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D. A. Clark - One of the best experts on this subject based on the ideXlab platform.

  • Tumor necrosis factor-alpha mRNA-positive cells in spontaneous Resorption in rodents
    American journal of reproductive immunology (New York N.Y.: 1989), 1998
    Co-Authors: R G Lea, S Mcintyre, J D Baird, D. A. Clark
    Abstract:

    PROBLEM: It has been proposed that high rates of Resorption/spontaneous abortion may result from interaction in the decidua of gamma-interferon-producing natural killer (NK) cells and tumor necrosis factor (TNF)-alpha-producing macrophages. An increased release of TNF-alpha from placental tissue of Resorptions has been reported, but macrophages producing TNF-alpha have so far not been demonstrated at the feto-maternal interface. Therefore, we have sought to identify TNF-alpha-producing cells by in situ hybridization at the feto-maternal interface in two inbred, well-characterized, and stable strains of laboratory rodents with high and low Resorption rates. METHOD OF STUDY: Pregnant DBA/2-mated CBA/J mice with a Resorption rate of 20% to 30% (dependent on NK cells and macrophages) and diabetes-resistant Bio-Breeding/Edinburgh (DR-BB/E) rats with low Resorption rates (presumed to result from chromosomal abnormalities) were studied. AsialoGM1+ cells were detected by immunohistochemistry, and TNF-alpha mRNA+ cells were detected by in situ hybridization. RESULTS: TNF-alpha mRNA+ cells were detected in DBA/2-mated CBA/J mice at the time of Resorption but only at the trophoblast-decidual junction. AsialoGM1+ cells were present in decidua, as assessed by immunohistochemistry, but few if any gave a positive signal for TNF-alpha. In rat Resorptions, TNF-alpha mRNA-positive cells were present within the yolk sac and in contact with the trophoblast, but not at the trophoblast-decidual junction. In neither species did a significant accumulation of detectable TNF-alpha mRNA+ cells occur before the usual time of onset of Resorption. CONCLUSIONS: In the DBA/2-mated CBA/J mouse, the removal of the placenta is associated with removal of a thin rim of adherent decidua similar to the location of the TNF-alpha mRNA+ cells detected in this study. Our data suggest that increased TNF-alpha in tissues associated with failing feto-placental units may arise from infiltration/activation of scavenger cells from decidua that are likely to be macrophages. Local TNF-alpha production in decidua, which occurs as a prelude to Resorption in the CBA x DBA/2 model, could not be detected due to the insensitivity of the TNF-alpha probe we used; the release of TNF-alpha from decidual tissue left after the removal of the placenta does not differ between resorbing and healthy implant sites. AsialoGM1+ cells did not seem to be major producers of TNF-alpha. TNF-alpha mRNA+ cells in a low rate of Resorption (rat) model were only found on the fetal side of the trophoblast, and they may also represent a macrophage response (to dying embryo tissue) derived from a nondecidual source. The location of TNF-alpha mRNA+ cells may identify distinct and different mechanisms of Resorption in rodents.

David W. Dempster - One of the best experts on this subject based on the ideXlab platform.

  • zinc is a potent inhibitor of osteoclastic bone Resorption in vitro
    Journal of Bone and Mineral Research, 2009
    Co-Authors: Baljit S Moonga, David W. Dempster
    Abstract:

    It is well established that zinc, an essential trace element, plays an important role in growth and stimulates bone formation. However, the effects or zinc on bone resorptiion have received little attention. We studied its effects on isolated rat osteoclasts. Unexpectedly, osteoclasts were exquisitely sensitive to zinc, with a significant decrease in bone Resorption occurring at concentrations as low as 10 -14 M. This effect was specific for zinc and was not observed with the other transitional or alkaline metals studied. There was no evidence of toxicity at concentrations up to 10 -4 M. Zinc also completely abolished the stimulatory effect of parathyroid hormone. Zinc is therefore a highly potent and selective inhibitor of osteoelastic bone Resorption in in vitro. The mode of action remains to be established and may represent a novel inhibitory mechanism in the osteoclast

  • Localization of Rat Cathepsin K in Osteoclasts and Resorption Pits: Inhibition of Bone Resorption and Cathepsin K-Activity by Peptidyl Vinyl Sulfones
    Biological Chemistry, 1999
    Co-Authors: J. M. Kilb, V Breuil, Alex Lipyansky, L. S. Stein, J. T. Palmer, David W. Dempster, Zhenqiang Li, Dieter Brömme
    Abstract:

