Cartilage proteoglycans: comparison of sectioned and spread whole molecules

The extracellular matrix of porcine mature oocytes: origin, composition and presumptive roles

The extracellular matrix (ECM) of porcine mature oocytes was revealed by transmission electron microscopy (TEM) after treatment with tannic acid and ruthenium red. Present in the perivitelline space (PVS) and on the surface of the zona pellucida (ZP), it appeared to be composed of thin filaments and granules at the interconnections of the filaments, which were interpreted respectively as hyaluronic acid chains and bound proteoglycans. In order to determine whether this material is produced by the corona cells (the same ECM was found also on the surface of the zona pellucida and between cumulus cells) or by the oocyte itself, the synthesis of glycoproteins and glycosaminoglycans was checked by autoradiography on semi-thin and thin sections observed by light and electron microscopy. Immature oocytes within or without cumulus cells, were incubated with L [3H-] fucose or L [3H-] glucosamine--precursors respectively of glycoproteins and hyaluronic acid or hyaluronan (HA) bound to proteoglycans--for various times (with or without chase) and at different stages during in vitro maturation. In the first case, incorporation was found in both cumulus cells and ooplasm (notably in the Golgi area for 3H-fucose) and labeled material accumulated in the ECM of the PVS and of the ZP surface. Labeling in the PVS with both precursors was maximum between metaphase I (MI) and metaphase II (MII) and was partially extracted by hyaluronidase but not by neuraminidase. Tunicamycin, an inhibitor of glycoprotein synthesis, significantly decreased the amount of 3H-fucose labeled molecules in the PVS and increased the incidence of polyspermic penetration during subsequent in vivo fertilization. Since cumulus-free oocytes also secreted 3H-glucosamine containing compounds, both oocyte and cumulus cells probably contribute to the production of the ECM found in the PVS of mature oocytes. ECM and particularly its HA moiety present on both sides of the ZP may constitute a favourable factor for sperm penetration.

13C NMR relaxation studies on cartilage and cartilage components

We have investigated the molecular motions of polysaccharides of bovine nasal and pig articular cartilage by measuring the 13C NMR relaxation times (T1 and T2). Both types of cartilage differ significantly towards their collagen/glycosaminoglycan ratio, leading to different NMR spectra. As chondroitin sulfate is the main constituent of cartilage, aqueous solutions of related poly- and monosaccharides (N-acetylglucosamine and glucuronic acid) were also investigated. Although there are only slight differences in T1 relaxation of the mono- and the polysaccharides, T2 decreases about one order of magnitude, when glucuronic acid or N-acetylglucosamine and chondroitin sulfate are compared. It is concluded that the ring carbons are motion-restricted primarily by the embedment in the rigid pyranose structure and, thus, additional limitations of mobility do not more show a major effect. Significant differences were observed between bovine nasal and pig articular cartilage, resulting in a considerable line-broadening and a lower signal to noise ratio in the spectra of pig articular cartilage. This is most likely caused by the higher collagen content of articular cartilage in comparison to the polysaccharide-rich bovine nasal cartilage.

Gene expression and immunohistochemical localization of biglycan in association with mineralization in the matrix of epiphyseal cartilage

This study has used in situ hybridization, Northern blot analysis, and immunohistochemistry at the light and electron microscope levels to localize mRNAs and core proteins of biglycan in developing tibial epiphyseal cartilage of 10-day old Wistar rats. The expression of mRNAs and core proteins of biglycan appeared prominent in hypertrophic and degenerative chondrocytes associated with the epiphyseal ossification centre and the growth plate cartilage, but was not seen in the rest of epiphyseal cartilage. Northern blot analysis confirmed biglycan mRNA expression in the epiphyseal cartilage. Ultrastructural immunogold cytochemistry of the growth plate revealed that prominent immunolabelling was confined to the Golgi apparatus and cisternae of rough-surfaced endoplasmic reticulum of the hypertrophic and the degenerating chondrocytes, the early mineralized cartilage matrices of the longitudinal septum of the lower hypertrophic and the calcifying zones, and fully mineralized cartilage mitrices, which were present in the metaphyseal bone trabeculae. Furthermore, Western blot analysis of biglycan in extracts of fresh epiphyseal cartilage revealed that an EDTA extract, after chondroitinase ABC digestion, contains core proteins of biglycan, indicating the presence of biglycan in mineralized cartilage matrices. These results indicate that the distribution of biglycan is associated with cartilage matrix mineralization.

Distribution and space-time relationship of proteoglycans in the extracellular matrix of the migratory pathway of primordial germ cells in mouse embryos

In this paper we present an in situ ultrastructural cytochemical study on the distribution and spatial-temporal expression of proteoglycans (PGs) in the extracellular matrix of the migratory pathway of mouse primordial germ cells (PGCs) during the different phases of migration, by the use of the cationic dye ruthenium hexammine trichloride (RHT). Embryos of 9, 10, 11 and 12 days of development were used. The treatment with RHT revealed PGs as electron dense layers, granules, and filaments. Whereas granules prevailed in the extracellular spaces of the migratory route during the whole migratory process, the amount of filamentous structures increased during the migration phase of PGCs. At the end of the migratory process the surface of the PGCs lost its reaction by RHT. There were differences in the size of the granules of PGs at the initial migratory period (9-day-old embryos) as compared with the other days of gestation. There was a strong reaction for PGs in the extracellular spaces, expressed as a meshwork of granules interconnected by filaments, as well as reaction on the basement membranes during the peak of the PGCs migration in 10-day-old embryos. These results support the hypothesis that these molecules may have an important role in the migration of PGCs, although the precise mechanism involved in this process is not yet clear.

Ultrastructural cytochemical study of proteoglycans in the endometrium of pregnant mice using cationic dyes

Decidualization in rodents is accompanied by remarkable modifications of both fibrillar and non-fibrillar components of the endometrial extracellular matrix. Biochemical studies have shown that the levels of synthesis of hyaluronic acid and sulfated glycosaminoglycans change during decidualization in rodents. As the rodent decidua has regions containing cells in different stages of decidual transformation, we decided to analyse, by an ultrastructural cytochemical technique, the distribution of proteoglycans (PGs) in each region of the decidua of mice on different days of pregnancy. Endometria of mice on days 4, 5 and 7 of pregnancy were processed for electron microscopy in the presence of safranin O, a cationic dye which preserves most of the tissue PGs. The endometrium of non-pregnant mice was used as control. We observed evident differences in the arrangement and distribution of the network of PGs between non-pregnant and 4-day pregnant endometria, as well as between different regions of pregnant endometria. The possible relationship between these modifications and cell transformation that occurs during decidualization is discussed.

Proteoglycans in articular cartilage revealed with a quick freezing and deep etching method

OBJECTIVES

To clarify the three dimensional ultrastructure of proteoglycans, and their relationship with other matrix components in articular cartilage.

METHODS

Specimens from rat femoral heads were examined using three techniques: (1) Histochemical staining with cationic polyethyleneimine (PEI), using a pre-embedding or a postembedding method. Some tissues were pretreated with chondroitinase ABC or hyaluronidase. (2) Quick freezing and deep etching (QF-DE). Some specimens were fixed with paraformaldehyde and washed in buffer solution before quick freezing; others were frozen directly. (3) Ultrathin sections were studied after conventional preparation.

