bluuebunny/crossref_metadata_2025 huggingface dataset:
Twin Studies of Coronary Heart Disease and Its Risk Factors
Authors: Berg Kåre
Published: July 2016

Traditional twin studies have resulted in higher concordance rates for premature coronary heart disease (CHD) in MZ than in DZ twin pairs. This is in agreement with strong evidence from several other studies, that genetic factors are of importance in the etiology of early onset CHD. Also, in a study of 291 Norwegian twin pairs the concordance rate for hypertension wa 0.36 in MZ and 0.08 in DZ pairs. Relationship between diseases and traditional gene markers have been extensively studied and several associations have been uncovered for CHD. Our group has developed a method to examine a possible permissive or restrictive effect of single genes on the degree of variation that environmental and/or life style factors can cause in a given parameter. This method for studying gene-environment interaction is based on the fact that MZ twins are identical with respect to genes, so that any difference between the two members of an MZ pair must necessarily be caused by environmental or life style factors. The possibility that a given gene influences the degree of variability in a parameter such as cholesterol is examined by comparing the within-pair difference in cholesterol level between MZ pairs possessing, and MZ pairs lacking the gene in question, and results of such studies will be presented. New possibilities to study restriction fragment length polymorphisms (RFLPs) at apolipoprotein loci have added a new dimension to research on genetics of CHD and hyperlipidemias. Association between apolipoprotein B, cholesterol and fasting triglyceride levels on one hand and DNA variation at the apolipoprotein B locus on the other has been found. We have studied RFLPs at apolipoprotein loci in twin families. The results are presented.
A Developmental Hypothesis for Adult Blood Pressure
Authors: Hewitt J.K. , Carroll D. , Sims J. , Eaves L.J.
Published: July 2016

Observed increases in phenotypic variance for blood pressure during adulthood are a predictable consequence of an a priori model for developmental change and continuity previously applied to cognitive development. The implications of this model for genetic and environmental covariances depend on the mechanism which maintains developmental continuity. Using data from young adult twins and their parents, it is shown how traditionally estimated genetic and environmental parameters may be reinterpreted in the light of the developmental model. Illustrative data suggest a hypothesis that genetic effects on blood pressure are largely temporally pleiotropic, acting consistently but not cumulatively throughout adulthood, while environmental influences act haphazardly but their effects are transmitted forward with high fidelity.
Unusual Vascular Malformation of the Kidney in Both Twins of a Monozygotic Pair: Short Case Report
Authors: Mastroberardino G. , Sciarra A. , Gualtieri R. , Di Fusco C. , Grammatico P. , Del Porto G.
Published: July 2016

A case of double bilateral renal vessels in both twins of a MZ pair is reported for the first time. Even in non-twins, the anomalies reported so far involved the inferior polar arteries in agreement with the embryological development. The two male twins, examined at the age of 14 years, had simultaneously developed a marked hypertension at the age of 7 years. Zygosity was determined by blood group and HLA analysis and various clinical tests were carried out to diagnose the condition. It is suggested that the anomaly is the result of a genetically induced early block in embryonic development.
Coitus-Induced Ovulation and Its Implications for Estimates of Some Reproductive Parameters
Authors: James William H.
Published: July 2016

It is estimated here that, at the time of conception, the mean coital rate of young women who subsequently bear DZ twins is about 6% higher than that of the general population of young married women. This differential seems too small to account wholly for the greater promptness in conceiving DZ twins. Accordingly, it is suggested that coital rate is associated with DZ twinning in two ways. The major link seems to be indirect and mediated by erotic response which causes an increase in gonadotrophin levels and thus in double ovulation. In a minority of cases, frequent coitus may give rise to DZ twins via superfecundation, but it seems that, in human beings, the corpus luteum of one ovum will usually inhibit fertilization of any further ova after a short interval. The evidence presented here, though indirect, seems to suggest that, under particularly erotic conditions, double ovulation is sometimes induced. It seems reasonable to infer that coitus also occasionally provokes or accelerates single ovulations, thus impugning some rhythm methods of contraception. But there seems no very good evidence that rape induces ovulation. Some notes are added on the implications of induced ovulation for estimates of fecundability and of the length of the fertile period.
Sense and Nonsense in Genetic Epidemiology: A Critique of the Statistical Model of Williams and Iyer
Authors: Heath A.C. , Martin N.G. , Eaves L.J.
Published: July 2016

The statistical model for the analysis of twin-family data of Williams and Iyer is examined. The model uses a large number of redundant parameters. It does not lead to quantitative predictions for new relationships. It allows for epistasisbut not dominance. It makes assumptions about assortative mating which are inconsistent with any biologically plausible mechanism. It assumes that the environmental correlation between parent and offspring is due to the direct effect of the parental genotypes, not phenotypes, on offspring environment. Other models which avoid these problems are more appropriate for the analysis of extended twin-family data.
Screening for Multiple Pregnancy Determination of Human Chorionic Gonadotropin (hCG), Alpha-Fetoprotein (α-FP) and Human Placental Lactogen (hPL) in Blood During the Second Trimester of Pregnancy
Authors: Vandekerckhove F. , Dhont M. , Thiery M. , Derom R.
Published: July 2016

