Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 82
Filtrar
1.
Int Rev Neurobiol ; 160: 223-250, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-34696874

RESUMEN

Adolescence is a critical period for brain development and behavioral maturation, marked by increased risk-taking behavior and the initiation of drug use. There are significant changes in gray matter volume and pruning of synapses along with a shift in excitatory to inhibitory balance which marks the maturation of cognition and decision-making. Because of ongoing brain development, adolescents are particularly sensitive to the detrimental effects of drugs, including alcohol, which can cause long-lasting consequences into adulthood. The extended amygdala is a region critically implicated in withdrawal and negative affect such as anxiety and depression. As negative affective disorders develop during adolescence, the effects of adolescent alcohol exposure on extended amygdala circuitry needs further inquiry. Here we aim to provide a framework to discuss the existing literature on the extended amygdala, the neuroadaptations which result from alcohol use, and the intersection of factors which contribute to the long-lasting effects of this exposure.


Asunto(s)
Amígdala del Cerebelo , Etanol , Glutamatos , Transducción de Señal , Adolescente , Amígdala del Cerebelo/efectos de los fármacos , Amígdala del Cerebelo/fisiopatología , Etanol/toxicidad , Glutamatos/efectos de los fármacos , Glutamatos/fisiología , Humanos , Transducción de Señal/efectos de los fármacos
2.
Neuropsychopharmacology ; 45(8): 1306-1315, 2020 07.
Artículo en Inglés | MEDLINE | ID: mdl-32268346

RESUMEN

Adolescent alcohol exposure increases the risk of developing alcohol use disorders (AUDs), yet the mechanisms responsible for this vulnerability remain largely unknown. One potential target for alcohol-induced changes is the circuitry that modulates negative affect and stress, two sexually dependent drivers of alcohol relapse. The bed nucleus of the stria terminalis (BNST) is a sexually dimorphic region that critically regulates negative affective- and stress-induced relapse. Group I metabotropic glutamate receptors (mGluR) are a target of interest due to their regulation of stress, anxiety behaviors, and BNST plasticity. The current studies investigate sex-dependent sensitivity to the effects of adolescent intermittent ethanol vapor exposure (AIE) on negative affect during acute and protracted alcohol withdrawal and following stress in adulthood. This work also assessed whether BNST group I mGluR-mediated long-term depression (LTD) was disrupted at these timepoints. During acute withdrawal, AIE altered LTD induced by the group I mGluR antagonist DHPG in females, but not males. During adulthood, stress unmasked persistent changes in DHPG-induced LTD and behavior that were not present under basal conditions. Females with an AIE history demonstrated enhanced negative affective-like behavior in the novelty-induced hypophagia test following restraint stress-a phenotype that could be blocked with systemic mGluR5 allosteric antagonism via MTEP. Conversely, males with an AIE history demonstrated elevated freezing in a contextual fear conditioning paradigm. These studies demonstrate long-lasting, sex-dependent phenotypes produced by AIE and suggest pharmaceutical interventions for alcohol use and comorbid disorders may be more effective if designed with sex differences in mind.


Asunto(s)
Alcoholismo , Núcleos Septales , Adolescente , Adulto , Consumo de Bebidas Alcohólicas , Etanol , Femenino , Humanos , Masculino , Caracteres Sexuales
3.
Int J Equity Health ; 16(1): 21, 2017 01 18.
Artículo en Inglés | MEDLINE | ID: mdl-28100226

RESUMEN

BACKGROUND: Economic burden to households due to out-of-pocket expenditure (OOPE) is large in many Asian countries. Though studies suggest increasing household poverty due to high OOPE in developing countries, studies on association of multidimensional poverty and household health spending is limited. This paper tests the hypothesis that the multidimensionally poor are more likely to incur catastrophic health spending cutting across countries. DATA AND METHODS: Data from the Poverty and Vulnerability Assessment (PVA) Survey carried out by the International Center for Integrated Mountain Development (ICIMOD) has been used in the analyses. The PVA survey was a comprehensive household survey that covered the mountainous regions of India, Nepal and Myanmar. A total of 2647 households from India, 2310 households in Nepal and 4290 households in Myanmar covered under the PVA survey. Poverty is measured in a multidimensional framework by including the dimensions of education, income and energy, water and sanitation using the Alkire and Foster method. Health shock is measured using the frequency of illness, family sickness and death of any family member in a reference period of one year. Catastrophic health expenditure is defined as 40% above the household's capacity to pay. RESULTS: Results suggest that about three-fifths of the population in Myanmar, two-fifths of the population in Nepal and one-third of the population in India are multidimensionally poor. About 47% of the multidimensionally poor in India had incurred catastrophic health spending compared to 35% of the multidimensionally non-poor and the pattern was similar in both Nepal and Myanmar. The odds of incurring catastrophic health spending was 56% more among the multidimensionally poor than among the multidimensionally non-poor [95% CI: 1.35-1.76]. While health shocks to households are consistently significant predictors of catastrophic health spending cutting across country of residence, the educational attainment of the head of the household is not significant. CONCLUSION: The multidimensionally poor in the poorer regions are more likely to face health shocks and are less likely to afford professional health services. Increasing government spending on health and increasing households' access to health insurance can reduce catastrophic health spending and multidimensional poverty.


