bluuebunny/crossref_metadata_2025 huggingface dataset:
NOR Variability in Twins
Authors: Weltens R. , Kirsch-Volders M. , Hens L. , Defrise-Gussenhoven E. , Susanne C.
Published: July 2016

The number of AgNOR (NOR+) and the amount of AgNOR (NORM+) were analysed by means of two multilevel analyses of variance in a total of 12 twin pairs: 3 female and 4 male MZ and 5 male DZ pairs. In the first analysis, only zygosity was controlled; in the second, chromosome types D and G were controlled as well as the interaction between chromosome type and zygosity. For NOR+ and NORM+, when chromosome types D and G are not distinguished, the within-pair variance is greater, though not significantly, in DZ than in MZ pairs; but it is highly significantly greater when chromosome type (D or G type) is under control. This confirms an important genetic determination of NOR+ and NORM+ when in the ANOVA model the D and G types are controlled. However, nongenetic factors also influence the Ag-NOR patterns, but not enough to conceal the genetically defined rDNA pattern. Indeed, about 50% of the cells transcribe their rDNA in a way not closely dependent on the rDNA background and significant intrapair differences of NOR+ pattern exist in MZ twins.
Premature Contractions: Are They Caused by Maternal Standing?
Authors: Schneider K.T.M. , Huch A. , Huch R.
Published: July 2016

In 33 out of 51 women studied in late gestation, the uterus was found to phasically compress the pelvic vessels and impede the venous blood flow during quiet standing. This caused a reduction of the cardiac stroke volume with resultant reduction of systemic blood pressure and a compensatory increased heart rate (range of increases 9-51 beats/min). In all cases uterine contractions (mostly subclinical) coincided with the phase of circulatory readjustment. Apparently, the contracting uterus, by changing its position and/or shape, relieves the venous obstruction and prevents decompensation. In the women displaying the uterine compression syndrome (UCS), uterine activity was markedly increased in standing compared to the left recumbent position.

It was also investigated whether the UCS appeared more often and earlier in gestation in women with twins. In all 9 women with twin pregnancies (mean gestational age 28 5/7 weeks) the UCS associated with uterine contractions was apparent in the standing posture. Although at present no definite conclusions can be reached on the effect on the cervix of these contractions, quiet standing especially in twin pregnancies seems to provoke an increased uterine activity and should therefore be avoided.
Discordant Monozygotic Twins with Trisomy 13
Authors: Loevy H.T. , Miller Marilyn , Rosenthal Ira M.
Published: July 2016

Monozygotic twins with typical trisomy 13 are reported. Despite an identical karyotype, the twins were dimorphic for the presence of an omphalocele. Reasons for the rarity of MZ twins with trisomy 13 are presented. It is suggested that the presence of a chromosomal abnormality in MZ twins may predispose to dimorphism.
Arterial Blood Pressure - The Pattern of Change in Twin Pregnancies
Authors: Campbell D.M. , Campbell A.J.
Published: July 2016

An epidemiological study of all primigravid twin pregnancies delivered in Aberdeen between 1950 and 1969 was performed to determine the pattern of arterial blood pressure changes. There is a greater fall from non-pregnant levels in diastolic blood pressure by mid pregnancy and a greater rise of diastolic pressure by delivery. These changes are independent of age, body size and rate of weight gain during pregnancy. The expected increased incidence of proteinuric pre-eclampsia is also independent of rate of weight gain when defined for twin pregnancies.
Twin Pregnancies: An 11-Year Review
Authors: Grothe W. , Rüttgers H.
Published: July 2016

From 1971 to 1981, 16752 women were delivered at the University Women's Clinic in Heidelberg; 228 of these were twin pregnancies (1.36%). The relationships between sex, gestational age, birthweight, mortality, and fetal outcome were investigated. For the reason of grading, so-called χ2 curves are used. These curves show the strength and the course of relationship between two parameters. Mortality of the twin (8.3%) depended on birthweight and on sex of the infant, but not on the mode of delivery. All twins were ‘small-for-date’ (25th weight percentile of single births). Starting at the 35th week of gestation, the increase in weight decelerated additionally. So, immaturity as well as twin-related factors led to the high mortality rate for twins. Fetal outcome was evaluated in respect to the birthweight and to the delivery interval.
Cultic Powers of Yoruba Twins:Manifestation of Traditional and Religious Beliefs of the Yoruba
Authors: Oruene T.O.
Published: July 2016

The birth of twins was believed by the earlier Yoruba communities to be an omen. Drastic measures were adopted in the form of infanticide, or, sometimes, banishment of the twins with their mothers. The ritual killings were gradually replaced by acceptance and reverence of the twins, and thus evolved the kinship cult of twins in which the orisa ibeji, a tutelary deity of twins, became part of the Yoruba pantheon. Twins could be identified in the community by their fixed names of Taiwo and Kehinde. The community prescribes occupations to the mothers, which is learned through consultation with the oracle. The usual forms of occupation, which reflect the nature of the twins, are trading in oil, beans, or clothing, or requesting alms. The orisa ibeji and, by association, the twins were attributed powers of fertility, prosperity, avenger, detector of thieves, and rainmaker. Propitiation and supplication with offerings and sacrifices are an integral part of the cult of twins.
Cigarette Smoking Behavior in Conjoined Twins
Authors: Jarvik Murray E. , Gritz Ellen R. , Rose Jed E.
Published: July 2016

