Showing papers on "Cartilage published in 1972"

Biochemical Sequences in the Transformation of Normal Fibroblasts in Adolescent Rats

Abstract: Coarse powders of acid-insoluble matrix of diaphysis and calvarial parietal bone rapidly and consistently transformed fibroblasts into masses of cartilage and bone containing hemopoietic marrow. The transformant was encapsulated by fibroblasts within 24 hr to form a plaque. Transformation was restricted to the central thicknesses of the plaque. Under the stated conditions the alteration of the phenotype, fibroblast to chondroblast, was an unstable transformation, whereas the phenotype change, fibroblast to osteoblast, was stable. The transformation occurred on a rigid timetable of sequences. Measurements of alkaline phosphatase activity and incorporation of radioactive sulfate, phosphate, and calcium were sensitive and quantitative assays for the appearance of the transformed products, cartilage and bone.

Light microscopy of Indian ink preparations of fibrillated cartilage.

Abstract: At present it is not known whether fibrillation of articular cartilage is initiated by abrasive or adhesive wear, by fatigue failure (Freeman, 1971) or overstressing, or by some other process such as the 'sliding damage' postulated by Walker, Sikorski, Dowson, Longfield, Wright, and Buckley (1969); moreover, it cannot be assumed that each instance of surface damage is always initiated in the same way. Morphological observations are relevant to this problem, since it is important that any hypothesis eventually put forward to explain fibrillation should be fully consistent with structural changes observed in the tissue. Previous studies have described the morphology offibrillation as seen by light microscopy of conventional histological sections cut vertical to the articular surface (Collins, 1949; Meachim, Ghadially, and Collins, 1965); as seen by transmission electron microscopy of ultrathin vertically cut sections (Meachim and Roy, 1969); as seen by scanning electron microscopy of the cartilage viewed from above the surface (McCall, 1968; Walker and others, 1969; Redler and Zimny, 1970); and as seen by macroscopic examination of Indian ink preparations (Bullough and Goodfellow, 1968). The present study employs the use of methods in which Indian ink preparations are examined by reflected light microscopy of the surface in situ and by transmitted light microscopy of tangential surface slices.

The management of gout

Abstract: Gout is a clinical syndrome resulting from the deposition of urate (monosodium urate monohydrate) crystals. The crystals may be deposited in a joint, leading to an acute inflammatory response, or in soft tissues, such as cartilage, causing no inflammation. Most cases of gout are characterized by the sudden onset of severe acute monarticular arthritis in a peripheral joint in the leg. The arthritis remits completely and then recurs with increasing frequency. After approximately 10 years of recurrent gouty arthritis, tophi develop in cartilage, tendons, and bursae in some patients. Established criteria for the diagnosis of gout include the presence of . . .

Leukocytic proteases and the immunologic release of lysosomal enzymes.

Abstract: LySoSOMES WERE I-NTRODUCED into the field of inflammation and connective tissue injury as a result of studies conducted at New York Univ-ersity and at the Strangewavs Research Laboratory in Cambridge.1 Shortly after it became clear that vitamin A acted to cause degradation of cartilage matrix both in vitro and in vivo by the release of proteases from cartilage lvsosomes, it was hypothesized that lvsosomal enzvme release in various forms of acute tissue injury could accouint for hydrolvsis of connective tissue macromolecules.5 Further studies in both laboratories have suggested the plausibility of this hypothesis. Thus, lvsosomal proteases present in cartilage and in leukocvtes hav-e been shown capable of degrading cartilage matrix, isolated proteoglvcans and simple chemical substrates." Leukocv-te lvsosomes of the rabbit contain at least two sorts of proteases capable of cleaving isolated cartilage proteoglvcans: an enzmne or enz-mes active at near neutral pH, and one enzyme active in the acid pH range.7When purified, high molecular-weight (10') proteoglvcan of bovine nasal cartilage (PP-L) was exposed to extracts of leukoc-te Ivsosomes (but not to other subcellular fractions), this substrate was readilv cleaved, releasing polvanions of lower molecular weight which resembled those released bv trvpsin. This uronic acid-containing, readilv diffusable material was nondialyzable and precipitated readilv with hexamine cobaltic chloride. Thus, in vitro as in vivo, when proteoglycans are exposed to excess vitamin A, they7 could be degraded bv Iysosomal hydrolases to release anionic polysaccharides; degradation proceeded as readily at neutral as at acidic pH. Since it became clear that proteolytic activity in the acid pH range could be attributed to the cathepsin D in rabbit leukocyte granules, the identification of a neutral protease capable of cleaving extracellular materials became of considerable interest.

