IGF-I production by mouse osteoblasts.

Mouse osteoblasts contain and secrete insulinlike growth factor I (IGF-I), which can be measured by radioimmunoassay after separation from endogenous IGF-I binding activity. Our studies indicate that IGF-I is produced by all bone cell populations prepared by sequential digestion of mouse calvaria with collagenase and protease. Furthermore, relatively small amounts of IGF-I are cell associated, and IGF-I is recovered primarily in the cell medium after 24 h of culture.

Mitogenic responses to and binding of insulin-like growth factor 1 and/or epidermal growth factor by bone cells.

Populations of cells with different biochemical characteristics can be obtained following enzymatic digestion of newborn mouse calvaria. Previous studies had suggested an enrichment for periosteal fibroblasts in early released cells, based on their proliferative response to PGE2 and for osteoblasts in late released cells due to their high cAMP response to PTH. Intermediate cells were presumed to be a mixture of those two phenotypes.

The ovary as a source of alpha-ecdysone in an adult mosquito.

The ovaries of the mosquito Aedes aegypti cultured in vitro secrete material that behaves like ecdysone in a radioimmunoassay. The material was identified as alpha-ecdysone by high-resolution liquid and gas-liquid chromatography. Secretion reached a maximum 16 hr after a blood meal as shown by bioassay and direct determination.

Ecdysone-mediated stimulation of DOPA decarboxylase activity and its relationship to ovarian development in Aedes aegypti.

Very little dopa decarboxylase activity is detectable in adult female mosquitoes Aedes aegypti which have not been allowed to engorge blood. However, when such females are injected with the molting hormone beta-ecdysone a marked stimulation of this enzyme's activity is observable. No stimulation is observed in males similarly injected, nor in females injected with cholesterol or a juvenile hormone mimic.