Inability of GSTT1 to activate iodinated halomethanes to mutagens in Salmonella.

Drinking water disinfection by-products (DBPs), including the ubiquitous trihalomethanes (THMs), are formed during the treatment of water with disinfectants (e.g., chlorine, chloramines) to produce and distribute potable water. Brominated THMs (Br-THMs) are activated to mutagens via glutathione S-transferase theta 1 (GSTT1); however, iodinated THMs (I-THMs) have never been evaluated for activation by GSTT1. Among the I-THMs, only triiodomethane (iodoform) has been tested previously for mutagenicity in Salmonella and was positive (in the absence of GSTT1) in three strains (TA98, TA100, and BA13), all of which have error-prone DNA repair (pKM101). We evaluated five I-THMs (chlorodiiodomethane, dichloroiodomethane, dibromoiodomethane, bromochloroiodomethane, and triiodomethane) for mutagenicity in Salmonella strain RSJ100, which expresses GSTT1, and its homologue TPT100, which does not; neither strain has pKM101. We also evaluated chlorodiiodo-, dichloroiodo-, and dibromoiodo-methanes in strain TA100 +/- rat liver S9 mix; TA100 has pKM101. None was mutagenic in any of the strains. The I-THMs were generally more cytotoxic than their brominated and chlorinated analogues but less cytotoxic than analogous trihalonitromethanes tested previously. All five I-THMs showed similar thresholds for cytotoxicity at ~2.5 µmoles/plate, possibly due to release of iodine, a well-known antimicrobial. Although none of these I-THMs was activated by GSTT1, iodoform appears to be the only I-THM that is mutagenic in Salmonella, only in strains deficient in nucleotide excision repair (uvrB) and having pKM101. Given that only iodoform is mutagenic among the I-THMs and is generally present at low concentrations in drinking water, the I-THMs likely play little role in the mutagenicity of drinking water.

Ultraviolet light triggers the conversion of Cu2+-bound Aß42 aggregates into cytotoxic species in a copper chelation-independent manner.

Increasing evidence indicates that abnormal Cu2+ binding to Aß peptides are responsible for the formation of soluble Aß oligomers and ROS that play essential roles in AD pathogenesis. During studying the Cu2+-chelating treatment of Cu2+-bound Aß42 aggregates, we found that UV light exposure pronouncedly enhances cytotoxicity of the chelator-treated and -untreated Cu2+-bound Aß42 aggregates. This stimulated us to thoroughly investigate (1) either the chelation treatment or UV light exposure leads to the increased cytotoxicity of the aggregates, and (2) why the chelator-treated and -untreated Cu2+-bound Aß42 aggregates exhibit the increased cytotoxicity following UV light exposure if the latter is the case. The data indicated that the controlled UV exposure induced the dissociation of Cu2+-free and -bound Aß42 aggregates into SDS-stable soluble oligomers and the production of ROS including H2O2 in an UV light intensity- and time-dependent, but Cu2+ chelation-independent manner. Although we can't fully understand the meaning of this finding at the current stage, the fact that the UV illuminated Aß42 aggregates can efficiently kill HeLa cells implies that the aggregates after UV light exposure could be used to decrease the viability of skin cancer cells through skin administration.

Progranulin enhances neural progenitor cell proliferation through glycogen synthase kinase 3ß phosphorylation.

Progranulin (PGRN) is an estrogen-inducible growth factor thought to affect multiple processes in the CNS, including brain sexual differentiation, adult neurogenesis in the hippocampus, and development of neurodegenerative diseases. However, the precise physiological functions of PGRN in individual nerve cells are not fully understood. The aim of the present study was to enhance the understanding of PGRN function in the CNS by investigating the effects of PGRN on neural progenitor cells (NPCs). We found that significant amounts of endogenous PGRN were secreted from isolated NPCs in cultures. To assess the bioactivities of endogenous and exogenous PGRN, we studied NPCs derived from wild-type mice (WT-NPCs) and PGRN-deficient mice (KO-NPCs). We found that proliferation of KO-NPCs was significantly enhanced by PGRN treatment; however, PGRN treatment apparently did not affect proliferation of WT-NPCs perhaps because of the high levels of endogenous PGRN expression. NPC death and asymmetric cellular division of KO-NPCs and WT-NPCs, which results in production of neural stem cells, astrocytes, or oligodendrocytes, were not affected by PGRN treatment. We also investigated the signaling mechanism(s) that mediate PGRN-induced NPC proliferation and found that phosphorylation of serine 9 (S9) of glycogen synthase kinase 3-beta (GSK3ß), which was dependent on phosphatidylinositol 3-kinase (PI3K) activity, was induced by PGRN treatment. In addition, a GSK3ß-specific inhibitor enhanced NPC proliferation. Taken together, our observations indicate that PGRN enhanced NPC proliferation, at least in part, via inducing GSK3ß phosphorylation.

