Action of degradative enzymes on the light fraction of bovine septa protein polysaccharide

Bioactive Composition of Pig Laryngeal Cartilage Extracts and Their Free Radical-scavenging Activity

This work focused on amino acid and mineral element analysis of pig laryngeal cartilage. Papain and DEAE-Sepharose fast flow ion exchange chromatography were used to hydrolyase cartilage and purify hydrolysate. Further study was performed to compare the free radical-scavenging activity of various fractions. Cartilage is abundant in bioactive amino acids such as glycine, glutamic acid and arginine and minerals such as calcium, magnesium and iron. Four polysaccahrides attached peptides and one peptide were isolated from hydrolysate. Weak 2,2-diphenyl-1-picryhydrazyl free radical scavenging activities of all substances were observed. Other fractions showed hydroxyl free radical and superoxide anion free radical scavenging ability in a concentration-dependent manner except fraction A. The hydroxyl free radical scavenging activity of tested samples decreased in the following order: fraction C crude chondroitin sulphate (ChS) peptide fraction B semi-purified ChS purified ChS. Significant differences were observed between purified ChS and other fractions (P 0.01). For superoxide anion free radical the order was: peptide purified ChS semi-purified ChS crude ChS fraction C fraction B. The peptide was significantly higher than purified ChS (P 0.01), which was significantly higher than the other components (P 0.01). According to the results, polysaccharides, ChS, amino acid and peptide present in cartilage had important bioactivity.

Pulsed electromagnetic fields influence hyaline cartilage extracellular matrix composition without affecting molecular structure

Pulsed electromagnetic fields (PEMF) influence the extracellular matrix metabolism of a diverse range of skeletal tissues. This study focuses upon the effect of PEMF on the composition and molecular structure of cartilage proteoglycans. Sixteen-day-old embryonic chick sterna were explanted to culture and exposed to a PEMF for 3 h/day for 48 h. PEMF treatment did not affect the DNA content of explants but stimulated elevation of glycosaminoglycan content in the explant and conserved the tissue's histological integrity. The glycosaminoglycans in sterna exposed to PEMF were indistinguishable from those in controls in their composition of chondroitin sulfate resulting from chondroitinase ABC digestion. Specific examination with [35S]-sulfate labels showed that PEMF treatment significantly suppressed both the degradation of pre-existing glycosaminoglycans biosynthetically labeled in ovo and the synthesis of new [35S]-sulfated glycosaminoglycans. The average size and aggregating ability of pre-existing and newly synthesized [35S]-sulfated proteoglycans extracted with 4 M guanidinium chloride from PEMF-treated cartilage explants were identical to controls. The chain length and degree of sulfation of [35S]-sulfated glycosaminoglycans also were identical in control and PEMF-treated cultures. PEMF treatment also reduced the amount of both unlabeled glycosaminoglycans and labeled pre-existing and newly synthesized [35S]-sulfated glycosaminoglycans recovered from the nutrient media. [35S]-Sulfated proteoglycans released to the media of both control and PEMF-treated cultures were mostly degradation products although their glycosaminoglycan chain size was unchanged. These results demonstrate that exposure of embryonic chick cartilage explants to PEMF for 3 h/day maintains a balanced proteoglycan composition by down-regulating its turnover without affecting either molecular structure or function.

Biosynthesis of chondroitin sulfate proteoglycan by P388D1 macrophage-like cell line

Macrophages are in large part responsible for the subendothelial deposition of lipid within the artery wall during the early stages of atherogenesis. Proteoglycans secreted by these cells may play a role in this pathological process either by trapping lipoproteins in the extracellular matrix or by enhancing the formation of lipid-laden foam cells. The synthesis and secretion of proteoglycan was studied in the P388D1 macrophage-like cell line cultured in the presence of 35S-sulfate. The radiolabeled proteoglycan had a Kd of 0.69 on Sepharose CL-2B corresponding to an Mr of 2.8 x 10(5). It consisted of approximately 13 chondroitin sulfate chains of Mr 20,000 attached to a core protein with an Mr of 18,000. The chondroitin sulfate chains contained both N-acetylgalactosamine 6-sulfate and N-acetylgalactosamine 4-sulfate residues. No disulfated N-acetylgalactosamine residues were present. The P388D1 proteoglycan bound specifically to immobilized human low density lipoprotein. These results suggest that, in the focal regions of the arterial wall in which macrophages are found during the development of fatty streaks, proteoglycans secreted by these cells may affect the transport and cellular metabolism of plasma-derived lipids.

