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Biomedical subjects

D Hall

Publications and source records attributed to D Hall.

At least 127 records · Page 7Linked to original sources
PubMed1991

The research imperative and bureaucratic control: the case of clinical research.

This paper examines the development of Research Ethics Committees and explores some of the conflicts of value and role which surround the practice of medical research. The case of medical research on children is discussed as one which raises in an acute form concerns about consent and risk/benefit analysis. The paper draws on a survey of Research Ethics Committees to illustrate their variety of structure and functioning, and to relate current practice to a model of bureaucratic control. Bureaucracy is considered both in its common-sense understanding of officious rule-making and delay, and in its theoretical formulation in terms of specialisation, standardisation, formalization and centralisation of procedures. It is argued that the concept of bureaucracy can aid an understanding of the problems of control over research, as well as providing a model for more informed, consistent and open decision making.

Child↗
PubMed1991

The St Croix disaster and the National Disaster Medical System.

The National Disaster Medical System was designed to respond to a catastrophic disaster by creating a group of specially trained civilian disaster medical assistance teams. The teams would be transported to the periphery of the event to triage, stabilize, and then prepare victims for evacuation to facilities elsewhere in the United States that have agreed in advance to accept such patients. Hurricane Hugo's devastation in St Croix offered the first opportunity to test the system. The event was an example of a type of medical disaster that resulted in a sudden reduction in medical resources without a great increase in casualties. Background information and operation of the New Mexico disaster medical assistance team are presented with a clinical profile of the patients seen during the disaster. We describe the first actual deployment of a disaster medical assistance team and the issues that must be addressed before future deployments.

Disaster Planning↗
PubMed1991

Clumsiness in children--do they grow out of it? A 10-year follow-up study.

The question of whether problems of motor co-ordination in early childhood recede with age has rarely been addressed. This paper reports the findings from a follow-up study of 17 children, identified by their teachers as having poor motor co-ordination at age six. Now age 16, these children and their matched controls completed a battery of assessments. The results suggest that the majority of children still have difficulties with motor co-ordination, have poor self-concept and are experiencing problems of various kinds in school. However, there are individual differences in the extent to which the children have learned to cope with their continuing difficulties over the years.

Achievement↗
PubMed1991

Copper loading of hearts increases postischemic reperfusion injury.

We studied the role of copper as a potential mediator of postischemic reperfusion injury in the isolated, perfused rat heart. Hearts were equilibrated with Krebs-Henseleit buffer for 10 minutes and then loaded with copper by way of perfusion with buffer containing 20 microM copper(II)-bis-histidial for 30 minutes. Control hearts were perfused with Krebs-Henseleit buffer alone during the loading period. Hearts than were washed with buffer for 10 minutes and subjected to 20 minutes of normothermic global ischemia followed by 30 minutes of reperfusion. Atomic absorption spectroscopy revealed a 67% increase in total copper content in loaded hearts by the end of the wash. By the end of the 30-minute period of reperfusion, control hearts demonstrated a 50-60% recovery of myocardial function as determined by peak systolic pressure, contractility, and heart rate. In contrast, copper-loaded hearts exhibited virtually no functional recovery within the 30-minute time period. Using salicylate as a probe, we determined that peak and duration of .OH formation appears to be increased in copper-loaded hearts during reperfusion. Furthermore, efflux of lactic dehydrogenase was significantly increased in copper-loaded hearts. Our results clearly demonstrate that increasing cardiac content of copper results in enhanced postischemic reperfusion injury associated with increased formation of .OH, thus suggesting an important catalytic role for this transition metal.

Analysis of Variance↗
PubMed1990

Comparison of enzyme immunoassay with radioimmunoassay for the detection of antibody to hepatitis B core antigen as the only marker of hepatitis B infection in a population with a high prevalence of hepatitis B.

