The presence of toxic substances in the workplace environment requires systematic evaluation of exposure and health status in exposed subjects. Cadmium is a highly toxic element found in water. Although free mediated cellular damage and reactive oxygen species (ROS), had been theorized as contributing to the cadmium mechanism of toxicity, and recent investigations have established that free radicals may be important contributors to cardiac dysfunction, there is little information on the effect of cadmium exposure on markers of oxidative stress in cardiac tissue. Cadmium exposure (Cd 2+ - 100 mg/l - from CdCl 2 ) in drinking water, during 15 days, significantly increased lipoperoxide and decreased the activities of superoxide dismutase and glutathione peroxidase. No alterations were observed in catalase activity in heart of rats with cadmium exposure. We also observed decreased glycogen and glucose concentration and increased total lipid content in cardiac tissue of rats with cadmium exposure. The decreased activities of alanine transaminase and aspartate transaminase reflected decreased metabolic protein degradation, and increased lactate dehydrogenase activity was related with increases in capacity of glycolysis. Since the metabolic pathways were altered by cadmium exposure, we can conclude that Cd 2+ exposure induced ROS and initiate some series of events that occur in the heart and resulted in metabolic pathways alterations.
5-Vinyl-2-norbornene (VNB: CAS Number 3048-64-4) is an industrial chemical with a potential for exposure to the vapor. To determine any hazards from repeated exposure to the vapor a subchronic exposure study was conducted in which male and female Sprague Dawley rats were exposed to VNB vapor for 6 hours per day, 5 days per week for 14 weeks at mean concentrations of 0, 5, 25.5, and 152 ppm. Subgroups at 0 and 152 ppm were kept for a 4-week post-exposure recovery period. This study was preceeded by a 9-day repeated vapor study in which male and female rats were exposed to mean concentrations of 50, 147, and 352 ppm. In both the 9-day and subchronic studies there were no significant exposure-related effects with respect to signs, mortality, body weights, serum chemistry, or urinalysis. The only hematological effect was an increase in the mean corpuscular volume and mean corpuscular hemoglobin in male rats of the 147 and 352 ppm groups. There were exposure-related increases in liver weights with the 9-day study, but no evidence for liver pathology based on serum chemistry and histology. Liver weights were also increased for males of the 152 ppm group in the subchronic study. Kidney weights were increased in an exposure concentration-related manner for the males of the 9-day study, and for 152 ppm males of the subchronic study. The only histopathological finding was proximal renal tubular hyaline droplet nephropathy in male rats. In the 9-day study, this was present in an exposure concentration-related manner.At 150 and 350 ppm this resulted in scattered areas of proximal tubular necrosis, but there was no serum chemistry or urinalysis evidence for renal dysfunction. At the end of the subchronic exposure period, minimal to mild hyaline droplet nephropathy was seen at 25.5 and 152 ppm, but not at 5 ppm, in the male rats. At the end of the 4-week recovery period, no hyaline droplet nephropathy was seen at any exposure concentration. An association of the nephropathy with f 2u -globulin was demonstrated for male rats of the 9-day study.
The role of superoxide dismutase (SOD) in the survival of diazotrophic bacteria exemplified by Azotobacter vinelandii in the disposition of crude oil-contaminated environment was investigated. The extent of survival, ranging between 57-64% relative to control, was based on colony-forming units of Azotobacter inocula taken from media contaminated with crude oil (0.5-1.5%, w/v), after plating on nutrient agar. The specific activity of superoxide dismutase in the crude protein extracts from cells harvested from oil-contaminated medium and Fenton reagent-containing mediumin creased by 1.25 and 1.28-fold,respectively, relative to control. These results suggest an induction in SOD enzyme protein as a defense mechanism to protect the exposed bacterial cells from the free radicals/reactive oxygen species generated during the oxidation (co-metabolism) of the petroleum hydrocarbons. Keywords: Azotobacter Vinelandii Contaminated Environment Crude Oil Superoxide Dismutase
(2000). SUPPLEMENTARY EFFECT OF a-TOCOPHEROL SUCCINATE (VITAMIN E) ON SODIUM ARSENITE-INDUCED OVARIAN STEROIDOGENIC FUNCTION AND PLASMA LEVELS OF GONADOTROPHINS IN MATURE ALBINO RATS. Toxic Substance Mechanisms: Vol. 19, No. 3, pp. 137-150.
(2000). AN ASSESSMENT OF IN VIVO ESTROGENIC ACTIVITY OF BUTYL BENZYL PHTHALATE AND ITS PRINCIPAL MAMMALIAN METABOLITES. Toxic Substance Mechanisms: Vol. 19, No. 1, pp. 1-24.