Friedreich's Ataxia: from the (GAA)n repeat mediated silencing to new promising molecules for therapy.

Friedreich's ataxia (FRDA) is a neurodegenerative disease due to a pathological expansion of a GAA triplet repeat in the first intron of the FXN gene encoding for the mitochondrial protein frataxin. The expansion is responsible for most cases of FRDA through the formation of a nonusual B-DNA structure and heterochromatin conformation that determine a direct transcriptional silencing and the subsequent reduction in frataxin expression. Among other functions, frataxin is an iron chaperone central for the assembly of iron-sulfur clusters in mitochondria; its reduction is associated with iron accumulation in mitochondria, increased cellular sensitivity to oxidative stress and cell damage. There is, nowadays, no effective therapy for FRDA and current therapeutic strategies mainly act to slow down the consequences of frataxin deficiency. Therefore, drugs that are able to increase the amount of frataxin are excellent candidates for a rational approach to FRDA therapy. Recently, several drugs have been assessed for their ability to increase the amount of cellular frataxin, including human recombinant erythropoietin, histone deacetylase inhibitors, and the PPAR-gamma agonists.

Freon: accidental ingestion and gastric perforation.

INTRODUCTION: Freons generally have a low order of toxicity, but exposure to relatively high concentrations (>100 ppm) may produce adverse effects on health. Currently, intoxication reports are unintentional inhalation of CFCs. We report an unintentional ingestion of a mixture of CFCs and the results of a rat study. CASE REPORT: A 43-year-old man was admitted to the Emergency Department with a chief complaint of acute abdominal pain that developed minutes after he ingested a clear liquid in a water glass, which contained a mixture of Freon and water. Subsequent surgical evaluation revealed perforation of the stomach and necrosis of the stomach wall. He developed a transient rise in his hepatic transaminases, which resolved spontaneously, and fully recovered from his surgery. METHODS: A murine model of the injury was created to evaluate threshold concentration and effect of time on injury grade. RESULTS: Injury grade increased with delay to histologic analysis from 8 to 24 hours after exposure to Freon. Increasing amounts of Freon also increased the lesion grade score. CONCLUSIONS: Patients ingesting Freon need to be closely evaluated for risk of gastric damage and perforation.

A possible mechanism of halocarbon-induced cardiac sensitization arrhythmias.

Cardiac sensitization is the term used for malignant ventricular arrhythmias associated with exposure to inhaled halocarbons in the presence of catecholamines. We investigated the electrophysiological changes associated with cardiomyocyte exposure to epinephrine and a halocarbon known to be associated with cardiac sensitization (halon 1301, CF3Br). Cardiomyocytes (CMs) were isolated from neonatal rats and grown on multielectrode arrays (MEAs). Upon exposure to epinephrine, the CM inter-spike interval (ISI) was decreased 14% at 10 microg/L (P<0.05) and 27% at 100 microg/L (P<0.05) as compared to baseline. Halon alone (50 mg/L) mildly prolonged the field potential (FP) duration (7%). CMs exposed to combinations of epinephrine (100 microg/L) and halon (50 mg/L) for 15 min showed a blunted increase in the ISI (35+/-12%) and a 38% decrease in conduction velocity (P<0.05) when compared to epinephrine alone. There was no change in field potential properties, but dephosphorylated connexin 43 (Cx43) was increased 60+/-16% with the combination as compared to epinephrine alone (P<0.05). Treatment with okadaic acid, a phosphatase inhibitor, prevented the Cx43 dephosphorylation and the reduction in conduction velocity upon exposure to halon and epinephrine. Moreover, the electrophysiological changes induced by epinephrine and halon were indistinguishable from those seen with the gap junction inhibitor heptanol. In conclusion, the combination of a halocarbon and epinephrine results in a unique electrophysiological signature including slow conduction that may explain, in part, the basis for cardiac sensitization. The slowing of conduction is most likely related to changes in the phosphorylation state of Cx43.

Trifluoromethyl group as a pharmacophore: effect of replacing a CF3 group on binding and agonist activity of a glucocorticoid receptor ligand.

