Endocrinological profile and follicular development in cyclic ewes subjected to repeated ovum pick-up.

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 2h before to 24h 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 3-5h 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.

Luteal stage dependence of pituitary response to gonadotrophin-releasing hormone in cyclic dairy ewes subjected to synchronisation of ovulation.

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.

Long-term stimulation of mouse hippocampal slice culture on microelectrode array.

To understand mechanisms of information processing, development and degeneration of the central nervous system, simultaneous multisite recording and stimulation have become extremely helpful. We have further developed the innovative approach to record from intact neural networks using planar microelectrode arrays (MEAs) with 60 substrate-integrated nano-columnar electrodes. To allow for long-term stimulation, mouse hippocampal tissue slices were immobilized onto MEAs and permanently moved between the gas and medium phase in a specifically designed tilting incubator that made it possible to electrically contact up to 90 MEAs with 5400 electrodes. After 2-3 weeks in vitro, histochemical staining, the intracellular microinjection of the fluorescent dye Alexa and the recording of spontaneous activity revealed in vivo-like characteristics of the organotypically cultured tissue. The feasibility of long-term stimulation during culturing was demonstrated with a low frequency paradigm. 0.003 Hz stimulation over a 16 h period resulted in a significant decline of field potentials and population spikes in two identified hippocampal subregions. Control experiments revealed that this effect was not due to tissue detachment or to induced cell death. In summary, the novel technology promises to open a new avenue for analyzing regulatory interactions of neuronal activity, cell differentiation and gene expression during development and in diseases.