Spermiogenesis
Mostrando 13-24 de 97 artigos, teses e dissertações.
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13. Estrogens and male reproduction: a new concept
The mammalian testis serves two main functions: production of spermatozoa and synthesis of steroids; among them estrogens are the end products obtained from the irreversible transformation of androgens by a microsomal enzymatic complex named aromatase. The aromatase is encoded by a single gene (cyp19) in humans which contains 18 exons, 9 of them being transl
Brazilian Journal of Medical and Biological Research. Publicado em: 2007-06
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14. Analise filogenetica da superfamilia Loricarioidea (Teleostei: Siluriformes) com base na ultra-estrutura da espermiogenese e dos espermatozoides / Phylogenetic analysis of superfamily Loricarioidea (Teleostei: Siluriformes) based on spermiogenesis and spermatozoa ultrastructure
The order Siluriformes comprises the most diverse and widely distributed ostariophysan groups, presenting thirty-six families with approximately 480 genera and over 3.000 species. Among the neotropical siluriform lineages likely to be monophyletic is the superfamily Loricarioidea. The relationships among catfish families suggest that Loricarioidea is sister
Publicado em: 2007
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15. Descrição ultra-estrutural da espermatogênese com ênfase na espermiogênese em Trypoxylon (Trypargilum) lactitarse (Hymenoptera: Sphecidae) / Ultra-structural description of the spermatogenesis with emphasis in the spermiogenesis in Trypoxylon (Trypargilum) lactitarse (Hymenoptera: Sphecidae)
Nos insetos, os testículos, que são em número de dois, são formados por folículos, que variam em número entre as espécies. Em Trypoxylon (Trypargilum) lactitarse observam-se três folículos em cada testículo. É nos folículos testiculares que as espermatogônias originam os espermatozóides, através do processo espermatogênico. Na espermiogênese
Publicado em: 2007
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16. Nucleolar activity during spermatogenesis of the cattle (Bos indicus) / Atividade nucleolar durante a espermatogenese de bovinos (Bos indicus)
A espermatogenese é um processo muito importante para a predição de fertilidade na pecuária moderna. Muitos aspectos desse processo tem sido estudados, inclusive as várias estruturas celulares, como o nucléolo. Sabe-se que, durante a divisão celular, o nucléolo se desorganiza, reorganizando-se apenas no final da telófase. O presente estudo teve como
Publicado em: 2007
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17. Ultraestrutura da espermiogenese e dos espermatozoides de representantes da ordem Gymnotiformes (Teleostei, Ostariophysi) com considerações filogeneticas
Fishes of the order Gymnotiformes compose a monophyletic group, among other characteristics, by the production and detection of electric fields. They have a knife-like appearance and an elongate anal fin. The order includes five families: Gymnotidae, Hypopomidae, Rhamphichthyidae, Sternopygidae, and Apteronotidae. Recent hypothesis about the relationships am
Publicado em: 2006
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18. Comparative description and discussion of spermiogenesis and spermatozoal ultrastructure in some species of Heptapteridae and Pseudopimelodidae (Teleostei: Siluriformes)
Os dados obtidos no presente estudo sobre a ultraestrutura da espermiogênese e dos espermatozóides de Pseudopimelodidae e Heptapteridae mostram que eles compartilham algumas características, mas são bastante diferentes uns dos outros. As principais diferenças são a ocorrência de espermiogênese do tipo I em Pseudopimelodidae e do tipo III em Heptapter
Neotropical Ichthyology. Publicado em: 2005-09
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19. Spermiogenesis and spermatozoa ultrastructure in five species of the Curimatidae with some considerations on spermatozoal ultrastructure in the Characiformes
A espermiogênese nas espécies Steindachnerina insculpta, Cyphocharax gillii, C. modestus, C. spilotus e Potamorhina altamazonica de Curimatidae é caracterizada pelo desenvolvimento lateral do flagelo, rotação do núcleo, formação excêntrica da fossa nuclear e cromatina compactada em fibras espessas. Estes espermatozóides exibem uma cabeça esférica
Neotropical Ichthyology. Publicado em: 2003-09
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20. Spermatogenesis and spermiogenesis in Didymocystis wedli Ariola, 1902 (Didymozoidae, Digenea)
The ultrastructure of the male reproductive system of Didymocystis wedli was studied for the first time, demonstrating spermiogenesis and spermatogenesis at different cell stages. The spermatozoa morphology was compared with that of other Digenea species. It was observed that the different cells of the spermatogenesis process follow the classic pattern repor
Memórias do Instituto Oswaldo Cruz. Publicado em: 2001-11
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21. Ultrastructure of spermatogenesis and sperm development in Saccocoelioides godoyi Kohn & Froes, 1986 (Digenea, Haploporidae)
Ultrastructural observations of spermatogenesis and sperm development of Saccocoelioides godoyi, an intestinal parasite of Leporinus friderici (Bloch, 1794) are described. The irregular-shaped spermatogonia form a peripheral layer, and show a prominent nucleus. Spermatocytes are larger than spermatogonia, and in the early stage present synaptonemal complex.
Memórias do Instituto Oswaldo Cruz. Publicado em: 2001-01
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22. Analise citogenetica, citoquimica e ultraestrutural da espermiogenese de especies de Physalaemus e Pseudopaludicola falcipes com enfase a caracterização taxonomica de Physalaemus biligonigerus e P. fuscomaculatus
The genus Physalaemus, belonging to the family Leptodactylidae, shows extensive polymorphism and an abundance of cryptic species. At least four species are currently recognized in this genus. In this work, we investigated some aspects of the cytogenetics and spermiogenesis of several species in this genus, with particular emphasis on P. fuscomaculatus and P.
Publicado em: 2000
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23. A espermiogenese em Boophilus microplus (Canestrini, 1887) (Acari:ixodidae) : aspectos estruturais e ultra-estruturais
The objective of this study was to describe the spermatogenesis of the cattle tick (Boophilus microplus) (Canestrini, 1887), based on histological, histochemical, morphologic and ultrastructural infromation. Spermatogenesis occurs in the testis of ticks which begin their blood repast. The gametic cell lineage is isolated in cysts. Spermiogenesis begins in th
Publicado em: 1998
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24. Estudo ultra-estrutural da espermiogenese e dos espermatozoides de Cosmopolites sordidus germar (Coleoptera : Curculionidae)
The spermiogenesis of Cosmopolites sordidus was investigated with the use of thin sections, negative staining preparations, and scanning electron microsoopy of spermatic cells obtained from the testicles or spermathecae.1n this species as with insects in general, this process is characterized by the following events: flagellar formation, chromatin condensati
Publicado em: 1993