothers, teachers, caretakers and peers with regard to the children's choices, plans, and actual activities. During the past two years, the parents of all kibbutz twins in Israel of age 1 to 18 have been contacted. They provided background information about themselves and their twin children. In each kibbutz, two control singletons were selected of the same sex and age for each twin pair, yielding a “quartet”. With the aid of a mapping sentence, questionnaires were constructed to help ascertain the child's role in life areas such as family, friendship, school, hobbies, work, amusement. Questionnaires with the same facet design are being administered to children (twin and singleton), mothers, fathers, teachers, and caretakers. In addition, each child is given a battery of tests — including the verbal WISC, Block Design, Raven Matrices, and Reading Comprehension. The children will be interviewed and tested in three successive years, beginning either in grade 4 or 5. Data will thus be obtained on changes in perception of permissiveness-restrictiveness and their relation to performance at ages 9 to 13. To date 9-year-olds in 14 kibbutzim have been interviewed. Analyses of responses to four questions are presented in this paper. The preliminary analyses indicate that twins and singletons have similar means and distributions with regard to the extent to which the children feel they are told what to do by either parent.
Birthweight Differences, The Transfusion Syndrome and The Cognitive Development of Monozygotic Twins
Authors: O'Brien P.J. , Hay D.A.
Published: July 2016

Monochorionic twins may differ from dichorionic monozygotic (MZ) twins because of the transfusion syndrome and the timing of the cleavage of the zygote. Intrapair birthweight differences may be an indicator of these intrauterine variables. Previous evidence concerning weight differences and intellectual ability in MZ twins is reviewed with recommendations that future research also incorporates full placental data. Poorer scores on a nonverbal test are found for the lighter male twin of pairs with large intrapair differences in birthweight. Co-twin concordance rates for test scores are also highest for this group indicating that they vary consistently from other groups. Some evidence is presented from the present and earlier studies implicating anomalies of asymmetry or the transfusion syndrome as possible causes of these differences in brain functioning. The study adds further doubts as to the validity of any assumption of developmental equivalence between MZ twins and the general population.
Weight and Height Growth in Twins and Children Born in the Last Decade
Authors: Alfieri A. , Gatti I. , Alfieri A.C.
Published: July 2016

Weight and height growth has been examined in 400 twins and 229 singletons born 1975-1985. Periodical measurements have been taken from 0 to 7 years of age. As compared to values obtained in a previous study of twins and singletons born 1960-1974, though limited to the first year of age, twins appear to continue to do worse than singletons in their growth. However, height values appear to have become higher in the first year of age in both twins and singletons born 1975-1985.
Autonomous Languages of Twins
Authors: Bakker Peter
Published: July 2016

Twins are regularly reported to invent languages of their own, unintelligible to others. These languages are known as autonomous languages, cryptophasia or idioglossia. Despite current belief, this is not a rare phenomenon. Autonomous languages exist in about 40% of all twins, but often disappear soon. In this study, nine autonomous languages are compared: the circumstances in which they emerge, how these languages relate to the parents' language (the model language) and how they are structured. The prototypical situation is one in which two or more close siblings (not necessarily twins) grow up closely together during the language acquisition period. If an adult model language is frequently absent, the children use each other as a model and acquire the language imperfectly. The language may stabilise at that level. If a model is completely absent, the children probably do not create a language. In all cases known, the language consists of onomatopoeic expressions, some invented words, but for the greatest part of words from the adult language adopted to the constrained phonological possibilities of young children. These words being hardly recognizable, the language may turn out to be completely unintelligible to speakers of the model languages, but they resemble each other in that they lack morphology and that word order is based on pragmatic principles such as saliency and the semantic scope of words. Neither the structure of the languages nor its emergence can be explained by other than situational factors.
Innovations in the Statistical Analysis of Twin Studies
Authors: Hopper J.L. , Derrick P.L. , Clifford C.A.
Published: July 2016

Advances in computer technology have made possible a greater sophistication in the statistical analysis of pedigree data, however this is not necessarily manifest by fitting more comprehensive causative models. Planned twin and family studies measure numerous explanatory variables, including perhaps genetic and DNA marker information status on all pedigree members, and the cohabitation of all pairs of individuals. A statistical analysis should examine the contribution of these measured factors on individual means, and in explaining the variation and covariation between individuals, concurrently with the postulated effect of unmeasured factors such as polygenes. We present two models that meet this requirement: the Multivariate Normal Model for Pedigree Analysis for quantitative traits, and a Log-Linear Model for Binary Pedigree Data. For both models, important issues are examination of fit, detection of outlier pedigrees and outlier individuals, and critical examination of the model assumptions. Procedures for fulfilling these needs and examples of modelling are discussed.
Design and Sampling Considerations, Response Rates, and Representativeness in a Finnish Twin Family Study
Authors: Kaprio J. , Rose R.J. , Sarna S. , Langinvainio H. , Koskenvuo M. , Rita H. , Heikkilä K.
Published: July 2016

Kinships composed of twin parents, their spouses and children, offer a robust and flexible sampling design for research in genetic epidemiology. Families-of-twins designs circumvent some of the sampling problems that arise when independent data sets are combined, and these designs provide unique evaluations of maternal influences, assortative mating and X-linkage. Unfortunately, empirical studies of families of twin parents have been limited by relatively small samples and by the self-selection biases intrinsic in ascertainment of families from volunteer twin registries.

