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Query: UMLS:C0027651 (tumor)
 685,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The purpose of this study was to measure uptake of tritiated digoxin by neoplastic tissues known to have differential contents of sodium-potassium adenosine triphosphatase (Na + K + ATPase), the presumed receptor for digoxin. Tumor samples were removed at the time of craniotomy in seven patients with meningiomas (Group 1) and seven patients with more malignant central nervous system tumors (Group 2) (three astrocytomas, three glioblastomas, one meduloblastoma). Patients with meningiomas were found to have a significantly higher digoxin uptake (21.8 +/- 7.3 ng/gm tumor versus 5.7 +/- 5.2 ng/gm tumor; (p less than 0.01) and a significantly greater tissue/serum ratio (13.9 +/- 11.7 versus 3.26 +/- 3.7, p less than 0.0). This study provides the first demonstration of increased uptake of digoxin by noncardiac pathologic tissues. The results are most likely due to differences in the number of digoxin receptor sites.
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PMID:Differential uptake of tritiated digoxin in benign and malignant central nervous system neoplasms. 13 73

An electron-microscopic study of a choroid plexus papilloma from the lateral ventricle of a child revealed fine structural features typical of normal choroid plexus tissue. Utilizing the Ernst technique for demonstrating ouabain-sensitive, potassium-dependent phosphatase activity, Na-K-ATPase was localized along the basal and lateral plasmalemmas of the tumor epithelium but not along the ventricular surface (apical plasmalemma). This localization is similar to that found in normal choroid plexus epithelium of all species studied to date.
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PMID:Choroid plexus papilloma. II. Ultrastructure and ultracytochemical localization of Na-K-ATPase. 13 1

Two patients with pancreatic cholera and islet-cell carcinoma were treated with intra-arterial streptozotocin. Before therapy, they had stool volumes from 2 to 8 liters per day and required 200 to 800 mEq per day of supplemental potassium. After three to five doses of streptozotocin (1.5 per square meter), both stool volume and number and size of hepatic metastases decreased markedly. One patient has had normally formed stools for 12 months; the other had a 90 per cent reduction in stool volume for 13 months with additional therapy. Both patients' serum potassium returned to normal without need for supplementation. Jejunal adenylate cyclase activity was normal in both, and plasma vasoactive intestinal peptide was detectable in only one. After chemotherapy, these findings showed no consistent change. Pharmacologic studies suggest that arterial administration increased either tumor or hepatic extraction (or both) of streptozotocin by two times and decreased renal exposure to this nephrotoxic drug by one third.
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PMID:Pancreatic cholera: benefical effects of treatment with streptozotocin. 16 65

An insulin-producing islet cell tumor of the Syrian hamster has been studied in vitro for its capacity to respond to known stimuli of insulin release. Insulin secretion during short term incubation and perifusion of fragments of tumor was detected by radioimmunoassay. Insulin release was increased 2-4 fold by 40 mM potassium in the presence of calcium, glucose (22 mM), glucagon (0.3-3.0 muM), N6,02'-dibutyryl adenosine 3',5'-monophosphate (cAMP; 6mM), and theophylline (10 mM). Concentrations of glucagon that induced insulin release were also effective in activating adenylate cyclase in the membranes of tumor cells. Thus, this tumor appears to possess a cAMP-mediated mechanism for insulin release. Somatostatin (0.8-25 mum) inhibited glucagon-induced insulin release without altering basal or glucagon stimulated adenylate cyclase activity. It would appear that inhibition of glucagon induced insulin release by somatostatin is not mediated by adenylate cyclase. We propose that insulin release by this tumor is sufficiently similar to that found in normal islets so as to make it a suitable model for biochemical studies that require large quantities of homogeneous tissue.
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PMID:Regulation of in vitro insulin release from a transplantable Syrian hamster insulinoma. 16 25

A factor inhibiting tumour growth in syngeneic hosts was found in the sera of inbred Lewis rats carrying Rous sarcoma virus-induced tumour (RSL). The findings presented here suggest that the serum factor is a tumour-associated transplantation antigen (TATA) shed from the neoplasm into the circulation. All the tumour bearers' sera tested with RSL cells were negative in indirect membrane immunofluorescence;however, on passive transfer into syngeneic rats, they protected the animals against the growth of an RSL tumour inoculum. A similar protective effect was also observed after injection of TATA prepared from RSL cell membranes by solubilization with potassium cholate. When incorporated into Freund's adjuvant, tumour-bearers' sera immunized the animals against a subsequent RSL sarcoma graft. Sera collected from immunosuppressed rats bearing large sarcomas which presumably contain neither tumour-specific antibody nor antigen-antibody complexes, transferred inhibition of tumour growth to syngeneic hosts. Intact immunological reactivity of recipients was a necessary prerequisite for the protective effect of sera, since the passive transfer of an inhibitory serum to immunosuppressed rats did not inhibit tumour growth. We assume that the TATA present in tumour-bearers' serum is released from the growing neoplasm as a result of either cell death or membrane metabolic turnover.
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PMID:Tumour-associated transplantation antigen in sera of rats with large RSV-induced sarcomas. 17 Feb 16