Compound 1, a potent glucocorticoid receptor ligand, contains a quaternary carbon bearing trifluoromethyl and hydroxyl groups. This paper describes the effect of replacing the trifluoromethyl group on binding and agonist activity of the GR ligand 1. The results illustrate that replacing the CF3 group with a cyclohexylmethyl or benzyl group maintains the GR binding potency. These substitutions alter the functional behavior of the GR ligands from agonists to antagonists. Docking studies suggest that the benzyl analog 19 binds in a similar fashion as the GR antagonist, RU486. The central benzyl group of 19 and the C-11 dimethylaniline moiety of RU486 overlay. Binding of compound 19 is believed to force helix 12 to adopt an open conformation and this leads to the antagonist properties of the non-CF3 ligands carrying a large group at the center of the molecule.

Study of sterilizing effectivity of different ethylene oxide gaseous mixtures using CFCs and HCFCs (Oxyfume 12R and 2002R).

The use of ethylene oxide as a sterilizing agent has been frequently practiced, especially taking into account the huge variety of medical devices produced with heat sensitive materials. Mixtures of ethylene oxide and inert gases have been widely adopted in order to decrease the undesirable flammable and explosive properties of ethylene oxide. This article provides a study regarding the sterilizing effectiveness of two ethylene oxide blends: Oxyfume 2002R (using HCFCs 22 and 124) and Oxyfume 12R (using CFC 12), at different temperatures (45, 55, and 65 degrees C). To accomplish this procedure, sub-lethal challenges were performed (0, 3, 6, 9, 12, and 15 minutes) using biological indicators (obtained in the laboratory) made of Bacillus subtilis var. niger ATCC 9372. The sterilizing efficacy of both mixtures was equivalent at the gas concentration of 600 mg/L. The influence of higher temperatures was thus proved.

Effects of halone 1301 on Lepidium sativum, Petunia hybrida and Phaseolus vulgaris.

Halone 1301 belongs to a group of widely used fire repellants. Although banned in several countries, the production has still not been discontinued, and thus hazards due to use or spill can be expected. The study reports on effects of the halone 1301 on three plant species frequently used for bioindication studies: Lepidium sativum (mouse-ear cress), Phaseolus vulgaris (bush bean) and Petunia hybrida. Plants were exposed to 1 ppbv of the gas in ambient air under controlled conditions for 18 days (L. sativum), and 45 days (P. vulgaris, P. hybrida), respectively. None of the plants showed visible stress symptoms. Chlorophylls in cress and petunia were unaffected whereas in beans significant changes of the photosynthetic pigments were observed. Photosynthesis and gas exchange of bean plants were monitored during the experiment, and a lowering of transpiration was noticed. In all investigated plants, protein contents declined significantly, but despite this reduction, activity of the glutathione S-transferases (GST) increased strongly in bean and petunia. The significance of this reaction as detoxification step is discussed.

Neuropsychological dose effects of a freon, trifluoromethane (FC-23), compared to N2O.

Animal studies show FC-23 to be a promising magnetic resonance imaging indicator of regional cerebral blood flow. In a Phase 1, dose ranging (investigative new drug) study, neuropsychological (NP) tests, subjective ratings, and intensive physiological monitoring were used to determine the maximum tolerated concentration of FC-23 for human application. Five normal healthy male volunteers were exposed to concentrations of FC-23 between 10% and 60% [randomly interleaved with exposures to both room air and 40% nitrous oxide (N2O)] in a within-subjects, double-blind design. Analyses of individual cases and ranked group data showed that individuals tolerated the 30% concentration of FC-23 according to established criteria. Planned comparisons indicated that inhalation of FC-23 produced smaller NP changes and fewer negative symptoms than 40% N2O but poorer NP performance and more negative symptoms than room air. This study indicated that FC-23 is not inert and that humans do not tolerate concentrations suitable for current MRI technology. NP and subjective data assisted in characterizing the sedative effect of FC-23.

Bacterial killing ability of 10% ethylene oxide plus 90% hydrochlorofluorocarbon sterilizing gas.

