Biocompatibility of gutta-percha solvents using in vitro mammalian test-system

OBJECTIVES

Taking into consideration that DNA damage and cellular death play important roles during carcinogenesis, the purpose of the present study was to evaluate in vitro genotoxic or cytotoxic effects of chloroform and eucalyptol by single cell gel (comet) assay and trypan blue exclusion test, respectively.

STUDY DESIGN

Chloroform and eucalyptol were exposed to Chinese hamster ovary cells in culture directly for 3 hours at 37 degrees C at final concentrations ranging from 1.25 to 10 microL/mL. The negative control group was treated with vehicle control (phosphate-buffered solution), and the positive control group was treated with methyl metasulfonate (MMS, at 1 microg/mL concentration). All data were analyzed by the Kruskal-Wallis nonparametric test followed by the Dunn test.

RESULTS

The results showed that both gutta-percha solvents were cytotoxic at concentrations of 2.5, 5, and 10 microL/mL (P < .05). On the other hand, both solvents did not induce DNA breakage at 1.25 microL/mL concentration.

CONCLUSIONS

These results suggest that both chloroform or eucalyptol are strong cytotoxicants, but they may not be a factor that increases the level of DNA lesions in mammalian cells.

The phytotoxic effect of C(1)/C(2)-halocarbons and trichloroacetic acid on the steppe plant Artemisia lerchiana

Artemisia lerchiana is a wormwood species of the Central Asian steppe regions, where it completely cover whole areas. For the first time it was possible to show through field experiments that C(1)/C(2) halocarbons (VCHCs), such as chloroform (CHL), tetrachloroethene (PER) and hexachloroethane (HEX), can be taken up by test plants of the species A. lerchiana via the soil/root pathway and metabolised inter alia into trichloroacetic acid (TCA) under semi-aride conditions. At the same time, chlorophyll a fluorescence measurements carried out on the test plants revealed a phytotoxic influence on plant vitality (max. decline in vitality of 52% with application of CHL) and less efficient energy flows in the photosynthesis mechanism of the A. lerchiana test plants. The authors examine possible links between the simultaneous appearance of VCHCs and additional drought stress in the acceleration of desertification processes.

Enhancement of renal carcinogenicity by combined inhalation and oral exposures to chloroform in male rats

Chloroform, ubiquitously present in indoor and outdoor air, drinking water, and some foodstuffs, enters the human body by inhalation, oral and dermal routes of exposure. In order to provide bioassay data for risk assessment of humans exposed to chloroform by multiple routes, effects of combined inhalation and oral exposures to chloroform on carcinogenicity and chronic toxicity in male F344 rats were examined. A group of 50 male rats was exposed by inhalation to 0 (clean air), 25, 50, or 100 ppm (v/v) of chloroform vapor-containing air for 6 h/d and 5 d/wk during a 104 w period, and each inhalation group was given chloroform-formulated drinking water (1000 ppm w/w) or vehicle water for 104 wk, ad libitum. Renal-cell adenomas and carcinomas and atypical renal-tubule hyperplasias were increased in the combined inhalation and oral exposure groups, but not in the oral- or inhalation-alone groups. Incidences of cytoplasmic basophilia and dilated tubular lumens in the kidney, as well as incidence of positive urinary glucose, were markedly increased by the combined exposures, compared with those after single-route exposures. It was concluded that combined inhalation and oral exposures markedly enhanced carcinogenicity and chronic toxicity in the proximal tubule of male rat kidneys, suggesting that carcinogenic and toxic effects of the combined exposures on the kidneys were greater than the ones that would be expected under an assumption that the two effects of single route exposures through inhalation and drinking were additive.

Subchronic chloroform priming protects mice from a subsequently administered lethal dose of chloroform

