Expression of a preproinsulin-beta-galactosidase gene fusion in mammalian cells..     ///    "The expression of preproinsulin-beta-galactosidase activity was measured in the presence of high glucose, insulin, dexamethasone, or epidermal growth factor but no regulatory changes were observed.. "    ///    The fused preproinsulin-beta-galactosidase was further characterized by gel electrophoresis of nondenatured cell extracts stained by a fluorogenic substrate and by immunoprecipitation and gel electrophoresis of 3H-labeled cell proteins. 