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  • 1
    Publication Date: 1994-09-23
    Description: The proposal that nitric oxide (NO) or its reactant products mediate toxicity in brain remains controversial in part because of the use of nonselective agents that block NO formation in neuronal, glial, and vascular compartments. In mutant mice deficient in neuronal NO synthase (NOS) activity, infarct volumes decreased significantly 24 and 72 hours after middle cerebral artery occlusion, and the neurological deficits were less than those in normal mice. This result could not be accounted for by differences in blood flow or vascular anatomy. However, infarct size in the mutant became larger after endothelial NOS inhibition by nitro-L-arginine administration. Hence, neuronal NO production appears to exacerbate acute ischemic injury, whereas vascular NO protects after middle cerebral artery occlusion. The data emphasize the importance of developing selective inhibitors of the neuronal isoform.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Huang, Z -- Huang, P L -- Panahian, N -- Dalkara, T -- Fishman, M C -- Moskowitz, M A -- NS10828/NS/NINDS NIH HHS/ -- NS2636/NS/NINDS NIH HHS/ -- New York, N.Y. -- Science. 1994 Sep 23;265(5180):1883-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Stroke Research Laboratory, Massachusetts General Hospital, Charlestown 02129.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7522345" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Oxidoreductases/antagonists & inhibitors/deficiency/*metabolism ; Animals ; Arginine/analogs & derivatives/pharmacology ; Brain/enzymology/*metabolism ; Brain Ischemia/complications/*metabolism ; Cerebral Infarction/*etiology ; Cerebrovascular Circulation ; Female ; Male ; Mice ; Mice, Inbred C57BL ; Mice, Knockout ; Mutation ; Neurons/*enzymology ; Nitric Oxide/*metabolism ; Nitric Oxide Synthase ; Nitroarginine
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 1994-07-22
    Description: Long-term potentiation (LTP) is a persistent increase in synaptic strength implicated in certain forms of learning and memory. In the CA1 region of the hippocampus, LTP is thought to involve the release of one or more retrograde messengers from the postsynaptic cell that act on the presynaptic terminal to enhance transmitter release. One candidate retrograde messenger is the membrane-permeant gas nitric oxide (NO), which in the brain is released after activation of the neuronal-specific NO synthase isoform (nNOS). To assess the importance of NO in hippocampal synaptic plasticity, LTP was examined in mice where the gene encoding nNOS was disrupted by gene targeting. In nNOS- mice, LTP induced by weak intensity tetanic stimulation was normal except for a slight reduction in comparison to that in wild-type mice and was blocked by NOS inhibitors, just as it was in wild-type mice. Immunocytochemical studies indicate that in the nNOS- mice as in wild-type mice, the endothelial form of NOS (eNOS) is expressed in CA1 neurons. These findings suggest that eNOS, rather than nNOS, generates NO within the postsynaptic cell during LTP.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉O'Dell, T J -- Huang, P L -- Dawson, T M -- Dinerman, J L -- Snyder, S H -- Kandel, E R -- Fishman, M C -- DA-00074/DA/NIDA NIH HHS/ -- DA-00266/DA/NIDA NIH HHS/ -- MH-45923/MH/NIMH NIH HHS/ -- etc. -- New York, N.Y. -- Science. 1994 Jul 22;265(5171):542-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Howard Hughes Medical Institute, College of Physicians and Surgeons of Columbia University, New York, NY 10032.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7518615" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Oxidoreductases/antagonists & inhibitors/genetics/*metabolism ; Animals ; Arginine/*analogs & derivatives/pharmacology ; Electric Stimulation ; Endothelium/enzymology ; Hippocampus/drug effects/enzymology/*physiology ; In Vitro Techniques ; *Long-Term Potentiation/drug effects ; Mice ; Mutation ; Nitric Oxide/*metabolism ; Nitric Oxide Synthase ; Nitroarginine ; Pyramidal Cells/drug effects/enzymology/*physiology ; Synaptic Transmission/drug effects
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 3
    Publication Date: 2019-01-25
    Description: Continuum 16 channel spectra obtained from in flight data are used to identify and correct for nonlinearities in the channel-to-energy conversion algorithm for the BATSE large area detectors. The Crab Nebula spectra obtained by the BATSE earth occultation technique are used to characterize any nonlinearities inherent in the low energy channel bin widths on a detector by detector basis. The bin widths are optimized to remove distortions from observed gamma ray spectra. The recalibrated bin edges are used in an analysis of Crab Pulsar data to verify the improvements in the calibration.
    Keywords: SPACE RADIATION
    Type: Alabama Univ., BATSE Data Analysis; 1 p
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  • 4
    Publication Date: 2019-01-25
    Description: SN1987A hard x ray continuum spectra obtained on 29 Oct. 1987, 9-10 Apr. 1988, and 11 Nov. 1988, from balloon flight measurements are presented. The spectra, spanning the energy range from 25 keV to 300 keV, were analyzed using a detector response matrix inversion technique that converts the spectra from counts/sec-sq cm-kev to photons/sec-sq cm-kev allowing direct comparison with theoretical models. The results indicate that the bulk of the Co-56 is mixed moderately through the inner regions of the SN envelope but they do not preclude the mixing of a small amount of the Co-56 further out into the envelope necessary to account for the observed Co-56 line fluxes. The effect of the ratio of Co-57 to Co-56 on the 11 Nov. 1988, continuum spectrum is discussed.
