D Rieger

University of Guelph, Guelph, Ontario, Canada

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Publications (21)30.16 Total impact

  • D. Rieger, E. Semple, S. P. Leibo
    Theriogenology 01/1997; 47(1):311-311. · 2.08 Impact Factor
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    ABSTRACT: The objective of this study was to compare the development and metabolic activity of cattle embryos co-cultured with bovine oviductal cells or cultured in serum-free medium previously conditioned by bovine oviductal cells. Zygotes were produced by in vitro fertilization of oocytes from bovine ovaries obtained from an abattoir. Development to the four-cell stage occurred by 48 h after fertilization in both culture systems, but co-cultured embryos reached the 16-cell stage by 96 h, whereas those cultured in conditioned medium did not do so until 24 h later. Similarly, the morula and blastocyst stages were reached 24 h earlier in co-culture than in conditioned medium. There were significantly more cells in the blastocysts from co-culture (96.8 +/- 6.1 versus 56.7 +/- 3.3; P < or = 0.0001). The metabolism of glutamine did not differ between embryos cultured in the two systems, but the metabolism of glucose was significantly greater in embryos cultured in conditioned medium. The first significant increase in glucose metabolism occurred between the four-cell and the 16-cell stages in embryos cultured in conditioned medium, but occurred between the 16-cell and morula stages in the co-cultured embryos, such that the glucose metabolism was significantly greater at the 16-cell stage in embryos cultured in conditioned medium compared with co-cultured embryos (6.5 +/- 1.0 versus 1.5 +/- 0.4 pmol per embryo per 3 h, P < or = 0.0001). The concentration of glucose was significantly less, and that of lactate significantly greater, in co-culture medium than in conditioned medium.(ABSTRACT TRUNCATED AT 250 WORDS)
    J Reprod Fertil 09/1995; 105(1):91-8.
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    ABSTRACT: Periovulatory gonadotrophin and steroid hormone profiles were compared between superovulated and unstimulated Holstein heifers. Treatment was induced in luteal-phase heifers with 8 injections of FSH (superovulated n=9) or saline (unstimulated n=3) given over 5 d. Both groups received 0.5 mg of cloprostenol (PG) with the sixth injection of FSH or saline to induce luteolysis. All animals were inseminated at estrus, and embryos were collected at Day 7 of gestation. Blood samples were taken hourly for 6 h after the morning injection of FSH (or saline) and then every 15 min for 3 h (from 1400 to 1700 h) on each of the 5 treatment days. Before PG, mean serum progesterone and estradiol concentrations were higher (P ≤ 0.05) and LH pulse frequency and amplitude were lower (P ≤ 0.05) in the superovulated than the unstimulated heifers. After PG, mean serum progesterone and estradiol concentrations were higher (P ≤ 0.05), LH pulse frequency and amplitude (P ≤ 0.001), and basal serum LH concentration (P ≤ 0.05) were lower in the superovulated than in the unstimulated heifers. After PG injection, the superovulated heifers had reduced FSH pulse amplitude compared with that before the injection (P ≤ 0.05). In the superovulated cows, the suppression of LH and FSH secretion was caused by the negative effects of higher concentrations of estradiol and progesterone in the hypothalamic-hypophysal axis. In the superovulated heifers, 30 h after PG treatment, serum estradiol concentration and LH pulse frequency were positively correlated with the number of CL, total number of embryos, and transferable number of embryos recovered (P ≤ 0.05).
    Theriogenology 01/1995; 44(1):59-70. · 2.08 Impact Factor
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    ABSTRACT: Beginning on Day 10 or 11 of the estrous cycle, mature Holstein heifers were given a superovulatory regimen of twice-daily injections of porcine FSH, together with injections of PG with the fifth and sixth FSH injections. Every 12 h from 24 to 60 h after PG administration, the animals received im injections of different doses of the LH releasing hormone antagonist [N-Ac-D-Nal(2)(1), D-pCl-Phe(2), D-Trp(3), D-Arg(6), D-Ala(10)]-LHRH or vehicle. Follicular development was monitored by transrectal ultrasonography every 12 h from 24 to 120 h after PG administration. All animals were given hCG at 72 h after PG injection, and were artificially inseminated. At Day 7 of gestation, the corpora lutea were counted by ultrasonography, and embryos were collected by nonsurgical flushing of the uterus. Treatment with the antagonist resulted in a dose-dependent decrease in the amplitude of the LH surge and in delays in the time of occurrence of the LH surge, ovulation and the shift from estradiol to progesterone production. These results indicate that LHRH antagonists can be used to delay the LH surge and ovulation in superovulated heifers. This finding may be beneficial to studies in the superovulation of cattle.
