Gaston Chevalier

Studies on lipid peroxidation in rat tissues following administration of low and moderate doses of cadmium chloride

The susceptibility to lipid peroxidation (LPO) of liver, kidneys, brains, lungs, heart, and testes was assessed in rats administered intraperitoneally with various doses of cadmium (Cd). Dose-response studies were carried out with male Long Evans rats (12-week-old; 300 +/- 33 g) injected with 25, 125, 500, and 1250 micrograms Cd/kg as CdCl2 and sacrificed after 24 h. In time-response studies, animals were administered with 25 and 500 micrograms Cd/kg as CdCl2 and sacrificed after 2, 6, 12, 24, and 72 h. Exposure of rats to low and moderate doses of Cd by the intraperitoneal route stimulated LPO in all the tissues investigated as assessed by the measurement of thiobarbituric acid reactive substances (TBARS). Lungs and brain were the most responsive, and these tissues and liver displayed early responses following Cd exposure. Comparison of LPO to various tissue indicators (for liver: alanine aminotransferase (ALT), sorbitol dehydrogenase (SDH), alkaline phosphatase (ALP); for lungs: ALP, gamma-glutamyl transpeptidase (GGT] suggested that low doses of Cd stimulated LPO without any evidence of acute damages. These results suggest that LPO is an early and sensitive consequence of Cd exposure as determined in various organs. Investigation of liver, lungs, and heart antioxidant defense system components (glutathione peroxidase (GPX), glutathione reductase (GR), glucose-6-phosphate dehydrogenase (G6PDH), superoxide dismutase (SOD] revealed that GPX might be considered as a potential modulator of the Cd-induced LPO reaction in lungs and heart tissues.

Impaired cortisol stress response in fish from environments polluted by PAHs, PCBs, and mercury

The cortisol stress response to capture was investigated in two species of fish (Perca flavescens and Esox lucius) from sites polluted by high levels of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and mercury, and from reference sites in the St. Lawrence river system. Fish from the reference sites exhibited the normal elevation of serum cortisol in response to the acute stress of capture and had large pituitary corticotropes. In contrast, fish from the most polluted sites were unable to increase their serum cortisol in response to the acute stress of capture and their pituitary corticotropes were atrophied. These results suggest that a life-long exposure to chemical pollutants may lead to an exhaustion of the cortisol-producing endocrine system, possibly as a result of prolonged hyperactivity of the system.

Effects of acute exposure to mercury chloride and methylmercury on plasma cortisol, T3, T4, glucose and liver glycogen in rainbow trout (Oncorhynchus mykiss)

Abstract Juvenile rainbow trout (Oncorhynchus mykiss) were exposed to mercury chloride HgCl2 (28 and 112 μg/l Hg2+), and to methylmercury chloride CH3HgCl (6, 12 and 24 μg/l Hg) for 4, 72 and 168 h to determine the effects of sublethal doses of these compounds on the hypothalamo-pituitary-interrenal and the hypothalamo-pituitary-thyroid axes. Exposure to both mercurial compounds significantly increased plasma cortisol, plasma thyroxine (T4) and plasma glucose levels. Similar trends were observed in plasma triiodothyronine (T3) levels. A decrease in liver glycogen reserves was detected after 1 week of exposure to 6 μg/l CH3HgCl. Our results indicate that both mercurial compounds stimulate the pituitary-interrenal and the pituitary-thyroid axis and modify the carbohydrate metabolism in juvenile rainbow trout, and that the organic mercury CH3Hg+ is a more potent chemical stressor than the inorganic Hg2+.

Relation between lipid peroxidation and inflammation in the pulmonary toxicity of cadmium

Lipid peroxidation (LPO), measured as thiobarbituric acid reactive substances (TBARS), was evaluated in lungs of rats 24 h after intraperitoneal injection of 50, 250, and 1000 μg Cd/kg body weight as CdCl2. In order to gain some insight into possible causative factors responsible for these oxidative phenomena, the redox-active elements iron (Fe) and copper (Cu), and total lung protein content (an indication of pulmonary inflammatory processes) were also measured. Results obtained demonstrate a similar dose-related, non-linear evolution of total lung TBARS and total lung protein as a function of increasing lung Cd concentrations. Standardization of total lung TBARS to lung protein content further resulted in a linear relationship with lung Cd concentrations, thus suggesting a possible cause-effect relationship between these parameters. No statistically significant association was observed between the dose-related evolution of lung TBARS, and iron (Fe) and copper (Cu) after Cd exposure. The results obtained provide support for the possible involvement of inflammatory phenomena as the most likely events responsible for the generation of LPO in lung tissue following acute exposure to Cd salts.

