Search PubMed⌕ Search

Biomedical subjects

A Taylor

Publications and source records attributed to A Taylor.

At least 217 records · Page 12Linked to original sources
PubMed1999

Lack of pharmacokinetic interaction between ropinirole and theophylline in patients with Parkinson's disease.

OBJECTIVE: Ropinirole and theophylline have the potential to interact, because they use the same hepatic cytochrome P450 (CYP1A2) as their major metabolic pathway. The present study investigated the effect of steady-state oral theophylline on the pharmacokinetics of ropinirole at steady state and the effect of steady-state ropinirole on the pharmacokinetics of a single intravenous (i.v.) dose of theophylline, both in patients with idiopathic Parkinson's disease (PD). METHODS: Pharmacokinetic parameters (AUC and Cmax) for i.v. theophylline were compared before and after a 4-week period of oral treatment with ropinirole (2 mg t.i.d.) in 12 patients with PD. Patients were then maintained at this dose of ropinirole, and oral theophylline was co-administered at doses of up to 300 mg b.i.d. The parameters AUC, Cmax and tmax for ropinirole were compared before, during and after oral theophylline co-treatment. RESULTS: Co-administration of ropinirole did not significantly change the pharmacokinetics of i.v. theophylline (mean AUC with and without ropinirole: 68.6 micog x h(-1) x ml(-1) and 70.0 microg x h(-1) x ml(-1), respectively: mean Cmax with and without ropinirole: 11.07 microg x ml(-1) and 11.83 microg x ml(-1), respectively). Similarly, there were no significant changes in ropinirole pharmacokinetics when the drug was co-administered with oral theophylline (mean AUC for ropinirole with and without theophylline: 21.91 ng x h(-1) x ml(-1) and 22.09 ng x h(-1) x ml(-1), respectively; mean Cmax for ropinirole with and without theophylline: 5.65 ng x ml(-1) and 5.54 ng x ml(-1), respectively; median tmax for ropinirole with and without theophylline: 2.0 h and 1.5 h, respectively). CONCLUSION: These results suggest a lack of significant pharmacokinetic interaction between the two drugs at current therapeutic doses.

Administration, Oral↗
PubMed1999

Radionuclide renography: a personal approach.

Recent advances have increased the value of radionuclide renography in evaluating the patient with suspected disease of the genitourinary tract. The use of the consensus process to help standardize procedures and recommend interpretative criteria provides guidance for the nuclear medicine practitioner, serves as a basis to improve the standard of practice, and facilitates pooling of data from different centers. This review draws on the consensus criteria to present a personal approach to radionuclide renography with a particular emphasis on diuresis renography and the detection of renovascular hypertension. Patients are encouraged to come well hydrated and void immediately prior to the study. Our standard radiopharmaceutical is 99mTc mercaptoacetyltriglycine (MAG3). Routine quantitative indices include a MAG3 clearance, whole kidney and cortical (parenchymal) regions of interest, measurements of relative uptake, time to peak height (Tmax), 20 min/max count ratio, residual urine volume and a T(1/2) in patients undergoing diuresis renography. A 1-minute image of the injection site is obtained at the conclusion of the study to check for infiltration because infiltration can invalidate a plasma sample clearance and alter the renogram curve. A postvoid image of the kidneys and bladder is obtained to calculate residual urine volume and to better evaluate drainage from the collecting system. In patients undergoing diuresis renography, the T(1/2) is calculated using a region of interest around the activity in the dilated collecting system. A prolonged T(1/2), however, should never be the sole criterion for diagnosing the presence of obstruction; the T(1/2) must be interpreted in the context of the sequential images, total and individual kidney function, other quantitative indices and available diagnostic studies. The goal of ACE inhibitor renography is to detect renovascular hypertension, not renal artery stenosis. Patients with a positive study have a high probability of cure or amelioration of the hypertension following revascularization. In patients with azotemia or in patients with a small, poorly functioning kidney, the test result is often indeterminate (intermediate probability) with an abnormal baseline study that does not change following ACE inhibition. In patients with normal renal function, the test is highly accurate. To avoid unrealistic expectations on the part of the referring physician, it is often helpful to explain the likely differences in test results in these two-patient populations prior to the study.

