Komei Miyaki

Effects of age and starvation on the gastrointestinal microflora and the heat resistance of fecal bacteria in rats.

The microflora of the gastrointestinal tract in rats 1 day to 100 weeks old, of the cecal contents and wall in starved rats, and of heat‐treated feces of normal rats was determined by cultural examination. Streptococci, staphylococci, lactobacilli, actinobacilli, and coliforms colonized the tract during the 1st week of life. Bacteroidaceae, veillonellae, catenabacteria (composed of eubacteria and anaerobic lactobacilli), clostridia, bifidobacteria, anaerobic gram‐positive cocci, fusiform bacteria, curved rods, and spirochetes appeared when the rats were 2 to 4 weeks old. Yeasts were slower in colonizing the tract than any other organism. Dramatic changes occurred in the microflora of rats 2 to 4 weeks of age. There was a time lag between the changes in enterococcal and coliform populations. The enterococcal population was depressed over a period from 2 to 6 weeks of age. Bifidobacteria showed a larger population at 4 to 9 weeks than at any other age. The microflora of the stomach was the same as that of the small intestine, with some exceptions. It differed markedly from that of the cecum. The ratio of total aerobic count to anaerobic count gradually increased in the stomach, but decreased in the cecum, with advance in age. The microorganisms distributed in the tract could be divided roughly into 3 types. The population of each organism, except spirochetes, in the cecal wall was approximately 1/1,000 of that in the cecal contents. One of the 2 types of spirochetes was found only in the cecal wall and in a high incidence, forming a large population. In rats starved for 48 hr, coliforms, Proteus spp., anaerobic gram‐positive cocci, Clostridia, and some bacteroidaceae showed an increase in population in the cecum, but lactobacilli, veillonellae, and spirochetes decreased. The major organisms cultured from the heat‐treated feces were fusiform and curved bacteria, some members of Bacillus, minor anaerobic cocci, and straight rods.

Annular nucleolus in hepatocyte of chicken embryo induced by aflatoxin B1

Summary Aflatoxin B 1 administred to the 5-day-old chick embryo induced an annular nucleolus in hepatocytes and its incorporation of 3 H-uridine, 3 H-thymidine, and 3 H- l -lysine was studied by radioautographic technique. In the case of all three precursors, fewer silver grains are found over the ring-shaped nucleolus than over the ordinary compact one. Under electron microscopic examination, the fibrillar and granular elements are observed in the area of the circumferential zone. In the central pale area, however, there are only scattered granular elements and fine, twisted fibres. From the above-mentioned facts, a proposition is made that the mechanism of the formation of the annular nucleolus seems to be related to the alteration of intranucleolar DNA-histone complexes. The fibrillar RNP may disappear from that part occupied by aflatoxin B 1 -affected intranucleolar chromatin.

Metabolic degradations of nitrofurans by rat liver homogenate.

Abstract The evidence of the metabolic degradations of some nitrofurans by rat liver homogenate was shown in the present study. Nitrofurans were incubated with 8500 g supernatant of rat liver homogenate with added NADPH 2 as a hydrogen donor and metabolic degradations of nitrofurans were followed by the changes of their characteristic optical absorbances and the loss of their nitro groups. These two properties of most of the tested nitrofurans changed slowly and independently in aerobic condition. In anaerobic condition, they disappeared much more rapidly and nearly to the same extents.

Intracellular localization and properties of trimethylamine-N-oxide reductase in Vibrio parahaemolyticus.

Summary Trimethylamine-N-oxide reductase in Vibrio parahaemolyticus was found to be a NADH-dependent enzyme and to be associated with the membrane portion of lysed spheroplasts. Centrifugal fractionations of cell extracts prepared with a French press showed that the amount of the reductase activity recovered in the sediments at 20 000 × g for 20 min and 100 000 × g for 100 min varied according to the pressure used for the preparation of cell extracts, and these fractions were considered to be derived from the membrane portion of the cells during the preparation of cell extracts. The stoichiometry of the enzymic reaction was established as follows: NADH + (CH3)3NO + H+→NAD+ + (CH3)3N + H2O The reaction was inhibited by p-cliloromercuribenzoate, cupric ion and by chelating agents that form stable complexes with heavy metals.

