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BACKGROUND: Tebentafusp demonstrated a superior overall survival (OS) benefit [hazard ratio (HR) 0.51] compared to investigator's choice (82% pembrolizumab) in a randomized, phase III trial (IMCgp100-202; N = 378) in untreated metastatic uveal melanoma (mUM). The 1-year OS rates for tebentafusp and pembrolizumab were 73% and 59%, respectively. In the single-arm GEM1402 (N = 52), the 1-year OS rate for nivolumab plus ipilimumab (N+I) in mUM was 52%. Due to limitations in conducting randomized trials in mUM, we compared OS on tebentafusp or pembrolizumab (IMCgp100-202) to N+I (GEM1402) in untreated mUM using propensity scoring methods. PATIENTS AND METHODS: Analyses were adjusted using propensity score-based inverse probability of treatment weighting (IPTW), balancing age, sex, baseline lactate dehydrogenase (LDH), baseline alkaline phosphatase, disease location, Eastern Cooperative Oncology Group status, and time from primary diagnosis to metastasis. OS was assessed using IPT-weighted Kaplan-Meier and Cox proportional hazard models. Sensitivity analyses using alternative missing data and weights methods were conducted. RESULTS: The primary IPTW analysis included 240 of 252 patients randomized to tebentafusp from IMCgp100-202 and 45 of 52 N+I-treated patients from GEM-1402. Key baseline covariates, including LDH, were generally well balanced before weighting. The IPTW-adjusted OS favored tebentafusp, HR 0.52 [95% confidence interval (CI) 0.35-0.78]; 1-year OS was 73% for tebentafusp versus 50% for N+I. Sensitivity analyses showed consistent superior OS for tebentafusp with all IPTW HRs ≤0.61. IPTW analysis of pembrolizumab versus N+I showed no significant difference in OS (HR 0.72; 95% CI 0.50-1.06). CONCLUSIONS: Tebentafusp was previously shown to provide an OS benefit compared to checkpoint inhibitors or chemotherapy in untreated mUM. Propensity score analysis demonstrated a similar OS benefit for tebentafusp compared with N+I. These data further support tebentafusp as the standard of care in previously untreated human leukocyte antigen (HLA)-A∗02:01+ adult patients with mUM.
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Protocolos de Quimioterapia Combinada Antineoplásica , Melanoma , Nivolumab , Proteínas Recombinantes de Fusión , Neoplasias de la Úvea , Adulto , Humanos , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapéutico , Ipilimumab , Puntaje de PropensiónRESUMEN
The important role of schools in supporting children experiencing bereavement is established, yet less is known about how school curricula include death as part of life and this limits our understanding of the systemic structures that shape children's knowledge and experience of death. To address this gap, this paper discusses an analysis of the Scottish curriculum to explore the extent to which death features in compulsory education for children aged 3 to 15 years. The findings show that whilst death is present across the curricula, certain types of 'knowing' death are promoted, largely situated across religious teaching, which may limit children's engagement with the multiple and complex ways in which death features across individual, social, physical, and relational domains. By integrating the concepts of death systems and death ambivalence, the paper develops new knowledge on the interplay between curricula and sense making around death in children's lives that has practical utility.
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OBJECTIVE: Osteoarthritis (OA) is the most common form of arthritis and a leading cause of disability. OA is characterized by articular chondrocyte deterioration, subchondral bone changes and debilitating pain. One strategy to promote cartilage regeneration and repair is to accelerate proliferation and matrix production of articular chondrocytes. We previously reported that the protein phosphatase Phlpp1 controls chondrocyte differentiation by regulating the activities of anabolic kinases. Here we examined the role of Phlpp1 in OA progression in a murine model. We also assessed PHLPP1 expression and promoter methylation. DESIGN: Knee joints of WT and Phlpp1(-/-) mice were surgically destabilized by transection of the medial meniscal ligament (DMM). Mice were assessed for signs of OA progression via radiographic and histological analyses, and pain assessment for mechanical hypersensitivity using the von Frey assay. Methylation of the PHLPP1 promoter and PHLPP1 expression were evaluated in human articular cartilage and chondrocyte cell lines. RESULTS: Following DMM surgeries, Phlpp1 deficient mice showed fewer signs of OA and cartilage degeneration. Mechanical allodynia associated with DMM surgeries was also attenuated in Phlpp1(-/-) mice. PHLPP1 was highly expressed in human articular cartilage from OA patients, but was undetectable in cartilage specimens from femoral neck fractures (FNFxs). Higher PHLPP1 levels correlated with less PHLPP1 promoter CpG methylation in cartilage from OA patients. Blocking cytosine methylation or treatment with inflammatory mediators enhanced PHLPP1 expression in human chondrocyte cell lines. CONCLUSION: Phlpp1 deficiency protects against OA progression while CpG demethylation and inflammatory cytokines promote PHLPP1 expression.
