bluuebunny/crossref_metadata_2025 huggingface dataset:
The death-associated protein kinase 2 is up-regulated during normal myeloid differentiation and enhances neutrophil maturation in myeloid leukemic cells
Authors: Rizzi Mattia , Tschan Mario P , Britschgi Christian , Britschgi Adrian , Hügli Barbara , Grob Tobias J , Leupin Nicolas , Mueller Beatrice U , Simon Hans-Uwe , Ziemiecki Andrew , Torbett Bruce E , Fey Martin F , Tobler Andreas
Published: March 2007

The death-associated protein kinase 2 (DAPK2) belongs to a family of Ca2+/calmodulin-regulated serine/threonine kinases involved in apoptosis. During investigation of candidate genes operative in granulopoiesis, we identified DAPK2 as highly expressed. Subsequent investigations demonstrated particularly high DAPK2 expression in normal granulocytes compared with monocytes/macrophages and CD34+ progenitor cells. Moreover, significantly increased DAPK2 mRNA levels were seen when cord blood CD34+ cells were induced to differentiate toward neutrophils in tissue culture. In addition, all-trans retinoic acid (ATRA)-induced neutrophil differentiation of two leukemic cell lines, NB4 and U937, revealed significantly higher DAPK2 mRNA expression paralleled by protein induction. In contrast, during differentiation of CD34+ and U937 cells toward monocytes/macrophages, DAPK2 mRNA levels remained low. In primary leukemia, low expression of DAPK2 was seen in acute myeloid leukemia samples, whereas chronic myeloid leukemia samples in chronic phase showed intermediate expression levels. Lentiviral vector-mediated expression of DAPK2 in NB4 cells enhanced, whereas small interfering RNA-mediated DAPK2 knockdown reduced ATRA-induced granulocytic differentiation, as evidenced by morphology and neutrophil stage-specific maturation genes, such as CD11b, G-CSF receptor, C/EBPε, and lactoferrin. In summary, our findings implicate a role for DAPK2 in granulocyte maturation.
ATF4 differentially regulates transcriptional activation of myeloid-specific genes by C/EBPε and C/EBPα
Authors: Gombart Adrian F , Grewal Jeffrey , Koeffler H Phillip
Published: March 2007

Dimerization between different basic region leucine zipper (ZIP) transcription factors is regarded as an important mechanism for integrating various extracellular signals to control specific patterns of gene expression in cells. The activating transcription factor 4 (ATF4) protein was identified as a principal partner for the myeloid-specific transcriptional factor C/EBPε. Dimerization required the ZIP motif of each protein and redirected DNA binding of C/EBPε and ATF4 from their respective symmetric consensus sites to asymmetric C/EBP and cAMP response element sites. The C/EBPε:ATF4 heterodimer bound to the C/EBP sites in the promoters of the myeloid-specific genes encoding neutrophil elastase (NE) and the G-CSF receptor (G-CSFR). Also, the heterodimer bound a previously uncharacterized site in the promoter of the mim-1 gene at nucleotide –174. Coexpression of ATF4 and C/EBPε in the presence of c-Myb synergistically activated the mim-1 and NE promoters compared with C/EBPε plus c-Myb alone. Synergistic activation was not observed for the G-CSFR promoter and only occurred in the presence of c-myb with the NE or mim-1 promoters. In contrast, ATF4:C/EBPα dimers bound to the C/EBP sites in the G-CSFR and NE promoters, but transcriptional activation was inhibited by 30–80% in the presence or absence of c-Myb. We propose that ATF4 may regulate myeloid gene expression differentially by potentiating C/EBPε but inhibiting C/EBPα-mediated transcriptional activation.
Accelerated Partial Breast Irradiation in Early-Stage Breast Cancer
Authors: Sanders Mary Ella , Scroggins Troy , Ampil Federico L. , Li Benjamin D.
Published: March 2007

Whole-breast irradiation, as part of breast-conservation therapy (BCT), has well-established results, good cosmesis, and low toxicity. Results from the BCT trials suggest that the risk for ipsilateral breast cancer recurrence resides within close proximity to the original tumor site. This leads investigators to consider the role of an accelerated and more tumor bed–focused course of radiotherapy. Accelerated partial-breast irradiation (APBI) involves treating a limited volume of breast tissue, with dose of irradiation per fraction increased and the treatment time course decreased. Four currently available methods of APBI are interstitial brachytherapy, intracavitary brachytherapy, intraoperative radiotherapy, and three-dimensional conformal external-beam radiotherapy. Patient selection is critical. This review article presents some preliminary clinical observations and limitations that suggest a potential role for APBI as a more user-friendly mode for delivering radiotherapy after lumpectomy for early breast cancer.
Particle Radiation Therapy Using Proton and Heavier Ion Beams
Authors: Schulz-Ertner Daniela , Tsujii Hirohiko
Published: March 2007

Particle beams like protons and heavier ions offer improved dose distributions compared with photon (also called x-ray) beams and thus enable dose escalation within the tumor while sparing normal tissues. Although protons have a biologic effectiveness comparable to photons, ions, because they are heavier than protons, provide a higher biologic effectiveness. Recent technologic developments in the fields of accelerator engineering, treatment planning, beam delivery, and tumor visualization have stimulated the process of transferring particle radiation therapy (RT) from physics laboratories to the clinic. This review describes the physical, biologic, and technologic aspects of particle beam therapy. Clinical trials investigating proton and carbon ion RT will be summarized and discussed in the context of their relevance to recent concepts of treatment with RT.
Evidence-Based Recommendations for Local Therapy for Soft Tissue Sarcomas
Authors: Pisters Peter W.T. , O'Sullivan Brian , Maki Robert G.
Published: March 2007

