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

Porcine and bovine strains of E. coli suspected to be enterotoxigenic, were tested for heat-labile enterotoxin (LT) production by means of a test measuring the stimulation of the synthesis of 3151 cyclic adenosin monophosphate (cAMP test) and rounding mouse adrenal tumor Y1 cells (Y1 test), and for heat-stable enterotoxin (ST) production by means of the baby mouse test (BM test). The test results were compared with those of the ligated gut test (LG test) using pig and calf intestine. One hundred and eleven strains of human origin were tested in the cAMP test, the Y1 test and the BM test. All strains were tested for the presence of the attachment factors K88, K99, P987 and CF10407. Seventy-four of 117 bovine strains produced only ST and all 74 ST-producing strains possessed K99 antigen. None of the 43 nonenterotoxigenic strains possessed K99. The presence of K99 antigen is therefore a reliable indicator of enterotoxigenicity in bovine strains. Porcine strains produced LT, ST or LT + ST. The K88 antigen was found in 52 out of 101 enterotoxigenic strains, K99 and P987 in 7 and 6 strains respectively and the latter 13 strains produced only ST. P987 was only detected after subculturing in liquid medium to enhance pilus formation. Eleven out of 111 strains of human origin stimulated cAMP synthesis but failed to round Y1 cells, whereas 4 known LT producers were positive in both tests. Attachment factors were found only in 2 of the latter 4 strains.
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PMID:Detection of enterotoxigenicity and attachment factors in Escherichia coli strains of human, porcine and bovine origin; a comparative study. 22 93

The content of cAMP and cGMP as well as their ratio in the tissues of different cerebral tumors in humans were studied. The concentration of both cyclic nucleotides in tumors of the brain was found to vary widely. The richest information on disorders of metabolism of these substances may be gained from the ratio of cAMP and cGMP concentrations, which statistically is significantly reduced in the neoplasm as compared to the ratio in the cerebral tissue. Bearing in mind the principal possibility of correcting this ratio, further study of the metabolism of cyclic nucleotides in cerebral tumors holds promise for their treatment.
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PMID:[Cyclic nucleotide metabolic disorder in brain tumors]. 22 53

The Ca2+ content of glial tumor (C6) cells was reduced approximately 5-fold by repeated treatment with media containing ethylene glycol bis(beta-aminoethyl ether) N,N'-tetraacetic acid (EGTA) without loss of cellular viability. The ability of the cells to accumulate cAMP in response to beta-adrenergic agonists was reduced 60 to 70% following Ca2+ depletion. Ca2+ did not affect the apparent KACT for norepinephrine, nor did it change the concentration of propranolol required to produce 50% inhibition of the maximal norepinephrine response. Phentolamine did not alter the Ca2+ dependence of the response. The binding of dihydroalprenolol by intact C6 cells was not influenced by Ca2+. Furthermore, pretreatment with norepinephrine did not affect the Ca2+ dependence of cAMP accumulation. The effects of Ca2+, therefore, appeared to be exerted on components of the adenylate cyclase system other than the catecholamine receptor. Micromolar free Ca2+ concentration in the extracellular medium were sufficient to restore a maximal norepinephrine response to Ca2+-depeleted cells. The effect of Ca2+ on cAMP accumulation in response to hormone was immediate and was rapidly reversible upon the addition of EGTA in excess of the cation. Cells in media containing Ca2+ exhibited a characteristic biphasic time course of cAMP accumulation; with Ca2+-depleted cells cAMP was accumulated more slowly and the subsequent decline in cAMP content was also reduced. Verapamil, an inhibitor of plasmalemmal Ca2+ influx, decreased the Ca2+-dependent component of the cAMP accumulation when added prior to the cation. The effect of Ca2+ on cAMP accumulation was reduced more extensively by pretreatment of cells at 45 degrees C under Ca2+-depleted (80% loss) than under Ca2+-restored (30% loss) conditions. Trifluoperazine at micromolar concentrations decreased the Ca2+-dependent increment in accumulation of cAMP in Ca2+-restored cells. This inhibition was not overcome by increasing concentrations of norepinephrine or of extracellular Ca2+.
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PMID:Calcium dependence of hormone-stimulated cAMP accumulation in intact glial tumor cells. 22 32

