Activation of rat alveolar macrophages by gamma interferon to inhibit Toxoplasma gondii in vitro.

We have investigated the effects of murine interferons on the ability of rat alveolar macrophages (AM) to inhibit the proliferation of the intracellular protozoan Toxoplasma gondii. This activity was determined by measuring suppression of 3H-uracil uptake into the Toxoplasma and by microscopic enumeration of the intracellular organisms. Recombinant gamma interferon (rMulFN-gamma), but not alpha/beta interferon (IFN-alpha/beta) was able to activate AM for antimicrobial activity in vitro. Maximum activation was achieved by incubation with 50-200 units/ml rMulFN-gamma and the activity was lost at one unit/ml. The highest levels of activation were obtained when macrophages were incubated with interferon for 48-72 h prior to the challenge with Toxoplasma organisms. Activation could still be obtained, however, when the interferon was added to the cultures as late as 2 h after the phagocytosis of Toxoplasma. Neither MDP nor low concentrations (1-1-ng/ml) of S. typhosa lipopolysaccharide (LPS) were able to activate these cells to inhibit the growth of Toxoplasma. Phagocytosis of Toxoplasma by AM did not result in the release of O2-, in fact the spontaneous release of O2- by these cells was inhibited by Toxoplasma. This inhibition was reversed by preincubation of the cells with rMulFN-gamma.

Anticalculus and antiplaque activity of 8-hydroxyquinoline sulfate.

The effect of 8-hydroxyquinoline sulfate on the formation of artificial calculi, rat calculus, and dog plaque plus its ability to remove dog plaque were studied. Several chemically related agents were also evaluated for their anticalculus effects. The most effective anticalculus agent was 8-hydroxyquinoline sulfate. At concentrations of 4 or 5%, swabbed over molar teeth, it was essentially equally effective in retarding the formation of rat calculus. Significant (1% level) reduction occurred with concentration as low as 3% in rats. When used so as to mimic mouthrinse use, 4% 8-hydroxyquinoline sulfate also significantly (5% level) reduced formation of calculus in rats. All rats showed normal behavioral and weight-gain patterns. Visual evaluation of oral tissues in the swabbing tests plus visual and histopathological evaluation of oral tissues in the mouthrinse procedure showed 8-hydroxyquinoline sulfate had no irritating or toxic effects. In dogs, the teeth treated with 4% 8-hydroxyquinoline sulfate nine times during a five-day period had 93.7 to 98.4% less buccal plaque than vehicle-treated teeth. The antiplaque effect was considerable in both canines and fourth premolars. In older dogs, teeth treated with 4% 8-hydroxyquinoline sulfate 15 times during a ten-day period had 33 to 46.1% less plaque than when treated with the vehicle. The effect was considerable on canines but slight on fourth premolars. In older dogs after 24 treatments during a 15-day period, 4% 8-hydroxyquinoline sulfate removed 25 to 57.5% of established plaque whereas the vehicle removed 2.5 to 22.5%. Again, 8-hydroxyquinoline sulfate was more effective on canine buccal plaque. These results show that 8-hydroxyquinoline sulfate is an effective anticalculus and antiplaque agent that is nontoxic to animal oral tissue. The results also indicate that the dog is a suitable animal model for the evaluation of antiplaque agents.