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1.
Dalton Trans ; 52(37): 13110-13118, 2023 Sep 26.
Artículo en Inglés | MEDLINE | ID: mdl-37675851

RESUMEN

Niobium based anodes are gaining increasing popularity for application in high-power lithium-ion batteries, due to their high theoretical capacities, inherent safety at high current densities, and long-term stability. Here, we report the discovery and characterisation of a new Wadsley Roth niobate system, Nb7Ti1.5Mo1.5O25, showing that it is isostructural with known systems: Nb9PO25 and Nb9VO25. To evaluate the material's electrochemical performance, including performance at high current densities (for potential high power applications), and long-term stability, Li half-coin cells were prepared. The material showed an initial capacity of 268(9) mA h g-1 at 0.01 A g-1 (voltage range of 2.5-1.0 V). However, in subsequent cycles, some of this initial capacity is lost, which is attributed to Li trapping associated with the presence of reducible MoO4 units, similar to the situation observed for isostructural Nb9VO25. After this initial irreversible capacity loss, the material showed good performance at high current density rates, such that at 2 A g-1 and 4 A g-1 respective capacities of 132(10) mA h g-1 and 115(14) mA g-1 were delivered. Moreover, the material showed respectable capacity retention (97%) after being cycled for 100 cycles at 0.2 A g-1. In order to identify the different Nb, Ti, Mo redox couples involved in this system, a Ta analogue was also synthesized (Ta7Ti1.5Mo1.5O25) and the electrochemical performance for this phase is also reported. This phase shows a lower initial capacity at 0.01 A g-1 (140(3) mA h g-1) than the Nb analogue in the same voltage range, which can be increased (225 mA h g-1) if a lower cutoff voltage (0.5 V) is applied. The capacity retention for this Ta system after 100 cycles at 0.2 A g-1 is similar to the Nb analogue (97%). Further work has explored whether the Nb-Ti-Mo contents could be varied, and these results showed that single phase Nb10-2xTixMoxO25 samples could be prepared for 1.5 ≤ x ≤ 1.75, and electrochemical testing results for the x = 1.75 endmember are also reported. Overall, this research highlights the synthesis and electrochemical characterisation of two new Wadsley Roth phases, and further highlights the challenges associated with the presence of reducible cations in tetrahedral sites in such structures with respect to minimising initial irreversible capacity loss.

2.
Dalton Trans ; 50(9): 3315-3323, 2021 Mar 09.
Artículo en Inglés | MEDLINE | ID: mdl-33595035

RESUMEN

Solar perovskites have received phenomenal attention and success over the past decade, due to their high power conversion efficiencies (PCE), ease of fabrication and low cost which has enabled the prospect of them being a real commercial contender to the traditional silicon technology. In one of the several developments on the archetypal MAPbI3 perovskite absorber layer, FAPbI3 was found to obtain a higher PCE, likely due to its more optimum band gap, with doping strategies focusing on the inclusion of MA+/Cs+ cations to avoid the unfavourable phase transformation to a photoinactive phase. To better understand the phase change from the photoactive cubic (Pm3[combining macron]m) black (α) phase to the unwanted photoinactive (P63/mmc) yellow (δ) phase, we make use of variable temperature Raman spectroscopy to probe the molecular species and its relationship to the inorganic framework. We show for the first time there to be no Raman active modes for the α phase up to 4000 cm-1, which can be correlated to the Pm3[combining macron]m cubic symmetry of that phase. Our detailed studies suggest that previous reports of the observation of Raman peaks for this phase are likely associated with degradation reactions from the localised laser exposure and the formation of Raman active lead oxide. In addition, we have identified water as a contributing factor to the transformation, and observed a corresponding signal in the Raman spectra, although confirmation of its exact role still remains inconclusive.

3.
J Chem Educ ; 97(8): 2231-2237, 2020 Aug 11.
Artículo en Inglés | MEDLINE | ID: mdl-32801390

RESUMEN

While Li-ion batteries are abundant in everyday life from smart phones to electric vehicles, there are a lack of educational resources that can explain their operation, particularly their rechargeable nature. It is also important that any such resource can be understood by a wide range of age groups and backgrounds. To this end, we describe how modified tower block games sets, such as Jenga, can be used to explain the operation of Li-ion batteries. The sets can also be utilized to explain more advanced topics such as battery degradation and challenges with charging these batteries at high rates. In order to make the resource more inclusive, we also illustrate modifications to prepare tactile tower block sets, so that the activity is also suitable for blind and partially sighted students. Feedback from a range of groups supports the conclusion that the tower block sets are a useful tool to explain Li-ion battery concepts.

