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  • Life and Medical Sciences  (121)
  • SOLAR PHYSICS
  • 1990-1994  (162)
  • 1980-1984
  • 1940-1944
  • 1905-1909
  • 1880-1889
  • 1993  (162)
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  • 1990-1994  (162)
  • 1980-1984
  • 1940-1944
  • 1905-1909
  • 1880-1889
Year
  • 1
    Electronic Resource
    Electronic Resource
    Microscopy in solid state science (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 24 (1993), S. 299-315 
    Details
    ISSN: 1059-910X
    Keywords: STEM ; PEELS ; HAADFI ; Nanolithography ; Super-resolution ; STM ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The Microstructural Physics group at the Cavendish Laboratory is actively involved in a considerable number of research projects which cover a broad range of materials science. In this paper, we describe briefly several such projects, with particular emphasis given to the application of parallel-detection electron energy loss spectroscopy (PEELS) on a scanning transmission electron microscope (STEM) to the analysis of materials such as stainless steels, catalysts, and high temperature superconductors. In addition, we describe a number of related projects that are currently being carried out in the group, particularly those which utilise and develop novel STEM imaging and analytical techniques. © 1993 Wiley-Liss, Inc.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1070240404
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  • 2
    Electronic Resource
    Electronic Resource
    Dibutyryl cyclic adenosine monophosphate differentially regulates cell proliferation in low and high alkaline phosphatase SaOS-2 human osteosarcoma cells: Evidence for mediation by the insulin-like growth factor-II system (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 156 (1993), S. 462-468 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In the present study, we have sought to determine whether a given signal transduction pathway can have diverse effects on subpopulations of cells of a lineage depending upon the stage of differentiation. To test this hypothesis, we selected the cyclic adenosine monophosphate (cAMP) signal transduction pathway because of its recognized importance in mediating the actions of many hormones, e.g., parathyroid hormone which acts on the bone-forming cells, the osteoblasts. Subpopulations of human osteosarcoma SaOS-2 cells with low (LSaOS) and high (HSaOS) alkaline phosphatase (ALP) content were chosen as model systems for preosteoblasts (pre-OB) and osteoblasts (OB), respectively. Dibutyryl cyclic AMP (DBcAMP) treatment of serum free cultures produced a differential effect on the proliferation of LSaOS cells (40 ± 5% of control at 1 mM DBcAMP, P 〈 0.001) compared with HSaOS cells (no statistically significant effect). The finding supports the hypothesis. Next, we sought evidence for mediation, at least in part, by the insulin-like growth factor (IGF)-II regulatory system. We report that the basal expression of IGF-II, IGF binding protein (IGFBP)-3, and IGFBP-4 was higher in LSaOS cells than in HSaOS cells with the opposite true for type I IGF receptor. DBcAMP treatment of LSaOS cells decreased IGF-II and IGFBP-3 but increased IGFBP-4 and type I IGF receptor; no effect was observed for the type II IGF receptors. DBcAMP treatment of HSaOS cells had no detectable effect on IGF-II; IGFBP-3, or type I and type II IGF receptor expression; only IGFBP-4 expression increased with DBcAMP. These observations suggest that the differential regulation of cell proliferation by the cAMP signal transduction pathway may be mediated, at least in part, by the IGF-II regulatory system. © 1993 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041560305
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  • 3
    Electronic Resource
    Electronic Resource
    Problems and paradigms: Altering sex ratios: The games microbes play (1993)
    New York, NY : Wiley-Blackwell
    BioEssays 15 (1993), S. 695-697 
    Details
    ISSN: 0265-9247
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The male gametes of most organisms lack cytoplasm. Consequently, most cytoplasmic genetic elements are maternally inherited: they cannot be transmitted patrilinnearly. The evolutionary interests of cytoplasmic elements therefore lie in transmission through the female. These elements may thus be in evolutionary conflict with nuclear genes which are transmitted by both sexes. This conflict is manifested in observations of cytoplasmically induced biased sex-ratios. Some cytoplasmic genes avoid this fate by biasing the primary sex ratio towards females, or by inducing parthenogenesis. Others kill male hosts, and either achieve transmission via dispersal, or benefit their clonal relatives in the dead male's female siblings. Still others cause the failure of zygotes resulting from pairings between males carrying specific microbes and females lacking them, causing an increase in the microbes through the sterilisation of non-bearing females. Many, but not all, of these ‘ultra-selfish’ microbes are closely related. Investigations of the significance of their phylogenetic affinities, or lack of them, their adaptability in terms of the methods by which they avoid, or ameliorate, the adverse effects of being in male hosts, and their importance as selective agents in the evolution of invertebrate sex determination systems, provide fertile spheres for future research.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bies.950151010
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  • 4
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    SCR neon and argon in Kapoeta feldspar: Evidence for an active ancient Sun (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-01-25
    Description: From etched feldspar size-fractions of Kapoeta, we determine a significant excess of cosmogenic Ne-21 and Ar-38 over that produced by galactic cosmic rays. This excess component is attributed to early production by energetic solar protons and suggest that the energetic proton flux from the ancient Sun was several hundred times more intense than that of the contemporary Sun.
