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1.
PeerJ ; 9: e10949, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-33777522

RESUMEN

OBJECTIVE: In consideration of the current nursing shortage in Saudi Arabia, we aimed to investigate the association among perceptions of work environment, communication satisfaction, and intentions to quit nursing profession among nurses. In addition, we aimed to investigate the mediating effect of communication satisfaction on the association between nurses' perception of work environment and their intentions to quit nursing profession. METHODS: This predictive correlational study was conducted at one of the major hospitals in Saudi Arabia from January 2020 to March 2020. It included a convenience sample of 367 full-time registered nurses who completed three types of close-ended questionnaires. We used IBM SPSS version 24.0 to analyze the collected data. Regression analyses were used to test the study's hypotheses. All regression assumptions were assessed and confirmed. Significance for all tests was set at p ≤ .05. RESULTS: The findings indicated an affirmative association between work environment perception and communication satisfaction (b = .764, p < .05) among nurses. In addition, findings showed that work environment perception (b = -.187, p < .05) and communication satisfaction (b = -.226, p < .05) have negative impacts on the nurses' intentions to quit; indicating that as work environment perception or communication satisfaction increases, the intention to quit decreases among nurses. Further, a mediation effect of communication satisfaction on the relationship between work environment perception and intention to quit was confirmed. CONCLUSION: This study presents a novel conceptual framework developed based on the literature about the predisposing factors for nurses' intentions to quit nursing profession. Our results suggest that work environment perception and communication satisfaction among the most contributing factors for nurses resignation. Effective communication was established as a crucial factor for establishing attractive and healthy working environment. Nursing managers can benefit by applying these findings to develop appropriate strategies to inhibit the shortage of nurses in Saudi Arabia.

2.
Int J Afr Nurs Sci ; 13: 100256, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-33072514

RESUMEN

The Saudi government is currently facing multiple challenges in achieving "The Gold Standard" in nursing practice. This is not limited to educational challenges, staffing shortage, paucity of international and national benchmark evidence, absence of clear and defined scope of nursing practice, and lack of appropriate policies and regulations. This study presented a comprehensive plan for developing a policy based on current challenges, recognition of policy goals, assessment of potential options and alternatives, identification of stakeholders, proposition of recommended solutions, and implementation of the framework to transform nursing standards and link these changes with the Saudi Vision 2030. However, amendments are required in the present strategic plan for the better management of the nursing profession. It is doubtful that the current nursing profession status quo is capable of meeting the golden standards for health care. Thus, the transformation of the nursing profession in Saudi Arabia is necessary.

3.
Cureus ; 12(7): e9471, 2020 Jul 30.
Artículo en Inglés | MEDLINE | ID: mdl-32874800

RESUMEN

In recent years, the field of environmental health promotion gained new prominence as awareness of physical environmental stressors and exposures escalated in Saudi Arabia. Although, several theories and conceptual models are routinely used for guiding health education and promotion interventions, they are rarely applied to environmental health issues in Saudi Arabia. This study theoretically reviews the educational and behavioral models for promoting health in Saudi Arabia. This study examines how education and behavioral models can reduce exposure to environmental health risks. In particular, this article describes the application of ecological theory with regard to its theoretical, analytical, and methodological challenges to future research in educational and behavioral studies. The implications of ecological theory are discussed for environmental health promotion. Ecological theory can further demonstrate the dimensions of health behaviors such as procedures for changing them. Health behaviors are also affected by many forces such as physical and social environments. This theory can assist planners in identifying the most appropriate target audiences, methods to improve change, and consequences for assessment. This theory is also important in including social, cultural, and physical factors that affect health consequences, which include factors such as social cohesion, behavioral patterns, emotional wellbeing, genetic heritage, and developmental maturation.