Previously, we reported that the antiandrogen cyproterone acetate (CA) modifies cadmium (Cd) distribution and metallothionein (MT) induction in mice given a non-toxic dose of Cd (10 w mol Cd/kg, sc). We have also observed that CA pretreatment will reduce Cd toxicity in in vitro systems. Thus, since the liver is a primary target of acute Cd toxicity, the effects of CA pretreatment on the acute hepatotoxicity of Cd in vivo were studied in male C57 mice. Mice were pretreated with CA (10 mg/kg, sc, at - 48, - 24, and 0 h) prior to Cd (35 or 45 w mol Cd/kg, at 0 h). Cd alone (35 or 45 w mol Cd/kg) induced significant increases in serum alanine aminotransferase (ALT) activity, indicative of hepatotoxicity, 24 h after injection. However, CA pretreatment either prevented (at 35 w mol Cd/kg) or significantly reduced (at 45 w mol Cd/kg) Cd-induced increases in serum ALT. Based on serum creatinine levels, Cd alone was not acutely nephrotoxic. Thus, CA pretreatment substantially reduced the hepatotoxic effects of Cd. CA pretreatment had no effect on hepatic Cd levels 24 h after Cd exposure. The hepatic levels of zinc, a metal known to antagonize Cd toxicity, were modestly altered by CA pretreatment, but not in a consistent fashion. Cd alone markedly increased hepatic MT, a metal-binding protein often associated with tolerance to Cd, 24 h after exposure. CA pretreatment alone did not alter hepatic MT levels and pretreatment with CA before Cd did not alter hepatic levels of MT compared to Cd alone 24 h after injection of the metal. To further examine the tolerance to Cd induced by CA, the effects of CA pretreatment on hepatic Cd levels at early stages were investigated. Hepatic Cd levels were significantly decreased by CA pretreatment 8 h after Cd treatment and returned to control levels by 16 h. These results indicate that CA can substantially reduce the hepatotoxic effects of Cd in C57 mice without activating MT synthesis. The early decreases in liver Cd content may be critical to decreasing the adverse effect of Cd in the liver. Thus, it appears CA induces tolerance to Cd through altered biokinetics and in a manner not involving the MT system.
Although liver diseases such as cholestasis are a significant clinical problem, the cellular mechanisms disturbed during these pathophysiological processes are still controversial. Progress along several lines of research have revealed several possible lines of action, pointing to new approaches to medical treatment. Impairment of mitochondrial function seems to be a central biochemical pathway of cell dysfunction during disease. Additionally, perturbation of other cellular functions could play a pivotal role in triggering these pathological events. Our review provides an overview of probable events involved in the cholestatic disease process.
The acute hemodynamic effects of organophosphate (OP) intoxication include positive chronotropic and inotropic changes along with increases in intraventricular pressure and coronary blood flow. These observations are consistent with an enhanced sympathetic tone that correlates neurogenic cardiomyopathy to adrenergic overactivity and subsequent, focal catecholamine (CA) release and cellular oxidative stress. Several mechanisms have been proposed to explain the cardiotoxicity associated with elevated CA concentrations. However, it is suggested that the oxidative metabolites of CA's, rather than (or in addition to) the parent CA's per se, may initiate or be in part responsible for the cardiotoxicity. The chromatographic profile of adrenochrome (1) and adrenolutin (2) (Figure 1) are described in this study in an isocratic, reverse phase HPLC method using UV/VIS and electrochemical (EC) detection. The aqueous adrenochrome standard shows a retention time of 1.9 minutes under employed conditions. Furthermore, using a flow rate of 0.6 mL/min and a UV/VIS detector set at a wavelength of 490 nm, several chromatographic peaks were detected, indicative of different species after injection of the aqueous adrenolutin standard. A similar multiple peak chromatographic profile was observed with EC detection. We hypothesized from the literature and observed complexity of the chromatogram (i.e. multiple intermediate species of the adrenolutin) that adrenolutin is being autooxidized over time. Based upon EPR spin trapping, we found the generation of a carbon-centered radical at the C-2 position that will interact with oxygen to give an intermediate peroxy radical. This may be eventually transformed to 5,6-dihydroxy-1-methyl-2,3-indoledione. The production of these proposed carbon- and oxygen-centered radicals in the autooxidation of adrenolutin was confirmed by spin trapping experiments using the spin trap, f -phenyl N-tert-butyl nitrone (PBN). When adrenolutin is dissolved in water at neutral pH in the presence of PBN, two different EPR spectra of PBN adducts are obtained. One observed PBN adduct has hyperfine splitting constants (hfsc's) of a N = 1.54 mT, a g H = 0.40 mT, and a n H = 0.13 mT; the other observed PBN adduct H H has the following hfsc's a N = 1.50 mT and a g H = 0.33 mT. The detection of these H reactive intermediates during the continued autooxidation of adrenolutin may account for the biochemical toxicity of catecholamine metabolism. These methods may allow for the quantification and/or characterization of the cardiotoxicity observed after organophosphate (OP) intoxication.