4.
Proc Biol Sci ; 285(1891)2018 11 21.
Artículo en Inglés | MEDLINE | ID: mdl-30464064

RESUMEN

The power of citizen science to contribute to both science and society is gaining increased recognition, particularly in physics and biology. Although there is a long history of public engagement in agriculture and food science, the term 'citizen science' has rarely been applied to these efforts. Similarly, in the emerging field of citizen science, most new citizen science projects do not focus on food or agriculture. Here, we convened thought leaders from a broad range of fields related to citizen science, agriculture, and food science to highlight key opportunities for bridging these overlapping yet disconnected communities/fields and identify ways to leverage their respective strengths. Specifically, we show that (i) citizen science projects are addressing many grand challenges facing our food systems, as outlined by the United States National Institute of Food and Agriculture, as well as broader Sustainable Development Goals set by the United Nations Development Programme, (ii) there exist emerging opportunities and unique challenges for citizen science in agriculture/food research, and (iii) the greatest opportunities for the development of citizen science projects in agriculture and food science will be gained by using the existing infrastructure and tools of Extension programmes and through the engagement of urban communities. Further, we argue there is no better time to foster greater collaboration between these fields given the trend of shrinking Extension programmes, the increasing need to apply innovative solutions to address rising demands on agricultural systems, and the exponential growth of the field of citizen science.


Asunto(s)
Agricultura/tendencias , Participación de la Comunidad , Alimentos , Investigación/tendencias , Agricultura/normas , Investigación/normas , Estados Unidos
5.
Chronic Dis Inj Can ; 34 Suppl 1: 1-30, 2014.
Artículo en Inglés, Francés | MEDLINE | ID: mdl-24898593

RESUMEN

INTRODUCTION: The Public Health Agency of Canada developed the Chronic Disease Indicator Framework (the Framework) with the goal of systematizing and enhancing chronic disease surveillance in Canada by providing the basis for consistent and reliable information on chronic diseases and their determinants. METHODS: Available national and international health indicators, frameworks and national health databases were reviewed to identify potential indicators. To make sure that a comprehensive and balanced set of indicators relevant to chronic disease prevention was included, a conceptual model with "core domains" for grouping eligible indicators was developed. Specific selection criteria were applied to identify key measures. Extensive consultations with a broad range of government partners, non-governmental organizations and public health practitioners were conducted to reach consensus and refine and validate the Framework. RESULTS: The Framework contains 41 indicators organized in a model comprised of 6 core domains: social and environmental determinants, early life / childhood risk and protective factors, behavioural risk and protective factors, risk conditions, disease prevention practices, and health outcomes/status. Also planned is an annual release of updated data on the proposed set of indicators, including national estimates, breakdowns by demographic and socioeconomic variables, and time trends. CONCLUSIONS: Understanding the evidence related to chronic diseases and theirdeterminants is key to interpreting trends and crucial to the development of public health interventions. The Framework and its related products have the potential of becoming an indispensable tool for evidence-informed decision making in Canada.


TITRE: Surveillance des maladies chroniques au Canada : Cadre conceptuel d'indicateurs des maladies chroniques. INTRODUCTION: L'Agence de la santé publique du Canada a conçu le Cadre conceptuel d'indicateurs des maladies chroniques (le Cadre) dans le but de systématiser et d'améliorer la surveillance des maladies chroniques au Canada en instaurant les fondements d'une information uniforme et fiable sur les maladies chroniques et leurs déterminants. MÉTHODOLOGIE: Des indicateurs de santé nationaux et internationaux, des cadres conceptuels ainsi que des bases de données sur la santé nationale ont été examinés pour identifier les indicateurs potentiels. Pour s'assurer d'obtenir un ensemble complet et équilibré d'indicateurs pertinents en matière de prévention des maladies chroniques, nous avons élaboré un modèle conceptuel comprenant des « champs de référence ¼ pour le regroupement des indicateurs. Plusieurs critères de sélection ont été appliqués pour le choix des mesures clés. Des consultations approfondies avec un large éventail de partenaires du gouvernement, d'organismes non gouvernementaux et de professionnels de la santé publique ont été réalisées pour en arriver à un consensus et pour perfectionner et valider le Cadre. RÉSULTATS: Le Cadre comprend 41 indicateurs structurés autour de 6 champs de référence : les déterminants sociaux et environnementaux, les facteurs de risque et de protection en bas âge, les facteurs de risque et de protection comportementaux, les conditions à risque, les pratiques de prévention des maladies, l'état de santé global et les impacts sur la santé. Nous avons aussi prévu une mise à jour annuelle des données touchant l'ensemble des indicateurs proposés, que ce soit les estimations nationales, les ventilations par variables démographiques et socioéconomiques ou les tendances temporelles. CONCLUSION: Comprendre les données probantes liées aux maladies chroniques et leurs déterminants est nécessaire pour interpréter les tendances et crucial pour élaborer des interventions efficaces en matière de santé publique. Le Cadre et ses produits connexes sont susceptibles de devenir un outil indispensable d'aide à la décision axée sur des données probantes au Canada.


