No description available.

Thesis (Ph. D.)--University of Washington, 1999. / Vita. Includes bibliographical references (leaves 148-168).

Using data from the Third National Health and Nutrition Examination Survey, we assessed measures of puberty in U.S. girls in relation to blood lead levels to determine whether sexual maturation may be affected by current environmental lead exposure. The study sample included 1,706 girls 8-16 years old with pubic hair and breast development information; 1,235 girls 10-16 years old supplied information on menarche. Blood lead concentrations (range = 0.7-21.7 pg/dL) were categorized into three levels: 0.7-2.0, 2.1-4.9, and 5.0-21.7 μg/dL. Sexual maturation markers included self-reported attainment of menarche and physician determined Tanner stage 2 pubic hair and breast development. Girls who had not reached menarche or stage 2 pubic hair had higher blood lead levels than did girls who had. For example, among girls in the three levels of blood lead described above, the unweighted percentages of 10-year-olds who had attained Tanner stage 2 pubic hair were 60.0, 51.2, and 44.4%, respectively, and for girls 12 years old who reported reaching menarche, the values were 68.0, 44.3, and 38.5%, respectively. The negative relation of blood lead levels with attainment of menarche or stage 2 pubic hair remained significant in logistic regression even after adjustment for race/ethnicity, age, family size, residence in metropolitan area, poverty income ratio, and body mass index. In conclusion, higher blood lead levels were significantly associated with delayed attainment of menarche and pubic hair among U.S. girls, but not with breast development.

Economic viability of Fraser River, Labrador Arctic charr (Salvelinus alpinus) aquaculture in Atlantic Canada may be greatly improved if grow-out could be completed in seawater (30 ppt), while having a low incidence of sexual maturation before harvesting. Growth and survival in seawater was investigated among individually PIT-tagged Arctic charr reared in tanks in the laboratory. Direct transfer from freshwater to brackish water (20 ppt), and then acclimation to 30 ppt was successful. The manipulation of photoperiod, temperature, and food ration can be used as practical applications in aquaculture to arrest maturation; this was investigated in two additional experiments. The most effective photoperiod was LD18:6 for 6 weeks starting December 21, which reduced maturation to 43% compared to 78% in controls. Restricted ration from December 21 through March 15 had no effect on maturation, however, rearing females in 5°C compared to 10°C reduced maturation to 15% compared to >80% in controls.

Diss. (sammanfattning) Göteborg : Göteborgs universitet, 2008. / Härtill 4 uppsatser.

Age at the initiation of puberty and at menarche are key maturational indicators. They reflect health both within and between populations; in that a declining average age is associated with improving health, nutrition, and socio-economic conditions. Knowledge of the timing of pubertal development and menarche is important as earlier development within a population, in particular, has been linked with an increased risk of negative sequelae including overweight and obesity, development of risk factors for non-communicable diseases such as hypertension and insulin resistance, and engagement in risk behaviours such as early sexual debut and substance abuse. The main aims of this study were to investigate the timing of, and the early life factors (such as body composition and growth velocities) associated with pubertal development and age at menarche in Black and White urban South African adolescents. Mixed-longitudinal data (n = 401) from the Birth to Twenty (Bt20) birth-cohort study, initiated in 1990 and set in SowetoJohannesburg, South Africa were used. Median age at the initation of puberty and at menarche was derived by fitting logistic curves to cumulative frequency plots. Logistic regression models were constructed to examine the early life predictors of the timing of puberty and menarche. Data were also collected from adolescents and Bt20 staff (n = 72) using focus groups to explore views on the pubertal development questionnaire used in the Bt20 study. Median age at the initiation of genitalia development was 10.4 years (95% Cl = 8.4, 12.4) for Black boys and 9.8 years (95% Cl = 9.4, 10.2) for White boys. Median age for the initiation of pubic hair development for Black males was 10.8 years (95% Cl = 9.6, 12.0) compared to White males, which was 10.2 years (95% Cl = 8.4, 12.0). Median age at the initiation of breast development in Black females was 10.1 years (95% Cl = 9.3, 10.9) compared to White females which was 10.2 years (95% Cl = 8.2, 12.2). Median