Histochemical and morphological studies on Trichinella spiralis larvae treated with high hydrostatic pressure

Histochemical and morphological observations were made on Trichinella spiralis larvae treated with hydrostatic pressures of 100, 150, 200 and 300 MPa using hematoxylin-eosin (HE), periodic acid-Schiff (PAS) and Azan staining. Few histochemical changes were observed in HE and PAS stained larvae after pressurization at 200 MPa and under. However, red staining by Azan changed to blue in the anterior stichosome of larvae and skeletal muscle of mice, when the hydrostatic pressure was raised from 150 to 300 MPa. At 150 and 200 MPa, boundaries among stichocytes were indistinct or irregular, and unstained areas were observed in stichocytes of larvae using Azan staining. At 300 MPa, all tissues of larvae and mouse muscle stained blue with Azan. At the same pressure, decrease in PAS positive staining of stichocytes and dilation of muscular cells were observed in larvae. It is assumed that these histochemical and morphological changes in pressurized larvae might be related to the loss of infectivity of larvae.