Enhancing oxygen delivery to ovarian follicles by three different methods markedly improves growth in serum-containing culture medium

Invitro ovarian follicle culture systems are routinely used to study folliculogenesis and may provide solutions for infertility. Mouse follicles are typically cultured in standard gas-impermeable culture plates under gas phase oxygen concentrations of 5% or 20% (v/v). There is evidence that these conditions may not provide adequate oxygenation for follicles cultured as non-attached intact units in medium supplemented with serum and high levels of FSH. Three different methods of enhancing follicle oxygenation were investigated in this study: increasing the gas phase oxygen concentration, inverting the culture plates and using gas-permeable culture plates. Follicles cultured under 40% O2 were significantly larger (P P P 2 . These effects were associated with reduced secretion of vascular endothelial growth factor (P P P invivo -matured follicles (~500μm in diameter). Such follicular development is not possible under hypoxic conditions.

Corrigendum to: Hypoxia limits mouse follicle growth in vitro

Ovarian follicle culture is useful for elucidation of factors involved in the regulation of follicular function. We examined the effects of gas phase oxygen concentration, an oil overlay, serum type and medium supplementation with FSH, insulin-transferrin-selenium (ITS) and I-ascorbic acid on cultured preantral mouse follicle growth in a spherical, non-attached follicle culture system. Follicle growth in 5% oxygen was significantly (P<0.01) inferior to growth in 20% oxygen in terms of follicle diameter. This was likely due to hypoxia, as evidenced by significantly (P<0.05) increased follicle secretion of vascular endothelial growth factor (VEGF), a marker of cell hypoxia. Follicular growth was not (P>0.05) affected by an oil overlay, ITS supplementation or serum type. Culture in medium with 5% mouse serum, 1 IU mL^-1 FSH, 25 μgmL^-1 l-ascorbic acid and 20% oxygen without an oil overlay supported the growth of follicles to a maximum diameter of 380 μm in 6 days. Compared with mature preovulatory mouse follicles in vivo that often have diameters >500 μm within the same time frame, in vitro-grown follicles clearly exhibit limited growth. Thus, adequate oxygenation is an essential factor in the process of optimising follicle growth.

Hypoxia limits mouse follicle growth in vitro

Ovarian follicle culture is useful for elucidation of factors involved in the regulation of follicular function. We examined the effects of gas phase oxygen concentration, an oil overlay, serum type and medium supplementation with FSH, insulin-transferrin-selenium (ITS) and l-ascorbic acid on cultured preantral mouse follicle growth in a spherical, non-attached follicle culture system. Follicle growth in 5% oxygen was significantly (P < 0.01) inferior to growth in 20% oxygen in terms of follicle diameter. This was likely due to hypoxia, as evidenced by significantly (P < 0.05) increased follicle secretion of vascular endothelial growth factor (VEGF), a marker of cell hypoxia. Follicular growth was not (P > 0.05) affected by an oil overlay, ITS supplementation or serum type. Culture in medium with 5% mouse serum, 1 IU mL-1 FSH, 25 μg mL-1 l-ascorbic acid and 20% oxygen without an oil overlay supported the growth of follicles to a maximum diameter of 380 μm in 6 days. Compared with mature preovulatory mouse follicles in vivo that often have diameters >500 μm within the same time frame, in vitro-grown follicles clearly exhibit limited growth. Thus, adequate oxygenation is an essential factor in the process of optimising follicle growth.

The role of nutrients, peptide growth factors and co-culture cells in development of preimplantation embryos in vitro

Our knowledge of the control of preimplantation embryo development and growth is deficient in many aspects as is evidenced by the great difficulty there is in growing embryos of many species in vitro while maintaining viability. This review discusses recent findings on the roles of nutrients, peptide growth factors and co-culture cells in embryo growth and development in vitro.

Self-renewal and differentiation of mouse embryonic stem cells as measured by Oct 4 gene expression: effects of lif, serum-free medium, retinoic acid, and dbcAMP

In this study we examined the interplay between serum, leukemia inhibitory factor (LIF), retinoic acid, and dibutyrl cyclic adenosine monophosphate (dbcAMP) in affecting IOUD2 embryonic stem cell self-renewal and differentiation as assessed by Oct 4 expression, and cell proliferation as measured by total cell protein. Removal of LIF, reduced levels of fetal calf serum (FCS), and addition of retinoic acid all induced embryonic stem cell differentiation as measured by reduced Oct 4 expression. Lower levels of retinoic acid (0.1-10 nM) promoted the formation of epithelial-like cells, whereas higher levels (100-10,000 nM) favored differentiation into fibroblastic-like cells. The effects of dbcAMP varied with the presence or absence of FCS and LIF and the concentration of dbcAMP. In FCS-containing media, a low level of dbcAMP (100 microM) increased self-renewal in the absence of LIF, but it had no effect in its presence. In contrast, at higher concentrations (1,000 microM dbcAMP), regardless of LIF, differentiation was promoted. A similar effect of dbcAMP was seen in the presence of retinoic acid. In media without FCS but with serum replacement supplements, there was no effect of dbcAMP. This study shows that the Oct 4 expression system of IOUD2 cells provides a novel, simple method for quantifying cellular differentiation.

Self-renewal and differentiation of mouse embryonic stem cells as measured by Oct 4 gene expression: effects of lif, serum-free medium, retinoic acid, and dbcAMP

In this study we examined the interplay between serum, leukemia inhibitory factor (LIF), retinoic acid, and dibutyrl cyclic adenosine monophosphate (dbcAMP) in affecting IOUD2 embryonic stem cell self-renewal and differentiation as assessed by Oct 4 expression, and cell proliferation as measured by total cell protein. Removal of LIF, reduced levels of fetal calf serum (FCS), and addition of retinoic acid all induced embryonic stem cell differentiation as measured by reduced Oct 4 expression. Lower levels of retinoic acid (0.1-10 nM) promoted the formation of epithelial-like cells, whereas higher levels (100-10,000 nM) favored differentiation into fibroblastic-like cells. The effects of dbcAMP varied with the presence or absence of FCS and LIF and the concentration of dbcAMP. In FCS-containing media, a low level of dbcAMP (100 microM) increased self-renewal in the absence of LIF, but it had no effect in its presence. In contrast, at higher concentrations (1,000 microM dbcAMP), regardless of LIF, differentiation was promoted. A similar effect of dbcAMP was seen in the presence of retinoic acid. In media without FCS but with serum replacement supplements, there was no effect of dbcAMP. This study shows that the Oct 4 expression system of IOUD2 cells provides a novel, simple method for quantifying cellular differentiation.