Inability of chrysotile asbestos fibers to modulate the 2-acetylaminofluorene-induced UDS in primary cultures of rat hepatocytes☆

There is now growing evidence that asbestos fibers could act in association with genotoxic compounds, either as cocarcinogens or promoters, in the process of carcinogenesis. The hepatocyte/UDS assay system has been taken to advantage to investigate the capacity of fibers to modulate the effects of genotoxic compounds on the cell, as we previously demonstrated the hepatocytes can engage in phagocytosis of chrysotile fibers. Measurement of UDS was performed by a biochemical procedure involving liquid scintillation counting (LSC) of a purified DNA fraction as well as by radioautography. Both LSC and radioautography revealed that chrysotile asbestos fibers UICC B at concentrations up to 100 micrograms/ml do not elicit UDS, whereas 2-acetylaminofluorene (2-AAF) at low concentrations (0.05-0.625 micrograms/ml) significantly induces it in parallel positive controls. In an attempt to test the cocarcinogen hypothesis, cultures of hepatocytes were simultaneously exposed for 20 h to 2-AAF (0.05 and 0.25 micrograms/ml) and asbestos fibers (1 and 10 micrograms/ml) given as simple mixtures. It was found that the 2-AAF-induced UDS activity was the same whether fibers were present or not. This was observed with both UDS evaluation procedures at all concentration combinations selected. An analysis of variance applied to the data collected from several experiments confirmed that there was no significant 2-AAF-fiber interaction. Our data suggest the absence of intrinsic genotoxic properties for chrysotile fibers. They also indicate that the modulation of the cellular response to genotoxic agents by asbestos fibers is not detected under our test conditions and may require longer-term exposures to be expressed.

Ultrastructural changes in the caudal neurosecretory cells of the trout Salvelinus fontinalis in relation to external salinity

Ultrastructural changes in the caudal neurosecretory cells of the teleost Salvelinus fontinalis were studied when fishes were exposed to fresh water, deionized water, and seawater. In freshwater-adapted fishes, most cells presented a pattern of reduced synthetic activity of proteinaceous secretory material. The rough endoplasmic reticulum and the Golgi complex were moderately elaborated whereas secretory material was rare in the cell bodies. The nucleus appeared slightly irregular, with masses of heterochromatin. Exposure to deionized water for 3 days led to doubling of the mean size of the cell perikarya. The formation of neurosecretory material was strikingly stimulated. The rough endoplasmic reticulum was highly developed, and the Golgi complex showed intense vesiculation of elementary secretory granules which were abundant in the cells. Numerous and large globules of secretory material were observed in the cytoplasm. Also, the enlarged nucleus was lobulated and contained homogeneous euchromatin. After a 7- or 10-day exposure, no sign of activation of cell secretory activity was found. Transfer from fresh water to 25% seawater for 1 day enhanced synthetic activity in certain caudal neurosecretory cells but the majority remained inactive. Progressive exposure to 100% seawater was accompanied by a decreased level of activity in all cells. These findings appear to provide further evidence for the involvement of the caudal neurosecretory system in osmo- (iono)-regulation in the fish.

Immunotoxicity of aminocarb. III. Exposure route-dependent immunomodulation by aminocarb in mice

Aminocarb, a phenylsubstituted methylcarbamate pesticide (4-dimethylamino-3-methyl-N-carbamate; matacil), previously suspected of a relatively low immunotoxic potential, was administered by four different exposure routes to C57BL/6 mice. A single sublethal exposure by oral and dermal routes stimulated humoral immune response at a relatively low dose; 1/256 LD50 of aminocarb. Intraperitoneal (i.p.) injection decreased the humoral PFC response, whereas inhalation of aminocarb had no marked effect on peripheral immune status in exposed animals. Thus, i.p. exposure resulted in higher immunotoxicity over oral administration of aminocarb. Similarly, marked route-related exposure differences in immunomodulatory effects of aminocarb were noted for mitogenic stimulation of spleen lymphocytes and mixed lymphocyte response. Other indices, such as delayed type hypersensitivity (DTH) and production of interleukin-2 (IL-2) were unchanged. Interestingly, expression of major histocompatibility complex (MHC) class II by purified, lipopolysaccharide (LPS)-stimulated B cells increased equally after i.p. and oral exposures to aminocarb. Overall, a weak immunosuppressive potential of aminocarb was concluded, which was possibly due to indirect interaction of the pesticide with the immune system. However, aminocarb may represent an autoimmunity-inducing toxic.

