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F T Hatch

Publications and source records attributed to F T Hatch.

At least 19 recordsLinked to original sources
PubMed1992

Quantitative correlation of mutagenic and carcinogenic potencies for heterocyclic amines from cooked foods and additional aromatic amines.

Aromatic amines have long been recognized as animal and human carcinogens. Recently heterocyclic aromatic amines (thermic amines) have been found in small amounts in cooked foods, primarily meats, and have proven to be potent mutagens and rodent carcinogens. Availability of quantitative databases for mutagenic potency in Salmonella and for carcinogenic potency in rodents has made possible a study of ten heterocyclic thermic amines and 24 aromatic amines. Potencies on mutagenic and carcinogenic scales were significantly correlated. By multiple linear regression analysis and multivariate analysis of variance, two descriptive structural factors were found to modulate the two modes of biological response. These factors were number of rings and methyl substitution at carbon atoms. The quantitative correlation between mutagenic and carcinogenic potencies and the modulating structural factors suggest a significant similarity of molecular mechanisms and support the utility of the short-term bacterial assay in evaluating hazard levels.

Amines↗
PubMed1991

Quantitative structure-activity relationships of heterocyclic amine mutagens formed during the cooking of food.

The major protein-rich foods, particularly muscle meats, contain part-per-billion quantities of potent mutagens formed by frying or broiling to a well-done state. Related mutagens are formed by pyrolysis of amino acids or proteins and in heated model systems. The thermic mutagens so far identified are heterocyclic aromatic amines of aminoimidazo-azaarene (AIA) and aminocarboline classes. The chemicals require activation by enzymes to form metabolites reactive with nucleic acids. These thermic mutagens, and numerous synthetic congeners, exhibit an enormous range of potency as frameshift mutagens in the Ames/Salmonella assay. However, structural variations are nominal within the two classes. Structural parameters that appeared relevant to determining potency were selected for 38 AIAs and 23 amino-carbolines. For the AIA class these were: the number of fused rings, the number of heteroatoms in Rings 2 and 3, methyl substitution on imidazo ring nitrogen atoms, and methyl substitution on ring carbon atoms. For the amino-carboline class the structural parameters were: the position of the pyridine-type nitrogen atom in Ring 1, the substitution position of the exocyclic amino group on Ring 1, and methyl substitution on ring carbon atoms. These structural parameters may influence mutagenic potency in the following ways. 1) Electronic or steric effects may determine the reactivity and stability of the ultimate mutagenic metabolite. Optimal balance of reactivity and lifetime of this transient intermediate may be required for access to and reaction with nuclear DNA to cause mutations. 2) Substitution on the rings may block detoxication reactions. The structural parameters identified should prove useful in predicting the mutagenicity of untested compounds of these types.

Amines↗
PubMed1986

The isolation and identification of a new mutagen from fried ground beef: 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP).

A new mutagenic compound has been isolated from ground beef which was fried at 300 degrees C for 5.5 min on each side. The new mutagen was purified using an aqueous acid extraction, XAD-2 adsorption-solvent elution, a series of preparative and analytical h.p.l.c. purification steps, and monitored with the Ames/Salmonella assay. This study reveals a new mutagen member of the amino-imidazoazaarene class of aromatic amines, having a mol. w of 224, and a formula of C13H12N4 as determined by high-resolution mass spectrometry. N.m.r. spectrometry supports the structure, 2-amino-1-methyl-6-phenyl-imidazo[4,5-b]pyridine (PhIP), for the new mutagen. The 1-methyl and 3-methyl synthesized isomers of PhIP were compared to the purified mutagen. The two isomers had identical mass spectra to the purified compound, but only the 1-methyl isomer showed similar u.v. and n.m.r. spectra. The two synthetic isomers were separable by h.p.l.c. and the beef derived component co-eluted with the 1-methyl-PhIP isomer. PhIP has a specific activity in the Ames/Salmonella assay of 1950 revertants/microgram. Although it is not as mutagenic as other compounds isolated from fried beef (e.g. MeIQx, 58 000 revertants/microgram) it is the most abundant mutagenic compound by mass in fried beef. PhIP is present at approximately 15 p.p.b. of the original weight of uncooked beef (accounting for 75% of the mass of genotoxic material) and contributes 18% of the total mutagenicity of the fried beef.

Animals↗
PubMed1986

Identification of the mutagens in cooked beef.

