Potential for release of pulmonary toxic ketene from vaping pyrolysis of vitamin E acetate.

A combined analytical, theoretical, and experimental study has shown that the vaping of vitamin E acetate has the potential to produce exceptionally toxic ketene gas, which may be a contributing factor to the upsurge in pulmonary injuries associated with using e-cigarette/vaping products. Additionally, the pyrolysis of vitamin E acetate also produces carcinogen alkenes and benzene for which the negative long-term medical effects are well recognized. As temperatures reached in vaping devices can be equivalent to a laboratory pyrolysis apparatus, the potential for unexpected chemistries to take place on individual components within a vape mixture is high. Educational programs to inform of the danger are now required, as public perception has grown that vaping is not harmful.

Enhanced stable production of ethylene in photosynthetic cyanobacterium Synechococcus elongatus PCC 7942.

Ethylene is a volatile alkene which is used in large commercial scale as a precursor in plastic industry, and is currently derived from petroleum refinement. As an alternative production strategy, photoautotrophic cyanobacteria Synechocystis sp. PCC 6803 and Synechococcus elongatus PCC 7942 have been previously evaluated as potential biotechnological hosts for producing ethylene directly from CO2, by the over-expression of ethylene forming enzyme (efe) from Pseudomonas syringae. This work addresses various open questions related to the use of Synechococcus as the engineering target, and demonstrates long-term ethylene production at rates reaching 140 µL L-1 h-1 OD750-1 without loss of host vitality or capacity to produce ethylene. The results imply that the genetic instability observed earlier may be associated with the expression strategies, rather than efe over-expression, ethylene toxicity or the depletion of 2-oxoglutarate-derived cellular precursors in Synechococcus. In context with literature, this study underlines the critical differences in expression system design in the alternative hosts, and confirms Synechococcus as a suitable parallel host for further engineering.

Methods for enhancing cyanobacterial stress tolerance to enable improved production of biofuels and industrially relevant chemicals.

Cyanobacteria are photosynthetic prokaryotes that can fix atmospheric CO2 and can be engineered to produce industrially important compounds such as alcohols, free fatty acids, alkanes used in next-generation biofuels, and commodity chemicals such as ethylene or farnesene. They can be easily genetically manipulated, have minimal nutrient requirements, and are quite tolerant to abiotic stress making them an appealing alternative to other biofuel-producing microbes which require additional carbon sources and plants which compete with food crops for arable land. Many of the compounds produced in cyanobacteria are toxic as titers increase which can slow growth, reduce production, and decrease overall biomass. Additionally, many factors associated with outdoor culturing of cyanobacteria such as UV exposure and fluctuations in temperature can also limit the production potential of cyanobacteria. For cyanobacteria to be utilized successfully as biofactories, tolerance to these stressors must be increased and ameliorating stress responses must be enhanced. Genetic manipulation, directed evolution, and supplementation of culture media with antioxidants are all viable strategies for designing more robust cyanobacterial strains that have the potential to meet industrial production goals.

The effect of two bromfenvinphos impurities: BDCEE and ß-ketophosphonate on oxidative stress induction, acetylcholinesterase activity, and viability of human red blood cells.

Numerous research works have shown that synthesis of pesticides leads to the formation of impurities that may substantially enhance pesticide toxicity. In this study, the effect of manufacturing impurities of pesticide bromfenvinphos (BFVF) such as 1-bromo-2-(2,4-dichlorophenyl)-2-ethoxy ethene (BDCEE) and diethyl [2-(2,4-dichlorophenyl)-2-oxo-ethyl] phosphonate (ß-ketophosphonate) on human erythrocytes, being significantly exposed to xenobiotics has been studied. The cells were treated with the compounds studied in the concentrations ranging from 0.1 µM to 250 µM for 4 h. In order to assess the effect of BDCEE and ß-ketophosphonate on red blood cells hemolytic changes, changes in cell size (FSC parameter) and oxidation of hemoglobin were studied. Moreover, alterations in reactive oxygen species (ROS) formation, reduced glutathione (GSH) level and acetylcholinesterase (AChE) activity were determined. BDCEE induced an increase in ROS level and caused strong oxidation of hemoglobin as well as a slight change in erythrocytes size and hemolysis, while it did not change GSH level and AChE activity. ß-ketophosphonate has not been shown to affect most parameters studied, but it strongly reduced AChE activity. Because changes in the parameters examined were noted at low concentrations of BFVF impurities (5-250 µM), those substances should not negatively affect on red blood cells of humans environmentally exposed to this pesticide.

