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J A CHAPMAN

Publications and source records attributed to J A CHAPMAN.

12 recordsLinked to original sources
PubMed1964

THE UPTAKE OF IRON IN RABBIT SYNOVIAL TISSUE FOLLOWING INTRA-ARTICULAR INJECTION OF IRON DEXTRAN. A LIGHT AND ELECTRON MICROSCOPE STUDY.

Iron dextran (molecular weight 7,000) diffuses rapidly from the joint cavity through the synovium, along lymphatics and extracellular tissue spaces; articular cartilage is impermeable to iron dextran. There is also rapid cellular uptake by synovial lining cells, particularly of the vacuolar type; endoplasmic reticulum-containing lining cells rarely take up iron dextran. Cellular uptake is probably effected by pseudopodial folds projecting from the cell surface and enclosing extracellular material. Cells containing iron may degenerate and be ingested by phagocytes, and this may account for the concentration of iron in a smaller proportion of cells on or below the synovial surface in the later stages. At 6 to 18 hours after injection there is a mild inflammatory reaction and some synovial proliferation; from this stage onwards intracellular iron occurs in the form of haemosiderin. Granules of haemosiderin are present in the synovium 3 months after injection and possibly longer.

Animals↗
PubMed1961

Morphological and chemical studies of collagen formation. II. Metabolic activity of collagen associated with subcellular fractions of guinea pig granulomata.

Electron micrographs of thin sections of nuclear, microsomal, and mitochondrial fractions obtained from a carrageenin-induced granuloma showed considerable contamination of the heavier by the lighter fractions. Striated collagen fibrils could be identified in the nuclei + debris fraction. Only a few striated fibrils occurred in the mitochondrial fraction; very fine filaments (diameter 50 A) could be seen in this fraction, but could not be distinguished with certainty from fibrillar material derived from broken nuclei. 35 per cent of the mitochondrial and 80 per cent of the microsomal collagen was extractable by 0.2 M NaCl and could be purified by the standard methods of solution and reprecipitation. The amino acid composition of these collagen fractions determined by ion exchange chromatography was within the range normally found for collagen and gelatin from other mammalian species, allowing for 10 to 20 per cent of some non-collagenous contaminant of the microsomal collagen. Hydroxyproline and proline were isolated by chromatography on paper from hydrolysates of the nuclear, mitochondrial, and microsomal collagen fractions, after incubation of tissue slices with L-(14)C-proline. The specific activities of the hydroxyproline from these collagens were in the approximate ratio 1:2:6, while that of bound hydroxyproline derived from the supernatant was only 1, indicating primary synthesis of collagen in the microsomes. Attempts to demonstrate incorporation of L-(14)C-proline into collagen or into free hydroxyproline in cell free systems were unsuccessful, nor was it possible to demonstrate non-specific incorporation of L-(14)C-valine into TCA-insoluble material by various combinations of subcellular fractions.

Animals↗
PubMed1961

Morphological and chemical studies of collagen formation. I. The fine structure of guinea pig granulomata.

This paper describes electron microscopic studies of developing connective tissue in granulomata induced by the subcutaneous injection of carrageenin into guinea pigs. Seven days after injection the granulomata contained many fibroblasts and exhibited rapid production of collagen. The fibroblasts were characterised by an extensively developed endoplasmic reticulum and showed numbers of fine, unstriated filaments in the outer regions of the cytoplasm. The filaments, about 50 A in diameter, tended to lie parallel to and closely adjacent to the cell boundary. The cytoplasmic membrane was frequently ill defined or disrupted, particularly bordering regions in which filaments occurred. In longitudinal sections of extended cell processes, filaments were abundant and, in some instances, the cytoplasmic membrane was barely detectable. In the extracellular space striated collagen fibrils were usually accompanied by filaments, 50 to 100 A in diameter, and these often exhibited the characteristic periodicity of collagen, particularly after intense electron bombardment. Much cellular debris was present in the extracellular space. These observations have led to the suggestion that connective tissue precursors are released from fibroblasts by the disintegration or dissolution of the cytoplasmic membrane and the shedding of cytoplasmic material, as in the apocrine gland cells. In some instances this release may take the form of the elongation from the cell of extended processes; disintegration of the cytoplasmic membrane surrounding these processes then leaves the contents in the extracellular phase.

Animals↗