Thomas Papanikolaou

University of Thessaly, Lárisa, Thessalia, Greece

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Publications (10)12.23 Total impact

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    ABSTRACT: Blood concentrations of progesterone, FSH and oestradiol in Karagouniko ewes subjected to laparoscopic ovum pick-up (OPU) at specific stages of induced oestrous cycle, were measured. Twenty-four cyclic ewes were randomly allocated into four equal groups (A, B, C and D). Oestrus was synchronized with progestagen intravaginal sponges and detected by teaser rams (oestrus: day 0). In group A, during the induced oestrous cycle, OPU was performed on days 4, 9 and 14 (sessions A1, A2 and A3, respectively). In group B and group D, OPU was performed once, on day 9 and 14, respectively. In group C (controls), endoscopic observation of follicular population was performed three times, as in group A. Starting at sponge removal, progesterone was measured in blood samples collected on 22 daily occasions and oestradiol in samples collected on 27 occasions collected at various time-points starting 2 h before to 24 h after OPU. Follicular populations did not differ among A1, A2, A3 or between C1, C2, C3 and A1, A2, A3 or A1, B, D, respectively. Oocytes of better quality (category ‘1’ or ‘2’) were collected at A3 session compared with A1 (P < 0.05). Progesterone concentration and oestrous cycle length did not differ among groups. Decreased oestradiol concentrations followed by FSH increase were recorded 3–5 h after OPU. The results confirm the regulatory role of oestradiol on FSH secretion. The quality of collected oocytes was improved in subsequent pick-up sessions in the oestrous cycle. Moreover, OPU at specific stages of the luteal phase of the cycle, even when applied repeatedly, do not affect the normal oestrous cycle length of ewes.
    Animal reproduction science 05/2013; 138(s 3–4):180–187. · 1.56 Impact Factor
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    ABSTRACT: Follicular development and oocyte quality were assessed by laparoscopic observation and in vitro fertilisation, respectively, in melatonin-treated (Group M) and control (Group C) anoestrous Chios ewes (n = 10 in each group). Fourteen days after melatonin insertion, all ewes had laparoscopic evaluation of the follicular population followed by oocyte pick-up (OPU); on day 22 intravaginal progestagen sponges were inserted for 14 days. Two days after sponge removal the follicular population was re-evaluated and a second follicular aspiration was performed. Collected oocytes from the second OPU underwent in vitro maturation, fertilisation and culture. The number of large follicles was higher in Group M than in the control ewes during the first OPU and tended to be so (P = 0.06) at the second. Morphologically, oocytes collected from controls were of better quality than those from Group M; however, more oocytes collected from melatonintreated animals fertilised and developed in vitro . These results indicate that melatonin is a potent regulator of follicular development and oocyte competence during the anoestrous period of the ewe.
    Acta Veterinaria Hungarica 07/2009; 57(2):331-5. · 1.17 Impact Factor
  • Acta Veterinaria Hungarica 01/2009; 57(2):331. · 1.17 Impact Factor
  • 12th Annual Conference of the European Society for Domestic Animal Reproduction, Utrecht, The Netherlands.; 11/2008
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    ABSTRACT: In the present study, four experiments were conducted to investigate the possible effects of plasminogen activators (urokinase-type plasminogen activator (u-PA) and tissue-type plasminogen activator (t-PA)), plasmin, and a plasmin inhibitor (epsilon-aminocaproic acid (epsilon-ACA)) on different stages of bovine in vitro embryo production (IVP). The concentrations of these modifiers in IVP media were conditioned according to the plasminogen activator activity of bovine preovulatory follicular fluid. Media were modified in a single phase of IVP with an 18 h or 24 h incubation for in vitro maturation (IVM) and a 24 h or 48 h incubation for the IVF or in vitro culture (IVC), respectively. After IVM the oocytes were either fixed and stained or underwent IVF and IVC. The main findings were: (1) plasmin added to the 18 h IVM medium increased maturation rate without affecting fertilisation or embryo development rates; (2) t-PA added to the IVF medium significantly increased cleavage; (3) u-PA added to the IVC medium significantly increased embryo development rates; (4) the efficiency of all phases of IVP was reduced after the addition of epsilon-ACA; and (5) plasminogen addition had no effect in any IVP phase tested. We conclude that the members of the plasminogen activator-plasmin system contribute in different ways to bovine IVM, IVF and IVC.