A study of cigarette smoking was undertaken in a pair of craniopagus twins to determine how a transfer of products of smoking is occurring between the twins. Alternately and independently, one twin smoked a nicotine-free cigarette, then the second twin smoked a nicotine-containing cigarette. The procedure enabled the investigators to study the migration of nicotine and carbon monoxide from one twin to the other. Salivary determination provided a noninvasive method of measuring cross circulation in conjoined twins. Measurements of salivary nicotine, however, indicated that, although the nicotine levels rose following smoking, there was relatively little transfer from one twin to the other through the circulation.
Neurofibromatosis in Monozygotic Twins: A Case Report
Authors: Åkesson Hans Olof , Axelsson Rolf , Samuelsson Birgitta
Published: July 2016

A case report is given of a pair of monozygotic twin girls with neurofibromatosis caused by a new mutation. The symptomatology was dominated by a neurofibrosarcoma on the leg of one twin and by a large plexiform neurofibroma on the neck of the other twin. Otherwise, the disease showed similar, although not identical or mirror-image distribution of subcutaneous neurofibromas and café-au-lait spots. The twins had identical HLA and blood group antigens and the same chromosome aberration. These case reports indicate that nonhereditary factors may influence the manifestations of neurofibromatosis. A review of the literature on monozygotic twins with neurofibromatosis is given.
Seasonality in Early Loss of One Fetus Among Twin Pregnancies
Authors: Nakamura I. , Uno M. , Io Y. , Ikeshita I. , Nonaka K. , Miura T.
Published: July 2016

Ultrasonographic examinations were performed on 519 pregnant women in the first trimester at three hospitals in Tokyo from August 1985 to March 1987. Among 519 women, two fetal heart movements (FHMs) were comfirmed in six cases. In two of these six cases, one of two FHMs disappeared two weeks later, and these were considered the “vanishing twin”. In eight cases among those with ultrasonographic image of echo-free-space (EFS) in the uterus, the observed EFS was considered to be a probable empty gestational sac (GS-like-EFS-image). Seven of eight GS-like-EFS-images were observed in October-December (p < 0.01) and two “vanishing twin” cases were also observed in the same season. Spontaneous abortion occurred in 11 cases and these were also more frequently observed in October-November (p < 0.05). Some abortive factor is supposed to have prevailed in October-December. All six women having twin fetuses (including the “vanishing twin” cases) were born in January-May (p < 0.05) and those having GS-like-EFS-images or terminating their pregnancy in spontaneous abortion were also born more frequently in the same season. Twin-prone and abortion-prone characteristics of the women born in this season are considered.
Fetal Deaths with Birth Defects Among Japanese Multiples, 1974
Authors: Imaizumi Y. , Asaka A. , Inouye E.
Published: July 2016

Source of data is “Survey on Socio-Economic Aspects of Vital Events – Plural Births in 1975”, including 12,392 twin pairs, 124 triplet sets, 7 quadruplet sets and 1 quintuplet set. Feal deaths were 3,285 for twins, 141 for triplets, 17 for quadruplets, and 5 for quintuplets, among which the numbers of birth defects were 78, 3, 0, and 0, respectively. Concordant twin pairs with the same category of birth defect were 20 among 56 pairs (0.36). As for the remaining 36 pairs, 2 pairs had different category of birth defects, 27 pairs had liveborn cotwins, and 7 pairs were both fetal deaths among which a twin had birth defect. The second-born twins had birth defects more frequently than the first-born twins among fetal deaths (28 vs 6).
Transfusion Syndrome in a Triplet Pregnancy
Authors: Pons J.C. , Olivennes F. , Fernandez H. , Ramdin I. , Mayenga J.M. , Bessis R. , Papiernik E.
Published: July 2016

A case is reported of a transfusion syndrome in a triplet pregnancy with intrauterine death of two of the fetuses. This is an exceptional occurrence in a triplet pregnancy and raises the problem of the management of multiple pregnancies associated with the death of one or more of the fetuses. The problem of the method of delivery and the complications arising in triplet dizygotic pregnancies is discussed.
Quantitative Genetic Analysis of Longitudinal Trends in Height: Preliminary Results from the Louisville Twin Study
Authors: Phillips K. , Matheny A.P.
Published: July 2016