A large and representative cohort of monozygotic and dizygotic twin parents, drawn from a population-based twin registry, provides the optimal sampling frame for twin-family research. This paper reviews the sampling considerations underlying the initial family study based on the Finnish Twin Cohort and evaluates the representativeness of the sampled twins. Spouses and adult children (over 18 years) of 236 pairs of twins, about equally divided by gender and zygosity, were evaluated by a postal questionnaire. Individual response rates exceeded 86% and in 464 of the 472 nuclear families (98.3% ), at last one member of the twin's family completed the questionnaire. The sampled twins, selected for fecundity to maximize statistical power of the obtained data, were broadly representative of non-selected twins drawn from the Cohort, with whom they were matched on age, gender, and zygosity. Such results suggest that the Finnish Cohort has excellent potential for extended twin-family research designs.
Differential Enrollment in Twin Registries: Its Effect on Prevalence and Concordance Rates and Estimates of Genetic Parameters
Authors: Kendler K.S. , Holm N.V.
Published: July 2016

In the NAS-NRC Registry, all major diseases are more common in DZ than in MZ twins. Furthermore, concordance rates for most disorders are lower in the registry than would be expected. In this article we propose a general model which seeks to explain these phenomena. The model explores the impact of traits which increase or decrease the probability of enrollment of individuals given that the registry, like the NAS-NRC, includes only pairs where both members are enrolled. If the trait decreases the probability of selection into the registry, both the prevalence of and concordance for the trait in the registry will be lower than that found in the population. A trait which increases the probability of selection has the opposite effects. However, the magnitude of these effects are a function of the population concordance. If population concordance differs in MZ and DZ twins, the effect of differential enrollment will not be the same for the two zygosity groups. The article examines the impact of differential enrollment on estimates of heritability and common environment and explores ways in which estimates of prevalence and concordance rates can be obtained which are free of the bias introduced by selection.
A Study of Multiple Biological Markers in Twins
Authors: Anton-Guirgis H. , Culver B.D. , Kurosaki T. , Elston R.
Published: July 2016

Genetic and environmental influences on the phenotypic expressions of several biological markers were studied in 18 monozygous (MZ) and 8 dizygous (DZ)twin pairs. Zygosity was determined using ABO, Rh, and HLA. The biomarkers studied included: T & B lymphocytes, suppressor and helper T lymphocytes (Tγ, Tμ), T cell (PHA) mitogen activation (MA), serum immunoglobulins (IgA, IgM, and IgG), plasma carcinoembryonic antigen (CEA), aryl-hydrocarbon hydroxylase (AHH) and sister chromatid exchange (SCE) in lymphocytes. Temporal variation of markers over a 6-month period was not significant. The mean absolute differences between levels from first and second blood draws were less than one standard deviation. Variability associated with age was not significant. Females had higher levels of T lymphocytes than males. A gender related association was observed for the IgM immunoglobulin test: females had a higher mean level of IgM. Smoking was found to influence the levels of SCE, T helper lymphocytes and mitogen activation. The variability of these biomarkers within and between twin pairs was quantified. Immunoglobulin levels, particularly that of IgM, showed statistically greater similarity within MZ twins than within DZ twins. Several other markers suggested heritability.
Acute Polyhydramnios Complicating Twin Pregnancies
Authors: Schneider K.T.M. , Vetter K. , Huch R. , Huch A.
Published: July 2016

Acute polyhydramnios in the second trimestr is a typical complication in monozygous twin pregnancies. It is caused by a feto-fetal transfusion with anemia on the donor and polycytemia on the recipient twin. Contrary to the chronic hydramnios, there is no increase in malformations. In view of the high mortality rate (100%, according to most authors), the clinical management has to be reconsidered. During the years 1979 to 1983, 10 cases of acute polyhydramnios have been observed at the University Hospital in Zurich. This corresponds to an incidence of 9% in our twin population. All cases investigated were MZ twin pregnancies. With the exception of one patient, who underwent an abortion, all women were hospitalized, had bed rest and received recurrent removals of amniotic fluid and prophylactic tocolysis. The mean gestational age at the time of diagnosis was 23 4/7 weeks and at delivery 30 3/7 weeks. In two cases – one of which is presented in detail – with an unintentional puncture of a placental vessel, the recurrence of the hydramnios did not appear. Eight of 18 newborns survived. No malformations were found. Bed rest, tocolysis and recurrent amniocenteses seem to have a positive influence on the prolongation and outcome of the gestation in acute polyhydramnios.
Is Routine Hospitalization in Twin Pregnancy Necessary? A Follow-up Study
Authors: Hartikainen-Sorri Anna-Liisa
Published: July 2016