The value of single determinations of serum hCG, hPL, and αFP for the detection of multiple pregnancy was investigated in a consecutive series of 992 women between the 14th and 24th week of pregnancy. With the 90th percentile as referent value, all twin pregnancies (n = 10) were detected by the combined results of the three determinations. Considered separately, hPL proved to be the most useful indicator of multiple gestation; the sensitivity of hPL alone was 70% and the predictive value of hPL concentrations above the 90th percentile was 8.1.
The Role of Parental Attitudes in the Development of Temperament in Twins at Home, School and in Test Situations
Authors: Hay D.A. , O'Brien P. J.
Published: July 2016

In the La Trobe Twin Study, data are collected on temperament and social development in 3-15 year old twins and singletons from four different sources: questionnaires to parents covering development from birth to the present plus the Bristol Social Adjustment Guide completed by the teacher, Sattler's Behavior and Attitude Checklist completed by the tester, and the Qualitative Score on the Porteus Maze Test. Particular stresses are identified which the parents perceive as distinguishing a multiple from a singleton birth. Whereas they perceive no differences between the first and second-born in birth complications, the second-born is judged less favourably particularly in MZ pairs. The distinction continues in the later assessments by the teacher and tester, where in addition the male twins are seen as being different from other children both in cognition and in temperament. It is proposed that social and cognitive development of twins are interrelated and have two unique components, one related to the greater problems accompanying a multiple birth and the other to comparisons between cotwins.
Does a Special Twin Situation Contribute to Similarity for Abilities in MZ and DZ Twins?
Authors: Vandenberg Steven G.
Published: July 2016

Evidence for and against the validity of the assumption of equal environments for MZ and DZ twins is reviewed, and the consequences of possible violations of the assumption are considered. Further methods of testing the validity of the assumption, as well as possible means of correcting in part for violations, are suggested.
Blood Uric Acid Level and IQ: A Study in Twin Families
Authors: Inouye E. , Park K.S. , Asaka A.
Published: July 2016

Applying newly devised model, heritability (VA/VP) of plasma uric acid level, corrected for age and sex and standardized, was estimated at 0.8 in families consisting of twin parents, spouses and children. Correlation between spouses due to common genotype (ρ) was approximately 0.1, and variance due to common familial environment (VEC/Vp) was -0.3. Analysis of families of selected twin children and their parents resulted in two estimates of heritability: approximately 0.7 and 0.3, ρ being 0.34 and 0.04, and VEC/Vpbeing 0.04 and 0.34, respectively. Regression of IQ (y) on corrected and standardized plasma uric acid level (x) in the twin children was y = 5.56x + 123, correlation being 0.334 (p < 0.025). The result indicates a genetic basis of blood uric acid level, which may have resulted from polymorphisms in purine metabolism pathway, end product of which is uric acid in man. The significant correlation between plasma uric acid level and IQ suggests a contribution of partly common gene loci to the two quantitative traits.
Swedish Early Separated Twins: Identification and Characterization
Authors: Pedersen N.L. , Friberg L. , Floderus-Myrhed B. , McClearn G.E. , Plomin R.
Published: July 2016

A sample of twins separated early in life has been identified in the Swedish Twin Registry. When the registry was compiled in 1961 (old cohort) and 1973 (young cohort), one or both members of 961 pairs indicated that they were separated by the age of 10. In May 1979, both members of 698 pairs were alive and were sent a questionnaire concerning the circumstances of separation. Items included reasons and timing of separation, biological relatedness of rearing parents, degree of contact after separation (including whether they lived in the same area, attended the same school, or lived together again), rough measures of selective placement, and current frequency of contact. An attempt was then made to categorize the pairs based on degree of separation. A total of 257 pairs met the criteria: rearing parents of one twin biologically unrelated to rearing parents of the cotwin, twins not living together again after separation, and contact after separation a few times a year or less. As much as 50% were separated by their first birthday, and 80% by the age of five. Various data from the twin registry are presented describing the entire sample of early separated twins as compared to a matched sample of twins reared together.
A Bivariate Path Analysis of Fear Data on Twins and Their Parents
Authors: Neale M.C. , Fulker D.W.
Published: July 2016

A simple path model applicable to twins and their parents and involving both cultural and genetic transmission in the presence of phenotypic assortative mating was extended to cover the bivariate case. The model allows for cross assortative mating as well as cross cultural transmission. It was applied to two correlated measures derived from a fear survey questionnaire given to 1000 subjects. In allowing for the impact of more than one variable, the model allows for a much more realistic picture of cultural transmission than provided by the univariate model. The logic of the model and an application are outlined. (The authors are indebted to Professor R.J. Rose for providing the illustrative data.)
Behavioural Genetics of Early Childhood: Fears, Restlessness, Motion Sickness and Enuresis
Authors: Abe K. , Oda N. , Hatta H.
Published: July 2016

Seventy-nine pairs of same-sex twins were examined at the age of three years at a municipal clinic and their mothers were interviewed to assess the twins' current and past behaviours. The zygosity was determined after the interview by fingerprints and/or bloodtyping in the majority of cases. The following significant differences in concordance between monozygotic and dizygotic twins were found: 1) fear of strangers during observation at the clinic; 2) marked fear of strangers in the first year of life; 3) whether or not the child was startled by sudden noises during infancy; 4) whether or not the child was able to sleep alone at three years without a parent sitting nearby; 5) susceptibility to motion sickness; 6) nocturnal enuresis; 7) short attention span or restlessness during the test.
Health Related Psychosocial Correlates of Neuroticism: A Study of Adult Male Twins in Finland
Authors: Koskenvuo M. , Langinvainio H. , Kaprio J. , Sarna S.
Published: July 2016