Compounded effects of chlorinated ethene inhibition on ecological interactions and population abundance in a Dehalococcoides - Dehalobacter coculture.

The development of rational and effective engineered bioremediation approaches for sites contaminated with chlorinated solvents requires a fundamental understanding of the factors limiting the in situ activity of dehalorespiring bacteria. Frequently, multiple dehalorespiring bacteria are present at contaminated sites, particularly when bioaugmentation is applied. The ecological interactions between different dehalorespiring populations can-along with hydrodynamic and other environmental factors-affect their activity and thus the rates and extent of dehalorespiration. An integrated experimental and modeling approach was used to evaluate the ecological interactions between two hydrogenotrophic, dehalorespiring strains. A dual Monod model of dehalorespiration provided a good fit to the chlorinated ethene concentrations measured in a coculture of Dehalococcoides mccartyi 195 and Dehalobacter restrictus growing on tetrachloroethene (PCE) and excess H(2) in a continuous-flow reactor. Inhibition of dehalorespiration by chlorinated ethenes was previously observed in cultures containing Dehalococcoides or Dehalobacter strains. Therefore, inhibition coefficients were estimated for Dhc. mccartyi 195 and Dhb. restrictus. The inhibition effects of PCE and TCE on VC dechlorination by Dhc. mccartyi 195, and of VC on PCE and TCE dechlorination by Dhb. restrictus, were compounded when these strains were grown in coculture, and dehalorespiring population abundance and survival could be accurately predicted only by incorporating these complex interactions into the dual Monod model.

Does 'Dry Hit' vaping of vitamin E acetate contribute to EVALI? Simulating toxic ketene formation during e-cigarette use.

Vitamin E acetate (VEA) is strongly linked to the outbreak of electronic-cigarette or vaping product use-associated lung injury (EVALI). It has been proposed that VEA decomposition to ketene-a respiratory poison that damages lungs at low ppm levels-may play a role in EVALI. However, there is no information available on the temperature at which VEA decomposes and how this correlates with the vaping process. We have studied the temperature-dependent kinetics of VEA decomposition using quantum chemical and statistical mechanical modelling techniques, developing a chemical kinetic model of the vaping process. This model predicts that, under typical vaping conditions, the use of VEA contaminated e-cigarette products is unlikely to produce ketene at harmful levels. However, at the high temperatures encountered at low e-cigarette product levels, which produce 'dry hits', ketene concentrations are predicted to reach acutely toxic levels in the lungs (as high as 30 ppm). We therefore hypothesize that dry hit vaping of e-cigarette products containing VEA contributes to EVALI.

Toxicity study of DE-EDCP as a potential drug for cancer therapy: Toxicity profile of DE-EDCP.

It was reported that novel O, O'-diethyl-(S, S)-ethylenediamine- N, N'-di-2-(3-cyclohexyl) propanoate dihydrochloride (DE-EDCP) displayed in vitro antiproliferative activity on several human and mouse cancer cell lines, which was comparable to that of the prototypical anticancer drug cisplatin. In order to reveal its toxicity profile, acute and repeated-dose toxicity studies were performed in Naval Medical Research Institute (NMRI) Han mice. The intravenous LD50 values of DE-EDCP were found to be 95.3 and 101.3 mg/kg body weight in female and male mice, respectively. In the subacute toxicity study, DE-EDCP was administered intravenously at the doses of 15, 25, and 40 mg/kg/day for a period of 28 days. There were no adverse effects on general condition, growth, feed and water consumption, and hematological parameters. There was a significant increase in urea and alanine aminotransferase in female mice and aspartate aminotransferase and alkaline phosphatase in both genders in 40 mg/kg/day dose-treated group. The histopathological changes confined to the liver and kidney, but in other organs were not found. Satellite group revealed that changes in the kidney and liver were less pronounced, suggesting their reversibility. Interactions with DNA could also be of importance for understanding DE-EDCP toxic side effects. Hyperchromic effect obtained with ultraviolet-visible, suggested electrostatic interactions between DE-EDCP and calf thymus DNA. The toxicity testing of DE-EDCP was conducted to predict human outcomes.