6.
J Mater Sci Mater Med ; 21(1): 99-108, 2010 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-19714301

RESUMEN

Silicon complexes in silicon doped calcium phosphate bioceramics have been studied using (29)Si magic angle spinning nuclear magnetic resonance spectroscopy with the objective of identifying the charge compensation mechanisms of silicon dopants. Three different materials have been studied: a multiphase material composed pre-dominantly of a silicon stabilized alpha-tricalcium phosphate(alpha-TCP) phase plus a hydroxyapatite (HA) phase, a single phase Si-HA material and a single phase silicon stabilized alpha-TCP material. NMR results showed that in all three materials the silicon dopants formed Q(1) structures in which two silicate tetrahedra share an oxygen, creating an oxygen vacancy which compensated the substitution of two silicon for phosphorus. This finding may explain the phase evolution previously found where silicon stabilized alpha-TCP is found at low temperature after sintering.


Asunto(s)
Materiales Biocompatibles/química , Fosfatos de Calcio/química , Fosfatos de Calcio/metabolismo , Compuestos de Silicona/química , Durapatita/química , Sustancias Macromoleculares/química , Sustancias Macromoleculares/metabolismo , Espectroscopía de Resonancia Magnética , Compuestos de Silicona/metabolismo , Temperatura
7.
J Vet Intern Med ; 23(5): 1003-6, 2009.
Artículo en Inglés | MEDLINE | ID: mdl-19737179

RESUMEN

BACKGROUND: The renin-angiotensin-aldosterone system (RAAS) is activated in states of decreased cardiac output and by certain cardiovascular therapeutic agents, such as loop diuretics and vasodilators. HYPOTHESIS: Short-term treatment with the inodilator, pimobendan, will not activate the circulating RAAS because its vasodilatory action will be offset by its positive inotropic property, thereby ameliorating RAAS stimulation at the juxtaglomerular apparatus. Furthermore, pimobendan will suppress RAAS activation produced by furosemide. ANIMALS: Nine healthy laboratory dogs were used in this study. METHODS: Experimental, cross-over study. Dogs were administered pimobendan (0.5 mg/kg q12h) for 4 days followed by furosemide (2 mg/kg q12h) and then, after a wash-out period, a combination of the drugs. Aldosterone : creatinine (A : Cr) was measured at the end of each treatment cycle. RESULTS: There was no significant increase in the average urinary A : Cr with the administration of pimobendan (control urinary A : Cr = 0.46, standard deviation (SD) 0.33; pimobendan A : Cr = 0.48, SD 0.28). There was a significant increase in the average urinary A : Cr after administration of furosemide (urinary A : Cr = 1.3, SD 0.70) and with the combination of furosemide and pimobendan (urinary A : Cr = 2.9, SD 1.6). CONCLUSIONS AND CLINICAL RELEVANCE: Short-term administration of high-dose pimobendan, does not activate the RAAS in healthy dogs. Pimobendan did not prevent RAAS activation associated with furosemide therapy. These results in healthy dogs suggest that furosemide therapy, with or without pimobendan, should be accompanied by RAAS suppressive therapy.


Asunto(s)
Perros/sangre , Furosemida/farmacología , Piridazinas/farmacología , Sistema Renina-Angiotensina/efectos de los fármacos , Inhibidores del Simportador de Cloruro Sódico y Cloruro Potásico/farmacología , Vasodilatadores/farmacología , Aldosterona/orina , Animales , Nitrógeno de la Urea Sanguínea , Cloruros/sangre , Estudios Cruzados , Perros/orina , Femenino , Masculino , Fósforo/sangre , Potasio/sangre , Sodio/sangre
8.
J Thromb Haemost ; 5(11): 2243-9, 2007 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-17958742

