Biomedical subjects

H J Leese

Publications and source records attributed to H J Leese.

At least 19 recordsLinked to original sources

PubMed2006

Fluorescence resonance energy transfer analysis of mitochondrial:lipid association in the porcine oocyte.

The role of endogenous lipid in the provision of energy during in vitro maturation of immature porcine oocytes has been studied. Fluorescence resonance energy transfer (FRET) acceptor bleaching methods have been used to examine mitochondrial:lipid droplet co-localisation in live oocytes. FRET experiments demonstrate whether organelles are within the FRET-distance (i.e. 6-10 nm), thus showing true association on a molecular scale. Immature and in vitro-matured porcine oocytes were stained with Mitotracker Green (MTG; mitochondria) and Nile Red (NR; lipid droplets). The data indicated sufficient overlap between MTG emission and NR excitation to support a FRET reaction and that mitochondria and lipid droplets were sufficiently co-localised for a FRET reaction to occur. When NR-stained lipid droplets were specifically bleached, a significant increase in the MTG signal in stained mitochondria was observed (FRET efficiency, E=22.2 +/- 3.18%). These results strongly suggest a metabolic role for lipid metabolism during oocyte maturation. This conclusion was reinforced by the use of inhibitors of fatty acid beta-oxidation, methyl palmoxirate or mercaptoacetate, exposure to which during oocyte maturation led to developmental failure post-fertilisation. These data provide strong evidence that MTG and NR can act as a FRET pair and that in porcine oocytes, mitochondria and lipid droplets lie within 6-10 nm of each other, indicating association on a molecular scale. The findings also suggest that endogenous triglycerides play an important role in energy metabolism during porcine in vitro maturation.

Aldehydes↗

PubMed2005

Amino acid metabolism of the porcine blastocyst.

The pattern of depletion and appearance of a mixture of amino acids by single porcine blastocysts incubated in two different media has been determined non-invasively using high performance liquid chromatography. Zygotes were produced by the in vitro fertilisation of in vitro-matured, abattoir-derived immature oocytes and cultured in medium NCSU 23 with or without amino acids. Embryos grown in the absence of amino acids up to the blastocyst stage were transferred to amino acid-containing culture medium for measurement of turnover (Experiment 1). Blastocysts grown in NCSU 23+amino acids were transferred into fresh droplets of the same medium (Experiment 2). Although the specific pattern of amino acid production and depletion varied between experiments, a general pattern emerged, with arginine being significantly depleted (p<0.001) and alanine consistently appearing in the media, in quantities that varied depending with culture conditions. The data suggest that arginine is important during porcine blastocyst development, most likely contributing to the formation of nitric oxide and polyamines and that alanine is produced as a means of disposing of excess amino groups. A model for the interactions of amino acids during porcine early embryo development is proposed. The profile of amino acid metabolism by porcine blastocysts is qualitatively and quantitatively similar to that given by human embryos during the morula:blastocyst transition suggesting that the porcine blastocyst is a good model for the human.

Alanine↗

PubMed2005

A biomimetic tissue from cultured normal human urothelial cells: analysis of physiological function.

The urinary bladder and associated tract is lined by the urothelium. Once considered as just an impermeable epithelium, it is becoming evident that the urothelium not only functions as a volume-accommodating urinary barrier but has additional roles, including sensory signaling. Lack of access to normal human urothelium has hampered physiological investigation, and although cell culture systems have been developed, there has been a failure to demonstrate that normal human urothelial (NHU) cells grown in vitro retain the capacity to form a functional differentiated urothelium. The aim of this study was to develop a biomimetic human urothelium from NHU cell cultures. Urothelial cells isolated from normal human urothelium and serially propagated as monolayers in serum-free culture were homogeneous and adopted a proliferative, nondifferentiated phenotype. In the presence of serum and physiological concentrations of calcium, these cells could be reproducibly induced to form stratified urothelia consisting of basal, intermediate, and superficial cells, with differential expression of cytokeratins and superficial tight junctions. Functionally, the neotissues showed characteristics of native urothelium, including high transepithelial electrical resistance of >3,000 Omega.cm(2), apical membrane-restricted amiloride-sensitive sodium ion channels, basal expression of Na(+)-K(+)-ATPase, and low diffusive permeability to urea, water, and dextran. This model represents major progress in developing a biomimetic human urothelial culture model to explore molecular and functional relationships in normal and dysfunctional bladder physiology.