Oxidative phosphorylation and the tricarboxylic acid cycle are essential for normal development of mouse ovarian follicles

BACKGROUND

Mouse ovarian follicles are typically grown in upright drops of culture medium. Recently we found that culture of follicles at the medium-gas interface in inverted drops markedly improved follicular development, possibly due to improved access of oxygen to the follicle. In this study, we examined the importance of aerobic energy metabolism for follicle development by culturing mouse follicles (198 6 16.5 initial microm diameter, mean 6 SD) in the presence of phosphorylation and tricarboxylic acid (TCA) cycle inhibitors.

METHODS

All inhibitors were tested in the inverted system using 100 microl medium drops in 96-well plates; certain inhibitors were also tested in upright drops with or without an oil overlay.

RESULTS

The oxidative phosphorylation inhibitor rotenone (0.1, 0.5 and 1 micromol/l) totally abolished follicle growth in the inverted system; cyanide (1 mmol/l) totally abolished growth in the upright with oil system but not in the inverted system (possibly due to loss of cyanide gas due to the absence of an oil overlay). The mitochondrial uncoupler 2,4-dinitrophenol (0.5 and 1 mmol/l) also abolished growth in the inverted system. The TCA cycle inhibitor monofluoroacetate (10 mmol/l), significantly inhibited growth in all three culture systems (P < 0.01) but malonate (10 mmol/l) had no effect.

CONCLUSIONS

Aerobic metabolism and an adequate oxygen supply are essential for normal follicular development.

Inositol transport in mouse embryonic stem cells

The uptake of myo-inositol by mouse embryonic stem (ES) cells was measured using [2-3H]myo-inositol. Uptake of myo-inositol by ES cells occurred in a mainly saturable, sodium-, time- and temperature-dependent manner, which was inhibited by glucose, phloridzin and ouabain. Self inhibition by inositol was much greater than inhibition by glucose indicating that transport was not occurring via a sodium-dependent glucose transporter. Uptake rate was much greater than efflux rate indicating a mainly unidirectional transport mechanism. Estimated kinetics parameters for sodium-dependent inositol uptake were a Km of 65.1 ± 11.8 μ mol L−1 and a Vmax of 5.0 ± 0.59 pmol μ g protein−1 h−1. Inositol uptake was also sensitive to osmolality; uptake increased in response to incubation in hypertonic medium indicating a possible role for inositol as an osmolyte in ES cells. These characteristics indicate that myo-inositol transport in mouse ES cells occurs by a sodium-dependent myo-inositol transporter protein.

The phosphatidylinositol signalling system in elongating bovine blastocysts; formation of phosphoinositides, inositol phosphates and stimulation by growth factors

The uptake of myo-inositol and its incorporation into the phosphoinositides and inositol phosphates of the phosphatidylinositol (PtdIns) signal transduction system by in vivo elongating cattle blastocysts was investigated using [3H]myo-inositol. Uptake was examined in 13-, 14- and 16-day-old blastocysts and was largely sodium-dependent throughout (P<0.001), indicating the presence of a sodium-dependent inositol transporter. Incorporation of inositol into the three phosphoinositides, PtdIns, PtdInsP and PtdInsP2, and the inositol phosphates of the phosphatidylinositol signal transduction system was examined at Days 14 and 16; incorporation into the three phosphoinositides and into the inositol phosphate species, InsP1, InsP2, InsP3 (including the second messenger, Ins(1,4,5)P3) and InsP4 was detected in both blastocyst stages. The effects of the peptide growth factor, epidermal growth factor (EGF), and the lipid growth factors, lysophosphatidic acid (LPA) and platelet activating factor (PAF), on the activity of the phosphatidylinositol signalling system in 14- and 16-day-old blastocysts were examined. All growth factors significantly stimulated phosphatidylinositol signalling activity. Epidermal growth factor was stimulatory (P<0.001) only in 16-day-old blastocysts, whereas LPA and PAF were active in both 14- (P<0.005 for LPA and P<0.001 for PAF) and 16-day-old blastocysts (P<0.001 for LPA and PAF). These results indicate that the phosphatidylinositol signalling system is present in cattle blastocysts at the elongation stage and is responsive to stimulation by growth factors.

In situ oviduct and uterine pH in cattle

Knowledge of oviduct and uterine pH in cattle is lacking mainly because of the difficulty of accessing these reproductive tissues, which for the oviduct at least necessitates anesthesia. Because halothane anesthesia is known to depress respiratory function and thus increase blood CO2 and decrease pH, oviduct and uterine pH was measured both in the presence and absence of halothane. Using short-term anesthesia with thiopentone only, oviduct pH was measured on days 2-4 of the estrous cycle and uterine pH on days 6 and 8; there was no significant effect of day of the cycle but oviduct pH ( 7.60+/-0.010 ) was greater ( P<0.001 ) than uterine pH ( 6.96+/-0.009 ). Oviduct pH was higher ( P<0.001 ) and uterine pH lower ( P<0.001 ) than venous blood pH ( 7.41+/-0.007 ). Using thiopentone/halothane anesthesia, oviduct pH was measured on days 0, 2, 3, 4 and 6, and uterine pH on days 6, 8 and 14; there was no effect of day of cycle but oviduct pH values were generally higher than uterine values and significantly so ( P<0.001 ) on day 6 where direct comparison was possible. To our knowledge these are the first published in situ measurements of oviduct pH in cattle.

