This research was conducted at the La Raya experiment station, Cusco, Peru (4200 m elevation, 15°S latitude, and 70°W longitude) using 60 Corriedale, and 60 Criollo ewes during three consecutive years (April 1981 - March 1984). Age, and weight at puberty, age at physical maturity, and the effects of breed, age (physically immature and mature), year, and month were measured on body weight, incidence of estrus, and incidence and rate of ovulation. There was a significant difference (P.05). Even though Criollo e wes weighed less than Corriedale, they attained puberty earlier, and showed less seasonality in estrus and ovulated throughout the year than the Corriedale.

A expressão do gene Kiss1 é essencial para o controle neuroendócrino da reprodução, pois esses neurônios regulam a atividade dos neurônios que secretam o hormônio liberador de gonadotrofinas, e portanto, o ciclo ovulatório. Em roedores sazonais, o aumento da síntese de melatonina durante o inverno é responsável pela inibição das funções reprodutivas, fato que é acompanhado pela diminuição da expressão desse gene. Devido à importância dos neurônios Kiss1 no desenvolvimento do sistema reprodutivo, o presente estudo investigou a participação da melatonina na regulação da expressão do gene Kiss1 e sua influência na reprodução, em um modelo animal não sazonal. Concluimos que condições de dias curtos (que possivelmente aumentam o período de circulação de melatonina) alteram parâmetros de amadurecimento sexual em fêmeas e, assim como o tratamento com melatonina, afetam o tamanho das gônadas de camundongos machos, mas que esses efeitos não alteram o número de neurônios que expressam o gene Kiss1 e não são suficientes para inibir a reprodução das fêmeas. / The expression of Kiss 1 gene is essential for the neuroendocrine control of reproduction, as these neurons regulate the activity of neurons that secrete gonadotropin-releasing hormone, and therefore the ovulatory cycle. In seasonal rodents, the increase in melatonin synthesis during winter is responsible for the inhibition of reproductive functions, a fact that is accompanied by decreased expression of this gene. Because of the importance of Kiss1 neurons in the development of the reproductive system, the present study investigated the involvement of melatonin in the regulation of expression of Kiss1 gene and its influence on reproduction in a non-seasonal animal. We conclude that short-day conditions (which possibly increase the period of melatonin circulation) alter sexual maturation parameters in females, and as well as melatonin treatment, affect the size of the gonads of male mice, but these effects do not change the number neurons expressing the Kiss1 gene and are not sufficient to inhibit the reproduction of female mice.

Como a incidência de obesidade em crianças têm aumentado e a leptina é um fator permissivo para o início da puberdade, os níveis circulantes de leptina elevados se tornaram um fator comum que pode causar um adiantamento da puberdade. Entretanto, o aumento no acúmulo de gordura nos organismos está associado à resistência ao hormônio leptina. Atualmente existem poucas informações sobre como a sensibilidade a esse hormônio afeta o desenvolvimento sexual. Portanto, este projeto teve como objetivo investigar como diferentes modelos de sensibilidade ou resistência à leptina agem na puberdade de camundongos fêmeas. Técnicas como acompanhamento in vivo das diferentes fases da maturação sexual e da composição corporal, testes de sensibilidade à leptina, testes de tolerância à glucose e à insulina, e PCR em tempo real foram utilizadas. Animais com maior peso corporal desde a infância apresentaram adiantamento da maturação sexual, maior acúmulo de gordura corporal e alterações na expressão de genes metabólicos. Já animais que sofreram inativação do gene Socs3 no sistema nervoso central ou em células que expressam o receptor de leptina, apresentaram um atraso na maturação sexual e alterações na expressão de genes relacionados ao consumo alimentar, porém nos casos de inativação em células Kiss1, os animais não apresentaram nenhum tipo de alteração. Dessa forma, concluímos que o peso corporal é mais importante para o desencadear da maturação sexual do que a sensibilidade do organismo ao hormônio leptina, sugerindo que a leptina atua na maturação sexual de forma indireta sobre o eixo hipotálamo hipófise gonadal. Além disso, na análise da expressão de genes ao longo do desenvolvimento traçamos um perfil de genes associados à reprodução e metabolismo, que servirão de base para comparação para outros estudos. / As the incidence of obesity in children has increased and leptin is a permissive factor for the onset of puberty, elevated circulating leptin levels have become a common factor that may cause puberty to progress. However, the increase in fat accumulation in organisms is associated with resistance to the hormone leptin. There is currently little information on how sensitivity to this hormone affects sexual development. Therefore, this project aimed to investigate how different models of leptin sensitivity or resistance act in the puberty of female mice. Techniques such as in vivo monitoring of the different stages of sexual maturation and body composition, leptin sensitivity tests, glucose and insulin tolerance tests, and real-time PCR were used. Animals with higher body weight since childhood presented an advance of sexual maturation, greater accumulation of body fat and alterations in the expression of metabolic genes. On the other hand, animals that underwent inactivation of the Socs3 gene in the central nervous system or cells expressing the leptin receptor showed a delay in sexual maturation and alterations in the expression of genes related to food consumption, but in cases of inactivation in Kiss1 cells, animals did not present any type of change. Thus, we conclude that body weight is more important for the onset of sexual maturation than the body\'s sensitivity to the hormone leptin, suggesting that leptin acts indirectly on sexual maturation on the hypothalamus - pituitary - gonadal axis. In addition, in the analysis of gene expression along the development we have traced a profile of genes associated with reproduction and metabolism, which will serve as a basis for comparison to other studies.

