Développementin vitro de la lignée germinale foetale mâle chez le rat, la souris et l’homme

The key role of the foetal germ cell line in the reproductive capacity of the adult has been known for a long time. More recently, the observed increase in male reproductive disorders such as the decline of sperm count and quality and the increased incidence of testicular cancer has been postulated to be due to alterations of foetal and neonatal testicular development in response to increasing environmental pollution. However, few tools are available to study foetal and neonatal germ cell line development and the effects of physiological or toxic substances on this process. The authors have developed an organ culture system in which foetal or neonatal testis is grown on a filter floating on a synthetic medium free of serum, hormones or biological factors. This study, using rats and mice, first compared the long-term morphological and functional development of Sertoli and germ cells in thisin vivo system. In rats, these cells developed normally over a period of two weeksin vitro. Fewer cells were produced thanin vivo, but a similar level of differentiated function was observed. Germ cells, which are difficult to maintainin vitro, resumed mitosis after a quiescent period, at the same time asin vivo. Similar results were obtained with mouse fetuses, but this model was less efficient. This culture model can be used to study post-natal development of the germ cell lineage in testes derived from foetuses on the last day of foetal life and invalidated for P63, that do not survive after birth. This gene was found to be involved in the regulation of germ apoptosis which resumes after birth in the mouse. Lastly, this model applied to the human species (from 6 to 12 weeks of gestation) showed that testicular architecture and germ cells can be maintained for 4 days with better efficiency at younger stages than at older stages. p]In conclusion, testicular architecture and intercellular communications are sufficiently preserved to sustain gametogenesisin vitro with no added factors. This method is potentially useful to study the effects of various factors, particularly xenobiotics.     

The history of three scientific societies: the Society for the Study of Fertility (now the Society for Reproduction and Fertility) (Britain), the Société Française pour l'Etude de la Fertilité, and the Society for the Study of Reproduction (USA)

Three scientific societies devoted to the study of reproduction were established in Britain, France and USA in the middle of the twentieth century by clinical, veterinary and agricultural scientists. The principal motivation for their establishment had been the study of sterility and fertility of people and livestock. There was also a wider perspective embracing other biologists interested in reproduction more generally. Knowledge disseminated through the societies' scientific meetings and publications would bear upon human and animal population problems as well as basic reproductive physiology and its applications. New journals dealing with reproductive physiology, having worldwide appeal, were established in Britain and USA. The financial resources of at least one of the societies and its journal are directed towards charitable functions, including financial support for travel to scientific meetings, for visits to particular laboratories, and for research in the short term, including that of undergraduates. Perhaps the example of the British society has given rise to others having a more specialised focus, as well as to the formation of the European Society for the Study of Human Reproduction and Embryology.     

Evolution de l’il et h’t’rochronie chez les trilobites ordoviciensormathops delo 1935 ettoletanaspis rabano 1989 (dalmanitidae,zeliszkellinae)

Ormathops species of Arenig (Fennian) and Llanvirn age(O. llanvirnensis, O. atava, O. clariondi) possess visual surfaces characterized by irregularities in the distribution of lenses. Yet, at early Caradoc time, the eyes ofOrmathops hupei are perfectly schizochroal. From the Arenig to the Lower Llanvirn, the same evolution can be noticed in the genusToletanaspis: the eyes ofT. borni andT. courtessolei n. sp., both from the Whitlandian of the Montagne Noire (southern France), show irregular lens-packing whereasT. trivignoi of Lower Llanvirn age has a schizochroal pattern of lenses. InOrmathops andToletanaspis, the schizochroal condition has developed independently from a primitive lens-packing system, probably through a paedomorphic (neotenic) “process”. Résumé: Les espèces d’Ormathops d’âges Arenig (Fennien) et Llanvirn (O.llanvirnensis, O. atava,O. clariondi) possèdent des surfaces visuelles caractérisées par des irrégularités de distribution des lentilles. Toutefois, au début du Caradoc, les yeuxd’Ormathops hupei sont parfaitement schizochroaux. De l’Arenig au Llanvirn Inférieur, la même évolution s’observe chez le genreToletanaspis: les yeux deT. borni etT. courtessolei n. sp., toutes deux du Whitlandien de la Montagne Noire (France méridionale), montrent une distribution irrégulière des lentilles tandis queT. trivignoi d’âge Llanvirn Inférieur présente des surfaces visuelles schizochroales. ChezOrmathops etToletanaspis, l’?il schizochroal s’est formé indépendamment à partir d’une surface visuelle primitive à lentilles irrégulièrement réparties, et ceci probablement par paedomorphose (néoténie).     