    We have localized cathepsin K in rat osteoclasts and within exposed Resorption pits by immuno-fluorescence microscopy. Intracellular staining using an antibody raised against recombinant mouse cathepsin K was vesicular and uniformly distributed throughout the cell. Confocal microscopy analysis did not reveal an accumulation of cathepsin K containing vesicles opposing the ruffled border and the Resorption lacuna. Exposed Resorption pits exhibited a uniform distribution of cathepsin K, and no differences were observed between the edges and the centers of the pits. The immunostaining of Resorption pits with anti-cathepsin K antibodies demonstrates that the protease is secreted into the sub-osteoclastic compartment. Cathepsin K-specific inhibition using peptidyl vinyl sulfones as selective cysteine protease inactivators reduced bone Resorption by 80% in a dose-dependent manner at sub-micromolar concentrations. No reduction of bone Resorption was observed at those low concentrations using a potent cathepsin L, S, B-specific inhibitor. That the inhibition of bone Resorption can be attributed to cathepsin K-like protease inhibition was corroborated by the selective inhibition of the osteoclastic Z-Gly-Pro-Arg-MbetaNA hydrolyzing activity by the cathepsin K, L, S, B-inhibitor, but not by the cathepsin L, B, and S inhibitor. Z-Gly-Pro-Arg-MbetaNA is efficiently hydrolyzed by cathepsin K but only poorly by cathepsins L, S, and B. On the contrary, the intracellular hydrolysis of the cathepsin B-specific substrate, Z-Arg-Arg-MbetaNA, was prevented by both types of inhibitors. The identification of cathepsin K in Resorption pits and the inhibition of bone Resorption and intracellular cathepsin K activity by selective vinyl sulfone inhibitors indicate the critical role of the protease in osteoclastic bone Resorption.

Conor Durak - One of the best experts on this subject based on the ideXlab platform.

  • internal root Resorption a review
    Journal of Endodontics, 2010
    Co-Authors: S Patel, Domenico Ricucci, Conor Durak
    Abstract:

    Abstract Introduction Internal root Resorption is the progressive destruction of intraradicular dentin and dentinal tubules along the middle and apical thirds of the canal walls as a result of clastic activities. Methods The prevalence, etiology, pathogenesis, histologic manifestations, differential diagnosis with cone beam computed tomography, and treatment perspectives involved in internal root Resorption are reviewed. Results The majority of the documentation that exists in the literature is in the form of case reports, and there are only a limited number of studies that attempted to examine the histologic manifestations and biologic aspects of the disease. This might be due, in part, to the relatively rare occurrence of this type of Resorption and the lack of an in vivo model, apart from the previous attempt on the use of diathermy, to predictably reproduce the condition for study. From a histologic perspective, internal root Resorption is manifested in one form that is purely destructive, internal (root canal) inflammatory Resorption, and another that is accompanied by repair, internal (root canal) replacement Resorption that is featured by the deposition of metaplastic bone/cementum-like tissues adjacent to the sites of Resorption. Conclusions From a differential diagnosis perspective, the advent of cone beam computed tomography has considerably enhanced the clinician's capability of diagnosing internal root Resorption. Nevertheless, root canal treatment remains the treatment of choice for this pathologic condition to date.

A. Qualtrough - One of the best experts on this subject based on the ideXlab platform.

  • Resorption: part 2. Diagnosis and management
    British Dental Journal, 2013
    Co-Authors: J. Darcey, A. Qualtrough
    Abstract:

    Provides an overview of the clinical indicators of root Resorption. Explains the role of modern imaging in classifying resorptive lesions. Discusses the management of Resorption considering classification and aetiology. Provides algorithms for practitioners to follow when considering the diagnosis and management of Resorption. In this second paper the clinical indicators of root Resorption and their diagnosis and management are considered. While the clinical picture can be similar, pathological processes of Resorption vary greatly from site to site and this paper proposes appropriate approaches to treatment for teeth that are affected by Resorption.

