Form and functions of the regular surface array (S-layer) of Aeromonas salmonicida

The principal virulence factor of Aeromonas salmonicida is its S-layer (A-layer) which is comprised of tetragonally arrayed approximately 50,000 Mr protein subunits tethered to the cell surface via LPS. The detailed composition of its LPS is known, as is the primary sequence, and three-dimensional disposition of the A protein subunits. The A-layer physically protects the cell against bacteriophage, proteases, as well as immune and non-immune complement. The A-layer appears to be uniquely adapted towards binding biologically important molecules such as heme, and to various basement membrane proteins. In addition, the A-layer is required for macrophage infiltration and resistance. Specific mutants containing a disorganized A-layer are avirulent and provide significant protection to salmonids when applied by immersion.     

Blood 5-hydroxytryptamine in rats with pulmonary hypertension produced by ingestion ofCrotalaria spectabilis seeds

Zusammenfassung Der pulmonare Blutdruck in Ratten kann durch Abfütterung vonCrotalaria spectabilis erhöht werden, ohne die Konzentration des plasmafreien und an die Thrombozyten gebundenen 5-Hydroxytryptamins zu verändern.     

Immunization of mice against transplantable tumor

Zusammenfassung Nach i.p. Injektionen von mit Tween 80 behandelten Ehrlich-Lettré Ascites Krebszellen immunisierten Mäusen ergab sich bei diesen eine Widerstandsfähigkeit gegenüber Transplantaten von lebensfähigen Tumorzellen, woraus geschlossen wird, dass diese Behandlung die spezifischen Antigene der Zelloberfläche freisetzt.

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The research was supported by a grant from the Medical Research Council of Canada. I wish to thank Mrs.I. Gower for valuable technical assistance.     

MEGF10 and MEGF11 mediate homotypic interactions required for mosaic spacing of retinal neurons

In many parts of the nervous system, neuronal somata display orderly spatial arrangements. In the retina, neurons of numerous individual subtypes form regular arrays called mosaics: they are less likely to be near neighbours of the same subtype than would occur by chance, resulting in 'exclusion zones' that separate them. Mosaic arrangements provide a mechanism to distribute each cell type evenly across the retina, ensuring that all parts of the visual field have access to a full set of processing elements. Remarkably, mosaics are independent of each other: although a neuron of one subtype is unlikely to be adjacent to another of the same subtype, there is no restriction on its spatial relationship to neighbouring neurons of other subtypes. This independence has led to the hypothesis that molecular cues expressed by specific subtypes pattern mosaics by mediating homotypic (within-subtype) short-range repulsive interactions. So far, however, no molecules have been identified that show such activity, so this hypothesis remains untested. Here we demonstrate in mouse that two related transmembrane proteins, MEGF10 and MEGF11, have critical roles in the formation of mosaics by two retinal interneuron subtypes, starburst amacrine cells and horizontal cells. MEGF10 and 11 and their invertebrate relatives Caenorhabditis elegans CED-1 and Drosophila Draper have hitherto been studied primarily as receptors necessary for engulfment of debris following apoptosis or axonal injury. Our results demonstrate that members of this gene family can also serve as subtype-specific ligands that pattern neuronal arrays.