A preliminary series of quantitative genetic models was applied to a subset of longitudinal height data, spanning birth to maturity, gathered from twin families in the Louisville Twin Study. Descriptive Cholesky factor parameterization was found to give more satisfactory results than did a system of constraints based on a model of developmental transmission of a time-constant and time-specific factors. The results from application of two autosomal sex-limitation models are contrasted with those from a model specifying both autosomal and sex-chromosomal patterns of inheritance. The latter model was more conducive to parameter reduction. Although these models do not constitute conclusive tests of autosomal sex-limitation versus sex-linkage, the more parsimonious model is consistent with previous research suggesting a stature locus on the long arm of the Y chromosome. Heritability of height is estimated at about 90% or greater from 6 years of age on. Substantial and fairly constant longitudinal genetic correlations are found from 3 years of age on. Shared environmental effects unrelated to parental height were seen for birth length, corrected for gestational age, to height at 3 years of age, but these are not satisfactorily differentiated from possible twin effects in the present sample. The genetic consequences of assortative mating are emphasized since failure to take assortment into account can lead to overestimation of shared environmental effects and under-estimation of genetic effects. The results indicate that about 20% of within-gender variability for mature height can be attributed to the genetic consequences of assortment, even though the phenotypic marital correlation of 0.22 is quite modest. The importance of testing the assumption of multivariate normality underlying the application of the method of maximum-likelihood is also highlighted.
Relationship Between Blood Uric Acid Level and Personality Traits
Authors: Ooki S. , Yamada K. , Asaka A.
Published: July 2016

The present study deals with the relationship between blood uric acid level and human behavior. Subjects were 37 MZ and 7 DZ twins aged from 18 to 45 years. In males, blood uric acid level increased with age, while it decreased with age in females. Blood uric acid level was corrected and standardized using regression lines separately for males and females. The distribution of standardized uric acid level corresponded well with the theoretical curve of normal distribution. The intraclass correlation coefficient for standardized uric acid level was r = 0.370 (P < 0.05) for the 37 MZ twins, but not significant for the 7 DZ twins. These findings suggest that blood uric acid level is genetically controlled. By the analysis of 12 personality traits in YG (Yatabe-Guilford) character test, it was revealed that “General activity” was more controlled by genetically than environmentally. In the evaluation of the correlation between standardized uric acid level and the YG 12 personality traits, significant correlation was observed in “Lack of agreeableness” and “Rhathymia”. Since these two personality traits include the factor of “activity”, it is concluded that the plasma uric acid level and activity in a broader sense are under genetic control. This conclusion is consistent with the generally accepted view that persons with high uric acid level are more active and energetic than those with low level.
Congenital Malformations in Twins: A Population Study
Authors: Källén Bengt
Published: July 2016

Malformations in twins were studied with the use of a Medical Birth Registry covering nearly all births in Sweden, 1973-1981. A total of 15,427 infants marked twins were identified and the malformation diagnoses were analyzed, comparing rates with the overall rates in the same data source. Problems in ascertainment and interpretation are discussed. No excess of neural tube defects was seen, but hydrocephaly was diagnosed more often in twins than in singletons. This can be partly, but not completely, explained by a higher rate of low-weight infants among twins. An excess was noticed in twins in the rates of cardiac defects, spine defects, gut atresias – notably esophageal and anal atresia – and severe kidney malformations. These are components of the so-called VACTERL syndrome – the last component (limb reductions) being more common in twins than in singletons, though statistical significance was not reached. A relation between monozygotic twinning and this syndrome is tentatively suggested.
Metric Analyses of the Teeth and Faces of South Australian Twins
Authors: Townsend G.C. , Brown T. , Richards L.C. , Rogers J.R. , Pinkerton S.K. , Travan G.R. , Burgess V.B.
Published: July 2016

Procedures are described for the acquisition and analysis of data in a study of the dental and facial characteristics of South Australian twins. Comparisons of the mesiodistal diameters of maxillary incisors in MZ and DZ twins revealed heterogeneity of total variances and evidence of inequality of mean values for some dimensions between MZ and DZ twins. Previous estimates of heritabilities for tooth size, relying on classical assumptions in twin research, may be exaggerated. A preliminary analysis of facial shape was undertaken using a procedure for shape matching based on a least squares fit of homologous coordinates. There was evidence of mirror-imaging in some MZ twin pairs and differences in facial asymmetry between male and female DZ twins. Future extensions of the study using methods for three-dimensional shape analysis are described.
Preterm Deliveries in Twin Pregnancies in Oxford
Authors: Watson P. , Campbell D.M.
Published: July 2016

The incidence of preterm delivery among twin maternities in Oxford between 1973 and 1983, was 39.4%. Preterm delivery was more common in MZ than DZ twins, and this was associated with higher incidence of spontaneous rupture of the membranes associated with monozygosity.
Twin Studies of Coronary Heart Disease and Its Risk Factors
Authors: Berg Kare
Published: July 2016

The ongoing comprehensive study of the updated population-based Norwegian Twin Panel (like-sexed twin pairs born since 1915) has already given results of interest to the research on coronary heart disease and its risk factors. Significantly more dizygotic (DZ) than monozygotic (MZ) pairs are discordant for death between 40 and 60 years of age. Presumably, several of the cases must have been coronary heart disease deaths. In pairs where both members are alive, concordance rate for coronary heart disease before the age of 60 years is significantly higher in MZ than in DZ pairs. Concordance rate for reported hypertension is significantly higher in MZ than in DZ pairs. These findings are compatible with a significant genetic effect on premature death, coronary heart disease and hypertension.

