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BACKGROUND: Discovery biological motifs plays a fundamental role in understanding regulatory mechanisms. Computationally, they can be efficiently represented as kmers, making the counting of these elements a critical aspect for ensuring not only the accuracy but also the efficiency of the analytical process. This is particularly useful in scenarios involving large data volumes, such as those generated by the ChIP-seq protocol. Against this backdrop, we introduce BIOMAPP::CHIP, a tool specifically designed to optimize the discovery of biological motifs in large data volumes. RESULTS: We conducted a comprehensive set of comparative tests with state-of-the-art algorithms. Our analyses revealed that BIOMAPP::CHIP outperforms existing approaches in various metrics, excelling both in terms of performance and accuracy. The tests demonstrated a higher detection rate of significant motifs and also greater agility in the execution of the algorithm. Furthermore, the SMT component played a vital role in the system's efficiency, proving to be both agile and accurate in kmer counting, which in turn improved the overall efficacy of our tool. CONCLUSION: BIOMAPP::CHIP represent real advancements in the discovery of biological motifs, particularly in large data volume scenarios, offering a relevant alternative for the analysis of ChIP-seq data and have the potential to boost future research in the field. This software can be found at the following address: (https://github.com/jadermcg/biomapp-chip).
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Algoritmos , Programas Informáticos , Análisis de Secuencia de ADN/métodos , Inmunoprecipitación de Cromatina/métodos , Sitios de Unión , Motivos de NucleótidosRESUMEN
The investigation of natural alternatives to conventional fungicides is of imminent need. Mosiera bullata (Britton & P. Wilson) Bisse is a Cuban endemic plant species belonging to the Myrtaceae family. The objective of the present study was to perform a bioassay-guided fractionation to explore the potential of extracts and fractions from M. bullata leaves against a panel of fungal plant pathogens. The M. bullata total extract was confirmed to have good antifungal activity against R. oryzae (IC50 = 4.86 µg/mL) and moderate activity against F. oxysporum (IC50 = 352.40 µg/mL) and F. solani (IC50 = 427.38 µg/mL) and fungicidal effect against R. oryzae. Five compounds belonging to the class of phloroglucinol dimers were tentatively characterized by UHPLC-HRMS and reported for the first time in M. bullata and the genus Mosiera. These results suggest the potential of M. bullata total extract as a natural antifungal product for the control of diseases in agriculture.
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Extracellular signaling is commonly mediated through post-translational protein modifications that propagate messages from membrane-bound receptors to ultimately regulate gene expression. Signaling cascades are ubiquitously intertwined, and a full understanding of function can only be gleaned by observing dynamics across multiple key signaling nodes. Importantly, targets within signaling cascades often represent opportunities for therapeutic development or can serve as diagnostic biomarkers. Protein phosphorylation is a particularly important post-translational modification that controls many essential cellular signaling pathways. Not surprisingly, aberrant phosphorylation is found in many human diseases, including cancer, and phosphoprotein-based biomarker signatures hold unrealized promise for disease monitoring. Moreover, phosphoprotein analysis has wide-ranging applications across fundamental chemical biology, as many drug discovery efforts seek to target nodes within kinase signaling pathways. For both fundamental and translational applications, the analysis of phosphoprotein biomarker targets is limited by a reliance on labor-intensive and/or technically challenging methods, particularly when considering the simultaneous monitoring of multiplexed panels of phosphoprotein biomarkers. We have developed a technology based upon arrays of silicon photonic microring resonator sensors that fills this void, facilitating the rapid and automated analysis of multiple phosphoprotein levels from both cell lines and primary human tumor samples requiring only minimal sample preparation.
