PubMed Health⌕ Search

Biomedical subjects

Ken-ichi Yamazaki

Publications and source records attributed to Ken-ichi Yamazaki.

4 recordsLinked to original sources
PubMed2006

A simple and extremely sensitive system for detecting estrogenic activity using transgenic Arabidopsis thaliana.

Numerous physiological processes are regulated by endocrine systems in animals. Endocrine-disrupting chemicals (EDCs) can affect physiological processes of organisms by binding to hormone receptors. Therefore, it is necessary to develop methods for detecting EDCs and removing them from the environment. We have developed a simple and low-cost reporter gene assay system for the comprehensive analysis of estrogenic activity using transgenic Arabidopsis thaliana. This transgenic plant constantly expresses two effector proteins: a chimeric estrogen receptor and a chimeric nuclear receptor coactivator. Estrogen-dependent interaction between the two effector proteins triggers transcriptional activation of reporter gene, beta-glucuronidase. We have demonstrated this transgenic plant's capability of detecting the existence of 17beta-estradiol at a concentration of 50 pM (13 pg/ml) in agar medium. This plant can also detect other estrogenic substances, such as diethylstilbestrol, p-n-nonylphenol, bisphenol A, and Genistein.

Animals↗
PubMed2005

Accumulation of intestinal intraepithelial lymphocytes in association with lack of polymeric immunoglobulin receptor.

Immunoglobulin A (IgA) is transported by the polymeric immunoglobulin receptor (pIgR) through epithelial cells of the gut, the airways, the tear and salivary glands, and the lactating mammary gland, and IgA accumulates in serum and the intestinal lamina propria of pIgR-deficient (pIgR(-/-)) mice. Intraepithelial lymphocytes (IEL) increased in number and Thy-1(+)CD8alphabeta(+)TCRalphabeta(+) IEL preferentially expanded in the small intestine (SI) of pIgR(-/-) mice. Cytotoxic activity of SI-IEL was comparable in pIgR(+/+) and pIgR(-/-) mice. Accumulation and cytotoxic activity of SI-IEL was attenuated in germ-free pIgR(-/-) mice. Furthermore, Thy-1(+)CD8alphabeta(+) IEL did not expand in pIgR(-/-)TCRbetadelta(-/-) mice compared with TCRbetadelta(-/-) mice, and SI-IEL from pIgR(-/-)TCRbetadelta(-/-) mice as well as TCRbetadelta(-/-) mice expressed perforin and granzyme B mRNA and serine esterase. The proliferative status of SI-IEL from pIgR(+/+) and pIgR(-/-) mice was similar, but adoptive transfer experiment showed that SI-IEL from pIgR(-/-) mice might have a stronger tendency to migrate into the intestinal epithelia than those from pIgR(+/+) mice. These results demonstrate that the accumulation of Thy-1(+)CD8alphabeta(+)TCRalphabeta(+) IEL in pIgR(-/-) mice triggered by intestinal microorganisms needed the expression of functional TCR and might be caused by lymphocyte migration into the intestinal epithelia.

Animals↗
PubMed2004

Three Arabidopsis MBF1 homologs with distinct expression profiles play roles as transcriptional co-activators.

Multiprotein bridging factor 1 (MBF1) is known to be a transcriptional co-activator that mediates transcriptional activation by bridging between an activator and a TATA-box binding protein (TBP). We demonstrated that expression of every three MBF1 from Arabidopsis partially rescues the yeast mbf1 mutant phenotype, indicating that all of them function as co-activators for GCN4-dependent transcriptional activation. We also report that each of their subtypes shows distinct tissue-specific expression patterns and responses to phytohormones. These observations suggest that even though they share a similar biochemical function, each MBF1 has distinct roles in various tissues and conditions.

Arabidopsis↗