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Biomedical subjects

E C Miller

Publications and source records attributed to E C Miller.

At least 127 records · Page 7Linked to original sources
PubMed1977

Comparative electrophilicity, mutagenicity, DNA repair induction activity, and carcinogenicity of some N- and O-acyl derivatives of N-hydroxy-2-aminoflourene.

N-Myristoyloxy-N-acetyl-2-aminofluorene, N-acetoxy-N-myristoyl-2-aminofluorene, N-myristoyloxy-N-myristoyl-2-aminofluorene, and N-hydroxy-N-myristoyl-2-aminofluorene each yielded a high incidence of sarcomas in male rats within 5 to 7 months after s.c. injection of 64 micronmoles in divided doses. N-Acetoxy-N-acetyl-2-aminofluorene and N-hydroxy-2-acetylaminofluorene, although potent carcinogens at the s.c. site, were less active than the above derivatives with a myristoyl substituent. N-Sulfonoxy-N-acety--2-aminofluorene (purity larger than or equal to 70%) had little or no carcinogenic activity when administered in large amounts by s.c. injection to rats. The low incidence of tumors could have resulted from N-hydroxy-2-acetylaminofluorene or other decompostion products of the N-sulfonozy derivative. Each of the N-acetoxy and N-myristoyloxy derivatives of N-acetyl-2-aminofluorene and of N-myristoyl-2-aminofluorene showed electrophilic activity toward methionine; N-acetoxy-N-acetyl-2-aminofluorene was the most reactive and N-myristoyloxy-N-myristoyl-2-aminofluorine was the least reactive. Each of these esters also induced unscheduled tritiated thymidine incorportation in nondividing cultured human fibroblasts and thus appeared to induce lesions in DNA that lead to repair synthesis. EACH OF THE N-acetoxy derivatives was highly mutagenic for Salmonella typhimurium strains TA98 and TA1538 without tissue activation; neither N-myristoyloxy derivative was mutagenic under these conditions. While there was a qualitative correspondence between several of the above activities of these 2-aminofluorene derivatives, the quantitative differences and the lack of detectable mutagenicity of the 2N-myristoyloxy derivatives for S. typhimurium indicate the need for multiple short-term tests in the qualitative prediction of potential carcinogenic activity.

Animals↗
PubMed1976

Carcinogens occurring naturally in foods.

Humans are susceptible to the carcinogenic action of a small group of organic and inorganic chemicals in certain industrial, medical, and social habit exposures. A larger number and wider variety of chemical carcinogens, primarily organic compounds, are known for experimental animals. Chemical carcinogens are also found among the metabolites of living cells. No common structure is evident among chemical carcinogens, and a majority of these agents are precarcinogens that require metabolic activation into reactive electrophilic ultimate carcinogens. These strong electrophiles combine covalently with nucleophilic sites in DNAs, RNAs, and proteins in target tissues. One or more of these adducts appear to initiate carcinogenesis. About 20 naturally occurring organic chemical carcinogens, primarily metabolites of green plants and fungi, are known; some occur in some human foods. Many other naturally chemical carcingens doubtless exist among the vast number of uncharacterized nonnutritive minor components of living systems, some of which are sources of human foods. The electrophilic forms of chemical carcinogens are mutagenic, and mammalian tissue-mediated mutagenicity assays appear promising in the detection of potential chemical carcinogens. These assays should serve at least as a prescreen for conventional lifetime tests in rodents for the carcinogenic activity of food components and contaminants. Epidemiological approaches appear necessary to evaluate the importance of the naturally occurring chemical carcinogens in the occurrence of human cancer.

Aflatoxins↗
PubMed1976

Hepatocarcinogenicity of estragole (1-allyl-4-methoxybenzene) and 1'-hydroxyestragole in the mouse and mutagenicity of 1'-acetoxyestragole in bacteria.