Relationship between GST Yp induction and hepatocyte proliferation in rats treated with phase II drug metabolizing enzyme inducers.

Butylated hydroxyanisole (BHA) and 1,2-bis(2-pyridyl)ethylene (2PY-e) are phase II drug metabolizing enzyme inducers which cause hepatomegaly without hepatocyte hypertrophy and induce glutathione S-transferase Yp (GST Yp, pi-class GST), which is known as a tumor marker. To evaluate the relationship between GST Yp induction and hepatocyte proliferation, male F344/DuCrj rats were treated with BHA, 2PY-e, or phenobarbital (PB) for three or seven days. All three chemicals caused increases in liver weight after three and seven days. Immunohistochemical examinations revealed that BHA and 2PY-e induced GST Yp in the hepatocytes of the periportal and centrilobular areas at three and seven days, respectively, whereas PB did not. Significant increases in the BrdU labeling indices were found in the livers of rats in each of the three-day treatment groups, but the labeling index of rat livers treated with BHA was decreased to the control level at seven days, although the high labeling indices of 2PY-e and PB persisted at seven days. Double immunostaining confirmed that BrdU-positive nuclei corresponded to GST Yp-positive hepatocytes in both BHA and 2PY-e treated rats. These results suggest that the GST Yp induction caused by BHA or 2PY-e has some kind of relationship with hepatocyte proliferation.

A physiologically based toxicokinetic model for inhaled ethylene and ethylene oxide in mouse, rat, and human.

Ethylene (ET) is the largest volume organic chemical. Mammals metabolize the olefin to ethylene oxide (EO), another important industrial chemical. The epoxide alkylates macromolecules and has mutagenic and carcinogenic properties. In order to estimate the EO burden in mice, rats, and humans resulting from inhalation exposure to gaseous ET or EO, a physiological toxicokinetic model was developed. It consists of the compartments lung, richly perfused tissues, kidneys, muscle, fat, arterial blood, venous blood, and liver containing the sub-compartment endoplasmic reticulum. Modeled ET metabolism is mediated by hepatic cytochrome P450 2E1, EO metabolism by hepatic microsomal epoxide hydrolase or cytosolic glutathione S-transferase in various tissues. EO is also spontaneously hydrolyzed or conjugated with glutathione. The model was validated on experimental data collected in mice, rats, and humans. Modeled were uptake by inhalation, wash-in-wash-out effect in the upper respiratory airways, distribution into tissues and organs, elimination via exhalation and metabolism, and formation of 2-hydroxyethyl adducts with hemoglobin and DNA. Simulated concentration-time courses of ET or EO in inhaled (gas uptake studies) or exhaled air, and of EO in blood during exposures to ET or EO agreed excellently with measured data. Predicted levels of adducts with DNA and hemoglobin, induced by ET or EO, agreed with reported levels. Exposures to 10000 ppm ET were predicted to induce the same adduct levels as EO exposures to 3.95 (mice), 5.67 (rats), or 0.313 ppm (humans). The model is concluded to be applicable for assessing health risks from inhalation exposure to ET or EO.

Results from a round robin test for the ecotoxicological evaluation of construction products using two leaching tests and an aquatic test battery.

