Two diterpene alcohols from Croton sublyratus

The isolation and structural elucidation of two diterpene alcohols from Croton sublyratus are described. These compounds are ent-3α-hydroxy-13-epimanool and ent-16β,17-dihydroxykaurane.     

Reduced DNase I sensitivity of the rearranged c-myc gene in somatic cell hybrids between murine plasmacytoma cells and fibroblasts

In mouse plasmacytoma (MPC) S194, the rearranged c-myc gene was much more sensitive to DNase I digestion than the nonrearranged gene. The sensitivity of the rearranged c-myc was markedly reduced to the same extent as that of the nonrearranged one in hybrids between the MPC cells and the fibroblasts, but not in a hybrid between the MPC and the spleen cells. These results suggest that trans-acting factors in fibroblasts alter the DNase I-sensitive structure of the rearranged c-myc gene.     

Fibroblasts inhibit mineralised bone nodule formation by rat bone marrow stromal cells in vitro

The ability of rat skin fibroblasts (RSF) and human periodontal ligament fibroblasts (HPL) to inhibit the formation of mineralised bone nodules in rat bone marrow stromal cell (BMSC) cultures was studied. Co-culture of HPL or RSF with BMSC resulted in a large reduction of bone nodule formation when compared with controls. Conditioned medium from HPL or RSF cultures inhibited bone nodule formation in a dose-dependent manner. HPL-conditioned medium depressed cell proliferation and alkaline phosphatase expression in BMSC cultures. These effects were not due to increased cytotoxicity or nutrient depletion. Inhibitory activity was recovered in a fraction of less than 1 kD following ultrafiltration and was insensitive to freeze-thawing. The inhibitory activity was blocked when HPL cultures were grown in the presence of 10(-5) M indomethacin. Dose-dependent inhibiton of bone nodule formation was also observed in cultures incubated with prostaglandins E2 (at 10(-6) M) or F2 alpha (at 10(-7) M). The results indicate that fibroblasts may inhibit osteoblast differentiation and function in part by release of soluble factors including prostaglandins.     

Poilaneic acid,a cembranoid diterpene from Croton poilanei

Poilaneic acid, a cembranoid diterpene from Croton poilanei, has been characterized as (1R*,2E,4Z,7E, 11Z)-12-carboxyl-1-isopropyl-4,8-dimethylcyclotetradecatetraene.     

Reversible and irreversible stages in the transition of cell surface marker during the differentiation of pluripotent teratocarcinoma cell induced with retinoic acid

Treatment of a pluripotent teratocarcinoma cell line with retinoic acid (RA) results in the disappearance of peanut agglutinin (PNA) receptors, accompanied with the decrease in F9 antigens and the enhanced secretion of plasminogen activator. However, this type of differentiation was inhibited by feeder cells. Furthermore, the transition of PNA receptor was reversible on the cells treated with RA for 2 days and became irreversible by an additional 2-day treatment with RA. Thus, two stages of teratocarcinoma cell differentiation—reversible and irreversible—were demonstrated.