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  • ASTROPHYSICS  (97)
  • Life and Medical Sciences  (58)
  • 1975-1979  (155)
  • 1970-1974
  • 1965-1969
  • 1905-1909
  • 1979  (155)
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  • 1975-1979  (155)
  • 1970-1974
  • 1965-1969
  • 1905-1909
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  • 1
    Publication Date: 2019-06-27
    Keywords: ASTROPHYSICS
    Type: PB80-144215 , Astrophysical Journal Supplement Series; 41; Nov. 197
    Format: text
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 98 (1979), S. 627-635 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The toxicity and extent of growth inhibition produced by chloramphenicol (CAP) in CAPs Chinese hamster cells (line V79-5) was found to be dependent on the type and concentration of hexose in the medium. In high levels of glucose (6.5 mM), cultures of CAPs cells underwent 7-8 population doublings in the presence of 100 μg/ml CAP and viability then dropped rapidly. In contrast, lower concentrations of glucose (1.0 mM) permitted only limited growth (2-3 doublings) in the presence of 100 μg/ml CAP, but the cells remained viable and apparently quiescent for prolonged periods of time. The growth potential of V79-5 cells in CAP appeared specifically dependent on glucose, as mannose and galactose could not substitute for glucose. The toxicity of CAP to these cells seemed to be determined primarily by the number of cell doublings in the presence of the drug.A CAPR derivative of V79-5, designated 5-3, was analyzed in order to determine whether the requirement for glucose for cell growth in the presence of CAP also occurred in cells that were isolated as resistant to the drug. In order to rigorously control the hexose in the medium, some experiments were performed with medium containing dialysed, instead of whole, fetal calf serum. It was seen that the growth of the CAPR line in the presence (but not the absence) of 100 μg/ml CAP was dependent on glucose in the medium. Thus, resistance to CAP in these cells appears to be a conditional state, dependent on glucose for expression. Furthermore, the glucose auxotrophy of these cells in the presence of CAP suggests that CAP is still affecting some activities in cells isolated as CAPR.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Gamete Research 2 (1979), S. 247-258 
    ISSN: 0148-7280
    Keywords: Bonellin ; Bonellia viridis ; Sphaerechinus granularis ; fertilization ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: We have studied the structural changes occurring in the eggs of the sea urchin Sphaerechinus granularis treated with bonellin, the green pigment of the sea worm Bonellia viridis, which is responsible for the masculinization of the larva of this animal. The two major targets of bonellin appear to be the cortical structures and the nuclear membrane, while the mitochondria do not appear to be affected. As a result of bonellin treatment, cleavage is prevented while nuclear divisions proceed. The possibility is discussed that the alteration of the cortical structures may interfere with the assembly of the surface microfilaments and hence with the formation of the cleavage furrows.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 1 (1979), S. 167-179 
    ISSN: 0192-253X
    Keywords: agouti locus ; hair pigment patterns ; melanocyte metabolism ; tissue microenvironment ; eumelanin ; phaeomelanin ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: This study was conducted to assess microenvironmental variability within integumental tissue of genetically identical mice with respect to a specific cellular response: cyclic synthesis of yellow and black pigment by hair bulb melanocytes. Crosses were performed within and between inbred strains of mice that were isogenic with the exception of a single gene substitution at the agouti locus. Agouti locus genes included the Avy, Aw, A, atd, at, ax, am, and a alleles. The pigment patterns of dorsal, flank, and ventral hairs of the first and third hair generations and of hairs growing in special integumentary areas such as the pinna, tail, and hind foot were studied. It was found that the amount of yellow pigment synthesized by hair bulb melanocytes within genetically identical mice is both agedependent and conditioned by the integumentary environment. Furthermore, the special integumentary regions produce hairs with a variety of pigment patterns in which the distribution and relative amounts of black and yellow pigments do not necessarily conform to dominance relationships expected among agouti locus alleles as judged by their effects on the pigmentation of the dorsal pelage. We conclude that within genetically uniform integumental tissues, microenvironmental differences occur and are reflected as alterations in the metabolic pattern of differentiated cells.