<p>Puberty is the process of becoming sexually mature and it has fundamental somatic and psychosocial implications. The focus of this dissertation was the short and long term developmental significance, concerning both soma et psyche, of female pubertal timing. Four studies were designed to accomplish these aims. Six samples of different ages from different countries and from different time points, comprising several thousand females some of which were followed longitudinally, were used. Age at menarche was used as the primary measure of pubertal maturation. The first main aim of this dissertation was to explore the mechanisms that might explain the well-established link between female pubertal timing and problem behavior, and to identify contextual conditions at which associations are stronger or weaker. Existing explanations are unsatisfactory and little is known about conditions that might affect the strength of the associations.</p><p>In Paper I, we tested and confirmed a peer socialization hypothesis as a satisfactory explanation for the link between early puberty and problematic adjustment. In short, this hypothesis posits that early developing girls associate with older peers and boyfriends because they feel more mature than their same age peers, and through these peers and boyfriends the early developed girls are channeled into more socially advanced behaviors, including normbreaking. This should be particularly true in contexts where heterosexual relationships are sanctioned and where there is an abundance of deviant youth. In Paper II, I used a biopsychosocial approach and studied pubertal timing along with self-perceptions of maturity and early romantic relationships. The findings revealed that early puberty had very different implications depending on the psychological and social contexts in which it was embedded. For instance, when early puberty was coupled with feeling mature and having early romantic relationships, it was associated with adjustment problems. When early puberty was coupled with neither, it was not linked to particularly high levels of problem behavior.</p><p>In stark contrast to the vast literature on the role of female pubertal timing in adolescence, the literature on long-term implications is remarkably limited. For this reason, the second main aim of this dissertation was to study the adult implications of female pubertal timing. In Papers III and IV, we examined long term implications of pubertal timing, particularly as it relates to somatic development. The findings suggested that pubertal timing does have future implications for women’s body perception and composition, with early developing females having higher body mass indexes in adulthood, but only under certain circumstances. The findings of this dissertation help further understanding of the soma et psyche implications of female pubertal timing. They indicate that pubertal timing has concurrent and future implications. It seems, however, that timing is not everything. The developmental significance of female pubertal timing appears to be very different under different contextual conditions. Thus, it is only when girls’ psychological and social contexts are considered that fruitful predictions can be made. As such, the findings have important implications for prevention, policy, and practice.</p>

