Morphological and histochemical aspects of glycoproteins at the surface of animal cells

Fasciola gigantica: Ultrastructural cytochemistry of the tegumental surface in newly- excysted metacercariae and in vitro-penetrated juvenile flukes informs a concept of parasite defence at the interface with the host

Cytochemical staining techniques were carried out en bloc with in vitro excysted and gut-penetrated Fasciola gigantica larvae in order to visualise the glycocalyx of the tegument, a structure which comprises the parasite component of the host-parasite interface, yet is incompletely preserved by conventional fixation and preparation techniques for electron microscopy. Positive reactivity with ruthenium red and periodic acid-thiocarbohydrazine-osmium (PATCO) techniques revealed that the glycocalyx is polyanionic and carbohydrate-rich throughout its depth. It comprises a trilaminate arrangement, with a thin dense zone and fibrillar layer closely apposed to the outer aspect of the apical plasma membrane, invested by an irregular thick mucopolysaccharide capsule. The latter, not recorded in adult flukes, may represent a specific adaptation to facilitate invasion in the face of host immunity, and may also protect the parasite surface from the action of host- and parasite-derived proteases. Early in the invasion of a naïve host, the glycocalyx may be partly responsible for triggering the responses of innate immunity, while later in infection, or when an anamnestic response is initiated in an immunocompetent host, the antibodies and activated lymphocytes of specific acquired immunity are invoked to interact with the parasite surface. The cytochemical properties of the glycocalyx, together with its potential for dynamic turnover due to exocytosis of the T0 tegumental secretory bodies, are likely to aid neutralisation of potentially damaging immune effectors and ensure their removal from the vicinity of the parasite by sloughing in complex with glycocalyx components.

The relevance of the aldehyde bisulfite toluidine blue reaction and its variants in the submicroscopic carbohydrate research

Carbohydrates are chemical compounds that contain only oxygen, hydrogen and carbon. They are classified by their number of sugar units: monosaccharides (such as glucose and fructose), and disaccharides (such as sucrose and lactose) are simple carbohydrates; oligosaccharides and polysaccharides (such as starch, glycogen and cellulose) are complex carbohydrates. Carbohydrates play a crucial role in diverse biological systems [Hricovín M. Structural aspects of carbohydrates and the relation with their biological properties. Curr Med Chem 2004;11:2565-83]. According to Roseman [Sugars of the cell membrane. In: Weissmann G, Clairborn E, editors. Cell membranes. Biochemistry, Cell Biology, Pathology. New York: H. P. Publ. Co; 1975. p. 55-64], two classes of glycoproteins are described. Free glycoproteins are localised in the surface coat of the membranes and form a thick mobile layer, without any association to the membrane itself. Functionally, however, they are located in a close association with the membrane (e.g. in the duodenal mucosa). The other group consists of the membrane glycoproteins, which are integral to the membranes and are located in the outer layer. The oligosaccharide chains are bound to the N-terminal part of proteins, and are situated in the hydrophilic zone. Glycoproteins have diverse functions. They are important in specific receptor functions, in immunological cell destruction and play a significant role in reactions with lectins, antibodies, as well as in cell association and mutual recognition of the cells. This paper focuses on aspects of a summary of polarisation optical investigations and biological functions of the following three groups of carbohydrates: oligosaccharides, glycoproteins and glycosaminoglycans.

Early stages of test formation in larva of Ascidia malaca (Tunicata, Ascidiacea): ultrastructural and cytochemical investigations

The swimming larvae of ascidians are entirely covered by a hyalin coat called tunic, or test. This covering consists of two cuticular layers, C1 and C2, which surround an inner compartment composed of an amorphous hyalin matrix with numerous fibrils dispersed inside. Data from the literature agree on the key role played by the cells of the larval ectodermic layer in the synthesis and secretion of larval test components. In the present article are reported ultrastructural and cytochemical investigations made during test formation in the swimming larva of Ascidia malaca. Besides confirming the role played by ectodermic cells during the early stages of test formation, the investigations highlight the way in which the fibrillar component of the test is synthetized and secreted. At the ultrastructural level it has been evidenced that the C1 and C2 cuticular layers originate from the tight packing of fibrils. Based on the data reported in the present study, it is hypothesized that while a relevant part of the fibrils, once secreted, remains dispersed inside the matrix of the inner compartment of the test, quite likely in order to increase its consistency, packing of the remaining fibrils leads to the formation of the C1 and C2 cuticular layers. Packing of the fibrils in C1 and C2 could be favoured by their chemically adhesive nature. This hypothesis is strongly supported by the herewith reported results of the cytochemical investigations carried out on the test of the swimming larva of A. malaca. The cytochemical PA-TCH-SP reaction has in fact evidenced that both fibril types, i.e. those dispersed inside the inner compartment and those packed in the C1 and C2 cuticular layers, are constituted by glycoproteins and/or proteoglycans substances whose adhesive properties are well documented in the literature.