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Osteoartritis/etiología , Animales , Cartílago Articular , Condrocitos , Desmetilación , Modelos Animales de Enfermedad , Humanos , Inflamación , Ratones , Proteínas Nucleares , Fosfoproteínas FosfatasasRESUMEN
The potato psyllid, Bactericera cockerelli (Sulc) (Hemiptera: Triozidae), and its associated pathogen "Candidatus Liberibacter solanacearum" (Ca. L. solanacearum), the putative causal agent of zebra chip (ZC) disease in potatoes (Solanum tuberosum L.), were sampled in commercial potato fields and untreated control plots for 3 yr in multiple locations in Texas, Kansas, Nebraska, and Colorado. Populations of the potato psyllid varied across years and across potato growing regions. However, the percentage of potato psyllids infected with Ca. L. solanacearum although variable across years, was consistently highest in the Lower Rio Grande Valley of Texas (LRGV), the reported overwintering location for this pest. The numbers of Ca. L. solanacearum-infected psyllids collected on field traps and large nymphs counted on leaf samples were both positively correlated with the final percentage of ZC in tubers. In the LRGV, where vector and disease pressure is the highest, population levels of immature life stages of the psyllid and percentage of ZC differed greatly between commercial and untreated fields. These results show that the pest management program that was used can be effective at controlling development of the psyllid and ultimately reducing the incidence of ZC.
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Alphaproteobacteria/fisiología , Hemípteros/fisiología , Solanum tuberosum/parasitología , Animales , Hemípteros/microbiología , América del Norte , Enfermedades de las Plantas/microbiología , Dinámica Poblacional , Estaciones del Año , Solanum tuberosum/microbiologíaRESUMEN
This paper analyzes the socioeconomic aspects of solid waste management in Rio de Janeiro. An "input-output" methodology was used to examine how the secondary product resulting from recycling is re-introduced into the productive process. A comparative profile was developed from the state of recycling and the various other aspects of solid waste management, both from the perspective of its economic feasibility and from the social aspects involved. This was done analyzing the greenhouse gas emissions and the decreased energy consumption. The effects of re-introducing recycled raw materials into the matrix and the ensuing reduction of the demand for virgin raw materials was based on the input-output matrix for the State of Rio de Janeiro. This paper also analyzes the energy savings obtained from recycling and measures the avoided emissions of greenhouse gases.
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Conservación de los Recursos Energéticos/economía , Modelos Teóricos , Eliminación de Residuos/economía , Condiciones Sociales , Argentina , Ciudades , HumanosRESUMEN
Parathyroid hormone (PTH)-related peptide (PTHrP) can modulate the proliferation and differentiation of a number of cell types including osteoblasts. PTHrP can activate a G protein-coupled PTH/PTHrP receptor, which can interface with several second-messenger systems. In the current study, we have examined the signaling pathways involved in stimulated type I collagen and alkaline phosphatase expression in the human osteoblast-derived osteosarcoma cells, MG-63. By use of Northern blotting and histochemical analysis, maximum induction of these two markers of osteoblast differentiation occurred after 8 h of treatment with 100 nM PTHrP-(1-34). Chemical inhibitors of adenylate cyclase (H-89) or of protein kinase C (chelerythrine chloride) each diminished PTHrP-mediated type I collagen and alkaline phosphatase stimulation in a dose-dependent manner. These effects of PTHrP could also be blocked by inhibiting the Ras-mitogen-activated protein kinase (MAPK) pathway with a Ras farnesylation inhibitor, B1086, or with a MAPK inhibitor, PD-98059. Transient transfection of MG-63 cells with a mutant form of Galpha, which can sequester betagamma-subunits, showed significant downregulation of PTHrP-stimulated type I collagen expression, as did inhibition of phosphatidylinositol 3-kinase (PI 3-kinase) by wortmannin. Consequently, the betagamma-PI 3-kinase pathway may be involved in PTHrP stimulation of Ras. Collectively, these results demonstrate that, acting via its G protein-coupled receptor, PTHrP can induce indexes of osteoblast differentiation by utilizing multiple, perhaps parallel, signaling pathways.
