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Biomedical subjects

R A Stockwell

Publications and source records attributed to R A Stockwell.

At least 19 recordsLinked to original sources
PubMed1992

Response of plasma membrane to applied hydrostatic pressure in chondrocytes and fibroblasts.

Effects of applied hydrostatic pressure on transmembrane potentials were investigated in sheep articular chondrocytes and human skin fibroblasts in non-confluent monolayer cultures. Resting potentials in chondrocytes (about -12 mv) and in fibroblasts (about -15 mV) were increased and decreased respectively by over 40% after pressure was applied cyclically (0.33 Hz, 120 mm Hg, 20 minutes). Continuous pressure (120 mm Hg, 20 minutes) caused deplorization in both cell types. Low frequency pressure application (less than 0.08 Hz) caused depolarization in chondrocytes and hyperpolarization in fibroblasts. Quinidine (2 x 10(-5) M) blocked and verapamil (10(-5) M) reduced hyperpolarization responses, suggesting involvement of Ca(2+)-dependent K+ channels. A23187 (1.9 x 10(-6) M) caused hyperpolarization in chondrocytes, augmented further by subsequent pressure application (0.33 Hz). Tetrodotoxin (10(-6) M) blocked depolarization responses indicating that these were due to Na+ influx. Blockade of histamine H1 receptors by chlorpheniramine maleate (5.1 x 10(-6) M), H2 receptors by cimetidine (7.9 x 10(-6) M) and beta-adrenoreceptors by sotolol (1.3 x 10(-4) M) had no effect on hydrostatic pressure-induced hyperpolarization in chondrocytes. Cytochalasin B (2 x 10(-5) M and at 4 x 10(-6) M) abolished pressure-induced hyperpolarization in chondrocytes; in contrast, applied cyclical hydrostatic pressure to cytochalasin-treated fibroblasts caused hyper-polarization, suggesting that cytoskeletal changes were involved.

Animals↗
PubMed1991

Morphometry of cytoplasmic components of mammalian articular chondrocytes and corneal keratocytes: species and zonal variations of mitochondria in relation to nutrition.

A morphometric analysis was made of nuclei and cytoplasmic structures in electron micrographs of chondrocytes in the non-calcified layer of articular cartilage of the femoral condyles in adult mouse and dog and of the human incus. Mitochondrial volume density (% cytoplasm) was lower in dog than in mouse cells or cells of the incus. It was also lower in the cells of deep zone cartilage than in superficial cells. Analysis of keratocytes of the corneal stroma in mouse and sheep gave similar findings to that in cartilage. Mitochondrial volume density was higher in mouse than in sheep keratocytes and, in sheep, higher in subepithelial (anterior) cells than in cells of the intermediate and subendothelial strata. Values in human stromal cells were similar to those in the sheep. Endoplasmic reticulum volume density was higher in mouse than in sheep keratocytes. Lipid and filaments were more abundant in dog than in mouse chondrocytes but keratocytes contained little or none. Mitochondrial volume densities correlate with diffusion distances (tissue thickness) from the sources of nutrition, for example, for oxygen, in the two tissues. The relationship to certain aspects of chondroitin sulphate and keratansulphate synthesis and topographical distribution in cartilage and cornea is discussed.

Animals↗
PubMed1990

Distribution of crystals in the superficial zone of elderly human articular cartilage of the femoral head in subcapital fracture.

Crystal distribution in articular cartilage of femoral heads resected at hip arthroplasty for fracture of the femoral neck was examined in 10 patients (77-91 years) by computerised image analysis of electron micrographs. Crystal content of the zenith did not differ from that of the infrafoveal region of the femoral head in the superficial 0.5 mm of the cartilage. Crystal area density (percentage area of the section occupied by crystal profiles) was higher in a zone 0-50 microns than in the subjacent zone 50-500 microns from the articular surface, particularly in the zenith of the femoral head. It was also higher on the superficial (towards the articular surface) aspect than on the deep aspect of cells in perilacunar matrix. Crystal area density was similar in lacunar matrix, perilacunar matrix, and matrix remote from cells. Matrix containing cell debris was more heavily impregnated with crystals than any other site. No difference in crystal content was observed in cartilage beneath articular surfaces which were ultrastructurally smooth or roughened. The diminishing gradient of crystal area density with depth from the articular surface, the absence of a marked spatial association with living cells, and the impregnation of sites containing cell debris suggest that crystal deposition in these cases is not due primarily to chondrocyte activity.

Aged↗
PubMed1989

Keratan sulphate: a functional substitute for chondroitin sulphate in O2 deficient tissues?

