Radiolabelling biodegradation

Diisopropyl methylphosphonate has not been shown to be amenable to biodegradation. Little if any degradation by indigenous bacteria occurred in soil "dosed" with radiolabelled diisopropyl methylphosphonate (Williams et al. 1989). Biodegradation by aquatic microorganisms has been shown to be equally ineffective (Spanggord et al. 1979 Van Voris et al. 1987), rendering it inappropriate as a means for the disposal of diisopropyl methylphosphonate. 

Support for this hypothesis on iso-LAS is given through the findings of Nielsen et al. [100] in a degradation study carried out with radiolabelled substrate, in which it was reported that most of the iso-LAS isomers underwent ultimate biodegradation (79-90%), although some of their carbon (10-20%) was released as water-soluble intermediates. Furthermore, Kolbener et al. [90] could identify structures... 

Thomas et al. (43) showed that phenanthrene is actively metabolized in salmonTds and Lee et al. (41) have shown that benzo[a]pyrene is biodegraded in three species of marine fish. Varanasi et al. (VI ) demonstrated for the first time that the skin of fish exposed to aromatic hydrocarbons via either force-feeding, intraperitoneal injection, or in flowing seawater accumulate substantial concentrations of metabolic products. This is of particular interest since studies of mammalian systems have shown that some alkyl naphthalenes can be accelerators of skin carcinogenesis (32). Varanasi et al. (11) also demonstrated that the mucus of rainFow trout exposed to radiolabeled naphthalene... 

Aquatic Ecosystem and Fish. Metcalf et al. (2) studied the fate of diflubenzuron (radiolabeled separately in three different positions) in their model ecosystem. Diflubenzuron was dubbed "moderately persistent" in algae, snails, salt marsh caterpillars, and mosquito larvae as evidenced by limited biodegradability (Table IV). However, diflubenzuron and its nonpolar metabolites were not prone to ecological magnification in Gambusia fish. The lack of bioaccumulation of diflubenzuron residues in fish was substantiated by Booth and Ferrell (14) who used the channel catfish, Ictalurus, in a simulated lake ecosystem. They treated separate soil samples at 0.007 and 0.55 ppm, respectively. 

Komarek, R.J., Gardner, R.M., Buchanan, C.M. and Gedon, S. (1993). Biodegradation of radiolabelled cellulose acetate and cellulose propionate. Journal of Applied Polymer Science, 50(10), 1739-1746. 

This paper will review the biodegradation of nonionic surfactants. The major focus will be on alcohol ethoxylates and alkylphenol ethoxylates—the two largest volume nonionics. In this paper the effect of hydrophobe structure will be discussed, since hydrophobe structure is considered more critical than that of the hydrophile in biodegradability of the largest volume nonionics. The influence of the hydrophobe on the biodegradation pathway will be examined with an emphasis on the use of radiolabeled nonionics. 

Pfaender FK, Bartholomew GW. 1982a. Measurement of aquatic biodegradation rates by determining heterotrophic uptake of radiolabeled pollutants. Appl Environ Microbiol 44 159-164. 

Standard test methods for determining aerobic biodegradation of radiolabeled plastic materials in an aqueous or compost environment, ASTM Standard ASTM D 6340-98, ASTM International, West Con-shohocken, PA, 2007. 

Plants may have a role to play in enhancing microbial biodegradation of halogenated solvents, for it has recently been shown that mineralization of radiolabelled trichlorodiylene is substantially greater in vegetated rather... 

The biodegradation of 2 mg of radiolabeled benzene in 100 g of soil with a mixed microbial population transformed only 47% of the added radioactivity to carbon dioxide after 10 weeks (Haider et al. 1981). 

Sediment G, = 23 d from calculated degradation rate constant k = 0.0030 d for radiolabeled 2,4,5-TCP in Skidway River water-sediment slurry (Lee Ryan 1979 quoted, Pritchard 1987) biodegradation ty, = 23 d in sediments (Howard 1991). 

Pfaender, F.K., Bartholomew, G.W. (1982) Measurements of aquatic biodegradation rates by determining heterotropic uptake of radiolabelled pollutants. Appl. Environ. Microbiol. 44, 159-164. 

PIBCA nanospheres were injected subcutaneously to rats. Autoradiographic pictures obtained after using radiolabelled polymer have shown a progressive staining reduction in the muscular tissue suggesting that nanospheres were slowly biodegraded. In the same study, nanospheres were found to release a peptide (GRF) in a sustained manner. Comparison of the AUC of free GRF and GRF-loaded nanospheres showed that in addition to the slow release process nanospheres were able to improve the bioavailability of the peptide. This improvement could be attributed to the fact that free administered GRF is very quickly metabolized at the injection site, whereas it is partly protected from massive enzymatic degradation when it is administered associated with nanospheres. ... 

TCP s low water solubility and high adsorption to particulates causes adsorption onto river or lake sediment and soil. Biodegradation in river water is rapid, almost complete within 5 days. Abiotic degradation is slower with a half-life of 96 days. BCFs of 165-2768 were measured for several fish species in the laboratory using radiolabelled TCP. Radioactivity was lost rapidly on cessation of exposure, depuration half-lives ranged between 25.8 and 90 hours. 

Batch tests using radiolabeled techniques were employed for both the solubilization and biodegradation tests (33, 52). The soil-water suspensions used... 

A polyurethane was synthesised from 1,6-hexane diisocyanate, polycaprolactone diol and a fluoroquinolone antibiotic, ciprofloxacin and characterised by size exclusion chromatography and elemental analysis. The PU was incubated in a solution of an inflanunatoiy cell-derived enzyme, cholesterol esterase or phosphate buffer for 30 days at 37C and its biodegradability determined by HPLC, mass spectroscopy and Carbon 14 radiolabel release. Analysis of the solution revealed that ciprofloxacin was released and able to inhibit the growth of Pseudomonas aeruginosa. 53 refs. 

Due to the potential health hazard, the application of radiolabeled substrates that have been the cornerstone of metabolic experiments is not generally acceptable in field experiments. Examples of experiments using stable isotopes have, however, been carried out to determine biodegradation under field conditions and to establish the source of contaminants. Further details of the procedure have been given in Chapter 2, Section 2.4.4. 

Figure 2. PNP biodegradation in sediment and water from the Escambia River. Radiolabeled PNP was added to the indicator core at a concentration of ISO ppm. Unlabeled PNP was added to the "pre-exposed" core at the same time. After 143 h radiolabeled PNP was added to the pre-exposed and control cores. (Reprinted with permission from ref. 7. Copyright 1980 American Society for Microbiology.)...

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