Combined alcian blue and silver staining of glycosaminoglycans in polyacrylamide gels: application to electrophoretic analysis of molecular weight distribution

Oligomeric and polymeric fragments of glycosaminoglycans may be separated for rapid analysis by electrophoresis through a 10% polyacrylamide matrix. A ladder-like series of bands is observed, in which adjacent major bands correspond to species differing in chain length by one disaccharide unit. The component species are detected by a combined alcian blue and silver staining protocol. Detection limits are less than 50 ng per band, or approximately 2-5 micrograms total load for polydisperse samples. Densitometry of the stained gel may be used to determine molecular weight averages and distribution. The applicable molecular weight ranges are approximately 4000 to 100,000 for hyaluronate, or 1500 to 40,000 for chondroitin and dermatan sulfate samples of moderate charge density heterogeneity.

Molecular weight estimation of sulfated glycosaminoglycans in human gingivae

The number-average molecular weights of human gingival epithelium and connective tissue glycosaminoglycans (GAG) have been determined. Radioactive labelled GAG were extracted from separated gingival epithelium and connective tissue following alkaline degradation of the tissue in the presence of tritiated sodium borohydride. They were identified by electrophoresis as heparan sulfate (HS), hyaluronic acid (HA), dermatan sulfate (DS) and chondroitin 4-sulfate (ChS-4). Following densitometric quantitation of the sulfated GAG (HS, DS and ChS-4), the amount of radioactivity associated with each species was determined by liquid scintillation of each band staining positively for these GAG. The number-average molecular weights for each GAG were determined by end group analysis. The values obtained for each sulfated GAG indicated a degree of similarity in molecular weight distribution between the two tissue types ranging from 15,000 to 27,000.

A comparative study of the binding of cartilage link protein and the hyaluronate-binding region of the cartilage proteoglycan to hyaluronate-substituted Sepharose gel

The hyaluronate-binding proteins from bovine nasal cartilage, i.e. the hyaluronate-binding region of the proteoglycan and the link protein, were labelled with 125I and separated from each other by gel chromatography. The proteins were characterized by molecular-weight determinations and their purity was established by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and immunodiffusion. The binding properties of the two proteins by hyaluronate-substituted Sepharose gel were compared. It was found that both proteins behaved similarly. They bound with the same efficiency to the gel, they showed the same time course of binding, had slightly different pH optima for binding and both proteins had a decreasing affinity for the gel with increasing ionic strength. The binding to the gel could be inhibited by soluble hyaluronate, and the minimum size of a hyaluronate oligosaccharide required for inhibition was in both cases a decasaccharide (only even-numbered oligosaccharides were tested). The proteins did not show any co-operative binding in the system tested, which could be explained by the large number of binding sites in the hyaluronate-substituted gel. Binding constants for the protein-hyaluronate interaction were estimated. A value of 1.3 x 10(7) M-1 was obtained for the hyaluronate-binding region of the proteoglycan, in agreement with literature data. The corresponding value for the link protein was 0.7 x 10(7) M-1.

Proteoglycan structure of bovine articular cartilage. Variation with age and in osteoarthrosis

Proteoglycan subunits (PGS) were isolated from bovine articular cartilage of calves and from cows, 18 months and 8 years old respectively. From the latter cartilage of osteoarthrotic and of non-osteoarthrotic sites was taken. PGS were characterized by gel-chromatography on Sepharose 2B columns and subjected to digestion with chondroitinase ABC and with papain. The isolated keratan sulphate-protein cores obtained from chondroitinase digestion were characterized on Sepharose 4B and the chondroitin sulphate chains on Sephadex G-200 gels. A larger molecular size of PGS was found in calf cartilage than in the other samples. This was attributed to the larger molecular size of chondroitin, whereas no change was observed in the keratan sulphate-protein cores. No change was observed in molecular size of PGS, isolated chondroitin sulphates or keratan sulphate-protein cores in osteoarthrosis in comparison with non-osteoarthrotic cartilage from the same joint or from younger adult animals.

