Ultrastructure of platelets in Porcine Stress Syndrome.

BOUVET,*'Alain, Shigeto YAMASHIRO, Wayne N. McDONELL and Parvathi K.BASRUR,* Department of Biomedical sciences and Department of Clinical Studies, University of Guelph, Guelph Ontario.

Porcine Stress Syndrome (PSS) which imposes severe economic drains on the swine industry through' sudden death loss and post mortem deterioration of the meat, is a pharmacogenetic trait detected at high frequency in certain breeds of pigs. The primary lesion in this inherited trait is not identified as yet, although the stress induced crisis is thought to be caused by a membrane defect affecting the control of free calcium in skeletal muscle which undergoes excessive contracture and myol sis. In an attempt to y investigate whether an alteration in the membrane system is evident in other cell types subject to calcium fluxes, an ultrastructural comparison of platelets from normal and stress susceptible pigs was undertaken. The most ' @ striking alteration detected in the platelets of stress reactors was the dilatation of the surŽace connected open canalicular system (OCS). A morphometric analysis of electron micrographs, using an MOP-AM03 Kontron manual optical photo analyzer, revealed that the platelet alteration is quantifiable on the basis of the extent of OCS dilatation and the proportion of affected platelets. The platelet alteration which was noted to be consistent through age groups and breeds of pigs tested, suggests that the defect is inherent to the PSS trait and that it may prove to be a useful criteria for developing a test to detect stress susceptibility in pigs.

#Supported by NSERC Canada, Agriculture Canada and OMAF.

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