FOLLICULOSTATINS, GONADOTROPINS AND A MODEL FOR CONTROL OF GROWTH IN THE GREY FLESHFLY, NEOBELLIERIA (SARCOPHAGA) BULLATA

The sequences of two folliculostatic peptides of the fleshfly Neobelli eria bullata have been determined recently. The first peptide (Neb-TMO F: H-NPTNLH-OH), originates from a 75 kDa precursor protein found in v itellogenic oocytes. The hexapeptide directly inhibits the synthesis o f trypsin-like enzymes in the gut, and thus lowers the concentration o f yolk polypeptides in the hemolymph. It also inhibits the biosynthesi s of ecdysone in the larval ring gland. Therefore, it could also be na med prothoracicostatic hormone (Neb-PTSH). The second peptide (Neb-col loostatin: H-SIV-PLGLPVPIGPIVVGPR-OH) acts on previtellogenic follicle s and is a cleaved product of a collagen-like precursor molecule. Our results indicate that peptides that are cleaved from matrix proteins c ould act as growth-inhibiting factors. Gonadotropin releasing hormone (GnRH)-immunolike peptides were not identified, but progress is being made in the isolation and characterization of factors which stimulate cAMP production by the ovary, Using these results, a novel model of gr owth control in which matrix proteins play an important role as a pote ntial source of growth regulators has been developed.