Enzyme immunoassay (EIA) and radioimmunoassay (RIA) for the detection of antibody to hepatitis B core antigen (anti-HBc) were compared using serum specimens from Alaska Natives screened during a hepatitis B control program that were initially positive by EIA for only anti-HBc. Of 36 specimens from persons previously HBsAg positive but who were now only anti-HBc positive by EIA, 94.4% were anti-HBc positive by both assays, with anti-HBc levels exceeding 93% inhibition. Low-level antibody to hepatitis B surface antigen (anti-HBs) (less than 10 SRU) and antibody to hepatitis Be (anti-HBe) were also present in 50% and 48% of specimens positive for anti-HBc, respectively. Of 148 specimens from persons initially positive for only anti-HBc by EIA who had no previous documentation of any hepatitis B virus (HBV) infection, 64.5% were positive by repeat testing for anti-HBc by both assays, and anti-HBc levels in this sample exceeded 70% in 91.6% and 80.2% of specimens by EIA and RIA, respectively. Low-level anti-HBs and anti-HBe were present in 45.8% and 15.6%, respectively. EIA detection of anti-HBc was found to be less specific than RIA. Of specimens positive for anti-HBc by EIA, 14.8% were negative by RIA. The specificity of the EIA could be improved with respect to RIA by increasing the cut-off from 48% to 68%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

Use of salicylate as a probe for .OH formation in isolated ischemic rat hearts.

Salicylic acid was used as a probe for .OH formed during reperfusion of the ischemic myocardium. .OH adds to the phenolic ring of salicylate to yield dihydroxybenzoic acid species. The two principal dihydroxybenzoic acids formed are the 2,3- and 2,5-derivatives and can be isolated and quantitated using HPLC combined with electrochemical detection. In these experiments, dihydroxybenzoic acids were detectable in the f molar range. Rat hearts were perfused in the Langendorff mode with Krebs-Henseleit buffer containing 100 microM salicylate. Following 20 min of global ischemia a 173% increase in tissue content of 2,5-dihydroxybenzoic acid was detected after 2.5 min of reperfusion. The duration of ischemia did not significantly affect tissue content of 2,5-dihydroxybenzoic acid peaked at 250 to 300% of control within 2.5 min of reperfusion. The inclusion of 100 microM salicylate in the perfusion buffer had no effect on myocardial function during the duration of the experiments. The results indicate that salicylate can be used as a very sensitive probe for .OH in the isolated ischemic heart.

Animals↗
PubMed1990

Screening for asbestos-related pleural disease with digital storage phosphor radiography.

Digital storage phosphor radiography (SR) has a wide dynamic range and unique postprocessing capabilities that may improve the performance of screening studies for asbestos-related pleural disease compared with conventional film radiography (FR). In a group of 32 asbestos-exposed and nine control subjects with established pleural data, we compared the screening performance of FR and SR obtained with a single isoexposure, dual-energy technique (system resolution 0.2 mm, 10 bits). Performance was evaluated for 7320 observations by eight readers using a paired t test (P less than .02 with Bonferroni correction) of averaged receiver operating characteristic curve (ROC) areas (Az +/- standard error). We found that SR alone and SR supplemented by dual-energy soft-tissue and calcium images (SRde) were superior to FR in the overall detection of pleural abnormalities (Az = 0.90 +/- 0.01, 0.90 +/- 0.01, and 0.88 +/- 0.01, respectively). In the specific detection of pleural calcification, SRde was superior to FR (Az = 0.91 +/- 0.01 and 0.87 +/- 0.01, respectively; P less than 0.01). Analysis of variance indicated that SRde most closely reproduced an established pleural score based on the International Labor Organization (ILO) classification of the pneumoconioses (P less than 0.05, Scheffé's multiple comparison test). We conclude that isodose SR performs at least as well as FR in screening for asbestos-related pleural disease. SR supplemented by dual-energy images might improve the specific detection of pleural calcifications compared with FR.

Asbestosis↗
PubMed1990

The diagnostic value of upper gastrointestinal radiography.

