Keratan sulphate in the tumour environment

Keratan sulphate (KS) is a bioactive glycosaminoglycan (GAG) of some complexity composed of the repeat disaccharide D-galactose β1→4 glycosidically linked to N-acetyl glucosamine. During the biosynthesis of KS, a family of glycosyltransferase and sulphotransferase enzymes act sequentially and in a coordinated fashion to add D-galactose (D-Gal) then N-acetyl glucosamine (GlcNAc) to a GlcNAc acceptor residue at the reducing terminus of a nascent KS chain to effect chain elongation. D-Gal and GlcNAc can both undergo sulphation at C6 but this occurs more frequently on GlcNAc than D-Gal. Sulphation along the developing KS chain is not uniform and contains regions of variable length where no sulphation occurs, regions which are monosulphated mainly on GlcNAc and further regions of high sulphation where both of the repeat disaccharides are sulphated. Each of these respective regions in the KS chain can be of variable length leading to KS complexity in terms of chain length and charge localization along the KS chain. Like other GAGs, it is these variably sulphated regions in KS which define its interactive properties with ligands such as growth factors, morphogens and cytokines and which determine the functional properties of tissues containing KS. Further adding to KS complexity is the identification of three different linkage structures in KS to asparagine (N-linked) or to threonine or serine residues (O-linked) in proteoglycan core proteins which has allowed the categorization of KS into three types, namely KS-I (corneal KS, N-linked), KS-II (skeletal KS, O-linked) or KS-III (brain KS, O-linked). KS-I to -III are also subject to variable addition of L-fucose and sialic acid groups. Furthermore, the GlcNAc residues of some members of the mucin-like glycoprotein family can also act as acceptor molecules for the addition of D-Gal and GlcNAc residues which can also be sulphated leading to small low sulphation glycoforms of KS. These differ from the more heavily sulphated KS chains found on proteoglycans. Like other GAGs, KS has evolved molecular recognition and information transfer properties over hundreds of millions of years of vertebrate and invertebrate evolution which equips them with cell mediatory properties in normal cellular processes and in aberrant pathological situations such as in tumourogenesis. Two KS-proteoglycans in particular, podocalyxin and lumican, are cell membrane, intracellular or stromal tissue–associated components with roles in the promotion or regulation of tumour development, mucin-like KS glycoproteins may also contribute to tumourogenesis. A greater understanding of the biology of KS may allow better methodology to be developed to more effectively combat tumourogenic processes

Volcanic plume thermal radiation: 1972 eruption of piton de la fournaise, Réunion Island

International audienc

A guard cell-specific MYB transcription factor regulates stomatal movements and plant drought tolerance

Stomatal pores located on the plant epidermis regulate CO2 uptake for photosynthesis and the loss of water by transpiration. The opening and closing of the pore is mediated by turgor-driven volume changes of two surrounding guard cells [1]. These highly specialized cells integrate internal signals and environmental stimuli to modulate stomatal aperture for plant survival under diverse conditions [2]. Modulation of transcription and mRNA processing play important roles in controlling guard-cell activity, although the details of these levels of regulation remain mostly unknown [3-5]. Here we report the characterization of AtMYB60, a R2R3-MYB gene of Arabidopsis, as the first transcription factor involved in the regulation of stomatal movements. AtMYB60 is specifically expressed in guard cells, and its expression is negatively modulated during drought. A null mutation in AtMYB60 results in the constitutive reduction of stomatal opening and in decreased wilting under water stress conditions. Transcript levels of a limited number of genes are altered in the mutant, and many of these genes are involved in the plant response to stress. Our data indicate that AtMYB60 is a transcriptional modulator of physiological responses in guard cells and open new possibilities to engineering stomatal activity to help plants survive desiccation

Simulation des transferts de contamination par les gaz et les aérosols

On dresse dans cet article le bilan des principales techniques utilisées par le Service de Protection Technique (S.P.T./S.T.E.P.) du C.E.A. dans la simulation des transferts de contamination. Ces techniques permettent d’optimiser les conditions de ventilation des installations nucléaires, elles ont lieu in situ ou sur maquette. Le traçage à l’hélium est une méthode particulièrement pertinente pour évaluer les transferts de contamination sous forme gazeuse et déterminer les débits de ventilation. D’autres applications sont en cours de développement. Les techniques de simulation par aérosols tests servent à étudier les fonctions de transfert d'un système selon des procédures normalisées. Lorsque réside un certain nombre d’incertitudes sur la source de contamination, on simule à la fois le transfert et la génération. La génération se fait à partir de poudre (ZnS... ) ou de solutions (solutions de sels de fluorescéine ou de sodium...). Les mesures s’effectuent sur le résidu sec ou sur les vésicules liquides. La qualité de la simulation dépend du respect d’un certain nombre de contraintes découlant de la théorie des similitudes. Un exemple d’application de ces techniques traite du transfert des aérosols de produits de fission émis lors d’une ébullition