L-selectin mediates lymphocyte migration to peripheral lymph nodes and leukocyte rolling on vascular endothelium during inflammation. One unique feature that distinguishes L-selectin from other adhesion molecules is that it is rapidly cleaved from the cell surface after cellular activation. The biological significance of L-selectin endoproteolytic release was determined by generating gene-targeted mice expressing a modified receptor that was not cleaved from the cell surface. Blocking L-selectin cleavage on antigen-stimulated lymphocytes allowed their continued migration to peripheral lymph nodes and inhibited their short-term redirection to the spleen. Blocking homeostatic L-selectin cleavage also resulted in a constitutive 2-fold increase in overall L-selectin expression by leukocytes. As a result, neutrophils entered the inflamed peritoneum in greater numbers or for a longer duration. Thus, endoproteolytic cleavage regulates both homeostatic and activation-induced changes in cell surface L-selectin density, which directs the migration patterns of activated lymphocytes and neutrophils in vivo.

Candida albicans is the leading cause of systemic fungal infections in immunocompromised humans. The ability to form biofilms on surfaces in the host or on implanted medical devices enhances C. albicans virulence, leading to antimicrobial resistance and providing a reservoir for infection. Biofilm formation is a complex multicellular process consisting of cell adhesion, cell growth, morphogenic switching between yeast form and filamentous states, and quorum sensing. Here we describe the role of the C. albicans EAP1 gene, which encodes a glycosylphosphatidylinositol-anchored, glucan-cross-linked cell wall protein, in adhesion and biofilm formation in vitro and in vivo. Deleting EAP1 reduced cell adhesion to polystyrene and epithelial cells in a gene dosage-dependent manner. Furthermore, EAP1 expression was required for C. albicans biofilm formation in an in vitro parallel plate flow chamber model and in an in vivo rat central venous catheter model. EAP1 expression was upregulated in biofilm-associated cells in vitro and in vivo. Our results illustrate an association between Eap1p-mediated adhesion and biofilm formation in vitro and in vivo.

Accumulation and coalescence of branching microcracks into arrays or clusters appears to eventually lead to the development of macroscopic subchondral cracks in the condylar groove and initiation of a condylar fracture.

The alewife (Alosa ~S B U~O~W I T B~~L~~S )is an obligate planktivore which rases a variety of methods for capturing zooplankton. Alewife eat Mysis rekictca, especially larger individuals, at night during a vertical migration by bath predator and prey. We proposed and tested the hypothesis that alewife use the lateral line to sense prey and feed particulately (single prey at a time) in the dark. We used Daphnia BnQgnwl and Artemia sakima adults as prey. Prey densities were such that they did not elicit filter feeding. Observations using infrared video showed that alewife captured individual prey and bit at a vibrating inert bead. We concluded that under appropriate conditions, alewife were size selective and that streptomycin (which blocks the lateral line sensory cells) eliminated this feeding behavior. RCsnmC : Ee gaspareau (Alosa pseudokarengus) est un planctivore obligC qui utilise des rnkthodes diverses pour capturer le zooplancton. t e gaspareau consomme des Mysis relicfa, particulikrernent les individus de grande taille, en se nourrissant la nuit au cours d' uame migration verticale effectuCe ii la fois par le prCdateur et par sa proie. Nous avons proposC et test6 l'hypothese selon laquelle le gaspareau se servirait de sa ligne latkrale pour percevoir la prCsence des proies et se amourrirait sklectivement (une proie h la fois) dans le noir. Nous avons utilisC comme proies des adultes de Daphnia rnagna et d7Artemia snlinca. Les densitCs des proies Ctaient telles qu'elles ne favorisaient pas un mode d'alimentation par filtration. Les observations rCalisCes ii l'aide de la vidCo dans 19infrarouge ont rnontrC que le gaspareau capture une proie 8 la fois et s'attaque B une perle de rnatikre inerte qui vibre. Nous concHuons que, dans des conditions apgropriCes, le gaspareau sklectionne ses proies en fonction de leur taille. Nous avons Cgalement observC que la streptomycine (qui bloque les cellules sensorielles de la ligne IatCrale) Climine ce comportement d'alimentation. [Traduit par la RCdaction]The tactics of interactions between fish and zooplankton, predator and prey, are diverse (lazzaro 1889). Where sizeselective feeding is indicated by field dietary studies, it is presumed (generally) that planktivsres operate by visually detecting prey. Vertical migration of zooplankton is inferred to minimize predation risk when the upper part of the water column is well lighted. Young and Watt (1983) argued that during the day, zooplankters ought to be deep enough to be visually undetectable and ascend into the phytoplankton-rich zone when it is too dark to be seen. This situation appears to be true for interaction of Mysis relicla with the alewife (Alma pseudohareragus). Janssen and Brandt (1988) found that during the day, at a 50-rn bottom depth, Wgysis were on the bottom and unavailable to the alewife because alewife have difficulty feeding on the bottom (Janssen 1998a). At night, W s i s migrated into the water column and larger individuals were eaten by alewife, although the mechanism by which Mysis were detecte...

Colloidal heavy metals, such as gold, can be produced in a variety of sizes in the nanometer range. For labeling purposes the metal particles can be directly conjugated to various ligands or to antibodies via nonspecific hydrophobic interactions [1,2]. The heavy metal colloids are electron dense and have a distinct spherical shape and thus are very useful for both TEM and SEM applications [1,2,3]. They have a high extinction coefficient and produce a visible, inflated diffraction image and thus can be identified in several forms of light microscopy [1]. However, the use of the heavy metal colloids as light microscopic labels, particularly in correlative studies, is often problematic. Either the particle size or specimen geometry limits information attainable by interference based light systems. Enlarging smaller particles via silver enhancement may provide visibility in light microscopy, but the spatial resolution necessary for EM is lost. Thus, for correlative studies both in living and fixed systems, probes which combine fluorescence and colloidal heavy metal particles are useful. If colloidal particles of differing shapes or elemental compositions are used for high resolution co-localization studies, it would be advantageous to link a particular probe with a specific fluor such that co-localization at the light microscopic level (as for living cells) via fluorescence can be directly correlated with co-localization at the molecular level via EM [4]. Unfortunately, studies using UV-excited fluoresceinated identifier proteins such as FITC or rhodamine conjugated to colloidal metal particles result in quenching of the fluorescence. The degree of quenching seen with indirect labeling via fluorescent labels has not been well understood and is a possible alternative to direct conjugates. The use of mixtures of fluoresceinated identifier proteins and colloidal metal labeled proteins is also an alternative but competition between probes reduces the overall efficiency of labeling and hence detectability and spatial resolution for either probe.