Natural infection of a horse with Fascioloides magna

A 25-year-old Quarterhorse mare was euthanized for a variety of medical reasons. At necropsy, 7 liver flukes, identified as Fascioloides magna, were recovered from the liver. This is the first report of F. magna in a horse.

Golgi proteins persist in the tubulovesicular remnants found in brefeldin A-treated pancreatic acinar cells

Brefeldin A (BFA) blocks protein export from the endoplasmic reticulum (ER) and causes dismantling of the Golgi cisternae with relocation of resident Golgi proteins to the ER in many cultured cell lines. We examined the effects of BFA on Golgi organization and the distribution of Golgi markers in the rat exocrine pancreas. Immediately after BFA addition, Golgi stacks began to disorganize and Golgi cisternae to vesiculate, and by 15 min no intact Golgi cisternae remained. However, even after prolonged BFA incubation, clusters of small vesicles surrounded by transitional elements of the ER persisted both in the Golgi region and dispersed throughout the apical cytoplasm. These vesicles were morphologically heterogeneous in the density of their content and in the presence of cytoplasmic coats. Immunogold labeling demonstrated that some vesicles within the clusters contained gp58, a cis Golgi marker, and some contained alpha-mannosidase II, a middle/trans Golgi marker in this cell type. Neither marker was detected in the rough ER by immunogold or immunofluorescence labeling. When AlF4- was added during BFA treatment some of the vesicles in the clusters appeared coated. When microsomes were subfractionated into Golgi (light) and rough ER (heavy) fractions on sucrose density gradients, greater than 65% of alpha-mannosidase II and galactosyltransferase activities were found in light fractions (1.14-1.16 g/ml) in both control and BFA-treated lobules. In both cases equally low enzyme activity was recovered in heavier fractions (1.2-1.23 g/ml) containing RNA and alpha-glucosidase activity. However, 5 to 8% of the total recovered RNA consistently codistributed with the Golgi enzyme peak. These results indicate that BFA rapidly inhibits secretion and causes dismantling of the Golgi stacks in pancreatic acinar cells, but clusters of vesicles consisting of bona fide Golgi remnants persist even with prolonged exposure to BFA. Many of the vesicles contain Golgi markers by immunolabeling. By cell fractionation Golgi membrane enzyme activities are recovered in equal amounts in light (Golgi) fractions in both controls and BFA-treated specimens. These findings indicate that in the exocrine pancreas there is a dissociation of BFA's effects on the exocytic pathway: there is a block in transport and Golgi organization is disrupted, but remnant Golgi vesicles and tubules persist and retain Golgi membrane antigens and enzyme activities.

Brefeldin A affects early events but does not affect late events along the exocytic pathway in pancreatic acinar cells

Brefeldin A (BFA) blocks protein export from the endoplasmic reticulum (ER) to Golgi complex and causes dismantling of the Golgi complex with relocation of resident Golgi proteins to the ER in some cultured cells. It is not known whether later steps in the secretory process are affected. We previously have shown that in BFA-treated rat pancreatic lobules, there is no detectable relocation of Golgi proteins to the ER and, although Golgi cisternae are rapidly dismantled, clusters of small smooth vesicles consisting of both bona fide Golgi remnants and associated vesicular carriers persist even with prolonged BFA exposure. We now report the effects of BFA on transport of proteins through the secretory pathway in exocrine pancreatic cells; we pulse-labeled pancreatic lobules with [35S]methionine and then chased for various times before adding BFA. When BFA was added at pulse, treated lobules released less than 10% of radioactive protein in comparison with controls, regardless of whether or not the lobule cultures were stimulated with carbamoylcholine. However, when lobules were pulsed and then chased for 30, 45, or 60 min before BFA addition, the amount of labeled protein released was comparable in both BFA-treated and untreated cultures. Furthermore, the kinetics and amounts of basal and carbamoylcholine-stimulated release of unlabeled alpha-amylase from storage in zymogen granules were similar in both control and BFA-treated lobules. Therefore, in the rat pancreas, BFA blocks ER to Golgi transport but does not affect later stages along the secretory pathway, including intra-Golgi transport, exit from the Golgi complex, formation and concentration of secretory granules, and exocytosis.