During the years 1979-1980, a prospective study was carried out to evaluate the value and efficacy of routine hospital bed rest in the prevention of premature birth and pregnancy complications in twin gestation. This was done by comparing hospital bed rest to special antenatal care at outpatient clinic. Since the results did not support the idea of using routine hospital bed rest, this was abandoned. Because the material was rather small, the results of the changed policy of management were controlled in the present follow-up study. The material consists of 102 twin pregnancies diagnosed during the years 1982-1983. The number of deliveries before the 34th gestational week and of < 1500 g weighing infants were still decreasing (9.0% and 3.0%). Perinatal mortality after the 24th gestational week was 2.0%. The follow-up study confirmed the unefficacy of routine hospital bed rest. Early diagnosis is the basis of the management of twin pregnancy. This allows counselling of the pregnant women, regular examinations to detect pregnancy complications, and also planning of the delivery.
TWINAN: Twin Data Analysis Program for Microcomputers
Authors: Kang Ke Won
Published: July 2016

A BASIC computer program designed to facilitate analysis of twin data is presented. The program estimates genetic parameters and tests their statistical significance based on the genetic and environmental hypothesis.
Triplets and Higher Order Multiple Births in Japan
Authors: Imaizumi Y.
Published: July 2016

Multiple birth rates in entire Japan were analyzed using vital statistics for 1951 to 1988. The triplet rate was nearly constant from 1951 to 1974, where the rate per million births was 58, then increased with the year up to 1982 (104), and decreased up to 1984, and suddenly increased thereafter (109 in 1987). The average rate of quadruplets per million births from 1951 to 1968 was 0.93, then increased with the year up to 1975 (7.5), and decreased until 1984 and suddenly increased thereafter (10.6 in 1987). The rate of quintuplets was 0.77 per million births during the period from 1975 to 1987. The higher multiple birth rate since 1975 was attributed to the higher proportion of mothers treated with ovulation-inducing hormones in Japan. Since 1985, higher multiple birth rates might be partially attributed to in vitro fertilization. The stillbirth rates for male triplets gradually decreased from 1960 to 1978 and thereafter remained constant at a little higher level except in 1988, whereas the rates for females gradually decreased with the year. The overall stillbirth rates decreased to 1/4 for triplets and to 1/5 for quadruplets during the 37-year period from 1951. The overall stillbirth rate of quintuplets was 0.60 (51/85) during the period 1975-1987.
Multiple Pregnancy: An International Perspective
Authors: Sciarra J.J. , Keith L.G.
Published: July 2016

This article discusses the following areas of interest related to the obstetric care of multiple pregnancy: 1) methods of diagnosis and ultrasound, 2) pregnancy protection through adequate maternal nutrition, 3) mode of delivery, 4) discordant twins, and 5) assisted reproductive technology. The article also emphasizes the FIGO/WHO concerns regarding safe motherood and proposes a four point program to reduce perinatal death rates in multiple pregnancy. These elements are: 1) adequate primary health care including access to family planning information and technology, 2) prenatal care with referral of high risk patients to specialized centers, 3) the presence of trained personnel for all women in childbirth, 4) effective access to obstetric care for women who are pregnant, giving birth, or recently delivered.
The Cost Effectiveness of Preventing Preterm Delivery in Twin Pregnancies
Authors: Papiernik E. , Keith L.G.
Published: July 2016

As an extension of previous work on the risk of prematurity in singletons and on the social cost of twin births, an analysis has been carried out into the cost effectiveness of preventing premature delivery in twin pregnancies. The cost of prevention is assessed in terms of early diagnosis through ultrasound screening and of an extra 11 weeks of work leave to expectant mothers. When this cost is compared to the social cost involved in the transfer of newborns to neonatal intensity care units and in supporting handicapped children, it is concluded that the total cost of prevention corresponds to one-third of the long-term costs associated to lack of prevention.
Guidelines for the Prevention of Multiple Pregnancy in Treatment by in Vitro Fertilization
Authors: Leroy F. , Puissant F. , Barlow P. , de Maertelaer G.
Published: July 2016

Within the same in vitro fertilization (IVF) program, treatment trials leading to single and multiple ongoing gestation were compared. Rates of cesarean delivery, prematurity and perinatal mortality were found much higher among twin and multiple IVF pregnancies. Our work thus attempts at defining characteristics of proneness to multiple gestation in IVF treatment, in order to try and avoid its occurrence. The mean vitality score of embryos replaced is the most reliable criterion for this purpose, enabling one to replace no more than two embryos when the average score is high. Age of the patient and cause of infertility are almost nondiscriminant in this respect. Ovarian stimulation parameters such as total dosage of gonadotropin treatment and level of estrogenic response, as well as numbers of oocytes and embryos obtained, may serve as secondary criteria for assessing the twinning risk.
A Study on Prognosis of Surviving Cotwin
Authors: Yoshida K. , Matayoshi K.
Published: July 2016