Asunto(s)
Enfermedad Crónica , Indicadores de Salud , Salud Pública , Canadá , Bases de Datos Factuales , Femenino , Encuestas Epidemiológicas , Humanos , Masculino , Monitoreo Fisiológico
6.
Proc Biol Sci ; 278(1709): 1183-8, 2011 Apr 22.
Artículo en Inglés | MEDLINE | ID: mdl-20926441

RESUMEN

Technological developments allow increasing numbers of markers to be deployed in case-control studies searching for genetic factors that influence disease susceptibility. However, with vast numbers of markers, true 'hits' may become lost in a sea of false positives. This problem may be particularly acute for infectious diseases, where the control group may contain unexposed individuals with susceptible genotypes. To explore this effect, we used a series of stochastic simulations to model a scenario based loosely on bovine tuberculosis. We find that a candidate gene approach tends to have greater statistical power than studies that use large numbers of single nucleotide polymorphisms (SNPs) in genome-wide association tests, almost regardless of the number of SNPs deployed. Both approaches struggle to detect genetic effects when these are either weak or if an appreciable proportion of individuals are unexposed to the disease when modest sample sizes (250 each of cases and controls) are used, but these issues are largely mitigated if sample sizes can be increased to 2000 or more of each class. We conclude that the power of any genotype-phenotype association test will be improved if the sampling strategy takes account of exposure heterogeneity, though this is not necessarily easy to do.


Asunto(s)
Simulación por Computador , Predisposición Genética a la Enfermedad , Modelos Genéticos , Tuberculosis Bovina/genética , Animales , Bovinos , Marcadores Genéticos , Genotipo , Repeticiones de Microsatélite , Polimorfismo de Nucleótido Simple , Procesos Estocásticos
7.
J Inherit Metab Dis ; 28(1): 21-33, 2005.
Artículo en Inglés | MEDLINE | ID: mdl-15702403

RESUMEN

Anderson-Fabry disease (referred to as Fabry disease) is an X-linked disorder characterized by a deficiency of the lysosomal enzyme alpha-galactosidase A and the subsequent accumulation in various tissues of globotriaosylceramide (Gb(3)), the main substrate of the defective enzyme. Enzyme replacement therapy (ERT) offers a specific treatment for patients with Fabry disease, though monitoring of treatment is hampered by a lack of surrogate markers of response. In this study, the efficacy of long-term ERT in six Fabry hemizygotes and two symptomatic heterozygotes has been evaluated. Patients were administered recombinant alpha-galactosidase A every 2 weeks for up to a year. The efficacy of ERT was assessed by monitoring symptomatology and renal function. Urinary glycolipid concentration was estimated by a novel tandem mass spectrometric method. Urine glycolipid (Gb(3)) was elevated at baseline and fell impressively on ERT where patients were hemizygotes and in the absence of renal transplantation. In heterozygotes and in a recipient of a renal allograft, elevations and changes in urine glycolipids were less pronounced. In one patient, after several months of ERT, there was a transient increase in Gb(3) concentrations to baseline (pre-ERT) levels, associated with the presence of antibodies to the recombinant alpha-galactosidase A. The marked decline in urine Gb(3) on ERT, and its subsequent increase in association with an inhibitory antibody response, suggest that this analyte deserves further investigation as a potential marker of disease severity and response to treatment.