Some health related psychosocial correlates of the Eysenck neuroticism scale were examined in a questionnaire study of 1501 monozygotic (MZ) and 3455 dizygotic (DZ) male twin pairs representing the adult male twin population in Finland. In analyses of the individuals, 34% of the variance in neuroticism was associated to: psychological variables (stress of daily activities, life satisfaction, quality of sleep, and extroversion – the explanatory rate of this variable set was 30%), psychotropic drugs (5%), alcohol use (4%), and smoking (2%). Neuroticism was also associated to social, life change, and medical variables. In pairwise analyses, the heritability estimate (h2) was 0.54 for pairs living together and 0.39 for pairs living apart. It seems that heritability estimates are confounded by the closer intrapair relationship between members of MZ than DZ pairs. In pairwise analyses, 23% of the intrapair difference of neuroticism in MZ pairs was associated to intrapair differences in the aforementioned variables. The following explanatory rates were found: psychological variables, 21%; psychotropic drugs, 2%; alcohol use, 2%; and smoking, 1%. Neuroticism of pairs discordant for background variables showed similar intrapair differences as between individuals in the following variables: service vs farming work, use of alcohol, use of antacids, hypertension, heavy physical work, quality of sleep, changes of workplace for negative reasons, smoking, and use of tranquillizers. It appears that in Finland environmental factors explain at least 61% of the variability in neuroticism, and that factors determining neuroticism are also associated to health related behavior such as smoking, use of alcohol and psychotropic drugs.
Intrauterine Fetal Demise in Multiple Gestation
Authors: D'Alton M.E. , Newton E.R. , Cetrulo C.L.
Published: July 2016

Fifteen cases were reviewed over a five-year period at a perinatal centre with intrauterine demise of one member of a multiple gestation. Nine cases were monozygotic twin pairs, two were dizygotic, and two were triples. Gestational age ranged from 27 to 39 weeks. The management protocol consisted of delivery in all cases after confirmation of the diagnosis. In 4 cases delivery was immediate because of spontaneous labor. In the other cases elective delivery was performed if the gestational age was 37 weeks or greater or there was evidence of preeclampsia or if amniocentesis revealed a mature lecithinsphingomyelin (L/S) ratio. Steroids were given if the L/S was immature or the attempt at amniocentesis was unsuccessful and delivery was performed 48 hours after initiation of steroid therapy. Cesarean section was the mode of delivery in 14 of the 15 cases. All of the cotwins and cotriplets survived. One survivor of a monozygous twin pair has multicystic encephalomalacia possibly implicating perinatal arterial occlusion or in utero disseminated intravascular coagulation (DIC). The intrauterine deaths are categorized into possibly avoidable deaths (2/15), unavoidable due to congenital anomalies (3/15), and unknown or unavoidable deaths (8/15).
Antenatally Detected Klinefelter's Syndrome in Twins
Authors: Flannery D.B. , Brown J.A. , Redwine F.O. , Winter P. , Nance W.E.
Published: July 2016

An increased incidence of twinning has been reported among patients with Klinefelter's syndrome (XXY) and their relatives, but no data have been reported about the incidence of XXY among twins. Results from our institution's antenatal testing clinic provide data about twins and XXY. In 1842 pregnancies tested, 21 were noted to be twin gestations. Five fetuses with XXY were detected in all pregnancies, of which there was a pair of MZ twins concordant for XXY and a pair of DZ twins discordant for XXY. The incidence of XXY in twins was thus 7,1%. The fetal phenotype of XXY was examined in aborted MZ twins and found to be mild. Notably, the testicular histology was normal. These cases confirm the previously reported association of twinning and XXY. The association of twinning and XXY implies a commonality of causation; however, a maternal age effect cannot be excluded. Our data suggest that there is an increased risk of XXY among twins.
Situs Viscerum Specularis in Monozygotic Twins
Authors: Gedda L. , Sciacca A. , Brenci G. , Villatico S. , Bonanni G. , Gueli N. , Talone C.
Published: July 2016

A case is reported of a 14-year old male MZ twin pair, with only one partner affected by situs viscerum inversus, whereby the condition is termed situs viscerum specularis. The high degree of mirror imaging is seen as an abnormal variation of the biological time of the cleavage giving rise to MZ twinning. Electrocardiographic findings are presented and the biological implications of the condition are discussed.
Multiple Birth Rates in Japan: Further Analysis
Authors: Imaizumi Y. , Inouye E.
Published: July 2016

The rates of MZ and DZ twin births and of triplet births slightly decreased in Japan in 1955-1967 and 1974, whereas that of trizygotic triplets tripled. The rates of triplet and quadruplet births were comparable to those of Caucasians. Although the sample size is small, Japan seems to be characterized by higher rates of triplets and quadruplets of polyembryonal origin and lower rates of those of polyovulational origin as compared to Caucasian populations. Stillbirth rates in both MZ and DZ twins gradually decreased in 1960-1967 and 1974. The rate was higher in MZ than DZ twins, and higher in males than females. The secular trends of stillbirth rates in like-sexed triplets was similar to that in twins, whereas the rate in unlike-sexed triplets remained almost constant for the entire period. The rate was higher in like-sexed than unlike-sexed triplets.
The Factors That Influence Twinning Rates
Authors: Nylander Percy P. S.
Published: July 2016