Adult↗

PubMed2004

Identification of viable embryos in IVF by non-invasive measurement of amino acid turnover.

BACKGROUND: IVF is limited by low success rates and an unacceptably high multiple pregnancy rate. These outcomes would be improved significantly if a single embryo of high viability could be replaced in each treatment cycle, but widespread acceptance of such a policy is hindered by the lack of predictive factors for embryo selection. We have conducted a retrospective clinical study of a novel non-invasive method of embryo selection based on the depletion/appearance of amino acids in the culture medium. METHODS: Fifty-three cycles of IVF treatment using ICSI were studied. Embryos were cultured for 24 h in 4 microl drops of medium containing a physiological mixture of 18 amino acids. The spent medium was analysed for amino acid content by high performance liquid chromatography. RESULTS: The turnover of three amino acids, Asn, Gly and Leu, was significantly correlated with a clinical pregnancy and live birth. These correlations were independent of known predictors, such as female age, basal levels of FSH, embryo cell number and embryo morphological grade. CONCLUSIONS: Non-invasive assay of amino acid turnover has the potential to improve significantly the prospective selection of the most viable embryos, or single embryo, for replacement in an IVF cycle.

Adult↗

PubMed2004

Effect of inhibiting nitric oxide production on mouse preimplantation embryo development and metabolism.

Nitric oxide (NO) is a free radical that functions as a cell signaling molecule but at high concentrations can be toxic. It is formed from arginine, which is consumed by the mouse blastocyst, but its effect on early embryo development has been little studied. In this study, the role of NO in mouse preimplantation development has been examined in terms of developmental rate and oxidative metabolism. Zygotes were cultured in one of four media; potassium simplex optimization medium (KSOM), KSOM with amino acids (KSOMaa), KSOM without glutamine (KSOM-glut), or KSOM with 0.5 mM arginine (KSOMarg) +/- l-NAME (a specific inhibitor of NO production). End points were Day 4 blastocyst rates, cell counts determined using bisbenzimide and oxygen consumption. In KSOM and KSOM-glut, the blastocyst rate was decreased by 1 mM l-NAME from 50.2% +/- 3.1% and 37.4% +/- 4.5% to 6% +/- 3% and 0%, respectively. In KSOMaa, cavitation rates were unaltered but the blastocysts contained fewer cells (P < 0.001). Blastocysts cultured in KSOM and KSOM-glut consumed significantly more oxygen than those cultured in KSOMaa (P < 0.001 and P < 0.05, respectively). However, the addition of 0.1 mM or 1 mM l-NAME to KSOMaa significantly increased the amount of oxygen consumed (P < 0.05 and P < 0.001, respectively). The data suggest a physiological role for NO in mouse preimplantation metabolism and development. One possibility is that NO may limit oxygen consumption at the blastocyst stage at the level of mitochondrial cytochrome c oxidase.

Amino Acids↗

PubMed2003

Energy metabolism in pig oocytes and early embryos.

Pig oocytes and embryos differ from those of other species in having a large quantity of endogenous lipid, a potential role for which has yet to be identified. In the present study, the hypothesis that endogenous triglyceride acts as a metabolic substrate during in vitro maturation and early embryo development was tested. Embryos were produced by in vitro fertilization (IVF) of in vitro-matured, abattoir-derived immature oocytes, cultured in medium NCSU23 up to the blastocyst stage. The triglyceride content of single oocytes and embryos was measured throughout development. Oxygen and glucose consumption and the formation of lactate were measured non-invasively over the same period, enabling total ATP production to be calculated. The triglyceride content of oocytes before maturation (135+/-4.9 ng) decreased by 13 ng (P<0.05) during in vitro maturation, but there was no apparent change in triglyceride content during embryo development (117.68 ng). Oxygen consumption was low throughout embryo cleavage before reaching a peak at the blastocyst stage (P<0.01), a pattern similar to that seen in other mammals studied. Glucose consumption and lactate production were also at a maximum at the blastocyst stage (P<0.05). These data indicate that pig oocytes may use endogenous triglyceride as an energy source during in vitro maturation and that most (91-97%) of the ATP produced during embryo development comes from oxidative phosphorylation. The high exogenous glucose concentration in NCSU23 (5.5 mmol l(-1)) may be needed to form pyruvate, which in turn, produces oxaloacetate, which is required to prime the tricarboxylic acid cycle. However, the reason for the high lipid content in early pig embryos remains to be elucidated.