Asunto(s)
Enfermedad de Fabry/terapia , Trihexosilceramidas/orina , Adulto , Biomarcadores , Análisis Mutacional de ADN , Enfermedad de Fabry/enzimología , Femenino , Glucolípidos/metabolismo , Heterocigoto , Humanos , Inmunoensayo , Isoenzimas/uso terapéutico , Trasplante de Riñón , Masculino , Espectrometría de Masas , Persona de Mediana Edad , Modelos Químicos , Dolor , Proteínas Recombinantes , Espectrometría de Masa por Ionización de Electrospray , Encuestas y Cuestionarios , Factores de Tiempo , alfa-Galactosidasa/química , alfa-Galactosidasa/uso terapéutico
8.
Circulation ; 104(7): 820-5, 2001 Aug 14.
Artículo en Inglés | MEDLINE | ID: mdl-11502709

RESUMEN

BACKGROUND: Prostanoid synthesis via the action of cyclooxygenase-2 (COX-2) is a component of the inflammatory response. Prostacyclin, a product of COX-2 in vascular endothelium, has important physiological roles, such as increasing blood flow to injured tissues, reducing leukocyte adherence, and inhibiting platelet aggregation. We examined the possibility that selective COX-2 inhibition could suppress the protective effects of prostacyclin, resulting in an alteration of the hemostatic balance and vascular tone. METHODS AND RESULTS: Circumflex coronary artery thrombosis was induced in dogs by vascular electrolytic injury. Orally administered celecoxib (COX-2 inhibition) or high-dose aspirin (HDA) (COX-1 and COX-2 inhibition) did not alter time to occlusive thrombus formation compared with controls (celecoxib 77.7+/-7.2 minutes, HDA 72.0+/-18.5 minutes, control 93.0+/-21.8 minutes). Oral HDA with an endothelial recovery period (HDA-ER) (COX-1 inhibition) produced a significant increase in time to vessel occlusion (257.0+/-41.6 minutes). The observed increase in time to occlusion was abolished when celecoxib was administered to animals dosed with HDA-ER (80.7+/-20.6 minutes). The vasomotor effect of endothelium-derived prostacyclin was examined by monitoring coronary flow during intracoronary administration of arachidonic acid or acetylcholine. In celecoxib-treated animals, vasodilation in response to arachidonic acid was reduced significantly compared with controls. CONCLUSIONS: The results indicate important physiological roles for COX-2-derived prostacyclin and raise concerns regarding an increased risk of acute vascular events in patients receiving COX-2 inhibitors. The risk may be increased in individuals with underlying inflammatory disorders, including coronary artery disease.


Asunto(s)
Trombosis Coronaria/tratamiento farmacológico , Vasos Coronarios/efectos de los fármacos , Inhibidores de la Ciclooxigenasa/farmacología , Isoenzimas/antagonistas & inhibidores , Sistema Vasomotor/efectos de los fármacos , Acetilcolina/farmacología , Animales , Ácido Araquidónico/farmacología , Aspirina/farmacología , Benzofuranos/farmacología , Velocidad del Flujo Sanguíneo/efectos de los fármacos , Celecoxib , Circulación Coronaria/efectos de los fármacos , Trombosis Coronaria/fisiopatología , Vasos Coronarios/fisiopatología , Ciclooxigenasa 2 , Inhibidores de la Ciclooxigenasa 2 , Inhibidores de la Ciclooxigenasa/efectos adversos , Modelos Animales de Enfermedad , Perros , Relación Dosis-Respuesta a Droga , Esquema de Medicación , Epoprostenol/farmacología , Agregación Plaquetaria/efectos de los fármacos , Prostaglandina-Endoperóxido Sintasas , Pirazoles , Sulfonamidas/efectos adversos , Sulfonamidas/farmacología , Tromboxano-A Sintasa/antagonistas & inhibidores , Factores de Tiempo , Vasodilatación/efectos de los fármacos , Sistema Vasomotor/fisiopatología
9.
Br J Pharmacol ; 132(7): 1493-500, 2001 04.
Artículo en Inglés | MEDLINE | ID: mdl-11264243