Protection offered by pre-exposure priming with a small dose of a toxicant against the toxic and lethal effects of a subsequently administered high dose of the same toxicant is autoprotection. Although autoprotection has been extensively studied with diverse toxicants in acute exposure regimen, not much is known about autoprotection after priming with repeated exposure. The objective of this study was to investigate this concept following repeated exposure to a common water contaminant, chloroform. Swiss Webster (SW) mice, exposed continuously to either vehicle (5% Emulphor, unprimed) or chloroform (150 mg/kg/day po, primed) for 30 days, were challenged with a normally lethal dose of chloroform (750 mg chloroform/kg po) 24 h after the last exposure. As expected, 90% of the unprimed mice died between 48 and 96 h after administration of the lethal dose in contrast to 100% survival of mice primed with chloroform. Time course studies indicated lower hepato- and nephrotoxicity in primed mice as compared to unprimed mice. Hepatic CYP2E1, glutathione levels (GSH), and covalent binding of (14)C-chloroform-derived radiolabel did not differ between livers of unprimed and primed mice after lethal dose exposure, indicating that protection in liver is neither due to decreased bioactivation nor increased detoxification. Kidney GSH and glutathione reductase activity were upregulated, with a concomitant reduction in oxidized glutathione in the primed mice following lethal dose challenge, leading to decreased renal covalent binding of (14)C-chloroform-derived radiolabel, in the absence of any change in CYP2E1 levels. Buthionine sulfoximine (BSO) intervention led to 70% mortality in primed mice challenged with lethal dose. These data suggest that higher detoxification may play a role in the lower initiation of kidney injury observed in primed mice. Exposure of primed mice to a lethal dose of chloroform led to 40% lower chloroform levels (AUC(15-360 min)) in the systemic circulation. Exhalation of (14)C-chloroform was unchanged in primed as compared to unprimed mice (AUC(1-6 h)). Urinary excretion of (14)C-chloroform was higher in primed mice after administration of the lethal dose. However, neither slightly higher urinary elimination nor unchanged expiration can account for the difference in systemic levels of chloroform. Liver and kidney regeneration was inhibited by the lethal dose in unprimed mice leading to progressive injury, organ failure, and 90% mortality. In contrast, sustained and highly stimulated compensatory hepato- and nephrogenic repair prevented the progression of injury resulting in 100% survival of primed mice challenged with the lethal dose. These findings affirm the critical role of tissue regeneration and favorable detoxification (only in kidney) of the lethal dose of chloroform in subchronic chloroform priming-induced autoprotection.

In vitro modulation of HERG channels by organochlorine solvent trichlormethane as potential explanation for proarrhythmic effects of chloroform

Acute chloroform intoxication can cause depression of the central nervous system and may lead to death from lethal arrhythmias or respiratory arrest. Thus, the organic solvent is no longer in clinical use as an anaesthetic, but still plays a role in cases of suicide, homicide or inhalation for psychotropic effects. Several cases of lethal arrhythmia after intoxication with chloroform have been described. Pharmacological inhibition of cardiac "human ether-à-go-go-related gene" (HERG) potassium channels is linked to proarrhythmic effects of cardiac and noncardiac drugs. To further investigate the electrophysiological basis of the arrhythmogenic potential of chloroform, we analysed inhibitory effects of chloroform on cloned HERG potassium channels, heterologously expressed in Xenopus oocytes and in Human Embryonic Kidney (HEK 293) cells using the double-electrode voltage-clamp technique and the whole-cell patch-clamp technique, respectively. In HEK cells, chloroform blocked HERG tail currents with an IC(50) of 4.97mM. Biophysical properties were further investigated in the Xenopus oocyte expression system. Onset and wash-out of block was fast and inhibition was completely reversible. Chloroform did not alter channel activation, however, direct channel inactivation was accelerated significantly. Steady-state-inactivation of HERG was not affected. Chloroform dependent block of HERG channels was voltage dependent with a decrease of inhibition at more positive membrane potentials. No frequency-dependence of block could be observed. In summary, chloroform blocked HERG potassium channels probably in a toxicologically relevant concentration. These findings contribute to the pathophysiology of proarrhythmic effects in acute chloroform intoxication.

Inhaled chemicals may enhance allergic airway inflammation in ovalbumin-sensitised mice

Occupational allergy and asthma is a challenging issue in the developing countries. Chemicals inhaled in the workplaces may act not only as allergens but also as immune response modifiers, contributing to asthma exacerbation. In this study, we tested the adjuvant effect of 20 ppm chloroform, 10 ppm 1,1-dichloroethylene, and 100 ppm styrene in mice. Female BALB/c mice were sensitised to ovalbumin (OVA) without using alum. During the OVA-sensitisation period, these mice were exposed by inhalation to the chemicals studied for 6h/day for four consecutive days. After two OVA-intratracheal challenges, a mild Th2 immune response was observed in the OVA-exposed groups. This response was characterised by a mild increase in serum specific IgE level, in local Th2 cytokine production, and in lung inflammatory reaction. Exposure to styrene or chloroform alone slightly increased Th2 cytokine production by lung-draining lymph node cells cultured with concanavaline A, except for the IL-4 level in the chloroform exposure group, which decreased. On the other hand, exposure to 1,1-dichloroethylene alone markedly increased the Th2 cytokine levels compared to those observed in the groups exposed to OVA alone. In the combined OVA+chemical-treated groups, styrene potentiated IL-4, -5 and -13 production efficiently (approximately two, four and three times higher, respectively), resulting in an increase in the total IgE levels and inflammatory reaction. On the other hand, the enhanced IgE levels and the exacerbation of the inflammatory response by 1,1-dichloroethylene or chloroform were associated with only minor changes in local cytokine levels. These findings suggest that exposure to chemicals through inhalation may aggravate the allergic lung inflammation. And this, depending on the chemical exposure conditions, may result from the synergistic effect of chemicals and allergen on local Th2 cytokine production.