A simple method for the specific detection of Ren-1 renin

BACKGROUND

Ren-1 and Ren-2 renin are expressed in the kidneys of all mice and in the submandibular gland of several mouse strains. The present study determined the usefulness of modified periodic acid silver-methenamine (PAM) staining for the specific detection of Ren-1 renin.

METHODS

Conventional paraffin sections were prepared from kidneys of ICR, BALB/cA, C57BL/6Cr, C3H/HeN, DBA/2Cr, angiotensin II type 1a receptor gene knockout (AT1aKO) mice, Wistar rats and a human, and submandibular glands of C57BL/6Cr and DBA/2Cr mice. Sections were analyzed for the presence of renin using PAM and immunohistochemistry. PAM reactions were terminated at generally or weakly intense (weak PAM staining; W-PAM). In addition, kidneys of DBA/2Cr mice were fixed using various fixatives (formalin, PFA, PLP, Zamboni's, Bouin's, or Carnoy's) and treated using identical procedures.

RESULTS

Although PAM-positive reactions were observed in juxtaglomerular (JG) cells, W-PAM reactions were particularly specific for these cells. These findings were observed in all mouse strains. Immunohistochemistry using mirror sections suggested that a W-PAM-positive reaction detected renin. This hypothesis was confirmed by the results from AT1aKO mice. Briefly, W-PAM detected an expansion of renin-positive areas in AT1aKO mice. Rat and human kidneys and mouse submandibular glands were negative for W-PAM. Levels of JG cell detection by W-PAM were similar in samples fixed in formalin, PFA, PLP, or Zamboni's.

CONCLUSIONS

The present findings show that W-PAM can identify Ren-1 renin, but not Ren-2, rat or human renin. The W-PAM method is useful for the specific detection of Ren-1 renin.

Specialized expression of simple O-glycans along the rat kidney nephron

Glycosyltransferases can exhibit tissue-specific expression. By histochemistry glycosyltransferases and their products can be localized to specific cell types in organs of complex cellular composition. We have applied the lectin Amaranthin, having a nominal specificity for Galbeta1,3GalNAcR and Neu5Ac2,3Galbeta1, 3GalNAcalpha-R, and a monoclonal antibody raised against Galbeta1, 3GalNAcalphaR to examine the distribution of these simple O-glycans in adult rat kidney. The monoclonal antibody stained ascending thin limbs of Henle, distal convoluted tubules, and collecting ducts of cortex and outer medulla. Remarkably, the ascending thick limb of Henle, located between ascending thin limb and distal convoluted tubules, was unreactive. However, Amaranthin staining was detectable in ascending thick limbs of Henle, in addition to the structures positive with the monoclonal antibody. In kidney extracts, two bands of approximately 160 kDa and >210 kDa were reactive with both Amaranthin and the monoclonal antibody. One band at approximately 200 kDa, and a smear at approximately 100 kDa, were reactive only with Amaranthin. Our data show that in rat kidney simple O-linked glycans are expressed in a highly specialized manner along the renal tubule and can be detected only on a few glycoproteins. This may reflect a cell-type-specific expression of the corresponding glycosyltransferases.

Basic surface properties of mononuclear cells from Didelphis marsupialis

The electrostatic surface charge and surface tension of mononuclear cells/monocytes obtained from young and adult marsupials (Didelphis marsupialis) were investigated by using cationized ferritin and colloidal iron hydroxyde, whole cell electrophoresis, and measurements of contact angles. Anionic sites were found distributed throughout the entire investigated cell surfaces. The results revealed that the anionic character of the cells is given by electrostatic charges corresponding to -18.8 mV (cells from young animals) and -29.3 mV (cells from adult animals). The surface electrostatic charge decreased from 10 to 65.2% after treatment of the cells with each one of trypsin, neuraminidase and phospholipase C. The hydrophobic nature of the mononuclear cell surfaces studied by using the contact angle method revealed that both young and adult cells possess cell surfaces of high hidrofilicity since the angles formed with drops of saline water were 42.5 degrees and 40.8 degrees, respectively. Treatment of the cells with trypsin or neuraminidase rendered their surfaces more hydrophobic, suggesting that sialic acid-containing glycoproteins are responsible for most of the hydrophilicity observed in the mononuclear cell surfaces from D. marsupialis.

Expression of the major basement membrane-associated proteins during postnatal development in the murine cochlea

The major basement membrane-associated proteins, including laminin-1, fibronectin, heparan sulfate proteoglycan (HSP), and entactin, were examined by immunofluorescence microscopy during postnatal development of the mouse cochlea. Samples were collected every 2 days through 8 days, and again at 14 days after birth. In the neonate, staining for HSP entactin and laminin-1 was barely visible; however, antibodies against fibronectin displayed intense immunoreactivity in nearly every cochlear tissue. Fibronectin is progressively inactivated in all tissues except the basilar membrane where it persists at high levels to adulthood. Laminin-1, entactin, and HSP illustrate remarkable temporal and spatial coordinate regulation. Elevated expression of these proteins is observed at 2 postnatal days (PND), and persists in the membranes surrounding the spiral ganglion cell bodies. Transient expression of laminin-1 and entactin, an to a lesser extent HSP, is observed from PND4 to PND8 in a track of membrane running from the interdental cells of the spiral limbus down the inner sulcus, across the basilar membrane, up the external sulcus to the spiral prominence, and branching into the spiral ligament ensheathing the root cell processes. By PND14 the abundance of these proteins is greatly reduced along this track. The abundance and dynamic regulation of these major basement membrane-associated proteins suggests that they play an important role in postnatal cochlear development.

