Une discordance ante albienne datée par une fauned'Ammonites et de Brachiopodes de type téthysien au Mexique central

Resume Au Nord de Leon (Guanajuato), la discordanced'un horizon carbonate neritique sur un substratum volcano-sedimentaire tectonise materialise une phase tectonique majeure dans la cordillere ouest mexicaine. L'âge albien superieur de ce temoin recifal est etabli par une petite faune d'Ammonites appartenant aux genres Eohypoturrilites, Pseudouhligella, Salaziceras et Eutrephoceras, et des Terebratules du genre Moutonithyris. La position de ce gisement montre l'extension vers l'ouest des facies carbonates connus sur la plate-forme est mexicaine.

Shell matrices of recent rhynchonelliform brachiopods: microstructures and glycosylation studies.

ABSTRACTLike most metazoan biomineralisations, the brachiopod shell is the end product of a biologically controlled calcification process. The main agent of the control is the extracellular matrix, which is secreted by the outer mantle epithelium. This matrix mediates the calcification process by allowing crystal nucleation and elongation in specific orientations and finally, by stopping crystal growth. The proteinaceous moiety of brachiopod shell matrices has been extensively studied. Less known are the post-translational modifications that occur in these matrices, in particular glycosylations. In this comparison of five species of Recent articulated brachiopods, the ratio of soluble to in…

Staining SDS-PAGE gels of skeletal matrices after western blot: a way to improve their sharpness.

7 pages; International audience; Denaturing 1D electrophoresis on acrylamide gels - also referred as SDS-PAGE - is a classical technique for fractionating and visualizing the macromolecular constituents of matrices associated to calcified tissues. This technique has been widely used in association with the subsequent silver nitrate staining. But because matrices associated to calcified tissues are very often glycosylated and constituted of numerous polydisperse macromolecules, the obtained pattern is frequently 'smeary' and discrete bands, when present on the gel, are often blurred, thickened or totally masked by the polydisperse macromolecules. In this paper, we present a simple protocol t…

Biochemical characteristics of the shell soluble organic matrix of some recent Rhynchonelliformea (Brachiopoda).

11 pages; International audience; To build up their shell, brachiopods secrete a mixture of proteins and polysaccharides, collectively called the shell organic matrix. This matrix is supposed to mediate the calcification process by allowing the crystal nucleation and elongation and finally, by stopping the crystal growth. The aim of this work is, firstly, to observe at nanoscale the close relationships between the mineral and the organic phases, and secondly, to characterize the acetic acid-soluble matrices extracted from different articulate brachiopods. Recent articulate brachiopod shells were observed according to a standard procedure, which emphasizes the microstructural details. For th…

Microstructural Organization of the Calcitic Skeleton of Terebratulid Brachiopods: Elementary Unit of the Carbonate Secretion

Shell proteome of rhynchonelliform brachiopods.

7 pages; International audience; Brachiopods are a phylum of marine invertebrates that have an external bivalved shell to protect their living tissues. With few exceptions, this biomineralized structure is composed of calcite, mixed together with a minor organic fraction, comprising secreted proteins that become occluded in the shell structure, once formed. This organic matrix is thought to display several functions, in particular, to control mineral deposition and to regulate crystallite shapes. Thus, identifying the primary structure of matrix proteins is a prerequisite for generating bioinspired materials with tailored properties. In this study, we employed a proteomic approach to identi…