Asunto(s)
Enfermedad Catastrófica/economía , Costo de Enfermedad , Financiación Personal , Gastos en Salud , Pobreza , Clase Social , Adolescente , Adulto , Asia , Niño , Países en Desarrollo , Composición Familiar , Femenino , Accesibilidad a los Servicios de Salud , Humanos , Renta , India , Seguro de Salud , Masculino , Mianmar , Nepal , Población Rural , Encuestas y Cuestionarios
4.
J Chromatogr A ; 1153(1-2): 186-93, 2007 Jun 15.
Artículo en Inglés | MEDLINE | ID: mdl-17141256

RESUMEN

We report the development and tests of several systems for the simultaneous determination of 18 energetic compounds and related congeners in untreated water samples. In these systems a Restricted Access Material trap or liquid-chromatography precolumn (with a C(18) or porous graphitic carbon, PGC, stationary phase) followed by a PGC analytical column are used for sample clean-up, enrichment and separation of the trace level analytes, which are then analyzed by mass spectrometry (MS). The relative merits of two MS ionization interfaces (atmospheric pressure chemical ionization, APCI, and atmospheric pressure photoionization, APPI) were also compared for the MS identification and quantification of these analytes. APCI was found to be superior in cases where both alternatives are applicable. A major drawback when applying APPI is that no signal is obtained for the cyclic nitramines and nitrate esters. Using APCI, a wide spectrum of unstable compounds can be determined in a single analysis, and the feasibility of using large volume samples (up to 100 mL) in combination with the sensitivity of the MS detection system provide method detection limits ranging from 2.5 pg/mL (for 2,4-dinitrotoluene and 2,6-diamino-6-nitrotoluene) to 563 pg/mL (for pentaerythritol tetranitrate, PETN), with repeatability ranging from 2 to 7%. Other chemometric parameters such as robustness, selectivity, repeatability, and intermediate precision were also evaluated in the validation of the extraction methods for use in water analysis. Tests with untreated groundwater and drinking water samples, spiked with 20 ng of the analytes, yielded results similar to those obtained with high purity water samples.


Asunto(s)
Cromatografía Líquida de Alta Presión/métodos , Sustancias Explosivas/análisis , Hidrocarburos Aromáticos/análisis , Espectrometría de Masas/métodos , Nitrocompuestos/análisis , Contaminantes Químicos del Agua/análisis , Métodos Analíticos de la Preparación de la Muestra , Sistemas en Línea , Triazinas/análisis
5.
J Clin Epidemiol ; 58(12): 1241-51, 2005 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-16291468

RESUMEN

OBJECTIVE: To estimate minimally important differences (MIDs) on the Functional Assessment of Cancer Therapy-Colorectal (FACT-C) instrument using anchor- and distribution-based methods. STUDY DESIGN AND SETTING: Preliminary MIDs were generated for FACT-C scores based on published results for two samples (n = 60 and n = 63) from the FACT-C validation study. Preliminary MIDs were confirmed using data from a Phase II randomized controlled clinical trial (n = 104) and a population-based observational study (n = 568). MIDs were estimated for the colorectal cancer subscale (CCS); the FACT-C Trial Outcome Index (TOI-C), which is the sum of the CCS, physical well-being, and functional well-being subscales; and the FACT-C total score. Both cross-sectional and longitudinal analyses were used. RESULTS: MIDs were stable across the different patient samples. The recommended MIDs ranged from 2 to 3 points for the CCS, 4 to 6 points for the TOI-C, and 5 to 8 points for the FACT-C total score. CONCLUSIONS: MIDs can enhance the interpretability of FACT-C scores, and they can be used to provide a basis for sample size estimation and to determine clinical benefit in combination with other measures of efficacy. General guidelines for estimating MIDs for other FACT instruments are suggested.