OBJECTIVES: To use a serum and salt challenge in narrow-lumen carriers to evaluate a 10% ethylene oxide plus 90% hydrochlorofluorocarbon (EO-HCFC) sterilant mixture in a retrofitted 12/88 sterilizer as an alternative to the banned chlorofluorocarbon-ethylene oxide (EO) sterilant mixture. DESIGN: An EO-HCFC sterilizing gas mixture in a retrofitted 12/88 sterilizer was compared to 100% ethylene oxide (100% EO) sterilizing gas to determine its relative ability to kill seven different bacteria (Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis, Bacillus subtilis spores, Bacillus stearothermophilus spores, Bacillus circulans spores, and Mycobacterium chelonei) in the presence or absence of a combined 10% serum and 0.65% salt challenge using both penicylinders (PC) and long narrow-lumen (LU) carriers. RESULTS: The EO-HCFC sterilant mixture (96% sterile carriers) was equivalent to the 100% EO sterilant (98% sterile carriers) for killing vegetative organisms, as well as spore suspensions, on the 27 PC and 27 LU carriers in the absence of serum and salt. In the presence of serum and salt, the EO-HCFC sterilant mixture was markedly better than the 100% EO sterilant at reducing the bacterial load on the 63 PC carriers (95% vs 62% sterile PC carriers, respectively), whereas both sterilizers were equivalent for the 63 LU carriers (49% vs 40% sterile LU carriers, respectively). Of the seven test organisms, E faecalis, B subtilis, B stearothermophilus, and B circulans were the most difficult to kill for both PC and LU carriers when serum and salt were present. CONCLUSIONS: The data presented in this report indicate that the EO-HCFC sterilant mixture is an effective alternative for gas sterilization. Indeed, the efficiency of bacterial killing for the EO-HCFC sterilant mixture was similar to that achieved by the 12/88 EO-CFC sterilant mixture.

Convulsant activity of nonanesthetic gas combinations.

Most nonanesthetics (inhaled compounds that neither cause anesthesia when given alone nor decrease the partial pressure of a known inhaled anesthetic required to produce anesthesia) and transitional compounds (inhaled compounds that are less potent than would be predicted by the Meyer-Overton hypothesis) cause convulsions. A possible exception is the perfluoroalkane series of nonanesthetics. The present study tested whether perfluoroalkanes do provide an exception. Further, we tested whether the convulsant effects of nonanesthetic and transitional compounds were additive. The nonanesthetic perfluoropropane caused convulsions at 7.5 +/- 0.7 atm (mean +/- SD). Convulsions also were produced by perfluorocyclobutane (0.976 +/- 0.002 atm), 1,2-dichlorotetrafluoroethane (0.358 +/- 0.011 atm), 2,3-dichlorooctafluorobutane (0.085 +/- 0.007 atm), 1,2-dichlorohexafluorocyclobutane (0.055 +/- 0.007 atm), and flurothyl (0.00156 +/- 0.00039 atm). Of these, 1,2-dichlorotetrafluoroethane is a transitional compound, the remainder being nonanesthetics. The combination of flurothyl plus 1,2-dichlorohexafluorocyclobutane gave evidence of antagonism (a 17% +/- 21% deviation from additivity; P < 0.05), whereas the combination of 1,2-dichlorotetrafluoroethane plus 2,3-dichlorooctafluorobutane gave evidence of synergy (a -13% +/- 8% deviation from additivity; P < 0.05). The combinations of perfluoropropane plus perfluorocyclobutane (-4% +/- 15%), and perfluoropropane plus 1,2-dichlorohexafluorocyclobutane (-1% +/- 26%) did not produce results that deviated significantly from additivity. We conclude that pairs of these compounds either produce convulsions in an additive manner, a finding consistent with (but not proving) a common mode of action; or deviate modestly from additivity, a finding suggesting that at least a portion of the mechanistic basis for convulsions might differ, particularly for flurothyl plus other nonanesthetics, or for the combination of non-anesthetics and transitional compounds.

Propellant-driven aerosols for delivery of proteins in the respiratory tract.

Metered-dose propellant-driven aerosols of an antigenically reactive protein were produced by combining bovine gammaglobulin (BGG) with one of several surfactants soluble in Freon or dimethylether propellants. Small-particle protein aerosols were most effectively produced by lyophilizing surfactants and proteins prior to the addition of propellants. Up to 26% of the total aerosolized protein was of respirable size. Aerosol metering valves delivering small volumes were most effective in producing respirable-sized (< or = 4 micron median mass aerodynamic diameter) protein aerosols. Proteins were suspended in liquified propellants as both propellant-soluble molecules and visible sedimenting clusters which both contributed to making respirable-sized protein aerosol particles. Electron microscopy showed that respirable-sized protein particles were composed of variable-sized chain aggregates of spherical subunits. Proteins were antigenic after suspension in liquified propellant and release as aerosols, but antigenicity diminished with extended propellant exposure. Local immunity in the respiratory tract is a key factor in resistance to respiratory infections. Metered-dose propellant-driven aerosols offer a potentially attractive method for delivering small-particle aerosols of immunizing antigens or other therapeutic proteins to the respiratory tract.