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Diferenciación Celular/efectos de los fármacos , Osteoblastos/efectos de los fármacos , Proteínas/farmacología , Transducción de Señal , Sulfonamidas , Alcaloides , Benzofenantridinas , Northern Blotting , Proteínas Quinasas Dependientes de AMP Cíclico/antagonistas & inhibidores , Proteínas Quinasas Dependientes de AMP Cíclico/metabolismo , Inhibidores Enzimáticos/farmacología , Subunidades alfa de la Proteína de Unión al GTP Gs/genética , Proteínas de Unión al GTP Heterotriméricas/genética , Proteínas de Unión al GTP Heterotriméricas/fisiología , Humanos , Isoquinolinas/farmacología , Proteínas Quinasas Activadas por Mitógenos/antagonistas & inhibidores , Mutación , Osteosarcoma , Proteína Relacionada con la Hormona Paratiroidea , Fenantridinas/farmacología , Fosfatidilinositol 3-Quinasas/metabolismo , Inhibidores de las Quinasa Fosfoinosítidos-3 , Proteína Quinasa C/antagonistas & inhibidores , Proteína Quinasa C/metabolismo , Transfección , Células Tumorales Cultivadas , Proteínas ras/antagonistas & inhibidores , Proteínas ras/metabolismoRESUMEN
BACKGROUND: Guided bone regeneration (GBR) is a viable treatment for osseous defects surrounding dental implants. Controversy exists regarding the choice of barrier membrane used and the method of membrane fixation to achieve GBR. METHODS: This study compared the efficacy of a porcine-derived bioabsorbable collagen membrane and an expanded polytetrafluoroethylene (ePTFE) membrane (non-resorbable) for GBR using a bovine bone xenograft/autograft bone composite in defects surrounding dental implants. The study also examined the effect of primary barrier fixation on GBR. Defect size was recorded at Stage 1 and 2 surgeries (performed 6 months apart). Forty-eight subjects (41% males, 59% females) requiring GBR were treated with either collagen (23) or ePTFE (25) barriers, respectively. Implants were titanium self-tapping screw-type. In 34 GBR sites, barrier fixation was achieved with polylactic acid resorbable pins. The remaining barriers were secured with the implant cover screw and/or embedded beneath the flaps. RESULTS: At 6 months, a decrease in defect width (collagen barrier 1.95 +/- 0.60 mm, ePTFE barrier 2.65 +/- 0.56 mm), length (collagen barrier 2.65 +/- 0.61 mm, ePTFE barrier 2.26 +/- 0.66 mm), and circumference (degrees) (collagen barrier 57.7 +/- 18.7, ePTFE barrier 80.2 +/- 19.9) was observed for both membranes. A significant number (chi2, P = 0.041) of postoperative complications occurred when barrier fixation was lacking at initial surgery. Furthermore, a significant difference (P <0.05) in the success of GBR with respect to defect size was observed when barrier fixation was taken into account. CONCLUSIONS: In conclusion, both collagen and ePTFE barriers proved suitable for achieving GBR of osseous defects surrounding dental implants. The results of this study stress the importance of barrier fixation at the time of initial surgery.
