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  • Life and Medical Sciences  (15,261)
  • Inorganic Chemistry  (10,398)
  • LUNAR AND PLANETARY EXPLORATION  (6,950)
  • 2015-2019  (5)
  • 1990-1994  (15,868)
  • 1985-1989  (12,789)
  • 1935-1939  (3,947)
Collection
Keywords
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Structure of the scales of Dermophis and Microcaecilia (Amphibia: Gymnophiona), and a comparison to dermal ossifications of other vertebrates (1990)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 206 (1990), S. 25-43 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The structures of the dermal scales and the cells surrounding the scales in two species of gymnophione amphibians were studied using histochemistry and light, scanning and transmission electron microscopy. Scales are composed of a basal platt of several layers of unmineralized collagenous fibers topped with mineralized squamulae. Squamulae are composed of numerous mineralized globules and mineralized, thick collagen fibers. Mineralization is therefore both spheritic and inotropic. Isolated flattened cells lie on the outer surface of the squamulae and seem to be involved in mineral deposition. Cells that line the basal plate synthesize the collagenous stroma of the plate. Each scale lies in a thin connective tissue pocket, and a large connective tissue pouch includes several scales in each annulus.The similarities of gymnophione scales to elasmoid scales of osteichthyans are largely superficial. Aspects of mineralization and of pocket development differ considerably. There are also similarities, as well as differences, in the gymnophione scales and osteoderms of amphibians and of reptiles. We consider that such dermal structures have arisen many times in diverse lineages of vertebrates, and that these are expressions of properties of dermal collagen to support mineralization by specialized dermal cells. However, we recommend that the term “dermal scale” be used for the mineralized dermal units of osteichthyans and gymnophiones, and “osteoderm” for the dermal structures of frogs and squamates, with the understanding that the terminology recognizes certain convergent attributes of shape and structure, but not of process.
    Additional Material: 36 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1052060104
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  • 2
    Electronic Resource
    Electronic Resource
    New data on the structure and the growth of the osteoderms in the reptile Anguis fragilis L. (Anguidae, Squamata) (1985)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 186 (1985), S. 327-342 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Light and electron microscopy shows the osteoderms of Anguis fragilis to be small, flat disks located in the dermis along the adult trunk: microradiography established the extent of the mineralization.Each osteoderm coincides exactly with an epidermal fold forming the keratinized scales characteristic of the skin of reptiles.Sections perpendicular to the surface show two mineralized layers differing in histological and histochemical characteristics and in fine structure, although both contain collagen fibrils. The structure of each layer can be related to that of the surrounding dermis.The outer superficial layer located in the loose dermis contains few collagen bundles that form a discontinuous sheet at the upper surface of the osteoderms. This superficial layer appears to be constituted of units separated by furrows and is composed of woven fibered bone.The basal plate comprises stratified lamellae formed of parallel-oriented collagen fibrils; the fibrils of successive lamellae lie at right angles. The densely packed collagen fibrils of the basal plate are distributed similarly to those of the dense dermis within which it lies. This layer exhibits structural and histochemical characteristics of a lamellar bone.The presence of two different layers in the osteoderms of Anguis fragilis may reflect their mode of formation, which consists of the deposit of mineral crystals in the preexisting dermal tissue. This mineralization process, considered as a “metaplastic ossification,” may reflect the potentiality retained by the dermis of reptiles to form mineralized structures.
    Additional Material: 28 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051860309
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  • 3
    Electronic Resource
    Electronic Resource
    Artenvielfalt und Evolution (1993)
    Weinheim : Wiley-Blackwell
    Biologie in unserer Zeit 23 (1993), S. 308-315 
    Details
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Die uns auf der Erde umgebende Vielfalt an Organismen-Arten ist eine selbst für den naturwissenschaftlichen Laien auffällige Erscheinung. Als ein wesentliches Merkmal der belebten Natur bietet die Artenvielfalt dem Biologen ergiebige Forschungsfelder. Dennoch wurde die Erscheinung der Artenvielfalt lange von der moderne biologischen Wissenschaft, aber auch im biologischen Uniterricht recht stiefmütterlich behandelt. Erst nachdem in den vergengenen Jahren Biologen und in der Folge der öffentlich- Keit der weltweite Artenschwund bewußt geworden ist, wird dem Phänomen der Artenvielfalt eine verstärkte Aufmerksam- Keit zuteil. Das zeigt sich in der schnellen Einbürgerung des dem Angelsächsischen entlethnten Schlagworts „Biodiversität“ oder in der wachsenden Zahl an Symposien und Schriften, die sich mit der biologischen Vielfalt befassen. Genannt seien hier nur Wilson [14], ein Buch, welches das Problem der Bedrohung der Vielfalt in den VOrdergrund stellt, Groombridge [4], eine umfassende, vom„ world conservation monitoring centre“ erarbeitete Darstellung der „globalen Biodiversität“ oder der von Schulze und Mooney [9] herausgegebene Symposiumsband, in dem von ökologischer Seite die Frage nach den Funktionen der biologischen Vielfalt behandelt wird. Auch die Evolutionsbiologie sucht nach dem Ur-sprung und den hinter der Artenvielfalt stehenden Kräften [3].
