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Biomedical subjects

D Abbott

Publications and source records attributed to D Abbott.

At least 19 recordsLinked to original sources
PubMed2007

Listen to me, too! Lessons from involving children with complex healthcare needs in research about multi-agency services.

BACKGROUND: Children with complex healthcare needs are often excluded, both from active involvement in research projects and from direct consultation in services. During a 3-year research study into multi-agency services for children with complex healthcare needs, the authors involved children in a number of innovative ways and endeavoured to discover what impact, if any, multi-agency working made to them. METHODS: The researchers 'spent time' with 18 children with complex healthcare needs. They used a variety of methods to engage with the children in a meaningful way. More than half of the children had no verbal communication, so it was necessary in some cases to work with an advocate, usually the parent, to aid the process. RESULTS: Children with complex healthcare needs can take part in research as long as the research is set up sensitively and flexibly. In terms of the impact of multi-agency working, the authors concluded significant advances had been achieved for this group: almost all the children were living at home and attending school. However, there were significant gaps in addressing children's human rights in relation to communication, independence and relationships. In addition, many of the children had very little effective direct consultation with the multi-agency services. CONCLUSIONS: There are significant advances in involving disabled children in research and in service delivery, but there is still some way to go in involving those with complex healthcare needs. The challenges are considerable, but the benefits far outweigh these, not least being the value that parents, carers and the children themselves place upon being listened to.

Adolescent↗
PubMed2004

Preclinical safety profile of sildenafil.

Sildenafil citrate, marketed as Viagra, for the treatment of erectile dysfunction, has a proven record of safety in humans as predicted by the results of extensive pharmacological and toxicological testing in animals and in vitro, and confirmed by pharmacokinetic exposure data. The aim of this paper is to review succinctly the main findings resulting from these experiments. Daily doses of sildenafil, within and far beyond the human therapeutic range, were given to dogs and rodents for up to 1 and 2 y, respectively. Plasma analyses were conducted to determine the exposure to sildenafil. We found species-specific effects in dogs (Beagle pain syndrome), mice (marked intestinal dilatation) and rats (adaptive reversible hepatocellular hypertrophy associated with secondary thyroid hypertrophy). All these effects in rodents and dogs have no relevance to humans. Morphometric thickness measurements of the retinal layers carried out in response to clinical observations of visual disturbances in humans indicated no difference between treated and control rats and dogs after up to 24 months of treatment. There was no evidence of histopathologic damage to any structures of the visual pathway. Sildenafil had no effects on fertility, no teratogenic potential, was not genotoxic and has no carcinogenic potential. In rats and dogs, safety ratios were 40:1 and 28:1, respectively, in terms of exposure over 24 h (AUC24 h) and 19:1 and 8:1, respectively, in terms of peak plasma concentration (Cmax). These safety ratios illustrate the separation between exposure to sildenafil of animals at large nontoxic doses and the much smaller human therapeutic exposure. This profile highlights the very low risk of human toxicity for sildenafil. The favourable results of the nonclinical safety evaluation of sildenafil in established animal models have been confirmed by many years of clinical experience during the development and marketing of sildenafil.

Abnormalities, Drug-Induced↗
PubMed2002

Towards evidence based emergency medicine: best BETs from Manchester Royal Infirmary. Routine use of antibiotic ointment and wound healing.

A short cut review was carried out to establish whether topical antibiotics improved the outcome of simple wounds. Altogether 71 papers were found using the reported search, of which one presented the best evidence to answer the clinical question. The author, date and country of publication, patient group studied, study type, relevant outcomes, results, and study weaknesses of this best paper are tabulated. A clinical bottom line is stated.

Anti-Bacterial Agents↗
PubMed2001

Measurement of the charged pion electromagnetic form factor.

Separated longitudinal and transverse structure functions for the reaction 1H(e,e(')pi(+))n were measured in the momentum transfer region Q2 = 0.6--1.6 (GeV/c)(2) at a value of the invariant mass W = 1.95 GeV. New values for the pion charge form factor were extracted from the longitudinal cross section by using a recently developed Regge model. The results indicate that the pion form factor in this region is larger than previously assumed and is consistent with a monopole parametrization fitted to very low Q2 elastic data.