Keratan sulphate and chondroitin sulphate can each fill space and exert swelling pressure in collagenous fibrillar matrices, but whereas the former is synthesised from glucose precursor without consuming NAD, the latter converts 2 mols of NAD for each uronate residue in the polymer chain. We suggest that the observed distribution of keratan sulphate and chondroitin sulphate in cartilage, cornea and intervertebral disc are determined by the ambient oxygen tension, and that keratan sulphate is preferentially synthesised in conditions of oxygen lack. The implications of this hypothesis in the physiology of contact lenses, cartilage degeneration, corneal scar repair and ageing are discussed.

Aging↗
PubMed1984

Early response of cartilage to abnormal factors as seen in the meniscus of the dog knee after cruciate ligament section.

Ultrastructural changes in the medial meniscus of the knee were studied following section of the anterior cruciate ligament in 7 dogs. As compared with the contralateral control knee, collagen fibrils became abnormally widely spaced and disoriented from 1 month after operation and amorphous material on the (femoral) articular surface increased in thickness. In superficial cells, granular endoplasmic reticulum and Golgi membranes were more profuse and lipid droplets increased in number from 1 week. Both superficial and deeper cells were very active at 1 and 2 months after operation and the nuclear fibrous lamina had increased in thickness. Some cell degeneration occurred in the superficial zone from 1 month. At 15 months both matrix and cells appeared to have returned to normal. These changes are compared with those in articular cartilage after cruciate ligament section and with the effects of intravenous papain on cartilage.

Animals↗
PubMed1983

Ultrastructural changes in articular cartilage after experimental section of the anterior cruciate ligament of the dog knee.

Ultrastructural changes in articular cartilage were studied in joint laxity induced by severing the anterior cruciate ligament of the right knee in sixteen mature dogs. The left knees provided controls; sham operations on six other dogs consisted of stab incision only, leaving the ligament intact. Cartilage from the medial tibial condyles was examined at intervals from two days to eighteen months later. In the superficial zone of the cartilage, collagen fibrils became abnormally widely spaced at four days, and narrower fibrils appeared from seven days after operation. Chondrocytes, particularly in the middle zone, became more active, with hypertrophy of cytoplasmic organelles detectable from four days. Superficial cells were initially healthy and became more numerous while their lipid content increased. The articular surface was fissured from two months and cell degeneration was rarely seen until several months after operation. These findings correlate with previous biochemical studies and are similar to early changes noted in degeneration of human articular cartilage.

Animals↗
PubMed1983

An ultrastructural study of the marginal transitional zone in the rabbit knee joint.

The ultrastructure of the marginal transitional zone of femoral articular cartilage has been studied in the rabbit knee. There is an abrupt boundary between the convex margin of the cartilage and the synovial membrane. This is due to the arrangement and amount of collagen and of cells, because cell ultrastructure changes gradually from synovium to cartilage. The densely fibrous marginal synovium contains scattered fibrocytic cells with sparse cytoplasm and long filopodia. Near the synovium/cartilage interface, oval boundary cells containing more abundant cytoplasm abut on the cartilage matrix. In the periphery of the cartilage, an edge-belt of collagen fibrils runs obliquely from articular surface to subchondral bone. Chondrocytes near the edge-belt, whatever their depth from the articular surface, ultrastructurally resemble middle zone (zone II) cells of articular cartilage generally. The synovial surface of the marginal zone is smooth and resembles articular cartilage surfaces. Most intimal cells contain plentiful granular endoplasmic reticulum and Golgi membranes and hence are intermediate between A and B synoviocytes commonly found elsewhere. Non-fenestrated (type I) capillaries lie in a superficial stratum beneath the synovial surface and in a deep stratum near the synovium/cartilage boundary, and are surrounded by pericytes. No mast cells, macrophages, lymph vessels or nerves could be identified in the marginal zone. Contrary to earlier accounts of collagen orientation in this zone, most of the fibrils in the marginal synovium appear to run around the perimeter of the cartilage and only a few bundles run radially from the synovium towards the cartilage. It is suggested that the circumferential collagen both contains the marginal cartilage and prevents displacement of synovial tissue on to the articular surface. The radial strata of collagen serve to anchor the circumferential collagen to the cartilage edge-belt. In agreement with earlier investigators, it is considered that the edge-belt withstands tensile stresses arising from deformation of the articular surface. The role of the marginal synovium is also discussed in relation to synovial fluid formation and cartilage nutrition.

Animals↗
PubMed1981

Glycosaminoglycan content and cell density of rabbit articular cartilage in experimental lipoarthrosis.

Glycosaminoglycan content and cell density of articular cartilage have been studied quantitatively in the adult rabbit in experimental lipoarthrosis. On the fourth day after injection of non-radioactive or tritium-labelled glyceryl trioleate into the synovial cavity of the knee joint, femoral condylar cartilage shows no change in cellularity. There is a 35% loss of chondroitin sulphate from the matrix, but little change in keratansulphate. The results are not affected by the presence or absence of radioactive isotope in the lipid: possible mechanisms accounting for glycosaminoglycan loss are discussed.

