Search PubMed⌕ Search

Biomedical subjects

J C Gray

Publications and source records attributed to J C Gray.

At least 127 records · Page 7Linked to original sources
PubMed1979

Synthesis of cytochrome f by isolated pea chloroplasts.

Chloroplasts, isolated from the leaves of 7-day-old pea seedlings, were incubated in the light with [35S]methionine or [3H]leucine. After extraction from the washed chloroplast membranes using a mixture of ethyl acetate, ethanol and ammonia, cytochrome f was precipitated with a monospecific antiserum and resolved by gradient polyacrylamide gel electrophoresis in sodium dodecylsulphate. The cytochrome f band was identified by its intrinsic fluorescence in ultraviolet light and was shown to be radioactive by autoradiography or fluorography of dried polyacrylamide gel. One-dimensional peptide mapping of the products of papain hydrolysis confirmed that the radioactivity was an integral part of cytochrome f. The incorporation of [35S]methionine into cytochrome f was inhibited by D(-)threo-chloramphenicol but not by cycloheximide and did not occur in the dark. The synthesis was resistant to ribonuclease. It is concluded that cytochrome f is synthesised in intact isolated pea chloroplasts.

Chloramphenicol↗
PubMed1978

Purification and properties of monomeric cytochrome f from charlock, Sinapis arvensis L.

Monomeric cytochrome f has been purified to homogeneity, as judged by polyacrylamide gel electrophoresis, isoelectric focusing and analytical ultracentrifugation, from the leaves of charlock, Sinapis arvensis L. The cytochrome was obtained in an aqueous extract following extraction of leaf lipids with butan-2-one, and was subsequently purified by acetone precipitation and chromatography on DEAE-cellulose, Sephadex G-100 and hydroxylapatite. The purified cytochrome had adsorbance ratios of A422/A280 = 7.3 and A554/A280 = 1.07 in the reduced form. There was no indication of the presence of an absorbance band at 695 nm in the oxidised form. The cytochrome had a midpoint redox potential of +365 mV and was oxidised very rapidly by parsley plastocyanin. The molecular weight of the cytochrome was approximately 27 000 as determined by sedimentation equilibrium and by polyacrylamide gel electrophoresis in the presence of dodecylsulphate. The sedimentation coefficient (so20,w) of cytochrome f was 2.48 S. The cytochrome had an isoelectric point at pH 5.50 determined by isoelectric focusing in polyacrylamide gels.

Amino Acids↗
PubMed1977

Preparation of thin cryo-sections for electron probe analysis of calcifying cartilage.

Conventional methods of fixation, dehydration, embedding and wet-sectioning can produce artefacts in the chemical composition of mineralizing tissues. Cryoultramicrotomy was adopted for a more reliable approach to electron probe analysis of initial apatite formation in calcifying cartilage. Fresh rabbit epiphyseal cartilage was mounted on silver pins, frozen by immersion in liquid nitrogen, and sectioned with the specimen temperature at 133 K and the knife temperature at 273 K. Dry cryo-sections (30-70 nm in thickness) were manipulated on to coated grids and examined the same day. These cryo-sections showed good morphological and cytoplasmic detail, with large areas relatively free of ice-crystal damage. Sections stained either with osmium vapour or negatively stained with silicotungstic acid showed areas with well-preserved mitochondria with granules and endoplasmic reticulum. Unstained sections also showed dense granules (50-120 nm in diameter) in the mitochondria of chondrocytes and preliminary electron probe analysis of these has indicated a Ca/P mass ratio of approximately 1.14. In the longitudinal septa, about 2 micrometer away from the chondrocytes, matrix-vesicle-like particles could be seen with crystal needles inside them. Micro-analysis of two of these gave a Ca/P mass ratio of 1.73 and 2.68. Cryo-ultramicrotomy appears to confirm a number of conclusions derived from conventional ultrastructural study of growth cartilage and suggests for the first time how amorphous calcium phosphate and crystalline apatite can be shown to exist in different organelles in the same cryo-section of the tissue.

Animals↗
PubMed1976

The cellular changes occurring with allografts of marrow-containing cortical bone.

The cell population within and around allografts of fresh, marrow-containing cortical bone has been studied. The grafts were implanted into intramuscular sites in rats and removed at intervals over a 4 week period for examination by light and electron microscopy to establish the sequence of changes at both the tissue and cellular levels. The tissue organization and the ultrastructural appearances of the cells found at different times after grafting are described; the possible relationships of the different cell types to each other and their likely roles in both the immunological and histogenic events are postulated and discussed. A comparison of the observations in the allograft and in the previously studied autograft suggests that the cells from the granulationtissue that become osteoblasts in the autograft differentiate into fibrocytes and giant cells in the allograft. Furthermore, the increased period of initial degeneration observed in the allograft (2 weeks) compared with the autograft (less than 1 week) may represent the destruction of early, graft-derived attempts at osteogenesis. This, together with the relative paucity of new bone in the allograft, suggests that some cells of graft origin may contribute to the early osteogenesis observed in the autograft.

