Effects of chorion type on variation in cord blood cholesterol of monozygotic twins

Cholesterol levels were measured in the cord blood of 30 pairs of monochorionic and 22 pairs of dichorionic monozygotic (MZ) twins. Cholesterol levels were found to be significantly higher in female twins when data was combined over chorion type. The type of chorionic development had no significant effect on variation among twin pairs. Chorion type did, however, have a significant effect on the within-pair variation. The variation within dichorionic pairs was more than five times that within monochorionic pairs (P less than .01). This result suggests that the variation in placentation has a significant effect on within-pair variation in serum cholesterol of newborn MZ twins.     

Modified intra-arterial calcium stimulation with venous sampling test for preoperative localization of insulinomas

BACKGROUND: Both genetic and environmental factors are thought to contribute to specific IgE responses, however, the relative contribution of each in the responses to individual ryegrass pollen allergens is largely unknown even though some responses to allergens have been linked to certain HLA complexes. OBJECTIVE: Using a large group of monozygotic and dizygotic twins, this study was designed to investigate the IgE binding profiles of individual ryegrass pollen (Lolium perenne) components to assess the relative contribution of genetic and environmental factors in determining IgE responses to specific allergens. METHODS: Ryegrass pollen proteins were separated by electrophoresis and immunoblotted with sera from 191 pairs of twins where at least one sibling had a SPT > 2 mm to perennial ryegrass. Concordance levels for individual ryegrass pollen components were compared between monozygotic and dizygotic twins in a subset group where both twins had SPT > 3 mm to perennial ryegrass. RESULTS: Immunoblotting revealed 23 individual IgE-binding components from ryegrass pollen. Although there was a significantly greater proportion of monozygotic twins with SPT wheals greater than 3 mm when compared with the dizygotic twins, the mean case-wise concordance for the immunoblot components was similar for both groups of twins. The mean case-wise concordance when at least four pairs of sera were involved was 44% for the MZ twins (n=11 components) and 45% for the DZ twins (n=12 components). We found no significant differences in concordance levels for any of the 23 individual components including allergens previously associated with HLA. CONCLUSION: Evidence for genetic control of allergen-specific IgE responses in a large population sample of twins to individual ryegrass allergens is limited, indicating that the IgE responses to specific ryegrass pollen allergens are determined largely by environmental factors.     

Zygosity and intrauterine growth of twins

Six hundred seventy-eight sonar measurements of the fetal biparietal diameter (BPD) were used to assess the intrauterine growth of 182 twins between 18 and 40 weeks' gestation. These values, as well as the weight and body length at birth, were related to the zygosity, which was determined by sex of the infants, histologic examination of placenta, or blood grouping. The mean BPD of twin 1 was larger than that of twin 2 in both monozygotic and dizygotic pairs throughout the study period (P less than .001). The size of BPD of the dizygotic infants exceeded that of the monozygotic among both twin 1 (P less than .001) and twin 2 (P less than .001). The absolute intrapair differences of birth length and weight were larger among dizygotic than among monozygotic twins. These findings suggest that in late pregnancy a substantial one-way intertwin transfusion among monochorial twins does not occur frequently enough to mask the inherent genetically determined similarity between the twins. The appearance already in the second trimester of the difference in the longitudinally monitored BPD between monozygotic and dizygotic twins suggests that the discrepancy is determined early in gestation.     

Liver histology in chronic hemodialysis patients infected with hepatitis C virus

To investigate the influence of genetic and/or environmental factors in the development and shaping of the human peripheral T cell repertoire the authors studied the T-cell receptor (TCR) V beta usage in 10 adult monozygous (Mz) and nine dizygous (Dz) twin pairs living in a Plasmodium falciparum endemic area in West Africa. The TCR repertoire was determined using a small panel of anti-V beta specific monoclonal antibodies (MoAbs) using conventional immunofluorescence assays. The results revealed that the V beta repertoire was similar to that recently described for a Caucasian population using a similar panel of antibodies. The frequencies of particular V beta genes tested were influenced neither by anti-malarial antibody titres nor by parasite densities, indicating that the P. falciparum parasite is not a dominating factor in determining the peripheral T cell repertoire. All donors were human leucocyte antigen (HLA) class I and II typed; no association was found between the expression of any V beta genes and MHC haplotype. The V beta usage was more concordant within the Mz than within the Dz pairs. For a group comprising four HLA class II identical individuals, the average within-pair difference was significantly greater than for the whole Mz group, but similar to that seen for the total Dz group. Thus, the data suggest that genetic, rather than environmental, factors have a profound effect on the shaping of the human circulating T cell repertoire and that the major genetic factors are encoded by non-HLA class II genes.     

