Jaime Palomino

Mitochondrial distribution and meiotic progression in canine oocytes during in vivo and in vitro maturation

The objective was to evaluate mitochondrial distribution, and its relationship to meiotic development, in canine oocytes during in vitro maturation (IVM) at 48, 72, and 96 h, compared to those that were non-matured or in vivo matured (ovulated). The distribution of active mitochondria during canine oocyte maturation (both in vitro and in vivo) was assessed with fluorescence and confocal microscopy using MitoTracker Red (MT-Red), whereas chromatin configuration was concurrently evaluated with fluorescence microscopy and DAPI staining. During IVM, oocytes exhibited changes in mitochondrial organization, ranging from a fine uniform distribution (pattern A), to increasing clustering spread throughout the cytoplasm (pattern B), and to a more perinuclear and cortical distribution (pattern C). Pattern A was mainly observed in germinal vesicle (GV) oocytes (96.4%), primarily in the non-matured group (P < 0.05). Pattern B was seen in all ovulated oocytes which were fully in second metaphase (MII), whereas in IVM oocytes, ∼64% were pattern B, irrespective of duration of culture or stage of nuclear development (P > 0.05). Pattern C was detected in a minor percentage (P < 0.05) of oocytes (mainly those in first metaphase, MI) cultured for 72 or 96 h. In vitro matured oocytes had a minor percentage of pattern B (P < 0.05) and smaller mitochondrial clusters in IVM oocytes than ovulated oocytes, reaching only 4, 11, and 17% of MII at 48, 72, and 96 h, respectively. Thus, although IVM canine oocytes rearranged mitochondria, which could be related to nuclear maturation, they did not consistently proceed to MII, perhaps due to incomplete IVM, confirming that oocytes matured in vitro were less likely to be competent than those matured in vivo.

In vitro sperm penetration through the zona pellucida of immature and in vitro matured oocytes using fresh, chilled and frozen canine semen

The aim of this study was to evaluate the effect of sperm cryopreservation and the maturation state of the oocyte on the time course of canine gamete interaction during co-culture for periods of 1-10 h. Semen samples were obtained by digital stimulation and ejaculates processed as fresh, chilled and frozen samples. Sperm were co-cultured with immature or in vitro mature bitch oocytes for up to 10 h. At hourly intervals, oocytes were evaluated for sperm penetration with epifluorescence microscopy. The results were analyzed statistically using generalized linear models. Spermatozoa treatments had a significant effect on the total percentage of oocyte penetration for both types of oocytes; fresh spermatozoa showed the highest average penetration rate, while frozen sperm showed the lowest value (p<0.05). At the 1st hour of co-culture, chilled and frozen dog sperm had a higher penetration percentage (p<0.05) of in vitro matured canine oocytes (43.6% and 45.7%, respectively) than the fresh sperm had (33.8%). Sperm penetration was directly proportional to the time of incubation, when fresh or chilled sperm were used (P<0.05); in contrast, frozen dog sperm did not change penetration rates with either immature or in vitro matured oocytes over time. There was a significant difference in the average of penetration rate between immature (47.3%) and in vitro matured oocytes (56.6%) throughout the 10h of culturing; irrespective of sperm treatment. The optimal incubation time in terms of maximizing penetration rates probably are dependent on how spermatozoa were processed prior to fertilization.

A scanning electron microscopy study of frozen/thawed dog sperm during in vitro gamete interaction.

The aim of this work was to study the effects of cryopreservation on the binding and penetration of dog spermatozoa to the zona pellucida (ZP) by scanning electron microscopy (SEM). The sperm-rich fraction of six ejaculates from five dogs was divided into two aliquots and washed by centrifugation. One aliquot was processed as fresh control sample and the other aliquot frozen in Tris-fructose extender. Gamete interaction was assessed using in vitro matured bitch oocytes, which were co-incubated for up to 3 h. At hourly intervals after the start of co-incubation, in vitro fertilized (IVF) oocytes were processed by SEM. The results were analysed statistically using the anova test. Differences in binding and penetration of the spermatozoa to the ZP occurred; a lower proportion of oocytes with spermatozoa bound to ZP was observed using frozen sperm (p < 0.05) than with fresh sperm (61%, 57% and 53% vs 42%, 40% and 44% at 1, 2 and 3 h, respectively). The percentage of ZP penetration by fresh sperm was directly proportional to the time of co-incubation (9%, 25% and 34%; p < 0.05); in contrast, no differences were observed in the penetration rate with frozen-thawed sperm (21%, 17% and 21%). More acrosome reacted sperm were observed in frozen sperm than in fresh sperm on the surface of the ZP. The differences in the percentage of binding and penetration between fresh and frozen sperm during the co-culture could indicate that the time course of penetration is faster in frozen-thawed dog spermatozoa than in fresh sperm, but that fresh spermatozoa can penetrate more oocytes over a given period of time, which may be related to their reacted or non-reacted initial status.

