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  • 1
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 192 (1987), S. 27-42 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The fate and possible roles of the cytoskeleton in the process of conjugation in the hyptrich ciliate Euplotes aediculatus were investigated. Following the coalescence of the plasma membranes of the conjugant cells, a fusion zone or bridge of cytoplasm contributed by both partners is constructed. The sub-alveolar microtubule layers of the vegetative cell cortex remain in place to define the fusion zone boundaries after cell union. The initial fusion zone consists primarily of featureless ground cytoplasm; soon the ground plasm becomes crowded with microtubules and anastomosing smooth endoplasmic reticulum, which become displaced only late in conjugation as the migratory pronuclei are exchanged between partners. Fusion zone microtubules, functioning in some undetermined way, may be involved in the nuclear migration. Resorption of the posterior portion of each partner's buccal apparatus results in the degradation of the component cilia within acid phosphatase-positive autophagic bodies. Silver staining for light microscopy shows that the late fusion zone contracts forward from the posterior border, then constricts to separate the conjugants. In some separating pairs remnants of a microfilamentous assembly are seen at the posterior edge of the fusion zone; the full extent of this system may be masked by partial degradation due to osmium tetroxide fixation. Treatment of conjugants for 6 hours with cytochalasin B prevents separation, possibly through inhibition of the actin-like microfilament assembly in the fusion zone. The observations and experiments favor a model of cell separation following conjugation in which the fusion zone is resorbed by motile or contractile processes occurring within or around the fusion bridge itself.
    Additional Material: 21 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 192 (1987), S. 43-61 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The formation and subsequent dissolution of a common bridge of cytoplasm between conjugating ciliated protozoan cells provides an excellent opportunity to follow the dynamics of the cellular membrane systems involved in this process. In particular, separation of conjugant partners offers the chance to observe, at a fixed site on the cell surface, how the ciliate surface complex of plasma and alveolar membranes (collectively termed the “pellicle”) is constructed. Consequently, cortical and cellular membranes of Euplotes aediculatus were studied by light and electron microscopy through the conjugation sequence. A conjugant fusion zone of shared cytoplasm elaborates between the partner cells within their respective oral fields (peristomes) to include microtubules, cytosol, and a concentrated endoplasmic reticulum (heavily stained by osmium impregnation techniques) that may also be continuous with cortical ER of each cell. Cortical membranes displacd by fusion are autolyzed in acid phosphatase-positive lysosomes in the fusion zone. As conjugants separate, expansion of the plasma membrane may occur through the fusion of vesicles with the plasma membrane, presumably at bare membrane, presumably at bare membrane patches near the fusion zone. The underlying cortical alveolar membranes and their plate-like contents are reconstructed beneath the plasma membrane, apparently by multiple fusions of dense-cored alveolar precursor vesicles (APVs). These precursor vesicles themselves appear to condense directly from the smooth ER present in the fusion zone. No Golgi apparatus was visible in the fusion zone cytoplasm, and no step of APV maturation that might involve the Golgi complex was noted.
    Additional Material: 22 Ill.