RESUMEN

BACKGROUND: Users of progestin-only contraceptives have raised protein S (PS) levels compared with baseline. This contrasts with the reduction in PS levels observed in users of combined oral contraceptives, which contain both a progestin and an estrogen. OBJECTIVES: To determine the effect of progesterone and other progestin isoforms on the expression of PS and to describe the mechanism involved. METHODS: Promoter activity of the PROS1 gene that encodes PS was assessed in vitro using breast and liver carcinoma cell lines grown in the presence of various progestins, with and without the addition of excess progesterone receptors. An electromobility shift assay (EMSA) was also performed to identify the progesterone receptor binding element. RESULTS: PROS1 transcriptional levels were directly upregulated by 25% by progesterone via a mechanism that was progesterone receptor isoform B (PR-B)-dependent. The process was blocked by the progesterone receptor modulator RU486. Results for the EMSA demonstrated that a probe comprising nucleotides -397 to -417 of the PROS1 promoter bound to ligand-activated PR-B, suggesting that the domain is a progesterone response element (PRE). The type of progestin isoform greatly influenced the level of PROS1 promoter upregulation, with medroxyprogesterone able to stimulate a > 2-fold stronger response compared with progesterone. CONCLUSIONS: The PROS1 promoter is responsive to progesterone and other progestins via a mechanism involving PR-B interacting with a PRE. The type of progestin is important as some elicit stronger upregulatory effects than others, which may influence the choice of progestin used for hormonal contraception by PS-deficient individuals.


Asunto(s)
Proteína S/genética , Regulación hacia Arriba/efectos de los fármacos , Línea Celular Tumoral , Anticonceptivos Orales , Humanos , Progesterona/farmacología , Progestinas/farmacología , Regiones Promotoras Genéticas , Isoformas de Proteínas/farmacología , Receptores de Progesterona/metabolismo , Elementos de Respuesta , Transcripción Genética , Regulación hacia Arriba/genética
9.
Biofouling ; 23(5-6): 343-56, 2007.
Artículo en Inglés | MEDLINE | ID: mdl-17852069

RESUMEN

A comparative study was carried out to evaluate the efficiency of a number of techniques commonly used for assessing the structure of subtidal epifaunal communities. Assessments were made of the epifaunal assemblages fouling two substrata: concrete and PVC plastic. Where possible, each technique was undertaken in three ways, namely, in situ underwater, in the laboratory and using image analysis on photographs taken in situ. Comparisons were also made of biomass estimates made on samples taken in situ and in the laboratory. All method and technique combinations assessed detected differences in the epibiotic communities associated with the two fouling substrata. Sampling in situ, in the laboratory and using image analysis gave similar estimates of percent cover. However, there were significant differences in measurements made for most taxa with respect to abundance and frequency counts depending on how the technique was carried out. Laboratory-based sampling of abundance and frequency counts and biomass determinations, rather than in situ or image-analysis based sampling, are recommended for use in future studies of epifaunal fouling.


Asunto(s)
Biodiversidad , Biomasa , Materiales de Construcción , Biología Marina , Animales , Océanos y Mares , Cloruro de Polivinilo , Dinámica Poblacional
10.
J Neurol Neurosurg Psychiatry ; 77(9): 1067-9, 2006 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-16914755

RESUMEN

BACKGROUND: An association between the phosphodiesterase 4D (PDE4D) gene and risk of ischaemic stroke in an Icelandic population has been suggested by the deCODE group. METHODS: A case-control study of 151 hospitalised patients with first-ever ischaemic stroke and 164 randomly selected age-matched and sex-matched community controls was conducted. PDE4D genotypes for the six single-nucleotide polymorphisms (SNPs) previously reported to be independently associated with stroke were determined, common haplotypes were inferred using the expectation-maximisation algorithm, and SNP and haplotype associations with stroke were examined. A meta-analysis of published studies examining the association between PDE4D and stroke was also carried out. RESULTS: Our study of Australian patients with stroke showed an independent association between ischaemic stroke and PDE4D SNP 89 (CC: odds ratio (OR) 5.55, 95% confidence interval (CI) 1.02 to 30.19; CA: OR 1.68, 95% CI 0.96 to 2.96; AA: OR 1 (reference)), SNP 87 (CC: OR 2.13, 95% CI 1.08 to 4.20; TC: OR 1.64, 95% CI 0.89 to 3.00; TT: OR 1 (reference)) and SNP 83 (TT: OR 2.16, 95% CI 1.08 to 4.32; TC: OR 1.37, 95% CI 0.77 to 2.43; CC: OR 1 (reference)), and between ischaemic stroke and PDE4D haplotypes at SNP 89-87-83 (A-C-C: OR 2.13, 95% CI 1.15 to 3.96; C-C-T: OR 2.25, 95% CI 1.29 to 3.92), but no association between ischaemic stroke and PDE4D SNP 56, SNP 45 or SNP 41, or with PDE4D haplotypes at SNP 56-45-41. A meta-analysis of nine case-control studies (including our current results) of 3808 stroke cases and 4377 controls confirmed a significant association between stroke and PDE SNP 87 (pooled p = 0.002), SNP 83 (0.003) and SNP 41 (0.003). However, there was statistical heterogeneity (p < 0.1) among the studies in the direction of association for each of the individual SNPs tested. CONCLUSIONS: Our results and the pooled analyses from all the studies indicate a strong association between PDE4D and ischaemic stroke. This strengthens the evidence that PDE4D plays a key part in the pathogenesis of ischaemic stroke. Heterogeneity among the studies in the direction of association between individual SNPs and stroke suggests that the SNPs tested are in linkage disequilibrium with the causal allele(s).