There has been a gradual migration in the local treatment of soft tissue sarcomas from amputation and similar radical resectional approaches to more conservative, function-preserving surgery combined with radiotherapy. This progress has been made possible by small, single-institution, randomized trials that demonstrated the superiority of this more conservative, combined-modality approach. In the new millennium, attention has shifted to defining subsets of patients who might be adequately treated by surgery alone and defining the optimal sequence of surgery and radiation for patients who require both types of local therapy. There remains considerable discussion and debate surrounding the issue of pre- and postoperative chemotherapy for patients with localized soft tissue sarcomas. Adjuvant chemotherapy is a standard of care for adults who have the subtypes of soft tissue sarcomas that typically occur in pediatric patients (Ewing sarcoma, rhabdomyosarcoma), and just as clearly, adjuvant chemotherapy is not warranted in patients with low- and intermediate-risk disease (stages I and II). For patients with higher risk disease (stage III), the available randomized trials do not convincingly demonstrate a clinical benefit to adjuvant chemotherapy. As such, a complete accounting of potential risks and benefits is appropriate when discussing adjuvant chemotherapy with patients who have stage III disease.
Advances in Image-Guided Radiation Therapy
Authors: Dawson Laura A. , Jaffray David A.
Published: March 2007

Imaging is central to radiation oncology practice, with advances in radiation oncology occurring in parallel to advances in imaging. Targets to be irradiated and normal tissues to be spared are delineated on computed tomography (CT) scans in the planning process. Computer-assisted design of the radiation dose distribution ensures that the objectives for target coverage and avoidance of healthy tissue are achieved. The radiation treatment units are now recognized as state-of-the-art robotics capable of three-dimensional soft tissue imaging immediately before, during, or after radiation delivery, improving the localization of the target at the time of radiation delivery, to ensure that radiation therapy is delivered as planned. Frequent imaging in the treatment room during a course of radiation therapy, with decisions made on the basis of imaging, is referred to as image-guided radiation therapy (IGRT). IGRT allows changes in tumor position, size, and shape to be measured during the course of therapy, with adjustments made to maximize the geometric accuracy and precision of radiation delivery, reducing the volume of healthy tissue irradiated and permitting dose escalation to the tumor. These geometric advantages increase the chance of tumor control, reduce the risk of toxicity after radiotherapy, and facilitate the development of shorter radiotherapy schedules. By reducing the variability in delivered doses across a population of patients, IGRT should also improve interpretation of future clinical trials.
Intraoperative Radiation Therapy
Authors: Willett Christopher G. , Czito Brian G. , Tyler Douglas S.
Published: March 2007

Intraoperative radiation therapy (IORT) is the delivery of irradiation at the time of an operation. This is performed by different techniques including intraoperative electron beam techniques and high-dose rate brachytherapy. IORT is usually given in combination with external-beam radiation therapy with or without chemotherapy and surgical resection. IORT excludes part or all dose-limiting sensitive structures, thereby increasing the effective dose to the tumor bed (and therefore local control) without significantly increasing normal tissue morbidity. Despite best contemporary therapy, high rates of local failure occur in patients with locally advanced or recurrent rectal cancer, retroperitoneal sarcoma, select gynecologic cancers, and other malignancies. The addition of IORT to conventional treatment methods has improved local control as well as survival in many disease sites in both the primary and locally recurrent disease settings. More recently, there has been interest in the use of IORT as a technique of partial breast irradiation for women with early breast cancer. Given newer and lower cost treatment devices, the use of IORT in clinical practice will likely grow, with increasing integration into the treatment of nonconventional malignancies. Optimally, phase III randomized trials will be carried out to prove its efficacy in these disease sites.
Apelin, an APJ Receptor Ligand, Regulates Body Adiposity and Favors the Messenger Ribonucleic Acid Expression of Uncoupling Proteins in Mice
Authors: Higuchi Keiko , Masaki Takayuki , Gotoh Koro , Chiba Seiichi , Katsuragi Isao , Tanaka Katsuhiro , Kakuma Tetsuya , Yoshimatsu Hironobu
Published: March 2007

Apelin, the endogenous ligand of the APJ receptor, has been identified in a variety of tissues, including stomach, heart, skeletal muscle, and white adipose tissue. We sought to clarify the effects of apelin on body adiposity and the expression of uncoupling proteins (UCPs) in C57BL/6 mice. Treatment with ip apelin at a dose of 0.1 μmol/kg·d for 14 d decreased the weight of white adipose tissue and serum levels of insulin and triglycerides, compared with controls, without influencing food intake. Apelin treatment also decreased body adiposity and serum levels of insulin and triglycerides in obese mice fed a high-fat diet. Apelin increased the serum adiponectin level and decreased that of leptin. Additionally, apelin treatment increased mRNA expression of UCP1, a marker of peripheral energy expenditure, in brown adipose tissue (BAT) and of UCP3, a regulator of fatty acid export, in skeletal muscle. In addition, immunoblot bands and relative densities of UCP1 content in BAT were also higher in the apelin group than controls. Furthermore, apelin treatment increased body temperature and O2 consumption and decreased the respiratory quotient. In conclusion, apelin appears to regulate adiposity and lipid metabolism in both lean and obese mice. In addition, apelin regulates insulin resistance by influencing the circulating adiponectin level, the expression of BAT UCP1, and energy expenditure in mice.
A Twin Study of Nitric Oxide Levels Measured by Serum Nitrite/Nitrate
Authors: Retterstol Lars , Lyberg Torstein , Aspelin Trude , Berg Kåre
Published: March 2007

