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The neural cell adhesion molecule (NCAM) is modified by polysialic acid (polySia or PSA) in embryonic brains. In adult brains, polySia modification of NCAM is only observed in restricted areas where neural plasticity, remodeling of neural connections, or neural generation is ongoing although the amount of NCAM remains unchanged. Impairments of the polySia-expression and several single nucleotide polymorphisms (SNPs) of the polysialyltransferase (polyST) ST8SIA2 gene are reported to be associated with schizophrenia and bipolar disorder. Chlorpromazine (CPZ) is well-known as an agent for treating schizophrenia, and our hypothesis is that CPZ may affect the polySia expression or the gene expression of polySTs or NCAM. To test this hypothesis, we analyzed the effects of CPZ on the expression of polySia-NCAM on human neuroblastoma cell line, IMR-32 cells, by immunochemical and chemical methods. Interestingly, the cell surface expression of polySia, especially those with lower chain lengths, was significantly increased on the CPZ-treated cells, while mRNAs for polySTs and NCAM, and the amounts of total polySia-NCAM remained unchanged. The addition of brefeldin A, an inhibitor of endocytosis, suppressed the CPZ-induced cell surface polySia expression. In addition, polySia-NCAM was also observed in the vesicle compartment inside the cell. All these data suggest that the level of cell surface expression of polySia in IMR-32 is highly regulated and that CPZ changes the rate of the recycling of polySia-NCAM, leading to the up-regulation of polySia-NCAM on the cell surface. We also analyzed the effect of CPZ on polySia-expression in various brain regions in adult mice and found that CPZ only influenced the total amounts of polySia-NCAM in prefrontal cortex. These results suggest a brain-region-specific effect of CPZ on the expression of total polySia in mouse brain. Collectively, anti-schizophrenia agent CPZ consistently up-regulates the expression polySia at both cellular and animal levels.

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Summary A determination method for individual natural vitamin B 6 compounds was developed. The vitamin B 6 compounds were specifically converted into 4-pyridoxolactone (PAL), a highly fluorescent compound, through a combination of enzymatic reactions and HCl-hydrolysis. PAL was then determined by HPLC. Pyridoxal was completely oxidized to PAL with pyridoxal 4-dehydrogenase (PLDH). Pyridoxine and pyridoxamine were totally converted into PAL through a coupling reaction involving pyridoxine 4-oxidase and PLDH, and one involving pyridoxamine-pyruvate aminotransferase and PLDH, respectively. The 5 ¢ -phosphate forms and pyridoxine-␤ -glucoside were hydrolyzed with HCl, and then determined as their free forms. Pyridoxine 5 ¢ -phosphate and pyridoxine-␤ -glucoside were not separately determined here. Three food samples were analyzed by this method. Key Words vitamin B 6 , 4-pyridoxolactone, pyridoxal 4-dehydrogenase, pyridoxine 4-oxidase, pyridoxamine-pyruvate aminotransferase There are six natural forms of vitamin B 6 : pyridoxine, pyridoxal, pyridoxamine, pyridoxine 5 ¢ -phosphate, pyridoxal 5 ¢ -phosphate, and pyridoxamine 5 ¢ -phosphate ( Fig. 1). In addition, plants contain pyridoxine-␤ -glucoside, a storage form of vitamin B 6 ; it is not counted as vitamin B 6 because its nutritional availability as a form of vitamin B 6 in the human body is controversial ( 1 ). The above six vitamin B 6 compounds have identical nutritional functions. On the other hand, recent studies have shown that individual vitamin B 6 compounds exhibit specific biochemical functions; pyridoxamine, in particular, can detoxify active carbonyl products and is undergoing a phase II clinical trial for the treatment of complications of diabetes ( 2 ). Vitamin B 6 compounds are strong quenchers of singlet oxygen ( 3 ), and pyridoxal 5 ¢ -phosphate and pyridoxamine 5 ¢ -phosphate, coenzyme forms of vitamin B 6 , show stronger protection of yeast cells from oxidative death than vitamin C, a representative antioxidative vitamin ( 4 ). Thus, the development of a method for the determination of individual vitamin B 6 compounds plus pyridoxine-␤ -glucoside in foods is required to estimate their functionality.Although many methods have been developed for the determination of individual vitamin B 6 compounds, no method can be satisfactorily applied to the analysis of food samples. Thus, a microbioassay involving a budding yeast, Saccharomyces cerevisiae (former name, S. uvarum ), which was developed about 40 y ago ( 5 ), has been used to determine the total content of vitamin B 6 in food samples; in the figure, the content of pyridoxine-␤ -glucoside is included because food samples are prehydrolyzed with HCl for the microbioassay, and pyridoxine-␤ -glucoside in the samples is converted into pyridoxine. The best method so far developed for individual determination may be cation-exchange HPLC with a fluorescence detection system ( 6 ), which is applicable to biological samples, such as serum, brain, liver, milk and so on, from experimental animals. The seco...

These results reveal a novel fatty acid-sensing mechanism in enteroendocrine cells.