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  • 1
    Digitale Medien
    Digitale Medien
    First spectroscopic evidence for a muonium-containing molecule: NeMu* chemiluminescence (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 1202-1218 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Evidence for the formation of NeMu*, an isotopic analog of the Rydberg molecule NeH*, has been obtained from the observation of chemiluminescent emission in the near-infrared region. This is the first spectroscopic detection of a muonium-containing molecule. NeMu* was formed by stopping a 4 MeV muon (μ+) beam in a target vessel containing 1–6 atm of Ne and ∼1 Torr Ar. The wavelength spectrum of the emission, from ∼680–1000 nm, was measured using a variable-wavelength filter, with a resolution of ±12.5 nm. Lower resolution spectra were also taken with a series of long pass filters. A complete histogram of photon events vs time was collected for each wavelength. Two strong transitions are observed, centered at 818 and 943 nm. Identification of NeMu* was made by a comparison of the experimental spectrum with a simulated spectrum based on detailed ab initio calculations, extended to higher excitation levels than had heretofore been reported. Both experimental and theoretical results are reported here. Although the mechanism by which the emitting states in NeMu* are formed remains unclear, radiolysis effects appear to play a dominant role, indicating that NeMu+ (the product of muon thermalization in Ne) undergoes charge exchange with metastable Ar* and/or is neutralized by a spur electron, both species produced during the slowing down of the high energy muon.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.467813
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  • 2
    Digitale Medien
    Digitale Medien
    NeMu* chemiluminescence: Radiolysis effects in gases (1994)
    Springer
    Hyperfine interactions 87 (1994), S. 985-990 
    Details
    ISSN: 1572-9540
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Near-infrared chemiluminescent emission from NeMu*, the analogue of the Rydberg molecule NeH, has been observed in Ne, Ar, and Ne/Ar gas mixtures. Three temporally distinct features were observed: First, a large sharp emission peak at time zero, observed in all gases (Ne, He, N2, Ar), is assigned to scintillation light during muon thermalization, probably caused by spur electrons. Second, a lowintensity broad region observed in all gases is attributed to e+ from muon decay. Finally, NeMu in 1–6 atm Ne with 0.1–2 torr Ar appeared as a high intensitydelayed emission, whose width and intensity depended linearly on the Ar concentration. Its wavelength spectrum from 680–960 nm was measured. Although questions remain as to how NeMu* is formed, the precursor is likely Neμ +. Possible electron donors include metastable Ar* (3 P 2 or3 P 0) and long-lived free (spur) electrons.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02068494
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  • 3
    Buch
    Buch
    Scholarly journals at the crossroads : a subversive proposal for electronic publishing; an Internet discussion about scientific and scholarly journals and their future (1995)
    Washington, :Ass. of Research Libraries,
    Details
    Titel: Scholarly journals at the crossroads : a subversive proposal for electronic publishing; an Internet discussion about scientific and scholarly journals and their future
    Beteiligte Person(en): Okerson, Ann S. , O'Donnell, James J.
    Verlag: Washington, :Ass. of Research Libraries,
    Erscheinungsjahr: 1995
    Seiten: 242 S.