A European round robin test according to ISO 5725-2 was conceptually prepared, realised, and evaluated. The aim was to determine the inter-laboratory variability of the overall process for the ecotoxicological characterization of construction products in eluates and bioassays. To this end, two construction products BAM-G1 (granulate) and HSR-2 (roof sealing sheet), both made of EPDM polymers (rubber), were selected. The granular construction product was eluted in a one stage batch test, the planar product in the Dynamic Surface Leaching test (DSLT). A total of 17 laboratories from 5 countries participated in the round robin test: Germany (12), Austria (2), Belgium (1), Czech Republic (1) and France (1). A test battery of four standardised ecotoxicity tests with algae, daphnia, luminescent bacteria and zebrafish eggs was used. As toxicity measures, EC50 and LID values were calculated. All tests, except the fish egg test, were basically able to demonstrate toxic effects and the level of toxicity. The reproducibility of test results depended on the test specimens and the test organisms. Generally, the variability of the EC50 or LID values increased with the overall level of toxicity. For the very toxic BAM-G1 eluate a relative high variability of CV = 73%-110% was observed for EC50 in all biotests, while for the less toxic HSR-2 eluate the reproducibility of EC50 varied with sensitivity: it was very good (CV = 9.3%) for the daphnia test with the lowest sensitivity, followed by the algae test (CV = 36.4%). The luminescent bacteria test, being the most sensitive bioassay for HSR-2 Eluate, showed the highest variability (CV = 74.8%). When considering the complex overall process the reproducibility of bioassays with eluates from construction products was acceptable.

Effects of ethylene oxide and ethylene inhalation on DNA adducts, apurinic/apyrimidinic sites and expression of base excision DNA repair genes in rat brain, spleen, and liver.

Ethylene oxide (EO) is an important industrial chemical that is classified as a known human carcinogen (IARC, Group 1). It is also a metabolite of ethylene (ET), a compound that is ubiquitous in the environment and is the most used petrochemical. ET has not produced evidence of cancer in laboratory animals and is "not classifiable as to its carcinogenicity to humans" (IARC, Group 3). The mechanism of carcinogenicity of EO is not well characterized, but is thought to involve the formation of DNA adducts. EO is mutagenic in a variety of in vitro and in vivo systems, whereas ET is not. Apurinic/apyrimidinic sites (AP) that result from chemical or glycosylase-mediated depurination of EO-induced DNA adducts could be an additional mechanism leading to mutations and chromosomal aberrations. This study tested the hypothesis that EO exposure results in the accumulation of AP sites and induces changes in expression of genes for base excision DNA repair (BER). Male Fisher 344 rats were exposed to EO (100 ppm) or ET (40 or 3000 ppm) by inhalation for 1, 3 or 20 days (6h/day, 5 days a week). Animals were sacrificed 2h after exposure for 1, 3 or 20 days as well as 6, 24 and 72 h after a single-day exposure. Experiments were performed with tissues from brain and spleen, target sites for EO-induced carcinogenesis, and liver, a non-target organ. Exposure to EO resulted in time-dependent increases in N7-(2-hydroxyethyl)guanine (7-HEG) in brain, spleen, and liver and N7-(2-hydroxyethyl)valine (7-HEVal) in globin. Ethylene exposure also induced 7-HEG and 7-HEVal, but the numbers of adducts were much lower. No increase in the number of aldehydic DNA lesions, an indicator of AP sites, was detected in any of the tissues between controls and EO-, or ET-exposed animals, regardless of the duration or strength of exposure. EO exposure led to a 3-7-fold decrease in expression of 3-methyladenine-DNA glycosylase (Mpg) in brain and spleen in rats exposed to EO for 1 day. Expression of 8-oxoguanine DNA glycosylase, Mpg, AP endonuclease (Ape), polymerase beta (Pol beta) and alkylguanine methyltransferase were increased by 20-100% in livers of rats exposed to EO for 20 days. The only effects of ET on BER gene expression were observed in brain, where Ape and Pol beta expression were increased by less than 20% after 20 days of exposure to 3000 ppm. These data suggest that DNA damage induced by exposure to EO is repaired without accumulation of AP sites and is associated with biologically insignificant changes in BER gene expression in target organs. We conclude that accumulation of AP sites is not a likely primary mechanism for mutagenicity and carcinogenicity of EO.

[Effect of metals, benzene, pesticides and ethylene oxide on the haematopoietic system]. / Wplyw narazenia na metale, benzen, pestycydy i tlenek etylenu na uklad krwiotwórczy.

