Search

Albumin is an attractive component for the development of biomaterials applied as biomedical implants, including drug carriers and tissue engineering scaffolds, because of its high biocompatibility and low immunogenicity. Additionally, albumin-based gelators facilitate cross-linking reactions under mild conditions, which maintains the high viability of encapsulated living cells. In this study, we synthesized albumin derivatives to undergo gelation under physiological conditions via the peroxidase-catalyzed formation of cross-links. Albumin was modified with phenolic hydroxyl groups (Alb-Ph-OH) using carbodiimide chemistry, and the effect of degree of substitution on gelation was investigated. Various properties of the Alb-Ph-OH hydrogels, namely the gelation time, swelling ratio, pore size, storage modulus, and enzymatic degradability, were easily controlled by adjusting the degree of substitution and the polymer concentration. Moreover, the viability of cells encapsulated within the Alb-Ph-OH hydrogel was high. These results demonstrate the potential applicability of Alb-Ph-OH hydrogels as cell-encapsulating materials for biomedical applications, including tissue engineering., (Copyright © 2023 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.)

In this study, we surveyed central neurons that might be activated after peripheral administration of a gut-brain peptide ghrelin, by examining neurons expressing c-Fos protein. First, we examined the relationship between the dose of ghrelin and the amount of gastric acid secreted. Ghrelin induced a significant increase in the amount of gastric acid secretion in a dose-dependent manner. Secondly, we examined central neurons that expressed c-Fos protein after intravenous injection of ghrelin. We found that intravenously injected ghrelin induced the neural expression of c-Fos protein in several nuclei and circumventricular organs in the brain. These results suggest that ghrelin released into the circulation may stimulate central neurons that have some role in the control mechanism for gastric acid secretion.

Ghrelin, a novel growth hormone-releasing peptide, is present in the rat and human stomach and is known to stimulate acid secretion and stomach motility. However, the mechanism of action of ghrelin is not fully understood. In the present study, we attempted to elucidate the role of histamine in ghrelin-induced acid secretion in rat stomach. Intravenous administration of ghrelin at 0.8 to 20 microg/kg dose dependently increased gastric acid secretion, as measured by the gastric lumen perfusion method. The maximum response was almost equal to that of gastrin (20 microg/kg). These actions were abolished by bilateral subdiaphragmatic vagotomy. Famotidine (0.33 mg/kg) also completely inhibited the effects of ghrelin. Furthermore, ghrelin increased histidine decarboxylase (HDC) messenger RNA (mRNA) levels, as measured by real-time reverse transcription-polymerase chain reaction using LightCycler. The action of ghrelin on HDC mRNA was abolished by vagotomy. Ghrelin did not affect histamine release from isolated vascularly perfused rat stomach. Taken together, these results suggest that ghrelin stimulates gastric acid secretion via a mechanism involving activation of vagal efferent nerve and histamine release from gastric enterochromaffin-like cells.