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Biomedical subjects

D Viceps-Madore

Publications and source records attributed to D Viceps-Madore.

12 recordsLinked to original sources
PubMed1985

The effect of transport system A and N amino acids and of nerve and epidermal growth factors on the induction of ornithine decarboxylase activity.

The induction of ornithine decarboxylase (EC 4.1.1.17) (ODC) by amino acids and by the peptide hormones nerve growth factor (NGF) and epidermal growth factor (EGF) in salts-glucose media has been studied. Only those neutral amino acids taken into the cell via one of the Na+ dependent transport systems stimulate ODC activity. Asparagine and the nonmetabolizable alpha-amino-isobutyric acid (AIB) were used as representatives of this class of inducing amino acids, and their intracellular concentrations were related to the levels of ODC induced. A threshold intracellular concentration of asparagine or AIB has to be attained before ODC can be induced. Further slight increases in intracellular concentrations of asparagine or AIB produce disproportionately large increases of ODC, resulting in a sigmoidal curve of ODC induction. These results, and the fact that the decrease in ODC levels caused by valine is associated with a concurrent decrease in the intracellular level of the inducing amino acid, suggest that the intracellular amino acid level is causally related to the induction of ornithine decarboxylase. Glutamic acid, EGF, and NGF do not induce ODC except in the presence of an inducing amino acid. They act synergistically with the inducing amino acid and produce higher ODC levels at the same intracellular concentration of the inducing amino acid.

Amino Acids↗
PubMed1984

Regulation of high- and low-affinity epidermal growth factor receptors by glucocorticoids.

It is reported that receptors for epidermal growth factor (EGF) in HeLa S3 cells exist in two forms, which differ in both affinity and capacity. Both the number of receptors and their distribution into low- and high-affinity forms are modulated by glucocorticoids. Scatchard analysis of saturation binding assays performed at 0 degrees C indicates that there is a low-affinity class of receptors (Kd approximately equal to 1.5 nM), which contains approximately 6 X 10(4) binding sites per cell, and a second, high-affinity class of receptors (Kd approximately equal to 0.16 nM) containing approximately 5 X 10(3) binding sites per cell. Exposure of HeLa S3 cells to 10(-7) M dexamethasone for 24 h increased EGF binding to whole cells by increasing the numbers of low- and high-affinity receptors by 20 and 114%, respectively. The increase in EGF binding depends upon the dose of dexamethasone, being raised from 10(-11) to 10(-6) M. EGF binding is half-maximal near 2-4 X 10(-9) M, a concentration equal to the Kd of dexamethasone for the glucocorticoid receptor in these cells. The increase in EGF binding is specific for glucocorticoids, occurring when the HeLa S3 cells are exposed to 10(-7) M cortisol or dexamethasone for 24 h, but not when the cells are similarly treated with testosterone, 5 alpha-dihydroxytestosterone, 17 beta-estradiol, or progesterone. The effect on EGF binding appears to be biphasic; the initial rapid increase occurs between 8 and 12 h, is blocked by both 10(-6) M cyclohexamide and 0.1 micrograms/ml actinomycin D, and is followed by a more gradual increase thereafter. These data indicate that glucocorticoids are able to regulate both the number of EGF receptors and their distribution into high- and low-affinity components.

Binding Sites↗
PubMed1984

A general immunochemical method for detecting proteins on blots.

Following horizontal electroelution, or blotting, of proteins from polyacrylamide gels to immobilizing matrices, such as nitrocellulose or Zeta-bind paper, the transferred proteins can be derivatized in situ with pyridoxal 5'-phosphate and sodium borohydride. After a quenching step to eliminate nonspecific binding of antibody to the protein-binding matrix, the blot is incubated with a solution containing a mouse monoclonal antibody specific for the 5'-phosphopyridoxyl group. The transferred proteins can then be located on the blot with second antibody staining procedures employing either a peroxidase-linked goat anti-mouse F(ab')2 antibody or a peroxidase-linked avidin/biotin system. The solid-phase enzyme-linked immunosorbent assay method described in this report is a mild, general, and sensitive immunochemical method for the detection of proteins on protein-binding matrices.

Animals↗
PubMed1983

Immunoblot detection of pyridoxal phosphate binding proteins in liver and hepatoma cytosolic extracts.

A monoclonal antibody, highly selective for the 5'-phosphopyridoxyl group, can be used to detect cytosolic pyridoxal-5'-phosphate binding proteins by an immunoblot procedure. This technique, when applied to sodium borohydride-treated cytosolic extracts obtained from normal rat liver at various stages of development as well as several liver-derived Morris hepatomas, reveals patterns of pyridoxal-5'-phosphate binding proteins that are characteristic of the various sources of cytosol. These findings suggest that there are developmental and tumor-specific requirements for pyridoxal-5'-phosphate, the coenzymatically active form of vitamin B-6.

Aging↗
PubMed1983

Preparation, characterization, and use of monoclonal antibodies to vitamin B6.