In vitro evaluation of macrophage viability after incubation in orange oil, eucalyptol, and chloroform

OBJECTIVE

The aim of this study was to evaluate the cytotoxicity of orange oil, eucalyptol, and chloroform in a cell culture assay by using peritoneal macrophages from Swiss mice.

STUDY DESIGN

Control (Dulbecco's modified Eagle's medium [DMEM] plus 1.25% ethyl alcohol) and experimental (orange oil, eucalyptol, and chloroform) groups were studied. Solvents used were tested at 0.025% and 0.050% concentrations in DMEM plus 1.25% ethyl alcohol.

RESULTS

Orange oil, eucalyptol, and chloroform were all cytotoxic in comparison to the control group (P < .001). Orange oil showed the least cytotoxicity (P < .001). No significant differences were observed regarding cell viability when comparing the eucalyptol and chloroform groups (P < .05). There were significant differences in the cytotoxicity of eucalyptol and chloroform with an increase in concentration (P < .0001). Nevertheless, this difference was not significant in the orange oil group (P < .05).

CONCLUSION

Orange oil was less cytotoxic than eucalyptol and chloroform.

Adaptive tolerance in mice upon subchronic exposure to chloroform: Increased exhalation and target tissue regeneration

The aims of the present study were to characterize the subchronic toxicity of chloroform by measuring tissue injury, repair, and distribution of chloroform and to assess the reasons for the development of tolerance to subchronic chloroform toxicity. Male Swiss Webster (SW) mice were given three dose levels of chloroform (150, 225, and 300 mg/kg/day) by gavage in aqueous vehicle for 30 days. Liver and kidney injury were measured by plasma ALT and BUN, respectively, and by histopathology. Tissue regeneration was assessed by (3)H-thymidine incorporation into hepato- and nephro-nuclear DNA and by proliferating cell nuclear antigen staining. In addition, GSH and CYP2E1 in liver and kidney were assessed at selected time points. The levels of chloroform were measured in blood, liver, and kidney during the dosing regimen (1, 7, 14, and 30 days). Kidney injury was evident after 1 day with all three doses and sustained until 7 days followed by complete recovery. Mild to moderate liver injury was observed from 1 to 14 days with all three dose levels followed by gradual decrease. Significantly higher regenerative response was evident in liver and kidney at 7 days, but the response was robust in kidney, preventing progression of injury beyond first week of exposure. While the kidney regeneration reached basal levels by 21 days, moderate liver regeneration with two higher doses sustained through the end of the dosing regimen and 3 days after that. Following repeated exposure for 7, 14, and 30 days, the blood and tissue levels of chloroform were substantially lower with all three dose levels compared to the levels observed with single exposure. Increased exhalation of (14)C-chloroform after repeated exposures explains the decreased chloroform levels in circulation and tissues. These results suggest that toxicokinetics and toxicodynamics (tissue regeneration) contribute to the tolerance observed in SW mice to subchronic chloroform toxicity. Neither bioactivation nor detoxification appears to play a decisive role in the development of this tolerance.

In vitro cytotoxic and non-genotoxic effects of gutta-percha solvents on mouse lymphoma cells by single cell gel (comet) assay

Chloroform and eucalyptol are widely used in clinical dentistry as gutta-percha solvents. However, these compounds may represent a hazard to human health, especially by causing injury to genetic apparatus and/or inducing cellular death. In this study, the genotoxic and cytotoxic potentials associated with exposure to chloroform and eucalyptol were assessed on mouse lymphoma cells in vitro by the single cell gel (comet) assay and trypan blue exclusion test, respectively. Both gutta-percha solvents proved to be cytotoxic at the same levels in concentrations of 2.5, 5 and 10 muL/mL (p<0.05). On the other hand, neither of the solvents induced DNA breakage. Taken together, these results suggest that although both tested compounds (chloroform and eucalyptol) are strong cytotoxicants, it seems that they are not likely to increase the level of DNA damage on mammalian cells.