Expression of basement membrane type IV collagen chains during postnatal development in the murine cochlea

An immunofluorescence study was performed to examine the temporal and spatial patterns of expression for the different type IV collagen chains during postnatal cochlear development. At birth, the classical chains (4A1 and 4A2) were widely expressed, while the novel chains (4A3, 4A4, and 4A5) were completely absent. Activation of the novel chains was observed at 4 days of age, with intense, widely distributed immunostaining suggesting that most of the cells in the cochlea express the novel chains at this developmental stage. From day 8 through day 14, developmental inactivation of the novel chains results in a reduction of generalized immunoreactivity with a concomitant elevation of specific staining in the membranous structures bounding the interdental cells of the spiral limbus, the inner sulcus, the basilar membrane, and in a fibrous bed of staining radiating from the spiral prominence into the region of the spiral ligament which corresponds to the location of the root cell processes. This pattern of intense immunostaining for the novel chains persists through adulthood. The classical chains are expressed in these same anatomical regions only transiently (from day 6 to day 10), after which a gradual developmental inactivation leads to the adult expression pattern where classical collagen chains are found primarily in the perineurium, in the membranes surrounding the spiral ganglion cell bodies, and in the vascular basement membranes of the spiral ligament and the stria vascularis. The complex developmental pattern of expression for the type IV collagen chains in the murine cochlea is similar to that observed in the murine kidney, which is the other major site for basement membrane pathology in Alport syndrome.

Distribution patterns in glycoconjugate expression during the development of the rat palate

The distribution of complex carbohydrate structures during the embryonic development of the rat palate was analysed by examining lectin-binding patterns in serial paraffin and cryostat sections. With few exceptions, the binding patterns showed a general increase in lectin receptors in the more developed stages of palatogenesis. High mannose oligosaccharides were especially amplified during development. Terminal fucose molecules were not expressed. In contrast, terminal sialic acid molecules were ubiquitously distributed in epithelial and mesenchymal tissues. Non-sialylated terminal N-acetylglucosamine was specifically restricted to evolving bone matrix. Before palatal fusion, quantitative but not qualitative differences were detected between oral, nasal, and medial-edge epithelial surfaces. The only exception was LCA, which specifically marked epithelial cells at the tip of palatal shelves. A very selective affinity for Jacalin was demonstrated in the oral epithelium of the palate after day 16, suggesting the presence of sialylated terminal galactose-(beta-1,3)-N-acetylgalactosamine. PNA specifically marked the basal lamina of the oral side of palatal processes. The binding patterns of DBA, GSL IA, SBA, and VVA indicated that the epithelium of the tongue is characterized by terminal alpha- and beta-galactose residues, whereas palatine cells possess only molecules with beta-anomery. During palatogenesis, glycosaminoglycans patterns were significantly modified. Our data suggest that alteration of complex carbohydrate structures may play a central role in modulating cell-cell and cell-matrix interactions. The significance of these findings, however, remains to be elucidated.

Ultrastructure and cytochemistry of the integument of Modiolicola gracilis, parasitic copepod in mussel gills (Mytilus galloprovincialis and Mytilus edulis)

Of mussels taken from the Ebro Delta River (E. Spain), 3% have a nonmodified copepod, Modiolicola gracilis, in the gill tissues. The cuticle of different segments of the body has an epicuticle with two layers, which show external microvilli-like projections. Weakly positive reactivity to the PTA technique has been detected in the external region. The procuticle has the helicoidal architecture of the chitinous tegument in arthropods, whereas the cuticle shows discontinuities in the regions of ducts in tegumental glands. The integument is comprised of three types of cells. Epidermal cells are flat with numerous mitochondria. Muscle cells show well-developed mitochondria with several longitudinally distributed cristae. A third and secretory cell shows a well-developed rough endoplasmic reticulum and Golgi complex in the basal zone. Its apical portion is full of secretory granules. Through the cuticle, these integumental glands open directly to the cuticular surface via a short duct coated by epicuticle. The composition and specializations of this complex cuticular architecture differ markedly from those shown by an endoparasitic copepod detected in the digestive gland of the mussel. It does not appear that the specializations detected in the cuticle of M. gracilis lead to any histopathological alteration in host tissues. © 1994 Wiley-Liss, Inc.

