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Intergenerational closure refers to parents’ knowing the parents of their adolescents’ friends. This study treated intergenerational closure—as reported by the parents of adolescent twins—as the dependent variable in a behavioral genetic analysis. The sample consisted of identical and fraternal twin pairs in the National Longitudinal Study of Adolescent Health (Add Health). Models that were fit to twin covariance matrices estimated that additive genetic influences accounted for 44% of the variance in intergenerational closure and shared environmental influences for 44%. These findings provide evidence that the heritable characteristics of adolescents influence the connections between their families and their extrafamilial social networks.

Background:A unique opportunity for genetic investigation was presented by a 3-generation family with fraternal twins, one of whom had Crohn's disease (CD) with 2 affected children and the other who was healthy with 3 unaffected children, suggesting an autosomal dominant inheritance. This study test

As a highly versatile intracellular signal, calcium (Ca) regulates many different cellular processes in both animal and plant systems. Disruption of Ca homeostasis contributes to several human diseases. Owing to the importance of Ca signalling, its research is now an active field in life science. There are numerous Ca signalling systems, consisting of a diverse array of signalling units that deliver Ca signals with different spatial and temporal properties [1,2], playing roles in ubiquitous biological processes including gene regulation, fuel generation, substance transport, hormone and neurotransmitter secretion, cell motility and muscle contraction [3]. Consequently, exquisite homeostasis of Ca cycling is the key for health of humans, the disruption of which is related to many human diseases such as heart failure, neuron-degeneration, and diabetes [46]. Many remarkable achievements have greatly enhanced our understanding of Ca signaling, including those from Chinese scientists [710]. The 17th International Symposium on Ca-binding Proteins and Ca Function in Health and Disease was held in Beijing, China, on July 16–20, 2011 [11], accompany which, a special issue of Science China Life Sciences was published for transducing Ca signals to effectors. The first part focused on the mechanisms in maintaining a low cytosolic level of Ca, with two articles reviewing the properties of the plasma membrane calcium ATPases (PMCA) in ejecting Ca into the extracellular space. First, Carafoli [12] reviewed the role of the plasma membrane calcium pump, PMCA2, in the hearing process. As an important plasma membrane Ca ATPases, PMCA2 plays an important role in maintaining intracellular Ca homeostasis in the inner ear. It is involved in the maintenance of intracellular free calcium levels and the dysfunction of which leads to deafness. Recent studies show that another important isoform of PMCA, PMCA4, has a number of roles for heart functioning [13,14]. Cartwright et al. [15] then reviewed the roles of plasma membrane calcium pumps related to cardiovascular disease, focusing on PMCA4, including its function in heart and vasculature, linking PMCA4 to contractile function, cardiac hypertrophy, cardiac rhythm, blood pressure control and hypertension. Undoubtedly, further understanding of the roles of PMCAs will facilitate the development of new treatment strategies for related diseases. As a versatile intracellular messenger, Ca performs roles in many different ways to regulate cellular processes [16]. The second part of this special issue focuses on mechanisms for spatiotemporally-specific increases in cytosolic Ca. First, Lee [17] reviewed studies on the fraternal twin messengers for calcium signaling, cyclic ADP-ribose (cADPR) and nicotinic acid adenine dinucleotide phosphate (NAADP). Since the initial finding by Lee and his colleagues that cADPR and NAADP could liberate stored Ca, they have been shown to be active in mobilizing Ca in a wide range of cells spanning three biological kingdoms. He summarized the cADPR/NAADP/CD38signalling pathway and also described the structure and function of its components. Kimlicka and van Petegem [18] then reviewed the structural biology aspect of ryanodine receptors (RyRs) which are high-conductance ion channels

The Mid-Atlantic Twin Registry (MATR) is a population-based registry of twin pairs ascertained from birth records and school system records of Virginia, North Carolina, and South Carolina. The MATR was formed in 1997 with the merging of the Virginia and North Carolina Twin Registries, and it expanded to include South Carolina when access to twin birth records in that state was granted in 1998. Registered twins ('participants') number more than 51,000, with approximately 46,000 of these individuals representing complete pairs. Roughly two-thirds of MATR participants are over age 18, with a mean age of approximately 35 years. These participants have primarily been drawn from the more than 170,000 identical and fraternal twin pairs born in the three states between 1913 and 2000. Twins and their family members have participated in numerous research projects, ranging from general health surveys to studies on specific health topics such as cardiovascular disease; depression and anxiety; seizures; behavioural development; pregnancy complications; conduct disorder; drug use, abuse, and dependence; cleft lip/palate; obesity; and chronic fatigue syndrome. The MATR has established a privacy policy and strict standard operating procedures to protect the confidentiality of participant data. The MATR considers a limited number of qualified requests per year from investigators interested in recruiting MATR participants into their research studies.

We administered a battery of both behavioral and electrophysiologic measures to a pair of fraternal twin girls, one of whom exhibited symptoms consistent with an auditory processing disorder. Both twins were within normal limits on standardized tests of cognitive and language skills. Basic audiometric measures, as well as behavioral tests of simultaneous masking, backward masking, gap detection, and frequency-sweep discrimination, showed little difference between the twins. Significant differences, however, were evident on event-related potentials (ERPs) in response to both within-channel and across-channel gap detection tasks. Substantial differences were also noted for ERPs to both linguistic and nonlinguistic targets in dichotic listening paradigms. The pattern of electrophysiologic results was consistent with a deficit in the efficiency of interhemispheric transfer of auditory information. A possible reason for the greater effectiveness of electrophysiologic over behavioral measures is discussed.

Host genetic factors may influence the course of human immunodeficiency virus (HIV) infection. In Blantyre, Malawi, polymerase chain reaction was used to identify twin pairs who were concordantly HIV-1-infected in utero or perinatally and then to examine strain divergence or virus levels in identical and fraternal twin pairs. Among 315 twin pairs, both infants in 14 fraternal and 5 identical pairs were found to be infected at the same visit. Among 10 pairs, HIV-1 sequences were determined for both infants at >or=1 time point. HIV levels had a common profile in both fraternal and identical twin pairs. Identical twins were not always infected by the same quasi species, indicating that their mothers had multiple quasi species capable of infecting their infants. Subsequent viral divergence appears to depend on quasi-species stability rather than on genetically controlled host immune responses. Thus, given infection, factors intrinsic to HIV-1 are more important than host genetics in viral evolution.