Nitrite and nitrate are the stable end products of the L-arginine-NO pathway, and the sum of nitrite and nitrate (NOx) is a common way to measure nitric oxide (NO) production or secretion. To uncover any genetic influence on NO, we measured NOx in serum samples from monozygotic twin pairs after an overnight fast. Heritability was estimated as intraclass correlation coefficient. We arrived at a heritability estimate of .32 (95% confidence interval 0.17–0.45) for NOx. The numerical heritability estimate was higher for females than for males (0.38 vs. 0.21), and higher for nonsmokers than for smokers (0.36 vs. 0.22). The heritability estimate of NOx was lower than the heritability estimate for other cardiovascular risk factors. This study suggests a low degree of heredity for NOx levels.
Twins Have Slightly Higher Self-Concepts Than Singletons in the Elementary School Period: A Study of South Korean Twins and Singletons
Authors: Yoon Young-Soon , Hur Yoon-Mi
Published: March 2007

The twin method assumes that the trait under study is similar in twins and singletons so that the results from twin samples can be generalized to the singleton population. The purpose of the present study was to compare self-concept in twins and singletons matched in parental level of education. The 6 cluster scales of the Piers-Harris Children's Self-Concept Scale (P-H) were administered to 630 singleton children and 635 twins aged 7 to 12 years. Model-fitting analyses yielded two conclusions. First, self-concept was generally similar between first- and second-born twins and between monozygotic and dizygotic twins across the 6 cluster scales of the P-H. Second, twins consistently exceeded singletons for all 6 cluster scales of the P-H. However, the effect sizes of differences between twins and singletons were small except for one scale, Physical Appearance and Attributes.
Determination of Zygosity by Questionnaire and Physical Features Comparison in Chinese Adult Twins
Authors: Gao Wenjing , Li Liming , Cao Weihua , Zhan Siyan , Lv Jun , Qin Ying , Pang Zengchang , Wang Shaojie , Chen Weijian , Chen Rongfu , Hu Yonghua
Published: March 2007

This study reports on the determination of zygosity in Chinese adult twins by simple questionnaire and physical features comparison. The subjects were 511 twin pairs from two cities and their town areas, consisting of 371 monozygotic (MZ) and 140 same-sex dizygotic (DZ) pairs, identified by ABO blood group and multiplex polymerase chain reaction of several polymorphic short tandem repeat markers. The twins themselves responded to 8 questionnaire items, 4 items on twin similarity, and 4 items on the frequency of mistaking one twin for another by parents, relatives, teachers and strangers when they were 6 to 13 years old. Research assistants responded to 20 items regarding twins' physical features at the moment of interview. A parsimonious model established using stepwise logistic regression analysis of the 28 items showed that the total accuracy of zygosity diagnosis was 90.1%. The accuracy was 89.2% when using only the items dealing with the confusion of twins and 85.4% using only similarity. In the questionnaire, ‘facial appearance’, ‘mistaken by teachers’ and ‘mistaken by strangers’ had stronger discriminating power between MZ and DZ twins. Two physical features — ‘eyelid’ and ‘middigital hair’ — were informative to some extent. There was no statistically significant sex and area difference in the validity of such questionnaire and physical features comparison-based classification. In conclusion, questionnaire-based zygosity assessment in this Chinese adult twin sample could still be regarded as a valid and valuable classification method. Physical features comparison, however, could only provide limited information for zygosity determination.
The Relationship Between Birthweight Discordance and Perinatal Mortality of One of the Twins in a Twin Pair
Authors: Kato Noriko , Matsuda Tomohiro
Published: March 2007

This study aimed to evaluate the prevalence of birth-weight discordance among twins, to determine the risk cut-off point for birthweight discordance, and to clarify whether perinatal deaths are aggravated by birthweight discordance or by low birthweight itself. A population-based analysis of all twins born between 1995 and 1999 in Japan was conducted using data collected from national birth, death and stillbirth certificates. Birthweight discordance was determined as: higher birthweight minus lower birthweight divided by higher birthweight multiplied by 100. Among twins with a birthweight discordance of more than 15%, the fetal and perinatal mortality rate was higher than that of twins with a discordance of less than 15%. Ninety per cent of the relative cumulative frequency of twin live-births were within 25% of the birthweight discordance. Logistic regression analysis showed that the stillbirth of at least one of the twins is associated with the birthweight of the larger twin and birthweight discordance. It also showed that the stillbirth of both twins in the twin pair is associated with the birth-weight of larger twins and the gestational weeks. It was clarified that birthweight discordance was associated with the stillbirth of only one twin in the twin pair, and the stillbirth of both twins in the twin pair was associated with low birthweight itself.
The Latent Class Structure of ADHD Is Stable Across Informants
Authors: Althoff Robert R. , Copeland William E. , Stanger Catherine , Derks Eske M. , Todd Richard D. , Neuman Rosalind J. , Van Beijsterveldt Toos C. E. M. , Boomsma Dorret I. , Hudziak James J.
Published: March 2007

