Glycosaminoglycan composition of electric organ basement membranes

The basement membranes of the innervated surface of the electric organ of Discopyge tschudii present a high concentration of mucopolysaccharides as revealed by intense ruthenium red-positive reaction. Glycosaminoglycans (GAGs) were isolated and characterized from these pure basement membranes by using a combination of agarose gel electrophoresis and enzymatic degradation with specific enzymes. The isolated basement membrane showed a high concentration of GAGs (130 mg/g of dry tissue); of this amount 49% was hyaluronic acid, 24% was chondroitin-6-sulfate, 12% was heparan sulfate, and 14% was dermatan sulfate. Controlled digestion with heparinase and heparitinases I and II was used to study the structural features of the heparan sulfate. Four unsaturated disaccharide units were found in the heparan sulfate: disulfated, N-sulfated, N-acetylated, and N-acetylated O-sulfated disaccharides. The disaccharide units of the cholinergic heparan sulfate present a high amount of disulfated disaccharides and a low amount of N-acetylated O-sulfated disaccharides. The N-sulfated disaccharides, in contrast to the N-acetylated ones, were found through all the structure of the cholinergic heparan sulfate. Finally our work shows for the first time the presence of dermatan sulfate in the basal lamina of the electric organ.

Ultrastructural localization of keratinocyte surface associated heparan sulphate proteoglycans in human epidermis

Fixation and staining procedures were developed for the electron microscopic demonstration of glycosaminoglycans (GAGs) in human epidermis. En bloc staining with cuprolinic blue (CB), ruthenium red (RR) and tannic acid (TA) in the primary fixative were applied for the localization of the GAGs. Removal of the epidermal basal lamina and underlying dermis was a prerequisite for stain penetration. In CB-fixed specimens 50 nm long, rod-like granules were found attached to keratinocyte cell surfaces, while the RR- and TA-fixed specimens contained round granules (luminal diameter 10 and 30 nm, respectively). The stainability of the CB-positive granules in the presence of 0.3 mol/l MgCl2 indicated that they contained sulphated GAGs. Prefixation digestions of epidermal sheets with chondroitinase ABC. Streptomyces hyaluronidase, and heparitinase showed that the RR-positive granules also contained sulphated GAGs, mostly heparan sulphate. The granules visualized with TA on keratinocytes were susceptible to heparitinase treatment, but the abundance of TA-staining suggested that TA also stained structures other than heparan sulphate. The EM data was in accordance with the 35SO4 labelling experiments showing that heparan sulphate was the major sulphated GAG synthesized in epidermis, whereas chondroitin/dermatan sulphates comprised about one fifth of the total activity incorporated. The distributions of the CB-, RR- and TA-positive granules on cell surfaces were similar. The morphology of the proteoglycan granules was probably determined by the extent of the GAG-chain collapse following binding to each of the dyes.

Decreased anionic sites in Bruch's membrane of spontaneous and drug-induced diabetes

The basal laminae of capillaries, glomeruli, and nerves are thickened in diabetes. Previous studies have shown that diabetic tissues produce increased levels of basal lamina collagen and reduced levels of proteoglycans. Since heparan sulfate and chondroitin sulfate proteoglycans are thought to act as anionic barriers regulating passage of proteins across Bruch's membrane of the eye, the cationic electron microscope tracers, polyethyleneimine (PEI) and ruthenium red, were used to study the distribution of anionic sites in Bruch's membrane of spontaneously diabetic Bio-Breeding/Worcester (BB-W) rats and streptozotocin-diabetic rats. The distribution of the two tracers is similar. In Bruch's membrane of control rats, electron dense particles are present at regular intervals along both sides of the basal laminae of the retinal pigment epithelium (RPE) and of the choriocapillary endothelium (CE), and along collagen fibers in the zone between the two basal laminae. Within 3-6 months after the onset of hyperglycemia in both diabetic rat models, quantitative analysis shows a significant reduction in binding sites along both RPE and CE basal laminae, while thickness of both basal laminae is significantly increased. Because reductions in anionic binding sites along basal laminae in the renal glomerulus have been found to accompany changes in glomerular filtration, these changes suggest that filtration through Bruch's membrane is altered in diabetes.

