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4 ungesichtete Fragmente: Plagiat

[1.] Sj/Fragment 010 01 - Diskussion
Bearbeitet: 30. May 2015, 12:27 (Kybot)
Erstellt: 19. May 2015, 23:01 Hindemith
Fragment, SMWFragment, Schutzlevel, Sj, Uldry and Thorens 2004, Verschleierung, ZuSichten

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Hindemith
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Untersuchte Arbeit:
Seite: 10, Zeilen: 1 ff. (entire page)
Quelle: Uldry and Thorens 2004
Seite(n): 481, 482, Zeilen: 481: r.col: 2ff; 482: l.col: 1ff
GLUT1 is found in almost every tissue with different levels of expression in different cell types. The expression level usually correlates with the rate of cellular glucose metabolism. As mentioned above, it is also expressed highly in blood-tissue barriers, in particular in the endothelial cells forming the blood-brain barrier. Several heterozygous mutations resulting in GLUT1 haploinsufficiency have been identified. These cause hypoglycorrachia, a condition characterized by seizures, developmental delay, acquired microcephaly, and hypotonia, and which is due to a decrease rate of glucose transport from the blood into cerebrospinal fluid.

The topological arrangement of GLUT1 within the plasma membrane has been confirmed using several experimental approaches. Recently, two models have been proposed for the tertiary structure of GLUT1. The first is based on data obtained from cysteine scanning mutagenesis of five of the α-helices of GLUT1 together with information from site-directed mutagenesis (32). The second is based primarily on the proposed helical bundle arrangement of the Lac permease and has been refined using energy minimization algorithm (33) These two models describe a key role for helix 7 in the formation of a water-filled channel which may form the path for glucose across the plasma membrane.

The transport of glucose may be described as an alternating confirmation model in which the transporter has mutually exclusive binding sites located on the extracellular (import site) and on the intracellular face (export site) of the transporter (Figure 4). Binding of glucose to one site induces the transporter to switch to the opposite conformation, a process that is accompanied by a movement of the substrate across the plasma membrane (34). In human erythrocytes, GLUT1 is thought to be present as homodimers or homotetramers, with the conversion between both oligomeric forms being dependent on the redox state, . GLUT1 transports glucose with an affinity constant (Km) of ~3 mM. Other transported substrates are galactose (30mM) (34), mannose (35) (20mM) and glucosamine 2.1+0.5mM (36). Glucose transport by GLUT1 is sensitive to several inhibitors that also block transport by other isoforms. Many of them are competitive inhibitors of sugar binding, either to the extracellular or the cytosolic sugar binding sites. Cytochalasin B binds to the inner surface of GLUT1 and inhibits its glucose transport activity with an IC50 of 0.44 μM. Binding of cytochalasin B is to a site which contains tryptophan 388 and 412. Also acting on the same intracellular site is the diterpene toxin forskolin. Forskolin has been used as a photoaffinity label with some specificity for the glucose transporter and its affinity is increased in the 3- iodo4-azidophenethylamido-7-O-succinyldeacetyl (IAPS) derivative.


32. Keymeulen,B, Ling,Z, Gorus,FK, Delvaux,G, Bouwens,L, Grupping,A, Hendrieckx,C, Pipeleers-Marichal,M, Van Schravendijk,C, Salmela,K, Pipeleers,DG: Implantation of standardized beta-cell grafts in a liver segment of IDDM patients: graft and recipients characteristics in two cases of insulin-independence under maintenance immunosuppression for prior kidney graft. Diabetologia 41:452-459, 1998

33. Fischbarg,J, Cheung,M, Li,J, Iserovich,P, Czegledy,F, Kuang,K, Garner,M: Are most transporters and channels beta barrels? Mol.Cell Biochem. 140:147-162, 1994

34. Joost,HG, Thorens,B: The extended GLUT-family of sugar/polyol transport facilitators: nomenclature, sequence characteristics, and potential function of its novel members (review). Mol.Membr.Biol. 18:247-256, 2001

35. Palfreyman,RW, Clark,AE, Denton,RM, Holman,GD, Kozka,IJ: Kinetic resolution of the separate GLUT1 and GLUT4 glucose transport activities in 3T3-L1 cells. Biochem.J. 284 ( Pt 1):275-282, 1992

36. Robinson,KA, Sens,DA, Buse,MG: Pre-exposure to glucosamine induces insulin resistance of glucose transport and glycogen synthesis in isolated rat skeletal muscles. Study of mechanisms in muscle and in rat-1 fibroblasts overexpressing the human insulin receptor. Diabetes 42:1333-1346, 1993

[page 481]

GLUT1 is found in almost every tissue with different levels of expression in different cell types. The expression level usually correlates with the rate of cellular glucose metabolism. It is also expressed highly in blood-tissue barriers, in particular in the endothelial cells forming the blood-brain barrier [45].