Glycoconjugates in the vestibular organs as revealed by the silver methenamine method

The glycoconjugates in the vestibular organs of the guinea pig were studied after staining by the silver methenamine method and by the periodic acid-Schiff (PAS) reaction. The organic matrix of otoconia, otolithic membranes and cupulae were stained to the same degree by the PAS reaction. In contrast, the mineralizing and non-mineralizing matrices were clearly distinguished by the silver methenamine method. The otoconia were surrounded by an intensely stained organic matrix, while the otolithic membranes and cupulae were moderately stained. This histochemical difference suggests that the positively stained organic matrix of otoconia is not identical to the otolithic membranes and cupulae in terms of its biochemical composition. The strongly stained material may play an important role in turnover of calcium in otoconia. The contact areas between type I hair cell and nerve calyx were contained silver methenamine-positive material which is probably involved in adhesion of these cell membranes.

Glycoconjugates in the cochlea as revealed by the silver methenamine method

The glycoconjugates in the cochlea of the guinea pig were studied by staining samples by the silver methenamine method as well as after periodic acid-Schiff (PAS) staining. Results obtained by the two methods were similar but not identical. The silver methenamine method was much better in terms of resolution. However, this method of staining seemed less specific than the PAS reaction. When the silver methenamine method was used, the tectorial membrane and outer hair cells were specifically stained. Two types of fibrils were observed in the tectorial membrane. Thick fibrils were located in the fibrous layer. Thin fibrils were situated in the marginal band, the cover net, Hensen's stripe and the fibrous layer. The thick and thin fibrils appeared to correspond to type A and type B protofibrils, respectively. The outer hair cells were found to contain strongly stained particles which, presumably, consisted of glycogen. The basement membrane of the capillaries in the stria vascularis also gave a positive reaction, while that of other capillaries was essentially unstained. This finding suggests structural differences between these capillaries.

The fine structure of the guinea pig tympanic membrane with special reference to the fiber arrangement

The tympanic membrane of the guinea pig was studied by electron microscopy. The pars tensa was composed of three layers, i.e., the outer epidermis, the middle lamina propria and the inner mucosal membrane. The pars flaccida was negligible in size. The fibers in the lamina propria of the tympanic membrane were not clearly observable by conventional electron microscopy. With the silver methenamine method the fibers were more intensely stained than the epithelial cells and could thus be distinctly demonstrated by this method. In the inferior larger portion of the pars tensa, the lamina propria contained the outer radial and the inner circular fiber bundles. The radial fiber bundles were thicker and more densely packed than the circular ones. This fact indicates that the radial fibers form the major skeleton of this portion. The superior smaller portion of the pars tensa contained several layers of irregularly arranged fiber bundles in the lamina propria and was considerably thicker than the inferior larger portion.

Schistosoma mansoni: the chemical nature of the secretions produced by the Mehlis' gland and ootype as revealed by cytochemical studies

The 'secretory pathway' of the Mehlis' gland secretion as well as the maturation of the secretory granules are described. The secretions produced by the Mehlis' gland and the distal ootype in Schistosoma mansoni were identified as neutral glycoproteins. They were both periodate reactive, stained with phosphotungstic acid at low pH, and sensitive to the proteolytic action of papain. The secretions did not strain with both the low-iron diamine and the high-iron diamine methods for the presence of acidic glycoconjugates, and they did not contain a detectable level of sulphydryl groups. The possible role of the secretion from the Mehlis' gland in egg-shell formation is discussed.

Light and electron microscopic observations on ciliated vacuoles and cysts in the oviductal and endocervical epithelia of the rabbit

Ciliated vacuoles and intraepithelial cysts have been observed in oviductal and endocervical epithelia of rabbits. In this study, rabbits under various hormonal conditions were studied by light and transmission electron microscopy and tissue culture in an attempt to determine their distribution and origin. Ciliated vacuoles most frequently lay in the basal cytoplasm, below or beside the nucleus, and very close to the basal lamina. A few were apically located. Their average diameter was 8.8 by 5.1 microns. Cilia and microvilli projected into the vacuolar lumen. These vacuoles were located intracellularly as evidenced first by the degeneration of both their cilia and microvilli and the moderately dense matrix that often filled the vacuolar lumen, as observed by electron microscopy. Secondly, phase microscopy of the living endocervical epithelium allowed us to observe the beating of the cilia within the vacuoles, not on the surface of such cells. Thirdly, ruthenium red stained the surface glycocalyx of ciliated and secretory cells, but not that of the cilia and microvilli within the vacuoles. The intraepithelial cysts were not observed in all tissue blocks. The largest numbers were found in ovariectomized animals treated for 3 and 5 days with estradiol. More were seen in the isthmus and cervix than in the fimbria and ampulla. The cysts were located most often within the epithelium along the sides of, and at the bases of, the mucosal folds. They were lined by flattened epithelium of various combinations of secretory and ciliated cells. An unusual cell type was associated with some of the cysts and ciliated vacuoles. Its cytoplasm contained aggregates of mitochondria and vesicles whose contents varied in density. Although the genesis of the ciliated vacuoles is not certain, our results indicate that they may arise from aberrant positioning of proliferating procentrioles or from a defect in targeting or transporting the centrioles to the apical plasma membrane to serve as basal bodies. Fusion of adjacent ciliated vacuoles with lumina lined by secretory cells having deep apical invaginations appeared to contribute to the formation of cysts.