Asunto(s)
Neoplasias Colorrectales/terapia , Indicadores de Salud , Evaluación de Resultado en la Atención de Salud , Calidad de Vida , Adulto , Anciano , Anciano de 80 o más Años , Inhibidores de la Angiogénesis/uso terapéutico , Anticuerpos Monoclonales/uso terapéutico , Anticuerpos Monoclonales Humanizados , Bevacizumab , Femenino , Humanos , Masculino , Persona de Mediana Edad , Ensayos Clínicos Controlados Aleatorios como Asunto , Estadística como Asunto , Resultado del Tratamiento
6.
Gene ; 273(2): 259-65, 2001 Aug 08.
Artículo en Inglés | MEDLINE | ID: mdl-11595172

RESUMEN

The purine-rich Shine-Dalgarno (SD) sequence located a few bases upstream of the mRNA initiation codon supports translation initiation by complementary binding to the anti-SD in the 16S rRNA, close to its 3' end. AUG is the canonical initiation codon but the weaker UUG and GUG codons are also used for a minority of genes. The codon sequence of the downstream region (DR), including the +2 codon immediately following the initiation codon, is also important for initiation efficiency. We have studied the interplay between these three initiation determinants on gene expression in growing Escherichia coli. One optimal SD sequence (SD(+)) and one lacking any apparent complementarity to the anti-SD in 16S rRNA (SD(-)) were analyzed. The SD(+) and DR sequences affected initiation in a synergistic manner and large differences in the effects were found. The gene expression level associated with the most efficient of these DRs together with SD(-) was comparable to that of other DRs together with SD(+). The otherwise weak initiation codon UUG, but not GUG, was comparable with AUG in strength, if placed in the context of two of the DRs. The +2 codon was one, but not the only, determinant for this unexpectedly high efficiency of UUG.


Asunto(s)
Codón Iniciador/genética , ADN Bacteriano/genética , Biosíntesis de Proteínas/genética , Secuencia de Bases , Escherichia coli/genética , Escherichia coli/crecimiento & desarrollo , Regulación Bacteriana de la Expresión Génica , Operón Lac/genética , Conformación de Ácido Nucleico , Plásmidos/genética , Estabilidad del ARN , ARN Mensajero/química , ARN Mensajero/genética , ARN Mensajero/metabolismo , Transcripción Genética , beta-Galactosidasa/genética , beta-Galactosidasa/metabolismo
7.
Am Heart J ; 142(5): 872-80, 2001 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-11685177

RESUMEN

BACKGROUND: Patients with severe myocardial ischemia who are not candidates for percutaneous or surgical revascularization have few therapeutic options. Therapeutic angiogenesis in animal models with use of recombinant human vascular endothelial growth factor (rhVEGF) has resulted in successful revascularization of ischemic myocardium. This was a dose escalation trial designed to determine the safety and tolerability of intracoronary rhVEGF infusions. METHODS AND RESULTS: Patients were eligible if they had stable exertional angina, a significant reversible perfusion defect by stress myocardial perfusion study, and coronary anatomy that was suboptimal for percutaneous coronary intervention or coronary artery bypass grafting. rhVEGF was administered to a total of 15 patients by 2 sequential (eg, right and left) intracoronary infusions, each for 10 minutes, at rates of 0.005 (n = 4), 0.017 (n = 4), 0.050 (n = 4), and 0.167 mg/kg/min (n = 3). Pharmacokinetic sampling and hemodynamic monitoring were performed for 24 hours. Radionuclide myocardial perfusion imaging was performed before treatment and at 30 and 60 days after treatment. Follow-up angiograms were performed on selected patients at 60 days. The maximally tolerated intracardiac dose of rhVEGF was 0.050 mg/kg/min. Minimal hemodynamic changes were seen at 0.0050 mg/kg/min (2% +/- 7% [SD] mean decrease in systolic blood pressure from baseline to nadir systolic blood pressure), whereas at 0.167 mg/kg/min there was a 28% +/- 7% mean decrease from baseline to nadir (136 to 95 mm Hg systolic). Myocardial perfusion imaging was improved in 7 of 14 patients at 60 days. All 7 patients with follow-up angiograms had improvements in the collateral density score. CONCLUSION: rhVEGF appears well tolerated by coronary infusion at rates up to 0.050 mg/kg/min. This study provides the basis for future clinical trials to assess the clinical benefit of therapeutic angiogenesis with rhVEGF.


