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PubMed1991

Fertility-related changes in maternal body composition among the Au of Papua New Guinea.

Evolutionary theory predicts that organisms make trade-offs between their somatic and reproductive energy budgets. Thus every round of reproduction should result in a concomitant decline in the parents' total energy reserves. Among humans this prediction was corroborated more than 25 years ago when fertility-related nutritional depletion was reported among mothers in the Highlands of New Guinea (Jelliffe and Maddocks, 1964). More recently, however, a number of studies of fertility and maternal nutritional status in both developed and developing nations have reported fertility-related increases in various indices of adiposity and lean body mass. Such findings have called the so-called "maternal depletion syndrome" into question, and have raised serious doubts as to whether the phenomenon is widely generalizable to all populations. In light of this recent controversy, data are presented here on fertility-related changes in maternal adiposity and lean body mass among the Au, a lowland forager-horticulturalist population in Papua New Guinea. While both a short-term decline in adiposity following childbirth, and a long-term fertility-related decline are seen among more traditional Au, individuals with a regular source of wage-income show only the former. There are no significant changes in lean body mass with increasing fertility in either group. The finding of significant socioeconomic variation in the capacity to withstand the stress of repeated reproduction even within this one extremely rural area of Papua New Guinea may lend insight into why previous studies have been unable to find evidence of maternal depletion. The fertility-related decline in adiposity that is reported for the more traditional Au is consistent with the predictions of evolutionary theory.

Adipose Tissue↗
PubMed1983

Actin-mediated surface motility during sea urchin fertilization.

The sea urchin egg at fertilization is an ideal model in which to study actin-mediated surface activity. Electron microscopy of unfertilized eggs demonstrates the presence of thousands of well-arrayed short microvilli, which appear supported by cytochalasin-sensitive actin oligomers as detected with rhodamine-labeled phalloidin staining of permeabilized eggs. At insemination, the previously short microvilli elongate and cluster around the successful sperm during incorporation. Phalloidin staining demonstrates a tremendous recruitement of polymerized actin into the site of sperm incorporation, resulting in the formation of the fertilization cone. Fertilization of cytochalasin-treated eggs results in the normal activation of the metabolic and bioelectric events, but sperm incorporation does not occur since the localized actin assembly required for fertilization cone formation is precluded. After sperm incorporation, the entire fertilized surface is restructured, as a result of a massive polymerization of actin to produce a burst in microvillar elongation. Addition of cytochalasin to eggs immediately following sperm incorporation demonstrates the recruitment of actin assembly for the proper progression through the first cell cycle. During normal cell division, the egg surface retains the long microvilli. The furrow which forms at cytokinesis does not appear as a unique new structure, but rather as a reorganization of the cortical microfilaments. Quantitative fluorescence microscopy argues against an increase in microfilaments during early cytokinesis. At the latest stages of cytokinesis, a thickening of the cortical actin is noted, which could possibly be interpreted as a contractile ring. A minor basal level of actin assembly with numerous nucleation sites in unfertilized eggs and a tremendous but localized assembly of microfilaments surrounding the sperm during incorporation, followed by a massive global microfilament assembly event to elongate the fertilized egg microvilli resulting later in the reorganization of these microfilaments to produce the forces necessary for cytokinesis, highlight the utility of the study of sea urchin eggs at fertilization for understanding actin-membrane interactions.

Actins↗
PubMed1992

Fertilization alters the orientation of pigment granule saltations in Arbacia eggs.

