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3.
Methods Mol Biol ; 1975: 131-156, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31062308

RESUMO

Cells are dynamic biological systems that interact with each other and their surrounding environment. Understanding how cell extrinsic and intrinsic factors control cell fate is fundamental to many biological experiments. However, due to transcriptional heterogeneity or microenvironmental fluctuations, cell fates appear to be random. Individual cells within well-defined subpopulations vary with respect to their proliferative potential, survival, and lineage potency. Therefore, methods to quantify fate outcomes for heterogeneous populations that consider both the stochastic and deterministic features of single-cell dynamics are required to develop accurate models of cell growth and differentiation. To study random versus deterministic cell behavior, one requires a probabilistic modelling approach to estimate cumulative incidence functions relating the probability of a cell's fate to its lifetime and to model the deterministic effect of cell environment and inheritance, i.e., nature versus nurture. We have applied competing risks statistics, a branch of survival statistics, to quantify cell fate concordance from cell lifetime data. Competing risks modelling of cell fate concordance provides an unbiased, robust statistical modelling approach to model cell growth and differentiation by estimating the effect of cell extrinsic and heritable factors on the cause-specific cumulative incidence function.


Assuntos
Neoplasias da Mama/patologia , Diferenciação Celular , Linhagem da Célula , Biologia Computacional/métodos , Doenças em Gêmeos/patologia , Análise de Célula Única/métodos , Proliferação de Células , Feminino , Humanos , Modelos Biológicos , Processos Estocásticos , Estudos em Gêmeos como Assunto
4.
Neuron ; 102(1): 91-103, 2019 04 03.
Artigo em Inglês | MEDLINE | ID: mdl-30946830

RESUMO

There have been several recent studies addressing the genetic architecture of depression. This review serves to take stock of what is known now about the genetics of depression, how it has increased our knowledge and understanding of its mechanisms, and how the information and knowledge can be leveraged to improve the care of people affected. We identify four priorities for how the field of MD genetics research may move forward in future years, namely by increasing the sample sizes available for genome-wide association studies (GWASs), greater inclusion of diverse ancestries and low-income countries, the closer integration of psychiatric genetics with electronic medical records, and the development of the neuroscience toolkit for polygenic disorders.


Assuntos
Transtorno Depressivo Maior/genética , Grupos de Populações Continentais/genética , Transtorno Depressivo Maior/classificação , Transtorno Depressivo Maior/diagnóstico , Estudo de Associação Genômica Ampla , Humanos , Herança Multifatorial , Estudos em Gêmeos como Assunto
5.
Neurosci Biobehav Rev ; 100: 324-334, 2019 05.
Artigo em Inglês | MEDLINE | ID: mdl-30822436

RESUMO

Self-control is the ability to control one's impulses when faced with challenges or temptations, and is robustly associated with physiological and psychological well-being. Twin studies show that self-control is heritable, but estimates range between 0% and 90%, making it difficult to draw firm conclusions. The aim of this study was to perform a meta-analysis to provide a quantitative overview of the heritability of self-control. A systematic search resulted in 31 included studies, 17 reporting on individual samples, based on a sample size of >30,000 twins, published between 1997 and 2018. Our results revealed an overall monozygotic twin correlation of 0.58, and an overall dizygotic twin correlation of 0.28, resulting in a heritability estimate of 60%. The heritability of self-control did not vary across gender or age. The heritability did differ across informants, with stronger heritability estimates based on parent report versus self-report or observations. This finding provides evidence that when aiming to understand individual differences in self-control, one should take genetic factors into account. Recommendations for future research are discussed.


Assuntos
Autocontrole , Humanos , Comportamento Impulsivo/fisiologia , Autorrelato , Estudos em Gêmeos como Assunto , Gêmeos Dizigóticos , Gêmeos Monozigóticos
6.
Neurosci Biobehav Rev ; 100: 85-97, 2019 05.
Artigo em Inglês | MEDLINE | ID: mdl-30817934

RESUMO

BACKGROUND: Callous-unemotional (CU) traits represent the affective features of psychopathy used to delineate youth at high risk for externalizing pathology. The genetic etiology CU traits is not currently well-understood. METHODS: The current review surveyed the literature for studies on the genetic underpinnings of CU traits and integrated information from 39 genetic studies. RESULTS: The results from 24 studies with quantitative data suggest that the heritability for CU traits is likely between 36-67%. A majority of the 16 molecular genetic studies focused on candidate genes in the serotonin and oxytocin systems with results that have not been well replicated. Although two genome-wide association studies have been conducted, no genome-wide significant loci have been discovered. DISCUSSION: There is some evidence to suggest that the serotonin and oxytocin systems may play a role in CU traits; however, there is currently not enough evidence to implicate specific genetic mechanisms. The authors encourage researchers to continue to apply the most up-to-date and relevant methodology, specifically collaborations and consortiums using genome-wide and polygenic methods.