A novel follicle culture system markedly increases follicle volume, cell number and oestradiol secretion

This study reports a novel, simple method for culture of mouse follicles which results in follicles with cell numbers similar toin vivofully grown follicles. Using this method, follicles (180–240 μm in diameter) were cultured in a 100 μl inverted drop of medium without oil and compared with culture in upright drops with and without a mineral oil overlay. Follicles, isolated from C57BL/6 × CBA/ca crossbred and MF1 inbred mice, were cultured individually at 37 °C in 96-well round-bottomed suspension cell tissue culture plates for 6 days. Follicles grown in the inverted drop culture system reached a markedly higher final diameter (means±s.e.m.; 471 ± 6.0 μm) as compared with the upright with oil (363 ± 2.7 μm) and without oil (358 ± 4.0) systems. There was no significant effect of mouse strain on follicle diameter. Follicular secretion of oestradiol and lactate into the medium was measured on days 2, 4 and 6 of culture. Secretion of oestradiol per follicle on day 6 was 2.49 ± 0.45 ng in the inverted and 0.90 ± 0.17 ng in the upright without oil system (P< 0.001). Follicular secretion of lactate on a per unit of follicle volume basis remained constant in the inverted system over days 2, 4 and 6 and was less (P< 0.001) than secretion in both the upright with and without oil systems. Follicle cell proliferation was markedly increased in the inverted as compared with the upright with oil system; the increases in cell numbers were significant on day 3 (P< 0.01) and on all subsequent days (P< 0.001). These results are discussed in relation to the supply of oxygen to the follicle in culture.

A review of in vitro gamete maturation and embryo culture and potential impact on future animal biotechnology

This review considers the relationship of in vitro gamete maturation and embryo culture to the future development of animal biotechnology. The areas reviewed are oocyte maturation in vitro and embryo culture and their importance for successful in vitro embryo production. The rapidly developing area of spermatogonial cell transplantation and culture is also reviewed. The scientific milestones leading to the development of each area, the problems and prospects for future development and the possible significance of major advances in each area are discussed.

Phospholipase C and protein kinase C involvement in mouse embryonic stem-cell proliferation and apoptosis

Activation of the phosphatidylinositol (PtdIns) signal transduction system involves stimulation of phospholipase C (PLC) by hormones and other agonists to produce two second messengers, the inositol phosphate, Ins(1,4,5)P3 which releases calcium from intracellular stores, and diacylglycerol which activates protein kinase C (PKC). This study, using activators or inhibitors of PLC and PKC and a calcium ionophore, examined the role of the PtdIns system in mouse embryonic stem (ES) cells. The PLC inhibitor, U-73122, inhibited ES-cell proliferation and also inhibited PLC activation as evidenced by a decrease in inositol phosphate formation in response to fetal calf serum stimulation. The two PKC activators, the diacylglycerol analogue 1,2, dioctanoyl-sn-glycerol (DOG) and the phorbol ester 12-O-tetra-decanoyl phorbol 13-acetate (TPA), increased cell proliferation in a dose-dependent manner, as did the calcium ionophore, ionomycin. However, co-stimulation with either ionomycin and DOG or ionomycin and TPA resulted in a reduced number of cells. The PKC inhibitor, bisindolylmaleimide II (Bis II), significantly decreased the number of ES cells, mainly due to increased apoptosis. The possible feedback effect of PKC on PLC was examined by preincubating ES cells with either the PKC inhibitor Bis II or the activator TPA before stimulation of inositol phosphate production with fetal calf serum; preincubation with Bis II increased inositol phosphate formation whereas preincubation with TPA decreased inositol formation. These results indicate that the PtdIns system is involved in the control of ES-cell proliferation and apoptosis.

Inositol transport in preimplantation rabbit embryos: effects of embryo stage, sodium, osmolality and metabolic inhibitors

The preimplantation period in the rabbit consists of a 3 day cleavage stage during which the number of cells increases with little change in embryo size, followed by a 3-4 day blastocyst stage during which the inner cell mass, the blastocoel and the trophectodermal layer are formed and the embryo grows rapidly in size and protein content. This study used [(3)H]inositol to investigate the transport of inositol, an essential component of the phosphatidylinositol signal transduction system, over the 6 days of preimplantation development by rabbit embryos. In the presence of 15 micromol inositol l(-1) in the incubation medium, there was a small linear increase in inositol uptake from 0.07 pmol per embryo per h at the one-cell stage (day 1) to 0.135 pmol at the late morula (day 3) stage. Inositol uptake increased to 0.58 pmol per embryo per h for early blastocysts (day 4) and 23.7 pmol for late blastocysts (day 6). There was a significant linear relationship between inositol uptake and blastocyst diameter and surface area. Efflux of inositol from early morulae was minimal (about 1.25% of embryo content per h), whereas efflux from mid-blastocysts (day 5) was much greater (about 15.6% of embryo content per h). Efflux of inositol from both early morulae and mid-blastocysts was increased by decreasing the osmolality of the incubation medium. Varying the osmolality had no effect on inositol uptake up to 2 h. Inositol uptake was dependent on sodium in cleavage-stage embryos but independent of sodium in blastocyst stages. In early morulae, inositol uptake was inhibited by glucose and the sodium-dependent hexose transport inhibitor, phloridzin, but not by the facilitated transport inhibitor, phloretin. Inositol uptake in early morulae was saturable; estimates of 0.227 and 0.288 pmol per morula per h for V(max) and 0.045 and 0.038 micromol l(-1) for K(m) were obtained for sodium-dependent transport in two separate experiments. All of these results are consistent with the hypothesis that transport in cleavage stages occurs via a sodium myo-inositol transporter (SMIT) protein. Uptake in blastocysts was non-saturable. Uptake into blastocysts appeared to take place by a transcellular rather than a paracellular route.

