Recommended default methodology for analysis of airborne exposures to mixtures of chemicals in emergencies.

Emergency planning and hazard assessment of Department of Energy (DOE) facilities require consideration of potential exposures to mixtures of chemicals released to the atmosphere. Exposure to chemical mixtures may lead to additive, synergistic, or antagonistic health effects. In the past, the consequences of exposures to each chemical have been analyzed separately. This approach may not adequately protect the health of persons exposed to mixtures. This article presents default recommendations for use in emergency management and safety analysis within the DOE complex where potential exists for releases of mixtures of chemicals. These recommendations were developed by the DOE Subcommittee on Consequence Assessment and Protective Actions (SCAPA). It is recommended that hazard indices (e.g., HIi = Ci/Limiti, where Ci is the concentration of chemical "i") be calculated for each chemical, and unless sufficient toxicological knowledge is available to indicate otherwise, that they be summed, that is, sigma i(n) = 1HIi = HI1 + HI2 + ... + HIn. A sum of 1.0 or less means the limits have not been exceeded. To facilitate application of these recommendations for analysis of exposures to specific mixtures, chemicals are classified according to their toxic consequences. This is done using health code numbers describing toxic effects by target organ for each chemical. This methodology has been applied to several potential releases of chemicals to compare the resulting hazard indices of a chemical mixture with those obtained when each chemical is treated independently. The methodology used and results obtained from analysis of one mixture are presented in this article. This article also demonstrates how health code numbers can be used to sum hazard indices only for those chemicals that have the same toxic consequence.

Dictyostelium discoideum fatty-acyl amidase II has deacylase activity on Rhizobium nodulation factors.

Dictyostelium discoideum (Amoebidae) secretes cell-lysing enzymes: esterases, amidases, and glycosylases, many of which degrade soil bacteria to provide a source of nutrients. Two of these enzymes, fatty-acyl amidases FAA I and FAA II, act sequentially on the N-linked long chain acyl groups of lipid A, the lipid anchor of Gram-negative bacterial lipopolysaccharide. FAA I selectively hydrolyzes the 3-hydroxymyristoyl group N-linked to the proximal glucosamine residue of de-O-acylated lipid A. Substrate specificity for FAA II is less selective, but does require prior de-N-acylation of the proximal sugar, i.e. bis-N-acylated lipid A is not a substrate. We have synthesized a 14C-labeled substrate analog for FAA II and used this in a novel assay to monitor its purification. Inhibitory studies indicate that FAA II is not a serine protease, but may have a catalytic mechanism similar to metalloprotein de-N-acetylases such as LpxC. Interestingly, rhizobial Nod factor signal oligosaccharides that induce root nodules on leguminous plants have many of the structural requirements for substrate recognition by FAA II. In vitro evidence indicates that Rhizobium fredii Nod factors are selectively de-N-acylated by purified FAA II, suggesting that the enzyme may reduce the N2-fixing efficiency of Rhizobium-legume symbioses. In contrast, N-methylated Nod factors from transgenic R. fredii carrying the rhizobial nodS gene were resistant to FAA II, suggesting a mechanism by which Nod factors may be protected from enzymatic de-N-acylation. Since FAA II and Nod factors are both secreted, and Nod factors that lack the N-acyl group are unable to induce nodules, dictyostelial FAA II may decrease the efficiency of symbiotic nitrogen fixation in the environment by reducing the available biologically active nodule inducer signal.

Studies on the luminescent response of the Ca2+-activated photoprotein, obelin.

1. The kinetics and stoicheiometry of the Ca2+-activated luminescent reaction of the photoprotein obelin were studied at different temperatures and in the presence of various substances, including the physiologically occurring cations K+, Na+, Ca+, Mg2+ and H+. 2. The results suggest Ca2+-independent rates of rise and fall in obelin luminescence following sudden changes in [Ca2+] and indicate that changes in [Ca2+] over the range 1 x 10(-6) - 3 x 10(-4) M are followed significantly faster by the obelin response (approx. 3 ms delay at 20 degrees C) than by the aequorin response (approx. 10 ms delay at 20 degrees C). 3. Obelin was found to emit low-intensity light (less than 10(-6) of the maximum Ca2+-activated response), which was independent of Ca2+ at concentrations below about 10(-7) M. The level of this Ca2+-independent light emission is sensitive to temperature and the ionic composition of the solution. 4. The log-log plot of light intensity against ionized Ca indicates a maximum slope of 2.5, suggesting the involvement of three Ca ions in the luminescent reaction. 5. Increase in the concentration of K+, Na+, Mg2+ and H+ generally shift the Ca2+ activation curve for obelin toward higher Ca2+ concentrations. These cations can also affect the maximum rate of obelin utilization at more extreme concentrations. 6. The maximal rate of obelin utilization was also affected to varying degrees by the presence of uncharged substances such as glucose, sucrose and polyvinylpyrrolidone. However, neither the sensitivity of obelin to Ca2+ nor the quantum yield were modified by the substances. 7. Caffeine (less than 20 mM), procaine (less than 20 mM) and sodium dantrolene (saturated solution), substances known to modify cellular Ca2+ movements, had little effect on the Ca2+-induced luminescent reaction. The general anaesthetics chlorpromazine and halothane appeared to lower greatly the quantum yield without, however, modifying the maximum rate of obelin utilization. 8. A scheme of reaction for obelin activation by Ca2+ is presented which adequately explains the experimental observations and allows one to make accurate predictions regarding the relative obelin response under a variety of ionic conditions at room temperature.

Migrating birds respond to Project Seafarer's electromagnetic field.

Radar tracking of individual migrating birds flying over a large alternating-current antenna system showed that the birds turned or changed altitude more frequently when the antenna system was operating than when it was not. These results suggest that birds sense low-intensity alternating-current electromagnetic fields during nocturnal migratory flight.