Aerobic mineralization of vinyl chloride by a bacterium of the order Actinomycetales.

A gram-positive branched bacterium isolated from a trichloroethylene-degrading consortium mineralized vinyl chloride in growing cultures and cell suspensions. Greater than 67% of the [1,2-14C]vinyl chloride was mineralized to carbon dioxide, with approximately 10% of the radioactivity appearing in cell biomass and another 10% appearing in 14C-aqueous-phase products.     

Aerobic biodegradation of vinyl chloride in groundwater samples

Studies were conducted to examine the biodegradation of 14C-labeled vinyl chloride in samples taken from a shallow aquifer. Under aerobic conditions, vinyl chloride was readily degraded, with greater than 99% of the labeled material being degraded after 108 days and approximately 65% being mineralized to 14CO2.     

Aerobic biodegradation of vinyl chloride in groundwater samples.

Studies were conducted to examine the biodegradation of 14C-labeled vinyl chloride in samples taken from a shallow aquifer. Under aerobic conditions, vinyl chloride was readily degraded, with greater than 99% of the labeled material being degraded after 108 days and approximately 65% being mineralized to 14CO2.     

Aerobic Mineralization of Trichloroethylene, Vinyl Chloride, and Aromatic Compounds by Rhodococcus Species

Two Rhodococcus strains which were isolated from a trichloroethylene (TCE)-degrading bacterial mixture and Rhodococcus rhodochrous ATCC 21197 mineralized vinyl chloride (VC) and TCE. Greater than 99.9% of a 1-mg/liter concentration of VC was degraded by cell suspensions. [1,2-¹⁴C]VC was degraded by cell suspensions, with the production of greater than 66% ¹⁴CO₂ and 20% ¹⁴C-aqueous phase products and incorporation of 10% of the ¹⁴C into the biomass. Cultures that utilized propane as a substrate were able to mineralize greater than 28% of [1,2-¹⁴C]TCE to ¹⁴CO₂, with approximately 40% appearing in ¹⁴C-aqueous phase products and another 10% of ¹⁴C incorporated into the biomass. VC degradation was oxygen dependent and occurred at a pH range of 5 to 10 and temperatures of 4 to 35°C. Cell suspensions degraded up to 5 mg of TCE per liter and up to 40 mg of VC per liter. Propane competitively inhibited TCE degradation. Resting cell suspensions also degraded other chlorinated aliphatic hydrocarbons, such as chloroform, 1,1-dichloroethylene, and 1,1,1-trichloroethane. The isolates degraded a mixture of aromatic and chlorinated aliphatic solvents and utilized benzene, toluene, sodium benzoate, naphthalene, biphenyl, and n-alkanes ranging in size from propane to hexadecane as carbon and energy sources. The environmental isolates appeared more catabolically versatile than R. rhodochrous ATCC 21197. The data report that environmental isolates of Rhodococcus species and R. rhodochrous ATCC 21197 have the potential to degrade TCE and VC in addition to a variety of aromatic and chlorinated aliphatic compounds either individually or in mixtures.     

The biological fate in rats of vinyl chloride in relation to its oncogenicity.