In a study carried out in an African population in Western Nigeria and a Caucasian population in Aberdeen, Scotland, it was found that DZ twinning rates varied with maternal age and parity, the MZ twinning rate remaining fairly constant. However, women aged 30–34 were found to have the highest rate in Western Nigeria whereas the peak in Aberdeen population occurred in the older age group, 35–39 years. Other factors that influenced DZ twinning rates were maternal height, social class and ethnicity (in the Nigerian population), and illegitimacy (in the Aberdeen population). No significant association was found between twinning and maternal blood groups or season of the year in either of the two populations. An important factor that also influenced twinning in the two populations was the maternal serum FSH level. The levels were much higher in the Nigerian population than in the Aberdeen population. Furthermore, in the Aberdeen population, twin-prone and non-twin-prone women had similar serum FSH levels, whereas the levels were much higher in twin-prone women in the Nigerian population. This finding is consistent with the fact that the Nigerian population has a much higher twinning incidence (approximately 50 per 1,000 maternities) than Aberdeen population (approximately 12 per 1,000 maternities).
Analysis of Multiple Birth Rates in Japan. II. Secular Trend and Effect of Birth Order, Maternal Age, and Gestational Age in Stillbirth Rate of Twins
Authors: Imaizumi Yoko , Asaka Akio , Inouye Eiji
Published: July 2016

Stillbirth rates of MZ and DZ twins in Japan gradually decreased during the period 1960–1967 and in 1974. The stillbirth rates of MZ and DZ twins were 0.270 and 0.224 in 1960, respectively, whereas the corresponding figures in 1974 were 0.135 and 0.099. The stillbirth rate was higher in MZ than DZ twins, in males than females, and in the second- than in the first-born. In both zygosities, the rates were higher in the first birth order than in the second, and then increased with birth order except in the sixth birth or more for MZ twins and for DZ twins born to mothers aged 35–39 years. The shorter the gestational age, the higher the stillbirth rate in both MZ and DZ twins, as expected. Mean gestational age was slightly shorter in MZ than in DZ twins. The decrease of the stillbirth rates can be explained partly by the reduction of twins with higher birth order, where high stillbirth rates of MZ and DZ twins are seen, and the reduction of older mothers.
Genetic and Environmental Determinants of 17 Serum Biochemical Traits in Brazilian Twins
Authors: Colletto Gloria M.D. Dal , Krieger Henrique , Magalhães José Reinaldo
Published: July 2016

The genetic and environmental effects on the levels of 17 serum biochemical quantitative traits (calcium, phosphorus, glucose, urea nitrogen, uric acid, total protein, albumin, total bilirubin, alkaline phosphatase, lactate dehydrogenase (LDH), glutamic-oxaloacetic transaminase (SGOT), total lipid, cholesterol, triglyceride, α-lipoprotein, pre-β-lipoprotein and β-lipoprotein) were estimated in 105 pairs of healthy twins of both sexes (57 MZ and 48 DZ) by path analysis. The genotype effectwas significant for all traits (P < 0.001) and its value extended from 0.52 (α-lipoprotein) to 0.81 (alkaline phosphatase), whereas environmental effectwas significant (P < 0.05) in only 10 traits of the 17 analyzed, with the maximum value of 0.13 (cholesterol). Correlations between genotypes of paired traits were estimated and, of 136 values, 47 were significant at the 5% levels, thus indicating partial and common genetic mechanisms.
Congenital Anomalies in Twins in Aberdeen and Northeast Scotland
Authors: Corney G. , MacGillivray I. , Campbell D.M. , Thompson B. , Little J.
Published: July 2016

Data with regard to the proportion of congenital malformations found at birth are presented from a survey of 657 pairs of twins of known zygosity and placentation delivered in Aberdeen and Northeast Scotland between 1968 and 1979. There was an excess of malformed individuals from monozygotic (MZ) pairs, but this did not reach statistical significance. The possible effect of monochorionic placentation in the causation of malformations in MZ twins in general is discussed. It seems that this type of placentation may be of less causative importance than has been previously suggested.
Genetic and Environmental Influences on Body Measurements of Belgian Twins
Authors: Dupae E. , Defrise-Gussenhoven E. , Susanne C.
Published: July 2016

A study of 100 MZ and 67 DZ twin pairs aged 18 to 25 years has shown a highly significant genetic contribution to the following measurements: standing and sitting height; height on tragus; arm length; biacromial, biiliac, and bitrochanteric diameter; weight; circumference of thigh and of upper arm relaxed and contracted; and head length and breadth. The twins were brought up together and of the same socioeconomical, geographical, ethnical, and cultural origin. Zygosity diagnosis was based on 22 to 26 blood groups. The means of the measurements were smaller in MZ than in DZ twins, some of them significantly so. The intraclass correlation coefficients of the MZ cotwins were all significant and greater than those of the DZ cotwins. In families of same geographical origin, sib-sib correlations were somewhat smaller than those of the DZ cotwins, but for the three diameters of the body the order was reversed.
Uterine Growth in Twin Pregnancy by Measurement of Total Intrauterine Volume
Authors: Redford David H.A.
Published: July 2016