Multivariate genetic analyses were applied to the six facets defining each of the five personality domains (Neuroticism, Extraversion, Openness to Experience, Agreeableness, and Conscientiousness) assessed by Costa and McCrae's Revised NEO Personality Inventory (NEO-PI-R). The analyses are designed to partition the observed covariance of facets defining each domain into their genetic and environmental bases to determine the basis for their coherence as a domain. The analyses were applied separately to a sample of 253 identical and 207 fraternal twin pairs from Canada and 526 identical and 269 fraternal pairs from Germany. Results showed that each of the NEO-PI-R domains is composed of multiple genetic and environmental factors common to the facets supporting the observed coherence of the NEO-PI-R facet sets. Differences between the German and Canadian sample appeared limited to the magnitude of the genetic and environmental effects on each facet, but not the number or type of genetic and environmental influences. (C) 2002 Elsevier Science Ltd. All rights reserved.

Results obtained from previous studies of word recognition, reading component skills, and reading composite measures suggest that genetic factors may be more important as a cause for reading disability among children with higher IQ scores than among those with lower IQ scores. To investigate the genetic etiology of reading disability further, measures of word recognition, phonological decoding, orthographic coding, and phoneme awareness were obtained from a total of 465 twin pairs with a positive school history of reading problems. The basic and extended DeFries and Fulker (DF) multiple regression models for the analysis of selected twin data were employed to investigate the etiology of group deficits in reading and language skills, as well as to assess differential genetic etiology for the reading-related measures as a function of IQ. Data from 168 sibling pairs (drawn from the twins' families), including fraternal twin pairs and their siblings, as well as non-twin siblings of identical twins were subjected to single-marker analyses using the DF basic linkage model to examine evidence for linkage of a quantitative-trait locus (QTL) for reading and language deficits to the short arm of chromosome 6. Lastly, to investigate the possible differential influence of this QTL as a function of IQ, the sibling pair data were fitted to an extension of the DF basic linkage model. Results indicated that reading and language deficits are significantly heritable and that differential genetic influences as a function of IQ are evident for measures of word recognition and phonological decoding. Results obtained from linkage analyses confirmed the presence of a QTL on chromosome 6p that influences phonological and orthographic skills, as well as phoneme awareness measures, and suggest that this QTL may influence phoneme awareness differentially as a function of IQ: however, future analyses with considerably larger samples are needed to test the hypothesis of differential QTL influence more rigorously.

Congenitally corrected transposition of the great arteries (ccTGA) is characterized by atrioventricular and ventriculoarterial discordance, with an incidence of 0.5% of all congenital heart disease. In ccTGA, the morphological left ventricle connects to the right atrium and the pulmonary artery and the right ventricle to the left atrium and the aorta.1 ccTGA may present as situs solitus or situs inversus. Of these, situs inversus, characterized by mirror-image atria and a right-sided systemic right ventricle, is uncommon, representing just 34% of ccTGA. The pathogenesis of ccTGA is currently unknown and is considered multifactorial. We present a unique case of fraternal twins with ccTGA and primary ciliary dyskinesia (PCD). One twin has ccTGA with situs solitus, whereas his twin brother has ccTGA with situs inversus and dextrocardia. Our aim is to outline the similarities and differences between the twins through their echocardiographic and electrocardiographic findings. Fraternal twin males, without prenatal diagnosis, were born at 36 weeks’ gestation and were well at birth. On day 1 of life, they developed respiratory distress and tachypnea. A chest radiograph was suspicious for dextrocardia in twin B, yet twin A had levocardia (Figure 1). Subsequent echocardiographic findings confirmed ccTGA in both twins; but twin A had situs solitus, whereas twin B had situs inversus (Figures 2 and 3). The electrocardiographic findings …

Incontinentia pigmenti is a rare X-linked dominant condition characterized by cutaneous, neural, ocular and dental manifestations. The condition has mainly been reported in Caucasian females. The aim of this case report is to highlight the clinical presentation in Afro-Caribbean twin girls. The girls demonstrated abnormal hair distribution, pigmented limbs and torso, small conical or missing teeth with delayed dental eruption.

Objective Our objective is to present the first case report of X-linked adrenal hypoplasia congenita in a child conceived by a donated egg and which also presented atypically, with initial mineralocorticoid deficiency. Methods Case report with literature review. Results A late preterm fraternal twin male, conceived by in vitro fertilization of donated eggs, presented shortly after birth with feeding intolerance, hyponatremia, and hyperkalemia. Testing revealed a low aldosterone level, high plasma renin activity, normal cortisol level, and normal 17-hydroxyprogesterone level. He was diagnosed with 18-hydroxylase deficiency based on low 18-hydroxycorticosterone levels and was treated with mineralocorticoid successfully for 17 months. At age 18 months, he presented with dehydration secondary to herpetic gingivostomatitis and was found to be hypoglycemic, hyponatremic, hyperkalemic, and acidotic, with a low serum cortisol level. An adrenocorticotropic hormone (ACTH) stimulation test revealed low levels of all adrenal cortex products, with an elevated ACTH level. He was started on glucocorticoids. Genetic testing confirmed X-linked adrenal hypoplasia congenita (AHC). His asymptomatic fraternal twin underwent genetic testing and the results were negative. The fertility center records indicated that the mother had donated eggs to other families, but none of the children were known to have this disorder. The egg donor was informed but did not pursue genetic testing. Conclusion We report a case of X-linked AHC presenting in the context of extraordinary ethical considerations. Our case raises a question unique to the era of assisted reproduction: should routine genetic screening of gamete donors be done for rare but potentially life-threatening conditions? (Endocr Pract. 2014;20:e126-e129)

Bovine neonatal pancytopenia (BNP) is a vaccine-induced alloimmune disease. The syndrome affects young calves and is characterised by haemorrhages, pancytopenia and severe destruction of the haematopoietic tissue. Recent evidence indicates that vaccine-induced alloantibodies target bovine major histocompatibility complex class I (MHC-I) antigens (bovine leucocyte antigen 1 (BoLA-1)). However, whether BoLA-1-specific antibodies suffice to induce BNP is still a matter of debate. In the current case study, we investigate samples from twin calves where only one calf succumbed to BNP. The fraternal twin also ingested high amounts of BoLA-1-specific alloantibodies but it did not develop BNP because the maternal antibodies did not recognise its BoLA-1 alleles. This association between lack of BoLA-1 binding and the absence of disease provides another important piece of evidence that BoLA-1-specific alloantibodies play a role in the induction of BNP.

