Yasue Hosoyamada

Structural and mechanical architecture of the intestinal villi and crypts in the rat intestine: integrative reevaluation from ultrastructural analysis

The ultrastructure of the rat intestinal interstitium was analyzed from the viewpoint of mechanical dynamics to stabilize the intestinal villi, crypts and mucosal folds. In the rat, the small intestine lacks circular folds, but the large intestine possesses spiral folds. The intestinal villi, the largest in the duodenum, decreased in size in the jejunum and ileum successively, and were absent in the large intestine. The intestinal interstitium consisted of lamina propria mucosae (LPM) and tela submucosa (TSM) separated by muscularis mucosae (MM), the LPM was subdivided into an upper part within the villi and a lower part among the crypts in the small intestine. The light microscopic density of interstitium in the intestinal wall was lowest in the upper LPM, moderately dense in the lower LPM and highest in the TSM, and that among the intestinal region was highest in the duodenum and decreased successively in the jejunum and ileum. In the large intestine, the TSM bulged to form spiral folds with very low density. The intestinal epithelium in the villi possessed wide intercellular spaces and that in the crypts had closed intercellular spaces. At electron microscopic level, the upper and lower LPM contained subepithelial supportive meshwork that consisted of collagen fibrils and myofibroblast processes. The lower LPM and TSM contained conspicuous bundles of collagen fibrils and, in addition, TSM contained minor populations of scattered collagen fibrils near the smooth muscle layer (SML). The diameter of collagen fibrils was the largest in the bundles of TSM, and decreased from the duodenum through the jejunum and ileum to the large intestine. On the basis of these observations, we hypothesize that the intestinal villi are mechanically stabilized by the balance between the expansive interstitial pressure and inward pull by the subepithelial supportive meshwork. This hypothesis explains the hitherto neglected fact that the intestinal epithelium possesses wide intercellular spaces only in the villi, and accounts for the counterforce against the perpendicular smooth muscle cells, which are supposed to contract the intestinal villi.

Are the precapillary sphincters and metarterioles universal components of the microcirculation? An historical review

The microcirculation is a major topic in current physiology textbooks and is frequently explained with schematics including the precapillary sphincters and metarterioles. We re-evaluated the validity and applicability of the concepts precapillary sphincters and metarterioles by reviewing the historical context in which they were developed in physiology textbooks. The studies by Zweifach up until the 1950s revealed the unique features of the mesenteric microcirculation, illustrated with impressive schematics of the microcirculation with metarterioles and precapillary sphincters. Fulton, Guyton and other authors introduced or mimicked these schematics in their physiology textbooks as representative of the microcirculation in general. However, morphological and physiological studies have revealed that the microcirculation in the other organs and tissues contains no metarterioles or precapillary sphincters. The metarterioles and precapillary sphincters were not universal components of the microcirculation in general, but unique features of the mesenteric microcirculation.

Ultrastructural localisation and size distribution of collagen fibrils in Glisson's sheath of rat liver: implications for mechanical environment and possible producing cells

The ultrastructure and size distributions of collagen fibrils in Glissons sheath were investigated in the rat liver to analyse the mechanical environment around the fibrils and their possible cells of origin. Glissons sheath was found to contain 2 populations of collagen fibrils with different diameters and distinct localisations, namely fibroblast‐associated and bile epithelium‐associated. Fibroblast‐associated collagen was composed of fibrils arranged in bundles and constituted the majority of the collagen in Glissons sheath. Bile epithelium‐associated collagen was represented by small dispersed groups of fibrils just beneath the basement membrane of the bile duct. The basement membrane of the bile duct was frequently reduplicated into a few or as many as 10 layers of laminae densae, with scattered collagen fibrils between these laminae. The diameters of the fibrils of both groups of collagen increased in relation to the calibre of the bile duct, whereas at any given place in Glissons sheath bile epithelium‐associated collagen fibrils had a smaller diameter compared with those of the fibroblast‐associated fibrils. The increment in fibril diameter along the bile duct is considered to be correlated with the increase in mechanical stress acting on Glissons sheath. The difference in diameter between the 2 populations as well as the incorporation of fibrils between the laminae densae of the basement membrane of the bile duct supports the view that the bile epithelium‐associated collagen is produced by the epithelial cells of the bile duct, thus having a different origin from that of fibroblast‐associated collagen. These findings provide the first evidence that the epithelial cells of the interlobular bile duct produce fibril‐forming collagen. Furthermore, it is suggested that cholestasis stimulates the epithelial cells of interlobular bile duct to increased synthesis of fibril‐forming collagen that is also produced by these cells under physiological conditions.

Structural arrangement of collagen fibrils in the periarterial connective tissue of the kidney: their functional relevance as a structural stabilizer against arterial pressure.