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Biomolecular signals within the native extracellular matrix are complex, with bioactive factors found in both soluble and sequestered states. In the design of biomaterials for tissue engineering applications it is increasingly clear that new approaches are required to locally tailor the biomolecular environment surrounding cells within the matrix. One area of particular focus is strategies to improve the speed or quality of vascular ingrowth and remodeling. While the addition of soluble vascular endothelial growth factor (VEGF) has been shown to improve vascular response, strategies to immobilize such signals within a biomaterial offer the opportunity to optimize efficiency and to explore spatially defined patterning of such signals. Here we describe the use of benzophenone (BP) photolithography to decorate three-dimensional collagen-glycosaminoglycan (CG) scaffolds with VEGF in a spatially defined manner. In this effort we demonstrate functional patterning of a known agonist of vascular remodeling and directly observe phenotypic effects induced by this immobilized cue. VEGF was successfully patterned in both stripes and square motifs across the scaffold with high specificity (on:off pattern signal). The depth of patterning was determined to extend up to 500 µm into the scaffold microstructure. Notably, photopatterned VEGF retained native functionality as it was shown to induce morphological changes in human umbilical vein cells indicative of early vasculogenesis. Immobilized VEGF led to greater cell infiltration into the scaffold and the formation of immature vascular network structures. Ultimately, these results suggest that BP-mediated photolithography is a facile method to spatially control the presentation of instructive biological cues to cells within CG scaffolds.
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Colágeno/química , Glicosaminoglicanos/química , Células Endoteliales de la Vena Umbilical Humana/citología , Andamios del Tejido/química , Rayos Ultravioleta , Factor A de Crecimiento Endotelial Vascular/farmacología , Animales , Benzofenonas/química , Células Endoteliales de la Vena Umbilical Humana/efectos de los fármacos , Humanos , Proteínas Inmovilizadas/farmacología , Fenotipo , TiburonesRESUMEN
Superantigens and genetic factors may play roles in the etiology and susceptibility to Kawasaki disease (KD). To investigate these roles, percentages of TCR-Vß2+ T cells were compared by flow cytometry using anti-Vß2 monoclonal antibodies and genotyping was done on HLA-DRB1 exon 2, the -308 site of the TNF-α promoter region, and ITPKC SNP rs28493229 by polymerase chain reaction followed by direct sequencing. There were higher percentages of Vß2+ T-cells in KD patients (9.5 ± 2.15%) compared to healthy controls (7.25 ± 1.48%) (P<0.05, Student's t-test, n=6-8/group). However, no polymorphisms were observed in exon 2 of HLA-DRB1 and in the -308 region of the TNF-α promoter. The ITPKC SNP rs28493229 G/C polymorphism was observed in 1 KD patient and 4 healthy controls. This study suggests that KD etiology may be associated with a superantigen and that HLA-DRB1 exon2, TNF-α -308 region and ITPKC SNP rs28493229 may not be associated with KD. This is the first study investigating Vß2+ T cells and candidate genes involvement among Filipino KD patients.
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INTRODUCCIÓN: la mayor parte de la producción mundial de enzimas está destinada a la obtención de proteasas. Las aplicaciones de estas biomoléculas con fines terapéuticos son muy variadas. Algunas se conocen como remedios naturales y otras son fármacos modificadores de la respuesta biológica. Las plantas de piña contienen varias cisteíno-proteasas, el componente mayoritario aislado del tallo es la bromelina de tallo (EC 3.4.22.32). En el campo de la salud se le atribuyen varias acciones entre las que se destaca la de inducir la diferenciación de células tumorales y atenuar el crecimiento del tumor. OBJETIVOS: caracterizar cinéticamente un preparado semipurificado de bromelina obtenida por un procedimiento desarrollado en Cuba para ser evaluado en el campo de la salud. MÉTODOS: el extracto crudo de bromelina, obtenido a partir de tallos de plantas adultas de Ananas comosus (L.) Merr cv Española roja (piña) se purificó por cromatografía de intercambio iónico en carboximetilcelulosa-52 en un sistema semibach. RESULTADOS: la caracterización cinética del extracto purificado permitió comprobar la existencia de un preparado activo y estable con una actividad específica de 0,94 U/mg de proteínas (2,34 veces superior a la del extracto crudo original), con una fracción proteica mayoritaria de masa molar 24 500 Da y un punto isoeléctrico, localizado en la zona de pH básico (9,55). Tiene pH óptimo 6,8 al utilizar hemoglobina 2 por ciento como sustrato a 37 ºC y una estabilidad en función del pH y de la temperatura aceptable. Si se conserva liofilizado a - 20 ºC mantiene 80 por ciento de la actividad durante 1 año. CONCLUSIONES: la cromatografía de intercambio iónico en carboximetilcelulosa-52 posibilitó la obtención de un preparado semipurificado de bromelina, con una actividad específica superior a la del extracto original que puede ser utilizado en la medicina como antitumoral(AU)