Perichondrial Potential for Cartilagenous Regeneration

Abstract: This preliminay investigation was conducted in 2-month-old rabbits. The perichondirum was stripped away from the ear cartilage, and raised as a flap. A segment of the exposed cartilage was then removed and the perichondrial flap was sutured back over the created defect. The other ear served as a control, but there the resection of cartilage included the covering perichondrium. In the first group there was a progressive regeneration of cartilage originating from the perichondrium; in the control study, no new cartilage developed. The chondrogenic activity of the perichondrium of the aural cartilage is thus demonstrated and will be further verified in succeeding experiments.

A comparison of the physical behavior of normal articular cartilage and the arthroplasty surface.

Abstract: A study of the rabbit metatarsophalangeal joints with arthroplasty surface and normal articular cartilage was done by using compression testing to compare the elastic and viscoelastic behaviors of these two surfaces. Consistent differences were observed. Articular cartilage exhibited less instantaneous deformation than the arthroplasty surface, that is, the cartilage was stiffer. Both the rate and magnitude of time-dependent deformation under constant load (creep) of the articular cartilage were less than that of the arthroplasty surface. These differences increased significantly as a function of load. However, within the range of three to twelve-month-old anthroplasties, the viscoelastic behavior remained approximately constant. Mechanical analogues were constructed in an attempt to characterize the physical behaviors of these tissues, and mathematical relations of the experimental data to the analogues were developed. The loading range used in this study was not felt to exceed physiological limits as no plastic or permanent deformation was observed. Our findings show that cartilage is superior to the anthroplasty surface for resistance to and for recovery from the repetitive and rapid deformations which might be experienced in normal joint function Clinical experience supports this finding. The difference in elastic and viscoelastic behaviors was related to histological and biochemical differences of the two surfaces.

Effects of proteolytic enzymes on structural and mechanical properties of cartilage.

Abstract: Cartilage has a great capacity to resist compressive force. This quality is related to its unique composition of proteinpolysaccharide in a mesh-work of collagen fibers. Although cartilage is not grossly altered in appearance in vitro by incubation with enzymes which can deplete proteinpolysaccharide, it becomes less stiff and more flexible. When slices of canine cartilage were incubated in 0.1M Tris-HCl, pH 7.6, 37°C, without prior freezing or addition of detergents, they spontaneously lost 60% of proteinpolysaccharide by the third day without concomitant loss of collagen. Specimens incubated with trypsin were depleted of 75% proteinpolysaccharide by the first 24 hours and, over a 1-week period, 20% of the collagen, although less than 2% was released during the last 2 days of incubation. Bacterial collagenase resulted in loss of approximately 9% of the total collagen during each day's incubation for 1 week, but the proteinpolysaccharide depletion followed a curve similar to controls. Functional studies, measuring strain under load, indicated that during 24-hour incubations of cartilage treated with trypsin or hyaluronidase these samples had much more evidence of strain than did collagenase-treated specimens. The latter lost actual thickness, however, while the trypsin-treated samples and controls remained the same size, suggesting that collagen has the primary role in determining form of cartilage and may be capable of significant water binding in the absence of proteinpolysaccharide. It is proposed that measurement of compressibility of articular cartilage is a suitable index of its effective proteinpolysaccharide content, and the total volume or thickness can be diminished only by agents capable of removing collagen.

Aggregation of cartilage proteoglycans.