RESUMEN

1. Tedisamil is a bradycardiac agent that prolongs the QT interval of the ECG and prevents cardiac arrhythmias. Given this profile, tedisamil might be expected to have proarrhythmic actions similar to Class III antiarrhythmic drugs. To address this question, the actions of dofetilide and tedisamil were examined in rabbit isolated hearts in which bradycardia was induced by AV ablation. 2. The QT interval was prolonged in a reverse rate-dependent fashion by dofetilide (3 and 30 nM) and tedisamil (0.3 and 3 microM). 3. Torsades de pointes was observed in 1/7 hearts treated with 3 nM dofetilide and 0/7 hearts treated with 0.3 microM tedisamil. The incidence of torsades de pointes was increased to 5/7 in hearts treated with 30 nM dofetilide and to 7/7 in hearts treated with 3 microM tedisamil (both P < 0.05 vs control). 4. The actions of 30 nM dofetilide and 3 microM tedisamil were also examined in hearts paced at 50, 100, 200 and 50 beats min(-1) successively. Both drugs caused torsades de pointes in 5/5 hearts paced at 50 beats min(-1); however, the incidence was reduced to 0/5 during pacing at 200 beats min(-1). Thus, drug-induced proarrhythmia was bradycardia-dependent. 5. Drug-induced prolongation of the interval between the peak and end of the T-wave (QTa-e) was reverse rate-dependent and was associated with the occurrence of torsades de pointes (r = 0.91, P < 0.01). 6. The results suggest that tedisamil, like dofetilide, presents a risk for development of torsades de pointes.


Asunto(s)
Antiarrítmicos/farmacología , Compuestos Bicíclicos Heterocíclicos con Puentes/farmacología , Ciclopropanos/farmacología , Fenetilaminas/farmacología , Sulfonamidas/farmacología , Torsades de Pointes/fisiopatología , Animales , Relación Dosis-Respuesta a Droga , Electrocardiografía , Corazón/efectos de los fármacos , Corazón/fisiopatología , Técnicas In Vitro , Masculino , Potasio/sangre , Potasio/farmacología , Conejos
10.
Thromb Haemost ; 86(5): 1296-304, 2001 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-11816721

RESUMEN

Thrombostatins are a group of compounds based upon a breakdown product of bradykinin, RPPGF. They inhibit alpha-thrombin-induced platelet activation by binding to protease activated receptor 1 and, at a lower affinity, by interacting with thrombin's active site. After a single intravenous infusion of MAP4-RPPGF (11.58 mg/kg), its t1/2alpha was 4.5 min with a clearance of 2.0 ml/min. MAP4-RPPGF administration had a sustained antiplatelet effect, preventing gamma-thrombin-induced (12.5 nM) platelet activation for 4 h. Its antiplatelet effect summated with that of aspirin and/or clopidogrel. MAP4-RPPGF was compared with aspirin and clopidogrel in the Folts model of coronary artery thrombosis. Dogs were randomized to 3 treatment groups: aspirin 1.14 mg/kg i.v., clopidogrel 0.5 mg/kg i.v., or MAP4-RPPGF 0.77 mg/kg i.v. Cyclic flow variations (CFV) were recorded in 5 untreated dogs hourly for 3 successive hours and for 1 h before (all groups >11 CFV/h), and for 2 h after drug infusion in each of the 3 treatment groups. After 1 h drug treatment, all groups of animals had <6 CFV/h; after 2 h treatment, all had <1 CFV/h. All agents significantly reduced CFV from control at each hour, but none was significantly better than any other. Thrombostatin was as effective as aspirin or clopidogrel in inhibiting coronary artery thrombosis in this canine model.


Asunto(s)
Bradiquinina/farmacocinética , Trombosis Coronaria/prevención & control , Fragmentos de Péptidos/farmacocinética , Flujo Sanguíneo Regional/efectos de los fármacos , Animales , Aspirina/administración & dosificación , Aspirina/farmacología , Pruebas de Coagulación Sanguínea , Bradiquinina/administración & dosificación , Bradiquinina/análogos & derivados , Bradiquinina/farmacología , Clopidogrel , Estenosis Coronaria , Trombosis Coronaria/tratamiento farmacológico , Modelos Animales de Enfermedad , Perros , Evaluación de Medicamentos , Tasa de Depuración Metabólica , Fragmentos de Péptidos/administración & dosificación , Fragmentos de Péptidos/farmacología , Pruebas de Función Plaquetaria , Equivalencia Terapéutica , Ticlopidina/administración & dosificación , Ticlopidina/análogos & derivados , Ticlopidina/farmacología , Factores de Tiempo
11.
J Pharmacol Exp Ther ; 295(2): 492-9, 2000 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-11046080