Previous studies have looked at the structure of attention-deficit/hyperactivity disorder (ADHD) using latent class analysis (LCA) of Child Behavior Checklist (CBCL) or Diagnostic and Statistical Manual of Mental Disorders (DSM) symptom structure. These studies have identified distinct classes of children with inattentive, hyperactive, or combined subtypes and have used these classes to refine genetic analyses. The objective of the current report is to determine if the latent class structure of ADHD subtypes is consistent across informant using the Conners' Rating Scales (CRS). LCA was applied to CRS forms from mother, father, and teacher reports of 1837, 1329 and 1048 latency aged Dutch twins, respectively. The optimal solution for boys was a 5-class solution for mothers, a 3-class solution for fathers, and a 4-class solution for teachers. For girls, a 4-class solution for mothers and a 3-class for fathers and teachers was optimal. Children placed into a class by one informant had markedly increased odds ratio of being placed into the same or similar class by the other informants. Results from LCA using Dutch twins with the CRS show stability across informants suggesting that more stable phenotypes may be accessible for genotyping using a multi-informant approach.
Subtypes of Illicit Drug Users: A Latent Class Analysis of Data From an Australian Twin Sample
Authors: Lynskey Michael T. , Agrawal Arpana , Bucholz Kathleen K. , Nelson Elliot C. , Madden Pamela A. F. , Todorov Alexandre A. , Grant Julia D. , Martin Nicholas G. , Heath Andrew C.
Published: March 2007

This article applies methods of latent class analysis (LCA) to data on lifetime illicit drug use in order to determine whether qualitatively distinct classes of illicit drug users can be identified. Self-report data on lifetime illicit drug use (cannabis, stimulants, hallucinogens, sedatives, inhalants, cocaine, opioids and solvents) collected from a sample of 6265 Australian twins (average age 30 years) were analyzed using LCA. Rates of childhood sexual and physical abuse, lifetime alcohol and tobacco dependence, symptoms of illicit drug abuse/dependence and psychiatric comorbidity were compared across classes using multinomial logistic regression. LCA identified a 5-class model: Class 1 (68.5%) had low risks of the use of all drugs except cannabis; Class 2 (17.8%) had moderate risks of the use of all drugs; Class 3 (6.6%) had high rates of cocaine, other stimulant and hallucinogen use but lower risks for the use of sedatives or opioids. Conversely, Class 4 (3.0%) had relatively low risks of cocaine, other stimulant or hallucinogen use but high rates of sedative and opioid use. Finally, Class 5 (4.2%) had uniformly high probabilities for the use of all drugs. Rates of psychiatric comorbidity were highest in the polydrug class although the sedative/opioid class had elevated rates of depression/suicidal behaviors and exposure to childhood abuse. Aggregation of population-level data may obscure important subgroup differences in patterns of illicit drug use and psychiatric comorbidity. Further exploration of a ‘self-medicating’ subgroup is needed.
Association Study of the Dystrobrevin-Binding Gene With Schizophrenia in Australian and Indian Samples
Authors: Holliday Elizabeth G. , Handoko Herlina Y. , James Michael R. , McGrath John J. , Nertney Deborah A. , Tirupati Sujit , Thara Rangaswamy , Levinson Douglas F. , Hayward Nicholas K. , Mowry Bryan J. , Nyholt Dale R.
Published: March 2007

Numerous studies have reported association between variants in the dystrobrevin binding protein 1 (dysbindin) gene (DTNBP1) and schizophrenia. However, the pattern of results is complex and to date, no specific risk marker or haplotype has been consistently identified. The number of single nucleotide polymorphisms (SNPs) tested in these studies has ranged from 5 to 20. We attempted to replicate previous findings by testing 16 SNPs in samples of 41 Australian pedigrees, 194 Australian cases and 180 controls, and 197 Indian pedigrees. No globally significant evidence for association was observed in any sample, despite power calculations indicating sufficient power to replicate several previous findings. Possible explanations for our results include sample differences in background linkage dis-equilibrium and/or risk allele effect size, the presence of multiple risk alleles upon different haplotypes, or the presence of a single risk allele upon multiple haplotypes. Some previous associations may also represent false positives. Examination of Caucasian HapMap phase II genotype data spanning theDTNBP1region indicates upwards of 40 SNPs are required to satisfactorily assess all nonredundant variation withinDTNBP1and its potential regulatory regions for association with schizophrenia. More comprehensive studies in multiple samples will be required to determine whether specificDTNBP1variants function as risk factors for schizophrenia.
Heritability of Testosterone Levels in 12-Year-Old Twins and Its Relation to Pubertal Development
Authors: Hoekstra Rosa A. , Bartels Meike , Boomsma Dorret I.
Published: March 2007

