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Biomedical subjects

S Burton

Publications and source records attributed to S Burton.

At least 37 records · Page 2Linked to original sources

Mexiletine for HIV-infected patients with painful peripheral neuropathy: a double-blind, placebo-controlled, crossover treatment trial.

Although mexiletine, an antiarrhythmic with local anesthetic properties, has been reported to relieve discomfort in diabetic neuropathy, its usefulness in the treatment of HIV-related painful peripheral neuropathy (PPN) has not been determined. The tolerance and effectiveness of mexiletine in HIV-related PPN were assessed in 22 patients who were randomized to receive mexiletine (maximum dose, 600 mg/day) or placebo for 6 weeks, followed by the alternative intervention for 6 weeks after a 1-week washout period. The daily pain response was assessed using a visual analogue scale card in 19 patients who received at least 2 weeks of the drug, 16 of whom were crossed-over to receive the alternate agent. No statistically significant difference was found between the mean daily pain scores for patients receiving mexiletine versus placebo, irrespective of the order in which the agents were received. Comparing the mean individual daily pain scores for each phase of study, 5 patients (31%) had significantly less pain while receiving mexiletine compared with their response to placebo, 5 patients (31%) had significantly less pain while receiving placebo, and no difference was noted in 6 patients (38%). Crossover and multivariate analyses for repeated measures showed no apparent difference in the response to mexiletine versus placebo. Dose-limiting adverse events occurred in 39% of those receiving mexiletine, but only 1 patient (5%) discontinued placebo. Mexiletine was only modestly well tolerated despite its relatively brief period of administration, and no evidence was found to support its benefit in HIV-related PPN. Although a first-drug effect was not demonstrated, a powerful placebo effect was seen in some patients.

Adult↗

A syndrome of peripheral lipodystrophy, hyperlipidaemia and insulin resistance in patients receiving HIV protease inhibitors.

OBJECTIVE: To describe a syndrome of peripheral lipodystrophy (fat wasting of the face, limbs and upper trunk), hyperlipidaemia and insulin resistance in patients receiving potent HIV protease inhibitor therapy. DESIGN: Cross-sectional study. SETTING: Outpatient clinic of a university teaching hospital. PATIENTS: HIV-infected patients either receiving at least one protease inhibitor (n=116) or protease inhibitor-naive (n=32), and healthy men (n=47). INTERVENTIONS AND MAIN OUTCOME MEASURES: Lipodystrophy was assessed by physical examination and questionnaire and body composition by dual-energy X-ray absorptiometry. Fasting triglyceride, cholesterol, free fatty acid, glucose, insulin, C-peptide and fructosamine levels, other metabolic parameters, CD4 lymphocyte counts, and HIV RNA load were also assessed. RESULTS: HIV protease inhibitor-naive patients had similar body composition to healthy men. HIV protease inhibitor therapy was associated with substantially lower total body fat (13.2 versus 18.7 kg in protease inhibitor-naive patients; P=0.005), and significantly higher total cholesterol and triglyceride levels. Lipodystrophy was observed clinically in 74 (64%) protease inhibitor recipients after a mean 13.9 months and 1(3%) protease inhibitor-naive patient (P=0.0001). Fat loss occurred in all regions except the abdomen after a median 10 months. Patients with lipodystrophy experienced a relative weight loss of 0.5 kg per month and had significantly higher triglyceride, cholesterol, insulin and C-peptide levels and were more insulin-resistant than protease inhibitor recipients without lipodystrophy. Patients receiving ritonavir and saquinavir in combination had significantly lower body fat, higher lipids and shorter time to lipodystrophy than patients receiving indinavir. Three (2%) patients developed new or worsening diabetes mellitus. CONCLUSION: A syndrome of peripheral lipodystrophy, hyperlipidaemia and insulin resistance is a common complication of HIV protease inhibitors. Diabetes mellitus is relatively uncommon.

Adult↗

Palliative care in the acute hospital setting.

