The dietary factors, as a cause on increasing incidence of gallstones in Japan, were studied. The increase in the incidence of gallstones at autopsy was nearly paralleled with that of fat intake on a line graph and reversely the carbohydrate intake including crude fiber showed a decreasing trend. In the nutritional survey of patients with gallstone, the fat intake was 22% higher than that of the control group, and the crude fiber intake was 18%lower. Comparing the incidence of cholesterol stones during each 10 years of 1953-1962 and 1969-1980 with the nutritional intake, the incidence of gallstones increased by 25% and the fat intake by 120%, but the carbohydrate intake including crude fiber decreased by 14%. Fromthe above, it was considered that the increase of the incidence of cholesterol gallstones was related to the increase of the fat intake and the decrease of the crude fiber intake. A study on black stone was carried out with an infrared spectroscopic analysis and scanning electron microscopic observation, and wenowproposed a new classification of this type of stones.

Hg2 -resistant mutants were isolated from Saccharomyces cerevisiae. Although they were very much like the parental strains in terms of colony-forming ability, they grew faster than the parental strains in the presence of sublethal doses of Hg2+. The Hg2+-resistant mutations were dominant. They were centromere linked and were divided into two groups by means of recombination; one of the mutations, designated HGRI-1, was mapped on chromosome IV because of its linkage to the TRPI locus. The Hg2+-resistant mutants took up Hg2+ as much as, or slightly more than, the parental strains did. The mutants and parental strains retained only about 5 and 15%, respectively, of the cell-associated Hg2+ after removal of the cell wall; therefore, the mutants had less spheroplast-associated Hg2+ than did the parental strains. These results indicate that the cell wall plays an important role in protection against Hg2+ by acting as an adsorption filter and that the mutations described confer Hg2+ resistance by increasing the Hg2+-binding capacity of the cell wall.For a better understanding of the toxicity of mercury and mechanisms of biological defense against mercury, studies at the cellular and subcellular levels are indispensable. Saccharomyces cerevisiae is suitable for such studies because it is easily manipulated genetically and readily analyzed biochemically. Singh and Sherman (17, 18) isolated mutants resistant to methylmercury and showed that the methylmercury-resistant mutations arose in only the ME72 and METI5 loci. On the other hand, mutants resistant to inorganic mercury were obtained by training; i.e., a wild-type strain was cultured in medium containing a sublethal concentration of mercury, and then the mercury concentration was gradually increased as the cells grew (5, 22). However, the resultant mutants were so unstable that they quickly lost resistance when they were cultured without mercury.We have been studying the toxicity of Hg2+ and the biological defense against Hg2+ by using S. cerevisiae. It has been shown that the Hg2+ sensitivity of a certain strain is caused by the joint action of two mutations (10). One of them blocks tyrosine biosynthesis, while the other blocks tyrosine uptake by enhancing catabolite repression of the tyrosine uptake system (11, 13). Hg2+ promotes depletion of cellular tyrosine by inhibiting the tyrosine uptake system (13). To search for other biological effects of Hg2 + we attempted to obtain stable Hg2+-resistant mutants. In this report, we describe the isolation and partial characterization of the mutants. From these results, we discuss a role of the cell wall in protection against Hg2+ in S. cerevisiae. MATERIALS AND METHODSGrowth media, strains, and isolation of mutants. YPD medium contained 1% yeast extract, 2% peptone, and 2% glucose (15). For solid media, 2% agar was added. Mutants were isolated from strain EH1-4A (MATot leu2-1 met8-1 gal2 msml-2) and EH1-4B (MATa leu2-1 met8-1 his5-2 MSMJ-1). was placed at the center of each plate, and 2.1 mg of HgCl2 in solution was applied ...

Several kinds of recently advanced microanalytical techniques—like electron probe x-ray microanalysis, laser Raman microprobe, and Fourier transform-infrared spectroscopy combined with a microsampling method—have been used for the study of the microstructure of gallstones. The organic and inorganic constituents of three kinds of gallstones are characterized on a microscopic scale. The microstructure of a cholesterol-bilirubin gallstone with a layered structure has been studied with particular emphasis. Small white particles contained in both a bilirubin gallstone and a cholesterol-bilirubin mixed gallstone have been found to consist of calcium salt of a fatty acid, probably calcium palmitate. The results obtained here will be very useful for understanding the mechanism of the gallstone-formation process.

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