The task of describing the birth of organ transplantation was simplified by an historical consensus development conference convened on March 25–27, 1999 at the University of California, Los Angeles (UCLA). The purpose was to identify the principal milestones leading to the clinical use of the various transplantation procedures. The 11-member consensus panel included eight recipients of the Medawar Prize (the highest distinction of the Transplantation Society) and three Nobel Laureates (Figure 1). Figure 1 Participants at the UCLA historical concensus development conference on transplantation milestones. Front row (left to right): Robert A Good, Norman E Shumway,* E Donnall Thomas,† Joseph E Murray,† Jean B Dausset,*† Jon J Van Rood;* ... Carl Groth of Stockholm, president-elect of the Transplantation Society, was invited to chair the deliberations and to prepare an executive summary of the group’s conclusions. The summary, and personal reminiscences of the 11 individual participants, were published in the July 2000 issue of the World Journal of Surgery.1 The collection of articles was reprinted in monograph form for distribution to members of the Transplantation Society. Milestone status was granted only to contributions made at least a quarter of a century ago. By 1975, 32 years had passed since convincing evidence was produced, first by Gibson and Medawar2 in a skin-grafted burn victim in Glasgow and then by Medawar3 in controlled animal experiments, that rejection is a host versus graft (HVG) immune response. Within the next few years, it was demonstrated that the same principle applied to renal allografts in unmodified dogs (Figure 2B).4,5 Figure 2 Misleading historical context of transplantation immunology, defined by unidirectional cell-mediated immune reactions. (B) A host-versus-graft (HVG) response against a tissue or organ (here a kidney). (A) A mirror image version after bone marrow transplantation ... In addition, confirmatory observations were made in more than a dozen cases in which kidney allografts were transplanted to the anterior thigh6 or to the pelvis7–10 of unmodified human recipients. These cases included the first reported live organ donation;7 the mother’s kidney functioned for 3 weeks in her nonimmunosuppressed son before undergoing irreversible rejection. It is noteworthy that, as early as 1951, the French surgeons Kuss and coworkers,8 Dubost and associates,9 and Servelle and colleagues,10 had developed for human use the extraperitoneal pelvic kidney transplant procedure that soon would be used by Murray and colleagues11 for the historic identical twin and fraternal twin transplantations12 of 1954 and 1959, respectively. Procedures for transplantation of the other vital organs had been developed in surgical laboratories by the late 1960s. By the end of the decade, therapeutic regimens were available with which successful clinical transplantation of five kinds of organ allografts, as well as allogeneic bone marrow cells, were accomplished (Table 1). 12–17 Table 1 Historical Firsts: Prolonged Patient and Allograft Survival In my individual contribution to the UCLA conference,18 I pointed out that almost all of the clinical transplantation milestones could be traced to two seminal discoveries that were turning points from which divergent management strategies evolved; one leading to bone marrow transplantation and the other to organ transplantation. The first discovery, made in the experimental laboratory and eventually applied in the clinic, was that acquired tolerance to allografts could be induced. The second discovery, that organs could induce tolerance to themselves (ie, were inherently tolerogenic), was made by clinical surgeons and taken to the laboratory in search of an explanation. When no explanation for the organ tolerogenicity could be found, the engraftment of organs was incorrectly attributed by consensus to different mechanisms than those of acquired tolerance. The error did not prevent the development of organ transplantation to a high level of efficacy. But it deprived transplantation immunology of an intelligible context for nearly three decades.

The aim of this study was to examine environmental and gene-environment processes linking parenting (i.e., affect, control, responsiveness) and preschool children's behavioral adjustment difficulties (e.g., noncompliance, conduct problems) by using bivariate genetic analyses of parents' and observers' ratings. The sample included 120 identical and same-sex fraternal twin pairs (M age = 43 months). Data sources included in-home observations, interviews, and parents' reports. Observers' ratings of children's difficult behaviors included shared and nonshared environmental variance. In contrast, parents' ratings of children's conduct problems showed genetic and nonshared environmental variance. Observer-rated maternal behavior included shared and nonshared environmental variance, although maternal responsiveness also included child genetic variance. Parent self-reported negative and positive affect included shared and nonshared environment as well as child genetic variance. There was no evidence for gene-environment interaction or dominance. Higher levels of difficult behavior and conduct problems covaried with higher levels of maternal negative affect and control and lower levels of maternal positive affect and control. Shared environmental mediation of these correlations was found for observations, whereas genetic and nonshared environmental mediation was found for parents' ratings. In general, estimates of shared environmental variance and mediation were greatest for observational data, and estimates of child genetic variance and mediation were greatest for parent-rated data. The implications of this pattern of findings for genetic research on family processes are discussed.

Myoclonus dystonia is a rare movement disorder caused by mutations in the SGCE gene on chromosome 7q21 (DYT11) encoding the epsilon-sarcoglycan. Myoclonus is present in almost all patients and affects most often neck, trunk and upper limbs. Dystonia is present in about half of the patients. The mode of inheritance is autosomal dominant with variable clinical expression and maternal imprinting. Onset is usually in childhood or adolescence. Alcohol might relieve symptoms. We present a 33 month old girl and her twin brother with disabling involuntary jerky movements during intentional tasks. Family history of this French family was positive for the paternal uncle, his two daughters and the paternal great grandfather. Sequencing of the SGCE gene revealed a novel nonsense mutation c.942C>A (p.Tyr314X) in exon 7, confirming the diagnosis of myoclonus dystonia. Treatment with valproic acid significantly reduced myoclonic episodes and ameliorated life quality.

In phase 1 of this study, we used a functional analysis to evaluate the thumb sucking of fraternal twin brothers (Josh and Andy). Results from phase 1 suggest that Andy's thumb sucking was maintained by automatic reinforcement, whereas data for Josh were inconclusive. In phase 2, independent of phase 1 results, we sequentially implemented the simplified habit reversal components of awareness training, competing response training, and social support. All three treatment components plus two booster sessions reduced thumb sucking to near-zero levels for Josh. The same components failed to suppress thumb sucking for Andy, therefore, a remote detection phase was implemented. A withdrawal and subsequent re-implementation of remote detection indicated that the intervention was responsible for reducing Andy's thumb sucking. Results and need for future research are discussed.

Dyadic perception between 108 older identical and same-sex fraternal twin pairs was examined using three different tasks: (i) an emotional sensitivity task, (ii) a Q-Sort rating of emotion-eliciting situations, and (iii) an assessment of each other's personality traits. Idiographic analyses related judgements of self and co-twin within and between twins. Projection approached the reliability of the judgements and was significantly higher than both empathic accuracy and actual similarity, suggesting that the process of dyadic perception was mainly shaped by projection. Significant correlations between empathic accuracy and projection were caused by the similarity of the twins in self-judgements. Empathic accuracy was much weaker once projection was controlled, indicating that twins had used valid projection to improve accuracy. Similarity-controlled projection was still high and reflected the fact that the twins overestimated their similarity to a large extent. Contrary to expectation but consistent across the three tasks, identical and fraternal twins differed neither in levels of actual similarity, empathic accuracy and projection, nor in similarity-controlled empathic accuracy and projection.