Assuntos
Transtorno da Conduta/genética , Transtorno da Conduta/psicologia , Emoções/fisiologia , Epigênese Genética , Predisposição Genética para Doença , Humanos , Personalidade/genética , Fatores de Risco , Estudos em Gêmeos como Assunto
7.
Eur J Pharm Sci ; 130: 65-77, 2019 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-30684656

RESUMO

Understanding and predicting inter-individual differences related to the success of drug therapy is of tremendous importance, both during drug development and for clinical applications. Importantly, while seminal twin studies indicate that the majority of inter-individual differences in drug disposition are driven by hereditary factors, common genetic polymorphisms explain only less than half of this genetically encoded variability. Recent progress in Next Generation Sequencing (NGS) technologies has for the first time allowed to comprehensively map the genetic landscape of human pharmacogenes. Importantly, these projects have unveiled vast numbers of rare genetic variants, which are estimated to contribute substantially to the missing heritability of drug metabolism phenotypes. However, functional interpretation of these rare variants remains challenging and constitutes one of the important frontiers of contemporary pharmacogenomics. Furthermore, NGS technologies face challenges in the interrogation of genes residing in complex genomic regions, such as CYP2D6 and HLA genes. We here provide an update of the implementation of pharmacogenomic variations in the clinical setting and present emerging strategies that facilitate the translation of NGS data into clinically useful information. Importantly, we anticipate that these developments will soon result in a paradigm shift of pre-emptive genotyping away from the interrogation to candidate variants and towards the comprehensive profiling of an individuals genotype, thus allowing for a true individualization of patient drug treatment regimens.


Assuntos
Efeitos Colaterais e Reações Adversas Relacionados a Medicamentos/genética , Variação Genética/genética , Sequenciamento de Nucleotídeos em Larga Escala/métodos , Preparações Farmacêuticas , Polimorfismo Genético/genética , Estudos em Gêmeos como Assunto/métodos , Citocromo P-450 CYP2D6/genética , Citocromo P-450 CYP2D6/metabolismo , Desenvolvimento de Medicamentos/métodos , Desenvolvimento de Medicamentos/tendências , Efeitos Colaterais e Reações Adversas Relacionados a Medicamentos/diagnóstico , Efeitos Colaterais e Reações Adversas Relacionados a Medicamentos/metabolismo , Previsões , Sequenciamento de Nucleotídeos em Larga Escala/tendências , Humanos , Preparações Farmacêuticas/metabolismo , Farmacogenética/métodos , Farmacogenética/tendências , Medicina de Precisão/métodos , Medicina de Precisão/tendências , Estudos em Gêmeos como Assunto/tendências
8.
Behav Genet ; 49(1): 99-111, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-30569348

RESUMO

For many multivariate twin models, the numerical Type I error rates are lower than theoretically expected rates using a likelihood ratio test (LRT), which implies that the significance threshold for statistical hypothesis tests is more conservative than most twin researchers realize. This makes the numerical Type II error rates higher than theoretically expected. Furthermore, the discrepancy between the observed and expected error rates increases as more variables are included in the analysis and can have profound implications for hypothesis testing and statistical inference. In two simulation studies, we examine the Type I error rates for the Cholesky decomposition and Correlated Factors models. Both show markedly lower than nominal Type I error rates under the null hypothesis, a discrepancy that increases with the number of variables in the model. In addition, we observe slightly biased parameter estimates for the Cholesky decomposition and Correlated Factors models. By contrast, if the variance-covariance matrices for variance components are estimated directly (without constraints), the numerical Type I error rates are consistent with theoretical expectations and there is no bias in the parameter estimates regardless of the number of variables analyzed. We call this the direct symmetric approach. It appears that each model-implied boundary, whether explicit or implicit, increases the discrepancy between the numerical and theoretical Type I error rates by truncating the sampling distributions of the variance components and inducing bias in the parameters. The direct symmetric approach has several advantages over other multivariate twin models as it corrects the Type I error rate and parameter bias issues, is easy to implement in current software, and has fewer optimization problems. Implications for past and future research, and potential limitations associated with direct estimation of genetic and environmental covariance matrices are discussed.