Adenosine Triphosphate↗

PubMed2003

Metabolic characterization of the bovine blastocyst, inner cell mass, trophectoderm and blastocoel fluid.

The formation of a viable blastocyst is dependent upon the establishment of a correct inner cell mass (ICM):trophectoderm cell ratio but little is known about the metabolism of the two cell populations or about the composition of blastocoel fluid. In this study, the metabolism of intact bovine blastocysts, isolated ICM and trophectoderm was examined in terms of glucose and pyruvate uptake, lactate production, and amino acid consumption or production. The concentration of these nutrients in blastocoel fluid was also determined. The metabolism of glucose, pyruvate and lactate differed significantly between the isolated ICM and trophectoderm. Isolated trophectoderm had a higher pyruvate (P<0.001) and lower glucose (P<0.05) consumption, and higher lactate production (P<0.05) than did ICM. The consumption or production of amino acids by ICM and trophectoderm also differed, with the trophectoderm displaying a higher turnover (the sum of production and consumption). The ICM and trophectoderm both depleted arginine, aspartate and leucine, whereas the production of alanine was consistent. Isolated ICM depleted a further six amino acids, which appeared during trophectoderm culture; the reverse trend was observed for the remaining amino acids. The concentration of lactate in blastocoel fluid was significantly higher than in synthetic oviductal fluid supplemented with amino acids and BSA (SOFaaBSA; P<0.05). However, glucose (P<0.05) and pyruvate (P<0.001) concentrations were both lower. Aspartate, glutamate, glycine, alanine and tryptophan were present at significantly higher concentrations in blastocoel fluid than in SOFaaBSA, whereas threonine and asparagine concentrations were significantly lower. The metabolism of composite blastocysts, obtained by summing the consumption and production profiles of the ICM and trophectoderm, and taking into account their respective number of cells, was higher than that of intact blastocysts, indicating that upon isolation of the two cell populations there may be disruption to paracrine interactions or the onset of culture-induced cellular stress or both.

Amino Acids↗

PubMed2002

Regulation of apoptosis in the bovine blastocyst by insulin and the insulin-like growth factor (IGF) superfamily.

Insulin and the insulin-like growth factors, IGF-I and IGF-II, have been reported to exert a mitogenic effect on the preimplantation mammalian embryo. Furthermore, it has been proposed that loss of imprinting of the insulin-like growth factor II receptor gene and the consequent over-production of IGF-II may be involved in the aetiology of the Enlarged Offspring Syndrome, which occurs as an artefact of in vitro embryo production. We have previously shown that apoptosis occurs in the preimplantation bovine embryo and is influenced by in vitro culture conditions. We have therefore sought to establish the effects of insulin, IGF-I and IGF-II on apoptosis and cell proliferation in bovine blastocysts in vitro. Zygotes, obtained by in vitro maturation and fertilization of follicular oocytes, were cultured to blastocysts, with or without exogenous growth factors. Embryos were stained with propidium iodide to label all nuclei and by TUNEL to label apoptotic nuclei and analyzed by epifluorescent and confocal microscopy. IGF-I and IGF-II, but not insulin, were found to increase the proportion of embryos which formed blastocysts. Insulin decreased the incidence of apoptosis without affecting blastocyst cell number. IGF-I acted to decrease apoptosis and increase total cell number and IGF-II increased cell number alone. These data suggest roles for insulin and the IGFs as mitogens and/or apoptotic survival factors during early bovine development. Perturbation of IGF-II regulated growth may be involved in fetal oversize.

Animals↗

PubMed2002

Effect of timing of urea feeding on the yield and quality of embryos in lactating dairy cows.

High protein diets, which lead to excess production of nonprotein nitrogen such as ammonia and urea, have been associated with reduced fertility in dairy cows. In this study we test the hypothesis that diets containing high levels of quickly degradable urea nitrogen (QDN) compromise embryo development. Lactating dairy cows were fed mixed silage and concentrates twice daily. At 60 days postpartum, a synchronized estrus was induced and the cows were subsequently superovulated and inseminated using a standard protocol. On Day 7 after insemination, the uteri were flushed and embryos retrieved. At the start of treatment, cows were randomly allocated into three nutritional groups: control (CONT, n = 8), long (L-) QDN (n = 8) and short (S-) QDN (n = 9). The L-QDN cows were fed a supplement of urea from 10 days before insemination, and the S-QDN cows were fed the supplement from insemination until embryo collection. Both L- and S-QDN diets produced significant increases in plasma ammonia and urea 3 h post-feeding. The S-QDN but not the L-QDN diet was associated with a significant reduction in embryo yield. Embryo quality was also significantly reduced in the S-QDN cows. This study indicates that there is no deleterious effect on the yield and quality of embryos recovered 7 days after breeding when QDN feeding is initiated during the previous midluteal phase. However, introduction of a similar diet 10 days later, at the time of insemination, was deleterious. We suggest that QDN is toxic to embryos but cows can adjust within 10 days.

