bluuebunny/crossref_metadata_2025 huggingface dataset:
Twinning Rate by Month of Mother's Birth in Japan
Authors: Miura T. , Nakamura I. , Shimura M. , Nonaka K. , Amau Y.
Published: July 2016

Records of two hospitals and of an association of mothers of twins were analysed for the years 1924-1980, finding a total of 656,109 and 1185 twin births, respectively. Twinning rates were higher in summer or fall, in general, but these seasonal variations occasionally changed within a short period of years, as in 1973-75 in the Association group. The twinning rate was also affected by the month of mother's birth. It was low among the mothers born around May-July in maternities up to 1960, and these mothers did not show seasonal variation of twin births. The unlike-sexed twinning rate of the mothers born in May-July was also lower than that of the other mothers, and constantly low even at higher maternal ages. A possible explanation for these phenomena is discussed.
On the Distribution of Nonrighthandedness Among Twins and Their Families
Authors: Boklage Charles E.
Published: July 2016

In 773 three-generation families of twins, individual probability of nonrighthandedness (NRH) depends significantly on the handedness of that individual's parents. The parents of twins are much more often NRH than are their nontwinbearing siblings. The twins and their siblings apparently inherit the excess liability for NRH shown by their parents. Monozygotic (MZ) pairs are significantly about twice as often concordant (casewise) for handedness as dizygotic (DZ) pairs. Overall, the best-fitting mode of transmission is autosomal, NRH dominant to RH with penetrance of about 50% in the heterozygote, or multifactorial, with heritability of 60–70%. Under the major-gene approach, heterogeneity seems likely, with about one-third of the families showing no NRH outside of the twin sibships. MZ/DZ concordance ratio is about four in those families, suggestive of recessive inheritance. A 1.16-fold excess of NRH in twins compared to their siblings, and a 1.8-fold excess in the second-born members of same-sex discordant pairs, leaves open the possibility that a minor portion of NRH in twins may be secondary to transient hypoxia and/or acidosis.
A Study of Dietary Intake in Adult Monozygotic Twins
Authors: Corey Linda A. , Nance Walter E.
Published: July 2016

As a part of a study of the dietary habits of monozygotic twins, a nutrition survey including a 24-hour dietary recall interview and a three-day dietary diary was conducted on the members of 15 male and 13 female pairs of identical Caucasian twins ranging from 25 to 61 years of age. In this study, overall mean caloric, protein, fat, and carbohydrate intake of males was significantly greater than females. Members of male twin pairs also tended to be more similar than female twins in mean intake of all major nutrient groups. In general, the observed differences in overall intake between males and females were maintained even after adjustment of body weight. Male twins were characterized by greater similarity in intake of sodium and potassium; however, there was no consistent difference in the degree of correlation in intakes of members of male and female twins for either iron, calcium or phosphorus.
Plasma Lipid Variability in the Toronto Twin Register
Authors: Milner Jean , Christian Joe C. , Hewitt David
Published: July 2016

Plasma lipids were studied on 92 pairs of twins (66 MZ and 26 like-sexed DZ). The DZ twins had significantly greater total variance than the MZ twins for total plasma cholesterol but not for triglycerides or the high, low, and very low-density lipoprotein cholesterol fractions.
Sex Differences in the Inheritance of Some Anthropometric Characters in Twins
Authors: Clarke P. , Jardine R. , Martin N.G. , Stark A.E. , Walsh R.J.
Published: July 2016

Biometrical genetical techniques have been applied to the analysis of certain anthropometric characters measured in 134 pairs of adult twins. After allowing for assortative mating it appears that there is a family environment (E2) component for variation in height larger than previously reported. “Fatness” traits – weight, ponderal index, and skinfold thickness – all show higher heritabilities in males and substantial E2components in females, and reasons for this are discussed. The same is true for cephalic index and forearm length but the reason for these differences is not so obvious. Head length shows a much higher heritability than head breadth. A larger sample of DZ opposite-sex pairs would allow more powerful discrimination, but the variety of patterns of variation revealed by the model-fitting approach used here justify its use over more traditional techniques.
A Note on Ascertainment Probability in the Allen/Hrubec Twin Model
Authors: Holm Niels V.
Published: July 2016

In their general model of twin concordance Allen and Hrubec recently introduced the concept of secondary ascertainment rate to consider partial ascertainment of secondary cases. This concept is found to be of limited interest because only pairs where valid information can be obtained from both twins should be included in genetic analyses. It is furthermore shown that the validity of the proband method and the Allen/Hrubec model depends on the equivalence of ascertainment in twins from concordant and discordant pairs. However, if this condition is fulfilled, it has been shown how the ascertainment probability in cotwins of probands is related to the overall ascertainment probability in the total twin population.
Intrauterine Growth Charts for Twin Fetuses
Authors: Leroy B. , Lefort F. , Neveu P. , Risse R.J. , Trévise P. , Jeny R.
Published: July 2016

