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Shigeo Hayashi

Publications and source records attributed to Shigeo Hayashi.

24 records · Page 2Linked to original sources
PubMed2003

Rac promotes epithelial cell rearrangement during tracheal tubulogenesis in Drosophila.

Cell rearrangement, accompanied by the rapid assembly and disassembly of cadherin-mediated cell adhesions, plays essential roles in epithelial morphogenesis. Various in vitro and cell culture studies on the small GTPase Rac have suggested it to be a key regulator of cell adhesion, but this notion needs to be verified in the context of embryonic development. We used the tracheal system of Drosophila to investigate the function of Rac in the epithelial cell rearrangement, with a special attention to its role in regulating epithelial cadherin activity. We found that a reduced Rac activity led to an expansion of cell junctions in the embryonic epidermis and tracheal epithelia, which was accompanied by an increase in the amount of Drosophila E-Cadherin-Catenin complexes by a post-transcriptional mechanism. Reduced Rac activity inhibited dynamic epithelial cell rearrangement. Hyperactivation of Rac, on the other hand, inhibited assembly of newly synthesized E-Cadherin into cell junctions and caused loss of tracheal cell adhesion, resulting in cell detachment from the epithelia. Thus, in the context of Drosophila tracheal development, Rac activity must be maintained at a level necessary to balance the assembly and disassembly of E-Cadherin at cell junctions. Together with its role in cell motility, Rac regulates plasticity of cell adhesion and thus ensures smooth remodeling of epithelial sheets into tubules.

Animals↗
PubMed2002

Single-bubble sonochemiluminescence in aqueous luminol solutions.

Sonochemiluminescence (SCL) of luminol due to a single bubble is studied through spectral measurement. No SCL was observed from a stable single bubble that emitted high-intensity sonoluminescence (SL). In contrast, SCL was observed under conditions of an unstable dancing bubble, where a bubble grows and ejects tiny bubbles, making it "dance" by counteraction. Furthermore, SCL was observed from dancing bubbles even when SL was not observed, depending on the dissolved gas content. The instability of bubble collapse is the key parameter governing SCL.

Journal Article↗
PubMed2002

Comparitive study of the formation of hydroxyapatite in simulated body fluid under static and flowing systems.

alpha-CaSiO3 ceramics of nominal composition CaO 46.0, SiO2 54.0, and Na2O 0.4 mass% were soaked in simulated body fluid (SBF). The soaking systems were maintained under both static and flowing conditions to study their effect on the formation of hydroxyapatite (HAp). Two different flowing systems were designed for soaking, namely, a closed system using a fast flow rate of about 2.8 mL/s (circulating system) and an open system using a slow flow rate of about 40 mL/day (slow flowing system). The HAp layer in all samples initially formed as a rough layer of ball-like particles. Under a fast flow of SBF solution, silica gel particles peeled from silica-rich interlayer during the first soaking period. The silica gel particles then reattached to the product HAp layer and induced the formation of new HAp particles of smaller size. In the slow flowing system, the rough HAp layer initially formed on the ceramic surfaces became gradually smoother after prolonged soaking. The formation rate and thickness of the HAp layer decreased with increasing flow rate of the SBF solution. These results indicate that flowing SBF solution gives rise to differences in the formation rates, formation behavior, and microstructure of the HAp layer.

Biocompatible Materials↗
PubMed2002

Evolving role of Antennapedia protein in arthropod limb patterning.

Evolutional changes in homeotic gene functions have contributed to segmental diversification of arthropodan limbs, but crucial molecular changes have not been identified to date. The first leg of the crustacean Daphnia lacks a prominent ventral branch found in the second to fourth legs. We show here that this phenotype correlates with the loss of Distal-less and concomitant expression of Antennapedia in the limb primordium. Unlike its Drosophila counterpart, Daphnia Antennapedia represses Distal-less in Drosophila assays, and the protein region conferring this activity was mapped to the N terminal region of the protein. The results imply that Dapnia Antennapedia specifies leg morphology by repressing Distal-less, and this activity was acquired through a change in protein structure after separation of crustaceans and insects.

Amino Acid Sequence↗
PubMedDate not supplied

Transcriptional readthrough of Hox genes Ubx and Antp and their divergent post-transcriptional control during crustacean evolution.

Hox genes are in principle tandemly arranged in an order colinear with their order of expression along the anterior-posterior axis. Combinations of Hox proteins encode information that specifies the unique characteristics of axial regions in the metazoan body plan. The independent regulation of Hox genes achieved by differential promoter activity is essential for the expression of Hox proteins in distinct territories and thereby creating a full repertoire of Hox codes. Here we report the abundant expression of transcriptional readthrough products of two adjacent Hox genes, Ubx, and Antp, in five crustacean species of Branchiopoda and Malacostraca. Bicistronic mRNA places Antp under the control of the Ubx promoter, which is active in the posterior segments of two branchiopodans Daphnia and Artemia, and would normally reduce the complexity of Hox codes if translated. This does not occur, however, as the translational capability of the bicistronic mRNA is limited. In Daphnia, bicistronic Ubx/Antp mRNA produced no significant level of either UBX or ANTP. In Artemia, on the other hand, the bicistronic mRNA produced only UBX, and replaced the role of monocistronic Ubx mRNA. In this way, multiple post-transcriptional control mechanisms in two extant branchiopodans can be seen as preventing the potentially deleterious consequences of Hox gene fusion.

Animals↗