Mutagenicity of chloroacetaldehyde, a possible metabolic product of 1,2-dichloroethane (ethylene dichloride), chloroethanol (ethylene chlorohydrin), vinyl chloride, and cyclophosphamide.
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We have previously described a very sensitive and efficient bacterial test designed to detect chemical carcinogens as mutagens. Chloroacetaldehyde is mutagenic in this system and is of interest because it is a possible metabolite in mammals of the large volume industrial chemicals 1,2-dichloroethane (ethylene dichloride) (3.5 billion kg/yr, U.S.) and vinyl chloride (2.5 billion kg/yr, U.S.), and of the antineoplastic agent cyclophosphamide. Chloroacetaldehyde reverts a new Salmonella bacterial tester strain (TA100). Chloroacetaldehyde is shown to be hundreds of times more effective in reversion of TA100 than is chloroethanol (ethylene chlorohydrin), a known metabolic precursor of chloroacetaldehyde and a possible metabolite of dichloroethane and vinyl chloride, or than vinyl chloride, which is itself mutagenic for TA100. Chloroethanol is shown to be activated by rat (or human) liver homogenates to a more highly mutagenic form with reversion properties similar to chloroacetaldehyde. Reversion properties of cyclophosphamide after in vitro metabolic activation suggest that chloroacetaldehyde is not the active mutagenic form of this antineoplastic drug. (+info)
Tetrachloroethylene and trichloroethylene fatality: case report and simple headspace SPME-capillary gas chromatographic determination in tissues.
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We describe a simple, precise, and sensitive assay of tetrachloroethylene and trichloroethylene in tissues, suitable both for emergency cases and forensic medicine. The method employs headspace solid phase microextraction-capillary gas chromatography and electron capture detection. The case is relative to a 45-year-old woman discovered unconscious in a laundry area. The concentrations of the solvents in tissues were determined and compared to other previously published fatalities. (+info)
Multiple effects of trichloroethanol on calcium handling in rat submandibular acinar cells.
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The effect of trichloroethanol (TCEt), the active metabolite of chloral hydrate, on the intracellular concentration of calcium ([Ca(2+)](i)) was investigated in rat submandibular glands (RSMG) acini loaded with fura-2. TCEt (1 - 10 mM) increased the [Ca(2+)](i) independently of the presence of calcium in the extracellular medium. Dichloroethanol (DCEt) and monochloroethanol (MCEt) reproduced the stimulatory effect of TCEt but at much higher concentrations (about 6 fold higher for DCEt and 20 fold higher for MCEt). TCEt mobilized an intracellular pool of calcium, which was depleted by a pretreatment with thapsigargin, an inhibitor of the sarcoplasmic and endoplasmic reticulum calcium-dependent ATPases, but not with FCCP, an uncoupler of mitochondria. TCEt 10 mM inhibited by 50% the thapsigargin-sensitive microsomal Ca(2+)-ATPase. DCEt 10 mM and MCEt 10 mM inhibited the ATPase by 20 and 10%, respectively. TCEt inhibited the increase of the [Ca(2+)](i) and the production of inositol phosphates in response to carbachol, epinephrine and substance P. TCEt inhibited the uptake of calcium mediated by the store-operated calcium channel (SOCC). ATP and Bz-ATP increased the [Ca(2+)](i) in RSMG acini and this effect was blocked by extracellular magnesium, by Coomassie blue and by oxydized ATP (oATP). TCEt potentiated the increase of the [Ca(2+)](i) and of the uptake of extracellular calcium in response to ATP and Bz-ATP. TCEt had no effect on the uptake of barium and of ethidium bromide in response to purinergic agonists. These results suggest that TCEt, at sedative concentrations, exerts various effects on the calcium regulation: (1) it mobilizes a thapsigargin-sensitive intracellular pool of calcium in RSMG acini; (2) it inhibits the uptake of calcium via the SOCC; (3) it inhibits the activation by G protein-coupled receptors of a polyphosphoinositide-specific phospholipase C. It does not interfere with the activation of the ionotropic P2X receptors. The use of chloral hydrate should be avoided in studies exploring the in vivo responses to sialagogues. (+info)
Differential effects of anesthetics on mitochondrial K(ATP) channel activity and cardiomyocyte protection.