There is a strong genetic effect on serum level of apoB, apoA-I and apoA-II, a weaker effect on cholesterol level and a doubtful effect on triglyceride level. Genes belonging to several normal genetic polymorphisms may participate in the control of environmentally/dietary caused variability in lipid and lipoprotein parameters. The study of MZ twins that was conducted to detect these effects holds considerable promise for the detection of gene control of many kinds of quantitative parameters. Further work with this twin panel may provide more definite answers to several questions raised during the present investigation. Application of more sophisticated models for twin family analysis on several normal and pathological traits may be very informative. Also, this updated Norwegian Twin Panel should in the long run make it possible to estimate the predictive value for the second member of a twin pair of having a twin contracting coronary heart disease (or any other reasonably frequent disease) by a given age. Finally, the subsample that is subjected to extensive laboratory analyses will provide useful data for genetic linkage analyses since in many cases, offspring of two members of a MZ pair can effectively be considered as one single (more informative) sibship.
Twin Analysis as a Potential Tool for Examining Psychosocial Factors Associated with and Preceeding Smoking Behaviors
Authors: Pedersen N.L. , Floderus-Myrhed B.
Published: July 2016

Data from the young cohort of the Swedish Twin Registry are being used in an attempt to describe characteristics which distinguish among current, non- and ex- smokers prior to the development of a smoking habit versus those present after establishment of the habit (or lack of one). With twins as a sample of individuals, the psychosocial variables instability, extroversion, leisure activity, relative weight, alcohol, coffee and psycho-pharmaceutic drug use were examined jointly as predictors of current smoking status in multiple regression analyses. This phase was intended to replicate and expand upon earlier studies characterizing current, non- and ex-smokers. These analyses were then performed on MZ nonsmoking twin individuals who were classified on the basis of their cotwins' smoking status. Pattern of variation in the psychosocial variables across the groups of nonsmokers were similar to the pattern seen for current, ex- and nonsmokers. Characteristics in MZ nonsmokers which are predictive of their cotwins' smoking status may be interpreted as those present prior to development of a smoking habit. Selected results from these analyses will be presented.
Finnish Twins Reared Apart. IV: Smoking and Drinking Habits. A Preliminary Analysis of the Effect of Heredity and Environment
Authors: Kaprio J. , Koskenvuo M. , Langinvainio H.
Published: July 2016

Data on alcohol use and smoking habits was available from the 1975 questionnaire of the entire cohort. Prior to pairwise analyses, the data of individuals was compared to that of age-sex matched groups of pairs reared together. The early separated twins had a higer alcohol consumption, while for smoking only slight differences were observed compared to twins reared together. Probandwise concordance rates were computed from smoking status (ever smoker/never smoker), alcohol use (user/nonuser) and “heavy” drinking (half-bottle of spirits on one occasion at least once a month). The following results were obtained in those pairs with the environmental dissimilarity score > 15:
Cancer and Senescence: Is There a Biological Link?
Authors: Burch P.R.J.
Published: July 2016

It is shown that sex- and age-specific death rates from all causes of death other than neoplasms have features that resemble those of corresponding rates for all neoplasms. The same generalization holds in connexion with specific neoplastic and non-neoplastic disorders. In both categories of disease many age-patterns suggest that the rate-governing mechanism for their occurrence is stochastic in character; a rather small number of random events, generally fewer than ten, suffice for their initiation. It is not immediately obvious how a widespread degenerative disorder, sometimes involving an astronomical number of target cells, can be initiated by only a few random events. We infer that all such disorders, together with natural cancers, are autoaggressive in nature. They are initiated by random somatic mutations in comparator stem cells of the central system of growth control. Mutant stem cells propagate forbidden clones of cells that attack target cells at one or multiple sites. (In certain disorders, the presence of an extrinsic precipitator in the host in essential to the propagation of forbidden clones). Autoaggressive attacks have consequences that range from the destruction of target cells to their transformation with invasive proliferation. Senescence can be regarded as the cumulative effect of predominantly late-onset autoaggressive disorders. The relevance of studies of twins to this unified theory is discussed.
Twin Studies of Disease Heritability Based on Medical Records: Application to Acne Vulgaris
Authors: Friedman Gary D.
Published: July 2016

Establishment of the Kaiser- Permanente Twin Registry permitted the study of disease heritability in twins based on review of the twins' medical records. The records of 930 pairs of twins were reviewed. Based on previous questionnaires, 342 pairs were MZ, 345 were DZ and 243 were of unknown zygosity. Because of the age distribution of these twins and the time period in which they received care, conditions of youth, such as acne vulgaris were most reliably studied Heritability of acne was assessed in three ways; all indicated a substantial genetic influence. Certain problems with twin studies using medical records became apparent: 1) Zygosity information is often lacking; 2) Differing times and durations of observation of the two twins in each pair must be accounted for; 3) Categorization by diagnosis is difficult and strict criteria for diagnosis may be impractical; 4) Patients' behavior that affects assessment of disease concordance must be considered; 5) The order in which records are reviewed may influence apparent concordance.
The Twins Foundation: Twins Take Up the Challenge
Authors: Cassill Kay
Published: July 2016

