PubMed Health⌕ Search

Biomedical subjects

H B NAYLOR

Publications and source records attributed to H B NAYLOR.

At least 19 recordsLinked to original sources
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↗
PubMed1962

Electron microscopy of Rhodotorula glutinis.

Thyagarajan, T. R. (Dartmouth Medical School, Hanover, N. H.), S. F. Conti, and H. B. Naylor. Electron microscopy of Rhodotorula glutinis. J. Bacteriol. 83:381-394. 1962.-The structure and manner of nuclear division in Rhodotorula glutinis was studied by electron microscopy of ultrathin sections. Parallel studies with the light microscope, employing conventional staining techniques and phase-contrast microscope observations on nuclei in living cells, were carried out. The nucleus is spherical to oval and is bounded by a nuclear membrane. Intranuclear structures, identified as nucleoli, and electron-transparent areas were observed. The nuclear membrane persists throughout the various stages of cell division. Observations of the nucleus with the electron microscope revealed that nuclear division occurs by a process of elongation and constriction similar to that seen in both living and stained cells. The fine structure of mitochondria and other components of the yeast cell and their behavior during cell division are described. The absence of vacuoles in actively dividing cells of Rhodotorula glutinis lends further support to the view that the vacuole is not an integral part of the nucleus. The results with the electron microscope generally support and considerably extend those obtained with living and stained cells.

Cell Division↗
PubMed1962

Induction of lysogenic Micrococcus lysodeikticus.

Field, A. K. (Cornell University, Ithaca, N.Y.) and H. B. Naylor. Induction of lysogenic Micrococcus lysodeikticus. J. Bacteriol. 84:1129-1133. 1962.-Between 50 and 60% of log-phase cells of Micrococcus lysodeikticus strain ML 53-40, lysogenic for N5 bacteriophage, were induced by an optimal dose of ultraviolet light. Induction of dilute cell suspensions caused a subsequent 200- to 800-fold increase in infective-center concentration. Cells in the stationary growth phase and cells adapted to a chemically defined medium were also induced by ultraviolet irradiation. Dimethyl sulfate induced the lysogenic culture to about the same extent as did ultraviolet light, whereas beta-propiolactone was less effective.

Bacteriophages↗
PubMed1960

Studies on the fine structure of microorganisms. V. Morphogenesis of nuclear and membrane structures during ascospore formation in yeast.

The fine structure of cells of Saccharomyces cerevisiae engaged in the formation of ascospores was studied in electron micrographs of ultrathin sections. Although the mode of the first reduction division could not be clearly determined, the second nuclear division appeared to proceed in a manner similar to that observed previously during vegetative division. That is, division by constriction of the existing nucleus occurs without dissolution of the nuclear membrane and without involvement of discrete chromosomes. Variously shaped areas of low electron density were discerned within the nucleoplasm; these had not been previously seen in the vegetative nucleus. The significance of this nuclear differentiation and its possible similarity to nuclear structures reported in bacteria and an imperfect fungus are discussed. The cytoplasmic membrane appears first in the developing ascospore. The formation of an outer coat and an inner coat then follows. The cytoplasmic vacuole was observed not to be incorporated into the spore. An unusual intracytoplasmic membrane was observed in the spore and appeared to be at least temporarily continuous with the nuclear membrane.

Cell Membrane↗