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Search Results: 1 - 10 of 462902 matches for " A Larsen "
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Infección por el virus de la Lengua azul: activación de se?ales celulares que inducen apoptosis
Mortola,E.; Larsen,A.;
Revista argentina de microbiolog?-a , 2009,
Abstract: bluetongue (btv) is a double-stranded rna virus that induces apoptosis both in mammalian cell cultures and in target tissues. to elucidate the apoptosis pathways in btv infection, we have examined in detail the apoptosis mechanism by examination of caspases, bax, cytochrome c, smac/diablo and nf-kb signalling pathways. in this report, after cell infection with btv, the activation of caspase 8 was detected, proving the extrinsic receptor binding apoptotic pathway. apoptosis followed a sequential pathway involving the detection of activated bcl-2 family members. furthermore, its translocation to the mitochondria, as well as the release of cytochrome c and smac/diablo confirmed that btv apoptosis involves the sequential intrinsic pathway. in addition, we demonstrated that nf-kb was activated following btv infection and cell treatment with an inhibitor peptide before btv infection, prevented nf-kb activation and substantially reduced cellular apoptosis. our accumulating data concerning the activation of bax, cytochrome c, smac/diablo and nf-kb clarify the mechanism of apoptosis during btv infection, and confer a better understanding of the primary role of apoptosis in btv pathogenesis.
Infección por el virus de la Lengua azul: activación de se ales celulares que inducen apoptosis Bluetongue virus infection: signaling pathway activated during apoptosis
E. Mortola,A. Larsen
Revista argentina de microbiolog?-a , 2009,
Abstract: El virus de la Lengua azul (VLA) es un ARN virus de doble cadena que induce apoptosis tanto en cultivos celulares como en tejidos blanco. Con el fin de dilucidar el mecanismo de apoptosis en la infección por el VLA, en el presente trabajo examinamos en detalle, por la técnica de Western blot, las se ales celulares de caspasas, Bax, citocromo c, Smac/DIABLO y factor nuclear kappa B (NF-kB) que se activan en la infección viral. Hemos comprobado que luego de la infección in vitro con el VLA, se detectó la activación de la caspasa 8 y con ello el mecanismo extrínseco de la apoptosis. También detectamos por primera vez no sólo la activación de miembros de la familia Bcl-2 (Bax), sino también la liberación del citocromo c y la proteína Smac/DIABLO, confirmando que en la infección por el VLA está involucrado el mecanismo secuencial intrínseco de la apoptosis. Asimismo, demostramos que la infección por el VLA activa el NF-kB y que la apoptosis es sustancialmente reducida mediante la inhibición del mismo. La activación de las se ales celulares tales como Bax, citocromo c, Smac/DIABLO y NF-kB presentados en este trabajo, esclarecen los mecanismos apoptóticos durante la infección por el VLA para una mayor comprensión del papel primario que juega la apoptosis en la patogénesis del virus. Bluetongue (BTV) is a double-stranded RNA virus that induces apoptosis both in mammalian cell cultures and in target tissues. To elucidate the apoptosis pathways in BTV infection, we have examined in detail the apoptosis mechanism by examination of caspases, Bax, cytochrome c, Smac/DIABLO and NF-kB signalling pathways. In this report, after cell infection with BTV, the activation of caspase 8 was detected, proving the extrinsic receptor binding apoptotic pathway. Apoptosis followed a sequential pathway involving the detection of activated Bcl-2 family members. Furthermore, its translocation to the mitochondria, as well as the release of cytochrome c and Smac/Diablo confirmed that BTV apoptosis involves the sequential intrinsic pathway. In addition, we demonstrated that NF-kB was activated following BTV infection and cell treatment with an inhibitor peptide before BTV infection, prevented NF-kB activation and substantially reduced cellular apoptosis. Our accumulating data concerning the activation of Bax, cytochrome c, Smac/DIABLO and NF-kB clarify the mechanism of apoptosis during BTV infection, and confer a better understanding of the primary role of apoptosis in BTV pathogenesis.
Chaotic string-capture by black hole
A. L. Larsen
Physics , 1993, DOI: 10.1088/0264-9381/11/5/008
Abstract: We consider a macroscopic charge-current carrying (cosmic) string in the background of a Schwarzschild black hole. The string is taken to be circular and is allowed to oscillate and to propagate in the direction perpendicular to its plane (that is parallel to the equatorial plane of the black hole). Nurmerical investigations indicate that the system is non-integrable, but the interaction with the gravitational field of the black hole anyway gives rise to various qualitatively simple processes like "adiabatic capture" and "string transmutation".