    Keywords: SPACE RADIATION
    Type: Alabama Univ., BATSE Data Analysis; 1 p
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  • 5
    Publication Date: 2019-01-25
    Description: Evidence is presented for the existence of two spectral states contributing simultaneously to the total spectrum observed in many gamma-ray bursts (GRB's). An ensemble of 120 GRB's measured by BATSE were studied, using 4 channel spectral data, to determine in which bursts the spectral states can be most effectively resolved. The technique of summing the low intensity spectra together to get an average spectrum allows for precise characterization of the average low intensity spectral behavior. The 4 and 16 channel spectra obtained by the BATSE Large Area Detectors (LAD's) are analyzed using a model-independent spectral inversion technique. The results of these analyses applied to an individual burst are discussed in detail.
    Keywords: SPACE RADIATION
    Type: Alabama Univ., BATSE Data Analysis; 1 p
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  • 6
    Publication Date: 2019-01-25
    Description: The continuum spectra of bursts are studied with particular emphasis placed on the search for spectral subcomponents. The spectra observed in individual bursts show significant evolution throughout their durations. The degree to which hard and soft spectra are combined in bursts and the effect this has on the complexity of the observed spectra are addressed. In particular the presence of broad cusps in spectra in the 50-100 keV range are studied to determine both the degree to which these features are present in the LAD data and whether superposition of hard and soft spectra simultaneously can account for them. Also the time histories of the power output (ergs/sec) from bursts are studied to investigate the dynamic coupling between hard and soft spectra in bursts as a probe of the autonomy of the hard and soft emission mechanisms.
    Keywords: SPACE RADIATION
    Type: Alabama Univ., BATSE Data Analysis; 1 p
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  • 7
    Publication Date: 2019-01-25
    Description: Distributions of the continuum spectral characteristics of 260 bursts in the first Burst and Transient Source Experiment (BATSE) catalog are presented. The data are derived from flux ratios calculated from the BATSE Large Area Detector (LAD) four channel discriminator data. The data are converted from counts to photons using a direct spectral inversion technique to remove the effects of atmospheric scattering and the energy dependence of the detector angular response. Although there are intriguing clusterings of bursts in the spectral hardness ratio distributions, no evidence for the presence of distinct burst classes based on spectral hardness ratios alone is found. All subsets of bursts selected for their spectral characteristics in this analysis exhibit spatial distributions consistent with isotropy. The spectral diversity of the burst population appears to be caused largely by the highly variable nature of the burst production mechanisms themselves.
    Keywords: SPACE RADIATION
    Type: Alabama Univ., BATSE Data Analysis; 1 p
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  • 8
    Publication Date: 2019-06-28
    Description: The demonstration of repeated gamma-ray bursts from an individual source would severely constrain burst source models. Recent reports of evidence for repetition in the first BATSE burst catalog have generated renewed interest in this issue. Here, we analyze the angular distribution of 585 bursts of the second BATSE catalog (Meegan et al. 1994). We search for evidence of burst recurrence using the nearest and farthest neighbor statistic ad the two-point angular correlation function. We find the data to be consistent with the hypothesis that burst sources do not repeat; however, a repeater fraction of up to about 20% of the bursts cannot be excluded.
    Keywords: SPACE RADIATION
    Type: NASA-TM-110835 , NAS 1.15:110835
    Format: application/pdf
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  • 9
    Publication Date: 2019-06-28
    Description: Observations have been made of a new terrestrial phenomenon: brief (approx. millisecond), intense flashes of gamma rays, observed with space-borne detectors. These flashes must originate at altitudes in the atmosphere above at least 30 km in order to be observable by orbiting detectors aboard the Compton Gamma-Ray Observatory (CGRO). At least a dozen events have been detected over the past 2 years. The photon spectra from the events are very hard and are consistent with bremsstrahlung emission from energetic (MeV) electrons. The most likely origin of these high energy electrons, while speculative at this time, is a rare type of high altitude electrical discharge above thunderstorm regions.
    Keywords: SPACE RADIATION
    Type: NASA-TM-110853 , NAS 1.15:110853
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  • 10
    Publication Date: 2019-07-13
    Description: We introduce the method of 'network synthesis,' which allows the detection of very weak gamma-ray transient signals in the data of the Ulysses gamma-ray burst (GRB) experiment from repeating sources. It consists of defining a grid of alpha, delta values, and for each BATSE detection of a burst from a soft gamma repeater, predicting the arrival time of the burst at Ulysses and co-adding the Ulysses data rephased so that the burst signals are aligned in time and produce a detectable pulse. We demonstrate that this method identifies the position of the soft repeater SGR 1806-20, and apply it to the repeater B1900+14. We show that the counterpart to this burst source is probably in or in the vicinity of the Galactic supernova remnant G42.8+0.6.
    Keywords: SPACE RADIATION
    Type: The Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 431; 1; p. L31-L34
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