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PubMed1994

Toxic effects of pollutants on the mineralization of chloroform in river sediments.

The influence of pollutants on the formation of 14CO2 from 3 micrograms/liter labeled chloroform was studied in anaerobic Dutch river sediments. All incubations were performed under anaerobic conditions. Addition of toxicants to sediment microcosms showed logistic dose-effect curves. The concentration giving 10% inhibition of the chloroform mineralization rate (IC10) was derived from these dose-effect curves. The IC10 values of added cadmium, chloropyrifos, benzene, mercury, or 1,2-dichloroethane were 1300, 1300, 140, 90, and 0.07 mg/kg dry sediment, respectively. Mud samples taken at different dates from the same site indicated a significantly different sensitivity to added pentachlorophenol and zinc. The IC10 of added pentachlorophenol was 150 mg/kg in one and 15 mg/kg in another sample. Chloroform-mineralizing bacteria are very sensitive to addition of zinc. The IC10 of added zinc was 700 mg/kg for one sample and 11 mg/kg for another sample of the sediment which contained a background concentration of 800 mg Zn/kg. Therefore, a partial inhibition of the mineralization of chloroform by the high concentrations of zinc present in Dutch river sediments cannot be excluded. The high concentration of zinc might cause persistence of otherwise biodegradable pollutants in Dutch sediments.

Anaerobiosis↗

PubMed1987

Dose-response of promotion by polychlorinated biphenyls and chloroform in rat liver foci bioassay.

Using the rat liver foci bioassay a dose-response relationship was evaluated for the promoting activity of the ubiquitous and persistent environmental pollutants polychlorinated biphenyls (PCBs) and chloroform. Initiation of liver foci was performed by oral administration of a single dose of 8 mg/kg body wt of diethylnitrosamine to weanling female Sprague-Dawley rats. For polychlorinated biphenyls (PCBs) and chloroform a dose-dependent promoting effect was found. The lowest effective dose of PCBs was 1 mg/kg body wt, given three times a week for 11 consecutive weeks. That of chloroform was 100 mg/kg body wt, administered twice a week for 11 consecutive weeks. The livers were screened for preneoplastic foci 12 weeks after starting the experiments. The amounts of PCBs as well as chloroform normally taken up by humans are greater than a factor of 1000 lower than the effective experimental doses. Thus the risk of human exposure to these chemicals is estimated to be very low. In the case of heavy pollution with PCBs, however, as happened in the yusho accident (Japan, 1968), the daily intake of PCBs was in the range of the effective doses used in the experiment.

Adenosine Triphosphatases↗

PubMed1985

"Experimentation" with chloroform.

A young patient presented with unconsciousness, cardiac arrhythmias, arterial hypotension, and mild intravascular hemolysis after intentional inhalation of chloroform. After the initial complications had resolved, nausea, loss of appetite, and mild transitory jaundice developed. Chloroform-associated hepatotoxicity was biochemically and histologically documented. Facilitating factors included long-term moderate alcohol consumption and an initial episode of arterial hypoxemia. Chloroform inhalation for recreational purposes is probably uncommon. Yet, because of its delayed onset, chloroform poisoning should be considered in acute liver disease without a clear antecedent cause.

Adult↗

PubMed1979

Stabilization of rat liver mitochondrial F1-adenosine triphosphatase during chloroform-induced solubilization.

1. Isolation of ATPase from rat liver submitochondrial particles by chloroform treatment requires the presence of ATP or ADP during enzyme solubilization. In the absence of adenine nucleotides the enzyme activity is very low although all protein components of F1-ATPase are released. The low concentrations of ATP or ADP required (5 microM) indicate that the high affinity nucleotide-binding sites are involved in enzyme stabilization. Other nucleotides tested (ITP, GTP, UTP, CTP) were found to be less effective. 2. Polyacrylamide gel electrophoresis and immunodiffusion in agar plates revealed that in the absence of adenine nucleotides a fraction of F1-ATPase released by chloroform treatment is split into fragments. The part of the dissociated enzyme molecule has a molecular weight identical with that of a beta-subunit of F1-ATPase. 3. Dissociation of the F1-ATPase molecule could also be prevented by aurovertin. 4. Crude F1-ATPase solubilized by chloroform treatment can be further purified by Sepharose 6B gel filtration. Specific ATPase activity of the purified enzyme was 90 mumol Pi/min per mg protein and the enzyme was composed of five protein subunits (alpha, beta, gamma, delta, epsilon) with molecular weights 58 000, 55 000, 28 000, 13 000 and 8000, respectively. 5. Chloroform-released F1-ATPase from rat liver mitochondria displayed immunochemical cross-reactivity with that isolated from beef heart mitochondria.

Adenosine Triphosphatases↗

PubMed1987

Chloroform markedly stimulates the phosphorylation of myelin basic proteins.