Studies of TSH release and production were performed in short term monolayer cultures of transplantable, thyroid hormone responsive, thyrotropin (TSH) producing mouse pituitary tumors. These tumors contained large amounts of TSH, small amounts of growth hormone (GH) and no detectable luteinizing hormone (LH), indicating that the predominant hormone product of tumor cells was TSH. The TSH content per tumor cell was similar to that of the normal pituitary where thyrotrophs represent a small fraction of the total cells, suggesting that the TSH content per tumor cell was less than that of the normal thyrotroph. There was a time dependent release and production of TSH by tumor cells in monolayer culture. Thyrotropin releasing hormone (TRH) increased the release into the media and the production of TSH in a dose dependent manner. Maximum effects were noted at 0.2 ng/ml. Thyroid hormones and somatostatin inhibited both basal and TRH induced effects on both TSH release and production. TSH release as induced by TRH was calcium dependent. TSH release was stimulated by ouabain (10(-3)M) and potassium (57 mM), agents known to promote cellular calcium uptake in a calcium dependent manner. These studies indicate that tumor derived cells function in monolayer culture in a similar fashion to normal thyrotrophs. Studies were conducted to test the hypothesis that TRH action is mediated by adenosine 3',5' monophosphate (cAMP). Dibutyryl cAMP (6 mM) and theophylline (10 mM) increased TSH release suggesting that cAMP is involved in TSH release. However, TRH had no detectable effect on tumor cell adenylate cyclase activity or levels of cAMP. In contrast, PGE1 (1-10 mug/ml) stimulated adenylate cyclase activity and elevated cellular levels of cAMP without increasing TSH release. Thus, we are unable to confirm the postulate that cAMP is the intracellular mediator of TRH action.
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PMID:Regulation of thyrotropin (TSH) release and production in monolayer cultures of transplantable TSH-producing mouse tumors. 17 85

By pre-treatment with serum of normal spleen cells used in the microcytotoxicity assay, a humoral factor which induces cytotoxic activity in normal spleen cells was demonstrated in about 40% of sera of Japanese quails as early as 3 days after inoculation with Rous sarcoma virus (RSV). This cytotoxicity-inducing activity was not present either in the IgM or the IgG fraction obtained by Sephadex gel filtration. In sera of quails with experimentally induced agammaglobulinemia, the cytotoxicity-inducing activity was demonstrated at the same frequency as in normal animals. Thus, it seems unlikely that the early cytotoxicity-inducing factor is an immunoglobulin. On the other hand, membrane fractions extracted with 3 M potassium chloride from the RSV-induced quail tumor (QT) cells used as target cells in the microcytotoxicity assay exhibited cytotoxicity-inducing activity. After spontaneous regression of an RSV-induced tumor the serum of the regressor quail contained antibodies specific to the QT cell extract. This serum removed the cytotoxicity-inducing activity of both QT cell extract and serum sampled 3 days after RSV inoculation. In contrast, serum without antibody to the QT cell extract failed to absorb the cytotoxicity-inducing activity of the extract. It is therefore suggested that soluble tumor antigens can act as an early cytotoxicity-inducing factor.
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PMID:Characterization of an early cytotoxicity-inducing factor in sera of Japanese quails after inoculation with Rous sarcoma virus. 17 59

Poly(A) polymerase was extracted from isolated nuclei of rat liver and a rapidly growing solid tumor (Morris hepatoma 3924A). The enzyme from each tissue was purified by successive chromatography on DEAE-Sephadex, phosphoecllulose, hydroxyapatite and QAE-Sephadex. Purified enzyme from both liver and tumor was essentially homogeneous as judged by polyacrylamide gel electrophoresis. Under nondenaturing conditions, enzyme activity corresponded to visible protein and, upon denaturation, a single polypeptide was detected. The enzymes had absolute requirements for Mn2+ as the divalent ion, ATP as the substrate and an oligonucleotide or polynucleotide as the primer. Both enzymes were inhibited by sodium pyrophosphate, N-ethylmaleimide, Rose Bengal, cordycepin 5'-triphosphate and several rifamycin derivatives. The reactions were unaffected by potassium phosphate, alpha-amanitin and pancreatic ribonuclease. However, the liver and hepatoma enzymes differed from each other with respect to apparent Km, primer saturation levels and sensitivity to pH changes. The most striking differences between the enzymes were in their calculated molecular weights (liver, 48000; hepatoma, 60000) and amino acid compositions. Finally, the level of the hepatoma enzyme relative to that of the liver enzyme was at least 1.5-fold higher when expressed per mg DNA.
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PMID:Nuclear poly(A) polymerase from rat liver and a hepatoma. Comparison of properties, molecular weights and amino acid compositions. 18 50

Poly(ADP-ribose) polymerase with a high specific activity was obtained from Ehrlich ascites tumor cells by extraction of nuclei with 175 mM potassium phosphate, followed by chromatography on DNA-agarose. Electrophoretic analysis indicated that the preparation contained two proteins, one of which was shown to catalyze the synthesis of poly(ADP-ribose). As expected from results obtained by other workers, the synthesis was inhibited by nicotinamide and thymidine, and stimulated by DNA. Addition of histones gave inhibition of the synthesis, unless DNA was present in the reaction mixture.
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PMID:Purification of poly(ADP-ribose) polymerase from Ehrlich ascites tumor cells by chromatography on DNA-agarose. 18 48

Various reagents used in the chemical modification of amino- and carboxy-groups of proteins, and of carbohydrates of glycoproteins and glycolipids, inhibit respiration in ascites tumor cells concomitant with release of potassium ion from those cells. The respiratory activity of washed ascites tumor cells is increased by exogenous addition of potassium ion. The lowered respiratory control index as well as oxidative phosphorylation of aged mitochondria are restored upon increasing the potassium concentration of the incubation mixture in the presence of respiratory substrates. The data suggest that the potassium ion level of cells is changed by modifying physicochemical properties of membrane components and that cellular energy metabolism is regulated by intracellular potassium ion concentration.
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PMID:Cellular metabolic control by chemical modification of cell membrane. 19


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