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  • 1
    ISSN: 1546-1718
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] Protamines are the major DNA-binding proteins in the nucleus of sperm in most vertebrates and package the DNA in a volume less than 5% of a somatic cell nucleus. Many mammals have one protamine, but a few species, including humans and mice, have two. Here we use gene targeting to determine if the ...
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Cells of the vaginal epithelium of ovariectomized mice undergo differentiation in response to estrogen or progesterone injection. Estrogen causes an increase in number of cytoplasmic filaments in the basal and newly formed spinous layer and mucification of surface cells already present. The cells derived from the basal layer under estrogen influence later form a keratinized epithelium. Progesterone causes heightening and mucification of surface cells and invasion of leucocytes into the epithelium without mucification or keratinization of other cells. When estrogen is followed two days later by progesterone, spinous and more superficial cells are lost and replaced my mucous cells derived from the basal layer. Although the fine structure of basal and spinous cell cytoplasm looks identical, the spinous cells do not form mucous cells under progesterone influence. The reverse sequence of progesterone followed by estrogen produces a low epithelium which is then replaced by a keratinized epithelium. The surface mucous cells present during progesterone influence do not keratinize, however. Thus, fine structural features of basal cells typical for the influence of a given hormone do not limit or characterize the potential of daughter cells derived from that layer. Conversely, when hormones are used in sequence, cells which leave the basal layer under the influence of one hormone do not acquire the fine structural features characteristically produced by the second hormone used, even though basal cells are readily altered.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: An initial study of the effects of long-term ovariectomy on fimbrial and ampullar epithelia from rabbit oviducts has been made with the scanning electron microscope. Several of the rabbits were given estradiol benzoate before they were killed. These observations were compared with those of epithelial cells from similar oviductal segments from post-ovulatory rabbits that served as controls.Fimbriae from oviducts of control animals were densely ciliated, partially concealing the bulbous processes of the secretory cells. In the ampullae the processes of the secretory cells were the predominant structure, their bulbous apices rising frequently above the tips of the cilia.When rabbits had been spayed for 16-18 months, the epithelial cells of both fimbriae and ampullae showed a remarkable change. A few cilia in small clumps were scattered among the secretory cells. The free surface of the secretory cells had become flattened and hexagonal in shape. Their microvilli were short, and from the center of each cell a thick, stubby central cilium protruded.Estrogen given the long-term spayed rabbits caused almost complete reciliation as well as restoration of the bulbous processes of the secretory cells.
    Type of Medium: Electronic Resource
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