The purification of cooking mutagens depends on the extraordinary sensitivity of the Ames/Salmonella mutagenicity test and its usefulness for tracking the mutagens during the purification steps. Following aqueous/acid (pH 2) extraction of fried ground beef (cooked at 200, 250, or 300 degrees C), XAD-2 column adsorption and elution with acetone, and acidic and basic liquid/liquid extractions, the samples are separated into six distinct peaks with preparative reverse-phase HPLC. A total of nine distinct mutagens can be separated after two additional HPLC steps. These compounds fall into a class of compounds called aminoimidazoazaarenes (AIAs). The majority of the mutagenic activity is made up of MeIQx1 (m/z 213, C11H11N5), DiMeIQx (m/z 227, C12H13N5), trimethylimidazopyridine (TMIP) (m/z 176, C9H12N4) and phenylimidazopyridine (PhIP) (m/z 224, C13H12N4). Smaller contributions are from IQ (m/z 198, C11H10N4), MeIQ (m/z 213, C12H12N4), a nonpolar peak containing oxygen and two unidentified trace polar mutagens. Mass estimates (per kilogram uncooked beef) include: 15 micrograms for PhIP, 1.0 micrograms for MeIQx, 0.5 microgram for DiMeIQx, and 0.02 microgram for IQ. Because of the uncoupling of mutagenic and carcinogenic potencies of these aromatic amines, the PhIP, which contributes the highest mass content to the cooked meat, but has the lowest mutagenic potency, might ultimately make a significant contribution to the carcinogenicity.

Animals↗
PubMed1986

A current genotoxicity database for heterocyclic thermic food mutagens. I. Genetically relevant endpoints.

Cooking, heat processing, or pyrolysis of protein-rich foods induce the formation of a series of structurally related heterocyclic aromatic bases that have been found to be mutagens. The primary genetic assay utilized to detect and isolate these mutagens has been the his reversion assay in Salmonella typhimurium. The classification and nomenclature of these chemicals is revised to reflect recent advances. The findings of short-term tests for genetic injury that have been applied to these agents are presented in a systematic way. Cell-free, bacterial, mammalian cell culture, and in vivo systems are included. Major results, the mutagens tested, and key references are presented in tabular form, with text commentary. Integrated conclusions on the state of current knowledge of the genetic toxicity of thermic food mutagens are presented. Areas in need of further research are defined. Finally, an outline is presented of a suggested path leading to the determination whether normal methods of food preparation and processing constitute a human health hazard.

Animals↗
PubMed1985

Effects of temperature, patty thickness and fat content on the production of mutagens in fried ground beef.

The high-pressure liquid chromatography (HPLC) profiles of mutagenic components were compared for extracts of ground beef patties fried at 200, 250 and 300 degrees C for 6 min/side. The HPLC profiles of the mutagenic samples were similar, although total mutagenic activity in Salmonella typhimurium TA1538 was roughly four times as high after the 300 degrees C than after the 200 degrees C frying. Six mutagenic peaks were analysed quantitatively at different temperatures and meat thicknesses. Two major components, 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline and 2-aminotrimethylimidazo[4,5-f]quinoxaline, and a minor component, 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), were all present at the three different temperatures. Thus, in general, cooking temperature seems to have a major effect on the quantities of mutagens produced but not on their HPLC profiles. The thickness of the meat patty did not affect the total yield of mutagens except at longer cooking times (8-10 min/side) and, in general, neither did it affect the HPLC profiles of the mutagenic components. Total mutagenic activity increased with increasing cooking times. Increasing the fat content lowered the total mutagenicity, with 150,000 revertants/kg of fresh beef at 30% fat compared with 230,000 revertants/kg at 15%, but had little effect on the mutagenicity due to IQ.

Animals↗
PubMed1979

Separation of satellite DNA chromatin and main band DNA chromatin from mouse brain.

Using restriction endonucleases which preferentially digest mouse main band DNA and leave satellite DNA intact, we have isolated highly purified chromatin fractions containing only mouse satellite or main band DNA. Following the digestion of mouse brain nuclei with EndoR Alu I, main band DNA chromatin is selectively extracted with 10mM Tris, 10mM EDTA. Satellite DNA chromatin is subsequently extracted from the nuclear pellet with Tris-3M urea and further purified on sucrose gradients. Chromatin extracted from digested nuclei with Tris-EDTA contains only main band DNA and has a molecular weight lower than 2 x 10(6). Chromatin fractions obtained from the lower regions of sucrose gradients of the Tris-Urea extracts contain 40--95% satellite DNA and have a molecular weight of 6 to 8 x 10(6). Both the satellite DNA and main band DNA chromatins contain all five histones and have a protein to DNA ratio of 1.3 to 1.

Animals↗
PubMed1977

Similarity of satilite DNA properties in the order Rodentia.

