PubMed · 7946735
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K A Aase. 1994-02-15. [Inside climate causes problems].. https://pubmed.ncbi.nlm.nih.gov/7946735/
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BACKGROUND: Epidemiological data indicate that in females cigarette smoking exerts antiestrogenic effects that manifest clinically in an increased incidence of osteoporosis, earlier menopause, increased spot bleeding, and decreased risk of endometrial cancer for female smokers. The molecular mechanism of this effect is unclear; however, decreased serum estrogen levels in female smokers have been correlated with increased concentrations of the metabolite 2-hydroxyestrogen in females who smoke. Induction of estrogen metabolizing enzymes, CYP1A1 and 1A2, is one mechanism by which increased 2-hydroxyestrogen concentrations may occur. It has also been suggested that the estrogen receptor (ER) may contribute to this anti-estrogenic effect by binding to antagonist(s) in cigarette smoke. METHODS: Gel retardation analysis was employed to determine if diluted mainstream cigarette smoke condensates (DMCSCs) could activate the aryl hydrocarbon receptor (AhR). AhR-regulated ethoxyresorufin-O-deethylase (EROD) activity and dioxin response element (DRE)-mediated luciferase induction were assessed in Hepa1c1c7 mouse hepatoma cells. A competitive ligand binding assay was utilized to determine if DMCSCs could bind to the ER. ER-dependent luciferase activity was assessed in MCF-7 cells. RESULTS: In gel retardation assays, DMCSCs induced a protein-DNA complex when incubated with a radiolabeled wild-type DRE oligonucleotide. The complex was effectively competed by excess unlabeled DRE but not by excess unlabeled mutant DRE. In Hepa1c1c7 mouse hepatoma cells transiently transfected with a DRE-regulated luciferase reporter gene, pGudluc1.1, treatment with DMCSCs resulted in a 23- and 25-fold increase in luciferase activity (P<0.01) and an 8.5- and 10.5-fold (P<0.01) induction in EROD activity, respectively. DMCSCs completely displaced bound tritiated E2 from the ER in a dose-dependent manner and induced ER-regulated luciferase activity significantly 6-fold (P<0.01), representing 86% of the maximal induction observed with E2. CONCLUSIONS: DMCSCs can bind to and transcriptionally activate the AhR and ER nuclear receptors and cause induction of DRE- and ER-regulated genes. Further study is required to identify the specific compound(s) responsible for these activities.
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Data for computation of primary and secondary shielding barriers in radiotherapy facilities are presented in the National Council on Radiation Protection and Measurements Report 49, which covers primary barriers for accelerating voltages up to 10 MV and secondary barriers up to 6 MV. Inconsistencies in reported scattered fraction values found in the literature for megavoltage accelerators are due, in part, to differences in measurement techniques. A consistent approach was used to measure the scattered fractions of 6, 10, 18, and 25 MV photon dose. A reference ion chamber was placed on the symmetry axis of a cylindrical water phantom, approximating the human torso, 25.6 cm diameter, at the gantry isocenter. Measurements were made with a second ion chamber at 2m from the isocenter at angles ranging from 10 degrees through 150 degrees from the beam central axis with a field size of 20 cm x 20 cm at the isocenter. The dose measured at each angle is reported as a fraction of the reference chamber dose at the center of the phantom and as calculated to a reference chamber depth of d(max), also at the isocenter. The results of these measurements were compared with Monte Carlo calculations and show reasonable agreement. A comparison with previously published data was not as good due to the differences in measurement techniques. However, after some adjustments to correct for the differences, the comparison is very good. Scattered fractions beyond 30 degrees are highest for the lowest energy beam investigated. This indicates that the scattered fraction values reported in NCRP 49 for 6 MV are sufficient for use in conservative shielding calculations for the higher energy x rays beyond 30 degrees. For angles smaller than 30 degrees, the new data are more appropriate and show the scatter fractions are larger for higher MV x rays.