INTRODUCTION: most of the world production of enzymes is devoted to proteases obtaining. Applications of these biomolecules for therapeutical objectives are very varied. Some are known as natural remedies and other are drugs modifying the biological response. Pineapple plants contain some cysteine-proteases, the majority component isolated from stem is the stem Bromelain (EC 3.4.22.32). In the health field it has attributed some actions including the differentiation induction of tumor cells and attenuation of tumor growth. OBJECTIVES: to characterize kinetically a semipurified preparation from Bromelain obtained by a procedure developed in Cuba to be assessed in the health field. METHODS: the crude extract from Bromelain obtained from the adult plant stems of Ananas comosus (L.) Merr Cv Spanish red (pineapple) was purified by ion-exchange chromatography in carboxylmethylcelulose-52 in semibatch system. RESULTS: kinetic characterization of purified extract allowed us to verify the existence of a stable and active preparation with a specific activity of 0,94 U/mg of proteins (2,34 times superior to that of original crude extract) with a protein fraction in the main of molar mass 24 500 Da and a isoelectric point, located in the basic pH zone (9,55). It has a 6,8optimal pH using the 2 percent hemoglobin as substrate at 37ºC and stability depending on pH and on acceptable temperature. If it is preserved lyophilized at 20 ºC it maintains the 80 percent of activity for a year. CONCLUSIONS: the ion-exchange chromatography in carboxyl methylcellulose-52 allowed the achievement of semipurified preparation from Bromelain with a specific activity higher to that of original extract that may to be used in medicine as antitumor agent(AU)
Asunto(s)
Ananas/química , Bromelaínas/uso terapéutico , Neoplasias/tratamiento farmacológicoRESUMEN
INTRODUCCIÓN: la mayor parte de la producción mundial de enzimas está destinada a la obtención de proteasas. Las aplicaciones de estas biomoléculas con fines terapéuticos son muy variadas. Algunas se conocen como remedios naturales y otras son fármacos modificadores de la respuesta biológica. Las plantas de piña contienen varias cisteíno-proteasas, el componente mayoritario aislado del tallo es la bromelina de tallo (EC 3.4.22.32). En el campo de la salud se le atribuyen varias acciones entre las que se destaca la de inducir la diferenciación de células tumorales y atenuar el crecimiento del tumor. OBJETIVOS: caracterizar cinéticamente un preparado semipurificado de bromelina obtenida por un procedimiento desarrollado en Cuba para ser evaluado en el campo de la salud. MÉTODOS: el extracto crudo de bromelina, obtenido a partir de tallos de plantas adultas de Ananas comosus (L.) Merr cv Española roja (piña) se purificó por cromatografía de intercambio iónico en carboximetilcelulosa-52 en un sistema semibach. RESULTADOS: la caracterización cinética del extracto purificado permitió comprobar la existencia de un preparado activo y estable con una actividad específica de 0,94 U/mg de proteínas (2,34 veces superior a la del extracto crudo original), con una fracción proteica mayoritaria de masa molar 24 500 Da y un punto isoeléctrico, localizado en la zona de pH básico (9,55). Tiene pH óptimo 6,8 al utilizar hemoglobina 2 por ciento como sustrato a 37 ºC y una estabilidad en función del pH y de la temperatura aceptable. Si se conserva liofilizado a - 20 ºC mantiene 80 por ciento de la actividad durante 1 año. CONCLUSIONES: la cromatografía de intercambio iónico en carboximetilcelulosa-52 posibilitó la obtención de un preparado semipurificado de bromelina, con una actividad específica superior a la del extracto original que puede ser utilizado en la medicina como antitumoral
