Role played by serum, a biological cue, in the adherence of Enterococcus faecalis to extracellular matrix proteins, collagen, fibrinogen, and fibronectin.

BACKGROUND: Most previous studies have found that Enterococcus faecalis isolates do not show significant adherence to fibronectin and fibrinogen. METHODS: The influence of various conditions on E. faecalis adherence to extracellular matrix (ECM) proteins was evaluated using a radiolabeled-cell adherence assay. RESULTS: Among the conditions studied, growth in 40% horse serum (a biological cue with potential clinical relevance) elicited adherence of all 46 E. faecalis strains tested to fibronectin and fibrinogen but not to elastin; adherence levels were independent of strain source, and adherence was eliminated by treating cells with trypsin. As previously reported, serum also elicited adherence to collagen. Although prolonged exposure to serum during growth was needed for enhancement of adherence to fibrinogen, brief exposure (<5 >min) to serum had an immediate, although partial, enhancing effect on adherence to fibronectin and, to a lesser extent, collagen; pretreatment of bacteria with chloramphenicol did not decrease this enhanced adherence to fibronectin and collagen, indicating that protein synthesis is not required for the latter effect. CONCLUSION: Taken together, these data suggest that serum components may serve (1) as host environmental stimuli to induce the production of ECM protein-binding adhesin(s), as previously seen with collagen adherence, and also (2) as activators of adherence, perhaps by forming bridges between ECM proteins and adhesins.

The relationship between the field-shifting phenomenon and representational coherence of place cells in CA1 and CA3 in a cue-altered environment.

Subfields of the hippocampus display differential dynamics in processing a spatial environment, especially when changes are introduced to the environment. Specifically, when familiar cues in the environment are spatially rearranged, place cells in the CA3 subfield tend to rotate with a particular set of cues (e.g., proximal cues), maintaining a coherent spatial representation. Place cells in CA1, in contrast, display discordant behaviors (e.g., rotating with different sets of cues or remapping) in the same condition. In addition, on average, CA3 place cells shift their firing locations (measured by the center of mass, or COM) backward over time when the animal encounters the changed environment for the first time, but not after that first experience. However, CA1 displays an opposite pattern, in which place cells exhibit the backward COM-shift only from the second day of experience, but not on the first day. Here, we examined the relationship between the environment-representing behavior (i.e., rotation vs. remapping) and the COM-shift of place fields in CA1 and CA3. Both in CA1 and CA3, the backward (as well as forward) COM-shift phenomena occurred regardless of the rotating versus remapping of the place cell. The differential, daily time course of the onset/offset of backward COM-shift in the cue-altered environment in CA1 and CA3 (on day 1 in CA1 and from day 2 onward in CA3) stems from different population dynamics between the subfields. The results suggest that heterogeneous, complex plasticity mechanisms underlie the environment-representating behavior (i.e., rotate/remap) and the COM-shifting behavior of the place cell.