Total intrauterine volume (TIUV) was determined serially in 27 twin pregnancies from which a nomogram was constructed. At the beginning of the second trimester, TIUV was similar to that in singleton pregnancy; by the 18th week it had become twice as large, and remained so until late in pregnancy. Labor was preceded more frequently by a slowing than by an acceleration of uterine growth.
Multiple Gestations:Management of Pregnancy and Delivery
Authors: Loucopoulos Andrew , Jewelewicz Raphael , Wiele Raymond L. Vande
Published: July 2016

The antenatal management and outcome of 31 higher-order multiple gestations, 24 triplets, six quadruplets, and one set of quintuplets were analyzed. Bedrest was advised as soon as the diagnosis was made; hospitalization along with the administration of betamethasone and phenobarbital was begun during the second trimester. Caesarian section was performed on 13 women (42%). The overall mortality rate was 14.8%; excluding neonates less than 28 weeks of age, however, it became 7.5%. The primary cause of death was respiratory distress syndrome.
Clustering of Twin Births in Space and Time
Authors: Zahálková Milada
Published: July 2016

Out of a total of 1025 twin births occurring in 11 South Moravian districts from 1972 to 1976, 638 occurred in the same time and space interval (P = 0.00037). The observed clustering suggests the existence of environmental factors influencing twinning rates.
Anaemia in Twin Pregnancy
Authors: Hall Marion H. , Campbell Doris M. , Davidson Ronald J.L.
Published: July 2016

A total of 123 twin pregnancies were studied, 68 by records analysis only, and 55 by serial haematological assessment in detail. The incidence of low haemoglobin levels is found to be greater than in singleton pregnancy; evidence of iron and folic acid deficiency is common in sternal marrow aspirates but not in peripheral blood films. Routine haematinic prophylaxis in twin pregnancy is not advocated.
The Value of Measurement of Pregnancy-Specific Proteins in Twin Pregnancies
Authors: Jandial V. , Horne C. H. W. , Glover R. G. , Nisbet A. D. , Campbell D. M. , MacGillivray I.
Published: July 2016

In this study of 53 twin pregnancies, the plasma concentrations of the placental proteins, placental lactogen (hPL), and pregnancy-specific glycoprotein (SP1) were measured. Placental lactogen was found to be of more value than SP1 both in the detection of twins and in assessment of fetal growth. Serial measurement of either protein would seem to be more useful in assessment of fetal growth than single measurements. Preliminary studies of the less well known placental protein, PP5, in a small series of twin pregnancies indicate that it may also prove to be of clinical value in the detection and monitoring of twin pregnancies.
Towards a Normalization of the Outcome of Twin Pregnancy
Authors: Persson Per-Håkan , Grennert Lars
Published: July 2016

During 1973/1978, more than 90% of the pregnant women in Malmö, Sweden, were examined by ultrasound to improve the early diagnosis of twin pregnancy. This screening programme detected 90% of the twin pregnancies delivered during this period, 105 were subjected to a preventive treatment with bed rest in hospital, usually from the 29th to the 37th week (mean: 55 days). This study evaluates the outcome of these pregnancies, compared with those not treated with bed rest and with all twin pairs born a decade earlier (1963/1965). All twins of this group born up to 1 May 1977 were also monitored by regular postpartum check-ups until at least 18 months of age. Perinatal mortality was reduced to 0.5% in the group with bed rest, but remained as high (8%) as ten years earlier in the group without bed rest. The bed rest group, compared with the group without bed rest and the group of twins born 1963/1965, also showed a significantly reduced frequency of deliveries before the 37th week; also, the incidence of twins born light-for-gestational age and with birth weight below 1500 g was reduced. The incidence of twins born with cerebral palsy, mental retardation, and late development was 3% in 1973/1977 and 8.1% in 1963/1965. The reduction of mortality and morbidity of twins paralleled the improved obstetric and neonatal care. The fact that perinatal mortality and preterm delivery were reduced only among twins subjected to special antenatal supervision suggests that large gains are to be made by early detection and antenatal hospitalization. The lower CNS morbidity provides evidence of the quality improvement among the twin survivers.
The Effect of Zygosity on the Birth Weight of Twins in Aberdeen and Northeast Scotland
Authors: Corney G. , Thompson B. , Campbell D.M. , MacGillivray I. , Seedburgh D. , Timlin D.
Published: July 2016

Birth weight data for 356 pairs of newborn twins of known zygosity and placentation are presented. The combined weights of dizygotic twins are heavier than those of monozygotic twins. The significance of this finding is discussed in relation to the association between increased maternal height and dizygotic twinning.
Optimization Procedures in Twin Zygosity Diagnosis by Genetic Markers. A Cost-Effectiveness Analysis
Authors: Sarna Seppo , Kaprio Jaakko
Published: July 2016