Unfertilized eggs of the sea urchin Arbacia punctulata contain pigment granules distributed throughout their cytoplasm. During the first 15 minutes after fertilization, these vesicles move out to the cortex where they become firmly anchored. We have used time-lapse video differential interference microscopy to analyze the motility of these organelles in unfertilized and fertilized Arbacia eggs. Pigment granules exhibit saltatory movement in both unfertilized and fertilized eggs. Quantitation of vesicle saltations before and after fertilization demonstrates that while there is no significant difference in the speed or path-length of vesicle movement, there is a dramatic change in the orientation of these saltations. Saltations in the unfertilized egg are very non-radial and are as likely to be directed toward the cortex as away. In contrast, saltations in the fertilized egg are more radially oriented and more likely to be cortically directed. This transition must reflect underlying changes in the cellular structures necessary for pigment granule saltations. The change in the orientation of pigment granule saltations following fertilization requires both a transient increase in the cytoplasmic concentration of Ca2+ and an elevation of cytoplasmic pH. Similarly, the ability of pigment granules to adhere to the cortex requires both the transient elevation of cytoplasmic Ca2+ and the alkalinization of the cytoplasm. As the reorganization of cortical actin at fertilization is regulated by these ionic fluxes, and both movement and adhesion are sensitive to cytochalasins, we hypothesize that the alterations in directed motility and adhesion reflect underlying changes in the actin cytoskeleton.

Animals↗
PubMedDate not supplied

Sperm morphology assessment as an indicator of human fertilizing capacity.

Semen samples from 95 men were examined by routine semen analysis and specific histologic staining for sperm morphology. The men were classified into fertile and infertile groups on the basis of clinical evaluation and in vitro testing, using the zona-free hamster egg penetration assay. Thirty men were designated as fertile, as they had fathered children and their sperm showed penetration of greater than 20% of the zona-free hamster eggs with the in vitro fertilization test. Subjects classified as infertile were men from infertile couples whose wives showed no evidence of infertility and whose in vitro fertilization ability was 10% or less. The semen analysis parameters of the fertile and infertile groups were significantly different. Fertile men had mean values of 108 X 10(6) sperm/ml, 61% motile, 64% normal forms (sperm with oval morphology), and 69% penetration in vitro. The mean values for infertile men were significantly lower: 42 X 10(6) sperm/ml, 45% motile, 32% normal forms, and 3.2% penetration in vitro. The importance of the morphology parameter was revealed by comparison of the percentage of penetration with count, motility, and morphology. Penetration correlated best with morphology (r = 0.730) as compared with motility (r = 0.451) and count (r = 0.605). The distribution of abnormalities in the infertile group revealed 81.6% with abnormal morphology (less than 50%), 53.8% with abnormal motility (less than 50%), and 38.5% with abnormal count (less than 20 million/ml). As a single parameter, decreased number of normal forms appears to be a good indicator for clinical infertility if in vitro fertilization testing is not available.

Animals↗
PubMedDate not supplied

Relationships between computerized measurements of motion of frozen-thawed bull spermatozoa and fertility.

A computerized system (CellSoft, CRYO Resources, Ltd.) was validated using video tapes of frozen-thawed bull spermatozoa diluted in filtered (0.2 micron) egg yolk-citrate extender (8 X 10(6) spermatozoa/ml) and analyzed at 30 frames/sec for the percentage of motile spermatozoa (greater than or equal to 20 microns/sec) and linear velocity of motile spermatozoa. Virtually all motile spermatozoa were detected and debris rarely were classified as immotile spermatozoa if the extender had been filtered. Variation about the mean for percent motile cells was similar when only 12 rather than 20 or 30 frames/field were analyzed. Use of 20 frames/field was adequate to determine the percentage of motile bull spermatozoa. Five mixtures of live and killed spermatozoa were analyzed (four bulls) to evaluate accuracy. Percent motile spermatozoa was correlated (r = 0.97) with the ratio of live:killed spermatozoa. Mean linear velocity of motile spermatozoa was similar for each mixture (P greater than 0.05). To further evaluate accuracy, percent motile spermatozoa was determined by computer and by "track motility" (20 samples; 0 to 63% motile spermatozoa); values were correlated (r = 0.95). The system was precise (CV of 6% based on triplicate analyses of the same samples) and reasonably accurate for evaluating bull sperm motility if the extender had been filtered and 20 to 25 fields (greater than or equal to 200 spermatozoa) were evaluated. Correlations between measurements of sperm motion and fertility were studied using cryopreserved semen from two fertility trials. For the first, 75-day nonreturn rate data for 20 samples of bull semen (10 bulls) were not significantly correlated with evaluations made by CellSoft. For the second fertility trial, the competitive fertility index (a measure of relative fertility) for nine bulls was correlated (r greater than or equal to 0.68; P less than 0.05) with percent motile spermatozoa, linear velocity and straight-line velocity. Multiple correlations based on six characteristics evaluated by CellSoft, at 0 or 1.5 hours, and the competitive fertility index were greater than or equal to 0.94. Based on the latter data, the system may facilitate prediction of the relative fertility of bull spermatozoa.

