Metabolites In Medium Research Articles

Aflatoxin toxicity in cultured human epidermal cells: stimulation by 2,3,7,8-tetrachlorodibenzo-p-dioxin.

Aflatoxin B1 (AFB1) at 1 microgram/ml was markedly toxic to human epidermal cells grown in the Rheinwald-Green 3T3 feeder layer system. At 0.1 microgram/ml, the toxicity was barely evident, as assessed by colony expansion during a 2 week exposure, but it was dramatically stimulated by 5 nM 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), which was non-toxic alone. Neither AFB1-dihydrodiol nor AFB2 were toxic in the presence or absence of TCDD, indicating that metabolism to the 8,9-epoxide was responsible for the AFB1 toxicity. Stimulation of AFB1 epoxidation by TCDD was also indicated by the > 20-fold increase in DNA adduct formation in cultures exposed to [14C]AFB1 and TCDD for 4 days as compared to AFB1 alone. Analysis of free metabolites in culture medium by reverse-phase HPLC revealed that confluent epidermal cultures metabolized AFB1 to AFM1, AFB2a and aflatoxicol. In the presence of TCDD, the levels of AFM1 were higher (14 versus 3% of dose) as were those of AFB2a (3 versus 0.5% of dose), while aflatoxicol levels were lower (0.8 versus 2% of dose). In the absence of irradiated 3T3, the toxicities of AFB1, AFB2, AFM1 and aflatoxicol to cells in serum-free medium (0.15 mM Ca2+) were similar to those in the feeder layer system. Although this moderately low calcium concentration appeared quite satisfactory for observing toxicity, the response was attenuated at a lower calcium concentration (0.09 mM Ca2+).

Selection and isolation of bacteria capable of degrading dinoseb (2-sec-butyl-4,6-dinitrophenol).

Dinoseb (2-sec-butyl-4,6-dinitrophenol) has been a widely used herbicide that persists in some contaminated soils, and has been found in groundwaters, causing health and environmental hazards. Persistence in some soils may stem from a lack of dinoseb-degrading organisms. We established a chemostat environment that was strongly selective for aerobic (liquid phase) and anaerobic (sediment phase) bacteria able to degrade dinoseb. The chemostat yielded five taxonomically diverse aerobic isolates that could transform dinoseb to reduced products under microaerophilic or denitrifying conditions, but these organisms were unable to degrade the entire dinoseb molecule, and the transformed products formed multimeric material. The chemostat also yielded an anaerobic consortium of bacteria that could completely degrade dinoseb to acetate and CO2 when the Eh of the medium was less than -200 mV. The consortium contained at least three morphologically different bacterial species. HPLC analysis indicated that dinoseb was degraded sequentially via several as yet unidentified products. Degradation of these intermediates was inhibited by addition of bromoethane sulfonic acid. GC-MS analysis of metabolites in culture medium suggested that regiospecific attacks occurred non-sequentially on both the nitro groups and the side-chains of dinoseb. The consortium was also able to degrade 4,6-dinitro-o-cresol, 3,5-dinitrobenzoic acid, 2,4-dinitrotoluene, and 2,6-dinitrotoluene via a similar series of intermediate products. The consortium was not able to degrade 2,4-dinitrophenol. To our knowledge, this is the first report of strictly anaerobic biodegradation of an aromatic compound containing a multicarbon, saturated hydrocarbon side chain.

Characterization of the human plasma binding protein for vitamin D and its metabolites synthesized by the human hepatoma-derived cell line, Hep 3B.

Screening of three human hepatoma-derived cell lines revealed the presence of an immunologically similar plasma binding protein for vitamin D and its metabolites in media from Hep 3B cells. Approximately 3% of protein synthesized and secreted by these cells was immunoprecipitated by specific antiserum to the D-binding protein. Medium content of the protein increased over 11 days following cell seeding, and negligible amounts of 125I-labeled binding protein added to cultures were degraded over 48 h. The hepatoma-derived binding protein was indistinguishable from plasma binding protein or reference pure protein in gel filtration, sucrose gradient ultracentrifugation, and polyacrylamide gel electrophoresis systems. The Hep 3B cell product was found to bind mole/mol with monomeric actin, and bind vitamin D sterols with an affinity and specificity characteristic of the human plasma binding protein. The findings argue strongly for the identity of the Hep 3B cell product and the human plasma protein. The continuous availability of the Hep 3B cell line provides a reasonable model for investigations of biosynthesis and release of this important plasma protein.

Stoffwechselprodukte von Mikroorganismen 6‐Chlorgenistein und 6,3′‐Dichlorgenistein. 164. Mitteilung

Metabolites from Microorganisms, 6‐Chlorogenistein and 6,3′‐DichlorogenisteinA strain of Streptomyces griseus produced chlorinated metabolites in media containing soybean meal. Two of these metabolites were isolated together with a chlorine free compound which could be identified as the isoflavone genistein (I) by its spectral properties and by comparison with an authentic sample. By NMR. and mass spectroscopy the chlorinated compounds were shown to be 6‐chlorogenistein (II) and 6,3′‐dichlorogenistein (III).The 7‐glucoside of genistein is a constituent of soybean meal; it is hydrolysed and chlorinated by Streptomyces griseus.

The effect of mouse embryo fibroblasts on the binding of carcinogenic polycyclic hydrocarbons by neoplastic L cells

Cocultivation of normal mouse fibroblasts and neoplastic L fibroblasts in a mixed culture leads to accumulation of 3 H-benzo(a)pyrene ( 3 H-BP) metabolites in L cells. These metabolites most probably are transferred directly into L cells from normal cells by passing the pool of 3 H-BP metabolites in culture medium. Accumulation of firmly-bound 3 H-BP metabolites in the mixed culture proceeds more slowly than in a pure culture of normal fibroblasts. This decline of accumulation rate of firmly-bound 3 H-BP metabolites in the mixed culture as compared to pure culture may be indicative of an influence of L cells upon normal ones.