We have characterized satellite DNAs from 9 species of kangaroo rat (Dipodomys) and have shown that the HS-alpha and HS-beta satellites, where present, are nearly identical in all species as to melting transition midpoint (Tm), and density in neutral CsCl, alkaline CsCl, and Cs(2)SO(4)-Ag(+) gradients. However, the MS satellites exist in two internally similar classes. The satellite DNAs from three other rodents were characterized (densities listed are in neutral CsCl). The pocket gopher, Thomomysbottae, contains Th-alpha (1.713 g/ml) and Th-beta (1.703 g/ml). The guinea pig (Caviaporcellus) contains Ca-alpha, Ca-beta and Ca-gamma at densities of 1.706 g/ml, 1.704 g/ml and 1.704 g/ml, respectively. The antelope ground squirrel (Ammospermophilusharrisi) contains Am-alpha, 1.708 g/ml, Am-beta, 1.717 g/ml, and Am-gamma, 1.707 g/ml. The physical and chemical properties of the alpha-satellites from the above four rodents representing four different families in two suborders of Rodentia were compared. They show nearly identical Tm, nucleoside composition of single strands, and single strand densities in alkaline CsCl. Similar comparisons on the second or third satellite DNAs from these rodents also indicate a close relationship to each other. Thus the high degree of similarity of satellite sequences found in such a diverse group of rodents suggests a cellular function that is subject to natural selection, and implies that these sequences have been conserved over a considerable span of evolutionary time since the divergence of these rodents about 50 million years ago.

Animals↗
PubMed1976

Satellite DNA and cytogenetic evolution. DNA quantity, satellite DNA and karyotypic variations in kangaroo rats (genus Dipodomys).

The genus Dipodomys (kangaroo rats) exhibits major interspecies variations in the proportions of highly reiterated satellite DNA sequences in the genome as well as in the chromosome number and the proportions of uni-armed and bi-armed chromosomes. For nearly all of the approximately 22 species of the genus and several subspecies, liver DNA was distributed in neutral CsCl buoyant density gradients into four fractions; principal DNA (1.698 g/ml), intermediate-density DNA (1.702 G/ML), MS satellite (1.707 g/ml) and HS (heavy satellites (1.713 g/ml). The total nuclear DNA content of diploid liver cells measured in eleven species by quantitative cytophotometry, ranged from 6.9 to 10.9 pg. These data were correlated with known features of the karotypes of individual species. The salient findings were: (1) that interspecies variations in diploid chromosome number cluster at 52-54, 60-64 and 70-72 (2) that high total nuclear DNA was associated with high chromosome number, and with relatively large amounts of satellite DNA (3) that a high ratio of HS satellites to intermediate-density DNA was generally correlated with a predominance of metacentric and submetacentric chromosomes (high fundamental number). The relationships of satellite DNA to karyotype structure reveal a new level of hierarchy in the genome that appears capable of exerting global control over environmental adaptation and the evolution of new species. This mechanism is consistent with recent hypotheses that changes in the macro-structure of the genome are more important than point mutations in facilitating the rapid phases of animal evolution.

Animals↗
PubMed1976

Single-strand nuclease action on heat-denatured spermiogenic chromatin.

The aim of this study was to compare the sensitivity of chromatin from representative cellular stages of spermiogenesis to a single-strandeded nuclease after heat denaturation. Thermal denaturation of chromatin was assayed in situ in fixed round, elongating and elongated spermatids and in testicular sperm from mice. Production of single-stranded deoxyribonucleic acid (DNA) at elevated temperatures was monitored by digesting chromatin with endonuclease specific for single-stranded DNA (S1 nuclease), staining the residual DNA with gallocyanin-chrome alum (GAC) and measuring the stain content by absorption cytophotometry. Changes in GCA staining were minimal over the temperature range of 22-90 degrees C in each cell type not exposed to nuclease. Staining of undigested cells decreased progressively with advancing cell maturity. Nuclease had no effect on the GCA content of round spermatids below 60 degrees C, but above this temperature there was a progressive decrease in GCA-stainable chromatin. Both round and elongating spermatid stages showed a significantly greater sensitivity to nuclease digestion than did more mature stages; sperm showed no effects of nuclease action below 80 degrees C. Progressive chromatin condensation and a concomitant decrease in the number of available DNA phosphate groups during spermiogenic cell maturation may be responsible for the observed decline in sensitivity to nuclease and decreased GCA staining. Thermal denaturation of round spermatids labeled with 3H-thymidine produced no change in autoradiographic mean nuclear grain counts, indicating no loss of thymidine-labeled DNA from the slides during denaturation. When round spermatids and sperm were hydrolyzed with hot tricholoroacetic acid before staining, both nuclear GCA content and autoradiograph grain count were partially reduced, indicating incomplete DNA removal. Almost complete loss of Feulgen-stainable material occurred in these cells and may be due to depurination and elimination of Feulgren-reactant aldehyde groups.

Animals↗