Clustering transfers the translocated Escherichia coli receptor into lipid rafts to stimulate reversible activation of c-Fyn

Enteropathogenic Escherichia coli (EPEC) mimic a ligand–receptor interaction to induce 'pedestal-like' pseudopodia on mammalian cells, providing a tractable system to study tyrosine kinase signalling to the actin cytoskeleton. EPEC delivers its own receptor (Tir), which is engaged by a bacterial surface ligand (intimin). When Tir delivery and activity are uncoupled, intimin-induced Tir clustering stimulates Tir^Y474 phosphorylation by the Src-family kinase (SFK) c-Fyn, triggering actin polymerization and pedestal formation. How c-Fyn specifically targets Tir and is regulated remains unknown. We show that clustering transfers Tir into cholesterol-rich detergent-resistant microdomains (DRMs), a signal prompting transient c-Fyn accumulation at bacterial adhesion sites. Co-clustering of Tir^Y474 and c-Fyn in DRMs rapidly stimulates robust kinase activation both by induced c-Fyn^Y531 dephosphorylation to unlock the inactive state and by reciprocal c-Fyn^Y417 autophosphorylation to promote activity. After signal induction, c-Fyn dissipates and the resting state restored by Csk-dependent phosphorylation of c-Fyn^Y531. These data illustrate a sophisticated mechanism evolved by a pathogen effector to reversibly regulate SFKs, and resolve early interactions at a model receptor initiating tyrosine kinase signalling.     

Certain hemocyte proteins of the medfly,Ceratitis capitata,are responsible for nonself recognition and immobilization of Escherichia coli in vitro

The results indicate that certain hemocyte proteins of the medfly, Ceratitis capitata, are responsible for the recognition of foreignness, since they are able to bind to the surface of Escherichia coli in vitro. Furthermore, when the E. Coli-hemocyte protein complex was incubated in the presence of tyrosine and phenoloxidase, the bacteria were immobilized, forming large aggregates. The formation of aggregates seems to be due to reactive tyrosine intermediate (quinone) generated by the action of phenoloxidase. © 1992 Wiley-Liss, Inc.     

On the occurrence of the Lesser White-fronted GooseAnser erythropus in Greece

Summary Since 1859, wintering Lesser White-fronted Geese have been recorded 25 times in Greece. Of the records obtained in the second half of the 19th century only two, based on museum specimens, are valid. There were four records in the first half of the present century, while all the others come from the second half due to increased coverage mostly during IWRB midwinter censuses. Their distribution had been more southerly in the past, but in recent years only northern Greek wetlands hold the bulk of the wintering population, with the Evros Delta being the most important area (12, or 48% of all records). The wintering population of the species in the Evros Delta is threatened by habitat destruction and shooting.

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Zum Vorkommen der Zwerggans in Griechenland

Zusammenfassung Seit 1859 wurden in Griechenland 25mal Zwerggänse festgestellt; aus dem 19. Jh. liegen nur 2 sichere Nachweise vor. 4 Nachweise fallen in die erste Hälfte des 20. Jh., die restlichen alle in die zweite Hälfte, Die Verteilung der Funde scheint in der Vergangenheit weiter nach Süden gereicht zu haben; heute liegen nur aus dem Norden Beobachtungen vor. Der wichtigste Platz ist das Evros-Delta (12 von 25 Nachweisen; einmal 1630 Ind. im Februar 1963). Die Winterpopulation ist durch Biotopzerstörung und Abschuß bedroht.

     

Local Dynamics During the Mixing of Saliva with a Model Colloidal Food

The events occurring during the spontaneous mixing of an okra mucilage-based model liquid food with saliva were recorded, with a focus on the local dynamics of colloidal particles contained therein. An okra mucilage containing fluorescent microsphere probes (assuming the role of model emulsion droplets), was brought into contact with reconstituted saliva on the welled slide of a confocal microscope. The movement of the probes at the saliva–mucilage interface and in the bulk mucilage has been recorded over periods of 60 min. Data have been obtained on the total mobility of individual model droplets, their diffusion coefficients, and the local viscosities, providing information on the dynamics of processes which occur during the oral processing of colloidal liquids. The role of osmotic pressure gradients on the spreading of the droplets into saliva is discussed in relation to the microrheology data.