Neuropeptide-induced inhibition of steroidogenesis in crab molting glands: involvement of cGMP-dependent protein kinase.

In crustaceans, ecdysteroid production by the molting glands (Y-organs) is negatively regulated by a neuropeptide, molt-inhibiting hormone (MIH). The involvement of cyclic nucleotide-dependent kinases in the mechanism of action of this neuropeptide was investigated with regard to the steroidogenic activity of Carcinus maenas Y-organs. Regardless of the activity level, the major phosphotransferase activity measured in cytosolic fraction was cGMP-dependent, indicating a relatively high cytosolic concentration of cGMP-kinase in these cells.

A transaldolase : An enzyme implicated in crab steroidogenesis.

In arthropods, development is controlled by cholesterol-derived steroid hormones: the ecdysteroids. In vertebrates and insects, steroidogenesis is positively regulated and this is mediated by cAMP. In crustaceans, ecdysteroid biosynthesis by steroidogenic organs (Y-organs) is negatively regulated by a neuropeptide, the Molt Inhibiting Hormone (MIH).

Effects of transforming growth factor-beta 1 on the extracellular matrix and cytoskeleton of cultured astrocytes.

The present study was performed on primary cultures and subcultures of cerebellar astrocytes in order to investigate the effects of transforming growth factor-beta 1 (TGF beta 1) on proliferation, extracellular matrix (ECM) components, and cytoskeletal structures in relation to morphological changes. The expression and cellular distribution of the ECM components laminin and fibronectin and the cytoskeletal proteins glial fibrillary acidic protein (GFAP) and actin were investigated by immunoblotting, immunocytochemistry, and phalloidin staining. The proliferation of primary cultures was strongly inhibited by TGF beta 1.

Effects of TGF beta 1 on the proliferation and differentiation of an immortalized astrocyte cell line: relationship with extracellular matrix.

The astrocyte cell line (C.LT.T.