La diatomée Chaetoceros simplex calcitrans Paulsen et son environnement. II. Effets de la lumière et des irradiations ultra-violettes sur la production primaire et la biosynthèse des stérols

12-day cultures of the diatom Chaetoceros simplex calcitrans Paulsen in sea water have been analysed under different conditions of light. With a $\text{12 h}\text{24 h}$ photophase the primary production is 106 % higher than under continuous light but the unsaponifiable fraction is lower (?42 %) and the sterols increase by 100 %. When ultra-violet irradiation is added to the $\text{12 h}\text{24 h}$ photophase the primary production is lowered (?56 %) but the unsaponifiable fraction increases by 191 %, and the sterols by 110 %. When ultra-violet irradiation is added to the continuous light there is an increase in primary production (+30 %) and a decrease in the unsaponifiable fraction (?16%).Modifications of the sterol composition are reported. C₂₆ sterols have never been detected in these experiments.     

Effets de la mise en eau du réservoir Desaulniers (Territoire de la Baie de James) sur le zooplancton d'une rivière et d'une tourbière reticulée

This paper presents the results of an investigation which lasted three years, on the effects of impounding a river on its zooplankton community. Forty zooplankton samples were collected from the Desaulniers River and from a string bog (53°35N, 77°35W) in 1976 before impoundment. Sampling was also conducted in 1977 (331 samples) and 1978 (153 samples) during and after impoundment. The population dynamics of zooplankton show different patterns in 1977 and 1978. The main impacts of impoundment on the river and the bog communities are the increase of the population density, particulary of Rotifera and Copepoda, the increase of the number of species of Rotifera and the increase of the diversity indices based on numbers and biomass. These changes are observed at each sampling station. The total biomass increases in lotic stations but decreases in the string bog because the density and the biomass of Cladocera increases in the river but drops in the bog. Results are compared to those obtained in natural lakes and bog of the same area and to those published in other studies.

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Effets de la mise en eau du réservoir Desaulniers (Territoire de la Baie de James) sur le zooplancton d'une rivière et d'une tourbière reticulée

     

Effets de la radiothérapie sur la fonction testiculaire de l'adulte

Radiation therapy plays a major role in the curative management of numerous neoplasms, such as Hodgkin's disease or testicular cancer. However, the adverse effects of low-dose radiation scattered to radiosensitive normal tissues adjacent to the radiation fields, such as the testes, have been recognized. Experimental studies performed on healthy volunteers showed that no lesion was detectable on sperm counts or testicular biopsies after single doses of less than 10 cGy. Oligospermia has been reported after 15 cGy and 100 cGy result in a 90% incidence of azoospermia. In the radiotherapy of cancer, fractionated regimens are used to increase the differential effect between normal and tumoral tissues. For the same dose, a fractionated radiation regimen results in a higher incidence and a longer period of azoospermia than a single dose irradiation. Fractionated doses of >50 cGy result in a 100% incidence of azoospermia. For doses up to 200 cGy, recovery occurs but normal sperm production remains uncertain. Although the recovery time can be very long (more than 10 years), there is a risk of definitive azoospermia after doses of >200 cGy. Spermatogonia are the most radio-sensitive cell type and their depletion after small irradiation doses explain the effect of radiotherapy on fertility. Clinical hypogonadism is very unfrequent in usual practice, what seems to prove a relative radio-resistance of the Leydig cells. However, functionals studies show that there is a rise in serum LH with increasing dose to the testes. A decrease in testosterone levels has been reported after high testicular doses.