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.     

Altérations morphologiques des spermatozoïdes en microscopie électronique: indications, phénotypes, fécondance, et pronostic de fertilité

Conventional semen analysis (sperm count) is limited to examination of spermatozoa at a magnification of x1,000, which may be insufficient in rare situations. Electron microscopy sperm examination allows high-power (x 100,000) analysis of sperm organelles and quantification of abnormalities of the constituents involved in sperm mobility and fertility potential. Electron microscopy sperm morphology examination is rarely indicated and is reserved to: 1) severe monomorphic and stable teratospermia (globozoospermia = spermatozoa with a round head and no acrosome, pinheads = decapitated spermatozoa), 2) partial (asthenospermia) or total (akinetospermia) alteration of sperm mobility and/or quality of sperm movement. All of these anomalies are associated with primary infertility. Globozoospermia and pinheads can be detected by light microscopy. Electron microscopy sperm morphology examination precisely identifies and quantifies sperm abnormalities. Pathological phenotypes have a heterogeneous expression. The organelles of spermatozoa other than those primarily involved in the pathological phenotype may also present alterations. Globozoospermia is generally characterized by the absence of elongation of the nucleus, and absence of the acrosome and the post-acrosomal region. The implantation fossa and basal plate are generally missing in decapitated spermatozoa. Asthenospermia may be an indication for electron microscopy sperm examination when it is not associated with necrospermia. Sperm with fibrous sheath dysplasia (FSD) generally present a short flagella and very low overall mobility, less than 5%. The various phenotypes are characterized by abnormal arrangements of the constituents of the fibrous sheath and 20% of patients also present respiratory tract disease. In primary ciliary dyskinesia (PCD), spermatozoa are often immobile and present a normal morphology on light microscopy. Apart from the complete form with absent axoneme, incomplete forms are also observed with absence of the dynein arms, peripheral doublets, microtubules. These phenotypes have a low prevalence in the population of infertile men. A familial incidence, parental consanguinity, and a high incidence in certain geographical regions are frequently reported, suggesting the existence of one or several genetic mechanisms. Despite the limited state of knowledge at the present time, couples must be informed about the possible transmission of the phenotype to their descendants. All men with these phenotypes are spontaneously infertile. The only alternative fertilization technique is intracytoplasmic sperm injection (ICSI). According to the literature and our own experience, the results of ICSI with sperm presenting these phenotypes are poorer than those of ICSI in general. Electron microscopy is not only a diagnostic tool in severe male infertility, but also a prognostic indicator of the success of management by ICSI, which must be evaluated for each case.     

Fluctuations morphologiques et hétérochronies chez Toxaster (échinides,Crétacé inférieur)

Morphological fluctuations and heterochronies of Toxaster (echinoid, Lower Cretaceous). Several steps of the diversification of the spatangoid Toxaster are described with an analysis of six species distributed over the north-west Tethyan margin, and ranging from the Lower Valanginian to the Barremian. Morphological variation was investigated with the analysis of two parameters (angles), which allowed recognition of three modules on the test. Comparison of ontogenetic trajectories of two reference species (T. granosus kiliani and T. retusus) suggests a peramorphic heterochronic pattern. However, no peramorphocline can be attested when comparisons are extended to adults of the six species. Evolution among these species is partially driven by allometric changes in one module, indicating an important influence of size. On the temporal and spatial scale of the study, the evolution of Toxaster appears globally quite conservative. To cite this article: É. François et al., C. R. Palevol 2 (2003).     

Les néoblastes dans la régénération antérieure deDendrocoelum lacteum,Turbellarié triclade

Résumé Les néoblastes de la région postérieure du corps de la PlanaireD. lacteum ont les mêmes propriétés migratrices et histogénétiques que les néoblastes de la région prépharyngienne. En cas de section transversale à quelque niveau que ce soit, les néoblastes du fragment postérieur se déplacent d'arrière en avant pour s'accumuler en un bourgeon de régénération normal. Mais la différenciation de ces cellules ne se produit qu'en cas de section nettement antérieure à la racine du pharynx (alors il y a régénération). Après une section postérieure à la racine du pharynx, les néoblastes dégénèrent.