It has been suggested that the surviving cotwin and the mother are seriously affected when intrautrine fetal death of one monozygotic twin occurs. Several authors have reported brain damage in the surviving twin coexisting in utero with dead monozygotic cotwin. Most of such instances are monochorionic and show vascular communication between paired twins in the placenta. In a total of 133 pairs of monochorionic twins, death of one twin during pregnancy occurred in 33 cases (24.8%). Of 33 surviving twins, 8 babies suffered from porencephaly, cerebral palsy and other abnormalities. More unfavorable prognosis was recognized when a cotwin died in the latter half of pregnancy, while when a monozygotic cotwin died in the early stage of pregnancy, the surviving twin uneventfully grew to term in most cases.
Genetic Influences on Respiratory Sinus Arrhythmia across Different Task Conditions
Authors: Boomsma D.I. , van Baal G.C.M. , Orlebeke J.F.
Published: July 2016

Respiratory sinus arrhythmia (RSA) has been shown to be a sensitive index of vagal cardiac control. We studied the genetic and nongenetic influences on individual differences in RSA in a sample of 160 adolescent twins. RSA was measured during rest and across two different tasks. Results show that heritability is task dependent. The amount of genetic variance is the same, however, during rest and task conditions. Because nonshared environmental variance decreases during tasks, heritability is larger for RSA measured under more stressful conditions than for RSA as measured during rest. Multivariate models assessed the continuity of the genetic and environmental influences and show genetic influences to be the same across different conditions, while environmental influences are different. More specifically, a one-factor model is found for genetic influences and a second-order autoregressive model for the environmental factors.
“Twins in School” — An Australia-wide Program
Authors: Gleeson C. , Hay D.A. , Johnston C.J. , Theobald T.M.
Published: July 2016

The multiple birth family is more likely to have a dispute with the education system than with any other service. So many potential areas of conflict exist over the abilities and behaviour of multiples and over such issues as separation or keeping back one twin. One reason for disputes is the lack of good data to adequately reflect the different perspectives of parents and teachers and the differing needs of families: the same solution does not apply to all. To provide the first large-scale data base and building upon an initial survey of 85% of all primary school teachers in South Australia, the LaTrobe Twin Study and AMBA worked with Education Departments to set-up in each state Education Research Teams (ERTs) of parents of multiples who were also teachers. The ERTs were crucial in three phases. 1) Developing and circulating questionnaires and publicising the nationwide survey. 784 families and 1264 teachers of their children completed these questionnaires, many reporting that simply having to address the issues raised in the questionnaire was a valuable learning experience. 2) Exploring the data base. Issues arising included the very different bases on which parents and teachers judged separation desirable, with teachers emphasising the unsubstantiated claim that separation is essential to individual development. Separation became more common over the first three years of schooling but 20-25% of twins separated one year were back together the next. 3) Running regional meetings of parents, teachers and administrators to discuss the results and to pool experiences and plan policies at the local level. A need clearly exists to improve the level of consultation between families and school personnel and to ensure the widespread availability of information which identifies key issues in making decisions for that multiple birth family.
Heritability of Substance Use in the NAS-NRC Twin Registry
Authors: Carmelli D. , Swan G.E. , Robinette D. , Fabsitz R.R.
Published: July 2016

This study examines the heritability of cigarette smoking, alcohol, and coffee consumption in 4,960 adult, male twin pairs (2,390 MZ and 2,570 DZ pairs) participants in an epidemiologic survey of the NAS-NRC Twin Registry conducted in the USA during 1972-73. Heritability estimates for smoking, alcohol and coffee use were calculated both before and after adjustment for shared variance between these behaviors and other demographic characteristics including socioeconomic status and an occupational adjustment score. The objective of the analysis was to determine the impact of adjustment for covariates on heritability estimates of smoking, alcohol and coffee use. Before adjustment, genetic effects in smoking, alcohol and coffee use accounted for 53%, 36%, and 45% of the variance, respectively. After adjustment, the corresponding estimates were 35%, 29%, and 36%. The fact that these estimates remained significant after adjustment for covariates leads to increased confidence about the role of genetic factors in substance use behaviors.
Zygosity Diagnosis of Twins by Questionnaire
Authors: Ooki S. , Yamada K. , Asaka A. , Hayakawa K.
Published: July 2016

Subjects were 189 twin pairs, 165 MZ and 24 same-sexed DZ, who entered the junior high school affiliated to Tokyo University (sample T), and 93 twin pairs, 71 MZ and 22 same-sexed DZ, who were registered at Kinki University (sample K). The zygosity was previously identified by many genetic markers, and this study aimed at zygosity diagnosis by questionnaire. The latter included three questions: “How are you alike?”, “How often are you mistaken?”, and “By whom are you mistaken?”. According to the degree, 1-3 points, 1-3 points, and 1-4 points were given for each question, and the sum of the points of each pair of twins was calculated. Zygosity was determined by the sum of points, distributed from 6 to 20. Namely, if the sum was 6-13, the twin pair was considered MZ, and if the sum was 14-20, DZ. More than 90% of twins were diagnosed correctly by use of this cutting point. This result was in accordance with that obtained by use of discriminant function analysis. It is concluded that zygosity diagnosis by questionnaire is convenient and useful, in particular for epidemiological research.
Incidence of Twinning in London from 1581 to 1760
Authors: Nonaka K. , Miura T.
Published: July 2016