Asunto(s)
3',5'-AMP Cíclico Fosfodiesterasas/genética , Isquemia Encefálica/genética , Accidente Cerebrovascular/genética , Anciano , Estudios de Casos y Controles , Fosfodiesterasas de Nucleótidos Cíclicos Tipo 3 , Fosfodiesterasas de Nucleótidos Cíclicos Tipo 4 , Femenino , Predisposición Genética a la Enfermedad , Humanos , Desequilibrio de Ligamiento , Masculino , Persona de Mediana Edad , Polimorfismo de Nucleótido Simple
12.
Stroke ; 36(6): 1123-7, 2005 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-15879328

RESUMEN

BACKGROUND AND PURPOSE: We aimed to determine whether A-13G or G79A polymorphisms of the protein Z gene that have been reported to be an important determinant of blood concentrations of protein Z are associated with risk of ischemic stroke in a broad range of stroke patients and controls. METHODS: We conducted a case control study of 151 hospital cases of first-ever ischemic stroke and 164 randomly selected community controls. Protein Z genotype was determined for the A-13G promoter polymorphism and the G79A intron F polymorphism, and plasma protein Z concentrations were measured during the first 7 days and at 3 to 6 months after the acute stroke event. RESULTS: Geometric mean concentrations of protein Z measured within 7 days of acute stroke were significantly higher in cases compared with controls (1.51 microg/mL versus 1.13 microg/mL; P<0.0001). Protein Z concentrations were highest among subjects with the A-13G AA genotype, intermediate among those with the AG genotype, and lowest among those with the GG genotype (1.39 microg/mL versus 1.05 microg/mL versus 0.76 microg/mL; P<0.0001); and highest among those with the G79A GG genotype, intermediate among those with the GA genotype, and lowest among those with the AA genotype (1.47 microg/mL versus 1.13 microg/mL versus 0.66 microg/mL; P<0.0001). The prevalence of A-13G and G79A genotypes was not significantly different between cases of ischemic stroke and controls. However, compared with the G79A GG genotype (reference), the odds of ischemic stroke was progressively lower for the heterozygote GA (odds ratio [OR], 0.83; 95% CI, 0.52 to 1.33) and the homozygote AA genotype (OR, 0.63; 95% CI, 0.20 to 1.98). A pooled analysis showed that compared with the G79A GG genotype (reference), the odds of ischemic stroke was progressively lower for the heterozygote GA (OR, 0.78; 95% CI, 0.57 to 1.07) and the homozygote AA genotype (OR, 0.31; 95% CI, 0.14 to 0.69). CONCLUSIONS: The consistency of the association between protein Z genotypes, blood concentrations of protein Z, and ischemic stroke, determined using 2 different methods that have different sources of bias strengthens the evidence that increased blood concentrations of protein Z concentrations are associated causally with an increased risk of ischemic stroke.


