RESUMO
The role of intracellular symbionts contributing to their host has been investigated in the planthoppers,Nilaparvata lugens Stal andLaodelphax striatellus Fallen. We have found that the isolated yeastlike symbionts, identified as a member of the genusCandida, from the host's egg produce ergosterol when cultured. A comparative study of sterols in the cultured symbionts, the host insects, aposymbiotic host insects, and dietary plants demonstrated that ergosterol produced in the symbiotes is provided to the host insects and possibly transformed in the host insects into cholesterol via 24-methylenecholesterol. The conversion of injected 24-methylenecholesterol-d3 into cholesterol has been shown in the brown planthopper (N. lugens).
RESUMO
1-Naphthyl N-alkylcarbamates (alkyl = methyl, ethyl, n-propyl and n-butyl) were synthesized and then nitrosated with a dichloromethane extract of nitrous acid. The respective N-nitrosated carbamates were purified and tested for mutagenicity using Salmonella typhimurium LT2 strain TA98 and TA100, and Saccharomyces cerevisiae strain D3. The reactivity of the four nitrosocarbamates toward 4-(p-nitrobenzyl)-pyridine (NBP) was measured in order to assess their strengths as alkylating agents. Bioassay results indicated an inverse relationship between the length of the N-alkyl chain and the mutagenicity of the N-nitrosonaphthylcarbamates. The NBP test results indicated an inverse relationship between chemical reactivity and N-alkyl chain length.