RESULTS

Proteoglycans were observed as aggregated clumps with PEI staining by the pre-embedding method, but as fine filaments by the postembedding method. They were lost with enzyme digestion; this was also demonstrated by the QF-DE method. The ultrastructure was well preserved by the QF-DE method when fixation and washing procedures were included, but not without these procedures. A fine mesh-like structure was connected to the cell membrane in the pericellular matrix. Filamentous structures suggestive of aggrecans were observed among collagen fibrils. They had side chains, approximately 50 nm in length, which branched from the central filaments at intervals of 10-20 nm, and were occasionally linked to other structures. Many thin filaments were also attached to the collagen fibrils.

CONCLUSIONS

The QF-DE method incorporating paraformaldehyde fixation and buffer washing procedures revealed three dimensional, extended structures suggestive of proteoglycans.

Basal lamina and other extracellular matrix produced by bovine granulosa cells in anchorage-independent culture

Bovine granulosa cells from 3-7 mm follicles were cultured without anchorage in soft agar/methylcellulose solution for 14 days, with or without 50 ng/ml basic fibroblast growth factor. The granulosa cells divided to form colonies of cells. These were analysed by light and electron microscopy, immunohistochemistry and Western immunoblotting. In approximately 20% of the colonies extracellular matrix was clearly visible at the light-microscope level. Ultrastructurally the matrix resembled a basal lamina 30-100 nm thick and was composed of tangled fibres or cords. Unidentified spherical structures of less than 50 nm diameter were sometimes present and attached to this basal lamina. The basal lamina of follicles had similar features, except that the basal lamina produced in vitro was a large aggregate of many convoluted layers. The cells produced collagen type IV and the cellular form of fibronectin. Intercellular areas not associated with basal lamina were identified. Ruthenium red staining revealed these areas to be rich in proteoglycan granules. Free granules were clustered near the cell surface, and the lumina of these areas were rich in fibres decorated with ruthenium red. This material did not resemble follicular fluid of antral follicles. Thus, granulosa cells in anchorage-independent cultures have a follicular cell morphology and secrete two distinct extracellular matrices, one similar to the follicular basal lamina.

Glycosaminoglycans in porcine lung: an ultrastructural study using cupromeronic blue

Glycosaminoglycans (GAGs) are essential components of the extracellular matrix contributing to the mechanical properties of connective tissues as well as to cell recognition and growth regulation. The ultrastructural localization of GAGs in porcine lung was studied by means of the dye Cupromeronic Blue in the presence of 0.3 M MgCl2 according to Scott's critical electrolyte concentration technique. GAGs were observed in locations described as follows. Pleura: Dermatan sulphate (DS) and chondroitin sulphate (CS) attached in the region of the d-band of collagen fibrils, interconnecting the fibrils; heparan sulphate (HS) at the surface of elastic fibers and in the basement membrane of the mesothelium and blood vessels. Bronchial cartilage: Abundant amounts of GAGs were observed in three zones: pericellular, in the intercellular matrix and at the perichondrial collagen. By enzyme digestion a superficial cartilage layer with predominantly CS could be distinguished from a deep zone with CS and keratan sulphate. The structure of the large aggregating cartilage proteoglycan was confirmed in situ. Airway epithelium: HS at the whole surface of cilia and microvilli and in the basement membrane of the epithelial cells. Alveolar wall: CS/DS at collagen fibrils, HS at the surface of elastic fibers and in the basement membranes of epithelium and endothelium.

Application of cationic probes for the ultrastructural localization of proteoglycans in basement membranes

The application of cationic probes for the ultrastructural detection of proteoglycans in basement membranes is reviewed. Proteoglycans are highly negatively charged macromolecules due to their glycosaminoglycan side chains. The interaction of cationic probes with proteoglycans is of an electrostatic nature. Methods are discussed to increase the specificity of probes for proteoglycans. The use of phthalocyanin-like dyes such as Cuprolinic blue, according to the critical electrolyte concentration method, results in a selective staining of proteoglycans. Enzymatic or chemical digestions, however, should be done to validate the proteoglycan nature of the dye-positive granules/filaments, and to establish the class of proteoglycan. The value of cationic probes in basement membrane research on development and pathology is discussed. The potential for deducting molecular information from the ultrastructural appearance of stained proteoglycans is indicated.

Immunoelectron microscopic study of proteoglycans in rat epiphyseal growth plate cartilage after fixation with ruthenium hexamine trichloride (RHT)

The localization of proteoglycans in rat epiphyseal growth plate cartilage was investigated immunoelectron microscopically by the post-embedding method, using mouse monoclonal antibody (2-B-6) which specifically recognizes 4-sulphated chondroitin or dermatan sulphate after digestion of proteoglycans with chondroitinase ABC. Fixation with ruthenium hexamine trichloride (RHT) and embedding in LR White served to preserve chondrocytes in the expanded state and matrix proteoglycans were observed as a reticular network of filaments. Immunoelectron microscopy revealed gold labelling of the secondary antibodies for the demonstration of proteoglycans on these filamentous structures and in elements of the Golgi apparatus. Filaments associated with matrix vesicles were also labelled. After fixation in the presence of RHT, it was clearly demonstrated that cartilage matrix proteoglycans are retained approximately in their original spatial distribution and their antigenicity is well preserved.

Ultracytochemical localization of basal lamina anionic sites in the rat epithelial attachment apparatus

The basal lamina anionic sites of the epithelial attachment apparatus (EAA) were investigated at the electron microscopic level in adult rat periodontium. After 1M NaCl junctional epithelium detachment, an irregular and fluffy basal lamina-like structure appeared to cover the cementum surface. This structure reacted positively with polyethyleneimine (PEI), a strongly cationized ultrastructural tracer, appearing to be composed of highly electron-dense microaggregates. Depending on section plane, double-tracked structures of undefined length were found within PEI precipitates and closely related to cementum collagen fibrils. After nitrous acid de-N-sulphation, 8 nm wide sets of two parallel lines were clearly identified. "Double tracks", i.e., sets of paired lines with peripherical PEI electron-dense material, were found to self-assemble to form dimers, clusters or more complex organizational patterns. From sensitivity towards nitrous acid oxidation and positive control observations, it was concluded that basal lamina anionic sites in the EAA, represented by PEI microaggregates, contain heparan sulfate proteoglycans (HSPGs). Furthermore, high resolution ultrastructural images demonstrated that HSPGs adopt a morphological appearance of "double tracks" in the tissue. On the other hand, the present findings suggest that HSPGs clusters, never found in the mucosal basement membrane used as positive control, may be related to a functional specificity of the tissue at the dento-gingival junction.

Preservation and visualization of the sea urchin embryo blastocoelic extracellular matrix

Several methods were utilized to visualize the structure and orientation of the blastocoelic extracellular matrix (ECM) in Strongylocentrotus purpuratus embryos at the mesenchyme blastula stage. Rapid freezing in liquid propane cooled to LN2 temperatures followed by freeze substitution was used to preserve the ECM without shrinkage due to dehydration. Scanning, transmission, and light microscopy were employed to elucidate the ECMs' structure. The blastocoelic ECM consisted of parallel fibrillar sheets that were interconnected by finer filaments and oriented along the animal-vegetal axis. The ECM completely filled the blastocoelic cavity as viewed by scanning electron microscopy. The basal lamina could be distinguished from the blastocoelic ECM as a thin coat on the plasma membrane of epithelial cells; the ECM was in contact with this coat. In contrast, the blastocoelic ECM attached directly to the plasma membrane of primary mesenchyme cells (PMC) which did not possess a basal lamina. The blastocoelic ECM was isolated as an intact "bag" and probed in a hydrated state with Con A and alcian blue. Confocal microscopy confirmed that the entire blastocoel was filled with a fibrillar ECM. These approaches offer advantages for future studies of the ECMs of sea urchin embryos and their roles in gastrulation.