    Additional Material: 1 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 1 (1979), S. 355-362 
    ISSN: 0192-253X
    Keywords: Dictyostelium discoideum ; spore maturation ; spore specific mutations ; cell patterning ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Three mutations affecting spore maturation in the asexual fruiting body of Dictyostelium discoideum are assigned to a new locus, sprJ, on linkage group IV. Strains carrying mutations at the sprJ locus do not form mature spores, yet the cell patterning (spore, stalk and disc cell ratios) is apparently normal. These mutations will be useful to delineate branch points between the cell patterning and spore maturation pathways. There are some unusual features of the sprJ-containing mutants. In particular each of the parent strains of the three mutants has incomplete spore maturation as determined by colony-forming ability after heat shocking at 45°C. A mutation allowing growth in the presence of benlate (600 μg/ml), benA351, is mapped to linkage group I.
    Additional Material: 1 Ill.
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  • 6
    Publication Date: 2011-08-17
    Description: A dual star-tracking system and a system including a telescope, an echelle spectrograph, and a SEC vidicon are the chief components of the Balloon-borne Ultraviolet Stellar Spectrograph (BUSS), which has flown four successful missions. The BUSS missions have yielded 81 spectra for 56 stars, recorded with a resolution of 0.1 A in the wavelength range from 2200 to 3400 A. BUSS observations include: profiles of Mg II lines indicating considerable mass flow in early-type supergiants; Mg II features suggesting a cool expanding outer shell above a hotter chromosphere; emission features in Zeta Tau (a shell star) indicating infalling material; and emission features of the Be star Phi Per suggesting mass outflow.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 230
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  • 7
    Publication Date: 2019-06-27
    Description: The formation of beryllium lines, with particular reference to the solar Be spectrum, is investigated in a non-LTE context with a 25-level model atom in which 15 levels are allowed to depart from LTE. In some transitions, particularly the Be I 2650-A line, the non-LTE effects can be quite dramatic, changing the deduced abundances by a factor of 4. Based on the non-LTE calculations and Copernicus observations of other stars, it is found that a solar spectral feature at 2650 A, previously identified by numerous investigators as a Be I line, cannot be produced by Be I. Non-LTE effects on the Be II 3131-A line, used for most Be abundance determinations in the literature, are small by comparison.
    Keywords: ASTROPHYSICS
    Type: Astronomical Journal; 84; Nov. 197
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  • 8
    Publication Date: 2019-06-27
    Description: The brightness distribution of IRC +10216 at a wavelength of 11 microns has been measured in detail by using spatial interferometer. This brightness distribution appears to have azimuthal symmetry; an upper limit of 1.1 may be set to the ellipticity at 11 microns if the object has a major axis oriented either along or perpendicular to the major axis of the optical image. The radial distribution shows both compact and extended emission. The extended component, which is due to thermal emission from circumstellar dust, contributes 91% of the total flux and has a 1/e diameter of 0.90 arcsec. The tapered shape of this component is consistent with a dust density dependence on the inverse square of radial distance. The compact component is unresolved (less than 0.2 arcsec in diameter) and represents emission from the central star seen through the circumstellar envelope.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 230
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  • 9
    Publication Date: 2019-06-27
    Description: The structure of the interstellar gas surrounding the Orion OB1 association and the neighboring lambda Orionis association is detailed. UV absorption lime spectra of various ionization stages of C, N, Si and S in the directions of 12 stars were obtained by means of the spectrometer on board the Copernicus satellite. The presence of a shell of material surrounding the two associations and expanding at 100 to 120 km/sec, designated Orion's Cloak, was revealed, together with sporadically occurring higher column density matter at lower velocities. Results are interpreted to indicate the presence of a rapidly moving radiative shock outside the H II region of the association stars and inside this feature, a lower velocity, higher column density cloud which appears to be directly ionized by association stars. It is suggested that the gas features are caused by the effects of a recent supernova and of multiple supernovae, stellar winds and rocket-accelerated clouds in addition to stellar ionization.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 230
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  • 10
    Publication Date: 2019-06-27
    Description: The implications of recent ultraviolet observations of stellar transition-region lines for calculations of the Ca II and Mg II resonance lines are investigated. It is found that the adoption of high transition-region pressures for stars with active chromospheres, such as Lambda And and Alpha Aur, can be consistent with observed Ca II fluxes, contrary to the results obtained by Kelch et al. (1978) for Alpha Aur. Furthermore, the adoption of the high-pressure models removes a long-standing difficulty in the line profile calculations, since the deep central absorption present in earlier calculations is less pronounced or absent, in closer agreement with observations. The apparent contradiction between these models and the recent density diagnostic of Doschek et al. (1978) is also discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 233
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