The topological arrangement of GLUT1 within the plasma membrane has been confirmed using several experimental approaches. Recently, two models have been proposed for the tertiary structure of GLUT1. The first is based on data obtained from cysteine scanning mutagenesis of five of the a-helices of GLUT1 together with information from site-directed mutagenesis [52]. The second is based primarily on the proposed helical bundle arrangement of the Lac permease and has been refined using energy minimization algorithm [79]. These two models describe a key role for helix 7 in the formation of a water-filled channel which may form the path for glucose across the plasma membrane.

The transport of glucose may be described as an alternating conformer model in which the transporter has mutually exclusive binding sites located on the extracellular (import site) and on the intracellular face (export site) of the transporter. Binding of glucose to one site induces the transporter to switch to the opposite conformation, a process that is accompanied by a movement of the substrate across the plasma membrane. In human erythrocytes, GLUT1 is thought to be present as homodimers or homotetramers, with the conversion between both oligomeric forms being dependent on the redox state [27, 28]. GLUT1 transports glucose with a Km of ~3 mM. Other transported substrates are galactose, mannose and glucosamine [75].

Glucose transport by GLUT1 is sensitive to several inhibitors that also block transport by other isoforms. Many of them are competitive inhibitors of sugar binding, either to the extracellular or the cytosolic sugar binding sites. Cytochalasin B binds to the inner surface of GLUT1 [4] and inhibits its glucose transport activity with an IC50 of 0.44 μM. Binding of cytochalasin B is to a site which contains tryptophan 388 and 412 (see Fig. 2). Also acting on the same intracellular site is the diterpene toxin forskolin. Forskolin has been used as a photoaffinity label with some specificity for the glucose transporter and its affinity is increased in the 3-iodo4-azidophenethylamido- 7-O-succinyldeacetyl (IAPS) derivative. [...]

[...]

Several heterozygous mutations resulting in GLUT1 haploinsufficiency have been identified. These cause

[page 482]

hypoglycorrachia, a condition characterized by seizures, developmental delay, acquired microcephaly, and hypotonia, and which is due to a decrease rate of glucose transport from the blood into cerebrospinal fluid [42, 67].


4. Baldwin SA, Lienhard GE (1989) Purification and reconstitution of glucose transporter from human erythrocytes. Methods Enzymol 174:39–50

27. Hamill S, Cloherty EK, Carruthers A (1999) The human erythrocyte sugar transporter presents two sugar import sites. Biochemistry 38:16974–16983

28. Hebert DN, Carruthers A (1992) Glucose transporter oligomeric structure determines transporter function. Reversible redoxdependent interconversions of tetrameric and dimeric GLUT1. J Biol Chem 267:23829–23838

42. Klepper J, Voit T (2002) Facilitated glucose transporter protein type 1 (GLUT1) deficiency syndrome: impaired glucose transport into brain—a review. Eur J Pediatr 161:295–304

45. Maher F, Vannucci SJ, Simpson IA (1994) Glucose transporter proteins in brain. FASEB J 8:1003–1011

52. Mueckler M, Makepeace C (2002) Analysis of transmembrane segment 10 of the Glut1 glucose transporter by cysteinescanning mutagenesis and substituted cysteine accessibility. J Biol Chem 277:3498–3503

67. Seidner G, Alvarez MG, Yeh JI, O’Driscoll KR, Klepper J, Stump TS, Wang D, Spinner NB, Birnbaum MJ, De Vivo DC (1998) GLUT-1 deficiency syndrome caused by haploinsufficiency of the blood-brain barrier hexose carrier. Nat Genet 18:188–191

75. Uldry M, Ibberson M, Hosokawa M, Thorens B (2002) GLUT2 is a high affinity glucosamine transporter. FEBS Lett 524:199– 203

