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  • Author: V. J. Chapman x
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Abstract

We studied (1) the dynamics of colonization by epilithic algae on mechanically damaged colonies of the coral Porites lutea, (2) the dynamics of algal colonization on dead coral fragments (coral pebbles), (3) and regeneration rates of the damaged corals under a broad range of natural light conditions on the fringing reef of Sesoko Island (Okinawa, Japan). After 1 month (of the experiment), 26 algal species occupied damaged coral areas with a projected areal cover of 1–7%. Colonizers were mainly diatoms, Cyanobacteria, filamentous green, brown and red algae. During this period, the algal settlers were not an impediment to coral polyp recovery. The recovery rate of damaged coral tissue was highest after the first month, amounting to approximately 0.15 mm day-1 under bright light (70–90% of incident surface photosynthetically active radiation, PAR0), 0.14 mm day-1 under moderate light (20–30% PAR0) and 0.07 mm day-1 under low light (2–5% PAR0). After 3 months, 58 algal species had settled onto lesions and 43 species onto coral pebbles. Projected areal cover of the algae was 30–90%. After the second month of the experiment, the recovery rates of corals declined sharply to 0.02–0.04 mm day-1. Under high and moderate light intensities, the measured parameters were similar (with the exception of the number of algal settlers). Under low light, the number, the density of algal settlers and the regeneration rate of polyps on damaged corals were significantly reduced. The algal turf community was formed under light intensities from 20% to 90% PAR0, but was not formed under low light.

Abstract

The urokinase receptor is a multifunctional protein that plays a central role in cell surface plasminogen activation, cell migration, and cell adhesion. We previously demonstrated that high affinity peptide ligands for the urokinase receptor, which are urokinase competitors, can be obtained from a 15mer peptide library (Goodson et al., 1994). In order to probe for additional urokinase receptor binding sites we affinity selected the same bacteriophage library on complexes of soluble urokinase receptor (suPAR) and the receptor binding domain of urokinase, residues 1 48 (uPA1 48). Bacteriophage were isolated which bound to suPAR and suPAR:uPA1 48 complexes with high yield. The peptide sequences encoded by these bacteriophage were distinct from those obtained previously on urokinase receptor expressing cells, and comprise two groups based upon effects on su PAR:1-anilino-8-napthalene sulfonate (ANS) fluorescence, and vitronectin binding competition. Alanine scanning mutagensis of the soluble peptides was used to define minimal regions and key residues for suPAR binding by competition with the parent bacteriophage. A comparison of these results with sequences of domains of both vitronectin and integrin αchains, which have been reported to be important for urokinase receptor binding, suggests that the homology with the peptide sequences selected is functionally significant.