The main eliminative route for [14C]vinyl chloride after oral, i.v. or i.p. administration to rats is pulmonary; both unchanged vinyl chloride and vinyl chloride-related CO2 are excreted by that route and the other [14C] metabolites via the kidneys. After intragastric administration, pulmonary output of unchanged vinyl chloride is proportional to the logarithm of reciprocal dose. Excretion patterns after i.v. and i.p. injections are predictable from the characteristics of excretion following oral administration. Pulmonary excretion of unchanged vinyl chloride after oral dosing is complete within 3-4 h, but pulmonary elimination of CO2 and renal excretion of metabolites occupies 3 days. In comparison, 99% of a small i.v. dose is excreted unchanged within 1 h of injection; 80% within 2 min. The rate of elimination of a single oral doses of [14C]vinyl chloride is uninfluenced by up to 60 days' chronic dosing with the unlabelled substance. The distribution volume of vinyl chloride as displayed by whole-animal autoradiography agrees with deductions from excretion data. Small localization of 14C in the para-auricular region of appropriate sections occurs in sectioned tubules, belonging possibly to the Zymbal glands. Biotransformation of vinyl chloride into S-(2-chloroethyl) cysteine and N-acetyl-S-(2-chloroethyl) cysteine occurs through addition of cysteine, and biotransformation into: (i) chloroacetic acid, thiodiglycollic acid and glutamic acid, and (ii) into formaldehyde (methionine, serine), CO2 and urea is explicable in terms of an associative reaction with molecular O2 involving a singlet oxygen bonded transition state in dynamic equilibrium with a cyclic peroxide ground state. There is no evidence for chloroethylene oxide formation.Thiodiglycollic acid is the major metabolite of chloroacetic acid in rats; more than 60% of the dose. The interaction of vinyl chloride and of its primary metabolites with the intermediates of mammalian metabolism is discussed in relation to the oncogenicity of that substance.     

Microbial Mineralization of Ethene Under Sulfate-Reducing Conditions

Previous investigations demonstrated that respiratoly reductive dechlorination of vinyl chloride (VC) can be efficient even at H₂ concentrations (≤2 nM) that are characteristic of SO₄-reducing conditions. In the study reported here, microorganisms indigenous to a lake-bed sediment completely mineralized [1,2-¹⁴C] ethene to ¹⁴14CO₂ when incubated under SO₄-reducing conditions. Together, these observations argue for a novel mechanism for the net anaerobic oxidation of VC to CO₂: reductive dechlorination of VC to ethene followed by anaerobic oxidation of ethene to CO₂. Moreover, the results of this study suggest that reliance on ethene and/or ethane accumulation as a quantitative indicator of complete reductive dechlorination of chioroethene contaminants may not be warranted.     

Chloroethene biodegradation in sediments at 4 degrees C

Microbial reductive dechlorination of [1,2-14C]trichloroethene to [14C]cis-dichloroethene and [14C]vinyl chloride was observed at 4 degrees C in anoxic microcosms prepared with cold temperature-adapted aquifer and river sediments from Alaska. Microbial anaerobic oxidation of [1,2-14C]cis-dichloroethene and [1,2-14C]vinyl chloride to 14CO2 also was observed under these conditions.     

Ethanol inhibition of vinyl chloride metabolism in isolated rat hepatocytes.

Isolated rat liver cells convert [14C]vinyl chloride into non-volatile metabolites. The metabolism is not increased by in vivo pretreatment with phenobarbital. It is sensitive to inhibition by ethanol, which at a concentration of 4 mM inhibits vinyl chloride metabolism to 50% in hepatocyte suspensions. The metabolic activity is NADPH-dependent and is localized in the microsomal fraction of the liver. The enzyme is also strongly inhibited by tetrahydrofuran, indicating that it could be identical to an ethanol-inducible cytochrome P-450 described in the literature [1].     

Nicotine affects mineralized nodule formation by the human osteosarcoma cell line Saos-2

Several in vitro and in vivo studies have indicated that tobacco smoking may be an important risk factor for the development and severity of inflammatory periodontal disease. In the present study, we examined the effect of nicotine on cell proliferation, alkaline phosphatase (ALPase) activity, mineralized nodule formation, and the expression of extracellular matrix proteins in the human osteosarcoma cell line Saos-2. The cells were cultured with Dulbecco's modified Eagle medium containing 10% fetal bovine serum with 0, 10(-4) M, and 10(-3) M nicotine for up to 14 days. Mineralized nodule formation was examined by alizarin red staining, and the calcium content in mineralized nodules was determined using a calcium E-test kit. The expression of extracellular matrix proteins was estimated by determining the levels of their mRNAs using the real-time polymerase chain reaction. Mineralized nodule formation and calcium content in mineralized nodules were remarkably suppressed by nicotine on days 10 and 14 of culture, respectively. ALPase activity as well as type I collagen and osteopontin expression also decreased in the presence of nicotine after 5, 10, and 14 days of culture, respectively. By contrast, the amount of bone sialoprotein increased during 14 days of culture with nicotine. These results suggest that nicotine suppresses osteogenesis through a decrease in ALPase and type I collagen production by osteoblasts.     

