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E Glover

Publications and source records attributed to E Glover.

At least 37 records · Page 2Linked to original sources
PubMed1987

Variation in the molecular mass of the Ah receptor among vertebrate species and strains of rats.

The Ah receptor in eight vertebrate species was characterized by labeling the cytosolic fraction of tissue with the photoaffinity ligand, [125I]-2-azido-3-iodo-7,8-dibromodibenzo-p-dioxin, and analysis of the products by denaturing gel electrophoresis. The apparent molecular mass of the dominant labeled peptide showed appreciable species variation: mouse-95 kDa; chicken (embryo)-101 kDa; guinea pig-103 kDa; rabbit-104 kDa; rat-106 kDa; human-106 kDa; monkey-113 kDa, and hamster-124 kDa. Seven inbred strains of rats, had a Ah receptor ligand binding peptide of 106 kDa; however outbred Long-Evans rats were shown to be polymorphic expressing a 101 kDa and/or 106 kDa allelic forms. The notable frequency of structural variation in the Ah receptor is in contrast to the analogous highly conserved steroid hormone receptors.

Animals↗
PubMed1987

The murine Ah locus: a new allele and mapping to chromosome 12.

The Ah locus in mice, the presumed structural gene for the Ah receptor, is polymorphic in mice: some inbred strains carrying the Ahb allele express a high affinity receptor and are sensitive to receptor agonists, while other strains carrying the Ahd allele express a lower affinity receptor and are less sensitive to agonists. Using the photoaffinity ligand for the Ah receptor, [125I]-2-azido-3-iodo-7,8-dibromodibenzo-p-dioxin, we have identified two allelic forms of the high affinity receptor (Ahb). In mouse strains of the C57 and C58 family and MA/MyJ, the photoaffinity labeled peptide in hepatic cytosol has an apparent molecular mass of 95 kDa (Ahb-1 allele), whereas in other responsive strains (e.g., C3H/HeJ, BALB/cByJ, A/J) the labeled peptide has an apparent mass of 104 kDa (Ahb-2 allele). In genetic crosses and backcrosses between C57BL/6J and C3H/HeJ mice, the expression of these peptides is consistent with codominant inheritance of two alleles at a single locus. From Scatchard plots of the specific binding of the reversible ligand, [3H]-2,3,7,8-tetrachlorodibenzo-p-dioxin, to hepatic cytosol, most strains of mice with the Ahb-1 allele were found to have an Ah receptor with a binding affinity, KD, of 0.4-0.7 nM, and a receptor concentration of 130-160 fmol/mg of protein, whereas most strains carrying the Ahb-2 allele have a slightly lower receptor affinity, KD = 0.8-1.3 nM, and a slightly lower receptor concentration, 80-110 fmol/mg of protein. From analysis of the strain distribution pattern of the Ahb-1 and Ahb-2 alleles in recombinant inbred strains, the Ah locus was linked to several unmapped loci (H-17, H-38, Ltw-2, Ly-18, D1Nyul, D1Nyu2), and this entire group mapped to chromosome 12.

Alleles↗
PubMed1986

Photoaffinity labeling of the Ah receptor.

A series of halodibenzo-p-dioxins with the photolabile aryl azide functional group were synthesized and screened as potential photoaffinity labels for the Ah receptor, and 2-azido-3-iodo-7,8-dibromodibenzo-p-dioxin was selected for radiosynthesis with 125I (specific activity 2176 Ci/mmol, equilibrium dissociation constant, KD = 0.76 nM). Following incubation of this 125I-labeled photoaffinity ligand with the protamine sulfate-precipitated fraction of C57BL/6J mouse liver cytosol, and irradiation with long wavelength ultraviolet light, the radiolabeled macromolecules were precipitated with acetone and analyzed by denaturing gel electrophoresis and autoradiography. Among the labeled products, two peptides with apparent molecular masses of 95,000 and 70,000 daltons had the following properties: 1) they were selectively labeled at low ligand concentrations; 2) they were labeled in approximately a 1:1 ratio; 3) co-incubation with receptor agonists inhibited the photoaffinity labeling of both peptides to a similar extent, and structure activity relationship for inhibition of labeling by these agonists corresponded to that for their binding affinity to the Ah receptor; 4) upon nondenaturing chromatographic separation of photoaffinity labeled cytosol on high performance liquid chromatography size exclusion and anion exchange columns, the 95- and 70-kDa peptides coelute; 5) the migration of these peptides upon denaturing electrophoresis is the same in the presence or absence of a thiol reducing agent; and 6) proteolysis of the 95- and 70-kDa peptides produces a similar pattern of cleavage peptides. The simplest structure of the Ah receptor in mouse liver cytosol, appears to be a dimer composed of two noncovalently linked subunits of apparent molecular masses of 95 and 70 kDa, which have homologous structure and similar ligand binding sites, but other possibilities are discussed.