    Materialart: Buch
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  • 4
    Digitale Medien
    Digitale Medien
    Hypertension in pregnancy (1994)
    Oxford, UK : Blackwell Publishing Ltd
    BJOG 101 (1994), S. 0 
    Details
    ISSN: 1471-0528
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1471-0528.1994.tb13662.x
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  • 5
    Digitale Medien
    Digitale Medien
    Birth underwater: sink or swim (1994)
    Oxford, UK : Blackwell Publishing Ltd
    BJOG 101 (1994), S. 0 
    Details
    ISSN: 1471-0528
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1471-0528.1994.tb13140.x
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  • 6
    Digitale Medien
    Digitale Medien
    Comparative Incorporation of Proenkephalin-Derived Peptides, Chromogranin A, and Dopamine β-Hydroxylase into Chromaffin Vesicles (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 57 (1991), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: The incorporation of enkephalin-containing peptides (ECPs) derived from proenkephalin into chromaffin vesicles was examined in primary cultures of adrenal medullary chromaffin cells. Cells were pulse-labeled with [35S]methionine and chased for periods up to 24 h. Chromaffin vesicles in cell homogenates were then fractionated by density gradient centrifugation and the presence of [35S]Met-enkephalin sequences in gradient fractions determined. 35S-ECPs were incorporated into particles suggestive of immature vesicles within 1–2 h after radiolabeling. Vesicle maturation, measured by co-equilibration of 35S-ECPs and total ECPs in the gradients, was complete within 9–12 h and was unaffected by treatments that increase proenkephalin synthesis. Incorporation of [35S]chromogranin A into chromaffin vesicles followed a similar time course, but 35S-labeled dopamine β-hydroxylase was much more slowly incorporated, possibly reflecting differences in incorporation of membrane and soluble components. In summary, the data demonstrate that ECPs are rapidly sequestered in immature chromaffin vesicles, a process unaltered by changing rates of proenkephalin synthesis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1471-4159.1991.tb08231.x
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  • 7
    Digitale Medien
    Digitale Medien
    Glutamate Neurotoxicity and the Inhibition of Protein Synthesis in the Hippocampal Slice (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 56 (1991), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract: In some animal models of ischemia, neuronal degeneration can be prevented by the selective antagonism of the N-methyl-D-aspartate (NMDA) glutamate receptor sub-type, suggesting that glutamate released during ischemia causes injury by activating NMDA receptors. The rat hippocampal slice preparation was used as an in vitro model to study the pharmacology of glutamate toxicity and investigate why NMDA receptors are critical in ischemic injury. Acute toxicity was assessed by quantifying the inhibition of protein synthesis, which we confirmed by autoradiography to be primarily neuronal. The effect of NMDA was prevented by the specific antagonists MK-801 and ketamine, as well as by the less selective antagonist kynurenic acid. The less selective antagonists kynurenic acid and 6,7-dinitroquinoxaline-2,3-dione antagonized the effects of quisqualate and NMDA. In contrast to previous observations with dissociated neurons in tissue culture, the toxicity of glutamate was unaffected by antagonists, regardless of the glutamate concentration, the duration of exposure, or the presence of magnesium. The high concentration of glutamate required to inhibit protein synthesis and the inability of receptor antagonists to block the effect of glutamate suggest that either glutamate acts through a non-receptor-mediated mechanism, or that the receptor-mediated nature of glutamate effects are masked in the slice preparation, perhaps by the glial uptake of glutamate. The altered physiology induced by ischemia must potentiate the neurotoxicity of glutamate, because we observed with a brain slice preparation that only high concentrations of glutamate caused neurotoxicity in the presence of oxygen and glucose and that these effects were not reversed by glutamate receptor antagonists.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1471-4159.1991.tb02020.x
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  • 8
    Digitale Medien
    Digitale Medien
    Purification and Amino Terminal Sequencing of Human Melanoma Nerve Growth Factor Receptor (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 48 (1987), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract: The nerve growth factor (NGF) receptor, solubilized with Triton X-100 detergent, has been purified from human melanoma cell line A875. Purification to near-homogeneity was achieved by chromatography on wheat germ agglutinin-agarose, followed by immunoaffinity chromatography on Sepharose columns coupled with anti-NGF receptor monoclonal antibody (MAb). The purified receptor, a 75, 000-dalton protein, retains the capacity to bind NGF as well as anti-receptor MAbs. Final purification was achieved by sodium dodecyl sulfate-polyacryiamide gel electrophoresis. The sequence of amino acid residues at the amino terminus has been determined. Possible sequence homology between the NGF receptor and several other proteins is discussed. Using the purified receptor as immunogen, new MAbs to the NGF receptor have been produced. The NGF receptor was visualized by immunoperoxidase staining in tissue sections of dorsal root ganglia from monkeys.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1471-4159.1987.tb13151.x