Resolution of liver fibrosis in chronic CCl4 administration in the rat after discontinuation of treatment: effect of silymarin, silibinin, colchicine and trimethylcolchicinic acid

The purpose of this work was to obtain a suitable model of fibrosis, in which spontaneous reversion was minimal, to study the ability of silymarin, silibinin, colchicine and trimethylcolchicinic acid (TMCA) to reverse it. Reversal of liver fibrosis was studied in male Wistar rats after one, two or three months of CCl(4) administration (0.4 g/kg intraperitoneally, three times per week), by discontinuation of the toxin for 2 months. Silymarin (50 mg/kg), silibinin (50 mg/kg), colchicine (10 microg/rat) and trimethylcolchicinic acid (100 microg/rat) were administered daily, by gavage, after 3 months of CCl(4) administration. Collagen content was determined by measuring hydroxyproline in liver samples; glycogen, was determined utilizing the anthrone reagent; Mallory's trichromic stains of liver sections were performed. The best scheme of treatment was obtained when CCl(4) was administered during three months (collagen increased 6 times). Discontinuation of the toxin for two months produced a significant but relative small reduction of fibrosis (collagen was still 4.5 times over control). Colchicine, TMCA, silymarin or silibinin treatment showed no significant fibrolitic effect. This scheme of treatment may be an excellent tool to study the ability of drugs to reverse fibrosis. The hepatoprotective properties of silymarin, silibinin, colchicine and trimethylcolchinic acid may be irrelevant to reverse established cirrhosis.

Dose-dependent liver regeneration in chloroform, trichloroethylene and allyl alcohol ternary mixture hepatotoxicity in rats

The present study was designed to examine the hypothesis that liver tissue repair induced after exposure to chloroform (CF) + trichloroethylene (TCE) + allyl alcohol (AA) ternary mixture (TM) is dose-dependent similar to that elicited by exposure to these compounds individually. Male Sprague Dawley (S-D) rats (250-300 g) were administered with fivefold dose range of CF (74-370 mg/kg, ip), and TCE (250-1250 mg/kg, ip) in corn oil and sevenfold dose range of AA (5-35 mg/kg, ip) in distilled water. Liver injury was assessed by plasma alanine amino transferase (ALT) activity and liver tissue repair was measured by (3) H-thymidine incorporation into hepatonuclear DNA. Blood and liver levels of parent compounds and two major metabolites of TCE [trichloroacetic acid (TCA) and trichloroethanol (TCOH)] were quantified by gas chromatography. Blood and liver CF and AA levels after TM were similar to CF alone or AA alone, respectively. However, the TCE levels in blood and liver were substantially decreased after TM in a dose-dependent fashion compared to TCE alone. Decreased plasma and liver TCE levels were consistent with decreased production of metabolites and elevated urinary excretion of TCE. The antagonistic interaction resulted in lower liver injury than the summation of injury caused by the individual components at all three-dose levels. On the other hand, tissue repair showed a dose-response leading to regression of injury. Although the liver injury was lower and progression was contained by timely tissue repair, 50% mortality occurred only with the high dose combination, which is several fold higher than environmental levels. The mortality could be due to the central nervous system toxicity. These findings suggest that exposure to TM results in lower initial liver injury owing to higher elimination of TCE, and the compensatory liver tissue repair stimulated in a dose-dependent manner mitigates progression of injury after exposure to TM.

Effects of betaine supplementation on hepatic metabolism of sulfur-containing amino acids in mice

BACKGROUND/AIMS

We previously reported that acute betaine treatment induced significant changes in the hepatic glutathione and cysteine levels in mice and rats. The present study was aimed to determine the effects of dietary betaine on the metabolism of sulfur-containing amino acids.

METHODS/RESULTS

Male mice were supplemented with betaine (1%) in drinking water for up to 3 weeks. Changes in hepatic levels of major sulfur amino acid metabolites and products were stabilized after 2 weeks of betaine supplementation. Betaine intake increased methionine, S-adenosylmethionine, and S-adenosylhomocysteine levels significantly, but homocysteine and cystathionine were reduced. Methionine adenosyltransferase activity was elevated to three-fold of control. Cysteine catabolism to taurine was inhibited as evidenced by a decrease in cysteine dioxygenase activity and taurine levels in liver and plasma. Despite the significant changes in the transsulfuration reactions, neither hepatic cysteine nor glutathione was altered. Betaine supplementation decreased the hepatotoxicity induced by chloroform (0.5 ml/kg, ip) significantly.

