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Biomedical subjects

R A Davidson

Publications and source records attributed to R A Davidson.

At least 19 recordsLinked to original sources
PubMed1997

Electrophoretic analysis of cyanide depletion by Pseudomonas alcaligenes.

Bacterial-facilitated depletion of cyanide is under development for remediation of heap leach operations in the gold mining industry. Capillary electrophoresis was found to be a powerful tool for quantifying cyanide depletion. Changes in cyanide concentration in aqueous suspensions of Pseudomonas alcaligenes bacteria and cyanide at elevated pH were easily monitored by capillary electrophoresis. The resulting data can be used to study rates of cyanide depletion by this strain of bacteria. Concentrations of these bacteria at 10(5) cells/mL were found to reduce cyanide from 100 ppm to less than 8 ppm in four days. In addition, other ions of interest in cyanide metabolism, such as formate, can be simultaneously analyzed. Direct UV detection of cyanide at 192 nm further simplifies the analytical method for these ions.

Culture Media↗
PubMed1996

Predictors of cure of hypertension in fibromuscular renovascular disease.

Patients with fibromuscular dysplasia (FMD) and hypertension are frequently treated with percutaneous transluminal renal angioplasty (PTRA). Because the goal of this procedure is the cure of hypertension, we reviewed the outcomes of 23 consecutive patients undergoing this procedure to determine factors associated with cure. Twelve (52.2%) of the patients were taking no antihypertensive medications at 6 months and were classified as cured. Using logistic regression, we found three variables to be independently associated with cure: level of systolic blood pressure before intervention (P = 0.02), duration of hypertension (P = 0.03), and age (P = 0.03). Younger patients with milder hypertension of a shorter duration were most likely to be cured. Analysis of the regression equation predicts that some patients with an extremely low chance of cure might be managed with a trial of medical therapy, because FMD is unlikely to progress to renal failure.

Adult↗
PubMed1996

Emotional arousal in temporal lobectomy: autonomic and performance effects of success and failure feedback.

Both theory and evidence suggest that right temporal lobectomy (RTL) patients show hypoarousal and left temporal lobectomy (LTL) patients show relative hyperarousal (Davidson, Fedio, Smith, Aurielle, & Martin, 1992). However, we hypothesized that these differences occur only under passive, nonevaluative stimulus conditions. The present study employed, instead, conditions of performance evaluation. We recorded the skin conductance responses (SCRs) and reaction times (RTs) of RTLs, LTLs, and normal controls (NCs) during easy and difficult trial blocks on a target-detection task, with auditory success/failure feedback. We found that LTLs exhibited relative hypoarousal and retarded RTs and that RTLs were normally aroused following success feedback. These results demonstrated that the arousal level of LTLs is contingent on stimulus conditions, thus calling into question the theory that this group is generally subject to hyperarousal. The two-dimensional theory of the neural processing of emotional experience partially explains our data.

Adolescent↗
PubMed1996

Introducing ambulatory care during the medicine clerkship: impact on evaluation and attitudes.

This article assesses student attitudes and the overall educational impact after a major curriculum change that implemented ambulatory care in an internal medicine clerkship. The study was cross-sectional with a historical comparison group and took place in a university teaching program with third-year students from three time periods. The 8-week clerkship was changed from 8 weeks of inpatient ward medicine to 4 weeks each of inpatient and ambulatory care in both primary care and subspecialty clinics. When students' responses before and after the curriculum change were compared, there was a significant improvement in evaluation of the clerkship experience (P = 0.001). Attitudes improved toward a general internal medicine career (P = 10(-5)) and there was improvement in evaluation of the inpatient experience (P = 0.01). Attitudes toward careers in subspecialty internal medicine and National Board examination scores were unchanged. The institution of ambulatory care into this internal medicine clerkship resulted in several significantly positive outcomes without a negative impact on the internal medicine knowledge base.

Ambulatory Care↗
PubMed1996

Prediction of cure of hypertension in atherosclerotic renal artery stenosis.

