Recently, it has been demonstrated by ultraviolet microscopy that S-adenosylmethionine is accumulated in the vacuole of Candida utilis (Svihla and Schlenk, 1959). The exceptional 1 Research performed under the auspices of the U. S. Atomic Energy Commission.

and properties of spheroplasts of the yeast Candida utilis, produced by digestion of the cell walls with snail gut juice (Helix pomnatia) in isotonic medium, were studied by l)hase, interference, and ultraviolet microscopy, and tracer

Ultraviolet microscopy of purine compounds in the yeast vacuole. J. Bacteriol. 85:399-409. 1962.-Yeast cells (Candida utilis and Saccharomyces cerevisiae) suspended in nitrogen-free medium were exposed to various ultravioletabsorbing biological compounds, particularly nucleic acid constituents. Ultraviolet photomicrography was used to locate these substances in the cells. Purines were taken up readily and concentrated in the vacuoles of C. utilis but not of S. cerevisiae. Crystallization occurred, as observed earlier by other techniques. Neither organism assimilated pyrimidine bases, or purine or pyrimidine nucleosides, at a detectable rate. From the selective uptake and release of some purine derivatives, it can be concluded that the properties of the vacuolar membrane and the cytoplasmic membrane differ in several respects. MATERIALS AND METHODS C. utilis ATCC 9950 and S. cerevisiae ATCC 7752 were cultured as specified earlier (Svihla, Schlenk, and Dainko, 1960, 1961). The washed cells were stored at 4 C until use. For experiments with the purines, pyrimidines, and other ultraviolet-absorbing compounds, the same salt medium was used without ammonium sulfate. Glu-399

No abstract

With a modified color-translating ultraviolet microscope, the distribution of material showing an absorption maximum at 265 m~t was studied in samples from whole cultures of Entamoeba invadens at intervals during growth and from cysts allowed to mature under controlled conditions. Absorption by the cytoplasm in general gradually increased as trophozoites approached the period of maximum encystment. In late trophozoites and precystic forms, the absorbing material was concentrated into small bodies which coalesced to form large crystalloids of very high specific absorption. Maximum crystallization occurred in early cysts, where cytochcmical tests have shown the large crystalloids to be ribonucleoprotein. Electron micrographs show that the crystalloids are composed of particles 200 to 300 A in diameter. During cyst maturation the amount of absorbing material per cyst is not visibly reduced, but the large bodies fragment into smaller units until finally there is only a very high diffuse absorption over the entire cyst. From these and other results the hypothesis is advanced that the large crystalloids ("chromatoid bodies") are a manifestation of a special parasite-host adaptive mechanism; ribonucleoprotein is synthesized under favorable conditions, crystallized in the resistant cyst stage, and dispersed in the newly excysted amebae thereby enabling them to establish themselves in a new host by a period of quick growth.