Baisse de la production et de la qualite spermatique chez l’homme: Facteurs de variation et problemes méthodologiques

In the last few years, the possible decline of human semen quality as well as the important geographical variations of semen quality have been discussed in several scientific articles. In a meta-analysis of 61 publications worldwide, Carlsen et al. found a trend of decreasing sperm count over the past 50 years. This work has been at the origin of many commentaries and controversy. Two kinds of questions were mainly raised: Is the phenomenon real? what could be the reason(s) for such a decline? Many sceptical attitudes facing the conclusions of Carlsen et al. came from the fact that the studies included in the meta-analysis were done in various countries at different times, that the men studied could be very heterogeneous in term of fertility status and that the sample sizes of many studies were very low. It was also advocated that the results could be influenced by cofactors as the man’s age or the duration of sexual abstinence before semen collection or by differences in the methodologies used to analyse the semen samples in the various centers. Interestingly, several retrospective studies from a single centre were published after the meta-analysis of Carlsen reporting data from different groups of men recruited during more than 10 years periods in the last decades. Some of these studies found a decline of sperm concentration while for others, no secular modification of sperm concentration could be observed. It was also noticed important differences between values of semen characteristics in these various studies raising the question of geographical or regional differences besides the secular trend observed. Most of the published studies were very imprecis or poor of information concerning the men included in the study, the technical conditions used for semen analysis, the statistical methods used and the interpretation of the data. We discuss here some of the data of these studies in the context of the actual debate on the modifications of semen quality with the aim to pin-point the methodological bias contributing to the variation in the evaluation of semen quality. Moreover we also discuss the current data on the factors related to the men and their environment which could modulate sperm production and quality. It is mandatory to determine if the man’s reproductive function is influenced by environmental factors and if yes how they act. May be one of the main interest of the ongoing debate will be to develop basic and prospective epidemiological research in the field.     

Regulation de la production ovarienne chez Acanthoscelides obtectus (Coleoptera: Bruchidae): Influence de l'age des femelles lors de la fecondation et de la presence des grains

Résumé Des femelles alimentées d'une souche francaise de bruche du haricot, fécondées peu après leur émergence, ne sont mises en présence des grains de la plante-hôte qu'après un délai plus ou moins long: jusqu'à 50 jours de délai, la stimulation de la production ovarienne est aussi forte que chez les femelles mises avec des grains dès la copulation, mais la proportion d'oeufs émis est plus faible.D'autre part, à âge identique, les effets de la stimulation de la production ovarienne sont plus marqués lorsqu'il y a retard simultané de la fécondation et de la présence des grains que lorsque celle-ci est retardée par rapport à la fécondation.Ce n'est pas chez les femelles les plus jeunes que les effects de la stimulation combinée et simultanée de la production ovarienne sont les plus importants, mais chez des femelles âgées de 20 à 30 jours. Cet âge correspond à la fin de la période de mâturation du stock de base d'ovocytes formés à partir du corps gras, mâturation qui s'effectue de toute façon, même en absence de tout stimulus externe.

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Regulation of egg production in Acanthoscelides obtectus (Coleoptera: Bruchudae): The change in stimulating effect of grain of females of different ages

Summary Females from a French strain of Acanthoscelides obtectus were mated soon after emergence, and after various lengths of time presented with host plant seeds. Even after a deley of 50 days, stimulation of the ovaries occurred as it did when females were presented with seeds as soon as copulation took place, but fewer eggs were produced. For insects of similar age, the stimulating effect of the seeds was greater if they were present when the females were first mated, than if they were presented after a delay. The stimulating effects were greatest in females aged between 20 and 30 days. This age corresponds to the end of the maturation period of the initial stock of ovocytes. This maturation would normally occur even in the absence of external stimuli.

     

Évolution horaire au cours d'une journée normale de la photosynthèse, de la transpiration, de la respiration foliaire et racinaire et de la nutrition N.P.K. chez Zea mays

Hourly development during a normal day of photosynthesis, transpiration, leaf and root respiration, and of N.P.K nutrition in Zea mays. Metabolism of Zea mays L. cv. INRA F₇×F₂ can be measured hourly with the “C₂3A system”, under favourable and constant growth conditions. The photosynthesis is especially stable and is submitted only to a development linked with the leaf surface growth. During the vegetative stage the leaf surface increases regularly both in the day and in the night. The water loss does not change during the diurnal period and remains important during the night if humidity is less than 100%. The leaf respiration is nearly stable. The root respiration, measured with O₂ and CO₂, fluctuates according to a typical rhythm with two maxima. Day and night mean rates were about the same. The respiratory quotient is about one during the vegetative stage. There is no decrease in the rate of phosphate absorption during the night, and a very small decrease in the rate of nitrate absorption. Ammonium is totally consumed in the first hours after renewal of the nutrient solution. At the same time the potassium consumption is decreased, and then presents a maximum followed by a night reduction. Under our conditions, all of the observations allowed us to assume the presence of an adequate reserve of assimilates and suggest the existence of a precise regulation process, which can ensure an even day night functioning of the plant metabolism, but which does not preclude the presence of internal rhythms, as indicated by the oscillation of the root respiration.     

Iatrogénicité de la chirurgie carcinologique. Ses effets sur la reproduction et la sexualité de l'homme

It is a review of vascular and neurologic iatrogenic effects of pelvis cancer surgery in men. The authors describe the principles of nerve-sparing prostatectomy. The main rules of retro-peritoneal Iymph nodes removal and the post surgery results in testis cancer are developped, except in specific cases of single tumour removal. The iatrogenic effects of rectal surgery are depending on the tumoral removal level connected itself with the tumour site.