ß-adrenergic receptor regulates embryonic epithelial extensibility through actomyosin inhibition.

During morphogenesis, epithelial tissues reshape and expand to cover the body and organs. The molecular mechanisms of this deformability remain elusive. Here, we investigate the role of the ß-adrenergic receptor (ADRB) in orchestrating actomyosin contractility, pivotal for epithelial extensibility. Chemical screens on Xenopus laevis embryos pinpointed ADRB2 as a principal regulator. ADRB2 promotes actomyosin relaxation, facilitating apical cell area expansion during body elongation. In contrast, ADRB2 knockdown results in heightened cell contraction, marked by synchronous oscillation of F-actin and myosin, impeding body elongation. ADRB2 mutants with reduced affinity for ligand binding lack the function to induce cellular relaxation, highlighting the ligand's essential roles even in the developing epidermis. Our findings unveil ADRB2's critical contribution to extensibility of the epidermis and subsequent body elongation during development. This study also offers insights into the physiology of mature epithelial organs deformed by the smooth muscle response to the adrenergic autonomic nervous system.

Nutritional control of thyroid morphogenesis through gastrointestinal hormones.

Developing animals absorb nutrients either through the placenta or from ingested food; however, the mechanisms by which embryos use external nutrients for individual organ morphogenesis remain to be elucidated. In this study, we assessed nutrient-dependent thyroid follicle morphogenesis in Xenopus laevis and investigated the role of secreted gastrointestinal (GI) hormones post-feeding. We found that feeding triggers thyroid follicle formation, and the thyroid cells showed transient inactivation of cell proliferation after feeding. In addition, the thyroid cells with multi-lumina were frequently observed in the fed tadpoles. The expression of the particular GI hormone incretin, glucose-dependent insulinotropic polypeptide (GIP), responded to feeding in the intestines of Xenopus tadpoles. Inhibition of dipeptidyl peptidase 4 (Dpp4), a degradative enzyme of incretin, increased the size of the thyroid follicles by facilitating follicular lumina connection, whereas inhibition of the sodium-glucose cotransporter (SGLT) reversed the effects of Dpp4 inhibition. Furthermore, injection of GIP peptide in unfed tadpoles initiated thyroid follicle formation-without requiring feeding-and injection of an incretin receptor antagonist suppressed follicle enlargement in the fed tadpoles. Lastly, GIP receptor knockout in neonatal mice showed smaller follicles in the thyroid, suggesting that the GI hormone-dependent thyroid morphogenesis is conserved in mammals. In conclusion, our study links external nutrients to thyroid morphogenesis and provides new insights into the function of GI hormone as a regulator of organ morphology in developing animals.

Effect of pH modified EDTA solution to the properties of dentin.

The purpose of this study was to evaluate the influence of smear layer removal with 3% EDTA solution (pH of 9.0) on the dentin in terms of the permeability of root canal disinfectants into the dentin, wetting by endodontic sealer, and adhesive strength of the sealer. Three types of disinfectant (formalin cresol, phenol, and calcium hydroxide) and 4 types of endodontic sealers (included eugenol, non-eugenol, polycarboxylic acid, and resin) were used. The contact angle between endodontic sealer solution and dentin decreased in the 3% EDTA group but increased in the 15% EDTA. The adhesive strength of endodontic sealer to dentin increased in the EDTA groups for all types of sealers. The permeability of root canal disinfectants increased to similar degrees in the 3% and the 15% EDTA groups. In comparing these properties, we propose that the 3% EDTA is more useful for clinical applications.