RESUMEN
The work was carried out to investigate differences in visual search characteristics between groups of observers with different levels of experience in the task of pulmonary nodule detection in chest radiology and we report here on these differences in respect of time related decisions. Volunteer observers were divided into three groups depending on their level of expertise. There were eight radiologists, eight radiographers and eight novices. Their task was to detect pulmonary nodules in a test bank of 120 digitized posteroanterior (PA) chest radiographs. Five of the eight radiographers were tested twice: once before and once after a 6-month training programme in interpretation of the adult chest radiograph. During each test session the observers' eye movements were tracked. Data on the observers' decisions through Alternate Free Response Operating Characteristic (AFROC) methodology were correlated to their eye-movement and fixation patterns. True negative decisions from all observers were associated with shorter fixation times than false negative decisions. No correct negative decisions were made after fixations exceeding 3 s.
Asunto(s)
Competencia Clínica , Radiografía , Radiología , Nódulo Pulmonar Solitario/diagnóstico por imagen , Adulto , Movimientos Oculares , Fijación Ocular , Humanos , Procesamiento de Imagen Asistido por Computador , Variaciones Dependientes del Observador , Curva ROC , TiempoRESUMEN
Two new 2,6-disubstituted piperidine alkaloids andrachcinine (1) and andrachcinidine (5) have been isolated from Andrachne aspera along with andrachamine and andrachcine (2). The absolute configurations of 1, 2, and 5 were established. (+)-Allosedridine and the new alkaloids (-)-8-epi-8-ethylnorlobelol I (4) and (-)-8-epihalosaline (7) were also identified as constituents of A. aspera. Structures were determined by MS and NMR techniques and by chemical conversions.
Asunto(s)
Alcaloides/aislamiento & purificación , Euphorbiaceae/química , Piperidinas/aislamiento & purificación , Alcaloides/química , Espectroscopía de Resonancia Magnética , Espectrometría de Masas , Modelos Químicos , Piperidinas/químicaRESUMEN
BACKGROUND: Vascular smooth muscle cell (VSMC) growth is responsible for intimal hyperplasia, a major cause of failure after vascular surgery and angioplasty. Heparin is the first described inhibitor of VSMC growth, but has not proved effective in the prevention of human intimal hyperplasia. Heparin is a heterogeneous substance, which may contain a mixture of components which differ in antiproliferative activity. Isolation of an active component may favourably influence its therapeutic profile. METHODS AND RESULTS: Growth of human VSMC cultured from operative specimens, assessed by cell counting and labelled thymidine incorporation, was used as a model of VSMC proliferation in intimal hyperplasia. Unfractionated (UFH) and low molecular weight (LMWH) heparins inhibit cell growth and thymidine uptake by human VSMCs in response to 15% foetal calf serum. UFHs are more active than LMWHs and this difference increases with increasing heparin dose. To confirm this effect, size-based fractions of heparin were prepared by gel permeation chromatography, and characterised by high performance liquid chromatography. High molecular weight fractions (MW > 21000) have higher activity than fractions of medium (MW 12000-21000) or low molecular weight (MW < 12000). These differences become more pronounced at higher dose, and are statistically significant at 100 micrograms/ml (Mann-Whitney, p < 0.05). CONCLUSIONS: The antiproliferative activity of heparin appears to be maximal in its high molecular weight component.