Baptism records of parishes in London and its vicinities from 1581 to 1760 (168,238 maternities) were investigated to estimate the twinning rate and its secular and seasonal variations. Total, estimated dizygotic (DZ), and estimated monozygotic (MZ) twinning rates were 1.1%, 0.8% and 0.3%, respectively. MZ twinning rate varied during the 18 decades, with a significantly low rate (0.11%) in the early 17th century (1621-1640). Significant seasonal variations of the twinning rate according to the month of baptism was observed in both DZ and MZ twins. DZ twins were born more frequently in spring and fall in general. Parish records obtained from four parishes near Manchester in England showed an inversed seasonal variation with peaks in winter and summer. An interpretation of this difference was discussed in a context of environmental factors. In the low MZ period, 1621-1640, MZ or like-sexed twins were apparently less frequent in summer (Aprii to October). This result could be explained by a decrease of MZ twins and/or a greater loss of like-sexed DZ twins.
The Monozygotic Twinning Rate: Is It Really Constant?
Authors: Allen G. , Hrubec Z.
Published: July 2016

Weinberg's difference method, applied to twin birth statistics, usually shows a dependence of the MZ rate on maternal age, like a thin shadow of the DZ rate. Some of this MZ variation could be explained away by James' finding of more same-sex (SS) than opposite-sex (OS) DZ twins, the excess being mistakenly classified as MZ by Weinberg's assumption of equal numbers. By several methods one can extract a Constant value for the MZ rate and a Constant or nearly Constant value for the DZ SS/OS ratio, but these “constants” are actually arbitrary and they vary between populations.
Increasing Trend in the Monozygotic Twinning Rate
Authors: Bressers W.M.A. , Eriksson A.W. , Kostense P.J. , Parisi P.
Published: July 2016

Recent changes in the estimated incidence of monozygotic twinning in 15 European populations are described. The overall trend was an increase in the monozygotic twinning rate (MZTR) since the 1960s, particularly in those countries in which the use of oral contraceptives (OC) was widespread. A slower increase or even a decrease in the MZTR was observed in countries with low use of OC. Some countries, eg, Sweden, demonstrated an unexpectedly sharp increase since the 1960s. In Poland and the Federal Republic of Germany the MZTR was already strongly increasing as early as in the 1950s, clearly before the introduction of the pill. The influence of several other factors on the MZTR is discussed, such as toxic and teratogenic agents, pelvic infection diseases caused by the use of intrauterine devices, the increased use of ovulation inducers and neuroleptics as well as changes in the registration of perinatal deaths.
Does the Use of Oral Contraception Depress DZ Twinning Rates?
Authors: Campbell D. , Thompson B. , Pritchard C. , Samphier M.
Published: July 2016

Data based on total births from a geographically defined population with zygosity determined from blood samples and placentation and with data on the use of oral contraceptives routinely collected in early pregnancy showed no association between oral contraceptive use prior to pregnancy in either MZ or DZ twinning. Three mutually exclusive control groups of singletons were used to take account of age, parity and secular trends.
The Organization of the Oocyte and Embryogenesis in Twinning and Fusion Malformations
Authors: Boklage Charles E.
Published: July 2016

Certain congenital malformations occur in excess among twins and also among first-degree relatives of twins. In the general population, these anomalies are familially associated with each other, and, like twinning, familially associated with unusual brain function asymmetry. They affect structures built by fusion of bilateral embryonic halves and remodeled under major influence of neural crest mesenchyme. This conjunction of associations suggests that twinning, symmetry development, and this group of malformations might share causai elements at least some of which are heritable. The problem here is the absence of zygosity differences in these relationships, because of which they cannot be explained within the biology of twinning as it has been understood. A potential resolution is offered by way of a mechanism common to MZ and DZ twinning, involving a relationship between oocyte organization and the determination of body symmetries.
The Possible Role of Homeotic Genes in the Causation of Malformations in Monozygotic Twins
Authors: Flannery David B.
Published: July 2016

It is proposed that the malformations observed to occur with increased frequency in monozygotic twins are similar to the types of malformations caused by mutation in homeotic genes in animals.
Familial and Individual Influences on Blood Pressure
Authors: Sims J. , Hewitt J.K. , Kelly K.A. , Carroll D. , Turner J.R.
Published: July 2016

Although familial aggregation of blood pressure is well documented, few studies have considered the changing contribution of genetic and environmental influences during adulthood. Applying maximum likelihood model fitting to blood pressure covariation in balanced pedigrees including both parents and their young adult twin offsprings (25 MZ, 32 DZ, aged between 16 and 24 years), it is shown that the increased variation in parents is explained by such developmental changes. For DBP, an apparent reduction in heritability from 68% to 38% from young adulthood to middle age results from the increasing impact of individual environmental experience (E1), with little or no influence from shared family environmental (E2). For SBP, shared environmental effects may play a part. Given the relatively small size of the present sample, the conclusions are to be seen as tentative. An augmented family study, incorporating middle aged twins and their young adult offspring, will clarify the causation of these developmental changes.
Heritability Estimation from Concordant Twin Pairs Alone
Authors: Sofaer Jeffrey A. , Holloway Susan M.
Published: July 2016