    Type of Medium: Electronic Resource
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  • 4
  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 141 (1989), S. 591-597 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Satellite cells, isolated from marcaine-damaged rat skeletal muscle, differentiate in culture to form contracting, cross-striated myotubes. Addition of 20 μM hemin (ferriprotoporphyrin IX chloride) to the culture medium resulted in increases in the number, size, and alignment of myotubes; in the number of myotubes that exhibited cross-striations; and in the strength and frequency of myotube contractions. Hemin increased satellite cell fusion by 27%, but decreased cell proliferative rate by 30%. Hemin increased the specific activity of creatine kinase (CK), a sensitive indicator of muscle differentiation, by 157%. Separation of CK isoenzymes by agarose gel electrophoresis showed that hemin increased only the muscle-specific CK isoenzymes (MM-CK and MB-CK). Thus, hemin seems to duplicate some of the effects of innervation on cultured myotubes by increasing contraction frequency and strength, appearance of cross-striations, and muscle-specific isoenzymes. In contrast, 3-amino-1,2,4-triazole, an inhibitor of heme biosynthesis, decreased the number of cross-striated myotubes, the strength and frequency of myotube contractions, and CK activity. These inhibitory effects were reversed by hemin. Collectively, these results demonstrate a physiologically significant role for heme in myotube maturation.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 167 (1970), S. 425-437 
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The histochemistry of developing connective tissues and its relation to early connective tissue fibrils was investigated in the perinotochordal area of the chick embryo. Chick embryos were sacrificed at one, two, three, four, six and ten days of incubation and were prepared for both light and electron microscopy. Five histochemical stains (PAS, alcian blue, Hale colloidal iron, metachromatic toluidine blue, methenamine silver) were used to demonstrate polysaccharides, mucoproteins and mucopolysaccharides. Mature connective tissue elements were demonstrated by Mallory's connective tissue stain and Weigert's resorcin-fuchsin stain. Routine electron microscopic techniques served to demonstrate extracellular connective tissue fibrils.The first positive response for all histochemical stains occurs on the third day of incubation. Moderate microfibrillar growth precedes this by one day. Light microscopic staining patterns differ from electron microscopic fibrillar arrangements. In the perinotochordal area microfibrils later contribute to the cartilaginous model of the future vertebral body. By the sixth day, dense microfibrillar concentrations appear in the precartilage area where acid mucopolysaccharides are intensely concentrated. Staining for mature connective tissue fibrils does not occur until the tenth day.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 230 (1991), S. 175-182 
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The fibronexus is a close transmembrane association between fibronectin filaments and actin microfilaments. It has been found at the surfaces of fibroblasts in tissue culture, as well as within contracting granulation tissue. This specialized connection has been proposed to play an important role in the adhesive properties of fibroblasts. The purpose of this study is to determine whether the fibronexus is present in other contracting tissues besides granulation tissue, specifically in Dupuytren's diseased tissue. Dupuytren's disease is a pathologic condition in which the palmar aponeurosis becomes shortened leading to irreversible flexion of the digits. Shortening of the aponeurosis is believed to be an active cellular process. Extracellular filaments and actin microfilaments form close transmembrane associations at the surfaces of actin-rich fibroblasts in Dupuytren's disease. Extracellular filaments extend from the cell surface into the surrounding tissue connecting fibroblasts with collagen fibrils and adjacent cells. In this study we have used immunoelectron microscopy to demonstrate that the extracellular filaments that participate in these close transmembrane associations contain fibronectin. High voltage electron microscopy has been used to examine the three-dimensional relationships between the cytoskeleton and fibronectin filaments in Dupuytren's diseased tissue. We propose that the fibronexus is a dominant adhesive structure at the surface of fibroblasts in Dupuytren's diseased tissue. The fibronexus, by mediating cell-to-cell and cell-to-matrix attachments, may serve to transmit contractile forces generated by actin microfilaments in these cells throughout the diseased tissue.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 234 (1992), S. 153-160 
    ISSN: 0003-276X