Abstract: Viscosimetric and centrifugal analyses of nasal and tracheal proteoglycan preparations indicate that: (I, the proteoglycan molecules from both cartilages have very similar physical properties (limiting viscosity numbers of 140 and 145 ml per g and so values of 25 and 20 S, respectively); b, about 80% of the proteoglycan molecules in each preparation can form aggregates; and c, the aggregates are much larger in nasal than in tracheal preparations (so values of 93 and 43 S, respectively). Hyaluronic acid is present at a concentration of 0.4 to 0.8% (w/w) in nasal proteoglycan aggregate preparations. Evidence is presented which suggests that the hyahuonic acid-proteoglycan interactions described by Hardingham and Muir ((1972) Biochim. Biophys. Acta 279, 401) are involved in aggregate formation and that the relative sizes of the aggregates are probably determined by the relative sizes of the hyaluronic acid molecules. Mild proteolysis of proteoglycan aggregates with papain removes the chondroitin sulfate and keratan sulfate from the aggregates while leaving about 25 % of the total protein still bound to hyaluronic acid. This bound protein fraction was separated from the hyaluranic acid by chromatography on Sephadex G-200 with 4 M guanidine hydrochloride as the solvent. Polyacrylamide gel electrophoresis indicated that this fraction contains two proteins (molecular weights approximately 40,000 and 65,000) both of which are reduced to smaller peptide fragments when treated with /3-mercaptoethanol. The two proteins retain their ability to bind to hyaluronic acid. The interactions between the proteins and the hyaluronic acid in the intact aggregates partially protect the hyalmonic acid from digestion with bacterial chondroitinase.

Reducible Crosslinks in Hydroxylysine-Deficient Collagens of a Heritable Disorder of Connective Tissue

Abstract: Reducible compounds that participate in crosslinking were analyzed in hydroxylysine-deficient collagens of patients with a heritable disorder of connective tissue. After treatment with [3H]sodium borohydride, new compounds, as well as a totally different pattern of tritiated compounds, were found in hydroxylysine-deficient collagen from skin as compared with age-matched controls. The amount of desmosines detected indicated that more elastin was present in abnormal skin than in control skin. Bone collagen, which was not as deficient in hydroxylysine as skin collagen, had the same compounds as normal bone collagen, but their relative proportions were altered, consistent with a deficiency of hydroxylysine, a precursor of the crosslinks. Although the content of hydroxylysine in collagen of cartilage is essentially normal in these patients, analysis after reduction revealed a different pattern of reduced compounds from that of normal cartilage. It is speculated that Type II collagen, the major collagen component in cartilage, contains a normal amount of hydroxylysine, while Type I collagen, which is the major source of the crosslinks, is hydroxylysine-deficient. This distribution would explain the findings of an abnormal profile of reducible compounds despite an almost normal total hydroxylysine content. The finding that the deficiency of hydroxylysine in the collagen of these patients is accompanied by changes in number, chemical nature, and, probably, distribution of crosslinkages, and the previously reported alterations in the solubility characteristics, suggest that at least some skeletal and connective tissue abnormalities are directly related to underlying molecular pathology.

Cartilage canals, their morphology and distribution†

Abstract: The proximal humeral chondroepiphysis of newborn pups was shown to be well-vascularized by a series of segmentally distributed cartilage canals which varied from short unbranched channels to channels which coursed half-way across the epiphysis. Cartilage canals were observed to contain a muscular arteriole, venule, loose connective tissue and perivascular capillaries. The muscular arterioles originated from the dense perichondrial vascular network at regular intervals, coursed in the central portion of the cartilage canal, and terminated by dividing into a capillary glomerulus in the cartilaginous matrix. These glomeruli were observed to assume a wide variety of sizes and shapes reflecting the metabolic needs of the areas they served. The capillaries of the glomerulus recombined into a single venule which rejoined the perichondrium via the same channel as the parent arteriole. The loose connective tissue surrounding these vessels was rich in fibroblasts and macrophages and was continuous with that of the perichondrium. From the structural relationship of the cartilage canals and the articular surface, it was concluded that at birth the synovial fluid had little nutritional significance for the epiphysis, but with age the nutritional contribution from the synovial fluid became more important. The particular arrangement of the venule and the perivascular capillaries allowed for metabolic exchange the entire length of the canal. Structures which appeared to be unmyelinated nerves and structures which contained a flocculent material and resembled lymphatics were seen in the connective tissue of the cartilage canals.

