Shift in FTIR spectrum patterns in methomyl-exposed rat spleen cells.

Methomyl is a highly toxic carbamate insecticide which is widely used in many agricultural countries. We have applied the Fourier-transformed infrared (FTIR) spectroscopic method to study the toxicity of methomyl on cytoskeletal protein and the nucleic acid of rat spleen cells. Rats were given methomyl by gavage at 2, 6 and 8 mg/kg in single doses. Colchicine, a microtubule-disrupting agent, was given to rats at 2, 4, and 6 mg/kg in single doses and mitomycin C, an alkylating agent which acts as a DNA-cross-linking agent, was given by an intraperitoneal route to rats at 1 mg/kg. It was shown that the wavenumber of FTIR spectra at amide I and amide II in both methomyl- and colchicine-exposed rats shifted in dose response manner when compared with the control (P < 0.05). The amide I and II shifts in these regions have been proposed to be the result of an alpha-helix protein conformational change. Toxic doses of mitomycin C, a DNA-cross-linking agent, did not result in this pattern. Moreover, all exposed rats showed an increase in the absorbance ratios that were related to the vibrational mode of the phosphodiester group in nucleic acid (P < 0.05).

Immunoglobulins from patients with amyotrophic lateral sclerosis affect human erythrocyte acetylcholinesterase.

Human erythrocyte acetylcholinesterase (AChE) solubilized with Triton X-100 and obtained as a complex with micelles containing Triton and membrane phospholipids was incubated with immunoglobulins (Igs) from patients with amyotrophic lateral sclerosis (ALS) and from normal individuals. The temperature dependence of the AChE activity was determined. Biphasic (broken) Arrhenius plots were obtained with control Igs with the break point at 32.8 +/- 0.3 degrees C (SD, n = 18) indicating that the enzyme changes its conformation at this temperature. With ALS-Igs monophasic (linear) plots were observed in 14 cases and a biphasic in one case. ALS-Igs prevent the conformational change occurring at the break point temperature. The activation energy at physiological temperature increased by 60% from 2.4 to 3.8 kcal/mol (10.0-15.9 kJ/mol) which implies that ALS-Igs inhibit AChE. Thus, ALS-patients have autoantibodies that change the normal behaviour of erythrocyte AChE and which bind to the enzyme molecule or/and to phospholipids associated with the enzyme. At least part of the autoantibodies should be directed against the enzyme molecule, since a change in the Arrhenius plot was also observed in a control experiment with AChE which probably had micelles without any phospholipids. This enzyme was isolated by affinity chromatography and was washed with a buffer containing Triton X-100 before desorption from the affinity column, a treatment known to remove all phospholipids from erythrocyte AChE.