Search PubMed⌕ Search

Biomedical subjects

W L Smith

Publications and source records attributed to W L Smith.

At least 181 records · Page 10Linked to original sources
PubMed1992

Effectiveness of teaching radiologic image interpretation in gross anatomy. A long-term follow-up.

This prospective study was designed to gauge the effectiveness of teaching radiologic interpretation during a gross anatomy course for first-year medical students by measuring short- and long-term ability to identify normal anatomic structures on radiologic diagnostic images. The evaluation required students to identify normal anatomic structures on radiographs, computed tomographs, ultrasonograms, and magnetic resonance images (MRIs). The assessments were made before (pre-test) and during (post-test) the experimental radiology portion of the gross anatomy course. The students were then retested 14 to 17 months later (long term). The pre-test correct response rate of 17% improved to 88% on the post-tests. After 14 to 17 months, the students had a 74% correct response rate on the same images and anatomic structures. This high level of long-term retention documents the effectiveness of integrating diagnostic radiologic imaging into normal gross anatomy instruction.

Anatomy↗
PubMed1992

The predictive utility of behavior-based interviewing compared with traditional interviewing in the selection of radiology residents.

RATIONALE AND OBJECTIVES: This study compares the predictive use of measures based on traditional faculty and resident interviews of residency applicants with measures obtained through behavior-based interviewing. A special emphasis was placed on predicting residents' noncognitive abilities. METHODS: One hundred fifty-one resident applicants, over a 3-year period, were interviewed using standard interviews by faculty and residents. These residents also were interviewed with an experimental behavior-based accomplishment interview. Four years later, during their diagnostic radiology residency, evaluations of performance were gathered on these applicants from their residency director. RESULTS: Results indicated that scores based on responses given during the accomplishment interviews added considerable predictive utility to the low prediction demonstrated by traditional interviews. CONCLUSIONS: These findings imply that improving unstructured faculty and resident interviews to obtain, in a more rigorous manner, desired information about noncognitive abilities may be a key to successful resident selection.

Behavior↗
PubMed1992

Evaluation of a digital workstation for interpreting neonatal examinations. A receiver operating characteristic study.

RATIONALE AND OBJECTIVES: The purpose of this study is to compare the diagnostic accuracy of interpreting clinical neonatal radiographs using a commercially available digital workstation versus conventional radiographic images. METHODS: The case sample consists of 100 chest or abdominal radiographs from the neonatal intensive care unit in which diagnosis was confirmed. Four radiologists served as observers. During two initial reading sessions, half of the studies were viewed on digital radiography monitors and the other half by plain film. Observers indicated whether each patient had normal or abnormal findings and their degree of confidence in this judgment. Six weeks later, observers viewed cases on the alternate presentation system. Two statistical analyses were performed: the data from each observer were treated as a separate experiment in the first analysis; the data from all observers were combined using a new method in the second analysis. RESULTS: No differences between areas under receiver operating characteristic (ROC) curves for viewing on the picture archiving and communication system (PACS) console and plain film were found for any observer (0.86 versus 0.86, 0.89 versus 0.86, 0.88 versus 0.85, 0.83 versus 0.82). CONCLUSIONS: The study suggests that for pediatric plain film images, video images offer diagnostic information comparable with that of conventional radiographs for neonatal examinations.

Evaluation Studies as Topic↗
PubMed1992

Prostanoid biosynthesis and mechanisms of action.

Prostanoids are local hormones formed from arachidonic acid that coordinate responses to circulating hormones which elicit prostanoid synthesis. For example, in the kidney, prostaglandin (PG) E2 synthesized by collecting tubule epithelia in response to arginine vasopressin (AVP) acts on the parent collecting tubule as well as the neighboring thick limb to modulate NaCl and water reabsorption occurring in response to AVP. Studies performed over the last 15 years have defined the major cellular and subcellular sites of PG synthesis in the kidney. In addition, it is now recognized that the multiple cellular actions of prostanoids in the kidney are mediated through receptors coupled to guanine nucleotide regulatory proteins. The goal of this review is to summarize recent biochemical and molecular biological studies on prostanoid biosynthetic enzymes and on prostanoid receptors. The major topics to be addressed are 1) phospholipid precursors of arachidonate, 2) membrane-associated and cytosolic phospholipase A2s, 3) PG endoperoxide (PGH) synthase isozymes, 4) thromboxane A (TxA) synthase, and 5) TxA/PGH and PGE receptors.

