Uptake and metabolism of ethene studied in a smoke-stop experiment

Knowledge of the relationships between exposure levels and levels of hemoglobin adducts are essential when the latter are to be used for exposure monitoring or risk estimation, the hygienic control being based on measurements of exposure. These ratios are mostly very uncertain, mainly due to difficulties of determining the time-weighted average exposure concentration. A solution to this problem has been suggested involving adduct measurement before and after two consecutive periods of about 1 week, the first with absence from exposure, the second with careful measurement of exposure. This model was tested in two smokers who abstained from smoking for one week. Analysis of inhaled ethene and of adducts from ethylene oxide (EO) to N-terminal valine of hemoglobin are compatible with metabolism of 2% of inhaled ethene to EO and a detoxification rate of 1 h-1 of EO.

Use of platinum as a modifier in the sensitive detection of tellurium in biological samples

Estimation of tellurium in biological samples by flameless atomic absorption spectrophotometry is hindered by the high volatility of the metal. This necessitates the use of low ashing temperatures which are inadequate to thoroughly ash the samples and thereby reduce interference due to smoke during the atomization stage. The use of platinum as a chemical modifier to thermally stabilize tellurium has, therefore, been explored. Thermal stability of tellurium was dependent on the concentration of platinum; maximum enhancement in stability was achieved at a platinum concentration of 10 microgram/ml or greater, which allowed ashing temperatures to be increased from 400 to 1300 degrees C. A threefold increase in the sensitivity for tellurium determination was also obtained in the presence of platinum. The thermal stability and the sensitivity, however, were susceptible to the presence of organic, inorganic, and biological matrices. This procedure for the determination of tellurium, stabilized probably in the form of an amalgam with platinum, has been used successfully to estimate tissue levels of the metal following administration to mice of a novel tellurium-containing immunostimulant agent. Detection limits in urine, plasma, and tissues were about 50, 5, and 170 ng of tellurium per milliliter or gram, respectively.

Ethylene formation by polymorphonuclear leukocytes. Role of myeloperoxidase

Ethylene formation from the thioethers, beta-methylthiopropionaldehyde (methional) and 2-keto-4-thiomethylbutyric acid by phagocytosing polymorphonuclear leukocytes (PMNs) was found to be largely dependent on myeloperoxidase (MPO). Conversion was less than 10% of normal when MPO-deficient PMNs were employed; formation by normal PMNs was inhibited by the peroxidase inhibitors, azide, and cyanide, and a model system consisting of MPO, H2O2, chloride (or bromide) and EDTA was found which shared many of the properties of the predominant PMN system. MPO-independent mechanisms of ethylene formation were also identified. Ethylene formation from methional by phagocytosing eosinophils and by H2O2 in the presence or absence of catalase was stimulated by azide. The presence of MPO-independent, azide-stimulable systems in the PMN preparations was suggested by the azide stimulation of ethylene formation from methional when MPO-deficient leukocytes were employed. Ethylene formation by dye-sensitized photooxidation was also demonstrated and evidence obtained for the involvement of singlet oxygen (1O2). These findings are discussed in relation to the participation of H2O2, hydroxyl radicals, the superoxide anion and 1O2 in the formation of ethylene by PMNs and by the MPO model system.

Evidence for hydroxyl radical production by human neutrophils

The possibility that neutrophils produce the hydroxyl radical (OH-) was studied by examining the ability of these cells to support the release of ethylene from methional, a reaction in which it has been shown that OH-, but not O2- or H2O2, may serve as the oxidizing agent. When neutrophils were exposed to opsonized zymosan in the presence of 0.35 mM methional, ethylene was released in quantities amounting to 44.6+/-3.6 pmol/10(6) cells/40 min. Ethylene production required the presence of neutrophils, opsonized zymosan, and methional, indicating that it was formed from methional by stimulated but not resting neutrophils. Ethylene was not produced by zymosan-treated cells from patients with chronic granulomatous disease, confirming the requirement for respiratory burst activity in this process. Ethylene production was suppressed by benzoic acid, an OH- scavenger. Superoxide dismutase (3 microgram/ml) reduced ethylene production to 21% of control levels, but catalase had no significant effect in this system. These findings indicate that stimulated neutrophils produce a highly reactive oxidizing radical, possibly OH-, which releases ethylene from methional, and that the O2-generated during the respiratory burst is involved in the production of this reactive species.