Aged↗
PubMed1999

Consensus report on quality control of quantitative measurements of renal function obtained from the renogram: International Consensus Committee from the Scientific Committee of Radionuclides in Nephrourology.

Among all the physiological indices that can be quantified using renography, measurement of renal function is the most basic. These measurements are used to make critical clinical management decisions and, as such, their reliability needs to be quality assured. This article seeks to address each aspect of the renography procedure, with particular emphasis on the effect on measurement of relative renal function. Estimation of individual kidney function is mentioned, but only briefly. A consensus approach was adopted, overseen, and directed by a chairman appointed by the Scientific Committee of the International Radionuclides in Nephro-Urology Group. The chairman selected the panel of experts from eight different countries based on their practical experience in the field. Where evidence exists to support the various recommendations it is given. Otherwise, the stated guidance represents the considered opinion of a body of experts, based on long experience and unpublished data. Some necessary compromises were made to account for the fact that renography is seldom performed solely with the purpose of measuring relative renal function. The technicalities of renography have always been a source of debate in nuclear medicine, which is reflected by the fact that a consensus could simply not be reached on a small number of issues. The structure of the report ensures that these are clearly indicated. This should serve to highlight gaps in our current knowledge, thus helping to direct future research. It is envisaged that the recommendations will be revised on a 2-year cycle to ensure that they remain up to date. An "open" process will be used to encourage participation and ownership. It is hoped that promotion of these guidelines, suitably complemented by audit processes, will raise standards in the practice of gamma camera renography.

Adult↗
PubMed1999

Report of the Radionuclides in Nephrourology Committee for evaluation of transplanted kidney (review of techniques).

Comprehensive evaluation of renal transplants has been important in differential diagnosis of medical and surgical complications in the early post-transplantation period and in the long-term follow-up. If performed well, it yields excellent functional and good anatomic information about the graft that can be effectively used in the patient. That includes selection of patients for biopsy and for various drug regimens. This is true especially in patients with anuric acute tubular necrosis (ATN) and in patients with developing chronic rejection. Improving indices of renal function (effective renal plasma flow, uptake of tubular tracers) can indicate resolution of tubular injury (ATN) while there is still no improvement in plasma creatinine. In patients with chronic rejection, plasma creatinine increases only after approximately 30% of renal function is lost due to graft fibrosis. Early recognition of this condition could permit treatment and delay of retransplantation. The protocol recommended at the Copenhagen meeting includes a flow study, scintigram of the kidneys, prevoid and postvoid bladder image, injection site image (quality control), time/activity curves of the graft and bladder, and quantitative data of perfusion, function, and tracer transit. The flow study obtained during the initial transit of the bolus through the graft could be performed either with 99mTc mercaptoacetyltriglycine, or 99mTc diethylenetriaminepentaacetate (DTPA). Quantitative analysis of perfusion facilitates interpretation of the study during the early post-transplantation period. ATN, common in cadaver transplants, typically shows adequate perfusion. The function phase should include images and time/activity curves. Images alone are insufficient. Quantitative data such as clearance or other indices of function and indices of tracer transit are essential for correct interpretation of the results. Normal images and normal graft function reliably exclude clinically important complications. A single scintigram demonstrating prolonged tracer transit with decreased function cannot separate acute rejection and ATN. On serial studies, decline in function and poor perfusion are indicative of acute rejection. A normally appearing scintigram without cortical retention, but with low function, is consistent with chronic rejection. Pharmacological intervention to exclude obstruction (diuretic renogram) or hemodynamically significant renal artery stenosis (angiotensin converting enzyme challenge) should be used whenever indicated.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1999

Dietary copper supplementation reduces atherosclerosis in the cholesterol-fed rabbit.