INTRODUCTION: most of the world production of enzymes is devoted to proteases obtaining. Applications of these biomolecules for therapeutical objectives are very varied. Some are known as natural remedies and other are drugs modifying the biological response. Pineapple plants contain some cysteine-proteases, the majority component isolated from stem is the stem Bromelain (EC 3.4.22.32). In the health field it has attributed some actions including the differentiation induction of tumor cells and attenuation of tumor growth. OBJECTIVES: to characterize kinetically a semipurified preparation from Bromelain obtained by a procedure developed in Cuba to be assessed in the health field. METHODS: the crude extract from Bromelain obtained from the adult plant stems of Ananas comosus (L.) Merr Cv Spanish red (pineapple) was purified by ion-exchange chromatography in carboxylmethylcelulose-52 in semibatch system. RESULTS: kinetic characterization of purified extract allowed us to verify the existence of a stable and active preparation with a specific activity of 0,94 U/mg of proteins (2,34 times superior to that of original crude extract) with a protein fraction in the main of molar mass 24 500 Da and a isoelectric point, located in the basic pH zone (9,55). It has a 6,8optimal pH using the 2 percent hemoglobin as substrate at 37ºC and stability depending on pH and on acceptable temperature. If it is preserved lyophilized at 20 ºC it maintains the 80 percent of activity for a year. CONCLUSIONS: the ion-exchange chromatography in carboxyl methylcellulose-52 allowed the achievement of semipurified preparation from Bromelain with a specific activity higher to that of original extract that may to be used in medicine as antitumor agent
Asunto(s)
Ananas/química , Bromelaínas/uso terapéutico , Neoplasias/tratamiento farmacológicoRESUMEN
Las enzimas proteolíticas aisladas de plantas de la familia Bromeliaceae se utilizan ampliamente en la industria médica, biotecnológica y alimenticia. Los estudios realizados en los últimos años sobre la actividad contra metástasis y tumores de las cisteíno-proteasas hacen que se incremente el interés por explorar nuevas fuentes naturales de obtención de fitoproteasas. En el presente trabajo se evaluó la actividad proteolítica de extractos enzimáticos obtenidos a partir de diferentes órganos de plantas de la familia Bromeliaceae. Se colectaron y clasificaron cinco grupos. Las plantas que se colectaron pertenecen a 3 géneros de la mencionada familia: 3 grupos son del género Tillandsia, 1 es del género Guzmania y otro del género Hohenbergia. Los mayores índices de actividad específica (3,3 U/mg de proteínas) se obtuvieron en los preparados obtenidos a partir de diferentes órganos de Hohenbergia penduliflora Mez, de cuyos extractos obtenidos se evaluó la influencia del pH de extracción y la actividad específica fue superior al realizarla a pH 3 a partir de sus tallos(AU)
Asunto(s)
Endopeptidasas , BromeliaceaeRESUMEN
Las enzimas proteolíticas aisladas de plantas de la familia Bromeliaceae se utilizan ampliamente en la industria médica, biotecnológica y alimenticia. Los estudios realizados en los últimos años sobre la actividad contra metástasis y tumores de las cisteíno-proteasas hacen que se incremente el interés por explorar nuevas fuentes naturales de obtención de fitoproteasas. En el presente trabajo se evaluó la actividad proteolítica de extractos enzimáticos obtenidos a partir de diferentes órganos de plantas de la familia Bromeliaceae. Se colectaron y clasificaron cinco grupos. Las plantas que se colectaron pertenecen a 3 géneros de la mencionada familia: 3 grupos son del género Tillandsia, 1 es del género Guzmania y otro del género Hohenbergia. Los mayores índices de actividad específica (3,3 U/mg de proteínas) se obtuvieron en los preparados obtenidos a partir de diferentes órganos de Hohenbergia penduliflora Mez, de cuyos extractos obtenidos se evaluó la influencia del pH de extracción y la actividad específica fue superior al realizarla a pH 3 a partir de sus tallos.
The proteolytic enzymes isolated from the Bromeliaceae family are widely used in the medical, biotechnological, and food industries. The studies conducted in recent years on the activity against metastasis and cysteine-proteases, increase the interest in screening new natural sources of obtention of phytoproteases. In the present paper, the authors assessed the proteolytic activity of enzymatic extracts obtained from different organs of the Bromeliaceae family plants. Five groups were collected and classified. Plants obtained belong to three genuses of the above mentioned family: 3 groups are of genus Tillandsia , one of genus Guzmania , and the other of genus Hohenbergia . The highest rates of specific activity (3.3 U/mg of proteins) were attained in preparations obtained from different organs of Hohenbergia penduliflora Mez. from whose extracts the influence of extraction pH was assessed. The specific activity was greater on carrying it out at pH3, starting from their stalks.
