Pseudomonas pseudomallei exotoxin was found to be a potent inhibitor of protein and DNA synthesis in cultured macrophages. Inhibition of DNA synthesis occurred at toxin concentrations as low as 1-2 micrograms/ml and inhibition of 3H-thymidine uptake was almost complete at concentrations of 8 micrograms/ml or more. A close correlation between cell damage and inhibition by DNA synthesis was observed. For protein synthesis, inhibition was obtained at much lower doses (0.06-2.0 micrograms/ml) of the toxin. At similar toxin concentrations, DNA synthesis was marginally affected. Further, it was shown that protein synthesis inhibition occurred almost immediately after incubation, reaching its maximal inhibitory effect of 70% after 6 hr. DNA synthesis, however, was minimally affected by a similar toxin concentration even after 10 hr of incubation. The inhibition of macromolecular synthesis in macrophages by P. pseudomallei exotoxin may be relevant to its modulatory effect on the host defense mechanism.
Lignosus rhinocerus (Tiger Milk mushroom) is distributed in South China, Thailand, Malaysia, Indonesia, Philippines and Papua New Guinea. In Malaysia, it is the most popular medicinal mushroom used by the indigenous communities to relieve fever, cough, asthma, cancer, food poisoning and as a general tonic. In China, this mushroom is an expensive traditional medicine used to treat liver cancer, chronic hepatitis and gastric ulcers. The sclerotium of the mushroom is the part with medicinal value. This rare mushroom has recently been successfully cultivated making it possible to be fully exploited for its medicinal and functional benefits. The present study was carried out to evaluate the chronic toxicity of the sclerotial powder of Lignosus rhinocerus cultivar (termed TM02), its anti-fertility and teratogenic effects as well as genotoxicity.