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Query: UMLS:C0029463 (osteosarcoma)
 16,637 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We present a new technique for the simultaneous measurement of cell volume changes and intracellular ionic activities in single cells. The technique uses measurement of changes in the concentration of intracellularly trapped fluorescent dyes to report relative cell volume. By using pH- or Ca(2+)-sensitive dyes and recording at the ion-sensitive and -insensitive (isosbestic) wavelengths, the method can measure both cell volume changes and intracellular ionic activities. The technique was used to study the mechanisms of regulatory volume decrease (RVD) in the osteosarcoma cell line UMR-106-01 grown on cover slips. Swelling cells in 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES)-buffered hypotonic medium was followed by stable cytosolic acidification and a decrease in cell volume back toward normal. The recovery of cell volume could be blocked by depolarization, treatment with ouabain, or depletion of cell Cl-. These suggest the conductive efflux of K+ and Cl- during RVD. The cytosolic acidification that accompanied cell swelling was not blocked by amiloride, bafilomycin A, or removal of Cl- and could not be reproduced by depletion of cellular ATP. These findings exclude Na+/H+ and Cl-/HCO-3 exchange, intracellularly generated acid, or increased metabolism, respectively, as the cause of the acidification. The cell swelling-induced acidification was inhibited by depolarization, suggesting the involvement of an electrogenic pathway. The acidification, as well as RVD, was inhibited by short incubation with deoxyglucose, and these effects could not be reversed by valinomycin. Thus, the anionic pathway(s) participating in RVD and the acidification are sensitive to the cellular level of ATP. Together, these studies indicate that RVD in UMR-106-01 cells in HEPES-buffered medium is mediated by the conductive efflux of K+, Cl-, and OH-.
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PMID:Simultaneous recording of cell volume changes and intracellular pH or Ca2+ concentration in single osteosarcoma cells UMR-106-01. 132 44

ATP released from damaged cells or by controlled secretion could be an important factor in the formation or remodeling of bone. In a variety of other tissues ATP has been shown to control cellular processes by acting on P2-purinoceptors and activating the calcium signaling pathway. Here we demonstrate for the first time that extracellular ATP increases the intracellular free calcium [Ca2+]i concentration in normal human osteoblasts and in SaOS-2 cells, a human osteosarcoma-derived cell line, but not in ROS 17/2.8 cells. The ATP-induced increase in [Ca2+]i was dose dependent, and the concentrations of ATP required were similar to those reported to regulate cellular functions in other cell types. Although ATP is metabolized rapidly by bone cells, the effects on [Ca2+]i appeared to be mediated directly by ATP rather than one of its metabolites. Adenosine 3-thiotriphosphate, a nonhydrolyzable analog of ATP, induced similar changes in [Ca2+]i. This indicates that P2-purinoceptors are present on osteoblast-like cells and that extracellular ATP from various sources might be an important factor in the regulation of osteoblast functions.
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PMID:Evidence for P2-purinoceptors on human osteoblast-like cells. 161 57

The effect of inositol 1,4,5 trisphosphate (IP3) on calcium mobilization was studied in human osteosarcoma lines, Saos-2 and G292, as well as isolated rat osteoblastic and osteoclastic cells. Cells were permeabilized with saponin and calcium mobilization was studied with the fluorescent dye, fura-2 in a recording spectrofluorometer. IP3 (10 microM) increased calcium release in all cell types studied. The effect was dependent on ATP and occurred in the presence of mitochondrial inhibitors. The effect was not seen with inositol 1-phosphate (IP) or inositol 1,4-diphosphate (IP2). Inositol 1,3,4,5 tetrakisphosphate (IP4) appeared to elicit a decrease in the calcium released. Depletion of the intracellular pool with the calcium ionophore, ionomycin, as well as incubation with the inhibitor of intracellular calcium mobilization, TMB-8, obliterated the IP3 effect. The results are consistent with the hypothesis that increases in IP3 can cause a rapid elevation of bone cell cytosolic calcium.
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PMID:Effects of inositol trisphosphate on calcium mobilization in bone cells. 178 74