Animals↗
PubMed1991

Fertilization of the mouse oocyte.

This paper presents morphological data on mouse oocyte maturation and fertilization, reviews evidence supporting the existence of a sperm receptor, and suggests future directions for this line of research. We used scanning electron microscopy to examine oocytes under a variety of conditions. The surfaces of mature mouse oocytes are seen to be similar whether maturation occurs in vivo or in vitro. Capacitated sperm (both acrosome-intact and acrosome-reacted) are observed to interact with the microvilli of the oocyte surface. Little is known about oocyte surface proteins that mediate fertilization in mammals. Data of ours and others show that enzyme treatment of live unfertilized eggs interferes with sperm binding. Enzyme treatment (trypsin, chymotrypsin treatment, or pronase) reduces the number of bound sperm, suggesting removal of a surface protein involved in fertilization. Trypsin treatment also causes some lengthening of surface microvilli in a belt surrounding the metaphase II region. After metabolic labeling, proteins of zona-free unfertilized eggs can be identified by SDS-PAGE and autoradiography. Comparison of 1-D gels from untreated and enzyme-treated eggs show the nearly complete disappearance of proteins of 263, 170, 137, 97, and 87 kD after digestion; an increase in a 66 kD protein after trypsin or chymotrypsin; and a major new band of 20 kD after chymotrypsin treatment. Fertilized eggs show the loss of a 255-265 kD band among other changes. Proteins of 97 kD and 87 kD were seen previously by surface labeling (Johnson and Calarco, 1980b), and our 97 kD and 66 kD bands are similar in molecular weight to those identified by Boldt et al. (1989). Taken together, these data identify a few candidate proteins for the role of sperm receptor on the egg surface. Future work should focus on identification of the surface protein(s) which functions physiologically in fertilization by developing fertilization-blocking antibodies. Relatedness to other mammalian sperm receptors and identification of the genes involved would provide valuable information to our understanding of fertilization and to the problems of infertility and contraception.

Animals↗
PubMed1975

Fertilizing ability of mouse sperm from different epididymal regions and after washing and centrifugation.

The ability of caput, corpus, and cauda epididymal and vasa deferentia mouse sperm to fertilize eggs in vitro was investigated. Cauda epididymal sperm fertilized 45 of 54 ova, whereas caput and corpus sperm fertilized a negligible number of ova, thus indicating their immaturity. Vasa deferentia sperm fertilized only 10 of 52 ova and their reduced fertility may be due to aging in vivo. No difference in preimplantation development of the resulting zygotes with respect to the sperm source was observed. Three centrifugations and resuspensions of cauda epididymal sperm in fresh medium did not affect their fertilizing ability. I conclude that fertilization in vitro can occur after removal of epididymal secretions.

Animals↗
PubMed1987

The Chaetopterus vitelline envelope is not necessary for the gamete interactions that lead to fertilization.