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  • 9
    Digitale Medien
    Digitale Medien
    Metabolic Pools of ATP in Cultured Bovine Adrenal Medullary Chromaffin Cells (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 47 (1986), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract: Cultured bovine adrenal chromaffin cells contain a pool of ATP sequestered within the chromaffin vesicles and an extravesicular pool of ATP. In a previous study it was shown that the turnover of ATP in the extravesicular pool was biphasic. One phase occurred with a t1/2 of 3.5–4.5 h whereas the second phase occurred with a t1/2 of several days. The studies described here were undertaken to characterize further the vesicular and extravesicular pools of ATP by examining the effects of metabolic inhibitors, adenosine, and digitonin on ATP utilization and subcellular localization immediately after and 48 h after labeling with [3H]adenosine and 32Pi. Immediately after labeling a combination of cyanide, 2-deoxy-D-glucose, the β-glucono-l,5-lactone resulted in a 90–95% depletion of the labeled ATP but only a 25% depletion of the endogenous ATP within 30 min. Forty-eight hours after labeling, addition of the inhibitors resulted in a 70% depletion of the [3H]ATP but only a 25% depletion of the [32P]ATP and endogenous ATP. Addition of 10 μM adenosine to the media resulted in a similar loss of [3HJATP in cells examined immediately after or 48 h after labeling. Adenosine increased the amounts of [32P]ATP when added immediately after labeling but had no effect on the [32P]ATP content when added 48 h after labeling. Permeabilization of the plasma membrane by treatment with digitonin resulted in a loss of 90–95% of the labeled ATP but only 20% of the endogenous ATP in cells examined immediately after labeling and in a 79% loss of [3H]ATP, a 32% loss of [32P]ATP, and a 23% loss of endogenous ATP in cells examined 48 h after labeling. These studies show that ATP contained within chromaffin vesicles is metabolically inert and does not exchange readily with cytosolic ATP, but they do not differentiate extravesicular pools of labeled ATP. Calculation of ATP disappearance after abrupt cessation of ATP production indicates that cultured adrenal chromaffin cells utilize ATP at a rate of 0.24 nmol/min/106 cells, corresponding to a turnover time of 12.5 min for the extravesicular pool.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1471-4159.1986.tb00702.x
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  • 10
    Digitale Medien
    Digitale Medien
    Protective Effects of Extracellular Acidosis and Blockade of Sodium/Hydrogen Ion Exchange During Recovery from Metabolic Inhibition in Neuronal Tissue Culture (1996)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 67 (1996), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract: Acidosis is a universal response of tissue to ischemia. In the brain, severe acidosis has been linked to worsening of cerebral infarction. However, milder acidosis can have protective effects. As part of our investigations of the therapeutic window in our neuronal tissue culture model of ischemia, we investigated the effects of acidosis during recovery from brief simulated ischemia. Ischemic conditions were simulated in dissociated cortical cultures by metabolic inhibition with potassium cyanide to block oxidative metabolism and 2-deoxyglucose to block glycolysis. Lowering the extracellular pH (pHe) to 6.2 during metabolic inhibition had no effect on injury, as measured by lactate dehydrogenase release from cultures after 24 h of recovery. Lowering the pHe during the first hour of recovery, in contrast, had profound protective effects. When the duration of metabolic inhibition was lengthened to 30 min, most of the protective effects of the NMDA receptor antagonist MK-801 were lost. However, the protective effects of acidosis were unchanged. This suggested that the protective effects of extracellular acidosis could be due to more than blockade of NMDA receptors. Intracellular acidosis might be responsible. To test this, recovery of intracellular pH (pHi) was slowed by incubation with blockers of Na+/H+ exchangers at normal pHe. The two compounds tested, dimethylamiloride and harmaline, had protective effects when present during recovery from metabolic inhibition. Measurements of pHi confirmed that the blockers slowed recovery from intracellular acidosis; more rapid pHi recovery was correlated with injury. The protective effects of acidosis could be reversed by brief incubation with the protonophore monensin, which rapidly normalized pHi. These results are the first demonstration of the protective effects of blocking Na+/H+ exchange in a model of cerebral ischemia. The protective effects of acidosis appear to arise either from suppressing pH-sensitive mechanisms of injury or from blocking sodium entry due to Na+/H+ exchange.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1471-4159.1996.67062379.x
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