686 resultados para vitellogenic follicles


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Tendo por base os novos conhecimentos oriundos de recentes estudos com Perciformes marinho, a origem e o desenvolvimento dos oócitos no Ostariophysi Gymnotus sylvius são aqui descritos. da mesma maneira que ocorre nos Perciformes, em Gymnotus sylvius as oogônias são encontradas no epitélio germinativo que margeia as lamelas ovígeras. No início da foliculogênese, a proliferação das oogônias e sua entrada em meiose dão origem a ninhos de células germinativas que se projetam em direção ao estroma ovariano, a partir do epitélio germinativo. Os ninhos e o epitélio germinativo são suportados pela mesma membrana basal que os separa do estroma. Coincidindo com a paralisação da meiose os oócitos, presentes nos ninhos, são separados uns dos outros por processos citoplasmáticos das células pré-foliculares. As células pré-foliculares derivam do epitélio germinativo sendo, portanto, inicialmente células epiteliais. Durante a foliculogênese, ao mesmo tempo em que envolvem os oócitos individualizando-os, as células pré-foliculares sintetizam a membrana basal ao seu redor. Os oócitos entram em crescimento primário ainda dentro dos ninhos. Ao término da foliculogênese, o oócito e as células foliculares que compõem o folículo são circundados pela membrana basal. O folículo permanece conectado ao epitélio germinativo uma vez que ambos compartilham uma porção comum da membrana basal. Células oriundas do estroma circundam o folículo ovariano exceto na região de compartilhamento da membrana basal formando a teca. O folículo, a membrana basal e a teca formam o complexo folicular. O desenvolvimento do oócito ocorre dentro do complexo folicular e compreende os estágios de crescimento primário e secundário, maturação e ovulação. Os alvéolos corticais surgem no ooplasma momentos antes do início do crescimento secundário ou estágio vitelogênico que tem início com a deposição de vitelo, progride até o oócito esteja completamente desenvolvido e o ooplasma preenchido pelos glóbulos de vitelo. A maturação é caracterizada pela migração do núcleo ou vesícula germinativa, pela quebra da vesícula germinativa, ou seja, pela fragmentação do envoltório nuclear e, retomada da meiose. Na ovulação o ovo é liberado do complexo folicular para o lúmen ovariano. em comparação com os Perciformes marinhos com ovos pelágicos, o desenvolvimento oocitário em Gymnotus sylvius tem menos etapas dentro dos estágios de desenvolvimento, sendo as duas mais notáveis delas as ausências da formação das gotas de lipídio durante os crescimentos primário e secundário (e a consequente fusão das gotas para formar um único glóbulo de lipídio durante a maturação) e, a hidrólise do vitelo antecedendo a ovulação.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Specimens of the zipper sand skate Psammobatis extenta were collected in the region of Ubatuba off the northern coast of the State of São Paulo, Brazil, monthly for once year (January - December 2000), at 25- to 40-m isobaths. A total of 123 individuals were caught. The total length (TL) of females averaged 224.6 mm, and of males 217 mm. The overall sex ratio was 1:1. Analysis of the length-weight relationship indicated the existence of positive allometry in females, and isometry in males. The length at onset of sexual maturity was determined for both sexes; females reached sexual maturity at smaller sizes than males (TL50 = 230.7 and TL50 = 237.7 mm respectively). Females showed functional parity of both ovaries and uteri. Females that were pregnant or were carrying vitellogenic oocytes were observed during nine of 12 months of the survey, indicating a continuous reproductive cycle. Psammobatis extenta was most abundant from January to April, and again from June to October. Most individuals were collected at the 40-m isobath. Both adults and neonates were collected in the study area. However, adolescent skates were scarce, which either indicates differential occupation of the area, or suggests that the shallow waters of the continental shelf are used as breeding grounds.

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Insect oocytes are surrounded by the follicular epithelium which is simple and cuboidal, wih the mainly functions of: synthesis of vitellin membrane and chorion and synthesis and transport of hemolymph products (proteins). In Pachycondyla (Neoponera) villosa ants workers aged less than 10 days do not present the formation of ovarian follicles (oocytes, nurse cells and follicular cells) indicating that vitellogenesis starts at approximately 10 days of age. Studies of participation of the follicular epithelium in Pachycondyla (Neoponera) villosa showed that in stage I oocytes the epithelium does not present the opening of intercellular spaces. In stage II these spaces begin to be observed together with separation of the follicular epithelium from the oocyte surface. In stage III two types of material were observed in the intercellular spaces: electrodense material in the basal region and compacted material in apical one as well as follicular epithelium/oocytes interface suggesting that the extraovarian material that reach oocytes undergoes some type of modification during passage through the intercellular spaces. The follicular epithelium spaces in queen are bigger than in workers oocytes.