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BACKGROUND: Mitochondrial adenosine triphosphate-sensitive potassium (mitoK(ATP)) channels play a pivotal role in mediating cardiac preconditioning. The effects of intravenous anesthetics on this protective channel have not been investigated so far, but would be of importance with respect to experimental as well as clinical medicine. METHODS: Live cell microscopy was used to visualize and measure autofluorescence of flavoproteins, a direct reporter of mitoK(ATP) channel activity, in response to the direct and highly selective mitoK(ATP) channel opener diazoxide, or to diazoxide following exposure to various anesthetics commonly used in experimental and clinical medicine. A cellular model of ischemia with subsequent hypoosmolar trypan blue staining served to substantiate the effects of the anesthetics on mitoK(ATP) channels with respect to myocyte viability. RESULTS: Diazoxide-induced mitoK(ATP) channel opening was significantly inhibited by the anesthetics R-ketamine, and the barbiturates thiopental and pentobarbital. Conversely, urethane, 2,2,2-trichloroethanol (main metabolite of alpha-chloralose and chloral hydrate), and the opioid fentanyl potentiated the channel-opening effect of diazoxide, which was abrogated by coadministration of chelerythrine, a specific protein kinase C inhibitor. S-ketamine, propofol, xylazine, midazolam, and etomidate did not affect mitoK(ATP) channel activity. The significance of these modulatory effects of the anesthetics on mitoK(ATP) channel activity was substantiated in a cellular model of simulated ischemia, where diazoxide-induced cell protection was mitigated by R-ketamine and the barbiturates, while urethane, 2,2,2-trichloroethanol, and fentanyl potentiated myocyte protection. CONCLUSIONS: These results suggest distinctive actions of individual anesthetics on mitoK(ATP) channels and provide evidence that the choice of background anesthesia may play a role in cardiac protection in both experimental and clinical medicine. (+info)
Exposure to trichloroethylene and its metabolites causes impairment of sperm fertilizing ability in mice.
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Trichloroethylene (TCE) is a prevalent occupational and environmental contaminant that has been reported to cause a variety of toxic effects. Here, we have undertaken studies to test the hypothesis that TCE exposure adversely affects sperm function and fertilization. Sperm retrieved from mice exposed to TCE (1000 ppm) by inhalation for 1 to 6 weeks were incubated in vitro with eggs isolated from superovulated female mice. The number of sperm bound per egg was significantly decreased when mice were exposed to TCE for 2 and 6 weeks but not at exposures of 1 and 4 weeks. In vivo fertilization was also determined in superovulated female mice mated with males exposed to TCE for 2 to 6 weeks. The percentages of eggs fertilized, as assessed by the presence of two pronuclei, were significantly decreased after 2 and 6 weeks of TCE exposure. A slight but insignificant decrease was observed after 4 weeks of TCE exposure. The direct effects of TCE and its metabolites, chloral hydrate (CH) and trichloroethanol (TCOH), on in vitro sperm-egg binding were also investigated. Sperm-egg binding was significantly decreased when sperm were pretreated with CH (0.1-10 microg/mL). Significantly lower levels of sperm-egg binding were also detected with TCOH (0.1-10 microg/mL), although the decreases were not as pronounced as those for CH. These results showed that TCE exposure leads to impairment of sperm fertilizing ability, which may be attributed to TCE metabolites, CH, and TCOH. (+info)
Phases of dormancy in Yam tubers (Dioscorea rotundata).