Assuntos
Genética Comportamental/métodos , Estudos em Gêmeos como Assunto/métodos , Viés , Biometria , Simulação por Computador , Genética Comportamental/estatística & dados numéricos , Humanos , Funções Verossimilhança , Modelos Genéticos , Modelos Estatísticos , Análise Multivariada , Projetos de Pesquisa , Estudos em Gêmeos como Assunto/estatística & dados numéricos
10.
Eat Behav ; 30: 83-87, 2018 08.
Artigo em Inglês | MEDLINE | ID: mdl-29933124

RESUMO

OBJECTIVE: Binge eating disorder (BED) is a clinical eating disorder that is strongly and bidirectionally related to overweight and obesity. Little is known about how subclinical features of BED relate to weight development in adolescence and young adulthood. METHOD: Women (n = 2825) and men (n = 2423) from the community-based longitudinal FinnTwin16 cohort participated. Seven eating-related cognitions and behaviors similar to the defining features of BED were extracted from the Eating Disorder Inventory-2 and were assessed at a mean age of 24. We used linear mixed models to assess the association of features of BED with BMI trajectories across four waves of data collection (mean ages 16, 17, 18, and 24). RESULTS: The number of features of BED at wave 4 (age 24) was significantly associated with BMI from age 16 years onwards. Those reporting more features of BED had gained more weight throughout adolescence and into their twenties. CONCLUSIONS: Features of BED in young adulthood were preceded by steeper BMI trajectories in adolescence. A higher number of features were consistently associated with higher BMI and more weight gain.


Assuntos
Transtorno da Compulsão Alimentar/psicologia , Ganho de Peso , Adolescente , Índice de Massa Corporal , Feminino , Finlândia/epidemiologia , Humanos , Estudos Longitudinais , Masculino , Obesidade/epidemiologia , Sobrepeso/epidemiologia , Estudos em Gêmeos como Assunto , Adulto Jovem
11.
Exerc Sport Sci Rev ; 46(3): 138-143, 2018 07.
Artigo em Inglês | MEDLINE | ID: mdl-29912036

RESUMO

Some individuals show little or no increase in maximal oxygen consumption (V˙O2max) in response to training programs consistent with public health guidelines. However, results from studies using more intense programs challenge the concept that some humans have limited trainability. We explore the implications of these divergent observations on the biology of trainability and propose a new set of twin studies to explore them.


Assuntos
Aptidão Cardiorrespiratória , Consumo de Oxigênio , Condicionamento Físico Humano , Humanos , Projetos de Pesquisa , Estudos em Gêmeos como Assunto
12.
Eur J Clin Invest ; 48(7): e12935, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-29635711

RESUMO

BACKGROUND: Gallstone disease (GD) belongs to the most frequent disorders in gastroenterology and causes high costs in our health-care systems. Gallstones are uncommon in children but frequent in adults, in particular in women, and are triggered by exogenous risk factors. Here, we summarize the current knowledge concerning the contribution of inherited predisposition to gallstone risk. DESIGN: In this review, we present the current data and recent research on the genetics of gallstone disease. RESULTS: Several GD-predisposing gene variants have been reported, with most prominent effects being conferred by a common variant (p.D19H) of the hepatic and intestinal cholesterol transporter ABCG5/G8. A smaller group of patients might develop gallstones primarily due low phosphatidylcholine concentrations in bile as a result of loss-of-function mutations of the ABCB4 transporter (low phospholipid-associated cholelithiasis syndrome). Regardless of the origin, the risk factors for gallstones lead to the supersaturation of bile with insoluble compounds, in particular cholesterol. As result, cholesterol stones develop and present the most frequent type of gallstones. Laparoscopic cholecystectomy with low morbidity and mortality is currently the most common and effective method for the therapy of symptomatic gallbladder stones. CONCLUSIONS: Gallstone disease represents a multifactorial condition and previous studies have identified the major genetic contributors to gallstone formation. The increasing knowledge about the pathomechanisms of hepatobiliary metabolism and GD as well as the identification of additional risk factors might help to overcome the current invasive therapy by specific lifestyle intervention and precise molecular treatment.


