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Results for “YEASTS/anatomy and histology”

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16 recordsLinked to original sources
PubMed1961

Studies on the oxidative metabolism of Saccharomyces cerevisiae. I. Observations on the fine structure of the yeast cell.

Vegetative cells of Saccharomyces cerevisiae were fixed with potassium permanganate followed by uranyl nitrate, embedded in methacrylate, and studied in electron micrographs of thin sections. Details of the structure of the cell wall, cytoplasmic membrane, nucleus, vacuole, and mitochondria are described. Cell membranes, about 70 to 80 A thick, have been resolved into two dense layers, 20 to 25 A thick, separated by a light layer of the same dimensions, which correspond in thickness and appearance to the components of the "unit membrane" as described by Robertson (15). The cell wall is made up of zones of different electron opacity. Underlying the cell wall is the cytoplasmic membrane, a sinuous structure with numerous invaginations. The nucleoplasm, often of uneven electron opacity, is enclosed in a pair of unit membranes in which nuclear pores are apparent. The vacuole, limited by a single unit membrane, is usually irregular in outline and contains some dense material. Rod-shaped mitochondria, 0.4 to 0.6 micro in length and 0.2 to 0.3 micro in diameter, are smaller in size, but similar in structure to some of those described in plant and animal cells. Attempts to use osmium tetroxide as fixative were unsuccessful, a result similar to that obtained by other workers. It is suggested that yeast cells are impermeable to osmium tetroxide, except when grown under specific conditions.

Animals↗
PubMed1961

Mitosis in the yeast Lipomyces lipofer.

A study of mitosis in Lipomyces has been carried out because preliminary observations by Ganesan and Roberts, 1959 (9), had indicated that the nucleus of this yeast might be unusually favourable for morphological observations. This impression has proved correct. The chromosomes of Lipomyces are visible as separate, countable bodies for the greater part of mitosis. The pattern of mitosis differs from the common one in that in Lipomyces the proper distribution of sister chromosomes is accomplished without the help of a spindle apparatus. At the end of prophase sister chromosomes are found in pairs which align themselves parallel to one another to form a palisade or stack whose long axis coincides with the axis of the impending division. At anaphase-telophase the stack of paired chromosomes fuses into a seemingly homogeneous cord which divides by constriction.

Anaphase↗
PubMed1962

Cytology of Rhodotorula glutinis.

Thyagarajan, T. R. (Cornell University, Ithaca, N. Y.) and H. B. Naylor. Cytology of Rhodotorula glutinis. J. Bacteriol. 83:127-136. 1962.-The structure and manner of division of nuclei in actively dividing cells of Rhodotorula glutinis were studied with the phase contrast microscope. The nucleus consists of a dense central body, surrounded by a shell of optically uniform material of low density. The entire structure is enclosed within a nuclear membrane. Various fixation and staining techniques were employed to confirm the observations made from living cells. Since the dense central body is Feulgen-negative and is readily stained by iron alum hematoxylin, it is identified as the nucleolus. The material surrounding the nucleolus has no marked affinity for hematoxylin but is Feulgen-positive and stains intensely with Giemsa and basic fuchsin. The nucleus appears to divide by a process of elongation and constriction during which roughly half of the nucleolus, along with the surrounding chromatin, passes into the bud. The nuclear membrane was found to persist during all stages of division. Vacuoles were seldom observed in actively dividing cells. The nucleus of R. glutinis is similar in structure to the nuclei of higher organisms, but its behavior during division is quite different.

Cell Nucleolus↗