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  • 1
    Electronic Resource
    Electronic Resource
    Cell death in cranial neural crest development (1992)
    Springer
    Anatomy and embryology 185 (1992), S. 583-588 
    Details
    ISSN: 1432-0568
    Keywords: Avian embryo ; Hindbrain ; Neural crest ; Cell death ; Cell migration pathways
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The rhombencephalic neural crest, crucial to the patterning and development of many craniofacial structures, migrates laterally from the dorsal hindbrain, but not as a continuous sheet. We have used a vital dye to demonstrate a discontinuous pattern of cell death in the dorsal midline of the avian rhombencephalon associated with the migration of the neural crest. Whilst cell death commences in the dorsal midline of the presumptive mesencephalon at stage 8, two distinct domains of cell death are apparent in the rhombencephalon by stage 11. The rostral domain lies over primary rhombomere RhA1 and rhombomere rh3, while the caudal domain occurs on the neural midline between the otic vesicles, in the region of rh5. Using a marker for the neural crest, we show that the rostral and caudal domains of cell death correlate with the absence of neural crest migration from rh3 and rh5. Thus segment-specific cell death in the dorsal region of particular rhombomeres may account for their subsequent failure to contribute to the cranial neural crest.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00185617
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    A segmented pattern of cell death during development of the chick embryo (1992)
    Springer
    Anatomy and embryology 185 (1992), S. 589-598 
    Details
    ISSN: 1432-0568
    Keywords: Chick embryo ; Development ; Segmentation ; Cell death ; Neural crest
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary During the early development of the chick embryo, specific groups of cells die in characteristic patterns. In this study, Nile Blue sulphate staining was used to reveal a novel pattern of segmentally repeated cell death in the paraxial mesoderm of the chick prior to stage 23. This pattern varies according to the developmental stage of the embryo and shifts rostrocaudally, corresponding to progressing somite differentiation. Initially, during early somite differentiation, cell death is restricted to the rostral half of the somite (the rostral pattern of cell death). After the somite has differentiated into dermomyotome and sclerotome, dead cells appear in superficial tissues in a pyramidal pattern which lies in register (rostrocaudally) with the central part of the sclerotome. Finally, small bands of dying cells are seen between the neural tube and the expanding sclerotome. This third pattern (the ventral path) lies in register with the rostral part of the caudal half of the sclerotome. We show by fluorescent labelling of the migrating neural crest that these patterns of cell death correspond to the routes of neural crest migration. In addition, serial sectioning of stage 23 chick embryos confirms that the position of dying cells correlates with the known routes of neural crest migration and with the sites of development of certain neural crest-derived tissues.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00185618
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    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    O2-dependent inhibition of photosynthetic capacity in intact isolated chloroplasts and isolated cells from spinach leaves illuminated in the absence of CO2 (1978)
    Springer
    Planta 142 (1978), S. 229-233 
    Details
    ISSN: 1432-2048
    Keywords: Chloroplasts ; Leaf cells ; Photoinhibition ; Photorespiration ; Photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract When isolated intact chloroplasts or cells from spinach (Spinacia oleracea L.) leaves are incubated in the light in the absence of CO2, their capacity for subsequent CO2-dependent photosynthetic oxygen evolution is drastically decreased. This inhibition is light and oxygen-dependent and can be prevented by addition of bicarbonate. It is concluded that the normal dissipation of photosynthetic energy by carbon assimilation and in processes related to photorespiration is an essential condition for the physiological stability of illuminated intact chloroplasts and cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00388218
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Photosynthetic response of Ulva rotundata to light and temperature during emersion on an intertidal sand flat (1992)
    Springer
    Oecologia 89 (1992), S. 516-523 
    Details
    ISSN: 1432-1939
    Keywords: Chlorophyll fluorescence ; Photoinhibition ; Photosynthesis ; Temperature stress ; Ulva
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have investigated the diurnal response of photosynthesis and variable photosystem II (PSII) chlorophyll fluorescence at 77 K for thalli of the chlorophyte macroalga, Ulva rotundata, grown in outdoor culture and transplanted to an intertidal sand flat in different seasons. The physiological response in summer indicated synergistic effects of high PFD and aerial exposure, the latter probably attributable to temperature, which usually increased by 8 to 10° C during midday emersion. Except at extreme emersed temperatures in summer (38° C), the light-saturated photosynthesis rate (Pm) did not decline at midday. In contrast, light-limited quantum yield of photosynthetic O2 exchange (τ) and the ratio of variable to maximum fluorescence yield (Fv/Fm) reversibly declined during midday low tides in all seasons. Shade-grown thalli exhibited a fluorescence response suggestive of greater photodamage to PSII, whereas sun-grown thalli had greater photoprotective capacity. The fluorescence decline was smaller when high tide occurred at midday, and was delayed during morning cloudiness. These results suggest that the diurnal response to PFD in this shallow water species is modified by tidal and meteorological factors. U. rotundata has a great capacity for photoprotection which allows it to tolerate and even thrive in the harsh intertidal environment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317158
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    Paper (German National Licenses)
    Fulltext
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