Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0027651 (tumor)
 685,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Adrenocorticotrophin (ACTH) produced an insignificant stimulation of pregnenolone biosynthesis from endogenous precursors in isolated cells prepared from the rat Snell adrenal carcinoma 494. On the addition of 25-hydroxycholesterol, the rate of pregnenolone synthesis increased 10-fold. These results, noting also the very low cholesterol content of the tumor cells, suggested that lack of cholesterol was responsible for the poor steroidogenic response of the cells to ACTH. Endogenous pregnenolone production was sensitive to cytochalasin B as well as cycloheximide. However, pregnenolone synthesis after the addition of 25-hydroxycholesterol was not affected by these inhibitors. Removal of cycloheximide from the cells resulted in the immediate restoration of the initial rate of pregnenolone synthesis from endogenous precursors. This suggested that cycloheximide was interfering with the action of a stable activated intracellular messenger.
Mol Cell Endocrinol 1978 Dec
PMID:Pregnenolone biosynthesis in isolated cells of Snell rat adrenocortical carcinoma 494. 21 96

The effect of mengovirus infection on the extent of phosphorylation of histone H1 was studied in Ehrlich ascites tumor cells. After prelabeling of the nuclear protein with [32P] orthophosphate, the excorporation of radioactivity was followed as a function of time postinfection. Employing high-resolution polyacrylamide gradient slab gel electrophoresis and autoradiography, it was found that, compared to a relatively slow turnover of phosphate groups in histone H1 in mock-infected cells, in mengovirus-infected cells the excorporation of radiolabel from histone H1 was significantly enhanced. In the latter case, the decrease of histone-bound radioactivity was paralleled by a reduction of the band multiplicity in the histone H1 region of the electrophoresis profile. It was also shown that the microheterogeneity in the histone H1 complements isolated at various times postinfection was reduced to the same basal 3-band level by incubation of the nuclear protein fractions in the presence of alkaline phosphatase. After this treatment, the band multiplicity equaled that found in histone H1 from stationary cells.
Mol Biol Rep 1978 Oct 16
PMID:Dephosphorylation of histone H1 after mengovirus infection of Ehrlich ascites tumor cells. 21 3

Calcium, in partnership with cyclic AMP, controls the proliferation of non-tumorigenic cells in vitro and in vivo. While it does not seem to be involved in the proliferative activation of cells such as hepatocytes (in vivo) or small lymphocytes (in vitro), it does control two later stages of prereplicative (G1) development. It must be one of the very many regulatory and permissive factors affecting early prereplicative development, because severe calcium deprivation reversibly arrests some types of cell early in the G1 phase of their growth-division cycle in vitro. However, calcium more specifically and much more often regulates a later (mid or late G1) stage of prereplicative development. Thus, regardless of its severity or the type of cell, calcium deprivation in vitro or in vivo reversibly stops proliferative development at that part of the G1 phase in which the cellular cyclic AMP content transiently rises and the synthesis of the four deoxyribonucleotides begins. The evidence points to calcium and the cyclic AMP surge being co-generators of the signal committing the cell to DNA synthesis. The evidence is best explained so far by the cyclic AMP surge causing a surge of calcium ions which combine with molecules of the multi-purpose, calcium-dependent, regulator protein calmodulin (CDR) somewhere between the cell surface and the cytosol. The resulting Ca-calmodulin complexes then stimulate many different (and possibly membrane-associated) enzymes such as protein kinases, one of which produces the DNA-synthetic initiator. Calcium has little or no influence on the proliferation of tumor cells. Some possible explanations of this very important loss of control are considered.
Mol Cell Biochem 1979 Nov 01
PMID:The regulation of cell proliferation by calcium and cyclic AMP. 22 7