5-Aza-2'-deoxycytidine (d-AZA) causes temporally-related defects in the mouse. At 1.0 mg/kg on gestational day (GD) 10, d-AZA causes hindlimb phocomelia. Sonic hedgehog (Shh) plays a significant role in the normal development of limbs in rodent species. Sonic hedgehog peptides, found in the posterior mesenchyme of limb buds, are involved in patterning functions and in the regulation of both anterior-posterior polarity and proximal-distal outgrowth of the limb. The objective of the present study was to analyze alterations in Shh expression subsequent to d-AZA exposure. Pregnant mice were treated with d-AZA via intraperitonlal injection on GD 10. Controls were untreated. The reverse transcription-polymerase chain reaction (RT-PCR), whole mount in situ hybridization (ISH), and whole mount immunohistochemistry (WMI) were used to analyze expression patterns of Shh . For RT-PCR, embryonic hindlimb buds (buds) were taken 0, 4, 8, 12, or 24 hr after exposure. Cyclophilin was used as the baseline monitor. RNA was transcribed to cDNA and used as template with Shh specific primers for amplification. Whole embryos were collected 12 and 24 hr posttreatment for ISH. An antisense primer specific for Shh was used in an oligo-based ISH protocol. Whole embryos were collected 36 and 48 hr posttreatment for WMI. The antibody corresponding to the amino terminal subunit of the Shh peptide was used. There was a treatment related up-regulation of Shh transcripts by 12 and 24 hr posttreatment. The protein response of up-regulation was detectable by 36 and 48 hr posttreatment. Our data suggest that 5-aza-2'-deoxycytidine-induced hindlimb defects may be associated with alterations in the level of Shh expression. This may be part of a cascade of signaling events involved in d-AZA-induced hindlimb defects. Work is ongoing to determine the relationship of other gene species that may cooperate with Shh in the induction of the hindlimb defects.
The incidence of cardiovascular disease has increased in the general population, and cardiac damage is indicated as one important cause of mortality. In addition, pollution and metal exposure have increased in recent years. For this reason, toxic effects of metals, such as nickel, and the irrelation to cardiac damage should be urgently established. Although free radical-mediated cellular damage and reactive oxygen species have been theorized as contributing to the nickel mechanism of toxicity, recent investigations have established that free radicals may be important contributors to cardiac dysfunction. However,there is little information on the effect of nickel exposure on markers of oxidative stress in cardiac tissue. Nickel exposure (Ni2+ 100 mg L-1 from NiSO4) significantly increased lipoperoxide and total lipid concentrations in cardiac tissue. We also observed increased serum levels of cholesterol(59%), lactate dehydrogenase (LDH-64%), and alanine transaminase (ALT-30%) in study animals. The biochemical parameters recovered to the control values with tocopherol intake (0.2 mg 200 g-1). Vitamin E alone significantly decreased the lipoperoxide concentration and increased superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities in the heart. Since no alterations were observed in catalase and GSH-Px activities by nickel exposure while SOD activities were decreased, we conclude that superoxide radical (O2 -) generated by nickel exposure is of primary importance in the pathogenesis of cardiac damage. Tocopherol, by its antioxidant activity, decreased the toxic effects of nickel exposure on heart of rats.
By means of a sensitive chemiluminescence's method, toxicity of fenofibric acid was demonstrated on respiratory burst of UVA-irradiated peripheral blood polymorphonuclear cells (PMNs). Through this method, it was possible detect such phototoxic effect at a minor concentration of fenofibric acid as compared with those previously reported in photohemolysis test. This effect was not related with losses of cell viability because PMNs did not lose its capabilities for excluding the trypan blue dye, when irradiated in presence of drug. In order to explain the results obtained in presence of scavengers of different reactive oxygen species, it was proposed a singlet oxygen-mediated (type II) mechanism of photosensitization and/or through formation of toxic photoproducts.
