Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0029463 (osteosarcoma)
 16,637 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

ROS17/2.8 cells, a cell line derived from a rat osteosarcoma, have abundant receptors for parathyroid hormone (PTH) and parathyroid hormone-related peptide (PTHrP). A particulate membrane fraction was prepared from these cells and it was solubilized using relatively mild conditions with digitonin (0.25%), a nonionic detergent. When radioligands of both PTH and PTHrP were incubated with this membrane fraction in the absence of any protease inhibitor at 15 degrees C, approximately 75% of these radioligands were degraded within 2 hours. This degradative activity was inhibited more effectively by bacitracin than by any of several other protease inhibitors tested. The digitonin-solubilized PTH/PTHrP receptors were radiolabeled in the presence of bacitracin using radioiodinated [Tyr36]PTHrP(1-36) amide (PTHrP(1-36)) and N-hydroxysuccinimidyl-4-azidobenzoate (HSAB), as cross-linker. When an aliquot of the reaction solution was subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and autoradiography, a broad band was observed that had an apparent molecular size of 90,000 daltons (M(r) = 90 kD). This band was no longer seen when the binding was conducted in the presence of 10(-6) M of unlabeled PTHrP(1-36), and it was decreased in density when binding was conducted in the presence of 10(-6) M of unlabeled [Nle8,18, Tyr34] bovine PTH(1-34) amide (NlePTH). The solubilized receptors retained their capacity to bind the radioligand after partial purification by wheat-germ agglutinin affinity-chromatography. The use of relatively mild detergent conditions thus offers a means to solubilize receptors that retain their capacity to bind PTH and PTHrP.
 ...
PMID:Solubilization of functional receptors for parathyroid hormone and parathyroid hormone-related peptide from clonal rat osteosarcoma cells, ROS17/2.8. 133 76

The frizzled (fz) locus of Drosophila encodes a protein (Fz) with a seven-transmembrane-domain profile characteristic of G-protein-coupled receptors. In Drosophila, genetic evidence suggests that Fz functions to transmit and transduce polarity signals in epidermal cells during hair and bristle development. We have isolated from a UMR 106 rat osteosarcoma cell library a cDNA (fz-1) encoding a predicted 641-residue protein (Fz-1) with 46% homology with Drosophila Fz. We also identified a second cDNA (fz-2) encoding a protein (Fz-2) of 570 amino acids that is 80% homologous with Fz-1, with divergence most evident in the extracellular domains. Southern blots of rat genomic DNA indicated that fz-1 and fz-2 represent distinct genes. Northern analysis revealed the presence of a single fz-1 mRNA (4.7 kilobases) and two fz-2 mRNAs (2.5 and 4.5 kilobases) in rat tissues. The fz-1 and fz-2 genes are widely expressed in rat tissues with the highest steady-state levels of mRNA in kidney, liver, heart, uterus, and ovary. fz-1 and -2 mRNA levels were greater in neonatal than in corresponding adult tissues. Treatment of UMR 106 cells with bone resorbing agents including parathyroid hormone, epidermal growth factor, and 1,25-dihydroxyvitamin D3 produced increases in fz-1 and -2 mRNA levels. We suggest that hormonal induction of Fz proteins in osteoblasts serves to promote intercellular signaling required for functional responses such as increased bone resorption. Fz-1 and Fz-2 may represent products of a gene family whose members serve as transducers or intercellular transmitters of signals required for normal morphogenesis and/or differentiated function in diverse tissues.
 ...
PMID:Two homologs of the Drosophila polarity gene frizzled (fz) are widely expressed in mammalian tissues. 133 84

The beta-adrenergic blocking agent propranolol was shown in previous studies to increase orthotopic bone formation in rats. To understand the cellular mechanisms underlying this observation, propranolol was tested for its effects on osteoblastic cells, which possess adenylate cyclase-coupled beta-adrenergic receptors. The ability of propranolol to modulate parathyroid hormone (PTH) and isoproterenol effects on adenylate cyclase activity and on alkaline phosphatase expression was studied in the osteoblast-like rat osteosarcoma cell line ROS 17/2.8. At concentrations between 0.1 and 10 microM, DL-propranolol specifically inhibited adenylate cyclase stimulation by the beta-adrenergic agonist isoproterenol, but did not alter either basal or PTH-stimulated activity. At these concentrations, propranolol also blunted the inhibition of alkaline phosphatase activity by isoproterenol but not PTH. Propranolol alone had minimal effects on ROS alkaline phosphatase activity at low concentrations (0.1-1 microM), but became inhibitory at high concentrations (10-100 microM). Thus, the direct effects of physiologically relevant propranolol concentrations on osteoblastic cells can be attributed principally to beta-adrenergic blockade. These findings further suggest that propranolol may enhance bone formation by preserving osteoblastic activity in the face of inhibition by beta-adrenergic agonists.
 ...
PMID:Effects of beta-adrenergic blockade in an osteoblast-like cell line. 134 41