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Pérdida de Hueso Alveolar/etiología , Pérdida de Hueso Alveolar/cirugía , Implantes Dentales/efectos adversos , Regeneración Tisular Guiada Periodontal/métodos , Membranas Artificiales , Implantes Absorbibles , Adulto , Animales , Regeneración Ósea , Sustitutos de Huesos , Bovinos , Distribución de Chi-Cuadrado , Colágeno , Implantación Dental Endoósea/efectos adversos , Fracaso de la Restauración Dental , Femenino , Humanos , Masculino , Minerales , Politetrafluoroetileno , Porcinos , Resultado del TratamientoRESUMEN
Sphingolipids mediate a number of cellular functions in a variety of cell systems. The role they play in osteoblast signaling is yet unknown. This study investigated the effects of epidermal growth factor (EGF) on the levels of ceramide, sphingosine (SPH), and sphingosine-1-phosphate (S1P) in rat calvariae osteoblastic cells, and whether these metabolites mediated cytosolic calcium ([Ca2+]i) mobilization in these cells. EGF significantly (P<0.05) increased the levels of all three sphingolipids, and the phorbol ester PMA partially inhibited these effects. SPH and S1P markedly increased [Ca2+]i levels, with thapsigargin (depletes [Ca2+]i pools) decreasing the response by 60%. Verapamil (calcium channel blocker) only inhibited ceramide's effects on [Ca2+]i. Furthermore, SPH enhanced the EGF' induced increase in [Ca2+]i. This study demonstrates that ceramide, SPH and S1P mediate [Ca2+]i mobilization in rat calvarial osteoblastic cells, and that EGF induces changes in the levels of these metabolites with PKC playing an important role in the mechanisms regulating these events.
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Calcio/metabolismo , Ceramidas/metabolismo , Factor de Crecimiento Epidérmico/farmacología , Osteoblastos/metabolismo , Esfingolípidos/metabolismo , Esfingosina/metabolismo , Animales , Bloqueadores de los Canales de Calcio/farmacología , Células Cultivadas , Citosol/metabolismo , Inhibidores Enzimáticos/farmacología , Colorantes Fluorescentes , Fura-2/metabolismo , Modelos Biológicos , Osteoblastos/efectos de los fármacos , Proteína Quinasa C/metabolismo , Ratas , Ratas Sprague-Dawley , Tapsigargina/farmacología , Verapamilo/farmacologíaRESUMEN
Voltage-activated calcium channels (VACCs) regulate extracellular calcium influx in many cells. VACCs are composed of five subunits. The alpha1 subunit is considered the most important in regulating channel function. Three isoforms of this subunit have been described: skeletal, cardiac, and neuroendocrine. It was the purpose of the present study to determine the molecular identity of the alpha1 subunit of the VACCs in rat calvarial osteoblasts and to study the nature of the regulation of these channels as a function of cellular growth. We also attempted to identify which isoform of the alpha1 subunit of the VACCs mediates the effects of epidermal growth factor (EGF) on osteoblastic cell proliferation. Reverse transcription-polymerase chain reaction was used to detect the isoforms of the VACCs that are expressed in osteoblastic cells. These analyses showed that the proliferative state of the cell and the time in culture influence RNA expression. The only alpha1 subunit detected in osteoblasts corresponds to the cardiac isoform. In additional experiments, the effects of EGF on cytosolic calcium and osteoblast proliferation were determined. For these experiments, the synthesis of the different isoforms of the VACCs was selectively blocked by antisense oligonucleotides prior to EGF stimulation. These studies showed that the cardiac isoform mediates the effects of EGF on cytosolic calcium and cellular proliferation in rat calvarial osteoblasts.