RESUMEN

P2Y1, P2X1, and P2T receptors mediate ADP-induced platelet aggregation. The antithrombotic effects of AR-C69931MX (N6-[2-methylthio)ethyl]-2-[3,3,3-trifluoropropylthio]-5'-adenylic acid, monoanhydride with dichloromethylenebiphosphonic acid), a selective P2T platelet receptor antagonist, was assessed in a canine model of arterial thrombosis. Placebo or AR-C69931MX (4.0 microg/kg/min for 6 h) pretreatment was administered as an intravenous infusion beginning 15 min before inducing vessel wall injury. A 300-microA anodal current was applied to the intima of the carotid artery for 180 min or discontinued 30 min after cessation of blood flow due to thrombus formation. Each of five control animals developed occlusive thrombi within 3 h after induction of vessel wall injury. In contrast, carotid artery blood flow in five of six AR-C69931MX-treated animals was maintained for the duration of the protocol. Ex vivo platelet aggregation in response to adenosine diphosphate was inhibited at the first measurement time point of 75 min after the start of drug infusion and remained inhibited during drug administration. Bleeding time values were increased in the drug-treated group. Values for both the ex vivo platelet aggregation and the bleeding times returned to control values shortly after discontinuation of AR-C69931MX. The results indicate that AR-C69931MX antagonizes the ex vivo and in vivo aggregatory actions of ADP, and displays a rapid onset and offset of action with the ability to prevent occlusive arterial thrombus formation. AR-C69931MX may be suitable for the management of patients who require short-term modulation of platelet function.


Asunto(s)
Adenosina Monofosfato/análogos & derivados , Adenosina Monofosfato/uso terapéutico , Trombosis de las Arterias Carótidas/prevención & control , Proteínas de la Membrana , Inhibidores de Agregación Plaquetaria/uso terapéutico , Antagonistas del Receptor Purinérgico P2 , Adenosina Difosfato/antagonistas & inhibidores , Adenosina Difosfato/toxicidad , Animales , Arteriopatías Oclusivas/etiología , Arteriopatías Oclusivas/prevención & control , Tiempo de Sangría , Velocidad del Flujo Sanguíneo/efectos de los fármacos , Plaquetas/efectos de los fármacos , Arterias Carótidas/efectos de los fármacos , Trombosis de las Arterias Carótidas/etiología , Modelos Animales de Enfermedad , Perros , Femenino , Hemodinámica/efectos de los fármacos , Inyecciones Intravenosas , Masculino , Agregación Plaquetaria/efectos de los fármacos , Receptores Purinérgicos P2Y12 , Túnica Íntima/lesiones
12.
Med Educ ; 34(10): 841-50, 2000 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-11012934

RESUMEN

BACKGROUND: The 1999 Cambridge Conference was held in Northern Queensland, Australia, on the theme of clinical teaching and learning. It provided an opportunity for groups of academic medical educators to consider some of the challenges posed by recent changes to health care delivery and medical education across a number of countries. PURPOSE: This paper describes the issues raised by the practical challenges posed by the current environment and how they might be addressed in ways that could promote more effective learning in clinical settings. METHOD: A SWOT analysis is a tool that can help in forward planning by identifying the strengths, weaknesses, opportunities and threats presented by any situation. Our SWOT analysis was used to generate a list of items, from which we chose those most feasible and most likely to promote positive change. RESULTS: Twenty different issues were identified, with four of them chosen by consensus for further elaboration. The discussion gave rise to four main recommended strategies: ensuring that clinical teachers thoroughly understand the purpose and process of learning in clinical settings; equipping learners with 'survival skills'; making the best use of learning resources within different clinical environments and making judicious use of information technology to enhance learning efficiency. CONCLUSIONS: The four strategies were selected not only because of their inherent importance, but also because of their feasibility. Modest changes can motivate students to feel part of a clinical team and a 'community of practice' and enhance their capacity for self-regulated practice.


Asunto(s)
Prácticas Clínicas/métodos , Aprendizaje , Computación en Informática Médica , Modelos Educacionales , Humanos
15.
Bioorg Med Chem ; 7(8): 1637-46, 1999 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-10482456

RESUMEN

Tacrine, one of the drugs available for Alzheimer's disease based on the cholinergic approach, suffers from considerable toxicity. Many analogues of tacrine have been prepared which retain the pharmacologically rich aminopyridine or aminoquinoline motifs. The current research was undertaken to produce an acetylcholinesterase inhibitor by employing 11-aminobenzoquinolizidines (4) and 10-aminobenzoindolizidines (5) as templates. Thus, we aimed to achieve three goals relative to tacrine: eliminate the pyridine and quinoline moieties and render the molecule less flat. Overall, the compounds we prepared were poorer inhibitors of acetylcholinesterase compared to tacrine. The single exception was compound 6f which exhibited an effect comparable to that of tacrine, but only at a dose of the order of 10(-3) M. However, despite the poor acetylcholinesterase inhibition by 6b, this compound proved to be an effective anti-amnesic agent at 45 mg/kg dose.