There has been considerable debate about how copper status may affect the biochemical and cellular processes associated with atherogenesis. In the present study we have attempted to address this issue directly by investigating the effects of dietary copper supplementation on processes likely to contribute to atherogenesis, using the cholesterol-fed New Zealand White rabbit model. Age matched rabbits (n = 16) were fed a 0.25-1% cholesterol diet to maintain plasma cholesterol concentrations at approximately 30 mmol/l. Eight of these animals also received 0.2% copper acetate. Control animals (n = 8) received rabbit chow without supplements. After 13 weeks on the experimental diets the animals were killed. Integrated cholesterol levels were similar for the cholesterol-fed animals (31.1+/-2.5 vs. 29.9+/-1.9 mmol/l weeks; P>0.05). Although integrated plasma copper levels were higher in the animals receiving the copper supplements, these did not differ significantly (19.0+/-4.8 vs. 15.1+/-2.9 micromol/l weeks; P>0.05). Tissue concentrations of copper were higher in the copper fed animals compared to those on cholesterol alone in aortic 14.0+/-0.75 vs. 1.8+/-0.2 microg/g wet tissue; P<0.05), carotid artery (11.4+/-3.5 vs. 4.9+/-0.9 microg/g wet tissue; P<0.05), and hepatic (332.5+/-28.6 vs. 3.3+/-1.1 microg/g wet tissue; P<0.0001) samples. The concentration of copper within the carotid artery was also significantly higher than that within the aorta (7.5+/-1.8 vs. 2.4+/-0.4 microg/g wet tissue; P<0.05). In animals fed a normal rabbit chow aortic, carotid and hepatic copper concentrations were 3.7+/-0.8, 9.4+/-3.4, and 5.0+/-1.6 microg/g, respectively. These values did not differ significantly from the cholesterol-fed animals (P>0.05). Plasma concentrations of caeruloplasmin, the major copper carrying protein, were estimated as plasma ferroxidase activity and were similar for the groups (P>0.05), as were aortic superoxide dismutase activity levels (P>0.05). Copper supplementation was associated with increased mononuclear cell adhesion to the endothelium of the carotid endothelium, with 2.6+/-0.3 adherent monocytes/1000 endothelial cells in the cholesterol plus copper-fed animals compared to 1.3+/-0.3 in the cholesterol-fed group (P = 0.0006), and 0.1+/-0.1 in the control animals (P<0.002). This may reflect the higher concentrations of copper found within the carotid artery. Histology of the thoracic aorta at the level of the third and sixth intercostal arteries, showed that copper supplementation was associated with significantly smaller intimal lesions (P<0.05 and P<0.01, respectively). These data suggest that copper supplements possibly inhibit the progression of atherogenesis.

Animals↗
PubMed1999

Serum prostate-specific antigen and prostate volume predict long-term changes in symptoms and flow rate: results of a four-year, randomized trial comparing finasteride versus placebo. PLESS Study Group.