Flavone acetic acid (FAA) is a new anticancer agent in Phase II trials in Europe. In preclinical testing FAA showed broad activity against murine solid tumors and minimal activity against murine leukemias. Our interest in studying the combination of FAA and radiation was based on two of its biological effects which might modify radiation damage. First, FAA depletes ATP and inhibits macromolecular synthesis which are needed to repair radiation-induced DNA strand breaks; and second, inhibition of tumor blood flow by FAA could lead to radiobiological hypoxia. Various schedules of FAA (170 mg/kg I.V.) (n = 9, SF = 0.44) and radiation (10 Gy) (n = 9, SF = 0.37) were investigated against s.c. implanted Glasgow osteogenic sarcoma. In the same model we studied both the kinetics of ATP depletion by 31P-Nuclear Magnetic Resonance Spectroscopy and the repair of radiation induced single and double strand breaks by alkaline elution. The combined response was not significantly different from log-additive when radiation was given 24, 5 or 1 hr before FAA. When FAA was given immediately before radiation an increase in tumor response, significantly different from log-additive (p = 0.03) was observed. This enhancement disappeared when radiation was delayed for between 1 and 48 hr after FAA. While decreased ATP levels and increased response to radiation occurred within minutes after FAA administration, no effect of FAA at either 180 or 200 mg/kg was observed on the repair of radiation induced single or double strand breaks (10 and 50 Gy, respectively; 5 hr after FAA) in spite of significant ATP depletion in the tumors.
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PMID:Interaction between flavone acetic acid (LM-975, NSC 349512) and radiation in Glasgow's osteogenic sarcoma in vivo. 237 Jan 85

The nervous system may play a role in regulation of bone metabolism. The effects of norepinephrine(NE), vasoactive intestinal peptide(VIP), and ATP on cytosolic Ca2+ were assessed in a rat osteoblast-like osteosarcoma cell line (UMR-106) responsive to PTH. All three transmitters transiently increased Ca2+, with ATP much greater than PTH greater than NE = VIP, and then caused sustained increases in Ca2+. The ATP-induced transient resulted from mobilization of intracellular Ca2+ store, while NE and VIP-induced transients also involved influx of Ca2+. Later sustained increases by all agonists were dependent upon extracellular Ca2+. Release of intracellular Ca2+ by ATP was associated with a marked increase in IP3 but without a significant change in cAMP. NE, VIP, and ATP, through regulation of Ca2+ metabolism, may be involved in various osteoporotic conditions.
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PMID:Neurotransmitter regulation of cytosolic calcium in osteoblast-like bone cells. 255 24

Activation of the 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] receptor-hormone complex was studied in-vitro using cytosolic preparations of rat osteogenic sarcoma cell ROS 17/2-8 and a DNA-cellulose assay. We found that salt was required for extraction of the unoccupied receptor indicating its possible nuclear localization. The 1,25(OH)2D3 receptor underwent an activation process similar to other steroid hormones which could be stimulated by heat and salt. At physiological ionic strength 100% of the complexes were, however, activated at 2 degrees C, indicating that the activation process is not absolutely temperature dependent. In contrast to other steroid hormones, 30-50% of the complexes were in an activated state in the absence of heat and salt moreover, alkaline phosphatase and ammonium sulphate had no effect on activation. Activation was also stimulated by ATP and ATP plus 8BrcAMP indicating the possible role of phosphorylation in the activation process; however, further work is required to clarify this point.
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PMID:Activation of the 1,25-dihydroxyvitamin D3 receptor in cultured rat osteogenic sarcoma cells. 299 3

The platelet-derived growth factor receptor (PDGF-R), a 180-kDa single-chain polypeptide, was purified from membranes of the human osteogenic sarcoma cell line MG-63. Purification was achieved by treatment of membranes with PDGF and ATP, followed by solubilization with nonionic detergent and successive chromatography on solid-phase anti-phosphotyrosine monoclonal antibody and DEAE-cellulose. The PDGF-R, which was estimated to be 50-80% pure by NaDodSO4/polyacrylamide gel electrophoresis of 32P-labeled preparations, was free of contaminating epidermal growth factor receptor and had no detectable phosphatase activity. It specifically bound 125I-labeled PDGF, a reaction quantified by binding of the ligand-PDGF-R complex to the anti-phosphotyrosine antibody. The purified receptor displayed PDGF-stimulatable tyrosine kinase activity, assayed by autophosphorylation of PDGF-R at tyrosine residues and by phosphorylation of angiotensin II. The Km for ATP in the autophosphorylation reaction was 7.5 microM. Addition of PDGF did not change the Km but increased the Vmax 1.7-fold.
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PMID:Purified human platelet-derived growth factor receptor has ligand-stimulated tyrosine kinase activity. 301 45