Palliative care, associated with the hospice movement, has achieved wide acceptance in many countries. Its focus has been care of cancer patients and more recently, those with AIDS. Most acute hospitals do not have avenues to care for these patients or others in the end of life stages. One method of providing care and comfort in an acute hospital setting for those who have chosen to discontinue treatment or whom aggressive treatment is no longer beneficial is the palliative care team. This team was developed to ensure that specialized services would be offered to the dying patient in the acute setting.

Acquired Immunodeficiency Syndrome↗

Effects of medetomidine on serum osmolality; urine volume, osmolality and pH; free water clearance; and fractional clearance of sodium, chloride, potassium, and glucose in dogs.

OBJECTIVE: To determine effects of i.v. medetomidine administration on selected clinicopathologic variables in dogs. ANIMALS: 6 healthy adult Beagles. PROCEDURE: Dogs were randomly assigned to each of 3 treatments in a crossover study design. Serum osmolality, urine osmolality, urine pH, and fractional clearances of sodium, chloride, potassium, and glucose were determined before and 20, 40, 60, 120, 180, 240, 300, 360, 420, and 480 minutes after i.v. administration of 0.9% NaCl (saline) solution (control) or medetomidine (10 or 20 micrograms/kg of body weight). The urinary bladder was emptied prior to saline or medetomidine administration, and urine volume was determined at the same posttreatment times as those described previously. Free water clearance was calculated for all posttreatment times. RESULTS: After medetomidine administration, serum osmolality, urine volume, free water clearance, and fractional clearance of potassium and glucose increased; urine osmolality decreased. Initially, urine pH and fractional clearance of chloride decreased, then subsequently increased. Fractional clearance of sodium did not change. CONCLUSIONS AND CLINICAL RELEVANCE: Because i.v. administration of medetomidine to dogs at dosages of 10 and 20 micrograms/kg induces a diuretic effect that lasts up to 4 hours, the drug should be used with discretion in hypovolemic or dehydrated dogs, and its use should be avoided in those with urinary tract obstruction.

Adrenergic alpha-Agonists↗

Preliminary assessment of PCB risks to human and ecological health in the lower Passaic River.

Concentrations of Aroclor mixtures and specific polychlorinated biphenyl (PCB) congeners were measured in surface sediments and aquatic biota (striped bass fillet, mummichog, and blue crab muscle and hepatopancreas) collected from the lower Passaic River. Several of the 47 surface sediment samples contained Aroclor concentrations that exceeded a National Oceanic and Atmospheric Administration (NOAA) benchmark level for "total PCBs" (22.7 micrograms/kg). Each of the 18 PCB congeners analyzed in aquatic biota was detected in one or more tissue samples, and numerous congeners were detected in every sample (IUPAC numbers 77, 105, 114, 118, 123, 126, 156, 157, 167, and 189). PCB congener concentrations were similar to those that have been reported in fish from other waterways that contain elevated levels of PCBs. Congener 118 was present at the highest concentration in almost all samples, and constituted 14-60% of the total PCB mass (sum of all congener masses) measured in any given tissue sample. In spite of the prevalence of PCB congeners in biota tissues (up to 1314 micrograms/kg total PCBs), Aroclors were not detected in bass or crab samples at a limit of detection of 33-55 micrograms/kg. This anomaly may be due to selective degradation of certain PCB congeners that are used to analytically recognize and quantitate Aroclors. Using the measured sediment concentrations, a food web model accurately predicted blue crab muscle concentrations of individual PCB congeners (typically within a factor of two) and was also fairly accurate for mummichog (typically within an order of magnitude). Concentrations in striped bass fillet were underestimated by factors of approximately 20-140. Increased cancer risk estimates associated with fish and crab consumption were obtained using four different methods. Using Aroclor tissue concentrations (one-half the limit of detection) and an Aroclor slope factor, total risks were 2.6 x 10(-6); using the "total PCB" measurements and an Aroclor slope factor, total risks were 1.9 x 10(-5); the "PCB-TEQ" method yielded total risks of 6.5 x 10(-4); and USEPA's recent suggested approach for evaluating "dioxin-like" and non-"dioxin-like" effects resulted in a total risk of 6.6 x 10(-4). This wide range in risk estimates indicates that it is critical to the risk management decision-making process that data requirements and risk assessment objectives be carefully evaluated early in the investigation process.