We reviewed the indications for and results of 788 consecutive upper gastrointestinal radiographs (UGIs) performed for ambulatory patients. Sixty-three percent of tests were ordered for the evaluation of abdominal pain, dyspepsia, or esophageal reflux. Of these tests, only 4.8% yielded results of major clinical importance to patient management. The yield for patients greater than 50 years of age was greater than for patients less than 50, 6.9 versus 3.0% (p = 0.04). There was a significant increase in yield with increasing age (chi trend = 11.6, p less than 0.001). Among patients with an indication of esophageal reflux alone (n = 62), there were no patients younger than age 60 with a test result that would significantly affect therapy or outcome. Among patients evaluated for fecal occult blood or weight loss (n = 120), 11.7% of tests ordered showed a finding of major clinical importance. In this group, the yield was higher in those greater than or equal to 50 years of age than in those less than 50, 14.7 versus 6.7%, (p = 0.2). These results indicate that UGIs ordered to evaluate pain or symptoms of esophageal reflux in the absence of bleeding or weight loss rarely yield results that significantly influence therapy. Such patients may be best served by an initial trial of empiric therapy or some other test. The UGI has greatest value when indications for it include bleeding or weight loss.

Age Factors↗
PubMed1990

Nitrate therapy in patients with coronary artery disease--preparations and doses with and without development of tolerance.

Rapid tolerance development with respect to hemodynamic, anti-anginal and anti-ischemic effects is a relevant clinical problem associated with any longterm treatment with nitroglycerin, isosorbide dinitrate or isosorbide 5-mononitrate. Tolerance occurs with any dosing regimen that results in nitrate accumulation in the plasma or nearly-constant plasma concentrations, as is the case with multiple daily doses of oral nitrates or continuous application of transdermal patch systems. Nitrate tolerance can be prevented by the interval treatment. This encompasses incorporation of an application-free interval which prevents meaningful nitrate accumulation such that, from a low baseline level, renewed drug administration leads to an increase in the nitrate plasma concentration greater than 2.5-fold. From controlled studies, dosing regimens for interval treatment proven to be effective have been designated for isosorbide dinitrate and isosorbide 5-mononitrate, as well as for transdermal nitroglycerin patch systems. The early attenuation of nitroglycerin, seen within the first 12 h of its use, according to the results of a recently completed study, can be counteracted through continuously increasing plasma concentrations during this period. Interval treatment does not enable 24-h therapeutic protection. Studies with ST-Holter monitoring, however, have shown that adequate coverage can be provided for the period during which the vast majority of ischemic episodes occur. Clinically-relevant rebound phenomena do not occur during interval treatment. Pharmacological approaches to prevent nitrate tolerance, on the basis of the limited and, in part, conflicting data available, do not provide an alternative to interval treatment.

Administration, Cutaneous↗
PubMed1990

[Nitrates in the treatment of heart failure].

Organic nitrates were the first peripherally-active vasodilators to be used for the treatment of heart failure. Currently, three nitrate derivatives, glycerol trinitrate, isosorbide dinitrate and isosorbide 5-mononitrate as well as the nitrate-like substance molsidomine are employed clinically. For treatment of heart failure, the decisive hemodynamic effect is a meaningful reduction in ventricular filling pressures with maintenance or even a slight increase in cardiac output. The individual response to nitrates is variable. An important indicator for the effect achievable for a certain dose or for the necessary dosage to affect a defined reduction in ventricular filling pressures, is the magnitude of right atrial pressure. It can be assumed that the latter statement is also valid for the nitrate-like substance molsidomine. An inherent problem with any long-term treatment with nitrates is the incurrence of tolerance. This can be expected with any dosing regimen which leads to nitrate cumulation in the plasma or to nearly-constant, high, plasma concentrations as rendered by multiple daily administration of orally-active nitrates or with continuous transdermal or intravenous nitrate administration. The cause of nitrate tolerance is regarded as an insufficient or absent stimulation of guanylate cyclase and, consequently, inadequate generation of cyclic GMP due to availability of thiol substrate. Since the nitrate-like substance molsidomine appears to be able to stimulate guanylate cyclase independent of thiol groups, tolerance development may not be a limiting factor with this agent. Comparable reduction of diastolic pulmonary artery pressure after acute administration and at the end of one week of treatment with 4 mg molsidomine four times daily has been reported.(ABSTRACT TRUNCATED AT 250 WORDS)