CONCLUSIONS

Betaine supplementation enhances recycling of homocysteine for the generation of methionine and S-adenosylmethionine while reducing its utilization for the synthesis of cystathionine and cysteine. However, the hepatic levels of cysteine or glutathione are not affected, most probably due to the depression of taurine generation from cysteine.

Biophotonic imaging in HO-1.luc transgenic mice: real-time demonstration of gender-specific chloroform induced renal toxicity

The metabolism of luciferin in mice transgenic for luciferase (luc) produces light that may be detected trans vivo by an intensified CCD camera (biophotonics). Thus, the generation of transgenic promoter-luciferase animals for genes regulated by specific toxic processes, coupled with real-time evaluation of site-specific gene expression may provide novel, non-invasive biomarkers which are predictive of developing toxicity in vivo. As part of a programme to evaluate the potential of biophotonics for predictive toxicology we have conducted a series of studies in HO-1.luc transgenic mice. Male and female animals were treated with chloroform (200 mg/kg, p.o., daily for 5 days) and imaged 2 and 6 h after dosing. During a 2-day washout period, female animals were treated daily with testosterone prior to repeat administration of chloroform for a further 5 days. Comparison of the in vivo response of the luciferase reporter with markers of toxicity measured ex vivo (differential gene expression of adaptive antioxidant response genes, clinical chemistry and microscopic examination) confirms the gender-specific difference in chloroform renal toxicity in HO-1.luc transgenic mice and its reversal following androgenisation of females and correlates with the expression of the endogenous haem oxygenase-1 (HO-1) gene. These studies demonstrate the capacity of biophotonics for real-time site-specific gene expression, which may be predictive of developing toxicity.

Oxidative DNA damage from potassium bromate exposure in Long-Evans rats is not enhanced by a mixture of drinking water disinfection by-products

Public drinking water treated with chemical disinfectants contains a complex mixture of disinfection by-products (DBPs) for which the relative toxicity of the mixtures needs to be characterized to accurately assess risk. Potassium bromate (KBrO(3)) is a by-product from ozonation of high-bromide surface water for production of drinking water and is a rodent carcinogen that produces thyroid, mesothelial, and renal tumors. The proposed mechanism of KBrO(3) renal carcinogenesis involves the formation of 8-oxoguanine (8-oxoG), a promutagenic base lesion in DNA typically removed through base excision repair (BER). In this study, male Long-Evans rats were exposed via drinking water to carcinogenic concentrations of KBrO(3) (0.4 g/L), 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (0.07 g/L), chloroform (1.8 g/L), bromodichloromethane (0.7 g/L), or a mixture of all these chemicals at the same concentrations for 3 weeks. Half of one kidney was processed for microscopic examination, and the remaining kidney was frozen for isolation of genomic DNA. Levels of 8-oxoG were measured using HPLC with electrochemical detection in DNA samples incubated with formamidopyrimidine-DNA glycosylase. Aldehydic lesions (e.g. abasic sites) in DNA samples were quantitated using an aldehyde-reactive probe slot-blot assay. Treatment with KBrO(3) produced a measurable increase of 8-oxoG in the kidney, and this effect was greater than that produced by treatment with the DBP mixture. No other single chemical treatment caused measurable increases of 8-oxoG. The mixture effect on the amount of 8-oxoG observed in this study suggests an interaction between chemicals that reduced the generation of oxidative DNA damage. No increases in abasic sites were observed with treatment, but a decrease was apparent in the rats treated with the DBP mixture. These data are consistent with previous studies where chronic exposure to this chemical mixture in drinking water resulted in a less than additive carcinogenic response in Tsc2 mutant Long-Evans rats.

Chlorination disinfection by-products and pancreatic cancer risk

Chlorination disinfection by-products (CDBPs) are produced during the treatment of water with chlorine to remove bacterial contamination. CDBPs have been associated with an increased risk of bladder cancer. There is also some evidence that they may increase the risk of pancreatic cancer. We report results from a population-based case-control study of 486 incident cases of pancreatic cancer and 3,596 age- and sex-matched controls. Exposure to chlorination by-products was estimated by linking lifetime residential histories to two different databases containing information on CDBP levels in municipal water supplies. Logistic regression analysis found no evidence of increased pancreatic cancer risk at higher CDBP concentrations (all odds ratios < 1.3). Null findings were also obtained assuming a latency period for pancreatic cancer induction of 3, 8, or 13 years.