Asunto(s)
Enfermedad Coronaria/tratamiento farmacológico , Factores de Crecimiento Endotelial/administración & dosificación , Linfocinas/administración & dosificación , Isoformas de Proteínas/administración & dosificación , Circulación Coronaria/efectos de los fármacos , Factores de Crecimiento Endotelial/farmacología , Factores de Crecimiento Endotelial/uso terapéutico , Humanos , Linfocinas/farmacología , Linfocinas/uso terapéutico , Neovascularización Fisiológica/efectos de los fármacos , Isoformas de Proteínas/farmacología , Isoformas de Proteínas/uso terapéutico , Proteínas Recombinantes/administración & dosificación , Proteínas Recombinantes/farmacología , Proteínas Recombinantes/uso terapéutico , Factor A de Crecimiento Endotelial Vascular , Factores de Crecimiento Endotelial Vascular
9.
J Clin Oncol ; 19(3): 843-50, 2001 Feb 01.
Artículo en Inglés | MEDLINE | ID: mdl-11157038

RESUMEN

PURPOSE: We investigated the safety and pharmacokinetics of a recombinant human monoclonal antibody to vascular endothelial growth factor (rhuMAb VEGF) in patients with cancer. PATIENTS AND METHODS: Cohorts of patients with metastatic cancer having failed prior therapy entered a phase I trial of rhuMAb VEGF administered by a 90-minute intravenous infusion at doses from 0.1 to 10.0 mg/kg on days 0, 28, 35, and 42. Patients underwent pharmacokinetic sampling on day 0 and had serum samples obtained during the subsequent 28 days. Response assessment was carried out on days 49 and 72. RESULTS: Twenty-five patients with a median Eastern Cooperative Oncology Group performance status of 0 were accrued. There were no grade III or IV adverse events definitely related to the antibody. There were three episodes of tumor-related bleeding. Infusions of rhuMAb VEGF were well tolerated without significant toxicity. Grades I and II adverse events possibly or probably related to study drug included asthenia, headache, and nausea. Pharmacokinetics revealed a linear profile with a half-life of 21 days. There were no objective responses, though 12 patients experienced stable disease over the duration of the study. CONCLUSION: rhuMAb VEGF was safely administered without dose-limiting toxicity at doses ranging up to 10 mg/kg. Multiple doses of rhuMAb VEGF were well tolerated, and pharmacokinetic studies indicate that doses of > or = 0.3 mg/kg have a half-life similar to that of other humanized antibodies. Subsequent trials will explore rhuMAb VEGF alone and in combination chemotherapy.


Asunto(s)
Anticuerpos Monoclonales/efectos adversos , Anticuerpos Monoclonales/farmacocinética , Factores de Crecimiento Endotelial/inmunología , Linfocinas/inmunología , Neoplasias/terapia , Adulto , Anciano , Anticuerpos Monoclonales/uso terapéutico , Relación Dosis-Respuesta Inmunológica , Esquema de Medicación , Factores de Crecimiento Endotelial/antagonistas & inhibidores , Factores de Crecimiento Endotelial/sangre , Femenino , Humanos , Infusiones Intravenosas , Linfocinas/antagonistas & inhibidores , Linfocinas/sangre , Masculino , Persona de Mediana Edad , Neoplasias/irrigación sanguínea , Neoplasias/metabolismo , Neovascularización Patológica/prevención & control , Factor A de Crecimiento Endotelial Vascular , Factores de Crecimiento Endotelial Vascular
10.
J Clin Oncol ; 19(3): 851-6, 2001 Feb 01.
Artículo en Inglés | MEDLINE | ID: mdl-11157039