In the present study our objectives were (1) to follow the temporal patterns of testicular LH and FSH receptor (LH-R and FSH-R) concentrations and affinity (Ka) during sexual maturation in bulls, to see if such patterns could explain the control of rapid testicular growth that occurs after 25 weeks of age, when serum gonadotropin concentrations are low; (2) to see if transformation growth factors (TGF- alpha and beta 1, 2 and 3) and interleukins (IL-1 and IL-6) are produced in the developing bovine testis and if their concentrations change during development; (3) to see if the onset of puberty could be hastened by treating bull calves subcutaneously (sc) with 3 mg of bLH (n=6) or 4 mg of bFSH (n=6) once every 2 days, from 4 to 8 weeks after birth. Mean LH-R concentrations decreased from 13 to 25 weeks of age and increased to 56 weeks of age (P<0.05). LH-RKa decreased from 9 to 17 weeks of age, increased to 29 weeks and declined to 33 weeks of age (P<0.05). FSH-R concentrations declined from 17 to 25 weeks of age then increased to 56 weeks of age (P<0.05). FSH-RKa increased from 17 to 25 weeks of age (P<0.05). Testicular TGF-alpha concentrations increased from 13 to 17 weeks of age, decreased to 21 weeks and from 33 to 56 weeks of age (P<0.05). Testicular TGF-beta 1 concentrations decreased from 17 to 21 weeks of age, increased to 25 weeks and decreased from 25 to 29 weeks of age (P<0.05). Testicular TGF-beta 2 concentrations increased from 5 to 17 weeks of age, decreased to 21 weeks, increased to 25 weeks and decreased at 29 weeks of age (P<0.05). Testicular TGF-beta 3 concentrations increased from 13 to 17 weeks of age, decreased to 21 weeks of age and from 25 to 29 weeks of age (P<0.05). Mean testicular IL-1 alpha concentrations decreased from 5 to 9 weeks of age and 13 to 21 weeks of age (P<0.01) while mean testicular IL-1 beta concentrations decreased from 13 to 17 weeks and 29 to 33 weeks of age (P<0.01). Mean IL-1 bioactivity increased from 13 to 17 weeks of age, decreased to 21 weeks, increased to 25 weeks, decreased to 29 weeks and decreased from 33 to 56 weeks of age (P<0.05). Mean testicular IL-6 concentrations decreased (P<0.05) from 9 to 13 weeks of age, increased (P<0.05) to 21 weeks, decreased (P<0.05) to 25 weeks of age, increased (P<0.05) to 29 weeks and decreased (P<0.01) to 56 weeks of age. <p>We concluded that high concentrations of gonadotropin receptors might be critical to initiate postnatal testis growth and support it after 25 weeks of age in the face of low serum gonadotropin concentrations. Testicular TGF-alpha concentrations were higher in calves than adults while concentrations of TGF-beta and IL-1 were higher in the early postnatal period than the peripubertal period. The changes in testicular concentrations of TGFs and ILs led us to suggest a possible local regulatory role in development. Testicular IL-6 concentrations were higher in prepubertal calves than adults. Treatment of bull calves with bFSH from 4 to 8 weeks of age increased testicular growth (SC), hastened the onset of puberty (SC ≥ 28 cm), and enhanced spermatogenesis.

Sammanfattning Syfte: Finna forskningsbaserade underlag för hur fysisk barn- och ungdomsträning bör bedrivas, från nybörjarnivå som barn (ca sex år) till avancerad nivå som ung senior (ca 18 år) och koppla detta till innebandy. Frågeställningar: Finns det perioder under uppväxten då unga idrottare är extra mottagliga för en viss typ av träning? Hur bör träningen utformas under uppväxten uppdelat i delkapaciteterna: aerobt, anaerobt, styrka, rörlighet och koordination/teknik? Metod: Systematisk litteraturöversikt av befintlig forskning inom det valda problemområdet. Sökningar i databasen EBSCOhost har utförts. Från sammanlagt i 713 st. artiklar har tolv artiklar sållats fram som gick vidare till dataextraktion. Inklusionskriterierna för artiklarna var: peer reviewed artiklar, publicerade på engelska januari 2003 – oktober 2012, population: 6-18 års ålder av båda könen. Exklusionskriterierna var: någon form utav diagnos, skada eller sjukdom hos populationen. Under tiden tillkom fyra relevanta artiklar från referenslistor hos de redan inkluderade artiklarna. Resultat: Utav de 16 st artiklar som ingick i dataextraktionen säger tolv att det finns perioder under uppväxten då idrottare är extra mottagliga för en viss typ av träning och två säger att det generellt inte finns sådana perioder. Två utav artiklarna säger både ja och nej på frågan. Inom den aeroba delkapaciteten, styrka/snabbhet och koordination sker utvecklingen kontinuerligt under hela uppväxten samtidigt verkar det också finnas perioder där utvecklingstakten i dessa delkapaciteter accelereras. Inom den anaeroba delkapaciteten finns det en acceleration av förmågan i samband med den ökning i muskelmassa som sker efter tillväxtspurten. Det finns motsägningar och oklarheter i forskningen gällande utvecklingstakten inom de olika delkapaciteterna. Slutsats: Den aeroba delkapaciteten, styrka/snabbhet och koordination/teknik är viktiga inom innebandy och i dem sker utvecklingen kontinuerligt under hela uppväxten. Därför bör de också tränas och ibland prioriteras under hela uppväxten. Det verkar även finnas perioder där utvecklingstakten i dessa delkapaciteter accelereras och därför kan en viss fokusering av träningen motiveras under dessa perioder även om övriga delkapaciteter inte skall försummas. En fokusering av träningen mot den anaeroba delkapaciteten innan muskelmassan börjar utvecklas skulle förmodligen ge begränsade resultat. Problemområdet behöver utforskas ytterligare för att kunna ge mer specifika rekommendationer om vilka träningssätt som är mest effektiva för barn och ungdomar. Forskning speciellt riktad mot flickor eftersökes. Nyckelord: Träning, utveckling, barn, ungdomar, pubertet, innebandy.

