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Notes: Our aim was to study the role of the olfactory amygdala (medial and cortical nuclei) and the ventromedial nucleus of the hypothalamus (VMN) in the ability of the male odour or live males to induce a release of luteinizing hormone in anoestrus ewes. To achieve this, we temporarily blocked the activity of these structures by localized retrodialysis administration of the anaesthetic lidocaine. The effect of ram odour on the secretion of luteinizing hormone was completely blocked by inactivation of the cortical nucleus of the amygdala. In contrast, inactivation of part of the accessory olfactory system (the medial nucleus of the amygdala or the VMN) had no effect. In the presence of the male, lidocaine never impaired the endocrine response of the ewes. These results show that modulation of reproduction by the sexual partner even through pheromonal cues does not occur via the direct circuit of the accessory system. On the contrary, the cortical nucleus of the amygdala is absolutely necessary for the treatment of and/or the response to the male olfactory signal but this structure can be bypassed when other sensory cues are available.

Notes: Much of the Paris Basin is covered with loess, dominated by particles 2–50 μm in diameter, which has undergone strong pedogenesis. We have investigated the mineralogical changes that have accompanied the development of a Podzoluvisol in such material. Four silt-size and two clay-size fractions from five horizons of a profile were separated and analysed by X-ray diffraction, chemical analysis, thermogravimetric analysis and transmission electron microscopy. The minerals present in the silt-size fractions are quartz, K- and Na-feldspars, mica, chlorite, vermiculite and kaolinite. Quartz and feldspars are more abundant in the 2–10-μm fraction, micas in the 0.2–5-μm fraction and chlorite in the 〈 0.2-μm fraction. These differences suggest preferential physical breakdown of phyllosilicates, particularly chlorites. Silt-size particles seem to be composed of crystals of the same mineralogy, but only 1/40–1/50 of the size. Their disintegration contributes to enrich the fine clay fraction of the loessial material in chlorite. The proportion of chlorite increases as particle size decreases in all horizons. It also increases with depth for particle sizes larger than 5 μm. These observations indicate that physical disintegration is an essential process in the pedogenesis.〈section xml:id="abs1-2"〉〈title type="main"〉Minéralogie des fractions limoneuses d’un Luvisol Dégradé développé sur un loess dans le Bassin Parisien
RésuméLes matériaux loessiques couvrent une grande partie du Bassin Parisien et renferment une grande majorité de particules comprises entre 2 et 50 μm. Nous avons étudié les particules de cinq horizons d’un profil qui ont été séparées en quatre fractions limoneuses entre 2 et 50 μm, et deux fractions argileuses entre 0 et 2 μm. Les échantillons des différentes fractions et différents horizons ont étéétudiés par diffraction des rayons X (DRX), analyse chimique, analyse thermogravimétrique et microscopie électronique à transmission (MET). Les résultats montrent que les fractions granulométriques limoneuses sont constituées de quartz, feldspaths alcalins, plagioclases, micas, chlorites, vermiculite et kaolinite. L’étude de la composition minéralogique effectuée parallèlement sur les différents horizons et sur les différentes fractions granulométriques montre une évolution différentielle selon le type de minéral considéré. Le quartz et les feldspaths sont plus abondants dans les fractions 2–5 μm et 5–10 μm, les micas dans les fractions 0,2–2 μm et 2–5 μm, et les chlorites dans la fraction 〈 0,2 μm. Ces minéraux se concentrent dans les différentes fractions par microdivision de particules plus grossières, principalement pour les phyllosilicates et en particulier pour les chlorites. Les particules de la taille des limons peuvent par microdivision, former directement des particules de taille quarante à cinquante fois plus petite que la particule dont ils sont issus. Ce processus contribue à enrichir en chlorite la fraction argileuse fine (〈 0,2 μm) de ces matériaux loessiques. Pour tous les horizons, la proportion de chlorite augmente avec la diminution de la taille des particules. Elle augmente également avec la profondeur dans les fractions supérieures à 5 μm. Ces observations indiquent que le processus de microdivision est essentiel dans la pédogenèse.

Notes: Abstract: In sheep, melatonin secretion occurs rapidly after the onset of darkness, but the interval fluctuates according to different authors. The aim of this study was to determine this interval in sheep subjected to a long or a short photoperiod. Blood samples were taken at the right jugular vein every 100 s for 1 hr after the onset of darkness. The experiment was repeated on three consecutive days either in long (LD 16:8) or in short photoperiod (LD 8:16) on the same animals. Melatonin secretion was found to begin within 11 min under long photoperiod and 20 min under short period. It can be concluded that the onset of melatonin secretion depends on the duration of the photoperiod.

Notes: Abstract: Previous data have demonstrated that a single 1-hr light pulse at night affects the secretion of melatonin in the ram if it was given at the appropriate time. This paper reports the effect on melatonin secretion of a 1 -hr light pulse given at two different times at night to two groups of rams kept in constant darkness the day following light application. It appears that the animals were able to remember the light pulse if it was given 12 hr but not 9 hr after the lights were turned off. This memory could possibly be stored in the suprachiasmatic nucleus as reported recently in the rat.