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  • 1
    Electronic Resource
    Electronic Resource
    Two distinct isoforms of sea urchin egg dynein (1992)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 21 (1992), S. 281-292 
    Details
    ISSN: 0886-1544
    Keywords: ATPase ; CTPase ; minus-end-directed microtubule motility ; cytoplasmic dynein ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Extracts of unfertilized sea urchin eggs contain at least two isoforms of cytoplasmic dynein. One exhibits a weak affinity for microtubules and is primarily soluble. The other isoform, HMr-3, binds to microtubules in an ATP-sensitive manner, but is immunologically distinct from the soluble egg dynein (Porter et al.: Journal of Biological Chemistry 263:6759-6771, 1988). We have now further distinguished these egg dynein isoforms based on differences in NTPase activity. HMr-3 copurifies with NTPase activity, but it hydrolyzes CTP at 10 times the rate of ATP. The soluble egg dynein is similar to flagellar dynein in its nucleotide specificity; its MgCTPase activity is ca. 60% of its MgATPase activity. Non-ionic detergents and salt activate the MgATPase activities of both enzymes relative to their MgCTPase activities, but this effect is more pronounced for the soluble egg dynein than for HMr-3. Sucrose gradient-purified HMr-3 promotes an ATP-sensitive microtubule bundling, as seen with darkfield optics. We have also isolated a 20 S microtubule translocating activity by sucrose gradient fractionation of egg extracts, followed by microtubule affinity and ATP release. This 20 S fraction, which contains the HMr-3 isoform, induces a microtubule gliding activity that is distinct from kinesin. Our observations suggest that soluble dynein resembles axonemal dynein, but that HMr-3 is related to the dynein-like enzymes isolated from a variety of cell types and may represent the cytoplasmic dynein of sea urchin eggs.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970210404
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  • 2
    Electronic Resource
    Electronic Resource
    Common senescent cell-specific antibody epitopes on fibronectin in species and cells of varied origin (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 150 (1992), S. 545-551 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The phenomenon of in vitro cellular senescence has been demonstrated in cultured cells derived from humans and various other species. We have previously shown that monoclonal antibodies SEN-1, SEN-2, and SEN-3 react to epitopes on fibronectin that are exposed when human diploid fibroblasts become senescent. We here present results demonstrating that exposure of these epitopes is specific to senescence for a variety of human cells: epidermal keratinocytes, mammary epithelial cells, as well as fibroblasts. Fibronectin from 11 additional species was also analyzed by Western immunoblot for ability to bind the SEN antibodies. SEN-1 bound only human and gorilla fibronectin, whereas SEN-2 and SEN-3 bound fibronectin from those two species as well as the horse, cow, sheep, goat, dog, and chick. None of the antibodies reacted with fibronectin from the rabbit, rat, or mouse. These data indicated a correlation between the ability of the SEN antibodies to bind fibronectin from a particular species and the ability of cells from that species to exhibit a stable senescent phenotype in vitro. Therefore, exposure of this region of fibronectin may be important in the establishment and maintenance of cellular senescence. In addition, the ability of the SEN antibodies to react with fibronectin from a variety of senescent cells emphasizes their usefulness as markers for cellular senescence.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041500315
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  • 3
    Electronic Resource
    Electronic Resource
    Intracellular expression of Kluyveromyces lactis toxin γ subunit mimics treatment with exogenous toxin and distinguishes two classes of toxin-resistant mutant (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 7 (1991), S. 617-625 
    Details
    ISSN: 0749-503X
    Keywords: Cell cycle ; toxin ; K. lactis ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The Kluyveromyces lactis toxin is a heterotrimeric protein which irreversible arrests proliferation of sensitive Saccharomyces cerevisiae cells in the G1 phase of the cell cycle. By expressing the γ subunit of the toxin in sensitive yeast cells from a conditional promoter, it was previously demonstrated that it alone is required for inhibition (Tokunaga et al. (1989). Nucleic Acids Res. 17, 3435-3446). Here we show that, like native exogenous toxin, intracellular γ subunit expression promoters a striking arrest of sensitive cells in G1. However, unlike the G1 arrest caused by native toxin, that induced by the γ subunit alone does not result in reduced cellular viability and is fully and rapidly reversible, suggesting that the G1 arrest and the irreversibility of action may reflect different aspects of the toxin's interaction with sensitive cells. We have selected a large number of S. cerevisiae mutants which are highly resistant to the toxin in order to study its mode of action in more detail. Complementation analysis demonstrated that all but one of the mutants were recessive and these defined four separate genes. Members of two complementation groups concurrently acquired resistance to intracellular γ subunit expression, suggesting that they contain a modified toxin target site. The other two genes appear to be required for entry of the γ subunit into the sensitive cell since these mutants, while refractory to exogenous toxin, were fully sensitive to intracellular γ subunit expression.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/yea.320070610
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  • 4
    Electronic Resource
    Electronic Resource
    Mosaicism of tyrosinase-locus transcription and chromatin structure in dark vs. light melanocyte clones of homozygous chinchilla-mottled mice (1991)
    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 12 (1991), S. 393-402 
    Details
    ISSN: 0192-253X
    Keywords: Clonal variation ; gene expression ; DNAase I hypersensitive sites ; matrix-associated regions ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The chinchilla-mottled (cm) mutation at the mouse tyrosinase-encoding locus leads to a transversely striped pattern of dark- and light-grey coat colors in homozygotes. The same basic pattern occurs in various other genotypes and has previously been found to represent the clonal developmental history of melanocytes. In a homozygote such as cm/cm, cis-acting mechanisms would be expected to account for the color differences. To search for these mechanisms, the genomic structure of the mutation was examined and compared with the wild-type, and its function was compared in cultured melanocyte clones of the respective colors. Evidence from restriction mapping indicated that the coding region of the mutant gene resembles that of the fully and uniformly pigmented wild-type. However, the upstream sequences are rearranged in the mutation. The rearrangement begins 5 kb 5′ of the transcription initiation site and is estimated to encompass at least 30 kb of distal upstream sequence. At least two stable functional states of the cm gene were detectable: Light-cell clones have low levels of tyrosinase-specific transcription, reduced DNAase I sensitivity of tyrosinase chromatin, and no detectable hypersensitive sites near the gene; dark-cell clones have higher (but subnormal) levels of transcription, greater sensitivity of chromatin to DNAase I, and a hypersensitive site in the promoter region. The changed relation between the structural gene and its upstream region may separate it from cis-acting control elements, resulting in reduced and variable ability to achieve the appropriate chromatin configuration near the time of melanocyte determination; differences in expression among clonal initiator cells are then mitotically perpetuated. © 1992 Wiley-Liss, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/dvg.1020120604
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  • 5
    Electronic Resource
    Electronic Resource
    Lectin and immunolabeling of microvascular endothelia (1991)
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 19 (1991), S. 305-315 
    Details
    ISSN: 0741-0581
    Keywords: Endothelium ; Immunocytochemistry ; Electron microscopy ; Lectins ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: A number of recently developed localization techniques are beginning to be applied in the study of endothelial cells and their structural components. In this article we will review a number of these cytochemical approaches as well as their advantages and disadvantages and their applications. The methods will be presented for processing tissues for either L.R. White embedding or semi-thin and thin frozen sections followed by subsequent lectin and immunolabeling for fluorescence and electron microscopic examination. These techniques are easily applied in the localization of perfused exogenous proteins and of endogenous endothelial-associated proteins. The results that can be obtained from such studies are presented and discussed.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1060190306
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