RESUMEN

PURPOSE: Tumor angiogenesis mediated by vascular endothelial growth factor (VEGF) is inhibited by the recombinant humanized (rhu) monoclonal antibody (MAb) rhuMAbVEGF, which has synergy with chemotherapy in animal models. The present study was designed to assess the safety and pharmacokinetics of weekly intravenous (IV) rhuMAbVEGF with one of three standard chemotherapy regimens. PATIENTS AND METHODS: Twelve adult patients were enrolled four on each combination. rhuMAbVEGF, 3 mg/kg IV, was administered weekly for 8 weeks with (1) doxorubicin 50 mg/m(2) every 4 weeks; (2) carboplatin at area under the curve of 6 plus paclitaxel 175 mg/m(2) every 4 weeks; and (3) fluorouracil (5-FU) 500 mg/m(2) with leucovorin 20 mg/m(2) weekly, weeks 1 to 6 every 8 weeks. RESULTS: The median number of rhuMAbVEGF doses delivered was eight (range, four to eight doses). Grade 3 toxicities were diarrhea (one 5-FU patient), thrombocytopenia (two patients on carboplatin plus paclitaxel), and leukopenia (one patient on carboplatin plus paclitaxel). These toxicities were likely attributable to the chemotherapy component of the regimen. The mean (+/- SD) peak serum level of rhuMAbVEGF was 167 +/- 46 microg/mL, and the mean terminal half-life was 13 days. Total (free plus bound) serum VEGF levels increased from 51 +/- 39 pg/mL (day 0) to 211 +/- 112 (day 49) pg/mL. Three responding patients continued treatment with rhuMAbVEGF and chemotherapy, receiving the equivalent of 36, 20, and 40 total rhuMAbVEGF doses with no cumulative or late toxicities. CONCLUSION: rhuMAbVEGF can be safely combined with chemotherapy at doses associated with VEGF blockade and without apparent synergistic toxicity. Its contribution to the treatment of advanced solid tumors should be evaluated in randomized treatment trials.


Asunto(s)
Anticuerpos Monoclonales/efectos adversos , Anticuerpos Monoclonales/farmacología , Protocolos de Quimioterapia Combinada Antineoplásica/efectos adversos , Protocolos de Quimioterapia Combinada Antineoplásica/farmacología , Factores de Crecimiento Endotelial/inmunología , Linfocinas/inmunología , Neoplasias/terapia , Adulto , Anciano , Carboplatino/administración & dosificación , Carboplatino/efectos adversos , Terapia Combinada , Doxorrubicina/administración & dosificación , Doxorrubicina/efectos adversos , Esquema de Medicación , Interacciones Farmacológicas , Factores de Crecimiento Endotelial/antagonistas & inhibidores , Factores de Crecimiento Endotelial/sangre , Femenino , Fluorouracilo/administración & dosificación , Fluorouracilo/efectos adversos , Humanos , Infusiones Intravenosas , Leucovorina/administración & dosificación , Leucovorina/efectos adversos , Linfocinas/antagonistas & inhibidores , Linfocinas/sangre , Masculino , Persona de Mediana Edad , Neoplasias/irrigación sanguínea , Neoplasias/tratamiento farmacológico , Paclitaxel/administración & dosificación , Paclitaxel/efectos adversos , Factor A de Crecimiento Endotelial Vascular , Factores de Crecimiento Endotelial Vascular
11.
Biochim Biophys Acta ; 1459(2-3): 449-55, 2000 Aug 15.
Artículo en Inglés | MEDLINE | ID: mdl-11004462

RESUMEN

Crystals of cytochrome bo(3) ubiquinol oxidase from E. coli diffract X-rays to 3.5 A and the structure determination is in progress. The limiting factor to the elucidation of the structural detail is the quality of the crystals; the diffraction spots from the crystals are diffused which leads to difficulties in processing the data beyond 4.0 A. Weak protein-protein contacts within the crystal lattice is assumed to be the cause of this problem. To improve these contacts, we have introduced protein Z to the C-terminal end of the subunit IV of cytochrome bo(3) and expressed both proteins as a single fusion. We have successfully obtained crystals of this fusion protein. The spot shape problem has clearly been solved in the crystals of the fusion protein although further optimization is necessary to obtain higher resolution. We also discuss the potential applications of this approach to the crystallization of membrane proteins in general.


Asunto(s)
Citocromos/biosíntesis , Escherichia coli/enzimología , Proteínas Recombinantes de Fusión/biosíntesis , Proteínas Bacterianas/química , Proteínas Portadoras/química , Proteínas Portadoras/genética , Cristalografía por Rayos X , Grupo Citocromo b , Citocromos/química , Citocromos/genética , Escherichia coli/genética , Proteínas de Escherichia coli , Proteínas de Unión a Ácidos Grasos , Técnicas Genéticas , Vectores Genéticos , Proteínas de la Membrana/química , Modelos Moleculares , Proteínas Recombinantes de Fusión/química
12.
J Biopharm Stat ; 9(4): 651-9, 1999 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-10576409

RESUMEN

We propose a procedure for establishing equivalence that determines whether a specified percentage of the treatment effect of a known active agent over placebo is maintained. This procedure accounts for the error in the estimates from the historical studies of the known active agent and placebo as well as the error in the estimates from the equivalence study of the new test treatment versus the active control. After the procedure is presented, it is compared analytically to a procedure in which the equivalence boundary is estimated from historical data and then used with a one-sided test. We address sample size requirements for the proposed equivalence procedure. We also illustrate the use of the proposed procedure with an example from the clinical area of thrombolytic therapy in acute myocardial infarction.