age for the initiation of pubic hair was 10.3 years (95% Cl = 9.3, 11.3) and 10.5 years (95% Cl = 8.7, 12.3) for Black and White girls, respectively. Results from logistic regression showed that a greater weight and height velocity in late childhood significantly increased the odds of achieving early breasU genitalia development. Furthermore, a low socio-economic status (SES) index at 9/10 years significantly reduced the odds of achieving early breasUgenitalia development. A greater weight, height, body mass index (BM I), and growth rate during infancy and childhood significantly increased the odds of achieving early pubic hair development. Median age at menarche for Black females was 12.4 years (95% Cl = 12.2, 12.6) and 12.5 . years (95% Cl = 11.7,13.3) for White females. Average menarcheal age for Black girls has declined by 0.56 years per decade and 0.32 years for White girls in South Africa, when comparing the current study findings with those from previous studies. Results from logistic regression showed that being taller, fatter and heavier in late childhood significantly increased the odds of achieving earlier menarche. The focus groups provided a range of opinions relating to the Bt20 pubertal development questionnaire and procedure. The majority of views were positive and included the ease of understanding and completion of the tool. Negative views revolved around the language used and privacy issues. These qualitative results provided a unique insight into the way in which pubertal development data are assessed and how these methods can potentially be improved to enhance the reliability and accuracy of pubertal development data collection. The results from this study provide the most recent estimates of age at the. initiation of puberty and age at menarche for urban Black and White South African adolescents. This is particularly important given the social, nutritional, and economic transition currently occurring in this country as these key maturity indicators reflect population health. This study has also added to our knowledge of the factors that are associated with pubertal development, showing that proximate rather than distal factors are the most sensitive indicators in this urban transitioning environment. In addition, the results from the focus groups provided a unique insight into how pubertal development data are assessed and how these methods could be improved. The negative health outcomes which have been associated with earlier pubertal development and age at menarche are major public health concerns, particularly in the South African context given the HIV/AIDS epidemic and rising levels of obesity. This study highlights the need for renewed research and resources for intervention strategies and policy programmes which target appropriate sex and obesity education in urban South African children.

Introdução - A avaliação do estado nutricional de adolescentes é usualmente realizada com base no índice de massa corporal (IMC) sem levar em consideração a maturação sexual. As alterações da composição corporal se expressam via modificações das características antropométricas, frações corporais e bioquímicas com impactos relevantes na análise do estado nutricional.A elevada variabilidade dessas características leva alguns autores a fundamentar de modo diverso a necessidade de ajuste prévio da maturação sexual para avaliação nutricional de adolescentes. Objetivo - Analisar os efeitos das relações entre maturação sexual e variáveis antropométricas, da composição corporal e dos parâmetros bioquímicos sobre o estado nutricional de adolescentes na faixa de 10 a 15 anos. Métodos- A amostra foi composta por 833 adolescentes escolares de 10 a 15 anos selecionados por amostragem complexa, residentes em Piracicaba (SP), 2012. Os fenótipos corporais foram inicialmente definidos por análise de componentes principais (ACP) a partir de dados antropométricos (massa corporal, altura, dobras cutâneas e circunferência da cintura), composição corporal (ângulo de fase), bioquímicos (triglicerídeos, glicose, razão colesterol total/LDL e hemoglobina), maturação sexual (auto-classificação segundo critério proposto por Tanner) e demográficos (sexo e idade). Esta primeira ACP apresentou caráter descritivo, para reconhecer a formação dos fenótipos corporais. Posteriormente, as variáveis de maturação sexual foram retiradas da ACP e aplicou-se novamente a ACP com as demais variáveis, os componentes gerados na ACP foram considerados desfechos na análise dos efeitos mistos para dimensionar o efeito da interferência da maturação sexual sobre os fenótipos corporais. No primeiro nível da análise utilizou-se sexo como ajuste. No segundo nível do modelo utilizou-se as variáveis de maturação sexual, e como