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  • 1
    ISSN: 0749-503X
    Keywords: Saccharomyces cerevisiae ; metal ion toxicity ; vacuole ; protein sorting ; gene regulation ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The metal ions, Cu2+/+ and Fe3+/2+, are essential co-factors for a wide variety of enzymatic reactions. However, both metal ions are toxic when hyper-accumulated or maldistributed within cells due to their ability to generate damaging free radicals or through the displacement of other physiological metal ions from metalloproteins. Although copper transport into yeast cells is apparently independent of iron, the known dependence on Cu2+ for high affinity transport of Fe2+ into yeast cells has established a physiological link between these two trace metal ions. In this study we demonstrate that proteins encoded by genes previously demonstrated to play critical roles in vacuole assembly or acidification, PEP3, PEP5 and VMA3, are also required for normal copper and iron metal ion homeostasis. Yeast cells lacking a functional PEP3 or PEP5 gene are hypersensitive to copper and render the normally iron-repressible FET3 gene, encoding a multi-copper Fe(II) oxidase involved in Fe2+ transport, also repressible by exogenous copper ions. The inability of these same vacuolar mutant strains to repress FET3 mRNA levels in the presence of an iron-unresponsive allele of the AFT1 regulatory gene are consistent with alterations in the intracellular distribution or redox states of Fe3+/2+ in the presence of elevated extracellular concentrations of copper ions. Therefore, the yeast vacuole is an important organelle for maintaining the homeostatic convergence of the essential yet toxic copper and iron ions. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 6 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 50 (1992), S. 143-150 
    ISSN: 0730-2312
    Keywords: aneuploidy ; chemoprevention ; chronic ulcerative colitis (CUC) ; colonic DNA content ; flow cytometry ; intermediate biomarker ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Aneuploid cell populations can be defined as those that contain an abnormal number of chromosomes or an abnormal amount of DNA. Aneuploidy can be reliably detected by flow cytometric analysis of DNA content. This technique not only identifies aneuploid cell populations but can also quantify the percent of cells in various phases of the cell cycle, thus giving an indication of the proliferative activity of a tissue. Aneuploidy occurs in approximately 60% of established colorectal cancers, and many studies have demonstrated that patients with aneuploid tumors have a poorer prognosis than patients with diploid colon cancers. Some studies have suggested that the proliferative rate of tumors, as assessed by the percent of cells in S phase, also has prognostic significance. Until recently, aneuploidy was thought to occur only in malignant tissues, but it has been clearly shown that aneuploid cell populations can be identified in benign adenomatous polyps as well as in non-neoplastic-appearing mucosa of patients with chronic ulcerative colitis and Barrett's esophagus. In chronic ulcerative colitis, aneuploidy occurs more frequently in patients with dysplasia or cancer than in those with no evidence of neoplasia. Similarly, dysplastic and malignant biopsies are more commonly aneuploid than non-neoplastic biopsies. Patients who have undergone colectomy for cance or dysplasia in the setting of chronic ulcerative colitis frequently have multiple areas of aneuploidy throughout the remainder of their colon. Whether aneuploidy can be useful as a marker of cancer risk in patients with chronic ulcerative colitis deserves further investigation. © 1992 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
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  • 3
    ISSN: 0002-9106
    Keywords: Heart ; Development ; Immunocytochemistry ; Immunofluorescence ; Myofibril ; Cell polarity ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The distribution of sarcomeric myosin heavy chain (MyHC) has been examined immunoctochemically in the presumptive myocardial cells of chicken embryos (stages 6-10) prior to the onset of the heart beat. Embryos were stained with monoclonal antibody MF20, a reagent which recognizes all chicken sarcomeric MyHCs (Bader et al., 1982), and then examined both in whole mount by immunofluorescence and in semithin, plastic-embedded sections following immunoperoxidase labeling. We observed that myosin could be detected as early as stage 7 (0-2 pairs of somites) in 29% of the 31 embryos examined, and by stage 8 (4 pairs of somites) more than 80% of the embryos were MF20+, Every embryo with 5 pairs of somites (stage 8+) labeled strongly with MF20. Labeling was first detected at stage 7 to 7+ as a diffuse fluorescent signal within pleomorphic cells of the splanchnic mesoderm located in two crescent-shaped regions bordering each side of the anterior intestinal portal (AIP). With progressive development, the two crescent-shaped regions merged at the apex of the AIP, and as the two heart tubes began fusion at stage 9, the MyHC+ regions extended cranially and medially. By somite stages 9-10, the myosin-positive cells completely encircled the heart tube. From stages 7 to 9 the myosin signal had no sarcomeric distribution; i.e., there were no MyHC striations nor periodic repeats evident in the presumptive myocytes until late stage 9 and stage 10. Semithin sections revealed that myosin was first distributed in apical regions of the myocytes, adjacent to the pericardial coelom. The implications of these findings for myocyte determination, differentiation and morphogenesis are discussed.© 1992 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 118 (1954), S. 57-71 
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 233 (1992), S. 409-414 
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The location of stem cells and the direction of colonocyte migration in the normal rat colonic crypt were investivageted using a serial bromodeoxyuridine (BrdU) and [3H]thymidine labeling protocol. The results demonstrate that in the distal colon the stem cells are located in the crypt base and that cells migrate up toward the luminal surface. In the proximal colon, however, the stem cells are located in the midcrypt, and the colonocytes migrate in two directions, up toward the luminal surface and down toward the crypt base. © 1992 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