Objective To discuss a case of asynchronous bilateral renal venous thrombosis with a review of current literature. Case A premature fraternal twin male was delivered via Cesarean section to a mother with a history of pre-eclampsia. He was initially diagnosed with a left renal venous thrombosis (RVT) but subsequently developed right RVT. Only intravenous fluids and supportive care were provided. Anticoagulation was withheld because of MRI findings of multiple areas of intracerebral bleeding. His serum creatinine concentration stabilized at 0.7 mg/dL, but follow-up renal ultrasound studies showed bilateral anechoic corticomedullary cysts. He also developed hypertension. Discussion Renal venous thrombosis usually occurs in neonates. Multiple clinical conditions are associated with RVT, two of which exist in this case. Recent work has focused on genetic prothrombotic risk factors, one of which our patient exhibits. Controversy exists over management, i.e. whether or not to initiate anticoagulation or antithrombotic therapy to decrease the development of renal atrophy, renal failure and hypertension. Conclusions This unusual case of asynchronous bilateral renal venous thrombosis recovered in the short term without antithrombotic therapy. Substantial insult early in life is reflected in the progressive worsening of his renal function, ultrasound findings and hypertension, highlighting the need for long-term vigilant observation of these patients.

This paper presents a series of observing system simulation experiments (OSSEs) which are intended as a design study for a proposed array of instrumented moorings in the tropical Atlantic Ocean. Fields of TOPEX/Poseidon sea surface height anomalies are subsampled with the goal being reconstruction of the original fields through the use of reduced-space Kalman filter data assimilation at a restricted number of locations. Our approach differs from typical identical and fraternal twin experiments in that real observed data (i.e., TOPEX/Poseidon data) are subsampled and used in place of synthetic data in all phases of the OSSEs. In this way the question of how closely a particular model-generated data set resembles nature is avoided. Several data assimilation runs are performed in order to optimize the location of a limited number of moorings for the proposed Pilot Research Moored Array in the Tropical Atlantic (PIRATA). Results of experiments in which data are assimilated at 2oN, 2oS and the equator and the longitude is systematically varied by 5 o show that the greatest impact of the assimilated data occurs when the observations are taken between 15oW and 30oW. Next, a more systematic technique is presented which allows us to determine optimal points in an objective fashion by applying a least squares regression approach to reconstruct the errors on a dense array of points from the data misfits at any three selected points. The forecast error structure from the Kalman filter is used in a novel way to assess the optimality of mooring locations. From a large sample of triads of points, the optimal mooring locations are found to be along the equator at 35oW, 20oW, and 10oW. Additional experiments are performed to demonstrate the efficacy of the initial and final PIRATA configurations and the added value that can be expected from PIRATA observations beyond existing expendable bathythermograph observations.

Although results obtained from recent twin and adoption studies suggest that individual differences in mathematics performance are due in part to heritable influences, no genetic analysis of mathematics disability (MD) has been previously reported. In this article we present data from the first twin sample ascertained for mathematics deficits (40 identical and 23 same-sex fraternal twin pairs in which at least one member had MD). When mathematics performance data from these twin pairs were subjected to a multiple regression analysis, evidence for a significant genetic etiology was obtained. However, tests for the differential etiology of MD as a function of reading performance level were nonsignificant. Results of this first twin study of MD indicate that the condition is significantly heritable, but data from additional twin pairs will be required to test hypotheses of differential etiology more rigorously.

A homologous series of “fraternal twin” molecules consisting of relatively short and relatively long mesogenic units connected by a flexible spacer group and flexible chains as the terminal groups was synthesized in an attempt to form a non-chiral longitudinal ferroelectric smectic phase. The shorter of the two mesogenic units consisted of a 4-alkyl/alkoxy substituted biphenyl ester; the longer a terbenzoate group. Mesomorphic properties were determined by hot-stage polarizing microscopy and DSC. Several smectic phases were observed as well as nematic phases. Characterization of the smectic phases by microscopic textures is discussed.

In order to compare the pattern of gender differences for cognitive measures in opposite-sex twin pairs to that in independent samples of twins from same-sex pairs, psychometric test data were obtained from four research-identified samples of children: (1) 96 pairs of opposite-sex fraternal twins in which at least one member of each pair is reading disabled; (2) 62 pairs of opposite-sex fraternal twins with no history of reading problems; (3) 167 males and 155 females from same-sex identical and same-sex fraternal twin pairs in which at least one member of each pair is reading disabled; and (4) a comparison sample of 126 males and 132 females from same-sex twin pairs with no history of reading problems. Results of multivariate analyses indicate that gender differences for cognitive measures are similar in twin pairs with and without reading disabilities. Moreover, a highly similar pattern of gender differences occurs for opposite-sex twin pairs who shared both prenatal and early postnatal influences and for independent samples of children from different families.

Familial hemophagocytic lymphohistiocytosis (FHLH) is a rare, rapidly progressive disorder of early childhood characterized by uncontrolled activation of T cells and macrophages. Although perforin gene mutations have been described in a proportion of patients with FHLH, the genotype/phenotype correlation is still limited. Only a few patients with late onset clinical manifestations have been reported. The biochemical and immunologic alterations in the asymptomatic phase are not well known. We report on a family in which 2 fraternal twins both homozygous for a perforin mutation previously described as causative of the disease, markedly differed in phenotypic expression of FHLH. The twins also had a second novel heterozygous mutation. Natural killer (NK) activity was severely impaired in the patient and was normal in the asymptomatic fraternal twin. Our report highlights that FHLH may present after a long disease-free interval during which biochemical or immunologic alterations may be not evident, thus implying a role for interfering factors. (Blood. 2004;103:4610-4612)

The Prince of Tidesis the characterological study of and interaction between two families, that of Savannah, the patient and Dr. Susan Lowenstein, the psychiatrist. In order to treat Savannah, recovering from a suicide attempt, fraternal twin Tom (Savannah's memory) comes to New York to assist in his sister's treatment. Tom becomes the patient relating the family dynamics in six cinematic flashbacks. These show the parental disharmony, Tom's strong Oedipal attachment, maternal betrayal and Tom's wish for revenge, his incomplete mourning for his older brother Luke, and its effects on his life. The relationship between Susan, her husband and son, Bernard, and how each interacts with Tom is also described. Susan's erotic countertransference is analyzed, and the role of the woman therapist in the cinema discussed.

