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Biomedical subjects

L M Nutter

Publications and source records attributed to L M Nutter.

27 records · Page 2Linked to original sources
PubMed1986

Demonstration of Epstein-Barr virus-specific DNA polymerase in chemically induced Raji cells and its antibody in serum from patients with nasopharyngeal carcinoma.

Epstein-Barr virus (EBV) has been found to be associated with nasopharyngeal carcinoma (NPC), and antibodies with high frequency and titer to EBV proteins have been found in sera from NPC patients. Raji cells, an EBV genome-carrying nonproducer cell line, treated with 12-O-tetradecanoylphorbol-13-acetate and n-butyrate induced a unique EBV DNA polymerase which has properties similar to the EBV DNA polymerase induced by 12-O-tetradecanoylphorbol-13-acetate in P3HR-1 cells, an EBV producer cell line. The possible presence of antibodies to this EBV DNA polymerase in NPC patient serum was examined. The mean number of EBV DNA polymerase units neutralized was 380 +/- 168 units/ml serum (mean +/- SD) in 48 sera from patients with NPC, whereas that in the sera from 52 healthy donors was 62 +/- 56 units/ml (p less than 0.01). The EBV DNA polymerase antibody was found to be associated with the immunoglobulin G but not the immunoglobulin A fraction, and its titer was not correlated with the titers against EBV DNase or virus capsid antigen-immunoglobulin A. Whether the EBV DNA polymerase antibody is against the EBV DNA polymerase core protein or its stimulating protein is still being investigated. This study demonstrated the high frequency and high titer of antibody against EBV DNA polymerase in serum from NPC patients and suggested the potential of utilizing this antibody titer to complement other methods for the early diagnosis or prognosis of NPC.

Antibodies, Viral↗
PubMed1985

The sources of thymidine nucleotides for virus DNA synthesis in herpes simplex virus type 2-infected cells.

The thymidine nucleotide sources present during herpes simplex virus type 2 (HSV-2) infection were examined. It was concluded that the source of dTTP in HSV-2-infected cells is not only derived from the ribonucleotide reductase-catalyzed de novo pathway, but also from host DNA. When the de novo pathway was inhibited by the addition of hydroxyurea, an inhibitor of ribonucleotide reductase, the dTTP levels were maintained by a compensatory increase in dTTP derived from host DNA. The utilization of host DNA-derived dTTP for viral DNA synthesis was demonstrated. In spite of an increased contribution of dTTP from host DNA in the presence of hydroxyurea, the level of utilization of host DNA-derived dTTP appeared to remain constant. More than one dTTP pool in virus-infected cells is implicated.

Animals↗
PubMed1985

Can ribonucleotide reductase be considered as an effective target for developing antiherpes simplex virus type II (HSV-2) compounds?

Herpes simplex viruses are known to induce virus specified ribonucleotide reductase (RR) in infected cells. RR is considered as a possible target for the development of antiviral agents. In this study, the role of RR in virus replication has been investigated. The sensitivity of RR to hydroxyurea (HU) from virus infected and uninfected HeLa S3 cells was similar with IC50 values of 0.12 and 0.14 mM. In the presence of 2 mM HU, and 10 microM tetrahydrouridine (THU), a cytidine deaminase inhibitor, the incorporation of [14C]cytidine into viral DNA was found to be inhibited by 95%; [32P]-incorporation into viral DNA under the same conditions was inhibited by 75%. The pool size of dCTP and dGTP was 50 and 70%, respectively, with no significant effect on dATP and dTTP pools in virus infected cells treated with 2 mM HU, as compared with virus infected cells receiving no drug treatment. HU at 2 mM could not inhibit HSV-2 yield by more than one log. These results suggest that virus RR is not an effective target for developing anti HSV-2 compounds.

Antiviral Agents↗
PubMed1983

Absence of pyridoxine- (pyridoxamine-) 5'-phosphate oxidase in Morris hepatoma 7777.

Morris hepatoma 7777 previously has been shown to have no detectable pyridoxine- (pyridoxamine-) 5'-phosphate oxidase activity [Thanassi, J. W., Nutter, L. M., Meisler, N. T., Commers, P., & Chiu, J.-F. (1981) J. Biol. Chem. 256, 3370-3375]. In order to determine if this enzyme was missing in the hepatoma, we purified rat liver oxidase and raised antibodies to it in rabbits. Final purification of rat liver oxidase for use as an antigen was accomplished by affinity chromatography and gel electrophoresis. The rat liver enzyme is similar to rabbit liver oxidase [Kazarinoff, M. N., & McCormick, D. B. (1975) J. Biol. Chem. 250, 3436-3442] having two noncovalently linked subunits with molecular weights in the range of 25 000-28 000. Evidence indicating that inactive enzyme was simultaneously purified with native enzyme was obtained. The IgG fraction was purified from the serum of a rabbit that had been immunized with rat liver oxidase. This was used in the development of ELISA and immunoblot analyses for the presence of antigenically active pyridoxine- (pyridoxamine-) 5'-phosphate oxidase in cytosolic preparations from normal rat liver and Morris hepatoma 7777. The results indicated that there was no immunologically detectable oxidase protein in the tumor. An alternate pathway of pyridoxal 5'-phosphate synthesis, involving oxidation of pyridoxine to pyridoxal followed by phosphorylation, was ruled out. The implications of these findings with respect to acquisition of nutrients by tumors are discussed.

