Composting of explosives and propellant contaminated soils under thermophilic and mesophilic conditions

Summary Composting was investigated as a bioremediation technology for clean-up of sediments contaminated with explosives and propellants. Two field demonstrations were conducted, the first using 2,4,6-trinitrotoluene (TNT), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetraazocine (HMX), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and N-methyl-N,2,4,6-tetranitroaniline (tetryl) contaminated sediment, and the second using nitrocellulose (NC) contaminated soil. Tests were conducted in thermophilic and mesophilic aerated static piles. Extractable TNT was reduced from 11840 mg/kg to 3 mg/kg, and NC from 13090 mg/kg to 16 mg/kg under thermophilic conditions. Under mesophilic conditions, TNT was reduced from 11 190 mg/kg to 50 mg/kg. The thermophilic and mesophilic half-lives were 11.9 and 21.9 days for TNT, 17.3 and 30.1 days for RDX, and 22.8 and 42.0 days for HMX, respectively. Known nitroaromatic transformation products increased in concentration over the first several weeks of the test period, but decreased to low concentrations thereafter.     

Cytochrome P-450 reduction exhibits burst kinetics

Cytochrome P-450 reduction kinetics can be described by sequential reactions involving a rapid reduction of cytochrome P-450 in the high spin state, followed by a slower reduction controlled by formation of high spin P-450 from the low spin configuration. The burst kinetics observed would be the result of the equilibrium between low and high spin states prior to addition of reducing equivalents. The initial reduction velocity (burst) can therefore be described as v_i=k₃m_hs⁰ and the slower velocity observed at longer times is controlled by the net rate of formation of the high spin conformation.     

Two arginines in the cytoplasmic C-terminal domain are essential for voltage-dependent regulation of A-type K+ current in the Kv4 channel subfamily

Contributions of the C-terminal domain of Kv4.3 to the voltage-dependent gating of A-type K+ current (IA) were examined by (i) making mutations in this region, (ii) heterologous expression in HEK293 cells, and (iii) detailed voltage clamp analyses. Progressive deletions of the C terminus of rat Kv4.3M (to amino acid 429 from the N terminus) did not markedly change the inactivation time course of IA but shifted the voltage dependence of steady state inactivation in the negative direction to a maximum of -17 mV. Further deletions (to amino acid 420) shifted this parameter in the positive direction, suggesting a critical role for the domain 429-420 in the voltage-dependent regulation of IA. There are four positively charged amino acids in this domain: Lys423, Lys424, Arg426, and Arg429. The replacement of the two arginines with alanines (R2A) resulted in -23 and -13 mV shifts of inactivation and activation, respectively. Additional replacement of the two lysines with alanines did not result in further shifts. Single replacements of R426A or R429A induced -15 and -10 mV shifts of inactivation, respectively. R2A did not significantly change the inactivation rate but did markedly change the voltage dependence of recovery from inactivation. These two arginines are conserved in Kv4 subfamily, and alanine replacement of Arg429 and Arg432 in Kv4.2 gave essentially the same results. These effects of R2A were not modulated by co-expression of the K+ channel beta subunit, KChIPs. In conclusion, the two arginines in the cytosolic C-terminal domain of alpha-subunits of Kv4 subfamily strongly regulate the voltage dependence of channel activation, inactivation, and recovery.     

The New York Consortium on Membrane Protein Structure (NYCOMPS): a high-throughput platform for structural genomics of integral membrane proteins

The New York Consortium on Membrane Protein Structure (NYCOMPS) was formed to accelerate the acquisition of structural information on membrane proteins by applying a structural genomics approach. NYCOMPS comprises a bioinformatics group, a centralized facility operating a high-throughput cloning and screening pipeline, a set of associated wet labs that perform high-level protein production and structure determination by x-ray crystallography and NMR, and a set of investigators focused on methods development. In the first three years of operation, the NYCOMPS pipeline has so far produced and screened 7,250 expression constructs for 8,045 target proteins. Approximately 600 of these verified targets were scaled up to levels required for structural studies, so far yielding 24 membrane protein crystals. Here we describe the overall structure of NYCOMPS and provide details on the high-throughput pipeline.     

