Platelet sequestration and activation during GalTKO.hCD46 pig lung perfusion by human blood is primarily mediated by GPIb, GPIIb/IIIa, and von Willebrand Factor.

BACKGROUND: Here, we ask whether platelet GPIb and GPIIb/IIIa receptors modulate platelet sequestration and activation during GalTKO.hCD46 pig lung xenograft perfusion. METHODS: GalTKO.hCD46 transgenic pig lungs were perfused with heparinized fresh human blood. Results from perfusions in which αGPIb Fab (6B4, 10 mg/l blood, n = 6), αGPIIb/IIIa Fab (ReoPro, 3.5 mg/l blood, n = 6), or both drugs (n = 4) were administered to the perfusate were compared to two additional groups in which the donor pig received 1-desamino-8-d-arginine vasopressin (DDAVP), 3 µg/kg (to pre-deplete von Willebrand Factor (pVWF), the main GPIb ligand), with or without αGPIb (n = 6 each). RESULTS: Platelet sequestration was significantly delayed in αGPIb, αGPIb+DDAVP, and αGPIb+αGPIIb/IIIa groups. Median lung "survival" was significantly longer (>240 vs. 162 min reference, p = 0.016), and platelet activation (as CD62P and ßTG) were significantly inhibited, when pigs were pre-treated with DDAVP, with or without αGPIb Fab treatment. Pulmonary vascular resistance rise was not significantly attenuated in any group, and was associated with residual thromboxane and histamine elaboration. CONCLUSIONS: The GPIb-VWF and GPIIb/IIIa axes play important roles in platelet sequestration and coagulation cascade activation during GalTKO.hCD46 lung xenograft injury. GPIb blockade significantly reduces platelet activation and delays platelet sequestration in this xenolung rejection model, an effect amplified by adding αGPIIb/IIIa blockade or depletion of VWF from pig lung.

Cross-sectional assessment of apical dye penetration following clinical simulation of various endodontic techniques.

This study compared apical leakage in mesial roots of mandibular molars that resulted from three different instrumentation/obturation techniques performed in a simulated clinical setting: hand instrumentation by nickel-titanium files followed by cold lateral condensation of gutta-percha/sealer; rotary instrumentation followed by the Microseal system of obturation with softened gutta-percha; and rotary instrumentation followed by obturation with the Thermafil system. Lateral condensation generally was measured superior to the Thermafil method for preventing apical dye penetration while no consistent statistical differences were seen between the lateral condensation and Microseal groups.

Effect of estrogen deficiency on skeletal and alveolar bone density in sheep.

BACKGROUND: This study provides a longitudinal assessment of changes in alveolar and skeletal bone mineral density (BMD) in ovariectomized animals. METHODS: Following ovariectomy (OVX) (n = 6) or sham-operation (n = 6) intraoral radiographs were made at 4-month intervals and serum 17-beta-estradiol, osteocalcin, and interleukin (IL)-6, urinary deoxypyridinium, and salivary IL-6, deoxypyridinium, and osteocalcin concentrations were evaluated. Twelve months after surgery, animals were sacrificed and the mandible and radius/ulna removed. Bones were sectioned and radiographed. Mean BMD and cortical thicknesses were calculated from each region. RESULTS: OVX animals had a progressive decrease in serum 17-beta-estradiol, increased serum osteocalcin and IL-6, urinary deoxypyridinium and salivary IL-6, osteocalcin and deoxypyridinium (P < 0.001), suggesting that they were becoming osteoporotic. The BMD of the radius/ulna and mandibular alveolar bone was significantly reduced in OVX animals (P < 0.05 and P < 0.001, respectively). Reduced alveolar bone BMD became evident in OVX animals 6 months after surgery and became more severe during the subsequent 6 months. Alveolar crestal height was also significantly reduced in OVX animals (P < 0.001). These biochemical and density changes preceded a significant reduction in serum 17-beta-estradiol, which occurred between 4 and 8 months following surgery. CONCLUSIONS: Serial measurements of alveolar BMD predicts loss of skeletal BMD in OVX sheep. Changes in alveolar BMD precede estrogen deficiency, suggesting that early signs of reduced BMD may be detected in peri-menopausal women. The presence of biomarkers of bone metabolism within saliva and their correlation with reduced BMD suggests that saliva could be used as an adjunct screening method for assessment of skeletal bone density.

Structure, metallurgy, and mechanical properties of a porous tantalum foam.

