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  • Cell & Developmental Biology
  • 2015-2019
  • 1980-1984  (33)
  • 1965-1969  (10)
  • 1955-1959
  • 1950-1954  (14)
  • 1980  (33)
  • 1969  (10)
  • 1954  (7)
  • 1951  (7)
Collection
Publisher
Years
  • 2015-2019
  • 1980-1984  (33)
  • 1965-1969  (10)
  • 1955-1959
  • 1950-1954  (14)
Year
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 1 (1980), S. 159-162 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 1 (1980), S. 63-71 
    ISSN: 0886-1544
    Keywords: Physarum polycephalum ; myosin light chains ; polyacrylamide gel electrophoresis ; calcium ; cytoplasmic streaming ; actomyosin ATPase regulation ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Myosin from the slime mold Physarum polycephalum contains three sizes of polypeptides: a heavy chain and two light chains, LC-1 and LC-2. Using a simple qualitative test for calcium binding by comparing electrophoretic migration of the polypeptides in sodium dodecy1 sulfate (SDS) acrylamide gels in the presence and absence of calcium, we have found that Physarum myosin light chain LC-2 migrates with an apparent molecular weight of 16,900 daltons in the presence of the metal ion chelator ethylene glycol bis (B-aminoethyl ether) N,N′-tetraacetic acid (EGTA). However, if calcium chloride is added to the sample prior to electrophoresis, the apparent molecular weight decreases to 16,100. Lanthanide and cadmium ions, but not magnesium, can substitute for calcium. Because the ionic radii of Ca2+, La3+, and Cd2+ are almost identical, we conclude that Physarum myosin LC-2 possesses a very size-specific binding site for calcium. Physarum myosin LC-1 and the heavy chain give no evidence for binding calcium by this test. Since cytoplasmic streaming in the plasmodium of Physarum requires calcium, our evidence indicates that the calcium-binding property of Physarum myosin LC-2 may be important in regulating the production of force by actomyosin in the ectoplasm. Unexpectedly, the myosin light chain in Physarum capable of binding calcium, LC-2, is the essential light chain, while LC-1 is a member of the regulatory class of myosin light chains [V. T. Nachmias, personal communication]. Until now, essential myosin light chains have not been shown to have high affinity divalent cation binding sites. This means a new version of the myosin-based model for actomyosin regulation by calcium may be required to explain cytoplasmic movement in Physarum, and perhaps in other motile systems involving cytoplasmic myosins as well.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 74 (1969), S. 239-240 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Assemblies of protein molecules represent a fundamental level of biological organization. The dynamic behavior of these systems-including both the assembly process and functional rearrangements-may be accounted for by the specificity of the protein interactions, which depend on environmental conditions. Analysis of the self-assembly of virus particles has established that the design of an ordered structure can be built into the specific bonding properties of the constituent proteins. Any structure which can change its state of organization is, by definition, polymorphic. The distinctive aspect of polymorphism in protein structures, contrasted with nonliving states of matter, is that the molecular design has been selected to carry out a function and that this function is part of an integrated system. The differences in molecular conformation and arrangement in all polymorphic structures-for example, allosteric enzymes or ice crystals-depend on the intrinsic interaction properties of the molecules themselves. The structures of ice and water illustrate relations between specificity and polymorphism which are relevant to the form and function of protein assemblies.Two types of polymorphism can be distinguished: modal polymorphism, which is externally moderated, as in phase transitions between different crystals forms; and positional polymorphism, which is internally moderated, as in the different disposition of identical molecules within a single crystal lattice. Positional polymorphism, exemplified by the quasi-equivalent bonding of icosahedral virus coat proteins and the different arrangement of myosin and paramyosin at the center and polar portions of the bipolar filaments, results from specific interactions that are not compatible with a strictly equivalent packing of identical molecules. The structural rearrangements in muscle contraction and the switching between the oxy and deoxy forms of hemoglobin represent the formation of different structures in response to altered external conditions. The different structural states of many protein assemblies are characterized by conserved connections which may be regarded as providing the framework for functional rearrangements. The types of polymorphism displayed by hemoglobin, virus, and muscle proteins demonstrate the relevance of the simple view that the function of a protein is determined by the potential structures it can form.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 102 (1980), S. 175-181 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A procedure has been investigated for sorting viable cells according to their DNA content. Cells are stained with the U.V. activated fluorochromes 4′6-diamidino-2-pheylindole (DAPI), Hoechst 33258 or Hoechst 33342, and sorted with a Fluorescence Activated Cell Sorter. Hoechst 33342 is a suitable vital stain for a varietyof cell types. Hoechst 33258 and DAPI, however, are quantitative vital stains for CHO cells only. Cloning efficiency is unaffected by the sorting procedure, and these stains are not mutagenic at concentrations suitable for vital staining. Potential applications of this procedure to cell biology are discussed.