Ultrastructural changes in articular cartilages of immature beagle dogs dosed with difloxacin, a fluoroquinolone

The ultrastructural features of quinolone-induced arthropathy were studied in the humeral and femoral heads of nine skeletally immature Beagle dogs (3 months old) that were dosed orally with difloxacin at 300 mg/kg body weight and euthanatized 24, 36, or 48 hours later in groups of three. Three age-matched dogs were given a placebo and euthanatized after 48 hours. Mitochondria in chondrocytes had significantly greater cross-sectional areas (P less than 0.05) in electron micrographs from dogs euthanatized after 48 hours of treatment than did those in other groups. There was also a significantly greater percentage of chondrocytes with swollen mitochondria in treated dogs than in the controls (P less than 0.05). These changes preceded the necrosis observed in some chondrocytes in the dogs of the 48-hour group. Disruption of extracellular matrix was first observed in the pericellular matrix of necrotic chondrocytes, indicating that this change was secondary to the changes in chondrocytes. Fissures within cartilages apparently resulted from the loss of the normal association of proteoglycans with collagen fibrils.

Alterations in the morphology of glycoconjugate molecules caused by histochemical procedures: comparison of renal glomeruli and articular cartilage

The fine structure of the glycoconjugate molecules was investigated in the glomerular capillary wall of the rat kidney fixed by vascular perfusion, and in the human and rat articular cartilage fixed by immersion. Kidney and cartilage were either prefixed in aldehyde alone (group a), or with the addition of Alcian Blue 8 GX (group b), or Alcian Blue and 0.3 M MgCl2 (group c), or Acridine Orange at a low (0.01%) and high (0.1%) concentration (group d). The specimens were postfixed either in OsO4 phosphate or cacodylate, with the exception of some of the samples in group a, for which a solution of potassium ferrocyanide-reduced OsO4 was used (group e). All samples were conventionally dehydrated and embedded in Epon. In addition, some of the tissue samples in group c were cryoprotected, frozen in liquid Freon (-150 degrees C) or in nitrogen slush (-210 degrees C), both postfixed and dehydrated by cryosubstitution, and embedded in Epon (group f). The present investigations demonstrate that some well known extracellular structures such as the laminae rarae of the glomerular basement membrane or the interfibrillar matrix of the articular cartilage can be considerably altered in their morphology by the histological procedures applied. Whereas the precipitated glycoconjugates, as seen after staining with cationic dyes or reduced OsO4 and conventional dehydration, can easily be recognized, the superposition of the extended molecules, as preserved by freezing and substitution, prevents their demonstration in native conformation.

Ultrastructural signs of altered intracellular metabolism in acral persistent papular mucinosis

An asymptomatic 24-year-old woman presented with multiple discrete papules on the extensor surfaces of the hands and wrists. Light microscopy revealed focal increase in the amount of dermal fibroblasts as well as deposition of hyaluronidase-labile mucoid substance. The collagen and elastin were decreased. The changes were consistent with acral persistent papular mucinosis (APPM). In electron microscopy, the intercellular glycosaminoglycans showed small ruthenium red-positive granules and thin filaments indicating normal morphology. The fibroblastic cells, however, were conspicuously altered. Endoplasmic reticulum was dilated, cytoplasm contained large amounts of osmiophilic, concentric lysosomal structures, and there was distinct fibrous lamina in the nuclear membrane. It was concluded that the primary event in APPM probably affects the intracellular metabolism of the dermal fibroblast. The accumulation of lysosomal structures may be a distinct feature of APPM differentiating it from the other reactive cutaneous mucinoses, or it may only reflect nonspecific degeneration in a long-standing lesion.

Changes in cells's secretory organelles and extracellular matrix during endochondral ossification in the mandibular condyle of the growing rat

The mandibular condyle from 20-day-old rats was examined in the electron microscope with particular attention to intracellular secretory granules and extracellular matrix. Moreover, type II collagen was localized by an immunoperoxidase method. The condyle has been divided into five layers: (1) the most superficial, articular layer, (2) polymorphic cell layer, (3) flattened cell layer, (4) upper hypertrophic, and (5) lower hypertrophic cell layers. In the articular layer, the cells seldom divide, but in the polymorphic layer and upper part of the flattened cell layer, mitosis gives rise to new cells. In these layers, cells produce two types of secretory granules, usually in distinct stacks of the Golgi apparatus; type a, cylindrical granules, in which 300-nm-long threads are packed in bundles which appear "lucent" after formaldehyde fixation; and type b, spherical granules loaded with short, dotted filaments. The matrix is composed of thick banded "lucent" fibrils in a loose feltwork of short, dotted filaments. The cells arising from mitosis undergo endochondral differentiation, which begins in the lower part of the flattened cell layer and is completed in the upper hypertrophic cell layer; it is followed by gradual cell degeneration in the lower hypertrophic cell layer. The cells produce two main types of secretory granules: type b as above; and type c, ovoid granules containing 300-nm-long threads associated with short, dotted filaments. A possibly different secretory granule, type d, dense and cigar-shaped, is also produced. The matrix is composed of thin banded fibrils in a dense feltwork. In the matrix of the superficial layers, the "lucency" of the fibrils indicated that they were composed of collagen I, whereas the "lucency" of the cylindrical secretory granules suggested that they transported collagen I precursors to the matrix. Moreover, the use of ruthenium red indicated that the feltwork was composed of proteoglycan; the dotted filaments packed in spherical granules were similar to, and presumably the source of, the matrix feltwork. The superficial layers did not contain collagen II and were collectively referred to as perichondrium. In the deep layers, the ovoid secretory granules displayed collagen II antigenicity and were likely to transport precursors of this collagen to the matrix, where it appeared in the thin banded fibrils. That these granules also carried proteoglycan to the matrix was suggested by their content of short dotted filaments. Thus the deep layers contained collagen II and proteoglycan as in cartilage; they were collectively referred to as the hyaline cartilage region.

Ultrastructure of proteoglycans in the tectorial membrane

The ultrastructure of proteoglycans (PGs) in the tectorial membrane (TM) of the mature chinchilla cochlea was investigated using the cationic dye Cuprolinic blue. When used at a high critical electrolyte concentration, Cuprolinic blue has been shown specifically to bind to the glycosaminoglycan residues of sulfated PGs. After Cuprolinic blue treatment, PGs were observed in the TM which were represented as rod-shaped, electron-dense structures. A perifibrillar, primarily orthogonal, array of PGs was associated with the type A protofibrils. These PGs were distributed in 50 nm intervals along the length of the type A protofibrils. A less common orientation was parallel to the axis of the type A protofibrils. PGs did not appear to be associated with the type B protofibrils. Based upon previous results by other investigators, the TM contains types II and IX collagen, and it appears likely that the type A protofibrils are composed of collagen type II. PGs visualized in the TM in this study thus may represent the glycosaminoglycan residue of type IX collagen which is associated with the type II collagen fibrils. Alternatively, the TM PGs may be small dermatan or chondroitin sulfate PGs.