Twin imitation for antisocial behavior: Implications for genetic and family environment research.

When twin pairs influence each other's behavior, observed variance is greater for monozygotic (MZ) twins than for dizygotic (DZ) twins under at least 1 of 2 conditions: (1) The trait has some heritability, and (2) MZ twins influence each other more than do DZ twins. Applied to a trait that has an underlying continuous distribution but is measured as a dichotomy, the presence of reciprocal twin influence predicts that if the base rate for the trait is not exactly 50%, then the prevalence of the trait should differ in MZ and DZ twin pairs. This prediction held for registered criminality in a large twin cohort. Methods of analysis that permit reciprocal twin interaction not only provide better statistical fits to the data but also yield estimates of heritability that agree with adoption data. Results suggest that the genetic influence on registered criminality may be more modest than previously thought. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Extrathymic and thymic origin of murine IEL: are most IEL in euthymic mice derived from the thymus?

Given the current explosion of knowledge of the genetics and molecular biology of cancer, the possibility of widespread testing for inherited predisposition to cancer has been raised. The main objective of this study was to assess the effect of inherited predisposition on cancer mortality among the National Academy of Sciences-National Research Council Twin Registry. The twins were white male United States veterans of World War II, who were born during the period 1917-1927. The follow-up period was from 1946 to 1990, and some cause of death was determined with the use of death certificates. We compared concordance for death from cancer among 5690 monozygotic twin pairs to that among 7248 dizygotic pairs. A possible effect of inherited predisposition to death from cancer was considered present if concordance for cancer mortality among monozygotic twin pairs was greater than it was among dizygotic twin pairs. Among monozygotic and dizygotic twins, a total of 1918 cancer deaths was observed. Concordance for death from cancer at all sites among monozygotic twins was higher than it was among dizygotic twins (overall rate ratio, 1.4; 95% confidence interval, 1.0-2.0). For each zygosity group, two or fewer pairs were observed to be concordant for death from cancer of a specific site, with the exception of lung cancer.(ABSTRACT TRUNCATED AT 250 WORDS)     

Are the brains of monozygotic twins similar? A three-dimensional MR study

PURPOSE: The role of genetic mechanisms and the influence of environmental events in human brain development have been difficult to evaluate. The purpose of this study was to compare the cerebral cortical morphology and midline structures of monozygotic twin pairs using MR imaging. METHODS: Six observers, blinded to twin pairings, evaluated the 3-D renderings of the cortical surface and midline structures from MR images of seven monozygotic twin pairs. A morphometric analysis of the corpus callosum and of the distance between the anterior and posterior commissures was also performed. RESULTS: Despite surprising anatomic differences, the brains of the twin pairs were similar enough to enable the observers to distinguish twin pairs from unrelated subjects. Five of six observers correctly identified the brains of all seven twin pairs; the remaining observer failed to make a correct match in only one of seven pairs. Three of six observers identified the midline sagittal images of the related twins in all seven pairs, and the other three identified the related midline sagittal images in five of seven pairs. The results were statistically significant. CONCLUSION: Although the observed differences in morphologic characteristics between twins necessarily reflect nongenetic influences, the cortical patterns and midline structures of monozygotic twins probably are genetically similar.     

Population based study of prevalence of islet cell autoantibodies in monozygotic and dizygotic Danish twin pairs with insulin dependent diabetes mellitus

OBJECTIVE: To study the comparative importance of environment and genes in the development of islet cell autoimmunity associated with insulin dependent diabetes mellitus. DESIGN: Population based study of diabetic twins. SETTING: Danish population. SUBJECTS: 18 monozygotic and 36 dizygotic twin pairs with one or both partners having insulin dependent diabetes. MAIN OUTCOME MEASURES: Presence of islet cell antibodies, insulin autoantibodies, and autoantibodies to glutamic acid decarboxylase (GAD65) in serum samples from twin pairs 10 years (range 0-30 years) and 9.5 years (2-30 years) after onset of disease. RESULTS: In those with diabetes the prevalence of islet cell antibodies, insulin autoantibodies, and autoantibodies to glutamic acid decarboxylase in the 26 monozygotic twins was 38%, 85%, and 92%, respectively, and in the dizygotic twins was 57%, 70%, and 57%, respectively. In those without diabetes the proportions were 20%, 50%, and 40% in the 10 monozygotic twins and 26%, 49%, and 40% in the 35 dizygotic twins. CONCLUSION: There is no difference between the prevalence of islet cell autoantibodies in dizygotic and monozygotic twins without diabetes, suggesting that islet cell autoimmunity is environmentally rather than genetically determined. Furthermore, the prevalence of islet cell antibodies was higher in the non-diabetic twins than in other first degree relatives of patients with insulin dependent diabetes. This implies that the prenatal or early postnatal period during which twins are exposed to the same environment, in contrast with that experienced by first degree relatives, is of aetiological importance.     