The aim of this study was to estimate the heritability of variation in testosterone levels in 12-year-old children, and to explore the overlap in genetic and environmental influences on circulating testosterone levels and androgen-dependent pubertal development. Midday salivary testosterone samples were collected on 2 consecutive days in a sample of 183 unselected twin pairs. Androgen-induced pubertal development was assessed using self-report Tanner scales of pubic hair development (boys and girls) and genital development (boys). A significant contribution of genetic effects to the variance in testosterone levels was found. Heritability was approximately 50% in both boys and girls. The remaining proportion of the variance in testosterone levels could be explained by nonshared environmental influences. The relatively high correlation between testosterone levels of opposite-sex dizygotic twins suggests that sex differences in genes influencing variation in testosterone levels have not yet developed in preand early puberty. Variance in pubertal development was explained by a large genetic component, moderate shared environmental influences, and a small nonshared environmental effect. Testosterone levels correlated moderately (r = .31) with pubertal development; the covariance between testosterone levels and pubertal development was entirely accounted for by genetic influences.
Familial Risks for Main Neurological Diseases in Siblings Based on Hospitalizations in Sweden
Authors: Hemminki Kari , Sundquist Kristina , Li Xinjun
Published: March 2007

Recent successes in identifying the underlying genetic mechanisms for neurological diseases, particularly for their Mendelian forms, have had profound implications for their diagnostics, treatment and classification. However, there has never been an attempt to compare familial risks in a systematic way among and between the main neurological diseases. Familial risks were here defined for siblings who were hospitalized because of a neurological disease in Sweden. A nationwide database for neurological diseases was constructed by linking the Multigeneration Register of 0- to 69-year-old siblings to the Hospital Discharge Register for the years 1987 to 2001. Standardized risk ratios were calculated for affected sibling pairs by comparing them to those whose siblings had no neurological disease. There were three main results. First, it was shown that all disease groups had a familial risk, with the exception of transient ischemic attacks, and the risks could be ranked from the highest (3451) for Huntington's disease to the lowest (2.1) for inflammatory diseases. Second, increased familial risks were shown for disease subtypes for which susceptibility genes or familial clustering have not been demonstrated previously, including multiple sclerosis, sleep apnea, nerve, nerve root and plexus disorders, and cerebral palsy. Third, based on the available sample size there was no convincing evidence for familial comorbidity between the disease groups, suggesting that the factors causing familial aggregation, probably usually heritable genes, are distinct for each subtype. The high familial risks for neurological disease imply heritable etiology and opportunities for identification of further susceptibility genes.
Factors Influencing the Stillbirth Rates in Single and Multiple Births in Sweden, 1869 to 1967
Authors: Eriksson Aldur W. , Fellman Johan
Published: March 2007

Temporal variations in the stillbirth rate among singletons, twins and triplets in Sweden between 1869 and 1967 were studied. Both among single and multiple births there were marked secular decreasing trends in the stillbirth rates. Based on our long time series since 1869, this study confirms that among twins and triplets the stillbirth rate was higher among same-sexed than among opposite-sexed sets. Comparisons between the stillbirth rates among twin births in urban and rural regions indicate higher stillbirth rates in rural areas. In addition, the stillbirth rates among twins of unmarried mothers were higher than those of twins of married mothers. These findings also hold for both same-sexed and opposite-sexed twin pairs. Analyses of the stillbirth rates for singletons and for different types of twins indicate that up to 1950 the risk of stillbirth among males was almost constantly between 15% to 20% higher than among females. After that the difference in the risk decreased. Comparisons with other populations were performed.
Cantrell's Pentalogy in Twins: Prenatal Diagnosis
Authors: Moreira de Sá Renato A. , de Souza Filho Gustavo P. A. , Lopes Laudelino M. , Faleiro Edson C. , Junior Joffre A.
Published: March 2007

The combination of an onphalocele, an anterior thoracic wall defect and an anterior diaphragmatic defect constitutes classical Cantrell's pentalogy. We present a case of Cantrell's pentalogy diagnosed prenataly in twins with conventional and three-dimensional sonography.
Suicidal Behavior in Surviving Co-Twins
Authors: Pompili Maurizio , Galeandro Piera Maria , Lester David , Tatarelli Roberto
Published: March 2007

Recent research has provided strong support for the existence of a familial risk for suicide, and efforts have been made to separate genetic from enviromental risk factors. Twin studies have played a major role in the identification of genetic factors, and the results indicate that the concordance rate for suicide is higher in identical than in fraternal twins (Baldessarini & Hennen, 2004). Moreover, Segal and Roy (1995) reported a significantly higher frequency of nonfatal suicidal attempts by monozygotic (MZ) than by dyzygotic (DZ) twins whose co-twins had committed suicide. However, doubts remain as to whether the increased risk of suicide in MZ twins is a response to the intense grief over the loss of a close relative, or whether a common genotype is associated with suicidal behavior. Sudden loss, which may carry a stigma in the case of a suicide, has been linked to increased persistent emotional stress and physiological changes (Epstein, 1993; Martin & Dean, 1993). A number of researchers have reported greater suicidal ideation among bereaved MZ twins as compared to DZ twins, suggesting that a loss due to suicide may increase the risk of suicidal behavior in the surviving co-twin (Segal & Bouchard, 1993; Segal & Roy, 1995; Segal et al., 1995). The aim of the present article is to address the issue of the intense grief experienced by twins after the co-twin suicide.
Maternal Dietary Intake in Twin Pregnancies: Does it Diminish Towards Term?
Authors: Morley Ruth , Umstad Mark P. , Bond Jodie , Moore Vivienne M. , Owens Julie A. , Dwyer Terence , Carlin John B.
Published: March 2007