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BACKGROUND AND AIMS: The control of dormancy in yam (Disocorea spp.) tubers is poorly understood and attempts to shorten the long dormant period (i.e. cause tubers to sprout or germinate much earlier) have been unsuccessful. The aim of this study was to identify and define the phases of dormancy in Dioscorea rotundata tubers, and to produce a framework within which dormancy can be more effectively studied. METHODS: Plants of 'TDr 131' derived from tissue culture were grown in a glasshouse simulating temperature and photoperiod at Ibadan (7 degrees N), Nigeria to produce tubers. Tubers were sampled on four occasions: 30 d before shoot senescence (149 days after planting, DAP), at shoot senescence (179 DAP), and twice during storage at a constant 25 degrees C (269 and 326 DAP). The development of the apical shoot bud was described from tissue sections. In addition, the responsiveness of shoot apical bud development to plant growth regulators (gibberellic acid, 2-chloroethanol and thiourea) applied to excised tuber sections was also examined 6 and 12 d after treatment. KEY RESULTS AND CONCLUSIONS: Three phases of tuber dormancy are proposed: Phase I, from tuber initiation to the appearance of the tuber germinating meristem; Phase II, from the tuber germinating meristem to initiation of foliar primordium; and Phase III, from foliar primordium to appearance of the shoot bud on the surface of the tuber. Phase I is the longest phase (approx. 220 d in 'TDr 131'), is not affected by PGRs and is proposed to be an endo-dormant phase. Phases II and III are shorter (<70 d in total), are influenced by PGRs and environmental conditions, and are therefore endo-/eco-dormant phases. To manipulate dormancy to allow off-season planting and more than one generation per year requires that the duration of Phase I is shortened. (+info)
Mutations of L293 in transmembrane two of the mouse 5-hydroxytryptamine3A receptor alter gating and alcohol modulatory actions.
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1 The goal of this study was to determine whether mutations of L293 at the 15' position of TM2 in the 5-HT(3A) receptor alter macroscopic current kinetics, and if these changes could account for alterations in alcohol modulation. Receptor function was assessed in Xenopus oocytes under voltage-clamp and in HEK293 cells with whole-cell patch-clamp recording and rapid drug application. 2 Examination of responses of L293C and L293S receptors to agonist alone revealed enhanced activation, deactivation, and desensitization rates relative to the wild-type receptor. The L293G mutation produced marked slowing of deactivation and desensitization rates. Increased potency of 5-HT and increased efficacy of the partial agonist, DA, was also observed in these mutant receptors. 3 Ethanol and trichloroethanol (TCEt) enhancement of receptor function was reduced or eliminated in receptors containing L293 mutations to C, G, or S. The L293I mutant receptor retained ethanol and TCEt sensitivity. Ethanol and TCEt enhanced activation rate in the wild-type, but not the L293G and L293S receptors. No relationship was observed between any physicochemical property of the substituted amino acids and the change in alcohol potentiation of function. 4 The changes in receptor-channel properties in the mutant receptors support the idea that the L293 residue has important roles in channel gating. Our findings indicate that loss of allosteric modulation by alcohols is not related in any simple way to changes in channel kinetic properties brought about by L293 mutants. We did not observe any evidence that L293 is part of an alcohol binding site. (+info)
Green chemistry in urinalysis for trichloroethanol and trichloroacetic acid as markers of exposure to chlorinated hydrocarbon solvents.
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The aim of the present study was to develop a method of urinalysis for trichloroacetic acid (TCA) and trichloroethanol (TCE), and therefore total trichloro-compounds (TTC) as the sum, with least use of hazardous chemicals, being green in that sense. After acid hydrolysis followed by dilution with an ethanol (EtOH)-methanol (MeOH)-water mixture, capillary gas-choromatography with an electron-capture detector can quantify TCA and TCE in the diluted hydrolyzate. Comparison studies showed that the results were identical among three methods, i.e., 1. the method developed in the present study, 2. a head-space GC with acid hydrolysis of conjugated TCE and methyl-esterification of TCA, and 3. traditional colorimetry with Fujiwara reaction. When applied to exposure-excretion analysis, the three methods gave results reproducible to each other. Over-all evaluation therefore was such that the method developed in the present study is as equally reliable as previously developed methods. It should be further noted that the procedures are very simple, with minimum use of occupationally or environmentally hazardous chemicals. In case the determination of only TCA is requested, it is possible to skip the hydrolysis step so that the treatment prior to the GC analysis is even simpler, i.e., just a 60-fold dilution of the urine sample with the EtOH-MeOH-water mixture. It was also demonstrated that correction of urinary analyte levels for urine density in terms of creatinine or specific gravity did not improve the correlation with the intensity of TRI exposure. (+info)