In addition to centile curves for birth weight and height of single infants, the authors offer similar biometric references for twins derived from a large French data base. The aim of the work is to assist in discovering small-for-date twins. In the actual prenatal environment, the curves show a decrease in the evolution of these growth parameters in comparison with the single pregnancy standards as early as the 30th week of pregnancy.
Preterm Deliveries in Twin Pregnancies in Aberdeen
Authors: MacGillivray Ian , Campbell Doris M. , Samphier Michael , Thompson Barbara
Published: July 2016

The incidence of preterm delivery was 28.2% of all twin deliveries. Preterm delivery was common in monozygotic twins due to a high incidence of spontaneous rupture of the membranes. In addition, preterm delivery was associated more often with boy rather than girl infants.
Maternal Nutrition in Twin Pregnancy
Authors: Campbell Doris M. , MacGillivray Ian , Tuttle Sheena
Published: July 2016

Energy and protein intake as measured by 24-hour urinary nitrogen values are similar in twin and singleton pregnancies. The relationship between urinary nitrogen and nitrogen intake is equally significant in twin and singleton pregnancies. Dietary zinc, copper, and iron are not different in women with twins, nor are the levels of these elements in plasma. These observations are surprising in view of the extra fetal demands on the mother and the different adaptation of twin pregnancies.
Fetal Adrenal Gland Maturation in Growth-Retarded Twin Pregnancies
Authors: Norman R.J. , Joubert S.M.
Published: July 2016

Twenty-two twin pregnancies each with one growth-retarded and one normal twin fetus were examined to determine the effects of fetal growth retardation on the maturation of the adrenal gland with respect to cortisol and dehydroepiandrosterone sulphate (DHEAS). The growth-retarded twin fetuses (IUGR) had lower umbilical arterial concentrations of DHEAS than their siblings (IUGR 5.25 ± 2.4; non-IUGR 6.51 ± 2.9 μmol/l; p < 0.01), whereas cortisol concentrations were not statistically different (no labor, IUGR 1,134 ± 751, non-IUGR 1,140 ± 958 μmol/l; labor IUGR 2,062 ± 929, non-IUGR 1,609 ± 469 μmol/l). These data suggest that while the definitive zone of the fetal adrenal is as well-developed as in non-growth-retarded twins, the fetal zone shows reduced secretory capacity of Δ5-steroids. This supports the hypothesis that in growth retardation the adrenal gland shows features of increased maturation.
A Model for the Analysis of Mate Selection in the Marriages of TwinsApplication to Data on Stature
Authors: Nance W. E. , Corey L. A. , Eaves L. J.
Published: July 2016

Analysis of the multiple correlations in body height within a sample of 117 monozygotic twin pairs and their spouses confirmed the existence of a high degree of assortative mating. However, the data also revealed an underlying asymmetry in the mate selection process. With respect to height, male twins were more selective than were members of female pairs, and among male twin pairs, those who were intermediate in height appeared to make the greatest contribution to the observed pattern of nonrandom mating. Because of their magnitude and potential asymmetry, the effects of phenotypic correlations between the spouses of related individuals must be correctly specified in any rigorous quantitative genetic analysis that extends beyond the nuclear family unit.
Estimates of Genetic Variance for Anterior Fontanelle Development in the NCPP Twin Population
Authors: Melnick Michael , Myrianthopoulos Ntinos C. , Christian Joe C.
Published: July 2016

There are several dynamic influences on anterior fontanelle development in infants; among them, brain growth, dural attachments, suture development, and osteogenesis. It thus seems reasonable to hypothesize that variation in anterior fontanelle development between infants, related and unrelated, might have a significant genetic component. Anterior fontanelle size was quantitated by the method of Popich and Smith for 94 monozygotic (MZ) and 187 dizygotic (DZ) four-month-old twin pairs. The general model for estimating genetic variance from quantitative twin data was applied to MZ and DZ twins and then separately by chorion type. Since there were significant mean differences between blacks and whites, races were analyzed separately. The within-pair mean square estimates of genetic variance (ĜWT) were highly significant for both blacks (P < 0.02) and whites (P < 0.002). Comparisons of means, total variances, and among-pair mean squares within races revealed no heterogeneity. There were also no significant chorion effects. Since the anterior fontanelle closes at around 1–1½ years of age, it was evaluated at age one in 95 MZ and 194 DZ twin pairs as a qualitative trait – ie, open vs closed, concordance vs discordance. There were no significant differences in proband concordance rates between MZ and DZ twin pairs for either blacks (P > 0.5) or whites (P > 0.10). Again, there were no significant chorion effects. These data suggest that anterior fontanelle developmental variation has a significant genetic variance component at four months of age but not at one year. This finding may be related to the rapid brain growth witnessed between birth and eight to nine months of age.
The Twinning Incidence in Nigeria
Authors: Nylander P.P.S.
Published: July 2016

The dizygotic twinning rate in Western Nigeria is the highest on record (45—50 per mil maternities). It is suggested that, rather than to peculiarities in the population structure or to genetic factors, such a high incidence might be due to the presence in the diet of estrogen-like substances.
Foetal Twin Ultrasound Biometry
Authors: Schneider L. , Bessis R. , Tabaste J. L. , Sarramont M. F. , Japhet N.
Published: July 2016

