No abstract

Cigarette smoking causes profound suppression of pulmonary T cell responses, which has been associated with increased susceptibility to respiratory tract infections and decreased tumor surveillance. Exposure of human T cells to cigarette tar or its major phenolic components, hydroquinone and catechol, causes an immediate cessation of DNA synthesis without cytotoxicity. However, little is known of the mechanisms by which this phenomenon occurs. In this report we demonstrate that hydroquinone and catechol inhibit lymphocyte proliferation by quenching the essential tyrosyl radical in the M2 subunit of ribonucleotide reductase.

No abstract

A line of transgenic mice harboring a fusion gene consisting of 1900 bp of proximal 5'-flanking region from the murine GnRH receptor gene linked to the complementary DNA encoding luciferase was established to determine whether this promoter can direct tissue-specific expression in vivo and serve as a model for identifying the molecular mechanisms underlying hormonal regulation of this gene. Of 10 tissues screened, luciferase was detected predominantly in pituitary gland, but also in brain and testis. To assess hormonal regulation, luciferase activity was measured in intact males and ovariectomized females treated with an anti-GnRH serum alone, and in combination with testosterone or 17beta-estradiol. No effect of steroid treatment on transgene expression was detected. However, immunoneutralization of GnRH resulted in decreased serum LH concentrations and suppressed pituitary expression of luciferase. Furthermore, the effects of GnRH antiserum could be prevented by the administration of a noncross-reactive GnRH agonist. Thus, 1900 bp of 5'-flanking DNA from the murine GnRH receptor gene are sufficient to target luciferase expression in transgenic mice to established sites of GnRH receptor gene expression. Furthermore, we suggest that GnRH regulation of GnRH receptor gene expression is mediated by regulatory elements residing within 1900 bp of the 5'-flanking region.