We tested the hypothesis that energy intake among women with twin pregnancies decreases in late gestation, as the uterus enlarges and they become increasingly uncomfortable. We asked women to recall dietary intake for the previous 24 hours, every 2 weeks from around 29 weeks of gestation, using a photographic atlas and other strategies to estimate portion size. Eighty women provided data at around 29, 31, 33 and 35 weeks of gestation. We calculated total energy intake, and energy intake from carbohydrate, fat and protein. Data were log transformed to reduce skewness. Using mixed effects linear regression models, we found minimal evidence that total energy intake changed over this time period, either before or after adjustment for potential confounding factors (95% confidence interval for relative change per week: −1.4%, 0.6%). There was weak evidence of a small decline in carbohydrate intake over time, both before and after controlling for energy intake. We cannot exclude change in energy intake or diet composition before 29 weeks or after 35 weeks of twin gestation.
Birthweight Discordance in Twins and the Risk of Being Heavier for Respiratory Distress Syndrome
Authors: Canpolat Fuat Emre , Yurdakök Murat , Korkmaz Ayse , Yigit Sule , Tekinalp Gülsevin
Published: March 2007

Twin pregnancies are becoming common as a result of increased assisted reproduction. Studies have shown that the smaller twin of a pair is at greater risk of morbidity and mortality. Our aim was to determine if there is a relation between birth-weight discordancy and neonatal morbidity and mortality and to test the occurrence of respiratory distress syndrome (RDS) in discordant twins. For 5 years all twins admitted to our intensive care unit were included in the study. Discordance was calculated as the difference between twins' weights divided by the heavier weight. Diagnosis of RDS was made by typical clinical and radiographic methods. Multiple logistic regression was performed with gender, weight order and birth order as the independent variables and RDS as the dependent variable. Two hundred and sixty-six twin pairs with a mean gestation of 33 weeks and a mean birthweight of 1890 g were evaluated. Multiple logistic regression revealed that being the heavier twin was a more important risk factor for RDS (odds ratio 4.5; 95% confidence interval 2.2–9.2) than being the male or second-born twin. Based on neonatal outcomes a birthweight discordance equal or greater than 20% in twin pairs was accepted as the discordance criterion. Discordant and concordant groups were statistically different in neonatal mortality, necrotizing enterocolitis, polycytemia and hypoglycemia. Our data demonstrated that being the heavier twin is a risk factor for RDS and a birth-weight difference of 20% or more in twin pairs should be accepted as discordance.
Curves of Placental Weights of Live-Born Twins
Authors: Gielen Marij , Lindsey Patrick J. , Derom Catherine , Loos Ruth J. F. , Derom Robert , Nijhuis Jan G. , Vlietinck Robert
Published: March 2007

The purpose of this study is to present curves of estimated placental growth in twins and to evaluate the relative contribution of gestational age, zygosity, chorionicity, fusion of the placentas, sex of the individual and of the twin pair, site of the umbilical cord insertion, birth order, maternal age, and parity. Perinatal data and placental data were obtained from 6315 live-born twin pairs from the East Flanders Prospective Twin Survey. Of 4318 twin pairs, with no missing values, the placental weights of different gestational ages were analyzed using a nonlinear multivariate Gaussian regression. Two groups were distinguished: (1) twins with two separate placentas, and (2) twins with only one placental mass (one placenta in case of monochorionic twins or two fused placentas in case of dichorionic placentas). Overall, placental weight was influenced by gestational age, fusion of the placentas, and parity. In the case of one placental mass, monozygotic dichorionic twins had the lowest weights. If two separate placentas were present, birth order played a role in favor of the first-born twin. For parity and zygosity, the differences were most pronounced between 27 and 29 weeks, whereas the difference for birth order was most pronounced between 33 and 37 weeks. In conclusion, basic physiological characteristics, routinely examined at birth, influence placental weight. Taking these covariates into account allows a better evaluation of the placental weight given a gestational age, as an indicator of growth.
Twinning and Risk of Stillbirth Subtypes in Pediatric Mothers
Authors: Salihu Hamisu M. , Sharma Puza P. , Peters Shillena
Published: March 2007

We sought to estimate levels of risk for stillbirth subtypes associated with twin gestations among pediatric mothers (10–14 years). Analysis was on twin pregnancies covering the period 1989 to 2000 in the United States. We classified stillbirth as term, preterm, small-for-gestational-age (SGA) or preterm-SGA. We then assessed the risks of these stillbirth subtypes in pediatric mothers using two comparison groups consisting of women aged 15 to 19 years old (adolescent mothers) and 20 to 24 years old (mature mothers). Adjusted risk estimates were by means of hazard ratios generated from a Cox proportional hazards regression model. We adjusted for dependence of observations within twin clusters using the robust sandwich estimator. The rate of stillbirth was highest among pediatric mothers (56/1000), followed by adolescent gravidas (29/1000) and lowest in mature mothers (20/1000; p for trend < .01). Overall, preterm stillbirth was the most frequent stillbirth phenotype while term stillbirth was the least frequent. Not a single case of term stillbirth was recorded in pediatric mothers. Among pediatric gravidas, the risk for preterm stillbirth was more than tripled (adjusted hazard ratio [AHR] = 3.4; 95% confidence interval [CI] = 2.5–4.6), and that of preterm-SGA stillbirth more than doubled (AHR = 2.6; 95% CI = 1.8–3.7) that of mature mothers respectively. The 30% risk elevation for SGA stillbirth among pediatric mothers was not found to be statistically significant (AHR = 1.1; 95% CI = 0.3–4.3). Pediatric motherhood is a risk factor for stillbirth in twin gestation, especially, preterm and preterm-SGA stillbirth phenotypes. Prevention of stillbirth among this category of mothers should target the period preceding full term.
Outcome of Twins Delivery; Predictors for Successful Vaginal Delivery: A Single Center Experience
Authors: Salim Read , Lavee Michal , Nachum Zohar , Shalev Eliezer
Published: March 2007

