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Biomedical subjects

A T Taylor

Publications and source records attributed to A T Taylor.

At least 37 records · Page 2Linked to original sources
PubMed1994

Evaluation of the hepatobiliary excretion of technetium-99m-MAG3 and reconstitution factors affecting radiochemical purity.

UNLABELLED: Technetium-99-MAG3 is a renal tubular function agent. However, sporadic liver and gallbladder visualization have raised questions about kit stability, impurities and nonrenal routes of excretion. To address these issues, studies were conducted to optimize the labeling efficiency of the TechneScan MAG3 kit and to evaluate the hepatobiliary excretion of the MAG3 complex. METHODS: Thirty-six vials of the commercial formulation of 99mTc-MAG3 were prepared according to manufacturer's instructions and evaluated for radiochemical purity using two methods: a combination of high-performance liquid chromatography and paper chromatography (HPLC/PC); and the manufacturer's miniature chromatography system (Sep-Pak procedure). RESULTS: The labeling efficiency was significantly higher when the kit was reconstituted with 10 ml (96.6%) of saline versus 5 ml (91.4%) (p < 0.01). The radiochemical purity of the kits remained stable for up to 6 hr, but the purity determined by Sep-Pak averaged 2.5% higher than that determined by HPLC procedures (p < 0.01). Rat studies to evaluate renal and hepatobiliary elimination of MAG3 showed no difference in the %ID excreted into the urine by 60 min in all groups of animals studied. However, the %ID excreted into the bile was significantly higher for the kit formulation than the HPLC-purified MAG3, 9.9% versus 6.6% (p = 0.0475). CONCLUSION: The radiochemical purity of the TechneScan MAG3 kit can be improved by reconstituting with larger volumes. In addition, the studies in rats suggest that fasting or kit impurities may be a contributing factor to increased hepatobiliary visualization in patient studies.

Animals↗
PubMed1993

Comparison of fine-needle aspiration biopsy, Doppler ultrasound, and radionuclide scintigraphy in the diagnosis of acute allograft dysfunction in renal transplant recipients: sensitivity, specificity, and cost analysis.

150 episodes of allograft dysfunction in 128 renal transplant recipients, 77 due to acute rejection, 32 secondary to acute-on-chronic rejection, 33 due to either prerenal factors, acute tubular necrosis, or ciclosporin A nephrotoxicity, and 8 secondary to multiple causes, were evaluated by fine-needle aspiration biopsy (FNAB), Doppler ultrasound (DUS), and radionuclide scintigraphy (RS), each performed within a 24-hour period and prior to any specific therapeutic intervention. Tests were interpreted by appropriate specialists in a large transplant center without access to clinical information. The final diagnosis was based primarily upon response to therapeutic maneuvers with histological (core biopsy) confirmation in 123 episodes. RS was the most sensitive (70%) test for the diagnosis of acute rejection during the early posttransplant period, exceeding both FNAB (52%) and DUS (43%). The predictive accuracy of either FNAB, DUS, RS, or core biopsy in the detection of a steroid-responsive component to acute rejection when superimposed upon chronic rejection was low at approximately 50%. When the underlying cause of renal dysfunction was either prerenal, acute tubular necrosis, or ciclosporin A nephrotoxicity, FNAB, DUS, and RS each gave an erroneous diagnosis of acute rejection in about 50% of the episodes. Cost analysis revealed that core biopsy was the most expensive test, but only 9% more than RS, with FNAB the least costly. In conclusion, the lack of ideal sensitivity and specificity combined with the expense of present-day FNAB, DUS, RS, and core biopsy in the diagnosis of a therapeutically reversible component to acute-on-chronic rejection and of FNAB, DUS, and RS in the diagnosis of acute rejection during the early posttransplant period should prompt research into ways to improve their diagnostic yield or alternate modalities.

Acute Disease↗
PubMed1993

Diabetic limb infections: identification of microorganisms and selection of treatment.

