11,273 research outputs found
Effect of phospholipase treatment on insulin receptor signal transduction
No full textTo study the role of membrane lipids in signal transduction by the insulin receptor, we have studied the effect of phospholipase C (Clostridium perfringens) and a phosphatidylinositol-specific phospholipase (Staphylococcus aureus) on insulin binding, a function of the alpha-subunit, and tyrosine kinase activity, a function of the beta-subunit in IM-9 lymphocytes and NIH 3T3 fibroblasts transfected with the human insulin receptor. Treatment of the cells with phospholipase C at concentrations up to 3.4 U/ml did not affect specific insulin binding, but reduced insulin-stimulated receptor phosphorylation by 50%. This effect of phospholipase C was observed within 10 min of treatment and occurred with no change in the basal level of phosphorylation. Pre-treatment of cells with insulin for 5 min prior to enzyme addition prevented any change in kinase activity. Insulin-stimulated phosphorylation of pp 185, the presumed endogenous substrate for the insulin receptor kinase, was also reduced following phospholipase C treatment, with an almost complete loss of insulin stimulation after exposure of cells to enzyme at concentrations as low as 0.6 U/ml. In contrast to these effects of phospholipase C on intact cells, receptor autophosphorylation was not affected in insulin receptors purified on wheat germ agglutinin-agarose from phospholipase C treated cells. Likewise, the phospholipase C effect was reduced by the addition of phosphatidylcholine, but not by the addition of the protease inhibitors, aprotinin and phenylmethylsulfonyl fluoride, to the incubation indicating its dependence on phospholipid hydrolysis. Treatment of cells with the phosphatidylinositol-specific phospholipase C did not affect any of the parameters studied.(ABSTRACT TRUNCATED AT 250 WORDS
Oral history interview with Robert E. Kahn
No full textCopyright to this oral history is held by Robert E. Kahn.Kahn briefly discusses his educational background and involvement with the development of ARPANET before focusing on the operations of the Information Processing Techniques Office (IPTO) of the Defense Advanced Research Projects Agency (DARPA). Kahn describes the development of computer networks with DARPA support and explains the process of contracting research at DARPA as well as the creation of DARPA budgets in detail. In this context he discusses the work of various DARPA and IPTO personnel including J. C. R. Licklider, Vinton Cerf, Larry Roberts, and George Heilmeier. This interview was recorded as part of a research project on the influence of the Defense Advanced Research Projects Agency (DARPA) on the development of computer science in the United States.Kahn, Robert E.. (1989). Oral history interview with Robert E. Kahn. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/107380
Molecular and solid-state (8-hydroxy-quinoline)aluminum interaction with magnesium: A first-principles study
No full textThe interaction between Mg and (8-hydroxyquinoline)aluminum, Alq(3), is investigated via ab initio molecular dynamics based on density-functional theory. We model the Alq(3) thin film both with a single Alq(3) molecule in vacuo (as is usually done in the literature) and with an Alq(3) crystalline structure. Comparing the results from these two models, we show that bulk calculations provide a better description of the chemical processes involved, allowing the Mg atom to react with two neighboring Alq(3) molecules, as was alluded to in a previous publication [S. Meloni, A. Palma, A. Kahn, J. Schwartz, and R. Car, J. Am. Chem. Soc. 125, 7808 (2003)]. Moreover, core-level shift calculations are in good agreement with experimental measurements only when using the solid phase approach. We also propose a different interpretation of the Al(2p) experimental core level presented in a previous work [C. Shen, A. Kahn, and J. Schwartz, J. Appl. Phys. 89, 449 (2001)]
Quantitative dissociation between EGF effects on c-myc and c-fos gene expression, DNA synthesis, and epidermal growth factor receptor tyrosine kinase activity
No full textThe exact relationship between EGF-stimulated tyrosine phosphorylation, induction of the cellular proto-oncogenes c-myc and c-fos, and DNA synthesis remains uncertain. Madin-Darby Canine Kidney (MDCK) cells possess EGF receptor sites with high binding capacity, and in contrast to A431 cells, respond to EGF by increasing DNA synthesis. Following EGF stimulation of intact MDCK cells, there was a rapid and marked increase in the autophosphorylation of the EGF receptor. This was associated with an increase in the tyrosine phosphorylation of a 120 kDa phosphoprotein believed to be an endogenous substrate of this receptor kinase. The ED50 for stimulation of phosphorylation of pp120 was approximately 0.05 nM versus 1.0 nM for receptor autophosphorylation, consistent with amplification of signalling at this step in EGF action. Stimulation of DNA synthesis occurred