The hematopoietic system, due to intensive cells proliferation, is very sensitive to toxic substances. Many chemicals, including benzene, pesticides (dithiocarbamines), ethylene oxide and metals (mercury, cadmium, chrome, cobalt, lead, aluminum) exert their toxic effect on the hematopoietic system. Exposure to each of these substances may occur in the work place due to environmental pollution and in municipal or residential areas. Exposure to lead, aluminum, cadmium, and benzene results in the incidence of anemia. In addition, exposure to benzene and its metabolites leads to myelodysplastic syndromes, leukemia, lymphomas and bone marrow aplasia. Ethylene oxide induces neoplasm of the hematopoietic system and lymphomas, especially non-Hodgkin lymphoma. Arsenic compounds act like immunosuppressants. Mercury and chrome affect the immune system by immunosuppression and by evoking autoimmune reactions. Dithiocarbamates are suspected to induce leukemia. An analysis of the pathophysiology of individual substances reveal universal toxic mechanisms. In this paper, the authors discuss the pathomechanism of toxic effects of the aforesaid chemicals on the haematopoietic system and peripheral blood cells from the viewpoint of mutagenesis, apoptosis, myelotoxicity, anemia, immunomodulation, and individual sensitivity.

Health- and vegetative-based effect screening values for ethylene.

Ethylene (ET) is ubiquitous in the environment and is produced both naturally and due to anthropogenic sources. Interestingly, the majority of ambient ET contribution is from natural sources and anthropogenic sources contribute only a minor portion. While microbes and plants naturally produce a large amount of ET, mammals are reported to produce only a small amount of ET endogenously. Anthropogenic sources of ET include the combustion of gas, fuel, coal and biomass. ET is also widely used as an intermediate to make other chemicals and products and is also used for controlled ripening of fruits and vegetables. Although, a review of human and laboratory animal studies indicate ET to be relatively non-toxic, there is concern about the potential toxicity of ET because ET is metabolically converted to ethylene oxide (EtO). EtO has been classified to be carcinogenic to human by the inhalation route by the International Agency for Research on Cancer (IARC) cancer. ET, however, has been classified as a Group 3 chemical which indicates it is not classified as a human carcinogen by IARC. Several studies have reported ET to cause adverse effects to plant species (vegetation effects) at concentrations that are not adverse to humans. Therefore, the Texas Commission of Environmental Quality (TCEQ) conducted detailed health and welfare (odor and vegetation) based assessments of ET to develop both health and vegetative based toxicity factors in 2008 in accordance with TCEQ guidelines. The health assessment based on well-conducted animal toxicity studies resulted in identification of higher points of departures and subsequently higher effect screening levels (ESLs) that were more than a magnitude higher than the threshold adverse effect level for vegetative effects for ET. Further, based on a weight-of-evidence evaluation of potential mutagenic and carcinogenic mode-of-actions for ET it appears the metabolic conversion of ET to EtO is of insufficient magnitude to cause concern of potential cancer risk. Therefore, the short-term ESL for air permit reviews and air monitoring evaluations is the vegetation-based ESL of 1200 ppb as it is more than a magnitude lower than the health-based acute ESL of 150,000 ppb. Similar to the acute derivation, the chronic evaluation resulted in the derivation of a chronic vegetation based ESL of 30 ppb that was much lower than the chronic ESL of 1600 ppb. In summary, the TCEQ's acute and chronic ESLs for vegetation will protect the general public from short-term and long-term adverse health and welfare effects. The general public includes children, the elderly, pregnant women, and people with pre-existing health conditions.

In vitro transformation of BALB/c-3T3 cells by chlorinated ethanes and ethylenes.

Eight chlorinated ethanes and 3 chlorinated ethylenes were tested in the BALB/c-3T3 cell transformation assay. Under the conditions of the assay, vinyl chloride and 1,1,1-trichloroethane induced a clear positive transformation response while 1,1,2-trichloroethane and trichloroethylene were weakly positive. Chloroethane, 1,1- and 1,2-dichloroethane, 1,1,1,2- and 1,1,2,2-tetrachloroethane, hexachloroethane and tetrachloroethylene were all negative in the assay conducted in the absence of an exogenous metabolic activation system. These results suggest that the BALB/c-3T3 cells possess capability to activate some, but not all, of the chlorinated hydrocarbons which exhibit species specificity in producing carcinogenicity in mice but not in rats.