Affinity Labels↗
PubMed1985

Studies on the mechanism of action of halogenated aromatic hydrocarbons.

The halogenated aromatic hydrocarbons (dibenzo-p-dioxins, dibenzofurans, azo[xy]benzenes and biphenyls), a group of toxic chemicals in the environment, (a) are approximate isostereomers; (b) produce a similar pattern of biologic responses and (c) appear to act by a common mechanism. These compounds reversibly bind to a soluble receptor protein to initiate a coordinate gene expression, analogous to the action of steroid hormones. This receptor controls two distinct and dissociable pleiotropic responses: (a) the induction of microsomal monooxygenase activity and other drug metabolizing enzymes and (b) morphologic (i.e. toxic) changes, many of which involve altered cell proliferation and/or differentiation in epithelial tissues.

Animals↗
PubMed1985

Structure-activity relationship of bispyridyloxybenzene for induction of mouse hepatic aminopyrine N-demethylase activity. Chemical, biological, and X-ray crystallographic studies.

1,4-bis-[2-(3,5-Dichloropyridyloxy)]-benzene (TCPOBOP) was previously shown to be an extremely potent phenobarbital-like inducer of hepatic microsomal monooxygenase activity in the mouse. To examine the structure-activity relationship, 31 congeners of TCPOBOP were synthesized and tested for their potency to induce hepatic aminopyrine N-demethylase activity in B6D2F1/J mice. For biological activity, the minimum requirement is a) a central 1,4-dioxygenated benzene ring, b) lateral pyridine rings linked to the central ring by ether bonds, but with other lateral heteroaromatic rings, e.g., quinoline or pyrimidine, also active, c) 5,5'-substituents of Cl, Br, or NO2 on the pyridine rings. For a series of 5,5'-substituted and 3,3'-dichloro,5,5'-substituted bispyridyloxybenzenes, no correlation was observed for Hansch pi and sigma p values. To account for this lack of correlation and conformational variability produced by the two ether bonds, we performed x-ray structure determinations on three compounds: a) TCPOBOP, b) the 5,5'-dichloro analogue, and c) the biologically inactive, 3,3'-dichloro analogue. In the two biologically active congeners the positioning of the pyridine rings is anti to the plane of the central benzene ring, and the dihedral angle between the central ring and the pyridines is approximately 60 degrees. In the inactive analogue the pyridine rings are syn and the dihedral angle is 84 degrees. The x-ray crystallographic data are consistent with the ether oxygen having an sp2-bonding conjugating with the heterodipolar bond of the pyridine C(2)--N(1), which strongly restricts rotation about the ether bonds. The potency of TCPOBOP and other bispyridyloxybenzene analogues to induce a phenobarbital-like pleiotropic response and the sharply defined structure-activity relationship among these congeners support the hypothesis that they act by binding to a specific recognition site.