Cytotoxicity evaluation of gutta-percha solvents: Chloroform and GP-Solvent (limonene)

OBJECTIVE

The purpose of this study was to compare the cytotoxicity of 2 gutta-percha solvents, chloroform and GP-Solvent, on cell line L929.

STUDY DESIGN

2 gutta-percha solvents were diluted into the concentrations of 1:100, 1:400, and 1:800. The experiment was done in a 96-well tissue-culture plate. Cell viability of L929 was determined after each gutta-percha solvent was left in contact with MTT solution for 3 hours.

RESULTS

Both solvents proved toxic at the same levels of concentrations of 1:100 and 1:400 (P>.05). At the dilution of 1:800 the GP-Solvent seems to be more toxic than the chloroform (P < .05).

CONCLUSIONS

Within the limitation of this experiment, GP-Solvent was not less cytotoxic than chloroform to the target cells. Because in clinical procedures we use a higher concentration of solvent to dissolve gutta-percha for retreatment than that used in this study, the overflowing of liquefied gutta-percha, or solvent out of apical foramen, should be a cause for concern.

Reduced mitochondrial membrane potential and metabolism correspond to acute chloroform toxicity ofin vitro hepatocytes

Chloroform is a non-genotoxic compound that is present in drinking water and ambient air as a result of water chlorination but whose carcinogenic mechanism in humans is unknown. Chloroform targets the liver in humans, where cytochrome P-450-dependent biotransformation to phosgene results in mitochondrial damage and cell death. The purpose of this study is to investigate the relationship between cell death, loss of mitochondrial membrane potential (MMP) and reduction of metabolic rates for in vitro cultured mouse hepatocytes after acute exposure to two doses of chloroform. Immediately following a 2-h exposure, culture viabilities were 70% and 54% for concentrations of 7.0 and 8.8 mM, respectively, in contrast with 90.0% for controls. Interestingly, the viabilities of these cultures decreased further, to 6% and 12%, respectively, over the next 24-h period despite being placed in fresh, chloroform-free medium. Measurement of MMP for viable cells at the end of the exposure revealed a decrease in Rhodamine 123 uptake, which indicates a loss of MMP. Additionally, glucose consumption and lactate production rates were reduced during the 6-h period following the exposure. These results support the hypothesis that a subpopulation of cells at the end of an acute exposure may be activated for apoptosis, suggesting a role for apoptosis markers during risk assessment for chloroform.

Comparative Study of Different Silymarin Formulations: Formulation, Characterisation and In Vitro / In Vivo Evaluation

The aim of the present study was to study the synergistic hepatoprotective effect of silymarin with phospholipids when it is encaged in microspheres so as to passively target it to liver and to compare these silymarin formulations with silymarin solution. Various silymarin loaded lipid emulsions were formulated which include formulation A prepared with soyabean oil as an internal oily phase, soya lecithin as surfactant and tween 80 as cosurfactant; formulation B which was same as formulation A but was filtered through 0.45 micro membrane filter and finally steam sterilized for intravenous administration; formulation C containing soyabean oil as an internal oily phase, soya lecithin as surfactant, tween 80 and propylene glycol as cosurfactant/ cosolvent. These formulations were compared for their release profile with silymarin solution in propylene glycol, i.e. formulation D. In vivo evaluation was carried out using three models i.e. phenobarbitone induced sleep time in mice, biochemical estimation of SGOT and SGPT enzyme levels and histopathological examination of rat livers. Results revealed that there was significant reduction in sleep time in the mice treated with silymarin loaded lipid microspheres (both p.o. as well as i.v.) when compared with control and even with plain lipid microspheres and silymarin solution and significant reduction in enzyme levels in silymarin lipid microspheres treated group when compared with control, plain lipid microspheres as well as silymarin solution treated group. Histopathological studies also supported the results obtained from the other two models. A positive outcome of these studies gave an insight that if silymarin is coupled with phospholipid in such microparticulate delivery systems, hepatoprotective effect of drug molecules can be pronounced further by self targeting nature and synergistic action.

