Etude de la sensibilité différentielle de l'hypothalamus à l'œstradiol pour induire le pic préovulatoire de LH et le comportement sexuel (comparaison entre Brebis Ile-de-France et Romanov.)

En utilisant un modèle de phase folliculaire artificielle, la quantité minimale d œstradiol (E) nécessaire pour induire le pic préovulatoire de LH et le comportement sexuel a été comparée chez des brebis de prolificité différentes : Ile de France (IF) vs Romanov (ROM). Un signal œstrogénique très faible induit le comportement sexuel chez la brebis ROM mais pas chez l IF. L induction du pic préovulatoire de LH nécessite des quantités d E très supérieures chez la ROM par comparaison à l IF. Le pic de LH apparaît plus tard chez la ROM. L étude de la sensibilité hypophysaire et hypothalamique à l E a montré que le moment du pic préovulatoire de LH est essentiellement contrôlé par l hypothalamus. Chez la ROM, des doses modérées d E stimulent une faible libération de GnRH dans le liquide céphalorachidien, sans qu elle ne soit traduite au niveau hypophysaire par une augmentation de libération parallèle de LH. Ce peptide, participerait au contrôle du comportement sexuel induit par l E. La grande différence de sensibilité à l E entre les deux races semble être liée à un seuil de lecture différent du signal œstrogénique pour induire le pic de LH et le comportement sexuel.Using an artificial follicular phase model, the minimum estradiol (E) requirement to induce the preovulatory LH surge and estrous behaviour, was compared between two breeds of ewes having either single (Ile de France= IF) or multiple (Romanov= ROM) ovulations. While a small E signal is sufficient to induce estrous behaviour, in ROM ewe, the same treatment has no effect on IF ewe. A much larger amount of E is required to induce the LH surge in the ROM compared to the IF. The onset of the LH surge occurred earlier in IF. Pituitary and hypothalamic sensitivity to E were studied in vivo and in vitro. The timing of the LH surge is essentially under the control of the hypothalamus. The latency to the onset of the LH surge is timed by a negative feedback effect of E at the hypothalamic level which is longer in ROM ewes. A moderate E signal stimulates a light GnRH secretion into the cerebrospinal fluid, which was not accompanied by a parallel pituitary LH discharge. GnRH appears involved in the control of estrous behaviour. The difference in sensitivity to E between IF and ROM ewes to induce LH surge and estrous behaviour is more than likely due to a different threshold in the lecture of the E signal.TOURS-Bibl.électronique (372610011) / SudocSudocFranceF

Impact of Wastewater Spreading on Properties of Tunisian Soil under Arid Climate

The environmental impacts of irrigating an olive field with olive mill wastewater (OMW) and treated wastewater (TWW) on soil properties were investigated. The effect of different irrigation treatments of OMW (50 m3 ha−1, 100 m3 ha−1, and 200 m3 ha−1) and TWW at different soil depths was studied. The obtained findings revealed that TWW application augmented soil pH; EC values; and P, K and Ca contents in all soil layers. However, Mg and Na concentrations, as well as organic matter content (OM), were proven to decrease with TWW irrigation throughout the experiment. Whereas soil adjusted with OMW showed a decrease in K, Ca, Mg and Na contents with soil depth, a significant increase was observed with the increase in applied OMW dose. On the other hand, total phenols and OM content increased significantly with the rise in OMW levels in all the investigated layers compared to the control sample

Impact of Wastewater Spreading on Properties of Tunisian Soil under Arid Climate

The environmental impacts of irrigating an olive field with olive mill wastewater (OMW) and treated wastewater (TWW) on soil properties were investigated. The effect of different irrigation treatments of OMW (50 m3 ha−1, 100 m3 ha−1, and 200 m3 ha−1) and TWW at different soil depths was studied. The obtained findings revealed that TWW application augmented soil pH; EC values; and P, K and Ca contents in all soil layers. However, Mg and Na concentrations, as well as organic matter content (OM), were proven to decrease with TWW irrigation throughout the experiment. Whereas soil adjusted with OMW showed a decrease in K, Ca, Mg and Na contents with soil depth, a significant increase was observed with the increase in applied OMW dose. On the other hand, total phenols and OM content increased significantly with the rise in OMW levels in all the investigated layers compared to the control sample