ajuste idade, sexo e escore socioeconômico. Resultados Na primeira ACP foram definidos 4 fenótipos corporais: FC1 composto por dobras cutâneas, massa corporal e circunferência da cintura (expressão de gordura e volume corporal); FC2 composto por maturação sexual (pelos pubianos, mama e gônada), altura e idade (expressão do eixo cronológico); FC3 composto por colesterol e triglicerídeos (expressão de marcadores metabólicos associados à gordura corporal) e FC4 composto por ângulo de fase, hemoglobina e glicose (carga fatorial negativa) (expressão de marcadores metabólicos associados à massa magra). Na segunda ACP manteve-se a formação de 4 fenótipos corporais: FC1 apresentou a mesma formação, com a inclusão da hemoglobina com carga negativa; FC2 inclusão da massa corporal, ângulo de fase e hemoglobina; FC3 triglicerídeo, colesterol, hemoglobina e ângulo de fase e FC4 triglicerídeo, glicose e carga negativa para hemoglobina. O único fenótipo corporal que se associou à maturação sexual foi o FC2, também associado à altura e idade. Esse fenótipo expressa o crescimento físico e composição corporal típicos da puberdade. Com a análise dos efeitos mistos mostramos que a maturação sexual explica 78 por cento do FC2, enquanto para FC1 31 por cento FC3 0,59 por cento e FC4 1,06 por cento para pelos pubianos, para gônada e mama a maturação sexual explica 73 por cento do FC2, enquanto para FC1 2,45 por cento FC3 0,25 por cento e FC4 6,9 por cento . Conclusões - O uso dos fenótipos corporais indica a independência da avaliação nutricional na adolescência com relação à maturação sexual / Introduction - Analysis of nutritional status of adolescents is usually based on body mass index (BMI) without taking to account sexual maturation. Changes in body composition are expressed via modifications of anthropometric characteristics, body and biochemical fractions with relevant impact on the analysis of the nutritional status. The high variability of these features takes some authors to substantiate otherwise the need for prior adjustment of sexual maturation for nutritional assessment of adolescent. Objective - To analyze the effects of the relationships between sexual maturation and anthropometric variables, body composition and biochemical parameters about the nutritional status of adolescents from 10 to 15 years. Methods - The sample was composed by 833 school teenagers of 10 to 15 years selected by complex sampling, living in Piracicaba (SP), 2012. The body phenotypes were defined by principal component analysis (PCA) from anthropometric data (body mass, height, skinfolds and waist circumference), body composition (phase angle), biochemical (triglycerides, glucose, total cholesterol/LDL and hemoglobin), sexualmaturation (self-assessment criterion proposed by Tanner) and demographic (sex and age). This first ACP presented descriptive character, to recognize the formation of the corporal phenotypes. Subsequently, the sexual maturation variables were withdrawn from the ACP and re-applied to the ACP with the other variables, the components generated in the ACP were considered outcomes in the analysis of the mixed effects to measure the effect of the sexual maturation interference on the body phenotypes.In the first level of analysis we used the body phenotypes as outcome and sex as. In the second level of the model using the sexual maturation, and variables as age, sex and socioeconomic score. Results The first 4 body phenotypes were defined: FC1 composed by skinfolds, body weight and waist circumference (FAT expression and body volume); FC2 composed by sexual maturation (pubic hair, breast and gonad), height, and age (chronological axis expression); FC3 composed by cholesterol and triglycerides (expression of metabolic markers associated with body fat) and FC4 composed by phase angle, hemoglobin and glucose (factorial a negative load) (expression of metabolic markers associated with lean body mass). In the second PCA, the FC showed the same composition: FC1 presented the same formation, with the inclusion of hemoglobin with negative loading; FC2 inclusion of body mass, phase angle and hemoglobin; FC3 triglyceride, cholesterol, hemoglobin and phase angle and FC4 triglyceride, glucose and negative loading to hemoglobin. The only body which phenotype was associated to sexual maturation was the FC2, also associated with height and age. This phenotype is the physical growth and body composition typical of puberty. With the analysis of the mixed effects we show that sexual maturation explains 78 per cent of FC2, while for FC1 31 per cent 0.59 per cent FC3 and FC4 1.06 per cent to pubic hair, for gonad and sexual maturation breast explains 73 per cent of FC2, while for FC1 2.45 per cent 0.25 per cent and FC3 FC4 6.9 per cent . Conclusions The use of body phenotypes indicates the independence of nutritional assessment in adolescence in relation to sexual maturation

