Isolation of an olfactory cDNA: similarity to retinol-binding protein suggests a role in olfaction.

Molecular cloning techniques were used to isolate and characterize a protein possibly involved in the signal transducing system in olfactory tissue of the frog Rana pipiens. A complementary DNA library was constructed with messenger RNA obtained from frog olfactory neuroepithelium. A 700-base pair complementary DNA clone encoding a protein with a molecular weight of 20,300 was identified by differential hybridization analysis with polyadenylated RNA from olfactory epithelium and nonsensory respiratory epithelium. The messenger RNA corresponding to this clone was abundant in the cells of Bowman's glands in olfactory tissue but not in respiratory epithelium nor in several other tissues. The predicted sequence of this protein is homologous to members of a family of proteins that bind and transport small molecules in serum, suggesting that this protein may also bind and transport odorants in the mucus secreted by Bowman's glands.

Projected uptake and toxicity of selenium compounds from the environment.

Industrial workers and members of the general public may be exposed to selenium by inhalation of selenium in the workplace or atmosphere or by ingestion of selenium in food. A model has been developed to evaluate the potential uptake of selenium in body tissues by these two exposure routes. Rates were estimated for transport of selenium between five compartments including lung, gastrointestinal tract, blood, liver and other tissues. Results of model simulations were compared to published tissue distribution information obtained from single inhalation exposures of rats and dogs to radiolabeled selenium compounds at concentrations from 20 mg/m3 to 20 micrograms/m3 with initial body burdens of selenium ranging from 28 to 0.09 micrograms Se/kg body wt. The model was then modified to predict equilibrium organ concentrations of selenium in people after continual exposure to selenium in the air or in the diet. Daily intake levels of 100 micrograms/day and a fractional absorption value of 0.8 were used. With an air concentration of 1 ng Se/m3, model predictions indicated that most of the total body selenium in people is likely to come from their diet because selenium in the urban atmosphere contributes a very small part of the total body selenium. However, continual inhalation of selenium at the threshold limit value (TLV; 200 micrograms/m3) could contribute significantly to the total body burden of selenium. Levels of selenium predicted in lung, liver, and blood after inhalation of selenium at the TLV were 22,000, 1200, and 440 ng Se/g tissue. Predicted lung concentrations were near those that produced toxic effects in animals after ingestion of Se.