Light and electron microscopic morphology of the temporomandibular joint in growing and mature crab-eating monkeys (Macaca fascicularis): the condylar articular layer

In an attempt to establish maturational alterations in the morphology of the articular tissue layer, mandibular condyles of four immature and four mature male monkeys (Macaca fascicularis) were studied using light microscopy as well as scanning and transmission electron microscopy. Specimens were fixed in situ by perfusion in the presence of ruthenium red to stabilize proteoglycans. Preparations intended for observation in the scanning electron microscope were first dehydrated and sputtered for the examination of articular surfaces, and afterwards treated with trypsin to expose the spatial arrangement of collagen fibrils. Gross anatomical relations between joint components indicated that the anterior and central, but not the posterior region of the condylar articular surface can be subject to compressional load. Load-bearing and non-load-bearing regions differed with respect to the morphology of the articular layer. Load-bearing surfaces were covered by a prominent articular surface lamina similar to that observed on articular cartilage. This lamina seemed to constitute an integral part of the articular layer, distinct from the lining of synovial fluid, and to be composed largely of proteoglycans. It was unaffected by maturation. The subjacent, load-bearing articular layer differed markedly in structure, both from articular cartilage, and between immature and mature animals. Articular cells of immature animals were classified as fibroblastlike, but unlike typical fibroblasts, were surrounded by a thin, often incomplete halo of fibril-free pericellular matrix, presumably consisting of proteoglycans. In mature animals, articular cells closely resembled chondrocytes, but exhibited prominent nuclear fibrous laminae, which usually are found only in fibroblasts. Thus, the load-bearing part of the articular layer seems to undergo a maturation-dependent metaplastic conversion, from a dense connective tissue with some features of fibrocartilage, to a fibrocartilage-like tissue containing chondrocyte-like cells with some features of fibroblasts. This conversion might reflect an adaptation to a maturation-associated increase in articular stress.

Immunogold localization of basal laminar heparan sulfate proteoglycan in rat brain and retinal capillaries

Heparan sulfate proteoglycan was localized in the basal lamina of the brain and retinal capillaries, using an antibody to the core protein of the proteoglycan and a postembedding immunogold labeling method at the ultrastructural level. Gold particles appeared to be randomly distributed in the basal lamina of both types of capillaries, in contrast to discrete ruthenium red-staining sites near the endothelial plasma membrane, as shown in previous studies of the retinal vessel. The present study not only agrees with previous biochemical and immunofluorescence studies, but also provides a more precise localization of the antigen. Furthermore, the method can be useful for quantitative studies.

The reaction of acridine orange with proteoglycans in the articular cartilage of the rat

Acridine Orange in concentrations from 0.01% to 0.2% was added to the first fixative solution in order to stain vibratome sections and small blocks of the articular cartilage of 2 month old rats. The interterritorial matrix of the radial or deep zone (zone 3) was examined. It contained reaction products with different morphology depending on the specimens used. In vibratome sections filaments were seen arranged in a homogenous pattern and changing in size with the concentration of the dye: diluted solutions produced finer filaments than concentrated ones. In contrast, in tissue blocks the staining pattern was not altered by different concentrations of Acridine Orange. However, with increase of the distance from the surface of the specimens the size of the filaments gradually decreased and formed a finer network. Since after preincubation with chondroitin ABC lyase only minute reaction products remained, an interaction of the dye with the sulphated glycosaminoglycans of the proteoglycans in the articular cartilage is suggested. The experiments show that by using mainly monocationic monomers of Acridine Orange the proteoglycans can be stained in a more expanded state than with polycationic dye polymers.

Visualization of sulfur-containing components associated with proliferating chondrocytes from rat epiphyseal growth plate cartilage: possible proteoglycan and collagen co-migration

Electron microscopy of epiphyseal growth plate cartilage from normal 4-5-week-old rats has revealed extensive fibrillar aggregates and globules in the pericellular spaces of proliferating chondrocytes. These cells contained small globules and diffusely coiled, fine filaments located within large, membrane-invested vacuoles. All such structures were observed after a variety of different tissue fixation regimes, including glutaraldehyde, osmium tetroxide, and potassium pyroantimonate. The fibrillar aggregates and globules were often overlapping and intermeshed and extended to 0.5 micron in length from their point of origin at cell membranes. Vacuoles were usually found at the periphery of cells, and some, by membrane fusion with the cell envelope, appeared contiguous with extracellular spaces wherein their contents could be discharged. Fine filaments and globules were occasionally observed in the Golgi complex and cisternae of endoplasmic reticulum of the chondrocytes. Further characterization of the cellular and pericellular components by electron microscopic radioautography, electron probe microanalysis, and electron spectroscopic imaging indicated the presence of sulfur, a result suggesting these aggregates, filaments, and globules in part represent proteoglycans in various stages of synthesis, secretion, and assembly. Additional radioautography utilizing 3H-proline implied that filament bundles are also composed of collagen, a result posing the possibility that this protein and the putative proteoglycans may co-migrate both intracellularly and within pericellular matrices. In extracellular matrices adjacent to cell lacunae, the fibrillar aggregates appeared in close association with typical collagen type II fibrils, an observation providing evidence for proteoglycan-collagen network formation in this region of the rat epiphysis. These microscopic and analytical data in situ would support certain studies in vitro of proteoglycan-collagen type II and IX association and are important in describing the interaction of such cartilage components ultimately involved in matrix formation.

Distribution of hyaluronic acid and chondroitin sulfate proteoglycans in the presumptive aganglionic terminal bowel of ls/ls fetal mice: an ultrastructural analysis

The terminal colon of the ls/ls mouse is aganglionic because an intrinsic defect prevents its colonization by cells migrating from the neural crest. Previous studies showed that laminin, type IV collagen, and glycosaminoglycans accumulate in the region of the presumptive aganglionic ls/ls bowel through which crest-derived cells would be expected to migrate. It was suggested that crest-derived cells might fail to enter the abnormal bowel because they receive inappropriate signals from a defective extracellular matrix. This hypothesis was evaluated by analyzing the ultrastructure of the extracellular matrix in mutant and control gut. Tissue was fixed in the presence of ruthenium red before or after selective enzymatic digestion. Heparan sulfate proteoglycan (diameter approximately equal to 15 nm) and chondroitin sulfate proteoglycan (diameter approximately equal to 20-50 nm) granules were found in both control and presumptive aganglionic gut. The heparan sulfate proteoglycan granules were primarily located within formed basal laminae, while chondroitin sulfate proteoglycan granules decorated plasma membranes and 5 nm hyaluronic acid microfibrils that formed a network in the extracellular matrix. At day E11.5, the mutant gut differed from the control in the following: 1) Hyaluronic acid microfibrils were longer and more numerous. 2) There were larger numbers of chondroitin sulfate proteoglycan granules associated with cell membranes and with hyaluronic acid microfibrils. By day E13 the spaces between mesenchymal cells of the outer wall of the control bowel contained a regular lattice of hyaluronic acid microfibrils studded with chondroitin sulfate proteoglycan granules. Instead of this lattice, tangles of excessively long hyaluronic acid microfibrils, coated more heavily than in the control with chondroitin sulfate proteoglycan granules, were found in the presumptive aganglionic gut. These results confirm that the extracellular matrix is abnormal in the presumptive aganglionic bowel of the ls/ls mouse; moreover, they also indicate that the defect involves not one, but several components of the extracellular matrix, as well as their distribution. The defective extracellular matrix is apparent at a time when crest-derived cells would be expected to be migrating in the terminal bowel and is located in their path. The observations thus support the idea that a localized abnormality of the extracellular matrix interferes with the colonization of the terminal bowel by crest-derived cells in the ls/ls mouse.