Sexual victimization in adolescent girls (age 15-20 years) enrolled in post-mandatory schools or professional training programmes in Switzerland

We investigated 21 pairs of twins for zygosity and idiopathic scoliosis. DNA fingerprinting confirmed that 13 pairs were monozygotic and eight were dizygotic. There was concordance for idiopathic scoliosis in 92.3% of monozygotic and 62.5% of dizygotic twins. Of the 12 pairs of monozygotic twins concordant for idiopathic scoliosis, six showed discordant curve patterns but eight had differences in Cobb angle of less than 10 degrees. Seven of the ten pairs of monozygotic twins had similar back shapes. Our findings suggest that there is a genetic factor in the aetiology of idiopathic scoliosis; they also indicate that there is a genetic factor in both the severity of the curve and the general shape of the back.     

The effect of hydration upon the conformation and dynamics of neocarrabiose, a repeat unit of beta-carrageenan

Population studies on human twinning are scarce in Argentina. In order to analyze frequencies and certain maternal and neonatal variables related to twin births, we studied a series of 69.678 consecutive newborns with 500 g of weight and over, which occurred at a public hospital in the province Buenos Aires, during 14 years (1982-1995). The frequency of twin births (10 per 1000 deliveries) and sex ratio were similar to other studies reported in Caucasian population. Maternal age and order of gravity/parity were positively correlated with twinning rates, more markedly so in dissimilar sex-pairs. Stillbirths and neonatal deaths were more frequent in twins than in singletons, but less frequent when comparing groups of same weight. Congenital malformations were not found to be significantly more frequent in twins than in the total newborn population. However, their occurrence, predominantly in like-sexed pairs and the concordance for defect type in doubly affected same-sex pairs, suggests that monozygotic twinning carries an increased risk for malformation.     

Receptor imaging: competitive or complementary to antibody imaging?

The hypothesis that a low concordance rate in monozygotic (MZ) twins with systemic lupus erythematosus (SLE) may be accounted for by differences in X-chromosome inactivation was examined. Five MZ twin pairs, four discordant and one concordant, were recruited, zygosity confirmed by DNA fingerprinting, and their pattern of X-chromosome inactivation in DNA samples prepared from peripheral blood and buccal cells were examined. X-chromosome inactivation was assessed by the methylation status of the CpG region near trinucleotide repeats in exon 1 of the androgen receptor gene on X-chromosome after digestion with the methylation-sensitive enzyme HpaII or HhaI and PCR amplification. X-chromosome inactivation patterns were found to be the same between affected and non-affected twins in all four discordant twin pairs, with random patterns in two pairs and skewed patterns in the others. The concordant twins demonstrated the same random patterns. X-chromosome inactivation was also examined from buccal smear DNA and shown to have the same pattern as that noted from peripheral blood DNA in one informative twin pair. Differences in X-chromosome inactivation patterns were not observed in these five MZ twin pairs. The results could not support the hypothesis that differences in X-chromosome inactivation is the mechanism accounting for the low concordance rate noted in MZ twins with SLE.     

Normal personality characteristics in identical twins discordant for schizophrenia.