It has been recently shown that, in several genera of annelids, including Chaetopterus, fertilizing sperm attach to and fuse with egg microvilli which penetrate the vitelline envelope. This suggests that the annelid vitelline envelope may have no direct or obligatory role in normal fertilization. The present study was undertaken to investigate the involvement of the vitelline envelope in fertilization in Chaetopterus experimentally, by examining the fertilization of vitelline envelope-free eggs quantitatively and qualitatively. Brief exposure of the eggs to isotonic sucrose-EDTA removed the vitelline envelope as determined by both phase-contrast and electron microscopy, rendered the eggs more sensitive to polyspermy and substantially reduced the binding of supernumerary sperm to eggs but did not decrease fertilizability as determined by sperm dilution assay and did not make the eggs more sensitive to cross-fertilization. The events of fertilization were examined by electron microscopy and found to be very similar in vitelline envelope-free eggs to those in intact eggs. We conclude that the vitelline envelope in Chaetopterus has binding sites for sperm but that it has no obligatory role in fertilization and is primarily involved in the prevention of polyspermy.

Animals↗
PubMed1990

In vitro fertilization of Siberian hamster oocytes.

Siberian hamsters were superovulated and various media were tested in an effort to fertilize the recovered oocytes in vitro. The highest percentage of fertilized ova was achieved by using a modified Tyrode's medium, designated MT (Bavister, J. Reprod. Fertil., 18:544-545, '69), previously formulated to fertilize Syrian hamster ova in vitro. Spermatozoa incubated in this medium in a concentrated state overnight (14 hr) and then diluted (1 hr) fertilized 39% of the ova. Similar results (40%) were obtained with this medium by adding 20% human follicular fluid to fresh concentrated sperm for 30 min and then diluting the sperm for 2-3 hr prior to the addition of ova. Ova fertilized in vitro cleaved to the two-cell stage but failed to develop any further in culture. Two-cell embryos recovered from mated hamsters and cultured did not undergo additional cleavage. Four-cell embryos collected from mated females and cultured cleaved to the six- to eight-cell stage and stopped. Techniques and media used for fertilizing large numbers of Syrian and Chinese hamster ova in vitro will have to be modified to achieve the same degree of success in the Siberian hamster.

Animals↗
PubMed1991

Culture medium and protein supplementation influence in vitro fertilization and embryo development in the domestic cat.

The influence of culture medium and protein supplements on in vitro fertilization (IVF) and morula-to-blastocyst development in culture was examined in the domestic cat. In Study I, follicular oocytes were fertilized and cultured in 1) modified Krebs Ringer bicarbonate (mKRB); 2) modified Tyrode's solution (TALP) without phosphate or glucose; or 3) Ham's F10. All media contained bovine serum albumin (BSA). Fertilization rates were similar (P greater than .05) among mKRB (75.0%), TALP (70.6%), and Ham's F10 (80.0%) treatments. Compared to TALP (77.8%), more (P less than .05) embryos in Ham's F10 (95.0%) developed to the morula stage; development of mKRB embryos (88.9%) was intermediate and not different (P greater than .05). Study II evaluated the effects of protein availability and type on IVF and embryo growth. Ham's F10 was supplemented with polyvinylalcohol (PVA, 2 mg/ml), BSA (4 mg/ml), fetal calf serum (FCS, 5%), or estrous cat serum (ECS, 5%) and used to fertilize and culture embryos. Fertilization was enhanced (P less than .05) using either FCS (84.0%) or ECS (85.2%) compared to PVA (67.3%). Oocytes exposed to BSA fertilized at a rate (76.1%) similar (P greater than .05) to other treatments. Embryos exposed to all four treatment groups (PVA, 82.8%; BSA, 82.8%; FCS, 92.9%; or ECS, 97.8%) were equally capable (P greater than .05) of becoming morulae. However, more FCS- or ECS-supplemented morulae continued to the early blastocyst stage (30.8%, 22.2%, respectively, P less than .05) than PVA- (10.3%) or BSA- (13.8%) exposed morulae. In the domestic cat IVF system, the type of medium and protein supplement used appears to have a greater impact on embryo development in vitro than on fertilization.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Developmental changes in the incidence of chromosome anomalies of bovine embryos fertilized in vitro.

