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

The substrate specificity and the effects of nucleotides and SH-blocking agents on the p-nitrophenylphosphatase activity of intact Ehrlich ascites tumor cells (EAT) cells were studied. DL-beta-Glycerophosphate, o-phosphoethanolamine, cholinephosphate, glucose-6-phosphate, o-carboxyphenylphosphate,, phosphoenolpyruvate and AMP were not attacked by intact cells. ATP is greater than GTP is greater than UPT is greater than PPi is greater than pNPP were cleaved with decreasing velocity. A stimulation of the cleavage of p-NPP by the following nucleotides was observed with decreasing effectivity: ATP is greater than ADP is greater than GTP is greater than UTP; AMP was ineffective. The phosphatase activity was not affected by malate, tartrate and glutathion disulfide. The SH blocking agents diamide and thimerosal were more effective inhibitors of the pNPPase than of the ATPase activity, whereas the hydrolysis of ATP is more affected by the ATP analog adenylylimidodiphosphate. The present data are best compatible with a double headed enzyme: Both active sites interact with ATP, only one is active against p-NPP and sensitive against SH-blocking agents.
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PMID:Further investigations on the p-nitrophenylphosphatase activity of intact Ehrlich ascites tumor cells. 20 18

Disturbances in the functional properties of tumor mitochondria have been studied during the course of induction of haemorrhage brought about by endotoxin in the murine Crocker sarcoma (S 180). Extensive impairment of function was already present in mitochondria isolated from control tumors, as shown by low respiratory control ratios. The existing mitochondrial damage intensified promptly in response to injection of endotoxin long before the onset of haemorrhage at 4 h. The nature of the additional damage took two forms, depending on the duration of exposure to endotoxin; first, at 30 min, a true uncoupling of oxidative phosphorylation was seen, largely reversible in vitro by pre-treatment of the isolated organelles with bovine serum albumin (BSA). Second, at 1 h and later, oxygen utilisation in the presence of succinate, ADP and inorganic phosphate (Pi) was depressed. The pre-addition of BSA consistently lowered respiration rates with succinate and Pi in all preparations. The extent of endogenous inhibition of the adenine nucleotide translocase appeared unaltered by endotoxin in vivo.
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PMID:Early mitochondrial damage in the induction of haemorrhagic necrosis in the Crocker sarcoma (S 180) by endotoxin. 38 16

ADP-Ribose is nearly quantitatively split to 5'-AMP by treatment with alkali at elevated temperatures. This unique behaviour, which is not shown by ADP and other adenine derivatives, was used as the basis of an optical test for the selective determination of ADPR in the presence of other adenine compounds including RNA. Poly(ADPR) could also be quantified when the polymer was degraded by poly(ADPR) glycohydrolase prior to alkaline treatment. When combined with the determination of the terminal AMP residues released by phosphodiesterase I treatment, the chain length of the polymer could be calculated. Application of the method to the quantitation of protein-bound mono(ADPR) residues in Ehrlich ascites tumor cells under different growth conditions is described.
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PMID:Conversion of ADP-ribose to 5'-AMP by alkaline treatment and its use for an optical quantitation of mono and poly(ADP-ribose) residues in the micromolar range. 55 24

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).
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PMID:2'(3'),5'-ADP inhibits initiation-dependent protein synthesis in a cell-free system from Ehrlich ascites tumor cells. 56 Jun 26

The addition of glucose to ELD and ELT/B1 mouse ascites tumor cell suspensions caused a 2.3-fold increase in the phosphorylation state ratio, (ATP)/(ADP) (Pi), because of a decrease in the intracellular Pi concentration. The addition of glucose to these cell suspensions has been reported by Chance and Hess ('59) to cause an increase in the study state reduction of cytochrome b and an increase in the steady state oxidation of cytochrome c. On a quantitative basis these two independent measurements suggest that a near equilibrium exists between the oxidation-reduction state of the mitochondrial electron carriers and the reactions of ATP synthesis (as expressed by the phosphorylation state ratio) both before and after glucose addition. We conclude that the mechanism of the inhibition of respiration by glycolysis (the Crabtree effect) is a decrease in the rate of electron transport caused by the mass action effect of the elevated phosphorylation state ratio.
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PMID:On the mechanism of the Crabtree effect in mouse ascites tumor cells. 56 9

A regulatory function of the cell membrane in controlling the cytoplasmic level of Pi has been proposed, and in Ehrlich ascites tumor cells an active influx of primary phosphate has been reported in the literature. In the present study, Ehrlich cells were incubated at 1.5--50 mM extracellular Pi at pH 7.4 (Pi mainly secondary phosphate) and at pH 6.0 (mainly primary phosphate), and the measured cell Pi was compared with the value expected from a passive distribution of Pi. At a low extracellular Pi concentration the cell Pi was 3--6 mumol/g or even more. It is suggested that a major part of this cell Pi can be accounted for by enzymic release of Pi during the sampling procedure. If this interpretation is correct, the present results show that both ionic species of Pi are in electrochemical equilibrium across the cell membrane at steady state. Moreover, in vivo the concentration of free Pi in the cytosol will presumably be maintained at a steady-state level of about 0.4 mM, one order of magnitude below the directly measured values. This implies that the ratio [ATP]/[ADP][Pi] which is important in the regulation of energy metabolism, is higher than reported in the literature.
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PMID:Inorganic phosphate in Ehrlich ascites tumor cells and its distribution across the cell membrane. 56 66