Revelations about twins are abundant, but the information often is inaccessible. Therefore, The Twins Foundation, a multifaceted, international, nonprofit agency has been formed. Through development of a Research Library, Museum and Hall of Fame, it will (1) provide archival and research support to the growing number of disciplines involved in twin studies; (2) provide a central repository and clearing house of information about twins for the general public; (3) enlist twin achievers to act as role models for adolescent twins; and (4) collect information about the contributions twins have made to their societies in order to dispel still prevalent negative stereotypes about multiples. (Note: The term “twin” is used generically and implies all multiples).
The Secular Trend of Twinning in Australia, 1853–1982
Authors: Doherty J.D.H. , Lancaster P.A.L.
Published: July 2016

The incidence of twinning in Australia from 1853 to 1982 is described. The overall trend was determined by changes in the dizygotic rate and, for more than a century, it has been similar to that found in Finland and the South of Italy. It is not explained by demographic changes and there is no clear relationship with industrialisation or psychosocial factors. Monozygotic twinning has increased, most markedly in the 1970s. No adequate explanation has been given for this increase, so continuing surveillance in many different populations is necessary.
Month of Birth by Zygosity in the NAS-NRC Twin Registry
Authors: Kendler Kenneth S. , Robinette C. Dennis
Published: July 2016

Previous results regarding a seasonality of twin births have been conflicting. Since the biology of monozygotic (MZ) twinning differs from that of dizygotic (DZ) twinning, it is possible that the seasonality of birth for these two twin types might differ. However, all previous studies examining the seasonality of birth by zygosity has estimated zygosity by Weinberg's method. In this report, the month of birth of all MZ and DZ veteran twins from the United States National Academy of Sciences-National Research Council (NAS-NRC) Twin Registry are compared with that found for an unselected group of veterans. Zygosity in the registry has been individually assigned to all twin pairs by a well-validated method. Compared to unselected veterans, the distribution of births by months did not differ significantly for all the veteran twin pairs or for the MZ and DZ twin pairs considered separately. The distribution of month of birth of the MZ and DZ twin pairs did not differ significantly from one another. These results are not consistent with a significant seasonality of MZ, DZ, or all twin births in the United States.
Genetic Expectations of Polar Body Twinning
Authors: Goldgar D.E. , Kimberling W.J.
Published: July 2016

The expected correlation between polar body twins depends upon the frequency and distribution of chiasmata occurring during oogenesis. We have estimated the expected values of these correlations using assumptions believed to be biologically valid. The expected value of the overall correlation between first polar body twins is estimated to be 0.38 and that between second polar body twins is estimated to be 0.51. There is little difference between the correlation of DZ twins and that expected for second polar body twins.

The correlation for a specific locus depends upon its distance from the centromere for both types of polar body twins. This effect is especially marked for second polar body twins. For second polar body twins, loci at or near the telomere will have a correlation close to that expected for first polar body twins. It is concluded that only those marker genes that lie at or close to the centromere are appropriate for the detection of polar body twinning.
Mortality Rate of Japanese Twins and Triplets II. Socioeconomic Factors Influencing Infant Deaths of Twins After Birth to One Year of Age
Authors: Imaizumi Yoko , Inouye Eiji , Asaka Akio
Published: July 2016

The rates of infant mortality of twin individuals were 4.38% and 7.76% for mothers healthy and nonhealthy after delivery, respectively, and the difference is significant at the 0.01 level. The lowest infant mortality rate was seen in the mothers with paid work during pregnancy (4.56%), followed by the mothers engaged only in housekeeping (4.72%) and by those self-employed during the pregnancy (4.99%). Infant mortality rate for MZ twins decreased with increased monthly expenditure of the household, whereas the rate for DZ twins remained constant with expenditure. Socioeconomic factors still affect the infant mortality of twins, and the infant mortality rate can be improved.
Spontaneous or Systematically Induced Labor for the Termination of Twin Pregnancies
Authors: Heluin G. , Papiernik E.
Published: July 2016

The best time for twin delivery is at 38 or 39 weeks gestation. Systematic Caesarean section or induction is decided upon during these weeks. Thanks to this policy, the good results formerly obtained have been maintained and an important decrease in emergency Caesarean sections has been noted thus reducing the risks inherent in this method. However, a randomized trial is necessary to confirm these results.
A Statistical Model and Analysis for Genetic and Environmental Effects in Responses From Twin-Family Studies
Authors: Williams James S. , Iyer Hariharan
Published: July 2016

A statistical model and analysis for genetic and environmental effects in twin-family data are presented. The model is used to derive expressions for phenotypic correlations of 22 essential pair relationships in twin-family units. The analysis proceeds in two steps. First, differential effects of sex, generation, and sex-zygosity of twin-family units and correlations due to cluster sampling are eliminated from correlation data. Then, estimates and tests of model parameters are calculated from the adjusted data. The theory and methods were developed for a Swedish twin-family study of many behaviors possibly related to the smoking habit. There, it is important to screen for behaviors that clearly are under genetic control and to assess relative influences of various biological and social environments on the development of all behaviors. Height data from the Swedish study are used to illustrate concepts and methods presented in this paper.
Quinacrine Mustard and Nucleolar Organizer Region Heteromorphisms in Twins
Authors: Morton C.C. , Corey L.A. , Nance W.E. , Brown J.A.
Published: July 2016

Patterns of NOR activity in 640 metaphase spreads from twelve monozygotic (MZ) and eight dizygotic (DZ) twin pairs were studied to evaluate the heritability of this chromosomal heteromorphism. NORs were stained by a modification of the Ag-AS technique and counterstained with quinacrine mustard dihydrochloride to facilitate chromosome identification and assess their value in zygosity determination. In this study, all karyotypes were read blind with respect to zygosity and pair membership.