Asunto(s)
Interpretación Estadística de Datos , Ensayos Clínicos Controlados Aleatorios como Asunto/métodos , Equivalencia Terapéutica , Humanos , Cómputos Matemáticos , Infarto del Miocardio/tratamiento farmacológico , Placebos , Distribuciones Estadísticas , Terapia Trombolítica
13.
Stroke ; 30(2): 389-92, 1999 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-9933276

RESUMEN

BACKGROUND AND PURPOSE: Detection of large, hypoattenuated brain-tissue volume on hyperacute CT scan has been suggested as an exclusion criterion for early intravenous tissue plasminogen activator (IV-tPA) treatment. This study assessed the reliability of detection for these findings and their relationship to outcome. METHODS: Fifty hyperacute CT scans (<6 hours after ictus) were selected from a randomized trial evaluating IV-tPA (ATLANTIS trial). Three neuroradiologists blinded to all clinical information evaluated scans for degree of MCA territory involvement (<33% or >33%) and the presence of a hyperdense MCA. Evaluations were compared with 24-hour scan results, 30-day infarct volumes, and baseline NIH stroke scale scores (NIHSS). RESULTS: Readers reliably evaluated the degree of MCA territory hypodensity (intraclass correlation=0.53, P<0.001), with all 3 readers agreeing in 36 of 50 cases (72%). They correctly called >33% involvement with a sensitivity of 60% to 85% and a specificity of 86% to 97%. The baseline NIHSS was higher when >33% MCA hypodensity was seen (P=0. 021). Detection of significant hypodensity (>33%) correlated with poorer outcome. When >33% hypodensity was not detected, mean 30-day infarct volumes were 27.0 to 33.0 cm3, versus 84.3 to 123.1 cm3 when >33% hypodensity was present (P=0.002). CONCLUSIONS: Detection of MCA territory hypodensity on hyperacute CT scans is a sensitive, prognostic, and reliable indicator of the amount of MCA territory undergoing infarction.


Asunto(s)
Isquemia Encefálica/diagnóstico por imagen , Tomografía Computarizada por Rayos X , Enfermedad Aguda , Encéfalo/irrigación sanguínea , Encéfalo/diagnóstico por imagen , Arterias Cerebrales/diagnóstico por imagen , Estudios de Seguimiento , Humanos , Variaciones Dependientes del Observador , Pronóstico , Reproducibilidad de los Resultados , Sensibilidad y Especificidad
14.
J Oral Implantol ; 24(2): 80-8, 1998.
Artículo en Inglés | MEDLINE | ID: mdl-9835834

RESUMEN

Finite element analysis (FEA) has been proven to be a precise and applicable method for evaluating dental implant systems. By means of FEA, a parasaggital model was digitized from a computed tomography (CT)-generated patient data set, and various single-tooth, osseointegrated, two-dimensional dental implant models were simulated. The specific aims of the study were to: (1) examine the effect of implant diameter variation (3.8 mm-6.5 mm) of both a press-fit, stepped cylindrical implant type and a press-fit, straight cylindrical implant type as osseointegrated in the posterior mandible; (2) compare the stress-dissipating characteristics of the stepped implant versus the straight implant design; and (3) analyze the significance of bite force direction (vertical, horizontal, and oblique 45 degrees) on both implant types. The results of the FEA suggested that (1) using the widest diameter implant is not necessarily the best choice when considering stress distribution to surrounding bone, but within certain morphological limits, for both implant types, an optimum dental implant exists for decreasing the stress magnitudes at the bone-implant interface; (2) stress is more evenly dissipated throughout the stepped cylindrical implant when compared to the straight implant type; and (3) it is important in FEA of dental implants to consider not only axial forces (vertical loading) and horizontal forces (moment-causing loads), but also to consider a combined load (oblique bite force), since these are more realistic bite directions and for a given force will cause the highest localized stress in cortical bone. The theoretical analysis performed implies that clinically, whenever possible, an optimum, not necessarily larger, dental implant should be used based on the specific morphological limitations of the mandible and that a stepped cylindrical design for press-fit situations is most desirable from the standpoint of stress distribution to surrounding bone.