Approximately 20% of a dose of estragole, a naturally occurring flavoring agent, was excreted in the urine of outbred male CD -1 mice as a conjuage (presumably the glucuronide) of 1'-hydroxyestragole, Estragole and its 1'-hydroxy metabolite caused significant increases in the incidences of hepatocellular carcinomas in male CD-1 mice that received the compounds by sc injection at 1-22 days of age. Estragole induced hepatocellular carcinomas by 15 months in 23 and 39% of the mice that received total doses of 4.4 and 5.2 mumoles, respectively, and lived to an age of 12 months or more. Of the 12-month survivors given a total dose of 4.4 mumoles of 1'-hydroxyestragole, 70% developed hepatocellular carcinomas; the incidence in mice that received only the vehicle (trioctanoin) was 12%. Multiple tumors ocurred in 5, 28, 64, and 0%, respectively, of the mice in each of these 4 groups. Of the mice given a total dose of 4.4 mumoles of 1'-hydroxysafrole, 59developed hepatocellular carcinomas; 39% of the mice bore multiple liver tumors. As previsously demonstrated for 1'-acetoxysafrole, 1'-acetoxyestragole and 1'-acetoxy-1-allyl-4-methoxynaphthalene reacted nonenzymatically with guanosine and inosine to form adducts. These electrophilic esters were strongly mutagenic for the Salmonella typhimurium missense mutant TA100. 1'-Acetoxyallybenzene had little or no activity in either of these tests. Attempts to demonstrate liver-mediated mutagenicty for 1'-hydroxysafrole and 1'-hydroxyestragole in the bacterial test system were unsuccessful.

Allylbenzene Derivatives↗
PubMed1976

Endogenous oncornaviruses in chemically induced transformation. II. Effect of virus production in vivo.

C3H/HeJ and AKR/J mice differed in their susceptibility to 3-methylcholantrhene (MCA)-induced sarcomagenesis (86% incidence of sarcomas in C3H by 18 wk; 5% incidence in AKR by 18 wk) and in the production of endogenous murine leukemia virus (MuLV) (AKR produced greater than 10(5) plaque-forming units/ml tail extract in XC test; C3H did not produce detectable virus.) A genetic corss between C3H and AKR mice was examined to determine the relationship of virus production to oncogenesis by MCA. Mice of the (C3H X AKR)F X C3H backcross were typed for the production of infectious MuLV by tail biospy and then inoculated with MCA. Of the backcross mice, 81% produced high titers of ecotropic MuLV; the remaining 19% did not contain detectable infectious MuLV. The virus-producing and non-virus-producing backcross mice were equally sensitive and highly susceptible to MCA-induced sarcomagenesis. Tumors of all virus-positive mice contained infectious MuLV. Some tumors (54%) of virus-negative mice also contained infectious MuLV; this indicated the induction of endogenous MuLV in the tumors of these mice. We concluded that the overt production of MuLV in mice of this backcross did not function in the sensitivity of the mice to sarcoma induction by MCA. Furthermore, the presence of virus in some chemically induced tumors was due to an induction pehnomenon independent of the primary oncogenic event.

Animals↗
PubMed1976

The metabolic activation of the carcinogen 1'-hydroxysafrole in vivo and in vitro and the electrophilic reactivities of possible ultimate carcinogens.

Administration of [2',3'-3H]-1'-hydroxysafrole to rats or mice resulted in the formation of hepatic DNA-, ribosomal RNA-, and protein-bound 3H derivatives. Alkaline digestion of the 3H-protein released 0.1 to 0.3% of the 3H as a derivative that was identified as 3'-methylmercaptoisosafrole by its cochromatography in five solvent systems with the synthetic compound. 1'-Hydroxysafrole was metabolized at a low rate by rat and mouse liver cytosols in a 3'-phosphoadenosine 5'-phosphosulfate-dependent reaction to a derivative (presumably the sulfuric acid ester) that was captured by its reaction with RNA. Likewise, 1'-hydroxysafrole was oxidized at a low rate by rat and mouse liver microsomes to 1'-hydroxysafrole-2',3'-oxide in a reduced nicotinamide adenine dinucleotide phosphate-dependent reaction. Both of these electrophilic metabolites are candidate ultimate carcinogenic derivatives of 1'-hydroxysafrole. The electrophilic reactivities of various safrole derivatives with nucleosides were determined to be in the order of 1'-oxosafrole greater than 1'-acetoxysafrole greater than 1'-acetoxysafrole-2',3'-oxide greater than 1'-hydroxysafrole-2',3'-oxide greater than safrole-2',3'-oxide greater than or equal to 1'-oxosafrole-2',3'-oxide. The major reactions were generally observed with guanosine. A major reaction product of 1'-acetoxysafrole and guanosine 5'-monophosphate yielded 3'-hydroxyisosafrole under very mild acidic conditions. These data further substantiate the previous characterization of this reaction product as O-6-(isosafrol-3'-yl)guanylic acid. The syntheses of 1'-oxosafrole, 2',3'-dehydrosafrole, [2',3'-3H]-1'-hydroxysafrole, and the 2',3'-oxed.

