Reinterpretation of the ultrastructure of cartilage matrix

Summary The epiphyseal cartilage from new-born mouse was treated with collagenase in two ways: either before fixation or after glutaraldehyde fixation. The electron dense granules of the matrix were not seen in the micrographs of cartilage treated with collagenase before fixation. It is concluded that collagen plays a definite role in the formation of the granules at the time of tissue fixation and that the granules are fixation artifacts.Commonwealth Academic Staff Fellow. Permanent address: Department of Zoology, University of Poona, Poona 411007, India.     

Biochemical and autoradiographical distribution of hyaluronic acid in calf rib cartilage.

In calf rib cartilage, about one half of total hyaluronate is soluble with guanidinium hydrochloride, the other half only after collagenase treatment. Evidence is presented for its pericellular and intracellular distribution.     

Biochemical and autoradiographical distribution of hyaluronic acid in calf rib cartilage

Summary In calf rib cartilage, about one half of total hyaluronate is soluble with guanidinium hydrochloride, the other half only after collagenase treatment. Evidence is presented for its pericellular and intracellular distribution.Acknowledgment. This work was supported by grants from the Deutsche Forschungsgemeinschaft (Kl 193/10, Mo 183/5).     

Annexin V interactions with collagen

Annexin V was originally identified as a collagen-binding protein called anchorin CII and was isolated from chondrocyte membranes by affinity chromatography on native type II collagen. The binding of annexin V to native collagen type II is stable at physiological ionic strength when annexin V is reconstituted in liposomes. The binding to native collagen types II and X, and to some extent to type I as well, was confirmed using recombinant annexin V. A physiological role for annexin V interactions with extracellular collagen is consistent with the localization of annexin V on the outer cell surface of chondrocytes, microvilli of hypertrophic chondrocytes, fibroblasts and osteoblasts. A breakthrough in our understanding of the function of annexin V was made with the discovery of its calcium channel activity. At least one of several putative functions of annexin V became obvious from studies on matrix vesicles derived from calcifying cartilage. It was found that calcium uptake by matrix vesicles depend on collagen type II and type X binding to annexin V in the vesicles and was lost when collagens were digested with collagenase; calcium influx was reconstituted after adding back native collagen II or V. These findings indicate that annexin V plays a major role in matrix vesicle-initiated cartilage calcification as a collagen-regulated calcium channel.     

Calcium and disease: molecular determinants of calcium crystal deposition diseases

Deposition of basic calcium phosphate (hydroxyapatite, octacalcium phosphate and tricalcium phosphate) (BCP) and crystalline calcium pyrophosphate dihydrate (CPPD) is associated with a variety of aging-related pathologies, including osteoarthritis, cartilage degeneration and pseudogout. These diseases of calcium deposition serve as some of the best-studied examples of how calcium-regulated changes in gene expression can directly lead to pathogenic consequences. Tissue damage can result when crystals stimulate cells to release matrix-degrading molecules or secrete cytokines that stimulate the release of matrix-degrading molecules. Exposure of cultured cells to crystals induces expression of cellular proto-oncogenes such as c-fos, c-myc and c-jun, by a calcium-dependent mechanism, and this response can be blocked by a potential therapeutic compound, phosphocitrate. Activation of the c-fos and c-jun genes is directly involved in expression of metalloproteinases such as collagenase and stromelysin, suggesting that crystal-mediated activation of these genes is directly involved in pathogenesis. In this review recent advances in the molecular mechanisms responsible for crystal-mediated cell activation are discussed.     

Suppression by the cyclohexanetrione Ro 31-0521 of retinoic acid-induced teratogenicity

The cyclohexanetrione Ro 31-0521, which stimulates prostaglandin synthesis, inhibited retinoic acid-induced cartilage degradation in vitro and suppressed the congenital forelimb malformations in rats treated with retinoic acid on day 13 of gestation in a dose-dependent manner.     

The response of costal cartilage to changes in hormonal environment

Résumé 1^o L'hypophysectomie diminue l'incorporation de S³⁵ dans le cartilage costal de jeunes rats. L'hydrocortisone renforce l'action de l'hypophysectomie. Au contraire, le propionate de testostérone stimule la fixation de S³⁵ dans le cartilage costal. Un traitement à l'hormone de croissance donne und réponse qualitativement identique à celle obtenue avec le propionate de testostérone. 2^o Le propionate de testostérone, l'hydrocortisone et l'hormone de croissance n'influencent pas l'incorporation de radiosulfate chez le rat normal.     