Introdução - A avaliação do estado nutricional de adolescentes é usualmente realizada com base no índice de massa corporal (IMC) sem levar em consideração a maturação sexual. As alterações da composição corporal se expressam via modificações das características antropométricas, frações corporais e bioquímicas com impactos relevantes na análise do estado nutricional.A elevada variabilidade dessas características leva alguns autores a fundamentar de modo diverso a necessidade de ajuste prévio da maturação sexual para avaliação nutricional de adolescentes. Objetivo - Analisar os efeitos das relações entre maturação sexual e variáveis antropométricas, da composição corporal e dos parâmetros bioquímicos sobre o estado nutricional de adolescentes na faixa de 10 a 15 anos. Métodos- A amostra foi composta por 833 adolescentes escolares de 10 a 15 anos selecionados por amostragem complexa, residentes em Piracicaba (SP), 2012. Os fenótipos corporais foram inicialmente definidos por análise de componentes principais (ACP) a partir de dados antropométricos (massa corporal, altura, dobras cutâneas e circunferência da cintura), composição corporal (ângulo de fase), bioquímicos (triglicerídeos, glicose, razão colesterol total/LDL e hemoglobina), maturação sexual (auto-classificação segundo critério proposto por Tanner) e demográficos (sexo e idade). Esta primeira ACP apresentou caráter descritivo, para reconhecer a formação dos fenótipos corporais. Posteriormente, as variáveis de maturação sexual foram retiradas da ACP e aplicou-se novamente a ACP com as demais variáveis, os componentes gerados na ACP foram considerados desfechos na análise dos efeitos mistos para dimensionar o efeito da interferência da maturação sexual sobre os fenótipos corporais. No primeiro nível da análise utilizou-se sexo como ajuste. No segundo nível do modelo utilizou-se as variáveis de maturação sexual, e como ajuste idade, sexo e escore socioeconômico. Resultados Na primeira ACP foram definidos 4 fenótipos corporais: FC1 composto por dobras cutâneas, massa corporal e circunferência da cintura (expressão de gordura e volume corporal); FC2 composto por maturação sexual (pelos pubianos, mama e gônada), altura e idade (expressão do eixo cronológico); FC3 composto por colesterol e triglicerídeos (expressão de marcadores metabólicos associados à gordura corporal) e FC4 composto por ângulo de fase, hemoglobina e glicose (carga fatorial negativa) (expressão de marcadores metabólicos associados à massa magra). Na segunda ACP manteve-se a formação de 4 fenótipos corporais: FC1 apresentou a mesma formação, com a inclusão da hemoglobina com carga negativa; FC2 inclusão da massa corporal, ângulo de fase e hemoglobina; FC3 triglicerídeo, colesterol, hemoglobina e ângulo de fase e FC4 triglicerídeo, glicose e carga negativa para hemoglobina. O único fenótipo corporal que se associou à maturação sexual foi o FC2, também associado à altura e idade. Esse fenótipo expressa o crescimento físico e composição corporal típicos da puberdade. Com a análise dos efeitos mistos mostramos que a maturação sexual explica 78 por cento do FC2, enquanto para FC1 31 por cento FC3 0,59 por cento e FC4 1,06 por cento para pelos pubianos, para gônada e mama a maturação sexual explica 73 por cento do FC2, enquanto para FC1 2,45 por cento FC3 0,25 por cento e FC4 6,9 por cento . Conclusões - O uso dos fenótipos corporais indica a independência da avaliação nutricional na adolescência com relação à maturação sexual / Introduction - Analysis of nutritional status of adolescents is usually based on body mass index (BMI) without taking to account sexual maturation. Changes in body composition are expressed via modifications of anthropometric characteristics, body and biochemical fractions with relevant impact on the analysis of the nutritional status. The high variability of these features takes some authors to substantiate otherwise the need for prior adjustment of sexual maturation for nutritional assessment of adolescent. Objective - To analyze the effects of the relationships between sexual maturation and anthropometric variables, body composition and biochemical parameters about the nutritional status of adolescents from 10 to 15 years. Methods - The sample was composed by 833 school teenagers of 10 to 15 years selected by complex sampling, living in Piracicaba (SP), 2012. The body phenotypes were defined by principal component analysis (PCA) from anthropometric data (body mass, height, skinfolds and waist circumference), body composition (phase angle), biochemical (triglycerides, glucose, total cholesterol/LDL and