Shin‐ichi Sakakibara

Endothelin is a potent vasoconstrictor/pressor peptide, which we recently characterized from the conditioned culture medium of porcine aortic endothelial cells. We report here the cloning and partial sequencing of the rat endothelin gene. The nucleotide sequence predicted a 21-residue peptide similar to, but distinct from, porcine endothelin; 15 residues of rat endothelin were identical and 3 residues were substitutions by chemically similar amino acid residues to those in the porcine peptide. Synthetic rat endothelin was then prepared according to its deduced amino acid sequence. This synthetic peptide had (i) potent vasoconstrictor activity in the rat aortic strip and in perfused rat heart and (ii) a characteristically long-lasting in vivo pressor activity by intraaortic bolus injection in the conscious rat.

In situ detection of neural progenitor cells including stem-like cells is essential for studying the basic mechanisms of the generation of cellular diversity in the CNS, upon which therapeutic treatments for CNS injuries, degenerative diseases, and brain tumors may be based. We have generated rat monoclonal antibodies (Mab 14H1 and 14B8) that recognize an RNA-binding protein Musashi1, but not a Musashi1-related protein, Musashi2. The amino acid sequences at the epitope sites of these anti-Musashi1 Mabs are remarkably conserved among the human, mouse, and Xenopus proteins. Spatiotemporal patterns of Musashi1 immunoreactivity in the developing and/or adult CNS tissues of frogs, birds, rodents, and humans indicated that our anti-Musashi1 Mabs reacted with undifferentiated, proliferative cells in the CNS of all the vertebrates tested. Double or triple immunostaining of embryonic mouse brain cells in monolayer cultures demonstrated strong Musashi1 expression in Nestin(+)/RC2(+) cells. The relative number of Musashi1(+)/Nestin(+)/RC2(+) cells increased fivefold when embryonic forebrain cells were cultured to form 'neurospheres' in which stem-like cells are known to be enriched through their self-renewing mode of growth. Nestin(+)/RC2(-) cells, which included Talpha1-GFP(+) neuronal progenitor cells and GLAST(+) astroglial precursor cells, were also Musashi1(+), as were GFAP(+) astrocytes. Young neurons showed a trace of Musashi1 expression. Cells committed to the oligodendroglial lineage were Musashi(-). Musashi1 was localized to the perikarya of CNS stem-like cells and non-oligodendroglial progenitor cells without shifting to cell processes or endfeet, and is therefore advantageous for identifying each cell and counting cells in situ.