Cannibalism and population dynamics of the grapsid crab Hemigrapsus penicillatus were investigated in a brackish lagoon in northeastern Japan, and in the laboratory. Crabs with carapace width < 0.5 cm were frequently preyed upon by larger individuals; prey size appeared to be related to the maximum gape of predator chelae. Field studies revealed that a rapid decrease in the number of small crabs occurred following a great increase as a result of settling of juvenile crabs in the fall. This was concluded to be caused by cannibalism. The availability of shelter such as narrow gaps between boulders and stones limited cannibalism. Avoidance of large individuals by small ones, and visual approach of large individuals to small ones, as well as the presence of suitable shelter for small crabs, are considered important factors in maintaining the stability of the H. penicillatus population.

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Burrowing and migration behaviour of the mud-crab Helice tr~dens (De Haan) were examined in relabon to cannibahsn~ using an experimental habitat simulating an estuarine area as well as under natural condtions in the field. In summer, when the population density was greater than the carrylng capacity of the number of burrows in an experimental habitat, large indviduals preyed upon emerged small ones and the number of smaller individuals decreased until total numbers approximated the carrylng capacity of burrows in the expenmental habitat. These results suggest that burrows provide protection from predation. In the field, large individuals ceased to burrow, and migrated to a brackishwater lagoon, whlle small individuals dug burrows, and became dispersed over all the reed marsh in summer. Habitat segregation due to migration of large individuals to the lagoon and dispersion of small ones in the reed marsh may lessen the chance of cannibalism.

The gene transduction method is a very powerful tool, not only in basic science but also in clinical medicine. Regenerative medicine is one field that has close connection with both basic and clinical. Recently, it has been reported that induced pluripotent stem (iPS) cells can be produced from somatic cells by a three or four gene transduction. We have also recently reported that lentiviral gene transfer of the tal1/scl gene can efficiently differentiate non-human primate common marmoset ES cells into hematopoietic cells without the support of stromal cells. In this study, we constructed a high-performance human fetal liver-derived lentiviral expression library, which contains a high number of individual clones, in order to develop a very helpful tool for understanding early hematopoiesis and/or hepatocytosis for future regenerative medicine. Our lentiviral cDNA library consisted of more than 8 x 10(7) individual clones, and their average insert size was >2 kb. DNA sequence analysis for each individual inserted cDNAs revealed that >60% contained the full-length protein-coding regions for many genes including cytokine receptors, cytoplasmic proteins, protein inhibitors, and nuclear factors. The transduction efficiency on 293T cells was 100% and the average size of an integrated cDNA was ~1.1 kb. These results suggest that our lentiviral human fetal liver cDNA expression library could be a very helpful tool for accelerating the discovery of novel genes that are involved in early hematopoiesis and hepatopoiesis and to make the use of iPS cells more efficient in the field of regenerative medicine.

We developed novel species and sex determination methods for three Japanese mustelid species. We used DDX3Y to determine sex and generated a primer set to amplify both DDX3X and DDX3Y DNA in Mustela itatsi, M. sibirica and Martes melampus. To determine species and sex simultaneously, we generated fluorescence-labelled primers that give different fragment lengths at D-loop, DDX3X and DDX3Y of these three species using a DNA sequencer.

Redox-switchable catalysis is an emerging research field that seeks to regulate chemical reactions by the simple reduction-oxidation manipulation. The modulation of electron density of redox-responsible ligands in the transition metal catalyzed reactions by changing oxidation state was usually used to control catalytic activity. Meanwhile, we have developed the cation pool method which involves generation and accumulation of organic cations in relatively high concentration.For example, the accumulation of an organo-dication 2 has been accomplished by the electrochemical oxidative C-C bond cleavage of compound 1 at low temperature (Scheme 1).1) The carbocations having two electron deficient carbon centers are expected to serve as effective Lewis acids, and we revealed that several reactions such as Mukaiyama-Aldol reaction,2) Diels-Alder reaction, and Nazarov cyclization, were significantly promoted by a catalytic amount of the organo-dications in a highly efficient manner (Scheme 2). We are highly motivated to investigate the utility of the dications as redox-switchable catalysts, and revealed the possibility to modulate Mukaiyama-Aldol reaction by using the reaction system (Scheme 3). 1) Okajima, M.; Suga, S.; Itami, K. Yoshida, J. J. Am. Chem. Soc. 2005, 127, 6930-6931. 2) Mukaiyama, T.; Kobayashi, S.; Murakami, M. Chem. Lett. 1984, 1759-1762.

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