Acetyltransferases↗
PubMed1976

Microsomal N-oxidation of the hepatocarcinogen N-methyl-4-aminoazobenzene and the reactivity of N-hydroxy-N-methyl-4-aminoazobenzene.

The N-oxidation of the hepatocarcinogen N-methyl-4-aminoazobenzene (MAB) was catalyzed by hepatic microsomes in a reduced pyridine nucleotide- and oxygen-dependent reaction. The initial N-oxidation product, N-hydroxy-N-methyl-4-aminoazobenzene (N-HO-MAB), was readily oxidized to a second product that yielded N-hydroxy-4-aminoazobenzene upon subsequent acid treatment. The secondary N-oxidation product may be formed nonenzymatically and is presumed to be N-HO-MAB N-oxide or its dehydrated derivative, N-(p-phenylazophenyl)nitrone. Under the same conditions, MAB was also oxidatively N-dealkylated to 4-aminoazobenzene, which was N-oxidized to N-hydroxy-4-aminoazobenzene. Unlike the latter reactions, the microsomal N-oxidation of MAB was independent of cytochrome P-450, as shown by its lack of sensitivity to inhibition by 2-[(2,4-dichloro-6-phenyl)phenoxy]ethylamine and its inability to utilize cumene hydroperoxide in place of reduced pyridine nucleotides and oxygen. The N-oxidation of MAB was also catalyzed by the purified microsomal flavoprotein mixed-function amine oxidase of Ziegler et al. The noncarcinogenic dye N-ethyl-4-aminoazobenzene was metabolized similarly to MAB. For male animals the hepatic levels of MAB N-oxidase activity were in the order: rat greater than hamster, guinea pig greater than mouse, rabbit. Little or no MAB N-oxidase activity was present in several extrahepatic rat tissues. N-HO-MAB, N-hydroxy-N-ethyl-4-aminoazobenzene, and N-hydroxy-4-aminoazobenzene catalyzed the aerobic oxidation of cysteine and glutathione. These hydroxylamines also bound covalently to proteins. The binding of N-HO-MAB with nucleic acids was only 3 to 6% that observed with serum albumin. Under anhydrous conditions the nitrone generated aerobically from N-HO-MAB reacted with carbon-carbon or carbon-nitrogen double bonds, or both, in fatty acids, retinol, purines, and pyrimidines to yield isoxazolidine and/or oxadiazolidine addition products. The nitrone from N-hydroxy-N-ethyl-4-aminoazobenzene was much less reactive under these conditions. Syntheses of N-HO-MAB and N-hydroxy-N-ethyl-4-aminoazobenzene are reported.

Aminobenzoates↗
PubMed1976

Hepatic metabolism of N-hydroxy-N-methyl-4-aminoazobenzene and other N-hydroxy arylamines to reactive sulfuric acid esters.

