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We proposed a research which aims to reveal the possibility for gravity to develop new functions of the biological systems through the collective interactions between the components of the systems. Bioconvection of the aquatic microorganisms has been focused as a research tool for the proposal. In this paper, responses were investigated of the bioconvection pattern of Tetrahymena and Chlamydomonas to the altered gravity during parabolic fight of an airplane. In Tetrahymena, patterns were observed to increase their size under hypergravity and disappeared under microgravity. In Chlamydomonas, changes in the pattern size under hypergravity was less clear, although the patterns were observed to be enhanced under hypergravity. The patterns by Chlamydomonas remained less changed under microgravity. These differences in the response between organisms may be informative for the investigations for the development of the new research fields in space and gravitational biology., 資料番号: AA0063349096

This paper experimentally investigates a behavior of a bioconvective pattern under super gravitational fields. Experimental materials are the high density culture media of Tetrahymena. A centrifugal force was used to synthesize various super gravity conditions by using a spin tester that can generate 1-12[G]. To realize the decreasing effect of bioconvection pattern size by the increase of synthesized gravity, different lengths of a rotative beam are used to change the rate of Corioli's force and synthesized gravity. The main results are as follows: (1) The size of the convection pattern is reduced by an increase of the synthesized gravity. (2) Under synthesized gravitational field, the stream mode of bioconvection is changed by the Corioli's force. (3) The maximum transition velocity (upward, downward) of Tetrahymana is obtaind with the 2-4[G] condition. (4) The decrease in the size of convection pattern is due to the composite gravity.

Changes in polyamine levels of a mammalian cell line, HeLa cell and an unicellular protozoan, Tetrahymena with heat shock and H_2O_2-treatment were analyzed by HPLC. Rapid and transient decreases of putrescine, spermidine and spermine levels in HeLa S3 cells were observed immediately after heat shock, then, the levels of these polyamines recovered to control levels by 2 hr after heat shock. For Tetrahymena pyriformis GL and Tetrahymena thermophila B VII, however, no obvious decreases in putrescine and spermidine contents were observed after heat shock. Similar polyamine behaviours were obtained by H_2O_2-treatment as oxygen radical generator. The kinetic analysis showed a rapid and temporary decrease of polyamine levels by H_2O_2-treatment in HeLa S3 cells, while putrescine and spermidine of the two strains of Tetrahymena increased temporarily after H_2O_2-treatment. Those differences in polyamine patterns induced by heat shock and H_2O_2-treatment between HeLa cell and Tetrahymena may reflect the difference in cellular response to such stresses between a self-sustaining unicellular system and a mammalian cell line.

Effects of 9 drugs known as inhibitors of ornithine decarboxylase (ODC), S-adenosyl-methionine decarboxylase (SAMDC), spermidine (Spd) synthase or polyamine oxidase (PO) and some polyamines on polyamine synthesis of the protozoa, Acanthamoeba castellanii and Tetrahymena pyriformis were determined. Cellular polyamines were analyzed by high-perfomance liquid chromatography after culture in the absence or presence of drugs. Effects of the drugs on ODC activity in vitro were also studied. Methylacetylenicputrescine (MAP) and α-difluoromethylornithine (DFMO), at 10-2.5mM, decreased putrescine (Put) levels and inhibited ODC activity. Diaminopropane (Dap) levels in A. castellanii were decreased by MAP or DFMO, suggesting an inhibitory effect on PO activity to produce Dap from Spd. Diaminobutene at the concentration of 1mM markedly decreased Put levels and markedly inhibited ODC activity in vitro. DL-α-Hydrazino-σ-aminovaleric acid (HAVA), at 2.5mM, decreased levels of both Put and Spd. HAVA had an inhibitory effect on ODC and Spd synthase. At 10-5mM, 2-mercaptoethylamine (MEA) and dicyclohexylamine (DCHA) weakly and 3-methyltiopropylamine (MTPA) strongly decreased Spd levels. The great increase in Put levels induced by MTPA suggests enhancement of ODC activity in addition to the inhibition of Spd synthase. Methylglyoxal-bis (guanylhydrazone) (MGBG), at 10-5mM, slightly decreased Spd levels, suggesting inhibition of SAMDC activity as in mammalian cells. Chloroquine preferentially decreased Dap levels in A. castellanii. Chloroquine might be specifically inhibit PO activity in the protozoon. Addition of spermine (Spm) and Dap into the media resulted in a decrease in Spd and Put levels, respectively. It was suggested that Spm suppressed Spd synthesis in both protozoa and that Dap reduced ODC activity in T. pyriformis.

Labeled ε-N-acetyl-Lys, ε-N-monomethyl-Lys, ε-N-dimethyl-Lys, 3-methyl-His, ω-N-monomethyl-Arg, O-phospho-Ser and O-phospho-Thr were detected in the hydrolysates of the isolated whole histones from Tetrahymena pyriformis GL cultured in the presence of ^3H-acetic acid, L-methionine (methyl-^3H) and ^P-H_3PO_4. When the isolated Tetrahymena nuclei were incubated with S-adenosyl-Met (methyl-^3H), ^3H-acetyl-CoA and γ-^P-ATP, labeled ε-N-monomethyl-Lys, ε-N-acetyl-Lys and O-phospho-Ser were also found in the histone hydrolysates. The methylation was found in H3, H4 and H1 histones; acetylation in H2A, H2B, H3 and H4; phosphorylation in H2A, H4 and H1. The phosphorylation activity found in the nuclei isolated from the expornentially growing cells was higher than that found in the nuclei from the cells at stationary phase or starvation. The phosphorylation of H1 in the isolated nuclei was stimulated by the presence of 1×10^ M of cyclic AMP or cyclic GMP while the modification of other histones was not stimulated by the cyclic mononucleotides.

A cilliate protozoon, Tetrahymena contains putrescine and spermidine as major polyamines. In subcellular distribution, putrescine occurred in high concentrations in cytosol and spermidine in nuclear and ribosomal fractions. Cellular polyamine levels increased during the logarithmic growth phase and then decreased in the stationary phase. Polyamine levels were lowest in the starved cells in the G_0 stage and then, with re-feeding, increased during the G_1 and S stages. With heat treatment, the polyamine levels started to rise in the G_1 stage in the synchronized cell division cycle. These findings show that polyamine synthesis was initiated prior to DNA and RNA syntheses. Isolated macronuclei from Tetrahymena retained rigid forms in the presence of 4mM spermidine, while the nuclei were transformed into chromatin fibers in the absence of polyamines. However, LG-1 (HMG) Protein was selectively extracted from the nuclei with O.1mM salmine (a protamine), 1mM spermine, 16mM putrescine, or 4mM spermidine. These concentrations are closely correlated with their positive chrge per molecule. Changes of cellular polyamine levels during growth or cell cycles may affect chromatin structure and function in eukaryotes.