Energy migration in the poly(ra-rU)-ethidium complex. determination of the unwinding angle of the polyribonucleic helix

The polarized fluorescence of the ethidium bromide (EB)-poly(rA-rU) complex has been studied by pulse fluorometry. As expected for a polynucleotide snowing one single kind of intercalation site, the decay of the whole emission is a single exponential (time constant 27 ns). The anisotropy decay is analysed as follows: (1) A brownian contribution having two correlation times, one of which characterizes local motions and the other a macromolecular motion. (2) A contribution due to transfers between EB molecules fixed to the same polynucleotide molecule, is analysed by a method analogous to the method used in previous work on EB-DNA complexes. That method consists in choosing a molecular model of the complex depending on geometrical parameters, and in simulating the energy migration on that model with a Monte Carlo calculation. Poly(rA-rU) is assumed here to adopt the structure A of RNA. Intercalated EB molecules modify the anale between two consecutive base pairs by δ. The angular position of the EB transition moment is defined by an angle φ. One finds that the angle φ is situated between 0° and 30°, which corresponds to a whole intercalation of the chroniophore as opposed to the semi-intercalation which has been proposed for certain dyes. The angle δ is negative; therefore there is an unwinding of the polyribonucleotide helix. Its absolute value is about 38°, sensibly greater than The value previously found for EB-DNA complexes.     

Inclusions of conifers,echinoids, foraminifers and sponges in flints from the Cenomanian of Charente-Maritime (France): Contribution of synchrotron microtomography

Deposits containing silica-rich nodules were recently collected from the Font-de-Benon quarry, between Archingeay and Les Nouillers, Charente-Maritime, western France. Nodules contain diverse fossil inclusions such as conifers, urchins, foraminifers and sponge spicules. Cenomanian deposits were transformed during the Eocene-Oligocene by a delayed silicification. This occurred under a warm climate and a long pedogenic alteration. X-ray synchrotron tomography was used to locate and produce three-dimensional reconstruction of flint fossil inclusions. The plant fossils constitute an unusual case of late permineralization. The conifer and invertebrate fossil assemblage suggests a coastal palaeoenvironment close to a forest.     

First Jurassic occurence of Enoploclytia M’Coy, 1849 (Crustacea: Decapoda: Erymidae)

Among the Erymidae Van Straelen, 1925, known as early as the Late Permian (Changhsingian) and widespread in the Jurassic, the genus Enoploclytia M’Coy, 1849 seems to have a late appearance because of its lack before the Cretaceous. Until now, the oldest representative was E. augustobonae Devillez, Charbonnier, Hy?ný and Leroy, 2016 from the Early Cretaceous (Barremian) of the eastern Paris basin (France). However, a new fossil collected in Normandy (France), showing the typical carapace groove pattern of Enoploclytia, attests the presence of the genus in the Late Jurassic (Oxfordian).     

The first non-pterodactyloid pterosaurian trackways and the terrestrial ability of non-pterodactyloid pterosaurs

New discoveries on the ichnological site known as “the Pterosaur Beach of Crayssac” (lower Tithonian, Upper Jurassic; south-western France) answer the question of terrestrial capabilities of non-pterodactyloid pterosaurs. If the terrestrial type of locomotion of pterodactyloid pterosaurs has been solved from ichnological evidence for more than twenty years, no tracks and trackways referable to non-pterodactyloid pterosaurs have ever been described. Thus, the debate on terrestrial capabilities of these non-pterodactyloids was based on morpho-functional studies, with the main conclusion that those pterosaurs were arboreal dwellers and bad walkers. Six trackways referable to three non-pterodactyloid new ichnotaxa, maybe closely related to Rhamphorhynchidae, are described in this work. Their study leads to the conclusion that grounded non-pterodatyloids, at least during the Late Jurassic, were quadrupedal with digitigrade manus and plantigrade to digitigrade pes. They were clearly good walkers, even if hindlimbs are supposed to be hampered by the uropatagium, what could have constrained the terrestrial agility of these animals. Thus, from ichnological evidence and contrary to the current hypotheses, non-pterodactyloid pterosaurs seem to have been good walkers even though their trackways are very rare or unidentified to date. This rarity could be due to behaviour rather than to functional capacities, many non-pterodactyloids being considered both littoral fishers and arboreal or cliff dwellers. However, the concept of non-pterodactyloid “good climbers and bad walkers” has to be modified to “good climbers and rare walkers”, unless many non-pterodactyloid ichnites have yet to be discovered.     

Les Spatangus du Miocène et du Pliocène de l’Ouest de la France

Numerous fragments of spatangoid echinoids have been discovered in the Pliocene deposits of Challans, in Vendée (western France). In spite of the fragmentary data of the samples, a reconstitution of a complete test could be realized using the different fragments and their symetrization. The general shape of the test, and its architectural and ornemental characters allow establishing the presence of the genus Spatangus in western France during the end of Neogene. It allows to precise the biogeography of the genus Spatangus and of the morphological group S. (S.) purpureus on the Atlantic coast after the Messinian crisis. The Pliocene species is compared to the Miocene Spatangus (Phymapatagus) brittanus, abundant in Anjou, Brittany and Touraine. This older species was refered to the subgenus Phymapatagus according to the presumed lack of primary tubercles on its posterior interambulacrum. The discovery of well-preserved specimens, with primary tubercles on every parts of the test, in the Middle Miocene of Brittany allows to refute this subgeneric distinction and to refer the species brittanus to the subgenus Spatangus (Spatangus). The presence of this subgenus in western France is finally confirmed from Middle Miocene to Pliocene.     