Polymicrobial lower limb infections are common complications among diabetic patients, yet their antimicrobial management remains mostly empiric. A retrospective study of the clinical circumstances of 74 patients accounting for 101 hospital admissions was performed. Risks for vascular disease, clinical and microbiologic evidence for infection, as well as antimicrobial drug selection in these patients, were compiled. Culture materials were obtained from either swab or incision and drainage techniques in 65 (64.4%) patients. Eighty-two (81.2%) patients received antimicrobial therapies. Of the 172 antimicrobial agents prescribed, cephalosporins were utilized 83 times. Twenty-nine (28.7%) patients received amputations. Average total hospital charges were $7,368 per hospital stay, $485 per day.

Adult↗
PubMed1991

Practical management of stress-related gastric ulcers.

Stress ulcers develop in patients who have been subjected to abnormally elevated levels of stress, especially stress caused by conditions associated with reduced gastric blood flow, such as major burns, hypovolemia, and sepsis. Since a significant, often fatal, upper gastrointestinal hemorrhage is a common sequela of stress ulcers, prevention of progression of the lesions is a sensible goal. In numerous clinical trials, antacids, H2-antagonists, and sucralfate have demonstrated comparable effectiveness in preventing bleeding and the associated life-threatening sequelae. The choice of the ideal agent depends on individual patient factors, concomitant disease states and drug therapy, administration requirements, nursing availability, potential adverse effects, and expense.

Antacids↗
PubMed1991

'White coat' hypertension in children.

BACKGROUND: Research with ambulatory blood pressure monitoring (ABPM) clearly demonstrates the importance of identifying "white coat" hypertension before making the diagnosis of hypertension. While the existence of white coat hypertension has been documented in adults, it is unknown whether this phenomenon is present during childhood. Therefore, the purposes of this study were to determine whether white coat hypertension exists in children with a positive family history of essential hypertension; and if it exists, to compare 24-hour ambulatory blood pressure patterns among normotensive, white coat hypertensive, and hypertensive children. METHODS: One hundred fifty-nine children (aged 5 to 15 years) participated in the study. Based on office systolic and diastolic measurements and 24-hour ABPM, subjects were placed into one of three groups: normotensive, white coat hypertensive, and hypertensive. RESULTS: Forty-four percent of 34 subjects with systolic blood pressures greater than or equal to 95th percentile were reclassified as white coat hypertensive; 56% remained hypertensive. Group comparisons of 24-hour ABPM patterns showed significant differences between groups. Also, the ABPM patterns of white coat hypertensive patients were significantly different from those of normotensive patients. CONCLUSIONS: This study documented the existence of white coat hypertension in children and showed that white coat hypertensive children were significantly different from normotensive and hypertensive children on most comparisons of 24-hour ABPM data. Also, when age and sex were controlled, heavier children had a more significant chance of having elevated systolic blood pressure than normal-weight children, regardless of their race, height, or body mass index.

Adolescent↗
PubMed1991

Ambulatory blood pressure monitoring in hypertension.

Compared with blood pressure measurements in the office setting, ambulatory blood pressure monitoring offers a more accurate and reliable method of diagnosing and managing hypertension. Indications for ambulatory blood pressure monitoring include borderline hypertension, a discrepancy between home and office blood pressure measurements, persistent blood pressure elevation in the office with no end-organ damage, episodic elevations of blood pressure or suggestive symptoms, hypertension resistant to treatment, episodic angina not related to exercise, end-organ damage but normal office blood pressure readings, and evaluation of the efficacy of antihypertensive agents. Several cases are presented for review.

Adult↗
PubMed1991

Glucocorticoids in clinical practice.