Inositol transport in preimplantation rabbit embryos: effects of embryo stage, sodium, osmolality and metabolic inhibitors

The preimplantation period in the rabbit consists of a 3 day cleavage stage during which the number of cells increases with little change in embryo size, followed by a 3-4 day blastocyst stage during which the inner cell mass, the blastocoel and the trophectodermal layer are formed and the embryo grows rapidly in size and protein content. This study used [3H]inositol to investigate the transport of inositol, an essential component of the phosphatidylinositol signal transduction system, over the 6 days of preimplantation development by rabbit embryos. In the presence of 15 micromol inositol-1 in the incubation medium, there was a small linear increase in inositol uptake from 0.07 pmol per embryo per h at the one-cell stage (day 1) to 0.135 pmol at the late morula (day 3) stage. Inositol uptake increased to 0.58 pmol per embryo per h for early blastocysts (day 4) and 23.7 pmol for late blastocysts (day 6). There was a significant linear relationship between inositol uptake and blastocyst diameter and surface area. Efflux of inositol from early morulae was minimal (about 1.25% of embryo content per h), whereas efflux from mid-blastocysts (day 5) was much greater (about 15.6% of embryo content per h). Efflux of inositol from both early morulae and mid-blastocysts was increased by decreasing the osmolality of the incubation medium. Varying the osmolality had no effect on inositol uptake up to 2 h. Inositol uptake was dependent on sodium in cleavage-stage embryos but independent of sodium in blastocyst stages. In early morulae, inositol uptake was inhibited by glucose and the sodium-dependent hexose transport inhibitor, phloridzin, but not by the facilitated transport inhibitor, phloretin. Inositol uptake in early morulae was saturable; estimates of 0.227 and 0.288 pmol per morula per h for V(max) and 0.045 and 0.038 mmol-1 [corrected] for Km were obtained for sodium-dependent transport in two separate experiments. All of these results are consistent with the hypothesis that transport in cleavage stages occurs via a sodium myo-inositol transporter (SMIT) protein. Uptake in blastocysts was non-saturable. Uptake into blastocysts appeared to take place by a transcellular rather than a paracellular route.

Inositol transport in mouse oocytes and preimplantation embryos: effects of mouse strain, embryo stage, sodium and the hexose transport inhibitor, phloridzin

The uptake of myo-inositol by mouse oocytes and preimplantation embryos of a crossbred (DBA x C57BL/6) and a purebred outbred strain (MF1) was measured using [2-(3)H]myo-inositol. Uptake in crossbred embryos increased about 15-fold between the one- and two-cell stages and increased again by about sixfold at the blastocyst stage compared with the morula stage. Uptake in purebred embryos increased about 42-fold between the one- and two-cell stages and increased more than threefold at the blastocyst stage compared with the morula stage. In all stages examined, except two-cell crossbred embryos, inositol uptake was, depending on the stage, either largely or partly sodium dependent and could be inhibited by the sodium-dependent hexose transport inhibitor, phloridzin. This is consistent with the hypothesis that transport occurs via a sodium myo-inositol transporter (SMIT) protein. In addition, there was strong evidence that a sodium-independent mechanism of uptake, possibly a channel, was switched on at the two-cell stage coincident with zygotic gene activation which resulted in 141-fold and 71-fold increases in sodium-independent uptake from the one-cell to two-cell stages in crossbred and purebred embryos, respectively. This mechanism was either abolished or drastically downregulated at the blastocyst stage, whereas sodium-dependent uptake was markedly upregulated. In two-cell crossbred embryos, there was a complete abolition of sodium-dependent uptake, again possibly regulated by zygotic gene activation. The hypothesis that the changes in mechanism of inositol uptake at about the two-cell stage are due to zygotic gene activation was supported by the finding that these changes did not occur in parthenogenetic two-cell embryos.

Nature of glycosylphosphatidylinositols produced by mouse embryonic stem cells

Incorporation of [(3)H]inositol into mouse embryonic stem cells of the CCE cell line leads to the labelling of the three common phosphoinositides, phosphatidylinositol, phosphatidylinositol 4-phosphate and phosphatidylinositol 4,5-bisphosphate, and a fourth unknown lipid (lipid X). Incubation with [(3)H]glucosamine results in the labelling of lipid X and at least one other lipid that co-migrates with phosphatidylinositol (lipid Y), indicating that both of these lipids are putative glycosylphosphatidylinositols. In this study, the incorporation of other possible glycosylphosphatidylinositol precursors, ethanolamine, mannose and galactose, into lipids X and Y was examined. Galactose was incorporated into lipids X and Y, and ethanolamine and mannose into lipid Y only. Inhibitors of glycosylphosphatidylinositol biosynthesis pathways, mannosamine and 2-fluoro-2-deoxyglucose, both significantly inhibited ethanolamine incorporation into lipid Y. A high glucose concentration (25 mmol l(-1)) abolished the action of both inhibitors. Phospholipase C treatment of embryonic stem cells that had been labelled in culture with [(3)H]ethanolamine caused a large release of ethanolamine label into the incubation medium and markedly decreased the amount of ethanolamine-labelled lipid Y remaining in the cell membranes. These effects were almost totally abolished by incubation with mannosamine before ethanolamine labelling. These studies strongly indicate that lipid Y is a member of the protein anchor class of glycosylphosphatidylinositol, whereas lipid X is a member of the signal transduction inositol phosphoglycan class of glycosylphosphatidylinositol.

Uptake and incorporation of myo-inositol by bovine preimplantation embryos from two-cell to early blastocyst stages

The uptake of myo-inositol and its incorporation into the phosphoinositides and inositol phosphates of the phosphatidylinositol (PtdIns) signal transduction system by in vivo preimplantation cattle embryos was investigated using [(3)H] myo-inositol. Uptake of inositol was examined in two-cell and four-cell embryos (day 2 after insemination), morulae (day 6) and early blastocysts (day 7). Uptake in all stages examined was largely sodium-dependent indicating the presence of a sodium-dependent inositol transporter. Uptake of inositol did not vary significantly from two-cell to early blastocyst stages when expressed either on a per embryo or a per microg of protein basis. Incorporation of inositol into the three phosphoinositides, PtdIns, PtdInsP, and PtdInsP(2), was detectable at all stages examined. In contrast, incorporation of inositol into inositol phosphates was not detected until blastocyst formation at day 7. The second messenger, Ins(1,4,5)P(3), was first detected in day 7 blastocysts.