We analysed the outcome of 63 consecutive, adequate interventions for atherosclerotic renal artery stenosis and hypertension: 34 patients had percutaneous transluminal renal angioplasty, and 29 had surgical correction. Hypertension was cured in 21% of patients and improved in 47%, but 32% failed to respond. We analyzed clinical variables predictive of cure. Duration of hypertension, level of diastolic blood pressure, and sex were found to be predictive of cure. The highest probability of cure was found in men with a duration of hypertension of less than 10 years and an initial diastolic blood pressure of greater than 80 mm Hg. Use of these clinical variables in a tree-based model correctly classified 80% of cases, with a sensitivity of 92% and a specificity of 77%. We conclude that a tree-based clinical algorithm based on only three clinical criteria correctly predicted cure of hypertension in most patients with renal artery stenosis and may be useful in decision making. A prospective analysis will be required to evaluate the clinical validity of the algorithm.

Algorithms↗
PubMed1994

The simplified captopril test: an effective tool to diagnose renovascular hypertension.

There is much variability among reports of the accuracy of the captopril test for renovascular hypertension. Factors that contribute to this variability include a lack of consistency in diagnostic criteria, the preparation of the patient and the performance of the test, and the criterion standard (renal artery stenosis or renovascular hypertension). We investigated the sensitivity and specificity of a simplified version of the test, based on a single postcaptopril value of plasma renin activity, in 36 patients who were undergoing either angioplasty or surgery for renal artery stenosis. The test demonstrated an excellent sensitivity (96%) but a poor specificity (55%). However, the poor specificity was related to certain clinical characteristics; high baseline plasma renin activity measurements, female gender, current smoking, renal dysfunction, and bilateral renal artery stenosis were all associated with false-positive results. This simplified captopril test, when applied to a population with a high prevalence of renovascular hypertension and performed in a standardized manner, can accurately identify those patients unlikely to respond to intervention. However, a positive test, especially in those with the characteristics noted above, does not help clinical decision making because of the limited test specificity.

Captopril↗
PubMed1994

Effect of a simple ambulatory experience on career choice and attitudes of medical students.

Students were allocated randomly to participate in a simple ambulatory experience during their third-year medicine clerkship. A convenience sample was surveyed by questionnaire in the fall of their fourth year, after decisions were made regarding future career plans. The questionnaire assessed medical student attitudes toward general internal medicine and career choice. Valuation of the effectiveness of the clerkship was associated with choosing a career in internal medicine (p = 0.007); having an ambulatory experience was not associated with subsequent career choice. Sixty-two percent of all students felt the clerkship affected their career choice a great deal or moderately; these students were likely to find a career in general internal medicine less attractive as a result of their clerkship (p = 0.008). When stratified, this association disappeared in those students who participated in the ambulatory experience (p = 0.39) but persisted in those who did not (p = 0.01). A simple experience in internal medicine clinics during a third-year clerkship was not associated with subsequent career choice, but had some positive effects on attitudes toward general internal medicine as a career.

Adult↗
PubMed1993

Effects of caffeine and gender on physiology and performance: further tests of a biobehavioral model.

The present study extended testing of our biobehavioral model describing the effects of arousal and caffeine to include an examination of gender differences and their interactions with habitual and acute caffeine ingestion. Males and females selected as high or low habitual caffeine users were randomly assigned to receive either caffeine or a placebo and exposed to novel and repetitive recall tasks and to simple auditory stimuli. Electrodermal activity and recall task performance were recorded. The four major factors examined, including habitual caffeine use, acute ingestion, gender, and stimulus novelty, affected behavior, physiology, or both. Results showed that habitual caffeine usage systematically affected tonic arousal (skin conductance level) and improved recall task performance. Acute caffeine ingestion increased phasic arousal (skin conductance response amplitude) and reduced habituation rates. Gender interacted with other factors to significantly affect both tonic and phasic arousal, and females performed better than males on the recall tasks. These results were partially supportive of the theoretical model, and further work is needed to examine the interactions of acute and chronic caffeine intake with gender and novelty.