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DNA delivery into fish is important for transient gene expression, (e.g., DNA vaccination). Previous studies have generally focused on intramuscular injection of DNA vaccines into fish. However, this method is obviously impractical and laborious for injecting large numbers of fishes. This study reports oral delivery of a construct expressing the beta-galactosidase reporter gene into fish by encapsulating the DNA in chitosan and incorporating it into fish feeds. We found that beta-galactosidase expression could be observed in the stomachs, spleens, and gills of fishes fed with flakes containing the chitosan-DNA complex. These results suggest that DNA vaccines and other constructs can be easily and cheaply delivered into fishes orally by use of carriers and incorporation into fish feeds.
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Alimentación Animal/análisis , Acuicultura/métodos , Expresión Génica , Tilapia/genética , Vacunas de ADN/genética , beta-Galactosidasa/metabolismo , Animales , Quitosano/metabolismo , Galactósidos , Mucosa Gástrica/metabolismo , Genes Reporteros/genética , Branquias/metabolismo , Técnicas Histológicas , Indoles , Nanotubos , Plásmidos/genética , Bazo/metabolismo , Tilapia/metabolismo , beta-Galactosidasa/genéticaAsunto(s)
Medios de Contraste/administración & dosificación , Embolia Aérea/diagnóstico , Ventrículos Cardíacos/diagnóstico por imagen , Enfermedad Iatrogénica , Tomografía Computarizada por Rayos X/efectos adversos , Dolor Abdominal/diagnóstico , Adulto , Electrocardiografía , Embolia Aérea/etiología , Embolia Aérea/terapia , Medicina de Emergencia , Femenino , Ventrículos Cardíacos/fisiopatología , Humanos , Oxigenoterapia HiperbáricaRESUMEN
BACKGROUND AND PURPOSE: There is an association between anticardiolipin antibodies (aCL) and ischemic stroke. There are, however, also occasional reports linking aCL with other CNS diseases (OND), particularly with multiple sclerosis (MS). Hence, we studied the specificity of aCL for ischemic stroke. METHODS: Prospective, consecutively identified patients evaluated for aCL (immunoglobulin G [IgG] and immunoglobulin M [IgM] isotypes) were divided into two groups: ischemic stroke (first ever) and OND (stroke-free subjects affected by OND). RESULTS: The ischemic stroke group (n = 300) and the OND (n = 149) differed in the following risk factors: age (64 +/- 14 versus 58 +/- 15 years; p < 0.001) and proportions of African Americans (67% versus 29%; p < 0.001); current cigarette smoker (26% versus 17%; p = 0.028); hypertensive (69% versus 34%; p < 0.001); diabetic (18% versus 7%; p = 0.001); history of angina (16% versus 8%; p = 0.015) or myocardial infarction (15% versus 3%; p < 0.001). There were higher rates of aCL positivity (26% versus 17%; p = 0.050), IgG-aCL > 10 GPL (23% versus 11%; p = 0.003) or IgG aCL > 20 GPL (12% versus 4%; p = 0.012) among the stroke group than among the OND group. No differences in IgG-aCL positivity were found between the MS group and the rest of the OND group but the MS patients had a higher rate of IgM-aCL positivity than the other OND patients. CONCLUSION: IgG-aCL positivity does not appear to be a marker for CNS disease generally but of ischemic stroke.
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Anticuerpos Anticardiolipina/sangre , Enfermedades del Sistema Nervioso Central/inmunología , Trastornos Cerebrovasculares/inmunología , Isotipos de Inmunoglobulinas/sangre , Anticuerpos Antifosfolípidos/sangre , Especificidad de Anticuerpos , Población Negra , Isquemia Encefálica/sangre , Isquemia Encefálica/inmunología , Enfermedades del Sistema Nervioso Central/sangre , Trastornos Cerebrovasculares/sangre , Femenino , Humanos , Técnicas para Inmunoenzimas , Inmunoglobulina G/sangre , Inmunoglobulina M/sangre , Masculino , Michigan , Persona de Mediana Edad , Oportunidad Relativa , Selección de Paciente , Valores de Referencia , Factores de RiesgoRESUMEN
Cutaneous silent period (CSP) was measured on stimulating digits 2 and 5 in 19 patients with carpal tunnel syndrome (CTS) and compared with 20 healthy volunteers. In 2 patients with severe CTS, CSP was absent on digit 2 but present on digit 5. In mild/moderate CTS digit 2 CSP mean duration was 50.9+/-13.9 ms, significantly longer than control subjects (36.9+/-8.7 ms) (P = 0.005). CSP was found to be abnormal in CTS, being absent in severe and prolonged in mild/moderate cases.