Amino Acids↗

PubMed2002

Effects of insulin-like growth factors I and II on tumour-necrosis-factor-alpha-induced apoptosis in early murine embryos.

The proposition that members of the insulin-like growth factor superfamily act as rescue factors from apoptosis in murine preimplantation embryos was tested. The cytokine tumour necrosis factor alpha (TNFalpha) was used to induce apoptosis. Zygotes were cultured for 5 days to the blastocyst stage in the presence or absence of TNFalpha and in the presence or absence of the insulin-like growth factors, IGF-I or IGF-II. Tumour necrosis factor alpha significantly increased the percentage of apoptotic cells and reduced the total cell count in Day 5 blastocysts. When IGF-I or IGF-II were added to the culture medium in the presence of TNFalpha, the cell number and apoptotic dead cell index (DCI) were restored to control values. Insulin-like growth factor-I alone had a greater effect on total cell number than IGF-II alone, but did not significantly decrease the apoptotic DCI. In contrast, IGF-II significantly reduced the number of apoptotic cells. This study shows that IGFs may play a role as apoptotic survival factors in the early mouse embryo.

Animals↗

PubMed2002

Functional significance of gap junctional coupling in preimplantation development.

Gap junctional intercellular coupling allows cells to share low molecular weight metabolites and second messengers, thus facilitating homeostatic and developmental processes. Gap junctions make their appearance very early in rodent development, during compaction in the eight-cell stage. Surprisingly, preimplantation mouse embryos lacking the gap junction protein connexin 43 develop normally and establish full-term pregnancies despite severely reduced gap junctional coupling. It was suggested that this might be explained by the presence of at least five additional connexins known to be expressed in blastocysts. In the present study, we set out to clarify the number of connexins present in preimplantation rodent embryos and the role of gap junctional coupling, if any, in blastocyst development. We provide evidence from reverse transcription-polymerase chain reaction analysis that the genes encoding 3 additional connexins (connexin 30 or beta6, connexin 36 or alpha9, and connexin 57 or alpha10) are also transcribed in preimplantation mouse embryos. Furthermore, we show that multiple connexins are expressed in rat preimplantation embryos, indicating that multiplicity of connexin expression may be a common feature of early mammalian embryogenesis. We could detect no up-regulation of any of 3 coexpressed connexins examined in mouse embryos lacking connexin 43. Impaired intercellular coupling caused either by the loss of connexin 43 or by treatment of cultured embryos with the gap junctional coupling blocker 18alpha-glycyrrhetinic acid (AGA) had no discernable effect on either apoptosis or glucose utilization, parameters known to be affected by gap junctional coupling in other contexts. These results, taken together with the reported inability of AGA to perturb blastocyst formation, imply that gap junctional coupling is not essential during this developmental period. We propose that connexin expression and the assembly of multiple types of gap junction channels in preimplantation embryos facilitates the diversification of communication pathways that will appear during postimplantation development. New evidence of this diversification is presented using rat blastocyst outgrowths.

Animals↗

PubMed2002

Effect of elevated systemic concentrations of ammonia and urea on the metabolite and ionic composition of oviductal fluid in cattle.