In vitro reconstruction of a cartilage matrix granule network

The cartilage extracellular matrix contains electron-dense granules and fine filaments when studied electron microscopically after staining with ruthenium red. The matrix granules contain proteoglycans, while the filaments are thought to represent hyaluronic acid. In the present study partial extraction of proteoglycans from the cartilage prior to staining reduced the density of matrix components to allow visualization of a well-developed network involving the matrix granules and hyaluronic acid filaments. The matrix granules frequently had multiple filamentous attachments and the network appeared to be formed by intersecting filaments with the matrix granules at points of intersection. A similar network was created in Sepharose CL-2B beads when proteoglycans, link proteins, and hyaluronic acid were concentrated in the beads. Elimination of any one of these components resulted in failure to form a complete network. Purified proteoglycan monomers alone were sufficient to create matrix granules in the beads. Filaments were seen only when hyaluronic acid was added to the beads. The nature of the network suggests that some type of association between separate aggregates is occurring both within cartilage and within the Sepharose CL-2B beads.

Proteoglycans in the pathogenesis of Alzheimer's disease and other amyloidoses

Proteoglycans and the amyloid P component are two constituents of amyloid that appear to be present regardless of the type of amyloid protein deposited, the extent of amyloid deposition and the tissue or organ involved. This article reviews the literature concerning proteoglycans and/or glycosaminoglycans in amyloidosis and describes recent studies which demonstrate their localization to the characteristic lesions of Alzheimer's disease and the amyloid plaques containing PrP protein in the prion diseases. Additionally, the possible interaction of proteoglycans with various amyloidogenic proteins, including the beta-amyloid protein in Alzheimer's disease is discussed. It is postulated that proteoglycans localized to a number of different amyloids play a common role in the pathogenesis of amyloidosis. Some of these hypothesized roles include 1) inducing amyloidogenic precursor proteins to form amyloid fibrils containing a predominant beta-pleated sheet structure, 2) influencing amyloid deposition to occur at specific anatomical sites within tissues and/or 3) aiding in prevention of amyloid degradation once amyloid has formed.

Application of the ferrocyanide-reduced osmium method for mineralizing cartilage: further evidence for the enhancement of intracellular glycogen and visualization of matrix components

The ferrocyanide-reduced osmium (FRO) fixation method was applied to neonatal mouse mandibular condylar cartilage for its processing for electron microscopy. The results were compared to those obtained by the conventional glutaraldehyde-osmium tetroxide fixation method. Three different stages in the life cycle of condylar cartilage cells were examined. FRO enabled the visualization of delicate fibrillar mesh in the matrix of all three zones of the cartilage, resulting in a dense appearance of the intercellular matrix. The classical stellate shape of matric granules seen in cartilage fixed with glutaraldehyde-osmium tetroxide was not observed in FRO-processed tissues. Chondrocytes that were FRO-processed almost entirely filled their lacunar space. In their pericellular area, fibrillar material and electron-dense aggregates could be demonstrated by the FRO method. As a conclusion of this study, it is recommended to supplement a conventional protocol with the FRO fixation method for routine and research purposes.

Ultrastructure of the absorptive cell glycocalyx in hyperplastic colonic polyps after staining with alcian blue and high iron diamine

The glycocalyx of absorptive cells in large intestinal hyperplastic polyp was characterized histochemically at the electron microscope level by the use of the Alcian Blue pH 2.5 and high iron diamine techniques with the aim of comparing their ability in preserving the fine reticular network of the structure. Both the reagents stained glycocalyx, indicating the presence of sulphated acidic glycoconjugates. However, they showed different degrees of condensation of the reactive sites. Alcian Blue preserved its filamentous appearance better.

Ultrastructural localization of proteoglycans by cationic dyes in the epithelial-stromal interface of the guinea pig lateral prostate

Proteoglycans (PGs) in the epithelial-stromal interface of the guinea pig lateral prostate were localized at ultrastructural level, using cuprolinic Blue (CB), alcian Blue (AB), and ruthenium red (RR). After staining with CB or AB according to the critical electrolyte concentration method (CEC), PGs appeared as short electron-dense filaments. According to their sizes and location, three type (T1, T2, T3) of CB-stained filaments were identified. T1 filaments were short (25 nm) and were found on both sides of the lamina densa of the basal laminae of the prostatic epithelium, smooth muscle cells, and capillary endothelial cells. They were regularly spaced with an interval of 60 nm. T1 filaments were more randomly distributed in the lamina densa. T2 CB filaments were approximately 30-40 nm long and closely associated with the collagen fibrils. They were usually arranged perpendicular to the long axis of collagen fibrils also at intervals of 60 nm. T3 filaments were found in different regions of the lamina propria, including: 1) reticular layer (pars fibroreticularis) below the basal lamina; 2) interstitial spaces; 3) closely associated with the cell surfaces of fibroblasts; and 4) around the collagen fibrils. Their sizes were variable (60-100 nm) and more densely stained. AB revealed similar patterns of PG distribution, except that the three types of PG filaments were longer but thinner. When the tissues were stained with RR, or RR-AB combined, PGs appeared as dense granules of various sizes, instead of filaments. Their locations and distributions were similar to those of the CB filaments, except that in the case of combined RR-AB treatment the PG granules were linked by a fine filamentous network, suggesting the interconnecting nature of the PGs and other extracellular components.

Cationic dyes reveal proteoglycans structurally integrated within the characteristic lesions of Alzheimer's disease

The cationic dyes ruthenium red (RR) and cuprolinic blue (CB) were used to preserve proteoglycans (PGs) for visualization at the ultrastructural level in brain tissue from seven cases of Alzheimer's disease (obtained at autopsy within 3-4 h after death). PGs were visualized as RR-positive granules specifically localized to the amyloid fibrils in neuritic plaques. In neurofibrillary tangles, RR granules were localized to the paired helical filaments and straight filaments usually at a consistent periodicity of 40-70 nm. CB, known to preserve PGs as short punctate filaments, also demonstrated PGs specifically localized to the amyloid fibrils in neuritic plaques and in association with paired helical filaments and straight filaments in neurofibrillary tangles. Persistent staining with CB at magnesium chloride concentrations of 0.3 and 0.7 M in the neuritic plaques suggested the presence of highly sulfated PGs, whereas abolishment of CB staining at 0.7 M magnesium chloride in the neurofibrillary tangles implied that different PGs and/or glycosaminoglycans were present in the neurofibrillary tangles. The specific ultrastructural localization of PGs to the characteristic lesions in Alzheimer's disease suggests that PGs are part of a complex structural network with amyloid fibrils in neuritic plaques and the filamentous structures present in neurofibrillary tangles.

