Benito Monis

Ultrastructure of transitional epithelium of man

SummaryBlocks of human normal renal pelvis and ureter obtained at the time of surgery were fixed in glutaraldehyde and osmium with or without ruthenium red, for electron microscopic observations. The transitional epithelium is arranged in three cell layers: basal, intermediate and superficial. All epithelial cells show numerous microvilli and contain the characteristic vesicles of transitional epithelium, bundles of cytoplasmic filaments, microtubules and numerous free ribosomes. The epithelial extracellular compartment is notably large and appears as an intricate, tridimensional network of canaliculi and cisternae which are wider in the intermediate and superficial layers and in which microvilli and cytoplasmic folds of vicinal cells are often attached or interdigitated. At these sites there are desmosomes.The surface of all transitional epithelial cells is covered by a fibrillar mucous coat which is more developed at the plasmalemma of the free border of luminal cells in which microvilli are also seen. Ruthenium red stains selectively the plasmalemma and the mucous coat of the free surface of the epithelium, indicating the presence of an acid polysaccharide. With this technic (Luft, 1965), it is observed, radiating from the plasmalemma, branching filaments which measure 100 Å in diameter forming a zone of varying density which is about 400 mμ wide and which corresponds, at the light microscopic level, to the luminal border of the transitional epithelial cells in which a sialomucin has been identified. The slender filaments have a beaded appearance. At the free border, superficial cells are attached by functional complexes in which tight junctions seal the epithelial intercellular space, which is opened at the level of the basement membrane where only desmosomes are observed.The ultrastructure of human transitional epithelium of urinary tract resembles the duct cells of the salt gland of certain marine birds (Fawcett, 1962) and the amphibian epidermis (Farquhar and Palade, 1965) in which there are active processes of transport. The mucous surface coat, selectively stained by the ruthenium red, contains a sialomucin (Monis and Dorfman, 1965, 1967).The ultrastructure and histochemistry of the mucous fluffy coat of man transitional epithelium and the observations of Porter and Tamm (1955), on the ultrastructure of preparations of the Tamm and Horsfall mucoprotein (1952) are bases for suggesting that transitional epithelium of urinary tract of man is the site of biosynthesis of certain urinary mucoids. Present investigations are directed to obtain evidence to substantiate this hypothesis.

On the glycocalyx, the external coat of the plasma membrane, of some secretory cells

SummaryThe free surface of epithelial cells of secretory organs (human placenta, lactating mammary gland of the rat, choroid plexus of man and rat) and of the accessory organs of the genital tract of the male rat is characterized by a plasmalemmal differentiation named glycocalyx or surface mucous coat. This structure is built up by filamentous or globular substructures.Two main ultrastructural types of the glyeocalyx were observed: 1) The filamentous type such as in the rat epididymis, which resembles the cat intestinal glyeocalyx (Ito, 1965) and that one of human transitional epithelium (Monis and Zambrano, 1968), and 2) The globular type, as observed in the lumen of the lactating mammary gland of the rat.Sialic acid was demonstrated histochemically in the luminal glyeocalyx of all organs studied. In addition, the glyeocalyx of acinar cells of the lactating mammary gland contains sulfate and phosphate groups which were identified by histochemical technics, using enzymatic digestion procedures, suggesting the chemical heterogeneity of this glyeocalyx.Present investigations follow the working hypothesis that the complex carbohydrates of glycocalyces become part of the product of activity of secreting cells.

Ultrastructural characterization by ruthenium red of the surface of the fat globule membrane of human and rat milk with data on carbohydrates of fractions of rat milk

SummaryThe fat globules of the cream fractions of human and rat milk were stained with ruthenium red. Under the electron microscope, discrete granules and an amorphous coat of lesser density are seen at the surface of the milk fat globules. Since ruthenium red binds anionic groups selectively, it is probable that the granules containe the greatest concentration of these groups.The cream fraction of rat milk contains hexoses, hexosamines, methylpentoses and sialic acid. Methylpentoses and hexosamines are significantly enriched in the cream fraction.It is concluded that the finding of a surface coat in milk fat globules is in keeping with the Bargmann-Knoop model and suggests a distinct mechanism for carrying certain complex carbohydrates in milk. The role of the negative charges at the outer surface of the membrane coat in maintaining fat globules in suspension and in binding certain cations such as calcium is suggested.

