Light and Transmission Electron Microscopy of Immature Camelus Dromedarius Oocyte

Estimation, morphometry and ultrastructure of ovarian preantral follicle population in agouti (Dasyprocta leporina)

ABSTRACT: The aim of this study was to characterize the preantral ovarian follicular population in agoutis (D. leporina) by estimating the number of follicles at each developmental category, and also describe the morphometry and the specific features of the follicle and the oocyte by using light and transmission electron microscopy. The length of each ovary was measured using a caliper rule, longitudinally sectioned into two halves and both were immediately fixed to perform the estimation of follicular population and ultrastructural analysis. The mean (±S.E.M.) population of follicular per pair of ovary was estimated at 4419.8±532.26 and 5397.52±574.91 for right and left ovaries, respectively, but no differences were observed between them. The diameters for follicles, oocyte and nuclei were: 18.62±3.40μm, 12.28±2.37μm and 6.10±0.93μm for primordial, 23.75±5.70μm, 14.22±3.00μm and 6.70±1.24μm for primary and 88.55±17.61μm, 52.85±17.56μm and 22.33±17.61μm for secondary follicles, respectively. The most of the follicles found belonged to the primordial category (86.63%), followed by primary (13.01%) and secondary (0.35%) one. Additionally, polyovular follicles were observed in all the animals and they represented 7.51% of the total follicles counted. The ultrastructural analysis showed that the oocyte presented a central and regular nuclei, displaying a homogenous mass. Among the organelles, the mitochondria were the most abundant and the oocyte Golgi apparatus was rarely observed. In conclusion, this work shows for the first time the characterization of the population of preantral follicles in the ovary of Dasyprocta leporina. Those information will be useful for further development and adaptation of biotechniques such as germplasm cryopreservation and in vitro gametes manipulation.

Shedding new light on the molecular architecture of oocytes using a combination of synchrotron Fourier transform-infrared and Raman spectroscopic mapping

Synchrotron Fourier transform-infrared (FT-IR) and Raman microspectroscopy were applied to investigate changes in the molecular architecture of mouse oocytes and demonstrate the overall morphology of the maturing oocyte. Here we show that differences were identified between immature mouse oocytes at the germinal vesicle (GV) and mature metaphase II (MII) stage when using this technology, without the introduction of any extrinsic markers, labels, or dyes. GV mouse oocytes were found to have a small, centrally located lipid deposit and another larger polar deposit of similar composition. MII oocytes have very large, centrally located lipid deposits. Each lipid deposit for both cell types contains an inner and outer lipid environment that differs in composition. To assess interoocyte variability, line scans were recorded across the diameter of the oocytes and compared from three independent trials (GV, n = 91; MII, n = 172), and the data were analyzed with principal component analysis (PCA). The average spectra and PCA loading plots show distinct and reproducible changes in the CH stretching region that can be used as molecular maturation markers. The method paves the way for developing an independent assay to assess oocyte status during maturation providing new insights into lipid distribution at the single cell level.

Morphology of Dromedary Camel Oocytes and their Ability to Spontaneous and Chemical Parthenogenetic Activation