In order to assess the genetic etiology of comorbid reading disability and attention deficit hyperactivity disorder (ADHD), reading performance and hyperactivity data (Diagnostic Interview for Children and Adolescents [DICA]; Herjanic, Campbell, & Reich, 1982) from 61 identical and 43 same‐sex fraternal twin pairs tested in the Colorado Reading Project were subjected to multiple‐regression analysis (DeFries & Fulker, 1985, 1988). Results suggest that approximately 45% of the proband deficit in reading is due to genetic factors that also influence hyperactivity. Moreover, heritable variation accounted for 70% of the observed covariance between the reading and hyperactivity measures. Thus, comorbid reading disability and ADHD (as measured by parental ratings on the DICA) is due, at least in part, to heritable influences.

CASE Cayden is a 6.3-year-old boy who you have been following in our practice since birth. He was born at 35.5 weeks at 6 pounds 4 ounces following a fraternal twin gestation. Both children were "on target" with their milestones, but Cayden did not seem to progress as quickly as his sister. He did not initiate play with his sister when they were toddlers and Cayden was the "shy" one.

We report a case of spontaneous familial pneumothorax in fraternal twin boys. The twins' family history is remarkable for reactive airway disease and a female sibling also born with spontaneous pneumothorax. The family had no history of connective tissue disorders, renal cancer, or dermatologic diseases. Analysis of the twins' α 1 -antitrypsin (AAT) genotype, phenotype, and serum concentration revealed that both were compound heterozygous for rare SERPINA1 alleles. These findings suggest a role for AAT deficiency in spontaneous pneumothorax of the newborn. To our knowledge, these are the first genetic data to support etiology of neonatal spontaneous familial pneumothorax.

In this article, we explore the effect of public policy on the extent to which genes influence smoking desistance. Using a sample of adult twins (nmz = 363, ndz = 233) from a large population registry, we estimate Cox proportional hazards models that describe similarity in the timing of smoking desistance among adult twin pairs. We show that identical twin pairs are significantly more likely to quit smoking within a similar time frame compared with fraternal twin pairs. Importantly, we then show that genetic factors for smoking desistance increase in importance following restrictive legislation on smoking behaviors that occurred in the early and mid-1970s. These findings support the social push perspective and make important contributions to the social demography and genetic epidemiology of smoking as well as to the gene-environment interaction literatures.

The synthesis and complete photophysical characterization of rigidified neutral hemicage iridium complexes are presented. The hemicage ligands were obtained via a modular synthesis, which will facilitate the expansion of future hemicage syntheses. Slight variations in structure between the two iridium hemicage podates reveal subtle differences in photophysical behavior, which will aid in the design of functional materials. A parallel computational investigation corroborates the experimental findings. The insight gleaned from this study will have an impact for the design of iridium-based luminophores for OLED-type applications.

Three recent studies have used twin data to explore the possibility of differential contributions of heritability and environmentality to individual differences in cognitive ability as a function of ability level (Detterman, D. K., et al., Behav. Genet. 20:369-384; 1990; Bailey, M. J. and Revelle, W., Behav. Genet. 21:397-404, 1991; Cherny, S. S., et al., Behav. Genet. 22:153-162, 1992). All arrived at different conclusions: higher heritability at the low end, higher heritability at the high end, and no differential influence, respectively. The current report involves a sample of 148 identical and 135 fraternal twin pairs from the Western Twin Project who were tested on a battery of intelligence and achievement tests to further explore the issue. The results suggest no significant differences in heritability at either the high or the low end, although a trend toward higher heritability for children of higher ability is evident. Individual differences for a composite ability/achievement score showed significantly greater influence of shared family environment at the low end than the rest of the distribution. In general, results for cognitive ability and academic achievement were highly similar.

Hand, foot, and mouth disease (HFMD) is a common childhood viral illness characterized by vesicles in the mouth, hands, feet, and sometimes the buttocks. HFMD has a predilection for the summer and autumn seasons, and historically has been treated with supportive care. Coxsackievirus A16 and enterovirus 71 are the most commonly reported viruses responsible for HFMD. Coxsackievirus A6 (CVA6), however, has been associated with more widespread skin lesions and profound tissue destruction. Recently, the term eczema coxsackium (EC) was coined to describe patients with underlying atopic dermatitis who present with an eczema herpeticum-like eruption caused by CVA6 with vesicles and erosions in pre-existing areas of eczema. Enteroviral infections, particularly CVA6, should be on the clinicians’ differential diagnosis of children who present with extensive erosions and vesicles, and with a history of eczema. We present the first case, to our knowledge, that documents wet wrap therapy (WWT) as a viable treatment option for CVA6 EC, a condition that previously has only been treated with supportive measures. Our patients were 8-month-old former 36-week fraternal twin boys with medical histories significant for eczema. A few days before their January admission, the eczema of both patients were noted to be worsening and not responding to step-up therapy. The primary care physician had escalated therapy from daily moisturizing, as needed over-the-counter class VII topical corticosteroids (TCS), and twice a week diluted bleach baths, to a class V TCS, Hydrocortisone Valerate 0.2% cream (Perrigo Pharmaceuticals, Bronx, New York, New York). The patients were presented to the emergency department with rapid progression of a vesiculobullous rash that involved the face, particularly the perioral area, upper and lower extremities, and trunk. Of note, twin B was diagnosed with otitis media on the day before presentation to the hospital, for which his pediatrician started him on cefdinir. The infants were referred for admission because of worsening skin lesions, fussiness, and dehydration. Laboratory evaluation included a complete blood cell count with differential, comprehensive metabolic panel, and blood cultures. Vesicular fluid was aspirated and sent for herpes PCR, enterovirus PCR, and viral cultures. Intravenous acyclovir and ceftriaxone were started for empiric treatment of herpes and possible bacterial superinfection. Differential diagnosis included eczema herpeticum, varicella, EC from HFMD, and a severe eczema flare with secondary bacterial infection. Complete blood cell count and comprehensive metabolic panel results were within normal limits. Results of herpes PCR, viral cultures, and blood cultures were negative. The enteroviral PCR results were positive. Further testing by the Centers for Disease Control and Prevention confirmed CVA6. Ceftriaxone and acyclovir were stopped when blood cultures and erpes simplex virus PCR results were negative, and WWT and low-potency Class VI TCS (desonide 0.05% ointment, Taro Pharmaceuticals Inc., Brampton, Ontario, Canada) were started. Although it is well known that WWT, in conjunction with TCS, is an effective and safe treatment for severe flares of atopic dermatitis refractory to increased TCS strength, to our knowledge there is no literature that mentions the use of WWT for treatment of EC. The benefits of WWT include an occlusive barrier that prevents scratch-induced skin trauma, increased skin hydration, decreased pruritus and inflammation by cooling of the skin, and increased penetration of the TCS. Complications, such as maceration of the skin or secondary skin infections, are possible but have been shown to be uncommon with proper application of WWT. Because standard skin therapy was unsuccessful for these patients before admission and because results of enteroviral PCR were positive, which raised our suspicion that this was a possible EC case, we considered the risks and benefits of increasing the potency of the TCS further, commensurate with the severity of the flare, versus implementing WWT with a low-potency TCS. Although there have been no reported complications with patients with CVA6 EC, there are no studies that evaluated whether the use of TCS, or occlusion from WWT, increases the risk of complication. Furthermore, there are no studies that evaluated whether the use of TCS, or occlusion from WWT, increases the risk of worsening the cutaneous findings of EC by immunosuppression and leads to more disseminated viral growth. When considering the large body surface area involved, and balancing the uncertainty of the theoretical risks of higher-potency corticosteroids inCVA6ECwith the knownbenefits ofWWTand TCS, we chose to continue treatment with a low-potency TCS with the addition of WWT. Systemic adverse effects from WWT with corticosteroid use were considered; however, prolonged suppression of the hypothalamic-pituitary-adrenal axis has not been reported after short-term treatment with WWT and TCS. Therefore, we pursued only short-term use of combined WWT and low-dose TCS for 3 days. Wet wraps were applied 3 times a day, with the morning and evening wraps to include Aquafor (Beiersdorf, Hamburg, Germany) to unaffected areas and desonide 0.05% ointment to the affected areas, and the mid day wrap included Aquafor head to toe. The morning and mid day wraps wereworn for an hour, and the eveningwrapswereworn overnight. Within 24 hours, the patients demonstrated significant clinical improvement, and were discharged after extensive family education to continue the same WWT regimen at home. Twin B also was discharged on cefdinir for the previously diagnosed otitis media. By day 3 after discharge, the patients had improved dramatically, and WWT was discontinued. The twins were seen for follow-up 5 days after discharge and were noted to have had an