Bacterial degradation of vinyl chloride

Summary Mycobacterium L1 can grow on vinyl chloride as sole carbon and energy source. Application of this bacterium to remove vinyl chloride from waste gases is proposed. From air containing 1% vinyl chloride 93% of the vinyl chloride was removed by passing the air through a fermentor containing a growing population ofMycobacterium L1.     

Biotransformation of tetrachloroethylene to trichloroethylene, dichloroethylene, vinyl chloride, and carbon dioxide under methanogenic conditions

Tetrachloroethylene (PCE) and trichloroethylene (TCE), common industrial solvents, are among the most frequent contaminants found in groundwater supplies. Due to the potential toxicity and carcinogenicity of chlorinated ethylenes, knowledge about their transformation potential is important in evaluating their environmental fate. The results of this study confirm that PCE can be transformed by reductive dehalogenation to TCE, dichloroethylene, and vinyl chloride (VC) under anaerobic conditions. In addition, [14C]PCE was at least partially mineralized to CO2. Mineralization of 24% of the PCE occurred in a continuous-flow fixed-film methanogenic column with a liquid detention time of 4 days. TCE was the major intermediate formed, but traces of dichloroethylene isomers and VC were also found. In other column studies under a different set of methanogenic conditions, nearly quantitative conversion of PCE to VC was found. These studies clearly demonstrate that TCE and VC are major intermediates in PCE biotransformation under anaerobic conditions and suggest that potential exists for the complete mineralization of PCE to CO2 in soil and aquifer systems and in biological treatment processes.     

Biotransformation of tetrachloroethylene to trichloroethylene, dichloroethylene, vinyl chloride, and carbon dioxide under methanogenic conditions.

Tetrachloroethylene (PCE) and trichloroethylene (TCE), common industrial solvents, are among the most frequent contaminants found in groundwater supplies. Due to the potential toxicity and carcinogenicity of chlorinated ethylenes, knowledge about their transformation potential is important in evaluating their environmental fate. The results of this study confirm that PCE can be transformed by reductive dehalogenation to TCE, dichloroethylene, and vinyl chloride (VC) under anaerobic conditions. In addition, [14C]PCE was at least partially mineralized to CO2. Mineralization of 24% of the PCE occurred in a continuous-flow fixed-film methanogenic column with a liquid detention time of 4 days. TCE was the major intermediate formed, but traces of dichloroethylene isomers and VC were also found. In other column studies under a different set of methanogenic conditions, nearly quantitative conversion of PCE to VC was found. These studies clearly demonstrate that TCE and VC are major intermediates in PCE biotransformation under anaerobic conditions and suggest that potential exists for the complete mineralization of PCE to CO2 in soil and aquifer systems and in biological treatment processes.     

Further Considerations on a Simple Histological, Method for Identification of Osteoid Matrix

The authors have proposed fixation in cyanuric chloride as a means of inducing marked differences in acidophilia between mineralized bone matrix and osteoid. The effects of cyanuric chloride fixation are investigated in more detail here. Dye-extinction tests performed on sections from decalcified rachitic rat calvariae fixed with cyanuric chloride demonstrated a much higher isoelectric point in osteoid matrix than in mineralized matrix. Cyanuric chloride fixation resulted in high isoelectric points for fixed un mineralized proteins in general. Micro radiography revealed no decalcification in bone during fixation in cyanuric chloride.     

Chloroethene Biodegradation in Sediments at 4°C

Microbial reductive dechlorination of [1,2-¹⁴C]trichloroethene to [¹⁴C]cis-dichloroethene and [¹⁴C]vinyl chloride was observed at 4°C in anoxic microcosms prepared with cold temperature-adapted aquifer and river sediments from Alaska. Microbial anaerobic oxidation of [1,2-¹⁴C]cis-dichloroethene and [1,2-¹⁴C]vinyl chloride to ¹⁴CO₂ also was observed under these conditions.     