    Keywords: SOLAR PHYSICS
    Type: Lunar and Planetary Inst., Twenty-Fourth Lunar and Planetary Science Conference. Part 3: N-Z; p 1193-1194
    Format: text
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    NASA TECHNICAL REPORTS
  • 5
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    Solar-flare implanted He-4/He-3 and solar-proton-produced Ne and Ar concentration profiles preserved in lunar rock 61016 (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: Depth profiles for Ne-21, Ne-22, and Ar-38 isotopes from oriented lunar rock 61016 are reported. Concentration profiles of cosmogenic GCR+SCR (Galactic cosmic ray and solar cosmic ray-produced) isotopes are determined, quantitatively resolving neon and argon produced by energetic solar flares from that produced by Galactic cosmic rays. The SCR component is resolved from the GCR component as a function of shielding, and excellent agreement is found between experimental SCR production profiles for the isotopes and theoretically calculated values. A characteristic SW He-4/He-3 ratio of 3450 +/- 81, representing energies down to as few keV/amu. In slightly deeper samples an SRF He-4/He-3 ratio of 3450 +/- 725 is found for He particles with E larger than about 1 MeV/amu. These results indicate that the isotopic composition of SF He, averaged over the long term, is energy-dependent. An implanted Ne-20/Ne-22 ratio of 12.4 is measured in unetched samples, representing E greater than 1 MeV/amu, and a ratio of 11.6 is inferred in the samples, representing E larger than about 5 MeV/amu.
    Keywords: SOLAR PHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 98; A5; p. 7827-7835.
    Format: text
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    NASA TECHNICAL REPORTS
  • 6
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    Detection of a long-duration solar gamma-ray flare on June 11, 1991 with EGRET on COMPTON-GRO (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The detection of high energy photon emission from a long-duration solar gamma-ray flare on June 11, 1991 is reported. Gamma rays were detected up to energies above 1 GeV. The solar origin of this emission is assured by the time profile of the gamma-ray count rate and by time-resolved sky maps, which show a clear maximum at the position of the sun. There are indications for a spectral evolution with time, such that the emission below 100 MeV fades away earlier than the 100-300 MeV radiation, roughly on the time scale of the fast component. The spectrum of the flare can be well fitted with a composite of a proton generated pi exp 0 spectrum and an electron bremsstrahlung component. The latter can be identified with the fast decaying component of the lightcurve.
    Keywords: SOLAR PHYSICS
    Type: Astronomy and Astrophysics Supplement Series (ISSN 0365-0138); 97; 1; p. 349-353.
    Format: text
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    NASA TECHNICAL REPORTS
  • 7
    Electronic Resource
    Electronic Resource
    PKC mediates 12(S)-HETE-induced cytoskeletal rearrangement in B16A melanoma cells (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 26 (1993), S. 49-65 
    Details
    ISSN: 0886-1544
    Keywords: fatty acid ; MHC ; MLC ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The fatty acid 12(S)-HETE may be a new second messenger capable of activating PKC. In tumor cells 12(S)-HETE stimulates cytoskeleton-dependent cellular responses such as adhesion and spreading. Analysis of 12(S)-HETE effects on B16a melanoma cell cytoskeleton revealed reversible rearrangement of microtubules, microfilaments, the actin-binding proteins, vinculin, myosin heavy (MHC) and light chains (MLC), as well as bundling of vimentin intermediate filaments. The alterations in microfilaments and intermediate filaments occurred very rapidly, i.e., 5 min after exposure of tumor cells to 12(S)-HETE. The 12(S)-HETE-induced cytoskeletal alterations were accompanied by centrifugal organelle-translocation. Interestingly, MLC exhibited clear association with the cytoplasmic organelles. Biochemical analysis of the 12(S)-HETE effect indicated a PKC-mediated reversible hyperphosphorylation of MLC, vimentin, and a 130 kD cytoskeletal-associated protein. Optimal effects were obtained after 5 min treatment with 12(S)-HETE at 0.1 μM concentration. 12(S)-HETE pretreatment induced tumor cell spreading on a fibronectin matrix which required the intactness of all three major cytoskeletal components. The spreading process was dependent upon the activity of PKC. Our data suggest that 12(S)-HETE is a physiological stimulant of PKC. Further, it induces rearrangement of the cytoskeleton of tumor cells in interphase resulting in the stimulation of cytoskeleton-dependent cell activity such as spreading. © 1993 Wiley-Liss, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970260106
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  • 8
    Electronic Resource
    Electronic Resource
    Interaction of brain mitochondria with microtubules reconstituted from brain tubulin and MAP2 or TAU (1993)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 24 (1993), S. 245-255 
    Details
    ISSN: 0886-1544