Presentation of Case A seven-year-old girl was admitted to the hospital because of a fourth episode of sore throat, dyspnea, and fever. The child had been born after 35 weeks of gestation to a mother 36 years old (her third pregnancy). The pregnancy was complicated by gestational hypertension but not by the use of medications, cigarettes, or alcohol. Elective cesarean section was performed under general anesthesia one day after spontaneous rupture of the membranes. The patient had been an unexpected fraternal twin, and her respiratory status at birth had been very depressed, with Apgar scores of 2.1 at one minute . . .

In this chapter, I will argue that social science and genomics can be integrated – however, the way this marriage is currently occurring rests on spurious methods and assumptions and, as a result, will yield few lasting insights. However, recent advances in both econometrics and in developmental genomics provide scientists with a novel opportunity to understand how genes and (social) environment interact. To presage my argument: Key to any causal inference about genetically heterogeneous effects of social conditions is that either genetics be exogenously manipulated while environment is held constant (and measured properly), and/or that environmental variation is exogenous in nature – i.e. experimental or arising from a natural experiment of sorts. Further, allele selection should be motivated by findings from genetic experiments in (model) animal studies linked to orthologous human genes. Likewise, genetic associations found in human population studies should then be tested through knock-out and over-expression studies in model organisms. Finally, gene silencing can be a promising avenue of research in humans if careful thought is given to when and which cells are harvested for analysis.

In this chapter, I argue that social science and genomics can be integrated – however, the way this marriage is currently occurring rests on spurious methods and assumptions and, as a result, will yield few lasting insights. Recent advances in both econometrics and developmental genomics provide scientists with a novel opportunity to understand how genes and (social) environment interact. Key to any causal inference about genetically heterogeneous effects of social conditions is that either genetics be exogenously manipulated while environment is held constant (and measured properly) and/or that environmental variation is exogenous in nature – i.e., experimental or arising from a natural experiment of sorts. Further, allele selection should be motivated by findings from genetic experiments in (model) animal studies linked to orthologous human genes. Likewise, genetic associations found in human population studies should then be tested through knock-out and overexpression studies in model organisms. Finally, epigenetic and gene expression analysis of corpse brains offers a potentially fruitful way to get at mechanisms by which social environment affects gene pathways.

Modern personality theories differ in their assumptions about the structure and etiology of the interplay between personality traits and motivational constructs The present study examined the genetic and environmental sources of the interplay between the Big Five and major life goals concurrently and across time in order to provide a more decisive evaluation of the conflicting assumptions stated in the five-factor theory as opposed to socioanalytic conceptions Traits and goals were assessed twice across a 5-year period in a sample of 217 identical and 112 fraternal twin pairs from the Bielefeld Longitudinal Study of Adult Twins About 30% of the variance in agency and communion life goals was genetic. the remaining variance was due to nonshared environmental effects, whereas shared environmental effects were negligible Both heritable and environmental variance in goals could partly be accounted for by genetic and nonshared environmental effects on personality traits Across time, we revealed reciprocal genetic and environmental effects between traits and life goals In sum, our findings yield partial support for both of the 2 competing personality theories, suggesting a readjusted picture of the interplay between traits and coals

Twin studies are a major research direction in imaging genetics, a new field, which combines algorithms from quantitative genetics and neuroimaging to assess genetic effects on the brain. In twin imaging studies, it is common to estimate the intraclass correlation (ICC), which measures the resemblance between twin pairs for a given phenotype. In this paper, we extend the commonly used Pearson correlation to a more appropriate definition, which uses restricted maximum likelihood methods (REML). We computed proportion of phenotypic variance due to additive (A) genetic factors, common (C) and unique (E) environmental factors using a new definition of the variance components in the diffusion tensor-valued signals. We applied our analysis to a dataset of Diffusion Tensor Images (DTI) from 25 identical and 25 fraternal twin pairs. Differences between the REML and Pearson estimators were plotted for different sample sizes, showing that the REML approach avoids severe biases when samples are smaller. Measures of genetic effects were computed for scalar and multivariate diffusion tensor derived measures including the geodesic anisotropy (tGA) and the full diffusion tensors (DT), revealing voxel-wise genetic contributions to brain fiber microstructure.