Inhibition of the reverse transcriptase activity and replication of human immunodeficiency virus type 1 by AS 101 in vitro.

In a search for compounds active against human immunodeficiency virus type 1 (HIV-1), it was found that the novel low-molecular weight immunoenhancer ammonium trichloro(dioxyethylene-O,O'-) tellurate (AS101) suppresses production of HIV-1 in vitro. Treatment of HIV-1-infected peripheral blood mononuclear cells (PBMC) with increasing concentrations of AS101 resulted in substantial inhibition of virus production as measured by both reverse transcriptase (RT) activity and antigen presence in supernatants of treated cells. AS101 had no effect on PBMC viability, growth, or morphology up to a concentration of 15 microM for 14 days. To elucidate a possible mechanism for the inhibition of AS101, we have analyzed the effect of the drug on the catalytic functions associated with HIV RT, namely the RDDP, DDDP, and RNase H activities. RDDP and DDDP activities were impaired by the drug with calculated IC50 value of about 4 microM. On the other hand, the RNase H activity was less sensitive to AS101, with an apparent IC50 value of about 30 microM. The anti-HIV-1 activity of AS101 as reflected by inhibition of the different catalytic functions associated with viral RT, in the absence of drug-related toxicity to lymphocytes, together with its immunomodulating activity strongly argues in favor of its evaluation, as a therapeutic agent for patients with HIV infection.

Toxicology of the fluoroalkenes: review and research needs.

In this review of the published literature on the toxicology of fluoroalkenes several features emerge and research needs are evident. The fluoroalkenes vary widely in acute inhalation toxicity. Those, such as perfluoroisobutylene, PFIB, the most highly toxic member, attacks the pulmonary epithelium of rats eventuating in edema and death after a delay of about one day. Other fluoroalkenes, such as hexafluoropropylene (HFP) or chlorotrifluoroethylene (CTFE), also cause pulmonary injury but at lower concentrations produce concentration dependent changes in the renal concentrating mechanism of the rat. Changes in the CNS of rats and rabbits have also been reported for CTFE. CTFE, in repeated exposures, has produced blood pressure changes in dogs, CNS effects and changes in the erythropoietic system. This variety of responses indicates the need for investigation. Chronic effects have not been sufficiently studied for PFIB and HFP. Thus pointing up the desirability for study. Mechanisms of action research for fluoroalkenes is an important area of need. While several ideas have been suggested, there are no data to support them. The nucleophilic sensitivity of the fluoroalkenes and the potential carcinogenic effects stemming therefrom suggests a need field for investigation. We also can readily perceive the needs for the evaluation of effects on reproduction (including mutagenesis and teratogenesis), metabolism pulmonary functions, cellular function and structure. Epidemiologic studies on occupationally exposed populations are desirable in order to adequately define human health hazard from these fluorocarbons.

Acute hepatotoxicity of ethylene and halogenated ethylenes after PCB pretreatment.

Previous studies from our laboratory have shown that ethylene, vinyl fluoride monomer (VFM), vinyl chloride monomer (VCM), and vinyl bromide monomer (VBM) are all acutely hepatotoxic in rats pretreated with polychlorinated biphenyl (PCB). The time course of hepatic injury development after exposure and several parameters, environmental and chemical, affecting this toxicity were evaluated in the work reported here. Liver injury, as measured by serum alanine-alpha-ketoglutarate transaminase (SAKT) or sorbitol dehydrogenase (SDH), develops progressively over a 24-hr period following a 4-hr inhalation exposure of PCB-pretreated rats to ethylene or VCM. Environmental temperature during exposure to VCM does not affect hepatotoxicity or mortality below 30.3 degrees C. At 33.8 degrees C, however, mortality and SAKT are dramatically increased. Overnight fasting, which depletes hepatic glutathione (GSH) of PCB-pretreated rats before exposure to ethylene or VCM, significantly increases the hepatotoxicity of these compounds as measured by SDH. The combined effects of fasting and of trichloropropane epoxide (TCPE), an inhibitor of epoxide hydrase (EH), were also examined. TCPE treatment of fasted PCB-pretreated rats immediately before exposure was synergistic in increasing the acute toxicity of ethylene and VCM. TCPE increased mortality in fed or fasted rats exposed to VFM, but there was no effect of fasting alone. Both fasting and TCPE increased the sensitivity of PCB-pretreated rats to VBM, but there was not a clearly synergistic effect of fasting plus TCPE. These data suggest that the acute toxicity of these compounds is mediated through epoxide intermediates.

