No abstract

This study investigated how handling juvenile Atlantic salmon Salmo salar and rearing them in fresh water at densities of 8,32, and 64 kg-m ~3 affect plasma cortisol concentration and ability to produce plaque-forming cells (pfcs) from anterior kidney lymphocytes. Chronic plasma cortisol concentrations were higher in fish reared at 64 kg-m~3 than in fish reared at 8 or 32 kg-m~3. The number of antibody-producing pfcs from anterior kidney lymphocytes in fish reared at a density of 64 kg-m~3 was significantly lower than in fish reared at 8 or 32 kg-m~3.

The Tpr protease of Porphyromonas gingivalis W83 is a membrane-associated enzyme capable of hydrolyzing a chromogenic bacterial collagenase substrate. An isogenic mutant lacking a functional tpr gene had a greatly reduced ability to hydrolyze the collagenase substrate. Activity was restored to the tpr mutant by introducing a shuttle plasmid containing the tpr gene. Expression of the gene is induced by nutrient limitation, as shown by enzymatic and Northern analyses.