Méthodes d'élevage deFormica polyctena

Résumé Une méthode d'élevage deFormica polyctena est décrite, basée sur l'utilisation de deux nids, de types différents suivant l'été ou l'hiver. Ce sont les fourmis elles-mêmes qui adoptent l'un ou l'autre type suivant la saison. Le développement de la colonie y parait satisfaisant, sauf la procréation des sexués au printemps. L'observation continue des fourmis y est facile.

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Summary A breeding technique convenient forFormica polyctena is described, using a winter and a summer nest of two different types. The ants themselves choose the summer or winter nest, following the time of the year. The colony development is good, except for the production of sexual forms in spring. The observation and experimentation are very easy.

     

Échanges protidiques entre fourmilières deFormica polyctena,mesurés a l'aide de radio-isotopes

Résumé Les échanges de matériel protidique s'effectuent entre fourmilières deFormica polyctena de la même manière que les échanges de sucres, tout en restant beaucoup moins actifs.

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Summary The exchanges of protidic material between ant-nests (F. polyctena) are going on the same way as for sugar exchanges, but at much less rate.

     

Solid angle as steric parameter of acyclic saturated groups

With the early aim of quantifying steric consequences of chirality, efforts to define a nonempirical steric parameter of chemical groups are reported. Steric hindrance of a reacting center by any acyclic saturated R group has been characterized by a geometric “axial steric parameter”: the solid angle of R. When the group is a “symmetric top substituent” (i.e., when all the terminal atoms are equivalent), the solid angle matches the solid angle of a cone envelope of R. The definition of this cone is compared with Tolman's definition of a ligand cone in organometallic complexes. The chemical significance of this parameter is shown by an excellent correlation with the Dubois' experimental steric parameter E′_s. Modeling steric repulsion by the cone of R, and correcting solid angles for conformational effects, only 3 empirical coefficients are needed to calculate 33 values of E′_s with less than 10% error. The cone model is suggested to be relevant within the limits of random and independent free rotations about all the bonds in the C–R group. A separation between “axial cone steric hindrance” and other steric effects is proposed. The basic model and the corrections proposed allow the conformational features of esters to be discussed.     

Detection of homologous oncogene sequences in the genome of Plasmodium falciparum

Homologous sequences of the acute RNA tumor virus oncogenes have been found to be highly conserved within vertebrates, insects and yeasts. In the present work, seven different oncogene DNA sequences have been used as probes to search for homologous sequences in the DNA of the protozoan Plasmodium falciparum. Both the v-fms v-Ha ras probes hybridized P. falciparum DNA. The oncogene study will allow an understanding of the biology of the parasite and particularly the host-parasite relationships which allow P. falciparum to develop, keeping the established harmony between the parasite and his host.