A novel target cell for c-fos-induced oncogenesis: development of chondrogenic tumours in embryonic stem cell chimeras.

Embryonic stem (ES) cells were used to investigate the target cell specificity and consequences of c-fos when expressed ectopically during embryonic development. Chimeric mice generated with different ES cell clones selected for high exogenous c-fos expression were not affected during embryonic development; however, a high frequency of cartilage tumours developed as early as 3-4 weeks of age apparently independent of the extent of chimerism. The tumours originated from cartilagenous tissues and contained many chondrocytes.

Continuously growing bipotential and monopotential myogenic, adipogenic, and chondrogenic subclones isolated from the multipotential RCJ 3.1 clonal cell line.

The clonal multipotential RCJ 3.1 cell line, which gives rise to myotubes, adipocytes, chondrocytes, and osteoblasts, contains different progenitor subpopulations. By limiting dilution analysis, of 296 single colonies identified, approximately 20% contained a single recognizable cell type, approximately 10% contained two cell types, and approximately 1% contained three cell types.

Forskolin has biphasic effects on osteoprogenitor cell differentiation in vitro.

Cells isolated from fetal rat calvaria (RC) and maintained in vitro in medium containing ascorbic acid and B-glycerophosphate form three-dimensional, mineralized nodules having the histological, immunohistological, and ultrastructural characteristics of woven bone. We have studied the effects of forskolin (FSK), a diterpene that activates adenylate cyclase, in this system. While 10(-7)-10(-5) M FSK significantly stimulated cAMP levels in RC cells, lower concentrations did not.

Effects of dexamethasone and vitamin D3 on cartilage differentiation in a clonal chondrogenic cell population.

We have investigated the regulation of chondroblast/chondrocyte differentiation using a unique clonal cell population, designated RCJ 3.1C5 (C5), which differentiates into discrete three-dimensional cartilage nodules when grown in the presence of 15% fetal calf serum. Histologically, the nodules resembled hyaline cartilage; they contained large rounded chondrocytes surrounded by a refractile matrix which stained intensely with Alcian blue, exhibited metachromasia after Toluidine blue staining, and stained with an antibody against type II collagen.

Differentiation of muscle, fat, cartilage, and bone from progenitor cells present in a bone-derived clonal cell population: effect of dexamethasone.

RCJ 3.1, a clonally derived cell population isolated from 21-d fetal rat calvaria, expresses the osteoblast-associated characteristics of polygonal morphology, a cAMP response to parathyroid hormone, synthesis of predominantly type I collagen, and the presence of 1,25-dihydroxyvitamin D3-regulated alkaline phosphatase activity. When cultured in the presence of ascorbic acid, sodium beta-glycerophosphate, and the synthetic glucocorticoid dexamethasone, this clone differentiated in a time-dependent manner into four morphologically distinct phenotypes of known mesenchymal origin.

1,25-Dihydroxyvitamin D3 increases epidermal growth factor receptors and transforming growth factor beta-like activity in a bone-derived cell line.

To investigate possible mechanisms through which 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) affects cell proliferation and differentiation, we have studied the effects of 1,25-(OH)2D3 on the binding and mitogenic activity of epidermal growth factor (EGF) in RCJ 1.20 cells, an established, non-tumorigenic cell line derived from 21-day-old fetal rat calvaria. 1,25-(OH)2D3 caused a dose- and time-dependent 2- to 3-fold increase in the number of receptors for EGF.

Retinoic acid-induced changes in 1 alpha,25-dihydroxyvitamin D3 receptor levels in tumor and nontumor cells derived from rat bone.

The inducibility of 1 alpha,25-dihydroxyvitamin D3 [1,25-(OH)2D3] binding by all-trans-retinoic acid (RA) was examined in tumor-derived clonal bone cell lines, in established clonal cell lines derived from normal embryonic bone, and in cultured bone cell populations freshly isolated from 18- and 21-day fetal and 5-day-old neonatal rat calvaria. Levels of 1,25-(OH)2D3 binding were determined using a single saturating dose (84 pM) of 3H-labeled 1,25-(OH)2D3. Bone-derived tumor cell lines (ROS 17/2.

Modulation by retinoic acid of 1,25-dihydroxyvitamin D3 effects on alkaline phosphatase activity and parathyroid hormone responsiveness in an osteoblast-like osteosarcoma cell line.

Based on the finding that retinoic acid (RA) increases 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] receptor number in ROS 17/2 cells, we investigated the effects of RA on the ability of 1,25-(OH)2D3 to regulate alkaline phosphatase activity and PTH-responsive adenylate cyclase in these cells. A maximally effective dose of 1,25-(OH)2D3 (10(-8) M) caused a 75-80% increase in alkaline phosphatase activity and an approximately 70-75% attenuation of the cAMP response to PTH, while RA (10(-6) M) decreased alkaline phosphatase activity by 30-45% and decreased PTH-stimulated cAMP levels by approximately 20%. Preincubation with RA did not enhance the 1,25-(OH)2D3-induced increases in alkaline phosphatase activity.

Subclone heterogeneity in a clonally-derived osteoblast-like cell line.

To analyze the phenotypic diversity of a clonal rat osteosarcoma cell line (ROS 17/2) we have subcloned the cell line and characterized four subclones, ROS 17/2-A.II, A.III, A.

The evaluation of cerebral atrophy in renal dialysis patients by computerized tomography.

Thirty nine patients undergoing chronic hemodialysis, were submitted to brain computerized tomography in order to investigate the probable existence of brain atrophy. Evaluation was done by measuring the size of brain ventricles by means of a planimeter. An enlargement of the ventricles ranging from 1.