High dietary protein leads to elevated systemic concentrations of ammonia and urea, and these, in turn, have been associated with reduced fertility in cattle. The effect of elevating systemic concentrations of ammonia and urea on the concentrations of electrolytes and nonelectrolytes in bovine oviductal fluid were studied using estrus-synchronized, nulliparous heifers (n = 25). Heifers were randomly assigned to 1 of 3 treatments consisting of jugular vein infusion with either ammonium chloride (n = 8), urea (n = 8), or saline (n = 9). Oviducts were catheterized, and fluid was recovered over a 3-h period on either Day 2 or 8 of the estrous cycle. No difference (P > 0.05) was found in the concentrations of any electrolyte or nonelectrolyte between oviducts ipsi- or contralateral to the corpus luteum. Plasma and oviductal concentrations of urea were increased by infusion with urea (P < 0.001) and ammonium chloride (P < 0.05) but not by saline (P > 0.05). Plasma and oviductal concentrations of ammonia were elevated by infusion with ammonium chloride (P < 0.001) but not by infusion with urea or saline (P > 0.05). No effect (P > 0.05) of treatment was found on oviductal or plasma concentrations of glucose, lactate, magnesium, potassium, or sodium or on plasma concentrations of insulin or progesterone. The concentration of calcium in oviductal fluid was reduced by urea infusion and was negatively associated with systemic and oviductal concentrations of urea. Oviductal concentrations of sodium were higher on Day 8 than on Day 2 (P < 0.05). No effect of sample day was found on any of the other electrolytes or nonelectrolytes measured (P > 0.05). Elevated systemic concentrations of ammonia and urea are unlikely to reduce embryo survival through disruptions in the oviductal environment.

Ammonia↗

PubMed2002

Effect of platelet-activating factor on the electrophysiology of the human Fallopian tube: early mediation of embryo-maternal dialogue?

Platelet-activating factor (PAF) is produced by preimplantation embryos and may be involved in the earliest stages of embryo-maternal dialogue. This study explored the potential effects of PAF acting as a signalling agent on human Fallopian tubal epithelial cells grown as a polarized layer in primary culture. The response of the tubal epithelium was assessed in terms of the transepithelial potential difference and short-circuit current (I(scc)), which were recorded using a modified Ussing chamber. Resistance was calculated from the measurements of potential difference and I(scc). PAF (1.9 nmol to 1.9 micromol l(-1)) administered to the apical surface of the cells produced a marked, transient increase in both potential difference and I(scc) in a dose-dependent manner. The mode of action of PAF on the electrophysiological responses of human tubal epithelial cells was investigated. Blockers of Na(+), K(+) and voltage-operated Ca(2+) channels had little effect on PAF action. However, incubation of the epithelial cells in Cl(-)free medium or with a blocker of the Na(+)-K(+)-2Cl(-) cotransporter (Furosemide) reduced the effect of PAF. Blockade of chloride-bicarbonate channels with 4-acetamido-4'-iso-thiocyanostilbene-2.2'-disulphonic acid (SITS) reduced the effect of low doses of PAF only. These results indicate that PAF influences the movement of chloride ions across the tubal epithelial cell and is a candidate molecule for initial embryo-maternal dialogue.

Adult↗

PubMed2002

Amino acid turnover by elongating cattle blastocysts recovered on days 14-16 after insemination.

Blastocyst elongation from day 14 to day 16 after insemination coincides with a major phase of embryo loss in cattle. Protein synthesis, reflected in protein content, increases markedly over this period but little is known about the amino acid requirement of elongating blastocysts at this time. Cattle blastocysts produced in vivo were recovered on days 14-16 after insemination and cultured individually for up to 8 h in synthetic oviduct fluid containing a physiological mixture of amino acids plus 1 mmol glutamine l(-1) and 0.1% (w/v) polyvinyl alcohol (SOFaaPVA). After 1, 4 and 8 h in culture, an aliquot of culture medium was removed and the rate of amino acid depletion or production was calculated per unit of protein and per hour of culture. Amino acids were depleted or produced at different rates. Arginine was depleted from the medium at a significant rate (P < 0.05) during all culture periods. Alanine and glutamate were produced at a significant rate (P < 0.05) during all culture periods. The rate of alanine production was significantly greater (P < 0.05) in blastocysts recovered on day 14 compared with days 15 or 16 after insemination. Alanine production and arginine depletion tended to be greater in smaller embryos recovered on day 14 compared with larger and later stage embryos, indicating that earlier stage embryos may have higher metabolic activity than later stage embryos. Qualitatively, the pattern of amino acid consumption and production during elongation was similar to that shown from the zygote to early blastocyst stage.

Alanine↗

PubMed2001

Protection against reactive oxygen species during mouse preimplantation embryo development: role of EDTA, oxygen tension, catalase, superoxide dismutase and pyruvate.