In total, 196 two- to 32-cell bovine embryo and 104 blastocysts were obtained by the in vitro fertilization of follicular oocytes matured in vitro, and 15 blastocysts fertilized in vivo were used. Chromosomal anomalies in these embryos and the inner cell mass (ICM) separated immunologically were investigated. Chromosomal anomalies were observed in 12.1% (5/41) of 2-cell embryos, 20.0-36.4% of 4- to 16-cell embryos, 7.1% (1/14) of 17- to 32-cell embryos, 44.2% (15/34) of blastocysts, and 18.6% (13/70) of ICM cells derived from in vitro fertilization. These anomalies were mainly 3N and 4N at 2-cell stage, 1N and 1N/2N at 4- to 32-cell stages, and 2N/4N in blastocysts and in their ICM cells. Chromosomal anomalies of blastocysts from in vivo fertilization and their ICM were observed in 20.0% (1/5) of blastocysts and 33.3% (3/9) of ICM cells and these compositions were mainly 2N/4N. These results indicate that the abnormalities at early and blastocyst stages of embryos derived from in vitro fertilization were caused by abnormal fertilization in vitro and abnormal cleavage, respectively. Furthermore, a definite location of the chromosomal anomalies was observed in the trophectoderm of blastocysts derived from in vitro fertilization.

Animals↗
PubMed2006

The outermost layer of egg-jelly is crucial to successful fertilization in the newt, Cynops pyrrhogaster.

The significance of egg-jelly layers in internal fertilization was evaluated in the newt, Cynops pyrrhogaster. In this species, six egg-jelly layers, J1, J2, J3, J4, J5 and the outermost J6 layers, are accumulated on the surface of the fertilizable eggs in pars convoluta of the oviduct. When a large number of sperm (about 6 x 10(5)) were placed on eggs having different numbers of jelly layers, all the eggs were fully fertilized, although many of the eggs developed abnormally. Upon insemination using about 600 sperm, only eggs with the full set of jelly layers were fertilized at a high rate with normal development. Since around 300 (the range of 48-1,192) sperm were observed on and in the egg-jelly in naturally spawned eggs, we conclude that the J6 layer must be present on the outermost surface of the egg-jelly for successful internal fertilization of the newt. Previous studies have suggested that the J6 layer is a prerequisite for the initiation of sperm motility and the acrosome reaction. In the present study, the fertilization rate decreased in eggs with a full set of jelly layers when inseminated using acrosome-reacted and motile sperm. However, the fertilization rate was high when motile sperm with intact acrosome was used. These results suggest that induction of the sperm acrosome reaction in the J6 layer is an important step in the internal fertilization of the newt.

Acrosome Reaction↗
PubMed1990

Effect of oviduct cells on the incidence of polyspermy in pig eggs fertilized in vitro.

The consequences of interactions between porcine sperm, eggs, and oviduct cells before and during fertilization in vitro (IVF) has been examined with particular reference to the block to polyspermy. The pattern of polypeptides secreted by porcine oviduct epithelial cells has been determined and its effects on sperm both during pre-fertilization co-culture and during fertilization have been examined. In standard IVF procedures with no oviduct cell involvement, high rates of penetration (91%) were accompanied by equally high rates of multiple sperm penetration (91% of penetrated eggs). Fertilization on oviduct cell monolayers or a combination of 1 h co-culture of sperm and oviduct cells before the addition of in vitro matured oocytes did not reduce polyspermy. However, a sperm-oviduct cell co-culture period of 2.5 h followed by IVF on oviduct cells selectively reduced the rate of polyspermy by 40% and 50% in two separate series of trials (United Kingdom and Japan, respectively): Overall fertilization rates after this treatment were high (95% or 84%, respectively). A 3.5 h period of pre-fertilization co-culture further reduced polyspermy to only 14% of penetrated eggs, but this treatment was accompanied by a sharp drop in the fertilization rate from an overall mean of 88% for all other groups to 19% after 3.5 h co-culture.

Animals↗
PubMed1991

Improvement of fertilizing performance by normal and abnormal mouse semen after zona opening of mature oocytes.