Several peptide hormones and growth factors have been found in human milk, and we present here the results of measurements of parathyroid hormone-related peptide (PTHrP). A radioimmunoassay (RIA) using a polyclonal antiserum against the mid-region of the molecule has been developed. In milk collected during the first 6 days after parturition, the PTHrP concentrations showed large interindividual variations ranging from 0.3 to 13.7 nmol-Eq/L (0.5 to 24.4 ng-Eq/mL) (n = 67) and increased between days 3 and five postpartum. PTHrP also increased during the first 4 collecting days when measured in milk from the same mother during a prolonged period. On fast-protein liquid chromatography (FPLC), the bulk of PTHrP eluted with a molecular weight of approximately 10 to 12 kd after treatment with urea. After mid-molecule immunoaffinity extraction of PTHrP from milk, higher levels were obtained by the mid-molecule RIA than by an aminoterminal assay, indicating that all fragments did not contain the aminoterminal. Parts of immunoextracted milk PTHrP stimulated cyclic adenosine monophosphate (cAMP) production in rat osteosarcoma cell line, UMR-106. In conclusion, we have found PTHrP-like immunoreactivity in human milk using a mid-region RIA. Parts of the immunoextracts also contained the aminoterminal and possessed PTH-like bioactivity. Whether PTHrP in human milk plays a physiological role in the maternal breast or in the newborn gastrointestinal tract is unknown, but the present observations demonstrate that a portion of the PTHrP is at least potentially biologically active.
 ...
PMID:Parathyroid hormone-related peptide in human milk measured by a mid-molecule radioimmunoassay. 153 39

1. Parathyroid hormone-induced down-regulation was studied in the osteosarcoma cell line UMR-106. 2. A maximal priming does of bPTH (1-84) down-regulated PTH-responsiveness to 40% of its initial value; bPTH (1-41) was less effective than bPTH (1-84), whereas bPTH (42-84) had no effect, alone or in combination with bPTH (1-41). 3. A tentative model for the function of different domains of parathyroid hormone in down-regulation is suggested.
 ...
PMID:Down-regulation of adenylate cyclase-coupled response to native bovine parathyroid hormone and fragments in the osteoblast-like cell line UMR-106. 155 56

Insulin-like growth factor-I (IGF-I) is a potent stimulator of bone formation. Whether this growth factor also induces bone resorption has not been studied in detail. We used two organ culture systems to examine the direct effect of IGF-I on bone resorption. Fetal mouse radii/ulnae, containing mature osteoclasts, showed no response to IGF-I, indicating that osteoclastic activity is not influenced by IGF-I. Fetal mouse metacarpals/metatarsals, containing just osteoclast precursors and progenitors, showed an increase in resorption in response to IGF-I, indicating that IGF-I stimulates the formulation of osteoclast precursors/progenitors and thereby increases the number of osteoclasts. Interleukin-6 (IL-6) has been hypothesized to be a mediator of bone resorptive agents such as parathyroid hormone (PTH). Both radii/ulnae and metacarpals/metatarsals reacted to IGF-I with an increase in IL-6 production. IL-6 production by UMR-106 osteogenic osteosarcoma cells was positively modulated by IGF-I, indicating that osteoblasts are likely to be the cells responsible for increased IL-6 production by the bones, and that IL-6 might be a mediatory of IGF-I-stimulated bone resorption.
 ...
PMID:Osteoclast formation together with interleukin-6 production in mouse long bones is increased by insulin-like growth factor-I. 156 29

In order to characterize fibroblastic colony-forming units (CFU-F) from murine bone marrow in relation to osteogenesis, adherent cells of 7-day-old BALB/c mouse bone marrow cultures were infected with a recombinant retrovirus (N2/ delta fosB) containing the bacterial neomycin resistance gene. One of the G418-resistant clones, MN7, was selected for further analysis on the basis of its high expression of the bone-specific alkaline phosphatase. The cells have now been in culture for more than 1 year and maintain a stable phenotype. The osteogenic nature of the immortalized clone MN7 was demonstrated as follows: (1) Mineralization was detected by 85Sr uptake and with the Von Kossa staining method only after in vitro cultivation on a collagen type I matrix. (2) Osteoblastic phenotype markers, including the synthesis of type I collagen, osteonectin, and the bone-specific isoenzyme of alkaline phosphatase were expressed in vitro. (3) MN7 cells responded to bone effectors such as parathyroid hormone and 1,25-dihydroxyvitamin D3. (4) Intraperitoneal injection of MN7 cells into 1-day-old BALB/c mice produced typical osteosarcomas in all animals. We conclude that MN7, derived entirely in vitro from a stromal CFU-F colony, represents a stable murine osteosarcoma cell line expressing the osteoblastic phenotype and provides the first direct evidence needed to establish adult mouse marrow-derived, nonhematopoietic stromal cells as osteoprogenitors.
 ...
PMID:Establishment of an osteogenic cell line derived from adult mouse bone marrow stroma by use of a recombinant retrovirus. 157 49