When tested in a poly(U)-dependent polyphenylalanine synthesizing system and in a postnuclear supernatant, both derived from Ehrlich ascites tumor cells, 2'(3'),5'-ADP did not affect chain elongation of polypeptide synthesis. In a cell-free system which was dependent on initiation and programmed by natural mRNA, however, the amino acid incorporating activity was suppressed to about 10% of the control in the presence of 1 mM 2'(3'),5'-ADP. The inhibitor was shown not to interfere with the attachment of poly(U) to the small ribosomal subunit and with the formation of mRNA-80S ribosome complexes in a complete protein synthesizing system. The subsequent attachment of a 40S ribosomal subunit to the mRNA-80S ribosome complex and the formation of polysomes, however, was depressed by the inhibitor. The experimental results suggest that 2',(3'),5'-ADP inhibits initiation-dependent protein synthesis between monosome formation and the formation of the first peptide bond(s).
Mol Biol Rep 1977 Jun
PMID:2'(3'),5'-ADP inhibits initiation-dependent protein synthesis in a cell-free system from Ehrlich ascites tumor cells. 56 Jun 26

Estrogens stimulate prolactin (PRL) synthesis by GH3 cells, a clonal strain of rat pituitary cells grown in culture. At 4 degrees C the binding of [3H]17 beta-estradiol to monolayer cultures of GH3 cells was specific and of limited capacity, with half-maximal and maximal binding after 1--2 h and 12 h, respectively. Scatchard analysis showed one single class of binding sites with Kd = 3.1 X 10(-10) M and n = 309 X 10(-15) mol 17 beta-estradiol/mg cell protein, calculated to give approx. 25,000 binding sites per cell. At 4 degrees C less than 10% of the specifically bound [3H]17 beta-estradiol was found in the nuclear fraction. When the incubation temperature was raised to 37 degrees C, the amount of radioactivity in the nucleus increased to 25% within 30 min with a corresponding reduction in the cytoplasm. The cytosol fractions from monolayer cultures as well as from tumors of GH3 cells contained specific 17 beta-estradiol binding proteins, having a sedimentation constant close to 8S in a salt-free buffer and 4S in the presence of 0.5 M KCl. scatchard analysis showed one single class of binding sites with Kd = 3.6 X 10(-10) M and n = 258 X 10(-15) mol 17 beta-estradiol/mg cytosol protein (GH3 tumor tissue). Thus, GH3 cells grown in culture and in the intact animal have similar binding characteristics as judged from the data for binding affinity, capacity and specificity. After the in vivo administration of [3H]17 beta-estradiol to GH3 tumor-bearing rats, radioactivity could be extracted (0.5 M KCl) from purified nuclei bound to 4.5S macromolecules. We suggest that the action of 17 beta-estradiol on GH3 cells involves an initial binding of the steroid to specific receptors in the cytoplasm, followed by transport of a fraction of the hormone-receptor complexes to the nucleus involving a temperature-sensitive step.
Mol Cell Endocrinol 1978 Oct
PMID:Receptors for 17beta-estradiol in prolactin-secreting rat pituitary cells. 56 89

A comparative study of rat kidney and carcinoma RA tRNA-methylase activity has been carried out using partially purified enzyme preparations and total E. coli tRNA. Also the nuclease activity of the methylase preparations from kidney and carcinoma was compared. It was established that the methylase activity in carcinoma preparations is higher, whereas the nuclease activity is lower in comparison to the enzyme preparations from liver. No formation of some specific methylated compounds could be established in the case of carcinoma. It was established that the relative contribution of individual methylases to the elevated level of total tRNA-methylase activity in carcinoma is different. Maximal enhancement of activity was established for the methylase forming m5U, whereas the activity of the enzymes, transfering the methyl group to the fifth position of C is practically equal in kidney and carcinoma tissues. Experimental results and theoretical evaluation of the hypotheses suggested to explain the higher methylase activity in tumor tissues allowed to reject some of them.
Mol Biol (Mosk)
PMID:[Comparative study of the tRNA-methylases of normal and tumor tissues. I. Spectrum of renal and carcinoma RA methylases]. 61 45

