Michihiro Yabu

Localization of heparin-binding epidermal growth factor-like growth factor in human gastric mucosa.

BACKGROUND & AIMS Heparin-binding epidermal growth factor-like growth factor (HB-EGF) has been recently identified as a member of the EGF family. EGF receptors to which HB-EGF can bind have been detected in some types of gastric epithelial cells. The aim of this study was to investigate whether HB-EGF is produced in gastric epithelial cells to maintain normal gastric mucosa. METHODS Gene expression and production of HB-EGF protein were investigated using Northern hybridization and immunohistochemistry, and the types of cells producing this protein were determined in human gastric mucosa. RESULTS HB-EGF messenger RNA was detected in the body and antrum. Immunohistochemical staining showed that HB-EGF was localized mainly in parietal cells of fundic glands and in gastrin cells of pyloric glands. Also, the immunoreactivity of EGF receptors was observed in parietal cells and gastrin cells and faintly in surface epithelial cells and mucous neck cells of the proliferative zone. CONCLUSIONS The results suggest that HB-EGF is synthesized mainly in parietal cells and gastrin cells and may act in an autocrine and/or paracrine manner in the regulation of proliferation and differentiation of the gastric mucosal cells through their surface EGF receptors.

Localization of the gene transcripts of 11 ?-hydroxylase and aldosterone synthase in the rat adrenal cortex by in situ hybridization

SummaryUsing in situ hybridization, localization of the gene transcripts of 11 β-hydroxylase and aldosterone synthase was investigated in order to clarify the sites for the synthesis of corticosterone (glucocorticoid) and aldosterone (mineralcorticoid) in the rat adrenal cortex. The gene transcript of 11 β-hydroxylase was localized in all the endocrine cells of the entire adrenal cortex, while that of aldosterone synthase was exclusively confined in zona glomerulosa cells. These results represent that every endocrine cell of all the cortical zones synthesizes 11 β-hydroxylase which converts 11-deoxycorticosterone to corticosterone, and only glomerulosa cells synthesize aldosterone synthase which produces aldosterone from corticosterone. Thus it is clearly shown that zona glomerulosa cells synthesize mineralcorticoid, while zona fasciculata as well as reticularis cells produce glucocorticoid.

Mucosal interleukin-1β production and acid secretion in enlarged fold gastritis

Background: We have previously shown that eradication of Helicobacter pylori increases acid secretion in H. pylori‐associated enlarged fold gastritis.

Activation of the β-catenin gene by interstitial deletions involving exon 3 as an early event in colorectal tumorigenesis

beta-Catenin has been identified as an oncogene in several tumors including colorectal cancers. beta-Catenin gene is activated by interstitial deletions involving exon 3 in colorectal carcinomas of Japanese population, in contrast to amino acid substitutions detected among Caucasian population. The aim of this study was to examine the type and frequency of beta-catenin gene mutation during early stages of colorectal tumorigenesis. We screened 100 colorectal adenomas for somatic mutations in the beta-catenin gene by single-strand conformation polymorphism method, as well as polymerase chain reaction amplification. In cases with mutations, sequencing analyses and immunohistochemical staining were also performed. Somatic interstitial deletions of 272-413 bp, each of which included all parts of exon 3, were detected in three tumors. However, no adenoma carried missense mutations. We confirmed accumulation of aberrant beta-catenin protein in cytoplasm and nuclei of adenoma cells by immunohistochemical analysis. Our results suggested that activation of the beta-catenin gene by interstitial deletions involving exon 3 might be less frequent compared with frequent alterations of adenomatous polyposis coli (APC) gene, but could be an early event in colorectal tumorigenesis equivalent to APC gene alterations in the Japanese population.

Immunohistochemical localization of basic fibroblast growth factor in the healing stage of mouse gastric ulcer

The aim of this study was to clarify the involvement of basic fibroblast growth factor (bFGF) in gastric ulcer healing. For this purpose, light and electron microscopic immunohistochemical studies for bFGF were performed using an experimental gastric ulcer model of mice. Ulceration was induced by the application of acetic anhydride to the serosal surface of the body of the stomach. Stomach tissues were investigated of mice at 5 days and 3 weeks respectively after treatment and also of untreated normal mice. Five days after treatment an ulcer was seen in the stomach of the experimental mice. Immunohistochemistry revealed that bFGF was localized in fibroblasts in the ulcer bed. The growth factor was distributed throughout the cytoplasm excluding organelles involved in the usual secretory system, such as rough endoplasmic reticulum, Golgi apparatus and secretory vacuoles. bFGF was also detected in the nucleus. Three weeks after treatment the surface of the ulcer lesion was completely covered by regenerated epithelium. The stomach tissues were immunohistochemically negative for bFGF both inside and outside the scar region; untreated normal stomach tissues were also negative for bFGF. These results suggest that the growth factor plays important roles in gastric ulcer healing.

Immunohistochemical, autoradiographic and electron microscopic studies on the transformation of fibroblasts into chondrocytes in the mouse subfascia induced by bone morphogenetic protein.

SummaryFunctional morphology on the transformation of fibroblasts into chondrocytes induced by bone morphogenetic protein (BMP) was studied by light and electron microscopy using 35S autoradiography and immunohistochemistry for S-100 protein and type-II collagen. A pellet containing BMP obtained from a murine osteosarcoma was transplanted into the mouse subfascia. By 3 days after implantation, many typical fibroblasts, which were free of the silver grains for 35S and devoid of both S-100 protein and type-II collagen, entered the pellet region. By 5 days, the fibroblasts in the pellet region became polygonal in shape, and cytoplasmic vesicles and vacuoles appeared, both containing a homogeneous substance of low electron density. At 5 days, autoradiography revealed many silver grains for 35S over the Golgi apparatus and vesicles and vacuoles of the cells in the pellet region as well as over the surrounding extracellular matrix. Moreover, the cells at 5 days displayed immunoreactivity to both proteins. The extracellular matrix around the cell began to show clear metachromasia and increased in amount with time. At 9 days all the cells in the pellet region were round or oval in shape and surrounded by an abundant cartilaginous matrix. The rough endoplasmic reticulum and Golgi apparatus were extremely well developed, and a large number of vacuoles and vesicles were seen in the cytoplasm. These cells showed intense immunoreactivity to both proteins, and strong accumulation of sulfur was visualized in the extracellular matrix by autoradiography. These results suggest that the fibroblasts in the pellet region change into chondroblasts by 5 days, and become typical chondrocytes by 9 days.

Inhibition of gastrin-stimulated enterochromaffin-like cell proliferation and mucosal histamine production in the rat stomach by the somatostatin analogue octreotide

The effect of octreotide, a potent and long-acting analogue of somatostatin, on gastrin-stimulated proliferation and function of enterochromaffin-like (ECL) cells were examined in rats. Animals were divided into four groups and each group was continuously infused with saline, octreotide alone (40 micrograms/kg per day), gastrin alone (60 nmol/kg per day), or octreotide (40 micrograms/kg per day) plus gastrin (60 nmol/kg per day) respectively for 9 days via osmotic minipumps. Gastrin induced the increase of the bromodeoxyuridine labeling index and density of oxyntic mucosal ECL cells as well as oxyntic mucosal histidine decarboxylase activity. Octreotide completely abolished the gastrin-induced increases in the labeling index and density of ECL cells and oxyntic mucosal histidine decarboxylase activity. These results indicate that octreotide inhibits gastrin-stimulated proliferation of ECL cells and histamine production by these cells.