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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 29 (1994), S. 20-28 
    ISSN: 0886-1544
    Keywords: proliferation ; large T antigen ; peripheral nervous system ; cytoskeleton ; microtubules ; myelination ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Schwann cells (SC), the myelinating cells of the peripheral nervous system, show a remarkable capacity to switch from a differentiated state to a proliferative state both during development and peripheral nerve regeneration. In order to better understand the regulatory mechanisms involved with this change we are studying a Schwann cell line transfected with the SV-40 large T gene (TSC). Serum-free medium combined with elevating intra-cellular cAMP levels produced a slower proliferating TSC whose morphology changed from pleiomorphic to process bearing, reminiscent of primary SC in culture. This change was abrogated by colcemid but was unaltered by cytochalasin D, indicating a major role for microtubules. Ultrastructural studies demonstrated numerous microtubules in the cellular extensions which correlated with strong immunocytochemical staining for tubulin in the processes. Analysis of cytoskeletal fractions from the treated cells revealed a greater proportion of tubulin in the polymerized state compared with untreated cells which closely resembled the distribution in primary SC. The cytoskeletal changes observed in the TSC as a result of elevating the intra-cellular cAMP levels may reflect the earliest cellular changes in the induction of myelination. © 1994 Wiley-Liss, Inc.
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  • 2
    ISSN: 1040-452X
    Keywords: Chick embryos ; Organogenesis ; δ-crystallin gene ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Extracellular signals are likely to be involved in the control of growth and differentiation during embyrogenesis of vertebrates. These signals include, among others, several members of the insulin family: insulin-like growth factor (IGF)-I, IGF-II, and insulin. In the chick embryo, maternal IGF-I is stored in the yolk. In addition, the embryonic IGF-I gene is expressed very early and in late development in multiple tissues. We have used reverse-transcribed (RT) RNA and amplification by the polymerase chain reaction (PCR) to detect IGF-I gene expression. IGF-I was preferentially expressed in cephalic regions during late neurulation and early organogenesis. During late organogenesis, in some tissues, such as the eye lens, IGF-I gene expression is compartmentalized to a subset of cells, the epithelial cells. In these lens cells, IGF-I stimulates transcription of the δ-crystallin gene. Competence to respond to IGF-I exists in multiple cell types, since, based on binding studies, receptors for IGF-I are widespread in the gastrulating and neurulating embryo. Target tissues in which an autocrine/paracrine role for IGF-I appears more likely are the developing eye lens and retina, which are avascular organs rich in IGF-I receptors. In late development, IGF-I may have an additional endocrine role, with an impact on the general growth of the chick embryo. In embryos developed ex ovo, that show growth retardation after day 10 of embyrogenesis, IGF-I serum levels are very low. By day 8, expression of IGF-I mRNA in these embryos is markedly reduced in multiple tissues. Future studies in which IGF-I and its receptor are overexpressed or abolished should clarify the function of this growth factor in development. © 1993 Wiley-Liss, Inc.
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  • 3
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Pancreatic ducts of young posthatching Rana temporaria tadpoles are the main component of the developing pancreas. At this stage (free-swimming tadpoles with internal gills), duct cells display a high degree of development of basal and lateral outfoldings of the cell membrane with extensive interdigitation, and numerous mitochondria are present throughout the cytoplasm. Wide intercellular spaces also exist, sometimes forming canaliculi-like structures. Since these traits are characteristic of cells engaged in osmotic regulation, we suggest the possibility that this temporary duct system participates in such control. Duct cells in tadpoles with well-developed hindlegs have diminished interdigitation, and mitochondria are localized apically. © 1993 Wiley-Liss, Inc.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 143 (1990), S. 439-444 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The level of HSP 70 mRNA is altered in Trypanosoma cruzi cells incubated at supra-optimal temperatures: the total amount of this RNA per cell is increased at 37°C, and slightly decreased at 40°C relative to its level at 29°C. However, its amount is greater in the polysomes at either temperature. The relative increase of this RNA is larger in the polysomes fraction than it is in the total RNA. In addition the level of HSP 70 protein in heat-shocked cells is greater than would be expected from the recruitment of HSP 70 mRNA in the polysomal fraction. Taken together the data are interpreted as indicating that at 37°C and 40°C the HSP 70 gene regulation in T. cruzi involves both the selective accumulation of the HSP 70 mRNA in the polysomes and its preferential translation. At 37°C, in addition, an increase in the total amount of this template is observed in the cells.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 53 (1993), S. 270-277 
    ISSN: 0730-2312
    Keywords: chemoprevention ; head and neck cancer ; N-acetylcysteine ; retinol ; second primary tumors ; lung cancer ; oral cancer ; EUROSCAN ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The most commonly used chemopreventive agents in the prevention of oral leukoplakia, head and neck cancer, and lung cancer are β-carotene, vitamin A, and other retinoids. One of the few chemopreventive agents not in this group and presently being used in a clinical trial is N-acetyl-l-cysteine (NAC). NAC, an antioxidant, is used in EUROSCAN, a European Organization of Research and Treatment of Cancer (EORTC) chemoprevention study in curatively treated patients with oral, laryngeal, or lung cancer. The rationale for choosing NAC is based on a variety of experimental data showing its ability to exert protective effects, including extracellular inhibition of mutagenic agents from exogenous and endogenous sources, inhibition of genotoxicity of reactive oxygen species, modulation of metabolism coordinated with blocking of reactive metabolites, protection of DNA and nuclear enzymes, and prevention of the formation of carcinogen-DNA adducts. NAC has also demonstrated an effect on mutagen-induced chromosomal sensitivity assays, and on anticarcinogenicity in experimental animal models. In addition, preliminary data from EUROSCAN show good compliance in treated patients and a low frequency of side effects.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    BioEssays 13 (1991), S. 455-462 