Transplantable rat liver tumors 5123 t.c., 7288 ct.c., 5123 t.c.(H) and the Novikoff hepatoma have active mixed function oxidase systems capable of metabolizing a variety of drug and polycyclic hydrocarbon substrates. The tumor drug metabolism systems are at best 20% as active as rat liver. The tumor drug metabolism activities are induced by pretreatment with phenobarbital or beta-naphthoflavone and can be inhibited with specific inhibitors such as carbon monoxide or 7,8-benzoflavone. Tumor drug metabolism systems appear to consist of cytochrome P-450 and cytochrome P-450 reductase. The properties of the two protein components from tumors are highly similar to the corresponding components of the liver drug metabolism system. Cytochrome P-450 reductase has been at least partially purified from the Novikoff hepatoma and hepatoma 5123 t.c.(H). The kinetic and physical properties of the tumor reductases are similar to those of the liver reductase except that the Km of hepatoma 5123 t.c.(H) reductase, but not of the Novikoff hepatoma reductase for NADPH, is elevated an order of magnitude over the Km of the liver reductase. The mechanism for the interaction of electron donor and electron acceptor with liver or tumor reductases seems to be a sequential reaction mechanism. Experiments on the NADP-inhibition of the interaction of NADPH and cytochrome c with liver reductase indicate that NADP is competitive with NADPH and noncompetitive with cytochrome c. This result is consistent with the postulate of a sequential reaction for NADPH-cytochrome P-450 reductases of liver and tumors. These data support the conclusions that an active drug metabolism system is present in liver tumors and that the tumor systems are constituted like the liver system.
Mol Cell Biochem 1978 Dec 22
PMID:The drug metabolism systems of liver and liver tumors: a comparison of activities and characteristics. 74 99

Several characteristics of the nucleic factor of tumors which is thought to play an important role in suppression of tumor immunity was investigated. This nucleic factor differs from native double-stranded DNA of eukaryotic nuclei by base composition (A: T: G : C = 1: 1.44 : 0.91: 0.69); its affinity to GAP and hyperchromic effect were lower than those in native DNA. Heating above 80 degrees in 1 N KOH destroyed the nucleic factor to fragments that could not be detected in 8% PAK electrophoresis. The results of this and previous reports lead us to a hypothesis that the nucleic factor is a DNA molecule consisting of single- and double-stranded regions, as well as short insertions of RNA. The double-stranded regions in this molecule possess non-parrallel breaks.
Mol Biol (Mosk)
PMID:[Structural peculiarities of the nucleic factor from ascitic fluid of tumors]. 74 2

The enzymatic destruction of oxidizing products produced during metabolic reduction of oxygen in the cell (such as singlet oxygen, H2O2 and OH radical) involves the concerted action of superoxide dismutase-which removes O-2 and yields H2O2-and H2O2 removing enzymes such as catalase and glutathione peroxidase. A difference in distribution or ratio of these enzymes in various tissues may result in a different reactivity of oxygen radicals. It was found that in red blood cells superoxide dismutase and catalase are extracted in the same fraction as hemoglobin, while glutathione peroxidase appears to be "loosely" bound to the cellular structure. This suggests that in red blood cells catalase acts in series with superoxide dismutase against bursts of oxygen radicals formed from oxyhemoglobin, while glutathione & peroxidase may protect the cell membrane against low concentrations of H2O2. On the other hand, catalase activity is absent in various types of ascites tumor cells, while glutathione peroxidase and superoxide dismutase are found in the cytoplasm. However, the peroxidase/dismutase ratio is lower than in liver cells, and this may provide an explanation for the higher susceptibility of tumor cells to treatments likely to involve oxygen radicals.
Mol Cell Biochem 1976 Jan 31
PMID:Enzyme defense against reactive oxygen derivatives. II. Erythrocytes and tumor cells. 81 6

The interaction of estradiol-receptor complexes and isolated human breast tumor chromatin was studied under equilibrium conditions. The estradiol-receptor complexes bound specifically to the chromatin of hormone dependent tumors and showed a single class of binding sites with a Ka of 0.96 X 10(10) M-1 and a binding capacity of 1.5 pmoles/mg DNA. The binding was a temperature-dependent process and involved a "transformation" of the receptor protein. The heat-activated hormone-receptor complex was more active than the 8S form in the binding phenomenon. The specific interaction of estradiol-receptor complex with isolated chromatin was saturable and sensitive to conditions of temperature and ionic strength. Furthermore under optimal conditions no acceptor sites were detected in chromatin of hormone independent tumors.
Mol Cell Biochem 1977 Jul 05
PMID:Binding of estradiol receptor complexes to isolated human breast chromatin. 88 94


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