The authors examined normal personality characteristics of monozygotic (MZ) twins discordant for schizophrenia. Twenty pairs of discordant twins were analyzed; 11 pairs of MZ twins concordant for schizophrenia served as a comparison group. Personality was assessed using the Multidimensional Personality Questionnaire (MPQ; A. Tellegen, 1995). Among discordant twin pairs, twins with schizophrenia were more deviant than normal co-twins on all but 4 of the MPQ's scales. Analysis of MZ twin correlations among the discordant twin pairs revealed substantial erosion of personality similarity as compared to normal individuals, although a cluster of scales related to Constraint/Psychoticism showed significant correlations. The results highlight striking personality divergence related to nonshared environmental influences. It is not possible to determine the point at which the twins diverged, although previous findings from this sample suggest that the observed personality differences may reflect effects of schizophrenia on normal personality. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mitogenic activity of neu differentiation factor/heregulin mimics that of epidermal growth factor and insulin-like growth factor-I in human mammary epithelial cells

BACKGROUND: Twin registers provide a valuable source for research into disease causation. The existing population-based registers comprise mostly old twins. In order to be able to study diseases which occur in childhood and youth a new Danish twin register has been established. METHODS: The register is based on the Danish Civil Registration, with information on number of twin births from the Danish Vital Statistics Office as the source of validation. All twins resident in Denmark at 1 March 1991 were sent a one-side questionnaire asking about diabetes, willingness to participate in other research projects and similarity in the twins. RESULTS: The register, comprising 20,888 twin pairs, covers 74.4% of all twin pairs born 1953-1967 (incl.) and 97.4% of those born 1968-1982 (incl.). The response rate to the questionnaire study was 92.3%. The responders represented 19,180 twin pairs distributed as 5304 monozygotic pairs, 6861 same-sex dizygotic pairs, 6244 opposite-sex dizygotic pairs and 771 pairs of unknown zygosity. Of the respondent twins, 96% declared their willingness to participate in additional studies. An analysis of trends in the twinning rates for the years 1968-1982 showed that the rate of monozygotic twinning is increasing and the twinning rate of opposite-sex twin pairs is decreasing. CONCLUSIONS: Earlier estimated trends in twinning rates have been confirmed. Due to the high response rate and opportunities for linkage with other Danish registers, the present material provides a valuable resource for twin studies in diseases and human traits.     

Determinants of plasma levels of plasminogen activator inhibitor-1 : A study of normotensive twins

We investigated whether plasma levels of the plasminogen activator inhibitor type 1 antigen (PAI-1:Ag) are genetically determined in monozygotic (MZ) and dizygotic (DZ) twins. Twenty-five pairs of healthy twins underwent measurements of PAI-1:Ag and other variables, including body mass index, mean blood pressure, plasma renin activity, insulin, and glucose. To ascertain the zygosity of twins, highly discriminating micro- and minisatellite systems with variable numbers of tandem repeats were analyzed by PCR amplification followed by polyacrylamide gel electrophoresis. Subjects were also genotyped for the 4G/5G polymorphism by PCR. Estimates of genetic variance and heritability were obtained for PAI-1:Ag, and for body mass index, mean blood pressure, plasma renin activity, glucose, and insulin by jointly examining data in a path analysis with TWINAN90. Results showed that 12 pairs of twins were MZ and 13 were DZ. All tests of genetic variance [within pair (WP): F=6.24, P=0.002; among component (AC): F=2.62, P=0.04; average absolute difference t test=3. 00, P=0.004] showed significant genetic variance of PAI-1:Ag, but not of the other variables. Three tests of heritability (WP=0.837, P=0.002; AC=1.791, P<0.05; intraclass correlation: 1.180, P=0.001) consistently showed significant PAI-1:Ag heritability. Additive genetic influences (A), dominance genetic effect (D), and random environmental influences (E) accounted for 0.714, 0.154, and 0.132 of PAI-1:Ag variance, respectively. No effect of different 4G/5G genotypes was found. Thus, these results show significant genetic variance and heritability of PAI-1:Ag and suggest that A is more important than both D and E in determining PAI-1:Ag variance.     

Lack of association of increased antibody levels to mycobacterial hsp65 with rheumatoid arthritis: results from a study of disease discordant twin pairs

OBJECTIVES: To investigate the role of humoral immunity to mycobacterial hsp65 in the aetiology of rheumatoid arthritis. METHODS: Levels of IgG antibodies to recombinant mycobacterial hsp65 were measured by enzyme linked immunosorbent assay (ELISA) in serum samples of 152 twin pairs discordant for RA and in serum samples from 62 normal blood donors. RESULTS: No significant differences between antibody levels in the subjects with RA compared either with their unaffected twins or with a group of normal blood donors was observed. In the monozygotic twins there was a strong but negative association between levels of antibody to hsp65 and disease status. Zygosity, sex, and HLA status did not significantly affect levels of antibody to hsp65. CONCLUSION: Previous reports of an association between hsp65 and RA were not confirmed.     