OBJECTIVES: To determine whether baseline prostate-specific antigen (PSA), in addition to prostate volume, is associated with long-term changes in symptoms and urinary flow rate. METHODS: Three thousand forty men with benign prostatic hyperplasia enrolled in the PLESS trial were randomly assigned to finasteride 5 mg or placebo for 4 years. Symptoms and flow rate were assessed every 4 months, and data were analyzed by dividing the patients into three groups by baseline PSA tertiles (0 to 1.3, 1.4 to 3.2, and 3.3 ng/mL or greater) and baseline prostate volume tertiles (14 to 41, 42 to 57, and 58 to 1 50 mL). RESULTS: After the initial placebo effect, a slow deterioration in symptoms over time was observed in the placebo-treated men with a baseline PSA 1.4 ng/mL or greater. However, placebo-treated men in the lowest PSA tertile (less than 1.4 ng/mL) had sustained symptomatic improvement that was not seen in placebo-treated men in the higher tertiles (P<0.001). In all finasteride-treated groups, there was initial improvement followed by maintenance or continued symptom improvement over time (approximately 3 to 3.5 points by the end of 4 years). The differences in symptom score improvement between placebo and finasteride were marginal for men with baseline PSA levels less than 1.4 ng/mL (P = 0.128) but were highly significant for men with PSA levels 1.4 ng/mL or greater (P<0.001). Urinary flow rate results were similar to those observed for symptoms. Analysis of symptom and flow rate data by prostate volume tertiles in a 10% subset of men yielded similar results, namely a deterioration of symptoms and flow rate in the two higher tertiles treated with placebo (greater than 41 mL) and a sustained improvement in all three groups of finasteride-treated patients. CONCLUSIONS: Baseline PSA and prostate volume are good predictors of long-term symptomatic and flow rate changes. Baseline PSA levels of 1.4 ng/mL or greater and enlarged prostate glands predict the best long-term response to finasteride compared with placebo.

Enzyme Inhibitors↗
PubMed1999

Fenoldopam: a new parenteral antihypertensive: consensus roundtable on the management of perioperative hypertension and hypertensive crises.

A panel of clinicians from anesthesiology, surgery, nephrology, hypertension, cardiology, and pharmacology was convened to discuss pharmacologic therapeutics in the management of hypertensive crisis and perioperative hypertension. The panel discussed the advantages and limitations of currently available parenteral drugs, and assessed the potential use of fenoldopam mesylate, a drug in clinical development since 1981, and recently approved by the U.S. Food and Drug Administration (FDA). Fenoldopam is a dopamine receptor (DA1 selective) agonist that is a systemic and renal vasodilator. It was concluded that fenoldopam offers significant advantages as a parenterally administered agent for the management of blood pressure in both hypertensive emergencies and in the perioperative setting.

Acute Disease↗
PubMed1999

Matrix protein of Chandipura virus inhibits transcription from an RNA polymerase II promoter.

Chandipura virus (CHPV) is a Vesiculovirus, related to, but phylogenetically distinct from, vesicular stomatitis virus (VSV). The matrix protein of VSV, as well as its role in virus assembly, inhibits the transcription from promoters for host RNA polymerases I and II. Cloning and expression of the matrix protein of CHPV in human cells showed that this protein is also functional in its inhibitory effect on transcription of a reporter gene from the cytomegalovirus immediate-early promoter, despite sharing only 28% amino acid sequence identity with the matrix protein of VSV.

Amino Acid Sequence↗
PubMed1999

Early sex differences in spatial skill.

This study investigated sex differences in young children's spatial skill. The authors developed a spatial transformation task, which showed a substantial male advantage by age 4 years 6 months. The size of this advantage was no more robust for rotation items than for translation items. This finding contrasts with studies of older children and adults, which report that sex differences are largest on mental rotation tasks. Comparable performance of boys and girls on a vocabulary task indicated that the male advantage on the spatial task was not attributable to an overall intellectual advantage of boys in the sample.

Adult↗
PubMed1999

The effect of steady-state ropinirole on plasma concentrations of digoxin in patients with Parkinson's disease.

