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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Gamete Research 4 (1981), S. 525-533 
    ISSN: 0148-7280
    Keywords: capacitation ; fertilization ; spermatozoa ; in vitro ; Little Brown Bat ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The temperature dependence of capacitation in bat sperm (Myotis lucifugus lucifugus) was studied by monitoring fertilizations rates of zona-free hamster ova at different temperatures. Spermatozoa were cultured in BWW medium at temperatures 4°C, 24°C, 32°C, 42°C, and 55°C from 0-24 hr. Activation of sperm could be determined visually due to the change in movement seen through light microscopy. Activation was later confirmed by higher rates of fertilization. Preincubation of the bat sperm was found to have a direct effect on the success of penetration of the zona-free hamster ova. Holding bat spermatozoa at low temperature for long intervals allowed them to remain motile but unable to fertilize. Sperm are not irreversibly damaged, however, and activation, when the temperature is increased to 32°C, is faster than when sperm are intitially put at 32°C, resulting in good fertilization rates.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Gamete Research 10 (1984), S. 153-163 
    ISSN: 0148-7280
    Keywords: mouse ; sperm ; egg ; sperm plasma membrane ; in vitro ; binding ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: We have studied the molecular mechanisms of gamete interaction in vitro in the laboratory mouse, Mus musculus. In particular, we were interested in whether this interaction is similar to a lectin-hapten-mediated process. Inhibition of sperm-zona binding was examined using various concentrations (.25 mM to 50 mM) of different sugars (sialic acid α-methylmannose, glucose, fucose, galactose, and N-acetyl-glucosamine). Sperm-zona binding was significantly decreased when eggs were pretreated with 10 mM of sialic acid or α-methylmannose but not by other sugars tested. Furthermore, treatment of capacitated sperm with neuraminidase destroyed their ability to bind and fertilize eggs. We have also used a specific lectin for sialic acid from the horseshoe crab (Limulus polyphemus) to agglutinate mouse sperm. The lectin (.120 ng/ml) mediated agglutination of mouse sperm (105 sperm/ml) was routinely observed to increase from a 10% agglutination immediately following their isolation from the epididymis to 100% agglutination 90 minutes later. Collectively, these results suggest the appearance of specific sugar moieties on the surface of the sperm plasma membrane which, in this particular species of mouse, are sialylated glycoproteins acting as ligands for specific receptors on the surface of the egg. These are the first data to indicate that sperm-egg recognition and attachment is a lectin-hapten-mediated process in the mouse.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Publication Date: 2016-06-07
    Description: The IUE spectra are presented for two old novae and for two of the symbiotic variables. Prominent emission line spectra are revealed as a continuum whose appearance is effected by the system inclination. These data provide evidence for hot companions in the symbiotic stars, making plausible the binary model for these peculiar stars. Recent IUE spectra of dwarf novae provide additional support for the existence of optically thick accretion disks in active binary systems. The ultraviolet data of the eclipsing dwarf novae EX Hya and BV Cen appear flatter than for the noneclipsing systems, an effect which could be ascribed to the system inclination.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center The Universe at Ultraviolet Wavelengths: The First Two Yrs. of Intern. Ultraviolet Explorer; p 461-467
    Format: application/pdf
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  • 4
    facet.materialart.
    Unknown
    In:  Other Sources
    Publication Date: 2019-06-28
    Description: International Ultraviolet Explorer short-wavelength, low-dispersion spectra were analyzed for four barium, two mild barium, and one R-type carbon star in order to test the hypothesis that the barium and related giants are produced by mass transfer from a companion now present as a white dwarf. An earlier tentative identification of a white dwarf companion to the mild barium star Zeta Cyg is confirmed. For the other stars, no ultraviolet excess attributable to a white dwarf is seen. Limits are set on the bolometric magnitude and age of a possible white dwarf companion. Since the barium stars do not have obvious progenitors among main-sequence and subgiant stars, mass transfer must be presumed to occur when the mass-gaining star is already on the giant branch. This restriction, and the white dwarf's minimum age, which is greater than 8 x 10 to the 8th yr, determined for several stars, effectively eliminates the hypothesis that mass transfer from an asymptotic giant branch star creates a barium star. Speculations are presented on alternative methods of producing a barium star in a binary system.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 270; July 1
    Format: text
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  • 5
    Publication Date: 2019-06-28
    Description: A low-resolution IUE spectrum (1200 A-1900 A) of the twin-degenerate white-dwarf binary star G61-29 is presented. A comparison is made to similar IUE spectra of the old novae DQ Her and V603 Aql. G61-29 shows N V 1240 A and He II 1640 A in emission. Unlike the old novae, the C IV 1550 A doublet is not present. It is proposed that the mass-losing He white dwarf (with a mass of 0.02 solar mass) is the H-exhausted, He-rich core of an old star in which the original CNO nuclei have been converted to N-14 by the CNO-cycles.
    Keywords: ASTROPHYSICS
    Type: Astronomical Society of the Pacific; vol. 93
    Format: text
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  • 6
    Publication Date: 2019-06-28
    Description: A survey of 15 lines of sight for the CN B2Sigma(+) X2Sigma(+) interstellar absorption lines shows that the CN column density in diffuse interstellar clouds follows the relation log N(CN) is proportional to m log N(H2), where m is approximately equal to 3. This result is reproduced by a reaction network in which CN is produced primarily from C2 by the neutral-neutral reaction C2 + N yields CN + C, and photodissociation is the main destruction pathway for the neutral molecules CH, C2, and CN. The CN radical is the first molecular species observed in diffuse clouds that requires a neutral-neutral reaction for its formation in the gas phase. The network also reproduces the observed ratio N(CN)/N(H2).
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 287; 219-227
    Format: text
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  • 7
    Publication Date: 2019-06-28
    Description: Ultraviolet and optical spectra of the old nova V603 Aql are discussed. The UV-optical continuum is dominated by emission from the accretion disk. Emission lines from ions of H, He, C, N, and O are identified. These lines are probably formed in a circumstellar shell with radius comparable to the binary separation, density ten billion per cu cm, and a roughly solar chemical composition. This corona is probably heated by radiation emitted by the underlying accretion disk. Photoionization calculations of the structure and emission-line spectrum of the corona are presented, and the effects of this gas on the X-ray continuum are discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 260
    Format: text
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  • 8
    facet.materialart.
    Unknown
    In:  Other Sources
    Publication Date: 2019-07-13
    Description: A general discussion of the UV spectra of symbiotic stars, including both the emission lines and the continua, is presented, with AG Pegasi considered as an illustrative example. It is noted that the IUE observations of the symbiotics have revealed UV properties which rival the diversity of the optical features. Nevertheless, the UV data have for the first time permitted the hot component to be studied relatively uncontaminated by the giant companion, which dominates the optical regime. The UV observations provide convincing evidence that many of the symbiotics have hot stellar companions embedded in the enshrouding nebula or accretion shell formed from the wind from one or possibly both of the components.
    Keywords: ASTROPHYSICS
    Type: In: The nature of symbiotic stars; Aug 26, 1981 - Aug 28, 1981; Alpes-de-Haute-Provence; France
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