Heritability estimation is possible from concordant twin pairs alone, based on the proportion of like-sexed pairs among all concordant affected pairs. The method is limited to conditions found in both sexes in the prevalence range 0.1% to 10%, and a relatively large population size is required to give an adequate sample of twin pairs. However, the method has the considerable advantage that zygosity determination is not required and that any bias due to incomplete diagnosis/ascertainment is likely to be small. The method is particularly suited to diseases where registration is obligatory and computerised so that the register can be scanned for pairs of individuals with the same date of birth, place of birth and birth surname.
Outcome of the Surviving Cotwin of a Fetus Papyraceus or of a Dead Fetus
Authors: Yoshida K. , Soma H.
Published: July 2016

Serial ultrasound examinations have demonstrated that one of two gestational sacs in a twin pregnancy may often disappear. When it disappears at an early stage of gestation, the pregnancy may advance without any disturbance and the cotwin can be delivered well developed and lively. When the intrauterine death occurs in the second trimester, the dead fetus usually results in a fetus papyraceus and the cotwin continues to be alive near term. However, when death occurs in the last trimester, the viable twin may be spontaneously delivered soon and be premature. In some cases of late fetal death, the dead fetus may induce intravascular thromboses in many organs of the surviving cotwin, so that the living infant may develop cerebral palsy later after birth.
Behavioral Responses to Amphetamines in Identical Twins
Authors: Crabbe John C. , Jarvik Lissy F. , Liston Edward H. , Jenden Donald J.
Published: July 2016

Male, monozygotic twins (six pairs) were repeatedly tested before and after d-amphetamine, l-amphetamine, or placebo administration. Drug effects on cognitive, psychomotor, personality, mood, and pain variables were assessed. Members of a twin pair tended to respond similarly on several tests under placebo conditions, indicating genetic determination of the behavioral variables. In addition, cotwins tended to show similar responses to amphetamine as measured by one test of cognitive function, by several mood and personality variables (hostility, autonomic arousal, friendliness, feelings of tension and loss of control), and tended to have similar plasma levels of both amphetamine isomers. Although shared environmental effects cannot be ruled out, the results are consistent with genetic mediation of a variety of behavioral effects of amphetamines.
Mortality Rate of Japanese Twins and Triplets III. Infant Deaths of Triplets After Birth to One Year of Age
Authors: Imaizumi Yoko , Inouye Eiji , Asaka Akio
Published: July 2016

The rate of infant mortality of triplet individuals (deaths under one year of age) was computed using 34 sets of triplets born in the first half of 1974. The rates were 8.82%, 9.68%, and 10.34% for the first-, second-, and the third-born triplets, respectively. For males and females the rates were 8.33% and 10.34%, respectively, and the difference was not significant. The rate decreased with gestational age up to 32-35 weeks. For those with heavier weight at birth (≤2,000 g) the rate was lower (0%) than for those with lighter weight (<2,000 g, 8.16%), but the difference is not significant (P = 0.087). Infant mortality rate of triplets decreased with increased monthly expenditure of the household.
Blood Typing and Twin Zygosity: A Comparison of Two Methods
Authors: Lykken David T.
Published: July 2016

In a recent paper in this journal [5], Wilson offers a revision of his previously published method [4] for diagnosing the zygosity of twins from bloodtype findings. Wilson notes that his revised method will yield the same results (given the same estimates of gene frequencies) as will the methods described by Smith and Penrose [2], Sutton et al [3], and Lykken [1], and he advocates his new method, over the others, as being “simplest and most direct.” He also reinterprets various quantities employed by Lykken and proposes a different index of the efficiency of a genetic marker for zygosity diagnosis. In this note, I attempt to clarify the relationship between Wilson's revised method and my own, so that the reader can more accurately assess their relative advantages.
Low Birth Weight in Twins Versus Singletons: Separate Entities and Different Implications for Child Growth and Survival
Authors: Gedda L. , Brenci G. , Gatti I.
Published: July 2016

The condition of low birth weight is compared in twins and in singletons in terms of birth weight distributions and with respect to factors such as the incidence of sillbirths, length of gestation, maternal age, parity, and legitimacy. In the light of demographic, biological, and developmental considerations, it is concluded that low birth weight in twins is a different condition from low birth weight in singletons and should be dealt with independently, especially in view of the different implications for child growth and survival.
Smoking and Drinking Discordance and Health Condition: Japanese Identical Twins Reared Apart and Together
Authors: Hayakawa Kazuo
Published: July 2016