Biparietal diameter growth differs considerably in the twin gestation compared to the singleton gestation; thus the use of a specific standard is recommended. A shift toward lower values is noticed in monochorial twins. In the case of the abdominal diameter growth, instead, no significant difference is found between twins and singletons.
Oxytocin Treatment in Twin Pregnancy Labour
Authors: Leroy F.
Published: July 2016

A continuous series of 483 twin deliveries was studied. In 30% of cases, intravenous oxytocic treatment was given for labour induction or to accelerate the first stage. In 13% of twin deliveries this treatment was applied only after the first twin's birth. In the group perfused during cervix dilatation, foetal mortality rate was significantly lower than in the nontreated group. In order to understand the reason(s) for this difference, the following factors were studied in relation to oxytocic treatment: parity, obstetrical complications, second stage duration, abnormal presentations, obstetrical maneuvers, and birth weight. Contrasting with mortality data, Apgar scores of first twins were significantly lower in the oxytocin-treated group. In summary, several variables indirectly linked to oxytocic treatment could have favoured or hampered foetal outcome in the treated group. Therefore, it is difficult to ascertain if the use of oxytocics is helpful in twin pregnancy management. In the majority of cases, however, it may at least be considered harmless.
Perinatal Mortality in Twins
Authors: Nylander P.P.S.
Published: July 2016

A study of perinatal mortality in twins has been carried out concurrently in Ibadan, Nigeria, and Aberdeen, Scotland. In both areas perinatal mortality rates have been found to be four times higher in twins than in singletons, reaching up to 310 per 1000 in the monochorionic group in Ibadan. Moreover, rates have been found to increase considerably with maternal age and parity.
EEC Concerted Action Project – European Congenital Anomalies and Twins (Eurocat)
Authors: Weatherall J. A. C. , Vlietinck R. F. , den Berghe H.Van
Published: July 2016

The European Economic Community (EEC) is promoting a network of locally funded centers in the nine EEC countries, surveying a total of approximately 140,800 births per year for selected congenital malformations and multiple births. The objectives and aims of the study are explained and some of the methods to set guidelines detailed.
Analysis of Multiple Birth Rates in Japan.1. Secular Trend, Maternal Age Effect, and Geographical Variation in Twinning Rates
Authors: Imaizumi Yoko , Inouye Eiji
Published: July 2016

Mean twin, triplet, and quadruplet birth rates in Japan from 1951 to 1968 were 6.41, 0.056, and 0.00094 per 1,000, respectively. In 1974 the corresponding figures were 5.83, 0.059, and 0.00329. No quintuplets were born in the former period, but a set was born in the latter year, the rate being 0.47 per million. From 1955 to 1966 the MZ twinning rate increased slightly, but decreased thereafter. This increase was limited to live-born MZ twins, particularly in the higher maternal age groups. The DZ twinning rate declined in the entire period, particularly in higher maternal age groups. This decline appeared to be essentially limited to fetal deaths. Among live births the MZ twinning rate underwent a nearly linear increase with maternal age, whereas the DZ twinning rate attained a mode in the maternal age group 35–39 years. The MZ and the DZ twinning rates among fetal deaths by maternal age had unimodal distributions with modes in maternal age groups 25–29 and 30–34 years, respectively. As to the DZ twinning rate, a geographical cline was noted, with a high rate in the northeast of Japan; the rate was positively correlated with latitude, which also positively correlated with the presence of multiple births among relatives. A negative but nonsignificant correlation was seen between the DZ twinning rate and the proportion of mothers treated with ovulation-inducing hormone. The proportion was higher in mothers of unlike-sexed twins than in those of like-sexed twins and in mothers of triplets than in those of twins. An association between DZ twinning rate and age-specific fertility per married woman is suggested to exist among higher maternal age groups in the northeast part of Japan in earlier years.
Probabilities of Concordance of Twins With Respect to Genetic Markers. A General Formulation
Authors: Sarna Seppo
Published: July 2016

The formulas needed in the determination of monozygosity in twin pairs using genetic markers are derived and presented. A general formula for the calculation of concordance probabilities independent of gene frequencies and allele number is derived, enabling either manual computation or computer programming for any Mendelian markers usable in twin zygosity diagnosis.
Holzinger's HC Revised
Authors: Allen Gordon
Published: July 2016

The formula H′C = 1 − CDZ/CMZ is suggested as a better summary of twin concordance data than the familiar Holzinger concordance formula, HC = (CMZ − CDZ)/ (1 − CDZ). The new formula better estimates degree of genetic determination, G, as calculated from a threshold model, but never exceeds unity, as G sometimes does. For high concordance rates, if CMZ + CDZ > 1, HC, may be more useful than either G or H′C.
Quantitative Twin Analysis of Radial and Ulnar Ridge Counts and Ridge Count Diversity
Authors: Reed Terry , Christian Joe C.
Published: July 2016

Analysis of variance was performed on the radial and ulnar finger ridge counts and ridge count diversity index in 360 twin sets from which estimates of genetic variance were obtained. Findings for radial and ulnar counts paralleled those previously obtained for finger pattern type and ridge count (larger of radial and ulnar count). In contrast, ridge count diversity showed no indication of unequal total variances, as previously found for the total ridge count. One must be cautious not to exclude genetic influences on traits, such as the thumb variables in this study, where there are unequal total variances between monozygotic and dizygotic twins and the more conservative estimate of genetic variance is not significant.
The Role of Chronogenetics and of Gemellology in the Prevention of Genetic Morbidity
Authors: Gedda Luigi
Published: July 2016

