Sakuji Koya

Morphological and functional maturation of the thyroid during early development of anuran larvae

In Bufo bufo japonicus, synthesis of thyroid hormones, as measured by 131I-incorporation, developed very early, and small but significant amounts of iodothyronines were formed as early as stage 26, at which time the thyroid was recognized only as a simple thickening of the pharyngeal epithelium. The thyroid appeared in its typical form, and 131I-labeled thyroglobulin was formed in an appreciable amount at stage 33. Before this stage, soluble 131I-proteins were formed only in small amounts, and the molecular sizes of these proteins were smaller than that of thyroglobulin. The changes in iodoamino acid formation were also quite critical between stages 32 and 33. The main iodotyrosine was monoiodotyrosine and the main iodothyronine was triiodothyronine before stage 32. After stage 33, diiodotyrosine was the main iodotyrosine and thyroxine the main iodothyronine. Similar sequential maturation of the thyroid function was observed also in Xenopus laevis.

Establishment of combined analytical method to extract the genes of interest from transcriptome data

Techniques for analyzing genome-wide expression profiles, such as the microarray technique and next-generation sequencers, have been developed. While these techniques can provide a lot of information about gene expression, selection of genes of interest is complicated because of excessive gene expression data. Thus, many researchers use statistical methods or fold change as screening tools for finding gene sets whose expression is altered between groups, which may result in the loss of important information. In the present study, we aimed to establish a combined method for selecting genes of interest with a small magnitude of alteration in gene expression by coupling with proteome analysis. We used hypercholesterolemic rats to examine the effects of a crude herbal drug on gene expression and proteome profiles. We could not select genes of interest by using standard methods. However, by coupling with proteome analysis, we found several effects of the crude herbal drug on gene expression. Our results suggest that this method would be useful in selecting gene sets with expressions that do not show a large magnitude of alteration.

Purification and Characterization of T3-Receptor from Beef Liver Plasma Membrane

Over the past two decades, it has been believed that the transport of thyroid hormones into cells was by simple diffusion. However, recent evidence indicates that the uptake of T3 into the cells occurs by receptor-mediated endocytosis (1), and that this mode of entry is physiologically significant (2). It is also known that the plasma membrane receptor is highly stereospecific for L-T3 (3). Two classes of T3-receptor (high affinity - low capacity and low affinity - high capacity sites) were determined in GH3 cells (3), swiss 3T3 cells (4) and human erythrocytes (5). Using affinity labeling with Bromoacetyl [125I]T3 (BrAc[125I]T3, the binding site of the T3-receptor was identified by SDS-PAGE to be a 55K dalton band (3). However, its structural details and the role of the plasma membrane receptor on the mechanism of T3 action have not been clearly defined.