A comparative ultrahistochemical study of glycosaminoglycans with cuprolinic blue in bone formed in vivo and in vitro

Histochemical and morphological studies have shown that proteoglygans (PG) are involved in mineralization process in vivo but such studies have not yet been conducted in vitro. A comparative histochemical study in electronic microscopy of the localization, organization, and morphology of the PG was performed with bones of calvaria rat formed in vivo and bone nodules formed in vitro from osteoblastic cells in culture. For this investigation, we used a cationic phthalocyanin dye, cuprolinic blue, in a critical electrolyte concentration which simultaneously stained the glycosaminoglycans and demineralized the bone. This histochemical technique demonstrated (1) osteoblast cells in vitro synthesized PG which were included in the matrix formed. (2) These PG were found in the calcified and uncalcified matrix both in vivo and in vitro. In the uncalcified matrix, PG were either free with a granular or rodlike structure or tightly connected to the periphery of the collagen fiber. Contrarily, in the calcified matrix, PG formed dense filamentous reticular patches between the collagen fibers. (3) Similarities in localization, organization, and morphology were noted in PG of bone formed de novo in vitro and in vivo with the exception of the mineralization front, where the staining in vivo compared with in vitro was faint or absent.

Ultrastructure of matrix vesicles in chick growth plate as revealed by quick freezing and freeze substitution

The ultrastructure of extracellular membrane-bound matrix vesicles (MVs), their biogenesis, and the surrounding matrix in chick tibial growth plate were studied after quick freezing and freeze substitution (FS) in an organic solvent. There were several notable differences in the ultrastructural preservation of cartilage when FS was used as compared with conventional fixation. The ultrastructural appearance of MVs after FS was extremely variable. Within the MVs, intravesicular filaments, amorphous material, and membrane-associated undercoat structures were observed. Intravesicular filaments, similar in diameter to microfilaments seen in the cytoplasm, were attached to the inside of MV membranes. This observation indicates the similarity of MV membranes and the plasma membrane. In some MVs in the proliferative zone an electron-dense material was present along the inner side of the MV membrane. In the prehypertrophic zone, crystalline material often appeared within the electron-dense material, which may be a precursor form of hydroxyapatite. The earliest crystals observed were in MVs but not in the extracellular matrix. Regarding MV formation, in addition to budding from cell surfaces and to cellular disintegration, this study also indicates that a sequential process of extrusion of preformed cytoplasmic structures may occur. Also, small MVs measuring 25-40 nm seem to arise from the disruption of large MVs. This is a previously unreported observation on MV biogenesis. FS preserves proteoglycans in the cartilage matrix as a fine, filamentous network. Initial extracellular calcification was not associated with this network.

Trabecular, nasal, branchial, and pericardial cartilages in the sea lamprey, Petromyzon marinus: fine structure and immunohistochemical detection of elastin

Immunohistochemical and ultrastructural methods were used to examine the distribution of elastin and the fine structure of the trabecular, nasal, branchial, and pericardial cartilages in the sea lamprey, Petromyzon marinus. The cells and matrix, as well as the overall organization of these components, in larval and adult trabecular cartilage resemble those of adult annular and piston cartilages (Wright and Youson: Am. J. Anat., 167:59-70, 1983) Chondrocytes are similar to those in hyaline cartilage. Lamprin fibrils and matrix granules, but no collagen fibrils, are found in a matrix arranged into pericellular, territorial, and interterritorial zones. Branchial, pericardial, and nasal cartilages differ from trabecular, annular, and piston cartilages in the organization of their matrix and in the structural components of their matrix and perichondria. Furthermore, immunoreactive elastin-like material is present within the perichondria and peripheral matrices of nasal, branchial, and pericardial cartilages in both larval and adult lampreys. Oxytalan, elaunin, and elastic-like fibers are dispersed between collagen fibers in the perichondrium. The matrix contains lamprin fibrils, matrix granules, and a band of amorphous material, which is reminiscent of elastin, in the periphery bordering the perichondrium. The presence of elastic-like fibers and elastin-like material within some lamprey cartilages implies that this protein may have evolved earlier in vertebrate history than has been previously suggested.

Structure of the cumulus matrix and zona pellucida in the golden hamster: a new view of sperm interaction with oocyte-associated extracellular matrices

Hamster oocyte-cumulus complexes (OCC), with and without sperm, were structurally analyzed by light- and electron microscopy using freeze substitution. This method has yielded a clear picture of the extracellular oocyte investments, the cumulus cell matrix and the zona pellucida. The cumulus matrix has an overall homogeneous fibrillar structure which appears to attach to cumulus cells at their filopodial extensions. The matrix also extends into the outer regions of the zona pellucida. The zona pellucida has a distinct porous configuration throughout its entire structure. During gamete interaction experiments, capacitated hamster sperm with ultrastructurally intact acrosomes were found throughout the matrix. Sperm had dramatic effects on the matrix, resulting in compression and stretching. Sperm found on the zona pellucida had initiated or completed the acrosome reaction. During the initial stages of the acrosome reaction, the matrix was in contact with the sperm. At later stages of the acrosome reaction, there was a complete loss of matrix material in regions near the sperm.

Proteoglycan in fast-frozen, freeze-dried, plastic-embedded rabbit arteries

In contrast to glutaraldehyde-fixed vascular tissue with or without staining with cationic dye, the nonfibrous extracellular matrix of fast-frozen, freeze-dried rabbit aorta and renal artery contained a continuous reticulum of fine filaments, closely associated with collagen, elastin, and smooth muscle cells. Three morphologically distinct types of filament were distinguished; one type was selectively sensitive to chondroitinase ABC degradation, and therefore contains chondroitin and/or dermatan sulfate. The remaining filaments of the reticulum may represent the protein core of the proteoglycan monomer, and the hyaluronic acid backbone of the aggregate. Filaments associated with the surface of smooth muscle cells were usually linked to a continuous filament parallel to the cell surface, which was degraded by heparitinase and therefore contains heparan sulfate. The filaments linked directly to the cell surface were not degraded by either enzyme. The preservation of PG in fast-frozen material provides a significant improvement over that obtained by any presently available technique.

Specific binding of peanut agglutinin and soybean agglutinin to chondroitinase ABC-digested cartilage proteoglycans: histochemical, ultrastructural cytochemical, and biochemical characterization

The binding of peanut agglutinin (PNA) and soybean agglutinin (SBA) to cartilage proteoglycans was investigated by histochemical, ultrastructural cytochemical, and biochemical methods. Following aldehyde fixation, specimens of rat epiphyseal cartilage were examined by horseradish peroxidase-labelled lectin cytochemistry with and without prior digestion in chondroitinase ABC. At the light microscope level neither PNA nor SBA exhibited any affinity for cartilage matrix, but became strongly bound following chondroitinase treatment. Similarly, at the ultrastructural level, extracellular matrix granules, presumed to be proteoglycan monomer(s), lacked PNA affinity in undigested specimens, and stained very weakly with SBA. Both PNA and SBA weakly to moderately stained the trans cisternae of the Golgi-flattened cisternae in chondrocytes. The chondrocyte plasmalemma lacked PNA staining, but reacted weakly with SBA. Following chondroitinase digestion, PNA and SBA stained matrix granules, and the cell surface of chondrocytes intensely, whereas the Golgi trans cisternae, the Golgi-derived vacuoles, and multivesicular bodies demonstrated weak to moderate reactivity. Proteoglycan aggregates purified from rat chondrosarcoma and bovine nasal cartilage bound PNA and SBA avidly after digestion with chondroitinase. Undigested proteoglycans lacked affinity for PNA and reacted very weakly with SBA. These results indicate that both PNA and SBA specifically react with chondroitinase-modified oligosaccharide(s) bound to core proteins of cartilage proteoglycans. This provided a specific histochemical and ultrastructural cytochemical procedure for localizing chondroitin sulphate-containing proteoglycans.

