51
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Safavi A, Peiravian F, Shams E. A selective uphill transport of copper through bulk liquid membrane using Janus Green as an anion carrier. Sep Purif Technol 2002. [DOI: 10.1016/s1383-5866(01)00178-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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52
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Safavi A, Abdollahi H. SIMULTANEOUS SPECTROPHOTOMETRIC DETERMINATION OF IRON, COBALT, AND NICKEL BY PARTIAL LEAST SQUARES CALIBRATION METHOD IN MICELLAR MEDIUM. ANAL LETT 2001. [DOI: 10.1081/al-100108425] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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53
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Safavi A, Abdollahi H. Spectrophotometric study on micelle-mediated shift in kinetic and equilibrium of complex formation between Ni2+ and 2-amino-cyclopentene-1-dithiocarboxylic acid. Microchem J 2001. [DOI: 10.1016/s0026-265x(01)00082-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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54
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Safavi A. Application of the H-point standard addition method to the speciation of Fe(II) and Fe(III) with chromogenic mixed reagents. Talanta 2001; 54:727-34. [DOI: 10.1016/s0039-9140(01)00321-6] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2000] [Revised: 01/04/2001] [Accepted: 01/05/2001] [Indexed: 11/28/2022]
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55
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Safavi A, Maleki N, Farjami F. Selective kinetic spectrophotometric determination of copper at nanograms per milliliter level. Talanta 2001; 54:397-402. [DOI: 10.1016/s0039-9140(00)00680-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2000] [Revised: 12/06/2000] [Accepted: 12/08/2000] [Indexed: 10/18/2022]
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56
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Safavi A, Absalan G, Maesum S. Simultaneous determination of V(IV) and Fe(II) as catalyst using “neural networks” through a single catalytic kinetic run. Anal Chim Acta 2001. [DOI: 10.1016/s0003-2670(00)01388-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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57
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Safavi A. Thermodynamic characterization of weak association equilibria accompanied with spectral overlapping by a SVD-based chemometric method. Talanta 2001; 53:1001-7. [DOI: 10.1016/s0039-9140(00)00591-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/1999] [Revised: 09/08/2000] [Accepted: 09/11/2000] [Indexed: 11/29/2022]
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58
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Safavi A, Mirzaee M. Kinetic spectrophotometric determination of traces of sulfide in nonionic micellar medium. FRESENIUS' JOURNAL OF ANALYTICAL CHEMISTRY 2000; 367:645-8. [PMID: 11221927 DOI: 10.1007/s002160000350] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
A sensitive kinetic spectrophotometric method for the determination of ng amounts of sulfide has been developed based on the reduction of Azure A by sulfide in the presence of Brij-35 at pH 7. The decrease in absorbance of Azure A at 600 nm is proportional to the concentration of sulfide over the range 25-1,400 ng mL(-1). The variables affecting the rate of the reaction were investigated and the optimum conditions were established. The method is simple, rapid, precise, sensitive, and widely applicable. The limit of detection is 17 ng mL(-1), and the relative standard deviation of seven determinations of 500 ng mL(-1) sulfide was 2.1%. The method was applied to the determination of sulfide in spring water.
