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Biomedical subjects

L R Brooks

Publications and source records attributed to L R Brooks.

At least 37 records · Page 2Linked to original sources
PubMed1996

Illustrating caffeine's pharmacological and expectancy effects utilizing a balanced placebo design.

Caffeine consumption, a ubiquitous cultural phenomenon with significant health implications may be governed by some of the same principles which affect other drug use [1]. We hypothesized that pharmacological and expectancy effects may be two of those principles. A balanced placebo design was used with 100 male undergraduates to separate caffeine's active drug effects from the expectancy of having consumed caffeine on mood, performance, and physiological measures. The manipulation of expectancies was highly effective on subjects' judgments of caffeine dosage, regardless of actual caffeine content. As predicted, expectancy set and caffeine content appeared equally powerful, and worked additively, to affect subjects' ratings of how much the coffee influenced their mood and performance. Main effects on systolic and diastolic blood pressure, pulse rate, and a fatigue measure were found for caffeine vs. no caffeine groups only. Additional increases in diastolic blood pressure for smokers were noted within the caffeine-receiving conditions. Results are discussed with heuristic and health implications.

Adolescent↗
PubMed1996

The glutathione S-transferase M1 (GSTM1) null genotype and benzidine-associated bladder cancer, urine mutagenicity, and exfoliated urothelial cell DNA adducts.

Multiple studies in the general population have suggested that subjects with the glutathione S-transferase M1 (GSTM1)-null genotype, who lack functional GSTM1, are at higher risk for bladder cancer. To evaluate the impact of the GSTM1-null genotype on bladder cancer caused by occupational exposure to benzidine and to determine its influence on benzidine metabolism, we carried out three complementary investigations: a case-control study of bladder cancer among workers previously exposed to benzidine in China, a cross-sectional study of urothelial cell DNA adducts and urinary mutagenicity in workers currently exposed to benzidine in India, and a laboratory study of the ability of human GSTM1 to conjugate benzidine and its known metabolites in vitro. There was no overall increase in bladder cancer risk for the GSTM1-null genotype among 38 bladder cancer cases and 43 controls (odds ratio, 1.0; 95% confidence interval, 0.4-2.7), although there was some indication that highly exposed workers with the GSTM1-null genotype were at greater risk of bladder cancer compared to similarly exposed workers without this allele. However, the GSTM1 genotype had no impact on urothelial cell DNA adduct and urinary mutagenicity levels in workers currently exposed to benzidine. Furthermore, human GSTM1 did not conjugate benzidine or its metabolites. These results led us to conclude that the GSTM1-null genotype does not have an impact on bladder cancer caused by benzidine, providing a contrast to its association with elevated bladder cancer risk in the general population.

Benzidines↗
PubMed1994

Fragmentary knowledge and the processing-specific control of structural sensitivity.

Perruchet (1994) suggested that "neither a specific-item retrieval process nor abstractive capacity" is required to explain Vokey and Brooks (1992) results, which instead can be accounted for in terms of knowledge of item fragments. The literature contains 2 definitions of abstractive. Rejecting abstractive in the sense of nonliteral units requires rejecting the results of studies on changed-letter transfer, some of which do not need the control group Perruchet claims and thus stand, confirming nonliteral (relational) abstraction. However, the rejection of pooled across items abstraction even in the form of our proposed retrieval-time pooling is feasible, which we had not previously appreciated. Perruchet's rejection of item retrieval ignores Vokey and Brooks' coding and retrieval variations. The coding and retrieval results cannot be ignored simply because they are nonstandard, however. Integrating this literature with known memory phenomena requires incorporating these processing factors, rather than assuming fixed, literal fragments.

Cognition↗
PubMed1994

Prevention of deep vein thrombosis and pulmonary embolism in acetabular and pelvic fracture surgery.

In a prospective nonrandomized study, a protocol was examined for prophylaxis of deep venous thrombosis and pulmonary embolism in patients with operative treatment of acetabular and pelvic fractures. There were 197 patients in the study with 203 fractures, including 148 acetabular and 55 pelvic fractures. There were 2 cases of bilateral acetabular fractures and 4 cases with both acetabular and pelvic fractures. The protocol involved preoperative noninvasive screening of the lower extremities, intraoperative and postoperative use of mechanical antithrombotic devices, and chemical prophylaxis with warfarin for 3 weeks following removal of surgical drains. There were 11 cases (6%) of preoperative deep venous thrombosis detected. There were 6 cases of postoperative deep venous thrombosis and 2 cases of pulmonary embolism. The incidence of postoperative venous thrombosis and pulmonary embolism was 3% and 1%, respectively. The protocol was found to be effective for preoperative detection of venous thrombosis and prevention of deep venous thrombosis and pulmonary embolism in trauma patients with minimal bleeding complications and no morbidity from embolic disease.