In vivo matrix-guided human mesenchymal stem cells

Microfracture of subchondral bone results in intrinsic repair of cartilage defects. Stem or progenitor cells from bone marrow have been proposed to be involved in this regenerative process. Here, we demonstrate for the first time that mesenchymal stem (MS) cells can in fact be recovered from matrix material saturated with cells from bone marrow after microfracture. This also introduces a new technique for MS cell isolation during arthroscopic treatment. MS cells were phenotyped using specific cell surface antibodies. Differentiation of the MS cells into the adipogenic, chondrogenic and osteogenic lineage could be demonstrated by cultivation of MS cells as a monolayer, as micromass bodies or mesenchymal microspheres. This study demonstrates that MS cells can be attracted to a cartilage defect by guidance of a collagenous matrix after perforating subchondral bone. Protocols for application of MS cells in restoration of cartilage tissue include an initial invasive biopsy to obtain the MS cells and time-wasting in vitro proliferation and possibly differentiation of the cells before implantation. The new technique already includes attraction of MS cells to sites of cartilage defects and therefore may overcome the necessity of in vitro proliferation and differentiation of MS cells prior to transplantation. Received 3 November 2005; received after revision 15 December 2005; accepted 4 January 2006     

Ultrastructural changes in the neural lobe of the rat pituitary induced by reserpine treatment.

The doses of reserpine, which are generally used to deplete amines from the nervous tissue caused marked ultrastructural changes in the neural lobes of reserpine treated rats. The findings suggested depletion of neurosecretory granules, increased lysosomal activity and changes in the pituicytes.     

Noncollagenous, nonproteoglycan macromolecules of cartilage

Extracellular matrix comprises approximately 90% of cartilage, with collagens and proteoglycans making up the bulk of the tissue. In recent years, several abundant cartilage proteins that are neither collagens nor proteoglycans have been characterized in detail. The putative roles of these proteins range from involvement in matrix organization or matrix-cell signaling (PRELP, chondroadherin, cartilage oligomeric protein and cartilage matrix protein) through to molecules that are likely to be involved with modulation of the chondrocyte phenotype (CD-RAP, CDMPs, chondromodulin and pleiotrophin). Other molecules, such as the cartilage-derived C-type lectin and cartilage intermediate layer protein have no role as yet. Due to the difficulties associated with experimentally manipulating a tissue that is 90% extracellular matrix in a manner that can be readily transferred to the whole organism, many of these molecules have been focused on by a surprisingly small number of researchers. This review focuses on newly discovered proteins and glycoproteins in cartilage, with a bias towards those that have structural roles or that are unique to cartilage. Received 7 January 1999; accepted 11 March 1999     

Effect of bromocriptine on the "prolactin-like cell" of Nectophrynoides occidentalis (Amphibia, viviparous Anura): optical and electronic microscopical studies]

Bromocriptin has an effect on prolactin-like cells of Nectophryno?des occidentalis. 16 days after delivery, these cells are fully active in normal animals. Retention of secretory granules and myelinic formations have been observed in the prolactin-like cells of females treated by CB 154.     

Early skin responses of hibernating and nonhibernating ground squirrels to topical applications of DMBA

Skin patches on hibernating and nonhibernating ground squirrels were treated with multiple topical applications of the carcinogen 7,12-dimethylbenza(a)anthracene. Nonhibernators showed blistering, peeling, drying, hair loss, increased vascularization and hyperpigmentation in proportion to DMBA concentration. The latter was apparently due to a) an increased number of dermal and epidermal melanocytes and b) the appearance of melanocytes with large coarse cytoplasmic granules. Notably, hibernators remained free of gross skin changes and were histologically similar to untreated controls.     

Increased release of tumour cells by collagenase at acid pH: A possible mechanism for metastasis

Summary The ability of collagenase to disaggregate a solid metastasizing lymphosarcoma has been shown to considerably increase with reducing environmental pH. It is suggested that this effect may be operating in vivo to release cells from a primary tumour.     