Journal Article↗
PubMed2001

Construct design for efficient, effective and high-throughput gene silencing in plants.

Post-transcriptional silencing of plant genes using anti-sense or co-suppression constructs usually results in only a modest proportion of silenced individuals. Recent work has demonstrated the potential for constructs encoding self-complementary 'hairpin' RNA (hpRNA) to efficiently silence genes. In this study we examine design rules for efficient gene silencing, in terms of both the proportion of independent transgenic plants showing silencing, and the degree of silencing. Using hpRNA constructs containing sense/anti-sense arms ranging from 98 to 853 nt gave efficient silencing in a wide range of plant species, and inclusion of an intron in these constructs had a consistently enhancing effect. Intron-containing constructs (ihpRNA) generally gave 90-100% of independent transgenic plants showing silencing. The degree of silencing with these constructs was much greater than that obtained using either co-suppression or anti-sense constructs. We have made a generic vector, pHANNIBAL, that allows a simple, single PCR product from a gene of interest to be easily converted into a highly effective ihpRNA silencing construct. We have also created a high-throughput vector, pHELLSGATE, that should facilitate the cloning of gene libraries or large numbers of defined genes, such as those in EST collections, using an in vitro recombinase system. This system may facilitate the large-scale determination and discovery of plant gene functions in the same way as RNAi is being used to examine gene function in Caenorhabditis elegans.

Arabidopsis↗
PubMed2001

Genetic polymorphisms of microsomal and soluble epoxide hydrolase and the risk of Parkinson's disease.

Oxidative stress is hypothesized to play a major role in the destruction of dopaminergic neurons, which is associated with Parkinson's disease. Epoxides are potentially reactive intermediates formed through the oxidative metabolism of both exogenous and endogenous substances that contribute to cytotoxic damage mediated by oxidative stress. The microsomal (EPHX1) and soluble (EPHX2) epoxide hydrolases function to regulate the oxidation status of a wide range of xenobiotic- and lipid-derived substrates; therefore, interindividual variation in these pathways may mitigate epoxide-related cellular injury. In this investigation, we examined the potential association between the risk of Parkinson's disease and genetic variation within the EPHX1 and EPHX2 genes. Fluorescent 5' nuclease-based assays were developed to identify the allelic status of individuals with respect to specific single nucleotide polymorphisms in exons 3 and 4 of the EPHX1 gene and exons 8 and 13 of the EPHX2 gene. EPHX1 and EPHX2 genotype data were obtained from 133 idiopathic Parkinson's disease patients and 212 control subjects matched on age, gender and ethnicity. No statistically significant differences were found in the distribution of the reference and variant alleles between Parkinson's disease and control subjects, or when results were stratified by gender. Therefore, common polymorphisms within EPHX1 and EPHX2 do not appear to be important risk factors for Parkinson's disease.

Adult↗
PubMed2001

A comparison of quantitative coronary angiography systems using a unique set of in vivo coronary stenosis images.

OBJECTIVE: To compare the accuracy and precision of measurements of minimum lumen diameter (MLD) among two existing, and one new, quantitative coronary angiography systems. MATERIALS AND METHODS: The analysis was performed using in vivo cinearteriograms of precisely drilled, radiolucent plastic beads that were inserted percutaneously into the coronary arteries of canines. The existing algorithms compared were the ArTrek and the Coronary Measurement System (CMS). The latter was applied in two modes: a mode based on a minimal cost analysis algorithm and a mode based on a gradient field transform. The new algorithm (CorTrek) was also applied in two modes: a mode called the ArTrek compatible mode and a mode known as the 'regression' mode. The latter mode uses a look-up table, based on a phantom calibration step, to readjust the measured MLD to overcome system nonlinearities (overestimation of small diameters and underestimation of large diameters). RESULTS: In the absence of editing, the optimal accuracy (no significant bias) was achieved with the ArTrek compatible algorithm (-0.03 mm for an MLD between 0.83 and 1.83 mm). All other algorithms showed significant under- or overestimation of the MLD within this range. The precision ranged from 0.18 to 0.40 mm without editing, and was best with the ArTrek algorithm. CONCLUSIONS: The present study provides in vivo validation and comparative performance characteristics of a new, accurate coronary quantitative angiography system.