The prevention of hereditary diseases after birth is essentially based on the detection of these diseases at their preclinical level. This may be made possible through a careful pedigree examination and possible identification of a “genealogical alarm”, as well as a detailed clinical examination of the subject and possible identification of preclinical signs of the pathogenesis, i.e., of a “clinical alarm”. The respective roles of chronogenetics and of gemellology in this approach are reviewed.
Genetic and Nongenetic Variation in the AB0 Agglutinin Levels of Plasma, Saliva and Milk
Authors: Barrantes R. , Salzano F.M.
Published: July 2016

The agglutinin levels of 250 parturient women and their newborn babies were studied and the modifying influence of 16 variables evaluated. The most important factor in this variability is the AB0 phenotype. The agglutinin titers are generally higher in milk than in plasma or saliva. Blacks always show salivary agglutinins in higher frequencies than Whites. Within each fluid the amount of anti-A and anti-B are always highly correlated (r0.59-0.79). Associations were also observed between the titers in plasma and milk (r0.25-0.30). The plasma and milk anti-A levels of the 0 mothers are correlated with those of their 0 children (r0.28-0.37), but the anti-B are not. Socioeconomic conditions may affect the salivary anti-A and anti-B titers.
Partial Trisomy 8q Resulting from Maternal Translocation t(2;8)(q373;q23)
Authors: Giorgi P.L. , Tarantino E. , Formica Adriana , Cipriani P. , Dallapiccola B.
Published: July 2016

A patient with multiple congenital malformations due to partial 8q trisomy is reported. Karyotype-phenotype correlations suggest the possibility that partial trisomy 8q is a nosologically distinct syndrome.
Ectodermal Dysplasias Revisited
Authors: Freire-Maia Newton
Published: July 2016

This paper presents a historical view of the development of the concept of ectodermal dysplasia, analyses five current “definitions” of the group, and classifies 52-57 ectodermal dysplasias into subgroups on the basis of criteria developed by the Author.
Type A2Brachydactily — Report of a New Family
Authors: Rasore-Quartino A. , Camera G.
Published: July 2016

A new family with the A2type brachydactily is described. It is the first one observed in Italy and the sixth of the world literature. Brachymesophalangy of index fingers and/or second toes is the typical osseous malformation which was present in 14 individuals from 4 generations. The defect is transmitted by an autosomal dominant gene with high penetrance and variable expressivity.
Physical Capacity in Twins
Authors: Engström Lars-Magnus , Fischbein Siv
Published: July 2016

A comparison of physical capacity, (measured by vital capacity, muscular strength and physical work capacity) in twin boys and controls failed to indicate significant differences. Intrapair correlations showed the MZ twins to be much more similar than the DZ twins in all the capacity measures. The correlations were lower, however, for both MZ and DZ twins for physical work capacity than for the other two capacity variables. When amount of physical exercise during leisure time is kept under control, the DZ twins tend to be more similar for physical work capacity or muscular strength, and the correlations tend to be of the same magnitude for MZ twins. Physical work capacity therefore appears, in this study, to be a more environmentally influenced variable than either vital capacity or muscular strength.
Partial Deletion of 1q, Following a Pericentric Inversion, in a Boy with Multiple Minor Morphologic Anomalies and Mental Retardation
Authors: Schwanitz G. , Schmid P. , Hägele CH. , Daffner H. W. , Grosse K.-P.
Published: July 2016

In a 3¾ year old boy with mental and physical retardation, a chromosome analysis from lymphocyte cultures revealed a partial deletion of chromosome 1q following a pericentric inversion. The chromosomes of the parents were normal. The clinical picture of the patient included the following characteristics: prominent occiput, small chin, deep-seated and dysplastic ears, abnormal vortices of the hair, divided tip of the tongue, high palate, small finger and toe nails, inguinal hernia both sides, undescended but normal sized testes, hypotonic musculature and overextensible joints, retardation of ossification in the left hand by 6-12 months, slight osteoporosis, EQ~0.5.
47,XX, + 13/46,XX Mosaicism: A Case Report
Authors: Toledo S.P.A. , Wajntal A.
Published: July 2016

We described a D1trisomy syndrome patient who had a normal 46,XX cell line and 15.4% of lymphocytes with a 47,XX,+D chromosome constitution as an occasion to review normal trisomy 13 mosaicism.
Sources of Information for Discriminating MZ and DZ Twins by Dermatoglyphic Patterns
Authors: Reed Terry , Norton James A. , Christian Joe C.
Published: July 2016

It is shown that the within twin-pair difference is the most important source of information in determination of twin zygosity using dermatoglyphic data. Inclusion of a measure of among-pair variability provides added discrimination beyond that found with the within-pair difference alone.
Use of Banding Techniques for Zygosity Diagnosis in Twins
Authors: Friedrich Ursula , Lyngbye Troels , Øster Jakob
Published: July 2016

