Effects of carrageenan and dextran sulfate on the expression and development of delayed hypersensitivity

Repellency of the Components of the Essential Oil, Citronella, to Triatoma rubida, Triatoma protracta, and Triatoma recurva (Hemiptera: Reduviidae: Triatominae)

The kissing bugs--Triatoma rubida (Uhler), Triatoma protracta (Uhler), and Triatoma recurva (Stal)--are common hematophagous bugs in southeastern Arizona and responsible for severe allergic reactions in some individuals who are bitten. They also possess the potential to transmit the blood parasite, Trypanosoma cruzi. We previously found the essential oil, citronella, to be an excellent deterrent of feeding of T. rubida on a restrained mouse. In this work, we tested major components--alcohols, aldehydes, and monoterpenes--of citronella oil for repellency against the three common triatome species endemic in southern Arizona. The following citronella oil components--geraniol, citronellol, limonene, and citronellal--in different concentrations and combinations were tested. All components of citronella oil demonstrated some inhibition of feeding, ranging from very weak inhibition (limonene) to significant inhibition (geraniol and citronellol). A mixture of geraniol and citronellol was found to be repellant at concentrations of .165 and .165 vol%, respectively, for all three triatome species. Citronellal and limonene had no significant repellent activity. The repellent activity of citronella oil appears to be acting through direct contact with the bugs rather than diffusion of vapors.

Effects of dextran sulfate 500 on protective responses to sublethal Trichomonas foetus infection in mice

In order to analyze the host-parasite interactions in experimental trichomoniasis, the growth of Trichomonas foetus in the peritoneal cavity and changes in the peritoneal exudate cells were followed in mice treated with dextran sulfate 500 (DS 500), a known macrophage-toxic agent. Light microscopic observation showed that DS 500 treatment induced degeneration of peritoneal macrophages within about 48 hr after the treatment and the damaged macrophages did not phagocytize the parasites, whereas peritoneal neutrophils and lymphocytes were not affected by the drug. In the DS 500-treated mice, growth of parasites in the peritoneal cavity was accelerated and a high susceptibility of the mice to T. foetus infection was observed. These results indicate that macrophages play the most important role among the peritoneal exudate cells in resistance to T. foetus infection, especially during the early stage of infection.