Regulatory control of indoor Rn

Regulation of indoor Rn is explored in the context of cost-effectiveness of regulatory action. Evaluation of cost (i.e., mitigation expenses) and benefits (i.e., savings associated with medical expenses and lost productivity related to lung cancer) at various action levels indicate that regulatory programs would be economically inefficient and unreasonable if standards were established at or below the current EPA action guide (150 Bq m-3 or less). For the approximately 95% of U.S. homes with Rn levels near or below 150 Bq m-3, government programs should continue to focus on public information and consumer protection. For the small number of homes with high Rn levels, government programs should focus on identifying high risk homes and encouraging homeowners to reduce Rn levels. Because of the potential for substantial risk reduction, such efforts would be cost-effective in these homes.     

A radiological evaluation of phosphogypsum.

Phosphogypsum is the by-product resulting from phosphoric acid or phosphate fertilizer production. The phosphate are used in these chemical processes contains the naturally occurring radioactive material U and all its subsequent decay products. During processing, the U generally remains in the phosphoric acid product, while the daughter, 226Ra, tends to be concentrated in the phosphogypsum. Phosphogypsum has physical properties that make it useful as a sub-base for roadways, parking lots, and similar construction. A radiological evaluation, to determine exposures to workers mixing this material with a stabilizing agent (portland cement), was performed at a South Louisiana phosphoric acid chemical plant. Measurements of the 226Ra content of the phosphogypsum showed an average of 1.1 +/- 0.3 Bq g-1 (0.7-1.7 Bq g-1). The average measured gross gamma exposure rate on the phosphogypsum pile corresponded to a dose equivalent rate of 0.368 +/- 0.006 mu Sv h-1 (0.32-0.42 mu Sv h-1). Radon daughter concentrations measured on top of the phosphogypsum pile ranged from 0.0006 to 0.001 working levels. An analysis of the airborne 226Ra concentrations showed only background levels.     

A review of lacrimal drainage surgery

The advent of improved silicone intubation sets, increased understanding of lacrimal and nasal anatomy and physiology, and refinements in surgical instrumentation and technique have led to higher success rates in lacrimal surgery. Recent clinical studies, combined with new techniques in canalicular reconstruction, have helped identify which patients will benefit from surgical intervention and which techniques are indicated. Fortunately, this has greatly reduced the number of CDCRs necessary.     

Dioxin treatment of rats results in increased in vitro induction of sister chromatid exchanges by alpha-naphthoflavone: an animal model for human exposure to halogenated aromatics

Recent reports have shown that alpha-naphthoflavone (alpha-NF) in vivo enhances the sister chromatid exchange (SCE) frequency in lymphocytes from human populations exposed to cigarette smoke or polychlorinated biphenyls and dibenzofurans. In this study, female Sprague-Dawley rats (9-11 weeks old) were administered a single oral dose of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and killed 6 days after treatment. Blood cultures were established with or without alpha-NF. The baseline and alpha-NF-induced SCE frequencies were assessed in lymphocytes after a 72-hr culture period. No effect on the SCE baseline frequency (cultures without alpha-NF) was detected in rats exposed to 0-30 micrograms TCDD/kg. However, the SCE frequencies from cultures incubated in the presence of alpha-NF were significantly higher in lymphocytes from rats treated with TCDD. Moreover, delta SCE values (SCE alpha-NF minus SCE baseline) were significantly higher in lymphocytes from rats treated with TCDD than in controls. A dose-dependent increase in delta SCE values was observed between 0 and 3 micrograms TCDD/kg, followed by a plateau at higher doses. This induction pattern closely resembled the induction of the liver microsomal aryl hydrocarbon hydroxylase activity by TCDD. In contrast to TCDD, phenobarbital treatment of rats (75 mg/kg/day) had no effect on alpha-NF-induced SCE frequencies in lymphocytes. Liver microsomes from TCDD-treated rats metabolized alpha-NF at a rate much faster than that of control microsomes. These studies indicate that TCDD-exposed rats provide a useful model to investigate the mechanism of enhanced in vitro induction of SCE frequency in lymphocytes from humans exposed to toxic halogenated aromatics or cigarette smoke.     