Amino Acid Sequence↗
PubMed1992

Critical performance behaviors of radiology residents: evaluation of two category systems.

OBJECTIVE: Previous research has suggested that certain behavioral aspects of job performance are critical for successful performance in a diagnostic radiology residency. We report two studies conducted to determine the long-term stability of critical performance behaviors for radiology residents and refine their definitions. SUBJECTS AND METHODS: A trained psychology graduate student conducted critical incident interviews with 20 senior faculty in diagnostic radiology. From these interviews, the faculty generated 120 descriptions of exemplary or poor resident performance. These descriptors were then independently sorted by two radiologists into the previously defined categories of behaviors to evaluate consistency of the behaviors. As a second study, the 120 descriptors were sorted into an expanded behavioral definition system and the reproducibility, using the expanded system, was compared with the original results. RESULTS: The interrater reliability for placing the current incidents in the originally described behavioral categories was good (Cohen's kappa 0.70). The overall distribution of incidents showed strong similarity to the original data. Sorting into the expanded categories improved the Cohen's kappa from 0.70 to 0.92, indicating that the expanded behavioral definitions improved reliability for categorizing a behavioral incident. CONCLUSION: The critical behaviors necessary for successful performance in diagnostic radiology residency are stable over time. The expanded and refined system of definitions of these behaviors is more efficacious than the original system was.

Attitude of Health Personnel↗
PubMed1992

AHR-9294: a novel inhibitor of H,K-ATPase antagonizes gastric HCl secretion in vivo.

8-Methoxy-4-[(2-isopropylphenyl)amino]-3-quinolinecarboxylate ethyl ester (AHR-9294) inhibited acid secretion stimulated by histamine, pentagastrin or carbachol in rats, and by histamine or feeding in dogs. AHR-9294 was about half as potent as omeprazole and exhibited a shorter duration of action. Based on its inhibition of acid secretion induced by different secretagogues and its lack of effect on histamine-stimulated adenylate cyclase activity, AHR-9294 does not appear to operate at the histamine receptor or adenylate cyclase. Rather, studies on enriched oxyntic microsomal preparations showed AHR-9294 to be an effective inhibitor of the H+ pump enzyme, H,K-ATPase, suggesting this might be the site of antisecretory activity. Kinetic studies revealed that inhibition of both K(+)-activated ATPase and p-nitrophenylphosphatase by AHR-9294 was purely competitive with K+ and its congeners, indicating that AHR-9294 and its analogs belong to the class of compounds known as "K+)-site" inhibitors. On the other hand, inhibition by AHR-9294 was noncompetitive with both ATP and p-nitrophenylphosphatase on their respective rates of hydrolysis (i.e., both Vmax and the apparent Km were reduced, but Vmax/Km was unchanged). Studies on partial reactions of the H,K-ATPase showed that the rate of ATP/ADP exchange was unaffected by AHR-9294 and the steady-state level of phosphoenzyme was only partially reduced (thus ATP/enzyme interaction was not affected); however, the rate of K(+)-catalyzed dephosphorylation of phosphoenzyme was markedly decreased.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphatases↗
PubMed1991

Intramuscular desferrioxamine in patients with Alzheimer's disease.

Although epidemiological and biochemical evidence suggests that aluminium may be associated with Alzheimer's disease (AD), there is no convincing proof of a causal link for aluminium in disease progression. We have completed a two year, single-blind study to investigate whether the progression of dementia could be slowed by the trivalent ion chelator, desferrioxamine. 48 patients with probable AD were randomly assigned to receive desferrioxamine (125 mg intramuscularly twice daily, 5 days per week, for 24 months), oral placebo (lecithin), or no treatment. No significant differences in baseline measures of intelligence, memory, or speech ability existed between groups. Activities of daily living were assessed and videorecorded at 6, 12, 18, and 24 month intervals. There were no differences in the rate of deterioration of patients receiving either placebo or no treatment. Desferrioxamine treatment led to significant reduction in the rate of decline of daily living skills as assessed by both group means (p = 0.03) and variances (p less than 0.04). The mean rate of decline was twice as rapid for the no-treatment group. Appetite (n = 4) and weight (n = 1) loss were the only reported side-effects. We conclude that sustained administration of desferrioxamine may slow the clinical progression of the dementia associated with AD.

Aged↗
PubMed1991

Essential histidines of prostaglandin endoperoxide synthase. His-309 is involved in heme binding.