Metabolism and mutagenicity of halogenated olefins--a comparison of structure and activity.

Chlorinated ethylenes are metabolized in mammals, as a first step, to epoxides. The fate of these electrophilic intermediates may be reaction with nucleophiles (alkylation), hydrolysis, or intramolecular rearrangement. The latter reaction has been studied in the whole series of chlorinated epoxiethanes. The rearrangement products found were: acyl chlorides (tetrachloro-, trichloro-, and 1,1-dichloroethylenes), or chlorinated aldehydes (1,2-dichloroethylenes, cis- and trans-, vinyl chloride). The metabolities found in vivo are identical with, or further derivatives of these rearrangment products, with one important exception: trichloroethylene. With this compound, in vivo rearrangement yields chloral exclusively. The mechanism of the different rearrangement has been identified as a Lewis acid catalysis. All chlorinated ethylenes have been investigated in a tissue-mediated mutagenicity testing system. The prominent molecular feature of those with mutagenic effects (trichloro-, 1,1-dichloro-, and monochloroethylene) is unsymmetric chlorine substitution which renders the epoxides unstable, whereas symmetric substitution confers relative stability and nonmutagenic property.

Mutagenicity of the halogenated olefin, 2-bromo-2-chloro-1,1-difluoroethylene, a presumed metabolite of the inhalation anesthetic halothane.

The presumed halothane metabolite, 2-bromo-1,1-difluoroethylene, produces both base substitution and frameshift mutations in Salmonella typhimurium. Direct mutagenesis of isolated DNA also was observed by using a Bacillus subtils transformation assay to score the production of mutagenic lesions in transforming DNA.

Pyrazine derivatives in cigarette smoke inhibit hamster oviductal functioning.

BACKGROUND: Our past studies have shown that cigarette smoke inhibits oviductal functioning in vivo and in vitro. The goals in this study were to identify pyrazine derivatives in cigarette smoke solutions that inhibit ciliary beat frequency, oocyte pickup rate, and infundibular smooth muscle contraction in the hamster oviduct and to determine their lowest observable adverse effect levels (LOAELs) using in vitro bioassays. METHODS: MS smoke solutions were fractionated using solid phase extraction cartridges and the fractions were both tested on the hamster oviduct in vitro and analyzed by gas chromatography-mass spectrometry to identify individual pyrazine derivatives. Commercial pyrazine standards were purchased, assayed for purity, and tested in dose-response studies on hamster oviducts. The LOAEL and efficacy were determined for each compound in the in vitro bioassays. Statistical significance was determined using the Student's t-Test where p < 0.05. RESULTS: The LOAELs for the most inhibitory pyrazine derivatives in the ciliary beat frequency, oocyte pickup rate, and infundibular smooth muscle contraction assays were as follows: for pyrazine (1 picomolar, 10 picomolar, and 1 nanomolar); for 2-methylpyrazine (1 picomolar, 10 picomolar, and 10 picomolar); and for 2-ethylpyrazine (1 picomolar, 10 picomolar, and 1 picomolar). Six of the seven pyrazine derivatives tested (pyrazine, 2-methylpyrazine, 2-ethylpyrazine, 2-methoxy-3-methylpyrazine, 2,5-dimethylpyrazine, and 2,3,5-trimethylpyrazine) were inhibitory in picomolar or nanomolar doses in all three bioassays, while the seventh derivative, 2,6-dimethylpyrazine, had LOAELs in the nanomolar to micromolar range. CONCLUSION: This work shows that very low doses of pyrazines significantly inhibit proper oviductal functioning, raising questions regarding the safety of these compounds in cigarettes and other consumer products.