Animals↗
PubMed1975

The evolution of fraction i protein during the origin of a new species of Nicotiana.

The polypeptide composition of Fraction I protein from Nicotiana digluta, a synthetic species which arose by chromosome doubling following the interspecific hybridization of N. glutinosa and N. tabacum, has been examined by isoelectric focusing. The composition of the protein from N. digluta, which was identical to the protein from the infertile F1 hybrid N. glutinosa x N. tabacum, showed 3 polypeptides in the large subunit and 4 polypeptides in the small subunit. The large subunit polypeptides were identical to those from N. glutinosa, the maternal parent in the original hybridization, whereas the small subunit polypeptides were a composite of the small subunit polypeptides from both N. glutinosa and N. tabacum. This analysis demonstrates how the polypeptide composition of Fraction I protein evolves during the origin of new species of Nicotiana.

Biological Evolution↗
PubMed1975

Demineralization of bone matrix: observations from electron microscope and electron-probe analysis.

Displacement or removal of mineral during the processing of calcified tissues for electron microscopy is a recognized phenomenon. An electron microscope analysis has been made of artefactual mineral loss during ultramicrotomy of osteogenic tissue. It is concluded from morphological investigation and the use of electron diffraction that this loss of crystalline mineral during sectioning can considerably change the morphology of calcified tissues and may lead to inaccurate interpretation of cell and matrix morphology. Electron probe X-ray microanalysis has been used to demonstrate in a semi-quantitative manner, the artefactual loss of calcium and phosphorus. Problems of specimen preparation for such analytical work are discussed.

Animals↗
PubMed1975

Polypeptide composition of fraction I protein from Nicotiana glauca and from cultivars of Nicotiana tabacum, including a male sterile line.

The polypeptide compositions of fraction I protein isolated from six collections of Nicotiana glauca and from ten cultivars of N. tabacum, as well as a polyploid series and a male sterile line, have been analyzed by isoelectric focusing in polyacrylamide gel slabs containing 8 M urea. Apart from the male sterile line, none of the plants showed any variation from the species pattern of polypeptides. Fraction I protein from the male sterile Burley 21 cultivar of N. tabacum contained the two small subunit polypeptides of N. tabacum and the three large subunit polypeptides of an Australian species, probably N. megalosiphon. This indicates a changed chloroplast genome in the male sterile line in comparison to the normal fertile N. tabacum.

Genetic Variation↗
PubMed1975

The cellular changes during osteogenesis in bone and bone marrow composite autografts.

Osteogenesis in and around autografts has been studied in the hope of identifying the osteoblast precursor. Fresh autografts of cortical bone with its constituent bone marrow were implanted into intramuscular sites in rats. The grafts were removed at intervals over a four week period and examined by light and electron microscopy. A chronological sequence of degenerative, reparative and differentiative events was found and described. The relative contributions of the host and graft components to post-grafting osteogenesis are discussed and the problem of the origin of the osteoblast cells is examined, taking into account present views about the interrelationships between skeletal connective tissue cells and their precursors. It is concluded that, in the investigation described, the presence of host granulation tissue was necessary for osteogenesis and it is postulated that osteoblast progenitor cells can arise from this granulation tissue, their differentiation along the osteogenic line being stimulated in some way by the presence of the graft bone.

Animals↗
PubMed1973

Mevalonate kinase in green leaves and etiolated cotyledons of the french bean Phaseolus vulgaris.

1. Partially purified preparations of mevalonate kinase were obtained from green leaves and etiolated cotyledons of Phaseolus vulgaris. 2. After removal of interfering polyphenols both enzyme preparations behaved identically on gel filtration, ion-exchange chromatography and density-gradient centrifugation. 3. The kinetic parameters of the preparations from the two sources were indistinguishable. The preparation from etiolated cotyledons had a K(m) of 4.26x10(-5)m for RS-mevalonate and 1.54x10(-3)m for ATP. The preparation from green leaves had a K(m) of 4.55x10(-5)m for RS-mevalonate and 1.75x10(-3)m for ATP. The pH optimum of both enzyme preparations was pH7.0. 4. The effect of inhibitors on the two enzyme preparations was similar, both being inhibited by reagents known to react with thiol groups, and the two preparations had similar inhibitor constants for competitive inhibition by prenyl pyrophosphates. 5. The molecular weight of the enzyme in both preparations was estimated to be 100000; the enzymes from the two preparations had similar mobilities on polyacrylamide-gel electrophoresis.

Carbon Isotopes↗