Acetabulum↗
PubMed1993

Perceptual manifestations of an analytic structure: the priority of holistic individuation.

Properties that make items perceptually distinctive may not be represented in the dimensional structure used by subjects for analysis. In a classification task, a single dimensional structure, actually used by subjects when analyzing, occurred in several perceptual forms. Two types of perceptual variation were compared: (a) feature individuation, whether a feature occurs in a unique form in different items and (b) holistic individuation, the extent to which an item's features cohere into an individuated whole. These types of individuation had separate effects on exemplar-based classification. However, holistic individuation had priority in that the presence of individuated features did not produce exemplar-based transfer if the item's holistic properties were altered. This priority of holistic individuation occurred whether the subjects had been given the classification rule or had attempted to discover it.

Adult↗
PubMed1992

Evaluation of high volume particle sampling and sample handling protocols for ambient urban air mutagenicity determinations.

An investigation of high volume particle sampling and sample handling procedures was undertaken to evaluate variations of protocols being used by the U.S. Environmental Protection Agency. These protocols are used in urban ambient air studies which collect ambient and source samples for subsequent mutagenicity analysis of the organic extracts of the aerosol fraction. Specific protocol issues investigated include: (a) duration of sampling period, (b) type of filter media used to collect air particles, (c) necessity for cryogenic field site storage and dry ice shipping of filter samples, and (d) sample handling at the receiving laboratory. Six PM10 Hi-Vol samplers were collocated at an urban site in downtown Durham, North Carolina and operated simultaneously to evaluate 12 h versus 24 h collection periods and filter media choices of glass fiber, Teflon impregnated glass fiber (TIGF), and quartz fiber. Filters from the samplers plus field blanks were collected during each of 25 sampling periods. TIGF filters from two samplers were immediately placed on dry ice in the field and transported directly to cryogenic storage. TIGF, quartz, and glass fiber filters from three samplers were transported at ambient and maintained at room temperature for three to six days prior to cryogenic storage. One TIGF sample, which was collected on a previously tared filter, was subjected to controlled environment equilibration (40 percent relative humidity, 22 degrees C) for 8 to 24 h and weighed prior to cryogenic storage. All filters were subsequently stored at -70 degrees C to -80 degrees C prior to a one-time extraction and Salmonella (Ames) mutagenicity bioassay of the entire sample set.(ABSTRACT TRUNCATED AT 250 WORDS)

Air Pollutants↗
PubMed1992

Development of source testing, analytical, and mutagenicity bioassay procedures for evaluating emissions from municipal and hospital waste combustors.

Incineration is currently being used for disposal of about 10% of the solid waste generated in the United States, and this percentage will likely increase as land disposal declines. Siting new incinerators, however, is often controversial because of concerns related to the possibility of adverse health effects and environmental contamination from long-term exposure to stack emissions. Specific concerns relate to the adequacies of a) stack emission testing protocols, b) existing regulations, and c) compliance monitoring and enforcement of regulations. U.S. Environmental Protection Agency laboratories are cooperatively conducting research aimed at developing new testing equipment and procedures that will allow a more comprehensive assessment of the complex mixture of organics that is present in stack emissions. These efforts are directed specifically toward developing source testing equipment and procedures, analytical procedures, and bioassay procedures. The objectives of this study were to field test two types of high-volume source dilution samplers, collect stack samples for use in developing analytical and mutagenicity bioassay procedures, and determine mutagenicity of organics associated with emission particles from two municipal waste combustors and a hospital waste combustor. Data are presented for particle concentrations and emission rates, extractable organic concentrations and emission rates, and Salmonella (Ames) mutagenic potency and emission rates. The mutagenic emission rates and emission factors are compared to other incinerators and combustion sources.

Air Pollutants↗
PubMed1992

The correlation of feature identification and category judgments in diagnostic radiology.

Expert and novice radiologists were given films accompanied by clinical histories that supported a diagnosis either of bronchiolitis or of normal. To provide a plausible task context, some films were radiologically unambiguous and were accompanied by histories consistent with them. For a set of radiologically difficult films from confirmed normal or bronchiolitis patients, fictitious normal or abnormal histories were counterbalanced with the films. The clinical histories affected ratings both of diagnosis and of features present on the difficult films. Thus, uncertainty about individual features evidently was affected by history, and features did not act as an independent source of information. The dependence of feature calls on an overall judgment was also suggested by intra-observer agreement in another study in which an explicit diagnosis was not requested. It is unclear whether the history increased discrimination between normal and abnormal films, or indiscriminately added evidence for or against the disease. Factors are discussed that make it appropriate for feature identification to be partially dependent on category identification.