Asunto(s)
Proteínas Sanguíneas/genética , Isquemia/genética , Polimorfismo Genético , Accidente Cerebrovascular/genética , Anciano , Proteínas Sanguíneas/biosíntesis , Estudios de Casos y Controles , Femenino , Genotipo , Humanos , Intrones , Masculino , Persona de Mediana Edad , Regiones Promotoras Genéticas , Trombosis/genética , Factores de Tiempo
13.
J Phys Chem B ; 109(42): 19579-83, 2005 Oct 27.
Artículo en Inglés | MEDLINE | ID: mdl-16853532

RESUMEN

Bioceramics based on silicon stabilized tricalcium phosphate [Si-TCP] have been investigated by attenuated total reflection infrared spectroscopy using an experimental preparation that ensures consistent high-quality spectral data. Phase normalized measurements show that changes in OH bands are primarily due to a decrease in the hydroxyapatite content; however, a band at 945 cm(-1) associated with dehydration of the apatite is visible and correlated with silicon doping. Changes in absorption bands with Si content associated with PO(4)(3-) differ for SiO(2) doping levels less than and greater than 0.2 mol of SiO(2)/mol of HA as the amount of Si-TCP phase saturates. Increased resolution allows the study of weak bands linked to Si at 668, 800, 863, and 892 cm(-1) and suggests that the loss of PO(4)(3-) coincides with the development of different silicate groups-SiO(4) at lower doping levels and a new silicon species at higher doping.


Asunto(s)
Fosfatos de Calcio/química , Silicio/química , Apatitas/química , Tamaño de la Partícula , Espectrofotometría Infrarroja , Difracción de Rayos X
14.
Biomaterials ; 26(16): 2887-97, 2005 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-15603784

RESUMEN

The sintering of silicon doped calcium phosphate ceramics prepared from a basic colloidal hydroxyapatite (Ca5(PO4)3OH or HA) precipitate mixed with silica over 800 degrees C yields a phase mixture of tricalcium phosphate phases (TCP) designated Si-TCP, beta-TCP and a silicon substituted dehydrated apatite (Si-Ap). The Si-TCP phase is defined as a combination of a silicon stabilized TCP in which the silicon content attains a saturated value (Ca3(P0.9Si0.1O3.95)2 or Si-TCP(sat)) and alpha-TCP (Ca3(PO4)2). Si-TCP(sat) has the same crystalline space group (P2(1)/a) as alpha-TCP, but with characteristically different lattice parameters due to the substitution of silicon in tetrahedral phosphorus sites. The nucleation and growth kinetics of Si-TCP in samples of composition 0.2 mol SiO2:mol HA (0.2:1) and 1 mol SiO2:mol HA (1:1) can be understood in terms of the initial growth of alpha-TCP at a silica-HA interface followed by a transformation to Si-TCP(sat) or beta-TCP. A thermodynamic model for the formation of Si-TCP(sat) predicts a nucleation temperature of 795 degrees C, in close agreement with experiment. If sufficient silicon is available, the alpha-TCP transforms to Si-TCP(sat) during extended sintering. In the absence of sufficient silicon, the alpha-TCP transforms to beta-TCP.


Asunto(s)
Apatitas/química , Materiales Biocompatibles/química , Fosfatos de Calcio/química , Dióxido de Silicio/química , Cerámica , Durapatita , Hidroxiapatitas/química , Cinética , Ensayo de Materiales , Modelos Químicos , Temperatura , Termodinámica , Factores de Tiempo , Difracción de Rayos X
15.
Biomaterials ; 24(3): 369-82, 2003 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-12423592