More and more genetic markers usable for twin zygosity determination have become available. A relatively small number of markers is sufficient to achieve a satisfactory probability of correctly classifying a twin pair. Previously only the genetic properties of markers have been considered when choosing the markers to be determined. A cost-effectiveness analysis, which considers both genetic properties and relative determination costs of markers, is presented and illustrated with data from the Finnish Twin Registry studies.
Glomerular Filtration Rate and Electrolyte Handling in Response to Sodium Loading and Depletion. A Twin Study
Authors: Grim C.E. , Miller Judy Z. , Christian Joe C.
Published: July 2016

Possible genetic influences on glomerular filtration rate and electrolyte excretion were investigated in 55 (37 monozygotic, 18 dizygotic) young adult white twin pairs. Subjects were studied during a five-day hospitalization involving sodium loading and sodium depletion. No evidence of genetic variability was found in the control levels of serum or urine sodium and potassium. Following a saline infusion it was possible to detect genetic influence in electrolyte handling. Creatinine clearance, used as a measure of glomerular filtration rate, did not appear to be genetically mediated. The results indicate that genetic factors are important in sodium handling in normal individuals and that this is independent of glomerular filtration rate.
Effects of Type of Placentation on Birthweight and its Variability in Monozygotic and Dizygotic Twins
Authors: Corey L.A. , Nance W.E. , Kang K.W. , Christian J.C.
Published: July 2016

Birthweight was measured on 188 monochorionic monozygotic, 54 dichorionic monozygotic, 102 like-sexed dizygotic, and 94 unlike-sexed dizygotic liveborn twin pairs. Overall, males were found to be significantly heavier than females. These differences were not significant, however, when birthweights were compared within zygosity/chorion-type categories. Males were also characterized by a slightly greater overall total variance. Comparisons of intrapair variation of monochorionic and dichorionic monozygotic twins revealed significant differences between monochorionic pairs and dichorionic separate pairs and no significant differences between monochorionic pairs and dichorionic fused pairs. The results of this study suggest that placental proximity may have as important an influence on variation in birthweight as does the presence or absence of vascular anastomoses.
ABO Saliva and Plasma Agglutinins in Twins
Authors: Callegari Sidia M. , Salzano F.M. , Peña Heloisa F.
Published: July 2016

The levels of ABO plasma agglutinins were studied in 47 MZ and 30 same-sex DZ pairs of twins having the same blood group. The degree of genetic determination of this characteristic, as ascertained by the comparison of average titers and titration scores, does not seem to be high; despite the fact that the correlation coefficients were always lower among DZ, theFratio was significant in relation to the anti-B of A persons only. The presence of these antibodies was also investigated in the saliva of 30 MZ and 26 DZ pairs. Since about the same degree of discordance was observed among these two types of twins, the role of inheritance in the variability of this trait must be low.
Taste Sensitivity to Phenylthiourea Among Leprosy and Filarial Patients in Coastal Andhra Pradesh
Authors: Busi B.R.
Published: July 2016

Taste blindness for PTC has been studied in (a) 416 leprosy patients and 424 healthy subjects, and (b) 261 filarial patients and 136 normal individuals of both sexes. A significant difference was found between leprosy patients and the healthy control group in the proportion of nontasters (χ2 = 4.096, for 1 DF, P〈0.05). No significant difference could be observed between the filariasis and the control group (χ2 = 0.605, for 1 DF, P〉0.30).
The Fingerprints of the Sayyads of Lucknow Uttar Pradesh
Authors: Srivastava A.C.
Published: July 2016

A study of the fingerprints of the Sayyads of Lucknow district, Uttar Pradesh, has given the following frequencies: whorls 40.87%, loops 56.33% and arches 2.80%. The mean pattern intensity is 13.81 ± 0.27, showing no significant differences with neither the upper nor the lower-caste Hindus of U.P., excepting the Purabia Chamar.

As for the ridge count, the Sayyads show a mean of 151.52 ± 3.62, which is highest as compared to Hindu populations of U.P. However, no significant differences are apparent between the Sayyads and Brahmins, Rajputs, and Ahirs. The Sayyads are found to differ significantly from the earlier Muslim sample reported by Singh (1961).

A comparison of the Sayyads with their coreligionists residing in the distant lands from India fails to reveal consistent dermatoglyphic affinities.
Twins in Nature, Science, and Society
Authors: Gedda Luigi
Published: July 2016

Signor Presidente della Repubblica Italiana,

Signor Sindaco,

Signor Ministro,

Eccellenza Rev.ma,

Signori Ambasciatori,

Signor Preside della Facoltà Medica dell'Università di Roma,

Onorevoli Autorità, Congressisti di 30 Nazioni, Gemelli e Amici dei Gemelli,

Nel settembre del 1953 veniva inaugurato in Roma l'Istituto di Genetica Medica e di Gemellologia Gregorio Mendel.

Per i vent'anni dell'Istituto Mendel abbiamo aperto la celebrazione con il Congresso Internazionale di Neurogenetica ed ora la chiudiamo con il Primo Congresso Internazionale di Studi Gemellari. La Neurogenetica come specializzazione della Genetica Medica e gli Studi Gemellari come espressione scientifica della Gemellologia inquadrano bene il significato del lavoro che l'Istituto Mendel va sviluppando, e la vostra presenza, cosí autorevole, significativa e cordiale, dona il più ambito coronamento civico, scientifico e umano al ricordo della nostra fondazione.

