Polyamines: essential factors for growth and survival.

Polyamines are low molecular weight, aliphatic polycations found in the cells of all living organisms. Due to their positive charges, polyamines bind to macromolecules such as DNA, RNA, and proteins. They are involved in diverse processes, including regulation of gene expression, translation, cell proliferation, modulation of cell signalling, and membrane stabilization. They also modulate the activities of certain sets of ion channels. Because of these multifaceted functions, the homeostasis of polyamines is crucial and is ensured through regulation of biosynthesis, catabolism, and transport. Through isolation of the genes involved in plant polyamine biosynthesis and loss-of-function experiments on the corresponding genes, their essentiality for growth is reconfirmed. Polyamines are also involved in stress responses and diseases in plants, indicating their importance for plant survival. This review summarizes the recent advances in polyamine research in the field of plant science compared with the knowledge obtained in microorganisms and animal systems.

Nuclear translocation and increased expression of Bax and disturbance in cell cycle progression without prominent apoptosis induced by hyperthermia.

Effects of hyperthermia at 42.5 degreesC for 6 h on cell survival, cell cycle progression, and the localization and expression levels of Bcl-2 and Bax, as well as the association between Bcl-2 and Bax in human lung cancer cells were investigated. Untreated human lung cancer cells, though immortalized, expressed Bax unlike peripheral lymphocytes with low Bax expression. Bcl-2 was localized only in the cytoplasm in all the cell lines tested, whereas Bax was localized in the cytoplasm and/or nucleus; (1) only in the nucleus in three cell lines, (2) either in the nucleus or the cytoplasm in three cell lines, (3) in both the nucleus and the cytoplasm in one cell line, and (4) only in the cytoplasm in three cell lines. Of 10 cell lines examined, 6 had a low sensitivity to hyperthermia with a viability of 50% or more, and four cell lines had a high sensitivity to hyperthermia with a viability of less than 50% regardless of cell type. In cell lines highly sensitive to hyperthermia, Bax was localized in the nucleus. Hyperthermia increased the cellular level of Bax, but not Bcl-2, and reduced the association between Bcl-2 and Bax expression in PC-10 cells. Although the Bax level increased, hyperthermia induced only mild apoptosis and caused prominent cell cycle disturbance, especially in the S and G2M phases. Thus, hyperthermia at 42.5 degreesC for 6 h had cytostatic effect as well as caused mild apoptosis. Interestingly, during 3 h of hyperthermia, Bax translocated from the cytoplasm to the nucleus, whereas Bcl-2 remained in the cytoplasm. These results raise the possibility that Bax may lose its function as the inducer of apoptosis by translocating into the nucleus or have an unknown role in the nucleus.

[Antigenicity studies of prulifloxacin (NM441)].

Antigenicity of prulifloxacin, a new antibacterial agent, and that of its active metabolite (NM394) were investigated using guinea pigs and mice in this study. In the study with guinea pigs, the animals were immunized with prulifloxacin by oral administration, the predetermined clinical route, and with prulifloxacin alone or emulsified with Freund's complete adjuvant (FCA) by s.c. When active systemic anaphylaxis (ASA) test and passive cutaneous anaphylaxis (PCA) test of these animals were conducted by eliciting with NM394 alone or protein conjugate (NM394-GPSA) of NM394 and guinea pig serum albumin (GPSA), no ASA and PCA reactions were observed. When guinea pigs were immunized subcutaneously with protein conjugate (NM394-BSA) of NM394 and bovine serum albumin (BSA) together with FCA, ASA and PCA reactions were positive by eliciting with NM394-GPSA or NM394-BSA, but were negative by eliciting with NM394 alone. In the study with mice, the animals were immunized orally with prulifloxacin and intraperitoneally with prulifloxacin alone or suspended with aluminum hydroxide gel (alum). When rat PCA test of sera from these mice was conducted by eliciting with NM394 or NM394-GPSA, no positive PCA reaction was observed. When mice were immunized intraperiotneally with NM394-BSA together with alum, PCA reactions were positive by eliciting with NM394-GPSA or NM394-BSA, but were negative by eliciting with NM394 alone. These results show that prulifloxacin has no immunogenicity to guinea pigs and mice, and NM394 as its active form has no eliciting potential to anti-NM394-BSA antibody.