The structure of fumitremorgin B (FTB), a tremorgenic toxin from Aspergillus fumigatus Fres

The structure of fumitremorgin B, one of the indole metabolites of Aspergillus fumigatus Fres. has been established as (1).

Different Susceptibilities of Chick Embryo Liver Cells in vitro to Aflatoxin, Actinomycin D, and Mitomycin C

Bei Anwesenheit von Aflatoxin erwiesen sich die Parenchymzellen der embryonalen Hühnerleber empfindlicher als die mesenchymalen Zellen; die toxische Wirkung der Substanz drückte sich in einer mittels Autoradiographie festgestellten Behinderung der RNS-Synthese aus, die von Protein- und DNS-Synthese gefolgt war. Im Gegensatz zuAflatoxin wirkte Actinomycin D auf die Mesenchymzellen stärker als auf die Parenchymzellen. Durch Mitomycin C wurde die RNS-Synthese beider Zelltypen anfänglich nicht gestört, doch war später eine mäßige Wirkung auf die RNS- und Protein-Synthese der Parenchymzellen und weiterhin auch der Mesenchymzellen nachweisbar. In the presence of aflatoxin, parenchymal cells of chick embryo liver were found to be more susceptible than mesenchymal cells, the toxic effect being an inhibition of RNA synthesis followed by protein and DNA synthesis studied by autoradiography. Actinomycin D, contrary to aflatoxin, acted on the mesenchymal cells more strongly than on the parenchymal cells. RNA synthesis of both cell types was not disturbed initially by mitomycin C, though later there was a moderate action on RNA and protein synthesis of parenchymal cells and subsequently also on those mesenchymal cells.

The distribution of tritium-labeled aflatoxin B1, dihydro-aflatoxin B1, and tetrahydrodesoxoaflatoxin B1 in liver cells cultured in vitro from the chicken embryo

The distribution patterns of 3H-aflatoxin B 1, B 2 and tetrahydrodesoxoaflatoxin B 1 (4H B 1) in the cultured liver cells originated from the 12-day-old chicken embryo were demonstrated. The fact that the hepatocytes were more heavily labeled than the mesenchymal cells by the incorporation of 3H-aflatoxins correlate well with the observation that the hepatocytes were more susceptible than the mesenchymal cells to the aflatoxins. There were no significant differences in the pattern of incorporation of 3H-aflatoxin B 1, B 2 and 4H B 1 into the hepatocyte, while the three mycotoxins show a wide variation in their inhibitory action in RNA synthesis. It may be concluded from the above mentioned facts that the toxicity of aflatoxins to the liver cells in vitro is closely related to the membrane permeability and the active portion of the molecule of aflatoxins, such as the double bond in the difuran structure and the carbonyl group in the cyclopentenone portion of B 1. Die Tatsache, daß die Leberzellen stärker durch Inkorporation von 3H-Aflatoxin markiert werden als die Mesenchymzellen entspricht der Beobachtung, daß Leberzellen gegenüber Aflatoxinen anfälliger sind als die Mesenchymzellen. Es zeigten sich keine signifikanten Unterschiede hinsichtlich der Inkorporation von 3H-Aflatoxin B 1, B 2 und 4HB 1 in die Leberzellen, während diese drei Mycotoxine eine weite Variation hinsichtlich ihrer Hemmwirkung auf die RNS-Synthese aufwiesen. Man kann also daraus den Schluß ziehen, daß die Toxizität von Aflatoxinen für Leberzellen in vitro eng zusammenhängt mit der Membrandurchlässigkeit und dem aktiven Teil des Aflatoxinmoleküls bzw. der Dop pelbindung in Difuranstruktur und der Carbonylgruppe in dem Cyclopentenon-Anteil von B 1.