Algorithms↗
PubMed2000

New paradoxical games based on brownian ratchets

Based on Brownian ratchets, a counterintuitive phenomenon has recently emerged-namely, that two losing games can yield, when combined, a paradoxical tendency to win. A restriction of this phenomenon is that the rules depend on the current capital of the player. Here we present new games where all the rules depend only on the history of the game and not on the capital. This new history-dependent structure significantly increases the parameter space for which the effect operates.

Journal Article↗
PubMed2000

Measurement of tensor polarization in elastic electron-deuteron scattering at large momentum transfer

Tensor polarization observables ( t(20), t(21), and t(22)) have been measured in elastic electron-deuteron scattering for six values of momentum transfer between 0.66 and 1.7 (GeV/c)(2). The experiment was performed at the Jefferson Laboratory in Hall C using the electron High Momentum Spectrometer, a specially designed deuteron magnetic channel and the recoil deuteron polarimeter POLDER. The new data determine to much larger Q2 the deuteron charge form factors G(C) and G(Q). They are in good agreement with relativistic calculations and disagree with perturbative QCD predictions.

Journal Article↗
PubMed2000

Location and gross morphology of the nasopalatine duct in human adults.

OBJECTIVE: To characterize the nasal opening of the human nasopalatine duct (NPD; a major duct of the vomeronasal system used in animals for chemical communication) by identifying its location, categorizing variations in physical characteristics, and assessing frequency of detection. DESIGN: Two studies: (1) general study incorporating endoscopic examinations documented by videotapes and photographs, and an investigation of detection bias in terms of method of visualization and defining criteria for NPD identification; and (2) cadaver dissections examining NPD gross anatomy and proximity to the putative vomeronasal organ (VNO), the second major duct of the vomeronasal system. SETTING: Department of Otolaryngology, University of Chicago Hospitals, Chicago, Ill. SUBJECTS: A total of 125 university community volunteers, with a mean age of 23 years. RESULTS: (1) General study: NPD was located 1.9+/-0.02 cm (mean+/-SEM) dorsal to the columella nasi, and 0.2+/-0.01 cm above the nasal floor/septum junction, in both nostrils (90% bilateral), and was symmetrical in shape. An NPD was detected in 94% of 221 nostrils unobstructed in the region of interest. Fossa shapes were oval (57%), round (18%), spindle-shaped (18%), and tubular (7%). A small, round aperture was visualized in 30% of fossae. Among 3 observers, NPD detection frequency ranged from 94% to 40%, with the disparity due to inclusion of different defining characteristics. (2) Cadaver dissection study: bilateral nasal NPD fossae were found in every specimen probed to maximum approximate depth of 8 mm. No buccal pits associated with patent NPD were detected. Putative VNOs superior and just anterior to NPD fossae were detected in fewer than half the specimens. CONCLUSIONS: The nasal opening of the NPD is bilateral and symmetrical, located at the base of the nasal septum. Unusually contradictory anatomical descriptions in the human putative VNO literature may be attributable to inexact descriptions or misidentification of structures. The function of NPD remains controversial.

Adolescent↗
PubMed1999

Lifestyle modifications to prevent and control hypertension. 2. Recommendations on obesity and weight loss. Canadian Hypertension Society, Canadian Coalition for High Blood Pressure Prevention and Control, Laboratory Centre for Disease Control at Health Canada, Heart and Stroke Foundation of Canada.

