New approaches for estimating risk from exposure to diethylstilbestrol.

A subgroup from a National Institute of Environmental Health Sciences, workshop concerned with characterizing the effects of endocrine disruptors on human health at environmental exposure levels considered the question, If diethylstilbestrol (DES) were introduced into the market for human use today and likely to result in low-dose exposure of the human fetus, what would be required to assess risk? On the basis of an analysis of the quality of data on human DES exposure, the critical times and doses for inducing genital tract malformations and cancer must be determined. This would be facilitated through analysis of the ontogeny of estrogen receptor expression in the developing human genital tract. Models of low-dose estrogenic effects will have to be developed for human and rodent genital tract development. Mouse models offer many advantages over other potential animal models because of the wealth of the earlier literature, the availability of sensitive end points, the availability of mutant lines, and the possibility of generating genetically engineered model systems. Through multidisciplinary approaches, it should be possible to elucidate the cellular and molecular mechanisms of endocrine disruption elicited by estrogens during development and facilitate an assessment of risk to humans

A survey of phytoestrogenic activity in Kansas flint hills pastures

The botanical composition and basal cover of three Kansas Flint Hills pastures located in Butler and Chase counties was surveyed to estimate the incidence of plant species that contain appreciable levels of estrogenic activity. Many-flowered scurfpea and Ladino clover were the only plant species classified as high in estrogenic activity. Although significant estrogenic activity existed in specific species, the willingness of livestock to consume those species is unclear

Effect of antiandrogen flutamide on measures of hepatic regeneration in rats

Male rat liver undergoes a process of demasculinization during hepatic regeneration following partial hepatectomy. The possibility that antiandrogens might potentiate this demasculinization process and in so doing augment the hepatic regenerative response was investigated. Adult male Wistar rats were treated with the antiandrogen flutamide (2 mg/rat/day or 5 mg/rat/day subcutaneously) or vehicle for three days prior to and daily after a 70% partial hepatectomy. At various times after hepatectomy, the liver remnants were removed and weighed. Rates of DNA and polyamine synthesis were assessed by measuring thymidine kinase and ornithine decarboxylase activities, respectively. Hepatic estrogen receptor status and the activity of alcohol dehydrogenase, an androgen-sensitive protein, were measured. Prior to surgery, the administration of 5 mg/day flutamide reduced the hepatic cytosolic androgen receptor activity by 98% and hepatic cytosolic estrogen receptor content by 92% compared to that present in vehicle-treated controls. After hepatectomy, however, all differences in sex hormone receptor activity between the treatment groups were abolished. The rate of liver growth after partial hepatectomy in the three groups was identical. Moreover, hepatectomy-induced increases in ornithine decarboxylase activity and thymidine kinase activity were comparable. These data demonstrate that, although flutamide administration initially alters the sex hormone receptor status of the liver, these affects have no effect on the hepatic regenerative response following a partial hepatectomy. © 1989 Plenum Publishing Corporation

Bisphenol A in Thermal Paper Receipts: Taylor et al. Respond

We agree with Schwartz and Landrigan that there is a need for change in the regulatory system for chemicals used in products in the United States. Bisphenol A (BPA) is one of thousands of chemicals of concern, but it provides a striking example of what happens when there is no requirement for premarket testing

Large Effects from Small Exposures. I. Mechanisms for Endocrine-Disrupting Chemicals with Estrogenic Activity

Reproduced with permission from Environmental Health Perspectives. doi:10.1289/ehp.5494Information concerning the fundamental mechanisms of action of both natural and environmental hormones, combined with information concerning endogenous hormone concentrations, reveals how endocrine-disrupting chemicals with estrogenic activity (EEDCs) can be active at concentrations far below those currently being tested in toxicological studies. Using only very high doses in toxicological studies of EEDCs thus can dramatically underestimate bioactivity. Specifically: a) The hormonal action mechanisms and the physiology of delivery of EEDCs predict with accuracy the low-dose ranges of biological activity, which have been missed by traditional toxicological testing. b) Toxicology assumes that it is valid to extrapolate linearly from high doses over a very wide dose range to predict responses at doses within the physiological range of receptor occupancy for an EEDC; however, because receptor-mediated responses saturate, this assumption is invalid. c) Furthermore, receptor-mediated responses can first increase and then decrease as dose increases, contradicting the assumption that dose-response relationships are monotonic. d) Exogenous estrogens modulate a system that is physiologically active and thus is already above threshold, contradicting the traditional toxicological assumption of thresholds for endocrine responses to EEDCs. These four fundamental issues are problematic for risk assessment methods used by regulatory agencies, because they challenge the traditional use of extrapolation from high-dose testing to predict responses at the much lower environmentally relevant doses.Support during the preparation of this manuscript was provided by the W. Alton Jones Foundation to K.A.T, as well as by grants from the National Institutes of Health (NIH) (CA50354) and the University of Missouri (VMFC0018) to W.V.W and NIH (ES08293 and ES11283), U.S. Environmental Protection Agency (U914991), and University of Missouri Research Board to F.v.S

