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Biomedical subjects

S W Cox

Publications and source records attributed to S W Cox.

68 records · Page 4Linked to original sources
PubMed1987

Mercury release, distribution and excretion from subcutaneously implanted conventional and high-copper amalgam powders in the guinea pig.

With both types of amalgam there was initial loss of material during healing of the implantation wounds. The rate of Hg release from the healed lesion was estimated by linear regression analysis of the content of implants when removed sequentially over 2 years. There were no significant differences between the amalgams, when expressed in absolute terms or as a percentage of the Hg content of the lesions immediately after healing, probably because gamma 1 (Ag2Hg3) phase breakdown was largely or solely responsible for Hg release with both materials. Hg levels in the blood, liver, renal cortex and faeces were all significantly lower with high-Cu amalgam which might be explained by the interference by Cu with Hg retention. There was no significant difference in urinary Hg excretion by the two groups of animals over the greater part of the study.

Animals↗
PubMed1987

Microscopy and X-ray microanalysis of subcutaneously implanted conventional and high-copper dental amalgam powders in the guinea pig.

With each material, there was only a mild early inflammatory response; particles were taken up by macrophages and giant cells. By 1.5 to 3 months, chronic granulomas had developed. With conventional amalgam, there were early changes in the intracellular material, associated with the rapid degradation of Sn-Hg particles, corresponding to the gamma 2 phase. Thereafter, intracellular particles from both types of amalgam underwent progressive degradation, producing halos of secondary material containing Ag and S. Apart from an initial loss of Cu and Sn from some high-Cu amalgam particles, there were no qualitative differences in the later changes between the two materials, although conventional amalgam particles appeared to degrade faster. With both, vast numbers of fine secondary particles containing Ag and S became widely distributed throughout the lesions and gave rise to macroscopic tattooing of the skin. Secondary material and small degrading primary particles from both types of amalgam were detected in the submandibular lymph nodes where they caused localized staining.

Animals↗
PubMed1987

Preliminary studies on cysteine and serine proteinase activities in inflamed human gingiva using different 7-amino-4-trifluoromethyl coumarin substrates and protease inhibitors.

The cysteine proteinases cathepsins B and L have collagenolytic potential and so have been implicated in connective-tissue breakdown in chronic periodontitis. Synthetic peptide substrates are often used to detect proteolytic enzymes. The action of homogenates of inflamed gingiva tissue against three such substrates of cathepsin B have been characterized here by protease inhibitors. Using the selective reagents ZPheAlaCHN2, BzValLysLysArgAFC, ZAlaArgArgAFC and ZPheArgAFC were susceptible to both cysteine and non-cysteine proteinase activity; the two types of enzymes had acidic and alkaline pH optima, respectively. The action of other inhibitors at acidic pH indicated the involvement of cathepsin B and, to a lesser extent, cathepsin L. The enzyme active at alkaline pH was a serine proteinase; it resembled glandular kallikrein in its inhibitor response and its ability to hydrolyse a fourth substrate, DValLeuArgAFC, but its greater reactivity with BzValLysLysArgAFC and ZAlaArgArgAFC was not consistent with kallikrein. ZPheArgAFC, though less sensitive than BzValLysLysArgAFC to cysteine proteinase action, was far less susceptible to hydrolysis by the serine proteinase and thus appears the best choice for selective assays of cathepsins B and L.

Adult↗
PubMed1987

Renal cortical mercury levels associated with experimental amalgam tattoos: effects of particle size and amount of implanted material.

Powdered dental amalgam that had passed through either a 106 microns or a 45 microns sieve was implanted subcutaneously in guinea pigs for periods of up to 2 yr. The renal cortical mercury levels associated with the 106 microns material were on average 16% of those produced by the 45 microns material. A reduction in the amount of 45 microns powder implanted, by a factor of 75%, resulted in a fall of only 27% in renal mercury concentrations. The marked effect of particle size on mercury release may be explained by the large increase in the proportion of implanted material that was degraded within phagocytic cells in the local lesions.

Animals↗
PubMed1987

Further investigations of the soft tissue reaction to the gamma 1 phase (Ag2Hg3) of dental amalgam, including measurements of mercury release and redistribution.

The subcutaneous implantation in guinea pigs of powdered gamma 1 phase induced a severe initial tissue response and the majority of the material was extruded from the healing wounds. This process was accompanied by the release of significant amounts of mercury which appeared in the body organs and excreta. The small numbers of particles which remained in the tissues were handled quite differently, undergoing slow degradation in macrophages and giant cells in chronic granulomata. Minute secondary particles containing silver and sulphur were deposited in the tissues and gave rise to macroscopic tattooing of the skin above the implants.