    Theriogenology 02/1994; 41(4):951-60. · 2.08 Impact Factor
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    D Rieger, N M Loskutoff
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    ABSTRACT: After maturation in vitro for 0, 6, 12, 18 or 24 h, the metabolism of radiolabelled glucose, glutamine, pyruvate and glycine by individual cattle oocytes was measured for 3 h. The metabolism of glucose through the Embden-Meyerhof (1.77-2.66 pmol per oocyte per 3 h) and pentose-phosphate (0.39-0.75 pmol per oocyte per 3 h) pathways was low and did not change over time. The oxidative metabolism of glucose carbon through the Krebs cycle was low throughout maturation, but increased significantly (P < or = 0.05) at 6 h (0.41 pmol per oocyte per 3 h) and 18 h (0.69 pmol per oocyte per 3 h). Pyruvate, glutamine and glycine metabolism in the Krebs cycle increased during culture. Pyruvate metabolism increased significantly from 0 h (17.3 pmol per oocyte per 3 h) to 6 h (23.3 pmol per oocyte per 3 h) and reached a maximum at 12 h (30.8 pmol per oocyte per 3 h). Glutamine metabolism was unchanged from 0 to 12 h (0.89 pmol per oocyte per 3 h), and then increased significantly at 18 h (2.25 pmol per oocyte per 3 h). Glycine metabolism increased significantly from 6 h (0.21 pmol per oocyte per 3 h) to 12 h (0.46 pmol per oocyte per 3 h) and reached a maximum at 18 h (0.68 pmol per oocyte per 3 h). The results suggest that oxidative metabolism increases, and is the major site of cellular energy production, during maturation of the cattle oocyte in vitro.
    J Reprod Fertil 01/1994; 100(1):257-62.
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    ABSTRACT: Superovulated Holstein heifers (n = 32) were given a depot injection of 500 mg recombinant bovine somatotropin (rBST) or vehicle at Day 4 of the estrous cycle (7 days before the first FSH injection); at Day 11, coincidentally with the first FSH injection; or at Day 15, the time of artificial insemination. Embryos were collected nonsurgically, and the number of corpora lutea was counted by ultrasonography at Day 7 after insemination. Blood samples were taken every second day, from Day 2 of the superovulatory cycle until the day of embryo collection, and were analyzed for progesterone, somatotropin and insulin-like growth factor-1 (IGF-1). Somatotropin-treated heifers at Day 11 had a significantly higher mean number of corpora lutea than the controls (18.1 vs 13.4; P </= 0.05). Day 4 treatment tended to increase the mean number of corpora lutea (15.4; P <- 0.10), and significantly increased the overall percentage of transferable embryos (74.6 vs 58.6%; P </= 0.01). In the control animals, plasma IGF-1 was uncorrelated to somatotropin (P > 0.63), but it was negatively correlated with progesterone (P </= 0.01), suggesting that IGF-1 production in the superovulated heifer may be related to ovarian development.
    Theriogenology 11/1993; 40(5):1003-13. · 2.08 Impact Factor
  • K J Betteridge, D Rieger
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    ABSTRACT: This report was commissioned by the Canadian government on the relevance of new techniques in animal embryology to the social, ethical and clinical applications of assisted human reproduction. It briefly describes the history of animal breeding, and the regulation of the female reproductive tract, ovulation and fertilization in laboratory and veterinary species. Embryo transfer is described in detail, including the synchronization of reproductive cycles, superovulation and embryo growth in vitro. Methods of experimental embryology, including bisection, sexing of spermatozoa and embryos, cloning and gene therapy are described. The relevance of these studies to human IVF are considered briefly.
    Human Reproduction 02/1993; 8(1):147-67. · 4.67 Impact Factor
  • D RIEGER, N LOSKUTOFF
    Theriogenology 01/1993; 39(1):298-298. · 2.08 Impact Factor
  • Theriogenology 01/1993; 39(1):252-252. · 2.08 Impact Factor
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    ABSTRACT: The metabolism of radiolabelled glucose and glutamine was measured in individual cattle embryos produced by in vitro maturation and fertilization of oocytes, and culture with bovine oviductal epithelial cells. Metabolism of glucose through the pentose-phosphate pathway increased almost 15 times and the total metabolism of glucose 30 times, during development from the two-cell to the expanded blastocyst stage. The first marked increase in glucose metabolism did not occur until between the eight- and 16-cell stages, the time of activation of the embryonic genome. Conversely, the metabolism of glutamine was high in two- and four-cell embryos and then decreased to reach a minimum at the compacted morula to blastocyst stage, possibly because of degradation of maternally derived enzymes. Blastocyst expansion was accompanied by significant increases in the metabolism of glucose and glutamine, presumably reflecting the increased energy demands of Na(+)-K+ ATPase necessary for formation and maintenance of the blastocoel.
