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  • Articles  (2)
  • Action spectra  (1)
  • 550 - Earth sciences
  • Humans
  • Life and Medical Sciences
  • 1995-1999  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Uses of biological spectral weighting functions and the need of scaling for the ozone reduction problem (1997)
    Springer
    Plant ecology 128 (1997), S. 67-76 
    Details
    ISSN: 1573-5052
    Keywords: Action spectra ; Global change assessment ; Higher plant response to UV ; Solar ultraviolet ; Stratospheric ozone layer ; UV-B radiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In several phases of assessing implications of stratospheric ozone reduction for plants, biological spectral weighting functions (BSWF) play a key role: calculating the increase of biologically effective solar ultraviolet-B radiation (UV-BBE) due to ozone reduction, assessing current latitudinal gradients of UV-BBE, and comparing solar UV-BBE with that from lamps and filters in plant experiments. Plant UV action spectra (usually determined with monochromatic radiation in the laboratory with exposure periods on the order of hours) are used as BSWF. Yet, many complicating factors cloud the realism of such spectra for plants growing day after day in polychromatic solar radiation in the field. The uses and sensitivity of BSWF in the stratospheric ozone reduction problem are described. The need for scaling BSWF from action spectra determined with monochromatic radiation in laboratory conditions over periods of hours to polychromatic solar radiation in the field is developed. Bottom-up mechanistic and top-down polychromatic action spectrum development are considered as not satisfactory to resolve realistic BSWF. A compromise intermediate approach is described in which laboratory results are tested under polychromatic radiation in growth chambers and, especially, under field conditions. The challenge of the scaling exercise is to resolve disagreements between expected spectral responses at different scales of time and radiation conditions. Iterative experiments with feedback among the different experimental venues is designed to reduce uncertainties about realistic BSWF in the field. Sensitivity analyses are employed to emphasize characteristics of BSWF that are particularly important in assessing the ozone problem. Implications for use of realistic BSWF both for improved research design and for retrospective analysis of past research is described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009775326900
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  • 2
    Electronic Resource
    Electronic Resource
    Culture of pachytene spermatocytes for analysis of meiosis (1995)
    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 16 (1995), S. 128-139 
    Details
    ISSN: 0192-253X
    Keywords: Spermatogenesis ; meiosis ; synapsis ; synaptonemal complex ; G2-M transition ; okadaic acid ; actinomycin D ; camptothecin ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: An impediment to the investigation of mammalian spermatogenic meiosis has been the lack of an appropriate system for experimental manipulation of meiotic prophase cells. We report here the use of a simple system for the short-term culture of pachytene spermatocytes. We have assayed parameters of cell function pertinent to meiotic prophase, namely chromosome pairing and synapsis. During the culture period of 24-48 hr, cells maintained typical pachytene morphology, chromatin condensation patterns, and chromosome pairing, as assessed by light and electron microscopy. Uridine incorporation, monitored by autoradiography, reflected the chromosomal distribution found in vivo in that the autosomal chromosomes were transcriptionally active, while the sex chromosomes were not. Thus features of chromosome pairing and sex chromatin inactivation are maintained in these cultures. We have conducted experiments to demonstrate that cultured pachytene spermatocytes can be useful for the analysis of agents, some of which may be suspected mutagens, that might affect chromosome structure and function during meiosis. Treatment of cells with actinomycin D revealed a differential effect on chromatin condensation in the autosomes versus the sex chromosomes. Carnptothecin, a topoisomerase inhibitor, induced desynapsis of paired chromosomes. Okadaic acid, a phosphatase inhibitor, induced premature metaphase-I condensation of pachytene chromosomes. This last experiment suggests that these cultured cells may be useful for analysis of meiotic cell cycle controls. Taken together, these results demonstrate a culture system that can be useful for analysis of meiotic events as well as in screening for potential mutagenic agents that might affect meiotic chromosome structure and function. © 1995 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/dvg.1020160206
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