Attention↗
PubMed1991

Role of specific similarity in a medical diagnostic task.

Three experiments are reported showing that diagnosis of skin disorders by medical residents and general practitioners was facilitated by similar cases previously seen in the same context. Diagnosis of similar cases was facilitated more than that of dissimilar cases in the same diagnostic category, demonstrating that facilitation was not solely due to activation of the diagnostic category as a whole. Because diagnosis was posed in a multiple-choice format that always included the correct diagnosis, the relative disadvantage of dissimilar items was not due to the unavailability of the category name. The similarity effect also occurred with 2-week delay between the initial case and the test cases. Variations in diagnostic procedure, ranging from giving a quick first impression to arguing for given alternative diagnoses before selection, did not interact with the effect of similarity. This result suggests that the similarity effect is not strongly dependent on a particular diagnostic strategy.

Adult↗
PubMed1991

Variability of breathlessness measurement in patients with chronic obstructive pulmonary disease.

The purpose of our study was to evaluate the reproducibility of a Borg rating of dyspnea in patients with COPD. We examined nine patients with COPD who performed a SST on four separate days within a ten-day period. The patients walked on a treadmill for 6 min. At the end of each minute, patients matched a Borg rating to the intensity of their breathlessness. We measured the HR, VE, VO2, VT and f at the end of each minute. While the mean VO2, VE, HR, VT and f stabilized after one or two attempts, the Borg ratings decreased with successive tests. We conclude that the Borg scale for measuring breathlessness shows progressive decreases with repetition whereas VO2, VE, HR, VT and f stabilize after one or two practice attempts. This suggests that desensitization to dyspnea may play a role in the improvement of patients after exercise.

Aged↗
PubMed1989

Episodic effects on picture identification: implications for theories of concept learning and theories of memory.

The effects of differences in study processing on free recall of picture names and on generalization in picture identification were investigated. Experience with degraded pictures produced poorer subsequent free recall of picture names than did naming intact pictures. For the test of picture identification, pictures that were identical to a studied picture, pictures that shared a name with a studied picture (same name), and new test pictures were presented, and the amount of clarification required to identify a picture was measured. Experience with degraded pictures produced better subsequent identification of identical test pictures but poorer later identification of same-name test pictures than did naming intact pictures. The importance of these episodic effects for theories of concept learning and theories of memory is discussed. It is argued that distinctions between memory systems (e.g., episodic-semantic) must be couched in terms of a theory of concept learning and that the data are inconsistent with a simple distinction.

Adult↗
PubMed1989

Recall by expert medical practitioners and novices as a record of processing attention.

Using recall of clinical protocols as a measure of expertise in medicine has yielded disappointingly small effects. Experiments using recall of clinical laboratory data are presented to provide an explanation. In one experiment, subjects either deliberately memorized or first diagnosed and then were incidentally asked for memory. With incidental instructions, experts recalled over twice as much data as did students, but with memorization instructions, student performance approximated that of experts. Experts also showed a large advantage over students in incidental recall of data that were not relevant to the problem solution. These results suggest that expert processing in this "discrete, independent inputs" domain requires effortful analysis with minimal reliance on default values, rather than relatively effortless pattern perception reported in highly visual areas of expertise. For this area, intentional memory is a misleading measure of expertise. However, incidental memory is a valuable measure of processing during diagnosis.

Adult↗
PubMed1989

The development of expertise in dermatology.

To examine the development of expertise in dermatology, accuracy of diagnosis and response times of subjects at five levels of expertise were assessed. A total of 100 slides, 2 typical and 3 atypical slides from each of 20 common skin disorders, were presented to six subjects at each of the following levels: second-year preclinical medical students, final year medical students, residents in family medicine, general practitioners, and dermatologists. Accuracy of diagnosis rose from 21% for medical students to 87% for dermatologists. Correct diagnosis was associated with a decrease in response time with expertise, whereas errors were associated with a dramatic increase in response time, and was slower than correct response times at all levels, suggesting that errors do not result predominantly from carelessness or speed. Typical slides accounted for a constant proportion of diagnostic errors at all higher levels of expertise, and experts continued to make a significant proportion of errors on slides shown to be relatively easy for residents. The results are shown to be at variance with any model that equates expertise with the mastery of complex rules, but they are consistent with models of expertise that propose that expertise is equated with a rapid "pattern-recognition" process, and errors result from unintended confusion with previous similar examples.

Dermatology↗