Torkel Wahlin

Histochemical observations with the light and the electron microscope on the mucosubstances of the normal mouse gallbladder epithelial cells

SummaryMucosubstances of the mouse gallbladder epithelial cells were investigated with light and electron microscopic techniques. Based on results obtained with light microscopic histochemical techniques, viz. staining with PAS, Azure A and different Alcian blue methods in combination with various digestion procedures, the mucosubstance could be classified as a so-called GC-mucin according to the nomenclature of Spicer et al. (1965). Applying the electron microscope for a closer study of epithelial cell structure and utilizing among other techniques the PA-CrA-silver staining method for polysaccharides of Rambourg et al. (1969) the mucosubstance was traced to membrane bounded cytoplasmic granules, 0.2–0.3 μ in diameter. The latter proved secretory in nature and their discharge from the cells could be brought about by feeding starved animals with olive oil. The cells also exhibited pinocytotic activity as judged by their uptake of thorotrast particles injected in vivo into the gallbladder.

Effects of Fasting and Refeeding on Secretory Granules of the Mouse Gallbladder Epithelium: A Quantitative Electron Microscopic Study

Mouse gallbladder epithelial cells were studied with the electron microscope during fasting and refeeding. Morphometric data were obtained from randomly selected epithelial cells of normal starved (12, 24, and 48 hr) and refed (12 hr) mice. Deprivation of food significantly diminishes the volume density of the mucinous secretory granules by about 70% after 48 hr of fasting. Upon refeeding, this secretory granule parameter increases significantly ( 2.5 times). Stereological measurements were also performed on nuclei, mitochondria, and lysosomes, but no major morphometric changes were observed in these organelles. The findings suggest that a basal secretion of mucin granules occur in the mouse gallbladder, irrespective of the animals nutritional state and that this discharge during starvation exceeds the formation of new granule material. The findings are discussed in relation to effects of fasting and refeeding on other secretory cell systems.

Effect of cholecystokinin-pancreozymin (CCK-PZ) on glycoprotein secretion from mouse gallbladder epithelium

SummaryStructural changes in the gallbladder epithelial cells of the mouse were studied following in vivo and in vitro stimulation of the gallbladder with the gastrointestinal hormone cholecystokinin-pancreozymin (CCK-PZ). Signs of increased secretory activity were observed within the first 2–3 min after hormone administration. At the ultrastructural level, best visualized with the PA-CrA-silver technique, granule discharge was observed, as was an overall increase in size of the granules. After prolonged in vitro incubation or repeated in vivo stimulation, there was an almost total depletion of secretory granules. This phenomenon is accompanied by an enhanced uptake of extracellular thorium dioxide by endocytotic vesicles at the apical cell surface. An exocytosisendocytosis coupling mechanism may be important for membrane conservation in the gallbladder epithelial cells. The findings establish that the hormone CCK-PZ stimulates the secretion of glycoproteins from the mouse gallbladder epithelium.

Effects of Intraluminal Prostaglandin E2 In Vivo on Secretory Behavior and Ultrastructural Changes in Mouse Gallbladder Epithelium

It has been suggested that glycoproteins play an important role as a nucleating agent in the pathogenesis of gallstone formation. Arachidonic acid, by an indomethacin-sensitive mechanism, is known to enhance gallbladder mucus release, suggesting that prostaglandins may regulate gallbladder epithelial release of mucus. In this study, the glycoprotein granules of the principal cells of the mouse gallbladder epithelium were morphometrically analyzed using electron microscopy. It was shown that 5 micrograms of prostaglandin E2, injected into the gallbladder lumen of the anesthetized mouse, reduced the relative volume of glycoprotein granules from 3.0% to 0.7% of the cytoplasmic volume within 20 min, whereas injection of the same amount of the solvent for prostaglandin E2 had no such effect.

Synthesis of glycoproteins in the Golgi complex of the mouse gallbladder epithelium during fasting, refeeding, and gallstone formation

SummaryThe mouse gallbladder epithelium was studied with light microscopic autoradiography and quantitative electron microscopy during fasting, refeeding and experimental gallstone formation. To determine the intracellular pathway of glycoproteins, H3-galactose was injected at different time intervals into the mice. At 10, 25 and 40 min after an intraperitoneal injection the gallbladders were fixed and prepared for light microscopy. As early as 10 min after injection, label was observed in supranuclear cytoplasmic regions and at 25 min, an increased radioactivity was present throughout the apical cytoplasm. At 40 min, silver grains were mainly present at the cell surface. Autoradiographs processed 25 min after an intraperitoneal H3-galactose injection after fasting for 48 h showed decreased supranuclear and apical radioactivity. After refeeding (12 h) there was an enhanced activity in both these regions. Animals fed a lithogenic diet for one month showed a marked increase of radioactive label mainly in cells of crypts and invaginations of the mouse gallbladder mucosa.Morphometric measurements of the Golgi apparatus revealed that deprivation of food significantly diminished the volume density of the Golgi apparatus. Refeeding the animals restored the volume density values to normal levels. In the course of gallstone formation there was a further significant increase in the volume density of the Golgi complexes as compared to controls.