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Safavi A. Highly sensitive and selective measurements of cobalt by catalytic adsorptive cathodic stripping voltammetry. Talanta 2000; 51:1117-23. [DOI: 10.1016/s0039-9140(00)00278-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/1999] [Revised: 11/24/1999] [Accepted: 12/10/1999] [Indexed: 10/16/2022]
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60
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Safavi A, Hormozi Nezhad M, Shams E. Highly selective and sensitive kinetic spectrophotometric determination of vanadium(IV) in the presence of vanadium(V). Anal Chim Acta 2000. [DOI: 10.1016/s0003-2670(99)00794-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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61
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Safavi A, Abdollahi H, Sedaghatpour F, Zeinali S. Kinetic spectrophotometric determination of V(IV) in the presence of V(V) by the H-point standard addition method. Anal Chim Acta 2000. [DOI: 10.1016/s0003-2670(99)00868-5] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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62
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Safavi A. Spectrofluorimetric kinetic determination of selenium (IV) by flow injection analysis in cationic micellar medium. Talanta 2000; 51:225-30. [DOI: 10.1016/s0039-9140(99)00260-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/1999] [Revised: 08/13/1999] [Accepted: 08/25/1999] [Indexed: 11/26/2022]
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63
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Sayeski PP, Ali MS, Safavi A, Lyles M, Kim SO, Frank SJ, Bernstein KE. A catalytically active Jak2 is required for the angiotensin II-dependent activation of Fyn. J Biol Chem 1999; 274:33131-42. [PMID: 10551884 DOI: 10.1074/jbc.274.46.33131] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Recent work with interleukins has shown a convergence of tyrosine phosphorylation signal transduction cascades at the level of the Janus and Src families of tyrosine kinases. Here we demonstrate that activation of the seven-transmembrane AT(1) receptor by angiotensin II induces a physical association between Jak2 and Fyn, in vivo. This association requires the catalytic activity of Jak2 but not Fyn. Deletion studies indicate that the region of Jak2 that binds Fyn is located between amino acids 1 and 240. Studies of the Fyn SH2 and SH3 domains demonstrate that the SH2 domain plays the primary role in Jak2/Fyn association. Not surprisingly, this domain shows a marked preference for tyrosine-phosphorylated Jak2. Surface plasmon resonance estimated the dissociation equilibrium constant (K(d)) of this association to be 2.36 nM. Last, in vivo studies in vascular smooth muscle cells show that, in response to angiotensin II, Jak2 activation is required for Fyn activation and induction of the c-fos gene. The significance of these data is that Jak2, in addition to serving as a critical angiotensin II activated signal transduction kinase, also functions as a docking protein and participates in the activation of Fyn by providing phosphotyrosine residues that bind the SH2 domain of Fyn.
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Safavi A, Shams E. Selective determination of ultra trace concentrations of molybdenum by catalytic adsorptive stripping voltammetry. Anal Chim Acta 1999. [DOI: 10.1016/s0003-2670(99)00450-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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65
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Safavi A, Shams E. Selective and efficient liquid membrane transport of gold as gold cyanide using an anion carrier. J Memb Sci 1999. [DOI: 10.1016/s0376-7388(98)00372-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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66
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Safavi A, Shams E. Determination of trace amounts of copper(II) by adsorptive stripping voltammetry of its complex with pyrogallol red. Anal Chim Acta 1999. [DOI: 10.1016/s0003-2670(98)00580-7] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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67
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Qiu WQ, Walsh DM, Ye Z, Vekrellis K, Zhang J, Podlisny MB, Rosner MR, Safavi A, Hersh LB, Selkoe DJ. Insulin-degrading enzyme regulates extracellular levels of amyloid beta-protein by degradation. J Biol Chem 1998; 273:32730-8. [PMID: 9830016 DOI: 10.1074/jbc.273.49.32730] [Citation(s) in RCA: 631] [Impact Index Per Article: 24.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Excessive cerebral accumulation of the 42-residue amyloid beta-protein (Abeta) is an early and invariant step in the pathogenesis of Alzheimer's disease. Many studies have examined the cellular production of Abeta from its membrane-bound precursor, including the role of the presenilin proteins therein, but almost nothing is known about how Abeta is degraded and cleared following its secretion. We previously screened neuronal and nonneuronal cell lines for the production of proteases capable of degrading naturally secreted Abeta under biologically relevant conditions and concentrations. The major such protease identified was a metalloprotease released particularly by a microglial cell line, BV-2. We have now purified and characterized the protease and find that it is indistinguishable from insulin-degrading enzyme (IDE), a thiol metalloendopeptidase that degrades small peptides such as insulin, glucagon, and atrial natriuretic peptide. Degradation of both endogenous and synthetic Abeta at picomolar to nanomolar concentrations was completely inhibited by the competitive IDE substrate, insulin, and by two other IDE inhibitors. Immunodepletion of conditioned medium with an IDE antibody removed its Abeta-degrading activity. IDE was present in BV-2 cytosol, as expected, but was also released into the medium by intact, healthy cells. To confirm the extracellular occurrence of IDE in vivo, we identified intact IDE in human cerebrospinal fluid of both normal and Alzheimer subjects. In addition to its ability to degrade Abeta, IDE activity was unexpectedly found be associated with a time-dependent oligomerization of synthetic Abeta at physiological levels in the conditioned media of cultured cells; this process, which may be initiated by IDE-generated proteolytic fragments of Abeta, was prevented by three different IDE inhibitors. We conclude that a principal protease capable of down-regulating the levels of secreted Abeta extracellularly is IDE.