AIMS: The aim of this single-blind study was to assess the effect of ropinirole, a novel treatment for Parkinson's disease, on the steady-state pharmacokinetics and safety of digoxin in 10 patients with Parkinson's disease. METHODS: There were three parts to the study: digoxin once daily plus placebo three times daily for 1 week; digoxin once daily plus ropinirole three times daily for 6 weeks; and digoxin once daily plus placebo three times daily for 1 week. Serial blood samples were collected over 24 h at the end of each part of the study for pharmacokinetic assessment. Pre-dose blood samples were collected on specific days throughout the study to assess the attainment of steady-state plasma levels of digoxin. The primary endpoints were AUC(0, tau) and Cmax for digoxin. RESULTS: There was a mean decrease of 10% in digoxin AUC (0, tau) (90% CI: 0.79, 1.01) and a 25% decrease in digoxin Cmax (90% CI: 0.58, 0.97) when ropinirole was co-administered, compared with digoxin alone Cmin plasma values for digoxin, however, were fairly constant throughout the study (point estimates 0.99, 95% CI: 0.85, 1.15). Changes in trough levels of digoxin are believed to be the most reliable way of assessing steady-state concentrations of digoxin, and therefore the clinical significance of an interaction. Changes in Cmax are too readily influenced by other factors. CONCLUSIONS: These results therefore indicate that on pharmacokinetic grounds no dose adjustment is necessary for digoxin co-administered with ropinirole.

Aged↗
PubMed1999

Cardiovascular response during head-up tilt in chronic fatigue syndrome.

This study examined the cardiovascular response to orthostatic challenge, and incidence and mechanisms of neurally mediated hypotension in chronic fatigue syndrome (CFS) during a head-up tilt test. Stoke volume was obtained by a thoracic impedance cardiograph, and continuous heart rate and blood pressure were recorded during a 45-min 70 degrees head-up tilt test. Thirty-nine CFS patients and 31 healthy physically inactive control subjects were studied. A positive tilt, i.e. a drop in systolic blood pressure of > 25 mmHg, no concurrent increase in heart rate and/or development of presyncopal symptoms, was seen in 11 CFS patients and 12 control subjects (P > 0.05). During baseline and the first 5 min of head-up tilt, CFS patients had higher heart rate and smaller pulsatile-systolic area than control subjects (P < 0.05). Among subjects who completed the test, those with CFS had higher heart rate and smaller stroke volume (P < 0.05) than corresponding control subjects. When comparing those who had a positive test outcome in each group, CFS patients had higher heart rates and lower pulse pressure and pulsatile-systolic areas during the last 4 min before being returned to supine (P < 0.05). These data show that there are baseline differences in the cardiovascular profiles of CFS patients when compared with control subjects and that this profile is maintained during head-up tilt. However, the frequency of positive tilts and the haemodynamic adjustments made to this orthostatic challenge are not different between groups.

Adult↗
PubMed1999

Fat-soluble nutrient concentrations in different layers of human cataractous lens.

PURPOSE: Recent epidemiologic studies suggest that differential risk for cataract in different areas of the lens may be related to intake of carotenoids, retinol, and tocopherol. Nevertheless, there is little information about differential localization of these nutrients in the lens. To determine the spatial distribution of fat-soluble nutrients within the lens, we determined levels of these nutrients in the epithelium/ outer cortex vs. inner cortex/nucleus. METHODS: Concentrations of carotenoids, retinol, and tocopherol were determined in the epithelial/cortical (younger, more metabolically active tissue) and nuclear (older, less metabolically active) layers of human cataractous lenses (n = 7, 64-75 yr) by reverse-phase high-performance liquid chromatography (HPLC). RESULTS: Lutein/zeaxanthin was the only carotenoid, which was detected, in human lens. Consistent with prior reports, no beta-carotene or lycopene were detected. Concentrations of lutein/zeaxanthin, tocopherol, and retinol in epithelium/cortex tissue were approximately 3-, 1.8-, and 1.3-fold higher than in the older lens tissue. Specifically, the epithelial/cortical lens layer, comprising about half of the tissue, contains 74% of lutein/zeaxanthin (44 ng/g wet wt), 65% of alpha-tocopherol (2227 ng/g wet wt), and 60% of retinol (30 ng/g wet wt). CONCLUSIONS: The data suggest that upon development and aging, there is differential localization of these nutrients. The data are also consistent with a protective role of these nutrients against oxidative damage in the epithelium and cortex of the human lens.

Aged↗
PubMed1999

Decreasing ascorbate intake does not affect the levels of glutathione, tocopherol or retinol in the ascorbate-requiring osteogenic disorder shionogi rats.

