Direct effects of hypoxia and nitric oxide on ecdysone secretion by insect prothoracic glands.

Insect molting and metamorphosis are controlled by the molt stimulating hormone ecdysone. A recent study suggests that reduced tissue oxygenation correlates with the size-sensing mechanism responsible for triggering molting. When reared in hypoxia, larvae of Manduca sexta and Drosophila melanogaster initiate molting at lower weights than do larvae reared in normoxia.

Amino acids and TOR signaling promote prothoracic gland growth and the initiation of larval molts in the tobacco hornworm Manduca sexta.

Molting in arthropods is orchestrated by a series of endocrine changes that occur towards the end of an instar. However, little is understood about the mechanisms that trigger these endocrine changes. Here, nutritional inputs were manipulated to investigate the minimal nutritional inputs required for a Manduca sexta larva to initiate a molt.

Human synovial fibroblast plasminogen activator. Modulation of enzyme activity by antiinflammatory steroids.

Human synovial fibroblasts in culture have been shown to have low plasminogen activator (PA) activity; however, conditioned medium from concanavalin A-stimulated peripheral blood mononuclear cells (c-MCCM) stimulates the cellular levels of this protease. The present study shows that low concentrations of a series of antiinflammatory steroids inhibit the PA activities of both unstimulated and c-MCCM-stimulated fibroblasts. Dexamethasone, the corticosteroid studied in greatest detail, suppresses both the extracellular and cell-associated enzyme activities; this inhibition is rapid, reversible, and is not due to the inhibition of cellular RNA, protein, or DNA synthesis.

Mechanism of thyroid allograft rejection.

Balb/c thyroids, held in organ culture for 26 days, survive and function as well as isografts for greater than 100 days in CBA recipients. Uncultured allografts are totally rejected by 20 days after transplantation. Prolonged allograft survival can also be achieved by the treatment of donor animals with cyclophosphamide prior to harvesting tissues for transplantation.