Detailed comparison of human variant chromosomes found by Q- and C-banding technique is performed in a pair of twins to show that these variants can be used for zygosity diagnosis.
Human Intelligence: Sex Differences
Authors: Jarvik Lissy F.
Published: July 2016

An extensive review of the literature on
sex differences in human intelligence leads to the
conclusion that there is strong evidence for sex
differences in processing both verbal and spatial
information. The few genetic studies that there
are all point toward a sex-linked mode of
inheritance of certain spatial abilities.
Abnormal Umbilical Vessels and Systemic
Circulatory Reversal in Thoracopagus Twins
Authors: Chaurasia B.D.
Published: July 2016

A human thoracopagus of slightly unequal
twins having a common umbilical cord with
exomphalos is described, with special reference to
the cardiovascular system. The larger twin had
single umbilical artery. The smaller twin had a
large left umbilical artery which was in direct
continuity with the aorta, a small right umbilical
artery with sole connection to the right external
and internal iliac arteries (right common iliac
artery was absent), missing umbilical vein, a
rudimentary nonfunctional heart with atresia of
the truncus arteriosus, and a right-sided aortic
arch. Exomphalos of both twins is accounted by the
possible defective growth of umbilical mesoderm
caused by abnormal umbilical vessels. Reversal of
systemic circulation in the upper part of the body
of smaller twin is discussed. The importance of a
careful study of umbilical veins is
emphasized.
Inheritance of a Peculiar Type of
Hypodontia
Authors: Mitter Navnit S.
Published: July 2016

A peculiar type of hypodontia is described
in two opposite sexed siblings and considered to
be inherited as an autosomal recessive
trait
Distribution of Gm and Inv Factors in Two
Samples of the Greek Population
Authors: Archimandrites A. , Fertakis A. , Stathopoulou R. , Kalos A. , Angelopoulos B.
Published: July 2016

Gm and Inv polymorphism has been
investigated on a sample of the general Greek
population (N = 256) and on a sample of the Achaia
population of Northwestern Peloponnesus (N = 150).
The estimated frequencies were, respectively in
the two groups: Gm1, 0.156
vs. 0.180; Gm1,2, 0.010 vs.
0.017; Gm4,12, 0.834 vs.
0.803; Inv (+1), 0.125 vs. 0.140.
Chromosome Studies on the Effect of Primidon (MylepsinumR) and Its Metabolites, Phenobarbital and Phenylethylmalondiamide, in Vitro
Authors: Foerst Dieter
Published: July 2016

Primidone and its metabolites Phenobarbital and Phenylethylmalondiamide were tested in cultures of human lymphocytes on possible effects of inducing chromosome aberrations. The substances examined ranged from concentrations lower than the therapeutic serum level to 10-75 times this value, which differed with the various substances. Phenylethylmalondiamide shows, besides an increase of spiralization defects at higher concentrations, which was typical for all three substances, no reaction on the chromosome structure.

By using the Friedman-test a statistically significant difference (P< 5%) could be found between the average aberration rates of the controls and the cultures which had been treated with Primidone and Phenobarbital. The test according to Wilcoxon and Wilcox shows that there is a statistically significant (P< 5%) difference between the aberration rates of controls and the respectively treated cultures. The higher values for percentage of aberrant mitoses are caused by the increase of gaps and breaks. There was, however, no proof for a linear dependence of the percentage of aberrant mitoses on the increasing concentrations of the substances. The number of tetraploid mitoses, endoreduplications and hyperploid cells was within the normal range.

Since in these investigations the number of chromosome exchanges was not increased, it can certainly be said that Primidone and Phenobarbital are not highly mutagenic substances.
Attitudes Towards Twinning in Primitive Societies
Authors: Leroy F.
Published: July 2016

In primitive societies twinning raises emotions varying from extreme terror to hope and joy. The first impulse prevailing among the less civilized people seems to be to regard twins as unnatural and monstrous and therefore as portending evil. Accordingly, they must be put to death and the offence repudiated. This negative attitude stems from a series of explanations which can generally be connected with the widespread belief in superfetation and double paternity. In a few cases only, would the custom of sacrificing twins arise from economic necessities. However, in many agricultural primitive tribes, twinning is regarded as a happy event. In this case, the worship of twins entrusts them namely with power over water allowing to confer fertility to the soil and also to women and animals. In the past, the mother of twins was often executed with her offspring or simply banished. In many tribes, she is still compelled to go through elaborate purification in order to forestall the evil omen. If twins are welcomed, their parents are similarly respected as they symbolize the fertility power of the clan. Superstitions and myths pertaining to twinning are universal and often present converging features among cultures without mutual contact. This would point to the twin cult as one of the earliest religious beliefs of mankind.
Is Weinberg's Method Valid?
Authors: Bulmer M.G.
Published: July 2016