Immunochemistry of cartilage proteoglycan. Immunodiffusion and gel-electrophoretic studies

Abstract: Cartilage proteoglycan is thought to be composed of subunits, core proteins with covalently attached sulphated polysaccharide side chains, which form aggregates by non-covalent association with a link protein. The new technique of non-disruptive extraction followed by fractionation in caesium chloride gradients provides a useful means of preparing relatively pure proteoglycan aggregate, subunit and link fractions. Immunological studies of these fractions led to the identification of an antigen associated with the proteoglycan subunit which was common to several species and to the demonstration of additional species-specific antigens in aggregate and link fractions derived from bovine nasal cartilage. Polyacrylamide-gel electrophoresis with sodium dodecyl sulphate of bovine proteoglycan aggregate and link fractions gave two protein bands in the gels and a protein–polysaccharide band at the origin; subunit fractions gave only the band at the origin. These results are consistent with the current concept of cartilage proteoglycan structure.

Immobilization and cartilage transformation into bone in the embryonic chick

Abstract: The fate of the secondary cartilage present on the membrane bones of the embryonic chick has been studied after immobilization. Immobilization was achieved by the in vivo injection of paralysing drugs (tubocurare or decamethonium), by grafting membrane bones onto the chorioallantoic membrane, or by organ-culturing membrane bones in vitro. In all three situations the cartilage was transformed into a bone-like tissue, the matrix losing its acid muco-polysaccharide, accumulating collagen and undergoing calcification. The chondrocytes shrank in size, came to resemble osteoblasts (osteocytes) and acquired alkaline phosphatase activity. In normal development this cartilage is not transformed into bone but is partly replaced by bone and partly converted into a fibrocartilage which forms the definitive articular cartilage. Immobilization prevented this normal sequence. Past studies on the transformation of cartilage to bone are reviewed and are seen to be adaptations of a highly labile tissue to functional demands.

Electrical behavior of cartilage during loading.

Abstract: When cartilage is deformed, it becomes electrically polarized. At least two mechanisms seem to underlie this phenomenon, namely, a short-duration, high-amplitude, piezoelectric-like response and a longer-duration, lower-amplitude response secondary to streaming potentials. The polarity of articular cartilage during loading could hypothetically facilitate joint lubrication.

Identification and concentration of the glycosaminoglycans of human articular cartilage in relation to age and osteoarthritis

Abstract: The glycosaminoglycans in articular cartilage from the femoral condyles of 119 human autopsy cases have been isolated and subsequently characterized using cetylpyridinium chloride Using the same column method in microscale the glycosaminoglycans were estimated quantitatively in normal articular cartilage from birth to 95 years of age and in osteoarthritic cartilage In normal cartilage chondroitinsulphate occurred as chondroitin-4-sulphate and chondroitin-6-sulphate, decreasing in ratio with age The chondroitinsulphate had a sulphate/hexuronic acid ratio below unity, below 20 years, above unity in the higher age groups Two types of keratansulphate and hyaluronic acid were isolated The glycosaminoglycans isolated from osteoarthritic cartilage showed no differences from normal cartilage as to the amount of their moities of chondroitin sulphate isomers In normal cartilage there was a significant decrease of total hexosamines from birth to 11–20 years, due to a reduction of chondroitinsulphate In adults, an increasing ratio of the keratansulphate plus glycoprotein fraction to chondroitinsulphate was observed Osteoarthritic cartilage showed a significant reduction of all glycosaminoglycan fractions without change of distribution Normal cartilage taken from osteoarthritic joints was unaltered Solubility profiles indicated decreases in molecular weight of chondroitin sulphate in normal cartilage from birth to 21–30 years, and a trend towards lower molecular weight in osteoarthritic cartilage