The simultaneous release by bone explants in culture and the parallel activation of procollagenase and of a latent neutral proteinase that degrades cartilage proteoglycans and denatured collagen

1. A latent neutral proteinase was found in culture media of mouse bone explants. Its accumulation during the cultures is closely parallel to that of procollagenase; both require the presence of heparin in the media. 2. Latent neutral proteinase was activated by several treatments of the media known to activate procollagenase, such as limited proteolysis by trypsin, chymotrypsin, plasmin or kallikrein, dialysis against 3 M-NaSCN at 4 degrees C and prolonged preincubation at 25 degrees C. Its activation often followed that of the procollagenase present in the same media. 3. Activation of neutral proteinase (as does that of procollagenase) by trypsin or plasmin involved two successive steps: the activation of a latent endogenous activator present in the media followed by the activation of neutral proteinase itself by that activator. 4. The proteinase degrades cartilage proteoglycans, denatured collagen (Azocoll) and casein at neutral pH; it is inhibited by EDTA, cysteine or serum. Collagenase is not inhibited by casein or Azocoll and is less resistant to heat or to trypsin than is the proteinase. Partial separation of the two enzymes was achieved by gel filtration of the media but not by fractional (NH4)2SO4 precipitation, by ion exchange or by affinity chromatography on Sepharose-collagen. These fractionations did not activate latent enzymes. 5. Trypsin activation decreases the molecular weight of both latent enzymes (60 000-70 000) by 20 000-30 000, as determined by gel filtration of media after removal of heparin. 6. The latency of both enzymes could be due either to a zymogen or to an enzyme-inhibitor complex. A thermostable inhibitor of both enzymes was found in some media. However, combinations of either enzyme with that inhibitor were not reactivated by trypsin, indicating that this inhibitor is unlikely to be the cause of the latency.

Degradation of cartilage proteoglycans by a neutral proteinase secreted by rabbit bone-marrow macrophages in culture

When cultivated together with pieces of cartilage biosynthetically labelled with 35S in their proteoglycans, rabbit macrophages, differentiated in vitro from bone-marrow cells, cause the release of soluble 35S-labelled material into the culture medium. This process is inhibited by killing the macrophages or by cycloheximide treatment, and is due to the secretion by the cells of a metal-dependent neutral proteinase capable of degrading cartilage proteoglycan subunits into fragments of high molecular weight. Enzyme activity is optimum at about pH7, and is inhibited by EDTA, o-phenanthroline, cysteine or serum, but not by di-isopropyl phosphorofluoridate nor by 4-hydroxymercuribenzoate. The effect of EDTA is partially reversed by Co2+ or Zn2+ ions. The enzyme is eluted from Sephadex G-150 columns as a single peak of material (apparent mol.wt. 17000) that contains also most of the proteolytic activity exerted by culture media on Azocoll (denatured collagen) or on casein. The possible role of this metalloproteinase in chronic inflammatory processes is discussed, particularly in connection with joint erosions in rheumatoid arthritis.

Studies on the polydispersity and heterogeneity of cartilage proteoglycans. Identification of 3 proteoglycan structures in bovine nasal cartilage

1. Three chondroitin sulphate components were isolated from adult bovine nasal cartilage after treatment with alkaline NaB3H. Average molecular weights of 13000, 18 600 and 28 000 were obtained for chondroitin sulphate species representing 10, 52 and 38% (w/w) of the total chondroitin sulphate respectively. Each chondroitin sulphate pool has a narrow molecular-weight distribution. 2. A proteoglycan subunit preparation, isolated from one nasal cartilage by extraction and density-gradient fractionation in dissociative solvents, partitioned on a CSCl density gradient according to size and composition. Variation of proteoglycan molecular weight across the gradient was directly related to the average chondrotin sulphate chain length, which in turn reflected the relative proportion of the three chondroitin sulphate pools in each proteoglycan fraction. Consideration of proteoglycan molecular parameters, compositions and behaviour on sedimentation leads to a proposal that nasal cartilage contains 3 distinct proteoglycan pools, each of which has a constant number of chondroitin sulphate side chains of different average molecular weight. 3. Molecular-weight distribution parameters for these proteoglycan preparations indicate that all serine residues on the protein core capable of initiating chondroitin sulphate biosynthesis are occupied and that proteoglycan polydispersity results directly from the polydispersity of the attached chondroitin sulphate component.