Suppose that L like-sexed and U unlike-sexed twins have been observed. Weinberg's method estimates the numbers of DZ andMZ twins as DZ = 2U and MZ = L—U. This method is based on the assumptions that (1) the sex ratio in DZ twins is 1/2 and (2) the sexes of DZ twins are determined independently and with the same probability in all parents; in consequence there should, on average, be equal numbers of like-sexed and unlike-sexed DZ twins. The first assumption is not exactly true, but the necessary correction is negligible. Departures from the second assumption would probably lead to an excess of like-sexed over unlike-sexed DZ twins; in consequence, Weinberg's method would underestimate the numbers of DZ twins and overestimate the numbers of MZ twins. The literature on the frequencies of like-sexed and unlike-sexed pairs among twins known to be DZ through other genetic markers is reviewed. It is concluded that there is no evidence of an excess of like-sexed twins among them, and that there is therefore no reason to doubt the validity of Weinberg's method. The extension of Weinberg's method to estimate the zygosity types of triplets and quadruplets is described; it is shown that the resulting estimates agree well with the results of direct zygosity determination by blood grouping.
Scope and Methodology of Twin Studies
Authors: Allen Gordon
Published: July 2016

The use of twins as a research tool is still proving its worth both by the number of scientists engaged in twin research and by the significance of their results. Old, familiar research designs are finding new applications, and new research designs are appearing. Of greatest current interest are the epidemiological studies made possible by the assembly and the aging of large numbers of twins in twin registries. As an outgrowth partly of the twin registries, partly of conceptual and mathematical progress, new methods have emerged for diagnosis of twin types and for analysis of twin data. One line of development started with the questionnaire method of zygosity diagnosis and has given rise most recently to zygosity diagnosis by principal component analysis. Another line started with probability calculations and has led to the use of generalized distance and noncentral chi-square. The appropriateness of these methods in different contexts needs to be critically considered. Also of importance are the psychologists' new methods of extracting genetic “factors”. The greatest weakness of twin studies, long recognized, is their dependence on the assumption that DZ pairs provide an adequate control on the environmental differences within MZ pairs. This may be valid with respect to environmental influences that are highly self-selected. It is debatable for self-selected influences that differ among families, and clearly untenable for most influences imposed by the social environment peculiar to twins.
Genetics of Plasma Cholesterol and Triglycerides: A Study of Adult Male Twins
Authors: Christian Joe C. , Feinleib Manning , Hulley Stephen B. , Castelli William P. , Fabsitz Richard R. , Garrison Robert J. , Borhani Nemat O. , Rosenman Ray H. , Wagner John
Published: July 2016

Fasting plasma triglycerides and cholesterol, as well as cholesterol in very low density, low density and high density lipoproteins, were measured in 250 MZ and 264 DZ adult male twin pairs. A new method was used to choose an estimate of genetic variance. This includes an estimate of genetic variance for use when the total variances of MZ and DZ twins are unequal. DZ twins had greater total variance for cholesterol. When genetic variance was estimated by subtracting the within-MZ-sets mean square from the within-DZ-sets mean square, all of the lipids had significant estimates of genetic variance; however, when genetic variance was estimated by a method designed to correct bias due to unequal total variances of MZ and DZ twins, only triglycerides had significant genetic variance. The heritability of plasma triglycerides was calculated to be 0.68.
A Twin Study on the Heritability of Lipoprotein Fractions
Authors: Hewitt D. , Milner J. , Breckenridge C. , Little J. A. , Kuksis A.
Published: July 2016

Volunteer adult twins (aged 18-65), after a 12-hour fast, provide two 15 ml samples of blood for analysis by Auto Analyzer II, by agarose electrophoresis and by direct gas chromatography. Provisional diagnosis of zygosity is based on subjects' own opinions, supported by dermatoglyphic analysis and, in any difficult case, substantiated by an enzymatic series. Analysis of the AA-II and electrophoresis data on the first 2 × 45 subjects shows a significant positive correlation within MZ pairs for each of the 7 lipid measurements considered, while the estimate of correlation within DZ pairs is lower in every case. Heritability appears to be higher for cholesterol than for triglyceride fractions. The electrophoretic band for the sinking pre-beta lipoprotein fractions has behaved like a simple genetic marker. Interrelationships among different lipoprotein fractions are studied in terms both of phenotypic and genetic correlations, both of which confirm the expected positive association between amounts of triglyceride and of cholesterol in the supernatant (Sf > 20), and both also show negative correlation between the pre-beta and the alpha fractions. Another aspect of the analysis is the study of lipid differences between MZ cotwins in relation to corresponding intrapair differences in body weight and medical history; male, but not female pairs, show a measurable statistical dependence of cholesterol and triglyceride levels on « excess » body weight.
Distribution of Blood Groups, Salivary Blood Group Substances, and Natural Antibodies in a Sample of MZ Twins
Authors: Pace D.P. , Saccucci F. , Britti F. , Casini D.
Published: July 2016

The distribution of A1A2BO, MN, and Rh-Hr blood groups, of salivary ABH substances, and of natural antibodies, was assessed in a sample of 47 MZ twin pairs. The resulting distribution provides indications as to the level of genetic control over the quantitative expression of these traits.
Twin Studies and Behavior Genetics
Authors: Jarvik Lissy F.
Published: July 2016