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Síndrome del Túnel Carpiano/fisiopatología , Adulto , Electromiografía , Dedos/fisiopatología , Humanos , Persona de Mediana Edad , Conducción Nerviosa/fisiología , Estimulación Física , Valores de ReferenciaRESUMEN
BACKGROUND AND PURPOSE: Headache is the most common neurologic symptom following minor closed head injury. There is often a lack of objective evidence supporting an organic basis of cerebral pathology in these cases. This pilot study considers the possibility of alterations in cerebral blood flow, indicating evidence of an organic disorder in posttraumatic headache. METHODS: Regional cerebral blood flow studies of 35 patients with chronic posttraumatic headache (PTH) (International Headache Society criteria), identified retrospectively from our cerebral blood flow data base, were compared with those of 49 nonheadache controls and 92 migraineurs (Ad Hoc Committee criteria). Regional cerebral blood flow (initial slope index method) was measured using the xenon Xe 133 inhalation technique. RESULTS: Compared to migraineurs and controls, and after adjusting for differences (analysis of covariance) in baseline variables such as blood pressure, hematocrit, and PCO2, patients with PTH had: (1) significantly lower mean initial slope indices (P < 0.001, P = 0.002, respectively); (2) regional interhemispheric flow differences (rIFD), with higher distribution of regional asymmetrical probe pairs (rIFD > or = 7%: P[PTH versus control] = 0.006, P[PTH versus migraine] = 0.016: rIFD > or = 10%; P[PTH versus control] = 0.011, P[PTH versus migraine] = 0.003); and (3) more hemispheric asymmetries (P[PTH versus control] = 0.023, P[PTH versus migraine] = 0.57). Lower mean initial slope indices and hemispheric asymmetry (mean interhemispheric flow difference > or = 3.2%) predicted PTH over control (P = 0.023 and 0.002, respectively). Lower mean initial slope indices predicted PTH over migraine (P = 0.002). CONCLUSIONS: Patients with PTH have reduced regional cerebral blood flow, and regional and hemispheric asymmetries. These cerebral hemodynamic alterations support an organic basis to chronic posttraumatic headache.
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Circulación Cerebrovascular , Traumatismos Craneocerebrales/complicaciones , Cefalea/fisiopatología , Adulto , Anciano , Enfermedad Crónica , Traumatismos Craneocerebrales/fisiopatología , Femenino , Cefalea/etiología , Humanos , Masculino , Persona de Mediana Edad , Trastornos Migrañosos/fisiopatología , Proyectos PilotoRESUMEN
No estado do Rio de Janeiro, assim como no resto do país, os serviços de saúde empregam grande quantidade de servidores nao habilitados, dificultando uma assistência à saúde de qualidade. Para reverter essa situaçao, os autores propoem a formaçao técnica, a nível de 1§ e 2§ graus, dos servidores nas habilitaçoes de saúde aprovadas pelo Conselho Federal de Educaçao e analisam a experiência da Escola Técnica Enfermeira Izabel dos Santos, da Secretaria de Estado de Saúde do Rio de Janeiro. O processo pedagógico tem por base a problematizaçao da realidade. Concebida como escola aberta, já implantou 8 núcleos descentralizados, com um total de 225 alunos-servidores
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Técnicos Medios en Salud , Fuerza Laboral en Salud , Escuelas para Profesionales de SaludRESUMEN
Aborda no Estado do Rio de Janeiro, assim como no resto do país, os serviços empregados na área da saúde, bem como a grande quantidade de servidores não habilitados, dificultando uma assistência a saúde de qualidade. Para reverter essa situação, há uma proposta de formação téccnica, a nível de primeiro e segundo graus, dos servidores nas habilitações de saúde aprovadas pelo Conselho Federal de Educação. Para isso é analisada a experiência da Escola Técnica Enfermeira Izabel dos Santos, da Secretaria de Estado de Saúde do Rio de Janeiro.(AU)
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Fuerza Laboral en Salud , Escuelas para Profesionales de Salud , Capacitación en Servicio , Servicios de Salud , BrasilRESUMEN