Monoaminergic innervation of the caudal neurosecretory system of the brook trout Salvelinus fontinalis in relation to osmotic stimulation

Abstract The distribution of monoamine fluorescence reaction (Falck and Hillarp technique) was investigated in the posterior spinal cord of the brook trout, Salvelinus fontinalis , in relation with the caudal neurosecretory system. A semiquantitative analysis of fluorescence was made following variations of external salinity, injections of salt solutions, and drugs aimed at modifying hydromineral balance. Under all experimental conditions, an extensive network of beaded fibers innervate a number of caudal neurosecretory cells whereas some others do not appear to be contacted by fluorescent varicosities. Three types of aminergic cells different from nonfluorescent caudal neurosecretory neurons were observed in the posterior spinal cord: (i) green fluorescent CSF-contacting neurons interspersed between ordinary ependymal cells; (ii) small perikarya with discrete spots of intense yellow fluorescence; (iii) small somata with diffuse green fluorescence. No fluorescence was observed in neurohemal region or urophysis. The action of nialamide and reserpine indicated that histofluorescent reaction was due to monoamines. In comparison to freshwater exposure to demineralized water for 3 days, but not 7 days, increased markedly the fluorescence of beaded fibers and varicosities contiguous to caudal neurosecretory cells while transfer to seawater for 1 and 7 days reduced them significantly. Injections of isotonic NaCl, hypertonic Na 2 SO 4 , and hypertonic choline chloride in freshwater fish, were less effective in producing fluorescence changes; however, these treatments showed a common tendency to enhance frequency of caudal neurosecretory cells with abutting varicosities in the most anterior part of the population. Acetazolamide and aldactone treatments also induced significant variations of aminergic innervations. These findings indicate a monoaminergic participation in the control of the function of caudal neurosecretory cells in relation to iono- and osmoregulation.

Toxicity of inhaled cadmium chloride: Early responses of the antioxidant and surfactant systems in rat lungs

In order to establish an animal model for assessing early and sensitive biochemical indicators of pulmonary damage, we studied the effects of inhaled CdCl2 (5 mg/m3.h; mass median aerodynamic diameter (MMAD) = 1.4 microns; SDg = 1.8) on the antioxidant defense and pulmonary surfactant systems of rat lungs. Rats were sacrificed 1, 4, 8, and 16 d after inhalation. Pulmonary edema (wet/dry weight) was observed on d 1. The total activities of the enzymes superoxide dismutase (SOD) and glucose-6-phosphate dehydrogenase (G6PD) in the lung homogenates of the treated animals were significantly throughout the 16-d period. Glutathione reductase (GR) was increased on d 4 and after. The general increases of SOD, GR, and the lysosomal enzymes acid phosphatase and beta-N-acetylglucosaminidase could be attributed to changes in the cellularity of the lung tissue. The significant increase in the specific activity of G6PD on d 4 suggested enzyme stimulation. Concurrently, the response of the surfactant system was measured by assaying the alkaline phosphatase (AKP) and the phospholipid content in the homogenates and in the cell-free bronchoalveolar lavage (BAL) fluids. The AKP activity in the homogenates decreased by 30%, while no activity was detected in the BAL on d 1, suggesting an inhibition of AKP by Cd. The secretion of surfactant seemed altered at this early time: phospholipid in the BAL decreased by 44%, although it increased by 61% in the tissue. The high recovery of phospholipid (312%) in the BAL on d 4 and the important changes in the AKP activity in the BAL from d 4 to 16 may reflect alterations in the processing of the surfactant. The effect of Cd on AKP makes this enzyme a potential marker of the metal redistribution in the pulmonary alveolar region, which could be a useful tool in long-term studies.

Absence of genotoxic effects of nonasbestos mineral fibers

The biological activity of natural and synthetic mineral fibers has been examined. Natural attapulgite [(Mg, Al)2Si4O10(OH).4H20], synthetic xonotlite [Ca3Si3O8(OH)2] and natural sepiolite [Mg2Si3O8.2H2O] were selected. Genotoxic effects were investigated by means of a well established cellular model based upon the measurement of unscheduled DNA synthesis (UDS) in rat hepatocytes in primary culture. The intrinsic capacity of the fibers (1 and 10 µ/ml) to induce UDS was first tested. None of the fiber types showed detectable UDS-eliciting activity. Also, the possible modulation of the cellular response to genotoxic agents by the materials was examined by exposing the cells to mixtures of 2-acetylaminofluorene (AAF) (0.05 and 0.25 µg/ml) and fibers (1 and 10 µg/ml). In these experiments, the UDS response was significantly diminished in the presence of xonotlite. This phenomenon may reflect changes in the uptake and/or metabolism of AAF or may result from an inhibition of DNA repair processes, the latter suggesting a possible cocarcinogenic potential for this synthetic silicate. These results point to the immediate necessity of studying more extensively the biological effects of fibrous materials that can be used as substitutes for asbestos.