Animals↗
PubMed1987

Further investigations of the soft tissue reaction to the gamma 2 phase (Sn7-8Hg) of dental amalgam, including measurements of mercury release and redistribution.

Following the subcutaneous implantation in guinea pigs of powdered gamma 2 phase with a mercury content only slightly greater than that indicated by the stoichiometric formula Sn7Hg, there was a limited initial release of mercury from extracellular material. Thereafter, chronic granulomata developed around the implants and particles degraded slowly in macrophages and giant cells. Vast numbers of fine secondary particles containing tin were produced and these were associated with macroscopic staining. Mercury seemed to be lost as the result of intracellular particle breakdown but it did not accumulate in the body organs or appear to any great extent in the excreta.

Animals↗
PubMed1986

The development of mercury- and selenium-containing deposits in the kidneys following implantation of dental amalgams in guinea pigs.

Examination of light microscopical sections of the kidneys of guinea pigs with chronic exposure to mercury as the result of the breakdown of subcutaneous implants of powdered dental amalgam demonstrated the development of black, refractile deposits in the cytoplasm and nuclei of cells in both the straight and convoluted portions of the proximal tubule. The more numerous cytoplasmic deposits were of a particulate nature with dimensions of approximately 1 microgram. The nuclear deposits, which appeared later but which were relatively more common in longer-term animals, took the form of prominent inclusions, 1 to 3 micrograms in diameter. The ratio of nuclear to cytoplasmic deposits was higher in animals receiving high copper as compared with conventional amalgam. At electron microscopical level, the cytoplasmic deposits were seen to consist of collections of fine particles within lysosomes. Similar deposits were also found in far smaller numbers in lysosomes in collecting duct cells. The nuclear inclusions in proximal tubular cells were made up of closely packed electron dense granules. X-ray microanalysis showed both lysosomal and nuclear deposits to contain mercury and selenium. The association of mercury with selenium, which was present in the animals' diet at low levels, probably aided the microscopical visualisation of the deposits.

Animals↗
PubMed1986

The release, tissue distribution and excretion of mercury from experimental amalgam tattoos.

Following the subcutaneous implantation of powdered dental amalgam in guinea pigs, there was an initial extrusion of material from the healing implantation wounds. Longer-term release of mercury from the lesions was demonstrated by linear regression analysis of the mercury contents of implant sites removed after time periods of up to 2 years. Raised mercury levels were detected in the blood, bile, kidneys, liver, spleen and lungs of implanted animals; by far the highest concentrations were found in the renal cortex. Mercury was excreted with the urine and, to a lesser extent, the faeces. The pattern of mercury redistribution resembled that seen following chronic exposure to mercuric compounds.

Animals↗
PubMedDate not supplied

Protease activities in peri-implant sulcus fluid from patients with permucosal osseointegrated dental implants. Correlation with clinical parameters.

The 15 patients included in this study each had 2-6 permucosal Branemark osseointegrated implants that had functioned successfully for 18 months or more. They were given a full oral examination which included measurements of probing depth and gingival, bleeding and plaque indices around the implants. Marginal bone reduction during the functional life of the implants was estimated from radiographs. At a separate visit, peri-implant sulcus fluid (PISF) was collected on filter paper strips from the deepest probing site of each implant. PISF volumes were measured and the samples eluted into buffer. Protease activities in the eluates were determined by fluorimetric assay with peptidyl derivatives of 7-amino-4-trifluoromethyl coumarin. Enzyme levels followed the order: cathepsin B/L greater than elastase greater than dipeptidyl peptidase IV greater than trypsin-like activity. Total enzyme activities and concentrations both correlated positively with all clinical parameters in linear regression analysis. This was true on both a patient level using mean patient values and a site level using pooled patient data. Nearly all of the site level correlations were statistically significant, though coefficients were generally higher for total enzyme activities than concentrations. Elastase-like activity gave the best overall correlations of the different proteases measured. Amongst the clinical parameters, correlations were generally best with gingival index and bone reduction. Total enzyme activities had good diagnostic specificity and sensitivity as predictors of clinical parameters and the figures were especially high for elastase-like activity as a marker of bone reduction. PISF proteases may thus be of value in monitoring tissue responses to osseointegrated implants.

Adult↗