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  • 1
    Electronic Resource
    Electronic Resource
    Gravity and seismicity analyses of the El Chichon volcano, Chiapas, Mexico (1990)
    Springer
    Pure and applied geophysics 133 (1990), S. 149-165 
    Details
    ISSN: 1420-9136
    Keywords: Volcanic seismicity ; volcanic gravity anomaly ; volcanic tectonics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Subduction induced compressional stress, lateral displacement faults probably linked to the NW extension of the Polochic-Motagua fault system, and local magma emplacement create a complex geological setting for the El Chichon volcano. Gravity analysis reveals that the principal structures in the area correspond to synclines and anticlines. Downward continuation of the gravity field suggests the presence of magma emplacement SE of the volcano. This magmatic emplacement appears to be the principal cause of the truncation of the syncline in which the volcano lies. Analyses of earthquakes occurring after eruptions show that the vertical distribution of events is confined to a roughly cylindrical zone which correlates well with the region of magmatic emplacement inferred from the gravity analysis. Even though more than 350 km separate the volcano from the Middle American trench, the compressional stress regime reported for the area may correlate with subduction stress (N30°E). However, the strike direction for the principal faults in the zone, N60°W, permits us to postulate that the NW extension of the Polochic-Motagua fault system is implicated in the local tectonics of the El Chichon area.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00876708
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  • 2
    Electronic Resource
    Electronic Resource
    Some aspects of ovular development during megasporogenesis inPisum sativum L. (1980)
    Springer
    Cellular and molecular life sciences 36 (1980), S. 657-658 
    Details
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary This work reports some findings which will aid us in our understanding of the female phase ofPisum sativum embryology. We have observed that the central planes between one ovule and the next form an angle of 60°. We suggest that this ovule arrangement may make it easier for the pollen tube to reach the ovular micropyle in the fertilization process. On the other hand, ovary and ovule growth do not depend on the megasporogenesis stage but have individual characteristics for each plant, every one depending on its own phenotype.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01970121
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  • 3
    Electronic Resource
    Electronic Resource
    A study on nucleolar silver staining in plant cells. The role of argyrophilic proteins in nucleolar physiology (1983)
    Springer
    Chromosoma 88 (1983), S. 149-155 
    Details
    ISSN: 1432-0886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Using a high resolution nucleolar silver staining technique, we have studied the distribution of silver grains at interphase and mitosis. The nucleolar fibrillar centers and the fibrillar component, as well as the mitotic nucleolar organizing region (NOR), are argyrophilic. Of the NOR structures, the fibrillar component is transcriptionally active, but the fibrillar centers and the mitotic NORs are not. Treatment with cycloheximide (CHM), which indirectly impairs rRNA synthesis, does not affect the pattern of silver staining. The currently assumed correlation between activity and Ag-NOR staining appears questionable. On the other hand, all Ag-NOR-stained structures contain decondensed chromatin, whereas condensed portions of this chromatin are not stained by silver. In CHM-treated cells there is apparently no chromatin condensation accompanying inhibition of rRNA synthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00327336
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  • 4
    Electronic Resource
    Electronic Resource
    Historic and holocene volcanic centers in NW Mexico (1989)
    Springer
    Bulletin of volcanology 51 (1989), S. 91-93 
    Details
    ISSN: 1432-0819
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01197481
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  • 5
    Electronic Resource
    Electronic Resource
    Enhancement of the immunocytochemical detection of antigens by microwave irradiation. Benefits and limitations analysed in isolated plant nuclei and Drosophila embryos in toto (1994)
    Springer
    Histochemistry and cell biology 102 (1994), S. 45-50 
    Details
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Performing the antibody reaction under controlled heating through microwave irradiation results in significant improvements in the immunovisualization of antigens, such as shortening the times of incubation, lowering the antibody titres used and allowing the detection of difficult, inaccessible antigens. In addition to investigate the basis of the enhancement, we have extended to more intact samples such as isolated plant nuclei and in toto Drosophila embryos the results previously reported only with tissue sections. A drop of heterologous anti-nucleolin antibody covering isolated nuclei from onion root meristems spread on a glass slide was microwave irradiated, resulting in clear immunofluorescent labelling of the nucleoli. This result was never previously obtained in the absence of microwave treatment, even using the complicated procedure previously reported for the homologous identification of this nuclear protein. Using the much larger and to some extent impermeable Drosophila embryos, we were able to show that the incubation time and concentration of the anti-myosin antibody can be strongly reduced by performing the reaction at 45° C under microwave irradiation. The controlled increase in temperature is the main factor responsible for these improvements; the importance of maintaining an adequate mixing of the samples is also emphasized. The proper implementation of these two experimental conditions will require the introduction of appropriate mixing accessories and temperature measuring probes for samples of small volume in current microwave laboratory ovens.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00271048