Circular String-Instabilities in Curved Spacetime
A. L. Larsen
Physics , 1993, DOI: 10.1103/PhysRevD.50.2623
Abstract: We investigate the connection between curved spacetime and the emergence of string-instabilities, following the approach developed by Loust\'{o} and S\'{a}nchez for de Sitter and black hole spacetimes. We analyse the linearised equations determining the comoving physical (transverse) perturbations on circular strings embedded in Schwarzschild, Reissner-Nordstr\"{o}m and de Sitter backgrounds. In all 3 cases we find that the "radial" perturbations grow infinitely for $r\rightarrow 0$ (ring-collapse), while the "angular" perturbations are bounded in this limit. For $r\rightarrow\infty$ we find that the perturbations in both physical directions (perpendicular to the string world-sheet in 4 dimensions) blow up in the case of de Sitter space. This confirms results recently obtained by Loust\'{o} and S\'{a}nchez who considered perturbations around the string center of mass.
Cosmic Strings and Black Holes
A. L. Larsen
Physics , 1996,
Abstract: In the first part of this talk, I consider some exact string solutions in curved spacetimes. In curved spacetimes with a Killing vector (timelike or spacelike), the string equations of motion and constraints are reduced to the Hamilton equations of a relativistic point-particle in a scalar potential, by imposing a particular ansatz. As special examples I consider circular strings in axially symmetric spacetimes, as well as stationary strings in stationary spacetimes. In the second part of the talk, I then consider in more detail the stationary strings in the Kerr -Newman geometry. It is shown that the world-sheet of a stationary string, that passes the static limit of the 4-D Kerr-Newman black hole, describes a 2-D black hole. Mathematical results for 2-D black holes can therefore be applied to physical objects; (say) cosmic strings in the vicinity of Kerr black holes. As an immediate general result, it follows that the string modes are thermally excited.
Scattering of string-waves on black hole background
A. L. Larsen
Physics , 1993, DOI: 10.1016/0550-3213(94)90507-X
Abstract: We consider the propagation of perturbations along an infinitely long stationary open string in the background of a Schwarzschild black hole. The equations of motion for the perturbations in the 2 transverse physical directions are solved to second order in a weak field expansion. We then set up a scattering formalism where an ingoing wave is partly transmitted and partly reflected due to the interaction with the gravitational field of the black hole. We finally calculate the reflection coefficient to third order in our weak field expansion.
Comment on thickness-corrections to Nambu-wall
A. L. Larsen
Physics , 1993, DOI: 10.1016/0375-9601(93)90390-L
Abstract: We comment on some calculations concerning the finite-thickness corrections to the (generalized) Nambu action for a curved domain wall in Minkowski space. Contrary to a recent claim in the literature, we find no first order corrections in the wall-thickness, and only one second order correction proportional to the Ricci curvature of the wall. These results are obtained by consistently expanding the action and the equations of motion for the scalar field.
Weiss-approach to pair of coupled non-linear reaction-diffusion equations
A. L. Larsen
Physics , 1993, DOI: 10.1016/0375-9601(93)90680-X
Abstract: We consider a pair of coupled non-linear partial differential equations describing a biochemical model system. The Weiss-algorithm for the Painle\'{e} test, that has been succesfully used in mathematical physics for the KdV-equation, Burgers equation, the sine-Gordon equation etc., is applied, and we find that the system possesses only the "conditional" Painlev\'{e} property. We use the outcome of the analysis to construct an auto-B\"{a}cklund transformation, and we find a variety of one and two-parameter families of special solutions.
Circular Strings in De Sitter Spacetime
A. L. Larsen
Physics , 1994,
Abstract: String propagation is investigated in de Sitter and black hole backgrounds using both exact and approximative methods. The circular string evolution in de Sitter space is discussed in detail with respect to energy and pressure, mathematical solution and physical interpretation, multi-string solutions etc. We compare with the circular string evolution in the 2+1 dimensional black hole anti de Sitter spacetime and in the equatorial plane of ordinary 3+1 dimensional stationary axially symmetric spacetime solutions of Einstein general relativity. Using an approximative string perturbation approach we consider also generic string evolution and propagation in all these curved spacetimes. (To appear in the proceedings of the 2eme Journee Cosmologie held in Paris, June 1994)
Stable and Unstable Circular Strings in Inflationary Universes
A. L. Larsen
Physics , 1994, DOI: 10.1103/PhysRevD.51.4330
Abstract: It was shown by Garriga and Vilenkin that the circular shape of nucleated cosmic strings, of zero loop-energy in de Sitter space, is stable in the sense that the ratio of the mean fluctuation amplitude to the loop radius is constant. This result can be generalized to all expanding strings (of non-zero loop-energy) in de Sitter space. In other curved spacetimes the situation, however, may be different. In this paper we develop a general formalism treating fluctuations around circular strings embedded in arbitrary spatially flat FRW spacetimes. As examples we consider Minkowski space, de Sitter space and power law expanding universes. In the special case of power law inflation we find that in certain cases the fluctuations grow much slower that the radius of the underlying unperturbed circular string. The inflation of the universe thus tends to wash out the fluctuations and to stabilize these strings.
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