Ramona McClain

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Our laboratory is testing the hypothesis that hypomethylation of DNA [a decreased content of 5-methylcytosine (5MeC) compared with cytosine] facilitates aberrant oncogene expression involved in tumorigenesis, using a model system of mouse strains with differing susceptibilities to liver tumorigenesis. The B6C3F1 (C57BL/6 x C3H/He) mouse serves as the(More)
The effect of phenobarbital on thyroid function and the metabolism and biliary excretion of thyroxine in rats was determined. Phenobarbital, administered for 2 weeks at a dose of 100 mg/kg/day, resulted in an increase in hepatic and thyroid gland weights, decreased circulating levels of T4, T3 and rT3, and increased TSH levels in male and female rats. After(More)
There are two basic mechanisms whereby chemicals produce thyroid gland neoplasia in rodents. The first involves chemicals that exert a direct carcinogenic effect in the thyroid gland and the other involves chemicals which, through a variety of mechanisms, disrupt thyroid function and produce thyroid gland neoplasia secondary to hormone imbalance. There are(More)
A study was conducted to determine the mode of action for phenobarbital promotion of thyroid follicular cell neoplasia in rats using an initiation-promotion model established by Hiasa et al. (Y. Hiasa, Y. Kitahori, M. Ohshima, T. Fujita, T. Yuasa, N. Konishi, and A. Miyashiro, 1982a, Carcinogenesis 3, 1187-1190). Seven groups of Charles River Crl: CD(SD)BR(More)
To provide new insights into ligand/A1 adenosine receptor (A1 AR) interactions, site-directed mutagenesis was used to test the role of several residues in the first four transmembrane (TM) domains of the human A1 AR. Based on multiple sequence analysis of all known ARs, both acidic (glutamic acid and aspartic acid) and polar hydroxy (serine and threonine)(More)
Hepatic microsomal enzymes play an important role in thyroid hormone homeostasis. Glucuronidation of thyroxine is the rate limiting step in the biliary excretion of thyroxine in the rat; the monodeiodinases are important in the conversion of T4 to T3 and reverse T3 and subsequent deiodinations. Phenobarbital is known to affect thyroid function in rats due(More)
There are two basic mechanisms whereby chemicals produce thyroid gland neoplasia in rodents. The first involves chemicals that exert a direct carcinogenic effect in the thyroid gland and the other involves chemicals which, through a variety of mechanisms, disrupt thyroid function and produce thyroid gland neoplasia secondary to hormone imbalance. These(More)
Chronic administration of reserpine is associated with the development of pheochromocytomas in rats. Short-term administration of reserpine to rats has been shown to stimulate chromaffin cell proliferation, leading to the hypothesis that reserpine causes pheochromocytomas indirectly by providing a proliferative backdrop on which genetic damage may occur.(More)
Genistein is a phytoestrogen that occurs naturally in the diet and is found in a wide variety of plant-derived foods especially in soybeans and soy-based foods. There is wide spread interest in genistein and related phytoestrogens as chemopreventive agents for a variety of human diseases and cancers based on epidemiologic evidence of reduced cancer rates in(More)