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Biomedical subjects

M Tokumoto

Publications and source records attributed to M Tokumoto.

At least 55 records · Page 3Linked to original sources
PubMed1995

Molecular heterogeneity among primary motoneurons and within myotomes revealed by the differential mRNA expression of novel islet-1 homologs in embryonic zebrafish.

Zebrafish embryos have three or four identifiable primary motoneurons per hemisegment. We previously reported that, while several ventral cells initially express the zebrafish Islet-1 (Isl-1) gene, a member of the LIM/homeobox gene family, the expression of this gene becomes restricted to a single or a pair of cells slightly anterior to each segment border by 16 hr after fertilization. Double staining by in situ hybridization and immunohistochemistry strongly suggested that these cells were mainly rostral primary motoneurons. Here, we have isolated two novel zebrafish cDNA clones for more Isl-1 family genes, termed zfIsl-2 and zfIsl-3. zfIsl-2 mRNA starts to be expressed in the ventral midsegmental cells per hemisegment around 15 hr. Double labeling experiments have shown that these midsegmental cells are the caudal primary motoneuron (CaP) and its variant equivalence pair. Our results revealed the heterogeneity in the expressed genes among primary motoneurons before the fates of the primary motoneurons are irreversibly determined, and further suggest the involvement of the Isl-1 and zfIsl-2 genes in the determination of cellular identities by primary motoneurons in embryonic zebrafish. zfIsl-3 mRNA is not expressed in motoneurons but is expressed at 17 hr, mainly in the ventral myotomes. This suggests that zfIsl-3 may be involved in the regional specification of the myotome and also in target recognition by CaP. zfIsl-2 is also expressed throughout the developing eye and tectal region of the midbrain, the target for the retinal axons. In the ventral spinal cord of the spadetail mutant embryo, which has defects in the somites, the cells expressing zfIsl-2 mRNA significantly decreased in number in contrast to the increase in cells expressing Isl-1 mRNA, suggesting the influence of the somites on the expression of both genes.

Amino Acid Sequence↗
PubMed1993

Aromatization of 4-oxocyclohexanecarboxylic acid to 4-hydroxybenzoic acid by two distinctive desaturases from Corynebacterium cyclohexanicum. Properties of two desaturases.

We have previously demonstrated that Corynebacterium cyclohexanicum degrades cyclohexanecarboxylic acid, a bacteriocide, through a pathway including the aromatization of 4-oxocyclohexanecarboxylic acid to 4-hydroxybenzoic acid [Kaneda, T. (1974) Biochem. Biophys. Res. Commun. 58, 140-144]. Aromatization has now been shown to be catalysed by two desaturase enzymes. Under the action of desaturase I, 4-oxocyclohexanecarboxylic acid is converted to (+)-4-oxocyclohex-2-enecarboxylic acid which is then aromatized by desaturase II to 4-hydroxybenzoic acid. The latter reaction is presumed to occur via the unstable intermediate, 4-oxocyclohex-2,5-dienecarboxylic acid, which is spontaneously isomerized to 4-hydroxybenzoic acid. Desaturase I has been purified in an electrophoretically homogeneous form. It is monomeric with a molecular mass of 67 kDa and contains one tryptophan, one histidine and two cysteine residues per enzyme molecule. The enzyme produces an equivalent amount of 4-oxocyclohex-2-enecarboxylic acid and hydrogen peroxide from 4-oxocyclohexanecarboxylic acid. The properties of desaturase I have been studied in detail. Desaturase II is unstable and has been partially purified. Its characterization is therefore limited. However, the molecular mass of desaturase II was estimated to be 43 kDa by gel filtration chromatography. The characterization of both desaturase enzymes is described in this paper. The possible environmental importance of microbial aromatization in the biodegradation of compounds with the cyclohexane structure is discussed.

Amino Acids↗
PubMed1993

Identification of 27-nor-3 alpha, 7 alpha, 12 alpha-trihydroxycoprostan-24-one apparently derived from 3 alpha, 7 alpha, 12 alpha-trihydroxy-24-oxocoprostanoic acid, a postulated intermediate of bile acid biosynthesis.

Incubation of [27-13C]-3 alpha, 7 alpha, 12 alpha-trihydroxycoprost-24-en-26-oic acid with rat liver homogenate followed by 13C-NMR analysis of the incubation product has resulted in the identification of [26-13C]-27-nor-3 alpha, 7 alpha, 12 alpha-trihydroxycoprostan-24-one, supporting the idea that the substrate has been metabolized into 3 alpha, 7 alpha, 12 alpha-trihydroxy-24-oxocoprostan-26-oic acid CoA derivative.

Animals↗