RESUMEN

Silicon stabilized tricalcium phosphate [Si-TCP] is formed within the calcium hydroxyapatite (HA)-tricalcium phosphate (TCP) system when a stoichiometric precipitate of hydroxyapatite is fired at 1,000 degrees in the presence of SiO(2). This paper proposes a composition range and crystallographic structure for Si-TCP. Reitveld XRD powder diffraction, transmission electron microscopy, infrared and proton nuclear magnetic resonance measurements show that crystalline Si-TCP is associated with the displacement of OH from an initial hydroxyapatite structure. The resulting calcium phosphate is modified by the incorporation of silicon into its structure with excess silica contributing to an amorphous component. Si-TCP has a monoclinic structure with a space group P2(1)/a akin to alpha-TCP with estimated lattice constants of a=12.863+/-0.004 A, b=9.119 +/-0.003 A, c=15.232+/-0.004 A, beta=126.3+/-0.1 degrees. It is proposed that Si(4+) substitutes for P(5+)in the TCP lattice with the average chemical composition of Si-TCP set primarily by the mechanisms available for charge compensation. While the formation of OH vacancies in HA initiates the transformation to Si-TCP, two mechanisms of charge compensation in the Si-TCP structure are plausible. If O(2-) vacancies provide charge compensation, the composition of Si-TCP is Ca(3)(P(0.9)Si(0.1)O(3.95))(2) derived for the addition of 0.33 mol SiO(2):mol HA. If excess Ca(2+) compensates, the composition is Ca(3.08)(P(0.92)Si(0.08)O(4))(2) derived for the addition of 0.25 mol SiO(2):mol HA. The reaction occurs most effectively when SiO(2) is added as a colloidal suspension rather than by the in-situ thermal decomposition of a silicon metallorganic compound. The material is a bioceramic of major biological interest because of its osteoconductivity and unique influence on skeletal tissue repair and remodeling.


Asunto(s)
Materiales Biocompatibles/química , Fosfatos de Calcio/química , Durapatita/química , Silicio/química , Absorción , Calcio/metabolismo , Fosfatos de Calcio/análisis , Imagen por Resonancia Magnética , Microscopía Electrónica , Microscopía Electrónica de Rastreo , Dióxido de Silicio/metabolismo , Difracción de Rayos X
16.
Ultrasonics ; 39(10): 675-80, 2002 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-12479598

RESUMEN

Thick film broadband ultrasonic transducers (UTs) produced by a sol-gel spray technique and operated below 10 MHz are presented. These UTs are formed by dispersing PZT and LiTaO3 particles, respectively in Al2O3 and PZT sol-gel solution. The 50-100 microm thick films have been deposited on curved steel, flat steel and aluminum substrates and steel rods. Ultrasonic pulse-echo signals with a signal to noise ratio of more than 25 dB are experimentally obtained for the operating temperatures up to 250 degrees C.

17.
Biomaterials ; 23(20): 4155-63, 2002 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-12182317

RESUMEN

Zn- and to a lesser extent Mg-releasing tricalcium phosphate (Zn- and Mg-TCP) have excellent bioactivities which do not exist in their parent TCP base. However, the mechanisms through which the dopants affect the properties are not known. In order to gain insight from geometrical and electronic structures and chemical bonding, ab initio density functional calculations have been performed for these materials using cluster models. The results show a distorted structure for Zn-TCP which may be related to its bioactivity, whereas no such distortion was found for TCP and Mg-TCP. The infrared spectra of these materials has been calculated, and the relationship to the structure investigated.


Asunto(s)
Fosfatos de Calcio/química , Magnesio/química , Zinc/química , Modelos Moleculares , Estructura Molecular , Espectrofotometría Infrarroja , Vibración
18.
Biomaterials ; 22(2): 135-50, 2001 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-11101158

RESUMEN

Synthetic materials capable of being remodelled in vivo by the same processes responsible for natural bone turnover have long been sought for use as an artificial bone substitute. These materials must ideally combine osteoinductive capacity with the ability to withstand random dissolution at normal physiological pH, while being resorbed by natural cell-mediated processes. Resorbable calcium phosphate based coatings and bulk ceramics have been developed which promote the uniform deposition of new mineralized bone matrix thus enabling rapid integration with the surrounding host bone tissue in vivo. Furthermore, a critical result of this study is the determination that the silicon-stabilized calcium phosphate ceramics are essentially insoluble in biological media but are resorbed when acted upon by osteoclasts. In vitro biological testing and preliminary in vivo testing show that the important features of this new biomaterial are a characteristic calcium phosphate phase composition and a unique microporous morphology.