5-Lipoxygenase has been expressed in a mammalian osteosarcoma cell line transfected with the cloned cDNA for human leukocyte 5-lipoxygenase. Two clonal cell lines derived from the transfected cells expressed the enzymatic activity. When incubated with arachidonic acid (100 microM), the major 5-lipoxygenase products of 10,000 X g supernatants from these cells were 5-hydroxyeicosatetraenoic acid (5-HETE), and the nonenzymatic hydrolysis products of leukotriene (LT)A4. The ratio of 5-HETE to LT (between 6:1 and 9:1) was similar to that observed in leukocyte supernatants. Furthermore, incubation of 10,000 X g supernatants from the transfected cells with 5-hydroperoxyeicosatetraenoic acid (5-HPETE) (75 microM) resulted in the synthesis of LTA4 hydrolysis products. Control osteosarcoma cell supernatants produced no 5-HETE or LT from arachidonic acid or 5-HPETE. Maximal activity of the expressed enzyme required Ca2+, ATP, and two cellular stimulatory factors prepared from human leukocytes. Immunoblot analysis of supernatants from the osteosarcoma cell clones revealed an immunoreactive 80,000-dalton band that was indistinguishable from the band observed in leukocyte supernatants. Therefore, the expressed enzyme was functional and exhibited characteristics that were identical to those of human leukocyte 5-lipoxygenase. When intact transfected osteosarcoma cells were challenged with ionophore A 23187, no 5-lipoxygenase products were formed. If arachidonic acid was added along with the ionophore, the cells synthesized 5-HETE and the nonenzymatic hydrolysis products of LTA4. These results verify that the cDNA used to transfect the osteosarcoma cells encodes for 5-lipoxygenase. Furthermore, these studies offer independent evidence that this single protein possesses both 5-lipoxygenase and LTA4 synthase activity, as has been reported previously from enzyme purification data.
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PMID:Characterization of cloned human leukocyte 5-lipoxygenase expressed in mammalian cells. 316 19

The energy metabolism of Dunn osteosarcoma subcutaneously implanted in C3H/He mice was studied in vivo by a 31P-NMR spectrometer with surface-coils. The spectra of Dunn osteosarcoma showed peaks of sugar phosphate, inorganic phosphate, phosphocreatine, phosphomonoester, and ATPs. In the early stage of the tumor growth phosphocreatine and ATP showed large signal intensities and the tissue pH was 7.23 +/- 0.08. Following the tumor growth phosphocreatine and ATP decreased and the tissue pH fell to 6.82 +/- 0.08. Immediately after a small dose of MTX (2 mg/kg) was administered, an increase of inorganic phosphate and a decrease of phosphocreatine were temporarily observed when MTX concentrations of the tumor tissues were maximum. High energy metabolites were apparently consumed with the active transport of MTX. After twelve hours of a high dose of MTX (500 mg/kg) was administered, disappearance of phosphocreatine and ATP with an increase of inorganic phosphate was observed previous to the histological change. In vivo 31P-NMR spectroscopy may be useful in the evaluation of chemotherapy.
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PMID:[In vivo 31P-NMR studies on energy metabolism and the effect of methotrexate in murine implanted osteosarcoma]. 346 60

The effects of Mg(2+) and Ca(2+) on bone and osteosarcoma adenylate cyclase were investigated. The concentrations of the cations and other ionic species in the assay mixture were calculated by solving the simultaneous equations describing the relevant ionic interactions (multiple equilibria). We re-examined the effects of HATP(3-) and ATP(4-) on enzyme activity and found that (i) the concentration of the minor ATP species is less than 1% of that of MgATP(2-), and their ratio to MgATP(2-) is constant if Mg(2+) and H(+) concentrations are unchanged; (ii) Mg(2+) addition decreased the ratio of the minor species to MgATP(2-) and increased the enzyme activity, but no meaningful kinetic model could attribute this effect of HATP(3-) or ATP(4-). On the other hand, kinetic analysis of Mg(2+) effects showed: (i) stimulation via two metal sites, separate from the catalytic (MgATP(2-)) site, with apparent K(m) values of approximately 1 and 8mm; (ii) that the low affinity increased towards the higher one when the enzyme activity rose as a result of increased substrate or guanine nucleotide concentrations, this effect being less pronounced in tumour; (iii) conversely, that two apparent affinities for MgATP(2-) merged into one at high Mg(2+) concentration; (iv) kinetically, that this relationship is of the mixed con-competitive type, which is consistent with a role for Mg(2+) as a requisite activator, and binding occurring in non-ordered sequence. Analysis of the Ca(2+) effects showed: (i) competition with Mg(2+) at the metal site (K(i) 20mum for bone and 40mum for tumour); (ii) that relative to the substrate the inhibition was uncompetitive, i.e. velocity decreased and affinity increased proportionally, which is consistent with Ca(2+) binding after substrate binding. These findings support the existence of interacting enzyme complexes, losing co-operativity at increased enzyme activity. They also indicate a potential physiological role for Ca(2+) in enzyme regulation and point to quantitative differences between bone and tumour with regard to these properties.
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PMID:Comparison of bone and osteosarcoma adenylate cyclase. Effects of Mg2+, Ca2+, ATP4- and HATP3- in the assay mixture. 677 Aug 47


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