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Michael Meyer

Bio: Michael Meyer is an academic researcher from University of Michigan. The author has contributed to research in topics: Planet & Exoplanet. The author has an hindex of 77, co-authored 456 publications receiving 21411 citations. Previous affiliations of Michael Meyer include University of Milan & Hungarian Academy of Sciences.
Topics: Planet, Exoplanet, Stars, Physics, Planetary system


Papers
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Journal ArticleDOI
01 Jan 1987-Nature
TL;DR: It is demonstrated that the effect of macrophages on NGF-mRNA levels in cultured explants of sciatic nerve can be mimicked by conditioned media of activated macrophage, and that interleukin-1 is the responsible agent.
Abstract: The Schwann cells and fibroblast-like cells of the intact sciatic nerve of adult rats synthesize very little nerve growth factor (NGF) (ref. 1). After lesion, however, there is a dramatic increase in the amounts of both NGF-mRNA and NGF protein synthesized by the sciatic non-neuronal cells1,2. This local increase in NGF synthesis partially replaces the interrupted NGF supply from the periphery to the NGF-responsive sensory and sympathetic neurons, whose axons run within the sciatic nerve1. Macrophages, known to invade the site of nerve lesion during wallerian degeneration3,4, are important in the regulation of NGF synthesis5. Here we demonstrate that the effect of macrophages on NGF-mRNA levels in cultured explants of sciatic nerve can be mimicked by conditioned media of activated macrophages, and that interleukin-1 is the responsible agent.

996 citations

Journal ArticleDOI
TL;DR: Different mechanisms of regulation of NGF and BDNF synthesis in non-neuronal cells of the nerve are suggested by the demonstration of differential regulation of these mRNAs in organ culture of rat sciatic nerve and Schwann cell culture.
Abstract: Nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) are molecules which regulate the development and maintenance of specific functions in different populations of peripheral and central neurons, amongst them sensory neurons of neural crest and placode origin. Under physiological conditions NGF is synthesized by peripheral target tissues, whereas BDNF synthesis is highest in the CNS. This situation changes dramatically after lesion of peripheral nerves. As previously shown, there is a marked rapid increase in NGF mRNA in the nonneuronal cells of the damaged nerve. The prolonged elevation of NGF mRNA levels is related to the immigration of activated macrophages, interleukin-1 being the most essential mediator of this effect. Here we show that transsection of the rat sciatic nerve also leads to a very marked increase in BDNF mRNA, the final levels being even ten times higher than those of NGF mRNA. However, the time-course and spatial pattern of BDNF mRNA expression are distinctly different. There is a continuous slow increase of BDNF mRNA starting after day 3 post-lesion and reaching maximal levels 3-4 wk later. These distinct differences suggest different mechanisms of regulation of NGF and BDNF synthesis in non-neuronal cells of the nerve. This was substantiated by the demonstration of differential regulation of these mRNAs in organ culture of rat sciatic nerve and Schwann cell culture. Furthermore, using bioassays and specific antibodies we showed that cultured Schwann cells are a rich source of BDNF- and ciliary neurotrophic factor (CNTF)-like neurotrophic activity in addition to NGF. Antisera raised against a BDNF-peptide demonstrated BDNF-immunoreactivity in pure cultured Schwann cells, but not in fibroblasts derived from sciatic nerve.