The present work was conducted to examine (1) the morphology of dromedary cumulus-oocytes complexes (COCs), (2) to study the incidence of spontaneous development of oocytes in vivo and (3) to assess the ability of in vitro matured dromedary oocytes to chemical parthenogenetic activation compared with in vitro fertilized (IVF) oocytes. COCs were recovered from dromedary ovaries classified according to their morphology into six categories. Oocyte diameter was measured using eye piece micrometer. For chemical activation, COCs with at least three layers of cumulus-cells were in vitro matured (IVM) in TCM 199 + 10 microg/ml FSH + 10 IU hCG/ml + 10% FCS + 50 microg/ml gentamycin. COCs were incubated for 40 h at 38.5 degrees C under 5% CO2 in humidified air. After IVM, matured oocytes with first polar body (first Pb) were divided into two groups. Group 1: activated in 7% ethanol (E) for 5 min followed by culture in 2 mM 6-dimethylaminopurin (6-DMAP, E D, subgroup 1) or 10 microg/ml cycloheximide (CHX, E CHX, subgroup 2) for 3.5 h at 38.5 degrees C under 5% CO2. In group 2, oocytes were activated using 50 microM Ca A23187 (Ca A) for 5 min followed by culture in 2 mM 6-DMAP (Ca D, subgroup 3) or 10 microg/ml CHX(Ca CHX, subgroup 4) for 3.5 h at 38.5 degrees C under 5% CO2. For control group, IVM oocytes were fertilized using frozen-thawed camel spermatozoa separated by swim-up method then suspended in Fert-TALP medium supplemented with 6 mg/ml BSA (FAF) + 10 microg/ml heparin. In all groups, oocytes were in vitro cultured in SOFaa medium + 5% FCS and 5 microg/ml insulin + 50 microg/ml gentamycin. Cleavage rate and embryo development were checked on Days 2, 5 and 8. An average of 11.3 +/- 0.3 COCs were recovered/dromedary ovary. Categories 1 and 2 represented 33.1% and 34.8%, respectively, and were significantly higher (p < 0.01) than the other categories (19.1, 9.2 and 2.6% for categories 3-5, respectively). Category 6 (embryo-like structures) represented 1.2% of the recovered oocytes, staining of these embryo-like structures with orcien dye indicated the presence of divided cells with condensed nuclei. Dromedary oocytes averaged 166.2 +/- 2.6 microm in diameter with black cytoplasm. Chemical activation of IVM dromedary oocyte with first Pb in 7% ethanol or 50 microM Ca A followed by culture in 2 mM 6-DMAP showed significantly higher (p < 0.01) cleavage and developmental rates to the morula stage than oocytes activated using 7% ethanol or 50 microM Ca A followed by 10 microg/ml CHX or in vitro fertilized control group. Higher (p < 0.01) proportion of oocytes sequentially cultured in 10 microg/ml CHX or that in vitro fertilized were arrested at the 2-4-cell stage compared with that cultured in 6-DMAP.

Update on reproductive biotechnologies in small ruminants and camelids

Recent advances in reproductive biotechnologies in small ruminants include improvement of methods for in vitro production of embryos and attempts at spermatogonial stem cell transplantation. In vitro production of embryos by IVM/IVF, intra-cytoplasmic sperm injection (ICSI), or nuclear transfer (NT) has been made possible by improvements in oocyte collection and maturation techniques, and early embryo culture systems. However, in vitro embryo production still is not very efficient due to several limiting factors affecting the outcome of each step of the process. This paper discusses factors affecting in vitro embryo production in small ruminants and camelids, as well as preliminary results with the technique of spermatogonial stem cell transplantation.

Chronological and ultrastructural changes in camel (Camelus dromedarius) oocytes during in vitro maturation

Cumulus-oocyte complexes (COCs) were collected from non-pregnant camels at a local slaughterhouse by aspiration from antral follicles (2-6 mm). In Experiment I, camel COCs (n=304) were matured in vitro in Hams-F10, fixed at different time intervals (6, 12, 18, 24, 30, 36, 42, or 48 h) and stained with 1% aceto-orcein to assess nuclear changes in culture. A majority of the oocytes (81.5%) underwent germinal vesicle break down (GVBD) between 6 and 12h. Forty-eight percent of the oocytes were observed at the metaphase I (M I) stage by 18 h culture. The percentage of matured oocytes (M II stage) at 30 and 42 h were 66.5 and 71% respectively, which were significantly (p<0.05) different to that observed at 24 h (42.5%). In Experiment II, after different periods of culture (12, 24, 36, or 48 h), the COCs (n=26) were processed for transmission electron microscopy. Expansion of both the cumulus and corona radiate cells occurred between 12 and 24 h in the majority of oocytes concomitant with enlargement of the cumulus cell process endings (CCPEs) in the developed perivitelline space. After 12 h of culture disruption of the junctions between CCPEs and the oolemma was observed together with and breakdown of the GV. For 24-36 h of culture cortical granules had spread and aligned along the oolemma. Signs of degeneration in the cytoplasmic organelles of the oocytes were also observed from less than 36 h. After 48 h of culture, larger vesicles and lipid droplets had appeared in the central part of the oocytes and showed uneven distribution throughout the ooplasm. Predominantly non-penetrating CCPEs were also observed in four oocytes by 48 h. In conclusion, based on both light and electron microscopic evaluations, the optimal culture time for the development of competent Camelus dromedarius oocytes in vitro appears to be 30 h using Hams-F10 medium.