OBJECTIVE: To provide updated, evidence-based recommendations concerning the effects of weight loss and maintenance of healthy weight on the prevention and control of hypertension in otherwise healthy adults (except pregnant women). OPTIONS: The main options are to attain and maintain a healthy body weight (body mass index [BMI] 20-25 kg/m2) or not to do so. For those at risk for hypertension, weight loss and maintenance of healthy weight may prevent the condition. For those who have hypertension, weight loss and maintenance of healthy weight may reduce or obviate the need for antihypertensive medications. OUTCOMES: The health outcome considered was change in blood pressure. Because of insufficient evidence, no economic outcomes were considered. EVIDENCE: A MEDLINE search was conducted for the years 1992-1996 with the terms hypertension and obesity in combination and antihypertensive therapy and obesity in combination. Other relevant evidence was obtained from the reference lists of the articles identified, from the personal files of the authors and through contacts with experts. The articles were reviewed, classified according to study design and graded according to level of evidence. VALUES: A high value was placed on the avoidance of cardiovascular morbidity and premature death caused by untreated hypertension. BENEFITS, HARMS AND COSTS: Weight loss and the maintenance of healthy body weight reduces the blood pressure of both hypertensive and normotensive people. The indirect benefits of a health body weight are well known. The negative effects of weight loss are primarily the frustrations associated with attaining and maintaining a healthy weight. The costs associated with weight loss programs were not measured in the studies reviewed. RECOMMENDATIONS: (1) It is recommended that health care professionals determine weight (in kilograms), height (in metres) and BMI for all adults. (2) To reduce blood pressure in the population at large, it is recommended that Canadians attain and maintain a healthy BMI (20-25). (3) All overweight hypertensive patients (BMI greater than 25) should be advised to reduce their weight. VALIDATION: These recommendations are similar to those of the World Hypertension League, the National High Blood Pressure Education Program Working Group on Primary Prevention of Hypertension, the Canadian Hypertension Society and the Canadian Coalition for High Blood Pressure Prevention and Control. They have not been clinically tested. SPONSORS: The Canadian Hypertension Society, the Canadian Coalition for High Blood Pressure Prevention and Control, the Laboratory Centre for Disease Control at Health Canada, and the Heart and Stroke Foundation of Canada.

Adult↗
PubMed1999

A technique to measure the ability of the human nose to warm and humidify air.

To assess the ability of the nose to warm and humidify inhaled air, we developed a nasopharyngeal probe and measured the temperature and humidity of air exiting the nasal cavity. We delivered cold, dry air (19-1 degrees C, <10% relative humidity) or hot, humid air (37 degrees C, >90% relative humidity) to the nose via a nasal mask at flow rates of 5, 10, and 20 l/min. We used a water gradient across the nose (water content in nasopharynx minus water content of delivered air) to assess nasal function. We studied the characteristics of nasal air conditioning in 22 asymptomatic, seasonally allergic subjects (out of their allergy season) and 11 nonallergic normal subjects. Inhalation of hot, humid air at increasingly higher flow rates had little effect on both the relative humidity and the temperature of air in the nasopharynx. In both groups, increasing the flow of cold, dry air lowered both the temperature and the water content of the inspired air measured in the nasopharynx, although the relative humidity remained at 100%. Water gradient values obtained during cold dry air challenges on separate days showed reproducibility in both allergic and nonallergic subjects. After exposure to cold, dry air, the water gradient was significantly lower in allergic than in nonallergic subjects (1,430 +/- 45 vs. 1,718 +/- 141 mg; P = 0.02), suggesting an impairment in their ability to warm and humidify inhaled air.

Adult↗
PubMed1998

Effects of glibenclamide on blood pressure and cardiovascular responsiveness in non-insulin dependent diabetes mellitus.