Reduced content and abnormal distribution of anionic sites (acid proteoglycans) in the diabetic glomerular basement membrane

Sulfated proteoglycans (fixed anionic sites) on the glomerular basement membrane (GBM) of kidneys from diabetic and nondiabetic patients have been demonstrated by electron microscopy using polycationic dyes (ruthenium red, polyethyleneimine). These substances were used for immersion fixation of renal biopsy specimens. The thickened GBM of diabetics revealed a reduced proteoglycan content within both the narrowed laminae rarae, where normally particles were seen at 60 nm intervals. Proteinuria was observed in all such cases, but no immunopathological alterations of the basement membranes were seen. With both tracer substances anionic sites were also demonstrated in different segments of the thickened lamina densa in diabetics. In polyethyleneimine-treated biopsies some segments of the membrane showed increased anionic moieties at the junction of the basement membrane and the epithelial and endothelial cell membranes. These are probably acid glycoproteins linked to the cell membrane and the synthesis of these basement membrane components may represent a compensatory mechanism seeking to restore normal permeability.

Basement membrane of central nervous system capillaries lacks ruthenium red-staining sites

We used the cationic dye ruthenium red to examine the distribution of anionic macro-molecules (presumably proteoglycans) in the basement membranes of the fenestrated capillaries and epithelium of the choroid plexus, and of the continuous capillaries forming the blood-brain barrier. Both the endothelial and epithelial basement membranes of choroid plexus displayed discrete, 10- to 20-nm-diameter, electron-dense sites after exposure to ruthenium red. These sites were similar in size, appearance, and distribution to those found in the vascular and epithelial basement membranes of a variety of tissues outside the central nervous system. In contrast, the basement membranes of continuous, blood-brain barrier capillaries did not display electron-dense sites following exposure to ruthenium red, even after measures had been taken to enhance penetration of the dye across the endothelial cells. The lack of discrete ruthenium red staining in the basement membrane of continuous blood-brain barrier capillaries could be due to a relative paucity of anionic macromolecules, or may be the result of the compact architecture of this particular basement membrane. Regardless of the final explanation, these findings suggest that the basement membrane of the blood-brain barrier, like its endothelium, is structurally (and perhaps functionally) unique.

A study of the odontoblast process with transmission electron microscopy

Freshly extracted human third molars with completely formed roots were sectioned and placed in Karnovsky's fixative. The specimens were decalcified in ethylenediaminetetraacetic acid (EDTA) for 91 days, followed by digestion in collagenase. They were then fixed in a solution of buffered osmium tetroxide or ruthenium red and buffered osmium tetroxide, embedded in Spurr's plastic mixture, and sectioned for transmission electron microscopy. Each section was stained with uranyl acetate and lead citrate and viewed with a transmission electron microscope. No odontoblast processes could be identified at the cemental third of the dentin with the described technique.

The surface charge of Toxoplasma gondii: a cytochemical and electrophoretic study

The surface charge of Toxoplasma gondii tachyzoites was evaluated by means of binding of colloidal iron hydroxide particles at pH 1.8, cationized ferritin particles at pH 7.2 and ruthenium red to the cell surface, as visualized by electron microscopy and by direct measurements of the electrophoretic mobility (EPM) of the cells suspended in solutions of different ionic strength and pH. At pH 7.2, T. gondii has a negative surface charge with a mean EPM of--1.1272 +/- 0.0917 micron.s-1 X V-1 X cm. No significant difference was observed between the EPM of living cells at 25 degrees C and that of glutaraldehyde-fixed cells. At lower pH, there is a decrease in the negative surface charge, with an isoelectric point at pH 3.5. At higher pH (greater than 10), there is an increase in the surface charge reaching an EPM of--1.5675 +/- 0.0848 micron.s-1 X V-1 X cm at pH 7.2. These results indicate that the surface of T. gondii contains both negatively and positively charged dissociating groups. Binding of cationized ferritin particles and ruthenium red throughout the cell surface of glutaraldehyde-fixed cells was observed. However, when living parasites were incubated at 4 degrees C in the presence of cationized ferritin some cells showed a uniform distribution of the label, others showed a patch-distribution and still in others no label was seen, indicating a process of mobility and shedding of surface anionic sites. Colloidal iron hydroxyde particles did not bind to the surface of T. gondii. Incubation of the parasites in the presence of neuraminidase from Clostridium perfringens or Vibrio cholerae or in the presence of proteolytic enzymes (trypsin or protease) did not interfere with the surface charge.(ABSTRACT TRUNCATED AT 250 WORDS)