Assuntos
Cálculos Biliares/genética , Predisposição Genética para Doença/genética , Colesterol/química , Cristalização , Feminino , Loci Gênicos/genética , Humanos , Masculino , Fosfolipídeos/química , Polimorfismo de Nucleotídeo Único/genética , Fatores de Risco , Estudos em Gêmeos como Assunto
13.
Dermatol Clin ; 36(2): 87-92, 2018 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-29499803

RESUMO

Rosacea is a common inflammatory skin disease with a multifaceted pathophysiology, including environmental stressors and neurovascular and immune dysfunction affected by the presence of pathogens. The genetic component of this disorder is not well understood. However, a possible genetic origin in Northern European descendants, family inheritance, twin concordance, and genetic associations with autoimmune disorders attest the genetic predisposition to rosacea. Currently, one single-nucleotide polymorphism has been identified in association with rosacea and is intergenic between HLA-DRA and BTNL2. Additional associations with HLA alleles and immune-mediated disorders support the role of immune-regulating genes and innate and adaptive immunity in rosacea.


Assuntos
Predisposição Genética para Doença , Rosácea/genética , Transcrição Genética , Doenças Autoimunes/genética , Humanos , Estudos em Gêmeos como Assunto
14.
Nature ; 555(7695): 210-215, 2018 03 08.
Artigo em Inglês | MEDLINE | ID: mdl-29489753

RESUMO

Human gut microbiome composition is shaped by multiple factors but the relative contribution of host genetics remains elusive. Here we examine genotype and microbiome data from 1,046 healthy individuals with several distinct ancestral origins who share a relatively common environment, and demonstrate that the gut microbiome is not significantly associated with genetic ancestry, and that host genetics have a minor role in determining microbiome composition. We show that, by contrast, there are significant similarities in the compositions of the microbiomes of genetically unrelated individuals who share a household, and that over 20% of the inter-person microbiome variability is associated with factors related to diet, drugs and anthropometric measurements. We further demonstrate that microbiome data significantly improve the prediction accuracy for many human traits, such as glucose and obesity measures, compared to models that use only host genetic and environmental data. These results suggest that microbiome alterations aimed at improving clinical outcomes may be carried out across diverse genetic backgrounds.


Assuntos
Dieta/estatística & dados numéricos , Meio Ambiente , Características da Família , Microbioma Gastrointestinal/genética , Estilo de Vida , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Estudos de Coortes , Feminino , Interação Gene-Ambiente , Glucose/metabolismo , Voluntários Saudáveis , Hereditariedade/genética , Humanos , Israel , Masculino , Pessoa de Meia-Idade , Obesidade/metabolismo , Fenótipo , Polimorfismo de Nucleotídeo Único/genética , RNA Bacteriano/análise , RNA Bacteriano/genética , RNA Ribossômico 16S/análise , Reprodutibilidade dos Testes , Estudos em Gêmeos como Assunto , Gêmeos/genética , Adulto Jovem
15.
EBioMedicine ; 28: 316-323, 2018 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-29398597

RESUMO

BACKGROUND: Acetaminophen (paracetamol) is one of the most common medications used for management of pain in the world. There is lack of consensus about the mechanism of action, and concern about the possibility of adverse effects on reproductive health. METHODS: We first established the metabolome profile that characterizes use of acetaminophen, and we subsequently trained and tested a model that identified metabolomic differences across samples from 455 individuals with and without acetaminophen use. We validated the findings in a European ancestry adult twin cohort of 1880 individuals (TwinsUK), and in a study of 1235 individuals of African American and Hispanic ancestry. We used genomics to elucidate the mechanisms targeted by acetaminophen. FINDINGS: We identified a distinctive pattern of depletion of sulfated sex hormones with use of acetaminophen across all populations. We used a Mendelian randomization approach to characterize the role of Sulfotransferase Family 2A Member 1 (SULT2A1) as the site of the interaction. Although CYP3A7-CYP3A51P variants also modified levels of some sulfated sex hormones, only acetaminophen use phenocopied the effect of genetic variants of SULT2A1. Overall, acetaminophen use, age, gender and SULT2A1 and CYP3A7-CYP3A51P genetic variants are key determinants of variation in levels of sulfated sex hormones in blood. The effect of taking acetaminophen on sulfated sex hormones was roughly equivalent to the effect of 35years of aging. INTERPRETATION: These findings raise concerns of the impact of acetaminophen use on hormonal homeostasis. In addition, it modifies views on the mechanism of action of acetaminophen in pain management as sulfated sex hormones can function as neurosteroids and modify nociceptive thresholds.