A comparison of digital luminescence mammography and conventional film - screen system: preliminary results of clinical evaluation

The heritability of total plasma testosterone levels, determined from blood samples, was examined in 160 adolescent twin pairs and their parents. Subjects were tested as part of a larger study of cardiovascular risk factors, conducted in Amsterdam. Each subject provided a sample of blood which was assayed to measure testosterone concentrations. Correlations of testosterone in monozygotic twins were higher than in dizygotic twins. No resemblance was found between testosterone values in fathers and those in their children and a moderate correlation was seen between mothers and their daughters. The lack of resemblance between family members of opposite sex suggests that different genetic factors influence plasma testosterone concentrations in men and women. In adolescent men, approximately 60% of the variance in testosterone levels is heritable. The lack of father-son resemblance suggests that different genetic factors may be expressed in adolescence and adulthood. In women, 40% of the variance in testosterone levels is heritable, both in adolescence and in adulthood.     

Neuroticism, extraversion, and related traits in adult twins reared apart and reared together.

The relative importance of genetic and environmental factors for neuroticism, extraversion, and impulsivity, and monotony avoidance were estimated in a sample of 99 monozygotic and 229 dizygotic pairs of twins reared apart (TRA) and a matched sample of 160 monozygotic and 212 dizygotic pairs of twins reared together (TRT). The average age was 58.6 (SD?=?13.6); 72% of the twins were 50 or older. Model-fitting analyses verified the importance of genetic factors for all four measures; from 23% to 45% of the total variation was attributable to genetic sources. There was considerable evidence that these factors were operating in a nonadditive manner for extraversion and impulsivity. Shared environment accounted for less than 10% of the variance, some evidence for selective placement was found for neuroticism. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Auditory lateralization in monozygotic twins

In an attempt to investigate whether auditory lateralization has a heritable component, 20 monozygotic (MZ) twin pairs were examined with four different dichotic listening tests known to produce reliable right-ear advantages (REAs) in right-handers. Ten twin pairs were concordantly right-handed (MZ-RR), and ten twin pairs were discordant for handedness (MZ-RL). Intraclass correlations for MZ twin pairs were weak or nonexistent for ear advantage, but relatively strong for overall correct scores and mean reaction times, measures unrelated to laterality scores. These results support the hypothesis that auditory lateralization, as measured with dichotic tests, is nongenetic in origin. A comparison of MZ twins and right-handed siblings (n = 20) showed that right-handed siblings exhibited strong REAs, whereas left-handed siblings (n = 20) and MZ twins showed weak or absent REAs, indicating that twins may be atypically lateralized with respect to auditory lateralization.     

The treatment of advanced ovarian carcinoma with high dose, intravenous cyclophosphamide

The equal environments hypothesis of twin methodology was examined for the variable of similarity of appearance as it affects the personality ratings of young twins. There were two separate samples, the first with 95 pairs of same-sex twins and the second with 111 pairs. The average age of the twins in both samples was 3-1/2 years. Mothers rated their twins on four personality traits and on confusability of appearance. Not surprisingly, identical twins were markedly more similar in appearance than fraternal twins. The effect of this inequality on the personality ratings of the two types of twins was examined by correlating ratings of similarity of appearance with the absolute difference on the four personality traits for each pair of twins. None of the correlations was significant for the identical twins, suggesting that greater resemblance in appearance in identical twins does not make them more similar in personality. Indeed, the data suggested a contrast effect in which identical twins who were easily mistaken in appearance tended to be rated as less similar in personality. Thus, although similarity of appearance may create unequal environments for the two types of twins, it does not appear to bias twin studies in the direction of inflated heritabilities, at least for rating studies of the personality of young twins.     

epsilon-COP is a structural component of coatomer that functions to stabilize alpha-COP

A behavior genetic analysis of the personality dimension of ego development, as assessed by the Washington University Sentence Completion Test, was carried out on a sample of 45 pairs of monozygotic twins and 28 pairs of same-sex dizygotic twins. The twins ranged in age from 16 to 70 years at the time of assessment, had been separated during infancy, and had been raised apart in adoptive homes before being reunited in adulthood. Analyses indicated that reared-apart twins were similar in trait levels of ego development and that such similarity could not solely be attributed to measured similarity in cognitive ability, including verbal reasoning. Estimates of broad similarity for ego development (46%) were comparable to values reported for other major personality dimensions. Phenotypic variance in adult levels of ego development appears to have substantial genetic and environmental sources.