Poisons and fever

Aerosol characterization and pulmonary responses in rats after short-term inhalation of fumes generated during resistance spot welding of galvanized steel

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An automated welder was designed to expose animals to galvanized spot welding fume.

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Generated particles generally were in the submicron and ultrafine size ranges.

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The primary metals present in galvanized spot welding fumes were iron and zinc.

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Zinc appeared to be the causative agent in the development of acute lung inflammation.

Resistance spot welding is a common process to join metals in the automotive industry. Adhesives are often used as sealers to seams of metals that are joined. Anti-spatter compounds sometimes are sprayed onto metals to be welded to improve the weldability. Spot welding produces complex aerosols composed of metal and volatile compounds (VOCs) which can cause lung disease in workers. Male Sprague-Dawley rats (n = 12/treatment group) were exposed by inhalation to 25 mg/m³ of aerosol for 4 h/day × 8 days during spot welding of galvanized zinc (Zn)-coated steel in the presence or absence of a glue or anti-spatter spray. Controls were exposed to filtered air. Particle size distribution and chemical composition of the generated aerosol were determined. At 1 and 7 days after exposure, bronchoalveolar lavage (BAL) was performed to assess lung toxicity. The generated particles mostly were in the submicron size range with a significant number of nanometer-sized particles formed. The primary metals present in the fumes were Fe (72.5%) and Zn (26.3%). The addition of the anti-spatter spray and glue did affect particle size distribution when spot welding galvanized steel, whereas they had no effect on metal composition. Multiple VOCs (e.g., methyl methacrylate, acetaldehyde, ethanol, acetone, benzene, xylene) were identified when spot welding using either the glue or the anti-spatter spray that were not present when welding alone. Markers of lung injury (BAL lactate dehydrogenase) and inflammation (total BAL cells/neutrophils and cytokines/chemokines) were significantly elevated compared to controls 1 day after exposure to the spot welding fumes. The elevated pulmonary response was transient as lung toxicity mostly returned to control values by 7 days. The VOCs or the concentrations that they were generated during the animal exposures had no measurable effect on the pulmonary responses. Inhalation of galvanized spot welding fumes caused acute lung toxicity most likely due to the short-term exposure of particles that contain Zn.

Fever of Unknown Origin in Childhood

Childhood fever of unknown origin (FUO) is most often related to an underlying infection but can also be associated with a variety of neoplastic, rheumatologic, and inflammatory conditions. Repeated, focused reviews of patient history and physical examination are often helpful in suggesting a likely diagnosis. Diagnostic workup should be staged, usually leaving invasive testing for last. Advances in molecular genetic techniques have increased the importance of these assays in the diagnosis of FUO in children.

Effect of four organophosphorus compounds on human blood acetylcholinesterase: in vitro studies

In the present investigation acetylcholinesterase (AChE) was estimated in erythrocytes from blood samples exposed to four commonly used organophosphorus pesticides in vitro. The aim of the study was to determine the IC50 concentration of the pesticides monocrotophos, chlorpyrifos, profenofos, and acephate as inhibitors of AChE. Cholinesterase was spectrophotometrically measured using acetylthiocholine iodide (AChI) as substrate and dithiobisnitrobenzoic acid (DTNB) as the coloring agent using different aliquots of the pesticides. It was found that as the concentration of the pesticides increased, the inhibition also increased, and a dose-response relationship was obtained in a time-dependent manner. The IC50 values for RBC-AChE were 0.12 muM, 0.25 muM, 0.35 muM, and 4.0 muM for chlorpyrifos, monocrotophos, profenofos, and acephate, respectively. Chlorpyrifos was found to be a more potent inhibitor of AChE followed by the rest of the pesticides used in this study. This investigation determined the relative toxicities of organophosphorus pesticides under laboratory conditions using statistical methods.

Dimethoate-induced oxidative damage in erythrocytes of female adult rats

Pesticide hazards have been accentuated by the sharp rise in their agricultural, industrial and domestic use. Acute exposure to pesticides can cause oxidative damage. Our study investigated the potential ability of selenium (Se) and/or vitamin E, used as nutritional supplements, to alleviate erythrocyte oxidative damage induced by dimethoate (DM), an organophosphate pesticide. Female Wistar rats were exposed to DM (0.2g/L−1 of drinking water), DM + Se (0.5 mg/kg of diet), DM + vitamin E (100 mg/kg of diet), or DM + Se + vitamin E. Rats exposed to DM for 30 days showed an increase in malondialdehyde levels, superoxide dismutase and glutathione peroxidase activities in their erythocytes, while Na+,K+-ATPase and catalase activities, glutathione, non-protein thiol, vitamin E and vitamin C levels decreased. We also noted an increase in lactate dehydrogenase activity, marker of haemolysis and a decrease in acetylcholinesterase, the principal mode of organophosphorus action. Co-administration of Se or vitamin E to the diet of DM-treated rats ameliorated the biochemical parameters cited above. But the combined effect of Se and vitamin E was more powerful in antagonizing DM-induced oxidative stress. Therefore, our investigation revealed that both Se and vitamin E were useful elements in preventing DM-induced erythrocytes damage.

