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Abstract:Baseline and apomorphine-induced extracellular levels of nigral substance P are increased in an animal model of Parkinson's disease. Orosz D, Bennett JP Jr. Department of Neurology, University of Virginia School of Medicine, Charlottesville 22908. Parkinson's disease arises from extensive premature loss of dopamine (DA)-utilizing midbrain neurons whose axons form the nigrostriatal pathway and densely innervate the striatum (caudate-putamen). The clinical symptoms of Parkinson's disease are improved by treatment with DA receptor agonists, including apomorphine. DA agonists modulate basal ganglia outflow at multiple sites and may affect synaptic activity of multiple basal ganglia neurotransmitters, including substance-P peptide (SP). With microdialysis in the substantia nigra reticulata (s.n.r.), a major striatal projection area, we monitored the extracellular level of SP-like immunoreactivity (SP-LI) in awake rats with neurotoxin-induced destruction of nigral DA neurons, before and after treatment with apomorphine (1 mg/kg i.p.). Loss of DA neurons produced a 60% increase in baseline extracellular SP-LI levels. Apomorphine treatment increased baseline extracellular SP-LI levels up to 60% in control rats and 100% in rats with loss of nigral DA neurons. Striatonigral SP endings increase SP release in response to loss of nigral target DA neurons, and DA agonist acting on supersensitive DA receptors, perhaps on SP terminals in the nigra, further increases synaptic SP concentrations. PMI D: 1699767 [PubMed - indexed for MEDLINE]
Abstract Moving ship tomography measures acoustic travel times between transmitters moored above the ocean floor and hydrophones on a cable tethered to a ship. The authors consider a Kalman filter that determines the location of a subarray of the hydrophones near the end of the cable. A long-baseline tracking system, consisting of floating buoys and the ship, acoustically measured the slant range to each hydrophone. The range to orbiting satellites was measured with the Global Positioning System (GPS). A short-baseline acoustic system measured...
The possibility of recovering earth rotation and network geometry (baseline) parameters are emphasized. The numerical simulated experiments performed are set up in an environment where station coordinates vary with respect to inertial space according to a simulated earth rotation model similar to the actual but unknown rotation of the earth. The basic technique of VLBI and its mathematical model are presented. The parametrization of earth rotation chosen is described and the resulting model is linearized. A simple analysis of the geometry of th...
The possibility of recovering earth rotation and network geometry (baseline) parameters are emphasized. The numerical simulated experiments performed are set up in an environment where station coordinates vary with respect to inertial space according to a simulated earth rotation model similar to the actual but unknown rotation of the earth. The basic technique of VLBI and its mathematical model are presented. The parametrization of earth rotation chosen is described and the resulting model is linearized. A simple analysis of the geometry of th...
NASA's Crustal Dynamics Project (CDP) has the objective to improve the understanding of geodynamics by measuring crustal deformation, tectonic motion, and polar motion and earth rotation. Three different approaches are utilized for obtaining these measurements. One is based on satellite laser ranging (SLR), while another makes use of very long baseline interferometry (VLBI) which uses reception of radio signals from quasars. The third approach involves laser ranging to the moon. An important part of the CDP is to compare baselines periodically ...
The possibility of recovering earth rotation and network geometry (baseline) parameters are emphasized. The numerical simulated experiments performed are set up in an environment where station coordinates vary with respect to inertial space according to a simulated earth rotation model similar to the actual but unknown rotation of the earth. The basic technique of VLBI and its mathematical model are presented. The parametrization of earth rotation chosen is described and the resulting model is linearized. A simple analysis of the geometry of th...
An investigation is conducted in order to expose errors in the formula for the elevation angle dependence of the hydrostatic atmospheric propagation delay, called the mapping function. A series of special VLBI experiments that involve a large fraction of group delay data from very low elevation angles are performed. Twenty-two experiments, each 26 hours in duration, were performed using VLBI antennas at Goldstone, California and at Westford, Massachusetts. Elevation angle cutoff tests were used to examine the contribution of these errors to the...
An investigation is conducted in order to expose errors in the formula for the elevation angle dependence of the hydrostatic atmospheric propagation delay, called the mapping function. A series of special VLBI experiments that involve a large fraction of group delay data from very low elevation angles are performed. Twenty-two experiments, each 26 hours in duration, were performed using VLBI antennas at Goldstone, California and at Westford, Massachusetts. Elevation angle cutoff tests were used to examine the contribution of these errors to the...
The possibility of recovering earth rotation and network geometry (baseline) parameters are emphasized. The numerical simulated experiments performed are set up in an environment where station coordinates vary with respect to inertial space according to a simulated earth rotation model similar to the actual but unknown rotation of the earth. The basic technique of VLBI and its mathematical model are presented. The parametrization of earth rotation chosen is described and the resulting model is linearized. A simple analysis of the geometry of th...
NASA's Crustal Dynamics Project (CDP) has the objective to improve the understanding of geodynamics by measuring crustal deformation, tectonic motion, and polar motion and earth rotation. Three different approaches are utilized for obtaining these measurements. One is based on satellite laser ranging (SLR), while another makes use of very long baseline interferometry (VLBI) which uses reception of radio signals from quasars. The third approach involves laser ranging to the moon. An important part of the CDP is to compare baselines periodically ...
Abstract This paper describes the evaluation of a GPS-based remote system for the calibration of precision clocks. Experiments were conducted using multi-channel GPS receivers. Results of zero baseline-common clock and short baseline-common clock common view measurements show that these receivers are suitable for remote calibrations after the correction of delays associated with the measurements
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