Differential staining of mucin granules from epoxy resin sections by a phosphotungstic acid-methyl green procedure

After treatment of epoxy resin semithin sections from glutaraldehyde fixed rat large intestine with 5% aqueous phosphotungstic acid (PTA), staining with unpurified 0.2% solutions of methyl green at 60 C for 5 min produces a color differentiation between mucin granules of goblet cells. Some mucin granules and the glycocalyx appear deep green while the remaining granules, luminal mucin and collagen fibers are pink. The known contamination of unpurified methyl green with crystal violet seems to be responsible for the pink staining reaction of the latter structures, which also present an orange-red fluorescence under green exciting light. Electron microscopic observations show selective contrast of mucin granules which appear with a different amount of PTA deposits. This procedure is useful to reveal the heterogeneity of mucin granules in light and electron microscopy.

Tungsten and molybdenum heteropolyacids as staining and contrasting agents: reactivity with epoxyresin-embedded cell and tissue structures

In this work, we carry out a further approach to the knowledge of the reaction mechanism of phosphotungstic and phosphomolybdic acids (PTA and PMA), as well as some derivatives, with cell structures from epoxyresin-embedded materials. Applied on thin sections from glutaraldehyde-fixed tissues, PTA and PMA induced a strong electron contrasting reaction in spermatid acrosomes, goblet cell mucin, callose and plant cell walls, endexine, intine and starch granules. In light microscopy, the localization of heteropolyacids on these structures was achieved by treatments of semithin sections with suitable reducing agents (titanous sulfate, stannous chloride, sodium borohydride, or p-phenylenediamine) to form the mixed-valence heteropolyblues, or with Schiffs's reagent. The use of PTA-dye complexes (pyronin-PTA and Mallory's PTA-hematoxylin) also showed the same staining pattern. Taking into account the chemical characteristics of the PTA- and PMA-reactive tissue elements, the present results indicate that heteropolyacids selectively enter into the highest hydrophilic structures from non-polar epoxy-embedded sections; after brief washing, they appear predominantly retained in tissue structures containing a great amount of carbohydrate components.

Junctional complexes and cell polarity in the urinary tubule

In this review, we demonstrate how differentiated membrane domains can be detected in epithelial cells using conventional light and electron microscopy, freeze-fracture electron microscopy and the immuno- and cytochemical detection of membrane components. Using specific examples from the kidney, we show how the polarized insertion of these components into either apical or basolateral plasma membrane regions on either side of the tight junction barrier is related to specific functions of principal and intercalated cells in the collecting duct. In addition, distinct basal and lateral membrane domains have been revealed in some cells that are maintained in the absence of a tight junctional barrier in the plane of the membrane. This suggests that other factors, possibly related to cytoskeletal elements, may be involved in the functional segregation of these membrane areas. We propose that epithelial cell plasma membranes should be subdivided into apical, lateral and basal regions, and that the term "basolateral" may be an oversimplification.

The suprastructure of the saccular macula

Inclusion of tannic acid in the primary fixative fortuitously preserved the macular suprastructure, from the macular surface to the otoconia, in rat. Results demonstrate that fluid-filled channels around the stereociliary tufts and a slit-like space immediately above the macula are artefacts of tissue preparation. Filaments fill the area between, and show linkage to, the macular surface and the more peripheral, closely knit layer identified here as the true otoconial membrane. The material also passes through the otoconial membrane at various sites to surround the otoconia and extends well beyond the maculas in all directions. Although it may prove later to be endolymph, it is referred to here as supramacular substance. Kinocilia and the tallest stereocilia as well as the otoconia are tethered to the otoconial membrane. Findings were confirmed in decalcified material. Results are discussed in terms of functional and biochemical implications, and by analogy to man-made acceleration sensing devices.

Ultrastructural location of complex carbohydrates in developing rat incisor enamel

The ultrastructural distribution of complex carbohydrates in an early formation stage of rat incisor enamel was investigated by staining with the periodic acid-thiocarbohydrazide-silver proteinate reaction (PA-TCH-SP) for vicinal glycol-containing glycoconjugates, the phosphotungstic acid-chromic acid mixture (PTA) for glycoproteins, and the cationic dyes alcian blue or bismuth nitrate for sulfated glycoconjugates. In order to remove selectively sulfated complex carbohydrates, half of the serial sections obtained were digested with a bovine testicular hyaluronidase prior to staining. Far fewer electron-dense deposits were observed with the PA-TCH-SP method on hyaluronidase-treated sections, especially those subsequently treated for 48 hours with TCH. On the other hand, the minimal staining obtained with PTA was much more intense on sections treated with hyaluronidase where linear fiberlike structures were observed. With cationic dyes, staining of dotlike alignment structures and ground substance was obtained but was completely abolished by hyaluronidase treatment. Cuprolinic blue in a critical electrolyte concentration, ruthenium hexamine trichloride used with aldehyde during fixation, as well as rapid-freezing followed by freeze-substitution validate that this dotlike distribution is not an artefact of processing. The staining results demonstrated that the glycoproteins and sulfated complex carbohydrates in developing rat incisor enamel each display a specific distribution pattern. The glycoproteins were present as fiberlike structures and the sulfated carbohydrates appeared as dotlike formations located close to the surface of the fiberlike structures, and/or in the spaces between them.