Macromolecular properties and end-group analysis of heparin isolated from bovine liver capsule

Glycosaminoglycans were extracted from bovine liver capsule with 4 M-guanidinium chloride, resulting in solubilization of approx. 90% of the total uronic acid-containing polysaccharide of the tissue. The extracted polysaccharide was purified and fractionated by anion-exchange chromatography on DEAE-cellulose, density-gradient ultracentrifugation in CsCl and finally gel chromatography on Sepharose 4B. By using these procedures, the two major polysaccharide components, dermatan sulphate and heparin, which constituted 55 and 30% respectively of the total glycosaminoglycan content of the tissue, were separated from each other. Analysis of the macromolecular properties of the two polysaccharides showed that heparin existed exclusively as single polysaccharide chains, whereas dermatan sulphate occurred largely as a proteoglycan (protein content, 74% dry wt.). The purified heparin preparation was subjected to sedimentation-equilibrium ultracentrifugation, indicating a molecular weight of 8800. Analysis for neutral sugars (by g.l.c.) showed 0.1 residue of xylose and 0.2 residue of galactose/polysaccharide chain; serine amounted to 0.3 residue/polysaccharide chain. Reduction of the heparin with NaB3H4 resulted in incorporation of 3H, approximately corresponding to one reducible group/polysaccharide chain. The 3H-labelled sugar residue was liberated by a combination of acid hydrolysis and deaminative cleavage of the polysaccharide with HNO2; it was subsequently identified as an aldonic acid by paper electrophoresis. Most of the heparin chains thus contained a uronic acid residue in reducing position. It is suggested that heparin isolated from bovine liver capsule is a degradation product released from larger molecules by an endo-glycuronidase.

The effect of calcium on the macromolecular properties of heparan sulfate

Heparan sulfate from human aorta has been subjected to a physico-chemical analysis in buffers of physiological ionic strength containing either sodium chloride or calcium chloride. A molecular weight of 50,000 was obtained both in sodium and calcium solutions by sedimentation equilibrium and from sedimentation and diffusion coefficients. The values obtained for So20,w in sodium and calcium chloride solutions were 2.28 X 10(-13) and 2.70 X 10(-13) sec, respectively, and the corresponding values for Dl20,w were 2.7 X 10(-7) and 3.1 X 10(-7) cm2/sec, respectively. Diffusion coefficients calculated from data obtained by gel chromatography were in excellent agreement with those determined by conventional techniques. The results indicated that the molecule contracts in the presence of calcium, presumably due to an increased binding of counter-ions with a concomitant decrease in charge density. Circular dichroism spectra above 200 nm, where the substituted amino group contributes to the absorption, gave no indication of a conformational change in the polysaccharide upon transformation from the sodium to the calcium salt. When the polysaccharide was dissolved in a salt solution, physiological both in ionic strength and in sodium to calcium ratio, it sedimented as the sodium salt. The sedimentation coefficient, the diffusion coefficient and the apparent molecular weight all displayed a concentration dependence. This dependence was much less in calcium chloride than in sodium chloride in determinations of molecular weight. Therefore there are advantages in performing molecular weight determinations of glycosaminoglycans in calcium solutions.

The linkage region in the polypeptide of pig costal cartilage proteoglycan

Proteoglycan from pig costal cartilage and fragments obtained by proteolytic digestion were characterized by equilibrium ultracentrifugation and amino acid analysis. The proteoglycan extractable in 4 M guanidinium chloride yielded, after proteolytic digestion with trypsin and chymotrypsin, a chondroitin sulfate peptide containing four chains of polysaccharide. The unextractable residue yielded chondroitin sulfate peptide containing only two chains. The amino acid composition indicated a fairly uniform spacing between all four chains with an average of eight amino acid residues between the serine residues involved in linkage. Following the alkaline sulfite elimination-addition reaction, free peptide was isolated and found to contain one unsubstituted serine residue for every two linked glycosidically. Glycine and glutamic acid were the only two amino acids sufficiently abundant to be part of an invariant sequence near to serine residues destined to be glycosylated. The linkage region of the polypeptide also contains some substituted serine residues which do not carry a full chondroitin sulfate chain.

