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  • Microtubules  (25)
  • Analytical Chemistry and Spectroscopy  (13)
  • SOLID-STATE PHYSICS  (13)
  • 1
    Electronic Resource
    Electronic Resource
    Nuclear cytoplasmic domains, microtubules and organelles in microsporocytes of the slipper orchid Cypripedium californicum A. Gray dividing by simultaneous cytokinesis (1996)
    Springer
    Sexual plant reproduction 9 (1996), S. 145-152 
    Details
    ISSN: 1432-2145
    Keywords: Cytokinesis ; Microtubules ; Microsporogenesis ; Orchids ; Phragmoplast ; Pollen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Microsporocytes of the slipper orchidCypripedium californicum A. Gray divide simultaneously after second meiosis. The organization and apportionment of the cytoplasm throughout meiosis are functions of nuclear-based radial microtubule systems (RMSs) that define domains of cytoplasm - a single sporocyte domain before meiosis, dyad domains within the undivided cytoplasm after first meiosis, and four spore domains after second meiosis. Organelles migrate to the interface of dyad domains in the undivided cytoplasm after first meiotic division, and second meiotic division takes place simultaneously on both sides of the equatorial organelle band. Microtubules emanating from the telophase II nuclei interact to form columnar arrrays that interconnect all four nuclei, non-sister as well as sister. Cell plates are initiated in these columns of microtubules and expand centrifugally along the interface of opposing RMSs, coalescing in the center of the sporocyte and joining with the original sporocyte wall at the periphery to form the tetrad of microspores. Organelles are distributed into the spore domains in conjunction with RMSs. These data, demonstrating that cytokinesis in microsporogenesis can occur in the absence of both components of the typical cytokinetic apparatus (the preprophase band of microtubules which predicts the division site and the phragmoplast which controls cell-plate deposition), suggest that plant nuclei have an inherent ability to establish a domain of cytoplasm via radial microtubule systems and to regulate wall deposition independently of the more complex cytokinetic apparatus of vegetative cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02221394
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  • 2
    Electronic Resource
    Electronic Resource
    Development of endosperm in Arabidopsis thaliana (1999)
    Springer
    Sexual plant reproduction 12 (1999), S. 32-42 
    Details
    ISSN: 1432-2145
    Keywords: Key words Arabidopsis thaliana ; Alveoli ; Development ; Endosperm ; Microtubules ; Seeds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The process of endosperm development in Arabidopsis was studied using immunohistochemistry of tubulin/microtubules coupled with light and confocal laser scanning microscopy. Arabidopsis undergoes the nuclear type of development in which the primary endosperm nucleus resulting from double fertilization divides repeatedly without cytokinesis resulting in a syncytium lining the central cell. Development occurs as waves originating in the micropylar chamber and moving through the central chamber toward the chalazal tip. Prior to cellularization, the syncytium is organized into nuclear cytoplasmic domains (NCDs) defined by nuclear-based radial systems of microtubules. The NCDs become polarized in axes perpendicular to the central cell wall, and anticlinal walls deposited among adjacent NCDs compartmentalize the syncytium into open-ended alveoli overtopped by a crown of syncytial cytoplasm. Continued centripetal growth of the anticlinal walls is guided by adventitious phragmoplasts that form at interfaces of microtubules emanating from adjacent interphase nuclei. Polarity of the elongating alveoli is reflected in a subsequent wave of periclinal divisions that cuts off a peripheral layer of cells and displaces the alveoli centripetally into the central vacuole. This pattern of development via alveolation appears to be highly conserved; it is characteristic of nuclear endosperm development in angiosperms and is similar to ancient patterns of gametophyte development in gymnosperms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004970050169
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  • 3
    Electronic Resource
    Electronic Resource
    Nuclear cytoplasmic domains, microtubules and organelles in microsporocytes of the slipper orchid Cypripedium californicum A. Gray dividing by simultaneous cytokinesis (1996)
    Springer
    Sexual plant reproduction 9 (1996), S. 145-152 
    Details
    ISSN: 1432-2145
    Keywords: Key words Cytokinesis ; Microtubules ; Microsporogenesis ; Orchids ; Phragmoplast ; Pollen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Microsporocytes of the slipper orchid Cypripedium californicum A. Gray divide simultaneously after second meiosis. The organization and apportionment of the cytoplasm throughout meiosis are functions of nuclear-based radial microtubule systems (RMSs) that define domains of cytoplasm – a single sporocyte domain before meiosis, dyad domains within the undivided cytoplasm after first meiosis, and four spore domains after second meiosis. Organelles migrate to the interface of dyad domains in the undivided cytoplasm after first meiotic division, and second meiotic division takes place simultaneously on both sides of the equatorial organelle band. Microtubules emanating from the telophase II nuclei interact to form columnar arrrays that interconnect all four nuclei, non-sister as well as sister. Cell plates are initiated in these columns of microtubules and expand centrifugally along the interface of opposing RMSs, coalescing in the center of the sporocyte and joining with the original sporocyte wall at the periphery to form the tetrad of microspores. Organelles are distributed into the spore domains in conjunction with RMSs. These data, demonstrating that cytokinesis in microsporogenesis can occur in the absence of both components of the typical cytokinetic apparatus (the preprophase band of microtubules which predicts the division site and the phragmoplast which controls cell-plate deposition), suggest that plant nuclei have an inherent ability to establish a domain of cytoplasm via radial microtubule systems and to regulate wall deposition independently of the more complex cytokinetic apparatus of vegetative cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004970050024