Monoclonal antibodies exhibiting various specificities for B6 vitamer forms have been prepared. The antigen preparation employed was a partially purified mixture of human placental proteins that had been derivatized by reaction with pyridoxal 5'-phosphate and sodium borohydride. Spleen cells obtained from mice immunized with the phosphopyridoxyl protein preparation were fused with the mouse myeloma cell line designated X63-Ag8.653. The resulting hybridomas were screened for production of antibodies to the haptenic phosphopyridoxyl group using an enzyme-linked immunosorbent assay. Clones producing such antibodies were isolated by limiting dilution methods. The monoclonal antibodies obtained in this fashion have been characterized with respect to their ability to interact with various forms of vitamin B6. In addition, these antibodies have been shown to be useful in the detection of cellular pyridoxal phosphate binding components using immunoblot techniques. Monoclonal antibodies to vitamin B6 derivatives are potentially powerful tools in the assessment of vitamin B6 nutritional status and in the study of the roles of pyridoxal phosphate binding components in relation to growth, differentiation, carcinogenesis, and steroid hormone action.

Animals↗
PubMed1983

Enzyme-linked immunosorbent assay for use with nuclear protein-DNA complex antigens.

An enzyme-linked immunosorbent assay (ELISA) was developed for identification and quantification of nuclear antigens (nonhistone protein-DNA complexes from chromatin). Until now, the complement fixation assay has been the only immunoassay routinely applied to nonhistone protein-DNA complexes. The ELISA is considerably more sensitive than the micro-complement fixation test for assaying the immunospecificity of nuclear protein-DNA complexes. Dilutions of rabbit antisera as great as 1:6400 could be used to detect nanogram quantities of antigen, chicken reticulocyte chromatin or dehistonized rat liver chromatin.

Animals↗
PubMed1982

Studies on the role of protein synthesis and of sodium on the regulation of ornithine decarboxylase activity.

The minimum requirements for eliciting or enhancing ornithine decarboxylase activity (EC. 4.1.1.17); L-ornithine carboxylase) in neuroblastoma cells incubated in salts-glucose solutions have been investigated. These incubation conditions permit the study of changes in ornithine decarboxylase activity independently of the growth-associated reactions that occur in cell culture media (Chen, K.Y. and Canellakis, E.S. (1977) Proc. Natl, Acad. Sci. U.S.A. 74, 3791-3795). Ornithine decarboxylase activity can be elicited by a variety of asparagine and other amino acid analogs, including alpha-aminoisobutyric acid, that cannot participate in protein synthesis. Of the eleven asparagine analogs tested, alpha-N-CH3-DL-asparagine is the most potent in eliciting ornithine decarboxylase activity and is equivalent to asparagine in this regard. Inclusion of polar groups into the asparagine molecule results in the loss of its ability to elicit ornithine decarboxylase activity. With the use of these analogs and of analogs of other amino acids it is shown that the rapid fall in ornithine decarboxylase activity that is noted following cycloheximide treatment may not be a consequence of the inhibition of protein synthesis. The rapid fall in ornithine decarboxylase activity is primarily due to the removal of the agent that elicits and stabilizes its activity. These results, the finding that alpha-aminoisobutyric acid stimulates ornithine decarboxylase activity and that sodium is required for the stimulation of ornithine decarboxylase activity are discussed in relation to the "A" amino acid transport system.

Amino Acids↗
PubMed1978

Effects of an acridine half-mustard (ICR 191) on growth and ploidy of frog cells in culture.

The effects of an acridine half-mustard, ICR 191, on the growth rate and ploidy of four haploid and two diploid lines of Rana pipiens cells in culture were studied. Growth curves indicate that the haploid and diploid cell lines were equally resistant to a 4-hour exposure of this drug (0.1 micrometer to 10 micrometer. ICR 191 treatment induced the haploid cell cultures to become diploid. The proportion of diploid cells increased progressively with respect to time after the 4-hour exposure period. The greater the concentration of ICR 191 applied, the more rapid the rate of conversion. Autoradiographic determinations of percent labelled nuclei indicate that DNA synthesis was not inhibited in haploid or in diploid cells. Therefore, the increased proportion of diploid cells did not originate from the small percentage of diploid cells in the initial population. Instead the haploid cells were converted to diploid cells. Time lapse cinematography indicated that the conversion mechanism was other than cell fusion. Conversion to higher ploidy did not occur when diploid cell cultures were exposed to ICR 191.

Acridines↗
PubMed1978

Age-associated changes in glutamine synthetase activity in WI-38 cells.

The human fibroblast cell line WI-38 shows a gradual decline in glutamine synthetase specific activity with increasing age in culture. However, the level of functional enzyme per cell does not change with age. Heat inactivation profiles indicate that glutamine synthetase from younger cell cultures is more heat labile than that from older cultures. A possible explanation for these observations is that alterations in the glutamine synthetase molecule occur with increasing age of WI-38 cells in culture.

Cell Line↗