    Additional Material: 8 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 104 (1980), S. 153-162 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: BALB/c or DBA/2 mice were infected with Abelson murine leukemia virus (A-MuLV), pseudotype Molony murine leukemia virus (M-MuLV). Infection of these mice with 104 focus-forming units of A-MuLV (M-MuLV) induced overt leukemia, detectable grossly or microscopically in 90% of the mice at 20-38 days. However, these methods did not detect leukemia at 17 days or before. Bone marrow cells from A-MuLV-infected leukemic or preleukemic mice were placed in tissue culture in a soft agarose gel. Cells from leukemic or preleukemic BALB/c mice grew to form colonies of 103 cells or more, composed of lymphoblasts, whereas marrow cells from normal uninfected mice did not. Cells from these colonies grew to form ascitic tumors after intraperitoneal inoculation into pristane-primed BALB/c recipient. Colony-forming leukemia cells could be detected in the marrow of A-MuLV-infected mice as early as 8 days after virus incoluation. The number of colony-forming leukemia cells increased as a function of time after virus inoculation.Colony-forming leukemia cells require other cells in order to replicate in tissue culture. Normal bone marrow cells, untreated or after treatment with mitomycin-C, provide this “helper” function. Only in the presence of untreated or mitomycin-C treated helper cells was the number of colonies approximately proportional to the number of leukemia cells plated.Marrow cells from leukemic BALB/c mice form more colonies than those from leukemic DBA/2 mice. The number of colonies formed per 103 microscopically identifiable leukemia cells plated was determined to be 2-3 for leukemic BALB/c mice and 0.3 for DBA/2 mice. Cocultivation of leukemic DBA/2 marrow cells with mitomycin-C treated normal BALB/c cells did not increase the number of colonies formed by the DBA/2 leukemic cells. Thus, the decreased ability of DBA/2 leukemia cells to form colonies appears to be a property of the leukemia cell population.
    Additional Material: 6 Tab.
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  • 6
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The effect of inhibition of the cell membrane Na+-K+ pump on the Balb/c-3T3 cell growth cycle was studied. Inhibition of the Na+-K+ pump resulted in a dose-dependent reduction of intracellular K+ concentration ({K+}i). However, inhibition of protein synthesis in G0/G1 and of subsequent entry into S phase occurred only after {K+}i fell below a critical threshold (50-60 mmoles/liter). Thus, when the {K+}i falls below a critical threshold, protein synthesis is inhibited, preventing cells from entering the S phase.The platelet-derived growth factor (PDGF) induces cells to become “competent” to traverse the cell cycle; the platelet-poor plasma component of serum allows competent cells to progress through G0/G1 and enter S phase. Inhibition of the Na+-K+ pump did not prevent the induction of competence by PDGF, but it did reversibly inhibit plasma-mediated events in early G0/G1. Similarly, cycloheximide inhibited plasma-mediated events but did not prevent PDGF-induced competence. Thus, protein synthesis may not be required for induction of competence; alternatively, the induction of the competent state may occur in these cells after removal of PDGF and protein synthesis inhibitor. Protein synthesis is required for subsequent plasma-mediated events in G0/G1.
    Additional Material: 7 Ill.
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  • 7
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Additional Material: 4 Ill.
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  • 8
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
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  • 9
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The complete regeneration of a new oral-disc and tentacles has been observed and described for Aiptasia diaphana. These structures are regenerated quite rapidly: seven to ten days at 20°C. At three days post-amputation, the new primary, secondary, and tertiary tentacle buds begin to develop in direct association with the underlying primary, secondary, and tertiary septae (respectively) of the column, suggesting that the latter organize the form of the regenerating oral-disc. Two days after amputation, the zooxanthellae of the presumptive oral disc arrange themselves into a ring which quite precisely delimits the area from which the tentacle buds will form. In spite of its suggestive proximity, this accumulation of algae plays no role in the induction of tentacle buds as was shown by studying regeneration in anemones which essentially lacked large quantities of these symbiotic algae.Cuts perpendicular to the longitudinal axis of the column result in an equal rate of tentacular regeneration around the entire circumference of the presumptive oral disc. Oblique amputations foster an asynchronous regeneration: the tentacle buds of the distal-most area of the severed column are larger and regenerate much sooner than those of the proximal region. Similar results were obtained by studying anemones which were cut perpendicular to their longitudinal axes at different levels along the column. The data suggest that an oral-aboral gradient exists concerning the time required for the initiation of tentacle budding and the rate of tentacle regeneration.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 127 (1969), S. 363-372 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Using the Colcemid technique, the mitotic incidence (MI) was measured in the epidermis, lung, spleen, liver, kidney and ovarian follicular cells of metamorphosed, immature Xenopus laevis laevis. The MI was higher at 25°C than at 20°C, and there was a significant ranking correlation between organs in respect of the MI in different animals. With the exception of the liver and kidney, organ cultures showed good preservation for up to six days in vitro using a medium supplemented with 10% fetal calf serum, and values for MI comparable with or even higher than in vivo were obtained.
    Additional Material: 2 Tab.
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