    Reproduction Fertility and Development 02/2008; 20(2):320-7. · 2.58 Impact Factor
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    ABSTRACT: This study was undertaken to investigate the effect of melatonin pretreatment on developmental competence of oocytes aspirated from Chios ewes. Fourteen adult ewes were allotted into two equal groups (M, C). During anestrus melatonin implants (Regulin, Ceva) were inserted (day 1) in ewes of group M. On day 14, in both groups laparoscopical follicular aspiration (OPU) of all visible follicles was carried out. On day 22 intravaginal progestagen sponges (MAP, Veramix, Upjohn/Veterin) were inserted for 14 days in all ewes. At the time of sponge withdrawal 400 IU eCG (Intergonan, Intervet) was administered and a second OPU was performed 2 days later (day 38). The collected oocytes from the 2nd OPU were matured and fertilized in vitro. The number of large follicles at the 1st OPU was greater in melatonin treated than in control ewes (mean ± SD: 4.4 ± 1.8 vs 1.8 ± 1.5; p < 0.05). However, at the 2nd OPU the follicular population did not differ between melatonin-treated and control ewes (6.4 ± 2.1 vs 4.2 ± 1.7; p > 0.05). Although the quality of collected oocytes (grade A and B) at the 2nd OPU was better in group C (87.5%) compared withM(42.9%), the fertilization rate was greater in group M (20/28, 71.4%) compared with C (6/21, 28.6%) (p < 0.05). In group M 30% (6/20) of fertilized oocytes reached the blastocyst stage but none from group C did so. It is concluded that melatonin treatment significantly affects the developmental competence of oocytes collected from ewes.
    10th Annual Conference of the European Society for Domestic Animal Reproduction, 2006. (Poster P126),, Portoroz, Slovenia; 09/2006
  • 9th Annual Conference of the European Society for Domestic Animal Reproduction; 09/2005
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    ABSTRACT: Possible hormonal aberrations precluding conception or maintenance of pregnancy in dairy ewes subjected to ovulation synchronisation were investigated in this study. The pituitary response to exogenous gonadotrophin-releasing hormone (GnRH) was tested at different luteal stages in 36 ewes. Oestruses were synchronised by using progestagen-impregnated sponges and the animals were randomly allotted into one of three treatment groups (A, B and C; n = 12 for each). Treatments commenced on Days 4, 9 and 14 of the new cycle (oestrus was defined as Day 0). Ewes were given two GnRH injections, 5 days before and 36 h after a prostaglandin F2+/- (PGF2+/-) injection, and the animals were inseminated 12-14 h after the second GnRH injection (modified OVSYNCH). For luteinising hormone (LH) determination blood samples were withdrawn from six ewes of each group at the time of GnRH administration, and 30, 90, 180, 270 and 360 min later. Progesterone was assayed in samples taken every other day starting from oestrus and for 17 days after the second GnRH injection, and in an additional sample collected on the day of insemination. After the first GnRH injection, the LH concentration was higher in Group C than in Groups B and A (mean +/- s.d.: 64.8 +/- 10.0 ng mL(-1), 41.3 +/- 3.7 ng mL(-1) and 24.6 +/- 9.0 ng mL(-1), respectively; P < 0.05), whereas after the second GnRH injection a uniform LH release was found in all groups. PGF2+/- caused a significant decrease in progesterone (P4) concentration in all groups; however, at artificial insemination ewes that conceived had significantly lower P4 concentration in comparison with those that failed to conceive. As early as Day 5, pregnant animals had higher P4 concentrations than non-pregnant animals. Overall, 21 animals conceived (seven, nine and five ewes from Groups A, B and C, respectively). These results indicate that the proposed protocol is equally effective in inducing a preovulatory LH surge at any stage of the luteal phase, and that elevated P4 concentration along with a delayed P4 increase should be considered as a causative factor for inability to conceive.
    Reproduction Fertility and Development 01/2005; 17(8):769-74. · 2.58 Impact Factor
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    The Veterinary record 06/2004; 154(22):698-9. · 1.80 Impact Factor
  • Journal of Veterinary Pharmacology and Therapeutics 11/2003; 26(5):387-90. · 1.35 Impact Factor