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  • 1
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We investigated the ultrastructural localization of annexin V a Ca2+-dependent phospholipid- and membrane-binding protein in the nervous system, heart, and skeletal muscles. The results indicate that in the cerebellum the protein is restricted to glial cells, where it is found diffusely in the cytoplasm as well as associated with plasma membranes. Bergmann glial cell bodies and processes and astrocytes in the cerebellar cortex and oligodendrocytes in the cerebellar white matter displayed an intense immune reaction product. In sciatic nerves, the protein was exclusively found in Schwann cells with a subcellular localization similar to that seen in glial cells in the cerebellum. Pituicytes in the neurohypophysis were intensely immunostained, whereas axons were not. In the heart, annexin V was restricted to the sarcolemma, transverse tubules, and intercalated discs. In skeletal muscles the protein was localized to the sarcolemma and transverse tubules. No evidence for the presence of the protein in the sarcoplasm or in association with mitochondria, the sarcoplasmic reticulum, or contractile elements was obtained. The observation that plasma membranes in cells expressing annexin V have the protein associated with them is in agreement with previous data on Ca2+-dependent binding of the protein to brain and heart membranes, and on existence of both EGTA- and Triton X-100-extractable and resistant fractions of annexin V in these membranes. The present data support the hypothesis that annexin V might be involved in membrane trafficking and suggest a role for this protein in the regulation of cytoplasmic activities in glial cells. © 1992 Wiley-Liss, Inc.
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  • 2
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The role of intracellular pH (pHin) in the regulation of cell growth in both normal and transformed cells is a topic of considerable controversy. In an effort to study this relationship NIH 3T3 cells were stably transfected with the gene for the yeast H+-ATPase, constitutively elevating their pHin. The resulting cell line, RN1a, has a transformed phenotype: The cells are serum independent for growth, clone in soft agar, and form tumors in nude mice. In the present study, we further characterize this system in order to understand how transfection with this proton pump leads to serum-independent growth, using defined media to investigate the effects of specific growth factors on the transfected and parental NIH 3T3 cells. While both cell lines show similar growth increases in response to platelet-derived growth factor (PDGF)-BB and epidermal growth factor (EGF), they respond differently to insulin, insulin-like growth factor-I (IGF-I) and PDGF-AA. RN1a cells exhibit increased growth at nanomolar concentrations of insulin but the parental cells had only a relatively minor response to insulin at 10 μM. Both cell lines showed some response to IGF-I in the nanomolar range but the response of RN1a cells was much larger. Differences in insulin and IGF-I receptor number alone could not explain these results. The two cell lines also respond differently to PDGF-AA. RN1a cells are relatively insensitive to stimulation by PDGF-AA and express fewer PDGF α receptors as shown by Northern blots and receptor-binding studies. We propose a unifying hypothesis in which the H+-ATPase activates a downstream element in the PDGF-AA signal transduction pathway that complements insulin and IGF-I signals, while leading to downregulation of the PDGF α receptor. © 1994 wiley-Liss, Inc.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 19 (1982), S. 305-313 
    ISSN: 0730-2312
    Keywords: anti-iodiotypic antibody ; thyrotropin ; receptor ; thyroid stimulating antibody ; Graves disease ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: We raised an antihuman thyrotropin anti-idiotypic antibody and showed that it was active at the thyrotropin receptor. Thus this antibody inhibited 125I b-TSH binding to thyroid plasma membranes, stimulated adenylate cyclase activity through a guanyl nucleotide-dependent mechanism, increased radioiodide entry rate into isolated porcine thyroid follicular cells, and induced such cultured cells to organize into follicles. All these parameters are typical of thyrotropin action. This work raises the possibility that thyroid stimulating antibodies that cause the hyperthyroidism of Graves disease may be, at least in some patients, anti-thyrotropin anti-idiotypic antibodies. It also offers a novel method whereby antireceptor antibodies used in the isolation and characterization of the receptor may be raised from ligands.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 34 (1987), S. 151-162 