Prostaglandin endoperoxide (PGH) synthase has a single iron protoporphyrin IX which is required for both the cyclooxygenase and peroxidase activities of the enzyme. At room temperature, the heme iron is coordinated at the axial position by an imidazole, and about 20% of the heme iron is coordinated at the distal position by an imidazole. We have used site-directed mutagenesis to investigate which histidine residues are involved in PGH synthase catalysis and heme binding. Individual mutant cDNAs for ovine PGH synthases were prepared with amino acid substitutions at each of 13 conserved histidines. cos-1 cells were transfected with each of these cDNAs, and the cyclooxygenase and peroxidase activities of the resulting microsomal PGH synthases were measured. Mutant PGH synthases in which His-207, His-309, or His-388 was replaced with either glutamine or alanine lacked both activities. Gln-386 and Ala-386 PGH synthase mutants exhibited cyclooxygenase but not peroxidase activities. Other mutants exhibited both activities at varying levels. Because binding of heme renders native PGh synthase resistant to cleavage by trypsin, we examined the effects of heme on the relative sensitivities of native, Ala-204, Ala-207, Ala-309, Ala-386, and Ala-388 mutant PGH synthases to trypsin as a measure of the heme-protein interaction. The Ala-309 PGh synthase mutant was notably hypersensitive to tryptic cleavage, even in the presence of exogenous heme; in contrast, the native enzyme and the other alanine mutants exhibited similar, lower sensitivities toward trypsin and, except for the Ala-386 mutant, were partially protected from trypsin cleavage by heme. Preincubation of the native and each of the alanine mutant PGH synthases, including the Ala-309 mutant, with indomethacin protected the proteins from trypsin cleavage. Thus, all the mutant proteins retain sufficient three-dimensional structure to bind cyclooxygenase inhibitors. Our results suggest that His-309 is one of the heme ligands, probably the axial ligand, of PGH synthase. Two other histidines, His-207 and His-388, are essential for both PGH synthase activities suggesting that either His-207 or His-388 can serve as the distal heme ligand; however, the trypsin cleavage measurements imply that neither His-207 nor His-388 is required for heme binding. This is consistent with the fact that only 20% of the distal coordination position of the heme iron of PGH synthase is occupied by an imidazole side chain.

Base Sequence↗
PubMed1991

Comparison of a PACS workstation with conventional film for interpretation of neonatal examinations: a paired comparison study.

The diagnostic value of neonatal examinations using picture archiving and communication systems (PACS) was compared with that of conventional radiographs. A total of 202 consecutive chest or abdominal radiographs from the newborn intensive care unit were digitized for display on a commercially available PACS console. Experimental design was a paired comparison study. Plain films and PACS images were reviewed alternately in unbiased fashion. After the examination was evaluated using the second modality, any change in diagnosis or confidence in diagnosis was noted. Overall evaluation showed slight preference for the PACS modality. Change of diagnosis or in confidence of diagnosis was more than twice as likely to occur with evaluation of PACS (35%) after hardcopy than with evaluation of conventional radiographs (14%) after PACS. Of the variety of image processing features available on PACS, only window and leveling were judged to be of significant value. These results indicate that PACS and conventional radiographs of the neonatal chest and abdomen are of similar diagnostic value.

Humans↗
PubMed1991

Prostaglandin and thromboxane biosynthesis.

We describe the enzymological regulation of the formation of prostaglandin (PG) D2, PGE2, PGF2 alpha, 9 alpha, 11 beta-PGF2, PGI2 (prostacyclin), and thromboxane (Tx) A2 from arachidonic acid. We discuss the three major steps in prostanoid formation: (a) arachidonate mobilization from monophosphatidylinositol involving phospholipase C, diglyceride lipase, and monoglyceride lipase and from phosphatidylcholine involving phospholipase A2; (b) formation of prostaglandin endoperoxides (PGG2 and PGH2) catalyzed by the cyclooxygenase and peroxidase activities of PGH synthase; and (c) synthesis of PGD2, PGE2, PGF2 alpha, 9 alpha, 11 beta-PGF2, PGI2, and TxA2 from PGH2. We also include information on the roles of aspirin and other nonsteroidal anti-inflammatory drugs, dexamethasone and other anti-inflammatory steroids, platelet-derived growth factor (PDGF), and interleukin-1 in prostaglandin metabolism.

Amino Acid Sequence↗