Immunization of rats and sheep against granulosa cell-inhibitory factor from bovine follicular fluid increases the number of large follicles in rats and the ovulation rate in sheep

Granulosa cell-inhibitory factor (GCIF), a low molecular weight factor from bovine follicular fluid, inhibits the proliferation of bovine granulosa cells in vitro and the growth of large follicles in rats in vivo. In this study the effects of (1) immunization of rats against GCIF on follicular growth and (2) immunization of sheep against GCIF on ovulation rate were studied. The ability of antiserum from sheep immunized against GCIF to reduce the inhibitory effect of GCIF on bovine granulosa cell proliferation in culture was also examined. Immunization of rats against GCIF increased the number of large follicles (P < 0.001) but decreased the number of small follicles (P < 0.05) per ovary. Ovarian mass (P < 0.05) and uterine wet (P < 0.05) and dry (P < 0.01) masses were increased in immunized rats. Immunization of sheep against GCIF, followed by boosting over two breeding seasons, increased ovulation rate (P < 0.01). Addition of antiserum from sheep immunized against GCIF reduced or abolished the inhibitory effect of GCIF on granulosa cell proliferation (P < 0.01). These data provide further evidence that GCIF has an important role in controlling follicle growth and ovulation in vivo.

Peptide growth factors and preimplantation development

This paper examines some of the problems and questions that must be considered in relation to research on the role of growth factors in preimplantation embryos. It reviews and summarizes the large body of work on gene expression of growth factor receptors and ligands in preimplantation embryos and in oviduct and uterine tissue. It also reviews the literature on the effects of gene knockout in preimplantation embryos and concludes with a review of work on the effects of growth factors on cultured embryos.

Modulation of the effects of FSH, androstenedione, epidermal growth factor (EGF) and insulin-like growth factor I (IGF-I) on bovine granulosa cells by GCIF, a growth-inhibitory factor of low molecular mass from bovine follicular fluid

A granulosa cell-inhibitory factor (GCIF) of low molecular mass from bovine follicular fluid inhibits the proliferation of bovine granulosa cells in vitro and the growth of large follicles in rats in vivo. The present study examined the ability of GCIF to modulate the effects of FSH, epidermal growth factor (EGF), insulin-like growth factor I (IGF-I) and androstenedione on the proliferation of bovine granulosa cells and on aromatase activity in vitro. Granulosa cell proliferation was assayed by counting haemocytometric cells and by measuring the incorporation of [3H]thymidine into acid-precipitable material. Assay of aromatase activity was based on the conversion of [3H]androstenedione to [3H]H2O. FSH, androstenedione, EGF and IGF-I all stimulated (P < 0.01) granulosa cell proliferation; however, the addition of GCIF reduced (P < 0.01) cell proliferation in their presence. In the case of EGF, the addition of GCIF almost abolished the stimulatory response. FSH and IGF-I, but not EGF, stimulated (P < 0.01) aromatase activity of granulosa cells. The stimulatory effect of IGF-I was decreased by GCIF. The inhibitory effects of GCIF indicate that it may play a significant role in regulating the effects of intraovarian growth factors on granulosa cells and the growth of follicles.

Partial purification from bovine follicular fluid of a factor of low molecular mass with inhibitory effects on the proliferation of bovine granulosa cells in vitro and on rat follicular development in vivo

Bovine follicular fluid was aspirated from follicles of 2-20 mm in diameter, charcoal-treated to remove steroids and then separated into low and high molecular mass fractions. The low molecular mass (< 10 kDa) fraction was purified on a Sephadex G-25 chromatography column with formic acid as the eluent. Seven peaks were isolated and assayed for biological activity in cultures of bovine granulosa cells at concentrations of 10, 100 and 1000 ng ml-1. One peak (peak 4) inhibited (P < 0.001) the proliferation of granulosa cells when measured by cell counting and by [3H]thymidine incorporation (33-37% inhibition). This peak inhibited proliferation of granulosa cells from both small (< 2 mm) and medium (2-10 mm) follicles, but not large (> 10 mm) follicles. The inhibitory effect of peak 4 was not due to a toxic effect on cells. Administration of peak 4 to rats did not affect liver or kidney masses but did decrease uterine (25%, P < 0.01) and ovarian (35%, P < 0.01) masses. Peak 4 also caused a reduction in the number of large follicles (65%, P < 0.01) but increased the number of small follicles (55%, P < 0.01). We have named the inhibitory factor associated with peak 4, granulosa cell-inhibitory factor (GCIF). The results presented suggest that GCIF may be a factor secreted by dominant follicles that inhibits the development of subordinate follicles.

Investigation of the role of inositol and the phosphatidylinositol signal transduction system in mouse embryonic stem cells

The aims of this study were to investigate in mouse embryonic stem cells (1) the requirement for myo-inositol for cell proliferation, (2) the incorporation of inositol into the phosphoinositides and inositol phosphates of the phosphatidylinositol (PtdIns) signal transduction system and (3) the effect of serum growth factors on PtdIns turnover. Exogenous myo-inositol was not essential for embryonic stem cell proliferation. Lithium, an inhibitor of endogenous inositol recycling, inhibited embryonic stem cell proliferation but this effect was not reversible by the addition of high concentrations of exogenous inositol. [3H]inositol was incorporated into the phosphoinositides, PtdIns, PtdIns4P and PtdIns(4,5)P2 in similar proportions as reported for other cells. [3H]inositol was also incorporated into a fourth lipid, tentatively identified as an inositolglycan. [3H]inositol was also incorporated into a number of inositol phosphates, with the greatest amount of incorporation after 24 h into an inositol pentakisphosphate. After serum starvation for 24 h, the addition of 10% whole or dialysed serum for 2 or 20 min increased (P < 0.05) incorporation into inositol tris- and tetrakisphosphates. These results demonstrate the presence of PtdIns system components in embryonic stem cells and increased PtdIns turnover in response to serum growth factors.