Animals↗

The use of nurse practitioners in the acute care setting.

A collaborative practice model was initiated in a university hospital to assist resident physicians to coordinate patient care on specialty services. Nurse practitioner (NP) data were collected on daily work activities and categorized as direct care, indirect care, administration, education, and research. Satisfaction surveys were collected from patients, physicians and nursing staff. Data on clinic evaluation and management service provided by the NPs were reported. The study supported the appropriateness of NPs in the acute care setting.

Hospitals, University↗

Hypoadrenocorticism in young related Nova Scotia duck tolling retrievers.

Five cases of hypoadrenocorticism in young related Nova Scotia duck tolling retrievers are discussed. Two were littermates and the others shared one or more common ancestors. No specific mode of inheritance was determined. Clinical and laboratory findings typical of hypoadrenocorticism were observed. Further documentation will be required to confirm a breed predisposition.

Adrenal Glands↗

Dynamic magnetic resonance imaging in the study of vocal tract configuration.

Studies of vocal tract configuration using magnetic resonance imaging (MRI) techniques have relied on static images. These images fail to identify transient movements and are subject to distortion from motion artifact limiting research application to stable motor events. This paper describes a dynamic MRI technique that permits study of transient movements within the vocal tract during speech and nonspeech tasks. Following description of the technique, results of two preliminary studies are presented. The initial study evaluated issues of measurement error and reliability. Results indicated that distance and area measurements obtained from this technique are accurate in reference to a calibration referent and reliable both within and among judges. The second study compared two aspects of vocal tract configuration in patients with adductor spasmodic dysphonia before and following treatment with Botox injection. Changes in vocal tract configuration are discussed in reference to prior observations of patients with spasmodic dysphonia. These preliminary investigations suggest that dynamic MRI has promise as a useful technique in the study of vocal tract configuration.

Aged↗

Vascular nurse practitioner: a collaborative practice role in the acute care setting.

A collaborative practice model was initiated in a 440-bed university teaching hospital to trial the appropriateness and effectiveness of placing a nurse practitioner (NP) in the acute-care setting with a group of vascular surgeons. The vascular NP and three physicians collaborated as providers of patient care in both ambulatory and hospital settings. The NP managed and coordinated patient care. After orientation, the NP used a data-tracking form to record daily work activities categorized as direct care, indirect care, administration, education, and research. Satisfaction surveys were distributed to patients, nurses, and physicians to measure key elements of the NP's job responsibilities as they related to each group. The NP's data were independently analyzed, implications were discussed, and results were collated for presentation. The data were also used to guide future practice. The data reflected the vascular NP's unique acute care role within a specialty service.

Humans↗

An endothelin-1 mediated autocrine growth loop involved in human renal tubular regeneration.

Renal tubules have the capacity to regenerate following injury. We have investigated the possibility that tubular-derived endothelins, acting as autocrine growth factors, may be involved in this response in human kidney. ET-1 immunoreactivity was demonstrated by immunohistochemical staining in proximal tubules, distal cortical tubules and medullary collecting ducts of human kidney. In cultured human renal proximal tubular cells, RNAase protection assays demonstrated the expression of ET-1 and ET-2 mRNA's, and radioimmunoassay, following separation of conditioned medium by reverse phase HPLC, showed immunoreactive material which co-eluted with ET-1 and ET-2. Competition binding studies revealed the presence of at least two types of endothelin receptor: one with high and one with low affinity for ET-3 relative to ET-1. Analysis of cellular RNA by RT-PCR demonstrated expression of mRNA's for both ETA and ETB receptor subtypes. Combined blockade of ETA and ETB receptors (by PD-145065) but not that of ETA receptors alone (by BQ-123) blocked the mitogenic effect of exogenous or endogenous ET-1 and also profoundly suppressed endogenous ET-1 synthesis. By contrast, incubation with the ETB receptor agonist, BQ-3020, stimulated endogenous ET-1 synthesis. Exposure of the cells to hypoxia (1% O2 for 16 to 24 hr) resulted in specific up-regulation of ET-1 but not ET-2 gene expression. These findings reveal the existence of a hypoxia-inducible, autocrine growth system in human proximal tubular cells, which is mediated by ET-1 through the ETB receptor, and which could function in vivo as an autoregenerative system for restoring tubular integrity after injury. The widespread distribution of ET-1 peptide in different tubular segment suggests that ET-1 mediated tubular regeneration may also occur in other nephron segments.

