Biomedical subjects

J Spivack

Publications and source records attributed to J Spivack.

12 recordsLinked to original sources

PubMed2001

Stable carbon isotope evidence for intrinsic bioremediation of tetrachloroethene and trichloroethene at area 6, Dover Air Force Base.

Area 6 at Dover Air Force Base (Dover, DE) has been the location of an in-depth study by the RTDF (Remediation Technologies Development Forum Bioremediation of Chlorinated Solvents Action Team) to evaluate the effectiveness of natural attenuation of chlorinated ethene contamination in groundwater. Compound-specific stable carbon isotope measurements for dissolved PCE and TCE in wells distributed throughout the anaerobic portion of the plume confirm that stable carbon isotope values are isotopically enriched in 13C consistent with the effects of intrinsic biodegradation. During anaerobic microbial reductive dechlorination of chlorinated hydrocarbons, the light (12C) versus heavy isotope (13C) bonds are preferentially degraded, resulting in isotopic enrichment of the residual contaminant in 13C. To our knowledge, this study is the first to provide definitive evidence for reductive dechlorination of chlorinated hydrocarbons at a field site based on the delta13C values of the primary contaminants spilled at the site, PCE and TCE. For TCE, downgradient wells show delta13C values as enriched as -18.0/1000 as compared to delta13C values for TCE in the source zone of -25.0 to -26.0/1000. The most enriched delta13C value on the site was observed at well 236, which also contains the highest concentrations of cis-DCE, VC, and ethene, the daughter products of reductive dechlorination. Stable carbon isotope signatures are used to quantify the relative extent of biodegradation between zones of the contaminant plume. On the basis of this approach, it is estimated that TCE in downgradient well 236 is more than 40% biodegraded relative to TCE in the proposed source area.

Biodegradation, Environmental↗

PubMed1994

Novel pathway for bacterial metabolism of bisphenol A. Rearrangements and stilbene cleavage in bisphenol A metabolism.

Bisphenol A (BPA) is metabolized by a Gram-negative aerobic bacterium via a novel pathway involving oxidative skeletal rearrangement of the BPA. Oxidation of the aliphatic methyl group of BPA leads to coproduction of the methyl-hyroxylated 2,2-bis(4-hydroxyphenyl)-1-propanol and a skeletally rearranged triol 1,2-bis(4-hydroxyphenyl)-2-propanol. The major route of metabolism (> 80%) is through the rearrangement. The 1,2-bis(4-hydroxyphenyl)-2-propanol is dehydrated to 4,4'-dihydroxy-alpha-methylstilbene, which is rapidly cleaved by oxidation to 4-hydroxybenzaldehyde and 4-hydroxyacetophenone. 4-Hydroxybenzaldehyde is oxidized to 4-hydroxybenzoic acid. Both 4-hydroxybenzoic acid and 4-hydroxyacetophenone are mineralized. The minor product of BPA hydroxylation, 2,2-bis(4-hydroxyphenyl)-1-propanol, is further oxidized to form both 2,2-bis(4-hydroxyphenyl)propanoic acid and a skeletally rearranged tetraol, 2,3-bis(4-hydroxyphenyl)-1,2-propanediol. As is the case in the hydroxylation of BPA, the major product is skeletally rearranged. 2,3-Bis(4-hydroxyphenyl)-1,2-propanediol is slowly transformed to 4-hydroxyphenacyl alcohol.

1-Propanol↗

PubMed1980

Malignant melanoma originating from intradermal nevi. A clinicopathologic entity.

Two cases of malignant melanoma arising in preexisting intradermal nevi without a junctional element are described. These cases and the two known to have been reported previously demonstrate similar clinical and morphologic findings. These include an innocuous gross appearance, a nodular growth pattern, and deep levels of invasion. It appears that the origin of the tumor in the dermis conceals malignant transformation. The consequent time lapse and the dermal position of the lesion favor deep penetration of the tumor prior to removal.

Adult↗

PubMed1972