Parasites and hepatic lesions among pink salmon, Oncorhynchus gorbuscha (Walbaum), during early seawater residence.

Juvenile pink salmon, Oncorhynchus gorbuscha (Walbaum), in the Broughton Archipelago region of western Canada were surveyed over 2 years for sea lice (Lepeophtheirus salmonis and Caligus clemensi), gross and microscopic lesions and evidence of infections with viruses and bacteria. The 1071 fish examined had an approximate ocean residence time no longer than 3 months. A high prevalence of degenerative liver lesions, renal myxosporean parasites and a low prevalence of skin lesions and sea lice were observed. No indications of viral or bacterial diseases were detected in either year. The monthly prevalence of sea lice in 2007 (18-51%) was higher than in 2008 (1-26%), and the infestation density exceeded the lethal threshold in only two fish. Degenerative hepatic lesions and renal myxosporean parasites occurred in approximately 40% of the pink salmon examined in June of both years, and the peak monthly prevalence of hepatocellular hydropic degeneration was greater in 2007 (32%, in May) than in 2008 (12%, in June). Logistic regression analysis found skin lesions and hepatocellular hydropic degeneration significantly associated with sea lice. Most parasites and lesions occurred during both years, but the prevalence was often higher in 2007. Fish weight was 35% less in June 2007 than in June 2008, but condition factor was not different. Further research is required to monitor inter-annual variations and aetiology of the liver lesions and to assess their potential role on pink salmon survival.

Characterization of Xenopus laevis oocyte farnesyl transferase.

Farnesyl transferase (FTase) activity, characterized in extracts of Xenopus laevis oocytes using an in vitro filtration assay, was observed to be at least 80% cytosolic with optimal product formation at pH 7.0. Oocyte FTase displayed enzyme activity that was specific for the Ras-CVIM construct but not Ras-CAIL or Ras-SVLS. Labeling of Ras-CVIM using [3H]farnesyl pyrophosphate was inhibited by addition of unlabeled farnesyl pyrophosphate to the assay mixture but not by addition of either geranylgeranyl pyrophosphate or stearic acid. Polyclonal rabbit antibodies against recombinant human FTase subunits were tested for cross-reactivity with oocyte proteins and were used to determine the apparent molecular masses of oocyte FTase enzyme subunits. Anti-alpha subunit antibodies labeled a band of approximately 53 kDa. Anti-beta subunit antibodies bound both a high molecular mass band (140 kDa) and a lower molecular mass band (38 kDa) on immunoblots of cytosolic oocyte proteins. When oocyte FTase activity was resolved by gel filtration, the peak of enzyme activity correlated with immunoblot detection of the 38- and 53-kDa bands as well as a doublet of 86- and 95-kDa. This correlation suggests that Xenopus laevis oocyte FTase is a heterodimer under reducing conditions with subunits of 53 +/- 1 and 38 +/- 2 kDa, and that the holoenzyme migrates on SDS-polyacrylamide gels with an apparent molecular mass of 86-95 kDa.