The genotoxic potential of 2,4-pentanedione (2,4-PD; CAS No. 123-54-6) was assessed using a battery of in vitro and in vivo tests. In vitro studies showed no mutagenic activity in a Salmonella typhimurium reverse mutation test or in a Chinese Hamster Ovary (CHO) forward gene mutation test (HGPRT locus), either in the absence or in the presence of an Aroclor 1245-induced rat liver S9 metabolic activation system. Increased frequencies of sister chromatid exchanges in cultured CHO cells were observed both in the absence and in the presence of S9 activation. 2,4-PD was highly clastogenic to CHO cells in vitro in the absence, but not in the presence, of S9. 2,4-PD produced significant, doserelated increases in the incidence of micronucleated polychromatic erythrocytes (PCE) in the peripheral blood and bone marrow of Swiss Webster mice after a single intraperitoneal injection. However, there was no significant induction of micronuclei in the bone marrow of Sprague Dawley® rats dosed with 2,4-PD by a single intraperitoneal injection. When rats and mice were exposed to 2,4-PD vapor for 6 hr/day for 5 consecutive days at target concentrations up to 800 ppm, there were no significant exposure-related increases in the incidences of chromosomal aberrations or micronucleated PCE in bone marrow samples taken 24 hr after the 5th day of exposure in either species.
Effects of sublethal and subchronic doses of dimethoate (DM), an organophosphorus pesticide, have been studied on hematological and immunological parameters in mice. The results revealed that DM-treated mice showed significant increase in red blood cells (RBC), white blood cells, percent monocytes, and percent basophils, whereas the percent neutrophils was significantly decreased.The antibody titres were higher on day 4 postantigen(sheep RBC/bovine serum albumin [BSA]) inoculation, but suppressed on day 7 and 11 postantigen inoculation in DM-treated mice. However, the three cell-mediated immune parameters-leukocyte migration inhibition (LMI), leukocyte adherence inhibition (LAI), and nitroblue tetrazolium (NBT) reduction-were invariably depressed in DM-treated BSA-immunized mice, whereas the percent LMI and LAI were lower and NBT was higher in the DM-treated SRBC-immunized mice. Our results show that exposure to DM suppresses humoral and cell-mediated immune response, but its effect on macrophage function varies with the immunizing antigen.
The NADPH- and NADH-dependent reduction of chromium(VI), a known carcinogen, by human hepatic and lung microsomes likely proceeds through cytochrome b 5 as the common mediator of electron transfer to Cr(VI). Consistent with the ability of cytochrome b 5 to transfer one electron at a time, Cr(V) was generated as a transient intermediate during human microsomal Cr(VI) reduction. The redox cycling of small amounts of iron or quinones significantly accelerated the rate of Cr(VI) reduction, which should accelerate Cr(V) formation. However, Cr(V) did not accumulate under these conditions, suggesting that Fe(II) and semiquinones also reduce Cr(V). This could accelerate the formation of Cr(IV), a highly reactive intermediate. An indirect electron paramagnetic resonance (EPR) method suggested that Cr(IV) was produced during microsomal Cr(VI) reduction. Since iron and quinones significantly altered the rates of formation of reactive Cr intermediates, they could potentially influence cytotoxic damage associated with these intermediates.
Tilapia (Oreochromis niloticus) were subacutely exposed to the environmental contaminant 2,3, 7,8-tetrachlorodibenzo-p-dioxin (TCDD) by intraperitoneal injection of 1 or 5 mu g/kg/day for five consecutive days. Cellularity and morphology of the spleen and pronephros were evaluated two days following dosing. Total cell counts in both the spleen and pronephros were significantly reduced by the 5-mu g/kg but not the 1-mu g/kg dose of TCDD. Cellular depletion was evident histologically at the higher dose level, particularly within lymphoid regions of the fish spleen and pronephros. Increased numbers of apoptotic cells were observed in the histologic preparations. Light microscopic analysis of cytospin samples from the pronephros of chemical-treated fish verified the increased incidence of cells displaying features typical of apoptosis (condensed nuclei and cytoplasmic fragmentation). Subsequent flow cytometric evaluation using the DNA-binding dye, 7-aminoactinomycin D (7-AAD) demonstrated a population of apoptotic immune cells in the pronephros of fish dosed with TCDD. Two assays of phagocytic cell activity (metabolic oxidative burst and phagocytosis) did not change with chemical exposure. Leukoproliferative assays (mitogen responses and the mixed lymphocyte response) suggested a limited antiproliferative effect may contribute, with apoptosis, to hypocellularity of hematopoietic centers in TCDD-treated fish.