699 citations

Journal ArticleDOI
Miriam Keppler1, Myriam Benisty2, Myriam Benisty3, André Müller1, Th. Henning1, R. van Boekel1, Faustine Cantalloube1, Christian Ginski4, Christian Ginski5, R. G. van Holstein5, Anne-Lise Maire1, Adriana Pohl1, Matthias Samland1, Henning Avenhaus1, Jean-Loup Baudino6, Anthony Boccaletti7, J. de Boer5, M. Bonnefoy3, Gael Chauvin2, Gael Chauvin3, Silvano Desidera8, Maud Langlois9, Maud Langlois10, C. Lazzoni8, G.-D. Marleau11, G.-D. Marleau1, Christoph Mordasini12, N. Pawellek13, N. Pawellek1, Tomas Stolker14, Arthur Vigan9, Alice Zurlo9, Alice Zurlo15, Tilman Birnstiel16, Wolfgang Brandner1, M. Feldt1, Mario Flock17, Mario Flock1, Mario Flock18, Julien Girard4, Julien Girard3, Raffaele Gratton8, Janis Hagelberg3, Andrea Isella19, Markus Janson1, Markus Janson20, Attila Juhasz21, J. Kemmer1, Quentin Kral21, Quentin Kral7, Anne-Marie Lagrange3, Ralf Launhardt1, Alexis Matter22, Francois Menard3, Julien Milli4, P. Mollière5, Johan Olofsson1, Johan Olofsson23, Laura M. Pérez2, Paola Pinilla24, Christophe Pinte3, Christophe Pinte25, Christophe Pinte2, Sascha P. Quanz14, T. Schmidt7, Stéphane Udry26, Zahed Wahhaj4, Jonathan Williams27, Esther Buenzli14, M. Cudel3, Carsten Dominik, Raphaël Galicher7, M. Kasper4, J. Lannier3, Dino Mesa28, Dino Mesa8, David Mouillet3, S. Peretti26, C. Perrot7, Graeme Salter9, E. Sissa8, Francois Wildi27, L. Abe22, Jacopo Antichi8, Jean-Charles Augereau3, Andrea Baruffolo8, Pierre Baudoz7, Andreas Bazzon14, Jean-Luc Beuzit3, P. Blanchard9, S. S. Brems29, Tristan Buey7, V. De Caprio8, Marcel Carbillet22, M. Carle9, Enrico Cascone8, A. Cheetham27, Riccardo Claudi8, Anne Costille9, A. Delboulbe3, Kjetil Dohlen9, Daniela Fantinel8, Philippe Feautrier3, Thierry Fusco9, Enrico Giro8, L. Gluck3, Cecile Gry9, Norbert Hubin4, Emmanuel Hugot9, M. Jaquet9, D. Le Mignant9, M. Llored9, F. Madec9, Yves Magnard3, Patrice Martinez22, D. Maurel3, Michael Meyer14, Michael Meyer30, O. Möller-Nilsson1, Thibaut Moulin3, Laurent M. Mugnier, Alain Origne9, A. Pavlov1, D. Perret7, Cyril Petit, J. Pragt, Pascal Puget3, P. Rabou3, Joany Andreina Manjarres Ramos1, F. Rigal, S. Rochat3, Ronald Roelfsema, Gérard Rousset7, A. Roux3, Bernardo Salasnich8, Jean-François Sauvage9, Arnaud Sevin7, Christian Soenke4, Eric Stadler3, M. Suarez8, Massimo Turatto8, L. Weber26 
TL;DR: In this article, the authors detect a point source within the gap of the transition disk at about 195 mas (~22 au) projected separation and detect a signal from an inner disk component.
Abstract: Context. Young circumstellar disks are the birthplaces of planets. Their study is of prime interest to understand the physical and chemical conditions under which planet formation takes place. Only very few detections of planet candidates within these disks exist, and most of them are currently suspected to be disk features.Aims. In this context, the transition disk around the young star PDS 70 is of particular interest, due to its large gap identified in previous observations, indicative of ongoing planet formation. We aim to search for the presence of an embedded young planet and search for disk structures that may be the result of disk–planet interactions and other evolutionary processes.Methods. We analyse new and archival near-infrared images of the transition disk PDS 70 obtained with the VLT/SPHERE, VLT/NaCo, and Gemini/NICI instruments in polarimetric differential imaging and angular differential imaging modes.Results. We detect a point source within the gap of the disk at about 195 mas (~22 au) projected separation. The detection is confirmed at five different epochs, in three filter bands and using different instruments. The astrometry results in an object of bound nature, with high significance. The comparison of the measured magnitudes and colours to evolutionary tracks suggests that the detection is a companion of planetary mass. The luminosity of the detected object is consistent with that of an L-type dwarf, but its IR colours are redder, possibly indicating the presence of warm surrounding material. Further, we confirm the detection of a large gap of ~54 au in size within the disk in our scattered light images, and detect a signal from an inner disk component. We find that its spatial extent is very likely smaller than ~17 au in radius, and its position angle is consistent with that of the outer disk. The images of the outer disk show evidence of a complex azimuthal brightness distribution which is different at different wavelengths and may in part be explained by Rayleigh scattering from very small grains.Conclusions. The detection of a young protoplanet within the gap of the transition disk around PDS 70 opens the door to a so far observationally unexplored parameter space of planetary formation and evolution. Future observations of this system at different wavelengths and continuing astrometry will allow us to test theoretical predictions regarding planet–disk interactions, planetary atmospheres, and evolutionary models.