The many unique features of glucocorticoids makes therapy with these steroids challenging. The anti-inflammatory potency, relative mineralocorticoid activity, plasma half-life, and route of administration of the synthetic cortisol preparations are compared. Because they produce profound anti-inflammatory and immunosuppressive effects, exogenously administered glucocorticoids are effective therapy for a variety of diseases and conditions. The appropriate dosing regimen is an adequate dose administered for a sufficient period to precipitate an acceptable response. It is impossible to predict the regimen that will suppress the hypothalamic-pituitary-adrenocortical (HPA) axis and thereby increase the risk of developing adrenal insufficiency during periods of stress. Until recovery of the axis is complete, patients require daily physiologic replacement doses; high-dose supplemental therapy may be required during a major illness or surgery. Once there are signs of improvement, the dosing regimen should be adjusted to a single morning dose, then to an alternate-day regimen, and, as soon as possible, the steroid should be discontinued. This tapering process maintains disease suppression while minimizing toxicity; however, it is often complicated by exacerbation of the disease and withdrawal symptoms. Potential complications associated with glucocorticoid therapy are numerous, involve all organ systems, and are potentially more devastating than the HPA axis suppression.

Contraindications↗
PubMed1990

Reversibility bull's-eye: a new polar bull's-eye map to quantify reversibility of stress-induced SPECT thallium-201 myocardial perfusion defects.

Myocardial ischemia is currently interpreted from SPECT thallium-201 (201Tl) tomograms by the subjective visual finding of stress-induced perfusion defects which "normalize" or "reverse" by 4 hr. Thus, we have developed a computer method to quantify and display the three-dimensional distribution of reversible segments. Circumferential profiles generated from the short axis slices are normalized to the reference area in the stress study. The stress is subtracted from the normalized delayed data, and then displayed as a polar bull's-eye plot so that positive values show areas that have "reversed" or "improved." Patient profiles are compared to means and standard deviations of reversibility for all pixels determined from the Emory normal male files. Criteria for reversibility were developed from studies of 42 male patients found to have 48 defects, as determined by the consensus of five blinded expert observers. There was computer agreement with the experts on 25 of 31 relatively fixed and 14 of 17 reversible defects. Our preliminary results indicate that this new method promises to aid observers to more consistently identify and quantify the reversibility of SPECT 201Tl myocardial perfusion defects.

Adult↗
PubMed1988

Uptake of cadmium-109, a metallothionein-binding radiometal, by tumors in mice as a function of the transformed phenotype.

Metallothionein (MT) is an intracellular protein that binds many metals with isotopes having imaging or radiotherapeutic potential. To determine whether uptake of radioisotopes that bind to MT is increased in tumors, we measured the uptake of cadmium-109 (Cd-109) in tumors and in normal tissues of mice. Tumors were grown in Balb/C mice from cultured Balb/3T3 cells transformed by the Moloney murine sarcoma virus (MMSV). Uptake of Cd-109 by MMSV tumors exceeded that by normal tissues examined, with the exception of liver and kidney (the organs known to be richest in metallothionein). The MMSV tumor:background ratios of activity were greater for Cd-109 than for gallium-67 for many of the normal tissues examined. The magnitude of uptake of Cd-109 by tumors from four related cell lines paralleled their degree of expression of two indices of the transformed, or malignant, phenotype. We conclude that metals that bind to MT may be useful for imaging or radiotherapy of cancer.

Animals↗
PubMed1988

Theophylline dosing and theophylline level testing in a family practice population.

Theophylline level testing enables the physician to monitor patients on theophylline and maintain benefit vs risk at an optimum ratio. This study consisted of a retrospective chart review of 53 patients who had a total of 103 serum theophylline level determinations (STLDs) over a 12-month period. The study was designed to look at reasons why physicians ordered STLDs and to what extent those results influenced subsequent theophylline prescribing. Findings showed that a large number of STLDs were ordered on asymptomatic patients with no recent dose change or initiation of therapy and no recent hospitalization or emergency room visit. The most common reason for ordering an STLD was presentation with symptoms or signs of asthma and no other recent events. On several occasions when low results were obtained, theophylline dosage was not increased. In some of these cases the patient's clinical presentation may have influenced the decision to maintain the same dosage. Use of erythromycin and smoking status were observed to affect theophylline clearance. Most physicians failed to document time of last theophylline dose, which hindered accurate interpretation of STLDs.

Adolescent↗
PubMed1987

SPECT thallium-201 scintigraphy for the detection of left-ventricular aneurysm.