This study evaluated a porous tantalum biomaterial (Hedrocel) designed to function as a scaffold for osseous ingrowth. Samples were characterized for structure, Vickers microhardness, compressive cantilever bending, and tensile properties, as well as compressive and cantilever bending fatigue. The structure consisted of regularly arranged cells having struts with a vitreous carbon core with layers of CVI deposited crystalline tantalum. Microhardness values ranged from 240-393, compressive strength was 60 +/- 18 MPa, tensile strength was 63 +/- 6 MPa, and bending strength was 110 +/- 14 MPa. The compressive fatigue endurance limit was 23 MPa at 5 x 10(6) cycles with samples exhibiting significant plastic deformation. SEM examination showed cracking at strut junctions 45 degrees to the axis of the applied load. The cantilever bending fatigue endurance limit was 35 MPa at 5 x 10(6) cycles, and SEM examination showed failure due to cracking of the struts on the tension side of the sample. While properties were variable due to morphology, results indicate that the material provides structural support while bone ingrowth is occurring. These findings, coupled with the superior biocompatibility of tantalum, makes the material a candidate for a number of clinical applications and warrants further and continued laboratory and clinical investigation.

Use of x-ray photoelectron spectroscopy and cyclic polarization to evaluate the corrosion behavior of six nickel-chromium alloys before and after porcelain-fused-to-metal firing.

STATEMENT OF PROBLEM: Nickel-chromium casting alloys rely on a surface oxide layer for corrosion resistance to the oral environment. Porcelain-fused-to-metal (PFM) firing procedures may alter the surface oxides and corrosion properties of these alloys. Changes in alloy corrosion behavior affect metal ion release and therefore local and/or systemic tissue responses. PURPOSE: The aim of this study was to evaluate changes in alloy surface oxides and electrochemical corrosion properties after PFM firing. MATERIAL AND METHODS: The electrochemical corrosion behavior of 6 commercial nickel-chromium alloys was evaluated in the as-cast/polished and PFM fired/repolished states. Surface chemistries of the alloys were analyzed by x-ray photoelectron spectroscopy. RESULTS: Results indicated an increase in corrosion rates after PFM firing and repolishing for alloys containing 14% to 22% Cr and 9% to 17% Mo. This increase in corrosion rates was attributed to a decrease, caused by the PFM and repolishing process, in the Cr and Mo levels in the surface oxides of these alloys. The PFM firing and repolishing process did not alter the corrosion behavior of the alloys containing lower levels of Cr and Mo and/or Be additions in their bulk composition. These alloys exhibited low levels of Cr and Mo surface oxides in both test conditions. Si particles became embedded in the surfaces of the fired alloys during repolishing and may have contributed to the changes in surface oxides and the corrosion behavior of some alloys. CONCLUSION: The effects of PFM firing and repolishing on Ni-Cr dental casting alloy surface oxides and corrosion properties appear to be alloy dependent.

Effect of camera angulation on adaptation of CAD/CAM restorations.

PURPOSE: A significant concern with computer-assisted design/computer-assisted manufacturing (CAD/CAM)-produced prostheses is the accuracy of adaptation of the restoration to the preparation. The objective of this study is to determine the effect of operator-controlled camera misalignment on restoration adaptation. MATERIALS AND METHODS: A CEREC 2 CAD/CAM unit (Sirona Dental Systems, Bensheim, Germany) was used to capture the optical impressions and machine the restorations. A Class I preparation was used as the standard preparation for optical impressions. Camera angles along the mesio-distal and buccolingual alignment were varied from the ideal orientation. Occlusal marginal gaps and sample height, width, and length were measured and compared to preparation dimensions. For clinical correlation, clinicians were asked to take optical impressions of mesio-occlusal preparations (Class II) on all four second molar sites, using a patient simulator. On the adjacent first molar occlusal surfaces, a preparation was machined such that camera angulation could be calculated from information taken from the optical impression. Degree of tilt and plane of tilt were compared to the optimum camera positions for those preparations. RESULTS: One-way analysis of variance and Dunnett C post hoc testing (alpha = 0.01) revealed little significant degradation in fit with camera angulation. Only the apical length fit was significantly degraded by excessive angulation. The CEREC 2 CAD/CAM system was found to be relatively insensitive to operator-induced errors attributable to camera misalignments of less than 5 degrees in either the buccolingual or the mesiodistal plane. The average camera tilt error generated by clinicians for all sites was 1.98 +/- 1.17 degrees.