    Keywords: tubulin ; microtubule-associated proteins ; membranous organelles ; interaction ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: To explore the behaviour of microtubule-associated proteins, MAP2 and TAU in the interactions of mitochondria with microtubules, an homologous acellular system has been reconstituted with organelles isolated from rat brain. We have established a quantitative in vitro binding assay based on the cosedimentation of 125I-labeled microtubules with mitochondria. We found that binding of microtubules to mitochondria was concentration dependent and saturable. Binding was insensitive to ATP. A comparison of taxol-stabilized microtubules prepared from MAP-free tubulin or tubulin coated with TAU or MAP2 showed that the microtubule-associated proteins diminished, or reduced to background levels, the formation of complexes with mitochondria. In contrast, the amount of MAP-free taxol microtubules that cosedimented with mitochondria increased two- and six-fold when mitochondria were coated with MAP2 or TAU. These studies suggest that the two major brain MAPs could have a crosslinking or a spacing role, depending on their organelle localization. © 1993 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970240405
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  • 9
    Electronic Resource
    Electronic Resource
    Cell cycle dependent distribution of proliferating cell nuclear antigen/cyclin and cdc2-kinase in mouse T-lymphoma cells (1993)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 52 (1993), S. 362-372 
    Details
    ISSN: 0730-2312
    Keywords: flow cytometry ; BrdU incorporation ; S-phase ; DNA synthesis ; p34-cdc2 ; colcemid ; mitotic inhibitors ; aneuploidy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The aim of the present study was to investigate bromodeoxyuridine (BrdU) uptake and coordinated distribution of proliferating cell nuclear antigen (PCNA) and p34-cdc2-kinase, two important proteins involved in cell cycle regulation and progression. Flow cytometric analysis of marker proteins in freshly plated mouse T-lymphoma cells (Yac-1 cells), using fluorescein isothiocyanate (FITC)-labeled specific antibodies, showed PCNA distributed throughout the cell cycle with increased intensity in S-phase. PCNA is essential for cells to cycle through S-phase and its synthesis is initiated during late G1-phase before incorporation of BrdU and remains high during active DNA replication. The intensity of PCNA fluorescence increases with the duration of incubation after plating. The cdc2-kinase was detectable in all phases of the cell cycle and the G2-M-phase appears to have the maximum concentrations. The cell cycle analysis of high dose colcemid (2 μg/ml) treated Yac-1 cells showed an aneuploid or hypodiploid population. Although the G2-M-phase seems to be the dominating population in aneuploid cells, the concentrations of cdc2-kinase were variable in this phase of cell cycle. The colcemid treatment at 25 ng/ml arrested 96% of cells in S-phase and G2-M-phase, but PCNA expression was evident in a portion of the cell population in G2-M-phase. Although cells blocked in M-phase seem to have high levels of cdc2-kinase, colcemid renders them inactive. From these data, it appears that the down regulation and/or inactivation of cdc2-kinase could be responsible for the colcemid arrest of cells in M-phase.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240520312
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  • 10
    Electronic Resource
    Electronic Resource
    Analysis of lipid peroxidation mechanisms in human spermatozoa (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 35 (1993), S. 302-315 
    Details
    ISSN: 1040-452X
    Keywords: Lipid peroxidation ; Reactive oxygen species ; Spermatozoa ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The mechanisms by which ferrous ion promoters induce malondialdehyde generation by human spermatozoa have been investigated in order to provide a rational basis for the quantification and interpretation of lipid peroxidation assays. Incubation of human spermatozoa with a ferrous ion promoter in the presence of thiobarbituric acid (TBA) led to the generation of the bone fide malondialdehyde-TBA adduct. The importance of iron in the stimulation of lipid peroxidation was emphasized by the ability of Desferal* and EDTA to suppress malondialdehyde generation. Paradoxically, when the concentration of EDTA relative to iron was equimolar or greater, the suppression of malondialdehyde formation was accompanied by the generation of hydroxyl radicals. These results suggested that the addition of promoter did not effect the first-chain initiation of lipid peroxidation but favored an alternative mechanism involving the catalytic decomposition of pre-existing lipid peroxides. This conclusion was reinforced by the inability of reagents that would limit the formation (superoxide dismutase and/or catalase) or availability (mannitol, formate) of hydroxyl radicals, to influence malondialdehyde generation. While hydroxyl radicals were not directly involved in Fe2+-promoted malondialdehyde generation, the existence of significant correlations between reactive oxygen species production and the outcome of the TBA assay, suggested that Fenton chemistry might be important in the initiation of peroxidative damage. It is proposed that the impeded propagation of peroxidation initiated by Fenton or Haber Weiss reactions would lead to the accumulation of lipid peroxides in the spermatozoa and it is these peroxides that are induced to decompose during the Fe2+-promoted TBA assay, stimulating a lipoperoxidative chain reaction and malondialdehyde formation. © 1993 Wiley-Liss, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1080350313
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