The aim of this study was to compare maternal and neonatal outcome of twin births according to mode of delivery and to isolate the factors predicting a successful vaginal delivery and those predicting a failed trial of labor (TOL) leading to an emergent cesarean section. We reviewed all twin deliveries during the years 1995 to 2004. Parameters studied include maternal age, parity, gestational age, maternal antepartum complications and postpartum complications, fetal presentations, birthweight, mode of delivery of each twin, Apgar scores and cord pH. During the study period there were 40,710 deliveries of which 804 (1.9%) were twin deliveries. Of the 804 twins, 398 (49.5%) had planned cesarean sections (PCS) and 406 (50.5%) entered a TOL. Maternal age and parity were similar among the groups. Neonatal outcomes and postpartum complications did not differ between the groups. Of 406 women who had a TOL, 84.9% eventually delivered both twins vaginally. A significantly higher percentage of antepartum complications were noted among those who failed the TOL compared to those with successful TOL (8.2% vs. 1.7%,p=.01). The number of neonates with pH of less than 7.0 did not differ between the groups although more neonates (2.5% vs. 0.4%,p=.05) among the failed TOL had an Apgar score of less than 7.0 at 5 minutes compared to successful TOL. Vaginal delivery of both twins after TOL occurred in 91% of vertex/vertex compared with 71.8% of vertex/nonvertex presenting twins (p< .01). Neonatal outcomes did not differ between both groups. Our results indicate that both vaginal and PCS are comparable options for vertex presenting first twin regardless of second twin presentation.
Wisconsin Twin Panel: Current Directions and Findings
Authors: Lemery-Chalfant Kathryn , Goldsmith H. Hill , Schmidt Nichole L. , Arneson Carrie L. , Van Hulle Carol A.
Published: March 2007

The Wisconsin Twin Panel is based on the population of all twins born in the state of Wisconsin, United States. Our research focus is the etiology and developmental course of early emotions, temperament, childhood anxiety and impulsivity, the autism spectrum, auditory and tactile sensory sensitivity, and related psychobiological and behavioral phenotypes. We employ a range of research methods including structured interviews with caregivers, observer ratings, child self-report, home-based behavioral batteries, biological measures of basal and reactive cortisol, palm prints, birth records, genotyping, cognitive testing, and questionnaires. Reported results highlight the utility of employing multiple modes of assessment when studying child development and psychopathology.
Twin Towers: The Ones Left Behind; Research Reviews: Chimeric DZ Twins, DZ Twin Mothers; Revisited: The New York Child Development Center Twin Study; New and Unusual Twins
Authors: Segal Nancy L.
Published: March 2007

Twin victims and survivors of the 2001 World Trade Tower attack are remembered. Central themes from the twin loss literature are also highlighted. Next, new research studies on dizygotic (DZ) twins and mothers of DZ twins are reviewed. Specifically, a rare monochorionic–diamniotic DZ twin pair with chimerism is described, and findings concerning genetic variants of GDF9 in mothers (that are associated with DZ twinning tendencies in families) are summarized. This is followed by another look at the controversial 1960s Child Development Center Twin Study that tracked the development of separated twins. Information on several new and unusual twins is also presented.
The Australian Twin ADHD Project: Current Status and Future Directions
Authors: Bennett Kellie S. , Hay David A. , Piek Jan , Pearsall-Jones Jillian , Levy Florence , Martin Neilson
Published: March 2007

This article describes the Australian Twin Attention-deficit/hyperactivity disorder (ADHD) Project (ATAP), the results of research conducted using this database and plans for future studies. Information has been actively collected from Australian families with twin children since 1991 for the ATAP database. The value of assessing siblings as well as twins is emphasized. Much work has gone into continuing the involvement of families in the study though this does become more difficult when twins reach maturity. The main focus of the project is ADHD in children and adolescents plus comorbid conditions including conduct disorder, oppositional defiant disorder, and generalized anxiety disorder. A major challenge has been how to retain continuity in the assessments, while at the same time covering changes in psychiatric classification, such as the move to Diagnostic and Statistical Manual of Mental Disorders (4th ed.; DSM-IV; American Psychiatric Association, 1994). Changes in the scale can affect the reports of twin similarity. Over the years, these twins have become part of other twin studies and future plans include linking different twin databases to investigate the relationships between childhood behavior and adult conditions. Recruitment, assessment and retention of twin families require a major commitment but create a significant resource for collaboration in areas outside the original aim.
Genetic and Environmental Influences on Dentofacial Structures and Oral Health: Studies of Australian Twins and Their Families
Authors: Townsend Grant , Richards Lindsay , Messer Louise Brearley , Hughes Toby , Pinkerton Sandra , Seow Kim , Gotjamanos Theo , Gully Neville , Bockmann Michelle
Published: March 2007