Covalent binding to apoprotein is a major fate of heme in a variety of reactions in which cytochrome P-450 is destroyed

The heme in rat liver microsomal cytochrome P-450 was labeled with 14C or 3H and the microsomes were fractionated after in vitro incubations with a variety of agents known to destroy cytochrome P-450 heme. A major fraction of the heme label was irreversibly bound to apoprotein in all cases, including incubations with fluroxene, 1-octene, vinyl bromide, trichloroethylene, vinyl chloride, parathion, cumene hydroperoxide, NaN3, or iron-ADP complex. Label was also extensively bound to apoprotein when purified and reconstituted cytochrome P-450 was incubated with NADPH and vinyl chloride. This process appears to be widespread and involved to a significant extent in the cytochrome P-450 heme destruction observed with many compounds.     

Studies on metabolic activation of vinyl chloride in Drosophila melanogaster after pretreatment with phenobarbital and polychlorinated biphenyls.

It is known that vinyl chloride is metabolized by the mixed function oxygenase system in the liver to reactive mutagenic and carcinogenic metabolites. This metabolic activation was studied in Drosophila melanogaster by measuring the uptake of 14C from labelled vinyl chloride in different strains and with different pretreatments with phenobarbital and polychlorinated biphenyl (PCB) Clophen A50), well known inducers of cytochrome P-450. In accordance with previously obtained data on vinyl chloride induced sex linked recessive lethals, it was shown that pretreatment with inducers increased the uptake of labelled compound up to ten times. There was, however, a marked difference in response between the five strains used. In particular, the strain Hikone, known to be resistant to insecticides, had a comparatively high initial radioactivity from vinyl chloride without any pretreatment, but it was not or insignificantly inducible with phenobarbital or PCB. Crosses between Hikone and an inducible strain indicated essentially a dominance for the Hikone genotype. Tests on inducible strains showed the same response to phenobarbital by 2 h old larvae and adult male and females. Dimethylsulphoxide (DMSO) used as a solvent decreased both the initial uptake of 14C and particularly the induction by PCB. The use of Tween 80 as an emulsifier did not have such an effect. It is emphasized that the interstrain variation in metabolic activation and inducability has to be taken into consideration in order to optimize the use of Drosophila for mutagenicity testing. This variation also opens up new possibilities of analyzing the mixed function oxygenase system biochemically and genetically.     

The persistence of sister-chromatid exchange frequencies in men occupationally exposed to vinyl chloride monomer.

The persistence of sister-chromatid exchange frequencies in a population occupationally exposed to the well known chemical mutagen vinyl chloride monomer was studied. It was shown that increased values of sister-chromatid exchange frequencies were still present in the lymphocytes of workers who had not been exposed for 8-120 days and retired persons for 5-10 years after exposure. The possible ability of vinyl chloride monomer alkylating metabolites to cause long-lasting damage of the DNA molecule is discussed.     

Mutagenic effects of vinyl chloride on Drosophila melanogaster with and without pretreatment with sodium phenobarbiturate.

Treatment of Drosophila males with 1--20% vinyl chloride in air gave an increased frequency of complete and mosaic recessive lethals. Pretreatment with phenobarbiturate for 24 h caused an increase in the mutagenic effect of vinyl chloride. This indicates that the mixed-function oxygenase system can be induced in Drosophila in the same way as in mammals.     

Mutagenic effects of vinyl chloride on Drosophila melanogaster with and without pretreatment with sodium phenobarbiturate

Treatment of Drosophila males with 1–20% vinyl chloride in air gave an increased frequency of complete and mosaic recessive lethals. Pretreatment with phenobarbiturate for 24 h caused an increase in the mutagenic effect of vinyl chloride. This indicates that the mixed-function oxygenase system can be induced in Drosophila in the same way as in mammals.