A total of 543 like-sex pairs of twins (407 MZ, 136 DZ) were sent mailed questionnaires on cigarette smoking, alcohol drinking and health conditions. The observed concordance rate for alcohol drinking was significantly higher than expected in both MZ and DZ pairs. The observed concordance rate for cigarette smoking was significantly higher than expected in the MZ, but not the DZ pairs. The observed rate of intrapair concordance for drinking was significantly higher than expected even in MZ pairs reared apart from infancy or very early childhood. Higher life satisfaction was observed more often in the higher alcohol consumers than in the lower consumers among MZ pairs discordant for alcohol drinking, while earlier onset of presbyopia was observed more often in the lower consumers. Physical symptoms, especially pains in the upper extremities, were reported more often by higher alcohol consumers than by lower consumers in the MZ pairs discordant for drinking.
Intrapair Similarity of Immunoglobulin Levels in Twins
Authors: Kouvalainen K. , Moilanen I.
Published: July 2016

Levels of immunoglobulins IgG, IgA, IgM and IgE were determined in 8 MZ and 14 DZ twin pairs at the ages of 6-11 years, 12-17 years and 15-20 years. Intrapair similarity in immunoglobulin levels was found to be higher in the MZ than in the DZ twins, especially in the case of immunoglobulins IgA and IgM.
Twin Studies on Urinary Pepsinogen A Phenotypes and Serum Pepsinogen A Levels
Authors: Pronk J.C. , Boomsma D.I. , Pals G. , Frants R.R. , Overbeke M. , Meuwissen S.G.M. , Orlebeke J.F. , Eriksson A.W.
Published: July 2016

Urinary pepsinogen A (PGA or PG I) phenotypes and serum PGA levels were studied in MZ and DZ twins and their parents. In 45 out of 48 MZ twin pairs PGA patterns were completely identical, while 3 MZ twin pairs showed minor differences in the relative intensity of the Pg5 isozymogen. This suggests that the intensity of this isozymogen may be influenced by nongenetic factors. There was little difference in the interclass correlations of serum PGA levels between MZ and DZ twins, indicating a large contribution of common environmental factors to serum PGA levels. This is in contrast with previous studies.
Genetic and Environmental Variation in Menstrual Cycle: Histories of Two British Twin Samples
Authors: van den Akker O.B.A. , Stein G.S. , Neale M.C. , Murray R.M.
Published: July 2016

Information about menstrual cycle variables was obtained by questionnaire using 462 female twin pairs. The twins were either members of the Institute of Psychiatry Volunteer Twin Register, or of the Birmingham Population-based Register. The two samples were analysed separately using univariate and multivariate methods so that an independent replication was obtained. Maximum likelihood estimation was used to fit simple models of genetic and environmental variation to these data. The results suggest that age of menarche, menstrual cycle regularity and premenstrual symptom reporting may be heritable, whereas menstrual cycle length is not. The results should be interpreted with caution as not all variables were replicated in the smaller sample, and the method of retrospective menstrual cycle data collection has been questioned.
Genetic and Environmental Variation of Ridge-Counts on Fingers, Palms, Soles and Toes: A Twin Study
Authors: Jantz R.L. , Brehme H. , Bender K.
Published: July 2016

A multivariate procedure for estimating heritable components from twin data was applied to ridge counts obtained from the entire dermatoglyphic system. Covariance matrices of MZ and DZ within-pair differences were used to estimate genetic correlation matrices for 20 finger ridge counts, 6 palmar interdigital counts, 20 toe counts, 4 hallucal counts, and 6 sole interdigital counts. The proportion of genetic variation was found to be greater in ridge counts of patterns than in ridge counts of interdigital areas. On digits, finger counts are more highly heritable than toe counts. Each of the dermatoglyphic areas yielded several independent genetic components, ranging from general to specific. Environmental variation was found to be local and to frequently involve reciprocal interaction between twin pairs.
Adaptation to Maximal Effort: Genetics vs. Environment. A Case History
Authors: DeMeersman R.E. , Schaefer D.C. , Miller W.W. , Nance W.E.
Published: July 2016

An individual's functional ability in physiological responsiveness is thought to be an interaction between his heredity and his environment. This hypothesis was tested to determine if different extragenetic influences would alter functional adaptability in a set of MZ triplets. After a 3-month aerobic physical fitness training program varying only in frequency, measured values for the triplets' maximum oxygen consumption (MaxVo2 ) were 59.1, 44.5, and 57.8 ml/min/kg, as compared to pretreatment values of 45.2,45.1, and 49.1 ml/min/kg respectively. These results clearly indicate intrapair differences in functional adaptability, stemming from difference in the training frequency program. The split-triplet design of this study indicates that environmental factors contribute substantially to the intrapair variance found among MZ siblings. Data extrapolation suggests that environmental stimulation of sufficient magnitude is likely to alter the functional adaptability in the individual set by his genotype.
Finnish Twins Reared Apart II: Validation of Zygosity, Environmental Dissimilarity and Weight and Height
Authors: Langinvainio H. , Koskenvuo M. , Kaprio J. , Sistonen P.
Published: July 2016