A discriminant function analysis of pair score differences in MZ and DZ twins revealed that, in our sample, the probability of accurately determining zygosity with NOR scores was 0.93 and with QFQ scores was 0.99. We conclude that NOR and QFQ scores are highly heritable and of great value in zygosity determination.

Data were collected from 687 metaphase spreads on the frequency with which an acrocentric chromosome was found in a satellite association. A significant correlation was found between this frequency and the degree of Ag-AS stain of the NOR. This study, therefore, confirms previous results showing that a high degree of NOR activity is found in those chromosomes most often involved in satellite associations.
The Effects of Hospitalization for Bed Rest on Duration of Gestation, Fetal Growth and Neonatal Morbidity in Triplet Pregnancy
Authors: Crowther C.A. , Verkuyl D.A.A. , Ashworth M.F. , Bannerman C. , Ashurst H.M.
Published: July 2016

Nineteen women attending a special multiple pregnancy antenatal clinic with a triplet pregnancy were randomly allocated to either bed rest in hospital from 24 weeks gestation onwards until delivery, or to continue conventional outpatient management. Conclusions are limited by the trial size, but the study suggests that routine hospitalization for bed rest decreases the incidence of preterm delivery and light-for-gestational age infants and reduces the need for intensive neonatal care. Although still compatible with change variation, the observations, if confirmed in a larger randomized study, would have considerable implications for clinical practice. The policy needs further evaluation in a large multicentred collaborative study.
Estimates of Genetic and Environmental Components of Serum Isocitrate Dehydrogenase (ICDH) in Normal Twins
Authors: Rapaport D. , Colletto G.M.D.D. , Vainzof M. , Zatz M.
Published: July 2016

Environmental (b2) and genetic heritability (h2) of serum isocitrate dehydrogenase (ICDH) were estimated in 96 pairs of healthy twins according to a path analysis model. The results showed significant heritability (0.42) and a very low environmental component (based on obesity and level of habitual physical activity), suggesting that these factors do not influence ICDH serum activity.
Presence of an Endothelioid Tubelike Structure at the Interface of the Amniotic Membranes in Twins with Single and Double Placenta. Growth Factors Involvement
Authors: Bondì M. , Brenci G. , Bondì M.
Published: July 2016

A histomorphological study of the amniotic membranes in full-term twins with double and single placenta was carried out by means of the silver impregnation staining technique suitably modified. Specimens of interface of amniotic membranes were prepared by means of sections. The constant presence of a tubelike structure was observed. Proceeding from the amniotic cavity, the following histological layers were noted: 1) single layer of amniotic cells; 2) amorphic substance with fibrocytes; 3) single layer of endothelial cells. The same order of single layer is present in the amniotic membrane of the second fetus. This tubelike structure is present only in cases of twins with double placenta. If the placenta is single with two umbilical cords, the tubelike structure is not present and only a central amorphic substance surrounded by two single layers of amniotic cells is observed, to confirm the single embryogenetic derivation (monovular). Therefore, through this histological method, we can recognize the true single placenta of twin pregnancy from the pseudosingle placenta so said for the presence of adherences of adjoining surfaces that make it appear single. On the contrary, by manual dissection it is possible to identify a twin pregnancy with two placentae. From the physiological point of view, the walls of the tubelike structure have probably the function to realize exchanges of amniotic liquids between the two fetuses, so as to obtain a balance of electrolytic ions and of intercavity pressure. Growth factors (vascular endothelial factor) are probably involved in the genesis of the endothelial tubelike structure.
Genetic and Environmental Control of Blood Pressure in Twins and Their Family Members
Authors: Tishler P.V. , Lewitter F.I. , Rosner B. , Speizer F.E.
Published: July 2016

An interdisciplinary study, in adult twins and their family members, of the genetic and environmental determinants of complex physiologic functions is in progress. This report summarizes our initial studies of the control of the level of systolic (K1) and diastolic (K5) blood pressure in 202 monogygotic (MZ) and 121 dizygotic (DZ) twins, their spouses and their children. Correlation coefficients for blood pressure were adjusted for the covariates age, sex, body mass index (wt/ht2) and screener, all of which significantly augment most correlations. These adjusted correlation coefficients in MZ twins are 0.5 for both K1 and K5 blood pressure. For DZ twins, the adjusted correlation coefficients are 0.21 (K1) and 0.24 (K5). MZ twin-offspring adjusted correlation coefficients are higher than MZ twin-niece/nephew adjusted correlation coefficients (0.12 and 0.06, respectively, for K1; 0.20 and 0.13, respectively, for K5), despite the genetic identity of these relationships. That environmental factors may explain these differences is suggested by other differences in adjusted correlation coefficients that are greater than those predicted by the degree of genetic similarity. In addition, we have assessed the relationship between two biochemical-physiological processes, the urinary excretion of kallikrein and transport of sodium in the erythrocyte (the sodium countertransport and the sodium-potassium-chloride cotransport systems), and blood pressure control, since both have been implicated in the control of blood pressure level. Although we found evidence for substantial genetic control of both phenomena, we were unable to establish any correlation between either function and the level of blood pressure in our normotensive subjects.

