Toshiko Hayatsu

Suppressing effect of Lactobacillus casei administration on the urinary mutagenicity arising from ingestion of fried ground beef in the human

It is known that the ingestion of cooked meat which contains carcinogenic heterocyclic amines causes increase in urinary mutagenicity in humans. Using 6 healthy non-smokers, we examined the effect of 3-week oral administration of Lactobacillus casei (bacilli commonly present in yoghurt), on the urinary mutagenicity derived from ingestion of fried ground beef. Comparison of the urinary mutagenicity found before and after the L. casei treatment showed that the treatment resulted in a decrease (6-67%, average 47.5%) of the mutagenicity. This suppressing effect is possibly related to the changes in the intestinal microflora population.

Adsorption of mutagens to cotton bearing covalently bound trisulfo-copper-phthalocyanine

A method for separating nonpolar mutagens from their dilute aqueous solutions is described. It utilizes the affinity of the mutagens to a phthalocyanine derivative attached to cotton through a covalent bond. For mutagens having 3 or more fused aromatic rings in their structures, efficient adsorption took place on soaking the cotton in their solutions. The mutagens adsorbed can be recovered by elution with ammoniacal methanol. Mutagenicity in smokers urine, cooked beef, and river water was detected by use of this method.

Inhibition of N-nitrosation of secondary amines in vitro by tea extracts and catechins

Inhibition of nitrite-mediated N-nitrosation of dimethylamine, morpholine and N-methylaniline by tea extracts and by 6 individual catechins in the extracts was studied. The inhibitions were detected by quantifying the nitrosamines formed. Eight different kinds of teas (5 green teas, a roasted green tea, an oolong tea, and a black tea) were examined for their inhibitory abilities and for their catechin contents, with an attempt to correlate the inhibitory activities to the catechin contents. The results showed that (1) the green tea extracts inhibit strongly the N-nitrosation of the three secondary amines tested, (2) the 6 catechins, notably epigallocatechin, are capable of blocking the N-nitrosations very efficiently, even more efficiently than ascorbic acid, and (3) the inhibition activities of green tea extracts are mostly ascribable to the catechins present in the extracts. These inhibitions occur by rapid reactions between nitrite and the catechins. It was observed that no mutagenicity results from the reaction between the tea extracts and nitrite.

Fecal mutagenicity arising from ingestion of fried ground beef in the human

Fried ground beef has been shown to contain mutagens, and the major mutagenic component has been identified as 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx). Mutagens in feces of 3 adult volunteers were fractionated by treatment of the feces with blue cotton followed by chromatography on a carboxymethyl cellulose column. The chromatographic fraction, corresponding to MeIQx in terms of the position of elution, was examined for mutagenicity in S. typhimurium TA98 with metabolic activation. When meals containing no heated meat were eaten, this fraction of feces showed little or no mutagenicity. On eating fried ground beef, the feces excreted in the next two days showed greatly increased mutagenicity in this fraction. By eating no-meat meal subsequent to the meat meal, the mutagenicity resumed the original low level on the fourth day after the meat meal. The components in the mutagenic fraction were probably metabolites of the mutagens present in cooked meat, since analysis by high pressure liquid chromatography of the mutagenic fraction showed that the active components in the feces were different from the mutagens in cooked meat.

Identification of mutagenic heterocyclic amines (IQ, Trp-P-1 and AαC) in the water of the Danube River

Three mutagenic heterocyclic amines, 2-amino-3-methylimidazo-[4, 5-f]quinoline (IQ), 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1) and 2-amino-9H-pyrido[2,3-b]indole (AalphaC), were isolated and identified in water from the Danube River in Vienna. Heterocyclic amines were extracted from river water by the blue rayon hanging method, and analyzed by gas chromatography with a nitrogen-phosphorous detector (GC-NPD) and GC-mass spectrometry (GC-MS) after conversion into their N-dimethylaminomethylene derivatives. Identity of IQ, Trp-P-1 and AalphaC in the river water was confirmed by GC-MS. The contents of IQ, Trp-P-1 and AalphaC were estimated by GC-NPD at 1.78+/-0.17, 0.14+/-0.02 and 0.44+/-0.02 ng/g blue rayon equivalent (n=3), respectively. The total amounts of these amines accounted for 26% of the mutagenicity of blue rayon extracts evaluated by the Ames test using TA98 with metabolic activation.