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  • 4
    Electronic Resource
    Electronic Resource
    Butyl nitrite: A novel chemical ionization reagent compound (1988)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 2 (1988), S. 77-78 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A Kratos MS-25RFA medium resolution mass spectrometer and a Concept IS high resolution mass spectrometer were used to analyse a range of highly substituted aromatic alcohols for kinetic studies.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290020408
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  • 5
    Electronic Resource
    Electronic Resource
    Ion detection limitations to mass resolution in matrix-assisted laser desorption time-of-flight mass spectrometry (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 690-696 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The ion detection process in a discrete-dynode electron multiplier can result in significant mass resolution losses in time-of-flight mass spectrometry (TOF-MS) for higher mass-to-charge (m/z) ion species. This resolution loss is attributed to propagation time delays and signal broadening in the ion detector. This is presumed tobe due to the generation o a distribution of secondary ion species produced initially upon impact of a primary ion with the first ynoe surface of the ion detector. Comparisons are made between the signals produced by a standard discrete dynode ion detector (which amplified the negatively chqrged species produced by impact of a primry ion) and a detector modified to respond to only the positively charged secondary ion species produced by a primary ion impact. Ion signals for higher m/z ions with the standard detector geometry are see to be due to a narrow signal component, most likely due to the generation o secondary electrons and/or very low mass secondary ions (H-), and a broad signal component, apparently due to secondary ions which take signifiant amounts of time to traverse the low potential fields between the first and second detector dynode. This results in ion signal tailing for higher m/z ion species. Numerical subtraction of the ion signal obtained with the standard and modified detector geometries (singly protonated molecular ion species of equine myoglobin) results in an improvement in mass resolution, such that a new adduct ion species (from trifluoroacetic acid) can be resolved.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290061112
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  • 6
    Electronic Resource
    Electronic Resource
    Isotope ratio measurements in lead using three-photon one-colour resonance ionization mass spectrometryBritish Crown Copyright 1993/MOD. Published with the permission of the Controller of Her Britannic Majesty's Stationery Office. (1993)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 7 (1993), S. 524-527 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Resonance effects on measured isotope ratios in lead using three-photon one-colour resonance ionization mass spectrometry are discussed. The shape of the ionization signal is considered for the case of a non-monochromatic laser field. The intensity of the laser radiation is adjusted to be low enough not to cause saturation of the transitions. The variation of the measured isotope ratio as a function of laser frequency is considered. It is shown that the deviation of the measured from the expected isotope ratio, for a Lorentzian laser lineshape equals the ratio of the isotope shift to the laser bandwidth. Unfortunately, the background noise in the experiments makes verification of this behaviour difficult for the isotopes of low abundance.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290070625
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  • 7
    Electronic Resource
    Electronic Resource
    Opimizing signal and mass resolution for matrix-assisted laser desorption utilizing a linear time-of-flight mass spectrometer (1992)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 6 (1992), S. 697-701 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Results are oresented for various instrumental configurations employed for matrix-assisted laser desorption mass spectrometry. Mass resolution is determined for a linear time-of-flight mass spectrometer for various lengths of the field-free region. A wire ion guide is utilized and is shown to improve ion transport efficiencies for longer field-free regions. It is also determined experimentally that a modest mass resolution increase is often obtained in configurations employing the wire ion guide when compared to the mass resolution obtained with the same geometr without the wire ion guide. Optimal applied potentials are determined for the wire ion guide. No mass dependence on the opitmal applied potential (-100 V) for the wire ion guide is observed for samples of equine myoglobin (MW 16 951.5 Da) and a bacterial protease (MW 27 228.4 Da). The optimal applied voltage was also found to b identical (-100 V) for the singly through quadruply charged molecular ion species of rabbit gamma globulin (MW ≍ 150 000 Da). It is shown that a 2 m flight tube with a wire ion guide provides better signal-to-noise mass spectra than a 1 m flight tube without the wire ion guide and can more than double the mass resolution obtainable. Utilization obtainable. Utilization of a 4 m flight tube gives minimal mass resolution enhancement at the expense of signal-to-noise.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290061113