The structure and composition of cartilage keratan sulphate

Keratan sulphate was isolated from bovine intervertebral disc and bovine nasal septum after hydrolysis with proteinases and treatment with dilute alkali. Each preparation was found to contain, per keratan sulphate chain: (a) 1 residue of mannose; (b) 3 residues of N-acetylneuraminic acid (2 residues after alkali treatment); (c) 1 residue of N-acetylgalactosamine (lost after alkali treatment); (d) 1 residue or less of fucose. N-Acetyl-neuraminic acid residues were at non-reducing termini and were bonded to keratan sulphate through galactose residues. Evidence is presented for two different types of linkage between skeletal keratan sulphate and protein. Consideration of molecular parameters and compositions leads to a proposed structure for keratan sulphate-protein as found in skeletal proteoglycans.

The molecular-weight distribution of glycosaminoglycans

1. A rapid and sensitive method for the accurate estimation of the molecular-weight distribution of keratan sulphate and chondroitin sulphate isolated from adult bovine nasal septum and intervertebral disc is described. The method utilizes gel chromatography of reductively labelled glycosaminoglycan and end-group estimation of number-average molecular weight for each fraction across the peak of eluted glycosaminoglycan. 2. Chain-length distribution data obtained by this procedure are used to evaluate mechanisms of chondroitin sulphate biosynthesis.

Comparative biochemistry of chondroitin sulphate-proteins of cartilage and notochord

Fragments that consisted mainly of two polysaccharide chains joined by a short polypeptide bridge (doublets) were prepared from chondroitin sulphate-proteins of lamprey, sturgeon, elasmobranch and ox connective tissues after hydrolysis with trypsin and chymotrypsin. Consideration of molecular parameters, compositions and behaviour on gel electrophoresis and density-gradient fractionation leads to a proposed parent structure for chondroitin sulphate-proteins. A single polypeptide chain of about 2000 amino acid residues contains alternating short and long repeating sequences. A short sequence consists of less than 10 amino acid residues with one N-terminal and one C-terminal serine residue, each of which carries a polysaccharide chain linked glycosidically to its hydroxyl group. This structure constitutes the doublet subunit. Some variation is introduced when the doublet subunit carries only a single polysaccharide chain. The long sequence contains about 35 amino acid residues and is subject to cleavage by trypsin and chymotrypsin. The main polypeptide is probably homologous in the vertebrate sub-phylum with strong conservation of structure suggested for the short sequence. However, polymorphism of polypeptide structures cannot be excluded.

Hurler's, Hunter's and Morquio's syndromes. A biochemical study in the light of current views of the underlying defects

Glycosaminoglycans were isolated from the urine of three patients with Hurler's, Hunter's and Morquio's syndromes and also from the liver and spleen of the case of Hurler's syndrome by a procedure avoiding further degradation. A method of determining the proportions of dermatan sulphate, heparan sulphate and chondroitin sulphate in each preparation is described. The relative proportions of these glycosaminoglycans in the urine and organs of the case of Hurler's syndrome were very similar. Glycosaminoglycans from the organs were of much lower molecular weight than normal, consisting of single chains of molecular weight about 5000 together with multiples of up to four such chains attached to peptide moieties. The linkage region normally attaching glycosaminoglycan chains to protein in whole protein-polysaccharides of connective tissue was degraded progressively towards serine. The total output and relative proportions of abnormal glycosaminoglycans in the urine were compared in two brothers with Hunter's syndrome examined on two occasions 4 years apart. At comparable ages they excreted about the same amount, and the relative proportions of each glycosaminoglycan remained essentially constant. The composition and chromatographic behaviour of the glycosaminoglycan in the urine from the case of Morquio's syndrome indicated that it consisted of material containing about one-third keratan sulphate and two-thirds chondroitin sulphate as part of the same molecule, as in proteoglycans of cartilage. The total output of glycosaminoglycans, although higher than normal, was considerably less than in other types of Mucopolysaccharidoses.