Role of magnesium cations in the yeast orotate phosphoribosyltransferase catalyzed reaction. Mechanism of the inhibition by Cu++ and Ni++ ions

The magnesium chelate of the N(3)H tautomer of orotate, L₃Mg, is the true substrate in the biosynthesis of orotidine 5′-monophosphate (OMP) catalyzed by yeast orotate phosphoribosyltransferase (OPRTase, E.C. 2.4.210) with a Michaelis constant K_m^L₃Mg equal to 12(2) μM. It is postulated that Mg⁺⁺ cations activate the transport of orotate to the active site by neutralizing the orotate charges; the ligand N(3)H is then exchanged between the incoming cation and the cation bound to the enzyme, thus ensuring the stabilization of the appropriate isomeric structure of orotate. This scheme, together with kinetic and thermodynamic data on orotate complexation by Mg⁺⁺ and Ca⁺⁺, accounts for the role of Ca⁺⁺ cations that neither activate nor inhibit OMP synthesis.Cu⁺⁺ and Ni⁺⁺ inhibiting properties arise from the formation of inert complexes of orotate. Ni⁺⁺ complexes have a poor affinity for the protein, whereas Cu⁺⁺ complexes have a Michaelis constant similar to that of the L₃Mg active species. The inertness of these complexes is tentatively understood in terms of low phosphoribosyl transfer rates as postulated from the kinetic study of the protonation of the complexes in water.     

De la géographie sociale en archéologie paléolithique : concepts et apports du Magdalénien des Pyrénées

Landscape archaeologies that pay attention to cultural importance of place have become increasingly common in recent years in many parts of the world. However, these approaches have largely failed to make inroads into Pleistocene European hunter-gatherer archaeology. This is partly due to a focus on economics, survival, and neo-liberal assumptions of “efficiency” in early modern human behavior. With evidence of lithic use drawn from cave sites, survey, and open-air excavation, I argue that Upper Paleolithic hunter-gatherers left clues to the importance of certain places in the landscape. Lithic tools in particular have been undervalued for their symbolic meaning, which goes well beyond style and ethnicity models. Raw material has been seen as evidence of mobility and trade, but possible cultural motives behind material choices have been downplayed or ignored.     

A new genus of praeaulacid wasp (Hymenoptera: Evanioidea) from the mid-Cretaceous Kachin amber (Myanmar)

The diversity of praeaulacid wasps in Kachin amber is relatively poorly documented. Here, a new genus and species of praeaulacid wasp are described and illustrated from the mid-Cretaceous Kachin amber as Archeogastrinus kachinensis gen. et sp. nov., and placed in the subfamily Praeaulacinae. This new genus is distinguishable from the other Praeaulacidae because of its particular tibial spurs formula 1-2-2; its forewings with a long and thin pterostigma, a 1-M longer than 1-Rs, a 1-Rs longer than its distance to pterostigma, a crossvein 2r-rs aligned (or nearly) with 2rs-m and originating near the middle of pterostigma, a 2rs-m present, a cell 3rm long, a 1cu-a postfurcal to 1-M, a vein 2-M distinct; its hind wings cu-a reaching Cu distad M + Cu fork; and its metasoma with a first segment petiole-like (i.e., long and thin) and ventrally inflated in its distal half. The position of the genus Mesevania is briefly discussed, as well as the validity of the genus Paleosyncrasis, both described from the mid-Cretaceous Kachin amber.     

The effect of the dung pad fauna on the emergence ofMusca tempestiva [Dipt.: Muscidae] from dung pads in southern France

The emergence ofMusca tempestiva Fallèn, from cow pads in southern France was reduced by a mean of 98% and 96% respectively in nine experiments concluded in 1979 and 1981, by the action of the complete dung fauna. Fauna emerging from dung pads and captured in simultaneous trapping using dung baited pitfall traps consisted of 13 Dipterous species (9 Muscidae, 2 Sepsidae and 2 Sphaeroceridae), 25 Coleopterous species (7 Scarabaeidae, 1 Geotrupidae, 2 Aphodiidae, 3 Hydrophilidae, 12 Staphylinidae), 3 Hymenopterous parasites and 1 species of macrochelid and 2 species of parasitoid mites carried phoretically by the dung beetles. The total number of insects and mites per trap was usually small. The Staphylinidae which included 4Aleochara species of whichAleochara tristits Gravenhorst andA. bipustulata (L.) are known parasitoids of Diptera pupae, and 6 predatory species, were the most abundant insects present. Whilst the overall abundance of insects and mites trapped was relatively low it is probable that the most important factor in the control ofM. tempestiva was the combined influence of the different elements making up the dung pad fauna.