Assuntos
Acetaminofen/efeitos adversos , Hormônios Esteroides Gonadais/metabolismo , Sulfatos/metabolismo , Adulto , Mapeamento Cromossômico , Estudos de Coortes , Análise Discriminante , Feminino , Humanos , Análise dos Mínimos Quadrados , Masculino , Análise da Randomização Mendeliana , Metaboloma , Reprodutibilidade dos Testes , Estudos em Gêmeos como Assunto
16.
Gac. sanit. (Barc., Ed. impr.) ; 32(1): 92-95, ene.-feb. 2018. tab
Artigo em Espanhol | IBECS | ID: ibc-170159

RESUMO

Los diseños genéticamente informativos, y en particular los estudios de gemelos, constituyen la metodología más utilizada para analizar la contribución relativa de los factores genéticos y ambientales a la variabilidad interindividual. Básicamente, consisten en comparar el grado de similitud, con respecto a una característica o rasgo determinado, entre gemelos monocigóticos y dicigóticos. Además de la clásica estimación de heredabilidad, este tipo de registros permite una amplia variedad de análisis únicos por las características de la muestra. El Registro de Gemelos de Murcia es un registro de base poblacional centrado en el análisis de conductas relacionadas con la salud. Las prevalencias de problemas de salud observadas son comparables a las de otras muestras de referencia de ámbito regional y estatal, lo que avala su representatividad. En conjunto, sus características facilitan el desarrollo de diversas modalidades de investigación, además de diseños genéticamente informativos y la colaboración con distintas iniciativas y consorcios (AU)


Genetically informative designs and, in particular, twin studies, are the most widely used methodology to analyse the relative contribution of genetic and environmental factors to inter-individual variability. These studies basically compare the degree of phenotypical similarity between monozygotic and dizygotic twin pairs. In addition to the traditional estimate of heritability, this kind of registry enables a wide variety of analyses which are unique due to the characteristics of the sample. The Murcia Twin Registry is population-based and focused on the analysis of health-related behaviour. The observed prevalence of health problems is comparable to that of other regional and national reference samples, which guarantees its representativeness. Overall, the characteristics of the Registry facilitate developing various types of research as well as genetically informative designs, and collaboration with different initiatives and consortia (AU)


Assuntos
Humanos , Gêmeos/genética , Estudos em Gêmeos como Assunto/métodos , Registros/normas , Sistema de Registros/ética , Sistema de Registros/normas , Estudos em Gêmeos como Assunto/ética , Genética Médica/métodos , Genética Comportamental/ética , Genética Comportamental/métodos
17.
Twin Res Hum Genet ; 21(1): 67-72, 2018 02.
Artigo em Inglês | MEDLINE | ID: mdl-29307333

RESUMO

Highlights from the 16th International Twin Congress, held in Madrid, Spain from November 16-18, 2017, are presented. The Twin Congress, formerly held every three years, now takes place biennially with a single-day meeting organized during the off years. This meeting is the largest gathering of scientific twin researchers, medical personnel, and representatives of multiple birth organizations in the world. This overview is followed by reviews of recent twin research and commentary concerning partner aggression, ABO incompatibility in dizygotic twins, growth discordance in a monoamniotic twin pair and twin implantation. The article closes with summaries of timely topics in the media, namely a father's finding of his long-lost twin children, early results from the NASA twin experiment, twin brothers at the center of the October 2017 Las Vegas attack, retired twin airline pilots, and clips from recent films with twin-based themes.


Assuntos
Congressos como Assunto , Estudos em Gêmeos como Assunto , Sistema do Grupo Sanguíneo ABO/imunologia , Agressão , Tipagem e Reações Cruzadas Sanguíneas , Humanos , Gêmeos Dizigóticos , Estados Unidos , United States National Aeronautics and Space Administration
18.
J Affect Disord ; 234: 346-350, 2018 07.
Artigo em Inglês | MEDLINE | ID: mdl-29100658

RESUMO

BACKGROUND: Although it has been consistently reported the important role of genetic and environmental risk factors on structural and functional alterations in Major Depressive Disorder (MDD), the mechanism and the magnitude of the interactions between specific genetic and/or environmental risk factors on brain structures in this disabling disorder are still elusive. Therefore, in the last two decades an increased interest has been devoted to neuroimaging investigations on monozygotic and dizygotic twin samples mainly because their intrinsic characteristics may help to separate the effects of genetic and environmental risk factors on clinical phenotypes, including MDD. METHODS: In this context, the present review summarizes results from structural and functional Magnetic Resonance Imaging studies that investigated twin samples in correlation with MDD. RESULTS: Overall the results confirmed that a) MDD is characterized by significant alterations in selective brain areas presiding over emotion recognition and evaluation, including amygdala, insula and prefrontal cortices, and b) both genetic and environmental risk factors play a key role in the pathophysiology of this disorder. LIMITATIONS: Few MRI studies exploring MDD in twin samples. CONCLUSIONS: The specific contribution of both aspects is still not fully elucidated especially because genes and environment have an impact on the same brain areas, which are particularly vulnerable in MDD. Expansion of the current twin sample sizes would help to clearly establish the potential relationship between risk factors and the development of MDD.


Assuntos
Encéfalo/metabolismo , Encéfalo/patologia , Transtorno Depressivo Maior/genética , Transtorno Depressivo Maior/patologia , Gêmeos/genética , Gêmeos/psicologia , Encéfalo/fisiopatologia , Transtorno Depressivo Maior/fisiopatologia , Transtorno Depressivo Maior/psicologia , Humanos , Neuroimagem , Estudos em Gêmeos como Assunto
19.
Scand J Med Sci Sports ; 28(3): 834-845, 2018 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-28801974

RESUMO

The aim of this study was to clarify heritability estimates for endurance-related phenotypes and the underlying factors affecting these estimates. A systematic literature search was conducted for studies reporting heritability estimates of endurance-related phenotypes using the PubMed database (up to 30 September 2016). Studies that estimated the heritability of maximal oxygen uptake (V˙O2max), submaximal endurance phenotypes, and endurance performance were selected. The weighted mean heritability for endurance-related phenotypes was calculated using a random-effects model. A total of 15 studies were selected via a systematic review. Meta-analysis revealed that the weighted means of the heritability of V˙O2max absolute values and those adjusted for body weight and for fat-free mass were 0.68 (95% CI: 0.59-0.77), 0.56 (95% CI: 0.47-0.65), and 0.44 (95% CI: 0.13-0.75), respectively. There was a significant difference in the weighted means of the heritability of V˙O2max across these different adjustment methods (P < .05). Moreover, there was evidence of statistical heterogeneity in the heritability estimates among studies. Meta-regression analysis revealed that sex could partially explain the heterogeneity in the V˙O2max heritability estimates adjusted by body weight. For submaximal endurance phenotypes and endurance performance, the weighted mean heritabilities were 0.49 (95% CI: 0.33-0.65) and 0.53 (95% CI: 0.27-0.78), respectively. There was statistically significant heterogeneity in the heritability estimates reported among the studies, and we could not identify the specific factors explaining the heterogeneity. Although existing studies indicate that genetic factors account for 44%-68% of the variability in endurance-related phenotypes, further studies are necessary to clarify these values.


Assuntos
Exercício , Consumo de Oxigênio , Fenótipo , Resistência Física/genética , Feminino , Humanos , Masculino , Estudos em Gêmeos como Assunto
20.
Twin Res Hum Genet ; 21(1): 57-66, 2018 02.
Artigo em Inglês | MEDLINE | ID: mdl-29258629

RESUMO

In the 19th century, a series of international statistical congresses began that were important for population studies, including twin research. The introduction of common rules for the national demographic registers enabled scientists to contribute to the genesis of statistical research. The congress in St. Petersburg in 1872, in particular, focused on the movements of the population, and how they should be registered. Among the facts to be recorded were in multiple births, the sex and number of children born alive or still-born, whether legitimate or illegitimate, and the age of the mother at the date of the births. During the history of twin research, Hellin's law has played a central role because it is an approximately correct association between the rates of multiple maternities. It has been mathematically proven that Hellin's law does not hold as a general rule. Analyses show divergences from the law that are difficult to explain and/or eliminate. Varying improvements of this law have been proposed. The majority of all studies of Hellin's law are based on empirical rates of multiple maternities, ignoring random errors. Such studies can never confirm the law, but only identify errors with respect to Hellin's law that are too large to be characterized as random. It is of particular interest to note and explain why the rates of higher multiple maternities are sometimes too high or too low when Hellin's law is used as a benchmark. Studies have shown that there were investigators before Hellin who have contributed substantially to Hellin's law. In this article, we re-examine some old data sets and contributions in which Hellin's law has been evaluated and also analyze recent data.


Assuntos
Congressos como Assunto/história , Prole de Múltiplos Nascimentos/estatística & dados numéricos , Estudos em Gêmeos como Assunto/história , Feminino , História do Século XIX , Humanos , Países Baixos/epidemiologia , Gravidez , Suécia/epidemiologia , Trigêmeos/estatística & dados numéricos , Gêmeos/estatística & dados numéricos
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