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Exposure of 1, 4, 7 & 10 day-old virgin queens of Apis mellifera Linne 1758 for 1 min to CO2 accelerated their ovarian development, having a similar effect as mating on the initial formation of the ovarian follicles. In 3 day-old queens the exposure to CO2 enhanced the initial stage of germ cell differentiation into oocytes and nurse cells in the ovarioles, a developmental stage only seen in 5 day-old untreated virgin queens, the age at which they are ready to mate. In 10 day-old untreated virgin queens, some regions of the ovarioles presented tissue disorganization and many cells with pycnotic nuclei. However, narcotized virgin queens of the same age did not present such ovary degeneration. Conversely, they showed nitid follicle formation, arising in the ovarioles' initial differentiation between nurse and oocytic chambers, although still without vitellogenesis. The accelerative effect of CO2 is limited to the ages near to those proper for mating, since 15 and 18 day-old treated virgin queens presented ovaries with extensive regions of high tissue disorganization and a great number of cells with pycnotic nuclei. According to the results, the narcosis presented three levels of effect on the ovary of honeybee virgin queens: 1) accelerated the germ cell differentiation, 2) preserved the tissue integrity even after the queen mating period and 3) stimulated the initial differentiation of a vitellarium. This later condition was only seen in untreated queens after mating. All these effects are not maintained if the queen is kept virgin beyond 15 days old.

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This study presents an ultrastructural analysis of the ovary of the tick, Amblyomma triste. The ovary of this species is of the panoistic type that is, without nursing and follicular cells. It is composed of a layer of epithelial cells forming a wall and of germinative cells that generate the oocytes which remain attached to the external margin of this wall by a multicellular pedicel. The different developmental stages in the oocytes had been described by Oliveira et al. [Oliveira, P.R., Bechara, G.H., Camargo-Mathias, M.I., 2006. Amblyomma triste (Koch, 1844) (Acari: Ixodidae): Morphological description of the ovary and of vitellogenesis. Experimental Parasitology 113, 179-185]. The results of the investigation suggest that besides exogenous production of vitellogenic elements, endogenous production can take place simultaneously, contributing to the development and growth of the oocytes. (c) 2007 Elsevier B.V. All rights reserved.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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The reproductive biology of the Brazilian sharpnose shark, Rhizoprionodon lalandii, off southeastern Brazil was investigated using data from gillnet landings. The size-at-maturity for males and females was estimated to be 59 and 62 cm total length (LT), respectively. Ovarian fecundity ranged from 3 to 7 follicles (mean = 4.S4), and uterine fecundity from 1 to S embryos (mean = 3.3). There was a slight positive relationship between female LT and the number of ovarian follicles, but uterine fecundity was not related to female LT. Embryonic growth is fast following fertilization during summer and autumn. Gestation requires 11 - 12 months, and peak parturition is between August and September. A comparison of size-at-maturity between animals from northeastern and southeastern Brazil suggests the existence of at least two stocks of R. lalandii along the Brazilian coast.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Twelve female ponies were examined daily for 30 days and classified as ovulating (OV; N = 6; 197 ± 6 kg) or prepubertal (PP; N = 6; 196 ± 9 kg). Follicles were detected by ultrasound and gonadotropins quantified by radioimmunoassay. The mean diameter of the largest follicles was significantly larger in OV (38 ± 1 mm) than in PP (26 ± 2 mm) but there was no difference between groups in the size of the second largest follicle. There were more small follicles (<24 mm) in the PP than in the OV group, but PP fillies had a smaller number of follicles >29 mm than the OV fillies. Follicle-stimulating hormone (FSH) levels did not differ between groups but PP fillies had lower luteinizing hormone (LH) peak (8 ± 1 ng/ml) and basal (4 ± 0.5 ng/ml) levels, lower peak magnitude (2 ± 0.2 ng/ml) and period average (5 ± 0.6 ng/ml) than OV fillies (32 ± 4.5, 8 ± 1.2, 17.1 ± 6, and 15 ± 2.3 ng/ml, respectively). The PP group, in contrast to the OV group, showed no relationship between FSH surge and follicle wave emergence. We conclude that an LH concentration higher than 8 ng/ml is needed for follicle growth to a preovulatory size. Wave emergence and FSH secretion seem to be independent events, probably due to an inhibitory neural system in these PP animals. PP fillies may provide a physiological model for the study of follicle wave emergence which apparently does not depend on gonadotropin levels.

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Avaliou-se o desenvolvimento de folículos pré-antrais ovinos após o cultivo in vitro do córtex ovariano em várias concentrações de ácido 3-indol acético (IAA). O córtex ovariano foi dividido em fragmentos de aproximadamente 3×3mm. Um fragmento foi imediatamente fixado em Bouin (controle - dia 0) e os demais destinados ao cultivo por dois ou seis dias em meio essencial mínimo (MEM+) acrescido de 10, 40, 100, 500 ou 1000ng/ml de IAA. Após o cultivo in vitro, não houve variação entre folículos dos tratamentos e folículos-controle, exceto nos suplementados com 40ng/ml de IAA. Nestes observaram-se redução de folículos primordiais e aumento de folículos em desenvolvimento (P<0,05). em relação aos folículos do grupo-controle, houve redução de pré-antrais normais no cultivo de seis dias (P<0,05). Após dois dias de cultivo, a redução foi observada somente nos folículos suplementados com 500 ou 1000ng/ml de IAA. Folículos pré-antrais ovinos podem ser ativados in vitro com sucesso após o cultivo em MEM+ suplementado com 40ng/ml de IAA.