Peroxidase activity of neutrophil granules in two cases of congenital myeloperoxidase deficiency]

The neutrophils and monocytes of two patients with hereditary myeloperoxidase deficiency lacked myeloperoxidase activity as determined by light and electron microscopic cytochemical staining. Using Graham-Karnovsky media, azurophils of neutrophils were devoid of peroxidase whereas all eosinophilic and basophilic granules exhibited normal peroxidase activity. After incubation in alkaline diaminobenzidine media which stains the catalase of microperoxisomes, some small granules were seen to be strongly stained in both immature and mature neutrophils. These small granules were distinct from all other neutrophilic granules which lacked a positive reaction. Only, in the presence of cyanide or aminotriazole, peroxidatic activity was also detected in some ellipsoid azurophils. This observation suggests that these substances activated an oxidase whose nature is discussed.     

Aggrecan, aging and assembly in articular cartilage

The primary function of articular cartilage to act as a self-renewing, low frictional material that can distribute load efficiently at joints is critically dependent upon the composition and organisation of the extracellular matrix. Aggrecan is a major component of the extracellular matrix, forming high molecular weight aggregates necessary for the hydration of cartilage and to meet its weight-bearing mechanical demands. Aggregate assembly is a highly ordered process requiring the formation of a ternary complex between aggrecan, link protein and hyaluronan. There is extensive age-associated heterogeneity in the structure and molecular stoichiometry of these components in adult human articular cartilage, resulting in diverse populations of complexes with a range of stabilities that have implications for cartilage mechanobiology and integrity. Recent findings have demonstrated that aggrecan can form ligands with other matrix proteins. These findings provide new insights into mechanisms for aggregate assembly and functional protein networks in different cartilage compartments with maturation and aging.     

Increased release of tumour cells by collagenase at acid pH: a possible mechanism for metastasis.

The ability of collagenase to disaggregate a solid metastasizing lymphosarcoma has been shown to considerably increase with reducing environmental pH. It is suggested that this effect may be operating in vivo to release cells from a primary tumour.     

Collagen treated with (+)-catechin becomes resistant to the action of mammalian collagenase

Treatment of radioactively labeled guinea-pig skin soluble collagen or calf skin collagen with the flavonoid (+)-catechin makes the collagen resistant to the action of mammalian collagenase but not to the action of bacterial collagenase. Complete resistance to the action of the mammalian enzyme may be achieved by incubating 0.6 mg of collagen (dry weight) with 0.1 mM (+)-catechin, followed by dialysis to remove the unbound flavonoid. Since incubation of the mammalian enzyme with (+)-catechin does not inhibit its activity, it is postulated that (+)-catechin binds tightly to collagen and modifies its structure sufficiently to make it resistant to enzyme degradation.     

Tissue antagonist of interferon : murine substance similar to plant lectins]

A tissue antagonist of interferon (TAI) extracted from mouse costal cartilage contains a substance which has many properties characteristic of plant lectins. After binding to the cell membrane receptors, it agglutines normal and transformed murine cells. In interferon treated cells, it restores virus sensitivity probably through a modification in the distribution of membrane bound cellular antigens.     

Molecular basis of osteoarthritis: biomechanical aspects

The unique biomechanical properties of healthy cartilage ensure that articular cartilage is able to transmit force between the joints while maintaining almost friction-free limb movement. In osteoarthritis, the biomechanical properties are compromised, but we still do not understood whether this precedes the onset of the disease or is a result of it. This review focuses on the physical changes to cartilage with age, disease, and mechanical loading, with specific reference to the increased collagen cross-linking that occurs with age (nonenzymatic glycation), and the response of chondrocytes to physiological and pathological loads. In addition, the biomechanical properties and matrix biosynthesis of cartilage from various joint surfaces of the knee and ankle are compared to elucidate reasons why the ankle is less affected by progressive osteoarthritis than the knee.     

Identification of hemolytic granules isolated from human myocardial cells

Human myocardial cells from fresh autopsy material contained granules which possessed hemolytic activity against guinea pig and rabbit erythrocytes. The hemolytic granules, which had a density of 1.02 and a diameter of 200-300 nm, were recovered as a microsome fraction from subcellular homogenates of human myocardial cells by differential centrifugation in 300 mM sucrose containing 0.1 mM PMSF and 10 mM EDTA. The membrane lesions caused by the granules were ring-like structures with an internal diameter of about 10-17 nm, analogous to that caused by perforin- and complement-induced lysis. However, the requirement for divalent cation differed from that for perforin-induced lysis, since the microsome-mediated lysis occurred in the presence of EDTA.