Noi vi ringraziamo con semplicità ma con schiettezza e rispettosamente ringrazio il Capo dello Stato per il prestigio della sua carica e della sua persona, ed anche perché proviene da una regione italiana, la Campania, che batte il record per la frequenza dei gemelli nella popolazione (25‰). Come ringrazio sentitamente il Sindaco che ci permette di aprire il Congresso in Campidoglio, luogo che ha il potere, come nessun altro al mondo, di evocare e sublimare quella singolare condizione umana che consiste nella gemellità: l'essere gemelli. Qui vi è la lupa che dà il suo latte ai gemelli dimostrando che la fiera è pietosa più della donna che espone i suoi figli alla morte. Qui sono Romolo e Remo che il mito esalta come fondatori di città, Romolo di Roma e Remo di Siena.
Retrospective Studies on the Twinning Rate in Scandinavia
Authors: Eriksson A.W. , Eskola M.R. , Fellman J.O.
Published: July 2016

The rates of human multiple maternities in the Nordic countries were studied from continuous series of data. In the Åland and Åboland archipelagos the parish records for births and baptisms since the 1650's were used. Various sources, some unpublished, in the archives of statistics were used for Sweden (since 1749) and Finland (since 1859) as a whole. Until recently, the rates of multizygotic multiple maternities in isolated island populations in the Åland and Åboland archipelagos have been some of the highest known among Whites (15-20‰). Highly significant temporal fluctuations in the twinning rates were noted. In Sweden, the twinning rate during the last part of 18th century was about twice as high as it was in 1966-70. The triplet and quadruplet rates were about three to four times as high as they are nowadays. There has been a secular decline in DZ twinning. This downward trend set in first in the isolated populations. In Sweden, it started in the 1930's, but in Finland, not until the 1960's. The steep downward trend in the twinning rates is shown to set in about one generation after the break-up of isolation. This can be interpreted as evidence that the changes in matrimonial migration patterns have affected the rates of DZ twinning.
Biology of the Twinning Phenomenon: Embryogenesis and Teratogenesis
Authors: Lutz Hubert
Published: July 2016

The twinning phenomenon has always interested the great public, the artists, and naturally the scientists. Isidore Geoffroy St. Hilaire has established a classification still now valid. This classification considers the different types of double monsters which are found in nature in all classes of vertebrates, including man. To explain the twinning phenomenon, the experimental realizations have progressed by successive bounds after the preliminary attempts of different authors. Now, when it is question of experimental duplication, anybody thinks of Speman for the amphibians, of Lutz for the birds, of Seidel for the rabbit, and of Tarkowsky for the mouse. Now, it is possible to conceive a twinning resulting from the separation of the first blastomeres (amphibian, rabbit, mouse) and a twinning originating from the fissuration of the blastoderm (bird, mammal). All these experiments confirm the unicist-theory. If a total or partial regulation of the excedents may be experimentally realized, no argument can however support this theory in the realization of the double monstrosity.
Familial Twinning: A Case for Superfetation in Man
Authors: Rhine S.A. , Nance Walter E.
Published: July 2016

A family is described in which the tendency to bear twins is expressed in the offspring of males as well as females. All of the twins born in this family show marked discordance in birth weight and gestational age. In 5 of the 6 pairs, one twin was normal while the other was either a macerated fetal mass, stillborn, or died of prematurity in the neonatal period. The one pair in which both twins did survive is known to be DZ and showed a difference in maturity and a 21% discrepancy in birth weight. Thus, twinning in this family appears to be transmitted as an autosomal dominant trait which is expressed in the offspring of both female and male carriers. Of all possible genetic mechanisms which could explain this familial aggregation of markedly discordant twins, supcrfetation seems most consistent with the genetic transmission and expression of the trait in the offspring of both males and females. The most plausible explanation of the pedigree is that a dominant gene is segregating in the family which is expressed in the fetal placenta where it acts to reverse the normal hormonal inhibition of ovulation. Since both the father and the mother contribute to the genotype of the placenta, superfeiation could occur among offspring of both males and females who carry the gene.
The Problem of Genotype-Environment Correlation in the Estimation of Heritability from Monozygotic and Dizygotic Twins
Authors: Jensen Arthur R.
Published: July 2016

It is commonly, but incorrectly, assumed that the presence of genotype × environment covariance must necessarily reduce the heritability (h2) as estimated from twin data, when the formula used to obtain h2 makes no assumption about G × E covariance or assumes that it is zero. But, in fact, G × E covariance does not always reduce the genetic variance, and it can be shown under some conditions, an increase in the G × E covariance implies a greater genetic variance. The effect of G × E covariance on h2 as estimated from data on MZ and DZ twins, depends jointly upon the degree of assortative mating and the degree of environmental correlation between MZ twins and between DZ twins. A method, based on the solution of a pair of simultaneous quadratic equations, is proposed for estimating the range of h2 from twin data under varying assumed values for assortative mating, the environmental correlations between MZ and DZ twins, and the G × E covariance. The solution of three simultaneous equations permits direct estimation of the genetic variance, environmental variance, and G × E covariance, under varying reasonable assumed values for assortative mating and the MZ and DZ environmental correlations. Examples of the method are based on intelligence tests scores of MZ and DZ twins.
Alcohol Consumption in Relation to Factors Associated with Ischemic Heart Disease - A Cotwin Control Study
Authors: Myrhed Marten , Floderus Birgitta
Published: July 2016

