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Mechanisms of extrahepatic tumor induction by peroxisome proliferators in male CD rats.
- L. Biegel, M. Hurtt, S. Frame, J. O'Connor, J. Cook
- Biology, MedicineToxicological sciences : an official journal of…
- 1 March 2001
It is suggested that estradiol may play a role in enhancement of Leydig cell tumors in the rat, and that peroxisome proliferators may induce tumors via a non-LH type mechanism.
The Toxicology of Perfluorooctanoate
The hepatocellular tumors observed in rats are likely to have been the result of the activation of the peroxisome proliferator activated receptor α (PPARα), and the proposed mechanism for Leydig-cell tumor formation is of questionable relevance to humans.
Effects of ammonium perfluorooctanoate on Leydig cell function: in vitro, in vivo, and ex vivo studies.
- L. Biegel, R. Liu, M. Hurtt, J. Cook
- Biology, MedicineToxicology and applied pharmacology
- 1 September 1995
The hypothesis that C8 produces an increase in estradiol by inducing cytochrome P450 XIX (aromatase), which converts testosterone to Estradiol, and that the elevated estradio levels ultimately produce Leydig cell hyperplasia and adenoma formation is investigated.
90-day feeding and one-generation reproduction study in Crl:CD BR rats with 17 beta-estradiol.
This 90-day/one-generation reproduction study with 17 beta-estradiol was designed to set dose levels for future multigenerational reproduction and combined chronic toxicity/oncogenicity studies, and to provide benchmark data for a risk assessment for chemicals with estrogen-like activities.
Screening methods for thyroid hormone disruptors.
There was a general consensus that all known chemicals which interfere with thyroid hormone function and homeostasis act by either inhibiting synthesis, altering serum transport proteins, or by increasing catabolism of thyroid hormones.
Effects of dietary 17 beta-estradiol exposure on serum hormone concentrations and testicular parameters in male Crl:CD BR rats.
The data demonstrate that in utero and postnatal dietary administration of 17 beta-estradiol at levels which increased serum estradiol levels to approximately 400% of control and decreased testosterone levels to 33% ofControl did not reduce the number of Sertoli cell nuclei per testis.
Effects of 17 beta-estradiol on serum hormone concentrations and estrous cycle in female Crl:CD BR rats: effects on parental and first generation rats.
- L. Biegel, J. Cook, M. Hurtt, J. O'Connor
- BiologyToxicological sciences : an official journal of…
- 1 August 1998
In evaluating a sampling strategy for measuring serum hormone levels, it appears that detection of compound-related alterations in serum hormone concentrations can be best detected by sampling during diestrus.
Effect of the peroxisome proliferator, ammonium perfluorooctanoate (C8), on hepatic aromatase activity in adult male Crl:CD BR (CD) rats.
- R. Liu, M. Hurtt, J. Cook, L. Biegel
- Biology, MedicineFundamental and applied toxicology : official…
- 1 April 1996
The results of this study suggest that the increased serum concentration of estradiol produced by C8 in rats is at least partly due to a direct effect on the liver to increase synthesis ofEstradiol through induction of aromatase cytochrome P450 in the endoplasmic reticulum.
2,2',4,4',5,5'-hexachlorobiphenyl as a 2,3,7,8-tetrachlorodibenzo-p-dioxin antagonist in C57BL/6J mice.
- L. Biegel, M. Harris, D. Davis, R. Rosengren, L. Safe, S. Safe
- Biology, ChemistryToxicology and applied pharmacology
At doses as high as 750 to 1000 mumol/kg, 2,2',4,4',5,5'-hexachlorobiphenyl (HCBP) did not cause fetal cleft palate, suppress the splenic plaque-forming cell response to sheep red blood cells, or…
90-Day Feeding and One-Generation Reproduction Study in Crl : CD BR Rats with 17 / 3-Estradiol 1
A 90-day/one-generation reproduction study with 170-estradiol was designed to set dose levels for future multigenerational reproduction and combined chronic toxicity/oncogenicity studies, and to provide benchmark data for a risk assessment for chemicals with estrogenlike activities.