David C Spink

Learn More
Most research on the effects of chemicals on biologic systems is conducted on one chemical at a time. However, in the real world people are exposed to mixtures, not single chemicals. Although various substances may have totally independent actions, in many cases two substances may act at the same site in ways that can be either additive or nonadditive. Many(More)
Rates of microsomal 17 beta-estradiol (E2) hydroxylation at the C-2, -4, -6 alpha, and -15 alpha positions are each induced greater than 10-fold by treating MCF-7 breast cancer cells with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The TCDD-induced activities at the C-2, -6 alpha and -15 alpha positions have been attributed to cytochrome P450 1A1 (CYP1A1);(More)
Three forms of glutamate decarboxylase from hog brain (termed alpha-, beta-, and gamma-GAD) were separated by hydrophobic interaction chromatography on phenyl-Sepharose, by isoelectric focusing, and by polyacrylamide gel electrophoresis. When rechromatographed on phenyl-Sepharose, each form migrated as a single entity, indicating that the forms are not(More)
Life-long estrogen exposure is recognized as a major risk factor for the development of breast cancer. While the initial events in the regulation of gene expression by estrogen have been described in detail, far less is known of the role of estrogen in the long-term regulation of gene expression. In this study, we investigated the effects of long-term(More)
Four molecular forms of rat-brain glutamate decarboxylase were resolved by hydrophobic interaction chromatography on phenyl-Sepharose and affinity chromatography on ATP-agarose. SDS-polyacrylamide gel electrophoresis of purified enzyme and immunoblots of SDS gels indicated a subunit molecular weight of approximately 60,000 for each form of the enzyme, and(More)
The catechol estrogen metabolites of 17beta-estradiol (E2), 2-hydroxyestradiol (OHE2) and 4-OHE2, differ in hormonal properties and carcinogenic potential. In Syrian hamster kidney, 4-OHE2 induces clear-cell carcinoma whereas 2-OHE2 does not, and an E2 4-hydroxylase appears to be involved in E2-induced carcinogenesis in these animals. Specific E2(More)
Cytochrome P450 (CYP)1A1 and CYP1B1, which are under the regulatory control of the aryl hydrocarbon (Ah) receptor (AhR), catalyze the metabolic activation of numerous procarcinogens and the hydroxylation of 17beta-estradiol (E2) at the C-2 and C-4 positions, respectively. There is evidence of cross-talk between estrogen receptor alpha (ERalpha)- and(More)
Human cytochrome P450 1B1 (CYP1B1) catalyzes the hydroxylation of 17beta-estradiol (E(2)) at C-4, with a lesser activity at C-2. The E(2) 4-hydroxylase activity of human CYP1B1 was first observed in studies of MCF-7 breast cancer cells. Sequencing of polymerase chain reaction products revealed that CYP1B1 expressed in MCF-7 cells was not the previously(More)
  • 1