Role of leukotoxin in the phagocytosis and killing of actinobacillus actinomycetemcomitans by localized aggressive periodontitis neutraphils

PLEASE NOTE: This work is protected by copyright. Downloading is restricted to the BU community: please click Download and log in with a valid BU account to access. If you are the author of this work and would like to make it publicly available, please contact [email protected] (M.Sc.D)--Boston University, Henry M. Goldman School of Dental Medicine, 2001 (Periodontology and Oral Biology).Includes bibliographical references (leaves 47-55).Localized Aggressive Periodontitis (LAP), previously called Localized Juvenile Periodontitis (LJP), is a unique form of periodontal disease with circumpubertal onset characterized by bone loss localized to first molars and incisors. In LAP, neutrophils exhibit a number of functional abnormalities such as depressed chemotaxis. Actinobacillus actinomycetemcomitans (A. a.) is a gram-negative capnophilic coccobacillus implicated in the pathogenesis of LAP. A. a. produces an 115KDa heat-labile leukotoxin, which lyses human neutrophils. However, infected patients rapidly produce neutralizing antibody to the leukotoxin (Kalmar et al., 1987), so its role beyond initial colonization is questionable. Previous reports by Kalmar et al., suggested that although neutrophils from LAP patients phagocytose A. a., they do not kill the ingested A. a. normally. The purpose of the study was to investigate the role of leukotoxin in the phagocytosis and killing of A. actinomycetemcomitans. In this study, chemotaxis, phagocytosis and killing were assessed in LAP. Two different strains of A. actinomycetemcomitans were used; a low producer of leukotoxin (Y4), and a high producer of leukotoxin (JP2). Bacteria were either not opsonized or opsonized with control serum, or immune (LAP) serum. The results revealed that overall, chemotaxis of neutrophils among LAP patients was less than 70% of chemotaxis of neutrophils among matched controls. The phagocytosis and killing assay demonstrated that in the presence of serum (Control, or LAP), the percentage of phagocytosing neutrophils was increased, and both sera (Control and LAP) increased killing of A. a by neutrophils. More specifically, in the presence of LAP serum, the percentage of phagocytosing neutrophils, and the number of phagocytosed bacteria were increased for both control neutrophils and LAP neutrophils. The JP2 strain (high leulotoxin) was not phagocytosed as well as strain Y4 (low leukotoxin), suggesting a role for leukotoxin in inhibition of phagocytosis, However, killing of A. a. by neutrophils (Control or LAP) increased with time, regardless of which strain was used. In summary, all LAP patients exhibited neutrophil chemotaxis abnormalities. Both control and LAP neutrophils phagocytosis of JP2 was reduced compared to Y4, but no abnormality of killing of either strain by LAP neutrophils was demonstrable

Bone Lid Technique Using a Piezoelectric Device for the Treatment of a Mandibular Bony Lesion

Different techniques for the enucleation of jaw cyst lesion in the oral and maxillofacial regions have been proposed, including the bone lid technique. The purpose of this case report is to describe the case of a cystic lesion, approached with the bone lid technique performed using a piezoelectric device, with an 8-month clinical and radiographic follow-up. A 14-year-old male patient was treated for a suspicious lesion detected on a panoramic radiograph. The concerned area was surgically accessed, and a radiographically predetermined bony window was drawn, and the beveled bony lid was removed. The underlying lesion was enucleated and sent for pathology as a routine procedure, and the removed bony lid was repositioned in situ and secured with a collagen tape. Healing was uneventful with limited swelling and reduced pain. A complete radiographic bone healing at the previously diseased site was confirmed with an 8-month cone beam computed tomography (CBCT) scan with no buccal bone resorption nor ridge collapse. The bone lid technique with a piezoelectric device was noninvasive and atraumatic in this case. Further studies are needed and could lead to the adaptation of this approach as a possible standard of care

Physicochemical Characteristics of Bone Substitutes Used in Oral Surgery in Comparison to Autogenous Bone

Bone substitutes used in oral surgery include allografts, xenografts, and synthetic materials that are frequently used to compensate bone loss or to reinforce repaired bone, but little is currently known about their physicochemical characteristics. The aim of this study was to evaluate a number of physical and chemical properties in a variety of granulated mineral-based biomaterials used in dentistry and to compare them with those of autogenous bone. Autogenous bone and eight commercial biomaterials of human, bovine, and synthetic origins were studied by high-resolution X-ray diffraction, atomic absorption spectrometry, and laser diffraction to determine their chemical composition, calcium release concentration, crystallinity, and granulation size. The highest calcium release concentration was 24. 94 mg/g for Puros and the lowest one was 2.83 mg/g for Ingenios β-TCP compared to 20.15 mg/g for natural bone. The range of particles sizes, in terms of median size D50, varied between 1.32 μm for BioOss and 902.41 μm for OsteoSponge, compared to 282.1 μm for natural bone. All samples displayed a similar hexagonal shape as bone, except Ingenios β-TCP, Macrobone, and OsteoSponge, which showed rhomboid and triclinic shapes, respectively. Commercial bone substitutes significantly differ in terms of calcium concentration, particle size, and crystallinity, which may affect their in vivo performance

Electrical Behavior of Vertical Pt/Au Schottky Diodes on GaN Homoepitaxy

International audienceSchottky barrier diodes on GaN on GaN substrates are fabricated for the purposeof material and technology characterization. The epitaxial layers are grown byMOCVD. I–V measurements as a function of the temperature in the range80–480 K show ideality factor (n) and barrier height (ϕB) variations not following athermionic (TE) model. Consequently, barrier height fluctuations are considered.In the temperature range 280–480 K, an average barrier height of 1.31 eV with arelatively large standard deviation (σ) of 0.15 eV is extracted using this model. Then(T ) variation is also analyzed in order to extract the field sensibility of 1) themean barrier height variation (ρ2 = -0.1) and 2) the barrier height standarddeviation (ρ3 = -15mV). The corrected Richardson plot usingϕB and σ values islinear and gives a Richardson constant of 31.5 A cm² K² close to the theoreticalvalue of 26.4 A cm² K². For a deeper understanding of ϕB fluctuation origins,micro-Raman mapping of the epitaxial layers and deep-level transient spectroscopy(DLTS) are used. μ-RS mappings show compressive strain for diodeshaving suffered electrical breakdown. DLTS analysis shows the presence of ninelevels whose signatures are extracted and nature discussed

Micro-Raman characterization of vertical GaN Schottky and PN diodes

In this work, measurements from Cathodo-Luminescence (CL), micro-Raman spectroscopy and Breakdown Voltage (BV) have been coupled to assess the effects of physical parameters such as threading dislocations and effective doping level homogeneity on the electrical performances of vertical GaN Schottky and PN diodes. Two different substrates from Saint Gobain Lumilog and Sumitomo Electric with different threading dislocation densities have been compared