Asunto(s)
Nootrópicos/síntesis química , Nootrópicos/farmacología , Quinolizinas/síntesis química , Quinolizinas/farmacología , Animales , Reacción de Prevención/efectos de los fármacos , Isomerismo , Espectroscopía de Resonancia Magnética , Masculino , Espectrometría de Masas , Nootrópicos/química , Quinolizinas/química , Ratas , Ratas Wistar , Tiempo de Reacción , Relación Estructura-Actividad
16.
Bioorg Med Chem ; 7(8): 1647-54, 1999 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-10482457

RESUMEN

Tacrine, one of the drugs available for Alzheimer's disease based on the cholinergic approach, suffers from considerable toxicity. Many analogues of tacrine has been prepared which retain the pharmacologically rich aminopyridine or aminoquinoline motifs. The current research is a continuation of our efforts in the area of 11-aminobenzoquinolizidines (4) and 10-aminobenzoindolizidines (5) (cf. ref9). A serendipitous discovery led us to the biologically active open chain analogue 9, and we proceeded to elaborate on this molecule. Overall, the compounds we prepared were poor inhibitors of acetylcholinesterase as compared to tacrine. The single exception was compound 20 which exhibited an effect comparable to that of tacrine, but only at a dose in the order of 10(-3) M. However, despite the poor acetylcholinesterase inhibition by 9, this compound was found to be an effective antiamnesic agent.


Asunto(s)
Alcoholes/síntesis química , Alcoholes/farmacología , Nootrópicos/síntesis química , Nootrópicos/farmacología , Piperidinas/química , Pirrolidinas/química , Alcoholes/química , Espectroscopía de Resonancia Magnética , Espectrometría de Masas/métodos , Estructura Molecular , Nootrópicos/química , Relación Estructura-Actividad
17.
Thromb Haemost ; 82(3): 1182-7, 1999 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-10494785

RESUMEN

Thrombostatin (RPPGF), an angiotensin converting enzyme metabolite of bradykinin, is an inhibitor of alpha-thrombin's ability to activate platelets. We examined the in vivo pharmacokinetics and pharmacodynamics of thrombostatin in rabbits and its ability to inhibit coronary thrombosis induced by electrolytic injury in dogs. Plasma half-life of thrombostatin had a t1/2alpha of 2.6 min and a t1/2beta of 24 min in rabbits. Ligating the renal arteries did not prolong clearance (t1/2alpha = 2.4 min; t1/2beta = 12 min). Thrombostatin produced a prolonged in vivo antiplatelet effect. At 30 min after a single intravenous administration in rabbits, thrombostatin's plasma concentration was <8.7 microM (5 microg/ml). However, ex vivo 20 and 40 nM gamma-thrombin-induced platelet aggregation of these rabbits' platelets was inhibited 40% for 2.75 and 1 h, respectively. In vitro, flow cytometry studies revealed that thrombostatin specifically bound to human platelets and washed human platelets treated with thrombostatin were less responsive to gamma-thrombin than control platelets. Using electrolytic injury to induce coronary artery thrombosis, dogs treated with thrombostatin, aspirin, or combined thrombostatin and aspirin occluded in 62+/-25 (mean +/- SD), 62+/-36, or 89+/-32 min versus untreated animals which occluded at 39+/-27 min, (p<0.01, p<0.01 and p<0.001, respectively). These studies show that thrombostatin binds to platelets and can delay coronary occlusion in vivo.


Asunto(s)
Bradiquinina/farmacología , Trombosis Coronaria/prevención & control , Fragmentos de Péptidos/farmacología , Secuencia de Aminoácidos , Animales , Aspirina/administración & dosificación , Aspirina/farmacología , Plaquetas/efectos de los fármacos , Plaquetas/metabolismo , Bradiquinina/administración & dosificación , Bradiquinina/farmacocinética , Trombosis Coronaria/etiología , Perros , Humanos , Técnicas In Vitro , Datos de Secuencia Molecular , Fragmentos de Péptidos/administración & dosificación , Fragmentos de Péptidos/farmacocinética , Péptidos/química , Agregación Plaquetaria/efectos de los fármacos , Inhibidores de Agregación Plaquetaria/administración & dosificación , Inhibidores de Agregación Plaquetaria/farmacocinética , Inhibidores de Agregación Plaquetaria/farmacología , Conejos , Trombina/farmacología
19.
Eur J Pharmacol ; 354(2-3): 289-99, 1998 Aug 07.
Artículo en Inglés | MEDLINE | ID: mdl-9754931