OBJECTIVE: To compare the effects of chronic glibenclamide therapy and placebo on blood pressure and cardiovascular responsiveness in patients with non-insulin-dependent diabetes. DESIGN AND METHODS: Fourteen patients with non-insulin-dependent diabetes mellitus, seven of whom were receiving angiotensin converting enzyme inhibitor therapy, received glibenclamide or placebo for 1 month in a double-blind, randomized crossover study. At the end of each treatment period patients attended for studies of forearm vascular responsiveness to intra-brachial arterial infusions of angiotensin II, acetylcholine, sodium nitroprusside and noradrenaline, responses of blood pressure to intravenous infusions of noradrenaline and angiotensin II and 24 h ambulatory blood pressure monitoring. RESULTS: Administration of glibenclamide produced significantly better glycaemic control than placebo (fasting blood glucose level 8.5 +/- 2.4 versus 13.5 +/- 4.5 mmol/l, P < 0.001) and plasma insulin levels were significantly higher during glibenclamide treatment than they were with placebo (12.9 +/- 4.4 versus 9.2 +/- 4.1 mU/l, P < 0.05). Body weights at the ends of the glibenclamide treatment and placebo phases were similar (92.1 +/- 14.3 versus 91.1 +/- 14.3 kg, P = 0.085). Night-time systolic blood pressures were significantly higher during glibenclamide treatment than they were with placebo (128 +/- 17 versus 118 +/- 10 mmHg, P < 0.05) due to there being a smaller day-night difference in systolic blood pressure during glibenclamide treatment that appeared to occur mainly in patients receiving angiotensin converting enzyme inhibitors. Responses of diastolic blood pressure to intravenous infusion of angiotensin II and forearm vascular responses to intra-brachial arterial infusion of angiotensin II were significantly greater during glibenclamide treatment than they were with placebo (P < 0.05). However, the enhancement of forearm vascular responses during glibenclamide treatment appeared to be restricted to patients receiving angiotensin converting enzyme inhibitors. Responses of blood pressure to intravenous infusion of noradrenaline and forearm vascular responses to infusions of noradrenaline, acetylcholine and nitroprusside did not differ between glibenclamide treatment and placebo; neither did basal forearm vascular resistance. CONCLUSIONS: Glibenclamide therapy is associated with greater responses of blood pressure and forearm vascular responses to infusion of angiotensin and higher nocturnal blood pressures. This effect appears to be influenced by concomitant angiotensin converting enzyme inhibition.

Acetylcholine↗
PubMed1998

Low dose oestrogen prophylaxis for recurrent urinary tract infections in elderly women.

OBJECTIVE: To assess the efficacy of oral oestriol in the prevention of recurrent urinary tract infections in elderly women. DESIGN: Double-blind, randomised, parallel group, placebo controlled trial SETTING: Urogynaecology Unit at King's College Hospital with some women recruited from the geriatric units of St. Pancras Hospital and Dulwich Hospital, London (UK). PARTICIPANTS: Seventy-two postmenopausal women older than 60 years of age (mean 73.2 years) suffering from recurrent urinary tract infections. INTERVENTION: Oral oestriol (3 mg per day) or placebo for six months. MAIN: outcome measures Urinary tract infection rates. RESULTS: The study was difficult to conduct because of its design and the age of the participants. Oral oestriol (3 mg per day) was not shown to be superior to placebo in the prevention of recurrent urinary tract infections, but both oestriol and placebo improved urinary symptoms during the trial. CONCLUSION: The power of the study might have been too low to detect a significant difference between the groups, or oral oestriol (3 mg per day) may have been either the wrong dose or the wrong route of administration for this indication.

Administration, Oral↗
PubMed1997

Racism is real.

Explore the source record for details and available documents.

Black or African American↗
PubMed1997

Lipoproteins and cardiovascular reactivity.

The observation that relatively short periods of cholesterol lowering therapy can reduce the incidence of coronary artery disease events has prompted interest in the short term effects of lipoproteins on cardiovascular responsiveness. Numerous studies in animals and humans have demonstrated that oxidized LDL-cholesterol can impair endothelial dependent vasodilation in coronary arteries and peripheral resistance vessels. Reduction of plasma LDL-cholesterol levels in hypercholesterolaemic patients improves nitric oxide mediated vasodilator responses in the coronary and peripheral circulation. LDL-cholesterol also potentiates responses to vasoconstrictors such as noradrenaline and endothelin-1 in the absence of endothelium, possibly by enhancing calcium influx into vascular smooth muscle cells. Pharmacological reduction of plasma LDL-cholesterol levels has been shown to reduce blood pressure responses to intravenous infusions of pressor hormones and to stress. However, the relative contribution of changes in endothelial dependent vasodilation and vasoconstrictor or inotropic responses remains to be established. Short term changes in LDL-cholesterol produce changes in cardiovascular responsiveness that may influence the development of ischaemic events.

Animals↗