Within the Finnish Twin Cohort of like-sexed adult twin pairs, a subgroup of pairs separated at an early age has been identified. In 165 pairs, both cotwins responded to questionnaires in 1975 and 1979. An environmental dissimilarity score was formed which consists of items on whether the twins had lived after separation in the same community, attended the same school, were on the same grade at school, how often the cotwins met, how often they met common friends and relatives and whether they attended the same clubs etc, or not. To validate the zygosity diagnosis obtained by questionnaire in 1975, those pairs whose zygosity was unknown as well as those with the least contact after separation were contacted for blood sampling (11 bloodgroups). Of 15 pairs with no zygosity diagnosis, 10 responded (1 no address,2 abroad,2 refused). Six pairs were classified MZ and 4 DZ. In 12 MZ and 8 DZ pairs undergoing bloodgroup determination, the classification of only one pair changed from DZ to MZ. The following intraclass correlations for height and weight were found:
Altruism and Genetics
Authors: Rushton J.P. , Fulker D.W. , Neale M.C. , Blizard R.A. , Eysenck H.J.
Published: July 2016

Three questionnaires measuring altruistic tendencies were completed by 573 adult twin pairs from the University of London Institute of Psychiatry Volunteer Twin Register. The questionnaires consisted of a 20-item Self-Report Altruism Scale, a 33-item Empathy Scale, and a 16-item Nurturance Scale, all of which had previously been shown to have construct validity. For the three scales, the intra-class correlations for the 296 MZ pairs were 0.53, 0.54, and 0.49, and for the 179 same-sex DZ pairs were 0.25,020, and 0.14, giving rough estimates of broad heritability of 56%, 68%, and 72%, respectively. Maximum-likelihood model-fitting revealed about 50% of the variance on each scale to be associated with genetic effects, virtually 0% to be due to the twins' common environment, and the remaining 50% to be due to each twins' specific environment and/or error associated with the test.
Depression, Criminality and Psychopathology Associated with Alcoholism: Evidence from a Twin Study
Authors: Gurling H.M.D. , Oppenheim B.E. , Murray R.M.
Published: July 2016

A study of 74 twin pairs with alcoholic probands from the Maudsley Hospital is reported. Pairwise concordance for alcoholism as categorised by the SADS-L Research Diagnostic Criteria is similar in MZ twins (29%, 8/22) and DZ twins (33%, 13/39). Concordance for all diagnoses other than alcoholism is however significantly greater in MZ twins (48%, 13/27) than DZ twins (21%, 8/39, P < 0.001). Concordance in MZ and DZ twins for all diagnoses other than alcoholism, inlcuding depression, did not coincide with concordance for alcoholism. Data on criminality revealed that 21% (32/148) of the twin sample had non-alcohol, non-traffic offences on record at the UK Home Office. Of the 32 with criminal records, 28 were alcoholic probands and pairwise concordance for criminality was found in only 1 MZ and 2 DZ pairs.
Spontaneous Abortions and Twinning
Authors: Zahálková M. , Zudová Z.
Published: July 2016

The relation between spontaneous abortions and twinning was studied in the years 1980-1981 in 22 towns of the South Moravian Region, Czechoslovakia. Each town has more than 10,000 inhabitants and less than 750 births per year. The number of spontaneous abortions and the number of twin births were evaluated separately for each town and for a time unit of three months. The comparison indicated that the group with a higher number of spontaneous abortions also had a lower number of twin births. The relation between spontaneous abortions and twinning is discussed.
A Study of Twin Placentation in Tokyo
Authors: Yoshida K. , Soma H.
Published: July 2016

A total of 178 placentas of twins born in Tokyo in 1961-1982 were examined. Only just over one third were dichorionic, 110 being monochorionic and DZ twins were estimated to account for 24.7% of the pairs. The lower frequency of DZ twinning in Japan is attributed to lower gonadotropin values in Japanese women as compared to European, American, or African women. High fetal morbidity was found in monochorionic twins and this is attributed to a frequent occurrence of vascular anastomoses.
Term Twins With Discordant Birth Weights: Observations at Birth and One Year
Authors: Philip Alistair G. S.
Published: July 2016

Sixteen pairs of term discordant twins (weight discrepancy of more than 20% when the, lighter twin was compared to the heavier) were evaluated at birth. Weight, length, head circumference, anterior fontanel area, and combined ossification of the knee epiphyses were measured, and ponderal index (weight/length ratio) calculated. The most severely growth retarded infants had markedly decreased ossification and larger anterior fontanels.

Eleven pairs had physical measurements at one year of age. With individual exceptions, the lighter twins at birth remained smaller in all dimensions. Despite these persistent differences between twin pairs, the values for length at one year of age were within normal limits for both the heavierandlighter twins. Infants without ossification at birth had a greater incremental linear growth by one year than those infants with ossification.
A Search for Stratification-Free Association Between Plasma Lipids and HLA Using Dizygotic Twins
Authors: Winata S. S. , Biegel A. A. , Kang K. W. , Harmath F. , Christian J. C.
Published: July 2016

A total of 71 pairs of like-sexed dizygotic twins were studied, comparing within-pair differences for plasma total, free and esterified cholesterol, and triglyceride with the number of HLA haplotypes the twins had in common. If associations are present between HLA and the blood lipids studied, the twins with no haplotypes in common would be expected to have the largest within-pair mean square, those with two in common the smallest, and those with one in common an intermediate value. No significant differences were found comparing within-pair mean squares for the variables studied.