    ISSN: 0730-2312
    Keywords: anti-idiotypic antibodies ; thyrotropin subunits ; thyrotropin receptor ; monoclonal antibody ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: TSH is a heterodimeric glycoprotein hormone, whose dissociated subunits are without biological activity. This has precluded the assessment of the relative contribution of each subunit to hormone action. We have raised anti-idiotypes to monoclonal antibodies specific, respectively, for the α and β hTSH subunits. The anti-β anti-idiotype inhibited l25I-hTSH binding to the β subunit-specific monoclonal quantitatively, whereas 125I-hTSH binding to the α subunit-specific monoclonal was not inhibited by anti-α anti-idiotypes, suggesting that only the former is an “internal image” anti-idiotype. Neither of the two anti-idiotypes nor equimolar mixtures thereof inhibited 125I-bTSH binding to thyroid membranes, even though radiolabelled anti-idiotypes showed saturable binding to thyroid plasma membrane which was inhibited 41-65% by bTSH. Each anti-idiotype alone caused 9% inhibition (compared to 50% by NRIgG) of thyroid plasma membrane adenylate cyclase. Equimolar mixtures (125 μg/ml IgG of each anti-idiotype) induced enzyme activity equivalent to 85% of that of 250 mU/ml of TSH. The TSH-like action of the two anti-idiotypes was also reflected in their capacity to increase (450% by 250 μg/ml IgG compared to normal rabbit IgG) the uptake of 131I into isolated thyrocytes and to promote the organization of such cells into follicular structures. At 250 μg/ml, anti-β anti-idiotype promoted the organization of small follicles and only at a concentration of 500 μg/ml did it enhance 131I uptake. Anti α idiotype was without effect in both assays. Lastly, mixture of anti-idiotypes bound to the ∼ 197,000 Mr band (TSH holoreceptor) on protein blots of thyroid plasma membranes resolved on NaDSO4-polyacrylamide gel electrophoresis under non-reducing conditions. Individual anti-idiotypes were without effect.The TSH α and β subunits apparently deliver two cooperative signals to the receptor and that specificity is associated with the β subunit, while the α subunit is important in enhancing receptor affinity for the heterodimer and in stablizing TSH-receptor complex.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 57 (1995), S. 630-640 
    ISSN: 0730-2312
    Keywords: internal pH ; transformation ; c-fos ; AP-1 ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Changes in intracellular pH (pHin) take part in the mitogenic response. Their importance has been stressed by the finding that mouse fibroblasts expressing a yeast proton pumping ATPase (PMA1) exhibit a transformed phenotype and are tumorigenic. These cells do maintain a higher pHin, supporting the idea that elevated pHin may act as a proliferative trigger. Here we show that cells constitutively expressing PMA1 have higher levels of the AP-1 transcription factor. The use of stable transfectants and transient transfection assays show that PMA1 activity induces transactivation of the c-fos promoter. The activation of the promoter is mediated throughout the serum response element (SRE). The use of protein kinase C inhibitors suggests that AP-1 activation is achieved through a pathway independent of protein kinase C.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 31 (1986), S. 107-120 
    ISSN: 0730-2312
    Keywords: Hashimoto's thyroiditis ; Graves' disease ; microsomal antigen ; TSH receptor ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Antimicrosomal antibodies are present in the sera of most patients with autoimmune thyroiditis, and Graves' disease. It has, in general, been difficult to separate antimicrosomal activity from that directed against the thyrotropin (TSH) receptor in Graves' IgG preparations. The “microsomal” antigen has been localized to the endoplasmic reticulum and microfollicular aspect of thyrocytes; its structure is however unknown. In an attempt to identify the thyroid microsomal antigen, we studied the interaction of Hashimoto's IgG with high microsomal antibody titre and negative for thyroglobulin with purified thyroid plasma and light microsomal membranes. We allowed Hashimoto's, Graves', and control IgGs to bind to protein blots of thyroid plasma membranes resolved on SDS-PAGE under nonreducing conditions. All seven Hashimoto's IgG at a concentration of 2 mg/ml interacted with an M ∼ 197,000 polypeptide corresponding to the TSH holoreceptor. By contrast to Graves' IgG (which were positive at 1 mg/ml), however, this binding was not blocked by pretreatment of the protein blots with TSH. Normal IgGs showed no binding at concentrations of up to 2 mg/ml.Both Hashimoto's and Graves' IgG