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Canales de Calcio/química , Osteoblastos/metabolismo , Fosfatasa Alcalina/genética , Fosfatasa Alcalina/metabolismo , Animales , Secuencia de Bases , Canales de Calcio/genética , Canales de Calcio/metabolismo , División Celular/efectos de los fármacos , Citosol/metabolismo , Cartilla de ADN/genética , Factor de Crecimiento Epidérmico/farmacología , Regulación de la Expresión Génica , Técnicas In Vitro , Potenciales de la Membrana , Oligonucleótidos Antisentido/farmacología , Conformación Proteica , ARN/genética , Ratas , Ratas Sprague-Dawley , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Cráneo/citología , Cráneo/metabolismoRESUMEN
Ceramide, ceramide-1-phosphate (C1P) sphingosine (SPH) and sphingosine-1-phosphate (S1P) effects on proliferation and extracellular-signal regulated kinases, ERKs (also known as MAPKs), activation were investigated in human and rat osteoblastic cells. MAPK activation was sphingolipid-specific in cells from both species. In human osteoblastic cells, S1P and C1P markedly stimulated ERK2 phosphorylation with a slight increase in phosphorylation of ERK1. SPH nor ceramide induced phosphorylation of either ERK isoform. In rat osteoblastic cells, SIP, ceramide and SPH stimulated phosphorylation of both isoforms. C1P did not induce phosphorylation of ERK1 but produced a mild increase in phosphorylation of ERK2. In human cells, only S1P significantly (P<0.05) increased osteoblastic cell proliferation, while in the rat cells all four sphingolipids significantly (P<0.05) induced proliferation. The calcium channel blocker verapamil blocked (P<0.05) these effects in both cell types. The MAPK inhibitor, PD98059, inhibited (P<0.05) the mitogenic effect of SIP in human cells. In rat cells, PD98059 effects were less substantial but significant for S1P and C1P. This study demonstrates that sphingolipids are mitogens for both human and rat osteoblastic cells with the MAPK pathway and calcium mediating in part these effects in a species specific manner.
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División Celular/efectos de los fármacos , Lisofosfolípidos , Proteínas Quinasas Activadas por Mitógenos/metabolismo , Osteoblastos/efectos de los fármacos , Esfingolípidos/farmacología , Animales , Bloqueadores de los Canales de Calcio/farmacología , Señalización del Calcio/efectos de los fármacos , División Celular/fisiología , Células Cultivadas , Ceramidas/farmacología , Activación Enzimática/efectos de los fármacos , Inhibidores Enzimáticos/farmacología , Flavonoides/farmacología , Humanos , Proteína Quinasa 1 Activada por Mitógenos/metabolismo , Proteína Quinasa 3 Activada por Mitógenos , Proteínas Quinasas Activadas por Mitógenos/antagonistas & inhibidores , Osteoblastos/citología , Osteoblastos/enzimología , Ratas , Esfingosina/análogos & derivados , Esfingosina/farmacología , Verapamilo/farmacologíaRESUMEN
The receptor-mediated activation of phospholipase D (PLD) is a major signaling pathway in several cell systems. This study determined the effects of epidermal growth factor (EGF) on PLD activity in normal rat osteoblastic cells. Primary cultures were obtained from fetal rat calvaria by sequential collagenase digestion and seeded in BGJb media supplemented with 10% fetal calf serum. PLD activity was assayed by the transphosphatidylation reaction in [H3]myristic acid (5 microCi/ml)-labeled cells treated with EGF in the presence of 5% ethanol and measuring the production of phosphatidylethanol (PEtOH). Lipids were extracted and separated by thin-layer chromatography, detected by iodine staining, and the areas of interest were scraped off and transferred to vials for scintillation counting. EGF significantly increased PEtOH production in a dose-dependent manner and at short (10-60 s) and long (up to 30 minutes) incubation periods (p < 0.05). Phosphatidic acid levels were also significantly increased (p < 0.05) compared with unstimulated controls, but the levels were approximately 60% less than those of PEtOH. 4b-phorbol 12-myristate, 13-acetate (PMA) also produced a significant increase in PEtOH levels when compared with unstimulated control cultures, but when PMA was added together with EGF, the production of PEtOH was reduced about 30%. Pretreatment of cells with the protein kinase C (PKC) inhibitor H-7 caused a significant increase in PEtOH levels, compared with cells stimulated with EGF alone. Preincubation of cells with pertussis toxin produced a partial decrease in PEtOH levels. This study demonstrates that EGF activates the PLD signaling cascade in normal rat osteoblastic cells and that the pathway appears to involve, at least in part, a PKC- and Gi protein-dependent mechanism.