Hepatic cytosols catalyzed a 3'-phosphoadenosine 5'-phosphosulfate (PAPS)-dependent O-sulfonation of N-hydroxy-N-methyl-4-aminoazobenzene (N-HO-MAB) and of several other N-hydroxy arylamines. The presumed product from N-HO-MAB, N-methyl-4-aminoazobenzene-N-sulfate, reacted with added guanosine to yield N-(guanosin-8-yl)-N-methyl-4-aminoazobenzene, with methionine to form a sulfonium derivative that decomposed to yield 3-methylmercapto-N-methyl-4-aminoazobenzene, and with ribosomal RNA to give a bound derivative. N-Methyl-4-aminoazobenzene was converted to N-(guanosin-8-yl)-N-methyl-4-aminoazobenzene in concerted N-oxidation and O-sulfonation reactions conducted aerobically with a fortified 10,000 X g rat liver supernatant. In the absence of an added nucleophile, metabolically formed N-methyl-4-aminoazobenzene-N-sulfate (or the nitrenium ion from this unstable ester) was reduced by N-HO-MAB to form N-methyl-4-aminoazobenzene; the N-HO-MAB was oxidized, probably through a nitrone intermediate, to yield products that included N-hydroxy-4-aminoazobenzene and formaldehyde. An analogous reaction was noted between N-benzoyloxy-N-methyl-4-aminoazobenzene and N-HO-MAB in the absence of cytosol and PAPS. Hepatic N-HO-MAB sulfotransferase activities were in the order: male rat greater than female rat, male rabbit, male guinea pig, male mouse greater than male hamster. Male rat kidney and small intestine cytosols had low activities; the other tissues studied had little or no activity. Hepatic sulfotransferase activities for N-HO-MAB and N-hydroxy-N-acetyl-2-aminofluorene displayed different pH optima and inhibitor and activator responses. The rates of PAPS-dependent rat liver cytosol-catalyzed esterification of N-hydroxy-N-ethyl-4-aminoazobenzene, N-hydroxy-4-aminoazobenzene, and N-hydroxy-1- and 2-naphthylamine were 20 to 50% of that for N-HO-MAB. Activities for trans-N-hydroxy-4-aminostilbene, N-hydroxy-2-aminofluorene, N-hydroxyaniline, and N-hydroxy-N-methyl-N-benzylamine were not detected. No microsomal reduced nicotinamide adenine dinucleotide-dependent reduction or reduced nicotinamide adenine dinucleotide phosphate-dependent oxidation or cytosolic transferase reactions for N-HO-MAB, except the above-described PAPS-dependent reaction, were detected in rat liver.

2-Naphthylamine↗
PubMed1975

The reactivity and carcinogenicity of aflatoxin B1-2,3-dichloride, a model for the putative 2,3-oxide metabolite of aflatoxin B1.

Aflatoxin B1-2,3-dichloride (AFB1-Cl2) was synthesized as a model for the probable ultimate carcinogen, aflatoxin B1-2,3-oxide. As expected for aflatoxin B1-2,3-oxide, AFB1-Cl2 has an electrophilic carbon 2; it decomposed in water (half-life of 0.5 min in 10% dimethyl sulfoxide, pH 7.4) with the formation of 3-chloro-2,3-dihydro-2-hydroxyaflatoxin B1 and 2,3-dihydro-2,3-dihydroxyaflatoxin B1. AFB1-Cl2 formed covalent adducts with DNA and RNA with retention of one-half of the chlorine; the major products apparently contained glycosidic bonds between carbon 2 of the aflatoxin residues and nitrogen or oxygen atoms in the nucleic acids. Polyguanylic acid was the most reactive homopolymer toward AFB1-Cl2. AFB1-Cl2 was less reactive toward mononucleotides than toward polynucleotides. The major adducts formed on incubation of AFB1-Cl2 with protein contained little chlorine and could have resulted from alkylation of primary amino groups or from reactions with the hydrolysis products. Similarly, incubation of AFB1-Cl2 with amino acids apparently resulted in Schiff base formation between primary amino groups and the dialdehyde rearrangement forms of the hydrolysis products of AFB1-Cl2. AFB1-Cl2 was much more active than aflatoxin B1 in inducing sarcomas at the s.c. injection site in rats, in the initiation of papillomas on the skin of mice, and in the induction of lung tumors in mice. AFB1-Cl2 was also highly mutagenic for Salmonella typhimurium TA 98 and TA 100. Aflatoxin B1 and its 2,3,-dihydro- (aflatoxin B2), 2,3-dihydro-2-hydroxy- (aflatoxin B2a), 2,3-dihydro-2,3-dihydroxy-, and 3-chloro-2,3-dihydro-2-hydroxy- derivatives were inactive in the mutagenicity tests; and the latter four compounds were also inactive as initiators of papillomas of the skin in mice. The structures of the macromolecular adducts of AFB1-Cl2 formed in vitro, the carcinogenicity of this electrophile, and the lack of carcinogenicity of its hydrolysis products indicate that alkylation of nucleic acids is a critical reaction in tumor induction with this carcinogen and aflatoxin B1.

Aflatoxins↗
PubMed1975

N-substitution of carbon 8 in guanosine and deoxyguanosine by the carcinogen N-benzoyloxy-N-methyl-4-aminoazobenzene in vitro.