Ultrastructural Study of the Canine Zona Pellucida Surface During In Vitro Maturation

The aim of the present study was to compare the ultrastructure of the surface of the zona pellucida (ZP) of immature and in vitro matured dog oocytes using scanning electron microscopy (SEM). Bitch oocytes were collected after ovariohysterectomy; the ovaries were sliced and the released cumulus-oocyte complexes (COCs) were washed with phosphate buffered saline (PBS). The selected COCs were randomly allocated into three groups, two groups were processed after in vitro maturation at both 72 and 96 h and a third group was processed immediately at immature state in PBS medium. After that, oocytes were fixed, critical point dried and viewed by using SEM. The diameters of the outer holes of the ZP were measured on a total of 93 oocytes; the results were analyzed with anova. The mean diameters of holes were different between groups (p < 0.05): 0.69 +/- 0.12, 1.56 +/- 0.19 and 1.42 +/- 0.27 mum, for immature and in vitro matured oocytes for 72 and 96 h, respectively. The difference in the hole sizes between immature and in vitro matured canine oocytes indicates that the ZP surface is related to oocyte maturity in canines.

Growth differentiation factor 9 and bone morphogenetic protein 15 expression in previtellogenic oocytes and during early embryonic development of Yellow-tail Kingfish Seriola lalandi

BackgroundDuring fish oocyte maturation, specific molecules are expressed and accumulated within oocyte until fertilization and embryo development. Special attention have been paid in members of the transforming growth factor (TGF-β) superfamily; growth differentiation factor 9 (GDF9/gdf9) and bone morphogenetic protein 15 (BMP15/bmp15), which exert regulatory functions during oocyte maturation and follicle development. However, little attention has been paid to the involvement of these molecules during embryogenesis considering its importance for the formation of a good quality egg and subsequent embryo survival. The purpose of this study was to analyze the expression of gdf9 and bmp15 in previtellogenic oocytes and during early embryonic development in Seriola lalandi, a pelagic fish with increasing prospect for its aquaculture development, which however, show high mortality at embryo and larval stages.ResultsThrough RT-qPCR it was found that gdf9 expression was higher in previtellogenic oocytes decreasing after ovulation. This expression profile agrees with its participation in early stages of the follicular development. The transcripts for bmp15 also showed the highest levels in previtellogenic oocytes, however this expression was lower than obtained with gdf9. Conversely, in recently spawned oocytes mRNA bmp15 levels were highest than observed to gdf9. This, is consequent with the main role proposed for this growth factor at the final fish oocyte maturation: avoid the ovulation of an immature oocyte. During embryo development, low levels of mRNA were detected to gdf9, with an increase in 48 H post-fertilization embryos. The bmp15 expression did not change throughout development and was higher than gdf9 at 16 cells, blastula and appearance embryos stages.ConclusionsBoth (gdf9 and bmp15) expression profiles in previtellogenic oocytes and newly spawned eggs are consistent with the described functions for these growth factors in vertebrate ovarian physiology in early and late stages of the follicular development. So, these genes could be considered as quality biomarkers at these stages. However, further studies of these proteins throughout folliculogenesis, are necessaries to fully understand their functions during the oocyte formation. In addition, the persistent expression of these growth factors during development, allows us to speculate possible roles in embryonic processes, which must also be addressed.