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Factor de Crecimiento Epidérmico/farmacología , Osteoblastos/enzimología , Fosfolipasa D/metabolismo , Análisis de Varianza , Animales , Células Cultivadas , Cromatografía en Capa Delgada , Activación Enzimática , Glicerofosfolípidos/metabolismo , Ácidos Fosfatidicos/metabolismo , Proteína Quinasa C/metabolismo , Ratas , Transducción de SeñalRESUMEN
Our previous studies show that epidermal growth factor (EGF) stimulates phospholipase D (PLD)-induced phosphatidic acid (PA) formation in rat calvarial osteoblastic cells. This study investigated the effects of PA on cytosolic calcium ([Ca2+]i) and proliferation, and the possible involvement of the PLD pathway in EGF effects on [Ca2+]i and proliferation in rat calvarial osteoblastic cells. PA markedly increased [Ca2+]i. This response was unaffected by thapsigargin, which depletes [Ca2+]i pools, blocked by verapamil, a calcium channel blocker, and enhanced by propanolol, an inhibitor of PA-phosphohydrolase. PA also reduced the EGF dependent-[Ca2+]i increase by 60%, while a PLD inhibitor blocked these effects. Furthermore, PA significantly increased cell proliferation (P < 0.05) which was inhibited by verapamil and enhanced by H-7 (PKC inhibitor). The PLD inhibitor significantly (P < 0.05) reduced the EGF-induced increase in proliferation. In summary, PA stimulates rat calvarial osteoblastic cell proliferation and mobilization of [Ca2+]i using extracellular pools, and EGF's mitogenic effect on these cells requires activation of PLD.
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Señalización del Calcio/efectos de los fármacos , Factor de Crecimiento Epidérmico/farmacología , Osteoblastos/efectos de los fármacos , Ácidos Fosfatidicos/farmacología , Fosfolipasa D/metabolismo , 1-(5-Isoquinolinesulfonil)-2-Metilpiperazina/farmacología , Animales , Calcio/metabolismo , Bloqueadores de los Canales de Calcio/farmacología , División Celular/efectos de los fármacos , Células Cultivadas , Citoplasma/metabolismo , Osteoblastos/citología , Osteoblastos/metabolismo , Ácidos Fosfatidicos/fisiología , Fosfolipasa D/antagonistas & inhibidores , Propranolol/farmacología , Proteína Quinasa C/antagonistas & inhibidores , Ratas , Ratas Sprague-Dawley , Cráneo/citología , Esfingosina/análogos & derivados , Esfingosina/farmacología , Tapsigargina/farmacología , Verapamilo/farmacologíaRESUMEN
Osteoporosis, an age-related condition, is classified into primary and secondary types. Primary osteoporosis encompasses the postmenopausal and senile types; secondary osteoporosis occurs "secondary" to endocrine and renal diseases. Subjects affected by osteoporosis have an overall reduced bone mass and become highly susceptible to bone fractures. Dual energy x-ray absorptiometry is the method most often used to determine the risk for osteoporotic fractures. In the past decade, a number of studies have suggested a possible correlation between systemic osteoporosis and alveolar bone loss in periodontal disease pathogenesis. It appears that a clear correlation between periodontal health and the general mineral status of the skeleton is still lacking. This review addresses the pathogenesis of osteoporosis and emphasizes the multifactorial nature of bone loss. The current concepts in alveolar bone loss resulting from osteoporosis and its implications as a risk factor in periodontal disease development are also presented.
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Pérdida de Hueso Alveolar/etiología , Osteoporosis/complicaciones , Anciano , Pérdida de Hueso Alveolar/fisiopatología , Calcitriol/fisiología , Citocinas/fisiología , Femenino , Humanos , Masculino , Persona de Mediana Edad , Osteoporosis/etiología , Osteoporosis/genética , Osteoporosis Posmenopáusica/complicaciones , Pérdida de Diente/etiologíaRESUMEN
This study investigated the effects of epidermal growth factor (EGF) on cytosolic calcium ([Ca++]i) levels in rat calvarial osteoblasts, the nature of the regulation of this event, and the role these EGF-induced [Ca++]i changes have in osteoblastic cell proliferation. EGF significantly increased [Ca++]i measured in fura-2-loaded, individual cells. This increase was related to extracellular calcium influx. Activation of protein kinase C(PKC) by pretreating the cells with phorbol esters blocked the EGF-induced increase in [Ca++]i. EGF failed to increase inositol trisphosphate levels measured by high performance liquid chromatographic analysis. However, it did increase inositol bisphosphate and inositol tetrakisphosphate production. The EGF-dependent increase in DNA synthesis was partially blocked by the addition of calcium channel blockers. Therefore, it appears that the mechanism of action of EGF-induced osteoblastic cell proliferation is mediated by changes in [Ca++]i primarily due to extracellular calcium influx.
