Studies on the production of indole-3-acetic acid with auxin-heterotrophic mutants derived from cultured crown gall cells

Mutants in the indole-3-acetic acid metabolism derived fromcultured crown gall cells were tested to see whether they couldutilize any one of eight indolic compounds in place of indole-3-aceticacid. Two auxin-heterotrophic mutant cell lines could not utilizeindolepyruvic acid, but growth recovered when there was a supplementof indole-3-acetic acid. Indoleacetonitril and indoleacetaldoximeinhibited the growth of mutant cell lines and their parentalcrown gall cells. Cultured crown gall cells may have synthesizedindole-3-acetic acid from tryptophan via indolepyruvic acidand indole-acetaldehyde, and also may be able to produce indole-3-aceticacid from tryptophan via tryptamine (Received May 6, 1980; )     

Thymus-independent anti-DNP antibody responses to DNP-casein and DNP-gelatin.

Although studies on the molecular nature of thymus-independent antigens suggested that the polymeric structure with repeated antigenic determinants and slow metabolism are responsible for thymus-independence, we found that anti-DNP antibody responses to DNP-casein and DNP-gelatin were thymus-independent as well as macrophage-independent. These antibody responses were not affected by in vivo treatment with carrageenan or anti-thymocyte serum. In addition, responses of athymic nude mice to both antigens did not show any significant differences when compared with heterologous nu/+ mice. The findings were confirmed by in vitro experiments; non-adherent spleen cells or T cell-depleted spleen cells responded well to both antigens to the same extent as normal spleen cells. Since both casein and gelatin are polyclonal B cell activators and are not presumed to be high polymer or slow-metabolizing substances, we suggest that thymus-independence in many kinds of antibody response should be reconsidered.     

Micronuclei formation and aneuploidy induced by Vpr, an accessory gene of human immunodeficiency virus type 1.

Vpr, an accessory gene of HIV-1, induces cell cycle abnormality with accumulation at G2/M phase and increased ploidy. Since abnormality of mitotic checkpoint control provides a molecular basis of genomic instability, we studied the effects of Vpr on genetic integrity using a stable clone, named MIT-23, in which Vpr expression is controlled by the tetracycline-responsive promoter. Treatment of MIT-23 cells with doxycycline (DOX) induced Vpr expression with a giant multinuclear cell formation. Increased micronuclei (MIN) formation was also detected in these cells. Abolishment of Vpr expression by DOX removal induced numerous asynchronous cytokinesis in the multinuclear cells with leaving MIN in cytoplasm, suggesting that the transient Vpr expression could cause genetic unbalance. Consistent with this expectation, MIT-23 cells, originally pseudodiploid cells, became aneuploid after repeated expression of Vpr. Experiments using deletion mutants of Vpr revealed that the domain inducing MIN formation as well as multinucleation was located in the carboxy-terminal region of Vpr protein. These results suggest that Vpr induces genomic instability, implicating the possible role in the development of AIDS-related malignancies.