An electron microscopic study of the intestinal villus. I. The fasting animal

Intercellular channels in the canine and porcine thyroid gland

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Fluid transport in the rabbit gallbladder. A combined physiological and electron microscopic study

The fine structure of the rabbit gallbladder has been studied in specimens whose functional state was undetermined, which were fixed either in situ or directly after removal from the animal; in specimens whose rate of fluid absorption was determined, either in vivo or in vitro, immediately prior to fixation; and in specimens from bladders whose absorptive function was experimentally altered in vitro. Considerable variation was found in the width of the epithelial intercellular spaces in the bladders whose functional state was undefined. In bladders known to be transporting fluid, either in vivo or in vitro, the intercellular spaces were always distended, as were the subepithelial capillaries. This distension was greatest in bladders which had been functioning in vitro. When either Na(+) or Cl(-) was omitted from the bathing media, there was no fluid transport across the wall of the gallbladder studied in vitro. The epithelial intercellular spaces of biopsies taken from several bladders under these conditions were of approximately 200 A width except for minor distension at the crests of mucosal folds. The addition of the missing ion rapidly led to the reestablishment of fluid transport and the distension of the intercellular spaces throughout most of the epithelium of these bladders. Studies of sodium localization (by fixation with a pyroantimonate-OsO(4) mixture) showed high concentrations of this ion in the distended intercellular spaces. Histochemical studies of ATPase activity showed that this enzyme was localized along the lateral plasma membrane of the epithelial cells. The analogy is drawn between the structure of the gallbladder mucosa and a serial membrane model proposed by Curran to account for coupled solute-solvent transport across epithelia. It is concluded that the intercellular compartment fulfills the conditions for the middle compartment of the Curran model and that active transport of solute across the lateral plasma membrane into the intercellular space may be responsible for fluid absorption by the gall bladder.

The surface area of the intestinal mucosa in the lactating rat

1. The mucosal and serosal surface dimensions of the rat duodenum, jejunum and ileum were obtained by measurement of photographs of histological sections. The surface areas were calculated from these data.2. Measurements were made on the intestines from virgin rats and from rats on the sixteenth day of lactation. The mucosal area/unit length of serosa was appreciably increased in all parts of the intestine during lactation. The mucosal area/serosal area (MA/SA) ratio was also markedly increased, but to a lesser extent distally, where an important component of the intestinal hypertrophy was dilatation of the intestine.

Electron-microscope evidence for intramicrovillous fat absorption by the small intestinal epithelium of rats

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Role of the intestinal brush border in the absorption of cholesterol in rats

1. Short-term incubation of the everted intestinal sacs of rats in media containing cholesterol oleate or cholesterol plus oleic acid resulted in rapid hydrolysis, but no synthesis, of the sterol ester. 2. On separation of the brush border from the rest of the mucosal cell, almost all of the hydrolytic activity and appreciable amounts of the synthetic activity of the whole cell were found to be present in the brush-border fraction. 3. The isolated brush-border fraction contained considerable amounts of cholesterol, which was always present in the unesterified state; the rest of the cell contained about an equal amount of unesterified cholesterol, but, in addition, small but definite amounts of the esterified sterol were also found in this fraction. 4. On feeding rats with [4-(14)C]cholesterol, which was diluted with 3mg. of cholesterol, it was found that the brush border very rapidly took up the fed sterol without changing its net content of cholesterol. No traces of radioactive cholesterol ester could ever be detected in the isolated brush border after feeding with (14)C-labelled esterified or unesterified cholesterol. 5. The appearance of the labelled sterol was quite rapid in the rest of the cell also, where small proportions were found in the esterified state. 6. Therefore the sequence of events in the absorption of cholesterol appears to be: the dietary cholesterol esters are hydrolysed by the cholesterol ester hydrolase of pancreas or of the mucosal brush border or both, after which the brush border rapidly absorbs the de-esterified sterol and transfers it into the mucosal cell, by a mechanism of displacement, where it is slowly re-esterified for transport through the lymph.

Lymphangioma of the duodenum: case report with light and electron microscopic observation

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Experimental bacillary dysentery. An electron microscopic study of the response of the intestinal mucosa to bacterial invasion

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ENDOTHELIAL PERMEABILITY. II. THE PASSAGE OF PARTICLES THROUGH THE LYMPHATIC ENDOTHELIUM OF NORMAL AND INJURED EARS

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THE ULTRASTRUCTURE OF THE PLACENTAL LABYRINTH OF THE FERRET (MUSTELA PUTORIUS FURO)

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ULTRASTRUCTURE OF ENDOTHELIUM OF THE FROG HEART

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