The precision of practice analysis results in the professions

A practice analysis, in which an appropriate sample of professionals is asked to describe what they do in their practices, is considered an essential part of the content-related validity evidence for licensure and certification tests. This article examines the precision of estimates of the mean frequencies for categories of activities in an activity inventory administered on two occasions about 6 weeks apart. In particular, it explores the variability in estimates of the mean frequencies for categories due to the sampling of respondents, activity statements, and occasions. The results suggest that samples of 200 respondents, about 10 to 20 activity statements per category, and one occasion are adequate for estimating the mean frequency for each category.

Validating interpretive arguments for licensure and certification examinations

To validate the interpretation assigned to test scores is to support the rationale for this interpretation. The interpretations for licensure and certification tests involve a sequence of inferences, or an argument, leading from the test score to decisions about licensure or certification. This article examines several possible interpretive arguments for licensure and certification test scores and analyzes the evidence required to support each type of argument. Particular attention is given to a competency-based argument that involves a sequence of several inferences leading from test scores to statements about competence, and then to conclusions about expected performance in practice. Decisions about licensure or certification are based on expected performance in practice.

Effects of lithium chloride on rabbit blastocyst expansion, and accumulation of phosphoinositides and inositol phosphates

The effects of lithium, an inhibitor of the recycling of inositol in the phosphatidylinositol cycle, on rabbit blastocyst growth and metabolism of phosphoinositides were investigated. Day 2 rabbit morulae were first cultured for 2 days in basic culture medium and then transferred to medium containing myo-[2-3H]inositol for culture for a further 3 days. At the end of culture, the resulting blastocysts were incubated with LiCl (0, 1, 5, 10, 20 mmol l-1) for 1 h. The blastocysts were then lysed and both the aqueous and lipid portions were analysed for incorporated radioactivity. Thin layer chromatographic separation of the lipid portion indicated that lithium had no significant effect on formation of radiolabelled phosphoinositides. However, high performance anion exchange chromatography indicated that lithium significantly stimulated accumulation of radiolabelled inositol monophosphate and inositol 1,4,5-trisphosphate. This result indicates that the phosphatidylinositol cycle is turning over in rabbit blastocysts. Continuous culture of rabbit embryos for 5 days in media containing LiCl (5, 10, 15 and 20 mmol l-1) significantly decreased blastocyst growth as measured by blastocyst expansion and incorporation of [3H]thymidine. However, supplementing the medium with excess inositol (up to 9375 mumol l-1), in an attempt to increase the intracellular uptake of inositol and thus compensate for the inhibitory effect of lithium on inositol recycling, did not reverse the inhibitory effect of lithium on blastocyst growth.

Incorporation of [3H]inositol into phosphoinositides and inositol phosphates by rabbit blastocysts

Preimplantation rabbit embryos collected at the early morula stage were cultured to blastocysts in the presence of [3H]inositol. The blastocysts were lysed, and both the aqueous and lipid portions were analysed for incorporated radioactivity. Thin-layer chromatographic separation of the lipid portion indicated that [3H]inositol was incorporated into phosphatidylinositol, phosphatidylinositol 4-phosphate, and phosphatidylinositol 4,5-bisphosphate. HPLC anion-exchange chromatography indicated that [3H]inositol was incorporated into inositol phosphates, including the two second messengers, inositol 1,4,5-triphosphate and inositol 1,3,4,5-tetrakisphosphate, and also inositol monophosphate and inositol 1,4-bisphosphate. These results provide evidence that rabbit blastocysts may have an active phosphatidylinositol second messenger system, which may be responsive to intrauterine factors or intraembryonic paracrine factors.

Protein content of rabbit embryos: one cell to peri-implantation blastocyst

The protein content of rabbit embryos during the first 7 days of development in vivo was determined. The protein content of intact embryos, embryonic cells (intact embryos without mucin coats for developmental stages up to 96 h post-coitum and free of blastocyst coverings for later stages) and blastocyst coverings were determined by the Pierce Micro BCA assay. The mean protein content of intact one-cell or two-cell embryos was 0.16 micrograms and increased at the four- to six-cell stage with no further increase until the late morula/early blastocyst stages (days 3 to 4). There was a 53-fold increase in protein from the early to late blastocyst stages. The protein content of embryonic cells was stable at a mean value of 0.16 micrograms until the late morula stage (day 3) and then increased to a mean of 6.85 micrograms on day 6 and 50.38 micrograms on day 7. The increase in protein content of intact embryos up to about 72 h appeared to be due solely to an increase in the protein content of the mucin coat. The protein content of the blastocyst coverings increased from a mean of 2 micrograms on day 5 to a mean of 35 micrograms on day 7. For blastocyst stages, the total protein content of intact blastocysts and of embryonic cells was correlated with the surface area of the embryos (r2 = 0.895 and 0.873, respectively) and, thus, an increase in blastocyst size is a true index of blastocyst development.

Uptake and incorporation of inositol by preimplantation mouse embryos

The uptake of myo-inositol by preimplantation mouse embryos was investigated using [3H]myo-inositol. Uptake increased about 12-fold between one- and two-cell stages and increased again at the blastocyst stage (> 6-fold compared with the two-cell stage). Uptake at the blastocyst stage was time and temperature dependent; it was stimulated by sodium, inhibited by glucose and appeared to take place mainly via a saturable mechanism. Uptake in the presence of 6.25 mmol inositol l-1 was 1424 fmol inositol per blastocyst per h. About 10% of the [3H]inositol taken up by blastocysts during 8 h in culture was incorporated into lipid. Thin layer chromatography of the lipid showed that most of this inositol was incorporated into lipid material co-migrating with phosphatidylinositol with a small proportion co-migrating with phosphatidylinositol 4-phosphate.

The assessment of professional competence

Valid assessment of professional competence has proven to be an elusive goal. Objective tests, direct observation of performance, overall ratings of competence, and simulations have been tried and found wanting in one way or another. Objective test items are criticized as being unrealistic and therefore invalid. Direct observation tends to be very unreliable and therefore invalid. Simulations and overall ratings of competence share both of these flaws to some extent. Basically, you can't win. This article outlines some of the many ways to lose and some ways to cut these losses. In doing so, it proposes a general framework for evaluating the validity of measures of competence, and it uses this framework to examine the strengths and weaknesses of three approaches to the assessment of professional competence: direct observation, simulation, and objective testing.