497 citations

Journal ArticleDOI
Miriam Keppler, Myriam Benisty, André Müller, Th. Henning, R. van Boekel, Faustine Cantalloube, Christian Ginski, R. G. van Holstein, Anne-Lise Maire, A. Pohl, M. Samland, Henning Avenhaus, Jean-Loup Baudino, Anthony Boccaletti, J. de Boer, M. Bonnefoy, Gael Chauvin, Silvano Desidera, Maud Langlois, C. Lazzoni, G.-D. Marleau, Christoph Mordasini, N. Pawellek, Tomas Stolker, Arthur Vigan, Alice Zurlo, Tilman Birnstiel, Wolfgang Brandner, M. Feldt, Mario Flock, Julien Girard, Raffaele Gratton, Janis Hagelberg, Andrea Isella, Markus Janson, Attila Juhasz, J. Kemmer, Quentin Kral, Anne-Marie Lagrange, Ralf Launhardt, Alexis Matter, Francois Menard, Julien Milli, Paul Mollière, Johan Olofsson, Laura M. Pérez, P. Pinilla, Christophe Pinte, Sascha P. Quanz, T. O. B. Schmidt, Stéphane Udry, Zahed Wahhaj, Jonathan Williams, Esther Buenzli, M. Cudel, Carsten Dominik, Raphaël Galicher, M. Kasper, J. Lannier, Dino Mesa, David Mouillet, S. Peretti, C. Perrot, G. Salter, E. Sissa, Francois Wildi, L. Abe, J. Antichi, Jean-Charles Augereau, Andrea Baruffolo, Pierre Baudoz, Andreas Bazzon, Jean-Luc Beuzit, P. Blanchard, S. S. Brems, Tristan Buey, V. De Caprio, Marcel Carbillet, M. Carle, Enrico Cascone, Anthony Cheetham, Riccardo Claudi, Anne Costille, A. Delboulbe, Kjetil Dohlen, D. Fantinel, Philippe Feautrier, Thierry Fusco, Enrico Giro, D. Gisler, L. Gluck, Cecile Gry, N. Hubin, Emmanuel Hugot, M. Jaquet, D. Le Mignant, M. Llored, F. Madec, Yves Magnard, P. Martinez, D. Maurel, Michael Meyer, O. Moeller-Nilsson, Thibaut Moulin, Laurent M. Mugnier, Alain Origne, A. Pavlov, D. Perret, Cyril Petit, J. Pragt, Pascal Puget, Patrick Rabou, Juan-Luis Ramos, F. Rigal, Sylvain Rochat, Ronald Roelfsema, G. Rousset, A. Roux, Bernardo Salasnich, Jean-François Sauvage, Arnaud Sevin, Christian Soenke, Eric Stadler, Marcos Suarez, Massimo Turatto, L. Weber 
TL;DR: In this paper, a point source was detected within the gap of the transition disk at about 195 mas (about 22 au) projected separation, and the detection was confirmed at five different epochs, in three filter bands and using different instruments.
Abstract: Young circumstellar disks are of prime interest to understand the physical and chemical conditions under which planet formation takes place. Only very few detections of planet candidates within these disks exist, and most of them are currently suspected to be disk features. In this context, the transition disk around the young star PDS 70 is of particular interest, due to its large gap identified in previous observations, indicative of ongoing planet formation. We aim to search for the presence of planets and search for disk structures indicative for disk-planet interactions and other evolutionary processes. We analyse new and archival near-infrared (NIR) images of the transition disk PDS 70 obtained with the VLT/SPHERE, VLT/NaCo and Gemini/NICI instruments in polarimetric differential imaging (PDI) and angular differential imaging (ADI) modes. We detect a point source within the gap of the disk at about 195 mas (about 22 au) projected separation. The detection is confirmed at five different epochs, in three filter bands and using different instruments. The astrometry results in an object of bound nature, with high significance. The comparison of the measured magnitudes and colours to evolutionary tracks suggests that the detection is a companion of planetary mass. We confirm the detection of a large gap of about 54 au in size within the disk in our scattered light images, and detect a signal from an inner disk component. We find that its spatial extent is very likely smaller than about 17 au in radius. The images of the outer disk show evidence of a complex azimuthal brightness distribution which may in part be explained by Rayleigh scattering from very small grains. Future observations of this system at different wavelengths and continuing astrometry will allow us to test theoretical predictions regarding planet-disk interactions, planetary atmospheres and evolutionary models.

