Discoidin I, the developmentally regulated carbohydrate binding protein from Dictyostelium discoideum, migrated as a broad band during electrophoretic analysis using 10% polyacrylamide gels in the presence of sodium dodecyl sulfate. The band could be resolved into two components by electrophoresis on 15% polyacrylamide gels. All highly purified preparations of discoidin I contained equal amounts of the two components, suggesting they are nonidentical subunits of the protein. The subunit molecular weights of discoidin I and discoidin II were found to be 29,500 and 26,500, values somewhat larger than those previously reported.

Carrier Proteins↗

PubMedDate not supplied

Extensive proliferation of mature connective-tissue type mast cells in vitro.

There are two phenotypically distinct subpopulations of mast cells in rodents: connective tissue-type mast cells (CTMC) and mucosal mast cells (MMC). These populations differ in their location, cell size, staining characteristics, ultrastructure, mediator content and T-cell dependency. Several investigators recently reported a further subclass of mast cells which arise when normal mouse haematopoietic cells are cultured with interleukin-3 (IL-3); IL-3 is an activity similar or identical to mast-cell growth factor, histamine-producing factor, or P-cell stimulating factor. These cultured mast cells are in many ways similar to MMC; they stain with Alcian blue but not safranin, contain chondroitin sulphate E proteoglycan rather than heparin proteoglycan and have relatively low histamine content, as do MMC. Although proliferation of MMC is known to be T-cell dependent in vivo and thought to be IL-3-dependent in vitro, the factors on which CTMC proliferation depends remain elusive. Here we show that mature CTMC purified from mouse peritoneal cells can proliferate in vitro in methylcellulose culture and maintain the appearance and function of CTMC. We also present evidence that mature CTMC cannot proliferate in the presence of pure IL-3 alone.

Animals↗