It is observed that neither the methodology of twin studies nor that of behavior genetics in general has been adequately explored in most investigations of human behavior. General distrust of genetic methodologies as well as the belief that genie disorders are unalterable appear to be salient factors in explaining the neglect of those areas by social scientists. A plea is made for putting aside biased attitudes that prevent utilization of the best available techniques for the study of human beings as distinguished from all other animals.
Nature-Nurture and Intelligence: The Twin and Adoption Studies Agree
Authors: Horn Joseph M. , Loehlin John C. , Willerman Lee
Published: July 2016

A large-scale adoption study is underway at the University of Texas where IQ test scores are available for over 1200 women who gave up their children for adoption immediately following delivery. The adopted children and their adoptive families are now being located and tested and, if current trends continue, complete data should eventually be available on over 400 families. About half of these families will contain two or more adopted children or both adopted and natural children. At present, data are available for 89 families. The results are consistent with twin data and support a genetic hypothesis. The biological mother-adopted child correlation is 0.37 whereas the adoptive mother-adopted child and adoptive father-adopted child correlations are only 0.22 and 0.04 respectively. There are 59 pairs of unrelated children reared together in this sample and the IQ correlation for these children is only 0.13.
The Role of Genetic Factors in the Child Drawing Behavior - A Preliminary Twin Study
Authors: Candelori Carla , Ferraris Anna Oliverio , Parisi Paolo
Published: July 2016

A sample of 27 MZ and 32 DZ twin pairs, aged 6 to 12 years, has been tested with the Draw A Family Test. Significantly higher concordance values in MZ than DZ twins have been found with respect to some graphic-structural factors (i.e.: line, hand pressure, area of the drawing, dimensions of the figures, distribution, and shading) as well as with respect to contents factors, such as spatial representation and cotwin's valorization. These correlates of personality development would thus appear to undergo significant genetic conditioning.
Heritability of Personality and Behavior Pattern
Authors: Rosenman Ray H. , Rahe Richard H. , Borhani Nemat O. , Feinleib Manning
Published: July 2016

As part of the National Heart and Lung Institute multicenter study of twins, 190 twin pairs (93 MZ, 97 DZ) residing in California and aged 44-55 years were comprehensively studied for all risk factors for coronary heart disease and for Behavior Pattern Type A or B. Psychological tests included MMPI, CPI, 16 Cattell PF, Cough Adjective Check List (ACL), Thurstone Temperament Schedule (TTS). Heritability at statistically significant levels was found only for scales of TTS. Twelve scales of ACL and five scales of TTS showed significant correlations with Behavior Pattern Type A-B as well as with several risk factors, including blood pressure and serum lipids. Multiple regression equations were constructed for those characteristics accounting for significant and unique portions of the total variance of Type A-B Behavior. The use of certain scales of ACL and TTS may provide a new questionnaire for screening purposes in the assessment of Behavior Pattern Type A-B.
Characteristics of the Twins of Schizophrenics as Fallible Indicators of Schizoidia
Authors: Gottesman I. I. , Shields J. , Heston L. L.
Published: July 2016

Further advances in research into the etiology of schizophrenia will depend on the identification of an unambigous indicator of the genotype associated with the development of schizophrenia. Such an indicator would permit accurate assessment of the relatives of probands as “affected” or not, so that the data generated in twin and family studies could be tested for the best fit to various genetic models that have been proposed. Schizoidia or schizoid personality has been considered by clinicians to be such an indicator, but it has been beset by semantic and logical difficulties. Most troublesome has been the extent to which the concept implies (merely) a phenotypic resemblance to schizophrenia, or a genotypie connection with it, or both. Four different but overlapping meanings for the concept of schizoidia are presented, in an effort to clarify the semantic and logic involved. Following Popper's notions about the testability and refutability of theories, the authors, identified with both monogenic and polygenic theories, apply the definitions to their first-hand observations of the cotwins in the Maudsley-Bethlem Schizophrenic Twin Study. Pushing the concept to its limit, 91 % of 22 MZ pairs and 45% of 33 DZ pairs contained “disordered” cotwins.
Gene Interaction in the Phenotypic Expression of Mental Diseases
Authors: Braconi Lucio
Published: July 2016

A genealogical analysis is carried out on the pedigrees of 10 twin pairs with two or more psychoses. The probands' symptoms reveal some peculiar aspects, i.e., an atypical phenomenology possibly due to the interference of more pathological genes. Schizophrenia, depression, epilepsy, and obsessive neurosis, are found in the pedigrees in different combinations. The study of these pedigrees would lead to the conclusion that interaction of more than one psychosis gives rise to atypical forms as a result of an attempt to establish a state of balance between opposing dynamic actions, as in reversible chemical reactions. Probands' symptoms are less severe and with an often more favourable prognosis. Epilepsy tends to become independent and the major psychoses seem to be epistatic on it. Af for obsessive-compulsive neurosis, probands may progress into schizophrenia or depression if one of these psychoses is present n the pedigree, or may represent the neurotic form of the major disease.
Genetic Factors in Myopia
Authors: Karlsson Jon L.
Published: July 2016