We have noted that the presence of left ventricular anterior/apical aneurysm on contrast ventriculography or echocardiography correlates well with the finding of failure of convergence of the left ventricular walls toward the apex on single photon emission computed tomography (SPECT) thallium-201 images. To assess this observation, we analyzed the SPECT thallium scans of 74 sequential patients who had SPECT thallium scintigraphy and contrast ventriculography and/or echocardiography for evaluation of coronary artery disease. Immediate post-stress and 4-hr redistribution thallium-201 SPECT images, obtained following i.v. administration of 2 mCi of thallium-201, were reconstructed with no attenuation correction using three-dimensional linear and nonlinear filters and displayed in short, vertical-long, and horizontal-long axes. Of the 74 patients, contrast ventriculography and/or echocardiography showed anterior/apical aneurysms in 15 and a posterolateral aneurysm in one. SPECT thallium scans detected 14 of the 16 aneurysms, based on the criterion of failure of convergence of the ventricular walls toward the apex. There were two false-positives. Thus SPECT thallium-201 scintigraphy for the detection of left-ventricular aneurysm in this series had a sensitivity of 94%, a specificity of 97%, and an accuracy of 96%.

Adult↗
PubMed1986

Variability of gastric emptying measurements in man employing standardized radiolabeled meals.

Radiolabeled liquid and solid portions of standardized 300-g meals were administered on four different study days to eight healthy subjects in an attempt to define the range of inter- and intrasubject variability in gastric emptying. Meal half emptying times, analysis of variance, and intraclass correlations were computed and compared within and between subjects. The mean solid half emptying time was 58 +/- 17 min (range 29-92), while the mean liquid half emptying time was 24 +/- 8 min (range 12-37). A nested random effects analysis of variance showed moderate intrasubject variability for solid emptying and high intrasubject variability for liquid emptying. The variability of solid and liquid emptying was comparable and relatively large when compared with other reports in the literature. The isotopic method for measuring gastric emptying is a valuable tool for investigating problems in gastric pathophysiology, particularly when differences between groups of subjects are sought. However, meal emptying time is a variable phenomenon in healthy subjects with significant inter- and intraindividual day-to-day differences. These day-to-day variations in gastric emptying must be considered in interpreting individual study results.

Adult↗
PubMed1986

Recovery of phenytoin from an enteral nutrient formula.

The recovery of phenytoin from phenytoin oral suspension dispersed in an enteral nutrient formula was determined. The study was conducted in two phases. In phase 1, diluted phenytoin oral suspension was added to 10 1-mL samples of full-strength Osmolite and 10 1-mL samples of a distilled water control solution to produce a theoretical concentration of 10 micrograms/mL. The samples were filtered through an ultrafiltration membrane and assayed for phenytoin concentration by a homogeneous enzyme-multiplied immunoassay technique. In phase 2, varying amounts of diluted phenytoin oral suspension were added to 30-mL quantities of half-strength Osmolite or control solution to determine the effect of phenytoin concentration on recovery of phenytoin; also, a constant amount of diluted phenytoin oral suspension was added to 30-, 60-, and 90-mL quantities of half-strength Osmolite or control solution to determine the effect of solvent volume on recovery of phenytoin. Duplicate samples of each phase 2 mixture were filtered and assayed in the same manner as phase 1 samples. The mean concentration of phenytoin in phase 1 samples was 3.70 +/- 0.28 microgram/mL for Osmolite and 9.87 +/- 0.27 microgram/mL for control solution; this difference was significant. The percentage of phenytoin recovered from phase 2 samples of Osmolite increased with increasing phenytoin concentration and decreased with increasing volumes of Osmolite. The decreased recovery of phenytoin from the enteral nutrient formula used in this study has potential clinical importance, but further research in humans is needed to substantiate these in vitro observations.

Enteral Nutrition↗
PubMed1986

Office therapeutic drug monitoring.

Considerations necessary for appropriate therapeutic drug monitoring in the office practice setting have been presented. Practical issues focusing on clinical pharmacokinetics as well as serum drug concentration evaluation methods and techniques have been reviewed, with emphasis on orally administered medications.

Digoxin↗