Immunohistochemical and ultrastructural observations on adenoid cystic carcinoma of salivary glands. With special reference to intermediate filaments and proteoglycan particles

In adenoid cystic carcinoma (ACC) of salivary gland origin, intermediate filaments of tumour cells were investigated by immunohistochemical techniques and complex carbohydrates within the pseudocysts by ultrastructural methods. The intermediate filament proteins vimentin and cytokeratin were found in most neoplastic cells. The pseudocysts of the tumours were found to contain proteoglycan particles stainable after glutaraldehyde fixation--but not after osmium fixation alone. Ruthenium red (cationic dye) enhanced the staining whereas periodic acid-chromic acid-silver methenamine staining or phosphotungstic acid staining did not visualize the proteoglycan particles mainly containing acid proteoglycans which are normally produced by mesenchymal tissue. The cells of adenoid cystic carcinoma thus have an intermediate filament content and produce complex carbohydrates characteristic of both epithelial and mesenchymal tissue. Hence, an origin in an undifferentiated pluripotential cell seems plausible.

Pyronin-phosphotungstic acid: spectral characteristics and staining pattern on Epon semithin sections

Phosphotungstic acid (PTA) binds to the basic dye pyronin Y to give a non fluorescent complex with absorption characteristics which are different from those of the free dye. The use of this complex on different cells and Epon embedded tissues revealed no staining affinity and only certain hydrated tissue components as starch showed a light reaction with the pyronin-PTA. The role played by the hydratation degree of certain components from epoxy-embedded tissues on the reaction mechanisms observed with some dyes and electron contrasting agents is briefly discussed.

Incorporation of 3H-fucose and the secretion of glycoproteins in the coagulating gland of the mouse

The coagulating gland of rodents, which is part of the prostatic complex, secretes components of semen. Although possessing some ultrastructural features of other exocrine glands, the mechanism of secretion by these cells has been problematic. In the present study the pathway, kinetics, and mode of secretion in the coagulating gland of the mouse were studied by light and electron microscope autoradiography at intervals between 10 minutes and 3 hours after injection of 3H-fucose. The majority of silver grains overlay the Golgi apparatus at the initial interval, but in addition, more than a third of the grains were associated with extremely distended cisternae of the rough endoplasmic reticulum. At later intervals, radioactivity of the Golgi apparatus and the endoplasmic reticulum declined, while labeling of secretory granules increased greatly. Luminal contents became labeled 1 hour after administration of precursor. The results indicate that the pathway for secretion of glycoproteins proceeds through the Golgi apparatus to secretory granules and the glandular lumen, as in many other cells. In particular, heavy labeling of secretory granules at later intervals indicates that merocrine secretion is the most likely mechanism in the coagulating gland. However, the unusual observation that a significant proportion of grains overlay the rough endoplasmic reticulum at the initial interval raises the possibility that some fucose is incorporated into glycoproteins in the endoplasmic reticulum, as has been reported for other cell types with similarly configured endoplasmic reticulum.

Glycoprotein synthesis in the Golgi apparatus of spermatids during spermiogenesis of the rat

During steps 1-7 of spermiogenesis the Golgi apparatus contributes to the formation of the acrosomic system which develops at the surface of the nucleus. Later, in step 8, the Golgi apparatus detaches from the acrosome and remains suspended in the elongated cytoplasm until it degenerates during step 16. Using 3H-fucose as a tracer and the radioautographic technique, we observed that the Golgi apparatus incorporates the tracer and delivers the labeled glycoproteins to the developing acrosomic system during steps 1-7 of spermiogenesis, to multivesicular bodies during steps 1-9, and to the remaining cytoplasm and plasma membrane during steps 1-15. Throughout these steps of spermiogenesis the Golgi apparatus does not show major changes in structure; it is composed of a cortex made up of connected stacks of saccules and a medulla showing a loose aggregate of vesicular profiles. Glycoprotein synthesis in this Golgi apparatus, before and after it contributes lysosomal glycoproteins to the growing acrosomic system, was quantitatively assessed in electron microscope EM radioautographs of tissue sections from animals sacrificed at 1, 4, 8, and 24 h of 3H-fucose injection. The incorporation of the labeled sugar was found to remain quantitatively similar during steps 1-15 of spermiogenesis, and therefore, no shift in glycoprotein synthesis took place following separation of the Golgi apparatus from the acrosomic system. Throughout these steps, fucose molecules are first incorporated in the cortex of the organelle and subsequently transported to the medulla, where they temporarily accumulate before being delivered, depending on the step of spermiogenesis, to the acrosomic system, to the multivesicular bodies, and also, presumably, to the plasma membrane.

