Alkaline hydrolysis of trinitrotoluene, TNT

The kinetics of the alkaline hydrolysis of trinitrotoluene, TNT, in an aqueous solution is a possible approach to destroying the active agent in unwanted munitions. The kinetics are shown to have a rapid initial step, step A, in which a highly coloured species, X (lambda(max) = 450 nm) is formed via an equilibrium reaction: TNT + OH- double left right arrow X. The bimolecular rate constant for the forward part of this equilibrium process, k(1), is: 0.099 +/- 0.004, 0.32 +/- 0.02 and 1.27 +/- 0.05 dm(3) mol(-1) s(-1), at 25, 40 and 60degreesC, respectively. The activation energy for the forward process is 60 kJ mol(-1). The first-order rate constant for the reverse of this process, k(-1), is: (5.3 +/- 2.6) x 10(-4), (1.2 +/- 1.0) x 10(-3) and (7.7 +/- 2.9) x 10(-3) s(-1) at 25, 40 and 60degreesC, respectively. The activation energy for the overall equilibrium process (k(1)/k(-1)) is ca. -5 kJ mol(-1). The subsequent alkaline hydrolysis of X to form the final product P, i.e. step B, is much slower than step A and appears to comprise two processes coupled in series, i.e. steps B1 (X +2OH(-) --> Z) and B2 (Z+OH- --> P). At 25degreesC, Step B1 appears rate determining throughout the decay process. At 45 degreesC and, more so, at 60degreesC, step B appears increasingly biphasic with increasing alkaline concentrations, as step B2 begins to compete with step B1 for position as the rate determining step. The trimolecular rate constant for step B1 is: 0.017 +/- 0.001, 0.0085 +/- 0.0002 and 0.0011 +/- 0.0001 dm(6) mol(-2) s(-1) at 25, 40 and 60degreesC, respectively, and the process has an activation energy of 64 kJ mol(-1). The transition from uniform kinetics, described by step B1, to mixed kinetics, described by steps B1 and B2, as the reaction temperature and alkali concentration are increased most likely occurs because (a) step B2 has a lower activation energy than B1, although it was not possible to measure the former parameter, and (b) step B2 has a lower (1st) order dependence upon [OH-] compared with that of step B1 (2nd). The bimolecular rate constant for step B2 is 0.0035 +/- 0.03 dm(3) mol(-1) s(-1) at 60degreesC. A brief NMR study of the initial hydrolysis product in water, acetone and chloroform, coupled with UV/visible spectra, provides evidence that species X is a Meisenheimer complex.

Biotransformation of 2,4,6-trinitrotoluene (TNT) by ectomycorrhizal basidiomycetes

The ability of four ectomycorrhizal basidiomycetes to biotransform 2,4,6-trinitrotoluene (TNT) in axenic culture was tested. All species were capable of TNT biotransformation to a greater or lesser extent. When biotransformation was expressed on a biomass basis 4 out of the 5 isolates tested were equally efficient at transforming TNT. The factors regulating TNT biotransformation were investigated in detail for one fungus, Suillus variegatus. When the fungus was grown under nitrogen limiting conditions the rate of biotransformation decreased relative to nitrogen sufficient conditions, but no decrease was observed under short term carbon starvation. Extracellular enzymes of S. variegatus could transform TNT, but transformation was greater in intact cells. The mycelial cell wall fraction did not degrade TNT. The TNT concentration that caused 50% reduction in biomass (EC₅₀) for S. variegatus was within the range observed for other basidiomycete fungi being between 2-10 μg mL^-1. The potential use of ectomycorrhizal basidiomycetes as in-situ bioremediation agents for TNT contaminated soils is discussed.

Mitochondrial Transfer via Tunneling Nanotubes (TNT) is an Important Mechanism by which Mesenchymal Stem Cells Enhance Macrophage Phagocytosis in the in vitro and in vivo Models of ARDS

Mesenchymal stromal cells (MSC) have been reported to improve bacterial clearance in pre-clinical models of Acute Respiratory Distress Syndrome (ARDS) and sepsis. The mechanism of this effect is not fully elucidated yet. The primary objective of this study was to investigate the hypothesis that the anti-microbial effect of MSC in vivo depends on their modulation of macrophage phagocytic activity which occurs through mitochondrial transfer. We established that selective depletion of alveolar macrophages (AM) with intranasal (IN) administration of liposomal clodronate resulted in complete abrogation of MSC anti-microbial effect in the in vivo model of E.coli pneumonia. Furthermore, we showed that MSC administration was associated with enhanced AM phagocytosis in vivo. We showed that direct co-culture of MSC with monocyte-derived macrophages (MDMs) enhanced their phagocytic capacity. By fluorescent imaging and flow cytometry we demonstrated extensive mitochondrial transfer from MSC to macrophages which occurred at least partially through TNT-like structures. We also detected that lung macrophages readily acquire MSC mitochondria in vivo, and macrophages which are positive for MSC mitochondria display more pronounced phagocytic activity. Finally, partial inhibition of mitochondrial transfer through blockage of TNT formation by MSC resulted in failure to improve macrophage bioenergetics and complete abrogation of the MSC effect on macrophage phagocytosis in vitro and the anti-microbial effect of MSC in vivo.

Collectively, this work for the first time demonstrates that mitochondrial transfer from MSC to innate immune cells leads to enhancement in phagocytic activity and reveals an important novel mechanism for the anti-microbial effect of MSC in ARDS.

Detection of visual-field deterioration by Glaucoma Progression Analysis and Threshold Noiseless Trend programs

BACKGROUND: To compare the ability of Glaucoma Progression Analysis (GPA) and Threshold Noiseless Trend (TNT) programs to detect visual-field deterioration.

METHODS: Patients with open-angle glaucoma followed for a minimum of 2 years and a minimum of seven reliable visual fields were included. Progression was assessed subjectively by four masked glaucoma experts, and compared with GPA and TNT results. Each case was judged to be stable, deteriorated or suspicious of deterioration

RESULTS: A total of 56 eyes of 42 patients were followed with a mean of 7.8 (SD 1.0) tests over an average of 5.5 (1.04) years. Interobserver agreement to detect progression was good (mean kappa = 0.57). Progression was detected in 10-19 eyes by the experts, in six by GPA and in 24 by TNT. Using the consensus expert opinion as the gold standard (four clinicians detected progression), the GPA sensitivity and specificity were 75% and 83%, respectively, while the TNT sensitivity and specificity was 100% and 77%, respectively.

CONCLUSION: TNT showed greater concordance with the experts than GPA in the detection of visual-field deterioration. GPA showed a high specificity but lower sensitivity, mainly detecting cases of high focality and pronounced mean defect slopes.