Tumor tissues obtained from two patients with the ectopic ACTH syndrome caused by medullary carcinoma of the thyroid and malignant epithelial thymoma were dispersed by tryptic digestion and mechanical agitation. Using the isolated cells, the effects of various agents on ACTH secretion and intracellular cAMP concentrations were studied. Addition of rat median eminence extract significantly stimulated ACTH secretion and increased levels of intracellular cAMP in both cell preparations, and a dose-response relationship appeared to exist between the dose of rat median eminence extract added and either ACTH secretion or intracellular cAMP formation in the thymic tumor cells. High concentrations of calcium also produced a marked ACTH secretion in both cases. In the thymic tumor cells, norepinephrine, serotonin, and TRH were found to be effective in increasing ACTH secretion and intracellular cAMP levels, whereas biogenic amines, hypothalamic hormones, and gastrointestinal hormones did not affect hormone secretion in the thyroid tumor cells. These results suggest that a corticortropin-releasing factor-like substance(s), as yet unspecified, may play some role in stimulating ectopic ACTH secretion by certain tumors, that both intracellular cAMP and Ca++ may be involved in ectopic hormone secretion, and that the inappropriate hormonal secretory responses of some tumors to a variety of stimuli might be mediated by altered membrane receptors of the neoplastic cells.
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PMID:Effect of hypothalamic extract and other factors on release of adrenocorticotropin from and adenosine 3',5'-monophosphate levels in dispersed nonpituitary tumor cells. 22 71

Adenosine 3',5'-monophosphate (cyclic AMP) receptor protein of 56,000 daltons increases markedly in mammary tumors induced by 7,12-dimethylbenz[a]anthracene (DMBA) after incubation of tumor slices with cyclic AMP, benzamide, and arginine. Incubation of cytosol from these tumor slices with nuclei from unincubated tumors results in nuclear uptake of the 56,000-dalton cyclic AMP receptor and in phosphorylation of the 76,000-dalton nuclear protein. Binding of the 56,000-dalton receptor and phosphorylation of the 76,000-dalton protein also occur in DMBA tumor nuclei when protein kinase type II of bovine heart is used. The results suggest that cyclic AMP receptor is involved in the nuclear events of a hormone-dependent mammary tumor.
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PMID:Cyclic AMP receptor triggers nuclear protein phosphorylation in a hormone-dependent mammary tumor cell-free system. 22 63

Two variant cell lines (Y6 and OS3), derived from the ACTH-sensitive mouse adrenocortical tumor clone Y1, are defective in the ACTH-sensitive adenylate cyclase system. This study further characterizes the nature of the defects in Y6 and OS3 cells using ACTH1-10, ACTH4-10, and cholera toxin. In Y1 cells, ACTH1-39, ACTH1-10, and ACTH4-10 stimulated steroidogenesis to the same maximum level with Kd' values of 5 x 10(-11) M, 5 x 10(-7) M and 10(-4) m respectively. ACTH1-10 (0.4 mM) and ACTH4-10 (3.2 mM) increased the accumulation of adenosine 3',5'-monophosphate (cAMP) in Y1 cells two- to three-fold. Cholera toxin increased steroidogenesis and cAMP accumulation in Y1 cells with Kd' values of 0.4 ng/mL and 9 ng/mL respectively. Y6 and OS3 cells responded to added cholera toxin with increased cAMP accumulation and increased steroidogenesis but did not respond to ACTH1-39, ACTH1-10, or ACTH4-10 at concentrations effective in Y1 cells. These data are interpreted to suggest that Y6 and OS3 cells are defective in a process or component that links the principal binding regions of the ACTH receptor to the catalytic subunit of the adenylate cyclase system. Attempts to were made to assess the interactions of ACTH with the principal binding regions of the ACTH receptor by analysis of binding of radioactive, iodinated ACTH1-24. ACTH binding, however, showed low affinity, high capacity, and no target-tissue specificity, and was considered not to be useful in evaluating the integrity of the ACTH receptor.
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PMID:Evaluation of receptor function in ACTH-responsive and ACTH-insensitive adrenal tumor cells. 22 81