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  • 8
    Electronic Resource
    Electronic Resource
    Ultrastructure of meiosis in the mossRhynchostegium serrulatum I. Prophasic microtubules and spindle dynamics (1982)
    Springer
    Protoplasma 110 (1982), S. 23-33 
    Details
    ISSN: 1615-6102
    Keywords: Meiosis ; Microtubules ; Polarity ; Ultrastructure ; Mosses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary An extensive system of microtubules develops during meiotic prophase in the mossRhynchostegium serrulatum (Hedw.)Jaeg. &Sauerb. Development of the cytoskeleton can be traced to early prophase when the nucleus is acentric and the single plastid divides into four plastids. The cytoskeletal microtubules are associated with equidistant positioning of the four plastids at the distal tetrad poles and with migration of the nucleus to a central position in the sporocyte. The cytoskeleton, which interconnects plastids and encloses the nucleus, contributes to the establishment of moss sporocyte polarity. Just prior to metaphase I evidence of the prophase cytoskeleton is lost as the bipolar metaphase I spindle develops in association with discrete polar organizers located in opposite cleavage furrows between plastids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01314678
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  • 9
    Electronic Resource
    Electronic Resource
    Microtubule organization and morphogenesis in young spores of the mossTetraphis pellucida Hedw (1983)
    Springer
    Protoplasma 116 (1983), S. 115-124 
    Details
    ISSN: 1615-6102
    Keywords: Microtubules ; Moss ; MTOC ; Sporogenesis ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Microtubule systems appear sequentially at the distal and proximal poles of tetrad members during mid-sporogenesis in the mossTetraphis pellucida Hedw. The distal microtubule system emanates from a microtubule organizing center (MTOC) located between the single plastid and the nucleus. The distal MTOC and associated microtubules, which appear immediately after cytokinesis, are ephemeral and do not appear to be associated with the deposition of exine occuring at the same time. The proximal microtubule system, which appears slightly later than the distal system, is a more stable component of mid-sporogenesis. The proximal MTOC is an irregularly lobed, patelliform aggregation of electron-dense granules located beneath the plasma membrane at the proximal spore pole. Several bundles of microtubules radiate from the proximal MTOC and traverse the cell, enclosing the nucleus in an cone of microtubules. The proximal microtubule system is thought to function in aperture development and organelle migration. The relatively large nucleus migrates a short distance in the small spore early in the tetrad stage and maintains its acentric position at the proximal pole throughout later stages of sporogenesis. The plastid migrates later in the tetrad stage from its meiotic position parallel to the distal surface to a position perpendicular to the distal surface with one tip in close proximity to the proximal MTOC. The proximal microtubule system reaches its maximum development by the end of the tetrad stage and all micrographic evidence of it is lost in the maturation stages of late sporogenesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01279828
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  • 10
    Electronic Resource
    Electronic Resource
    Further evidence from sectioned material in support of the existence of a linear terminal complex in cellulose synthesis (1987)
    Springer
    Protoplasma 136 (1987), S. 96-103 
    Details
    ISSN: 1615-6102
    Keywords: Boergesenia forbesii ; Microfibrils ; Microtubules ; Plasma membrane ; Sectioned material ; Terminal complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Transmembrane linear terminal complexes considered to be involved in the synthesis of cellulose microfibrils have been described in the plasma membrane ofBoergesenia forbesii. Evidence for the existence of these structures has been obtained almost exlusively using the freeze etching technique. In the present study an attempt has been made to complete these studies using conventional fixation, staining, and sectioning procedures. In developing cells ofBoergesenia forbesii, strongly stained structures traversing the plasma membrane and averaging 598.9 nm ± 171.3 nm in length, 28.7 nm ± 4.2 nm in width, and 35.2 nm ± 6.6 nm in depth have been demonstrated. These structures are considered to be linear terminal complexes. At their distal (cell wall) surface, they appear to be closely associated with cellulose microfibrils. At the proximal (cytoplasmic) surface, they are associated with microtubules and polysomes. A model of the possible interrelation of the terminal complexes and microtubules leading to the generation of cell wall microfibrils is proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01276358
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