Clastogenicity of the fungicide afugan in cultured human lymphocytes

The genotoxic effects of the fungicide afugan were analysed by measuring chromosomal aberrations (CAs), sister chromatid exchange (SCE) and micronuclei (MN) in cultured human peripheral lymphocytes. Concentrations of 2.5, 5, 10 and 20 microg/ml of afugan were used during 24 and 48 h. Afugan significantly increased the frequency of CAs at 5, 10 and 20 microg/ml concentrations during a 48 h treatment period. A significant increase was observed for induction of SCE and MN at all treatments compared with the negative control. A significant dose-response correlation was found in all tests. Afugan did not affect the replicative index (RI), however it significantly decreased the mitotic index (MI) at all treatment concentrations except 2.5 microg/ml, and at both treatment times. The present results indicate that afugan is clastogenic and cytotoxic to cultured human lymphocytes.

Immunological abnormalities in humans chronically exposed to chlorpyrifos

Twenty-nine individuals with chronic health complaints following exposure to chlorpyrifos were compared with 3 control groups (i.e., 1 positive and 2 negative) with respect to the following: (1) peripheral lymphocyte phenotypes; (2) autoantibodies (nucleic acids and nucleoproteins, parietal cell, brush border, mitochondria, smooth muscle, thyroid gland, and central nervous system/peripheral nervous system myelin); (3) mitogenesis to phytohemagglutinin and concanavillin. The data revealed an increase in CD26 expression, a decrease in percentage of CD5 phenotype, decreased mitogenesis in response to phytohemagglutinin and concanavillin, and an increased frequency of autoantibodies. The alterations in these peripheral blood markers were unaffected by medications, age, sex, or season. The authors concluded that chronic exposure to chlorpyrifos causes immunological changes.

Organophosphate-based pesticides and genetic damage implicated in bladder cancer

Organophosphate-based pesticides have been associated with pathology and chromosomal damage in humans. There are also epidemiologic links with cancer. The few screening tests for low-level occupational exposure are of doubtful sensitivity; this investigation evaluated four methods. Blood samples were studied from 10 farmers before and after occupational exposure to organophosphate-based pesticides and five unexposed controls. The standard cholinesterase test was insensitive to the exposure (P=0.815). However, a significant increase in Howell-Jolly bodies within erythrocytes was observed (P=0.001). Cytogenetic studies on routine and aphidicolin-induced blood cultures revealed that following organophosphate exposure the total number of gaps and breaks on human chromosomes was significantly increased (P=0.004 and P=0.0006, respectively). We concluded that Howell-Jolly body and fragile site analysis were sensitive indicators of nuclear damage resulting from low-level occupational exposure to organophosphate. Such nuclear damage could be implicated in carcinogenesis. The development of bladder cancer is one such example.

Prolonged elevation in blood pressure in the unrestrained rat exposed to chlorpyrifos

Organophosphate (OP) pesticides are likely to alter the regulation of blood pressure (BP) because (i) BP control centers in the brain stem utilize cholinergic synapses and (ii) the irreversible inhibition of acetylcholinesterase activity by OP's causes cholinergic stimulation in the CNS. This study used radiotelemetric techniques to monitor systolic (S), diastolic (D), mean (M) BP, pulse pressure (systolic-diastolic), heart rate (HR), core temperature (T(c)), and motor activity in male Long-Evans rats treated with the OP pesticide chlorpyrifos (CHP) at doses of 0, 5, 10, and 25 mg/kg (p.o.) at 15:00 h 10 and 25 mg/kg CHP led to parallel elevations in S-BP, M-BP, and D-BP within 2 h after dosing. BP increased 15-20 mmHg above controls and increases persisted throughout the night and into the next day. HR decreased slightly in rats administered 25 but not 10 mg/kg CHP. T(c) was reduced by treatment with 25 mg/kg CHP and then increased above controls the next day. Motor activity was reduced by treatment with 25 but not 10 mg/kg CHP. Pulse pressure was elevated by 2-4 mmHg for 40 h after exposure to 10 and 25 mg/kg CHP. The increase in BP without an increase in HR suggests that CHP increases total peripheral resistance and may alter the baroreflex control of BP. Cholinergic stimulation of the CNS may explain the initial effects of CHP on BP; however, the persistent elevation suggests an involvement of neurohumoral pressor pathways.

Are circulating cytokines interleukin-6 and tumor necrosis factor alpha involved in chlorpyrifos-induced fever?

Oral exposure to chlorpyrifos (CHP) in the rat results in an initial hypothermic response followed by a delayed fever. Fever from infection is mediated by the release of cytokines, including interleukin-6 (IL-6) and tumor necrosis factor (TNF alpha). This study determined if the CHP-induced fever involves cytokine-mediated mechanisms similar to that of infectious fevers. Long-Evans rats were gavaged with the corn oil vehicle or CHP (10-50 mg/kg). The rats were euthanized and blood collected at various times that corresponded with the hypothermic and febrile effects of CHP. Plasma IL-6, TNF alpha, cholinesterase activity (ChE), total iron, unsaturated iron binding capacity (UIBC), and zinc were measured. ChE activity was reduced by approximately 50% 4 h after CHP. There was no effect of CHP on IL-6 when measured during the period of CHP-induced hypothermia or fever. TNF alpha levels nearly doubled in female rats 48 h after 25 mg/kg CHP. The changes in plasma cytokine levels following CHP were relatively small when compared to > 1000-fold increase in IL-6 and > 10-fold rise in TNF alpha following lipopolysaccharide (E. coli; 50 microg/kg; i.p.)-induced fever. This does not preclude a role of cytokines in CHP-induced fever. Nonetheless, the data suggest that the delayed fever from CHP is unique, involving mechanisms other than TNF alpha and IL-6 release into the circulation characteristic of infectious fevers.