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  • Life and Medical Sciences  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    Subtraction scanning acoustic microscopy reveals motility domains in cells in vitro (1994)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 29 (1994), S. 231-240 
    Details
    ISSN: 0886-1544
    Keywords: cell motility ; scanning acoustic microscopy ; domains of motility ; mechanical properties of the cell ; neoplastic cells ; metastasis ; malignancy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Scanning acoustic microscopy (SAM) observes all mechanical properties of living cells. Subtraction of the SAM images (SubSAM) of live cells was developed as a method for investigating minimal changes in cellular topography and elasticity. The image formation in the SubSAM takes into account the motion of cell mass as well as the changes of tension. High spatial and temporal resolution of the SubSAM revealed the structure of motile processes that develops at increasing time intervals, thus allowing the arising complexity of motion to be registered and investigated. Independent spots of activity emerge on a quiescent background as motility domains; they may change position, divide, merge, or disappear after a long time interval. In addition, zones of quiescence were identified over central parts of cytoplasmic lamellae. Nonmalignant (Ep: tadpole epidermal cells, XTH2: endothelial cells from tadpole hearts, 3T3 cells) and neoplastic cells (K2 cells of rat fibrosarcoma, A870N cells selected from K2) were investigated with the SubSAM. Three types of domains of subcellular cytoplasmic motility were identified in time series of two-dimensional SubSAM images in normal and neoplastic cells. Of them only the wave-like domain is self-evident, being derived from ruffling and protruding activity at the cell margin. Two other domains wait for detailed analysis. The oscillating domain is a visualization of tension within the cell(s), and the nucleating domain indicates intracellular processes possibly preceding locomotion. Differences in motile domains were found between low K2 and high A870N metastatic cells. The dynamics of motility domains of the A870N cells resembled that of the highly motile Ep cells. Cell morphotype and motile activity of the A870N cells are significantly influenced by the pH of the medium. It became evident that identification of the otherwise invisible motile domains in living cells by SubSAM opens a new approach to a characterization of cell motility in vitro and to an understanding of early cellular reactions to various stimuli. © 1994 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970290306
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  • 2
    Electronic Resource
    Electronic Resource
    The Pichia pastoris dihydroxyacetone kinase is a PTS1-containing, but cytosolic, protein that is essential for growth on methanol (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 14 (1998), S. 759-771 
    Details
    ISSN: 0749-503X
    Keywords: Pichia pastoris ; methylotrophic yeasts ; dihydroxyacetone kinase ; DNA sequencing ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Dihydroxyacetone kinase (DAK) is essential for methanol assimilation in methylotrophic yeasts. We have cloned the DAK gene from Pichia pastoris by functional complementation of a mutant that was unable to grow on methanol. An open reading frame of 1824 bp was identified that encodes a 65·3 kDa protein with high homology to DAK from Saccharomyces cerevisiae. Although DAK from P. pastoris contained a C-terminal tripeptide, TKL, which we showed can act as a peroxisomal targeting signal when fused to the green fluorescent protein, the enzyme was primarily cytosolic. The TKL tripeptide was not required for the biochemical function of DAK because a deletion construct lacking the DNA encoding this tripeptide was able to complement the P. pastoris dakΔ mutant. Peroxisomes, which are essential for growth of P. pastoris on methanol, were present in the dakΔ mutant and the import of peroxisomal proteins was not disturbed. The dakΔ mutant grew at normal rates on glycerol and oleate media. However, unlike the wild-type cells, the dakΔ mutant was unable to grow on methanol as the sole carbon source but was able to grow on dihydroxyacetone at a much slower rate. The metabolic pathway explaining the reduced growth rate of the dakΔ mutant on dihydroxyacetone is discussed. The nucleotide sequence reported in this paper has been submitted to GenBank with Accession Number AF019198. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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