Western Blot Analysis of Proacrosin/Acrosin in Frozen Dog Sperm During In Vitro Capacitation

Acrosin is an acrosomal protease synthesized as an inactive precursor, proacrosin, which is processed via autoproteolysis into active forms alpha- and beta-acrosin. In this paper, a comparative study on the immunoreactivity of acrosin during in vitro capacitation of frozen and fresh (control) canine sperm using Western blot analysis is reported. Semen samples were obtained by digital stimulation and ejaculates processed as fresh and frozen samples and then capacitated for 0, 30, 60 and 90 min. At each time period, samples were analyzed with monoclonal antibody C5F10 by Western blot. The antibody specifically recognized, in fresh and frozen/thawed spermatozoa, a 40-, 32- and 27-kDa bands corresponding to proacrosin, alpha- and beta-acrosin, respectively, during capacitation. Western immunoblots showed that the beta-acrosin reactivity in fresh sperm was directly proportional to the time of capacitation, whereas a decreased reactivity of active form of acrosin was observed with frozen-thawed sperm (p < 0.05). These results suggest that proacrosin is activated to beta-acrosin earlier in frozen/thawed dog spermatozoa than in fresh dog spermatozoa.

Evaluation of cortical granules and viability of canine oocytes during long-term in vitro maturation

THE morphological appearance of the canine cumulusoocyte complex (COC) is known to influence the rate of in vitro maturation (IVM) (Farstad 2000). The low rate of IVM in dogs might also be related to the unsuitability of the culture medium to support oocyte viability and development. Canine ovulation of oocytes occurs at the germinal vesicle stage; completion of the maturation process continues in the oviduct, requiring an extended period of two to five days (Renton and others 1991). In order to mimic this process in vitro, it is necessary to use prolonged culture periods, and thus the viability of the gametes becomes an issue. Correct culture conditions have been determined by the preservation of oocyte morphology, and thus sustained oocyte viability (Figueiredo and others 1994). In addition to nuclear maturation, proper cytoplasmic and membrane maturation are critical for continued viability of oocytes. Most studies on canine oocytes have evaluated nuclear maturation in culture, but there has been little attention given to cytoplasmic maturation. An oocyte that has not completed cytoplasmic maturation is of poor quality, and thus unable to successfully complete the normal developmental processes (Krisher 2004). Cytoplasmic maturation mainly involves the redistribution of cortical granules around the periphery of the oocyte (Sun 2003), which then contribute to the inhibition polyspermy (Hoodbhoy and Talbot 1994). Considering the long culture period required for IVM in dogs, the aims of this study were to evaluate the viability of the plasma membrane of canine oocytes recovered from the ovaries before and during culture, and to identify and observe the distribution of cortical granules before and after culture. In each experimental replicate, oocytes were obtained from normal bitch ovaries following ovariohysterectomy. In the laboratory, COCs were released by slicing the ovarian cortex. Oocytes with uniform ooplasm and a compact cumulus cell mass were selected. After two washes in phosphate buffered saline (PBS) the COCs were placed in maturation medium (TCM 199; Earle’s salt, buffered with 25mM Hepes; Invitrogen), supplemented with 10 per cent fetal calf serum and 2·5 μl/ml pyruvic solution (11·2 mg/ml pyruvic acid), 10 iu/ml of human chorionic gonadotrophin and 5 μl/ml antibiotic solution (12·2 mg/ml penicillin and 20 mg/ml streptomycin) (Sigma Chemical). The cultures were performed at 38·5°C in a humidified atmosphere of 5 per cent carbon dioxide for up to 96 hours (De los Reyes and others 2005). To verify the viability of oocytes matured in vitro, several oocytes (approximately 15 from each replicate) were submitted for IVM in parallel to the experiment carried out for the cortical granule evaluation. Oocyte viability was assessed before culture and then every 24 hours in culture up to 96 hours. After each culture time the COCs were incubated with 5 μg/ml fluorescein diacetate (FDA; Sigma) in PBS for 5 minutes, and evaluated under an epifluorescence microscope, with green fluorescence indicating cell viability (Barros and others 1982). Evaluation of cortical granules was performed before incubation and after 96 hours of culture. Oocytes were fixed in 2 per cent paraformaldehyde/PBS for 30 minutes, and permeabilised for 5 minutes in PBS containing 0·1 per cent Triton X-100 with 0·3 per cent BSA to block non-specific binding sites. The oocytes were incubated with 20 μg/ml lectin Lens culinaris agglutinin (LCA) coupled to fluorescein isothiocyanate, in PBS for 30 minutes. The oocytes were washed and subsequently mounted with Vectashield (Vector Laboratories) under coverslips supported with vaseline/paraffin dots. The samples were evaluated with an epifluorescence microscope (UV emission 480 nm) (Nikon Optiphot II; Nikon).