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  • 6
    ISSN: 0091-7419
    Keywords: cytochalasin B ; insulin action ; adipocytes ; plasma membranes ; D-glucose transport ; protein reagents ; membrane reconstitution ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Sensitivity of the adipocyte D-glucose transport system in intact plasma membranes or following solubilization and reconstitution into phospholipid vesicles to several protein-modifying reagents was investigated. When intact plasma membranes were incubated with N-ethylmaleimide (20 mM) or fluorodinitrobenzene (4 mM), D-glucose transport activity was virtually abolished. However, washing the membranes free of unreacted reagents restored transport activity, indicating that covalent interaction with the membranes did not mediate the transport inhibition. Reaction of [3H] N-ethylmaleimide with plasma membranes under similar conditions resulted in extensive labeling of all protein fractions resolved on dodecyl sulfate gels. Similarly, addition of N-ethyl-maleimide to cholate-solubilized membrane protein had no effect on transport activity in artifical phospholipid vesicles reconstituted under conditions where the membrane protein was free of unreacted N-ethylmaleimide. Transport activity in plasma membranes was also inhibited by both reduced and oxidized dithiothreitol or glutathione (15 mM) in a readily reversible manner, consistent with a noncovalent mode of inhibition. Thus, the insulin-responsive adipocyte D-glucose transport system differs from the red cell hexose transport system in its remarkable insensitivity to modulation by covalent blockade of sulfhydryal or amino groups by the reagents studied.
    Additional Material: 2 Ill.
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  • 7
    ISSN: 0091-7419
    Keywords: dimethylmaleic anhydride ; cytochalasin B ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Plasma membrane vesicles prepared from adipocytes incubated with insulin exhibited accelerated D-glucose transport activity characteristic of insulin action on intact fat cells. Both control and insulin-stimulated D-glucose transport activities were inhibited by cytochalasin B and thiol reagents. Extraction of plasma membranes with dimethylmaleic anhydride eluted 80% of the protein from plasma membrane vesicles. The two major glycoprotein bands (94,000 and 78,000 daltons) and small amounts of a 56,000-dalton band were retained in dodecyl sulfate gels of the extracted membranes. Both control and insulin-activated D-glucose transport activities were retained by plasma membrane vesicles extracted with dimethylmaleic anhydride. Cytochalasin B binding activity was also retained by extracted membrane vescles and D-glucose uptake into extracted vescles derived from untreated or insulin-treated fat cells was inhibited by cytochalasin B. These results suggest that the modification of the adipocyte hexose transport system elicited by insulin action is not altered by a major purification step which involves quantitative extraction of extrinsic membrane proteins.
    Additional Material: 2 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 151 (1992), S. 1-7 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The kinetics of zinc transport were examined by measuring the uptake of 65Zn into cultured endothelial cells. This served as a suitable model for characterizing the transport of zinc across a biological membrane (i.e., the plasma membrane). The transport process was saturable under physiological conditions, which indicates a facilitating transport mechanism. Within the physiological range of zinc concentrations, the maximum zinc transport rate was 27 pmoles zinc/(min × mg protein) and it was half maximal at 4.1 μM zinc. Cadmium competitively inhibited zinc transport (Ki = 6.5 μM), while equimolar concentrations of copper and manganese were ineffectual. The rate of zinc transport was substantially reduced at lower temperatures and in the presence of sulfhydryl blockers (sodium iodoacetate and N-ethylmaleimide). Inhibitors of energy metabolism (2,4-dinitrophenol and sodium azide) failed to disrupt zinc transport. These results demonstrate that zinc transport into endothelial cells is a facilitated process (i.e., it is carrier mediated and energy-independent). © 1992 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 125 (1985), S. 243-250 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Sulfate transport in a fibroblast cell line derived from human lung (IMR-90) occurred mainly via high- and low-affinity, SITS-sensitive pathways and to a lesser extent by an SITS-insensitive mechanism. In low-ionic-strength media (sucrose substituted for salts) the apparent Km of the carrier-mediated sulfate influx was 1 mM. At 0.3 mM, the sulfate concentration normally found in human serum, the contribution of the SITS-insensitive pathway was negligible. In physiological salts solution, an SITS-sensitive, high-affinity (Km 34 ± 14 μM) sulfate influx system was observed at extracellular sulfate concentrations less than 100 μM. Between 100 and 500 μM sulfate, the range normally found in human serum, sulfate influx occurred via an SITS-insitive, lowaffinity pathway and to a small extent by an SITS-insensitive mechanism. Extracellular chloride inhibited the influx and stimulated the efflux of sulfate. Bicarbonate and thiosulfate inhibited sulfate influx but had no effect on sulfate efflux. Phosphate, arsenate, or Na+ did not affect sulfate uptake. These results indicate that in human lung fibroblast IMR-90 cells sulfate is transported mainly via an SO42-/Cl- exchange system independent of the phosphate or Na+ transport. Since sulfate concentration as high as 50 mM only slightly increased sulfate efflux, SO42-/SO42- exchange is probably a minor component of sulfate uptake.
    Additional Material: 9 Ill.
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  • 10
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Additional Material: 2 Ill.
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