Bone metabolism is regulated by a wide variety of both circulating and locally produced peptides. The activity of such agents must be regulated, and one potential regulating mechanism is the inactivation of these peptides by locally produced proteolytic enzymes. One candidate for such a class of enzymes is enkephalinase (EC 2.3.24.11), a membrane-bound neutral metalloendopeptidase that inhibits the activity of a range of biologically active peptides, including interleukin-1 (IL-1), a potent bone-resorbing agent. In this study, we examined the effects of human enkephalinase on bone resorption in cultures of fetal rat long bones. We found that partially purified and highly purified enkephalinase inhibited bone resorption stimulated by parathyroid hormone (PTH) and IL-1 alpha. The effects on PTH-stimulated resorption were reversible, but enkephalinase did not inhibit prestimulated resorption. Enkephalinase also inhibited resorption induced by the nonpeptide stimulators 1,25-(OH)2D3, retinoic acid, and prostaglandin E2 (PGE2). In addition, preliminary studies confirmed a previous report of the presence of an enkephalinase-like activity in osteoblast-like osteosarcoma cells. These data are consistent with the hypothesis that proteolytic enzymes, such as enkephalinase, may play a role in the local regulation of bone resorption.
 ...
PMID:Inhibition of bone resorption in vitro by human enkephalinase (EC 3.4.24.11), a neutral metalloendopeptidase. 158 28

The skeleton is the major reservoir of lead and calcium in humans, and plays an important role in systemic calcium regulation. Lead perturbs normal calcium transport and second messenger function, directly or indirectly, in virtually all cells studies so far. Therefore, we and others have postulated that an early and discrete toxic effect of lead is perturbation of one or more loci within the calcium messenger system. To understand further the role of lead on calcium homeostasis in bone, we undertook this study to characterize calcium homeostasis and the effect of lead on calcium homeostasis in rat osteosarcoma (ROS 17/2.8) cells, which exhibit the osteoblast phenotype. ROS cells were incubated in medium containing 45Ca for 20 hours. Monitoring the efflux of 45Ca from the cultures for 210 minutes allowed for the determination of kinetic parameters defining steady state calcium homeostasis. Three distinct intracellular kinetic calcium pools characterized 45Ca homeostasis. Treatment with either 400 ng parathyroid hormone (PTH)/ml culture medium for 1 hour or 25 microM lead for 20 hours increased total cell calcium. Treatment with PTH caused a larger increase of cell calcium in lead-intoxicated cells than either lead intoxication or PTH treatment alone. This increase suggests that lead may perturb normal calcium-mediated PTH responsiveness of the osteoblast. These experiments further establish a kinetic model for the study of calcium homeostasis in osteoblastic bone cells. The studies also advance the hypothesis that lead-induced perturbations of calcium-mediated processes represent an early effect of lead toxicity at the cellular level.
 ...
PMID:Lead intoxication alters basal and parathyroid hormone-regulated cellular calcium homeostasis in rat osteosarcoma (ROS 17/2.8) cells. 159 81

Regulation of the synthesis of collagenase was investigated in the osteoblastic cell line, UMR 106-01. The cells were stained by the avidin-biotin-complex technique for the presence of the enzyme. By this method, it was possible to identify cells producing collagenase. Synthesis, but not secretion, was found to be constitutive in these cells with the enzyme located intracellularly in cytoplasmic vesicles and the Golgi apparatus. The amount of collagenase contained within UMR cells and the number of cells synthesizing the enzyme were proportional to the concentration of fetal bovine serum in the incubating medium. When serum was withdrawn from the osteosarcoma cells, the content of collagenase decreased with time and the enzyme became undetectable by 48 h of serum depletion. The decrease in collagenase content could be completely reversed by resupplying serum to the cells. The collagenase promoting activity of serum could not be eliminated by adsorption on activated charcoal but was retained by a dialysis membrane with a 12,000 mol wt cutoff. A range of bone-seeking hormones or agents known to affect collagenase secretion was added to the medium in an attempt to mimic the effect of serum on collagenase accumulation. None of these agonists, including parathyroid hormone, could reproduce the effect of serum on these cells, although parathyroid hormone could act as a collagenase secretagogue in the presence or absence of serum. It is concluded that fetal bovine serum contains a yet unidentified factor or factors greater than 12,000 mol wt responsible for the continued synthesis of collagenase by UMR 106-01 cells.
 ...
PMID:A serum factor promotes collagenase synthesis by an osteoblastic cell line. 164 67


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>