Chick embryo fibroblasts produce two forms of hyaluronidase

Cultured chick embryo fibroblasts derived from skin and skeletal muscle exhibit hyaluronidase activity both associated with the cell layer and secreted into the medium. Although both forms of the enzyme have a number of similar characteristics (R.W. Orkin and B.P. Toole, 1980, J. Biol. CHem. 255), they differ in thermal stability at neutral pH and in behavior on ion-exchange chromatography. Both forms of the enzyme are equally stable at acidic pH for long intervals, but the cell-associated hyaluronidase is significantly less stable than the secreted froms at neutral pH and at temperatures more than or equal to 30 degrees C. Neither the presence of proteases nor inhibitors of hyaluronidase appear to be involved in the cell-asspcoated enzyme. Chromatography of the two forms of hyaluronidase on carboxymethyl cellulose reveals that most (60-90 percent) of the secreted form of the enzyme elutes at a lower ionic strength than the cell- associated enzyme. Treatment of the secreted form of hyaluronidase with neuraminidase shifts its elution profile on carboxymethyl cellulose toward that of the cell-associated form, and also decreases its thermal stability at neutral pH. In contrast, treatment of the secreted form of hyaluronidase with alkaline phosphatase has no detectable effect. These data suggest that the secreted hyaluronidase differs from the cellular form in possessing additional sialic acid residues which endow the former with increased stability in the extracellular milieu.     

THE EFFECTS OF STEADY AND CYCLING TEMPERATURES ON THE ACTIVITY OF THE SLUG DEROCERAS RETICULATUM

At constant temperatures, crawling activity in the slug Derocerasreticulatum has an optimum at 13°C in late winter, and 17°Cin early summer. The optimum for feeding remains at 14°C.Activity has anendogenous basis, but daytime activity increaseswith temperature and long daylengths. Cycling temperatures producemore locomotor activity and less feeding in 24 h than constanttemperatures, even when the temperature is higher at night.However, cooling stimulates and warming inhibits activity duringthe period of change and when cooling occurs at dusk, over halfthe 24 h activity occurs in the next three hours. Faster ratesof cooling produce greater responses, but can result in loweroverall activity because the slugs remain longer at low temperatures. (Received 25 May 1984;