Basal lamina anionic sites in the embryonic submandibular salivary gland: resolution and distribution using ruthenium red and polyethyleneimine as cationic probes

The basal lamina of the embryonic submandibular epithelium is a dynamic compartment of the extracellular matrix required for branching morphogenesis. A transmission electron microscopy (TEM) structural analysis of the basal lamina, at a time of intense branching activity, was conducted, comparing standard glutaraldehyde-fixed preparations with ones that included tannic acid in the primary fixative, and comparing anionic site resolution and distribution with two cationic probes, ruthenium red (RR) and polyethyleneimine (PEI). Standard TEM revealed a conventional basal lamina structure, with a lamina densa, a lamina lucida interna and a lamina lucida externa. Fine filaments emanated from the lamina densa, traversing both lamina lucidae. Tannic acid revealed approximately 35 nm diameter electron-dense particles in the lamina densa with a spacing repeat of approximately 45 nm. Basal lamina anionic sites were resolved as approximately 26 nm diameter RR-particles and approximately 50 nm diameter PEI-particles, present in the lamina lucida interna and associated with the lamina lucida externa. RR-particle linear spacing was 70 nm in the externa and 50 nm in the interna, while the PEI-particle spacing repeat was 90 nm in both compartments. Binding of both probes was blocked by testicular hyaluronidase or chondroitinase treatment, a result suggesting that the anionic sites were chondroitin sulfate proteoglycan, hyaluronic acid, or both. The greater particle spacing observed with PEI was not simply a physical limitation resulting from the average PEI particle diameter being almost twice that of RR particles, since PEI-resolved anionic sites on interstitial collagen were much more closely spaced (approximately 60 nm) than RR-resolved sites (approximately 105 nm).(ABSTRACT TRUNCATED AT 250 WORDS)

Staining of O-specific polysaccharide chains of lipopolysaccharides with ruthenium red

S-form lipopolysaccharides (LPS) from Klebsiella strain LEN-1 (O3: K1-) and from Salmonella minnesota strain 1114 were positively stained with ruthenium red, whereas R-form LPS from Klebsiella strain LEN-111 (O3-: K1-) and Ra, Rb1, RcP+, Rd1P-, and Re LPS from the respective mutant strains of S. minnesota were not or only faintly stained by such treatment. From these results it was concluded that ruthenium red stains the O-specific polysaccharide chains of LPS. The appearance of stained preparations of S-form LPS suggested that the material responsible for this positive staining corresponded to the surface projections which were seen by the negative staining technique as attached to the ribbon-like structures and spherules of the LPS.

Further characterization of spontaneous arthritic changes in murine squamo-mandibular joint: histopathological aspects

The appearance of age-related ulcerative changes in the mouse mandibular condyle were evaluated by light and electron microscopy examinations. Fibrillations appeared along the articular surface and in deeper tissue regions, as early as at six months of age. Such changes were characterized by a marked loss of the tissue's cellularity and by a marked reduction in matrix metachromasia and safranin-0 staining. These microscopical changes were accompanied by a reduced reactivity for both ruthenium red and colloidal iron binding, as noted ultrastructurally. At the same time, increasing numbers of erythrocytes appeared to be adhered to the surface irregularities and were also found in deeper regions within the articular lesions. Using morphological criteria, it became apparent that the degenerative changes of aging articular cartilage started at the more superficial regions of the tissue and only thereafter proceeded toward the chondro-osseous junction. Also, with the advancement of age, the degenerative changes became more severe.