These data point to the operation of three broad categories of control of level of blood pressure: constitutional factors (age, sex, body mass), genetic factors and environmental factors. The identities of the genetic and environmental factors are unknown at this time.
A Family Study of Developmental Effects upon Blood Pressure Variation
Authors: Sims J. , Carroll D. , Hewitt J.K. , Turner J.R.
Published: July 2016

In an earlier study of blood pressure variation in middle aged parents and their young adult twin offspring, the greater blood pressure variation observed in the parent sample was accounted for in terms of an increasing influence of individual environmental experiences with increasing age and a commensurate reduction in the impact of heredity. In the present study, the sample size was enlarged to provide a more powerful test of these effects. Maximum likelihood model-fitting techniques were applied to blood pressure covariation in balanced pedigrees, consisting of 85 families (40 MZ and 45 DZ twin pairs). As before, our analysis indicated that a developmental effect was a salient factor in the older age group.
Genetic Variance Estimates and Familial Resemblance for Body Size Traits
Authors: Sharma Krishan
Published: July 2016

To study genetic contribution to complex body size traits, the intrafamilial correlation and regression analyses along with twin study method have been used. The data are based on a sample of 45 MZ and 101 DZ twin pairs, their 125 singleton siblings, 104 fathers and 103 mothers in 146 Punjabi families living in Chandigarh, India. Twin study gives no evidence of inequality of means and variances between zygosities. Within-pair genetic variance ratios, correlations, regressions of offspring on midparent and single parent are all significant at 0.1%, thus indicating strong genetic component. Heritability estimates are higher for longitudinal body traits than the breadth dimensions. The resemblance of the children with the parents of either sex is not equal. Higher maternal influence is indicated for a number of body traits. The results on familial correlations do not support the hypothesis of sex-linked inheritance for any of the traits considered in this investigation. These results have been compared with those from other such studies.
Twins and Chronogenetics: Correlated Pathways of Development
Authors: Wilson Ronald S.
Published: July 2016

The study of developmental processes in twins furnishes a powerful resource for examining the role of gene-action systems in guiding the course of growth [2,9].

While there is a steady and rapid progression from birth onward, the growth rate is not entirely uniform for a given child, but rather moves in episodes of acceleration and lag. The timing of the growth spurts follows a distinctive pattern for each child, and consequently a child who may be smaller than average at one age may then enter a phase of rapid growth, and ultimately catch up with or surpass his peers at a later age.

The effect of such individualized patterns of growth is that many children may change in relative size from one age to the next; and in this sense it may appear that the underlying developmental processes are erratic, rather than coherent. But if there is an underlying ground plan, a chronogenetic pattern, then the distinctive developmental gradients should unfold in synchrony for twins sharing the same genetic make-up. Episodes of acceleration and lag in growth would then occur in parallel for both twins and would presumably represent the activity of timed gene-action systems, which switch on and off according to a predetermined plan.
Features of Interaction in Infant Twins
Authors: Clark P.M. , Dickman Z.
Published: July 2016

Twins, more than any other home reared infants, experience intimate and usually continuous interaction with an age-mate from early infancy. The effects of this situation are examined and its implications for both the emotional and cognitive development are discussed in the light of evidence from two studies in which play sessions were video-recorded and subsequently analysed into behavioural categories. The first was a longitudinal study of a single pair of twins, while the second was a short-term study of interaction and cooperation in infants in the 9 to 20 months range. Five pairs of twins, 5 pairs of familiar peers, and the children's mothers were observed playing a structured cooperative game. The hypothesis is advanced that twins enjoy more emotional support but less intellectual stimulation than singletons and it is suggested that social enrichment of the environment of twins could foster social and cognitive development.
Twin Similarity in the Developmental Transformations of Infant Temperament as Measured in a Multi-Method, Longitudinal Study
Authors: Matheny Adam P.
Published: July 2016

In the Louisville Twin Study, laboratory observations of twin infants' temperament at 12, 18, and 24 months were linked with parental ratings from temperament questionnaires. Core dimensions of temperament were extracted by factor analysis applied to each set of measures at each age. The laboratory temperament dimension was recurrently represented by emotional tone, social orientation, attentiveness, and reaction to restraint. The questionnaire temperament dimension was recurrently represented by mood, approach/withdrawal and adaptability. The laboratory and questionnaire dimensions were found to be correlated at each age (convergent correlations: 0.38 to 0.52) and to be stable across ages (stability correlations 0.37 to 0.66). The temperament dimensions were used to demonstrate that temperament profiles were more concordant for identical than for fraternal twin pairs. The results demonstrate the genetic influences on (a) the primary dimensions of temperament and (b) the developmental transformations of temperament.
The High Incidence of Reading Disability in Twin Boys and Its Implications for Genetic Analyses
Authors: Hay D.A. , O'Brien P.J. , Johnston C.J. , Prior M.
Published: July 2016