We have investigated the effect of chloroform on the phosphorylation of myelin basic proteins because tumor-promoting agents such as phorbol esters and chloroform are known to enhance the activity of protein kinase C. We report that the presence of chloroform, at a concentration known to enhance protein kinase C activity, stimulated the phosphorylation of myelin basic proteins 15-17 fold over control conditions. The phosphorylation of a 50 kiloDalton myelin protein was also stimulated but to a lesser extent. The concentration of chloroform required for the maximal phosphorylation of myelin basic proteins and the 50 kiloDalton protein was approximately 2% (v/v).

Adenosine Triphosphate↗

PubMed1987

Tumor promoter chloroform is a potent protein kinase C activator.

The major interaction site for tumor-promoting phorbol esters is the calcium-activated, phospholipid-dependent protein kinase (protein kinase C), a key-element in signal transduction. Binding of phorbol esters results in enzyme activation which mediates, at least in part, the action of these agents. We have investigated the effects of tumor promoter chloroform on protein kinase C activity. Like thrombin and 12-O-tetradecanoylphorbol-13-acetate (TPA), chloroform was able to activate protein kinase C in intact rabbit platelets. In addition, chloroform stimulated enzyme activity as well as TPA binding capacity in cell-free system. Scatchard analysis of the data has shown that chloroform increased the number of phorbol ester binding sites. Structurally related compounds, carbon tetrachloride and methylene chloride, activated the enzyme similarly.

Animals↗

PubMed1991

Trihalomethanes and maximum contaminant levels: the significance of inhalation and dermal exposures to chloroform in household water.

Our review of the literature on the importance of inhalation and dermal exposures to volatile organic compounds in household water relative to ingestion exposures sought to answer two questions. First, how well do the inhalation and dermal doses predicted by simple models, complex simulations, and measurements agree with one another? And second, what are the implications for the cancer risk from chloroform in household water? The literature yields a coherent and credible range of dose estimates: the ratio of lifetime inhalation dose to lifetime ingestion dose is probably in the range of approximately 0.6 to approximately 1.5, but may be as high as approximately 5.7; and the ratio of lifetime dermal dose to lifetime ingestion dose is probably about approximately 0.3, but may be as high as approximately 1.8. However, because the U.S. Environmental Protection Agency's (EPA's) Cancer Potency Factor (CPF) for inhalation of chloroform is much higher than the CPF for ingestion, the ratios of incremental lifetime cancer risk from inhalation of chloroform to risk from ingestion are much larger than the corresponding ratios for dose. The incremental lifetime cancer risk from chloroform by all three pathways is probably approximately 9 to approximately 21 times the ingestion risk and may be as much as approximately 79 times the ingestion risk. As the EPA reviews the drinking water standard for total trihalomethanes, it is essential that the Agency take account of all exposure pathways in estimating cancer risk.

Administration, Inhalation↗

PubMed1985

Covalent adduct formation and chloroform production after free radical attack on fatty acids by carbon tetrachloride reactive intermediates.

The interactions of fatty acids and the trichloromethyl free radical generated anaerobically by the benzoyl peroxide model system were studied. Chloroform was produced due to the interaction of the trichloromethyl free radical with the unsaturated fatty acid ester methyl oleate, indicating the hydrogen in chloroform may result from abstraction from fatty acids. In addition, chloroform was detected in incubations containing the saturated fatty acid ester methyl stearate, indicating hydrogen abstraction is not limited to allylic hydrogens. Mass spectral analysis identified one adduct resulting from additional reactions to methyl oleate, and an adduct resulting initially from hydrogen abstraction on methyl stearate. These findings describe previously unreported reactions of the trichloromethyl free radical with saturated fatty acid, and inhibition of chloroform production by 3 free radical inhibitors.

Benzoyl Peroxide↗

PubMed1992

The hepatotoxicity of chloroform in precision-cut rat liver slices.

Chloroform hepatotoxicity was investigated in precision-cut liver slices from male Sprague-Dawley rats pretreated with phenobarbital to predispose animals to CHCl3 intoxication. Liver slices were exposed to 0.2, 0.5 and 1.0 mM chloroform for a total of 9 h in a roller culture system. Intracellular K+ loss was found to be concentration- and time-dependent over the duration of the experiment. Histopathological changes were also evident. Glucose 6-phosphate dehydrogenase and beta-glucuronidase were significantly decreased at 3 h relative to controls where a loss of 61% and 36% occurred, respectively. Enzyme levels of alanine aminotransferase and lactate dehydrogenase, both found predominantly in periportal hepatocytes, remained identical to controls over the duration of the experiment. A significant time-dependent depletion of glutathione occurred as early as 3 h following the administration of 0.5 mM chloroform. Mitochondrial viability, measured by the reduction of a specific dye, was significantly lower than controls in treated slices at 6 h following chloroform administration. Precision-cut liver slices appear to be especially useful for the biochemical and histopathological examination of site-specific hepatotoxicants such as CHCl3.

