A dominant negative mutant Friend murine leukemia virus (FMLV) env gene was cloned from an immunoselected Friend erythroleukemia cell. The mutant env had a point mutation which resulted in a Cys-to-Arg substitution at the 361st amino acid in the FMLV envelope protein (Env). The mutant Env was retained in the endoplasmic reticulum (ER) and accumulated because of its slow degradation. The NIH 3T3 cells expressing the mutant env were resistant to ecotropic Moloney MLV (MoMLV) penetration, suggesting that the mutant Env traps the ecotropic MLV receptors in the ER. When the mutant env gene was transfected into and expressed in the cells persistently infected with MoMLV, the wild-type Env was trapped in the ER, and the MoMLV production was suppressed. Thus, the mutant Env accumulating in the ER trans-dominantly and efficiently interfered with the ecotropic MLV infection at both the early and the late stages.

Among Moloney murine leukemia viruses (Mo-MuLVs) having stop codons other than UAG at the gag-pol junction, Mo-MuLV with UAA, but not with UGA, had a replication disadvantage. Mo-MuLV with a glutamine codon (CAG) at the junction did not replicate. A revertant of this virus consisted of the original virus and a virus with a deletion of the pol region. Protease and Pr65sag encoded by their respective genomes complemented each other. In murine leukemia virus (MuLV), genome-sized mRNA * Corresponding author.

One of the shortcomings of percutaneous ethanol injection therapy (PEIT) is that many sessions are necessary to accomplish the treatment. In order to reduce the number of treatment sessions, we inserted two or three needles before injection of ethanol was begun. Using the multiple-needle insertion method, we markedly reduced the number of treatment sessions. Histopathologic examination, imaging techniques, and serum alpha-fetoprotein levels showed efficacy of PEIT using the multiple-needle insertion method. No serious complication occurred. Levels of transient pain, fever, and the feeling of intoxication did not seem to be different from those occurring with the conventional method. Multiple-needle insertion method may be valuable as a method for reducing the number of treatment sessions necessary and thus shortening the treatment period.

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