There is a figural basis of grammatical logic to be found in the norms of figural design within human expression. Husserl suggests this in his discussion of part and whole in the Logical Investigations. His notion of a “sprachlosen Denkungsform” “thought form without speech” emanates from this figural realm of knowing, a learning to express the visual field that begins from infancy. I explore “styles” of figuration which express the “part-whole” diaeresis of knowing natural to every human. These styles are pre-egoically formed, as a function of the “pure I” in its passive syntheses of judgment. The learning of verbal grammar accommodates one’s style of figural diaeresis.

200 pairs of twins were assessed at 14 months of age in the laboratory and home. Measures were obtained of temperament, emotion, and cognition/language. Comparisons between identical and fraternal twin correlations suggest that individual differences are due in part to heritable influences. For temperament, genetic influence was significant for behavioral observations of inhibition to the unfamiliar, tester ratings of activity, and parental ratings of temperament. For emotion, significant genetic influence was found for empathy and parental ratings of negative emotion. The estimate of heritability for parental report of expression of negative emotions was relatively high, whereas that for expression of positive emotions was low, a finding consistent with previous research. For cognition and language, genetic influence was significant for behavioral indices of spatial memory, categorization, and word comprehension. Shared rearing environment appears influential for parental reports of language and for positive emotions, but not for other measures of emotion or for temperament.

In order to assess the genetic etiology of attention deficit hyperactivity disorder (ADHD), the basic regression model for the analysis of selected twin data (DeFries & Fulker, 1985, 1988) was fitted to questionnaire data (DICA: Diagnostic Interview for Children and Adolescents; Herjanic, Campbell, & Reich, 1982) for 37 identical and 37 fraternal twin pairs tested in the Colorado Reading Project. Results of this analysis suggest that ADHD is highly heritable. Moreover, adjusting DICA scores for either IQ or reading performance differences did not substantially change parameter estimates. In future analyses of larger data sets, distinguishing between possible subtypes of attentional problems (e.g., ADD with or without hyperactivity) may facilitate tests of more searching etiological questions.

Data on five tests of general and specific cognitive abilities, cognitive styles, and creativity, obtained from members of 60 identical and 63 fraternal Russian adolescent twin pairs, are presented. All tests are adaptations of standardized instruments widely used outside of the Soviet Union. Identical and fraternal twin correlations for general cognitive ability yielded a lower estimate of heritability (0.29) than generally found in other countries worldwide (0.52) although the twin correlations themselves are fairly comparable to figures from other countries and cultures — 0.83 and 0.69 for Russian identical and fraternal twin pairs, respectively, vs 0.86 and 0.60 for non-Russian identical, and fraternal twin pairs. Twin correlations for other cognitive-related abilities assessed were also comparable to correlations obtained outside the Soviet Union with the exception of creativity which yielded higher within-pair resemblance than reported in previous twin studies.

Objectives Educational opportunities for African-Americans expanded throughout the 20th century. Twin pairs are an informative population in which to examine changes in educational attainment because each twin has the same parents and childhood socioeconomic status. We hypothesized that correlation in educational attainment of older twin pairs would be higher compared to younger twin pairs reflecting changes in educational access over time and potentially reflecting a “ceiling effect” associated with Jim Crow laws and discrimination. Methodology and Principal Findings We used data from 211 same-sex twin pairs (98 identical, 113 fraternal) in the Carolina African-American Twin Study of Aging who were identified through birth records. Participants completed an in-person interview. The twins were predominantly female (61%), with a mean age of 50 years (SD = 0.5). We found that older age groups had a stronger intra-twin correlation of attained educational level. Further analysis across strata revealed a trend across zygosity, with identical twins demonstrating more similar educational attainment levels than did their fraternal twin counterparts, suggesting a genetic influence. Discussion These findings suggest that as educational opportunities broadened in the 20th century, African-Americans gained access to educational opportunities that better matched their individual abilities.

Fraternal twin studies on normal subjects have demonstrated low heritability (intra-class correlation coefficient) estimates for frontal brain regions (r = 0.43). Here we aimed to investigate the relatedness/similarity estimates of the frontal brain regions in fraternal subjects concordant for Tourette syndrome (TS). We sought to identify regional brain similarities between siblings concordant for TS as an exploratory step towards the identification of potential brain structures involved in the TS phenotype. The identified brain structures may then serve in subsequent molecular genetic and linkage studies. In addition, we regressed cortical thickness and TS clinical severity scores to assess the relation between TS clinical symptoms and cortical structures. Sixteen sibling pairs concordant for TS were scanned using a 1.5 T magnetic resonance imaging scanner (age range 10-25, mean 17.19 +/- 4.1). Brain morphology was assessed using the fully automated Civet pipeline at the Montreal Neurological Institute. TS was assessed using the Children's Yale-Brown Obsessive Compulsive Scale (CY-BOCS), Yale Global Tic Severity Scale (YGTSS) and the Goetz Tic Scale. We report high relatedness/similarity estimates for fraternal siblings concordant for TS (r = 0.86-0.60) in the middle frontal-motor/cingulate/insular cortices. Regression analysis revealed significant negative correlations in the right insula with the YGTSS (r = -0.41, F = 6.09, P < 0.02) and the left cingulated cortex with the (CY-BOCS) (r = -0.35, F = 4.30, P < 0.05). Since previous findings have concluded that normal fraternal siblings are less alike in frontal cortices, the present findings may be attributed to TS. We speculate that the high ICC between siblings and the negative correlation between TS symptoms severity and cortical thickness measurements are related to the disturbances in the maturation of the motor-cingulate-insular cortical neural system that mediate self-regulatory processes. Such delayed maturation may consequently contribute to the development of TS by releasing motor and vocal tics from regulatory control. These findings may have important genetic implications.

Objective A multifactorial combination of predictors may increase anterior cruciate ligament (ACL) injury risk in athletes. The objective of this twin study was to examine these risk factors to identify commonalities in risk factors that predisposed female fraternal twins to ACL injury. Methods Female twins in high-risk sports were prospectively measured prior to an injury for neuromuscular control using three-dimensional motion analysis during landing, hamstrings and quadriceps muscular strength on a dynamometer and joint laxity using a modified Beighton–Horan index and a Compu-KT arthrometer. Intraoperative measures of femoral intercondylar notch width were recorded during ACL reconstruction. Results Abduction angles were increased at one knee in both of the twin sister athletes relative to uninjured controls at initial contact and at maximum displacement during landing. The twin female athletes that went on to ACL injury also demonstrated decreased peak knee flexion motion at both knees than uninjured females during landing. The twin athletes also had increased joint laxity and decreased hamstrings to quadriceps (H/Q) torque ratios compared to controls. Femoral intercondylar notch widths were also below the control mean in the twin siblings. Conclusions Prescreened mature female twins that subsequently experienced ACL injury demonstrated multiple potential risk factors including: increased knee abduction angles, decreased knee flexion angles, increased general joint laxity, decreased H/Q ratios and femoral intercondylar notch width.