A school population has been screened to locate same-sexed twins with myopia and also to compare intelligence test performance of myopic and nonmyopic individuals. Augmentation of the twin data by a survey of the world literature has led to the identification of a total of 106 MZ twin pairs, 100 of them concordant for myopia, as well as 41 DZ pairs, 12 concordant. Myopic students score eight points higher on IQ tests than nonmyopes, the entire bell shaped distribution curve being shifted to a higher range. The intellectual gain precedes in time the development of nearsightedness.
The Process of Identity in Twins
Authors: Cirillo S.
Published: July 2016

The Blacky Picture Test was administered to a sample of 12 pairs of male MZ twins, aged 17 to 19 years, and to an equal number of singletons. A score for 30 factors was assigned to each protocol. By comparing the scores of the two groups using the Mann-Whitney U test, only one significant difference emerged, relative to the factor concerned with positive identification and fraternal relationship. Twins chose the sibling figure as the identification object significantly less often than singletons did. A more qualitative elaboration was undertaken in order to interpret this result. From the final data, the pre-cariousness of the sense of identity in the twins comes out indirectly in their passive and conformistic acceptance of the paternal model. It would seem that the twin is induced by his relationship with his cotwin, seen as the origin of this uncertainty as to his own identity, to adhere closely to the paternal image.
Language Development in Young Twins: Biological, Genetic and Social Aspects
Authors: Mittler Peter
Published: July 2016

The present study has confirmed previous evidence that young twins show a marked delay in language development. This delay averaged six months at the age of 48 months, compared to a control group of singletons; it was evenly reflected in all nine subtests of the Illinois Test of Psycholinguistic Abilities, and was shown equally in MZ and DZ twins. Biological variables such as birth weight, gestational age and reproductive complications were only weakly associated with language scores at four years. The twins were not significantly retarded on non-verbal tests of general intelligence, compared with population norms or with the singleton controls. Environmental factors, particularly social class and family size were strongly correlated with language scores, though the association was stronger in singletons than in twins. Middle class twins were relatively much more retarded in language development compared with middle class singletons than working class twins compared with working class singletons. Comparison of intra-class correlations between 28 MZ and 64 DZ pairs yielded a heritability index of 44% for the test as a whole, with considerable variations in h2over the nine subtests. Heritabilities were highest for tests sampling the visual motor channel, and lowest for tests on the auditory-vocal channel. In confirmation of this finding, an examination of the test profiles of the singleton controls suggested that social class differences were most marked on tests of the auditory-vocal channel. It is suggested that the latter are more susceptible to environmental variables.
The Threefold Cord of Mothers of Twins Clubs
Authors: Maxey Joyce E.
Published: July 2016

Local, State and National are the threefold cord that binds us together at Mothers of Twins Clubs. Local, State and National share a mutual responsibility and interdependence with one another. This threefold cord helps us to grow and develop our potential for the benefit of all. It is cooperation between the three levels that unites us and though each serves in different ways, each is vital to the full scope of Mothers of Twins Clubs.

On the Local level we realize that research is the responsibility of every member and some clubs have research participation as a requirement of membership. Researchers could insure greater participation if they would issue periodic progress reports. Though we realize research is a long, slow process, we are often asked, “Why fill out forms if we never hear what is done with them?”. Mothers of Twins Clubs are glad to make time for research if they are made to feel it is worthwhile. Since some clubs belong to State or National, while others belong to State and National and still others belong to neither State or National, research work on the Local level has different outlets. The prime concern of the Local Mothers of Twins Club however is to learn to raise our twins as individuals while respecting the bonds and blessings of twinship.

The bridge of States is loosely knit with great resources still untapped for research. The growing number of State groups and the ever changing needs of Locals require the combined efforts of State Mothers of Twins Clubs to participate in Interstate communications and cooperation. There are 20 State groups in the U.S.A., representing over 303 clubs and over 9275 members. Most of the State groups have their own Research Chairman and Twin Registry. Those States without a Research Chairman are for the most part new groups and plan to participate in research when they are able. Even now State Mothers of Twins Club is being worked on by a group in Canada. Since more mothers can attend a State Convention, interest and enthusiasm for research on the State level is high among mothers of twins.
Supertwin Records
Authors: Lauve Helen Kirk
Published: July 2016

My fascinating yet productive hobby began only with details of the delivery of quadruplets in my home city. The quadruplets were delivered by one of my psysician-employers and, because of predelivery contacts with the mother who was a member of my church, a scrap book about the quadruplets was started. Through outside pursuits, correspondence, detailed study and research this single scrap book has developed into what is believed to be the most extensive collection of authentic data and photographs of twins and supertwins in the world.

Files are kept as authentic as possible, yet by no means are internationally complete. Unfortunately, all multiple births are not recorded in medical, or public, registers and/or literature and some are never registered as multiple births due to circumstances surrounding the birth. A set of quadruplets about whom I have many news items from birth to age one year comes to mind… although the quadruplet birth was recorded by articles in newspapers, medical archives have no record of it because the physician expired before he formally recorded the birth in medical literature. Some births are recorded individually not indicating a multiple birth and others are lost because of a stillborn infant or a macerated fetus accompanying a live birth. Even parents are not always informed of the birth of a macerated fetus that accompanies a live birth.