    J Reprod Fertil 08/1992; 95(2):585-95.
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    ABSTRACT: The metabolism of, and retention of radioactivity from, radiolabelled glucose, glutamine and pyruvate were measured in individual cattle embryos produced in vitro from the 2-cell to hatched blastocyst stage. Uptake was defined as the numeric sum of metabolism and retention of radiolabel. Glucose metabolism increased significantly between the 8- and 16-cell stages, but was accompanied by a much larger increase in glucose uptake. Consequently, the proportion of glucose uptake that was metabolized through the pentose-phosphate and Embden-Meyerhof pathways reached a minimum at those stages. From the compacted morula stage onward, the calculated uptake of [14C]glucose was only 25 to 33% of that calculated for [5-3H]glucose. This suggests that 66 to 75% of glucose carbon leaves the embryo, after metabolism to phosphoenolpyruvate, in some form other than CO2. Little or no glucose metabolism by the Krebs cycle could be detected at any stage. Both glutamine and pyruvate metabolism were relatively high at the 2- and 4-cell stages, declined to a minimum at the compacted morula stage and then increased with blastulation. Glutamine metabolism continued to increase with expansion and hatching of the blastocyst, but pyruvate metabolism did not. This suggest that, relative to the activity of the pathway from pyruvate to 2-oxoglutarate, the activity of the 2-oxoglutarate-to-oxaloacetate segment of the Krebs cycle is of increasing significance during expansion and hatching of the cattle blastocyst.
    Reproduction Fertility and Development 02/1992; 4(5):547-57. · 2.58 Impact Factor
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    ABSTRACT: Individual Day-7 embryos (morulae to expanded blastocysts) were incubated with radiolabelled substrates and karyotyped to determine the sex. In Exp. 1, embryos were incubated for 3 h with D-[1-14C]glucose, as a measure of the activity of the pentose-phosphate pathway (PPP) and D-[5-3H]glucose, as a measure of total glucose metabolism. The labelled products 14CO2 and 3H2O were collected throughout the measurement period. Total glucose metabolism in male embryos was twice that in female embryos and increased between the morula and expanded-blastocyst stages. Relative to total glucose metabolism, PPP activity was four times greater in female than in male embryos. In Exp. 2, embryos were cultured with D-[1-14C]glucose, and L-[3,4-3H(N)]glutamine (a measure of Krebs cycle activity) in the presence of brilliant cresyl blue, a stimulator of the PPP. Glutamine metabolism increased from the morula to expanded-blastocyst stages. Relative to the metabolism of glutamine, the activity of the PPP was one-third greater in female than in male embryos.
    J Reprod Fertil 10/1991; 93(1):125-32.
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    ABSTRACT: The ability of purified preparations of platelet-activating factor (PAF), from three different suppliers, to induce thrombocytopaenia in mice after splenectomy and to activate mouse platelets in vitro was examined. Although the PAF preparations were potent activators of horse and cow platelets in vitro, injections of up to 1 microgram PAF failed to elicit thrombocytopaenia responses in either CD1 or Swiss Webster random-bred mice. However, when thrombin was injected into Swiss Webster mice, a dose-dependent decrease in the concentration of platelets was observed. Furthermore, isolated platelets from these strains and from 3 inbred lines (C3H/He, BALB/c, C57BL/6) of mice, were not aggregated by PAF in vitro but were sensitive to adenosine diphosphate and thrombin. No change in circulating platelet concentrations was observed over the initial 7 days of gestation in intact Swiss Webster and C57BL/6 or splenectomized C57BL/6 mice, suggesting either an absence of PAF production during early pregnancy in these strains or insensitivity of their platelets to PAF. These results suggest that many mouse strains are unsuitable for the bioassay of PAF.
    J Reprod Fertil 08/1991; 92(2):483-94.
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    ABSTRACT: Mature Holstein heifers were induced to superovulate with twice-daily injections of porcine follicle-stimulating hormone (FSH), and were given either 20 mg i.m. of recombinant bovine somatotrophin (rBST) or saline with each FSH injection. The animals were artificially inseminated and the embryos were collected nonsurgically at Day 7. There was no significant difference in the mean (+/-S.D) total number of embryos collected from rBST-treated animals (8.3+/-5.3) when compared with that of the controls (7.2+/-6.6), or in the mean number of transferable embryos (5.3+/-4.0 vs 5.2+/-4.5). However, co-treatment with rBST tended to increase the ovulatory response, and it significantly increased plasma progesterone concentrations at Day 6 (P = 0.04). Based on these latter observations, we conclude that treatment with rBST enhanced the superovulatory response in heifers.