Animals↗

PubMed1984

Sex and strain differences in mouse kidney: Bowman's capsule morphology and susceptibility to chloroform.

Chloroform (CHCl3) produces liver damage in male and female mice but renal injury only in male mice. Previous reports demonstrated that the parietal epithelium of Bowman's capsule in female mice is composed of squamous cells, whereas the parietal cells of Bowman's capsule from male mice consist of a mixture of squamous and cuboidal cells or purely cuboidal cells. These data suggested that the factor(s) associated with these histological differences may similarly be associated with factors that determine susceptibility to tubular damage from chloroform. The susceptibility of male mice to chloroform nephrotoxicity varies with animal strain. In the present study, administration of CHCl3 to male C57BL/6J (C57) and male and female DBA/2J (DBA) mice produced dose-dependent kidney tubular damage in male C57 and male DBA mice. However, CHCl3 nephrotoxicity was considerably greater in male DBA mice than in male C57 mice. Female DBA mice failed to develop renal damage following administration of CHCl3. Male DBA mice had a higher percentage of cuboidal parietal epithelial cells in Bowman's capsule whereas male C57 mice had a higher percentage of squamous cells in the parietal epithelium. The parietal epithelium in Bowman's capsule of female DBA mice was predominantly squamous. Since morphological differences between sex and strain of mice occurred in the capsular epithelium, and the differences in susceptibility to CHCl3 appear to be a tubular phenomenon, it is unlikely that there is a causal relationship between the structure of Bowman's capsule and chloroform-induced renal tubular necrosis; rather, these two independent phenomena are regulated by some common factor(s), possibly testosterone.

Alanine Transaminase↗

PubMed1995

The role of regenerative cell proliferation in chloroform-induced cancer.

Chloroform produces cancer by a nongenotoxic-cytotoxic mode of action, with no increased cancer risk expected at noncytotoxic doses. The default risk assessment for inhaled chloroform relies on liver tumor incidence from a gavage study with female B6C3F1 mice and estimates a virtually safe dose (VSD) at an airborne concentration of 0.000008 ppm of chloroform. In contrast, a 1000-fold safety factor applied to the NOAEL for liver cytotoxicity from inhalation studies yields a VSD of 0.01 ppm. This estimate relies on inhalation data and is more consistent with the mode of action of chloroform.

Animals↗

PubMedDate not supplied

Immunologic detection of protein antigens after phenol-chloroform denaturation.

The study of gene expression in cells and tissues often begins with phenol-chloroform extraction of the biologic material of interest for the isolation of intact mRNA. In most cases, the proteins denatured by phenol-chloroform are discarded. However, we found that the proteins recovered from phenol-chloroform extractions maintain their antigenicity. Therefore a method was developed for recovering the proteins from phenol-chloroform-denatured extracts that could be saved in lyophilized form until immunologic analysis. In this way, the RNA and the protein analysis can utilize exactly the same sample, and the biologic material can be saved. This is important because often these materials are available only in limited quantities. The method has been used to examine the sea urchin ets-related antigen and sea urchin ets-2 mRNA.

Animals↗

PubMed2006

Traces of phosgene in chloroform: consequences for extraction of anthracyclines.

Chloroform is commonly used to extract anthracyclines from various biological matrices. However, their determination can be seriously compromised by phosgene traces present as a result of failing stabilization of chloroform. Out of the three varieties in which chloroform exists (not stabilized, stabilized with an alcohol and stabilized with a hydrocarbon) only the ethanol stabilized type minimizes chances on creating artifacts. Chromatographic separation after extraction of four anthracyclines (doxorubicin, epirubicin, daunorubicin and idarubicin) and two metabolites (13-S-dihydrodoxorubicin and 13-S-dihydroepirubicin) with chloroform under various conditions indicate that the appropriate choice of stabilizer in this extraction solvent is highly relevant.

Amines↗

PubMed2006

C-H...O hydrogen bond in chloroform-triformylmethane complex: blue-shifted or red-shifted?

B3LYP/6-311+G** level of theory is used to investigate the C-H...O hydrogen bond formed by chloroform and two conformers of triformylmethane (TFM), i.e. cis-TFM (concerned with C1 configuration) and trans-TFM (concerned with C2 and C3 configurations). Polarized continuum model (PCM) is used to study the solvent (chloroform) effect on this hydrogen bond. The C3 configuration is more stable than the C1 configuration whether the absolute energy or the stabilization energy is concerned. For the C1 and C2 configurations this hydrogen bond is of blue-shifted type both in gas phase and in chloroform solution. For the C3 configuration this hydrogen bond is of red-shifted type in gas phase but turns into blue-shifted type in chloroform solution instead. It's inappropriate to simply designate this hydrogen bond as blue-shifted type or red-shifted type.