The usefulness of opening the zona pellucida by partial zona dissection (PZD) to enhance fertilization of mature mouse oocytes was studied after insemination with three types of semen: normal and diluted semen and semen from long-term-vasectomized males. Zona opening did not by itself induce parthenogenetic cleavage of mature oocytes and did not significantly increase mono- and polyspermic fertilization of oocytes inseminated with normal semen. While a fertilization rate of 62% was obtained among intact oocytes, of which 4.5% were polyspermic, a 66.8% fertilization rate was observed among PZD oocytes, 6.3% of which were polyspermic. However, after using diluted semen, only 54 of 193 intact oocytes were fertilized (28%), and PZD improved the fertilization rate to 65.4%. Cleavage rate of nonmanipulated oocytes inseminated with abnormal semen from vasectomized males was dramatically decreased in comparison with those inseminated with normal semen (7.6% vs. 65%). PZD induced a moderate but significant improvement of fertilization performance when using this abnormal semen (19.6%).

Animals↗
PubMed1992

Fertilization and developmental competence of bovine oocytes derived from different categories of antral follicles.

This study investigated the capacity of healthy oocytes derived from follicles of different size to undergo normal fertilization and early embryonic development in vitro and full-term development in vivo. Ovaries were collected from a local abattoir and dissected and classified as follows: group A, greater than 4-8 mm (large); group B, greater than 2-4 mm (medium); and group C, greater than 1-2 mm (small). Oocytes were isolated by puncturing the follicular wall and pressing of the follicle. Only healthy-looking cumulus-oocyte complexes (COC) were used for in vitro maturation. Oocytes were fertilized in vitro by frozen/thawed semen from one bull. Approximately one-fourth of all oocytes was fixed and stained 15-20 h after fertilization, to determine penetration rates. The remaining eggs were transferred to culture medium and were cultivated for up to 9.5 days. Cleavage was observed 65 h and 7 days after fertilization. Expanded, hatching, and hatched blastocysts were fixed and stained after 9.5 days of culture. A total of 86 blastocysts derived from group A and B oocytes was nonsurgically transferred to synchronized recipients 7-8 days after onset of culture. A total of 6.624 follicles were dissected from 265 ovaries, and 1,485 oocytes were isolated from 1,671 group A follicles, 3,509 oocytes from 3,862 group B follicles, and 965 oocytes from 1,091 group C follicles. The fertilization rate, rate of normal fertilization, rate of polyspermy, and rate of other abnormal fertilization features were as follows: group A, 84.9%, 43.2%, 34.1%, 7.6%; group B, 83.6%, 44.8%, 31.1%, 7.8%; and group C, 61.7%, 13.1%, 33.7%, 19.1%.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Microfilaments during sea urchin fertilization: fluorescence detection with rhodaminyl phalloidin.

Rhodaminyl-labeled phalloidin is used to demonstrate the distribution of microfilaments during fertilization and early development in eggs of the sea urchins Arbacia punctulata and Lytechinus variegatus. The surface of unfertilized eggs have numerous punctate fluorescence sites at which rhodaminyl phalloidin binds, indicating the presence of actin oligomers or polymers. During fertilization this punctate pattern of fluorescence begins to change. Within thirty seconds of insemination, the fertilization cone is first detectable with this technique as an erect structure on the surface of the egg. The fertilization cone grows to a maximum size by 8-9 minutes, and is resorbed by 16 minutes after insemination. The surface of the fertilized egg displays numerous fluorescent fibers by 10 minutes after rather than the punctate fluorescence observed in unfertilized eggs, indicative of the burst of microfilament assembly resulting in microvillar elongation. The elongated microfilaments persist through cytokinesis. Staining is also detected throughout the cortices of unfertilized, fertilized, and cleaving eggs. Cytochalasin E (10 micromoles, 30 min) prevents microfilament elongation and cytokinesis and reduces the cortical staining intensity after fertilization. At cleavage, contractile rings, appearing as narrow equatorial bundles of fibers, have been detected in Lytechinus variegatus as transient structures.