Bioactivation, toxicokinetics and acute effects of chloroform in Fisher 344 and Osborne Mendel male rats

Chloroform has been regarded as a renal carcinogen, based on results obtained with Osborne Mendel (OM) rats. Fisher 344 (F344) rats, considered representative of OM rats on the basis of comparable acute toxic effects, have been used in most of the studies aimed to elucidate the mechanisms of kidney tumour induction. In the present work, in vitro and in vivo chloroform bioactivation in the liver and kidney of F344 and OM rats has been reported, as well as additional toxicokinetics and acute toxicity information. Complete similarity of chloroform metabolism and toxicokinetics was evidenced in the two rat strains. Chloroform metabolism was fully saturated at the OM rat bioassay doses (90-180 mg kg(-1) body wt.), working at a maximal rate of 40-50 micro mol (14)CO(2) expired kg(-1) h(-1). No acute hepatotoxicity, nephrotoxicity or consequent cell proliferation was evidenced at 180 mg kg(-1) body wt. chloroform. In the rat liver, phosgene was confirmed as the major metabolite. Renal microsomes from both F344 and OM rats in vitro were unable to produce any oxidative metabolite; at variance, adducts due to oxidative and reductive metabolites were detected in vivo. Our results indicated the presence in the rat kidney of electrophilic metabolites other than phosgene, representing either oxidative metabolites formed elsewhere and sufficiently stable to be transported to the kidney or electrophilic metabolites secondary to the formation of reductive radicals. Therefore, the rat kidney represents a suitable model to study the toxicological effects, including genotoxicity, of chloroform metabolites in the absence of cytotoxic effects produced by phosgene formed in situ.

The effects of in utero and lactational exposure to chloroform on postnatal growth and glucose tolerance in male Wistar rats

Water chlorination results in the formation of trihalomethanes (THMs) including chloroform. In human stud-ies, fetal growth restriction has been associated with exposure to THMs during pregnancy and impaired fetal growth has been associated with an increased risk of type 2 diabetes. Therefore, the objective of this study was to determine the effect of in utero and lactational exposure to chloroform on birthweight and postnatal indicators of type 2 diabetes. Female Wistar rats were given chloroform (0 microg/L, 75 microg/L) in their drinking water for 2 wk prior to mating until parturition (in utero exposure only) or until weaning (in utero+lactational exposure). At postnatal d 1 (PND1) pups of dams exposed to chloroform had significantly higher serum glucose levels and lower insulin levels, but this effect was not due to b<FONT "Optima">-cell depletion in the neonatal pancreas. Glucose homeostasis in response to a glucose challenge was not changed by chloroform treatment. Chloroform exposure did not affect birthweight; however, offspring of dams exposed to chloroform had significantly impaired postnatal growth. Although fetal and neonatal exposure to chloroform did not elicit physiological changes associated with the onset of type 2 diabetes, there were physiological changes resulting in impaired postnatal growth.

[The influence of halogenorganic compounds on radiation induced damage of rat eye lens components]

In experiments with white rats the damages of eye lens components of the animals are investigated under combined action of halogenorganic compounds (chloroform and sodium trichloroacetate) and radiation (137Cs) in vivo. It was shown that the injection of these compounds into animals amplifies the radiation-induced oxidation of eye lens components. The effect is manifested in the increase in the content of chromophors with fluorescence in the visible range and products of lipid peroxidation, the decrease in the amount of reduced glutathione. The data support the increased risk of development of radiation-induced cataract in the conditions of tehnogenic pollution of the environment.

Liver necrosis and fulminant hepatic failure in rats: protection by oxyanionic form of tungsten

The hepatic lesion produced as a result of oxidative stress is of wide occurrence. In the present study, the effect of tungsten on liver necrosis and fulminant hepatic failure (FHF) has been studied in rats treated with various compounds known to produce oxidative stress. Supplementation of animals with sodium tungstate for 7 weeks before the induction of liver injury by chemicals including thioacetamide (TAA), carbon tetrachloride (CCl(4)), or chloroform (CHCl(3)) could protect progression of hepatic injury. Various biochemical changes associated with liver damage and oxidative stress were measured. Hepatic malondialdehyde content, endogenous tripeptide, and reduced glutathione were measured as oxidative stress markers. The activity of xanthine oxidase, which generates reactive oxygen species (ROS) as a by-product, was also determined and found to be perturbed. Tungsten supplementation to rats caused a significant decrease in lipid peroxidation and lowered the levels of the biochemical markers of hepatic lesions produced by TAA, CCl(4) (CCl(4)), or CHCl(3). Tungsten could also cause an increase in the survival rate in rats receiving lethal doses of TAA, CCl(4), or CHCl(3). The protective effect of tungsten, however, is suggested to be limited to the conditions where the hepatic lesion is reported to be due to the generation of ROS. The progression of liver injury produced by the compounds causing oxidative stress without initiating the generation of free radicals such as bromobenzene (BB), or acetaminophen (AAP), could not be inhibited by tungsten. The possible mechanism explaining the role of oxyanionic form of tungsten in free radical-induced hepatic lesions is discussed.