Properties of fractionated chondroitin sulphate from ox nasal septa

1. Chondroitin sulphate was isolated from bovine nasal septa by precipitation with cetylpyridinium chloride after digestion of the tissue with papain. 2. The material was divided into two portions, one of which was partially degraded with testicular hyaluronidase. 3. Untreated and hyaluronidase-digested material were fractionated into a total of eleven subfractions by gel chromatography on Sephadex G-200 and Sephadex G-100 respectively. 4. Chemical analyses indicated that the composition of all the fractions was similar to that of chondroitin sulphate. However, electrophoresis revealed a charge-inhomogeneity in the low-molecular-weight fractions obtained after hyaluronidase digestion. 5. The physicochemical properties of the subfractions were investigated by sedimentation-velocity, diffusion and sedimentation-equilibrium studies, osmometry, viscometry and gel chromatography. The individual fractions were essentially monodisperse and showed molecular weights ranging from 2400 to 36000. 6. The relationship between the intrinsic viscosity and the molecular weight was [eta]=5.0x10(-6)xM(1.14), indicating that the chondroitin sulphate molecules assume a shape intermediate between that of a random coil and a stiff rod. 7. The relationship between the sedimentation constant and the molecular weight (>10(4)) was s(0) (20,w)=2.3x10(-2)xM(0.44).

A new chondrodystrophic mutant in mice. Electron microscopy of normal and abnormal chondrogenesis

The occurrence of a new mutation affecting cartilage and bone in mice is reported. The gene is lethal, shows autosomal recessive inheritance, and has high penetrance. It is not allelic to shorthead and probably not to phocomelia or achondroplasia. It results in a foreshortened face, cleft palate, defective trachea, and shortened long bones with flared metaphyses. Chondrocytes of epiphyseal cartilage from the mutant are not aligned in columns, and there is a decrease in the usual staining of the cartilage matrix. Electron microscope observations show large, wide collagen fibrils with "native" banding in the matrix of mutant cartilage, which are not present in normal cartilage. Possible explanations for the expression of this genetic disorder of cartilage development are put forward.

Isolation and properties of chondroitin sulphates from bovine heart valves

1. Several protein-polysaccharides were isolated from the soluble extracts of bovine heart valves by sedimentation equilibrium in a caesium chloride density gradient (Meyer, Preston & Lowther, 1969). 2. Compositional and structural studies indicated that the polysaccharide moiety was chondroitin sulphate. Differences in the protein content of the products were observed. There was no evidence suggesting the presence of keratan sulphate. 3. Sedimentation studies indicated that the molecular weights of the samples were between 4.2x10(4) and 6.5x10(4). The results are discussed in terms of a basic model for the protein-polysaccharides of two polysaccharide chains linked by a protein of variable size.

Attempted isolation of a heparin proteoglycan from bovine liver capsule

(1) Polysaccharides were isolated from bovine liver capsule by extraction with 2m-potassium chloride followed by precipitation from 0.8m-potassium chloride with cetylpyridinium chloride. Chondroitin sulphate was eliminated by digestion with hyaluronidase. The yield of heparin was approx. 40% of that obtained after extraction of the papain-digested tissue. (2) The macromolecular properties of the hyaluronidase-digested polysaccharide were studied by gel chromatography on Sephadex G-200 of the intact, as well as of the alkali-degraded, material. The results suggested the presence of single heparin chains in addition to a dermatan sulphate proteoglycan. (3) A purified heparin preparation was analysed for amino acids and neutral sugars. Xylose, galactose and serine were found in amounts corresponding to 0.1, 0.2, and 0.4 residue/polysaccharide chain (mol.wt. 7400), respectively. It is suggested that the isolated material had been degraded by a polysaccharidase with endo-enzyme properties.

Studies on protein-polysaccharides from pig laryngeal cartilage. Heterogeneity, fractionation and characterization

