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An improved method for determination of hydra-methylnon residues in pasture grass is described. The method uses (1) the hydrochloride salt of hy-dramethylnon to improve its water solubility and (2) an acid–methanol precipitation to remove chlorophylls while leaving the analyte in solution. The liquid chromatographic method has a validated sensitivity of 0.05 ppm with controls showing

Amphotericin B (AmB) is a membrane-active antibiotic which has been shown to increase ion and small molecule permeability in a variety of model and biological membrane systems. A major mechanistic model, based on BLM systems, proposes that amphotericin forms barrellike pores with cholesterol which are cation selective when added to one side of the membrane and anion selective when added to both sides. We have tested this hypothesis on small and reverse-phase large unilamellar vesicles (SUV and REV) with and without cholesterol. The method used to measure K+, Cl-, and net ion currents is based on ion/H+ exchange detected by the entrapped pH probe pyranine. We find that AmB forms channels which have net selectivity for K+ over Cl- regardless of sidedness or sterol content in SUV. REV with 10% cholesterol also show net K+ selectivity with double-sided addition. Differences are noted between cholesterol- and non-sterol-containing vesicles consistent with at least two separate modes of action: (1) cholesterol-containing SUV form some larger diameter pores which allow the passage of larger ions especially when added to both sides; (2) SUV without sterol form pores which are still K+ over Cl- selective, but larger ions do not pass. The latter mode of action precludes a sterol/pore type of model but not necessarily a barrellike model consisting only of amphotericin molecules.(ABSTRACT TRUNCATED AT 250 WORDS)

Eleven farmers were monitored for dermal and respiratory exposure to terbufos [phosphorodithioic acid, S-(tert-butylthio) methyl O,O-diethyl ester] during a typical working day while planting corn and applying COUNTER® 15-G systemic insecticide-nematicide. The average estimated dermal exposure was 72 Μg/hr while the estimated respiratory exposure was 11 Μg/hr. The results of urinary alkyl phosphate analyses were all negative showing no detectable absorption of terbufos. Plasma and red blood cell cholinesterase values of exposed farmers showed no significant difference in activity when compared to either preexposure or control values indicating no adverse physiological effects from the exposure. Based on these results, the use of COUNTER 15-G does not present a significant hazard, in terms of acute toxicity, to farmers using this product for the control of corn insects.