Chloroform↗

PubMed1985

Activation of chloroform and related trihalomethanes to free radical intermediates in isolated hepatocytes and in the rat in vivo as detected by the ESR-spin trapping technique.

When hepatocytes isolated from phenobarbital-induced rats were incubated with chloroform and the spin trap phenyl-t-butyl nitrone (PBN) under anaerobic conditions, a free radical-spin trap adduct was detectable by ESR spectroscopy. A similar incubation of hepatocytes in the presence of air resulted in an ESR signal that was eight times less intense than that seen under anaerobic conditions; incubation mixtures exposed to pure oxygen had no detectable adduct signal. A significant reduction in the signal intensity was also produced by the addition of cytochrome P-450 inhibitors such as SKF-525A, metyrapone and carbon monoxide, indicating that free radical formation depended upon the reductive metabolism of chloroform mediated by the mixed oxidase system. The origin of the CHCl3-derived free radical has been confirmed by using [13C]CHCl3, while the comparison between the ESR spectra obtained in the presence of deuterated chloroform (CDCl3) and bromodichloro-methane (CHBrCl2) suggests that the free radical derived from CHCl3 may be CHCl2. Free radical intermediates were also detected during the aerobic and anaerobic incubation of isolated hepatocytes with bromoform (CHBr3), and iodoform (CHI3). The intensity of the ESR signal obtained with the various trihalomethanes increases in the order CHCl3 less than CHBrCl2 less than CHBr3 less than CHI3. The formation of PBN-free radical adducts has also been observed in phenobarbital-induced rats in vivo when intoxicated with chloroform, bromoform or iodoform, suggesting that the reductive metabolism of trihalomethanes might be of relevance to their established toxicity in the whole animal.

Animals↗

PubMed1986

Biochemical alterations elicited in rat liver microsomes by oxidation and reduction products of chloroform metabolism.

The feasibility of an oxygen-independent mechanism of chloroform bioactivation was indicated by the covalent binding to lipid and protein occurring in anaerobic incubations of CHCl3 and microsomes in the presence of NADPH. Under these conditions, the loss of cytochrome P-450 and the inhibition of related monoxygenases were also observed. The chloroform anoxic biotransformation was negligible in uninduced microsomes and seemed to be catalyzed mainly by phenobarbital-inducible P-450 isozymes. Biotransformation could also be supported by NADH as the source of reducing equivalents. Anaerobic metabolism of chloroform led to decreased levels of the main PB-induced P-450 isozymes even at low CHCl3 concentration and did not affect benzo[a]pyrene hydroxylase activity. These effects were not decreased by thiolic compounds. The oxidation products of chloroform caused a general impairment of the monoxygenase system, probably related to the formation of protein aggregates with very high molecular weight. In the presence of physiological concentrations of GSH, the targets of aerobically-produced metabolites were lipids and, to a smaller extent, P-450. At low CHCl3 concentrations and/or in the presence of GSH the most changes to microsomal structures seemed to be produced by the reductively-formed intermediates.

Animals↗

PubMed2002

Adsorption and adsorption mechanism of rice bran for chloroform from tap water.

We have found that rice bran effectively adsorbed chloroform from tap water. The amount of chloroform adsorbed was plotted against the equilibrium concentration of chloroform in solution on a logarithmic scale. A linear relationship was obtained, indicating that the adsorption reaction was a Freundlich type. The removal of chloroform by rice bran was attributed to the uptake into intracellular particles called spherosomes.

Adsorption↗

PubMed1995

Endodontic retreatment with halothane versus chloroform solvent.

Chloroform has been the most widely used solvent in endodontics, but due to concerns about its safety, alternatives have been sought. The purpose of this study was to compare the effectiveness of gutta-percha removal and time of retreatment between halothane and chloroform used as solvents. Thirty mandibular premolars were prepared, obturated, and stored in a humidor for 14 months, after which they were randomly divided into two groups for retreatment. The teeth were retreated using either halothane or chloroform as the solvent. The time of retreatment was measured to the nearest minute. Retreatment was deemed complete when there was no evidence of gutta-percha or sealer on the files or paper points. Teeth were split longitudinally and photographed. The resulting slides were projected, the canals traced, and the areas of the canal, gutta-percha, and sealer were measured using a sonic digitizer. The results were analyzed statistically by t test. The results showed no significant difference in gutta-percha removal between the two groups. The chloroform group took significantly less time to retreat than halothane (7.7 min. versus 10.8 min, respectively).

Chloroform↗