Antidiuretic hormone response in the amphibian urinary bladder: time course of cytochalasin-induced vacuole formation, an ultrastructural study employing ruthenium red

Cytochalasin is known to inhibit the antidiuretic hormone-induced hydro-osmotic response (bulk water flow) in the amphibian urinary bladder without altering hormone-stimulated diffusional water permeability or short-circuit current. In addition, histological studies have shown that the mold metabolite induces the formation of large intracellular vacuoles or lakes in the epithelial cells. We report here a transmission electron microscopic time-course study which indicates that during the early phases of the ADH response cytochalasin causes the formation of numerous multivesicular bodies or aggregates derived from individual basolateral pinocytotic vesicles. Because of their apparent hypertonic nature, the vesicles, as well as the vesicular aggregates, accumulate water during hormone-stimulated hydro-osmotic flow. As a result, the multivesicular bodies dilate and fuse to form the large intracellular lakes characteristic of cytochalasin treatment in the presence of both an applied osmotic gradient and vasopressin. In the presence of mucosal ruthenium red, the luminal glycocalyx was heavily stained with this tracer. At no time, however, even in the presence of hormone, was there any evidence for the uptake of this dye at the apical epithelial border. In the presence of serosal ruthenium red, the lateral intercellular spaces, basolateral pinocytotic vesicles, basal lamina, and collagen, as well as other subepithelial structures, were ruthenium positive. With cytochalasin D, vasopressin, and serosal ruthenium red, both the pinocytotic vesicles and the multivesicular bodies demonstrated an apparent membrane associated ruthenium positive coat. The tracer data indicates that the basolateral pinocytotic vesicles, increased by the presence of hormone, are indeed endocytotic in nature. The mucopolysaccharide coat associated with these structures may be involved in ionic and/or fluid transport.

Localizations of ruthenium red positive material in rabbit peripheral nerves

The penetration and distribution of ruthenium red in the axon-myelin-Schwann cell complex of developing rabbit peripheral nerve fibers are investigated. Ruthenium red positive material is established in the axoplasm, axolemma, periaxonal space, major dense lines and intraperiod lines of the compact myelin, mesaxons, split peripheral myelin lamellae, Schmidt-Lanterman and longitudinal incisures, paranodal loops and axo-glial contacts, Schwann cell cytoplasm and basal lamina, nodal extracellular matrix, desmosome-like structures, endoneural collagen. Some features of the distribution of the contrast material in the developing myelin sheath are described. Regional differences of the axolemma and of the Schwann cell cytoplasm and plasmalemma are established. The prevalence of glycoproteins or glycolipids in the ruthenium red stained material in its different localizations is discussed on the basis of trypsin and hyaluronidase digestion performed.

The carbohydrates of secretory granules and the glycocalyx in developing mucoid cells

Complex carbohydrates in secretory granules and at the apical cell surface of mouse gastric mucoid cells were studied during embryogenesis and in the early postnatal period by various cytochemical methods; the periodic acid-thiocarbohydrazide-silver proteinate (PA-TCH-SP) and tannic acid-uranyl acetate (TA-UA) procedures made neutral mucosubstances (NMS) visible, whereas the hexose residues of glycoconjugates were identified using WGA-, RCA II- and ConA-ferritin. The glycocalyx was stained with ruthenium red (RR). During differentiation of the embryonic mucoid cells the number of secretory granules increased in parallel to the increase in their carbohydrate component. NMS-stainable parts in secretory granules also had binding sites for the conjugates RCA II- and WGA-ferritin, but the binding of ConA could not be identified. The increasing quantity of NMS in secretory granules was correlated with the increased amount of PA-TCH-SP and TA-UA positive substances in the apical glycocalyx only in 14- and 18-day-old embryos. The observed uniform affinity for RR and lectin conjugates in all analysed developmental stages remains to be explained.

