Spatial and seasonal distribution of the ichthyofauna of Lake Nokoué, Bénin,west Africa

The fish biodiversity of Lake Nokoué, a lagoon in Bénin, was monitored for one year from August 2000 to July 2001 by means of samples from the artisanal fishery collected once a month at three stations. A total of 5 933 fish weighing 95 322g (mean individual weight 16.0g) belonging to 51 species, 47 genera and 34 families were sampled. An abundance of juveniles was observed, confirming the importance of the lake as nursery grounds, rich in exploitable habitats like other tropical estuaries and lagoons. The fish fauna comprised three main components: i) an estuarine component (strict, freshwater and marine origins) which is the basis of the lagoon fauna community and which is stable in space and time; ii) a marine component containing fishes which appeared in the lagoon during the dry season where the salinity remains high (>20‰) and iii) a freshwater component with fishes coming into the lagoon from the river during the flood period. The magnitude of the spatial and seasonal fluctuations of the last two components varies depending on the area: marine (Zogbo), freshwater (Vêki) or intermediate (Ganvié). The global species richness and the relative abundances of fish vary between stations and from month to month. November, with 20 species on average, and January, with 6 species on average, are significantly different as regards species richness.     

Caractéristiques sérologiques des antigènes HLA-A,B et C.

Human leukocyte antigens (HLA) are transmembrane bicatenar glycoproteins; their heavy chain is coded by chromosome 6 and carries allotypic determinants. These molecules are present in nearly every cell, tissue and biologic fluid. Their congenital absence from fibroblasts is associated with progeria, while their absence from lymphocytes is associated with immunodeficiency. HLA antigens are usually studied microlymphocytotoxicity tests. The numerous cross-reactions encountered make the interpretation of results quite difficult. To clearly understand these reactions a complex-complex model is mandatory. The antigen, the HLA molecule, is complex since it carries many antigenic determinants; some of them are private ("subtypic"), while others are public ("subtypic"). Anti-HLA antibodies are also complex since they are heterogeneous, reacting with variable affinity with different antigenic determinants. The in vitro cross-reactions represent a partial explanation for varying cross-immunogenicity in vivo.     

L'Inhibine B chez les blessés radiculo-médullaires. Résultats préliminaires

Spinal cord injuries in adult men sometimes results in semen alteration and in ejaculation missing. Testicular biopsies showed spinal cord injury is bound with testicular and germinal cells alterations. An endocrine profile for thirteen patients without semen at the time of the study is performed: total testosterone, bioavailable testosterone, FSH and inhibin B. Compared with seven normal controls, subjects with spinal cord injury had a significantly lower value of total testosterone, bioavailable testosterone and inhibin B. The FSH values higher in spinal cord injury are not significative. These results allowed to expect inhibin B like a good marker of testicular function and spermatogenesis. A longitudinal and on more subjects will answer to this question.     

Les bélemnites de la carrière de Serra San Quirico (Province d'Ancona,Apennin Central,Italie) et la paléobiogéographie des Bélemnites de la Téthys Méditerranéenne au Tithonique inférieur

About a hundred belemnites, together with numerous other fossils, were collected in a quarry near Serra San Quirico (Ancona Province, Central Apennines). The belemnite fauna is studied with a palaeontological — systematical and palaeogeographical regard. In regard to systematics, thirteen species ascribed to five genera are described, particularly Duvalia apenninica nov. sp., D. aesinensis nov. sp., Rhopaloteuthis siciliensis nov. sp. and Quiricobelus italicus nov. gen., nov. sp., of the Diplobelidae family. During the Tithonian, this family was represented, up to day, only by the genus Diplobelus.According to literature, the geographical distribution of the species recognized in the quarry of Serra San Quirico allows us to think that in a mobilist palaeogeography, the Apulian plate was a diffusion center, with an evident dispersion towards the southern margin of the euroasiatic craton, from Spain to Iran. The African margin, with the exception of Sicily, does not seem to have been affected by this dispersion, probably for palaeogeographic reasons.     

Principaux effets neurotropes et psychotropes des méthylxanthines (caféine, théophylline, théobromine, paraxanthine)

Caffeine, the main alkaloid in coffee, corresponds to the 1-3-7 trimethylxanthine. Its concentration is lower in tea and chocolate, where it is associated with theophylline, 1-3 dimethylxanthine, in tea and with theobromine, 3-7 dimethylxanthine, in chocolate. Paraxanthine, 1-7dimethylxanthine, for its part, is produced by the hepatic metabolism of caffeine operated by a cytochrome of 1A2 type. The effects of these methylxanthines on awaking, anxiety, neuroprotection in Alzheimer’s and Parkinson’s diseases, mood, schizophrenia and nociception are briefly considered. This review is concluded by indicating that these effects of methylxanthines may be modified by various associated substances, such as polyphenols displaying antioxydant properties.     