hemoglobin), sexualmaturation (self-assessment criterion proposed by Tanner) and demographic (sex and age). This first ACP presented descriptive character, to recognize the formation of the corporal phenotypes. Subsequently, the sexual maturation variables were withdrawn from the ACP and re-applied to the ACP with the other variables, the components generated in the ACP were considered outcomes in the analysis of the mixed effects to measure the effect of the sexual maturation interference on the body phenotypes.In the first level of analysis we used the body phenotypes as outcome and sex as. In the second level of the model using the sexual maturation, and variables as age, sex and socioeconomic score. Results The first 4 body phenotypes were defined: FC1 composed by skinfolds, body weight and waist circumference (FAT expression and body volume); FC2 composed by sexual maturation (pubic hair, breast and gonad), height, and age (chronological axis expression); FC3 composed by cholesterol and triglycerides (expression of metabolic markers associated with body fat) and FC4 composed by phase angle, hemoglobin and glucose (factorial a negative load) (expression of metabolic markers associated with lean body mass). In the second PCA, the FC showed the same composition: FC1 presented the same formation, with the inclusion of hemoglobin with negative loading; FC2 inclusion of body mass, phase angle and hemoglobin; FC3 triglyceride, cholesterol, hemoglobin and phase angle and FC4 triglyceride, glucose and negative loading to hemoglobin. The only body which phenotype was associated to sexual maturation was the FC2, also associated with height and age. This phenotype is the physical growth and body composition typical of puberty. With the analysis of the mixed effects we show that sexual maturation explains 78 per cent of FC2, while for FC1 31 per cent 0.59 per cent FC3 and FC4 1.06 per cent to pubic hair, for gonad and sexual maturation breast explains 73 per cent of FC2, while for FC1 2.45 per cent 0.25 per cent and FC3 FC4 6.9 per cent . Conclusions The use of body phenotypes indicates the independence of nutritional assessment in adolescence in relation to sexual maturation

Humanos e camundongos deficientes tanto na produção da leptina quanto na expressão do seu receptor (LepR) são obesos, hiperfágicos e inférteis; o tratamento com reposição de leptina em indivíduos deficientes na produção desse hormônio garante que haja redução no peso corporal, seja retomada ciclicidade estral e a fertilidade. Ainda, o tratamento com leptina em fêmeas prépúberes normais acelera o início da puberdade, sugerindo que esse hormônio tem papel crucial no tempo de início da puberdade. Ao relacionarmos leptina e puberdade, uma informação interessante é que, neurônios que secretam hormônio liberador de gonadotrofinas (GnRH), localizados na área pré-óptica medial (MPO) não coexpressam o LepR. Além disso, embora poucos neurônios que expressam o RNAm que codifica o gene Kiss1 do núcleo arqueado sejam responsivos à leptina, a sinalização da leptina nesses neurônios só ocorre após a puberdade e, a inativação do LepR nesses neurônios não afeta a reprodução. Por esses motivos, acredita-se que a leptina atue de forma indireta no controle da reprodução. Além dos núcleos MPO e ARH, o núcleo pré-mamilar ventral (PMv), que apresenta uma parcela de neurônios que expressam o LepR, também está envolvido na regulação neuroendócrina da reprodução. Estudos anteriores demonstraram que alterações nos níveis circulantes de estrógeno alteram características biofísicas e morfológicas de neurônios que expressam o gene Kiss1. Embora a leptina seja fundamental na maturação sexual não sabemos se os neurônios que expressam o LepR são suscetíveis a essas alterações durante a maturação sexual. Portanto, o objetivo deste trabalho foi investigar se neurônios LepR presentes nos núcleos MPO, ARH e PMv sofrem alterações morfológicas durante a maturação sexual e mediante ausência de hormônios gonadais. Foram utilizados camundongos (fêmeas) LepR-Cre tdTomato, divididas em 4 grupos experimentais: pré-púberes, púberes, adultas e ovarectomizadas (OVX). A maturação sexual foi avaliada, para determinação do dia da abertura vaginal e primeiro estro. Nas idades específicas os encéfalos foram processados e coletados para posterior quantificação e aferição da área de superfície de neurônios LepR. Realizamos, também, imunoistoquímica de fluorescência para pSTAT3 para quantificar o percentual de neurônios responsivos à leptina. Os resultados obtidos demostraram que ocorreu um aumento no número de neurônios LepR no núcleo ARH com o avanço da idade. Porém, não houveram diferenças significativas quanto ao número de neurônios nos núcleos MPO e PMv. Também não observamos