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Showing 1 to 3 of 3 (0.044 seconds)Spelling suggestions: "subject:"germinal vesicle breakdown"" "subject:"germinal vesicle breakdowns""
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O sistema peptídeos natriuréticos está presente no complexo cumulus-oócito e regula o reinício da meiose em bovinos / The natriuretic peptides system is present in the cumulus-oocyte complex and regulate meiotic resumption in bovineCesaro, Matheus Pedrotti de 20 February 2013 (has links)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The process of meiotic resumption in oocytes, arrested since fetal life, and the
expansion of compact layers of cumulus cells is triggered by intrafollicular mediators
stimulated by LH. These events are extremely complex. In mice, among system
components of natriuretic peptides (NP), only the C-type NP (CNP) has a role to
inhibit the resumption of meiosis. However, little is know about the function of NPs
on resumption of meiosis, nuclear maturation and cumulus expansion in monovular
species. The aim of this study was to characterize the natriuretic peptide system,
studing its role in the resumption of meiosis and cumulus expansion. We also
proposed a new model to study cumulus expansion. Initially, we detected the presence
of mRNA for the ANP, CNP, natriuretic peptide receptor 1 (NPR-1), NPR-2 and
NPR-3 in the cumulus cells and NPR-2 mRNA in the oocyte. Using an in vitro model,
in which the oocytes are arrested in germinal vesicle (VG) by the action of forskolin
(100 μM), we demonstrated that ANP, BNP and CNP, alone or in combination,
induce resumption of meiosis after 12 h of maturation. In another experiments, we
observed that the concentration of 100 μM forskolin inhibited cumulus expansion
stimulated by FSH for12 h, which was reversed by adding ANP, BNP and CNP in the
COC culture system. Thus, we demonstrated for the first time the localization of
mRNA for the NP system in COCs. Furthermore, we found that the ANP, BNP and
CNP are likely mediators of LH to induce meiotic resumption and cumulus expansion
in monovuluar species, using the bovine as the animal model. / O processo de retomada da meiose no oócito, bloqueada desde a vida fetal, e a
expansão de compactas camadas de células do cumulus que o envolvem é
desencadeado por mediadores intrafoliculares estimulados pelo LH, sendo eventos
extremamente complexos. Em camundongos, dentre os componentes do sistema
peptídeos natriuréticos (NP) somente o NP tipo C (CNP) apresenta função,
bloqueando a retomada da meiose. Entretanto, em espécie monovular, o
conhecimento sobre a ação dos NP, na maturação nuclear de oócitos e expansão do
cumulus, é extremamente escasso. O objetivo do presente estudo foi caracterizar o
sistema peptídeo natriurético, demonstrar sua função na retomada da meiose e
expansão do cumulus, além de propor um novo modelo para estudo da expansão do
cumulus. Inicialmente, demonstramos a presença de RNAm para ANP, CNP, receptor
peptídeo natriurético 1 (NPR-1), NPR-2 e NPR-3 nas células do cumulus, sendo que
no oócito somente foi detectado RNAm do NPR-2. Utilizando um modelo in vitro, no
qual os oócitos permanecem bloqueados em vesícula germitava (VG) por ação do
forskolin (100 μM), demonstramos que os ANP, BNP e CNP, isoladamente ou em
associação, induzem o reinício da meiose após 12 h de maturação. Em outros
experimentos, observamos que a concentração de 100 μM de forskolin inibiu, por 12
h, a expansão das células do cumulus estimulada por FSH e que o ANP, BNP e CNP
revertem o efeito inibitório do forskolin sobre a expansão do cumulus. Dessa forma,
demonstramos pela primeira vez a localização de RNAm para o sistema NP em
CCOs. Além disso, foi demonstrado que em espécie monovuluar, utilizando o bovino
como modelo animal, os peptídeos natriuréticos (ANP, BNP e CNP) apresentam
função de mediadores intrafoliculares do LH, na qual estimulam a retomada da
meiose e expansão do cumulus.
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The role of the kinetochore in chromosome segregation during Meiosis ITurrin, Evelyne 12 1900 (has links)
La ségrégation des chromosomes est un processus complexe permettant la division égale du matériel génétique entre les cellules filles. Contrairement aux cellules somatiques, ce processus est sujet à des erreurs dans les cellules germinales telles que les ovocytes. Lorsque des erreurs surviennent lors de la ségrégation des chromosomes durant la méiose cela peut conduire à une aneuploïdie. L’aneuploïdie est la présence d’un nombre incorrect de chromosomes dans une cellule et est connue pour causer l’infertilité et des arrêts de grossesses chez l’humain. L’incidence de l’aneuploïdie augmente avec l’âge maternel (1).