    Theriogenology 06/1991; 35(5):863-8. · 2.08 Impact Factor
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    ABSTRACT: The decrease in embryo viability caused by cryopreservation may be due, in part, to metabolic disturbances. To determine the effect of cryopreservation on metabolism, Day -6.5 horse embryos were either frozen and thawed using glycerol as the cryoprotectant, given only the glycerol treatment or washed an equal number of times in phosphate buffered saline (PBS). Before and after treatment, individual embryos were incubated with L-[14C(U)]-glutamine, to measure Krebs cycle activity, and D-[5-3H]-glucose, to measure Embden-Meyerhof pathway activity. Before treatment, glucose metabolism ranged from 110-625 pmol/2 h and glutamine metabolism from 4.1-15.9 pmol/2 h, both being highly correlated with embryo volume. Mean glucose metabolism in the control group increased 76% between the pre-treatment and post treatment measurements compared with 1% in the pooled treated groups, whereas mean glutamine metabolism increased only 10% in the control group but 50% in the treated embryos. Before treatment, there was no difference in mean ratio of glucose to glutamine metabolism between groups, but after treatment this ratio was almost 2-fold greater in the control group than in the treated group. These results indicate that cryopreservation inhibits anaerobic glucose metabolism and stimulates aerobic glutamine metabolism. However, this is an effect of the cryoprotectant, rather than of freezing and thawing.
    Journal of reproduction and fertility. Supplement 02/1991; 44:411-7.
  • Theriogenology 01/1990; 33(1):306-306. · 2.08 Impact Factor
  • D RIEGER, J WALTON, W JOHNSON, D COY
    Theriogenology 01/1990; 33(1):307-307. · 2.08 Impact Factor
  • Theriogenology 01/1990; 33(1):339-339. · 2.08 Impact Factor
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    ABSTRACT: Mature cyclic Holstein heifers were given a luteolytic dose of cloprostenol followed by two i.v. injections, 12 h apart, of various doses of [Ac-D-Nal1, D-p-Cl-Phe2, D-Trp3, D-Arg6, D-Ala10]-LHRH, beginning either at the time of first observation of behavioural oestrus, or 48 h after the cloprostenol injection. When treatment began at the first observation of oestrus, the time of ovulation, as determined by ultrasonic echography, was significantly delayed by total doses of 0.8 mg or more of the antagonist. When given at 48 and 60 h after cloprostenol injection, a total dose of 1.5 mg of the antagonist significantly delayed the growth of the ovulating follicle, the onset of oestrus, the preovulatory surges of oestradiol, LH and FSH, and ovulation. It is concluded that the LHRH antagonist can effectively suppress endogenous LH secretion and may therefore be useful in the study of follicular development, ovulation, and other events in the oestrous cycle of the cow.
    J Reprod Fertil 06/1989; 86(1):157-64.
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    D Rieger, P Guay
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    ABSTRACT: Individual blastocysts from cows were cultured for 3 h under 5% CO2 in air, in 4 microliters droplets of Ham's F-10 medium containing D-[5-3H]glucose, D-[1-14C]-glucose, D-[6-14C]glucose, [2-14C]pyruvate, or L-[U-14C]glutamine, and with or without 2,4-dinitrophenol (DNP) or phenazine ethosulphate (PES). The 14CO2 or 3H2O produced were collected by exchange with an outer bath of 400 microliter 25 mM-NaHCO3. All combinations of substrate and treatment (control, DNP or PES) produced measurable quantities of labelled product except for D-[6-14C]glucose in the presence of PES. Untreated and DNP-treated embryos developed normally during a subsequent 48-h culture period in fresh medium, but PES-treated embryos degenerated. Pyruvate and glutamine metabolism both increased markedly in the presence of DNP, indicating that the Krebs' cycle is active, and that glutamine can be used as an energy substrate. Conversely, DNP has no significant effect on glucose metabolism, indicating that glycolysis is blocked in the bovine blastocyst due to a lack or inhibition of pyruvate kinase. The production of 14CO2 from D-[1-14C]glucose increased significantly in the presence of PES, indicating that the activity of the pentose shunt is less than maximal.
    J Reprod Fertil 08/1988; 83(2):585-91.

Publication Stats

506 Citations
30.16 Total Impact Points

Institutions

  • 1991–1995
    • University of Guelph
      • • Department of Biomedical Sciences
      • • Department of Population Medicine
      Guelph, Ontario, Canada
  • 1988–1989
    • Université du Québec à Montréal
      Montréal, Quebec, Canada