Our studies of the teeth and faces of Australian twins commenced at the School of Dentistry, The University of Adelaide in the early 1980s. There are now over 900 pairs of twins enrolled in our continuing investigations, together with 1200 relatives. There are 3 main cohorts of participants. The first cohort comprises around 300 pairs of teenage twins for whom various records have been collected, including dental casts, facial photographs, finger and palm prints and information on laterality, including handedness. The second cohort comprises around 300 pairs of twins who have been examined at 3 stages of dental development from approximately 4 years of age to about 14 years: at primary, mixed, and permanent dentition (excluding 3rd molars) stages. The most recent study of tooth emergence and oral health, for which we are currently recruiting twins, will provide a third cohort of around 500 twin pairs aged from around birth to 3 to 4 years of age. Our broad aim in these studies has been to improve our understanding of how genetic and environmental factors contribute to variation in dental and facial features, and to oral health. We have also used our data to investigate aspects of the determination of laterality, particularly the fascinating phenomenon of mirror imaging. We plan to maximize the use of the longitudinal data and DNA we have collected, and continue to collect, by performing genome-wide scans for putative genetic linkage peaks for a range of dental features, and then to test for association between a series of likely candidate genes and our phenotypes.
The Qingdao Twin Registry: A Focus on Chronic Disease Research
Authors: Pang Zengchang , Ning Feng , Unger Jennifer , Johnson C. Anderson , Wang Shaojie , Guo Qian , Cao Weihua , Lee Liming
Published: March 2007

With the changing patterns of morbidity and mortality in China, noncommunicable chronic diseases have become the major threats to the health of the Chinese population. The causes of chronic diseases include genetic factors and behavioral risk factors such as the use of tobacco, alcohol, and other drugs, unhealthy dietary behaviors, and lack of physical activity. Twin studies offer a unique opportunity to disentangle the genetic and environmental risk and protective factors for chronic disease. The Qingdao Twin Registry (QTR) was initiated in 1998 as part of the National Chinese Twin Registry. Over 11,000 pairs of twins and multiples of all ages have been recruited into the registry. Several studies of physical and mental health are underway. Many of the adult twins have completed health and behavioral risk factor surveys, and the adolescent twins are participating in a study of gene–environment interactions in tobacco and alcohol use. Studies of the heritability of personality factors have been conducted. In 2002, Qingdao established the Qingdao Twin Health Promotion Association, a nonprofit organization that supports health services for twins and their parents, organizes special events and health-related activities for twins, and raises funds to conduct twin health examinations. The QTR will be a useful resource for future studies of population genetics in human health and disease.
The Danish Twin Registry in the New Millennium
Authors: Skytthe Axel , Kyvik Kirsten , Bathum Lise , Holm Niels , Vaupel James W. , Christensen Kaare
Published: March 2007

The Danish Twin Registry is the oldest national twin register in the world, initiated in 1954, and, by the end of 2005, contained more than 75,000 twin pairs born in the between 1870 and 2004. The Danish Twin Registry is used as a source for studies on the genetic influence on normal variation in clinical parameters associated with the metabolic syndrome and cardiovascular diseases, clinical studies of specific diseases, and aging and age-related health problems. The combination of survey data, clinical data and linkage to national health-related registers enables follow-up studies of both the general twin population and twins from clinical studies. This paper summarizes the newest extension of the register and gives examples of new developments and phenotypes studied.
Twin Studies in Finland 2006
Authors: Kaprio Jaakko
Published: March 2007

In studies on the Finnish Twin Cohorts, genetic and environmental determinants of common, complex diseases, and their behavioral risk factors have been investigated in Finland. In 1974, the older twins were identified, with a total of 13,888 like-sexed pairs of known zygosity. They have participated since 1975 in mail surveys, clinical examinations for subsamples, have been used to recruit families, and have been followed up for morbidity using national medical registers. Opposite twin pairs were added later. Two longitudinal studies of adolescent twins and their families, known as the FinnTwin12 and FinnTwin16 studies, have focused on determinants of health-related behaviors and disease in adolescents and young adults. This article describes current, ongoing data collection and analyses.
The Jena Twin Registry and the Jena Twin Study of Social Attitudes (JeTSSA)
Authors: Stößel Katharina , Kämpfe Nicole , Riemann Rainer
Published: March 2007

The Jena Twin Registry focuses on identifying twins in eastern Germany. It is based in part on registers of multiple births and data from registration offices, and in part on a volunteer sample approached by media calls and twin clubs. The Jena Twin Study of Social Attitudes (JeTSSA) is the first study based on the Jena Twin Registry. In a sample of 226 monozygotic and 168 dizygotic adult twin pairs, self- and independent reports of significant others (peers, spouses, parents) are collected to estimate genetic and environmental effects on social attitudes and the covariation of genetic influences on personality traits and social attitudes. In addition, the effects of measured environmental variables on attitude formation are examined.
The Longitudinal Israeli Study of Twins (LIST): Children's Social Development as Influenced by Genetics, Abilities, and Socialization
Authors: Knafo Ariel
Published: March 2007

The goals, prospects and methods of the Longitudinal Israeli Study of Twins (LIST) are described. This study is interested in children's prosocial development from phenotypic, genetic and environmental perspectives. It focuses on measuring prosociality with a multi-trait multi-method approach, and relating it to children's general cognitive and sociocognitive abilities, and to parenting in the family. Other variables of interest such as children's temperament and parental values are discussed, as are ideas for further research.