Observers with four different levels of radiological experience performed a recognition memory task on slides of faces and chest X-ray films. Half of the X-ray films revealed clinically significant abnormalities and half did not. Recognition memory for faces was uniformly high across all levels of radiological experience. Memory for abnormal X-ray films increased with radiological experience and, for the most experienced radiologists, was equivalent to memory for faces. Surprisingly, recognition memory for normal films actually decreased with radiological experience from above chance to a chance level. These results indicate that radiological expertise is associated with selective processing of clinically relevant abnormalities in X-ray images. Expert radiologists appear to process X-ray images the way that we all process faces, by quickly detecting and devoting processing resources to features that distinguish one stimulus from another. However, the selective processing of X-ray films appears to be restricted to clinically relevant abnormalities. As they develop the ability to detect these abnormalities, radiologists appear to lose the ability to detect variations in normal features.This study investigates the relation between expertise and information processing by examining a particular type of expertise, diagnostic radiology, and its effect on the processing of information specific to that domain of expertise, namely,

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Mononuclear cells containing small amounts of cytoplasmic IgM (clgM+) a but lacking stable surface immunoglobulin (sIg) appear in both mouse and human fetal liver before the earliest sIg + B lymphocytes (1-3). These eIgM+'sIg -cells, called pre-B cells, are the least mature members of the B-cell lineage so far identified in mammals. Well defined allotypic markers on the kappa light chains of rabbit immunoglobulins Co-allotypes) provide a means for the further analysis of pre-B and B-cell development (4). The expression of immunoglobulin molecules by rabbit B cells is controlled by regulatory and/or structural genes for the variable and constant regions of heavy, kappa, and lambda chains occurring as separate clusters at three unlinked, complex loci. The particular immunoglobulin polypeptide chains synthesized by each cell result from the activation of selected members of the linked gene clusters. In heterozygous rabbits, individual plasma cells synthesize Ig of only one of the alternative allotypes (5-6), apparently using genes inherited from one parent but not both. The mechanism of this allelic exclusion has not been established and the stage of B-cell differentiation at which it occurs is uncertain because of the conflicting results of tests for allotype exclusion by B lymphocytes.When blood lymphocytes from b4b 5 rabbits were treated with 125I anti-b4 and antib5 (7), or studied by combined immunofluorescence and radioautography (8), the majority of B lymphocytes had only one sIg allotype detectable but a small percentage *

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The validity of using radioactive microspheres (15 +/- 5-mum diameter) to measure gastric blood flow and its partition between gastric wall layers was investigated in anesthetized dogs with a chambered segment of gastric corpus. Total flow measured by a venous effluent technique demonstrated close correlation with microsphere-measured flow (r = 0.98, slope = 0.95) in 12 dogs given histamine, gastrin, or isoproterenol. In 12 histamine-stimulated dogs, mucosal flow measured by aminopyrine clearance and by microspheres also showed good agreement (r = 0.96, slope = 0.83). No evidence was found to indicate that microspheres altered hemodynamic or gastric function. In all experiments less than 1% of the total gastric radioactivity passed through arteriovenous shunts. The mucosa always contained a statistically adequate number of spheres (greater than 400), but the submucosa and muscularis frequently did not. Microspheres of all sizes mixed adequately in large arteries, but a significant difference was found in the distribution of 16- and 26 mum spheres between mucosa and submucosa, presumably because of streaming of the larger spheres past mucosal arteries. It was concluded that, with the techniques developed in our laboratory, microspheres could be a highly useful tool for quantitating gastric regional blood flow under a variety of experimental conditions.

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