interacted with TSH-affinity column-purified receptor preparations.Two of the Hashimoto's IgGs induced adenylate cyclase activation in thyroid plasma membranes, three inhibited TSH-stimulated enzyme activation, and two were without effect. Two classes of autoantibodies, other than TSH receptor directed, were encountered; one class raised to antigens common to all seven patients and another class unique to individual patients, eg, Mr 210,000 and Mr 20,000 polypeptides.We propose that the TSH receptor has multiple epitopes (functional domains), and the one to which antimicrosomal antibody bind is likely to be spatially separated from that with which Graves' IgG and TSH interact. Differences in affinity or number of sites allows for the demonstration of Graves' IgG against a background of antimicrosomal antibody.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 136 (1988), S. 226-236 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: In the light of accumulating data that implicate cell surface heparan sulfate proteoglycans (HSPGs) with a role in cell interactions with extracellular matrix molecules such as fibronectin, we have compared the properties of these molecules in wild-type BHK cells and an adhesion-defective ricin-resistant mutant (RicR14). Our results showed that the mutant, unlike BHK cells, cannot form focal adhesions when adherent to planar substrates in the presence of serum. Furthermore, while both cell lines possess similar amounts of cell surface HSPG with hydrophobic properties, that of RicR14 cells had decreased sulfation, reduced affinity for fibronectin and decreased half-life on the cell surface when compared to the normal counterpart. Our conclusions based on this data are that these altered properties may, in part, account for the adhesion defect in the ricin-resistant mutant. Whether this results from the known alteration in assembly of N-linked glycans affecting the carbohydrate chains on the proteoglycan or some other combination of factors is discussed.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 8 (1992), S. 107-115 
    ISSN: 0749-503X
    Keywords: Yeast ; Saccharomyces cerevisiae ; glycolysis ; hexokinase ; phosphofructokinase ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The enzymatic steps involved in the inhibition of glycolysis by 2-deoxygalactose in Saccharomyces cerevisiae have been investigated. Yeast, incubated with 2-deoxygalactose, accumulates up to 8 mM-2-deoxygalactose, 30 mM-2-deoxygalactose-1-phosphate and 0·25 mM-UDP-2-deoxygalactose and UDP-2-dexyglucose. An inverse correlation between 2-deoxygalactose-1-phosphate content and rate of glycolysis has been observed. The intracellular concentration of glycolytic intermediates and related metabolites point to the hexokinase and phosphofructokinase steps as the targets for the inhibition of glycolysis by 2-deoxygalactose and rule out all other mechanisms that have been proposed to explain this inhibition.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 7 (1991), S. 1-14 
    ISSN: 0749-503X
    Keywords: Saccharomyces cerevisiae ; cell cycle ; budding ; spore germination ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Cloning and sequencing of RCS1, a Saccharomyces cerevisiae gene whose product seems to be involved in timing the budding event of the cell cycle, is described. A haploid strain in which the 3′-terminal region of the chromosomal copy of the gene has been disrupted produces cells that are, on average, twice the size of cells of the parental strain. The critical size for budding in the mutant is similarly increased, and the disruption mutation is dominant in a diploid heterozygous for the RCS1 gene. Spores from this diploid have a reduced ability to germinate, the effect being more pronounced in the spores carrying the disrupted copy of RCS1. However, disrupted cells recover from α-factor treatment equally as well as wild-type cells.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 11 (1995), S. 1393-1398 
    ISSN: 0749-503X
    Keywords: glucose transport ; hexose diffusion ; sugar transport ; Saccharomyces cerevisiae ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: It has been claimed that the low-affinity component of glucose transport in Saccharomyces cerevisiae is due to passive diffusion of the sugar across the plasma membrane. We have investigated this possibility. For this purpose we have measured the permeability coefficient of hexoses in this organism. We have found that this coefficient is at least two to three orders of magnitude lower than required to account for the low-affinity component of glucose transport, and have concluded that this component is not due to passive diffusion.
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