Abstract
Ultrastructure of IPN virus, a pathogen of the fingerling rainbow trout (Salmo gairdneri Richardson), was examined by the ultracvtochemical techniaues.
Mature virions are unenveloped and hexagonal or round in profile, having an average diameter of approximately 66 mμ (size range of 65-68 mμ) after phosphotungstic acid (PTA) or ethanol-phosphotungstic acid (E-PTA) staining technique.These techniques revealed that five capsomeres were sharply present on a capsid edge of the hexagonal virions on the ultrathin sections, suggesting that the IPN virus capsid is made up of 162 capsomeres.Probably, IPN virus may be unenveloped icosahedra and a member of the reovirus group.The capsomeres are often penta-or hexa-gonal on the ultrathin sections, and at each apex small units with an average diameter of approximately 21Å.are located.
PTA, E-PTA, ruthenium red, and lanthanum staining techniques revealed a positive reaction on the capsomeres of IPN virus, suggesting the presence of polysaccharides. The ruthenium red staining technique was applied to penetrate into small pancreatic tissue by means of mechanical damage.Further, PTA and E-PTA staining techniques revealed fine particles with the positive reaction on the outer surface and in the interior of tubular structures (or rod-like bodies) often located near the virions of various numbers.
Among IPN virions within cytolysomes small particles with an average diameter of approximately 210A appeared often singly or in beads-like chains.They consisted of a group of a few capsomeres and appeared penta-or hexagonal in profile.It is not clear what is the meaning of small particles.