Levels of glutathione in liver and kidney, and other nutrients in plasma were evaluated in male and female ascorbate-requiring osteogenic disorder Shionogi (ODS) rats fed semipurified diets in which the concentrations of ascorbate were gradually decreased from 1965 to 180 mg/kg. Plasma ascorbate levels in ODS rats were unaffected when ascorbate levels in the diet were decreased from 1965 to 768 mg/kg. However, plasma ascorbate levels decreased progressively when levels of ascorbate in the diet were decreased from 527 to 180 mg/kg. Plasma ascorbate levels decreased up to 77% when the dietary ascorbate concentration decreased from 1965 to 180 mg/kg. Ascorbate levels in liver and kidney fell as much as 60-70% when the dietary ascorbate levels were reduced from 1965 to 180 mg/kg. However, the glutathione levels in these tissues were not affected. Plasma retinol and vitamin E levels were not affected by decreasing dietary ascorbate intake. Total cholesterol levels increased significantly in female rats as dietary ascorbate intake declined. Levels of glycated hemoglobin decreased significantly when dietary ascorbate levels decreased from 1965 to 527 mg/kg. This study suggests that levels of vitamin E, retinol and glutathione are not affected by decreased dietary intake of ascorbate under nonscorbutic conditions, whereas elevated ascorbate intake is associated with a decrease in levels of plasma cholesterol in female ODS rats. However, excessive intake of ascorbate may be associated with elevated glycation of hemoglobin. To achieve the maximal health benefit of ascorbate supplementation, further studies are necessary to define optimal ascorbate intakes.

Administration, Oral↗
PubMed1999

Disseminated intravascular coagulation in a patient treated with strontium-89 for metastatic carcinoma of the prostate.

Strontium-89 is effective in the palliation of bone pain caused by skeletal metastases. Its primary side effect is mild thrombocytopenia that typically recovers in 3 or 4 months. Subclinical disseminated intravascular coagulation is reported to be present in approximately 10% to 20% of patients with advanced prostate cancer. These patients may be at increased risk for severe marrow depression after radionuclide therapy for bone pain palliation. This report describes a patient with painful bony metastases resulting from prostate carcinoma. He had a normal platelet count and no clinical evidence of a coagulation disorder at the time of strontium-89 therapy, and a severe disseminated intravascular coagulation developed and lead to death after treatment. A normal platelet count before strontium-89 therapy does not preclude subsequent disseminated intravascular coagulation, and we support the Society of Nuclear Medicine's bone pain treatment procedure guideline that patients referred for bone palliation should be screened for disseminated intravascular coagulation before therapy.

Adenocarcinoma↗
PubMed1999

A pilot controlled family study of DSM-III-R and DSM-IV ADHD in African-American children.

BACKGROUND: Very little is known about attention-deficit hyperactivity disorder (ADHD) in African-American children, and although the familial transmission of ADHD has been well established in white samples, prior work has not evaluated this feature of ADHD in African-American families. METHOD: Subjects were 37 first-degree relatives of children with DSM-III-R-defined ADHD and 52 first-degree relatives of non-ADHD comparison children matched for ethnicity, age, and gender. DSM-III-R-based structured interviews (modified to include DSM-IV diagnoses) provided the basis for psychiatric diagnoses in relatives. RESULTS: The risks for both DSM-III-R and DSM-IV ADHD were significantly greater in first-degree relatives of ADHD probands than in relatives of controls. In addition, the relatives of ADHD probands also were at higher risk for oppositional defiant disorder, antisocial personality disorder, major depression, generalized anxiety, and substance use disorders. CONCLUSIONS: These results suggest that ADHD and related disorders are familial in African-Americans. Further work is needed to confirm the familial transmission of ADHD in African-American children and to explore the role of genetics as well as environmental factors in the transmission of the disorder.

Adolescent↗