79. Zuniga FA, Shi G, Haller JF, Rubashkin A, Flynn DR, Iserovich P, Fischbarg J (2001) A three-dimensional model of the human facilitative glucose transporter Glut1. J Biol Chem 276:44970–44975

Anmerkungen

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Sichter
(Hindemith)

[2.] Sj/Fragment 030 02 - Diskussion
Bearbeitet: 26. November 2016, 16:02 (LieschenMueller)
Erstellt: 26. November 2016, 15:25 LieschenMueller
BauernOpfer, Fragment, Palmada et al 2006, SMWFragment, Schutzlevel, Sj, ZuSichten

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LieschenMueller
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Untersuchte Arbeit:
Seite: 30, Zeilen: 1 - 11
Quelle: Palmada et al 2006
Seite(n): 422, Zeilen: r.col:13ff
Table 2. Enzymes used for invitro transcription and amount of cRNA injected per oocyte.

Isolation of mouse adipocytes

Adipocytes were isolated from epididymal fat pads of 129/SvJ mice by collagenase digestion as described previously (117). Epididymal fat pads were minced and digested with 2 mg/ml type II collagenase for 1h at 37°C in Krebs Ringer bicarbonate Hepes buffer (KRBH: 120 mmol/l NaCl, 4 mmol/l KH2PO4, 1 mmol/l MgSO4, 1 mmol/l CaCl2, 10 mmol/l NaHCO3, 200 nmol/l adenosine, 30 mmol/l Hepes, pH 7.4) containing 1 % fraction V BSA. The resulting cell suspension was filtered through a nylon mesh (250 μm) and washed 3 times with KRBH buffer containing 3 % BSA. Then adipocytes were resuspended in KRBH buffer with 3 % BSA. An aliquot of the final cellular suspension was taken to measure lipocrit and cell number.


117. Palmada,M, Boehmer,C, Akel,A, Rajamanickam,J, Jeyaraj,S, Keller,K, Lang,F: SGK1 Kinase Upregulates GLUT1 Activity and Plasma Membrane Expression. Diabetes 55:421-427, 2006

Isolation of mice adipocytes.

Adipocytes were isolated from 129/SvJ mice epididymal fat pads by collagenase digestion as previously described (35). The fat pads were minced and digested with 2 mg/ml type II collagenase for 1 h at 37°C in Krebs Ringer bicarbonate HEPES buffer (120 mmol/l NaCl, 4 mmol/l KH2PO4 , 1 mmol/l MgSO4 , 1 mmol/l CaCl2 , 10 mmol/l NaHCO3 , 200 nmol/l adenosine, and 30 mmol/l HEPES, pH 7.4) containing 1% fraction V BSA. The resulting cell suspension was filtered through a nylon mesh (250 m) and washed three times with Krebs Ringer bicarbonate HEPES buffer containg 3% BSA. Then adipocytes were resuspended in Krebs Ringer bicarbonate HEPES buffer with 3% BSA. An aliquot of the final cellular suspension was taken to measure lipocrit and cell number.


35. Ruan H, Zarnowski MJ, Cushman SW, Lodish HF: Standard isolation of primary adipose cells from mouse epididymal fat pads induces inflammatory mediators and down-regulates adipocyte genes. J Biol Chem 278: 47585–47593, 2003

Anmerkungen
Sichter
(LieschenMueller)

[3.] Sj/Fragment 032 04 - Diskussion
Bearbeitet: 28. November 2016, 05:08 (Klgn)
Erstellt: 27. November 2016, 00:27 LieschenMueller
BauernOpfer, Fragment, Palmada et al 2006, SMWFragment, Schutzlevel, Sj, ZuSichten

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LieschenMueller
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Untersuchte Arbeit:
Seite: 32, Zeilen: 4
Quelle: Palmada et al 2006
Seite(n): 423, Zeilen: r.col:9f
3.7 Western blotting