Actin Cytoskeleton↗
PubMed2002

Consequences of bovine oocyte maturation, fertilization or early embryo development in vitro versus in vivo: implications for blastocyst yield and blastocyst quality.

The aim of this study is to examine the effect of bovine oocyte maturation, fertilization or culture in vivo or in vitro on the proportion of oocytes reaching the blastocyst stage, and on blastocyst quality as measured by survival following vitrification. In Experiment 1, 4 groups of oocytes were used: (1) immature oocytes from 2-6 mm follicles; (2) immature oocytes from > 6 mm follicles; (3) immature oocytes recovered in vivo just before the LH surge; and (4) in vivo matured oocytes. Significantly more blastocysts developed from oocytes matured in vivo than those recovered just before the LH surge or than oocytes from 2-6 mm follicles. Results from > 6 mm follicles were intermediate. All blastocysts had low survival following vitrification. In Experiment 2, in vivo matured oocytes were either (1) fertilized in vitro or (2) fertilized in vivo by artificial insemination and the resulting presumptive zygotes recovered on day 1. Both groups were then cultured in vitro. In vivo fertilized oocytes had a significantly higher blastocyst yield than those fertilized in vitro. Blastocyst quality was similar between the groups. Both groups had low survival following vitrification. In Experiment 3a, presumptive zygotes produced by in vitro maturation (IVM)/fertilization (IVF) were cultured either in vitro in synthetic oviduct fluid, or in vivo in the ewe oviduct. In Experiment 3b, in vivo matured/in vivo fertilized zygotes were either surgically recovered on day 1 and cultured in vitro in synthetic oviduct fluid, or were nonsurgically recovered on day 7. There was no difference in blastocyst yields between groups of zygotes originating from the same source (in vivo or in vitro fertilization) irrespective of whether culture took place in vivo or in vitro. However, there was a dramatic effect on blastocyst quality with those blastocysts produced following in vivo culture surviving vitrification at significantly higher rates than their in vitro cultured counterparts. Collectively, these results indicate that the intrinsic quality of the oocyte is the main factor affecting blastocyst yields, while the conditions of embryo culture have a crucial role in determining blastocyst quality.

Animals↗
PubMed2005

Involvement of the pentose phosphate pathway and redox regulation in fertilization in the mouse.

Glucose metabolism is necessary for successful fertilization in the mouse. Both spermatozoa and oocytes metabolize glucose through the pentose phosphate pathway (PPP), and NADPH appears required for gamete fusion. The aims of this study were to further characterize the utilization of glucose by the fertilizing spermatozoon and the fertilized oocyte, to demonstrate the importance of the PPP in different steps of fertilization, and to examine whether the beneficial effect of glucose could be mediated by a NADPH-dependent enzyme involved in redox regulation. By using a fluorescent analog of 2-deoxyglucose, glucose uptake was evidenced in both the head and flagellum of motile spermatozoa. After sperm-oocyte fusion, an increase in glucose uptake by the fertilized oocyte was observed but not before the formation of the male and female pronuclei. By using a microphotometric technique, activity of glucose 6-phosphate dehydrogenase (G6PDH), the key enzyme of the PPP, was localized to the sperm head and midpiece. When epididymal spermatozoa were released into a glucose-containing medium, the NADPH/NADP ratio increased with capacitation. Sperm-oocyte fusion and meiosis reinitiation of the fertilized oocyte was inhibited by the PPP inhibitor 6-aminonicotinamide (6-AN); inhibition of sperm-oocyte fusion was relieved by NADPH. Sperm-oocyte fusion and meiosis reinitiation were also inhibited by diphenylamine iodonium, which is a flavoenzyme inhibitor reported to prevent reactive oxygen species (ROS) generation in mouse spermatozoa and embryos. These findings indicate that the PPP is involved in different steps of fertilization. Subsequent regulation of a NADPH-dependent flavoenzyme responsible of ROS production is envisaged.

Animals↗