Evaluation of ergonomic dental stools through clinical simulation.

Work-related musculoskeletal pain occurs commonly within the dental community. Three stool designs were utilized in this study: a standard dental stool, a stool with dual arm supports, and a stool with dual arm supports and chest support. Electromyographic data from four muscle groups were collected on 13 clinicians during a simulated crown preparation procedure. Clinical simulation suggests that a potential musculoskeletal benefit to the clinician exists through utilization of dental stool designs which incorporate static arm supports.

Creeping attachment: autogenous graft vs dermal matrix allograft.

For many years, free autogenous grafts have been used as a method of gaining keratinized tissue around teeth with mucogingival problems. Creeping attachment using autogenous graft material has been actively studied. In addition, biocompatible, acellular connective-tissue material has recently been used as an alternative to free gingival grafts to increase the zone of keratinization. This report presents a patient with bilateral mucogingival defects in the canine and premolar areas. The patient received an autogenous graft on one side and a dermal matrix allograft on the contralateral side. Creeping attachments were measured and compared at 3 months and 12 months after surgery. After 12 months of healing, an average of 1.23 mm of creeping attachment was measured on the free gingival graft side and 0.96 mm of creeping attachment was measured with the dermal matrix allograft.

Betamethasone valerate foam 0.12%: a novel vehicle with enhanced delivery and efficacy.

BACKGROUND: A new topical formulation of betamethasone valerate (BMV) with enhanced dermal penetration has been developed. OBJECTIVE: These studies were designed to evaluate: (1) the relative bioavailability of BMV foam, and (2) the safety and efficacy of BMV foam in the treatment of scalp psoriasis as compared to a lotion formulation of BMV and placebo. METHODS: Safety and efficacy were evaluated in a randomized, multicenter, double-blind, active-and placebo-controlled trial in adult patients with moderate to severe scalp psoriasis. A separate study in 18 patients was conducted to evaluate the potential for suppression of the hypothalamic-pituitary-adrenal (HPA) axis. Relative bioavailability was measured using the human cadaver skin model. RESULTS: 72% of patients using BMV foam were clear or almost clear of disease at the end of 28-days of treatment as judged by the investigator's global assessment of response. Only 47% of BMV lotion patients and 21% of placebo showed a similar level of response. There was no evidence of increased toxicity or HPA-axis suppression for BMV foam, but assessment of relative bioavailability showed BMV penetration into the skin to be more than two-fold greater than from BMV lotion. CONCLUSIONS: A novel foam formulation with enhanced BMV bioavailability has been shown to be of increased efficacy in the treatment of scalp psoriasis without an associated increase in toxicity.

Relaxin stimulates expression of vascular endothelial growth factor in normal human endometrial cells in vitro and is associated with menometrorrhagia in women.

Although the role of the reproductive hormone, relaxin, in rodents is well documented, its potential contribution to human reproduction is less well defined. In this study, we examine the effects of relaxin on human endometrial cells in vitro and describe the clinical effects of relaxin on menstrual flow in women. In cultured endometrial cells, relaxin specifically induces the expression of an angiogenic agent, vascular endothelial growth factor (VEGF). cAMP is implicated as a second messenger involved in VEGF stimulation. VEGF expression is temporally regulated in the endometrium, and our results suggest that relaxin, which is secreted by the corpus luteum and is present in the endometrium during the menstrual cycle and pregnancy, may be involved in regulating endometrial VEGF expression. Relaxin was recently tested in a clinical trial for efficacy in the treatment of progressive systemic sclerosis, and was administered at levels up to 10 times higher than that measured during pregnancy. The most frequent relaxin-related adverse event reported during the course of the study was the onset of menometrorrhagia, defined in this study as heavier-than-usual or irregular menstrual bleeding. The intensification of menstrual flow observed in these patients is consistent with the hypothesis that relaxin mediates neovascularization of the endometrial lining.

Relationship between oral alveolar bone loss and aging among African-American and Caucasian individuals.