The nature of endochondral ossification in the mandibular condyle of the mouse

Abstract: Through the application of histological and histochemical techniques, this study demonstrates that the ossification process of the mandibular condyle differs basically from that of other endochondral growth sites. In the epiphyseal plate of a typical long bone, the cartilage cells are known to undergo degenerative processes and death. In the mandibular condyle, however, the cartilage cells keep their vitality throughout the cartilage zones. In the lower border of the calcified cartilage, adjacent hypertrophic cartilage cells fuse after the dissolution of the intervening matrix to form multinuclear chondroclasts. These giant cells reveal marked positive reaction to mitochondrial and lysosomal enzymes. It is suggested that these enzymes are active in the resorption process of the calcified cartilage matrix, which is an integral phase of the ossification mechanism of the condylar growth center. It is believed that the mandibular condyle of the mouse demonstrates a specific type of endochondral ossification, in which the hypertrophic chondrocytes are not dying cells, but contribute actively to the process of bone formation.

Replacement of proteoglycans in embryonic chick cartilage in organ culture after treatment with testicular hyaluronidase.

Abstract: Explants of cartilage from tibiae of 11–12 days chick embryos were grown in organ culture. To one group hyaluronidase was added to the medium during the first 2 days of culture; the treated tissue was then cultured in medium without enzyme for a further 4 days. Control explants grown in hyaluronidase-free medium for 6 days grew rapidly in size and the total hexosamine content more than doubled during this time. After exposure to hyaluronidase, much of the hexosamine was lost from treated cartilage and appeared in the culture medium, but it was mostly replaced in the tissue during the subsequent recovery period. Analysis of cartilage and medium showed that net synthesis of hexosamine increased greatly in treated cartilage. The proteoglycans were extracted by two procedures from control and treated cartilage after 2, 4 and 6 days in culture. The hydrodynamic sizes of the purified proteoglycans were compared by gel chromatography and the composition of the gel-chromatographic fractions was determined. The proteoglycans from controls did not change during culture, but after exposure to hyaluronidase the proteoglycans from treated cartilage were of much smaller size and lower chondroitin sulphate content. During recovery, even though new proteoglycans were formed, they were nevertheless of smaller size and lower chondroitin sulphate content than control proteoglycans. They gradually became more like control proteoglycans during recovery from treatment, but even after 4 days they were not yet the same. After 2 days of treatment with the enzyme, the chondroitin sulphate in the cartilage was of shorter chain length than in controls but during recovery after 4 and 6 days in culture, the chain lengths in control and treated cartilage were similar. It is concluded that the proteoglycans formed in embryo cartilage in response to their depletion by enzyme treatment contained fewer chondroitin sulphate chains attached to the protein moiety of proteoglycans. This may have resulted from a failure under stress to glycosylate the protein moiety to the usual extent; alternatively the synthesis of normal proteoglycans of low chondroitin sulphate content may have increased, thus changing the proteoglycan population.

Relationship between pyrophosphate, amorphous calcium phosphate and other factors in the sequence of calcificationin vivo

Abstract: The amounts of inorganic pyrophosphate (PPi), orthophosphate and calcium have been measured in resting, proliferating, hypertrophic and calcified cartilage from foetal calf epiphyses and also in cancellous, periosteal and compact bone. In the cartilage samples, the content of PPi increased progressively in the order named above, from values of 8.59 μg P/g dry weight in resting cartilage to 236 μg P/g dry weight in calcified cartilage. However, the ratio of PPi to orthophosphate followed the reverse relationship and was highest in the resting zone and fell dramatically as the tissue calcified. The possible role of PPi in inhibiting the precipitation of amorphous calcium phosphate (ACP) and in the slowing the transformation of ACP to hydroxyapatite (HA) in calcifying tissues is discussed in relation to other factors, such as collagen, magnesium, phospholipids and proteinpolysaccharides, which might also influence the processin vivo. At present, no single factor can be identified as a proven physiological regulator.

