Differentiation and morphogenesis of mammary cells in vitro

Cells of a mammary cell line isolated from a DMBA-induced rat mammary carcinoma undergo differentiation in vitro. A reversible differentiation leads to the formation of two types of microstructure (domes and ridges); this paper is concerned with the mechanism of dome formation. This differentiation is initiated by inducers, some of which are generated in the cultures and act locally; their effect is strongly dependent on cell concentration and requires hydrocortisone. There are, in addition, exogenous inducers as well as inhibitors. In the pathway to dome formation important roles are played by cAMP (probably both intracellular and extracellular), the organization of the cytoskeleton, and the Thy-1 antigen. The pathway and the significance of the phenomenon for mammary gland development are discussed.     

Distribution of post-proline cleaving enzyme in human brain and the peripheral tissues

Summary We have studied the distribution of post-propline cleaving enzyme activity in the various tissues in humans using 7-(succinyl-Gly-Pro)-4-methylcoumarinamide as substrate. The post-propline cleaving enzyme activity was high in muscle, testes, kidney and submandibular gland, but was low in the heart, mesenterium and aorta. In the brain, relatively high post-propline cleaving enzyme activity was observed in the cerebral cortex, but other brain regions showed a very low enzyme activity.On Sephadex G-100 column chromatography, enzyme activity in human kidney showed a major peak and a minor peak. The major peak coincided with the enzyme in human cerebral cortex, but was different from human serum enzyme. Diisopropylfluorophosphate, a serine protease inhibitor, strongly inhibited the enzyme activity of each active fraction. The enzyme in the cerebral cortex and kidney was inhibited by heavy metals and thiol blocking agents. However, inhibition of enzyme activity in the serum was not observed with such inhibitors. Therefore, we suppose that post-proline cleaving enzyme activity in the brain is similar, if not identical, to that in the kidney.