SERGE, the subcellular site of initial hepatic glycogen deposition in the rat: a radioautographic and cytochemical study

Hormonal control of hepatic glycogen and blood glucose levels is one of the major homeostatic mechanisms in mammals: glycogen is synthesized when portal glucose concentration is sufficiently elevated and degraded when glucose levels are low. We have studied initial events of hepatic glycogen synthesis by injecting the synthetic glucocorticoid dexamethasone (DEX) into adrenalectomized rats fasted overnight. Hepatic glycogen levels are very low in adrenalectomized rats, and DEX causes rapid deposition of the complex carbohydrate. Investigation of the process of glycogen deposition was performed by light and electron microscopic (EM) radioautography using [3H]galactose as a glycogen precursor. Rats injected with DEX for 2-3 h and [3H]galactose one hour before being killed displayed an increasing number of intensely labeled hepatocytes. EM radioautography revealed silver grains over small (+/- 1 micron) ovoid or round areas of the cytosome that were rich in smooth endoplasmic reticulum (SER) and contained a high concentration of small dense particles. These distinct areas or foci of SER and presumptive glycogen (SERGE) were most numerous during initial periods of glycogen synthesis. After longer exposure to DEX (4-5 h) more typical deposits of cytoplasmic glycogen were evident in the SERGE regions. Several criteria indicated that the SERGE foci contained glycogen or presumptive glycogen: resemblance of the largest dense particles to beta-glycogen particles in EM; association of 3H-carbohydrate with the foci; removal of particles and label with alpha-amylase; and positive reaction with periodic acid-chromic acid-silver methenamine. The concentration of SER in the small foci and the association of newly formed glycogen particles with elements of SER suggest a role for this organelle in the initial synthesis of glycogen.

Histochemical detection of glycoproteins in the gastric epithelia of Columba livia

A histochemical investigation was carried out to detect glycoproteins in the lining and glandular epithelia of 4 regions of the stomach of Columba livia: proventriculus, intermediate region between proventriculus and gizzard, gizzard, intermediate region between gizzard and duodenum. It was noticed the presence of neutral and sulphoglycoproteins, with a clear predominance of the latter in the lining epithelia and in the simple tubular glands of the mucosa of these regions, except for the gizzard. Absence of glycoproteins was noticed in the oxynticopeptic cells of the branched tubular glands of the proventriculus. Neutral glycoproteins and traces of sulphoglycoproteins were present in the lining epithelia of the folds of its central cavity and of its exit duct. Lining the above mentioned structures, the correspondent of the gizzard, inclusively there was a pellicle of sialoglycoproteins.

Polarization optical analysis of blood cell membranes

The present study deals with investigations of membrane structure using polarization topo-optical reactions. Polarization microscopy is a special field of biological submicroscopic morphology. It represents a powerful tool well able to reveal the features of organization of biological structures, and the regularity of macromolecules building cells and tissues - properties that cannot directly be studied by other approaches to complex biological systems. Only in "pure" systems can X-ray diffraction, or the analysis of circular dichroism and the dispersion of optical rotability provide data equivalent to those obtained by polarization microscopy in complex systems. One of the main drawbacks of molecular biology is that most information is relevant to isolated, purified particles or macromolecules. Thus, no conclusions can be drawn concerning the original arrangement of molecules. The gap between biochemical-biophysical and morphological approaches to molecular arrangement in complex structures is bridged by the polarization optical technique. As was pointed out in the introduction, polarization microscopy became a routine biological research method following the pioneering work of Romhányi. His enlightening topo-optical reactions (Romhányi 1960, 1963, 1966) were based on the oriented dye binding of the original charge carriers of regularly arranged tissue constituents. The second group of Romhányi's topo-optical reactions comprised procedures such as sulfation (Romhányi et al. 1973, 1974), the aldehyde-bisulfite-toluidine blue (ABT) reaction (Romhányi et al. 1974, 1975), the permanganate-bisulfite-toluidine blue (PBT) reaction (Fischer 1979, 1979a), and the sialic acid-specific reaction (Makovitzky 1980) all of which operate with induced dye-binding groups; i.e. dye-binding moieties on biological macromolecules are produced by specific chemical reactions.