In the present study our objectives were (1) to follow the temporal patterns of testicular LH and FSH receptor (LH-R and FSH-R) concentrations and affinity (Ka) during sexual maturation in bulls, to see if such patterns could explain the control of rapid testicular growth that occurs after 25 weeks of age, when serum gonadotropin concentrations are low; (2) to see if transformation growth factors (TGF- alpha and beta 1, 2 and 3) and interleukins (IL-1 and IL-6) are produced in the developing bovine testis and if their concentrations change during development; (3) to see if the onset of puberty could be hastened by treating bull calves subcutaneously (sc) with 3 mg of bLH (n=6) or 4 mg of bFSH (n=6) once every 2 days, from 4 to 8 weeks after birth. Mean LH-R concentrations decreased from 13 to 25 weeks of age and increased to 56 weeks of age (P<0.05). LH-RKa decreased from 9 to 17 weeks of age, increased to 29 weeks and declined to 33 weeks of age (P<0.05). FSH-R concentrations declined from 17 to 25 weeks of age then increased to 56 weeks of age (P<0.05). FSH-RKa increased from 17 to 25 weeks of age (P<0.05). Testicular TGF-alpha concentrations increased from 13 to 17 weeks of age, decreased to 21 weeks and from 33 to 56 weeks of age (P<0.05). Testicular TGF-beta 1 concentrations decreased from 17 to 21 weeks of age, increased to 25 weeks and decreased from 25 to 29 weeks of age (P<0.05). Testicular TGF-beta 2 concentrations increased from 5 to 17 weeks of age, decreased to 21 weeks, increased to 25 weeks and decreased at 29 weeks of age (P<0.05). Testicular TGF-beta 3 concentrations increased from 13 to 17 weeks of age, decreased to 21 weeks of age and from 25 to 29 weeks of age (P<0.05). Mean testicular IL-1 alpha concentrations decreased from 5 to 9 weeks of age and 13 to 21 weeks of age (P<0.01) while mean testicular IL-1 beta concentrations decreased from 13 to 17 weeks and 29 to 33 weeks of age (P<0.01). Mean IL-1 bioactivity increased from 13 to 17 weeks of age, decreased to 21 weeks, increased to 25 weeks, decreased to 29 weeks and decreased from 33 to 56 weeks of age (P<0.05). Mean testicular IL-6 concentrations decreased (P<0.05) from 9 to 13 weeks of age, increased (P<0.05) to 21 weeks, decreased (P<0.05) to 25 weeks of age, increased (P<0.05) to 29 weeks and decreased (P<0.01) to 56 weeks of age. <p>We concluded that high concentrations of gonadotropin receptors might be critical to initiate postnatal testis growth and support it after 25 weeks of age in the face of low serum gonadotropin concentrations. Testicular TGF-alpha concentrations were higher in calves than adults while concentrations of TGF-beta and IL-1 were higher in the early postnatal period than the peripubertal period. The changes in testicular concentrations of TGFs and ILs led us to suggest a possible local regulatory role in development. Testicular IL-6 concentrations were higher in prepubertal calves than adults. Treatment of bull calves with bFSH from 4 to 8 weeks of age increased testicular growth (SC), hastened the onset of puberty (SC ≥ 28 cm), and enhanced spermatogenesis.

