| Popis: |
The rickettsia of Rocky Mountain spotted fever, Rickettsia rickettsii, under certain conditions was more stable in partially purified suspensions than in crude yolk-sac suspensions. To demonstrate the presence in yolk sac of substances detrimental to infectivity, and to learn something of their nature, yolk sacs of normal embryonated chicken eggs were fractionated with lipid solvents. Fractions obtained were tested for their effect on the infectivities of R. rickettsii and the viruses of eastern and Venezuelan equine encephalitis (EEE and VEE). The water-soluble fraction of an acetone extract contained substances that were inactivating to both rickettsial and viral infectivity, and the water-soluble fraction of an ethanol extract stabilized viral infectivity. Thin-layer chromatographic analyses indicated that the inactivating fraction contains, in addition to the cholesterol, a mixture of bile acids, including deoxycholate, that probably are responsible for the viral inactivation. The inactivating effect was partially neutralized by 0.3% bovine serum albumin. Thin-layer chromatography of the stabilizing fraction produced several bands that fluoresced under ultraviolet light. The stabilizing and UV- absorbing properties of this fraction were dialyzable. Qualitative tests for protein and carbohydrate were negative for both the stabilizing and inactivating fractions. Results of tests for purines and pyrimidines in the stabilizing fraction are inconclusive. When the two fractions were mixed and tested with partially purified VEE virus, each fraction modified the effect of the other; rapid inactivation was prevented, but the inactivating fraction markedly reduced the effect of the stabilizing fraction. |