Asunto(s)
Implantes Dentales , Diseño de Prótesis Dental , Análisis del Estrés Dental/métodos , Análisis de Elementos Finitos , Proceso Alveolar/fisiología , Fuerza de la Mordida , Aleaciones Dentales/química , Elasticidad , Estudios de Evaluación como Asunto , Mandíbula/fisiología , Titanio/química
16.
J Biopharm Stat ; 7(2): 301-11, 1997 May.
Artículo en Inglés | MEDLINE | ID: mdl-9136071

RESUMEN

This paper presents a model-based assessment of the relationship between the dose of a test treatment and response. The data set used in the analysis describes the results of two clinical trials that were designed to assess the dose-response relationship of a test treatment. The models described in the paper are fit using weighted regression as implemented by the SAS procedure CATMOD. Relationships between weighted regression and other similar procedures are discussed.


Asunto(s)
Ensayos Clínicos como Asunto/estadística & datos numéricos , Relación Dosis-Respuesta a Droga , Modelos Estadísticos , Anticolesterolemiantes/uso terapéutico , Colesterol/sangre , LDL-Colesterol/sangre , Análisis Multivariante , Distribución Aleatoria , Análisis de Regresión
17.
Arch Phys Med Rehabil ; 77(11): 1109-14, 1996 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-8931519

RESUMEN

OBJECTIVE: To analyze the structure of a combination of physical items from the Functional Independence Measure (FIM) and seven instrumental activity items using ratings of dependence and perceived difficulty. DESIGN: Disability in terms of dependence and subject's perceived difficulty was studied in patients with cerebral palsy (CP) and spina bifida (SB). Rasch analysis was used to construct calibrated linear measure and to identify suitable models with respect to rating steps. SETTING: Interviews were performed at home with patients from an outpatient university rehabilitation unit for young disabled persons. PATIENTS: Fifty-three CP and 20 SB patients (including 5 with other early acquired spinal cord lesions), 20 to 39 years of age, participated and represented 62% and 80%, respectively, of available patients. All had fulfilled an elementary school program. RESULTS: The best scoring model using Rasch analysis was achieved using 5 levels for dependence and 4 levels for perceived difficulty. Hierarchic orders for all items are presented. The FIM items Bowel and Bladder showed different characteristics in the two groups of patients, especially for perceived difficulty, and were excluded in the joint calibrations. There was close overall agreement between the ratings of dependence and perceived difficulty. Person measure values from the Rasch analyses were separated between wheelchair users and walkers. CONCLUSION: The combination of physical items from FIM and instrumental activity measure (IAM) are useful for disability assessment in community-living persons and should be further studied in other impairment groups.


Asunto(s)
Actividades Cotidianas , Parálisis Cerebral/diagnóstico , Evaluación de la Discapacidad , Disrafia Espinal/diagnóstico , Adolescente , Adulto , Interpretación Estadística de Datos , Demografía , Femenino , Humanos , Locomoción , Masculino , Autoimagen
18.
Eur J Biochem ; 220(3): 893-900, 1994 Mar 15.
Artículo en Inglés | MEDLINE | ID: mdl-8143743

RESUMEN

Two staphylococcal protein-A signal sequences were constructed and tested for function in Escherichia coli, after being linked to human parathyroid hormone (hPTH) cDNAS representing the intact form (1-84 amino acids) and two N-terminal (1-37 and 1-7 amino acids) peptides. One signal sequence was identical to the wild type, and the other signal contained a deletion of 12 bp at the 3' end. The truncated hPTH cDNAs were fused at their 3' ends to IgG-binding domains (ZZ) derived from protein A in order to facilitate purification and characterization. The expression plasmid pSPTH, containing the wild-type signal sequence, secreted efficiently the intact recombinant hPTH (1-84) into the medium. Plasmids containing the truncated hPTH genes after the wild-type signal, gave rise to hPTH-ZZ hybrid proteins which were correctly processed at the N-terminal, but the major fractions appeared in the periplasmic compartment. In contrast, the plasmid pS'PTH which harboured the 4-amino-acid signal deletion did not promote a uniform secretion of intact hPTH (1-84) to the medium, but released a non-processed form both into the periplasmic compartment and to the medium. The related plasmids pS'PTH37ZZ and pS'PTH7ZZ with the mutated signal sequence gave rise to small or trace amounts of unprocessed forms of fusion proteins in the medium and periplasm, thus the secretion competence was markedly reduced. Thus, for correct N-terminal processing, we conclude that the amino acid sequence in the signal adjacent to the expressed protein, is a key determinant. However, release into the medium or periplasmic space appeared to be dependent also on protein folding, irrespective of signal-sequence cleavage. Furthermore, we observed that the peptides with the wild-type signal sequence and correct N-terminal processing, were the only forms that showed internal cleavage of hPTH. Uncleaved signals may contribute to folding characteristics of the ensuing protein and e.g., prevent internal proteolysis.