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/biuz.960230508
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  • 4
    Electronic Resource
    Electronic Resource
    Artenvielfalt und Evolution (1993)
    Weinheim : Wiley-Blackwell
    Biologie in unserer Zeit 23 (1993), S. 308-315 
    Details
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Die uns auf der Erde umgebende Vielfalt an Organismen-Arten ist eine selbst für den naturwissenschaftlichen Laien auffällige Erscheinung. Als ein wesentliches Merkmal der belebten Natur bietet die Artenvielfalt dem Biologen ergiebige Forschungsfelder. Dennoch wurde die Erscheinung der Artenvielfalt lange von der moderne biologischen Wissenschaft, aber auch im biologischen Unterricht recht stiefmütterlich behandelt. Erst nachdem in den vergangenen Jahren Biologen und in der Folge der öffentlich-keit der weltweite Artenschwund bewußt geworden ist, wird dem Phänomen der Artenvielfalt eine verstärkte Aufmerksam- Keit zuteil. Das zeigt sich in der schnellen Einbürgerung des dem Angelsächsischen entlehnten Schlagworts „Biodiversität“ oder in der wachsenden Zahl an Symposien und Schriften, die sich mit der biologischen Vielfalt befassen. Genannt seien hier nur Wilson [14], ein Buch, welches das Problem der Bedrohung der Vielfalt in den Vordergrund stellt, Groombridge [4], eine umfassende, vom„ world conservation monitoring centre“ erarbeitete Darstellung der „globalen Biodiversität“ oder der von Schulze und Mooney [9] herausgegebene Symposiumsband, in dem von ökologischer Seite die Frage nach den Funktionen der.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/biuz.19930230508
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  • 5
    Electronic Resource
    Electronic Resource
    Transcription of circular and noncircular forms of Sry in mouse testes (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 37 (1994), S. 370-381 
    Details
    ISSN: 1040-452X
    Keywords: Sex determination ; Sex determining region Y ; Postmeiotic expression ; HMG box containing proteins ; Interstitial cells ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Although its expression in adult testis was immediately apparent, the role for Sry (sex determining region, Y) in testicular function remains elusive. We have performed transcriptional studies in an effort to elucidate potential roles of Sry by studying the time and location of its transcription in mouse testes. Northern analyses and more sensitive nuclease protection assays detected transcripts in 28-day-old testes and beyond. The highly sensitive technique of reverse transcription polymerase chain reaction (RTPCR) could not detect Sry expression in 14-day testes when primers for the most conserved portion of the gene, the high mobility group (HMG) box, were used, but primers for the circular form detected Sry transcription at all postnatal stages studied. The same HMG box primers were able to detect expression of Sry in XX, Sxra or Sxrb testes. This suggested that Sry is expressed in cells other than germ cells, which was confirmed with studies on fractionated cells - RTPCR detected transcription of Sry in the highly pure interstitial cell fraction. However, Leydig cells and a Leydig cell tumor were negative for Sry expression. We performed in situ studies in an attempt to localize the expression of Sry in the testes. Abundant expression of an Sry cross-hybridizing transcript was found in spermatogonia, in early spermatocytes, and in some interstitial cells with antisense probes to the HMG box or a more specific, 3′ region, whereas the sense probe gave little or no hybridization. It is probable that the circular transcripts, which are seen in reverse transcriptase positive (RT+) and RT- reactions by PCR because of the RT activity of Taq polymerase, are responsible for the hybridization seen in spermatogonia and spermatocytes, whereas linear and circular forms are detected later. Thus Sry is expressed in pre- and postmeiotic germ cells and in somatic cells of the testes. © 1994 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrd.1080370403
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  • 6
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    Direct detection of C4H2 photochemical products - Possible routes to complex hydrocarbons in planetary atmospheres (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: The photochemistry of diacetylene (C4H2), the largest hydrocarbon to be unambiguously identified in planetary atmospheres, is of considerable importance to understanding the mechanisms by which complex molecules are formed in the solar system. In this work, the primary products of C4H2's ultraviolet photochemistry were determined in a two-laser pump-probe scheme in which the products of C4H2 photoexcitation are detected by vacuum ultraviolet photoionization in a time-of-flight mass spectrometer. Three larger hydrocarbon primary products were observed with good yield in the C4H2 + C4H2 reaction: C6H2, C8H2, and C8H3. Neither C6H2 or C8H3 is anticipated by current photochemical models of the atmospheres of Titan, Uranus, Neptune, Pluto, and Triton. The free hydrogen atoms that are released during the formation of the C8H3 and C8H2 products also may partially offset the role of C4H2 in catalyzing the recombination of free hydrogen atoms in the planetary atmospheres.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science (ISSN 0036-8075); 258; 5088; p. 1630-1633.