457 citations


Cited by
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Journal ArticleDOI
28 Aug 1998-Science
TL;DR: Bcl-2 and related cytoplasmic proteins are key regulators of apoptosis, the cell suicide program critical for development, tissue homeostasis, and protection against pathogens.
Abstract: Bcl-2 and related cytoplasmic proteins are key regulators of apoptosis, the cell suicide program critical for development, tissue homeostasis, and protection against pathogens. Those most similar to Bcl-2 promote cell survival by inhibiting adapters needed for activation of the proteases (caspases) that dismantle the cell. More distant relatives instead promote apoptosis, apparently through mechanisms that include displacing the adapters from the pro-survival proteins. Thus, for many but not all apoptotic signals, the balance between these competing activities determines cell fate. Bcl-2 family members are essential for maintenance of major organ systems, and mutations affecting them are implicated in cancer.

5,380 citations

Journal ArticleDOI
TL;DR: The evidence for this hypothesis, and the origins of the different kinetic phases of synaptic enhancement, as well as the interpretation of statistical changes in transmitter release and roles played by other factors such as alterations in presynaptic Ca(2+) influx or postsynaptic levels of [Ca(2+)]i are discussed.
Abstract: ▪ Abstract Synaptic transmission is a dynamic process. Postsynaptic responses wax and wane as presynaptic activity evolves. This prominent characteristic of chemical synaptic transmission is a crucial determinant of the response properties of synapses and, in turn, of the stimulus properties selected by neural networks and of the patterns of activity generated by those networks. This review focuses on synaptic changes that result from prior activity in the synapse under study, and is restricted to short-term effects that last for at most a few minutes. Forms of synaptic enhancement, such as facilitation, augmentation, and post-tetanic potentiation, are usually attributed to effects of a residual elevation in presynaptic [Ca2+]i, acting on one or more molecular targets that appear to be distinct from the secretory trigger responsible for fast exocytosis and phasic release of transmitter to single action potentials. We discuss the evidence for this hypothesis, and the origins of the different kinetic phases...

4,687 citations

Journal ArticleDOI
04 Apr 1997-Science
TL;DR: Details of how these signals control wound cell activities are beginning to emerge, and studies of healing in embryos have begun to show how the normal adult repair process might be readjusted to make it less like patching up and more like regeneration.
Abstract: The healing of an adult skin wound is a complex process requiring the collaborative efforts of many different tissues and cell lineages. The behavior of each of the contributing cell types during the phases of proliferation, migration, matrix synthesis, and contraction, as well as the growth factor and matrix signals present at a wound site, are now roughly understood. Details of how these signals control wound cell activities are beginning to emerge, and studies of healing in embryos have begun to show how the normal adult repair process might be readjusted to make it less like patching up and more like regeneration.

4,558 citations

Journal Article
TL;DR: The first direct detection of gravitational waves and the first observation of a binary black hole merger were reported in this paper, with a false alarm rate estimated to be less than 1 event per 203,000 years, equivalent to a significance greater than 5.1σ.
Abstract: On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0×10(-21). It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203,000 years, equivalent to a significance greater than 5.1σ. The source lies at a luminosity distance of 410(-180)(+160) Mpc corresponding to a redshift z=0.09(-0.04)(+0.03). In the source frame, the initial black hole masses are 36(-4)(+5)M⊙ and 29(-4)(+4)M⊙, and the final black hole mass is 62(-4)(+4)M⊙, with 3.0(-0.5)(+0.5)M⊙c(2) radiated in gravitational waves. All uncertainties define 90% credible intervals. These observations demonstrate the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger.

4,375 citations

Journal ArticleDOI
TL;DR: Neurotrophins regulate development, maintenance, and function of vertebrate nervous systems, and control synaptic function and synaptic plasticity, while continuing to modulate neuronal survival.
Abstract: Neurotrophins regulate development, maintenance, and function of vertebrate nervous systems. Neurotrophins activate two different classes of receptors, the Trk family of receptor tyrosine kinases and p75NTR, a member of the TNF receptor superfamily. Through these, neurotrophins activate many signaling pathways, including those mediated by ras and members of the cdc-42/ras/rho G protein families, and the MAP kinase, PI-3 kinase, and Jun kinase cascades. During development, limiting amounts of neurotrophins function as survival factors to ensure a match between the number of surviving neurons and the requirement for appropriate target innervation. They also regulate cell fate decisions, axon growth, dendrite pruning, the patterning of innervation and the expression of proteins crucial for normal neuronal function, such as neurotransmitters and ion channels. These proteins also regulate many aspects of neural function. In the mature nervous system, they control synaptic function and synaptic plasticity, while continuing to modulate neuronal survival.

3,968 citations