BACKGROUND: The periodontal attachment apparatus consists of the periodontal ligament, alveolar bone, cementum and supra-crestal connective tissue. They are interdependent and provide protection and support to the dentition. It is theorized that the integrity of the periodontal apparatus can be maintained throughout life by exercising comprehensive oral hygiene practices and routine dental care. Additionally, it appears to be unaffected by aging. As a consequence, the investigators performed a study to determine the effects of chronological aging on alveolar bone loss. OBJECTIVE: The present study was conducted to determine the relationship between oral alveolar bone loss, oral hygiene, and aging among African-American and Caucasian populations. METHODS: The population consisted of 229 individuals. There were 131 men and 98 women. With respect to race there were 89 African-Americans and 140 Caucasians. Oral examinations, oral hygiene and missing teeth determinations and bitewing radiographs were performed on all the individuals. Radiographs were digitized and measurements were made from the cementum/enamel junction to the alveolar bone crest. Measurements were made for both the maxillary and mandibular jaws. RESULTS: The results of the study showed a significant multiple linear regression model relationship between oral bone loss and aging. Oral hygiene was a factor, but contributed only slightly to the overall model. Race, gender and the number of missing teeth were not significant variables in the overall model. CONCLUSION: The results of this study suggest age-related alveolar bone loss.

Sensitivity of various radiographic methods for detection of oral cancellous bone lesions.

OBJECTIVE: The purpose of this study was to determine the effectiveness in diagnosing cancellous bone defects of the following radiographic methods: conventional film, digitized film, enhanced digitized film, direct digital imaging, enhanced direct digital imaging, digital subtraction, and enhanced digital subtraction. STUDY DESIGN: Mechanical lesions of varying depths were generated beneath cadaver molar and premolar mandibular tooth roots. A portfolio of radiographic images of random types and lesion sizes was presented to 20 clinicians, and their diagnoses were evaluated. RESULTS: Positive identification of lesions was significantly improved by enhanced subtraction radiography over all other forms of radiography for the 4-mm lesions and was better than all forms except enhanced digital radiography and film for the 6-mm lesions. Subtraction radiography and enhanced subtraction radiography significantly reduced false positive diagnoses at all lesion sizes in comparison with the other radiographic methods except enhanced digital radiography at the 6-mm lesion size. CONCLUSIONS: For the methods evaluated, only subtraction radiography and enhanced subtraction radiography can significantly improve the clinician's diagnostic abilities for detection of oral cancellous bone lesions through increased rates for detection of existing defects and, even more importantly, through decreased rates of defect misdiagnosis.

The ATPase activity of Hsp104, effects of environmental conditions and mutations.

Hsp104 is crucial for stress tolerance in Saccharomyces cerevisiae, and both of its nucleotide-binding domains (NBD1 and NBD2) are required. Here, we characterize the ATPase activity and oligomerization properties of wild-type (WT) Hsp104 and of NBD mutants. In physiological ionic strength buffers (pH 7.5, 37 degreesC) WT Hsp104 exhibits Michaelis-Menten kinetics between 0.5 and 25 mM ATP (Km approximately 5 mM, Vmax approximately 2 nmol min-1 microg-1). ATPase activity is strongly influenced by factors that vary with cell stress (e.g. temperature, pH, and ADP). Mutations in the P-loop of NBD1 (G217V or K218T) severely reduce ATP hydrolysis but have little effect on oligomerization. Analogous mutations in NBD2 (G619V or K620T) have smaller effects on ATPase activity but impair oligomerization. The opposite relationship was reported for another member of the HSP100 protein family, the Escherichia coli ClpA protein, in studies employing lower ionic strength buffers. In such buffers, the Km of WT Hsp104 for ATP hydrolysis decreased 10-fold and its stability under stress conditions increased, but the effects of the NBD mutations on ATPase activity and oligomerization remained opposite to those of ClpA. Either the functions of the two NBDs in ClpA and Hsp104 have been reversed or both contribute to ATP hydrolysis and oligomerization in a complex manner that can be idiosyncratically affected by such mutations.

The effect of amalgam overhangs on alveolar bone height as a function of patient age and overhang width.

The purpose of this study was to compare the effects of amalgam restorations with and without overhangs on alveolar bone loss via digitized radiographs for subjects of varying ages and overhang widths. The first phase of this study compared the alveolar bone loss among teeth with clinically acceptable two-surface amalgam restorations with a control surface on the same tooth. The second phase was similar to the first phase with the exception that it compared defective amalgam restorations (those containing amalgam overhanging approximal margins) with the control surface on the same tooth. The collected data showed a significant loss of alveolar bone as a result of amalgam overhang presence (P < 0.02). However, overhang width and patient age did not affect the significance of the detrimental effects of the amalgam overhangs. Overall alveolar bone height was seen to decrease with patient age, independent of amalgam restorations. Digital radiography was seen to be an accurate method for evaluating alveolar bone height changes due to the local environment created by overhanging amalgam margins.