The short, tragic life of Robert M. Glover

Robert Mortimer Glover (1815-1859) was a contemporary of John Snow and James Young Simpson. Although he did not reach the standing of those two giants, his researches, writings and lectures were important contributions to the early development of British anaesthesia. Glover was the first to explore the physiological action of chloroform in the laboratory and to discover its anaesthetic effect in 1842. He helped Sir John Fife in Hannah Greener's autopsy in January 1848 and influenced Fife's conclusions on the cause of the young girl's death. His numerous and extensive articles reviewing the history, chemistry, pharmacology and clinical applications of various anaesthetics were widely read and quoted by his colleagues, including John Snow. While in Edinburgh and Newcastle, Glover was recognised as a remarkably astute physician, original researcher, prolific writer and enthusiastic lecturer with an enormous knowledge of medicine, the physical sciences, mathematics and philosophy. His brilliant career deteriorated after his arrival in London and, especially, after his return from the Crimea, although he continued to publish until the week before his death. The causes of his decline remain obscure. The last year of his life was ruined by his addiction to chloroform, to whose development he had contributed so much, and which killed him at the early age of 43.

Residual toxicity after biodegradation: interactions among benzene, toluene, and chloroform

A microbial enrichment originating from a pristine aquifer was found to aerobically biodegrade benzene and toluene, but not chloroform. This enrichment culture was used to study changes in pollutant toxicity as affected by biodegradative activity. Two assays for toxicity were used: (1) a 48-h acute toxicity test using the freshwater invertebrate Ceriodaphnia dubia and (2) microbial biodegradation activity as affected by the presence of mixed pollutants. At 20-ppm concentrations, toluene was significantly more toxic (99% mortality) to C. dubia than benzene (48% mortality) or chloroform (40% mortality). Also at 20-ppm concentrations, but before biodegradation, toluene was significantly more toxic (88% mortality) to C. dubia than benzene (33% mortality). After biodegradation of 98% of toluene and benzene, significant residual toxicity still remained in the bacterial supernatant: toluene-degraded supernatant caused 33% mortality in C. dubia and benzene-degraded supernatant caused 24% mortality. In the second toxicity assay, examining the effect of mixed pollutants on biodegradation activity, the presence of benzene slowed the biodegradation of toluene, but chloroform had no effect on either benzene or toluene biodegradation. Results indicate that significant toxicity remain after biodegradation and that halogenated aliphatic hydrocarbons may have little or no effect on aromatic hydrocarbon biodegradation at sites impacted by mixed pollutants.

Changes in cecal microbial metabolism of rats induced by individual and a mixture of drinking water disinfection by-products

Disinfection of drinking water has been one of the greatest public health successes. Numerous halogenated disinfection by-products (DBPs) occur and chronic ingestion has been associated with an increased risk for colorectal cancer in human populations. Because the intestinal microbiota can bioactivate xenobiotics, studies have been performed to examine the effects of individual DBPs on intestinal microbial metabolism. No studies have been conducted on a defined mixture of DBPs to determine if there is an enhancement of response to a mixture. Ten-week-old male Long-Evans rats were treated in their drinking water for 17 weeks with 0.4 g/l potassium bromate, 1.8 g/l chloroform, 0.7 g/l bromodichloromethane (BDCM), 0.07 g/l 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX), or a mixture of the four chemicals or distilled water. Cecal nitroreductase (NR), azoreductase (AR), dechlorinase (DC), beta-glucuronidase (GLR), beta-galactosidase (GAL), and beta-glucosidase (GLU) were assayed. No change in GLU or GLR activity was detected after treatment. BDCM treatment reduced DC and GAL activities and elevated NR and AR activity. GAL, AR, and NR activities were significantly different after treatment with bromate, chloroform, BDCM, and MX, but not the mixture. DC activity after chloroform-, MX-, or BDCM-treatment was significantly below control levels. The present study shows that changes in intestinal microbial metabolism do occur after treatment with individual and a mixture of DBPs but the changes were not additive in the mixture group.