Aminopyrine N-Demethylase↗
PubMed1984

Histologic changes produced by 2,3,7,8-tetrachlorodibenzo-p-dioxin in the skin of mice carrying mutations that affect the integument.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) produces epidermal hyperplasia and hyperkeratosis, squamous metaplasia of the sebaceous gland, and keratinized cyst formation in 8 strains of mice with the recessive mutation, hairless (hr/hr). The extent of these histologic changes is dependent on the genetic background. No cutaneous lesions are produced in haired (hr/+) mice. In examination of mice with 7 other mutations affecting the integument, TCDD produced similar histologic skin changes in cryptothrix, nude, plucked, and atrichosis; a marginal squamous metaplasia of sebaceous glands in Repeated epilation, and had no effect in fur deficient and Naked mutants. These genetically determined epidermal responses are discussed in light of the mechanism of action of TCDD.

Alleles↗
PubMed1984

Nutrient intakes of female adolescents from eight southern states.

Nutrient intakes were calculated from two 24-hour recalls for 1,247 adolescent black and white girls. Whites consumed more vitamins E, C, and B-12, niacin, folacin, calcium, phosphorus, magnesium, and zinc and had higher intakes per 1,000 kcal of those nutrients, protein, vitamin D, and iron than blacks. Intakes of calcium (whites) and magnesium (both races) decreased with age. Urban girls consumed more energy and magnesium than rural ones. Folacin intake increased with income. Folacin intakes were most frequently below 67% RDAs, followed by intakes of iodine, vitamin D, iron, calcium, vitamin B-6, zinc, magnesium, and vitamin A. The majority of diets met or exceeded RDAs for protein, vitamins E, C, and B-12, riboflavin, and thiamin. Intakes are reported for most nutrients for which safe ranges have been set.

Adolescent↗
PubMed1983

The iron status of Black and white female adolescents from eight Southern states.

Hb, hematocrit, plasma iron, and transferrin saturation were measured in approximately 1000 girls aged 12, 14, or 16 yr in eight southern states. The iron status parameters did not differ significantly among the three age groupings or between menstruating and nonmenstruating girls. Blacks had significantly lower mean Hb (p less than 0.0001), hematocrit (p less than 0.0001), and transferrin saturation (p less than 0.05) levels than whites and a greater proportion of Blacks exhibited low Hb (p less than 0.05) and low hematocrit levels (p less than 0.01). Adjusting for dietary iron intakes and per capita income levels did not adequately account for significant race differences for iron status parameters. These findings support the contention that genetic as well as environmental factors are responsible for the frequently reported Black-white differences in Hb and hematocrit levels.

Adolescent↗
PubMed1979

An estimate of the maximum in vivo covalent binding of 2,3,7,8-tetrachlorodibenzo-p-dioxin to rat liver protein, ribosomal RNA, and DNA.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), an extraordinarily potent toxin, has recently been found to be a potent carcinogen producing mucosal, lung, and liver tumors in female rats. In light of this carcinogenicity, we reexamined the in vivo covalent binding of [3H]TCDD to rat liver macromolecules. Immature Sprague-Dawley rats, receiving [3H]TCDD (0.87 mCi/kg; specific activity, 39 Ci/mmol) concentrated 18 to 64% of the total administered dose in their livers, but virtually all of this radioactivity (greater than 99.9%) was extractable. The maximum unextractable radioactivity was: protein, 60 pmol TCDD per mol of amino acid residue; rRNA, 12 pmol TCDD per mol of nucleotide residue; and DNA, 6 pmol TCDD per mol of nucleotide residue. If one assumes that this small residual amount of radioactivity represents covalent binding, this binding is 4 to 6 orders of magnitude lower than that of most chemical carcinogens, and the binding to DNA is equivalent to one molecule of TCDD per DNA, equivalent to 35 cells. The results suggest it is unlikely that TCDD-induced oncogenesis is through a mechanism of covalent binding to DNA and somatic mutation.

Animals↗
PubMed1977

The interaction of hepatocyte plasma membranes with an azide derivative of procaine.