Bisphenol A Is Released from Used Polycarbonate Animal Cages into Water at Room Temperature

doi:10.1289/ehp.5993Bisphenol A (BPA) is a monomer with estrogenic activity that is used in the production of food packaging, dental sealants, polycarbonate plastic, and many other products. The monomer has previously been reported to hydrolyze and leach from these products under high heat and alkaline conditions, and the amount of leaching increases as a function of use. We examined whether new and used polycarbonate animal cages passively release bioactive levels of BPA into water at room temperature and neutral pH. Purified water was incubated at room temperature in new polycarbonate and polysulfone cages and used (discolored) polycarbonate cages, as well as control (glass and used polypropylene) containers. The resulting water samples were characterized with gas chromatography/mass spectrometry (GC/MS) and tested for estrogenic activity using an MCF-7 human breast cancer cell proliferation assay. Significant estrogenic activity, identifiable as BPA by GC/MS (up to 310 µg/L), was released from used polycarbonate animal cages. Detectable levels of BPA were released from new polycarbonate cages (up to 0.3 µg/L) as well as new polysulfone cages (1.5 µg/L), whereas no BPA was detected in water incubated in glass and used polypropylene cages. Finally, BPA exposure as a result of being housed in used polycarbonate cages produced a 16% increase in uterine weight in prepubertal female mice relative to females housed in used polypropylene cages, although the difference was not statistically significant. Our findings suggest that laboratory animals maintained in polycarbonate and polysulfone cages are exposed to BPA via leaching, with exposure reaching the highest levels in old cages.Support during the preparation of this manuscript was provided by grants from the National Institutes of Health (CA50354) and the University of Missouri (VMFC0018) to W.V.W., NIH (ES08293 and ES11283) to F.v.S., and the U.S.G.S

Degradation of Gamma Globulin Amyloid Fibrils by Serine Proteases

The formation of amyloid-beta fibrils within the human brain has shown to be a possible cause for Alzheimer’s disease. Amyloid fibrils can also be formed from various non-disease causing proteins. In this study, in vitro formation of amyloid fibrils from bovine gamma globulin and the subsequent degradation provided an exploration of amyloid fibril properties. Two serine proteases, trypsin and pepsin were studied. The fibril formation from bovine gamma globulin at pH 2 was monitored using thioflavin T (ThT), which is known to bind amyloid fibril to form a complex, which gives off fluorescence. The excitation wavelength used was 420 nm with an emission wavelength of 482 nm. The proteases were subsequently added to the pre-formed amyloid fibril to induce degradation. Pepsin’s properties allowed for the pH of the fibril networks to remain at 2, while for trypsin an adjusted pH of 7 ensured that the trypsin molecules would be active. Changes in fluorescence of the ThT-gamma globulin amyloid complex confirmed that degradation occurred to the amyloid fibril. The rate constant and the half-life for the degradation were calculated to compare influences from changes in pH to that of the proteases. Final half-life calculations for degradation of the amyloid fibril came to be 1.3 hours for pepsin, 9.2 hours for the pH change from 2 to 7, and 14 hours for trypsin. Calculations show that pepsin at pH 2 had significantly catalyzed degradation faster than trypsin or changes in pH. Future studies will expand the exploration of these degradation processes for amyloid-beta fibril and applications for developing potential anti-amyloid agents

Low Phytoestrogen Levels in Feed Increase Fetal Serum Estradiol Resulting in the “Fetal Estrogenization Syndrome” and Obesity in CD-1 Mice

doi:10.1289/ehp.10448Although estrogenic chemicals can disrupt development of the reproductive system, there is debate about whether phytoestrogens in soy are beneficial, benign, or harmful. We compared reproductive and metabolic characteristics in male and female mice reared and maintained on non-soy low-phytoestrogen feed or soy-based high-phytoestrogen feed. Removing phytoestrogens from mouse feed produces an obese phenotype consistent with metabolic syndrome, and the associated reproductive system abnormalities are consistent with FES due to elevated endogenous fetal estradiol. Laboratory rodents may have become adapted to high-phytoestrogen intake over many generations of being fed soy-based commercial feed; removing all phytoestrogens from feed leads to alterations that could disrupt many types of biomedical research