Animals↗
PubMed1978

Chondrocytes.

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Calcification, Physiologic↗
PubMed1977

Histological and biochemical studies on cartilage from osteoarthrotic femoral heads with special reference to surface characteristics.

A study has been made of cartilage from osteoarthrotic femoral heads in an attempt to relate histological to biochemical and metabolic changes. Cartilage showing different surface characteristics and originating from different areas of the femoral head has been studied. Depending on its surface characteristic and location, the osteoarthrotic cartilage ranged in composition and sulphate metabolism from practically normal to glycosaminoglycan depleted and metabolically depressed. There was no indication of elevation in the sulphate incorporation in the osteoarthrotic cartilage.

Bone Diseases↗
PubMed1976

Changes in articular cartilage following intraarticular injection of tritiated glyceryl trioleate.

The effects of intra-articular injections of non-radioactive and tritium-labelled glyceryl trioleate into the mandibular and knee joints of adult rabbits have been investigated using autoradiographic and histochemical techniques and electron microscopy. As observed at the fourth day after operation, fat droplets accumulate in cells of the fibrous, intermediate and cartilaginous layers of mandibular condylar, and in the superficial and upper middle (rather than the deeper) zones of femoral condylar cartilage. Autoradiography of frozen sections shows that numerous silver grains are located over these fat-laden cells following injection of trioleate which has been labelled in the fatty acid moiety of the molecule. In the knee joint the number of grains is directly related to the amount of lipid in the cell. Following injection of glyceryl-labelled trioleate no such result is obtained; it seems doubtful whether or not there is any uptake of this label. However, synovial membrane from the knee joint appears to take up both kinds of trioleate. Results of histochemical methods of NADH diaphorase, lactic dehydrogenase, acid phosphatase and beta-glucosaminidase are consistent with ultrastructural evidence of degeneration in some chondrocytes and of loss of ground substance from the matrix. A raised level of alpha-glycerophosphate dehydrogenase activity is probably associated with synthesis of endogenous glycerol for re-esterification of absorbed fatty acids, and enhanced activity of UDPglucose dehydrogenase with the chondrocytic reaction to matrix depletion. Apart from the increase in fat content, ultrastructural features in injected knee joints include flattening of cell processes against the chondrocyte surface and more abundant intracytoplasmic filaments. Injected mandibular joints show little evidence of these changes although the number of cells in the cartilage appears to be greatly reduced. No extracellular fat droplets occur in femoral cartilage, but material similar in electron density to intracellular fat is observed at the external aspect of some mandibular chondrocytes. The findings indicate that the fatty acid portion of triglyceride injected intra-articularly is taken up by the chondrocytes and retained until at least the fourth day after injection. It is suggested that prior lipolysis takes place either in the synovial cavity (or membrane) or at the chondrocyte surface, but it is uncertain how or in what form fat traverses the matrix. Lipoarthrosis appears to produce changes in the chondrocytes which are thought to be pathological; a number of cell deaths occur. The possibility that gross degeneration of the articular cartilage may ensue is subject to further investigation.

Acid Phosphatase↗
PubMed1975

Structural and histochemical aspects of the pericellular environment in cartilage.

Mature cartilage contains pericellular regions of matrix of fine texture, consisting of filamentous material and granules containing proteoglycan. Intercellular matrix contains collagen fibres with structural elements resembling those of the pericellular regions in the spaces between the fibres. Membrane bound bodies may be present at the margin of the pericellular region. Histochemically, chondroitin sulphate is found in the pericellular region in all zones but keratan sulphate is similarly stainable only in the deep zones of ageing cartilage.

Adult↗
PubMed1975

Factors involved in the nutrition of the human lumbar intervertebral disc: cellularity and diffusion of glucose in vitro.

Post-mortem specimens of the human lumbar (L4-L5) intervertebral disc have been studied histologically and physico-chemically. Blood vessels were found only at the margin of the anulus fibrosus and in the vertebral marrow spaces. Contact between disc tissue and marrow spaces occupied about 10% of the bone-cartilage interface. The disc was most cellular at the periphery of the anulus fibrosus and in the hyaline cartilage next to the vertebral bone. Cellularity declined towards the nucleus pulposus where it achieved a low constant value. The cell density of the disc as a whole was about 60000 cells/mm3. For glucose, the diffusion coefficient of the anulus fibrosus and hyaline cartilage end plate was 2.5 cm2/sec and 2.4 cm2/sec respectively at 37 degrees C, comparable to that of cartilage elsewhere. The permeability of the bone-cartilage interface was low, particularly in the peripheral part. Calculations, based on the present findings and derived values for glucose utilization in disc tissue, indicate that nutritional conditions in the intervertebral disc are more critical than, for example, in articular cartilage.

Adolescent↗