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Ali MS, Sayeski PP, Safavi A, Lyles M, Bernstein KE. Janus kinase 2 (Jak2) must be catalytically active to associate with the AT1 receptor in response to angiotensin II. Biochem Biophys Res Commun 1998; 249:672-7. [PMID: 9731195 DOI: 10.1006/bbrc.1998.9054] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Angiotensin II evokes a variety of biological responses by binding to a seven transmembrane cell surface receptor termed AT1. Ligand binding to the AT1 receptor induces the physical association and activation of the intracellular kinase Jak2. To elucidate the mechanism of this association, COS-7 cells were co-transfected with the AT1 receptor and either wild type Jak2 or a catalytically inactive Jak2. AT1 receptor-Jak2 association was assessed in vitro by a GST-AT1 receptor fusion protein binding assay and in vivo by direct co-immunoprecipitation of the receptor-Jak2 complex. Both studies showed that Jak2 must be catalytically active to form a complex with the AT1 receptor, and that complex formation is associated with Jak2 tyrosine phosphorylation. These results were confirmed using the Jak2 specific inhibitor AG-490. We also found that over-expression of wild type Jak2 in COS-7 cells leads to in vivo complex formation of spontaneously autophosphorylated Jak2 with the AT1 receptor. No such complex formation was observed with a dominant negative Jak2. Thus, the physical association of Jak2 with the AT1 receptor is regulated by an angiotensin II mediated autophosphorylation event.
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Thiele DL, Sarada B, Dang T, Safavi A, Hersh LB, Cottam GL. Regulated expression of an endopeptidase that hydrolyses beta-endorphin during differentiation of macrophages and T cells. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1998; 437:291-300. [PMID: 9666282 DOI: 10.1007/978-1-4615-5347-2_32] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
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71
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Maleki N, Safavi A, Shahbaazi H. Teflon tubing mercury electrode for electrochemical analysis. J Electroanal Chem (Lausanne) 1998. [DOI: 10.1016/s0022-0728(98)00042-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Sarada B, Thiele D, Dang T, Safavi A, Hersh LB, Cottam GL. Increased expression of an endopeptidase (gamma-EGE/IDE) hydrolyzing beta-endorphin during differentiation and maturation of bone marrow macrophages. J Leukoc Biol 1997; 62:753-60. [PMID: 9400816 DOI: 10.1002/jlb.62.6.753] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The presence and regulated expression of peptidase activity is a powerful mechanism with the potential to terminate or alter receptor recognition, cell membrane signal transduction, and physiological responses of immune cells to exogenous opioid peptides. In this study, the expression of an endopeptidase that hydrolyzes beta-endorphin to gamma-endorphin and other peptide products was investigated during in vitro differentiation and maturation of recombinant granulocyte-macrophage colony-stimulating factor (rGM-CSF) -derived, bone marrow-derived macrophages. In freshly isolated intact isolated mouse bone marrow cells the rate of beta-endorphin hydrolysis is undetectable (<0.1 nmol beta-endorphin hydrolyzed/h/10[6] cells). However, total intracellular beta-endorphin hydrolytic activity was increased significantly to 20.0 +/- 1.7 nmol/h/10(6) cells in the mature mouse macrophages derived in vitro by culture with rGM-CSF. rGM-CSF-derived macrophages expressed significantly higher levels of both protein and mRNA for the major beta-endorphin endopeptidase, gamma-endorphin-generating enzyme/insulin-degrading enzyme (gamma-EGE/IDE). Moreover, this enzymatic activity appears to be responsible for cleavage of exogenous beta-endorphin by intact rGM-CSF-derived macrophages or peritoneal macrophages to generate gamma-endorphin and other peptide products.
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Haghighi B, Maleki N, Safavi A. Standard additions in flow injection analysis with atomic absorption spectrometry. Anal Chim Acta 1997. [DOI: 10.1016/s0003-2670(97)00552-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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75
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Haghighi B, Maleki N, Safavi A. A Modified Z-Type Flow-through Cell for Optical, Electrochemical, and Optoelectrochemical Flow Injection Analysis Measurements. Microchem J 1997. [DOI: 10.1006/mchj.1997.1484] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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