To determine whole-cell GLUT1 and SGK1 expression in HEK-293 and adipocytes, cells were homogenized in lysis buffer and 30 μg protein were separated on a 10% polyacrylamide gel and transferred to a nitrocellulose membrane. After blocking with 5% non fat dry milk in PBS/0.15% Tween-20 for 1 h at room temperature, blots were incubated overnight at 4°C with a goat anti- GLUT1 antibody (diluted 1:100 in PBS/0.15% Tween 20/5% nonfat dry milk; Santa Cruz Biotechnology), a rabbit anti-SGK1 antibody (diluted 1:1,000 in PBS/0.15% Tween 20/5% nonfat dry milk; Upstate, Dundee, U.K.), or a rabbit anti–glyceraldehyde-3-phosphate dehydrogenase (GAPDH) horseradish peroxidase conjugated antibody (diluted 1:1,000 in PBS/0.15% Tween 20/5% nonfat dry milk). GAPDH was used to demonstrate equal protein loading. Secondary peroxidase-conjugated donkey anti-goat IgG antibody (diluted 1:2000 in PBS/0.15% Tween 20/5% nonfat dry milk; Santa Cruz Biotechnology) or sheep anti-rabbit IgG antibody (diluted 1:1,000 in PBS/0.15% Tween 20/5% nonfat dry milk; Amersham, Freiburg, Germany) was used for chemiluminescent detection of GLUT1 or SGK1 with an enhanced chemiluminescence kit (Amersham), respectively. Band intensities were quantified using Quantity One Analysis software (Biorad, Munich, Germany).

Western blotting. To determine whole-cell GLUT1 and SGK1 expression in oocytes, transfected HEK-293 cells, and adipocytes, cells were homogenized in lysis buffer, and 30 μg protein were separated on a 10% polyacrylamide gel and transferred to a nitrocellulose membrane. After blocking with 5% nonfat dry milk in PBS/0.15% Tween 20 for 1 h at room temperature, blots were incubated overnight at 4°C with a goat anti-GLUT1 antibody (diluted 1:100 in PBS/0.15% Tween 20/5% nonfat dry milk; Santa Cruz Biotechnology), a rabbit anti-SGK1 antibody (diluted 1:1,000 in PBS/0.15% Tween 20/5% nonfat dry milk; Upstate, Dundee, U.K.), or a rabbit anti– glyceraldehyde-3-phosphate dehydrogenase (GAPDH) horse- radish peroxidase–conjugated antibody (diluted 1:1,000 in PBS/0.15% Tween 20/5% nonfat dry milk). GAPDH was used to demonstrate equal protein loading. Secondary peroxidase-conjugated donkey anti-goat IgG antibody (diluted 1:2000 in PBS/0.15% Tween 20/5% nonfat dry milk; Santa Cruz Biotechnology) or sheep anti-rabbit IgG antibody (diluted 1:1,000 in PBS/0.15% Tween 20/5% nonfat dry milk; Amersham, Freiburg, Germany) was used for chemiluminescent detection of GLUT1 or SGK1 with an enhanced chemiluminescence kit (Amersham), respectively. Band intensities were quantified using Quantity One Analysis software (Biorad, Munich, Germany)
Anmerkungen

Text aus Quelle 117, letzter Hinweis auf diese Quelle S. 30 Zeile 3

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[4.] Sj/Fragment 041 01 - Diskussion
Bearbeitet: 27. November 2016, 14:47 (LieschenMueller)
Erstellt: 27. November 2016, 14:46 LieschenMueller
BauernOpfer, Fragment, Palmada et al 2006, SMWFragment, Schutzlevel, Sj, ZuSichten

Typus
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LieschenMueller
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Untersuchte Arbeit:
Seite: 41, Zeilen: 1ff
Quelle: Palmada et al 2006
Seite(n): 424, Zeilen: 1: Bildunterschrift FIG.6
4.6 S422DSGK1 enhances 2-DOG transport in HEK-293 cells without affecting total protein expression levels of GLUT1

It was already observed the upregulation of GLUT1 by SGK1 in Xenopus oocytes. GLUT1 modulation by SGK1 was observed in mammalian cells (HEK-293). HEK-293 cells were transfected with pIRES2EGFP-S422DSGK1, pIRES2EGFPK127NSGK1 or with empty vector (as a control) and two days later 2-DOG uptake was measured in the presence and absence of GLUT1 inhibitor phloretin (0.1 mM).

FIG. 6. S422DSGK1 enhances 2-DOG transport in HEK-293 cells without affecting total GLUT1 expression levels. HEK-293 cells were transfected with pIRES2EGFP-S422DSGK1, pIRES2EGFP-K127NSGK1, or empty vector, and 2 days later labeled 2-DOG uptake was studied in the presence and absence of GLUT1 inhibitor 0.1 mmol/l phloretin (A)....
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Text aus Quelle 117, letzter Hinweis auf diese Quelle Seite 30 Zeile 3

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