Periarterial connective tissue with a moderate amount of collagen fibrils is known to be a specialized domain in the renal interstitium. This study aimed to clarify the microscopic architecture of the periarterial connective tissue as a mechanical supportive structure of the intrarenal arteries. Transmission and scanning electron microscopy revealed two populations of collagen fibrils in the periarterial connective tissue. The major one was composed of many bundles of collagen fibrils running in longitudinal directions, whereas the minor one was represented by a few circumferential bundles adjacent to the smooth muscles. The amount of collagen fibrils was obviously variable and correlated with the arterial caliber. The correlation between abundance of collagen fibrils and the arterial caliber was confirmed by morphometric analysis of the collagen fibril area per arterial perimeter on electron micrographs. The size of individual collagen fibrils was measured in periarterial connective tissue of arteries with various calibers. A positive correlation between the diameter of collagen fibrils and arterial caliber was confirmed, indicating the supportive function of collagen fibrils in the periarterial connective tissue. The accumulated morphological findings supported the hypothesis that the collagen fibrils in the periarterial connective tissue develop longitudinal tension with their tensile strength, whereas the smooth muscle cells in the media develop circumferential tension with active regulation of contracting force.

Effects of Dietary Fish Oil and Apple Polyphenol on the Concentration Serum Lipids and Excretion of Fecal Bile Acids in Rats

We studied the effects of fish oil and apple polyphenol combined with a high cholesterol diet in rats, and assessed serum and liver lipids concentrations, serum oxidative stress and fecal bile acid excretion. Young male rats were fed a diet containing the control (Control), apple polyphenol (AP), fish oil (FO) or fish oil+apple polyphenol (FO+AP) for 4 wk. The control diet contained a lard component. Posterior abdominal wall fat and testicle peripheral fat weights decreased in the FO+AP group compared to the AP group. The concentration of total cholesterol in the serum and liver decreased in the FO group and the FO+AP group compared to the Control and the AP groups. The concentration of adiponectin and biological antioxidant potential in the serum increased in the FO group compared to the other groups. The diacron-reactive oxygen metabolites in serum decreased in the FO group and the FO+AP group compared to the Control and the AP groups. The bile acid excretion in feces increased in the AP group, the FO group and the FO+AP group compared to the Control group. These results suggested that the combination of fish oil and apple polyphenol in the diet improved serum and liver lipids, which should assist in the prevention and improvement of metabolic syndrome.

Organ Specificity and Functional Relevance of the Arterial Structure: A Comparative Study in the Kidney and the Skeletal Muscle with Electron Microscopy

The differences in circulation among various organs are well known, but the structural differences have only been poorly investigated. In the present study the wall structure of arteries was observed with electron microscopy in rat kidney and skeletal muscle. The wall thickness was almost equal in both organs at about 40 μm in luminal diameter, while it was relatively thin in the larger arteries and thick in the smaller arteries in the kidney compared with that in the skeletal muscle. The smooth muscle cells were regularly arranged in parallel in circular or slightly spiral orientation in the kidney, whereas those in the skeletal muscle were irregularly arranged in heterogeneous orientations. Extracellular matrices were more abundant in the arterial media in the skeletal muscle than in the kidney. The inner elastic lamina was continuous in the kidney, and arranged in longitudinal bundles in the skeletal muscle. The adventitial collagen fibers were abundant and dense in the skeletal muscle, and were scattered in small bundles in the fluid-filled spaces in the kidney. While the arteries in the skeletal muscle are under severe mechanical stress during muscle contraction and dilate dramatically during exercise, those in the kidney regulate glomerular pressure almost constantly.

Investigation of bacterial contamination and usage survey of water-bottles

近年,水筒を持ち歩く人が増えており,その形状は直 接口をつける形状のものが多い。水筒の衛生状況につい ては,児童が使用していた水筒の水筒口あるいは水筒水 で,一般細菌および大腸菌群が検出されたことが報告さ れている。同様に直接口をつけて飲むペットボトル についても,その飲料中で一般細菌が増殖していたこと が報告されている。 水筒および水筒内飲料の細菌汚染の要因の一つとして, 洗浄不足による飲み口および水筒内の細菌残存,使用す る布巾等の細菌汚染等が考えられる。その他の要因とし ては,口腔内細菌の付着や混入が考えられる。経時的に その数は減少したものの,口腔中の細菌がペットボトル 内で検出された報告もある。 本研究は,水筒の飲み口と水筒内飲料の一般細菌およ び大腸菌群数による汚染状況を知ることで,水筒の衛生 的な使用方法を検討することを目的とした。併せて,水 筒の使用実態調査も行った。 2 .実験方法