Differential expression of GDF-9 and BMP- 15 during follicular development in canine ovaries evaluated by flow cytometry.

Growth differentiation factor 9 (GDF-9) and bone morphogenetic protein 15 (BMP-15) play important functions in follicular and oocyte development in many species. This study evaluated the dynamic expression of GDF-9 and BMP-15 in canine follicles cells using flow cytometry analysis. Follicular cells were removed from three sizes of antral follicles (small, medium and large) from ovaries of bitches throughout the estrus cycle. Cells were incubated with anti-human GDF-9 polyclonal and anti-mouse BMP-15 monoclonal antibodies. A size and complexity discriminatory gate was used for the cytometryc analysis in the initial dot plot and, additionally, a CD45 marker for leukocyte and propidium iodide (PI) were used for erythrocyte and debris discrimination. The evidence corroborated the presence of both proteins in canine follicle cells, but these proteins were not expressed equally during follicular development. The results analyzed by ANOVA showed that GDF-9 expression decreased (P<0.05) during follicular growth in anestrus and proestrous/estrous, but increased in diestrus (P<0.05). The expression levels of BMP-15 rose (P<0.05) from small to medium sizes in anestrous without changing at diestrus. Small antral follicles expressed the highest values of GDF-9 at anestrus while only BMP-15 showed higher value in small antral follicles at proestrous-estrus compared to diestrus and anestrus. Both proteins decreased in proestrous/estrous (P<0.05) with increasing follicle size, registering the lowest levels in large follicles. The flow cytometric assay was able to assess GDF-9 and BMP-15 expression in canine follicular cells, showing that these proteins were differentially expressed during follicular development, possibly related to the special features of canine reproduction.

Golgi apparatus and endoplasmic reticulum dynamic during meiotic development in canine oocytes.

The Golgi apparatus (GA) and endoplasmic reticulum (ER) play a central role in the events related to intracellular trafficking distribution. This work evaluated the dynamics and localization of the GA and ER in canine oocytes during meiotic development in vitro. Cumulus-oocytes complexes (COCs) from ovaries of adult bitches were incubated for IVM for 0, 48, 72 and 96 h. At each time, the nuclear status was determined using DAPI staining, and the GA was evaluated by immunofluorescence using two antibodies against Golgi proteins: GM130 and Giantin. ER was analysed with fluorescent lipid probes (ER-Tracker), for living cells. Golgi structures were homogeneous in the cytoplasm in non-matured oocytes, mainly in those GV-arrested oocytes. In contrast, at 48 h and from GVBD stage, the immunolocalization began to be subcortical, increasing at 72 h and 96 h. Meiotic development increased with time and the majority of oocytes at MI-MII stages showed cortical distribution of Golgi structure. Living ZP intact non-matured oocytes showed a reticular pattern of ER that covered oocyte cortex. Confocal microscopy showed that, in all levels cuts the fluorescence marks were located in the cortical region, irrespective of culture time. The changes and localization in these organelles during IVM might be related to meiotic development, but in a non-synchronous manner.

Acrosin release and acrosin activity during incubation in capacitating media using fresh and frozen-thawed dog sperm

We evaluated the effect of time and temperature on acrosin release from the acrosomal cap and the activity of this enzyme during in vitro capacitation in fresh and frozen/thawed dog sperm. Sperm-rich fractions of six ejaculates from three dogs were processed as fresh and frozen samples. Each sperm sample was incubated in canine capacitation medium (CCM) for 0, 1, 2 and 3 h at 20°C and at 37°C. After incubation, the samples were assessed by the indirect immunofluorescent staining technique. The probability of having unlabeled sperm (PUS), indicating acrosin loss, was modelled by a binomial distribution using logistic regression. There was a linear relationship between PUS and time at both temperatures (p<0.001); however, a major percentage of unlabeled sperm was observed in frozen/thawed samples soon after incubation, indicating that the release of acrosin was affected by capacitation time, mainly in frozen samples. Temperature influenced acrosin release only in cryopreserved sperm (p<0.05). Acrosin activity was measured by digestion halos on slides coated with gelatin-substrate film during each time period; a significant increase in the number of large halos was observed in fresh samples throughout the experiment, whereas frozen/thawed sperm showed a decreased rate of halo diameters during culture. Thus, there appears to differences between fresh and frozen dog sperm in terms of acrosin release and the level of acrosin activity in the course of in vitro capacitation.