Electron microscopic studies of cartilage proteoglycans

Proteoglycans, molecules consisting of glycosaminoglycan chains bound to protein, form a significant part of the cartilage extracellular matrix. Biochemical and biophysical methods describe the average composition and physical properties of these polydispense molecules. Electron microscopy reveals the structure and dimensions of individual proteoglycans. Examination of individual molecules can confirm or challenge concepts of their structure developed from studies of their chemical composition and physical properties, and may suggest new directions for biochemical investigation. Electron microscopy has confirmed that cartilage proteoglycans exist on two levels of organization: monomers consisting of central protein core filaments with attached glycosaminoglycan chains and aggregates consisting of central hyaluronate filaments with multiple attached monomers. Most aggregated monomers have a thin segment which attaches to the hyaluronate filament and probably represents primarily the keratan sulfate rich region of the protein core, and a peripheral thick segment that represents the chondroitin sulfate rich region and in some monomers part of the keratan sulfate rich region. Proteoglycans vary considerably in size, charge and composition. Direct visualization of proteoglycan aggregates and nonaggregated monomers has helped explain the structural basis of this polydispensity. Monomers vary in protein core length, number of glycosaminoglycan chains and length of the glycosaminoglycan chains. Aggregates vary in hyaluronate filament length, spacing between monomers, number of monomers per aggregate, and aggregated monomer length. In most populations of aggregates, from most tissues, variability in the number of monomers per aggregate produces most of the difference in aggregate size. Link proteins, small proteins that bind to monomers and hyaluronate, help determine aggregate size and the proportion of monomers that aggregate. Experiments in vitro show that link protein can increase aggregate size four fold, make the spacing between aggregated monomers more regular and increase the proportion of monomers that aggregate ten fold. With increasing age, cartilage proteoglycan monomers become shorter, more variable in length, have shorter chondroitin sulfate chain clusters and have a shorter thin segment which may result from an increase in keratan sulfate content. Study of monomers newly synthesized by calf and steer chondrocytes suggests that the age related changes in monomer structure result largely from changes in proteoglycan synthesis or intracellular processing. Aggregates also change with age. They become shorter, have fewer monomers per aggregate and have shorter aggregated monomers. In addition, the proportion of monomers that aggregate decreases. These age related changes in proteoglycan aggregation may result from a decreasing concentration of functional link protein or from accumulation of fragments of the protein core containing the hyaluronic acid binding region.(ABSTRACT TRUNCATED AT 400 WORDS)

Influence of cetylpyridinium chloride on the ultrastructural appearance of sulphated glycosaminoglycans in human colonic mucosa

The effect of adding cetylpyridinium chloride to the fixative on the preservation of sulphated glycosaminoglycans (SGs) was studied in human normal colonic mucosa. SGs were visualized at the ultrastructural level through the application of Spicer's High Iron Diamine (HID) technique followed by a post-fixation with potassium ferrocyanide-reduced osmium tetroxide. SGs were mainly localized in basement membranes of epithelium and capillary wall and along collagen fibers. The morphology of the reactive sites depended on the presence of cetylpyridinium chloride, SGs being granular in absence of the salt and more or less elongated when cetylpyridinium chloride was added to the fixative. We suggest that the use of cetylpyridinium chloride during fixation may help to preserve SG molecule at the ultrastructural level.

Isolation of glycosaminoglycans from basement membranes of brain microvessels

Although the core protein of a heparan sulfate proteoglycan has been detected in brain microvessel basement membranes by immunoperoxidase staining, cytochemical evidence of a glycosaminoglycan component, in the form of discrete staining with ruthenium red, is not found. To resolve this discrepancy, we examined the glycosaminoglycan content of this basement membrane directly. Microvessels were isolated from pig cerebral cortex, and basement membranes freed from cellular elements. Following digestion with papain and Pronase, the glycosaminoglycans were precipitated with cetyl pyridinium chloride and ethanol. The resulting extract contained uronic acid, and after electrophoresis on Super Sepraphore revealed 2 bands: One co-migrated with heparan sulfate standard, the other with chondroitin sulfate A and C. The first was completely eliminated by nitrous acid and heparitinase, but not by hyaluronidase or chondroitinase ABC and was therefore confirmed as heparan sulfate; the other band was eliminated by chondroitinase ABC but not by the other three treatments. The findings suggest that basement membrane of brain microvessels, like other vascular basement membranes, contains heparan sulfate and chondroitin sulfate A and/or C. The failure of staining with ruthenium red is probably a result of unique structural features of this basement membrane, rather than an absence of glycosaminoglycan.

Isolation and characterization of a collagen fibril-associated dermatan sulphate proteoglycan from bovine lung

Dermatan sulphate proteoglycans have been extracted from bovine lung with 2.0 M CaCl2 and isolated using CsCl density gradient centrifugation, DEAE ion-exchange chromatography, gel chromatography and preparative sodium dodecyl sulphate-polyacrylamide gel electrophoresis. Ultrastructurally these proteoglycans are specifically associated with collagen fibrils. Dermatan sulphate (Mr 15.10(3)-35.10(3), with a strong prevalence for the higher Mr) is link via an O-glycosidic bond to a protein core, which is rich in Asx, Glx and Leu. Of the total uronic acid, 91% is iduronic acid. A part of the glucuronic acid residues is located near the protein core and a large cluster of disaccharides is devoid of glucuronic acid residues. An inhibition enzyme immunoassay has been developed to quantitate the proteoglycan. A model for the interaction between dermatan sulphate proteoglycans and collagen fibrils is proposed.

Nerve terminal anchorage protein 1 (TAP-1) is a chondroitin sulfate proteoglycan: biochemical and electron microscopic characterization

The plasma membranes of the nerve terminal and the postsynaptic cell of electric organ are separated by a basal lamina. We have purified, biochemically characterized, and visualized in the electron microscope a macromolecule which appears to anchor the nerve terminal to this basal lamina. This molecule, terminal anchorage protein 1 (TAP-1) is associated with the nerve terminal membrane of electric organ, has the properties of an integral membrane protein, and is tightly bound to the extracellular matrix (Carlson, S.S., P. Caroni, and R.B. Kelly. 1986. J. Cell Biol. 103:509-520). TAP-1 can be solubilized from an electric organ extracellular matrix preparation with guanidine-HCl/3-[(3-cholamidopropyl)-dimethylammnio]-1-propane sulfonate and purified by a combination of permeation chromatography on Sephacryl S-1000, sedimentation velocity, and ion exchange chromatography on DEAE Sephacel. The total purification from electric organ is 91-fold and results in at least 86% purity. Digestion of the molecule with chondroitin ABC or AC lyase produces a large but similar shift in the molecular weight of the molecule on SDS-PAGE. The presence of chondroitin-4- or 6-sulfate is confirmed by identification of the isolated glycosaminoglycans with cellulose acetate electrophoresis. Gel filtration of the isolated chains indicates an average molecular weight of 42,000. Digestion of TAP-1 with other glycosaminoglycan lyases such as heparitinase indicates that only chondroitin sulfate is present. These results demonstrate that TAP-1 is a proteoglycan. Visualization of TAP-1 in the electron microscope reveals a "bottlebrush" structure expected for a proteoglycan. The molecule has an average total length of 345 +/- 17 nm with 20 +/- 2 side projections of 113 +/- 5 nm in length. These side projections are presumably the glycosaminoglycan side chains. From this structure, we predict that the TAP-1 glycosaminoglycan side chains should have a molecular weight of approximately 50,000, which is in close agreement with the biochemical studies. Both biochemical and morphologic data indicate that TAP-1 has a relative molecular weight of approximately 1.2 X 10(6). The large size of TAP-1 suggests that this molecule could span the synaptic cleft and make a significant contribution to the structure of the nerve terminal basal lamina of electric organ.

