Search results for "Meiosis"
showing 10 items of 55 documents
Inducción de la meiosis en células germinales obtenidas in vitro a partir de células madre pluripotentes humanas mediante expresión ectópica de las p…
2012
Entre las diversas afecciones que pueden causar infertilidad, la baja calidad gamética juega un importante papel. El estudio del desarrollo de la línea germinal es, por tanto, necesario para comprender las causas de la mala calidad gamética y así ayudar a mejorarla. Sin embargo, nuestro conocimiento actual acerca del desarrollo de la línea germinal in vivo en humanos es limitado, debido en gran parte a las limitaciones éticas y técnicas para obtener embriones humanos en estadíos tempranos del desarrollo. En este sentido, las células madre embrionarias humanas (hESCs, del inglés human Embryonic Stem Cells) y las células madre de pluripotencia inducida (iPSCs, del inglés induced Pluripotent S…
Impact of polyploidy on fertility variation of Mediterranean Arundo L. (Poaceae)
2015
International audience; Failure of seed production in the genus Arundo L. (Poaceae) is often attributed to polyploidy. This study tested the impact of two ploidy levels (2n = 12 and 18x) on the fertility of four Mediterranean Arundo. Viable pollen was screened from its production to its germination, and seed occurrence was monitored in admixture or isolated conditions. In addition, insights on restructuration of polyploid genornes were analysed using molecular cytogenetics. Our results show that high ploidy levels do not automatically induce failure of sexual reproduction. The two ploidy levels are able to produce viable pollen and seed set depending on species and cultural conditions. The …
The oxidizing agent tertiary butyl hydroperoxide induces disturbances in spindle organization, c-meiosis, and aneuploidy in mouse oocytes
1996
It has been recently proposed that a concomitant generation of oxidative stress of oocytes with increasing maternal age may be a major factor responsible for the age-related increase in aneuploid conceptions. As a preliminary step in the testing of this hypothesis, we need to confirm that oxidative stress in itself can induce errors in chromosome segregation. In order to achieve this goal, germinal vesicle (GV)-stage mouse oocytes from unstimulated ICR and (C57BL x CBA) F1 hybrid female mice were matured in vitro for 9 h for metaphase I (MI) oocytes or 16 h for metaphase II (MII) oocytes in the presence of varying concentrations of the oxidizing agent tertiary-butyl hydroperoxide (tBH). MII…
Stage of the estrous cycle at the time of pregnant mare's serum gonadotropin injection affects the quality of ovulated oocytes in the mouse
2002
The present study aims to analyze the effect of the stage of the estrous cycle at the time of pregnant mare's serum gonadotropin (PMSG) injection on number and quality of mouse oocytes retrieved from oviducts after exogenous ovarian stimulation. Cellular and morphological traits of ovulated oocytes from hybrid (C57Bl/6JIco female X CBA/JIco male) female mice of 12, 40-42, 50-52 or 57-62 weeks of age were analyzed. Superovulation was induced by a priming injection of PMSG at different stages of the estrous cycle followed after a 48-hr interval by human chrorionic gonadotropin. Injection of PMSG at diestrus-1 was associated with: (1) increased percentage of cumulus-free oocytes; (2) raised to…
Replication of linkage of familial hypobetalipoproteinemia to chromosome 3p in six kindreds
2002
Familial hypobetalipoproteinemia (FHBL) is a genetically heterogeneous condition characterized by very low apolipoprotein B (apoB) concentrations in plasma and/or low levels of LDL-cholesterol (LDL-C) with a propensity to developing fatty liver. In a minority of cases, truncation-specifying mutations of the apoB gene (APOB) are etiologic, but the genetic basis of most cases is unknown. We previously reported linkage of FHBL to a 10 cM region on 3p21.1-22 in one kindred. The objectives of the current study were to identify other FHBL families with linkage to 3p and to narrow the FHBL susceptibility region on 3p. Six additional FHBL kindreds unlinked to the APOB region on chromosome 2 were ge…
Mapping of Friedreich's ataxia locus by identification of recombination events in patients homozygous by descent
1994
The Friedreich's ataxia locus (FRDA) maps on chromosome 9q13. Genetic data, obtained from a small number of recombination events, indicated that the FRDA locus might be located centromeric to the D9S15/D9S5 linkage group, the most probable order being cen-FRDA-D9S5-D9S111-D9S15-D9S110-qter. Recently, new centromeric markers have been reported. Analysis of these markers allowed us to localize the recombination breakpoint in some of the recombinant families. However, only one proximal recombination has been found with these markers. To increase the genetic information from FRDA families, we have analyzed the centromeric markers FR1, FR2, FR7, FR8, and FR5 in patients homozygous by descent. Th…
Cellular and Morphological Traits of Oocytes Retrieved from Aging Mice after Exogenous Ovarian Stimulation1
2001
The present study aims to shed light on the origin of abnormal oocytes ovulated by aged females. In order to reach this goal, cellular and morphological traits of ovulated oocytes from hybrid (C57Bl/6JIco female x CBA/JIco male) female mice retrieved after exogenous ovarian stimulation at the age of 12, 40-42, 50-52, or 57-62 wk were analyzed. Aging of female mice was associated with 1) decreased number of ovulated oocytes; 2) increased percentage of cumulus-free oocytes; 3) raised percentage of oocytes with intracellular mitochondrial aggregates; 4) reduced percentage of oocytes displaying a normal distribution of chromosomes in the metaphase-II plate; 5) increased percentage of normal ooc…
Karyotype analysis, nucleolus organizer regions and C-banding pattern of Eisenia foetida (oligochaeta, lumbricidae)
1991
The diploid number 2n=22 and haploid number n=11 found for Eisenia foetida from Palermo, Italy, confirm earlier data for this species from other localities. Analyses of silver-stained and C-banded mitotic and meiotic chromosomes suggest that a single chromosome pair has active NORs which correspond with C-positive regions. The occurrence of nucleolus activity during spermatogenesis of E. foetida is ascertained.
Scanning electron microscopy of heterochromatin in chromosome spreads of male germ cells in Schistocerca gregaria (Acrididae, Orthoptera) after tryps…
1996
Chromosome spreads, prepared from testes of the desert locust Schistocerca gregaria, were analyzed using scanning electron microscopy (SEM) after varying periods of preincubation in trypsin. The emphasis of the study was on the appearance of heterochromatin. A trypsin pretreatment of 5 sec resulted in a smooth surface on the chromatin throughout and the heterochromatin was highly electron-emissive. The facultatively heterochromatic X chromosome was clearly visible in interphase spermatogonia and in pachytene and late prophase I spermatocytes. Chromomeres of autosomal bivalents could be recognized in pachytene cells. Centromeric heterochromatin segments were very prominent in autosomes of la…
Strange vesicles with a homogeneous content in spermatocytes and spermatids of a click beetle, Adelocera murina (Elateridae). A fine structure study
1996
Abstract The restructuring of primary spermatocytes of Adelocera murina, a click beetle, is described using electron microscopy of ultrathin sections. Emphasis is on spherical or rod-shaped cytoplasmic inclusions, invested by a unit membrane. The content of the inclusions is slightly more electron-dense than that of the surrounding cytoplasm and homogeneously textured in most cases. The inclusions are missing in spermatogonia but are abundant in prophase I through anaphase I spermatocytes. Their number declines in telophase I. Very similar elements are associated with the distal ends of the outgrowing flagella in metaphase I through telophase I spermatocytes and form the so-called flagellar…