Mechanically isolated hepatocytes are unsuitable to detect antibodies directed against plasma membrane determinants

The ultrastructural morphology of mechanically and enzymatically isolated hepatocytes was compared. Plasma membrane integrity was evaluated by electron microscopy, both in the absence and in the presence of ruthenium red, which stains cell coat glycoproteins and makes it possible to identify even partially permeable cells, and by indirect immunofluorescence using experimental antibodies directed against epithelial submembranous components (prekeratin, actin). In order to evaluate the antigenic integrity of the hepatocellular plasma membrane after the isolation procedures, an immuno-electronmicroscopical technique (Staph. pA-colloidal gold) was applied using the IgG fraction from two liver-kidney microsomal antibody (LKM) positive sera, known to react with both plasma membranes and smooth endoplasmic reticulum (SER). Enzymatic procedure made it possible to isolate hepatocytes with a good preservation of both plasma membranes and subcellular organelles. Ruthenium red staining was confined to plasma membranes, thus indicating the preservation of both cell-coat glycoproteins and plasma membrane. Most cells were negative after exposure to experimental antibodies. After exposure to LKM positive sera colloidal gold was strictly confined to the plasma membrane. On the other hand, mechanically isolated hepatocytes showed wide interruptions of the plasma membrane and gross alterations of subcellular organelles. Most cells were stained by ruthenium red, thus confirming the plasma membrane permeability. In addition, a linear peripheral positivity was found in the vast majority of the cells tested with anti-prekeratin and anti-actin antibodies. LKM-colloidal gold complexes were found at the level of both residual plasma membrane and SER.(ABSTRACT TRUNCATED AT 250 WORDS)

Distribution and characterization of anionic sites in the basal lamina of developing human amniotic epithelium

We have studied the distribution of anionic sites in the basal lamina of developing human amniotic epithelium by using the cationic stain ruthenium red. Amnions at 7-12 weeks of gestation and at term contained ruthenium red-positive granules in a quasi-regular array on both the cellular and interstitial sides of the lamina densa. In order to characterize the anionic sites, small pieces of amnion were incubated in the presence or absence of either chondroitinase ABC, neuraminidase, Streptomyces hyaluronidase, or heparitinase in appropriate buffer systems. Incubation in the presence of heparitinase resulted in the complete disappearance of the basal lamina-associated granules, but other enzymes tested had no demonstrable effect on these granules. We conclude that the anionic sites associated with amnion basal lamina, and demonstrable with ruthenium red, consist of glycosaminoglycans rich in heparan sulfate, probably present as heparan sulfate proteoglycan. Because amniotic fluid has a low protein content and amniotic epithelium (at least at term) lacks tight junctions, we postulate that the heparan sulfate proteoglycan associated with the amnion basal lamina may have an important function as a permeability barrier to anionic macromolecules.

Ruthenium red staining of vaginal epithelial cells and adherent bacteria

The vaginal epithelium of the rhesus monkey is a keratinized stratified squamous epithelium throughout the menstrual cycle and early pregnancy. The superficial cells have a thickened cell envelope, surface microridges, and numerous adherent bacteria. During later pregnancy the cells mucify and have a typical cell membrane, microvilli, and no adherent bacteria. In the present study we have extended these observations by examining vaginal surface structures after ruthenium red staining. Throughout the cycle, the superficial cells have a thin layer of stained material closely associated with the cell membrane, but in some cases a much thicker mucous blanket was observed. During later pregnancy the epithelial cells had a moderately thick, somewhat clumped ruthenium red-positive material associated with the cell membrane. Glycocalyx components of the surface of many bacteria also stained with ruthenium red. The adherence of many types of bacteria to the vaginal epithelial cells appears to be effected by the interaction of polyanionic components on the surface of both the bacterial and epithelial cells.

