Biomedical subjects

J M Ferrier

Publications and source records attributed to J M Ferrier.

At least 19 recordsLinked to original sources

PubMed1997

Evidence of ectokinase-mediated phosphorylation of osteopontin and bone sialoprotein by osteoblasts during bone formation in vitro.

Osteopontin (OPN) and bone sialoprotein (BSP) are phosphorylated glycoproteins that, together with osteonectin/secreted protein, acidic, rich in cysteine (SPARC) and osteocalcin, comprise the major non-collagen proteins of bone. Although phosphorylation of OPN and BSP, which is known to influence the biological properties of these proteins, has been shown to occur intracellularly, recent studies have demonstrated ectokinase activity in bone cell populations [Mikuni-Takagaki, Kakai, Satoyoshi, Kawano, Suzuki, Kawase and Saito (1995) J. Bone Miner. Res. 10, 231-241]. To determine whether OPN and BSP are phosphorylated by ectokinase activity we have used [gamma-32P]ATP and [gamma-32P]GTP as cell-impenetrable phosphate donors to analyse for ectokinase activity in osteoblastic UMR106.06 cells and fetal rat calvarial cells (FRCCs). By pulse-labelling confluent cells with radiolabelled nucleotides, the phosphorylation of endogenous and exogenously added OPN and BSP was demonstrated together with the labelling of a number of cell surface proteins. These phosphorylation reactions were inhibited by a cell-impermeable ectokinase inhibitor, K252b, and cell surface phosphorylation was also inhibited by exogenously added OPN and BSP substrates, indicating competition for the ectokinase enzyme. However, phosphorylation of OPN and BSP, both of which can mediate cell attachment through Arg-Gly-Asp (RGD) motifs, was not inhibited by an RGD peptide, suggesting that binding of OPN and BSP to cell surface integrins is not required. In similar experiments, ectokinase-mediated phosphorylation of OPN and BSP was demonstrated during mineralized tissue formation by FRCCs in vitro. These studies demonstrate that OPN and BSP secreted by bone cells are phosphorylated by a casein kinase II-like ectokinase present on the surface of osteoblastic cells.

Animals↗

PubMed1989

Studies on the alignment of fibroblasts in uniform applied electrical fields.

Uniform electrical fields have been applied to human gingival fibroblasts by means of uniform ionic currents passed through a thin chamber. Cells were observed to align in fields between 0.1 and 1.5 V/mm but did not display directed motion toward the anode or the cathode of the chamber. Statistical analysis of directional data was used to distinguish threshold levels of orientation at low field intensities, to quantify the dependence of alignment on time and field intensity, and to analyze differences between alignment of cells treated with the Ca2+ transport modifiers A23187, verapamil, and lanthanum. Alignment occurred at a steady rate and was dependent in a saturating fashion on field strength. The Ca2+ ionophore A23187 had a significant inhibitory effect on cell alignment in applied electrical fields; however, the Ca2+ channel blockers lanthanum and verapamil did not have a significant effect on alignment.

Biological Transport↗

PubMed1988

Analysis of the diffusion theory of negative capacitance: the role of K+ and the unstirred layer thickness.

The diffusion theory of negative capacitance is extended to take into account potassium transport as well as proton or hydroxyl transport. It is shown that both the capacitance spectrum and the frequency at which the capacitance is zero can be used to experimentally test the theory. The effects of the fraction of potassium current, membrane conductance, NaCl concentration, and unstirred layer thickness on these two characteristics is investigated. Maximum negative capacitance can be obtained when the current flowing through the membrane is mainly carried by protons, the membrane conductance is high, the solution conductivity is low, and the unstirred layer thickness is large. The effect of a dominant hydroxyl transport in place of a proton transport is also discussed. We suggest simple experiments to test the theory on Characeaen plant cells.

Cell Membrane↗

PubMed1988

Collagen remodelling in rat periodontal tissues: compensation for precursor reutilization confirms rapid turnover of collagen.

Measurement of collagen turnover is complicated by the reutilization of isotopic precursors used to label the collagen. In an earlier study a novel approach was used to circumvent the problems of precursor recycling and unusually short half-lives were determined for collagen in adult rat periodontal tissues (Sodek, 1977). To verify these results we have used an alternate procedure devised by Poole (1971) in which the decay profile for the radiolabelled protein is corrected in accordance with the decay of the radiolabelled precursor. In this manner real half-lives for mature, neutral salt-insoluble collagen were determined as 3 days in the molar periodontal ligament, 6 days in the continuously erupting incisor ligament and approximately 10 days in the lamina propria of the gingiva, compared to apparent half-lives for these tissues of 6, 12 and approximately 20 days, respectively. The values calculated for actual half-lives are, therefore, approximately two-fold faster than values determined without compensating for reutilization, a difference that is in agreement with other protein turnover studies in which the effects of precursor reutilization have been measured. Although the real half-lives determined in this study indicate turnover rates for the periodontal tissues that are slightly slower than reported previously, the relative differences between the tissues in the rates of collagen turnover are similar. Moreover, the study confirms the existence of a remarkably high rate of collagen remodelling in these tissues.

Animals↗

PubMed1987

Voltage-Dependent K-Channel in Protoplasmic Droplets of Chara corallina: A Single Channel Patch Clamp Study.

Passive transport of potassium through the plasma membrane of a protoplasmic droplet isolated from large internodal cells of Chara corallina Klein ex Willd., em, R.D.W. has been investigated using the patchclamp technique. When the membrane is hyperpolarized the conductance of a single K(+)-channel is of the order of magnitude of 100 picoSiemens and is reduced by tetraethylammonium chloride. Its open time is voltage dependent. This voltage-dependent K(+)-channel displays rectifying properties. The channel density is about 0.1 channel per square micrometer of membrane. When the membrane is depolarized the conductance of a single channel is of the order of magnitude of 30 picoSiemens and is insensitive to tetraethylammonium chloride. These results suggest that K(+)-channels are incorporated in the plasma membrane during membranogenesis of a protoplasmic droplet. They constitute further evidence for the existence of voltage-dependent K(+)-channels in plant cells.

Journal Article↗

PubMed1986

Correlation of collagenolytic enzymes and inhibitors in gingival crevicular fluid with clinical and microscopic changes in experimental periodontitis in the dog.

The quadrants of the jaw in 2 beagle dogs had various forms of periodontal disease induced by ligatures placed around second, third and fourth premolars in one quadrant and, 2.5 months later, around the same teeth in a second quadrant; gingivitis was allowed to develop in a third quadrant after 4 months; the fourth quadrant served as a healthy control. Crevicular fluid flow, plaque index, gingival index, attachment levels and recession were determined at intervals and collagenolytic activity measured in the fluid. The dogs were killed after 5 months and sections of each site prepared for histomorphometry. Clinically-inflamed and degenerating sites had significantly higher collagenolytic activities (p less than 0.001), lower collagenase inhibitor activities and greater fluid flow than control sites which showed abundant inhibitor activity and minimal active enzyme. Periodontitis sites had higher active enzyme, compared to latent enzyme activities, whereas latent collagenase was predominant in control and gingivitis sites. The collagenolytic activities in periodontitis sites fluctuated with time, suggesting a cyclical pattern. Active enzyme activities correlated strongly with gingival crevicular fluid flow and attachment loss. Periodontitis sites had much more inflammatory-cell infiltration than control and gingivitis sites (p less than 0.001). Thus periodontal disease may be monitored by examination of crevicular fluid collagenolytic enzymes, inhibitors and fluid flow, and these criteria may prove more meaningful than current clinical criteria.

Animals↗

PubMed1986