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M U NYLEN

Publications and source records attributed to M U NYLEN.

9 recordsLinked to original sources
PubMed1964

INTERNAL STRUCTURES OF A EUBACTERIUM SP. DEMONSTRATED BY THE NEGATIVE STAINING TECHNIQUE.

Bladen, Howard A. (National Institute of Dental Research, Bethesda, Md.), Marie U. Nylen, and Robert J. Fitzgerald. Internal structures of a Eubacterium sp. demonstrated by the negative staining technique. J. Bacteriol. 88:763-770. 1964.-Thin sections as well as negatively stained whole cells of a Eubacterium sp. isolated from the rat cecum were examined in a Siemens Elmiskop I electron microscope. The cell wall usually appeared in thin sections as a single dense layer about 130 A thick; however, occasionally it was demonstrated to be composed of three layers. The plasma membrane was approximately 130 A wide, and was composed of a denselight-dense arrangement. Intracytoplasmic membranous elements continuous with the plasma membrane were also observed in thin sections. When whole cells were negatively stained with phosphotungstic acid, the cell wall became transparent, and structures comparable in morphology to intracytoplasmic membranous elements were observed. These were demonstrated by stereomicroscopy to be in the interior environment of the cell, and appeared in many cases continuous with the cell wall. Frequently, they seemed to open to the exterior of the cell through what may be termed a pore. Small stalked structures similar to those described in mitochondria were observed along the periphery of the cell and occasionally along the walls of the internal elements.

Cecum↗
PubMed1963

Crystal growth in rat enamel.

Observations have been made, using electron microscopy and x-ray diffraction, on the changes in crystal size and shape which occur in developing rodent enamel during mineralization. Small enamel pieces isolated from ground sections of rat molars and incisors were either embedded in methacrylate and sectioned with a diamond knife for electron microscopy, or they were mounted intact on glass fibers in a Debye-Sherrer type powder camera for x-ray diffraction. By either approach it was found that the apatite crystals were very long in the c axis direction from the beginning of enamel mineralization. Morphologically, the early crystals took the shape of extremely thin, long plates arranged in such a manner that there seemed to be little room for any further length-wise growth. It was demonstrated clearly, on the other hand, that the crystals increased in both thickness and width with advancing mineralization. As a result, the thin crystal plates gradually developed into hexagonal rods, which in the most mature enamel examined measured 500 to 600 A in width and 250 to 300 A in thickness.

Animals↗