The integrity of host lymphocyte plasmalemma during its invasion by Theileria annulata sporozoites as demonstrated by ruthenium red staining

The integrity of host lymphocyte plasma membrane during its invasion by Theileria annulata sporozoites was examined in an in vitro system using ruthenium red staining. It was demonstrated that during interiorisation of the sporozoites, the dye was completely excluded from the intracellular milieu, indicating that the continuity of the host-cell plasmalemma was not disrupted throughout the process of penetration, and confirmed a previous observation that the fragmentation of the host lymphocyte membrane only occurs later, after the parasite is intracellular.

The cell coat of inner ear sensory and supporting cells as demonstrated by ruthenium red

The ultrastructure of the cell coat of sensory and supporting cells of chinchilla and lizard inner ears was studied using ruthenium red. On the apical surface of both cell types, in both animals, the glycoproteins in the cell coat stain positively with this cationic dye. The apical surface of the sensory hair cells displays no regional variations in cell coat thickness. The uniform staining along the length of the stereocilia is not influenced by the normal presence or absence of a tectorial membrane. Although no micro-domains in the glycoproteins that stain positively with ruthenium red were observed that might correlate with the ultrastructural localization of sites of initiation of the transduction event, the cell coat material on the apical cell surface might play an important role in sequestering ions (particularly calcium) which are required for the transduction process.

Transport of horseradish peroxidase across monkey trophoblastic epithelium in coated and uncoated vesicles

This study used membranous chorion of the macaque monkey placenta to examine uptake and processing of exogenous proteins. Tissue was incubated with either cationic or anionic horseradish peroxidase. Incubation time was varied between 5-25 min to follow the endocytic pathways. In spite of some differences in binding, uptake and processing of the isozymes was similar. In the presence of tracers at 37 degrees C both horseradish peroxidases were taken up in large (150-175) nm diameter) coated vesicles. In addition, coated tubules 300-400 nm in length and 50-100 nm in diameter were seen in the apical cytoplasm. Studies using ruthenium red indicated that the coated tubules were derived from long coated invaginations of the free surface that pinch off into the apical cytoplasm. Often, the tubules bud off small (85-105 nm diameter) protein-filled coated vesicles which traversed the cytoplasm and fused with the basal-lateral plasma membrane. In other cases, the tubules or vesicles lost their clathrin coats and fused to form larger endocytic vesicles which later fused with phagolysosomes. After long incubation, larger uncoated vesicles (endosomes) were seen releasing their contents at the basal-lateral membrane. These results suggest that multiple transport pathways exist in this epithelium. The first, involving only coated structures, may function to sort and concentrate specific ligands important for embryonic development. The second, involving the formation and translocation of large uncoated vesicles to the basal-lateral membrane, may also provide nutrients to the embryo. A third pathway directs the protein to phagolysosomes where it is presumably degraded.(ABSTRACT TRUNCATED AT 250 WORDS)

Relation of capsular materials and colony opacity to virulence of Vibrio vulnificus

Colonies which varied in opacity were isolated from the four strains of Vibrio vulnificus. Opaque and translucent colonial types of the strains were distinguished from the corresponding parent strains. Variation in the opacity of colonies formed by each strain was accompanied by variation of capsular material formation, which was clarified by electron microscopy of the organisms stained with ruthenium red. The opaque-type colonies of the strains had capsular materials. On the other hand, three translucent-type colonies had no observable capsular materials, and one had incomplete capsular materials, in contrast to the corresponding opaque type. The corresponding opaque and translucent types of the strains were compared for points of virulence in mice and guinea pigs. By having capsular materials, the bacterial strains acquired resistance to serum bactericidal action, antiphagocytic activity, high lethality for mice, and strong invasiveness in the subcutaneous tissue of guinea pigs. Capsular materials of V. vulnificus were considered to be important for the expression of virulence.