[Cryoanesthesia by freon spray for venepuncture in children]. / Cryoanesthésie par pulvérisation de fréon pour ponction veineuse chez l'enfant.

This prospective study was designed to assess the quality of skin analgesia provided by cryoanesthesia induced by a spray of freon (dichloro-tetrafluoro-ethane) for venous cannulation (22 or 24 Gauge cannulas). Eighty children between the ages of 5 and 15 years were allocated to two groups: 40 children had a conventional venepuncture, 40 others had a venepuncture under cryoanesthesia. The spray of freon was applied for ten seconds on the area of skin to be anaesthetised. The venous cannulation was carried out by an anaesthetist of the paediatric surgical unit. The intensity of pain at venepuncture was quantified with a visual analogic scale (range 0 to 100). The median values of the pain scores were 11.5 (0 to 50) in the cryoanesthesia group and 48 (11 to 75) in the control group respectively. It is concluded that freon spray provides a convenient analgesia for venepuncture in children aged 5-15 years.

Trifluoromethanesulfonamide anthelmintics. Protonophoric uncouplers of oxidative phosphorylation.

A series of trifluoromethanesulfonamides (TFMS) was synthesized and tested for uncoupling activity in rat liver mitochondria. With succinate as the mitochondrial substrate, and the respiratory control index (RCI) as an indicator of their uncoupling ability, we found that all of the TFMS tested were uncouplers of oxidative phosphorylation; the effective concentration (RCI I50) ranged from less than 1 microM to greater than 1000 microM. Correlation techniques were used to assess the strength of the relationship between the ability of a TFMS to uncouple oxidative phosphorylation and its ability to lower the electrical resistance of planar bimolecular lipid membranes. There was a highly significant (P < 0.001) positive linear relationship (r = 0.97) between the ability of a TFMS to uncouple oxidative phosphorylation and its ability to lower electrical resistance. These findings are consistent with the view that the TFMS are lipophilic protonophoric uncouplers of mitochondrial oxidative phosphorylation. Quantitative structure-activity relationship studies using experiment and semiempirical molecular orbital theory revealed that the hydrophobicity of a TFMS and its molecular dipole moment were the principal determinants of mitochondrial uncoupling activity within the pKa range examined.

Dehalogenation of trichlorofluoromethane (CFC-11) by Methanosarcina barkeri.

Methanobacterium barkeri was found to catalyze the reductive dehalogenation of trichlorofluoromethane (CFC-11), also known as FREON 11. Products detected were CHFCl2, CH2FCl, CO and fluoride.

Inhaled respiratory medications and the use of chlorofluorocarbons (CFCs). Thoracic Society of Australia and New Zealand.

OBJECTIVE: To assess the use of chlorofluorocarbons (CFCs) in metered-dose aerosols against the background of community concerns regarding the adverse environmental effects of CFCs. DATA SOURCES: Data on the constituents of currently available metered-dose aerosols were supplied by the manufacturers, and details of chemistry and safety were obtained from monographs and papers published in the medical literature. STUDY SELECTION: Five papers, published in the early 1970s when metered-dose aerosols first became popular, were reviewed for safety data on CFCs. Several chapters in monographs were searched for data on the nature and function of CFCs in metered-dose aerosols, and five papers were the source of information on alternatives to CFCs as vehicles for the delivery of inhaled respiratory drugs. DATA SYNTHESIS: The medical use of CFCs accounts for only 1.5% of the total production in Australia, the majority being used for refrigeration, air-conditioning and other commercial or industrial purposes. The physicochemical properties of CFCs are such that they function as a suitable storage medium for active drugs within the canister and as an ideal vehicle for drug delivery. Approximately 20 s after inhalation of a clinically recommended dose of a bronchodilator metered-dose aerosol, CFCs are detectable in the blood, but the concentrations decline rapidly (half-life less than 40 s). Although CFCs have been shown to sensitise the myocardium to the arrhythmogenic effects of catecholamines in experimental animals, the requisite concentrations can only be achieved by patients if they inhale from a canister on every breath for approximately 20 successive breaths. CONCLUSIONS: CFCs used in metered-dose aerosols are an effective storage medium and a convenient vehicle for drug delivery. They are non-toxic--unless amounts far in excess of the clinically recommended doses are used, when arrhythmogenic effects may occur. The medical use of CFCs has minimal environmental impact compared with their industrial and commercial use. Dry powder delivery systems offer an alternative approach, and future research will yield nonozone-depleting CFCs suitable for replacing those in current metered-dose aerosols.