Steroid conversion and prostaglandin production by chorionic and decidual cells in relation to term and preterm labour

The production of progesterone from pregnenolone, of cortisol from cortisone and of prostaglandin E (PGE) under basal and arachidonic acid-stimulated conditions was measured in cells dispersed from chorion and decidua. The cells were obtained after delivery from four groups of women: following spontaneous labour at term (38-42 weeks gestation), at elective caesarean section at term before the onset of labour, after induced labour at term, and after uncomplicated preterm (27-36 weeks) labour. Chorionic cells had a high progesterone output with relatively low cortisol and PGE production, whereas decidual cells had a high cortisol and PGE production rate. Free arachidonic acid stimulated PGE production in both decidual and chorionic cells. There were no significant differences in either steroid or PGE production among the four groups studied. These data suggest that steroid dehydrogenase activity in choriodecidual cells is not related to the mode of onset of labour and that the increased prostaglandin production in intrauterine tissues associated with parturition is due to enhanced availability of arachidonic acid.     

Reactive oxygen species: a breath of life or death?

New insights into cancer cell-specific biological pathways are urgently needed to promote development of rationally targeted therapeutics. Reactive oxygen species (ROS) and their role in cancer cell response to growth factor signaling and hypoxia are emerging as verdant areas of exploration on the road to discovering cancer's Achilles heel. One of the distinguishing and near-universal hallmarks of cancer growth is hypoxia. Unregulated cellular proliferation leads to formation of cellular masses that extend beyond the resting vasculature, resulting in oxygen and nutrient deprivation. The resulting hypoxia triggers a number of critical adaptations that enable cancer cell survival, including apoptosis suppression, altered glucose metabolism, and an angiogenic phenotype. Ironically, recent investigations suggest that oxygen depletion stimulates mitochondria to elaborate increased ROS, with subsequent activation of signaling pathways, such as hypoxia inducible factor 1alpha, that promote cancer cell survival and tumor growth. Because mitochondria are key organelles involved in chemotherapy-induced apoptosis induction, the relationship between mitochondria, ROS signaling, and activation of survival pathways under hypoxic conditions has been the subject of increased study. Insights into mechanisms involved in ROS signaling may offer novel avenues to facilitate discovery of cancer-specific therapies. Preclinical and clinical evaluation of agents that modify ROS signaling in cancer offers a novel avenue for intervention. This review will cover recent work in ROS-mediated signaling in cancer cells and its potential as a target for developmental therapeutics.     

Blood serum protein sorption on the surface of perfluorocarbon emulsion particles

The amount of protein bound per 1 mL of the perfluorocarbon (PFC) emulsion depends on the emulsifier composition and the particle size. A relationship between the amount of bound protein on the particle surface and the physicochemical parameters of the PFC emulsion interaction with the blood serum, which indirectly characterize the surface properties of the PFC particles, is established. __________ Translated from Khimiko-Farmatsevticheskii Zhurnal, Vol. 41, No. 12, pp. 40–43, December, 2007.     

West Nile virus quantification in feces of experimentally infected American and fish crows.

To better understand the potential environmental health risk presented by West Nile virus (WNV)-contaminated feces, we quantified the amount of WNV present in the feces of experimentally infected American crows (Corvus brachyrhynchos) and fish crows (Corvus ossifragus). Peak fecal titers ranged from 10(3.5) to 10(8.8) plaque-forming units (PFU)/g for 10 American crows and from 10(2.3) to 10(6.4) PFU/g for 10 fish crows. The presence of infectious WNV in bird feces indicates a potential for direct transmission of WNV. Thus, handlers of sick or dead birds should take appropriate precautions to avoid exposure to fecal material.