Cyclic-AMP-dependent protein kinase activity was depressed in whole spleen as well as in isolated splenic lymphocytes from 3-methylcholanthrene (MCA), R3230 AdCa mammary adenocarcinoma, N-hydroxy-2-acetylaminofluorene, and 4-dimethylaminoazobenzene (DMAAB) tumor-bearing Fischer rats as compared to control animals. The magnitude of depression increased with the immunogenicity of the tumor. The depressed enzyme activity was the result of a reduced Vmax for adenosine 3',5'-monophosphate (cAMP)-stimulated histone phosphorylation.
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PMID:Correlation of immunogenicity with suppression of lymphocyte adenosine 3',5'-monophosphate-dependent protein kinase. 22 14

Changes in the concentration of cyclic AMP as well as cyclic GMP were measured in different murine tumors and in human tumors of varying malignancy. The quotient of cAMP and cGMP seems to be an important parameter for the molecular-biological derangement. Because of the recently much discussed importance of cAMP and cGMP in the immune defence the changes in the concentration of both nucleotides were measured in the T-lymphocytes of tumor patients. Significant changes occurred in patients with malignant melanoma. Investigations of the stimulatibility of the cAMP and cGMP levels revealed a diminished activatibility of the cAMP level and a higher stimulatibility of the cGMP level in the T-lymphocytes of patients with malignant melanoma as compared with those of the controls. On the basis of the working hypothesis that there is a causal relationship between the deranged dualism of cAMP and cGMP in the T-lymphocytes and the failure of the immunological tumor cell defence, an increase in the cAMP level is offered as a possible therapy. Therapeutic results in tumor-bearing mice and first results in melanoma patients are discussed.
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PMID:[Cyclic nucleotide concentration changes in different tumors and therapeutic success through increasing the cAMP level]. 23 Apr 37

Transplantable Brown-Pearce carcinoma was adapted successfully in the rabbit anterior chamber. Regression of tumor growth was attained on tri-weekly perfusion of the AC with 10 micromolar of methotrexate. Tumor cyclic nucleotide phosphodiesterase (PDE) and protein activator were found to be markedly depressed during the course of chemotherapy and the PDE cAMP/cGMP ratio was similarly altered. Corroborative light and electron-microscopic studies showed specific alterations of intracellular organelles in relation to MTX and tumor cell death. These findings suggest that metabolic pathways of cyclic nucleotides are important biochemical modulators of neoplastic cells. The method of intraocular perfusion precludes systemic toxic effects and avoids compromising the animals' immunocompetence.
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PMID:Experimental intraocular malignancy: the effect of intracameral perfusion. 23 85

Synthesis of hCG and its alpha subunit (hCG-alpha) by trophoblastic tumor cell lines (JEG-3, Reid, and BeWo) and by nontrophoblastic tumor cell lines [ChaGo and three HeLa lines (HeLa CCL2, HeLa S3, and HeLa 65)] was studied. cAMP, dibutyryl cAMP, and 8-bromo-cAMP induced, but 5-bromo-2'-deoxyuridine inhibited, the synthesis of hCG-alpha and hCG in trophoblastic tumor cells, Addition of 5-bromo-2'-deoxyuridine partially blocked the induction by dibutyryl cAMP in these cells. The synthesis of hCG-alpha and hCG in nontrophoblastic tumor cells was stimulated by dibutyryl cAMP. cAMP and 8-bromo-cAMP, however, did not affect the synthesis of hCG-alpha, although the synthesis of hCG was enhanced. 5-Bromo-2'-deoxyuridine induced hCG-alpha synthesis but did not affect hCG synthesis in nontrophoblastic tumor cells. In HeLa S3 and HeLa 65 cells, the amount of hCG-alpha and hCG produced in the presence of dibutyryl cAMP and 5-bromo-2'-deoxyuridine together was greater than the total hormone produced by each inducer separately. Our data indicate that the regulation of the production of hCG-alpha and hCG differs in trophoblastic and nontrophoblastic tumors.
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PMID:Regulation of the synthesis of human chorionic gonadotrophin by 5-bromo-2'-deoxyuridine and dibutyryl cyclic AMP in trophoblastic and nontrophoblastic tumor cells. 23 62


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