The Chinese hamster lung cell line DC-3F contains two polymorphic di hydro l'oliile reducÃ-ase (DHFR) alÃ-elesthai are defined by an Asp-Asn amino acid sequence difference al posilion 95 in Ihe prolein. Previously, we reported thai Ihe anlifolale-resistant subline DC-3F/A3 overexpressed a I cu.* -»Phe mulanl of Ihe Asp95 (21k) alÃ-eleand that this was Ihe basis of its resistance to melholrexal...

Oxidative stress exerted by superoxide-generating (redox-cycling) agents such as paraquat triggers the soxRS regulon of Escherichia coli. In this system, SoxR protein is the redox-sensitive activator of the soxS gene, the product of which then activates the —¿ 10 promoters of this regulon. We found that 4-nitroquinoline-iV-oxide (4NQO) is a powerful inducer of soxS, > 10-fold more potent than...

Dehydroepiandrosterone (DHEA), the major steroid precursor of androgens and estrogens produced in peripheral tissues in primates, is an effective chemopreventive agent in the A/-methyl-A/-nitrosourea (MNU)induced rat mammary tumor model. Dietary 1)111 \ (5-600 ppm; 600 mg/kg diet) was administered beginning 1 week before MM and admin istered continually throughout the duration of the experiment...

Mammalian O'-alkylguanine-DNA alkyltransferases (AGTs) are readily inactivated by incubation with the pseudosubstrate, O6-benzylguanine, but the equivalent protein from the Escherichia coli ogt gene is much less sensitive and the Saccharomyces cerevisiae and E. coli oda gene prod uct AGTs are completely resistant to this compound. We have expressed the normal human ACT and various point mutatio...

The LEC (Long-Evans with a cinnamon-like color) rat is a mutant of the Long-Evans strain which develops hereditary hepatitis and hepatoma with age. Activities and mRNA levels of A'-acetylglucosaminyltransferase III and V (GnT-III and GnT-V, respectively) were determined during hepatocarcinogenesis in this rat using a LEA (Long-Evans with an agouti color) rat as a control. GnT-III activity in LE...

Tumor cells undergo self-destruction when incubated with cytotoxic T-cells (CTL) consistent with the observation that suppression of target protein synthesis causes resistance to apoptosis. Resistance to CTL is also induced by stress, suggesting that pathways exist suppressing apoptosis. Here we examine whether stress induced lysis resistance to CTL and tumor necrosis factor a involves stress p...

a-Tocopherol (a-T) uptake and its relationship to cell proliferation and lipid peroxidation was studied in a baby hamster kidney cell line (BHK21/C13) and its polyoma virus-transformed malignant counterpart i IÃŽIIK21/PyY cells). The principal findings were as follows, (a) The level of lipid peroxidation judged by malondialdehyde (MDA) measurement by HPLC, was higher in the transformed cells th...