Le kinétochore est une structure cellulaire impliqué dans la ségrégation des chromosomes. Il est composé de plus de 100 protéines et se situe entre les microtubules et les centromères. Les microtubules se lient aux kinétochores, et ces derniers s’attachent sur les centromères afin de séparer les chromosomes homologues durant la méiose et les chromatides des sœurs pendant la mitose (1–3). Dans les cellules somatiques, cette structure est bien connue (2). Pourtant, moins d’informations sont connues à dans l’ovocyte de mammifère en développement au cours de la méiose I (3,4).
Ce projet vise à étudier le rôle du kinétochore durant la ségrégation des chromosomes dans l’ovocyte de souris en développement. Plus spécifiquement, l’assemblage, le désassemblage, la dynamique et la tension des protéines du kinétochore seront évalués. Ce projet permettra de mieux comprendre le rôle du kinétochore durant la méiose I, ses implications durant la séparation des chromosomes, et éventuellement ses implications dans l’aneuploïdie. / Chromosome segregation is an intricate process in dividing genetic material equally between daughter cells. This process, unlike in somatic cells, is error prone in germ cells like the oocyte. When errors occur during meiosis in segregating chromosomes, aneuploidy results when the cell has an incorrect number of chromosomes. This can result in infertility and birth defects in human reproduction. The incidences of aneuploidy are also seen to increase with increasing maternal age (1).
The kinetochore is a cellular structure at the heart of chromosome segregation. It is composed of more than 100 proteins and is located between the microtubules and the centromeres. The microtubules attach onto the kinetochores, which themselves attach onto the centromeres, in order to pull the homologous chromosomes apart during meiosis and the sister chromatids during mitosis (1–3). Much is known about this multi-protein structure in somatic cells (2). Yet, very little is known about this in the developing mammalian oocyte during Meiosis I (1,3,4).
This project aims to investigate the role of the kinetochore in chromosome segregation in a developing mouse oocyte. More specifically, kinetochore protein assembly, disassembly, dynamics and tension will be assessed. This project will achieve a better understanding of the kinetochore’s role in Meiosis I, its implications in chromosome segregation in a developing mouse oocyte, and how it may be involved in aneuploidy.
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Spindle-Localized CPE-Mediated Translation Controls Mediotic Chromosome SegregationEliscovich, Carolina 11 June 2008 (has links)
La progresión meiótica y el desarrollo embrionario temprano están programados, en parte, por la activación tradcuccional de mRNAs maternos como lo son los que codifican para las proteinas de ciclina B1 o mos. Estos mRNAs no son traducidos al mismo tiempo ni en el mismo lugar. Por lo contrario, su traducción está especificamente regulada por elementos de poliadenilación citoplasmática (CPEs) presentes en sus 3'UTRs. Los elementos CPEs reclutan a la proteina de unión a CPE (CPE-binding protein CPEB (Colegrove-Otero et al., 2005; de Moor et al., 2005; Mendez and Richter, 2001; Richter, 2007)). Esta proteina de unión al RNA no sólo determina cuándo y en qué medida un mRNA será activado traduccionalmente por poliadenilación citoplasmática (Mendez et al., 2000a; Mendez et al., 2000b; Mendez et al., 2002) sino que también participa, junto con el represor de la traducción Maskin, en el transporte y la localización de sus mRNAs diana hacia los sitios de localización subcelular donde su traducción ocurrirá (Huang et al., 2003; Huang and Richter, 2004). Durante el desarrollo embrionario de Xenopus, CPEB se encuentra localizada en el polo animal de los oocitos y más tarde, sobre el huso mitótico y centrosomas en el embrión (Groisman et al., 2000). Se ha demostrado que embriones de Xenopus inyectados con agentes que interrumpen la traducción dependiente de poliadenilación citoplasmática, detienen la división celular y presentan estructuras mitóticas anormales (Groisman et al., 2000). En este trabajo que derivó en mi tesis doctoral, hemos demostrado que la activación traduccional localizada en el huso mitótico de mRNAs regulados por CPEB que codifican para proteinas con una conocida función en aspectos estructurales del ciclo celular como la formación del huso mitótico y la segregación cromosómica, es esencial para completar la primera división meiótica y para la correcta segregación cromosómica en oocitos de Xenopus.
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