Inositol stimulates DNA and protein synthesis, and expansion by rabbit blastocysts in vitro

The effect of different concentrations (0, 0.6, 3, 15, 75 and 375 microM) of myo-inositol on the development of rabbit morulae to expanded blastocysts was investigated in terms of blastocyst expansion and synthesis of DNA and protein, as measured by incorporation of [3H]thymidine and [14C]amino acids into acid-precipitable material. A concentration of 15 microM inositol caused a 2.8-fold increase in blastocyst expansion (P less than 0.01), a 9.9-fold increase in thymidine incorporation into DNA (P less than 0.01) and a 3.6-fold increase in amino acid incorporation into protein (P less than 0.01). There were no significant differences in the range from 15 to 375 microM inositol.

Purification of an embryotrophic factor from commercial bovine serum albumin and its identification as citrate

A factor of low M(r) with growth-promoting effects on rabbit embryos was extracted and purified from commercial bovine serum albumin (BSA). This embryotrophic factor was extracted from BSA dissolved in formic acid by membrane filtration (membrane cutoff of M(r) 10,000) and then freeze-drying of the filtrate. The extract was purified successively by chromatography on G-10 Sephadex, QAE-Sephadex A-25 anion exchange and high-performance liquid chromatography (HPLC) reverse-phase columns. Mass spectrometry of the active reverse-phase material indicated that the major component in this material had an M(r) of 192. The embryotrophic factor in the low M(r) extract of BSA was shown to be citrate, because: (i) the mass spectra of the active reverse-phase material and citrate were identical, (ii) the activity was eluted at the identical position to citrate on an analytical HPLC anion-exchange column, (iii) the original BSA sample was shown by enzyme assay to be heavily contaminated by citrate and (iv) citrate stimulated cell proliferation and expansion of blastocysts.

Successful co-culture of 1-4-cell cattle ova to the morula or blastocyst stage

Bovine ova (n = 326) collected at the 1-4-cell stage were cultured in TCM-199 + 10% foetal calf serum with or without oviducal cells. The bovine oviducal cells were collected and seeded either on the day of ovum recovery (BOC-0) or 3 days earlier (BOC-3). In Exp. 1, the effect of age of oviducal cells in co-culture on ovum development was examined. In the BOC-0 and BOC-3 treatments, respectively, 36/46 (78%) and 30/37 (81%) of ova developed to morulae or blastocysts, while no ova developed past the 8-16-cell stage in the absence of oviducal cells. In Exp. 2, the effect of age of oviducal cells and of physical contact between the oviducal cells and ova on ovum development was examined. In the BOC-0 and BOC-3 treatments, respectively, 29/42 (69%) and 23/43 (53%) of the ova developed to morulae or blastocysts, while 1/42 (2%) developed to the morula stage in the absence of oviducal cells. Physical separation of the ova using a microporous membrane inserted between the oviducal cells and the ova did not affect ovum development, with 26/42 (62%) and 22/42 (52%) of ova developing to morulae or blastocysts in the BOC-0 and BOC-3 treatments, respectively. A high proportion of the morulae and blastocysts in Exp. 1 (57/66, 86%) and Exp. 2 (67/100, 67%) were of quality grades 1 or 2, with mean nuclei counts of 85 for morulae and 111 for blastocysts.(ABSTRACT TRUNCATED AT 250 WORDS)

Control of growth in preimplantation embryos

I would like to thank the President and the Selection Committee of the Academy for the honour of an invitation to present the 1990 Conway Review Lecture. The subject of the topic is the Control of Growth in Preimplantation Embryos.

Role delineation for dietetic practitioners: empirical results

In order to meet its need for a current, integrated picture of the dynamic profession of dietetics, The American Dietetic Association, with assistance from American College Testing, undertook a study focusing on the roles of entry-level dietetic technicians and registered dietitians and beyond-entry-level registered dietitians. A nationwide mail survey was conducted on random samples of 3,559 dietitians who had been registered for up to 3 years, 6,647 dietitians who had been registered for more than 3 years, and all 1,226 graduates (in the previous 3 years) from the 70 ADA-approved programs preparing dietetic technicians that agreed to participate (out of the 77 ADA-approved programs). Response rates of 77.5%, 78.7%, and 68.5% were achieved for the two samples of registered dietitians and the sample of dietetic technicians, respectively. The results show that the most commonly chosen work setting for the three respondent groups was "inpatient-care, acute-care facility." There were substantial differences among the three groups in the types of activities performed and in the level of responsibility for various kinds of activities. The beyond-entry-level registered dietitians were involved in the broadest range of activities and had the most responsibility for policy setting and other administrative activities, such as preparing budgets. The results of the study provide a detailed description of dietetic practice over a broad range of practitioner-experience levels, practice settings, and client groups.

Effects of the putative phospholipid precursors, inositol, choline, serine and ethanolamine, on formation and expansion of rabbit blastocysts in vitro

Rabbit morulae were cultured to blastocysts in various concentrations of the potential phospholipid precursors, myo-inositol, choline, serine and ethanolamine. Serine (20-2500 microM) had a significant stimulatory effect on blastocyst formation and blastocyst expansion and inositol (3-375 microM) had a significant stimulatory effect on blastocyst expansion. There was no significant stimulatory effect of choline or ethanolamine.

Vitamin requirements for development of eight-cell hamster embryos to hatching blastocysts in vitro

We have shown in previous studies that development of 8-cell hamster embryos to hatching and hatched blastocysts in vitro is stimulated by the addition to the culture medium of a group of 11 water-soluble vitamins and growth factors from Ham's F10 medium. In the present study, the requirement for each of these vitamins for blastocyst hatching was examined by using a chemically defined protein-free medium. Eight-cell hamster embryos were cultured for 3 days either in medium with all 11 vitamins or in media with a single vitamin omitted at a time or in medium without any vitamins. The only vitamins whose omission caused a significant decrease in blastocyst hatching at any stage were inositol, pantothenate, and choline, with the omission of inositol having the most severe effect. This finding was confirmed in a subsequent experiment in which the addition of these 3 vitamins stimulated the same degree of hatching as all 11 vitamins.