Adult↗
PubMed1992

Newer tests for the diagnosis of renovascular disease.

OBJECTIVE: To evaluate published reports of diagnostic methods for renovascular hypertension, including Doppler ultrasonography, magnetic resonance imaging, the captopril test, and captopril scanning. DATA SOURCES: MEDLINE and selected references from appropriate published articles. STUDY SELECTION: Studies included those that calculated sensitivities and specificities; studies that derived diagnostic criteria without application to another population of patients were excluded. Consensus of both authors was necessary for inclusion. DATA EXTRACTION: Articles were critically assessed independently by the authors and a consensus critique was developed. DATA SYNTHESIS: Major sources of variability exist in the investigations of recently developed tests for renovascular hypertension. These include variability in patient populations, performance of tests, and determination of outcome measures. CONCLUSIONS: Among the newer diagnostic tests, both magnetic resonance imaging and Doppler ultrasonography hold promise for the anatomic detection of renal artery stenosis, but clear diagnostic criteria have not been universally accepted. There is more information concerning the captopril test, which has a sufficiently high sensitivity to be useful in the screening of high-risk patients for renovascular hypertension. Scans after captopril administration, which appear to be more specific, may enable the prediction of a blood pressure response to angioplasty or surgery.

Captopril↗
PubMed1992

Lateralized mediation of arousal and habituation: differential bilateral electrodermal activity in unilateral temporal lobectomy patients.

The purpose of the present study was to increase our understanding of the differential hemispheric processing of arousal and habituation. Subjects were unilateral temporal lobectomy patients and controls. Each was exposed to an arousal/habituation task consisting of a series of tones and an auditory discrimination paradigm. Electrodermal activity was recorded from the left and right hands throughout. Results provide evidence for a state of hypoarousal in right temporal patients and some support for hyperarousability in lefts. This is consistent with data showing that right hemisphere damage is associated with inattention and denial and left hemisphere damage with hypervigilance and anxiety. The concept of laterally differentiated mediation of arousal and habituation was supported.

Adult↗
PubMed1992

Reduction of caregiver stress by respite care: a pilot study.

The purpose of this study was to determine whether providing respite care to persons with Alzheimer's disease and other dementias decreased stress and mood disturbances in caregivers. Caregivers of persons receiving respite care (n = 7), and not receiving respite care (n = 8) were tested at entry into the study and at 5 weeks and 10 weeks, using the Profile of Mood States and the Relative's Stress Scale. Using repeated measures analysis of variance, a downward trend for study subjects and an upward trend for controls was found for Relative's Stress Scores. Similar trends were found on the Personal Distress Subscale of the Relative's Stress Scale. No difference occurred in rates of institutionalization between those receiving and not receiving day care. Our study suggests that respite care for demented persons living at home significantly reduces the stress among caregivers.

Affect↗
PubMed1991

Caffeine and novelty: effects on electrodermal activity and performance.

Caffeine has been shown to affect both physiological functioning and certain aspects of performance. These effects are typically attributed to a simple increase in general arousal. The present study was based on the theory that the effects of caffeine are actually multidimensional. Specifically, we hypothesized that the drug raises arousal, acts to maintain elevated arousal under conditions otherwise conductive to habituation, and enhances the impact of situational and psychological sources of arousal. Subjects were given caffeine (300 mg) or placebo and white noise or no noise and exposed to a series of pure tones and two Backwards Recall Tasks, one novel, the other repetitive. Electrodermal activity (EDA) and task performance were recorded. Caffeine increased arousal as measured by EDA. It also acted to slow habituation during repetitive stimulation, thus maintaining heightened arousal. Finally, it enhanced the effects of novel stimulation, which also independently raised arousal. These results support a multidimensional theory of caffeine effects and provide some understanding of the popularity of caffeine as a psychotropic agent.

Acoustic Stimulation↗