Document Detail


Photochemical oxygen consumption, oxygen evolution and spectral changes during UVA irradiation of EMT6 spheroids.
MedLine Citation:
PMID:  11421079     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Remarkable rates of oxygen consumption are observed via microelectrode measurements immediately upon the onset of 325 nm irradiation of multicell tumor spheroids. Consumption is irradiance dependent over the range 20-200 mW cm-2, and its magnitude is comparable to that observed previously in the same system using exogenous photosensitizers. Oscillations in the oxygen concentrations suggest that oxygen is also being evolved during irradiation. Oxygen evolution is likely the result of enzymatic dissociation of hydrogen peroxide, which is formed through UV-induced photochemistry. Irradiation of spheroids at 442 and at 514 nm produces a much more modest but detectable oxygen consumption. The dynamics of oxygen concentration changes are quite different at these wavelengths, suggesting a different photochemical mechanism. In these cases, initial oxygen depletion is followed immediately by a more gradual, monotonic increase in the oxygen concentration, consistent with irreversible photobleaching. No oscillations in the oxygen concentration are detectable. At 662 nm, no oxygen consumption was observed over the range of irradiances studied. Fluorescence spectra of cells prior to irradiation include contributions from anthranilic acid and reduced nicotinamide adenine dinucleotide (NADH). During 325 nm irradiation, anthranilic acid is rapidly and irreversibly bleached, while NADH emission undergoes only modest reduction.
Authors:
S Mitra; J C Finlay; D McNeill; D L Conover; T H Foster
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Photochemistry and photobiology     Volume:  73     ISSN:  0031-8655     ISO Abbreviation:  Photochem. Photobiol.     Publication Date:  2001 Jun 
Date Detail:
Created Date:  2001-06-25     Completed Date:  2001-07-26     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0376425     Medline TA:  Photochem Photobiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  703-8     Citation Subset:  IM    
Affiliation:
Departments of Biochemistry and Biophysics, University of Rochester, Rochester, NY, USA.
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MeSH Terms
Descriptor/Qualifier:
Animals
Mice
Oxygen / metabolism
Oxygen Consumption / radiation effects*
Photochemistry
Spectrometry, Fluorescence
Spheroids, Cellular / metabolism*,  radiation effects*
Tumor Cells, Cultured
Ultraviolet Rays*
Grant Support
ID/Acronym/Agency:
CA68409/CA/NCI NIH HHS
Chemical
Reg. No./Substance:
7782-44-7/Oxygen

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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