Moderately alcohol-discordant male twin pairs, aged 45-65 years, have been examined with respect to ischemic heart disease (IHD) and associated factors. No conclusion can yet be drawn with regard to manifest or subclinical IHD, while significant disparities were found with regard to systolic and diastolic blood pressures, high cigarette consumption, hyperglycemia, and serum cholesterol; the greater number of findings of pathological values were found in the high alcohol-consumption as compared to the low alcohol-consumption cotwins. These findings offer a possible explanation for the increased number of reports showing a connection between high consumption of alcohol and occurrence of ischemic heart disease.
Genetic Variance in Blood Pressure
Authors: Borhani N. O. , Feinleib M. , Garrison R.J. , Christian J. C. , Rosenman R. H.
Published: July 2016

The National Heart and Lung Institute Twin Study has examined 514 white adult male twin sets aged 42-56 with respect to blood pressure. The data were analyzed by a method of Christian et al. which eliminates possible biases in estimated genetic variances that could result from different total variances in MZ and DZ twins. Results of the test for the presence of genetic variance indicate that both systolic and diastolic blood pressure are to a considerable extent genetically controlled with an estimated heritability of 0.8 for systolic and 0.6 for diastolic pressure. Although these findings are at variance with some previous reports, it is thought that much of the discrepancy results from application of different analytic techniques, not in the data themselves. The application of these findings to our understanding of hypertension epidemiology and community hypertension control programs are discussed.
Plasma Protein Variability in MZ Twins
Authors: Milani-Comparetti M. , Saccucci F.
Published: July 2016

A previous study had shown that only MZ twins are easily exchanged by trained police dogs. This is certainly due to the superimposability of the biochemical basis of body scent. A different approach has now been tried, based on plasma protein fractionating procedures. A pilot study has shown that PolyAcrilamide Gel Electrophoresis (PAGE) results, as expected, in widely different patterns only in DZ twin pairs. Plasma specimens from a sample of 55 supposedly MZ twin pairs were analysed by PAGE. The substantial superimposability of MZ cotwin patterns was confirmed. Analysis of the different fractions indicates the extent of environmental variability. Application to zygosity determination is suggested.
Dermatoglyphic Investigations in Twins and Siblings
Authors: Plato C. C. , Schwartz J. T. , Wertelecki W.
Published: July 2016

The present report describes the preliminary results of an extensive dermatoglyphic investigation among 491 pairs of MZ and DZ twins, and sibs of both sexes. Paired homolateral comparisons were performed for the determination of the degree of discordance for each dermatoglyphic trait and the results were presented in a series of histograms. Some of the outstanding points brought forth by this study are: (1) different dermatoglyphic traits at different digits or palmar areas have different degrees of discordance; (2) in MZ twins the frequency of discordance for each trait is constant regardless of sex or laterality, whereas in DZ twins and sibs both sex and lateral differences are observed; (3) the higher number of significant differences in concordance between the MZ twins vs. sibs than between MZ vs. DZ twins suggests that, at least in the female, the dermatoglyphics may be affected by changing intrauterine environments.
Psychological Follow-up Study of Twins from Birth to Five Years
Authors: De Coster W. , Lerou J. , Dutoit C. , De Zutter M. , Derom R. , Thiery M. , Vandierendonck A.
Published: July 2016

Classical psychological twin studies have yielded in part equivocal and sometimes contradictory results. Besides the complexity of the problem, the delicate character of the diagnosis, and the rudimentary tools which were used, several other factors are underlying this situation: (1) insufficient systematization of the set-up and the careless design of the investigations; (2) lack of follow-up studies; (3) uncertain diagnosis of zygosity; in MZ twins no attention to the age of the ovum at the time of cleavage; (4) lack of consideration for antenatal and perinatal influences; (5) no attention to the typical circumstances linked to the twin situation. All this makes it difficult to balance nature against nurture on the basis of comparison between MZ twins, DZ twins, and singletons. Interactions may also appear between the effect of twinning and other factors such as the socioeconomic circumstances. A new investigation was therefore started where, besides the twins, a group of matched control singletons was constituted. The follow-up study is now completed up to the age of 5 years in 13 MZ and 20 DZ twin pairs (+ controls, that is to say, 99 children).

The children were observed and subjected to psychological tests at the age of 6 months and of 1, 2, 3, 4, and 5 years.
Twin Resemblances in Creativity and in Esthetic and Emotional Expression
Authors: Barron Frank , Parisi Paolo
Published: July 2016

Three sources of observation relevant to the measurement of individual differences in emotional and esthetic expressiveness were employed to study their heritability by application to a sample of some 60 pairs of young adult like-sexed twins, approximately evenly divided between male and female and MZ and DZ pairs. The sources of observation were objective test performances, trait ascription using a standard list of adjectives, and videotaped enactments of mood and esthetic performances. Perceptual and esthetic abilities do appear to have substantial heritability, although esthetic preferences do not. Heritability is also indicated for such adjectives as artistic, inventive, original, and independent. Ratings of the videotape performances yielded somewhat ambiguous results, due to the presence of a marked halo effect; the most likely interpretation congruent with earlier results is that greater MZ twin resemblances in social extroversion generated greater resemblances in the videotape situation on such other trait-rating variables as creativity, naturalness, and dominance.