The genetic diversity of the ciguatera fish poisoningrelated dinoflagellate distributed in Japanese coastal areas was investigated. The entire sequence of the 5.8S rRNA gene and two internal transcribed (ITS) regions were determined, which included putative pseudogenes, from 19 strains of dinoflagellates assigned to the genus Gambierdiscus Adachi et Fukuyo collected from Japanese subtropical and temperate coastal areas. The sequences obtained from the 19 strains were divided into two types based on sequence similarity. Here we designate the two types as type 1 and type 2. For the relationship between the genotypes and origins of the strains used, the strains collected from subtropical areas possessed the type 1 sequence; whereas those from temperate areas possessed the type 2. This observation led us to question former reputations that Gambierdiscus cells observed in Japanese temperate areas are immigrants from Japanese subtropical areas. Subsequently, we sequenced a part of the 18S rRNA gene from two strains from subtropical areas and two from temperate areas. Unfortunately, phylogenetic analysis including the sequences obtained from various gonyaulacales dinoflagellates failed to determine the species phylogenetically closely related to and possible origin(s) of the Gambierdiscus sp. from the Japanese coastal areas.

A toxic dinoflagellate responsible for paralytic shellfish poisoning (PSP), Alexandrium catenella (Ac) was fed to the short-necked clam Tapes japonica, and the accumulation and depuration profiles of PSP toxins were investigated by means of high-performance liquid chromatography with postcolumn fluorescence derivatization (HPLC-FLD). The short-necked clams ingested more than 99% of the Ac cells (4 Â 10 7 cells) supplied once at the beginning of experiment, and accumulated a maximal amount of toxin (185 nmol/10 clams) after 12 h. The rate of toxin accumulation at that time was 23%, which rapidly decreased thereafter. Composition of the PSP toxin accumulated in the clams obviously different from that of Ac even 0.5 h after the cell supply, the proportion of C1+2 being much higher than in Ac, although the reason remains to be elucidated. In contrast, a higher ratio of gonyautoxin (GTX)1+4 than in Ac was detected in the toxin profiles of clam excrements. The variation in toxin composition derived presumably from the transformation of toxin analogues in clams was observed from 0.5 h, such as reversal of the ratio of C1 to C2, and appearance of carbamate (saxitoxin (STX), neoSTX and GTX2, 3) and decarbamoyl (dc) derivatives (dcSTX and dcGTX2, 3), which were undetectable in Ac cells. The total amount of toxin distributed over Ac cells, clams and their excrements gradually declined, and only 1% of supplied toxin was detected at the end of experiment. r

The neurotoxic effects of excitatory amino acids (EAAs) are suggested to be connected with the chronic loss of neuronal cells, thereby being responsible for the age-related neurodegenerative diseases. Therefore, it seems conceivable that the excitatory amino acid transporters may contribute to the protection of neuronal cells against the excitotoxic damage by facilitating the removal of EAAs from the brain tissue. On the other hand, previous studies have suggested that glial cell differentiation may be involved in the protection and recovery of neural function probably through the elevation of BDNF gene expression in the brain. Based on these findings, histone deacetylase (HDAC) inhibitors are assumed to induce glutamate transporter-1 (GLT-1) gene expression probably through the promotion of glial cell differentiation. Then, we examined the effects of HDAC inhibitors on GLT-1 mRNA levels in rat C6 glioma cells and found that trichostatin A can induce GLT-1 gene transcription following steroid 5α-reductase and GFAP gene expression. Therefore, it seems conceivable that glial cell differentiation may play a potential role in the removal of EAAs probably through the expression of GLT-1, thereby being involved in the protection of neuronal cells against the chronic excitotoxic insults in the brain.

The polyamines caldopentamine and homocaldopentamine were detected in axenic strains of Chattonella antiqua and Heterosigma akashiwo (Raphidophyceae), respectively, as well as spermidine, the most abundant polyamine in both phytoplankton species. Trace amounts of putrescine, diaminopropane and norspermine were also detected in both species. Spermine was detected only from C. antiqua. These long linear polyamines are characteristic components of thermophilic bacteria. The detection from two species of Raphidophyceae indicates that the occurrence of long linear polyamines is not restricted to thermophilic microorganisms.

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