Animals↗
PubMed1982

Vitamin B6 metabolism in liver and liver-derived tumors.

Vitamin B6 metabolism has been investigated in several highly and well-differentiated Morris hepatomas. Comparisons have been made with two poorly differentiated Morris hepatomas, with host livers obtained from tumor-bearing animals, and with fetal, neonatal, and adult rat liver. The pyridoxal phosphate content and the activities of pyridoxine kinase and pyridoxine phosphate oxidase of all Morris hepatomas examined were significantly less than those in adult host or control livers and generally fell in the range determined for fetal and neonatal liver. A similar pattern was not evident for the activity of pyridoxine phosphate phosphatase. Relative to control and host livers, the activity in hepatomas of the pyridoxal phosphate (PLP)-dependent enzyme, ornithine decarboxylase, was generally elevated. Dexamethasone, at a dose which caused an elevation in the activity of PLP-dependent tumor tyrosine aminotransferase, had no effect on PLP metabolism. The data indicate that tumor progression in the Morris hepatoma spectrum in relation to vitamin b6 metabolism falls into an onco-developmental pattern characterized by a diminished amount of tissue PLP and a diminished capability to metabolize precursor vitamer forms to PLP.

Animals↗
PubMed1981

Vitamin B6 metabolism in Morris hepatomas.

The enzymes involved in the metabolism of vitamin B6 were measured in Morris hepatomas and livers of female Buffalo rats fed pyridoxine-sufficient and deficient diets. Pyridoxal phosphate levels in plasmas hepatomas, and livers were also determined. Nontumor-bearing animals were maintained as controls. Regardless of the B6 nutritional status, the concentration of pyridoxal phosphate was lower in the hepatomas than in the livers of the host animals. The apoenzyme levels of ornithine decarboxylase, a pyridoxal phosphate-dependent enzyme, were higher in the hepatomas from animals fed the B6-deficient diet. Liver pyridoxine kinase activity was higher in B6-sufficient animals. In contrast, tumor pyridoxine kinase activity was influenced by B6 intake and was significantly lower than that in host liver. Liver pyridoxine phosphate oxidase activity was not significantly affected by B6 intake or by the presence of tumor. In contrast, hepatomas had little or no pyridoxine phosphate oxidase activity. Pyridoxine phosphate phosphatase activity was elevated in tumors relative to livers. These data indicate that the metabolism of vitamin B6 is markedly different in the hepatomas than in host or control livers and suggest that the tumor is apparently incapable of the complete synthesis of co-enzymatically active pyridoxal phosphate from inactive precursor forms such as pyridoxine.

Animals↗
PubMedDate not supplied

An o-quinone form of estrogen produces free radicals in human breast cancer cells: correlation with DNA damage.

The o-quinone forms of 2,3- and 3,4-catechol estrogens have been implicated in the carcinogenicity of these hormones. The concomitant production of reactive oxygen species during reduction of the o-quinone estrogens has been inferred to play a mechanistic role in their mutagenic potential. Conclusive evidence documenting the production of hydrogen peroxide, the hydroxyl radical, and the estrone 3,4-semiquinone in estrone 3,4-quinone (3,4-EQ)-treated human breast cancer subcellular fractions was demonstrated in the absence of exogenously added catalysts. Subcellular fractions of MCF-7 cells treated with 3,4-EQ and NADPH, including nuclei, mitochondria, and microsomes, were shown to support significant amounts of hydrogen peroxide production. Hydrogen peroxide production in 3,4-EQ-treated cellular fractions and the chromosomal DNA damage induced in 3,4-EQ-treated MCF-7 cells were abolished by the addition of catalase. A significant and potentially physiologically relevant spontaneous reduction of 3,4-EQ by NADPH resulting in hydrogen peroxide production was demonstrated. The results unequivocally demonstrate that free radicals are produced during the metabolism of estrone 3,4-quinone in human cells.

Breast Neoplasms↗
PubMedDate not supplied

Cellular biochemical determinants modulating the metabolism of estrone 3,4-quinone.

The metabolism of the o-quinone derivative of estrone, 3,4-estrone quinone (3,4-EQ), has been investigated in human breast cancer cells. Unlike the p-quinone, diethylstilbestrol 4',4"-quinone, 3,4-EQ was not a substrate for the two-electron reduction catalyzed by the putative detoxifying enzyme, NAD(P)H:quinone reductase (DT diaphorase; DT D). Accordingly, the DNA damage induced by 3,4-EQ in human MCF-7 cells was not affected by an inhibitor of DT D. Although 3,4-EQ was not an apparent substrate for the two-electron reduction catalyzed by DT D, this o-quinone was a substrate for the one-electron reduction catalyzed by cytochrome P450 reductase. The one-electron reduction of 3,4-EQ catalyzed by cytochrome P450 reductase occurred in the face of a significant and potentially physiologically relevant spontaneous reduction of 3,4-EQ by NADPH. The impact of purified superoxide dismutase (SOD) upon the production of hydrogen peroxide produced as a consequence of 3,4-EQ metabolism was evaluated; surprisingly, SOD inhibited the hydrogen peroxide produced by this o-quinone. Possible reasons for the SOD-mediated inhibition of redox cycling of 3,4-EQ are discussed. In summary, important differences in the metabolism of 3,4-EQ vis-a-vis o- and p- quinones have been observed, and the implications of these differences are discussed.

Animals↗