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Calcio/metabolismo , Factor de Crecimiento Epidérmico/farmacología , Osteoblastos/efectos de los fármacos , Análisis de Varianza , Animales , Calcio/fisiología , Bloqueadores de los Canales de Calcio/farmacología , División Celular/efectos de los fármacos , Células Cultivadas , Cromatografía Líquida de Alta Presión , Citosol/efectos de los fármacos , Citosol/metabolismo , ADN/biosíntesis , Activación Enzimática/efectos de los fármacos , Fura-2/química , Inositol 1,4,5-Trifosfato/metabolismo , Fosfatos de Inositol/metabolismo , Osteoblastos/citología , Osteoblastos/enzimología , Proteína Quinasa C/metabolismo , Ratas , Ratas Sprague-Dawley , Acetato de Tetradecanoilforbol/farmacologíaRESUMEN
The usefulness of subtraction radiography for detecting small changes in crestal bone is dependent upon achieving reproducible geometry between x-ray beam and patient structures when serial radiographs are taken. This study evaluates 2 methods currently employed to maintain geometric correspondence: 1) a stent-based system which rigidly fixes a custom-made stent to the x-ray tube by the use of a rod and 2) an extra-oral system which positions a patient in the x-ray unit by means of ear rods. The projection of a light beam from a fixed subject reference was used to measure the change of the orientation of the reference at 2 different measurement times. The rod-stent system was able to maintain a discrepancy of less than 2 degrees 75% of the time over a time period of 6 months. For the extra-oral system this ranged from 72% to 92% during a 1-month period.
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Pérdida de Hueso Alveolar/diagnóstico por imagen , Proceso Alveolar/diagnóstico por imagen , Radiografía Dental/instrumentación , Humanos , Rayos Láser , Periodontitis/diagnóstico por imagen , Postura , Radiografía Dental/métodos , Reproducibilidad de los Resultados , Stents , Técnica de Sustracción/instrumentaciónRESUMEN
Radiographic frames used for longitudinal studies may be in part unreadable for measuring crestal bone change. Sites may not be present on the film, or the measurement reliability may be compromised because of dissimilar geometry. Several techniques used to address this problem are expensive, time-consuming, and required great skill. For the present study a commercially-available alignment system was simply modified by addition of a reference pin in the bite block, facilitating the repositioning of the film holder for a second exposure. This study determined the ability of the modified instrument to: 1) improve the geometrical correspondence between serial radiographs; and 2) reduce the frequency of missed sites in the film. Two pairs of x-rays were taken for each of 40 subjects, 1 pair with the standard alignment instrument of an assigned site and 1 pair with the modified instrument of the contralateral site. Measurements of alveolar bone height were performed using the "side by side" technique. The modified instrument yielded significantly smaller measurement differences and a significantly better geometrical correspondence than the conventional system (P < 0.05). Also, the modified instrument yielded significantly greater (P < 0.01) readable sites (86%) as compared to the conventional instrument (62%). The simply-modified instrument facilitates the correct interpretation of serial radiographs.
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Pérdida de Hueso Alveolar/diagnóstico por imagen , Proceso Alveolar/diagnóstico por imagen , Radiografía de Mordida Lateral/instrumentación , Resinas Acrílicas , Humanos , Radiografía de Mordida Lateral/métodos , Radiografía de Mordida Lateral/normas , Reproducibilidad de los ResultadosRESUMEN
The aim of this study was to develop a computerized measurement system for analysis of unstandardized serial radiographic images. A new approach for estimating the error associated with the determination of alveolar crest loss is described. The study shows that a difference of 0.87 mm in cemento-enamel junction-crest measurement between unstandardized serial radiographs taken within accepted clinic routine is required for a significant loss in crestal bone height. The ability to detect with significance a difference of less than 1 mm in crestal bone height makes the appropriate use of traditional bite-wing radiographs a useful diagnostic tool for the assessment of periodontal maintenance.