Ultrastructural cytochemistry of the secretory granules of the hamster submandibular gland

SummaryThe ultrastructure and cytochemistry of the secretory granules of the male hamster submandibular salivary gland were studied. After fixation in glutaraldehyde followed by osmium tetroxide the granules exhibit a characteristic bipartite substructure, with an electron lucid crescenteric rim and a more dense central core. A differentiation into two regions of the granules could also be visualized in specimens primarily fixed in Millonigs osmium tetroxide or in potassium permanganate. The electron lucid peripheral portion of the membrane bounded secretory granules further displays a strong positive reaction after staining of ultrathin sections with the periodic acid-chromic acid-(PA-CrA)-silver technique. The strong periodate reactivity of the rim relative to the core, suggests a difference in mucin composition of the two granule regions. With the PA-CrA-silver staining technique a positive reaction was also observed within the Golgi apparatus of the acinar cells.

Effects of lithogenic diets on mouse gallbladder epithelium

SummaryMice fed a cholesterol-cholic acid-containing lithogenic diet developed gallstones within 2 months. The gallbladders were grossly distended and morphometric studies of the gallbladder revealed a significant epithelial hyperplasia after 2 weeks.Based on results obtained with histochemical techniques an increase of glycoproteins could be demonstrated in the principal cells of the invaginations and crypts in the gallbladder mucosa after 2 weeks. At the ultrastructural level the principal cells showed increased numbers of secretory granules and in crypts so-called gland cells with large amounts of secretory droplets appeared. There were numerous signs of excytotic release of cell secretory products during gallstone formation.The findings suggest an increased synthesis of glycoproteins in the gallbladder epithelium and an enhanced secretion prior to or concomitant with gallstone formation.

Zur Entwicklung des Gallenblasenepithels des Meerschweinchens@@@The development of the guinea pig gallbladder epithelial cells: I. Frberisch-lichtmikroskopische und kohlenhydrat-histochemische Untersuchungen@@@I. Light Microscopical and carbohydrate-histochemical investigations

SummaryThe development of the guinea pig gallbladder epithelium was studied from the 19th day of intrauterine life to the 31st postnatal day by means of histological and histochemical staining reactions. At first, the epithelium is a columnar pseudostratified one. Its transformation into a simple columnar eptihelium is terminated by the 31st day of the intrauterine life. Then the epithelial cells become more columnar and their nuclei acquire a basal position. Somewhat later the epithelium invaginates the underlying mesenchyme. Up to the 57th day the epithelium contains much glycogen. Neutral and carboxylated muscosubstances are demonstrable after the 30th day. From the 48th day onwards sulphated mucosubstances can be visualized in some cells in the depth of the invaginations and from the 51st day in the epithelial cells of the gallbladder. “Light” mucoid cells appear first in the epithelium of day 58. After the 6th postnatal day the “light” cells are rarely seen in the invaginations. The development of the gallbladder epithelium is completed about the 10th postnatal day.—The epithelial mucosubstances of the gallbladder of the adult animal could be classified as GC mucins and S-mucinsA, 1.0 MgCl2.ZusammenfassungEs wird die Entwicklung des Gallenblaseneptithels des Meerschweinchens vom 19. Embyonaltag (ET) bis zum 31. Lebenstag (LT) färberisch-lichtmikroskopisch und histochemisch untersucht. Das zunächst mehrreihige Zylinderepithel wird bis zum 31. ET einschichtig. In der Folgezeit werden die Epithelzellen hochprismatisch und die Kerne wandern nach basal. Außerdem entstehen Epithelbuchten. Das Gallenblasenepithel enthält zunächst viel Glykogen, das bis zum 57. ET wieder verschwindet. Ab 30. ET können im Gallenblasenepithel neutrale und carboxylierte Mucosubstanzen nachgewiesen werden. Ab 48. ET treten in der Tiefe der Buchten und ab 51. ET in allen Gallenblasenepthelzellen sulfatierte Mucosubstanzen auf. Ab 58. ET kommen im Gallenblasenepithel „aufgehellte” mucoide Zellen vor, die nach dem 6. LT nur noch in den Buchten zu finden sind. Abgeschlossen ist die Entwicklung des Gallenblasenepithels etwa am 10. LT. — Bei den epithelialen Mucosubstanzen im Gallenblasenepithel des erwachsenen Meerschweinchens handelt es sich um GC-Muzine und S-Muzine A, 1,0 MgCl2.