Ultrastructural studies of bovine retinal microvascular basement membranes with the cationic dye ruthenium red

Our recent observation that the basement membranes of brain microvessels do not stain with the cationic dye ruthenium red has raised the question of whether the basement membranes of this and other vascular beds functioning as barriers between blood and neural tissues are deficient in the polyanionic macromolecules, such as glycosaminoglycans, which are responsible for the ruthenium red staining of other vascular basement membranes. We therefore attempted to produce staining in the only barrier-type microvascular basement membrane known to contain heparan sulfate. Bovine retinas were fixed by immersion in aldehyde fixatives containing ruthenium red, buffered with either 10 mM or 100 mM sodium cacodylate. We found discrete, electron-dense deposits of ruthenium red in vascular basement membranes, quite similar to those seen in vascular basement membranes of nonneural tissues after exposure to ruthenium red. These deposits were more distinct and more frequent in tissue exposed to ruthenium red-aldehyde solutions buffered with 10 mM cacodylate. They were not seen if ruthenium red was omitted from the fixative. The results demonstrate that anionic macromolecules in basement membranes of barrier-type microvessels can be stained with cationic dyes, and suggest that the failure of brain microvessels to stain with ruthenium red may be the result of a relative or total lack of polyanion in this basement membrane, or of other unique properties.

Improved ultrastructural preservation of epiphyseal chondrocytes by the freeze-substitution method

The ultrastructure of epiphyseal chondrocytes was studied following quick-freezing and freeze-substitution, and was compared to that of cells fixed with aqueous aldehydes. The former approach provided an improved ultrastructural preservation whereby every type of chondrocyte exhibited a smoother cell contour. The plasma membrane as well as intracytoplasmic membranes revealed a trilaminar substructure. The intracytoplasmic ground substance was composed of flocculent materials which were in direct contact with the inner leaflet of the plasma membrane. Within the extracellular matrix the proteoglycan network adhered to the outer leaflet of the plasma membrane. Whenever cellular shrinkage took place, the flocculent matrix within the cytoplasm and the proteoglycan network in the pericellular matrix disappeared. The contents of the RER, the Golgi apparatus, and the intracellular vesicles and vacuoles were well retained. In the proliferative zone, the Golgi saccules of young cells contained a thread-like structure showing a clear periodicity. The cytoplasmic vesicles and vacuoles showed marked variation in their electron density. Intramitochondrial granules were sensitive to aqueous treatments, as evidenced by the observation that they disappeared after either floating on water or staining with aqueous solution. In the calcifying zone, mitochondrial granules were noted within hypertrophic chondrocytes, a feature that was not observed following conventional processing. Cytoskeletal elements were well preserved in all types of cells. A dense microfilamentous network occupied the pericellular cytoplasm. Bundles of microfilaments were seen in the cellular peripheral processes. Microtubules were distributed throughout the cytoplasm, and the Golgi complex was intimately associated with the microtubule network; it appears that the secretory processes are involved with the microtubules.

Ultrastructural localization of proteoglycans in tissue using cuprolinic blue according to the critical electrolyte concentration method: comparison with biochemical data from the literature

Several connective tissues were stained for proteoglycans using the cationic dye Cuprolinic Blue according to the critical electrolyte concentration method. With this method, proteoglycans are visualized as electron-dense filaments. In most tissues, two types of proteoglycan filaments are present: a small (maximum length 60 nm), thin, collagen fibril-associated filament, and a thick, heavily-staining filament which is predominantly localized between bundles of collagen fibrils. Cartilage contains very large (about 300 nm) proteoglycan filaments while in cornea they are very small. Comparison with biochemical data from the literature suggests that the appearance of the proteoglycan filaments may be indicative for the glycosaminoglycan-protein ratio and for the molecular weight of the part of the protein core to which glycosaminoglycans are attached. The data thus obtained on the localization and structure of a proteoglycan may be useful when planning a strategy for its isolation.

Decrease of proteoglycan granule number but increase of their size in articular cartilage of young rabbits after physical exercise and immobilization by splinting

The effects of physical exercise (running) and immobilization by splinting on the number and size of proteoglycan (PG) granules and the diameter of collagen fibers of the articular cartilage were studied with the transmission electron microscope with a stereological method. The lateral tibial condyles of 24 young rabbits were examined. The analysis was carried out in the superficial, middle, and deep zones of uncalcified articular cartilage and also in the pericellular, territorial, and interterritorial regions of each zone. PGs were demonstrated in situ by using en bloc staining with the cationic dye ruthenium red, which binds to negative groups of glycosaminoglycans. Results of the control group showed that there was a large pericellular number of PG granules, and the number of granules tended to increase through cartilage depth. The mean diameter of PG granules was highest in the superficial zone and decreased through cartilage depth. The collagen fibers were thicker in the interterritorial than in the territorial region and their diameters increased from superficial toward the deep zone of uncalcified cartilage. Results of the experimental groups showed that the number of ruthenium-red-positive PG granules decreased by 3-46% in all zones and regions after both physical exercise and joint immobilization. On the other hand, the diameter of PG granules increased by 4-42% in all zones and regions in all groups. Collagen fibers in the territorial region of the middle zone were thinner in the exercised and in the splinted knee, while thicker in the contralateral knee to the splinted limb, as compared with the controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Extracellular mammalian polysaccharides: glycosaminoglycans and proteoglycans

This review of the mammalian extracellular matrix polysaccharides covered the glycosaminoglycans (GAGs) and their association into proteoglycans. As they necessarily pertain to the chromatographic and electrophoretic separations of these molecules, the structural features of the five principal GAGs were briefly reviewed. Much of the current structural work as well as the separation technology has been concerned with the sulfation state and copolymeric sequences of the individual classes of GAGs. The separation methods discussed included electrophoresis by agarose, acrylamide and cellulose acetate, high-performance liquid chromatography (HPLC), ion-exchange, gel permeation and biospecific affinity methods. Since detection systems are an integral part of chemical separation technology, current thoughts about the best methods to assay GAGs or detect column fractions were discussed. These included polysaccharide-specific detection systems such as Alcian blue dye, 1,9-dimethylmethylene blue, bovine serum albumin-Coomassie blue, as well as non-specific carbohydrate detection systems such as the carbazole or indole hydrochloride methods. Instrumentation used in the detection of chromatography fractions for these molecules was discussed, since the usual ultraviolet detector, standard with HPLC equipment, is often unsatisfactory. The most sensitive specific detection method for GAGs is the use of monoclonal antibodies, which are only now becoming commercially available. The use of these antibodies, combined with HPLC separation, appears to be the best available biochemical technology for studying the extracellular matrix polysaccharides. Finally, the association between proteoglycans, GAGs and mammalian disease processes was reviewed, emphasizing mucopolysaccharidoses and arthritis. The early detection of both of these diseases is desired for effective counselling and treatment. Many of the methods discussed here have been applied, but others are yet to be tried in efforts to further that goal.