Porphyrins as potential inhibitors against exposure to carcinogens and mutagens

Studies have shown that there are many substances that can interfere with the actions of carcinogens and mutagens. Porphyrins, which often are constituents of diet, are a class of such inhibitors. Hemin can inhibit selectively the activity of mutagens having polycyclic structures by forming complexes with them. These effects were found with the use of bacterial assays and also by in vitro chemical experiments. A survey of porphyrins for similar effects has been done in our laboratory and it was found that chlorophyll and chlorophyllin act like hemin. These green pigments are antimutagenic in Salmonella and in Drosophila. Work from other laboratories also has supported the antimutagenic character of chlorophyllin. The possibility of modifying human exposure to carcinogens by use of these porphyrins is discussed. A porphyrin-like molecule, copper phthalocyanine trisulfonate, has been shown to have strong affinity to polycyclic compounds. Blue cotton, a cotton preparation bearing this blue pigment as a covalently bound ligand, has been demonstrated to be an adsorbent useful for isolating heterocyclic amines from food and other materials.

Inhibition of the mutagenicity of cooked-beef basic fraction by its acidic fraction

By using the Salmonella/microsome system, it was found that the activity of mutagens present in the basic fraction of cooked-ground-beef was completely suppressed by addition of the acidic fraction obtained from the cooked-beef. The suppression was ascribable to the presence of oleic acid in the acidic fraction. This finding indicates that no, or diminished, mutagenicity would be found in materials containing fat.

Protection against the bacterial mutagenicity of heterocyclic amines by purpurin, a natural anthraquinone pigment.

Purpurin (1,2,4-trihydroxy-9,10-anthraquinone) is a naturally occurring anthraquinone pigment found in species of madder root. We have found that the presence of purpurin in bacterial mutagenicity assays is responsible for a marked inhibition of mutagenicity induced by food-derived heterocyclic amines. Purpurin was found to be a better inhibitor of Trp-P-2-dependent mutagenicity than either epigallocatechin gallate or chlorophyllin both of which are well-established anti-mutagenic components of diet. Inhibition of Trp-P-2(NHOH) mutagenicity by purpurin was dependent upon pH. It was a better inhibitor in neutral than acidic conditions. Purpurin was protective against the direct mutagen Trp-P-2(NHOH) in both the presence and the absence of hepatic S9 but required pre-incubation. Finally, purpurin was responsible for the inhibition of human CYP1A2 and human NADPH-cytochrome P450 reductase and a decrease in the bioactivation of Trp-P-2 by these enzymes when they were expressed in Salmonella typhimurium TA1538ARO. However, inhibition of Trp-P-2(NHOH)-dependent mutations suggests purpurin also has a direct effect on this mutagen in addition to inhibiting its formation by CYP1A2.

Mutagenicity of chalks a case in which the test results led to the improvement of the quality of commercial goods

Mutagenicity testing, of methanolic extracts of chalks, by the Salmonella/mammalian-microsome system revealed that the blue and the green chalks contained mutagens. A positive mutagenic response was observed on Salmonella typhimurium strain TA98, both in the presence and absence of the microsome system (S9). The source of the mutagenicity was traced to the blue pigment used for manufacturing these chalks. The pigment, copper phthalocyanine, a product of a Japanese chemical industrial company, was found to contain impurities that were mutagenic. The mutagenic principle giving positive response in the TA98 in the presence of S9 was purified 10(5)-fold from the original pigment. Although its structure is yet to be elucidated, this indirect frame-shift mutagen had a strong activity: 5700 His+ revertants per microgram. This information, delivered in the beginning of 1981, prompted the manufacturer to start supplying a mutagen-free product. As a result, the blue chalks on the market became no longer mutagenic in the summer of 1982.