Tissue Interactions in the Regeneration of Rabbit Ear Holes

Abstract: SYNOPSIS It a hole is cut through the ear of a rabbit it will fill in by the comergent growth of new tissue from around the margins Centimeter wide holes are usually obliterated in 6 to 8 weeks The regenerated tissues include newly differentiated cartilage and occasional tufts of hair To determine the specificity of skin in this kind of growth that on both sides of the eai was replaced by grafts of belly sVin When holes were subsequently punched through the transplant regions limited regeneration ensued but no new cartilage was produced If sheets of cartilage were removed fiom poitions of rabbit eais and the resultant aieas perforated through the remaining two layers of skin no regeneration whatever occurred Not even the missing cartilage gieu back These remits indicate that replacement of the ciitilaginous sheet requnes the proximity of a healing wound in the oveilying ear skin, ind that skin from clscwhcie on the body canno' support its regeneiation

Human cartilage lysozyme

Abstract: The lysozyme content of human cartilage was measured by incubation of lyophilized, powdered cartilage in a variety of buffers and salt solutions, and the factors controlling the binding of lysozyme within cartilage were studied. Lysozyme was extracted from hyaline cartilage by buffers of pH greater than 9.0 by solutions 1 M in monovalent cations, and by solutions 0.12-0.40 M in divalent cations. The ability of cations to extract lysozyme from cartilage agreed with their known affinities for binding to chondroitin sulfate. The total extractable lysozyme content of five samples of human costal cartilage ranged from 1.45 to 3.36 mug lysozyme per mg of cartilage; for five samples of hyaline cartilage from peripheral joints the range was 0.80-3.03 mug lysozyme per mg of cartilage. Cartilage incubated in excess exogenous lysozyme could bind 0.053 equivalents of lysozyme per equivalent of chondroitin sulfate. Fibrocartilage and synovium from knee joints yielded no detectable lysozyme, despite the fact that synovium, a tissue rich in lysosomes, contained measurable quantities of beta-glucuronidase. Lysozyme extraction from cartilage was not augmented by incubation with streptolysin S. When incubation was carried out with mild extraction techniques, lysozyme extraction from cartilage tended to parallel uronic acid release, both as a function of time and from one specimen to another. The active material as lysozyme. Lysozyme occurs in human hyaline cartilage as a counterion to polyanionic glycosaminoglycans. Carextracted from cartilage met five criteria for identification tilage lysozyme appears to be extracellular and nonlysosomal. Degradation of cartilage may contribute to the increased serum and synovial fluid lysozyme levels often present in patients with rheumatoid arthritis.

The influence of microscopic technology on knowledge of cartilage surface structure.

Abstract: FIG. 1 Proposed mechanisms of joint lubrication (Redrawn after Walker and others, 1968) (Lancet, 1969; Dowson, Wright, and Longfield, 1969) and a further possibility, 'weeping' lubrication, has been proposed (McCutchen, 1959, 1962). More recently, the role ofelectrostatic forces at articulating surfaces has been investigated (Roberts, 1971). In each of these hypothetical mechanisms the thesis had been accepted that these, surfaces are 'strikingly smooth' (Davies, 1969). The demonstration that normal load-bearing surfaces might not, after alf, be smooth (Dowson, Longfield, Walker, and Wright, 1968; Gardner and Woodward, 1968; Jones and Walker, 1968; Walker, Dowson, Longfield, and Wright, 1968; Inoue, Kodama, and Fujita, 1969; Walker, Sikorski, Dowson, Longfield, Wright, and Buckley, 1969), dramatically changed the theoretical approach to articulation mechanisms. A suggestion emerged (Fig. 2), supported by substantial data obtained with cartilage in vitro, that pools oflubricant, trapped betweenopposing undulationsonthecartilage surfaces, could lose fluid, concentrate hyaluronateprotein, and ensure efficient lubrication by a unique 'boosted' system (Longfield, Dowson, Walker, and Wright, 1969). Much of the support for this proposed mechanism of 'boosted lubrication' would be lost if it could be shown that the gentle surface undulations detected by talysurf tracings and identified by scanning electron microscopy were artefacts caused by the methods used to isolate and manipulate cartilage in vitro. During the past 2 years it has therefore been a main interest of this laboratory to examine loadbearing cartilaginous surfaces in detail under conditions that approximate as closely as possible to

The effect of systemic corticosteroids on rabbit articular cartilage.