Values of serum and plasma LDH in rats were comparatively studied, and the following results were obtained: 1) The activity of LDH increased in serum with time during clotting, but no changes of LDH activity were found in plasma. 2) When platelet rich plasma (PRP) was recalcified and allowed to clot, LDH-release from platelets with a corresponding increase of serum LDH was observed, but addition of ADP or thrombin to PRP did not have an effect on LDH-release. 3) LDH-release from platelets by calcium was not inhibited by aspirin, and it was influenced by the quality of the test tube. 4) Values of serum and plasma LDH on experimentally induced liver-damaged or kidney-damaged rats and tumor-bearing rats were examined in relation to their tissue damages, revealing that plasma LDH activity represents the condition of a disease better than serum LDH activity.
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PMID:[Comparative studies on lactate dehydrogenase in serum and plasma of rats (author's transl)]. 66 15

Walker 256 carcinoma cells form irreversible aggregates with rat platelets activated by ADP or serotonin. Since serotonin induces platelet shape change but not platelet aggregation the degree of activation indicated by the disc-sphere transformation is sufficient for platelets to interact with these tumor cells. This is confirmed by experiments with spheroid washed platelets which form irreversible mixed aggregates with Walker 256 carcinoma cells without a stimulus being required. This type of tumor cells could react with platelets in vivo, provided the platelets are activated by disturbed blood flow or contact with subendothelium. Our observations can explain why other authors found no interaction between Walker 256 carcinoma cells and non-activated platelets in vitro even though platelets contributed to the formation of bloodborne metastases of this tumor.
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PMID:Aggregation of activated platelets with Walker 256 carcinoma cells. 75 60

Periodate-oxidized inosine (Inox; NSC 118994) and periodate-oxidized 5'-inosinic acid (PI-IMP) were prepared and studied for their effects on ribonucleotide reductase activity in partially purified extracts from Ehrlich tumor cells and on nucleic acid synthesis in intact tumor cells in culture. Ribonucleotide reductase activity in cell-free extracts from Ehrlich tumor cells was inhibited by Inox and PI-IMP. PI-IMP was more inhibitory to the reductase activity than was Inox. Furthermore, the inhibition of ribonucleotide reductase activity by Inox and PI-IMP was greater for cytidine-5'-diphosphate reductase activity than for adenosine-5'-diphosphate reductase activity. The ribonucleotide reductase activity in cell-free extracts prepared from Ehrlich tumor cells treated with Inox or PI-IMP in culture was decreased compared with the activity in the extracts from untreated cells. Incorporation of labeled cytidine into the RNA and DNA of Ehrlich tumor cells in culture was inhibited by both Inox and PI-IMP. The conversion of cytidine to deoxycytidine nucleotides in the acid-soluble pool was likewise inhibited. These data indicate that Inox and PI-IMP inhibit the ribonucleotide reductase step as one of the sites of action of these compounds. However, the inhibition of RNA synthesis indicates that there must be additional sites of action of these nucleoside analogs.
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PMID:Inhibition of ribonucleotide reductase activity and nucleic acid synthesis in tumor cells by the dialdehyde derivatives of inosine (NSC 118994) and inosinic acid. 98 50

1. The regulatory properties of two interconvertible kinetic forms of class A pyruvate kinase from Ehrlich ascites tumor cells have been studied with a partially purified enzyme preparation free of interfering enzymatic activities. 2. The hyperbolic form shows Michaelis-Menten kinetics for P-pyruvate, with high affinity for this substrate and low affinity for the inhibitory amino acids alanine and phenylalanine. The sigmoidal form displays positive cooperativity respect to P-pyruvate (n=1.4), with lower affinity for this substrate and higher affinity for the inhibitory amino acids. 3. The equilibrium between the hyperbolic and the sigmoidal forms of the enzyme is affected by substraetes and effectors. P-pyruvate, ADP and Fru-P2 shift the equilibrium to the hyperbolic form while ATP, alanine and phenylalanine stabilize the sigmoidal form. 4. Effector metabolites affect the molecular weight of the protein, acting on an equilibrium between dimers and tetramers. P-pyruvate and ADP associate the enzyme to a tetramer while ATP, alanine and phenylalanine favor the occurrence as a dimer. The positive modifier Fru-P2 did not associate the enzyme to the tetramer, even at 1 mM concentration. 5. A tentative molecular model for pyruvate kinase A on the basis of the kinetic and aggregation interconversion is proposed.
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PMID:Interconversion phenomena between two kinetic forms of class a pyruvate kinase from Ehrlich ascites tumor cells. 100 94


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