  • Resorption: part 1. Pathology, classification and aetiology
    British Dental Journal, 2013
    Co-Authors: J. Darcey, A. Qualtrough
    Abstract:

    This paper will explore the pathological process involved in dental Resorption as well as its classifications and aetiology. The second subsequent paper will look at its diagnosis and management. Explains the pathological process involved in dental Resorption. Discusses the classification of differing resorptive lesions. Highlights the most common stimuli to Resorption.

  • Resorption: part 2. Diagnosis and management
    British Dental Journal, 2013
    Co-Authors: J. Darcey, A. Qualtrough
    Abstract:

    In this second paper the clinical indicators of root Resorption and their diagnosis and management are considered. While the clinical picture can be similar, pathological processes of Resorption vary greatly from site to site and this paper proposes appropriate approaches to treatment for teeth that are affected by Resorption.

Keith T Killingbeck - One of the best experts on this subject based on the ideXlab platform.

  • 14 – Nutrient Resorption
    Plant Cell Death Processes, 2004
    Co-Authors: Keith T Killingbeck
    Abstract:

    Publisher Summary Resorption in an individual plant or plant population can vary significantly from year to year. The plants often resorb amounts of nutrients lower than amounts that could be resorbed under optimum conditions. This chapter introduces two quantitative models—model I for potential Resorption and model II for realized Resorption—that serve as a framework for an analysis of the mechanisms controlling Resorption of nutrients. Unlike realized Resorption that can vary widely from year to year, potential Resorption remains more fixed during the lifetime of a plant. It is essentially an evolved, nutrient-specific set-point, the magnitude of which is ultimately determined for each nutrient by biochemical limitations. These biochemical limitations prevent complete evacuation of a nutrient from a senescing leaf. Of all the parameters that have an impact on nutrient Resorption, the nine that appear to be most strongly linked to the realized Resorption in empirical studies, and/or in theory, constitute the determinants of realized Resorption presented in model II. These determinants are of particular significance to the understanding of changes in realized Resorption because they themselves are susceptible to significant year-to-year variation. The chapter discusses all parameters in brief.

  • nutrients in senesced leaves keys to the search for potential Resorption and Resorption proficiency
    Ecology, 1996
    Co-Authors: Keith T Killingbeck
    Abstract:

    Analyses of nitrogen and phosphorus in the senesced leaves of 89 species of deciduous and evergreen woody perennials were used (1) to discover the limits of ultimate potential Resorption (maximal withdrawal of nutrients from senescing leaves), (2) to determine a means by which Resorption can be categorized as complete or incomplete, (3) to develop the concept of Resorption proficiency (measured as the levels to which nutrients have been reduced in senesced leaves), (4) to compare Resorption in evergreen vs. deciduous species, (5) to assess the impact of phylogeny on Resorption, (6) to compare Resorption in actinorhizal vs. non—nitrogen—fixing species, and (7) to consider the efficacy of using multiple measures of Resorption to answer questions regarding the function and evolution of this process, rather than relying solely on analyses of Resorption efficiency (percentage reduction of nutrients between green and senesced leaves). Concentrations of 0.3% nitrogen and 0.01% phosphorus in senesced leaves represent ultimate potential Resorption of these nutrients in woody perennials. Resorption proficiency and potential Resorption were quantitatively defined in two models that describe both Resorption that is maximal and biochemically complete, and that which is not. Resorption is highly proficient in plants that have reduced nitrogen and phosphorus in their senescing leaves to concentrations below 0.7% and 0.05%, respectively. An important feature of knowing the levels to which nutrients can be reduced in senescing leaves is that these values offer an objective gauge by which to measure the success of Resorption as a nutrient conservation mechanism. Evergreens were significantly more proficient at resorbing phosphorus than were deciduous species (0.045% vs. 0.067% P in senesced leaves, respectively) and plants capable of symbiotic nitrogen fixation were significantly less proficient at resorbing nitrogen than were nonfixers (1.6% vs. 0.9% N in senesced leaves, respectively). Resorption proficiency appeared to parallel some phylogenic trends, yet the influence of phylogeny was not so significant as to overwhelm the effects of recent selection. The ability of plants to reduce nitrogen in senescing leaves was significantly correlated with their ability to reduce phosphorus. Measurement and analysis of Resorption proficiency, when coupled with concurrent consideration of potential Resorption and Resorption efficiency, should facilitate and expedite the ongoing attempt to resolve complex questions regarding the environmental constraints that influence Resorption, and the selection pressures that have directed the evolution of this process.