alterações na área de superfície nos núcleos analisados. Em relação a ativação de neurônios LepR via marcação de pSTAT3, o núcleo MPO apresentou uma diminuição no percentual de neurônios ativos quando comparamos os grupos pré-púberes com os grupos adulta e OVX. O oposto aconteceu no núcleo ARH onde obtivemos um aumento desse percentual com o avanço da idade. Em ambos os núcleos (MPO e ARH) o percentual de neurônios LepR ativados no grupo OVX foi estatisticamente semelhante ao grupo adulta, diferindo somente do grupo pré-púbere. O núcleo PMv não apresentou diferenças estatísticas entre os grupos analisados. Nossos dados sugerem que estrógeno e leptina podem interagir de formas distintas em diferentes regiões hipotalâmicas. / Leptin or leptin receptor (LepR) deficient humans and mice are obese, hyperphagic and infertile; leptin replacement in leptin deficient subjects is capable of reducing body mass and restores estrous cyclicity and fertility. In addition, leptin accelerates the onset of puberty in normal female mice, suggesting that this hormone plays a critical role in the timing of puberty. Interestingly, the gonadotropin releasing hormone neurons, located at the medial pre-optic área (MPO) does not coexpress the LepR. Although few kisspeptin neurons in the arcuate nucleus (ARH; 15%) are responsive to leptin, leptin signaling in kisspeptin neurons arises only after pubertal development and leptin receptor inactivation in kisspeptin cells did not affect reproduction. Therefore, the effects of leptin on reproduction is believed to occur indirectly. In addition to ARH and MPO, the ventral premammillary nucleus (PMv) is also involved in the neuroendocrine regulation of reproduction and a fraction of PMv neurons coexpress LepR. Curiously, previous studies have shown that changing levels of estrogen alters the biophysical properties and morphology of hypothalamic neurons, such as expressing the ones expressing the Kiss1 gene. Although leptin has an important role on the puberty onset, it is not known whether LepR-expressing neurons are also susceptible to changes in their morphology during sexual maturation. Therefore, our goal was to investigate whether LepR-expressing neurons in the MPO, ARH and PMv nuclei are susceptible to cell morphology modifications throughout the sexual maturation and after manipulation of estrogen levels. LepR-Cre tdTomato mice (females) were divided into 4 experimental groups: prepubertal, pubertal, adult and ovarectomized (OVX). The sexual maturation was evaluated to determine the day of vaginal opening and first estrus. At specific ages the brains were processed and collected for further quantification and measurement of the surface area of LepR neurons. We also performed fluorescence immunohistochemistry for pSTAT3 to quantify the percentage of neurons responsive to leptin. The results showed that there is an increase in the number of LepR neurons in the ARH nucleus with advancing age. However, there were no significant differences in the number of neurons in the MPO and PMv nuclei. We also did not observe changes in the surface area in the nuclei analyzed. In relation to the activation of LepR neurons via pSTAT3 labeling, the MPO nucleus showed a decrease in the percentage of active neurons when comparing the prepubertal groups with the adult and OVX groups. The opposite happened in the ARH nucleus where we had an increase of this percentage with the advancement of the age. In both nuclei (MPO and ARH) the percentage of LepR neurons activated the OVX group was statistically similar to the adult group, differing only from the pre-pubertal group. The PMv nucleus did not present statistical differences between the analyzed groups. Our data suggest that estrogen and leptin may interact differently in different hypothalamic regions.

Parent child communications about sex play an important role in influencing adolescent’s sexual behaviors and attitudes. The present study was conducted to examine how sexual communications between African American mothers and their children change over a period of three years in the areas of sex education, communication about risk reduction, and child and parent report of responsiveness. Hierarchical linear modeling (HLM) analyses found significant linear or curvilinear trajectory in communication with sons and daughters in all areas. Gender differences were found such that daughters received more communication than sons. Furthermore, daugthers’ sexual maturation was found to be associated with a decrease in the rate of decline of communication about general sex information. For sons, mothers decreased in rates of responsiveness as sons got older; however, as sons’ sexual maturation increased, rates of declining responsiveness slowed down.