Sharing similar genetic traits makes the investigation of twins an important study in forensics and biometrics. Fingerprints are one of the most commonly found types of forensic evidence. The similarity between twins' prints is critical establish to the reliability of fingerprint identification. We present a quantitative analysis of the discriminability of twin fingerprints on a new data set (227 pairs of identical twins and fraternal twins) recently collected from a twin population using both level 1 and level 2 features. Although the patterns of minutiae among twins are more similar than in the general population, the similarity of fingerprints of twins is significantly different from that between genuine prints of the same finger. Twins fingerprints are discriminable with a 1.5%~1.7% higher EER than non-twins. And identical twins can be distinguished by examine fingerprint with a slightly higher error rate than fraternal twins.

Information from the full diffusion tensor (DT) was used to compute voxel-wise genetic contributions to brain fiber microstructure. First, we designed a new multivariate intraclass correlation formula in the log-Euclidean framework [1]. We then analyzed used the full multivariate structure of the tensor in a multivariate version of a voxel-wise maximum-likelihood structural equation model (SEM) that computes the variance contributions in the DTs from genetic (A), common environmental (C) and unique environmental (E) factors. Our algorithm was tested on DT images from 25 identical and 25 fraternal twin pairs. After linear and fluid registration to a mean template, we computed the intraclass correlation and Falconer's heritability statistic for several scalar DT-derived measures and for the full multivariate tensors. Covariance matrices were found from the DTs, and inputted into SEM. Analyzing the full DT enhanced the detection of A and C effects. This approach should empower imaging genetics studies that use DTI.

In this study we analyzed the etiology of the relationship between personality traits and retrospectively recalled family environment. The data of 226 identical and 168 fraternal twin pairs reared together from the Jena twin study of social attitudes were available. Personality traits were measured using the self- and peer report versions of the German NEO-personality inventory-revised. A German version of Blocks Environmental Questionnaire was applied to measure two broad dimensions of the family environment retrospectively: support and organization. We could replicate earlier findings that retrospective reports of these family environment dimensions were in part genetically influenced. A total of 66% of the genetic variance in support and 24% in organization could be accounted for by heritable variance in self-rated personality. That was replicated by using peer reports of personality, 41% explained genetic variance in support and 17% in organization. Environmental mediations were negligible. This indicates that the relationship between personality and retrospectively recalled family environment is largely genetically mediated.

The other study offers the first evidence that asthma also may be linked to PTSD. Renee D. Goodwin, MPH, PhD, of the Mailman School of Public Health at Columbia University in New York City, and colleagues found that Vietnam veterans who report the most symptoms of PTSD are 2.3 times more likely to have asthma than those who report the least PTSD symptoms, based on an analysis of 3065 male twin pairs from the Vietnam Era Twin Registry (Goodwin RD et al. Am J Respir Crit Care Med. 2007;176[10]:983-987). The work also confirmed other studies’ findings of an association between asthma and depression in adults. Further analysis involving a comparison of the results within identical and fraternal twin pairs did not find a substantial difference between the two groups, suggesting that genes do not play a large role in the association between asthma and PTSD. The scientists also probed the relative contributions of some environmental or behavioral factors, including body mass index, smoking, exposure to combat trauma, and the sociodemographic characteristics of the individuals, and found none that fully explained the link between asthma and PTSD. Goodwin and her team are planning longitudinal studiesofchildrentoexamine whether prenatal factors, such as havingamotherwhosmokedduringpregnancy, may explain the association betweenasthmaandpsychiatricproblems. In the meantime, Goodwin said, physicians should be aware that patients with asthma who are exposed to trauma or other difficult life events might have an elevated risk of developing PTSD or other psychiatric disorders, and consider screening them for such comorbities.

Any two people can travel the same road and see different things. Thus, others discussing the history of renal transplantation might have noted different landmarks. Valuable personal reminiscences have been written by R.Y Calne of England1 and J.E. Murray of Boston,2 whose initially separate careers came together in a remarkable joint venture at Harvard in 1960. In addition, original articles, which are usually cited in historical reviews, but rarely read because of their inaccessibility, were republished recently in a volume of the Clio Chirurgica series.3 Perusal of this material gives unusual insight into the process of discovery and development. Another prime source of historical information was published in 1972 by Professor Carl Groth, the Swedish transplantation surgeon who examined the medical literature from the crucial period of 1950 to 1970 and interviewed or corresponded with almost all of the physicians and surgeons who were working during this time.4 Kidney transplantation as a practical therapeutic option came from a series of steps that began to appear in the literature at the turn of this century. At first, the steps were small, widely spread in time, and often quixotic enough to be overlooked or condemned. As late as 1961, the Nobel Laureate Macfarland Burnet wrote in the New England Journal of Medicine that “… much thought has been given to ways by which tissues or organs not genetically and antigenically identical with the patient might be made to survive and function in the alien environment. On the whole, the present outlook is highly unfavorable to success . . . .”5 This opinion was published on the eve of the successful clinical renal transplantations in 1962 and 1963 that extended such procedures beyond the occasional identical and fraternal twin cases of the mid and late 1950s. These clinical trials in 1962 and 1963 provoked editorials questioning the inherent feasibility of such efforts, as well as their ethical basis.6 Yet, these trials were already late in a long, but at first slowly unfolding, story of whole organ transplantation, which was dominated by but not confined to the kidney.

Family, linkage, and twin studies of reading disability are briefly reviewed, and evidence is presented from the twin component of the Colorado Reading Project that implicates genetic factors in the expression of reading disability. Recently developed behavioral genetic methodology is outlined, which provides an estimate of the magnitude of these genetic effects. The present report details the application of this methodology to reading performance data obtained from 96 identical twin pairs and 72 fraternal twin pairs in which at least one member of each pair was identified as reading disabled. Results indicate that approximately 50% of the reading deficit observed in the probands may be attributed to genetic factors. Although such an analysis assumes that reading disability is a homogeneous disorder, there may exist alternative forms with differing genetic etiologies. To test this hypothesis, the methodology can be extended to assess differential genetic etiology in alternative subgroups of disabled readers.