after 12 to 24 hours and revealed even further amplification with an ED50 of about 0.1 nM. Intermediate between these events was a time-dependent activation of c-fos and c-myc gene expression. However, the ED50 for these processes was approximately 10 nM, indicating a relatively lower sensitivity of EGF for stimulation of proto-oncogene expression. Tyrphostin (RG 50864), a compound reported to inhibit specifically the EGF receptor kinase, completely blocked EGF stimulation of proto-oncogene induction. Interestingly, under the same experimental conditions, EGF receptor autophosphorylation was decreased only 60%. These data, along with the dose-response studies, indicate that proto-oncogene induction requires near maximal stimulation of EGF receptor autophosphorylation. They also suggest that, in MDCK cells, the EGF dependent induction of the c-fos and c-myc genes is not strictly correlated to the extent of EGF receptor autophosphorylation or EGF-stimulated DNA synthesis, and that EGF stimulation of DNA synthesis likely involves additional rate-limiting intermediate steps
Richard Ferdinand Kahn
No full textThere are three areas in which Kahn (1905–1989) made contributions which secured
him a prominent place in the history of economics: imperfect competition, the theory of
employment, and monetary and international economics
Sarah Kahn
No full textSarah Kahn (Cohen) was the widow of Samuel Kahn. Samuel Kahn was a Jewish pioneer and merchant
Kahn, Mrs. Samuel
No full textKahn, Mrs. Samuel. Kahn, Sarah Cohen Wife of "Col." Kahn, early Jewish pioneer and merchant
THE LOW-LYING ELECTRONIC STATES OF HgCl AND HgBr
No full text L. R, Kahn, P. J. Hay, and R. D. Cowan, J, Chem. Phys., in press. L. R. Kahn, P. Baybutt, and D. G. Truhlar, J. Chem. Phys. 65, 3826 (1976). ""Author Institution: Los Alamos Scientific Laboratory; Los Alamos Scientific Laboratory, Battelle Columbus LaboratoriesAb initio configuration interaction calculations are reported on the Low-lying electronic states of HgCl and HgBr. The calculations employ a relativistic effective core on Hg and nonrelativistic effective core on chlorine and bromine. Emission energies and spectroscopic constants for the lasing transition are compared to experiment. Spin-orbit coupling effects are included using a simple, effective, one-electron spin-orbit operator. The production of electronically excited HgCl and HgBr by photodissociation of and will be considered briefly
Sobre a nova technica da Reacção de Kahn
No full textNuloL\u27 A. fait une étude compara tive entre la nouvel e technique de la réaction de Kahn, le Wassermam et le Kahn routinier. Il décrit rapidement les techniques, employées pour:es trois réactions, appuie son travail sur 400 réactions, et arrive aux conclusions suivantes: I. o La nouvelle technique de la réaction de Kahn offre sur la R. de Wassermam quelques avantages: a) annulation des réactions dites anti complémentaires; b) haute spécificité; c) lecture facile, etc. 2. o La nouvelle technique de la réaction de Kahn comparée á l\u27ancienne technique, c\u27est á dire avec un seul tube, n\u27a sur celle-ci qu\u27un trés petit avantage, quant aux résultats obtenus. Malgré sa technique bien plus compliquée elle présente un énorme avant.age sur le procédé rout.inier: la rapidité avec laquelle ou obtient les résultats
On Joan Robinson’s role in creating the myth that R. Kahn originated the multiplier concept
No full textAn enduring myth accepted by all Orthodox and heterodox economists is that it was Richard Kahn who discovered and originated the concept of the multiplier. Kahn then supposedly showed Keynes how the multiplier concept could be specified mathematically so as to provide hard support for Keynes’s views in the late 1920s about increased initial government spending on public infrastructure generating much larger increases in total spending than the original injection, leading to decreasing levels of unemployment. There are three major problems with this story. First, Kahn, himself, in a 1936 response to Hans Neisser in the Review of Economics and Statistics stated that most of his ideas about the multiplier concept came from Keynes. Second, the mathematical and logical development of the multiplier concept had already been formalized and formulated precisely by Keynes in 1921 on p. 315 in footnote 1 of the A Treatise on Probability in section 8 of chapter 26. Third, Keynes provided an arithmetic example of the mathematical technique worked out in the A Treatise on Probability in May, 1929 (Kent, 2007). There is simply no foundation for the myth, promoted by Joan Robinson, that Kahn was the author of the multiplier concept. Kahn went along with Robinson because he was involved in a 54-year old relationship with Joan Robinson. Keynes taught Kahn the theory of the multiplier concept and left it up to Kahn to write a full blown article on it, which was then published by Keynes in the June,1931 issue of the Economic Journal
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