Asunto(s)
Escherichia coli/metabolismo , Hormona Paratiroidea/metabolismo , Señales de Clasificación de Proteína/metabolismo , Secuencia de Aminoácidos , Secuencia de Bases , Transporte Biológico , Compartimento Celular , Cartilla de ADN/química , Humanos , Datos de Secuencia Molecular , Procesamiento Proteico-Postraduccional , Proteínas Recombinantes de Fusión/metabolismo , Proteína Estafilocócica A/química
19.
J Mol Biol ; 229(3): 656-70, 1993 Feb 05.
Artículo en Inglés | MEDLINE | ID: mdl-7679447

RESUMEN

The structure of untranslated regions of mRNA is thought to play a key role in the degradation of mRNAs by specific RNases. As a model system, in vitro transcripts of the stability determining 5' non-coding region of bacterial ompA mRNA were investigated by calculation of secondary structure models and by experiments applying the temperature-gradient gel electrophoresis (TGGE). For the theoretical prediction of secondary structures an algorithm was used, which yields the structure of lowest free energy as well as a large set of suboptimal structures. Three structures were predicted to co-exist in similar concentrations under native conditions. They denature in a low temperature transition leading to a unique structure which denatures in a high temperature transition. The prediction of three structures and two transitions could be confirmed experimentally by TGGE. Due to the use of transcripts of different length the conformational transitions could be attributed to distinct parts of the molecules. A pseudoknot structural motif was predicted theoretically, but could not be confirmed experimentally. Comparing ompA transcripts of E. coli and S. marcescens, a conservation of structural features could be shown in spite of a sequence homology of only 63%. Regarding the sequential folding of the transcript after synthesis, a metastable structure is formed first and is converted slowly into structures of lower free energy. The biological implications for in vivo degradation are discussed.


Asunto(s)
Proteínas de la Membrana Bacteriana Externa/genética , Escherichia coli/genética , Conformación de Ácido Nucleico , ARN Mensajero/química , Serratia marcescens/genética , Secuencia de Bases , ADN Bacteriano , Electroforesis en Gel de Poliacrilamida , Endorribonucleasas , Datos de Secuencia Molecular , ARN Bacteriano/química , Temperatura , Transcripción Genética
20.
J Biotechnol ; 25(3): 269-87, 1992 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-1368804

RESUMEN

A novel gene fusion system has been constructed for fusions to the 5' end of gene zz, encoding a two-domain analogue of staphylococcal protein A designated ZZ. Four different genes were fused to the 5' end of zz, and their gene products were analyzed. One of the genes encodes a protein located intracellularly in Escherichia coli and the other three genes encode gene products destined for secretion across the cytoplasmic membrane by the presence of an amino terminal signal sequence. After production in E. coli, the fusion proteins were purified in a single step by IgG-affinity chromatography. The purified ZZ fusions could be used directly for amino terminal sequencing to confirm the start of translation of the intracellular product and the processing of the signal peptide of the translocated products. This is the first example of ZZ fusions to the C-terminus of gene products. To simplify the general use of fusions to the 5' end of zz, a new plasmid vector was constructed containing a multi restriction enzyme cloning linker and the lacZ' gene which enables screening for production in alpha-complementing supE strains of E. coli on indicator plates.


Asunto(s)
Clonación Molecular , Proteína Estafilocócica A/genética , Secuencia de Aminoácidos , Secuencia de Bases , Escherichia coli/genética , Datos de Secuencia Molecular , Plásmidos , Señales de Clasificación de Proteína/análisis , Proteínas Recombinantes de Fusión/biosíntesis , Proteínas Recombinantes de Fusión/aislamiento & purificación , Proteína Estafilocócica A/biosíntesis , Proteína Estafilocócica A/aislamiento & purificación
SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA