RESUMO
One of the most important applications of genomic selection in maize breeding is to predict and identify the best untested lines from biparental populations, when the training and validation sets are derived from the same cross. Nineteen tropical maize biparental populations evaluated in multienvironment trials were used in this study to assess prediction accuracy of different quantitative traits using low-density (~200 markers) and genotyping-by-sequencing (GBS) single-nucleotide polymorphisms (SNPs), respectively. An extension of the Genomic Best Linear Unbiased Predictor that incorporates genotype × environment (GE) interaction was used to predict genotypic values; cross-validation methods were applied to quantify prediction accuracy. Our results showed that: (1) low-density SNPs (~200 markers) were largely sufficient to get good prediction in biparental maize populations for simple traits with moderate-to-high heritability, but GBS outperformed low-density SNPs for complex traits and simple traits evaluated under stress conditions with low-to-moderate heritability; (2) heritability and genetic architecture of target traits affected prediction performance, prediction accuracy of complex traits (grain yield) were consistently lower than those of simple traits (anthesis date and plant height) and prediction accuracy under stress conditions was consistently lower and more variable than under well-watered conditions for all the target traits because of their poor heritability under stress conditions; and (3) the prediction accuracy of GE models was found to be superior to that of non-GE models for complex traits and marginal for simple traits.
Assuntos
Genômica/métodos , Polimorfismo de Nucleotídeo Único , Característica Quantitativa Herdável , Zea mays/genética , Cruzamento , Interação Gene-Ambiente , Genótipo , Modelos Genéticos , Modelos Estatísticos , Fenótipo , Estresse Fisiológico , Água/fisiologiaRESUMO
This cross-sectional study reports on the menopausal transition of Mayan women from Yucatan, Mexico. A total of 228 women completed the study, and 118 women were classified by history as postmenopausal; the others were premenopausal. Demographic information, reproductive history, physical examination, hormone concentrations, radial bone density, food samples, and history of physical activity were obtained. The average age at which menopause occurred by history was 44.3 +/- 4.4 years; this is reflected in the distribution of FSH levels by age. None of the women reported symptoms of hot flashes, and none recalled any history of significant symptoms associated with their menopausal transition. Hormone levels were similar to U.S. reference values with elevated FSH (66.6 +/- 29.1 mIU/ml), low estradiol (9.4 +/- 8.3 pg/ml) and estrone (13.3 +/- 7.8 pg/ml), E1 > E2, and normal levels of testosterone and androstenedione. BMD declined with age, and values were lower than reference values for United States women. Clinical evidence of fracture was not detected by history or physical examination even for those who were 20 years postmenopausal. The endocrine characteristics of menopause among Mayan women in Yucatan are similar to hormonal changes reported for women in the United States, but signs, symptoms, and apparent consequences are different in the two populations.
Assuntos
Densidade Óssea/fisiologia , Fraturas Ósseas/etiologia , Indígenas Norte-Americanos/psicologia , Indígenas Norte-Americanos/estatística & dados numéricos , Menopausa/etnologia , Menopausa/fisiologia , Osteoporose Pós-Menopausa/etnologia , Osteoporose Pós-Menopausa/patologia , Adulto , Distribuição por Idade , Estatura , Índice de Massa Corporal , Estudos Transversais , Estradiol/sangue , Estrona/sangue , Feminino , Hormônio Foliculoestimulante/sangue , Humanos , México/epidemiologia , Pessoa de Meia-Idade , Osteoporose Pós-Menopausa/complicações , Inquéritos e QuestionáriosRESUMO
OBJECTIVE: Our purpose was to determine the characteristics of menopause among Mayan women who did not have menopausal symptoms. STUDY DESIGN: A cross-sectional study of Mayan women from Chichimila, Mexico, was performed. Demographic information, history and physical examination, hormone concentrations, and radial bone density measurement were obtained. RESULTS: Fifty-two postmenopausal women were compared with 26 premenopausal women. Menopause occurred at 44.3 +/- 4.4 years. None of the women admitted to hot flushes and did not recall significant menopausal symptoms. Hormone levels included elevated follicle-stimulating hormone (66.6 +/- 29 mlU/ml), low estradiol and estrone (9.4 +/- 8.3 and 13.3 +/- 7.8 pg/ml), estrone greater than estradiol levels, normal levels of testosterone and androstenedione (0.17 +/- 0.14 and 0.31 +/- 0.17 ng/ml). Bone mineral density declined with age, but height did not. Clinical evidence of osteoporosis was not detected. CONCLUSIONS: Lack of symptoms during the menopausal transition is not attributable to a difference in endocrinology. Postmenopausal Mayan women are estrogen deprived and experience age-related bone demineralization but do not have a high incidence of osteoporotic fractures.
Assuntos
Glândulas Endócrinas/fisiologia , Indígenas Norte-Americanos , Menopausa/fisiologia , Adulto , Androgênios/sangue , Densidade Óssea , Estrogênios/sangue , Feminino , Humanos , Menopausa/sangue , México/etnologia , Pessoa de Meia-IdadeRESUMO
The perception and experiences of menopause vary cross-culturally. However, the lack of physiological symptoms such as hot flashes, in some cultures, calls for more explanations beyond social and cultural factors alone. Like other developmental events, menopause is a biocultural experience. Therefore, research on menopause should consider biocultural factors such as environment, diet, fertility patterns and genetic differences that may be involved in the variations of menopausal experience.