    ISSN: 0265-9247
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A number of roles have been ascribed to poly(ADP-ribose) polymerase* including involvement in DNA repair, cell proliferation, differentiation and transformation. Cloning of the gene has allowed the development of molecular biological approaches to elucidate the structure and the function(s) of this highly conserved enzyme. This article will review the recent results obtained in this field.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 18 (1991), S. 192-196 
    ISSN: 0741-0581
    Keywords: F1 mitochondrial ATPase ; Immunocytochemistry ; Mouse heart muscle cells ; Protein A-gold complexes ; Electron spectroscopic imaging (ESI) ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: Immunocytochemistry was used to investigate the localization of F1 ATPase in mitochondria of cryosections of adult mouse heart muscle cells. The initial aldehyde fixation was the only denaturation step for antigens. The fine structure was preserved with contrast enhancement as the sections were maintained hydrated, with the advantage that the entire procedure is completed in one working day. The reaction was highly specific, and entire mitochondria were labeled with the Protein A-gold complex. A new analytical technique, electron spectroscopic imaging (ESI), contributed to a better visualization of the localization of the F1 factor.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 26 (1993), S. 1-6 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Additional Material: 1 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 18 (1991), S. 63-75 
    ISSN: 0886-1544
    Keywords: nuclear rotation ; nucleus ; nuclear lamina ; acrylamide ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Motion of nucleoli within interphase nuclei, known as nuclear rotation, may be used as a measure of motion of chromatin domains within the global confines of the nucleus. Mechanisms by which chromatin domains are transposed remain enigmatic. It has been established that nuclei are anchored by a network of intermediate filaments, structural proteins which share epitopes with nuclear lamins and possibly representing a constraint on nuclear rotation. It is postulated that selective removal of this constraint, by acrylamide, would result in increased chromatin motion. Mean rates of nucleolar displacement were quantified in neurons, in vitro. Nuclear rotation increased from a mean control rate of 0.102 ± 0.002 μm/min (n = 52) to a maximum mean rate of 0.207 ± 0.026 μm/min (n = 11), after 23 hr of exposure to 4 mM acrylamide. Despite this significant increase in motion of intranuclear domains, cytoplasmic structures in the immediate juxtanuclear area did not exhibit increases in rates of motion. Immunocy-tochemistry was used to visualize cytoskeletal structures and to assay selective disruption of neurofilaments by acrylamide. Increased rates of chromatin motion coincided with breakdown of the intermediate filament network. Ultrastructural analyses showed that the increase in chromatin motion induced by acrylamide was also associated with a significant (P 〈 0.005) change in the thickness of the nuclear lamina, decreasing from 20.9 ± 5.10 nm (n = 159) in controls to 18.9 ± 3.1 nm (n = 148), to 19.5 ± 3.6 nm (n = 240) and to 16.1 ± 4.4 nm (n = 103) at 4, 8 and 22 hr exposure, respectively. Moreover, the number of mito-chondria per unit area changed significantly (P 〈 0.0001) with exposure to acrylamide, increasing from 9.1 ± 2.2 mitochondrial profiles in controls to 16.5 ± 5.3 profiles after 22 hr exposure to acrylamide. Distribution of other cytoskel-etal components, actin and microtubules, was not altered and does not appear to play a significant role in the observed increase in rates of nuclear rotation. We conclude that the removal of the damping effects on chromatin motion normally imposed by the nuclear lamina and by intermediate filaments results in increased chromatin motion.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 20 (1991), S. 203-214 
    ISSN: 0886-1544
    Keywords: T-cells ; lymphoma ; invasion ; in vitro ; motility ; video microscopy ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have used an in vitro model system to analyze cytomechanical aspects of tissue infiltration by T-lymphocytes. The interaction of metastatic T-lymphoma cells with a precultured monolayer of 10T½ fibroblast-like cells was recorded in time-lapse video with alternating phase contrast and reflection interference contrast microscopy. Sectioning of embedded specimens as well as cytoskeletal stainings have been performed on matching cocultures.The lymphoma cells did not strongly attach or spread on the dorsal surface of the monolayer cells. Invasion started with the protrusion of a pseudopodium through a narrow gap, and conspicious constriction of the invading cell's body and nucleus was a consistent feature during the later steps. Overt retraction of the target cells was not seen, but the invading lymphoma cells elevated the fibroblasts over relatively large areas, thereby creating dome-shaped open spaces, allowing for further migration under the monolayer with minimal resistance. Invasion was not unidirectional but was readily reversible at any stage. Due to this wavering character, an invasion event could take more than 1 hour, although the shape alterations involved were fast. Even after the invasion process had been completed, the lymphoma cells could come out from below the monolayer again. Therefore we propose that invasion in this model should be considered as a dynamic equilibrium.Invading T-lymphoma cells displayed diffuse F-actin staining and a well-organized microtubular complex with the centrosomes behind the nucleus in the uropod, which also contained most vesicular organelles.
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