Ultrastructural analysis of bovine oocytes from ovarian follicles with different diameters

Abstract

A produção in vitro de embriões é uma técnica importante para facilitar a reprodução de animais com elevado mérito genético. O maior desafio para a reprodutibilidade desta técnica é a qualidade do oócito destinado à maturação in vitro. O objetivo deste trabalho foi avaliar as características ultra-estruturais de oócitos provenientes de folículos com diferentes diâmetros por microscopia eletrônica de transmissão. Os animais foram divididos em dois grupos e receberam uma única injeção im de 250 UI de FSH (Pluset, Serono, Itália). Para sincronizar o crescimento folicular, todos os folículos > 2 mm foram aspirados durante o ciclo estral, que foi considerado o dia zero (D0). O Grupo 1 (G1, n = 4) recebeu FSH no dia 1 (D1), e os folículos de 2 a 5 mm foram aspirados no dia 2 (D2). Os animais do grupo 2 (G2, n = 5) receberam FSH no dia 2 (D2), e os folículos de 10 a 15 mm foram aspirados no dia 5 (D5). Após a aspiração, os oócitos de ambos os grupos foram fixados e preparados para análise ultra-estrutural. Os oócitos analisados de ambos os grupos apresentaram características ultra-estruturais semelhantes. A presença e distribuição de organelas no citoplasma dos oócitos não diferiram entre os grupos, sugerindo AbstractIn vitro embryo production is an important technique for facilitating the reproduction of animals with high genetic merit. The greatest challenge for the reproducibility of this technique is the quality of the oocyte that is submitted for in vitro maturation. The aim of this work was to evaluate the ultrastructural characteristics of oocytes from follicles of different diameters using transmission electron microscopy. The animals were divided into 2 groups and were given a single i.m. injection of 250 IU FSH (Pluset, Serono, Italy). To synchronize the follicular growth, all follicles > 2 mm were aspirated during the estrous cycle, which was considered day zero (D0). Group 1 (G1; n = 4) received FSH on day 1 (D1), and the 2-to 5-mm follicles were aspirated on day 2 (D2). The animals in group 2 (G2; n = 5) received FSH on day 2 (D2), and their 10-to 15-mm follicles were aspirated on day 5 (D5). After aspiration, the oocytes from both groups were fixed and prepared for ultrastructural analysis. The oocytes analyzed from both groups had similar ultrastructural characteristics. The presence and distribution of organelles in the cytoplasm of the oocytes did not differ between groups, suggesting that, in relation to the ultrastructural characteristics, oocytes from 2 to 5 mm and 10 to 15 mm follicles are similar.

L‐Cysteine improves bovine oocyte developmental competence in vitro via activation of oocyte‐derived growth factors BMP‐15 and GDF‐9

“…In all L‐cysteine‐treated oocytes that were examined, we found vesicles with various shape, size, number and arrangement distributed throughout the cytoplasm, and most of vesicles had no apparent content. The possible role of these vesicles was attributed as nutrient reserves (Russe, 1983) or it could participate in the formation of CGs because of the close proximity of these two organelles (Fair et al., 1997; Lisboa et al., 2011). Besides, an electron‐dense content and intra‐vesicular membranous structures were observed in L‐cysteine‐treated oocytes, suggesting their secretory activity.…”

Endocytotic Activity during the Cortical Granules Genesis in Marine Planarian Oocytes (Platyhelminthe, Tricladida)

“…Cortical granules are membrane-bound, electron dense cell inclusions known in oocytes of many animals, invertebrates [1][2][3][4][5] and vertebrates [6]. They are distributed in the peripheral ooplasm forming a monolayer beneath the plasma membrane [1,3,5].…”