ABSTRACT
In Escherichia coli, fur mutants that constitutively express their native iron chelating agent, enterobactin, are significantly more sensitive to near-UV radiation (NUV) than wild type, An entA mutant, which is incapable of synthesizing enterobactin, is equal to wild type in resistance to NUV irradiation. However, the addition of Fe+3 enterobactin but not AI+3 enterobactin to entA cell suspensions just prior to irradiation results in an increased sensitivity to NUV irradiation. A fes mutant, which is unable to reduce and release iron from enterobactin, is significantly more sensitive to NUV irradiation than wild type. The addition of nontoxic levels of H2O2 (5 microM) just prior to irradiation significantly increases sensitivity of both fur and fes mutants. These results suggest that one mechanism by which NUV irradiation leads to cell lethality is by creating a transient iron overload, producing very favorable conditions for the production of highly deleterious free radicals through a variety of mechanisms that lead to oxidative stress and DNA damage including lethal and mutagenic lesions. These results are consistent with the hypothesis that enterobactin is an endogenous chromophore for NUV and contributes to cell lethality via the destruction of its ligand, releasing Fe+2 into the cytoplasm to catalyze the production of highly reactive hydroxyl radicals and other toxic oxygen species via the Haber-Weiss reaction.
Subject(s)
Enterobactin/metabolism , Escherichia coli/metabolism , Escherichia coli/radiation effects , Iron/metabolism , Escherichia coli/genetics , Mutation , Radiation Tolerance , Reactive Oxygen Species/metabolism , Siderophores/metabolism , Ultraviolet RaysSubject(s)
Strabismus/complications , Accommodation, Ocular , Adolescent , Adult , Age Factors , Aged , Child , Diplopia/etiology , Female , Humans , Male , Middle Aged , Strabismus/physiopathology , Strabismus/surgery , Visual AcuitySubject(s)
Echothiophate Iodide/therapeutic use , Esotropia/drug therapy , Eyeglasses , Miotics/therapeutic use , Strabismus/drug therapy , Child , Child, Preschool , Female , Humans , Infant , MaleABSTRACT
This paper involves the research of 30 patients, all of whom exhibited a head tilt, turn, or a combination of the two. We report the sensory aspects of 8 of these individuals and demonstrate the fusional ability of each patient. In the majority of the cases, the results were positive. It was found that most abnormal head positions were developed to maintain fusion.
