MAST-CELLS IN THE SWIMBLADDER OF ATLANTIC SALMON SALMO-SALAR - HISTOCHEMISTRY AND RESPONSES TO COMPOUND 48 80 AND FORMALIN-INACTIVATED AEROMONAS-SALMONICIDA/

Observations were made on tissue spreads from the swimbladder of the A tlantic salmon Salmo salar. The tissues were fixed in ethyl alcohol an d stained with alcoholic thionin. All preparations showed numerous tis sue mast cells. The distribution of the mast cells resembled their dis tribution in mammalian tissues, with a concentration in the vicinity o f the vascular network. Mast cell degranulation could be demonstrated at 2 h after intraperitoneal injections of compound 48/80, but in fish killed at 24 and 48 h, no signs of degranulation were found. Intraper itoneal injections of formalin-inactivated Aeromonas salmonicida subsp . salmonicida produced an inflammatory reaction and degranulation of t he mast cells of the swimbladder.