    Format: text
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    NASA TECHNICAL REPORTS
  • 7
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    Energetic ions upstream of Jupiter's bow shock (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: In an analysis of the Jovian ion events, Baker et al. (1984) have found that there appears to be a spectral hardening as the interplanetary magnetic field (IMF) changed orientation from the postnoon to a prenoon connection point. It was also observed that ion events were accompanied by long-period (approximately 10 min) waves whose presence was weakly related to a decrease in the ion anisotropy. The present investigation examines in substantial detail the development of the ion energy spectrum over the full range (approximately 30 keV to approximately 4 MeV). The results of the investigation show that the energy spectra are dominated by heavy ions (presumed to be oxygen and sulfur) at higher (approximately equal to or greater than 300 keV) energies.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 90; 3947-396
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    NASA TECHNICAL REPORTS
  • 8
    Electronic Resource
    Electronic Resource
    Ökologie von Fließgewässern (1993)
    Weinheim : Wiley-Blackwell
    Biologie in unserer Zeit 23 (1993), S. 316-321 
    Details
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Die Struktur von Fließgewässer'-Ökosystemen ist zu komplex, um die ökologischen Zusammenhänge auf wenigen Seiten umfassend darzustellen. Stattdessen soll anhand weniger Beispiele aktueller Grundlagenforschung gezeigt werden, wie abiotische, mikrobiologische und verschiedene andere biologische Fließgewässern zusammenwirken müssen. Am Beispiel des Eintrags gelösten organischen Materials mit dem Grundwasser, aber auch an den terrestrischen Populationsverluste von Wasserinsekten wird gezeigt, daß man ökologische Prozesse in Fließgewässern nur dann verstehen kann, wenn man deren besonders enge Wechselbeziehungen mit dem terrestrischen Umland, ihren Einzugsgebieten, beachtet. Diese enge Vernetzung mit dem Umfeld hat auch eine besondere Verletzlichkeit von Fließgewässern zur Folge.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/biuz.19930230509
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  • 9
    Electronic Resource
    Electronic Resource
    Creation of ARS activity in yeast through iteration of non-functional sequences (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 6 (1990), S. 179-186 
    Details
    ISSN: 0749-503X
    Keywords: DNA replication ; replication origin ; eukaryotic chromosome ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Replication origins in Saccharomyces cerevisiae have been identified through the clonning of autonomous replication sequence (ARS) elements that allow the extrachromosonal maintenance of plasmid molecules. ARS activity requires a close matcht to an 11 bp consensus sequence and A+T-rich flanking DNA. ARS elements with a wide range of capacities for promoting plasmid maintenance have been described. We determined the ARS activity of plasmid with inserts consisting of repetitions of a 64 bp 100% A+T sequence that has sequence similarities to known ARS elements. An insert with approximately four repeats did not yield transformants, but inserts with either eight or eleven repeats did. The cooperative of ARS activity did not require a contiguous arrangement since a plasmid containing two inserts of four repeats each, separated by about 1 kb, was functional. Our results show that a charge from non-function to function can be accomplished by the cumulative action of individually inactive sequences. We conclude that the probability of replication initiation is too low with only four repeats to allow plasmid maintenance, but the overall probability is increased by further sequence iteration to provide origin activity. We suggest that chromosomes may contain streches with dispersed, weak origin elements, each undetected by the conventional ARS assay, that in sum provide origin function.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/yea.320060302
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  • 10
    Electronic Resource
    Electronic Resource
    Enterocytic differentiation of a subpopulation of the human colon tumor cell line HT-29 selected for growth in sugar-free medium and its inhibition by glucose (1985)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 122 (1985), S. 21-29 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In order to study the effect of glucose on the differentiation of cultured human colon cancer cells, a subpopulation of HT-29 cells was selected for its capacity to grow in the total absence of sugar. These cells (GIc-cells) exhibit, after confluency, an enterocytic differentiation, in contrast to cells grown with glucose (Glc+ cells), which always remain undifferentiated. The differentiation is characterized by a polarization of the cell layer with apical brush borders and tight junctions, and by the presence of sucrase-isomaltase. The differentiation of Glc-cells is reversible: the addition of glucose to postcon-fluent cultures of Glc- cells results in an inhibiting effect on the expression of sucrase-isomaltase; switching growing cultures of Glc-cells to the Glc+ medium for several passages results in a progressive reversion to the undifferentiated state, which is completed after seven passages. The dedifferentiation process is associated with a parallel, passage-related, increase in the rates of glucose consumption and lactic acid production, and decreases of intracellular glycogen content, which return to the values of the undifferentiated original Glc+ cells. The values of these metabolic parameters are correlated, at each passage, with the degree of dedifferentiation of the cells. When these dedifferentiated cells, after having been cultured in Glc+ medium for 20 passages, are switched back to the Glc- medium, they readily grow without mortality, and reexpress the same enterocytic differentiation as the parent Glc- cells. These results show that the capacity of this subpopulation to grow and differentiate in the absence of sugar is a stable characteristic. They further suggest that glucose metabolism interferes with the program of differentiation of HT-29 cells.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041220105
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