Despite teleosts being the largest and most diverse group of vertebrates, fish models currently used to study photoperiodic effects on fish physiology have been limited to a few species, most of which are temperate seasonal breeders. The overall aim of this work was to expand our knowledge on circadian biology and environmental physiological effects in Nile tilapia (Oreochromis niloticus niloticus), a continuous breeding species of tropical-subtropical origin. The circadian light axis of Nile tilapia is described with regards to melatonin production. Circadian melatonin profiles of fish under 12L:12D photoperiods were observed to be low at day and high at night, suggesting melatonin to be an entraining signal as observed in all other vertebrates. When constant light (LL) was used, such day and night fluctuations where abolished. However when fish where exposed to constant darkness (DD) a strong robust endogenous melatonin rhythm was found, suggesting the presence of circadian oscillators in this species. Importantly, this endogenous rhythm was observed to be maintained for at least three weeks under darkness and proved to be circadian in nature. Moreover, although the melatonin system was able to produce day and night melatonin rhythms when exposed to a different (6L:6D) photocycle, the oscillator appeared to not be entrainable to such a short photo cycle when exposed to DD, as melatonin levels remained high. When comparing the circadian organization of different teleost species including Nile tilapia, preliminary studies showed at least three divergent circadian light organizations in teleosts. Nile tilapia was characterised by a pineal gland far less sensitive than in other fish species as demonstrated through in vitro studies. Furthermore, pineal melatonin production was clearly dependent on the light perceived by the eyes as ophthalmectomy resulted in basal plasma melatonin levels during the dark period. These findings are the first to be reported in a teleost and could be comparable to the circadian light organization of higher vertebrates such as mammals. The onset of puberty of Nile tilapia was studied with regards to the newly discovered Kiss1/GPR54 system. Such a system has recently been discovered in mammals and found to be the primary switch of the brain-pituitary-gonadal (BPG) axis. The results of this study not only suggest a link between the Kiss1/GPR54 system and the onset of III puberty in this tropical batch spawning teleost, that would be a highly conserved feature across vertebrates, but also that the transcriptional mechanisms regulating GPR54 expression could be directly or indirectly influenced by light. Finally, a study was conducted on the effects of different intensities of continuous light (LL) on the growth and sexual development of Nile tilapia up to first maturation. The results showed a significant growth response of fish in all LL treatments compared to control fish. Importantly, this confirmed that LL enhances growth in this species and suggests that it is the light regime more than the intensity which is having an effect. This work thus provides important basic knowledge of the light entrainment pathway and circadian melatonin rhythms in Nile tilapia. Of special importance is the discovery of a strong endogenous melatonin oscillator and a novel circadian organization in fish which would seem to be homologous to that observed in higher vertebrates. Moreover, this work provides evidence that the newly discovered Kiss1/GPR54 system has a similar role in fish as has been found in mammals and that such a system could be directly or indirectly regulated by light. If so, Nile tilapia and other fish species could become important models in the chronobiology and reproduction fields. Finally, this work not only increases our basic and applied knowledge of this species, but also broadens our understanding of the circadian light axis in teleosts and its mediatory effects on reproduction.

In certain species, puberty is thought to be a period of susceptibility to various stressors, resulting in pathological behavioral and physiological changes subsequent to exposure during this period. However, juvenile male golden hamsters appear to be fairly resilient to pubertal stress, as compared to adult hamsters and many other species. In these experiments, repeatedly stressed juvenile male hamsters were found to be avoidant of aggressive adult male social stimuli, but did not display anxious behavior outside of a social context. In addition, several long-term changes in neural activity were associated with social stress during early puberty. The medial preoptic area and medial preoptic nucleus, and ventral tegmental area showed decreased neural activity in subjugated juveniles than in naïve individuals. Since these brain areas are involved in the expression of motivated behaviors, specifically sexual behavior, and reward pathways, we next investigated sexual behavior in virgin juveniles. When placed in a confined space with receptive females, consummatory behavior in subjugated juveniles was similar to those observed in naive juveniles. Appetitive aspects of sexual behavior were also tested in a Y-maze to allow subjects to choose whether to approach a social stimulus. When given a choice between a sexually receptive and non-receptive female social stimulus, socially stressed individuals showed anxiety related behaviors and did not show a preference. However, naïve hamsters preferred the non-receptive female. Interestingly, this effect was less significant in naïve animals tested during late puberty and early adulthood, and a preference for sexually receptive females was not observed. In addition, stressed hamsters tested with harnessed females at mid-puberty were slower to approach females, indicating altered motivation to approach adult conspecifics. This research is unique in that it is the first to suggest the disconnect between the development of consummatory and appetitive aspects of sexual behavior. Together, these data examine the effects of stress on the development of pubertal social behaviors. / text

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