Ultrastructural distribution of acidic glycosaminoglycans associated with matrix vesicle-mediated calcification in mouse progenitor predentine

The ultrastructural localization of acidic glycosaminoglycans, presumed to be proteoglycans, was examined during initial matrix vesicle-mediated calcification in dentine, by using ruthenium red (RR) staining, high iron diamine thiocarbohydrazide silver proteinate (HID-TCH-SP) staining, and an enzymatic digestion method. Progenitor predentine 2-10 micron width of developing mouse molar tooth germs was used throughout the present study. The outer surface membrane of the intact matrix vesicles had a strong affinity for RR. The RR positive materials appeared beaded and extended perpendicularly from the vesicle membrane. They tended to disappear with the disruption of the vesicular membrane, which resulted from overextension due to needle-like, crystal-like structures. The HID-TCH-SP stain deposits, approximately 10 nm in diameter, were densely distributed around the intact matrix vesicles, though few were found inside them. Some matrix vesicles that were presumably disrupted, however, contained smaller stain deposits. On the outer surface membrane of the disrupted vesicles, HID-TCH-SP stain deposits were fewer in number. The results obtained from enzymatic degradation studies showed that the anionic materials on the outer surface membrane of the matrix vesicles were represented by chondroitin-4-sulfate and/or chondroitin-6-sulfate. We suggest that chondroitin sulfates attached to the outer leaflet of the vesicular membrane play an important role during the incipient stage of the matrix vesicle-mediated calcification process.

An electron microscopic histochemical study of the histogenesis of major salivary gland pleomorphic adenoma

Six pleomorphic adenomas were studied histochemically by electron microscopy after staining with ruthenium red, high iron diamine-thiocarbohydrazide-silver proteinate (HID-TCH-SP), and tannic acid-ferric chloride (TA-FeCl3); the latter two are quite specific for sulfated glycoconjugates. With ruthenium red staining, the proteoglycans of the myxochondroid stroma could be visualized as numerous extracellular 25 to 50-nm polygonal matrix granules with fine projecting filaments. Similar positive ruthenium red-stained intracellular granules were observed within the Golgi-derived vacuoles of the modified "myoepithelial" cells in the myxochondroid region. Secretion of these granules by exocytosis was occasionally observed. The modified myoepithelial cell in the myxoid region exhibited strong HID-TCH-SP- and TA-FeCl3-reactive sites within the Golgi-derived vacuoles. The intercellular space or microcyst of the cellular clusters and the extracellular matrix granules stained strongly positive with both HID-TCH-SP and TA-FeCl3. Some cells located at the periphery of the cellular clusters also showed similar but weaker reactive sites. No staining was obtained in neoplastic ductal epithelium. The above cytochemical observations indicate that the modified "myoepithelial" cell probably derives from the periphery of the cellular clusters and is the cellular source of the stromal matrix. Moreover, the observations are compatible with the histogenetic model recently proposed by Dardick et al. that the neoplastic, modified myoepithelial cell is the principal proliferating cell in pleomorphic adenoma.

Ultrastructure of nematocyst discharge in catch tentacles of the sea anemone Haliplanella luciae (Cnidaria: Anthozoa)

The mature nematocyst lies just beneath the cnidodyte plasma membrane. A microtubule array surrounds the nematocyst capsule just beneath the capsule tip. We propose that the array helps to hold the capsule at the cnidocyte cell surface until discharge. The undischarged capsule tip is sealed by three apical flaps, joined together along complex radial seams. The seams are filled with subunits that appear to bind the flaps together. Upon discharge, the flaps separate along the radial seams to permit thread eversion. The everted thread is lined on both sides by subunits that are stained by antimonate, indicating that they bind calcium. We suggest that, together, the subunits hold the uneverted thread in its folded and coiled configuration. Thread eversion would follow subunit uncoupling. The capsule and thread interiors of partially discharged nematocysts are stained by antimonate. In contrast, the capsule and thread interiors of fully discharged nematocysts are not stained by antimonate. Thus, nematocyst calcium might be injected into the target tissue where it is presumed to act in conjunction with nematocyst venom to promote cell death.