Protein-free culture medium containing polyvinylalcohol, vitamins, and amino acids supports development of eight-cell hamster embryos to hatching blastocysts

In vitro development of eight-cell hamster embryos to hatching blastocysts requires the presence of amino acids and a group of water-soluble vitamins in the culture medium. The present studies investigated the effect of type of macromolecule on blastocyst hatching and on the requirement for vitamins. Embryos were cultured for 3 days in the presence of the synthetic macromolecule polyvinylalcohol (PVA) and of different types of bovine serum albumin (BSA), both with and without vitamins. The results showed th at eight-cell embryos develop to hatching blastocysts in the presence of vitamins and amino acids with PVA as the only macromolecule in the medium. The presence of certain types of BSA reduced but did not eliminate the need for vitamins. Glutamine alone was as efficient as a complete amino acid supplement in supporting blastocyst hatching. These results demonstrate for the first time that eight-cell hamster embryos can be cultured to hatching blastocysts in a chemically defined medium.

The effects of water-soluble vitamins on the expansion of rabbit blastocysts in vitro

The vitamin requirements for culture of rabbit morulae to expanded blastocysts were examined. Early morulae were cultured for 5 days either in a control complete medium containing all the 11 water-soluble vitamins of F10 culture medium (biotin, pantothenate, choline, inositol, niacinamide, pyridoxine, riboflavin, thiamine, folic acid, B12, and lipoic acid) or in media with each vitamin omitted individually. Blastocyst diameters were measured at the end of culture. The omission of inositol, pyridoxine, riboflavin, and niacinamide resulted in large statistically significant decreases in blastocyst expansion. The omission of B12 resulted in a significant increase in blastocyst expansion indicating that the level present in F10 is toxic to rabbit blastocysts.

Minimal nutrient requirements for culture of one-cell rabbit embryos

The minimal nutrient requirements of one-cell rabbit embryos for cleavage during in vitro culture were investigated. One-cell rabbit embryos were cultivated in a simple salt solution supplemented with the macromolecule polyvinylalcohol (PVA) either alone or with bovine serum albumin (BSA), amino acids, or one of a number of potential energy sources. At the end of 48 h culture, the embryos were stained with aceto-orcein HCl and the number of nucleated cells per embryo counted. One-cell embryos in medium with PVA but without an exogenous, fixed nitrogen source or energy substrate cleaved to a mean of 10.4 cells per embryo. Addition of the putative energy substrates--phosphoenolpyruvate, malate, acetate, and lactate--resulted in nonsignificant increases in cleavage rate. Glucose, pyruvate, a group of 20 amino acids from Ham's F-10 medium, and BSA gave a statistically significant doubling of the cleavage rate. These results indicate that the one-cell rabbit embryo, unlike the mouse embryo, has significant endogenous energy sources and that an exogenous, fixed nitrogen source is not essential for cleavage.

A survey of the effects of proteases and glycosidases on culture of rabbit morulae to blastocysts

The effects of a range of commercially available proteases and glycosidases on blastocyst development and hatching were examined on rabbit embryos cultured from the morula stage in a defined medium supplemented with charcoal-treated bovine serum albumin. The proteases tested were trypsin, alpha-chymotrypsin, thrombin, elastase, plasmin, papain, clostripain, collagenase, Streptomyces griseus protease and cathepsin C. The glycosidases tested were neuraminidase, alpha-mannosidase, beta-galactosidase and hyaluronidase. None of these enzymes appeared to stimulate blastocyst growth. The only enzymes which digested the embryonic investments, the zona and mucin coat, sufficiently to cause complete blastocyst hatching were trypsin and Streptomyces griseus protease at relatively low concentrations (250 ng/ml) and chymotrypsin and elastase at higher concentrations.

A low molecular weight extract of bovine serum albumin stimulates rabbit blastocyst cell division and expansion in vitro

Fraction V bovine serum albumin (BSA) was dissolved in 5% formic acid and filtered through a molecular filter with a cutoff of Mr 10 000. The freeze-dried filtrate stimulated increased cell division of cultured rabbit morulae to blastocysts (up to 8-fold increase in cell number) and increased blastocyst expansion (greater than 2-fold). These results show that some samples of commercial BSA contain an embryonic growth factor of a low molecular weight.

Variability in different lots of commercial bovine serum albumin affects cell multiplication and hatching of rabbit blastocysts in culture

Rabbit morulae were cultured in vitro for 4 days in a synthetic culture medium supplemented with two different lots of commercial bovine serum albumin (BSA) and two different amino acid formulations in a factorial 2 x 2 arrangement. One lot of BSA caused complete hatching of a proportion of blastocysts and formation of more than twice as many cells per blastocyst (hatched and unhatched) as that of the second BSA lot which did not cause complete hatching of any blastocysts. The mean cell numbers of hatched blastocysts were more than twice those of non-hatched blastocysts. There was no significant effect of amino acid formulation.

Evidence that protease action is not specifically involved in the hatching of rabbit blastocysts caused by commercial bovine serum albumin in culture

Commercial samples of bovine serum albumin (BSA) in a complex medium caused growth of 1-cell rabbit embryos to completely hatched blastocysts. Heat treatment of the BSA at 65 or 80 degrees C significantly decreased blastocyst formation and expansion and destroyed the ability to cause blastocyst hatching. Addition of trypsin at levels down to 20 ng/ml caused the formation of hatched blastocysts which degenerated rapidly. The effects of 5 protease inhibitors (ovomucoid trypsin inhibitor, alpha-1-antitrypsin, TAME, TLCK and soybean) were tested. Ovomucoid trypsin inhibitor, TAME and TLCK significantly inhibited blastocyst hatching but only at the highest concentration used. These inhibitors also reduced blastocyst formation and expansion, indicating that their effect was not specifically on blastocyst hatching in vitro. It is concluded that hatching of rabbit blastocysts is probably not dependent on protease action.