Two anatomical pathways for the renewal of surface glycoproteins in chloride cells of fish gills

The cytoplasm of chloride cells found in the epithelium lining the gills of guppies (Lebistes reticulatus) contains, in addition to the Golgi apparatus and cisternae of endoplasmic reticulum, two distinct membranous components, the vesiculotubular and the tubular systems. While the latter is connected to the laterobasal plasma membrane, the former, made up of small vesicles and short membranous tubules, is seen mainly between the Golgi apparatus and the apical cavity which invaginates the apex of the cell. The role of these two systems in the transport of glycoproteins from the Golgi apparatus to the cell surface was investigated in fishes maintained in fresh and salt water, injected with 3H-fucose, and sacrificed at various intervals thereafter (10 and 30 min; 2.5, 8, 15.5, 24, and 48 hours). The distribution of the label was analyzed by quantitative radioautography in sections examined with the light and electron microscopes. The light microscopic data suggested that the label incorporated in the supranuclear region, where the Golgi apparatus is located, migrated toward the apical and the laterobasal regions of the chloride cells. The relative concentration of the tracer over the various components of the cytoplasm of these cells was calculated from data collected on electron microscope radioautographs at various intervals after 3H-fucose injection. The curves obtained supported the view that glycoproteins synthesized in the Golgi apparatus were transported to the apical surface via the vesiculotubular system, and to the laterobasal membrane via the tubular system.

The influence of embedding media and fixation on the post-embedment ultrastructural demonstration of complex carbohydrates. I. Morphology and periodic acid-thiocarbohydrazide-silver proteinate staining of vicinal diols

The influence of fixation and embedding medium on the periodic acid-thiocarbohydrazide-silver proteinate (PA-TCH-SP) staining reactivity in the mouse intestine was studied. It was found that the combination of osmium tetroxide and epoxy resins was the least sensitive for the demonstration of complex carbohydrate with the PA-TCH-SP method. Post-osmication reduced, but did not abolish, PA-TCH-SP reactivity (except for the Golgi complex) when non-epoxy resins were used. The staining pattern of a particular organelle differed depending on the embedding medium used. Golgi cisternae exhibited the most intense PA-TCH-SP reactivity in non-osmicated tissues embedded in non-epoxy resins. Post-osmication of tissues was required to reveal the fine structure of the glycocalyx as well as to preserve the fine structure of tissues embedded in styrene-methacrylate and styrene-Rigolac 2004. The choice of fixation procedures and embedding media in a given study should be governed primarily by the sites of interest.

Fine structure of human chorionic membrane. Ultrastructural and histochemical examinations

Normal human term chorionic membrane was examined by electron microscopy and histochemistry. In comparison with previous studies of the human chorion, our findings showed the following new morphological aspects: (1) The cellular junctions between adjacent trophoblastic cells were made up not only of desmosomes but also of gap junctions and occasional tight junctions. (2) The epithelial basement membrane was stratified and discontinuous. (3) Besides the fibroblasts and macrophages (Hofbauer cells), the connective tissue of the human chorion also contained myofibroblasts. Histochemically, the surface coat of the plasma membrane of the chorionic epithelial cells, the microfibrils, and the proteoglycans associated with the collagen fibrils showed a positive reaction to ruthenium red. This was not so for the basement membrane of the chorionic epithelium. Since the tight junctions are seldom present in the chorionic membrane, they are apparently not significant for the paracellular protein transfer. Similar to the amnion epithelium, it is assumed that the intercellular spaces and the discontinous basement membrane of the chorionic epithelium represent a paracellular route for non-placental protein transfer. As the myofibroblasts in human amnion, we suggest that the myofibroblasts in the chorionic membrane may contribute to the protection of the fetal membranes from overdistension.

Distribution of polyanionic sites in the developing gonads and the dorsal mesentery of the chick embryo

The distribution of glycoconjugates was investigated in the embryonic trunk mesoderm used as a substrate by migrating primordial germ cells (PGCs) by means of ultrastructural cytochemistry. In both mesentery and developing gonads polyanionic sites were abundant in epithelial and mesenchymal cell coats, basal laminae, and extracellular matrices (ECM). In the latter, polyanions distributed on microfibrils and granules were associated with collagen fibers, forming an entangled network. No preferential association of this fibrillo-granular material with PGCs was observed, suggesting that polyanions present in ECM likely act by promoting inflation of the extracellular spaces rather than by providing mechanical guides for the moving cells.

The effects of colchicine on the distribution of glycoprotein-containing vesicles in epithelial cells of the murine colon

In murine colonic epithelial cells, cell-coat glycoproteins are transported to the cell surface in vesicles that originate at the Golgi apparatus. To determine the role of microtubules in the movement of these vesicles the antimicrotubule agent colchicine was injected into mice at several time intervals prior to sacrifice. In the mice that were treated with colchicine for 4.5 h it was observed that the polarity of the cells was disturbed. The Golgi apparatus and nucleus often appeared interchanged in their positions. The glycoprotein-containing vesicles, normally located apically, were sparse in that location, but abundant near the lateral plasma membranes of the cells at the level of the nucleus and Golgi apparatus. Straining by the periodic acid-chromic acid-silver methenamine technique for glycoproteins clearly revealed the reduction of vesicles apically and accumulation of vesicles laterally. The mechanism responsible for the movement of the vesicles to this location is unclear. It is suggested that the accumulation of vesicles in the lateral region may reflect some hindrance in the fusion of the vesicles with the lateral cell membranes.