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  • 6
    Electronic Resource
    Electronic Resource
    Evolution of the cytoplasmic organelles during female meiosis in Pisum sativum L. (1981)
    Springer
    Planta 151 (1981), S. 215-225 
    Details
    ISSN: 1432-2048
    Keywords: Metosis (organelles) ; Organelles (during meiosis)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In this paper we have traced the evolution of the cytoplasmic organelles in the female germinal cell of Pisum sativum L., from the beginning of meiosis to the early stages of the maturing megaspore, in order to correlate the morphological changes with the physiological aspects of megasporogenesis. A process of intense cytoplasmic vacuolation takes place in the megaspore mother cell (MMC) during prophase I, probably proceeding from the smooth endoplasmic reticulum and dictyosomes; it results in the formation of big vacuoles, which play a role in MMC polarization. By means of this polarization most plastids and mitochondria are incorporated into the functional megaspore at the end of meiosis. There are plastid and mitochondria cycles which consist of dedifferentiation followed by redifferentiation, During these cycles a transient morphology appears, called a cup-shaped form, which we interpret as an expression of low organelle activity. The wall of the MMC thickens throughout megasporogenesis and loses its plasmodesmata during middle prophase I. The ribosome population is reduced during prophase I and then restored during the early stages of the megaspore maturing process, as shown by the quantitative study that we have carried out. The nucleolar cytoplasmic bodies play a part in this restoring process. These bodies have a special morphology and appear to be originated from the activity of the nucleolar organizing region (NOR) during nucleolar disorganization in prophase I. We think that this cytoplasmic evolution is a response to nuclear genic recombination, in order to provide the most adequate expression of the zygote genome.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00395172
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  • 7
    Electronic Resource
    Electronic Resource
    TPD study about the surface modification of some Ni/spinel catalysts in the hydrodechlorination of 1,2,4‐trichlorobenzene. Influence on hydrogenation ability (2000)
    Springer
    Catalysis letters 67 (2000), S. 147-153 
    Details
    ISSN: 1572-879X
    Keywords: cyclohexane ; Ni/spinel ; 1,2,4‐trichlorobenzene ; surface chlorination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract NiAl2O4 supports and fresh and reactivated Ni/NiAl2O4 catalysts were tested in the gas phase hydrodechlorination of 1,2,4‐trichlorobenzene. Fresh catalysts hydrogenate 1,2,4‐trichlorobenzene to cyclohexane in the first 30 min of reaction at 523 K. An irreversible partial chlorination of the catalytic surface makes the hydrogenation of the aromatic ring difficult.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019057219750
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  • 8
    Electronic Resource
    Electronic Resource
    Further investigations on the functional role of two nuclear bodies in onion cells (1992)
    Springer
    Protoplasma 167 (1992), S. 175-182 
    Details
    ISSN: 1615-6102
    Keywords: Centromeric structures ; Nuclear bodies ; Plant cells ; RNA processing ; Silver staining-nucleolus organizer proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary “Micropuffs” and coiled bodies are two nuclear bodies which have previously been described in a wide range of plant species. In this work, we have demonstrated, by means of ultrastructural cytochemical, autoradiographic and immunocytochemical methods, that the so-called “micropuffs” contain chromatin, which is organized in a supranucleosomal structure, is inactive in transcription, and has no apparent relationship with the nucleolus. These features, as well as the distribution of these structures during the interphase periods, allowed us to conclude that they represent centromeric structures, so, we propose that they be denoted by this name. Coiled bodies show the same silver-staining pattern as the nucleolus organizer (NOR), but do not appear to contain NOR chromatin nor does the early processing of rRNA precursor seem to take place in them. We postulate they are involved in later nuclear RNA processing and storage. This work clarifies some previous misunderstandings with regard to these bodies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01403381
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  • 9
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    A study on nucleolar silver staining in plant cells. The role of argyrophilic proteins in nucleolar physiology (1983)
    Springer
    Details
    Publication Date: 1983-07-01
    Print ISSN: 0009-5915
    Electronic ISSN: 1432-0886
    Topics: Biology , Medicine
    Published by Springer
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  • 10
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    Some aspects of ovular development during megasporogenesis inPisum sativum L. (1980)
    Springer
    Details
    Publication Date: 1980-06-01
    Print ISSN: 0014-4754
    Topics: Biology , Medicine
    Published by Springer
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