A pure strain of Azotobacter vinelandii was isolated from soil samples with no known history of contamination by crude oil, mercury, silver or any other heavy metal salts. The isolate was grown to a density of 10 8 cells/ml as the primary culture, in an enriched mineral Azotobacter medium. From this, 90 ml was pipetted into each of 15 conical flasks divided into five sets of three replicates. A set was treated with mercury (II) chloride (2.5 mmol/l), silver chloride (4.6 mmol/l), Bonny light crude oil (1.0%, w/v), or Fenton reagent. A set with normal Azotobacter medium served as the control. The mean total cell protein harvested from the various flasks ranged from 0.503 to0.245 mg/ml within 48 hr of incubation. The differences in the mean total protein concentrations were statistically significant (p < .05). The protein carbonyl contents from the flasks also were significantly different but for the pair of control/Hg2+ -treated media. Lipid peroxidation levels in all the treated media were significantly higher than that of control. Lipid peroxidation and protein oxidation products signaled cell injury or damage, which might comprom ise cell growth/proliferation and biological nitrogen-fixing activity of the micro-organism in the soil.
Small intestinal injury induced by nonsteroidal anti-inflammatory drugs (NSAIDs) has gained increasing attention in the past years. The mechanism underlying NSAID enteropathy has remained elusive but may be different from that in the stomach. Three important factors include the presence of bile or biliary constituents, enterohepatic circulation of NSAIDs, and enteric bacteria. This article summarizes new lines of evidence indicating that acyl glucuronides, which are metabolites of many carboxylic acid NSAIDs, may be causally linked with small intestinal ulceration. Acyl glucuronides are formed in the liver; excreted into the biliary tree by the conjugate export pump, Mrp2; and subsequently delivered to the lower intestine. Acyl glucuronides are chemically reactive and can covalently modify a number of target proteins in the liver biliary tree, and intestine The following article focuses on the positive correlation between the degree by which the small intestine is exposed to NSAID acyl glucuronides and the severity of NSAID enteropathy. It also shows that firm conclusions cannot yet be drawn until the consequences of the protein reactivity of these NSAID acyl glucuronides are more firmly established.
In this study, the interaction of three types of calcium channel blockers-nifedipine, diltiazem, and verapamil-on the effects of lead acetate on two types of pain (nociception and inflammation) induced by formalin in mice were examined. To study nociception, the formalin test was selected because of greater resemblance to clinical pain. Lead acetate (50, 75, 100 125 150 mg/kg) was administered intraperitoneally 90 min before formalin injection. Nifedipine (5 mg/kg), diltiazem (10 mg/kg), and verapamil (5 mg/kg) alone or in combination with different doses of Lead acetate were used. Lead acetate induced a dose-dependent antinociception in both phases of the formalin test. When animals were administered calcium channel blockers alone, diltiazem and verapamil did not induce any significant effect in either phase of the formalin test, but nifedipine induced anti-inflammatory effects in the late phase (p <.01). Pretreatment with nifedipine or diltiazem potentiated the bead acetate antinociceptive effect (early phase) in doses of 50 and 75 mg/kg and 50 mg/kg, respectively. Both nifedipine and diltiazem augmented bead acetate anti-inflammatory effects (late phase) in all doses used. Pretreatment of animals with verapamil did not affect lead acetate antinociceptive or anti-inflammatory effects. Based on these data, the association between calcium channel blockers and lead acetate may be explained as a synergistic action rather than a simple dose combination of both agents. It is concluded that L-type calcium channels may be blocked during lead acetate poisoning, but different L-type calcium channel subtypes have different sensitivities to lead neurotoxicity.
Structural changes of rat submandibular glands (SMG) after long-term treatment with various doses of lead (0.01%, 0.04%, 0.05%) were investigated in this study. After termination of treatment, SMGs were removed and homogenized for measurement of total protein, DNA, calcium, and lead concentrations. Also ultrastructural examination of glands by electron, microscopy was carried out. Total protein, DNA, and intracellular calcium concentrations of treated glands at 0.04% and 0.05% lead concentrations showed significant reduction when compared with those of controls. Data of lead measurement, as determined by atomic absorption spectroscopy, showed that lead treatment resulted in accumulation of lead in rats' SMGs. Lead treatment also caused degenerative changes in the cells. Dilation of rough endoplasmic reticulum (RER) and swollen, mitochondria were observed in the (0.05%) treated group. Transformation and enlargement of mitochondria also were determined in the (0.04%) treated group. We propose that Lead treatment can reduce exocytosis processes by the reduction, in energy level of the cell and destruction of RER or mitochondria. Considering properties of lead to substitute for calcium in many intracellular events different types of alterations can result, including interaction with protein and DNA synthesis. To elucidate the exact mechanisms of observed alterations requires further studies.
