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  • 1
    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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  • 2
    Electronic Resource
    Electronic Resource
    A cytoskeletal system predicts division plane in meiosis ofSelaginella (1985)
    Springer
    Protoplasma 127 (1985), S. 101-109 
    Details
    ISSN: 1615-6102
    Keywords: Division polarity ; Microtubules ; Meiosis ; Selaginella ; Sporogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary An ultrastructural investigation of the monoplastidic microsporocytes ofSelaginella arenicola revealed a unique cytoskeletal array that predicts the future division plane before nuclear division takes place. By midprophase of the first meiotic division, the single plastid has divided once and the two plastids lie on opposite sides of the nucleus which is elongated in the plane of the incipient metaphase I spindle. A cytoplasmic structure, the procytokinetic plate (PCP), predicts the division plane of of both plastid and cytoplasm. The PCP consists of a distinct concentration of vesicles lying in the future division plane and an elaborate system of microtubules aligned parallel to the long axis of plastids and nucleus. Microtubules of the axially aligned system appear to terminate in clusters of vesicles in the central zone of the PCP. The PCP with axially aligned microtubules is as predictive of the division plane in these meiotic cells as is the girdling preprophase band of microtubules in mitotic cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01273706
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  • 3
    Electronic Resource
    Electronic Resource
    Division polarity, development and configuration of microtubule arrays in bryophyte meiosis (1987)
    Springer
    Protoplasma 138 (1987), S. 1-10 
    Details
    ISSN: 1615-6102
    Keywords: Meiosis ; Microtubules ; Cytokinesis ; Immunofluorescence ; Bryophytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary First and second division spindles and the three cell plates of moss meiosis are oriented in accordance with polarity established during meiotic prophase. Plastids are located at the second division poles and cytoplasmic infurrowing marks the planes along which the cytoplasm will cleave into four spores. Anaphase I spindles that terminate in two focal points of microtubules straddling opposite cleavage furrows reflect the unusual tetrahedral origin of the functionally bipolar spindle. The organelles (except for the plastids which remain in the four cytoplasmic lobes) are polarized in the first division equatorial region at the time of phragmoplast microtubule assembly and remain in a distinct band after microtubule disassembly. Prophasic spindles appear to be directly transformed into metaphase II spindles in the predetermined axes between mutually perpendicular pairs of plastids. Cell plates form by vesicle coalescence in the equatorial regions of the two sets of second division phragmoplasts at approximately the same time as a cell plate belatedly forms in the organelle band. The cytoplasmic markers (plastid migration, cytoplasmic lobing and infurrowing) that predict poles and cleavage planes in free cells lacking a preprophase band strongly strengthens the concept that division sites are capable of preserving preprogrammed signals that can be triggered later in the process of cell division.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01281179
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  • 4
    Electronic Resource
    Electronic Resource
    Division polarity and plasticity of the meiosis I spindle inCypripedium californicum (Orchidaceae) (1998)
    Springer
    Protoplasma 203 (1998), S. 168-174 
    Details
    ISSN: 1615-6102
    Keywords: Confocal laser scanning microscopy ; Cytoplasmic domains ; Meiosis ; Microtubules ; Organelle band ; Polarity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Establishment of division polarity and meiotic spindle organization in the lady's slipper orchidCypripedium californicum A. Gray was studied by immunocytochemistry, confocal and transmission electron microscopy. Prior to organization of the spindle for meiosis I, the cytoplasmic domains of the future dyad and spindle polarity are marked by: (1) constriction of the prophase nucleus into an hourglass shape; (2) reorganization of nuclear-based radial microtubules into two arrays that intersect at the constriction; and (3) redistribution of organelles into a ring at the boundary of the newly defined dyad domains. It is not certain whether the opposing microtubule arrays contribute directly to the anastral spindle which is organized in the perinuclear areas of the two hemispheres. By late prophase each half-spindle consists of a spline-like structure from which depart the kinetochore fibers. This peculiar spindle closely resembles the spline-like spindle of generative-cell mitosis in certain plants where the spindle is distorted by physical constraints of the slender pollen tube. In the microsporocyte, the elongate spindle of late prophase/metaphase is curved within the cell so that the poles are not actually opposite each other and chromosomes do not form a plate at the equator. By late telophase the poles of the shortened halfspindles lie opposite each other. Plasticity of the physically constrained plant spindle appears to be due to its construction from multiple units terminating in minipoles. Cytokinesis does not follow the first meiosis. However, the dyad domains are clearly defined by radial microtubules emanating from the two daughter nuclei and the domains themselves are separated by a disc-like band of organelles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01279473
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  • 5
    Electronic Resource
    Electronic Resource
    Morphogenetic plastid migration and microtubule organization during megasporogenesis inIsoetes (1989)
    Springer
    Protoplasma 152 (1989), S. 136-147 
    Details
    ISSN: 1615-6102
    Keywords: Isoetes ; Megasporogenesis ; Monoplastidy ; Meiosis ; Microtubules ; Mitotic apparatus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The large megasporocytes ofIsoetes provide an exceptional system for studying microtubule dynamics in monoplastidic meiosis where plastid polarity assures coordination of plastid and nuclear division by the intimate association of MTOCs with plastids. Division and migration of the plastid in prophase establishes the tetrahedrally arranged cytoplasmic domains of the future spore tetrad and the four plastid-MTOCs serve as focal points of a unique quadripolar microtubule system (QMS). The QMS is a dynamic structure which functions in plastid deployment and contributes directly to development of both first and second division spindles. The nucleation of microtubules at discrete plastid-MTOCs is compared with centrosomal nucleation of microtubules in animal cells where growth of microtubules involves dynamic instability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01323073
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  • 6
    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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  • 7
    Electronic Resource
    Electronic Resource
    Potential of inductively coupled plasma mass spectrometry for trace element metabolism studies in man (1988)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 16 (1988), S. 377-380 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new inorganic mass spectrometric technique is described which allows sensitive, rapid and economic determination of trace element concentrations and isotope ratios in aqueous samples. This paper illustrates the potential of the technique in one particular application area, namely the measurement of strontium isotope ratios in human blood and urine following ingestion of an enriched stable strontium isotope. The data from a human volunteer experiment illustrate the viability of the analytical method, with measurement precisions of ± 0.2% (1σ) achieved for the isotope ratio in urine samples, which contained approximately 300 ng 86Sr in the volume required for analysis. Measurement precision is limited by counting statistics.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200160174
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  • 8
    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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  • 9
    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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  • 10
    Electronic Resource
    Electronic Resource
    A quantitative adhesion test for thin polymer films on silicon substrates (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 43 (1991), S. 1287-1292 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The standard 90° peel test was modified in order to apply it to testing adhesion of thin polymer films to surfaces of silicon substrates, such as the silicon nitride passivation layer used in our solid-state chemical sensors. The goal of this task was to develop a procedure for testing adhesion of both dry and wet films, which would yield repeatable, quantitative results quickly, and with simple sample preparation. It is important to produce valid comparisons of adhesion both over variations of a given polymer composition, and between films made of dissimilar polymer matrices. The method described herein could be applied to adhesion testing of a wide variety of thin polymer layers to solid surfaces.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1991.070430709
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