Oxidative damage due to the production of reactive oxygen species (ROS) is one of a number of culture-induced stresses which may compromise preimplantation embryo development in vitro. Ethylenediaminetetraacetic acid (EDTA), reduced oxygen tension, superoxide dismutase (SOD) and catalase (CAT) offer protection against oxidative stress, but few attempts have been made to determine which of these agents, or which combination, is the most effective. In particular, no systematic investigation of their actions and interactions has been made using a multifactorial experimental design. Murine zygotes were cultured in the presence or absence of 10 miccroM EDTA, SOD (100-7,000 U/ml) and CAT (50-100 U/ml) at atmospheric (20%) and reduced (5%) oxygen tensions. Blastocyst formation and hatching rates (at various time points), and cell numbers were recorded, whilst parallel groups of embryos had their consumption of pyruvate, a hydrogen peroxide scavenger, measured. All parameters interacted significantly and affected blastocyst formation, hatching rate and cell numbers but the effect of EDTA was the most pronounced. There were beneficial effects of 5% O2, CAT and SOD, while 20% O2 had a deleterious effect on development. EDTA improved blastocyst formation and hatching rates but paradoxically led to a reduction in cell number. 5% O2 was the next most significant parameter to enhance embryo development and also increased cell numbers. No differences in pyruvate uptake were apparent between the various treatment groups. The results suggest that embryo culture in EDTA-free medium under 5% O2 provides the most practical and physiological conditions for in vitro murine embryo culture.

Animals↗

PubMed2001

Regulation of the transition from research to clinical practice in human assisted conception.

This review discusses the place of regulation in the transition from research to clinical practice in human assisted conception, with particular emphasis on the United Kingdom and the role of the Human Fertilisation and Embryology Authority (HFEA). A contrast is drawn between advances in other areas of medical practice, in which the evidence base is considerable, and in assisted conception, in which it is often weak. This comparison leads to the central issue: how to balance the needs of patients with the need to ensure safety and efficacy in the introduction of new techniques. Comfort is derived from biological considerations that indicate that early human embryos are remarkably resilient and adaptable to challenges to their physiology. Regulatory practice in other countries is considered briefly. The review concludes that there are no easy rules or answers in managing the transition from research into the clinic, but that bodies such as the HFEA have a responsibility to: (i) encourage research to widen the evidence base and (ii) err on the side of caution when faced with decisions on licensing new techniques.

Animals↗

PubMed2001

Formation of Fallopian tubal fluid: role of a neglected epithelium.

Fluid produced and secreted by the Fallopian tube provides the environment in which gamete transport and maturation, fertilization and early embryo development occur. This review describes the composition of oviductal fluid in terms of ions and nutrients such as glucose, lactate, pyruvate and amino acids. The function of oestrogen-specific glycoprotein is discussed. The mechanisms of fluid secretion and agents known to influence fluid production and secretion are described. Clinical implications of abnormal oviductal fluid production and secretion in hydrosalpinx and pelvic inflammatory disease are also discussed.

Animals↗

PubMed1999

Embryo metabolism during the expansion of the bovine blastocyst.

Embryo metabolism was evaluated during re-expansion of in vitro produced bovine blastocysts collapsed with cytochalasin D (CCD) and incubated in the presence and absence of ouabain, a specific inhibitor of the Na+, K+ pump. Day 8 expanded blastocysts were treated for 2 to 4 hr with 20 microg/ml CCD. Four conditions were tested: untreated embryos and embryos collapsed with CCD and allowed to re-expand for 4 hr in the presence of 0 M, 1 nM, or 1 microM ouabain. Incubation of collapsed embryos for 4 hr in the presence of 1 nM or 1 microM ouabain significantly inhibited blastocyst re-expansion. Glucose, pyruvate, and amino lactate uptake/release were not significantly affected by ouabain treatment and did not correlate with the degree of blastocyst re-expansion. Few variations in the uptake/release of amino acids by the embryos were observed. Ouabain treatment significantly decreased oxygen uptake which directly correlated with the degree of blastocyst re-expansion. For embryos allowed to re-expand in the presence or absence of ouabain, a direct correlation was observed between the uptake of oxygen and of glucose. One mM cyanide or 2,4 dinitrophenol inhibited blastocyst re-expansion although 0.01 and 0.1 mM were ineffective. This study indicates a role for oxidative metabolism in providing the energy necessary for blastocoel expansion in the bovine. Nevertheless, blastocyst expansion is relatively insensitive to inhibition of oxidative phosphorylation indicating the ability of the bovine blastocyst to adapt to hypoxic conditions.

Animals↗