Relaxin binds to and elicits a response from cells of the human monocytic cell line, THP-1.

Relaxin is a 6-kDa peptide of the insulin family that is present at increased levels in the circulation during pregnancy. Its functions at that time are thought to include maintenance of myometrial quiescence, regulation of plasma volume, and release of neuropeptides, such as oxytocin and vasopressin. The protein also promotes connective tissue remodeling, which allows cervical ripening and separation of the pelvic symphysis in various mammalian species. In this report, we provide evidence for a novel target of relaxin, the human monocytic cell line, THP-1. Relaxin bound with high affinity (Kd = 102 pM) to a specific receptor on THP-1 cells. Receptor density was low ( approximately 275 receptors/cell), but binding of relaxin triggered intracellular signaling events. Receptor density was not modulated by pretreatment with estrogen, progesterone, or a number of other agents known to induce differentiation of THP-1 cells. Cross-linking studies showed radiolabeled relaxin bound primarily to cell surface proteins with an apparent molecular mass of >200 kDa. Other members of the insulin-like family of proteins (insulin, insulin-like growth factors I and II, and relaxin-like factor) were unable to displace the binding of relaxin to THP-1 cells, suggesting that a distinct receptor for relaxin exists on this monocyte/macrophage cell line.

Mercury release during autoclave sterilization of amalgam.

Natural teeth are an invaluable teaching tool for preclinical instruction in operative dentistry and endodontic techniques. Cavity preparation in teeth containing amalgam restorations is a realistic simulation of an often experienced clinical situation. As various pathogens are contained in saliva, teeth must be disinfected before use by students. The purpose of this study is to indirectly evaluate whether mercury vapor is released from amalgam restorations in such teeth during steam autoclave sterilization. Mercury vapor detection, sample mass changes and x-ray fluorescence data were collected from experimental steam autoclave sterilization of amalgam samples sealed in autoclave bags. All of the data showed evidence of mercury vapor generation coincident to steam autoclave sterilization. Mercury vapor levels within the room where amalgam was exposed to steam autoclave sterilization reached levels that constitute an unnecessary health risk to dental personnel. The volume of amalgam tested simulated that contained in 175 amalgam restored teeth. Initial venting of the autoclave chamber produced mercury vapor concentrations significantly in excess of OSHA vapor concentration ceiling levels. Thus, the use of a steam autoclave for sterilization of amalgam containing teeth for use in preclinical laboratory exercises may be harmful to personnel involved.

Interrelationship between buffer systems and particle sizes of TCPL drug delivery system.

The specific objective of this investigation is to study the effect of tricalcium phosphate delivery system (TCPL) particle sizes on the final density as well as the delivery profiles of various organic compounds in three different buffer environments. Each TCPL matrices were fabricated using three different particle sizes ranges between 1-38, 45-63 and 63-75 microns. The sintered microcrystal material was impregnated with either progesterone (P, 100 mg each) or bovine serum albumin (BSA, 100 mg each). In phase I of the study, each device was suspended in a serum bottle containing 100 mls of ethanol solution (50% wt/vol.) for P release or 100 mls of PBS (pH 7.4) for BSA release. In phase II, similar capsules were suspended in human plasma instead of standard buffers. The vials were agitated at 100 cycle per minute in a water bath set at 37 degrees C. The amount of P or BSA released from the devices into the buffered medium was measured spectrophotometrically. The results of this investigation revealed that a significant difference in the densities of the devices made from the range of individual particle sizes. The rate of steroid hormone and protein released from the devices made from 1-38 micron particle sizes was slower (p < 0.05) than the rate of delivery of P and BSA released from devices fabricated from either 45-63 or 63-75 micron particles. Regardless of the particle sizes effect the results show that the delivery profiles of BSA was higher than the rate of P. This observation could be attributed to the molecular structure as well as the physiochemical characteristics of the drug. In conclusion the data obtained from this study suggest that: (1) Particle sizes variations influence the density of the TCPL delivery system, (2) the rate of release of organic compounds from the ceramic devices is considerably affected by the physiochemical characteristics of medium or buffer system, and (3) the delivery rate of drugs from TCPL devices is directly proportional to the size of the device initial particles and macropores, and inversely proportional to the number of micropores within each device.