    Keywords: Extracellular matrix ; Wound healing ; Morphogenesis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Fibroblasts cultured within free-floating collagen gels can bind to and reorganize the surrounding collagen fibrils into a more dense and compact arrangement. Collagen gel contraction provides an in vitro model for studying fibroblast-collagen interactions important in wound healing, fibrosis, scar contraction, and connective tissue morphogenesis. We have assessed the role of fibronectin and its interaction with the α5β1 “high affinity” fibronectin-specific integrin receptor in collagen gel contraction. A variety of agents, which specifically inhibit fibronectin-α5β1 interactions, were tested for their abilities to inhibit fibroblast-mediated collagen gel contraction. These included anti-α5β1 monoclonal antibodies, the synthetic peptide GRGDSP, the cell adhesive fragment of fibronectin, and an antibody against the cell adhesive region of fibronectin. None of these agents inhibited collagen gel contraction. Therefore, it is concluded that fibronectin-α5β1 interactions are not necessary for collagen gel contraction. However, collagen gel contraction is dependent on a member or members of the β1 subfamily of integrin matrix receptors. A polyclonal antiserum and a monoclonal antibody, both directed against the β1 subunit of integrin matrix receptors, inhibited the spreading of fibroblasts in the collagen gel and inhibited collagen gel contraction. This study demonstrates that fibroblast-mediated collagen gel contraction is independent of fibronectin-α5β1 interactions but dependent on an interaction of β1 integrin matrix receptors with collagen fibers.© Willey-Liss, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 0730-2312
    Keywords: bone morphogenetic protein ; defined media ; in vitro ; development ; stem cell ; ascorbic acid ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: During embryonic development, cartilage formation involves the condensation of mesenchymal stem cells and a series of maturation steps that ultimately results in the mineralized hypertrophic chondrocyte. The embryonic, murine, mesenchymal stem cell line, C3H/10T1/2, is pluripotent; exposure to azacytidine or to bone morphogenetic protein-2 or -4 results in low rates of differentiation to three mesengenic lineages. In contrast to previous studies, we report conditions for 10T1/2 differentiation specifically to the cartilage lineage and at high yields. These conditions include high cell density micromass cultures, a purified mixture of osteoinductive proteins (BP; Intermedics Orthopedics, Denver, CO), a serum substitute, 50 μg/ml ascorbic acid, and 10 mM β-glycerophosphate. The cartilagenous fate was confirmed by 1) histological detection of sulfated proteoglycans, 2) electron microscopic detection of proteoglycan and rounded cells separated by extracellular matrix containing short, disorganized collagen fibrils, 3) morphological detection of a chondrocytes surrounded by a territorial matrix and encompassed within a distinct perichondrium, and 4) immunocytochemical detection of type II collagen and link protein. After 4 weeks in culture, mature although unmineralized cartilage was observed, as indicated by hypertrophic morphology, immunocytochemical detection of osteocalcin, and histological detection of lacunae. These conditions promote overt chondrogenesis for most of the treated cells and preclude lineage determination to the fat, muscle, and bone lineages, as assayed by electron microscopy and histomorphology. The faithful recapitulation of cartilage differentiation that we have established in vitro provides a versatile alternative to the use of chondrocyte and limb bud explant cultures. We propose this as a model system to study the factors that regulate commitment to the chondrogenic lineage, exclusion to related mesengenic pathways, and maturation during chondrogenesis. J. Cell. Biochem. 65:325-339. © 1997 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 1561-1573 
    ISSN: 0887-6266
    Keywords: glass transition ; isobaric ; isochoric ; polymer ; poly(carbonate) ; PVT behavior ; free volume theory ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Pressure-volume-temperature (PVT) studies were performed on a glass-forming polymer, poly(carbonate) (PC), under both isobaric and isochoric (constant volume) conditions. An isochoric glass transition was observed and the formation points were found to be consistent with those obtained isobarically. Although the isobaric and isochoric responses were, as expected, the same in the rubbery state, the glassy state values were found to be different and dependent upon the glass formation history. The isobaric data exhibited larger changes in going from the rubber to the glass, hence a “stronger” glass transition, than did the isochoric data. Inserting the experimental values for the thermal expansion coefficient α and isothermal compressibility β, into appropriate thermodynamic relations, measures of the strength of each transition are defined. Strength estimates based on literature values of α and β are compared to the experimental measures of the isochoric and isobaric transitions. In addition, both the isobaric and isochoric PVT results were analyzed in terms of the Fox and Flory free volume theory which assumes that the glass transition is an iso-free volume state. While the isobaric results were consistent with the Fox and Flory theory, the isochoric results were not consistent with the idea of an iso-free volume glass transition. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1561-1573, 1997
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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