Abstract: Rabbits were treated for up to 9 weeks with daily doses of cortisone. Cartilage from the distal femur was studied biochemically at regular intervals, and no change in the content of DNA but a significant and progressive decline in the concentration of hexosamine were noted. In vitro incorporation of 35SO4 and 3H-glycine was depressed markedly. Because the test animals lost 25% of their body weight, a separate group of starved controls were studied and the changes noted were similar to those seen with corticoid treatment but were not as marked.

Mode of degradation of the chondroitin sulphate proteoglycan in rat costal cartilage.

Abstract: 1. Chondroitin sulphate was isolated from different regions of rat costal cartilage after extensive proteolysis of the tissues. The molecular weight, determined by gel chromatography, of the polysaccharide obtained from an actively growing region (lateral zone) near the osteochondral junction was higher than that of the polysaccharide isolated from the remaining portion of the costal cartilage (medial zone). 2. In both types of cartilage the molecular weight of chondroitin sulphate, labelled with [(35)S]sulphate, remained unchanged in vivo over a period of 10 days, approximately corresponding to the half-life of the chondroitin sulphate proteoglycan. The molecular-weight distribution of chondroitin [(35)S]sulphate, labelled in vivo or in vitro, was invariably identical with that of the bulk polysaccharide from the same tissue. It is concluded that the observed regional variations in molecular-weight distribution were established at the time of polysaccharide biosynthesis. 3. In tissue culture more than half of the (35)S-labelled polysaccharide-proteins of the two tissues was released into the medium within 10 days of incubation. The released materials were of smaller molecular size than were the corresponding native proteoglycans. In contrast, the molecular-weight distribution of the chondroitin [(35)S]sulphate (single polysaccharide chains) remained constant throughout the incubation period. 4. A portion (about 20%) of the total radioactive material released from (35)S-labelled cartilage in tissue culture was identified as inorganic [(35)S]sulphate. No corresponding decrease in the degree of sulphation of the labelled polysaccharide could be detected. These findings suggest that a limited fraction of the proteoglycan molecules had been extensively desulphated. 5. It is suggested that the initial phase of degradation involves proteolytic cleavage of the proteoglycan, but the constituent polysaccharide chains remain intact. The partially degraded proteoglycan may be eliminated from the cartilage by diffusion into the circulatory system. An additional degradative process, which may occur intracellularly, includes desulphation of the polysaccharide, probably in conjunction with a more extensive breakdown of the polymer.

Composite auricular graft in laryngeal reconstruction.

Abstract: When injury to the larynx and/or trachea results in significant loss of tissue, primary closure may predispose to stenosis. Reconstruction of the airway should include the addition of cartilage to maintain the lumen as well as a replacement for interior mucoperichondrium and exterior skin. The auricle provides an excellent source for a composite graft consisting of cartilage with its attached skin on one side and perichondrium on the other. A case is presented in which a 2 cm. defect was successfully closed with such a composite graft. The patient sustained a self-inflicted wound which removed the lower portion of the thyroid cartilage in the midline, the anterior third of the cricoid cartilage and the anterior third of the first tracheal lumen. Several weeks later a composite graft was taken from the auricle, and a three-layer closure was accomplished. After an initial period of cyanosis, the graft remained viable and survived in toto. Long term follow-up showed survival of the graft, normal laryngeal function and normal tracheal diameter.

The molecular weight of chondroitin sulphate from human articular cartilage. Effect of age and of osteoarthritis.

Abstract: The molecular weight distributions of chondroitin sulphate from normal articular cartilage of the lower femoral epiphysis from human autopsy cases of different ages and from osteoarthritic cartilage have been determined by gel chromatography on Sephadex G-200. The polysaccharide samples fell within the same molecular weight range but differed with respect to molecular weight distribution. The average molecular weight of chondroitin sulphate from normal articular cartilage was higher in newborn and young individuals than in adults or the aged. Chondroitin sulphate from osteoarthritic cartilage had a lower molecular weight than that from macroscopically normal cartilage. The observed variations in polysaccharide chain length are discussed.