Increased proliferation of the epithelium of the proximal alimentary tract of EFA-deficient rats: A light and electron microscopy study

Abstract Rats of a Wistar strain fed a lipid-poor diet which is deficient in essential fatty acids (EFA) developed hyperkeratosis and increased cell proliferation of the stratified squamous epithelium of the upper alimentary tract. The frequency and severity of hyperkeratosis was significantly increased in the forestomach in both male and female EFA-deficient rats but, in the esophagus, only in the male, whereas hyperkeratosis was not seen in mouth epithelium. In EFA-deficient rats, the mitotic index was increased in the epithelium of palate and tongue ( P P P

Transitional epithelium of urinary tract in normal and dehydrated rats

SummaryThis report is a light microscopic histochemical and fine structural study of transitional epithelium of the urinary tract of normal and dehydrated rats. Four types of cells were recognized: basal, intermediate, squamous or luminal and bundle cells. The transitional epithelium of normal rat ureter and bladder shows distinct cytoplasmic staining of the squamous cells layer by PAS. The luminal free border stains more intensely with PAS. With the electron microscope, abundant cytoplasmic tonofilaments, free ribosomes and the characteristic thick-walled fusiform and round vesicles are observed, which were in greater number in the squamous cells. Lysosomes are identified with PAS, and Toluidine Blue 0, by their content of acid phosphatase and non-specific carboxylic esterase, and by their ultrastructural appearance. The bundle cell (Hicks, 1965) is characterized by histochemical technics. These cells form about 2.5% of the total cell population of normal transitional epithelium. The bundle cell contains basophilic metachromatic granules, which indicates the presence of a weakly acid mucosubstance. It is suggested that bundle cell granules are released in the intercellular spaces of transitional epithelium and that the mucosubstance may regulate flow of ions and metabolites in the epithelial intercellular channels.Several ultrastructural changes occur in the transitional epithelium of dehydrated rats: marked increase in number of thick-walled vesicles, development of polysomes, relative increase of cytoplasmic filaments and greater number of enlarged lysosomes. Bundle cells decrease in number. These ultrastructural changes promptly regressed by allowing the animal to drink water.It is suggested that the rate of formation of the characteristic vesicles of transitional epithelium, a function of membrane synthesis, may be under the control of the antidiuretic hormone.

Ultrastructural changes of the luminal plasma membrane of the transitional epithelium of the rat urinary tract in essential fatty acid deficiency

Rats fed an essential fatty acid deficient diet (EFAD) showed a statistically significant decrease in the thickness and ultrastructural asymmetry of the luminal membrane and cytoplasmic vesicles of transitional epithelium of the urinary tract, due to a marked thinning of the peculiar thick luminal leaflet. These changes were reversed by adding EFA to the diet. This indicates that the unusual EM appearance of urothelial membrane depends on its content in EFA.

Cytochemical changes of a glycocalyx of human placenta with maturation

En la superficie libre, en contacto con la sangre materna, del sinciciotrofoblasto de la placenta humana se observó un glicocáliz en el que se han caracterizado carbohidratos complejos, grupos sulfato y ácido siálico. En este glicocáliz se observaron cambios citoquímicos con la edad de la placenta. Con el microscopio electrónico, se describe la apariencia filamentosa del glicocáliz de placenta humana.

Glycosaminoglycans in separated tubules of the guinea-pig and rat kidney medulla*

Isolated tubules of the renal medulla of guinea-pig and rat contained glycosaminoglycans. 20–25% of the uronic acids corresponded to hyaluronic acid. In the guinea-pig, chondroitin and dermatan-sulfates accounted for at least 50% of the uronic acids, whereas, in the rat, heparan sulfates comprised 65–70% of them.

Histochemistry and ultrastructure of the cell surfaces of the guinea pig kidney with quantitative data on carbohydrate components of glycosaminoglycans of kidney

SummaryThis report deals with a histochemical, electron microscopic and chemical study of carbohydrates of the guinea pig kidney. Histochemical reactions were positive for glycoproteic components in the lumenal surface of the proximal convoluted tubules as well as in the basal aspects of tubular cells. Mucosubstances containing carboxyl and sulphate groups and sialic acid were present at the cell surfaces of the Bowmans capsule, proximal and distal convoluted tubules, loop of Henle and, in greater concentrations, at the cell surfaces of the collecting tubules and papillary epithelium. Data seemed to indicate that glycosaminoglycans were present at the cell surfaces of the collecting tubules.By electron microscopy, the alcian blue stained a dense coat of granular appearance at the lumenal surface of the loop of Henle, measuring up to 100 nm in thickness. Ruthenium red stained the glycocalyx of the collecting tubules which measured up to 60 nm in thickness. The glycocalyx of the collecting tubules was made up of thin filaments and a dense component of about 10 nm thick which merged with the outer leaflet of lumenal plasma membrane, which thus appeared asymmetric. With Alcian blue, the glycocalyx of the collecting tubules, which measured 600 to 1500 nm in thickness, was made up of a meshwork of filaments containing globular or irregular structures measuring 50 to 150 nm in diameter. Chemical assays of kidney homogenates revealed carbohydrate components and sulphate of glycosaminoglycans.

Carbohydrate content of transitional epithelium of the urinary system

El epitelio de transición tiene alto contenido de carbohidratos. Este tejido posee una de las concentraciones más elevadas de ácido siálico en el organismo. Se describe un procedimiento simple para exfoliar epitelio de transición.