Dose-Response Relationship, Drug↗
PubMed1990

[Treatment of heart failure with calcium antagonists].

Vasodilators have a well-established role in the treatment of congestive heart failure. By virtue of their vasodilating properties, the calcium channel blockers have been advocated for use in the treatment of heart failure, in particular, in consideration of the fact that the left ventricular dysfunction in 60 to 70% of the patients with this condition is due to ischemic heart disease, the primary disorder for which the calcium channel blockers are intended to treat. The net hemodynamic effect of calcium channel blockade is the result of two opposing actions: negative inotropy and systemic vasodilation with reflex-induced sympathetic stimulation. The balance is dependent on the prevailing cardiovascular status prior to administration of the drug. In the presence of no or only mild-to-moderate left ventricular dysfunction and intact adrenergic reflexes, a small amount of negative inotropy is readily offset by afterload reduction and adrenergic stimulation. In the presence of severe left ventricular dysfunction sufficiently extensive to lead to heart failure, a condition in which homeostatic reflexes are already attenuated, even a slight amount of negative inotropy can lead to unequivocal deterioration of hemodynamics. Of the three conventional calcium channel blockers, verapamil exerts the most marked negative inotropic effects. Even verapamil, however, has been shown to lead to hemodynamic improvement in some patients, at least after acute administration. Apparently, the cut-off point between beneficial and adverse actions lies at an ejection fraction between 30 and 40% and a pulmonary capillary pressure of about 20 mm Hg. In patients beyond these limits, if treated with verapamil, worsening of heart failure is not uncommon.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium Channel Blockers↗
PubMed1990

Associations of early childhood infections and reduced hemoglobin levels in a historic cohort of Alaska Native infants.

A retrospective study was carried out to determine the effect of common childhood infectious diseases on the hemoglobin level of a cohort of Alaskan Eskimo children born between 1960 and 1962. Hemoglobin and health records were available on 308 children between 6-11 and 12-17 months of age. Additional records were available on 187 of these children at 18-23 months of age. Episodes of chickenpox, measles, pertussis, and lower respiratory infections were reviewed. Between 38 and 50% of infants between 6 and 23 months of age had hemoglobin levels below 11.0 g/dl. The mean hemoglobin level of infants 6-11 and 12-17 months of age decreased with increasing number of total infectious episodes occurring within the 3 months before hemoglobin measurement. This trend was not apparent for infants in the 18-23 months age interval nor were low hemoglobins predictive of illness during the 3 months after the hemoglobin determination. At the 6-11 and 12-17 month age interval the number of lower respiratory infectious were most significantly associated with a decreased hemoglobin value. These observations are consistent with more recent reports that document iron deficiency anemia among children with antecedent infections and again emphasize the role of infection in the development and maintenance of anemia in children about 1 year of age.

Alaska↗
PubMed1989

Atonic pupil after cataract surgery.

A dilated, atonic pupil is a recognized but unusual complication of cataract surgery. It appears to be a more common occurrence than the paucity of previously published reports would suggest. In this article, seven cases of post-cataract extraction atonic pupil are described. All patients underwent uneventful cataract extraction with posterior chamber intraocular lens (IOL) implantation. In all except one patient, there was a delay from the time of surgery to the development of the atonic pupil. Pharmacologic testing demonstrated that the site of the lesion was the iris sphincter. Possible pathogenic mechanisms are discussed.

Aged↗