A photoreactive derivative of procaine, p-azidobenzoyldiethylaminoethanol hydrochloride, has been synthesized and used as a site-directed probe to label hepatocyte plasma membranes. The procaine derivative was shown to have membrane binding and Ca2+ displacement characteristics quite similar to that of procaine. Photolysis of the derivative in the presence of hepatocyte plasma membranes resulted in the covalent incorporation of the probe into both the protein and lipid fractions. Analysis of the labeled membranes by sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated that one membrane protein was significantly labeled with a molecular weight of 21 400 in addition to membrane lipids. Both binding and labeling could be inhibited in the presence of an excess of procaine. The labeled membrane components may be involved in the binding of Ca2+ to the membrane system.

Animals↗
PubMed1976

3,4,3',4'-Tetrachloro azoxybenzene and azobenzene: potent inducers of aryl hydrocarbon hydroxylase.

Two unwanted contaminants, 3,4,3',4'-tetrachloroazoxybenzene (TCAOB) and 3,4,3',4'-tetrachloroazobenzene (TCAB), formed in the commercial synthesis of 3,4-dichloroaniline or of herbicides made from 3,4-dichloroaniline, were responsible for three outbreaks of acne among chemical workers. TCAOB and TCAB are approximately isosteric to 2,3,7,8-tetrachlorodibenzo-p-dioxin and 2,3,7,8-tetrachlorodibenzofuran, two well-known contaminants that cause acne. All four of these agents are potent inducers of hepatic aryl hydrocarbon hydroxylase activity and compete for stereospecific binding sites in the hepatic cytosol, which are thought to be the receptor sites for the induction of this enzyme. Among the chlorinated azoxy and azobenzenes, the potency of a congener to induce aryl hydrocarbon hydroxylase activity correlates with its binding affinity for the hepatic cytosol specific binding sites and its capacity to induce acne; this relation between structure and activity parallels that observed for the chlorinated dibenzo-p-dioxins and dibenzofurans.

Acne Vulgaris↗
PubMed1976

Stereospecific, high affinity binding of 2,3,7,8-tetrachlorodibenzo-p-dioxin by hepatic cytosol. Evidence that the binding species is receptor for induction of aryl hydrocarbon hydroxylase.

We previously hypothesized that the genetic trait of aromatic hydrocarbon nonresponsiveness (the failure in certain inbred strains of mice of polycyclic hydrocarbons to induce aryl hydrocarbon hydroxylase activity, and the diminished sensitivity to the more potent inducer 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is due to mutation which results in an induction receptor with a diminished affinity for the inducing compound. Following the intraperitoneal administration of [14C]TCDD (6 nmol/kg), hepatic accumulation of the radiolabel was greatest in C57BL/6J mice, intermediate in the hybrid B6D2F1/J mice, and least in DBA/2J mice, a pattern which mirrors the strain sensitivity to hydroxylase induction by TCDD (C57BL/6J greater than B6D2F1/J greater than DBA/2J). These data are compatible with receptor mutation theory and suggested that the hepatic uptake of TCDD is determined by the affinity of the receptor. In vitro experiments on the binding of [3H]TCDD to hepatic cytosol from C57BL/6J mice revealed a small pool of high affinity sites which stereospecifically and reversibly bind TCDD. The specific binding of [3H]TCDD to hepatic cytosol had an equilibrium dissociation constant KD of 0.27 nM and a maximum binding capacity of 84 fmol/mg of cytosol protein. Much less high affinity specific binding of [3H]TCDD was observed in hepatic cytosol from DBA/2J mice, but the KD was not estimated because of the limited aqueous solubility of the ligand. The binding affinity of 23 halogenated dibenzo-p-dioxins and dibenzofurans for this hepatic cytosol-binding species closely correlated with the potencies of these compounds as inducers of hepatic aryl hydrocarbon hydroxylase activity. The polycyclic hydrocarbons that induce hepatic hydroxylase activity competed with [3H]TCDD for hepatic cytosol binding, but phenobarbital, pregnenolone-16alpha-carbonitrile, and the steroid hormones had no specific binding. The data suggest that the hepatic cytosol species which binds TCDD is the receptor for the induction of hepatic aryl hydrocarbon hydroxylase activity, and that the mutation in nonresponsive mice results in an altered receptor with a diminished affinity for inducing compounds.

Animals↗