Marie-Christine Guérin

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Plasma melatonin was measured at the winter and summer solstices and the autumn and spring equinoxes in four mares held under natural conditions at 35 degrees S. At all seasons the onset of the nightly elevated melatonin was coincident with or after the time of sunset and the melatonin offset after the time of sunrise. The duration of elevated melatonin was(More)
Well-established circadian physiology supports the view that photoperiodic time measurement utilizes the coincidence between the presence of light and a photosensitive phase of a 'biological clock' to alter reproductive status--the so-called external coincidence model of seasonal breeding. In this review, we examine the mechanism whereby photoperiod(More)
PURPOSE Poly(ADP-ribosyl)ation is a reversible post-translational modification that requires the contribution of the enzymes poly(ADP-ribose) polymerase-1 (PARP-1) and poly(ADP-ribose) glycohydrolase (PARG). Our study explores expression and activity of PARP-1 and PARG in uveal melanoma cell lines with varying tumorigenic properties. METHODS Gene(More)
The timing of reproductive activity in the seasonal breeding Romney Marsh ewe depends on the measurement of photoperiodic time. In this experiment, artificial light and dark signals are provided in a measured sequence at an inappropriate time of year to induce breeding out of phase with environmental photoperiod. The endogenous circadian responses and(More)
Two experiments, using Romney Marsh ewes, tested for the existence and role of a critical interval of the circadian pacemaker located near dusk that may be integrally involved in the precise timing of the breeding season. Groups of Romney Marsh ewes (n = 6) were provided with exogenous melatonin by injection at dusk (Experiment 1) or by infusion at dawn or(More)
Groups of Romney Marsh ewes (n = 24) were injected with exogenous melatonin or subjected to extended darkness or a combination of both at dusk from the winter to the summer solstice before being re-exposed to the natural photoperiod at 35 degrees S. The animals were at all times exposed to natural dawn. The onset of subsequent oestrus was delayed when(More)
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