In 1975 the Australian Council of Educational Research (ACER) conducted a nationwide survey of literacy and numeracy in 10- to 14-year olds. A total of 297 of the 12875 children involved were twins. By age 14, only 42% of the twin boys achieved adequate standards of literacy compared with 71% of single-born boys. The deficit in twin girls was much less and twins of both sexes were only moderately behind in numeracy. A survey of 9-13-year-old twin boys in the La Trobe Twin Study (LTS) produced similar results with 75% being below average in reading skills and 23% behind by 18 months or more, despite above average IQs. The ACER data are corroborated by teachers' reports obtained in the same survey, which indicate also how few of the twins with problems are receiving remediation and the high incidence of classroom problems in spelling and reading reversals. The pattern of mistakes twins make on specific items in the ACER survey can be explained as resulting either from specific cognitive deficits or from problems in concentration. The same factors influence performance on different tasks, so that literacy and numeracy are much more closely interrelated in twins than in singletons, and also correlate more with a measure of verbal intelligence. Implications for genetic analysis of scholastic achievement are examined, centering around the different factor structure of abilities in twins and common family environmental effects which are unique to twins.
Antenatal Genetic Studies in Twin Pregnancies
Authors: Redwine F.O. , Cruikshank D.P. , Brown J.
Published: July 2016

The diagnosis of multiple gestation at the time of genetic amniocentesis is a routine occurrence. In a combined series of 2765 patients referred for antenatal genetic studies from the Medical College of Virginia and the University of Iowa, 34 twin pregnancies were encountered (1.2%). Twenty-six of the patients with twins were referred for advanced maternal age. The other indications were previous neural tube defects (1), previous trisomy 21 (2), known carriers of Tay Sachs disease (2), previous Turner's syndrome (1), family history of trisomy 21 (1), and one pregnancy was referred because of an abnormal ultrasound. Amniocentesis procedures, outcome of the twin pregnancies, and genetic counseling issues, are discussed.
Congenital Heart Defects and Twinning
Authors: Burn J. , Corney G.
Published: July 2016

A preliminary analysis of twins or triplets with heart defects, ascertained in five centres, confirms earlier suggestions that monozygotic (MZ) twins are over represented among twins with heart defects, even after excluding persistent ductus arteriosus and conjoined twins. An MZ twin individual has a risk of cardiovascular malformation approximately twice that of DZ twins and singletons. It is suggested that the twinning process itself affects one of the pair. Disturbance of laterality (‘mirror imaging’) is probably a more important mechanism than twin-twin transfusion. Inappropriate use of the twin method in the past has caused the importance of genetic factors in the etiology of congenital heart defects to be underestimated. Neverthless, twins do provide a useful illustration of the likely importance of epigenetic factors in heart development.
Malformations in Twins and Their Siblings, Norway, 1967-79
Authors: Windham G.C. , Bjerkedal T.
Published: July 2016

During 1967-79 the population-based Medical Birth Registry of Norway registered 7,660 twin pairs (1% of births) born to 7,596 mothers, who gave birth to 6,608 additional infants (twin siblings). The total rate of malformations among twins (278.1/10,000) was not significantly different than among singletons (302.1/10,000), nor among twin siblings (314.8/10,000). By specific type of defect, twins had significantly higher rates than singletons of central nervous system (CNS) defects (Rate Ratio = 1.8) and cardiovascular defects (RR = 1.5). The twins also had a significantly low rate of congenital hip dislocation (RR = 0.4), which may explain the relatively low incidence of malformations in twins. Like-sex (LS) twins had a slightly higher rate of malformations than unlike-sex (US) twins (RR = 1.1), as well as a higher rate of CNS defects (RR = 3.0). The siblings also had a significantly increased rate of CNS defects compared to singletons (RR = 1.9), but not of cardiovascular defects (RR = 0.9). The results indicate that twins have elevated rates of at least some congenital malformations. The observations about CNS defects suggest common factors that can lead to either like-sex twinning, CNS defects, or both. The increased frequency of cardiovascular defects in twins appears to be associated with the biologic conditions of twinning.
Problems of Ascertainment of Congenital Anomalies
Authors: Little J. , Carr-Hill R. A.
Published: July 2016

Problems of ascertainment bedevil the investigation of the etiology of congenital anomalies in singletons and in multiple births by epidemiological methods. It is shown that the definition of the population of affected births is ambiguous and that the problem of tracing etiology is complicated by the systematic way in which anomalies may be missed at birth. The available methods of dealing with problems of ascertainment are reviewed. Methods of adjusting for possible bias of ascertainment of affected births, by fitting statistical models to data from several sources, have been employed in some previous studies. In these methods, it is assumed that there are no errors of diagnosis or of recording. However, it is shown that there may be discrepancies in recorded diagnoses between sources, rendering this assumption untenable. In these methods, it is also assumed that the model which is the best fit to the data on the ascertained cases in also the best model for the cases which were not ascertained. This assumption is tested indirectly in a retrospective analysis of data from Aberdeen and Belfast collected concurrently through routine recording systems. It is demonstrated that there was a social process in ascertainment which renders the methods of adjusting for bias of ascertainment at best very complicated and at worst inapplicable.