Search results for "Oogenesis"
showing 10 items of 21 documents
Oogenesis and reproductive investment of Atlantic herring are functions of not only present but long-ago environmental influences as well
2017
Following general life history theory, immediate reproductive investment (egg mass × fecundity/body mass) in oviparous teleosts is a consequence of both present and past environmental influences. This clarification questions the frequent use of season-independent (general) fecundity formulas in marine fish recruitment studies based on body metrics only. Here we test the underlying assumption of no lag effect on gametogenesis in the planktivorous, determinate-fecundity Atlantic herring (Clupea harengus) displaying large plasticity in egg mass and fecundity, examining Norwegian summer–autumn spawning herring (NASH), North Sea autumn-spawning herring (NSAH), and Norwegian spring-spawning herri…
In the ovary of Ciona intestinalis (Type A), immune-related galectin and phenoloxidase genes are differentially expressed by the follicle accessory c…
2017
Abstract Riboprobes (in situ hybridization) and antibodies (immunohistochemistry), previously used to show the upregulation of Ciona intestinalis (Type A) galectins (CiLgals-a, CiLgals-b) and phenoloxidase (CinPO2) immune-related genes, were tested on histological sections of the ovary. The ovarian follicles are composed of oocytes encased by follicular cells (FCs) and test cells (TCs). Results show the transcription upregulation of both CiLgals and CinPO2 genes in the vitellogenic FCs, conversely distinct cytolocalization of the proteins are shown. At vitellogenic stage, the CiLgals are localized in the FCs, in the oocyte cytoplasm, and close to the germinal vesicle (GV), whereas the CinPO…
Mitochondria during sea urchin oogenesis.
2017
SummarySea urchin represents an ideal model for studies on fertilization and early development, but the achievement of egg competence and mitochondrial behaviour during oogenesis remain to be enlightened. Oocytes of echinoid, such as sea urchin, unlike other echinoderms and other systems, complete meiotic maturation before fertilization. Mitochondria, the powerhouse of eukaryotic cells, contain a multi-copy of the maternally inherited genome, and are involved directly at several levels in the reproductive processes, as their functional status influences the quality of oocytes and contributes to fertilization and embryogenesis. In the present paper, we report our latest data on mitochondrial…
High progesterone levels in women with high ovarian response do not affect clinical outcomes: a retrospective cohort study
2014
Background The potentially detrimental role of progesterone during the follicular phase has been a matter of controversy for several years; however, few studies have analyzed the effects of combined raised estradiol and progesterone levels on pregnancy outcomes. The aim of the present study was to determine the influence of high progesterone levels on clinical outcomes in the context of high ovarian response. Methods We performed a retrospective cohort study that included 2850 women classified as high responders. The women were subdivided into six groups depending on their progesterone concentration on the day of human chorionic gonadotropin (hCG) administration: 1.81 ng/ml (>p90). Ovarian …
DNA integrity, growth pattern, spindle formation, chromosomal constitution and imprinting patterns of mouse oocytes from vitrified pre-antral follicl…
2010
Cryopreservation of follicles for culture and oocyte growth and maturation in vitro provides an option to increase the number of fertilizable oocytes and restore fertility in cases where transplantation of ovarian tissue poses a risk for malignant cell contamination. Vitrification for cryopreservation is fast and avoids ice crystal formation. However, the influences of exposure to high concentrations of cryoprotectants on follicle development, oocyte growth and maturation, and particularly, on the DNA integrity and methylation imprinting has not been studied systematically. Follicle survival and development, DNA damage, oocyte growth patterns, maturation, spindle formation and chromosomal c…
340 EPIGENETIC ANALYSIS OF DEVELOPMENTALLY IMPORTANT GENES IN BOVINE OOCYTES OF DIFFERENT ORIGINS
2010
A critical step in assisted reproductive technologies (ART) is the IVM of oocytes. The quality of the oocyte is crucial for successful fertilization and subsequent embryo development. Studies in bovine ART, and epidemiological studies in children from ART, reveal a degree of abnormal development thought to be primarily caused by aberrant DNA methylation patterns in imprinted and non-imprinted genes. Due to the inherent similarities in bovine and human preimplantation embryonic development, bovine oocyte and embryo development is increasingly being used as a model for human development. The goal of this project is to investigate the effects of specific IVM conditions on the DNA methylation …
261 INFLUENCE OF IN VITRO MATURATION ON EPIGENETIC MARKS AND GENE EXPRESSION IN BOVINE OOCYTES
2011
In cattle, in vitro maturation (IVM) of oocytes is an integral part of assisted reproduction technology. However, only 30% of in vitro matured bovine oocytes develop to the blastocyst stage after fertilization (compared with 60% for in vivo matured oocytes), indicating critical involvement of maturation conditions in the developmental competence of oocytes. Oocytes for IVF and intracytoplasmic sperm injection in humans are typically allowed to mature in vivo after superovulation because IVM is not considered to be a safe medical procedure. Several studies have shown that assisted reproduction technology involving prolonged in vitro culture of human and ruminant embryos can be associated wi…
Piwi proteins and piRNAs in mammalian oocytes and early embryos: From sample to sequence
2015
AbstractThe role of the Piwi/piRNA pathway during mammalian oogenesis has remained enigmatic thus far, especially since experiments with Piwi knockout mice did not reveal any phenotypic defects in female individuals. This is in striking contrast with results obtained from other species including flies and zebrafish. In mouse oocytes, however, only low levels of piRNAs are found and they are not required for their function. We recently demonstrated dynamic expression of PIWIL1, PIWIL2, and PIWIL3 during mammalian oogenesis and early embryogenesis. In addition, small RNA analysis of human, crab-eating macaque and cattle revealed that piRNAs are also expressed in the female germline and closel…
MITOCHONDRIOGENESIS IN MATURING SEA URCHIN OOCYTES: A COMPUTERIZED RECONSTRUCTION ANALYSIS
1996
Abstract The dynamics of chondriome changes in oogenesis of the sea urchinParacentrotus lividuswere studied by electron microscopy. An oocyte-enriched fraction obtained by gonad mechanical dissociation without protease treatment was used. The shape, size and arrangement of mitochondria (Mt) in cells were quantitatively analysed on the basis of data from reconstruction experiments, with serial sections performed using a specific computer program. At all stages of oogenesis, the chondriome was shown to consist of rod-shaped Mt of various lengths and also of small amounts of globular Mt about 0.3 μm in diameter. Chondriome transformation during oogenesis is shown to involve the following proce…
The expression of an immune-related phenoloxidase gene is modulated inCiona intestinalisovary, test cells, embryos and larva
2015
Two distinct Ciona intestinalis phenoloxidases (CinPO1, 2) had previously been cloned and sequenced. The CinPO2 is involved in innate immunity and is expressed by inflammatory hemocytes that populate the tunic and pharynx vessels as a response to LPS inoculation. In situ hybridization and immunohistochemistry assays on histological section, showed that the expression of this gene and the produced protein are shared with oogenesis, embryogenesis and larval morphogenesis. Intriguingly, upregulation of gene transcription was found in the test cell layer that envelopes the ovary follicle, ovulated egg, and gastrula, as well as it was modulated in the zygotic nucleus of outer balstomers of 32-ce…