Temperature scrotale et fertilite chez le belier

Numerous animal studies have shown that elevated testicular, scrotal or ambient temperature induces alterations in spermatogenesis that reduce fertility. In this study, fertilization rate and embryonic mortality were assessed in 636 ewes inseminated in each uterine horn with 50 × 10⁶ cryopreserved spermatozoa from one of either four control rams or four rams submitted to a moderate (2°C), but repeated intermittent (16 hours/day for 21 consecutive days), elevation in their subcutaneous scrotal temperature by means of scrotal insulation. Pregnancy was assessed twice in each ewe at 17 days (blood plasma progesterone) and 65 days (ultrasound) after insemination. No differences were observed in the 17-day pregnancy rate between ewes inseminated with semen from control or experimental rams at up to 21 days of scrotal heating. In contrast, the rate of embryonic mortality between 17 and 65 days post-insemination was significantly higher after 4, 15 and 21 days of treatment in the experimental rams (78.7, 78.6 and 92.7 % respectively) compared to the control rams (55.0, 59.1 and 69.4 % respectively). These results indicate that ani intermittent slight increase in scrotal temperature induces a significant increase in embryonic mortality rate. As these changes were already apparent after only 4 days of scrotal heating, the effect must have ocurred either on the epididymis or on the spermatozoa stored in the epididymis     

Corrélations de croissance entre le mycélium et les rhizomorphes chez le Sphaerostilbe repens

Correlation of Growth between Mycelium and Rhizomorphs in Sphaerostilbe repens In Sphaerostilbe repens Berkeley and Broome, cultured on a solid medium in Petri dishes, growth of mycelium and chizomorphs depends on the thickness of the culture medium underlying the thallus. On shallow layers of agar medium, aggregated units were fewer and rhizomorph growth reduced. Vegetative mycelium which starts growth earlier than rhizomorphs contributed to inhibit the development of these latter. On deep layers of substrate, rhizomorphs were numerous, elongated rapidly, and eventually inhibited undifferentiated mycelium. – There was no evidence for the involvement of any inhibitor substance diffusing into culture medium or located in the thallus. Development of aerial mycelium and rhizomorphs, could, on the contrary, be interpreted as nutritional competition between these two parts of the colony.     

Isolement d'une alcool déshydrogénase chez Rhizobium et rôle dans le métabolisme indolique

Rhizabium meliloti contains an alcohol dehydrogenase (E.C.1.1.1.1.) which can be isolated by breaking the cells. This soluble enzyme was purified 16.1-fold by fractional precipitations with ammonium sulfate followed by gel filtration on Sephadex. The activity of the enzyme was tested with various aldehydes as substrates in the presence of NADH. Indole-3-acetaldehyde (IAAld) can be reduced to tryptophol (Tr-ol), and the optimal pH for this reaction is ca. 6.5. The reaction can be reversed, and Tr-ol is oxidised in the presence of NAD, but is was found that the yield was very poor; the optimal pH was ca. 8.6. This alcohol dehydrogenase is responsible for Tr-ol formation in Rhizobium, but under our experimental conditions tryptophol cannot really be considered as a precursor of IAAld and indole-3-acetic acid.     

Relations entre production et localisation de mycosporine et morphogenèses reproductrices chez le Pyrénomycète Gnomonia leptostyla

Relations between production and localisation of mycosporin and reproductive morphogenesis in the Pyrenomycete Gnomonia leptostyla.
The production of mycosporin (P310) has been analysed in Gnomonia leptostyla (FT.) Ces. et de Not. during mycelial growth and reproductive morphogenesis (macroconidiogenesis, microconidiogenesis and differentiation of perithecia). Conidiogenesis is induced in illuminated cultures while darkness promotes perithecial development. At 20°C, the cultures produce either macroconidia or perithecia with abortive sporophyte. Microconidia differentiation and perithecia maturation require low temperature (10°C). Mycosporin is, at all times, present in the thallus. However, the concentration of mycosporin in highest in the conidiogenous thallus, intermediate in the perithecial thallus. and lowest in the vegetative mycelium. In the conidiogenous thallus, macroconidia and microconidia are both sites of mycosporin accumulation. On the contrary, in the perithecial thallus, mycosporin levels are not higher in perithecia than in mycelia, even during their maturation period. The quantitative variations of mycosporin during the thallus development and its accumulation inside conidia suggest translocation from sites of synthesis towards reproductive cells.     