Asunto(s)
Implantes Absorbibles , Sustitutos de Huesos , Fosfatos de Calcio , Cerámica , Animales , Huesos/citología , Masculino , Ensayo de Materiales , Microscopía Electrónica , Microscopía Electrónica de Rastreo , Osteoblastos/citología , Osteoclastos/citología , Ratas , Ratas Wistar , Difracción de Rayos X
19.
J Biol Chem ; 275(33): 25292-8, 2000 Aug 18.
Artículo en Inglés | MEDLINE | ID: mdl-10842186

RESUMEN

In this study, regulation of transcription factor NF-E2 was examined in differentiating erythroid and myeloid cells, and the impact of raising NF-E2 concentrations within these cell types was assessed. NF-E2 was expressed in the J2E erythroid cell line, but the levels increased only marginally during erythropoietin-induced differentiation. In contrast, rare myeloid variants of J2E cells did not express NF-E2. Although NF-E2 was present in M1 monoblastoid cells, it was undetectable as these cells matured into macrophages. Compared with erythroid cells, transcription of the NF-E2 gene was reduced, and the half-life of the mRNA was significantly shorter in monocytoid cells. Ectopic expression of NF-E2 had a profound impact upon the J2E cells; morphologically mature erythroid cells spontaneously emerged in culture, but the cells failed to synthesize hemoglobin, even in the presence of erythropoietin. Although proliferation and viability increased in the NF-E2-transfected J2E cells, their responsiveness to erythropoietin was severely diminished. Strikingly, increasing the expression of NF-E2 in M1 cells produced sublines that contained erythroid or immature megakaryocytic cells. Finally, overexpression of NF-E2 in primary hemopoietic progenitors from fetal liver increased erythroid colony formation in the absence of erythropoietin. These data demonstrate that elevated NF-E2 (i) had a dominant effect on the phenotype and maturation of J2E erythroid cells, (ii) was able to reprogram the M1 monocytoid line, and (iii) promoted the development of erythroid colonies by normal progenitors.


Asunto(s)
Proteínas de Unión al ADN/metabolismo , Células Precursoras Eritroides/citología , Células Precursoras Eritroides/metabolismo , Leucemia Mieloide Aguda/metabolismo , Factores de Transcripción/metabolismo , Northern Blotting , Western Blotting , División Celular , Línea Celular , Núcleo Celular/metabolismo , Supervivencia Celular , Factores de Unión al ADN Específico de las Células Eritroides , Citometría de Flujo , Inhibidores de Crecimiento/metabolismo , Hemoglobinas/biosíntesis , Humanos , Interleucina-6/metabolismo , Factor Inhibidor de Leucemia , Hígado/embriología , Linfocinas/metabolismo , Macrófagos/metabolismo , Megacariocitos/metabolismo , Factor de Transcripción NF-E2 , Subunidad p45 del Factor de Transcripción NF-E2 , Fenotipo , ARN Mensajero/metabolismo , Retroviridae/metabolismo , Factores de Tiempo , Células Tumorales Cultivadas
20.
Artículo en Inglés | MEDLINE | ID: mdl-18238526

RESUMEN

A sol gel composite process has been used to produce lead zirconate titanate coatings in the thickness range of 3 to 100 microm on aluminum substrates. The complex permittivity (epsilon(33)(S )), elastic stiffness (c(33)(D)), and the piezoelectric constant (h(33)) of the coating and the complex elastic stiffness (c(33)(D)) of the substrate have been determined using impedance measurements and a commercially available software program [Piezoelectric Resonance Analysis Program PRAP 2.0, TASI Technical Software, Kingston, Ontario, Canada]. The complex components of the material parameters account for the losses within the film and the substrate. Sol gel composite films on aluminum have a dielectric constant of 220 with an imaginary component of 1% and an electromechanical coupling coefficient of up to 0.24 with an imaginary component of 3%. These films are applied to the fabrication of a high frequency transducers suitable for ultrasound biomicroscopy (UBM). By combining the sol gel composite material with existing transducer fabrication techniques, single-element focusing transducers have been produced that operate in the frequency range of 70 to 160 MHz. Devices have -6-dB bandwidths up to 52% and minimum insertion losses ranging from -47 to -58 dB. Real-time images of phantom materials and ex vivo biological samples are shown.

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