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The macromolecular reguirements for the initiation and maintenance of macronuclear DNA replication were studied in heat synchronized Tetrahymena pyriformis GL-C. Previous work had established that macronuclear S periods could occur in a consecutive fashion without intervening cell divisions during a multiple heat shock treatment, as well as immediately following the synchronized cell divisions. Cycloheximide treatment prior to or during the S period which follows the first synchronized cell division resulted in abolition of the initiation of DNA synthesis or an almost immediate cessation of DNA synthesis in progress. Temporary inhibition of DNA synthesis occurred when cycloheximide was added late in the S period. Treatment with actinomycin D was found to block the initiation of DNA synthesis but did not appreciably affect the continuation of the S period. It was concluded that RNA synthesis was required for the initiation but not the maintenance of DNA replication, whereas protein synthesis was necessary for both processes. The dependency of the initiation of an S period on prior RNA and protein synthesis was also shown to exist when a second consecutive S period was initiated without a preceding cell division. Treatment with actinomycin or cycloheximide prior to a supernumerary S period during a multiple heat shock treatment completely abolished the initiation of DNA synthesis. In T. pyriformis the synthesis of RNA and protein related to the initiation of the S period is tightly coupled to each cycle of DNA replication. 相似文献
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Brodie J. Foster Graham A. McCulloch Jonathan M. Waters 《New Zealand journal of zoology.》2020,47(2):141-147
ABSTRACTA new wing-reduced species of the stonefly genus Zelandoperla Tillyard is described from Otago, New Zealand. Zelandoperla maungatuaensis sp. n. differs from a related species, Z. denticulata, primarily by lacking full wing development. We used morphological, geographical, and genetic evidence to assess the proposed status of Z. maungatuaensis sp. n. and Z. denticulata as separate monomorphic species, as opposed to conspecific members of a polymorphic species. High genetic divergence was found between distinctly allopatric populations, supporting the status of Z. maungatuaensis sp. n. as a distinct monomorphic species. 相似文献
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C. A. Grove R. Nagtegaal J. Zinke T. Scheufen B. Koster S. Kasper M. T. McCulloch G. van den Bergh G. Jan A. Brummer 《Coral reefs (Online)》2010,29(3):579-591
Inshore massive corals often display bright luminescent lines that have been linked to river flood plumes into coastal catchments
and hence have the potential to provide a long-term record of hinterland precipitation. Coral luminescence is thought to result
from the incorporation of soil-derived humic acids transported to the reef during major flood events. Corals far from terrestrial
sources generally only exhibit dull relatively broad luminescence bands, which are attributed to seasonal changes in coral
density. We therefore tested the hypothesis that spectral ratios rather than conventional luminescence intensity provide a
quantitative proxy record of river runoff without the confounding effects of seasonal density changes. For this purpose, we
have developed a new, rapid spectral luminescence scanning (SLS) technique that splits emission intensities into red, green
and blue domains (RGB) for entire cores with an unprecedented linear resolution of 71.4 μm. Since humic acids have longer
emission wavelength than the coral aragonite, normalisation of spectral emissions should yield a sensitive optical humic acid/aragonite
ratio for humic acid runoff, i.e., G/B ratio. Indeed, G/B ratios rather than intensities are well correlated with Ba/Ca, a
geochemical coral proxy for sediment runoff, and with rainfall data, as exemplified for coral records from Madagascar. Coral
cores also display recent declining trends in luminescence intensity, which are also reported in corals elsewhere. Such trends
appear to be associated with a modern decline in skeletal densities. By contrast, G/B spectral ratios not only mark the impact
of individual cyclones but also imply that humic acid runoff increased in Madagascar over the past few decades while coral
skeletal densities decreased. Consequently, the SLS technique deconvolves the long-term interplay between humic acid incorporation
and coral density that have confounded earlier attempts to use luminescence intensities as a proxy for river runoff. 相似文献
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Summary Bone sialoprotein (BSP) is a prominent component of bone tissues that is expressed by differentiated osteoblastic cells. Affinity-purified antibodies to BSP were prepared and used in combination with biotin-conjugated peroxidase-labeled second antibodies to demonstrate the distribution of this protein in sections of demineralized foetal porcine tibia and calvarial bone. Staining for BSP was observed in the matrix of mineralized bone and also in the mineralized cartilage and associated cells of the epiphysis, but was not observed in the hypertrophic zone nor in any of the soft tissues including the periosteum. In comparison, SPP-1 (osteopontin) and SPARC (osteonectin), which are also major proteins in porcine bone, were observed in the cartilage as well as in the mineralized bone matrix, In addition, SPARC was also present in soft connective tissues. Although SPP-1 distribution was more restricted than SPARC, hypertrophic chondrocytes, periosteal cells and some stromal cells in the bone marrow spaces were stained in addition to osteoblastic cells. The variations in the distribution and cellular expression of BSP, SPARC and SPP-1 in bone and mineralizing cartilage indicate these proteins perform different functions in the formation and remodelling of mineralized connective tissues. 相似文献