Molecular mechanisms for environmentally induced and evolutionarily rapid redistribution (plasticity) of meiotic recombination

It has long been known (circa 1917) that environmental conditions, as well as speciation, can affect dramatically the frequency distribution of Spo11/Rec12-dependent meiotic recombination. Here, by analyzing DNA sequence-dependent meiotic recombination hotspots in the fission yeast Schizosaccharomyces pombe, we reveal a molecular basis for these phenomena. The impacts of changing environmental conditions (temperature, nutrients, and osmolarity) on local rates of recombination are mediated directly by DNA site-dependent hotspots (M26, CCAAT, and Oligo-C). This control is exerted through environmental condition-responsive signal transduction networks (involving Atf1, Pcr1, Php2, Php3, Php5, and Rst2). Strikingly, individual hotspots modulate rates of recombination over a very broad dynamic range in response to changing conditions. They can range from being quiescent to being highly proficient at promoting activity of the basal recombination machinery (Spo11/Rec12 complex). Moreover, each different class of hotspot functions as an independently controlled rheostat; a condition that increases the activity of one class can decrease the activity of another class. Together, the independent modulation of recombination rates by each different class of DNA site-dependent hotspots (of which there are many) provides a molecular mechanism for highly dynamic, large-scale changes in the global frequency distribution of meiotic recombination. Because hotspot-activating DNA sites discovered in fission yeast are conserved functionally in other species, this process can also explain the previously enigmatic, Prdm9-independent, evolutionarily rapid changes in hotspot usage between closely related species, subspecies, and isolated populations of the same species.     

Platelet Recruitment Promotes Keratocyte Repopulation following Corneal Epithelial Abrasion in the Mouse

Corneal abrasion not only damages the epithelium but also induces stromal keratocyte death at the site of injury. While a coordinated cascade of inflammatory cell recruitment facilitates epithelial restoration, it is unclear if this cascade is necessary for keratocyte recovery. Since platelet and neutrophil (PMN) recruitment after corneal abrasion is beneficial to epithelial wound healing, we wanted to determine if these cells play a role in regulating keratocyte repopulation after epithelial abrasion. A 2 mm diameter central epithelial region was removed from the corneas of C57BL/6 wildtype (WT), P-selectin deficient (P-sel^-/-), and CD18 hypomorphic (CD18^hypo) mice using the Algerbrush II. Corneas were studied at 6h intervals out to 48h post-injury to evaluate platelet and PMN cell numbers; additional corneas were studied at 1, 4, 14, and 28 days post injury to evaluate keratocyte numbers. In WT mice, epithelial abrasion induced a loss of anterior central keratocytes and keratocyte recovery was rapid and incomplete, reaching ~70% of uninjured baseline values by 4 days post-injury but no further improvement at 28 days post-injury. Consistent with a beneficial role for platelets and PMNs in wound healing, keratocyte recovery was significantly depressed at 4 days post-injury (~30% of uninjured baseline) in P-sel^-/- mice, which are known to have impaired platelet and PMN recruitment after corneal abrasion. Passive transfer of platelets from WT, but not P-sel^-/-, into P-sel^-/- mice prior to injury restored anterior central keratocyte numbers at 4 days post-injury to P-sel^-/- uninjured baseline levels. While PMN infiltration in injured CD18^hypo mice was similar to injured WT mice, platelet recruitment was markedly decreased and anterior central keratocyte recovery was significantly reduced (~50% of baseline) at 4–28 days post-injury. Collectively, the data suggest platelets and platelet P-selectin are critical for efficient keratocyte recovery after corneal epithelial abrasion.     

Vertical Migration and Mortality of Marine Benthos in Dredged Material: A Synthesis

This account describes the comparative response of four species of benthic invertebrates to burial in terms of vertical migration and mortality, and provides a synthesis of studies and recommendations upon which to assess future impacts. The species featured were the bivalve Mercenaries mercenaria, the amphipod crustacean Parahaustorius longimerus, and the polychaetes Scoloplos fragilis and Nereis succinea. There was evidence of synergistic effects on burrowing activity and mortality with changes in time of burial, sediment depth, sediment type and temperature. In sediment with silt-clay, N. succinea was the most resistant species followed by M. mercenaria, S. fragilis and P. longimerus. In sediment without silt-clay the order of percent mortality was reversed. Studies of surface water chemistry and sediment geochemistry showed that dissolved oxygen decreased significantly and ammonia and sulfide increased significantly between the surface and below 2.0 cm within a 15-day period. Based on these results and physiological tolerances from the literature it was concluded that M. mercenaria and N. succinea would be relatively resistant to chemical effects of spoil disposal, whereas S. fragilis and P. longimerus would be less resistant to such effects. Vertical migration of benthic invertebrates through dredge disposal can be a viable mechanism of recolonization under certain conditions. Some effects of burial of benthos can be predicted based on morphology, behavior and physiology. These biological features were discussed with examples dealing with molluscs, crustaceans, and polychaetes. Finally, recommendations were made concerning the type of studies to provide additional data to aid management agencies in decision making about future dredging and disposal practices.