L'accessibilité, terme nouveau en Phytogéographie

Accessibility a new term in plant ecology (Summary) For a better understanding of the causal relations between a certain unit of vegetation and its station the proposal is put forward to designate as accessibility factors the totality of conditions prevailing at a certain locality, that may influence the possibility of diaspores to reach that spot and settle there.The accessibility factors must be considered as a separate group of ecological conditions beside and comparable to, but specifically differentiated from the climatical, edaphical and biotical groups of factors.Exactly in the same way as plants become distributed according to their specific faculties to meet the local conditions of climate and soil, they are in a similar way selected on account of the interaction between their migratory faculties and the accessibility factors occurring at a certain locality.The habitat of a certain plant association must therefore be defined on the basis of its climatic, edaphic, biotic and accessibility factors.Objections raised against this proposal may be refuted by compairing the significance of accessibility conditions with the effect exercised by conditions of climate and soil with reference to settling.A mountain range e.g. may influence the accessibility together with the climate of the leeside country by acting as a screen to the winds that bring over rain as well as plant seeds.Accessibility conditions are of great importance with respect to pioneer vegetations on bare soil and in those plant groupings within which phytosociological succession is in rapid progress. However there are many other cases where they surely must be taken into consideration.An illustration of the aforesaid considerations is furnished by vegetations of microscopical algae in small ponds. The astonishing richness in species of one such pond as compaired to some others, may in some cases be explained by exceptionally favorable accessibility, caused for example by the regular visit of migratory water birds.The study of accessibility conditions is quite necessary for the selection and conservation of small nature reserves in highly cultivated regions.

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Reçu par la rédaction le 11.I.1954.     

Activité cytokinine de dérivés acylés,alkylés,acyl-alkylés de l'adénine et d'isost`eres azotés de la γ,γ-diméthylallyladénine

The cytokinin activities of various 6-acylaminopurines, 6-alkylaminopurines, 6-acylamino-9-benzyl-purines as well as a series of isosteric-nitrogen derivatives of N⁶-(γ, γ-dimethylallyl)adenine (I⁶Ade) have been tested using the tobacco pith and the pea bud bioassays. The interactions between active, slightly active and inactive compounds have been studied with the last assay. Acylation decreases the biological activity; e.g., N⁶-benzoyl and N⁶-furoyladenines are less active than Na⁶-benzyladenine and kinetin. Substitution at the 9-position reduces (tobacco-pith assay) or suppresses (pea-bud assay) the phytohormonal activity of otherwise active 6-acylaminopurines. In isosteric derivatives, maximum activity occurs when the side chain has the same length as in 1⁶Ade. After the analysis of interactions between more or less active compounds, it is suggested that the differences in cytokinin activity could be related to unequal affinities for a hypothetical receptor site.     

Expérience de biologie délocalisée,télémaintenance et CQ interlaboratoire...

Dans le cadre de la gestion des analyses urgentes de biologie, le site d’Argenteuil a mis en place une organisation originale (Filière “urgence” mise en place depuis avril 1998) assurant en particulier rapidité et sécurité dans la production des résultats. Nous avons recueilli le témoignage des acteurs principaux à l’origine de cette mise en place.     

Depth-related ecological zonation of a carboniferous carbonate ramp: Upper Viséan of Béchar Basin,Western Algeria

Summary Following the demise of the stromatoporoid-coral reef community in Late Frasnian time, Lower Carboniferous carbonate shelf profiles possessed a ramp geometry, with major organic buildups represented by mud-rich mounds. Microfacies petrography of the exceptionally well-preserved Upper Viséan (Lower Carboniferous) carbonate ramp of the Béchar Basin, Algerian Sahara, may well contribute significantly to our understanding of the paleoecological zonation of Carboniferous non-rimmed platforms, and of the still enigmatic mounds commonly referred to as Waulsortian banks or mounds. Facies are grouped into two broad groups: (a) a mound facies group which comprises sponge wackestone-bafflestone, sponge-fenestellid bafflestone-wackestone, crinoid wackestone-packstone, and bedded flanks of intraclastic wackestone-packstone, all four facies composing the actual mud-rich mounds, and (b) a supramound facies group composed of coral-microbial framestone, crinoid packstone-grainstone, algal-foraminiferal grainstone and oolite grainstone. Calcareous algae are important bathymetric indicators and are used to delineate three bathymetric zones based on light penetration: the aphotic zone, which contains no calcareous algae; the dysphotic zone, where there is little ambient light, and which is characterized by the presence of red algae (Fasciella, Ungdarella, Stacheia, Epistacheoides) and absence of green algae; and the euphotic zone, which receives the full spectrum of sunlight, and is characterized by the occurrence of both green algae (Koninckopora, Kamaenella, Kamaena, Palaeoberesella, Calcisphaera, Anthracoporellopsis, Issinella, Exvotarisella) and red algae. Integration of algal zonation, distribution of the other biota, and recurrence of distinct assemblages, enable recognition of seven depth-related benthic assemblages. Together with the physical properties of the facies, the benthic assemblages were used to define seven bathymetric zones, from upper to lower ramp: (1) algal assemblage (upper ramp); (2) crinoid-ramose bryozoan assemblage (mid-ramp); and (3) productid brachiopod assemblage, (4) colonial rugose coral-microbial encruster assemblage, (5) crinoid-fenestellid assemblage, (6) sponge-fenestellid, and (7) sponge assemblage (lower ramp). The vertical zonation of the mud-rich mounds and associated facies differ from that reported from the classical Upper Tournaisian-Lower Viséan Waulsortian mound-bearing successions.