A rapid and accurate method has been developed for measuring the elastic response of vesicle bilayer membranes to an applied osmotic pressure. The technique of dynamic light scattering is used to measure both the elastic constant and the elastic limit of dioleoylphosphatidic acid (DOPA) and DOPA-cholesterol vesicles and of submitochondrial particles derived from the inner membrane of bovine heart mitochondria. The vesicles prepared by the pH-adjustment method are unilamellar and of uniform size between 240 and 460 nm in diameter. The vesicles swell uniformly upon dilution. The observed change in size is not due to any change in the shape of the vesicles. The data also indicate that the vesicles are spherical and not flaccid. The total vesicle swelling in these studies resulted in a 3-4% increase in surface area for vesicles swollen in 0.15 M KCl and a 5-10% increase in surface area for vesicles swollen in 0.25 M sucrose. This maximum represents the elastic limit of the vesicles. Evidence is presented to show that the vesicles release contents after swelling to this maximum, reseal immediately, and reswell according to the osmotic pressure. For DOPA vesicles in a 0.15 M KCl-tris(hydroxymethyl)aminomethane hydrochloride (Tris-HCl) buffer (pH 7.55), the observed membrane modulus is found to be in the range of 10(8) dyn/cm2. The modulus was found to be in the order of 10(7) dyn/cm2 for DOPA vesicles in a 0.25 M sucrose-Tris-HCl buffer (pH 7.55). This is comparable to that of submitochondrial particles in the same sucrose-Tris-HCl buffer. The observed membrane modulus also decreases with vesicle size. Its magnitude and its variation with ionic strength indicate that the major component of bilayer elasticity is neither the inherent elasticity of the bilayer nor the bending modulus. The variation of the membrane modulus with respect to curvature suggests that its principal component may be related to surface tension effects including the negative charges on the vesicle surface. There is considerable variation between vesicles swollen in sucrose and those swollen in KCl in the membrane modulus, in the elastic limit at which the vesicles burst, and in the transbilayer pressure difference at bursting. The latter was found to be 4-6 mosM (10(5) dyn/cm2) in sucrose solution and 20-4 mosM (10(6) dyn/cm2) in KCl solution.
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Membrana Dobles de Lípidos , Mitocondrias Cardíacas/ultraestructura , Dilatación Mitocondrial , Ácidos Fosfatidicos , Partículas Submitocóndricas/ultraestructura , Animales , Bovinos , Elasticidad , Matemática , Modelos Biológicos , Presión Osmótica , Análisis EspectralRESUMEN
A method has been developed for making large unilamellar vesicles (LUV) with low polydispersity. The LUV, constituted of dioleoylphosphatidic acid (DOPA), 300 nm in diameter are made by a modification of the pH adjustment technique (Hauser, H. and Gains, N. (1982) Proc. Natl. Acad. Sci. USA 79, 1683-1687). This size is 10 times that (30 nm) of vesicles prepared by prolonged sonication. Vesicle size is increased stepwise by adding cholesterol (to a maximum of 40 mol% cholesterol) to form vesicles in 0.15 M KCl with up to 600 nm diameter. The vesicle size is measured by photon correlation spectroscopy, electron microscopy, and by measurement of the internal volume with cyanocobalamin while calculating the number of DOPA molecules per vesicle. Vesicles are stable for at least three weeks. Sepharose 4B column chromatography of the preparation yields a peak of fractions with the same polydispersity as the original sample and shows that 30 to 40% of the original lipid in a sample is recovered as LUV. Less than 2% of the sample forms small unilamellar vesicles (SUV) (diameter = 30 nm), which emerge from the column in a separate peak. Since the remaining lipid is not suspended in the buffer during vesicle formation, for most purposes the vesicles may be used immediately after titration so that they can be prepared in less than 40 min.