Gene expression in mouse muscle over time after nickel pellet implantation.

The transition metal nickel is used in a wide variety of alloys and medical devices. Nickel can cause a range of toxicities from allergy in humans to tumors when implanted in animals. Several microarray studies have examined nickel toxicity, but so far none have comprehensively profiled expression over an extended period. In this work, male mice were implanted with a single nickel pellet in the muscle of the right leg with the left leg used as a control. At 3 week intervals up to 12 months, nickel concentrations in bioflulids and microarrays of surrounding tissue were used to track gene expression patterns. Pellet biocorrosion resulted in varying levels of systemic nickel over time, with peaks of 600 µg L-1 in serum, while global gene expression was cyclical in nature with immune related genes topping the list of overexpressed genes. IPA and KEGG pathway analyses was used to attribute overall biological function to changes in gene expression levels, supported by GO enrichment analysis. IPA pathways identified sirtuin, mitochondria, and oxidative phosphorylation as top pathways, based predominantly on downregulated genes, whereas immune processes were associated with upregulated genes. Top KEGG pathways identified were lysosome, osteoclast differentiation, and phasgosome. Both pathway approaches identified common immune responses, as well as hypoxia, toll like receptor, and matrix metalloproteinases. Overall, pathway analysis identified a negative impact on energy metabolism, and a positive impact on immune function, in particular the acute phase response. Inside the cell the impacts were on mitochondria and lysosome. New pathways and genes responsive to nickel were identified from the large dataset in this study which represents the first long-term analysis of the effects of chronic nickel exposure on global gene expression.

Subchronic Oral Toxicity of Sodium Tungstate in Sprague-Dawley Rats.

The subchronic toxicity of sodium tungstate dihydrate aqueous solution in male and female Sprague-Dawley rats was evaluated by daily oral gavage of 0, 10, 75, 125, or 200 mg/kg/d for 90 days. Measured parameters included food consumption, body weight measurements, hematology, clinical chemistry, and histopathological changes. There was a significant decrease in food consumption and body weight gain in males at 200 mg/kg/d from days 77 to 90; however, there was no effect in food consumption and body weights in females. There were no changes in the hematological and clinical parameters studied. Histopathological changes were seen in kidney of male and female and epididymis of male rats. Histopathological changes were observed in the kidneys of male and female rats dosed at 125 or 200 mg/k/d consisting of mild to severe cortical tubule basophilia in 2 high-dose groups. Histological changes in epididymides included intraluminal hypospermia with cell debris in the 200 mg/kg/d dosed male rats. Histopathological changes were observed in the glandular stomach including inflammation and metaplasia in the high-dose groups (125 or 200 mg/kg/d) of both sexes of rats. Based on histopathology effects seen in the kidneys, the lowest observable adverse effect level was 125 mg/kg/d and the no observable adverse effect level was 75 mg/kg/d in both sexes of rats for oral subchronic toxicity.

Calcium signaling in neuronal cells exposed to the munitions compound Cyclotrimethylenetrinitramine (RDX).

Cyclotrimethylenetrinitramine (RDX) has been used extensively as an explosive in military munitions. Mechanisms for seizure production, seen in past animal studies, have not been described. Increased calcium levels contribute to excitotoxicity, so in this study neuroblastoma cells are loaded with calcium-indicating dye before application of 1.5 microM to 7.5 mM RDX, with fluorescence recorded for 30 cycles of 11 seconds each. The lowest concentration of RDX increases calcium fluorescence significantly above baseline for cycles 2 to 8; millimolar concentrations increase calcium fluorescence significantly above baseline for cycles 2 to 30. Increases in calcium, like those of 200 nM carbachol, are prevented with 10 mM of calcium chelator ethylene glycol-bis(beta-aminoethyl ether)-N,N,N,N tetra-acetic acid (EGTA, tetrasodium salt). Calcium channel blocker verapamil (20 microM), Ca(2+)-ATPase inhibitor thapsigargin (5 microM), and general membrane stabilizer lidocaine (10 mM) partially attenuate carbachol- and RDX-induced increases in calcium, suggesting that RDX transiently increases intracellular calcium by multiple mechanisms.

Antibodies to neural proteins in organophosphorus-induced delayed neuropathy (OPIDN) and its amelioration.

The development of OPIDN and the efficacy of experimental intervention using the calcium-channel blocker verapamil were used as a model to test the serial time-measurements of serum autoantibodies against neuronal cytoskeletal proteins [e.g., neurofilament triplet (NF)] and glial proteins [myelin-basic protein (MBP) and glial fibrillary-acidic protein (GFAP)] as biomarkers of neurotoxicity and its amelioration. Ten White Leghorn hens (>7 months, 1.2-1.8 kg) were administered phenyl-saligenin phosphate (PSP; 2.5 mg/kg; im), a dose reported to induce a 70% decrease in neurotoxic esterase (NTE) activity. Five of the hens were administered verapamil (7 mg/kg; im) for 4 days starting one day before PSP administration. Serum was isolated from blood collected by serial brachial venepuncture before PSP (day 0) administration and on days 3, 7 and 21 after PSP administration, each hen acting as its own control. Serum antibodies (IgG) to NF-L, NF-M, NF-H, MBP, and GFAP were assayed using an ELISA. There were no detectable levels of antibodies on days 0 and 3. IgG against all neural proteins were detected on days 7 and 21, with titer levels being significantly (p< or =0.05) higher in sera of hens receiving PSP only. Anti-NF-L titers were highest compared to those against NF-M, NF-H or MBP at 21 days. Titers of anti-NF-L and anti-MBP significantly (p< or =0.01) correlated with clinical scores at days 7 and 21. Detection of anti-NF and anti-MBP antibodies confirms the neuroaxonal degeneration accompanied by myelin loss reported in this model of OPIDN and the amelioration of neuropathy using verapamil. The detection of anti-GFAP antibodies suggests CNS involvement in OPIDN, since astrocytes are only found therein. This study demonstrates that detection of neuroantibodies can be used as biomarkers of neuropathy development and to monitor the amelioration resulting from therapeutic intervention. Together with biomarkers of exposure neuroantibodies can be used to monitor neuropathogenesis due to environmental or occupational exposures.