Testicule et sperme dans le Syndrome de Klinefelter chez l'adulte

Klinefelter's syndrome is characterised by azoospermia, gynecomastia and hypogonadotropic hypogonadism. The testes are reduced in volume. Microscopically, seminiferous tubules show a reduced diameter and a thickening of peritubular sheath. The seminiferous epithelium contains Sertoli cells with a clear typical nucleus and a heterogeneous nucleolus. Usually there are no germ cells. When present they degenerate at the spermatocyte stage. Very few achieve a complete maturation until the spermatozoon form. The interstitial gland appears relatively hypertrophied, due to the decrease in volume in the other components of the testis. Sometimes Leydig cells display an adenomatous morphology. Therefore the steroidogenic function is impaired. Azoospermia is a major event in Klinefelter's syndrome but sometimes restricted to severe oligozoospermia. In that cases, fertility may be somewhat preserved, and the caryotype usually reveals a mosaicism, 47,XY/47,XXY with a better prognosis than in pure syndrome.     

Strategies alimentaires et statut social chez le sanglier en captivite

We have studied feeding and social behaviours in 7 captive wild boars before and after farrowing and their early development.The individual feeding strategies are varying between two types : “Feeding at the feeders” and “Rooting”. Most of the individuals (5) are changing their feeding strategy in the second period, after farrowing. The social interactions in the group are also changed after farrowing ; thus in the second period, females with youngs reduced their agonistic interactions, established affiliated relationships and keep away from the rest of the group. The frequency of approach of the feeders is positively correlated to the degree of affinity and not to the dominance hierarchy. Furthermore, the correlation between the feeding strategy and the individual social status is positive only before farrowing : the social capacity of affiliated behaviour units and the polarity of agonistic interactions is linked to the strategy “Feeding at the feeders”.From the third week of age, different individual feeding and social behaviours are appearing : the youngs develop the same types of strategy as their genetic or adoptive mother. Then it appears a relation between the social status of the mothers and the feeding strategies of the youngs.     

Pigments et salinité chez Porphyridium

Pigments and salinity in Porphyridium.—An opal glass light transmission method is used for estimating the proportions of pigments in Porphyridium sp. Lewin, grown in artificial media. The cells show an Increase in chlorophyll/B–phycoerythrin ratio in media twice or thrice as saline as sea water, Chlrophyll/carotenoïds ratio is low in media the salinity of which is either low or high. In the case of phycoerythrins, light–absorption ratio at 500 nm and 545 nm vary also with the salinity. Une méthode de mesure par transmission de lumière á travers des lames opalines est utilisée pour évaluer les proportions de pigments chez Porphyridium sp. Lewin cultivé milieux artificiels. Les cellules montrent une augmentation du rapport chlorophylle/B.-phycoérythrine dans les milieux deux outrois fois plus salés que l'eau de mer. Le rapport chlorophylle/carotenoïdesest faible dans les milieux dont la salinityé est soit faible soit élevée. Dans le cas des phycoérythrines, le rapport des absorptions de lumière à 500 nm et 545 nm varie aussi avec la salinityé.     

Tchernobyl : le vrai, le probable et le faux

The Japanese earthquake and tsunami drew attention worldwide to nuclear power plant accidents and associated health risks. Since Chernobyl 25 years ago, several studies were published and we now have precise information concerning the long-term health of the population living near nuclear power plants and also in different European countries. The authors hope to bring some answers to the key questions from the public concerning radioactive units used and their significance, the evaluation of the number of radio-induced cancers within the different countries of Europe, other eventual health effects and the problem of possible congenital anomalies. Finally, French public perception on nuclear risk is examined and the feedback of the Japanese experience is evoked.     

Rôle de L'éthylène dans L'Accumulation de Capsidiol et la Sensibilité a Phytophthora capsici chez le Piment Traite par un Eliciteur

Role of ethylene in both the synthesis of capsidiol and the susceptibility to Phytophthora capsici of pepper treated with an elicitor With inoculated plants, there is a strong increase of ethylene, specially with Phyo 636. But, with plants inoculated and treated with G5 15 the quantities of ethylene are less important than with those ones inoculated and untreated with G5 15. After contamination (and only in this case), there is capsidiol synthesis as well wit h treated plants as with untreated ones, and the quantities are not significantly different. Generally, the level of induced resistance is higher wit h Phyo 636 (genetically resistant) than with Yolo Wonder (genetically susceptible). The adjunction of ethylene precursor (ACC) to G5 15 elicitor increases induced resistance with Yolo Wonder but decreases with Phyo 636: the inverse effect is observed when using ethylene inhibitor (AVG). It is suggested that, in the interaction Pepper—Phytophthora capsia, neither ethylene production nor capsidiol synthesis can be considered as biochemical tracers of induced resistance.     

Cartographie de Restriction Comparée du Satellite DNA chez l'Homme et le Chimpanzé

Highly repeated DNA satellite α sequences from man and chimpanzee (Pan troglodytes) have been compared, using restriction endonucleases. The two species share a 340 base pairs tandemly represented DNA, that is cut once by EcoRt. Pan troglodytes differ from man by loss of the two MboI and EcoRI star sites and by the gain of an Hae III site in the repeated sequence.