1. Protein-polysaccharides from pig laryngeal cartilage extracted by two procedures described in the preceding paper (Tsiganos & Muir, 1969) were shown to consist of macromolecules of various sizes as assessed by gel filtration in 4% and 6% agarose. 2. A larger proportion of the smaller molecules was present in the preparation obtained by brief extraction in iso-osmotic sodium acetate (procedure I) than in that obtained by more prolonged extraction in 10% (w/v) calcium chloride (procedure II). 3. Two fractions were separated by gel filtration in 6% agarose and by electrophoresis in compressed glass fibre. These fractions differed in chemical composition and in antigenic determinants. The gel-retarded fraction R and that of higher electrophoretic mobility possessed the same single antigen, whereas the gel-excluded fraction E and the slower electrophoretic fraction contained all the antigens of the starting material including that of fraction R. 4. Five N-terminal amino acid residues were identified in preparation I and fraction E, only two of which were present in fraction R. 5. The relative proportions of gel-excluded and gel-retarded fractions did not change when solutions of high ionic strength, urea or guanidine hydrochloride were used for elution. 6. The differences in chemical and amino acid composition between fractions R and E showed that the latter was not a simple aggregate of the former. Fraction E contained more basic and aromatic amino acids, and some methionine and cystine; the last two were absent from fraction R. Hydroxyproline was not detected in either fraction. 7. The number of glycosidic linkages in both fractions was estimated by alkaline beta-elimination. Appreciable amounts of threonine as well as serine were destroyed in both fractions. An average chain length for chondroitin sulphate was calculated from the galactosamine content of both fractions and the amounts of hydroxy amino acid destroyed. Average chain lengths were also calculated from the xylose and galactosamine content of each fraction. Each independent method gave a value of approximately 28 disaccharide units for the chain length in both fractions and hence their difference in size could not be explained by differences in the length of carbohydrate chains. 8. All fractions contained glucosamine, which was attributed to keratan sulphate. Content of both protein and keratan sulphate increased with the size of the macromolecules. 9. It is suggested, from these results, that chondroitin sulphate-protein complexes normally exist as a heterogeneous population of macromolecules in cartilage, and that keratan sulphate is involved in the formation of larger molecules.

The effect of chondroitin sulphate-protein on the formation of collagen fibrils in vitro

1. It was found that the precipitation of collagen fibrils at 37 degrees from mixtures of chondroitin sulphate-protein and tropocollagen at physiological ionic strength and pH takes place in two distinct phases. The first occurs immediately on mixing either at 4 degrees or at 37 degrees , and the second occurs only at 37 degrees and after a lag phase whose magnitude depends on the proportions of components. 2. When the second stage of precipitation was inhibited by mixing the reactants at 4 degrees , the initial precipitate was found to contain ;native-type' collagen fibrils and chondroitin sulphate-protein. 3. On the basis of kinetic experiments it was concluded that aggregates of chondroitin sulphate-protein and tropocollagen form instantaneously and that these act as sites for the second stage of precipitation of fibrils. 4. The gels that result after continued incubation at 37 degrees are fibrous in appearance if formed in the presence of the initial precipitate of chondroitin sulphate-protein and tropocollagen. 5. On the basis of these experiments in vitro the authors propose a sequence of events for collagen fibrogenesis in vivo.

The acid mucopolysaccharides of cattle retina

1. Two polysaccharides were isolated from the interstitial matrix surrounding the photoreceptor cells of cattle retina. They were liberated from this region of the tissue in a soluble form after agitation of whole retinas in 0.9% sodium chloride. One, which comprises two-thirds of the polysaccharides present, is a hyaluronidase-sensitive ;half-sulphated' chondroitin sulphate containing uronic acid, galactosamine and sulphate in the molar proportions 1.27:1.0:0.54. The other is a hyaluronidase-resistant non-sulphated heteropolysaccharide for which the name sialoglycan is proposed. It contains galactose, glucosamine and sialic acid in the molar proportions 2.4:1.0:0.4. Both polysaccharides contain only small amounts of nitrogen in excess of the amount calculated from their amino sugar and sialic acid content. 2. A similar combination of mucopolysaccharides is associated with the pigment epithelial-cell layer but in quantities only one-fifth of those present in the adjacent matrix area. 3. The ease with which they are released into aqueous media is consistent with the assumption that they are present in the extracellular spaces in both of these tissue layers. 4. The retinal residue left after removal of the two soluble polysaccharides is rich in amino sugar- and sialic acid-containing polymers, which appear to be firmly bound to the tissue fragments. 5. About one-third of the sialic acid and one-tenth of the amino sugar could be extracted with chloroform-methanol. The components in this fraction were tentatively identified as gangliosides. 6. Digestion of the chloroform-methanol-insoluble residue with Pronase yielded as the principal product a heteropolysaccharide containing 16.5% of glucosamine, 24.3% of neutral sugar (galactose plus fucose) and 18.1% of sialic acid. This substance has been classified as a sialoglycan of composition similar to (but not identical with) that of the soluble one isolated from the matrix area of the tissue.