Lower limb bone structure of Middle Pleistocene hominins from the Caune de l’Arago (Tautavel,France): Evolutionary and functional comparison with the penecontemporaneous hominins of Sima de los Huesos (Atapuerca,Spain)

The Caune de l’Arago (Arago) and Sima de los Huesos (Sima) human bones from the European Middle Pleistocene are penecontemporaneous, although the Sima hominins are closely related to Neandertal, and Arago hominins present more archaic features. In previous and in press studies, the cross-sectional geometric properties (CSG) of lower limb bones of Arago and Sima have been studied separately without comparative analyses. Here, in order to bridge this gap, we use the same criteria for both samples to highlight evolutionary affinities and to compare their level and pattern of mobility. This study focuses on the femur, fibula and tibia from Arago and Sima with references to fossils from the sites of Trinil, Zhoukoudian and Lazaret, and ancient and recent Homo sapiens (including athletes and non-athletes). We analyze the cross-sectional areas, biomechanical bone “shape” indices (Ix/Iy, Imax/Imin) and pattern of cortical bone distribution. All lower limb bones from Arago have noticeably high to very high relative cortical areas and low to very low medullary areas. The overall femoral pattern in Arago, like Sima, is similar to that of Middle Pleistocene hominins (e.g., low femoral shape indices, Ix/Iy) and Neandertals (e.g., large cross-sectional size). However, the femoral midshaft in Sima presents prominent posteromedial cortical thickening, as a result of a spiral cortical reinforcement along the medial side of the diaphysis. This characteristic is specific to Neandertal and some Middle Pleistocene hominins. In contrast, the midshaft femoral pattern in Arago is close to that of some Homo erectus. We also note that the femoral cross-sectional size and relative cortical area in Arago differ drastically to the small size and low relative cortical area of Lazaret and Trinil hominins. The very high shape index at midshaft (i.e., high Imax/Imin) of the Arago tibia is observed in ancient H. sapiens and runners; the tibial posterior “pilaster” is found in Neandertals and ancient H. sapiens; and the flat or convex tibial faces are similar to Neandertals. Furthermore, the Arago fibulas show marked fibular posterolateral cortical reinforcement with low anteroposterior strengthening. These leg features (tibia, fibula) are also found in some Sima hominins (but not in all individuals). Consequently, this study confirms the presence of archaic features in Arago and the close evolutionary relationship between Sima and Neandertal. This proposition is mainly based on the femoral midshaft pattern influenced by the pelvofemoral complex, considered to be substantially genetically controlled. The leg functional analysis highlights a high level of mobility and travelling in uneven terrains or in mountainous areas in Arago, consistent with known environments and hunting practices. Previously, an analogous hypothesis was proposed put forward for Sima hominins.     

Predictive Modeling for Diagnostic Tests with High Specificity,but Low Sensitivity: A Study of the Glycerol Test in Patients with Suspected Menière’s Disease

A high specificity does not ensure that the expected benefit of a diagnostic test outweighs its cost. Problems arise, in particular, when the investigation is expensive, the prevalence of a positive test result is relatively small for the candidate patients, and the sensitivity of the test is low so that the information provided by a negative result is virtually negligible. The consequence may be that a potentially useful test does not gain broader acceptance. Here we show how predictive modeling can help to identify patients for whom the ratio of expected benefit and cost reaches an acceptable level so that testing these patients is reasonable even though testing all patients might be considered wasteful. Our application example is based on a retrospective study of the glycerol test, which is used to corroborate a suspected diagnosis of Menière’s disease. Using the pretest hearing thresholds at up to 10 frequencies, predictions were made by K-nearest neighbor classification or logistic regression. Both methods estimate, based on results from previous patients, the posterior probability that performing the considered test in a new patient will have a positive outcome. The quality of the prediction was evaluated using leave-one-out cross-validation, making various assumptions about the costs and benefits of testing. With reference to all 356 cases, the probability of a positive test result was almost 0.4. For subpopulations selected by K-nearest neighbor classification, which was clearly superior to logistic regression, this probability could be increased up to about 0.6. Thus, the odds of a positive test result were more than doubled.     

A new method of three-dimensional morphometry for analyzing the functional potentialities of bifaces. Contribution to the study of artefacts from AU P3 from the “Caune de l’Arago” (France)

The analysis of the functional potential of bifaces, which are artefacts extending beyond our technical memory, is based on direct (micro-wear) or indirect approaches (experimentation, relationship between form/function, comparative ethnography). Indirect approaches are fundamental when artefacts are not well enough preserved for micro-wear analysis, which is frequent for the middle Pleistocene. This article proposes a new method based on the three-dimensional acquisition of artefact images, enabling us to measure cutting edge angles and depth of cut. This process allows us to distinguish, in particular, between cutting edges created for longitudinal or transverse cutting. The application of this analysis to bifaces from UA P3 of the “Caune de l’Arago” brings to light tools with a high functional potential for longitudinal cutting, some of which were used for incising, others for deep cutting. These results corroborate those obtained by most micro-wear analyses and present new ways of interpreting the functional potential of bifaces.