The major reaction products of the carcinogenic electrophile N-benzoyloxy-N-methyl-4-aminoazobenzene with guanosine or deoxyguanosine were characterized as N-(guanosin-8-yl)- and N-(DEOXYGUANOSIN-8-YL)-N-methyl-4-aminoazobenzene from the following chemical, radiochemical, and spectroscopic studies: (a) the presence of equimolar amounts of both N-methyl-4-aminoazobenzene (MAB) and guanosine or deoxyguanosine residues was shown by the 3H:14C ratios of the products from the reaction of (prime ring-3H)-N-benzoyloxy-N-methyl-4-aminoazobenzene with (8-14C)guanosine or (8-14C)deoxyguanosine and by the molecular weights of the trimethylsilyl derivatives of both products: (b) substitution of the dye residue on its amino nitrogen was indicated by the retention in the products of the 3H:14C ration of (CH2-3H + 14CH3)-N-BENZOYLOXY-N-methyl-4-aminoazobenzene and by the release of MAB on treatment of the nucleoside-dye derivatives with strong alkali in air; (c) substitution of the guanine residues in positon 7 or 8 was demonstrated by loss of 3H from (8-3H)guanosine or (8-3H)deoxyguanosine in the formation of the nucleoside-dye derivatives; (d) the stability of the products to mild alkali (as contrasted to the lability of 7-alkylguanosines) provided strong evidence that the substitution was in position 8 of the guanine residue; (e) direct evidence of 8-substitution came from the acid hydrolysis of guanosinyl- and deoxyguanosinyl-N-methyl-4-aminoazo benzene to N-(guan-8-yl)-N-methyl-4-aminoazobenze in up to 50% yield; (f) comparisons of the proton or 13C nuclear magnetic resonance spectra or both of N-(guan-8-yl)- N-methyl-4-aminoazobenzene, MAB, N-(guanosin-8-yl)-2-acetylaminofluorene, 2-acetylaminofluorene, guanosine, and 7 -methylguanosine with the spectra of the guanosine-MAB product further confirmed that substitution had occurred at position 8 of the guanosine residue. The new compound N-(guan-8-yl)-N-methyl-4-aminoazobenzene was synthesized. Attempts to devise an unambiguous synthesis of N-(GUANOSIN-8-YL)-N-methyl-4-aminoazobenzene were not successful.

Amines↗
PubMed1975

Structures of hepatic nucleic acid-bound dyes in rats given the carcinogen N-methyl-4-aminoazobenzene.

Rats were given the hepatocarcinogenic dye N-methyl-4-aminoazobenzene labeled in the prime ring with tritium. The hepatic ribosomal RNA and DNA from these rats were hydrolyzed to uoe;d imce;psode-dye products. The major nucleoside-dye derivatives cochromatographed with synthetic N-(guanosin-8-yl)-and N-(deoxyguanosin-8-yl)-N-(methyl-4-aminoazobenzene, respectively, on cellulose and silica gel thin layers in several solvent systems. Additional evidence for the characterization of the hepatic RNA-nucleoside derivative was obtained through its degradation by alkali in air to N-methyl-4-aminoazobenzene and -4-aminoazobenzene, as previously described for N-(guanosin-8-yl)-N-methyl-4-aminoazobenzene. The same nucleoside derivatives were also derived from ribosomal RNA and DNA reacted in vitro with the carcinogenic electrophilic derivative N-benzoyloxy-N-methyl-4-aminoazobenzene, esterification of the N-hydroxy derivative, and reaction of the resultant electrophilic esters with DNA and RNA.

Amines↗
PubMed1975

The carcinogenic and electrophilic activities of N-benzoyloxy derivatives of N-methyl-4-aminoazobenzene and related dyes.

The N-benzoyloxy derivatives of N-methyl-4-aminoazobenzene, its 4'-methyl and 4'-ethyl derivatives, and N-ethyl-4-aminoazobenzene were synthesized for comparison of their carcinogenic activities and their reactivities with nucleophilic reagents. Each of the 4 esters had a similar degree of nonenzymatic reactivity with methionine and guanosine at neutral pH. Each of the dyes induced sarcomas at the site of s.c. injection in rats, but N-benzoyloxy-N-methyl-4-aminoazobenzene was considerably more carcinogenic than were any of the other dyes. N-benzoyloxy-N-methyl-4-aminoazobenzene was also more stable in neutral lipid, and this stability may have contributed to its greater carcinogenicactivity. Neither the electrophilic reactivities nor the s.c. carcinogenicities of these dyes paralleled the hepatocarinogenic activities of the parent dyes.

Aniline Compounds↗