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Neoblasts in the anterior regeneration ofDendrocoelum lacteum, Turbellaria tricladida

Summary Neoblasts of the posterior region of the body in the PlanarianD. lacteum have the same migratory and histogenetic properties as neoblasts of the prepharyngeal region. With transverse cuts at whatever level, neoblasts of the posterior fragment migrate forward to accumulate as a normal regeneration bud. But differentiation of these cells only occurs in ease of a section clearly anterior to the root of the pharynx (regeneration then follows). After a transection posterior to this level, the neoblasts degenerate.

     

Étude des Radiolaires d'un nodule phosphatédu Carbonifère inférieur de Bareilles,Hautes-Pyrénées,France

The discovery of well-preserved Radiolaria yielded into a single phosphatic nodule from Carboniferous lydites of Bareilles (Hautes-Pyrénées, France) allowed the identification of ten genera and nineteen species. Four of these species are new. The separation of the fauna from the phosphatic matrix has permitted it to be studied with the scanning electron microscope and to be correlated with faunas recently described by the same process. At least, seven species are identical with middle and upper Tournaisian phosphatic nodules from the Montagne Noire (Deflandre and Deflandre-Rigaud, 1944, Deflandre, 1973b) and from Istanbul, Turkey (Holdsworth, 1973), and eight others with Visean from the «Rheinische Schiefergebirge, West Germany (Won, 1983). The author questions the age of lydites from Hautes-Pyrénées, attributed to middle to upper Tournaisian (early Mississippian).     

Nouvelles données paléontologiques,paléoécologiques et sédimentologiques sur le Berriasien de la région de Lamoricière (ouled Mimoun et E1 Rhoraf,Monts de Tlemcen,Algérie)

In the Western Algerian area, the Ouled Mimoun and El Rhoraf sections are particularly appropriate for the study concerning the berriasian formations.From tha lithostratigraphical point of view, the upper section of the carbonated platform corresponds to the lower Berriasian and a part of the middle Berriasian. The «Argiles de Lamoricière which dominate it belong to the middle and upper Berriasian. The subjacent detritic formation known as «Grès de Berthelot probably begins with the lower Valanginian. The stratigraphical results are based on an abundant fauna (ammonites, ostracods) collected in situ, the main species of which have been the subject of a paleontological review and abondantly illustrated.The studied series offer a good example of the evolution of sedimentary conditions which accompany the temporary opening of a carbonated platform towards the open sea.The variations in fauna composition are closely related to changes in environment. In particular, the presence of ammonites in the Boissieri zone can be connected to the highest point of marine advance, although the depth remained relatively shallow (an upper infratidal zone being likely). It is to note that during this period the low level of sedimentary activity favored the settling of some remarkable epilithic fauna.Above the «Argiles de Lamoricière, the massive detritic sedimentation (grès de Berthelot) could indicate an important paleogeographical change in the interior. In the area studied, the ostracods encountered in the basal section of the last formation still mean a shallow marine environment.     

Relation fonctionnelle entre la masse grasse,les plis cutanés,le déficit ou l'excédent pondéra et le « poids théorique idéal

Underscoring a functional relation between fat mass, skinfolds, under or overweight and the ‘ideal theoretical weight’, constitutes a fundamental datum in anthropology. Indeed, this relation, which differs according to age, sex, ethnic group and physical activity, provides information on the distribution of fat contained in the skinfolds, the under or overweight and the ‘ideal theoretical weight’. The value of this relation lies not only in limiting the use of the corpulence index (W/H²) as an indicator of fat mass, but above all in the importance of physical activity and in the existence of a significant change in the distribution of fat according to the factors mentioned above.