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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Evolução das estratégias reprodutivas de Bothrops jararaca (Serpentes: Viperidae) / Evolution of reproductive strategies of Bothrops jararaca (Serpentes: Viperidae)

Karina Nunes Kasperoviczus Braz 13 August 2013 (has links)
Esse trabalho teve como objetivo estudar aspectos importantes das estratégias reprodutivas de machos e fêmeas de Bothrops jararaca do clado norte (CN) e sul (CS) e das ilhas de Búzios (SP), Ilhabela (SP) e ilha dos Franceses (ES). Para isso, foram analisados exemplares de B. jararaca preservadas de diversas coleções zoológicas. Machos e fêmea de B. jararaca do CN foram significativamente maiores que os machos e fêmeas CS, no entanto tiveram cabeças relativamente menores e foram menos robustos. Fêmeas do CN têm em média maior fecundidade e filhotes maiores do que fêmeas do CS. O ciclo reprodutivo de machos e fêmeas de ambas as populações é sazonal e não variou entre as estações do ano. Fêmeas do CN e do CS tem cópula outonal. A vitelogênese tem início no final do verão e fêmeas grávidas são observadas a partir do final do inverno. Nascimentos de B. jararaca de ambos os clados podem ser observados principalmente no verão e podem se estender até o início do outono. A estocagem de espermatozoides no útero e no infundíbulo foi observada principalmente no outono e inverno. Ciclos reprodutivos de machos de ambos os clados são considerados do tipo pós-nupcial ou do tipo I. O início da produção de espermatozoides é na primavera e a fase ativa pode ser observada no verão. No outono e no inverno, os testículos estão inativos. Estocagem de espermatozoides nos ductos deferentes foi observada durante todos os meses do ano e o segmento sexual renal (SSR) apresentou a fase mais ativa (fase secretora) na primavera e verão (sincronizado com a espermatogênese nos testículos) e fase não secretora no outono e no inverno. Esse padrão dos ciclos dos machos foi observado em ambos os clados. Dessa forma, foram observadas variações geográficas nas características de histórias de vida entre as populações do CN e CS, porém, não foram observadas diferenças entre os padrões de ciclos reprodutivos. Assim, o ciclo reprodutivo de machos e fêmeas de B. jararaca do CN e do CS são conservativo na espécie. / This research aimed to study important aspects of reproductive strategies in male and female of Bothrops jararaca from north clade (CN), south clade (CS) including the islands of Búzios (SP), Ilhabela (SP), and Franceses (ES). We analyzed specimens of B. jararaca preserved on several zoological collections. Male and female of B. jararaca from CN were significantly longer than male and female from CS, however they had relatively smaller heads and were less robust. Male and female of B. jararaca from CN were significantly larger than individuals from CS, had relatively smaller heads and were less robust. Females from CN had on average higher fecundity and larger offspring than females of CS. The reproductive cycle of males and females from both populations was seasonal and the timing of events was also similar between clades. Females of CN and CS have autumn mating season. The vitellogenesis starts in the end of the summer and pregnant females are observed from late winter. Births of B. jararaca occurred from early summer to the beginning of autumn. Sperm storage in the uterus and infundibulum was mainly observed during autumn and winter. Reproductive cycles of male of both clades are type postnuptial or a type I. The beginning of the sperm production occurs in spring and the active phase was observed in the summer. During autumn and winter, the testicles are inactive. Sperm storage in the different ducts was observed throughout the year and the sexual segment of the kidney (SSK) shows a more active phase during spring and summer and non-secretory phase on autumn and winter. This pattern of cycles of male was observed in both clades. In conclusion, there is geographical variation in life-history characteristics between CN and CS populations. However, differences among the reproductive cycle pattern were not evident. Then, the reproductive cycles of male and female of CN and CS are conservative in the species.
12

Time trends in childhood cancer : Britain 1966-2005

Kroll, Mary Eileen January 2009 (has links)
Increasing time trends in the recorded incidence of childhood cancer have been reported in many different settings. The extent to which these trends reflect real changes in incidence, rather than improvements in methods for diagnosis and registration, is controversial. Using data from the National Registry of Childhood Tumours (NRCT), this thesis investigates time trends in cancer diagnosed under age 15 in residents of Britain during 1966-2005 (54650 cases), and considers potential sources of artefact in detail. Several different methods are used to estimate completeness of NRCT registration. The history of methods for diagnosis and registration of childhood cancers in Britain is described, and predictions are made for effects on recorded incidence. For each of the 12 main diagnostic groups, Poisson regression is used to fit continuous time trends and ‘step’ models to the annual age-sex-standardised rates by year of birth and year of diagnosis. Age-specific rates by period, and quinquennial standardised rates for diagnostic subgroups, are shown graphically. For three broad groups (leukaemia, CNS tumours and other cancer), geographical variation is compared by period of diagnosis. The results of these analyses are discussed in relation to the predicted artefacts. The evidence for a positive association between affluence and recorded incidence of childhood leukaemia is briefly reviewed. A special form of diagnostic artefact, the ‘fatal infection’ hypothesis, is proposed as an explanation of both this association and the leukaemia time trend. This hypothesis is examined in a novel test based on clinical data. The recorded incidence of childhood cancer in Britain increased in each of 12 diagnostic groups during 1966-2005 (from 0.5% per year for bone cancer to 2.5% for hepatic cancer, with 0.7% for leukaemia). Evidence presented here suggests that these increases are probably artefacts of diagnosis and registration. The potential implications for epidemiological studies of childhood cancer should be considered.

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