Binding, Competitive↗

Transfer of a mutated gene encoding active transforming growth factor-beta 1 suppresses mitogenesis and IL-1 response in the glomerulus.

Using in vivo gene transfer, we examined the anti-inflammatory potential of transforming growth factor-beta 1 (TGF-beta 1) in the renal glomerulus. TGF-beta 1 cDNA, modified to allow for secretion of the active form of TGF-beta 1, was introduced into cultured rat mesangial cells. The responses of the established transfectants were examined in culture. In vitro, the transduced mesangial cells showed a reduced mitogenic response to fetal calf serum and were insensitive to induction of matrix metalloproteinase-9 (MMP-9) by the proinflammatory cytokine IL-1 beta. To examine whether glomeruli which express active TGF-beta 1 in vivo are insensitive to these same stimuli, TGF-beta transfectants were transferred into normal rat glomeruli via renal artery injection. After 24 hours, isolated glomeruli containing transfectants exhibited TGF-beta bioactivity, a reduced mitogenic response, and repressed expression of MMP-9 in response to IL-1 beta. We further examined the responses of these chimeric glomeruli to an in vivo mitogenic stimulus by transferring TGF-beta transfectants into glomeruli of kidneys one day after the induction of anti-Thy-1 nephritis. The mitogenic activity of isolated glomeruli was examined four days after the cell injection. Compared to unmodified or mock cell-containing glomeruli, the in vivo mitogenic activity of glomeruli containing TGF-beta transfectants was significantly repressed. Furthermore, cellular outgrowth from nephritic glomeruli expressing active TGF-beta 1 was also suppressed ex vivo compared to controls. These data indicate that TGF-beta 1 inhibits mitogenesis and IL-1 response of the glomerulus and may, in part, act as a potential early suppressor of glomerular inflammation.

Animals↗

Reducing intensive care unit length of stay. A stepdown unit for first-day heart surgery patients.

The restructuring of healthcare delivery systems has increased the demand for successful, low-cost, alternative approaches to providing care. The authors detail the design, implementation, and evaluation of one alternative approach for delivery of care to thoracic surgery patients. The authors describe the use of a stepdown unit for the care of patients 24 to 36 hours after cardiothoracic surgery.

Bed Conversion↗

Intragastric distribution of ion-exchange resins: a drug delivery system for the topical treatment of the gastric mucosa.

Previous studies by this group on freeze-dried oral dosage forms containing finely-divided ion-exchange resins revealed prolonged gastric residence and uniform distribution within the stomach. The present study was carried out to ascertain whether this was due to freeze-drying, properties of the radiolabelled ionic exchange resin, or the small dosing volume used. 99mTc-labelled cholestyramine resin was administered in two dosage forms, a freeze-dried tablet which dissolved in the oral cavity (orally dissolving tablet; ODT) and a 1.5 mL aqueous suspension. Two resin particle sizes (20-40 and 90-125 microns) were studied. Oesophageal transit and intragastric distribution and residence were followed by gamma scintigraphy. In a second study, in six subjects, gastric emptying of the water-soluble fraction of the ODT and 1.5 mL of water, was measured using 99mTc diethylenetriaminepentaacetic acid. Oesophageal transit of a water-soluble marker and resin in suspension was rapid, but the transit of the resin in the ODTs was significantly prolonged. Regardless of particle size or dosage form, the resin was evenly distributed throughout the stomach with 20-25% remaining for 5.5 h. In contrast, the water-soluble marker cleared from the stomach rapidly from both dosage forms. We suggest that oral dose forms containing finely-divided ion-exchange resins may form a useful system for topical treatment of the gastric mucosa, for example in targeting to Helicobacter pylori infection.

Adult↗