RESUMEN

Propyl-4-yn-valproic acid (2-propyl-4-pentynoic acid), an analogue of valproic acid with a triple bond in one alkyl side chain, potently induces exencephaly in mice. Given that propyl-4-yn-valproic acid is a branched chain carboxylic acid, we synthesized a series of analogues with n-alkyl side chains of increasing length and correlated their potential to induce neural tube defects and to inhibit proliferation and induce differentiation in cells of neural origin, the latter being crucial to the orderly structuring of the embryo. All analogues significantly increased the incidence of neural tube defects in the embryos of dams exposed to a single dose of 1.25 mmol/kg on day 8 of gestation. This effect occurred in a dose-dependent manner and the rate of exencephaly increased with the progressive increase in n-alkyl side chain length. Moreover, increasing chain length resulted in a dose-dependent inhibition of C6 glioma proliferation rate over a concentration range of 0-3 mM and this was independent of the cell type employed and mode of estimating proliferative rate. The antiproliferative action of these analogues was associated with profound shape change in neuro-2A neuroblastoma involving extensive neuritogenesis and an associated increase in neural cell adhesion molecule (NCAM) prevalence at points of cell-cell contact, the latter exhibiting a dose-dependent increase when the n-alkyl chain was extended to five carbon units. These results suggest an interaction with a specific site in which the n-alkyl side is proposed to serve as an 'anchor' within a hydrophobic pocket to facilitate the ionic and/or H-bonding of the carboxylic acid and high electron density of the carbon-carbon triple bond.


Asunto(s)
Teratógenos/farmacología , Ácido Valproico/análogos & derivados , Ácido Valproico/farmacología , Animales , Diferenciación Celular/efectos de los fármacos , División Celular/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Femenino , Glioma/metabolismo , Glioma/patología , Masculino , Ratones , Moléculas de Adhesión de Célula Nerviosa/efectos de los fármacos , Moléculas de Adhesión de Célula Nerviosa/metabolismo , Neuroblastoma/metabolismo , Neuroblastoma/patología , Ratas , Relación Estructura-Actividad , Teratógenos/síntesis química , Células Tumorales Cultivadas , Ácido Valproico/síntesis química , Ácido Valproico/química
20.
Pharmacology ; 57(1): 35-46, 1998 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-9670211

RESUMEN

Cardioprotective effects of the angiotensin-converting enzyme inhibitors captopril and ramiprilat were studied in two in vivo canine models of myocardial ischemic injury: 90 min of regional ischemia with 18 h reperfusion (protocol I) and 6 h of continuous ischemia without reperfusion (protocol II). In protocol I, neither ramiprilat (50 micrograms/kg) nor captopril (5 mg/kg + 0.25 mg/kg/h) reduced infarct size after 18 h of reperfusion (vs. controls). In protocol II, drugs were administered directly into both left anterior descending coronary artery and left circumflex branch. Compared to controls, continuous intracoronary administration of ramiprilat (40 ng/kg/min) or captopril (400 ng/kg/min) did not reduce infarct size. Thus neither captopril nor ramiprilat protected the heart from injury under conditions of ischemia with reperfusion or ischemia without reperfusion.


Asunto(s)
Inhibidores de la Enzima Convertidora de Angiotensina/uso terapéutico , Captopril/uso terapéutico , Infarto del Miocardio/prevención & control , Infarto del Miocardio/fisiopatología , Ramipril/análogos & derivados , Inhibidores de la Enzima Convertidora de Angiotensina/farmacología , Animales , Presión Sanguínea/efectos de los fármacos , Presión Sanguínea/fisiología , Captopril/farmacología , Circulación Coronaria/efectos de los fármacos , Circulación Coronaria/fisiología , Vasos Coronarios/efectos de los fármacos , Vasos Coronarios/fisiopatología , Modelos Animales de Enfermedad , Perros , Estudios de Evaluación como Asunto , Frecuencia Cardíaca/efectos de los fármacos , Frecuencia Cardíaca/fisiología , Hemodinámica/efectos de los fármacos , Hemodinámica/fisiología , Masculino , Isquemia Miocárdica/fisiopatología , Isquemia Miocárdica/prevención & control , Reperfusión Miocárdica/efectos adversos , Daño por Reperfusión Miocárdica/etiología , Daño por Reperfusión Miocárdica/fisiopatología , Ramipril/farmacología , Ramipril/uso terapéutico
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