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In the Drosophila eye, activation of the sevenless (sev) receptor tyrosine kinase is required for the specification of the R7 photoreceptor cell fate. In a genetic screen for mutations that result in the activation of the sev signaling pathway in the absence of the inducing signal, we identified a gain-of-function mutation in rolled (rlSevenmaker [rlSem]),(More)
The fate of the R7 photoreceptor cell in the developing eye of Drosophila is controlled by the Sevenless (Sev) receptor tyrosine kinase. Sev activates a highly conserved signal transduction cascade involving the proteins Ras1 and Raf and the Rolled/mitogen-activated protein (Rl/MAP) kinase. Here we show that the ETS domain protein encoded by the P2(More)
Mitogen-activated protein (MAP) kinases have been proposed to play a critical role in receptor tyrosine kinase (RTK)-mediated signal transduction pathways. Although genetic and biochemical studies of RTK pathways in Caenorhabditis elegans, Drosophila melanogaster and mammals have revealed remarkable similarities, a genetic requirement for MAP kinases in RTK(More)
Nuclear magnetic resonance (NMR) is one of the most versatile experimental methods in chemistry, physics and biology, providing insight into the structure and dynamics of matter at the molecular scale. Its imaging variant-magnetic resonance imaging (MRI)-is widely used to examine the anatomy, physiology and metabolism of the human body. NMR signal detection(More)
PURPOSE Zero echo time (ZTE) imaging is a robust and silent 3D radial technique suitable for direct MRI of tissues with very rapid transverse relaxation. Given its successful application on micro- and animal MRI systems, the purpose of this work is to enable and demonstrate ZTE imaging in humans using a whole-body magnet. METHODS A commercial 7 T MRI(More)
PURPOSE Applications of dynamic shimming require high field fidelity, and characterizing the shim field dynamics is therefore necessary. Modeling the system as linear and time-invariant, the purpose of this work was to measure the impulse response function with optimal sensitivity. THEORY AND METHODS Frequency-swept pulses as inputs are analyzed(More)
PURPOSE Sinusoidal gradient oscillations in the kilohertz range are proposed for position tracking of NMR probes and prospective motion correction for arbitrary imaging sequences without any alteration of sequence timing. The method is combined with concurrent field monitoring to robustly perform image reconstruction in the presence of potential dynamic(More)
Multiple-channel RF transmission holds great promise for MRI, especially for human applications at high fields. For calibration it requires mapping the effective RF magnetic fields, B(1) (+), of the transmitter array. This is challenging to do accurately and fast due to the large dynamic range of B(1) (+) and tight SAR constraints. In the present work, this(More)
In this study, a new approach to measure local electrical conductivity in tissue is presented, which is based on the propagating B1(+) phase and the homogeneous Helmholtz equation. This new MRI technique might open future opportunities for tumor and lesion characterization based on conductivity differences, while it may also find application in radio(More)
The specification of the R7 photoreceptor cell fate in the developing eye of Drosophila depends on the local activation of the sevenless (sev) receptor tyrosine kinase (RTK) by boss, a protein expressed on the membrane of the neighboring R8 cell. Constitutive activation of the sev receptor results in a dosage dependent increase in the number of R7 cells per(More)