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Biomedical subjects

David Williams

Publications and source records attributed to David Williams.

At least 55 records · Page 3Linked to original sources
PubMed2005

Is sphincter electromyography a helpful investigation in the diagnosis of multiple system atrophy? A retrospective study with pathological diagnosis.

Sphincter electromyography (spEMG) is often used as an ancillary test when multiple system atrophy (MSA) is suspected. Our aim was to determine the clinical features associated with spEMG being performed, the influence of the result on the final clinical diagnosis, and its utility as a clinical investigation. A retrospective audit of all cases in the Queen Square Brain Bank between 1989 and 2002 was performed. The clinical features and diagnostic accuracy were compared between patients in whom spEMG was performed and those in whom it was not. From 845 sets of complete clinical records, we identified 37 (4.4%) cases that had been investigated with spEMG. Thirty of these cases had a pathological diagnosis of MSA. Of these 30, 24 had abnormal spEMGs, 5 had a borderline result, and only 1 had a normal spEMG. Sixty-six cases had pathologically proven MSA but no spEMG. Those investigated with spEMG were younger at disease onset (P < 0.001), more frequently male (P = 0.03), and more likely to have had other investigations performed. They had a greater incidence of pyramidal tract signs at final clinical diagnosis, and the final clinical diagnostic accuracy was higher (P = 0.04). Due to the retrospective nature of the study, balanced populations for calculation of sensitivity and specificity were not available. In this selected series of pathologically confirmed cases, investigation with spEMG was one of several factors associated with improved clinical diagnostic accuracy. A normal spEMG is unlikely in pathologically proven MSA, at least in cases with a mean symptom duration of more than 5 years when the test is performed.

Adult↗
PubMed2005

Quantitative assessment of ventricular function in sickle cell disease: effect of long-term erythrocytapheresis.

BACKGROUND: Previous studies on cardiac function in patients with sickle cell disease (SCD) demonstrated abnormalities of systolic and diastolic function including elevated left ventricular myocardial performance index (LVMPI) on chronic transfusion protocols. LVMPI has been validated as a useful and easy non-invasive measure of overall cardiac function. Up to now, there are no reported studies on cardiac function in patients with SCD maintained on long-term erythrocytapheresis (LTE). PROCEDURES: We recorded LVMPI in 22 patients with SCD aged 3-20 years and we compared the results between non-transfused patients (NT-SCD) and patients on LTE (T-SCD). RESULTS: Males with SCD had higher mean LVMPI than females (P = 0.04). There were significant differences among T-SCD, severe NT-SCD, and mild NT-SCD patients with respect to hemoglobin (Hb) levels (P = .003) and TR velocity (P = .03). T-SCD patients showed elevated LVMPI compared to NT-SCD patients with severe and mild disease (P = 0.002). Pair-wise comparisons demonstrated that T-SCD patients had LVMPI that was significantly higher than NT-SCD (mild) patients (P = 0.01). CONCLUSIONS: Our study demonstrates that patients SCD on LTE have cardiac dysfunction based on elevated LVMPI. This may be a reflection of the global severity of disease. Our findings merit further investigation with serial monitoring of LVMPI on a larger number of patients with SCD.

Adolescent↗
PubMed2005

Ion transport blockers inhibit human rhinovirus 2 release.

Picornavirus replication causes leakage of cytoplasmic K+ and an influx of Na+ and Ca2+. In this study, we have explored the possibility that a blockade of Ca2+ and Na+ influx would reduce rhinovirus production and/or release. The Ca2+-channel blockers, verapamil and diltiazem, as well as the blocker of Na+/H+ exchange and the epithelial Na+ channel, EIPA, inhibited both virus production and release. The effect on virus release was more pronounced than the effect on production, thus raising the possibility that rhinovirus release may serve as a target for antiviral agents. Unexpectedly, our results also showed that the antiviral activity of the Ca2+-channel blockers was not due to the block of Ca2+ influx. Similarly, the antiviral activity of EIPA appeared to be unrelated to the blockade of cellular Na+/H+ exchanger or the epithelial Na+ channel. Potential alternative mechanisms of the antiviral activity of these compounds are discussed.

Calcium↗
PubMed2005

Endovascular treatment of thoracic aortic aneurysms: results of the phase II multicenter trial of the GORE TAG thoracic endoprosthesis.

OBJECTIVE: A decade after the first report of descending thoracic aortic aneurysm (DTA) repair with endografts, a commercial device is yet to be approved in the United States. The GORE TAG endoprosthesis, an investigational nitinol-supported expanded polytetrafluoroethylene tube graft with diameters of 26 to 40 mm, is the first DTA device to enter phase II trials in the United States and has been used worldwide for a host of thoracic pathologies. METHODS: A multicenter prospective nonrandomized phase II study of the GORE TAG endoprosthesis was conducted at 17 sites. Enrollment was from September 1999 to May 2001. Preoperative workup included arteriography and spiral computed tomography scans of the chest, abdomen, and pelvis. Follow-up radiographs and computed tomography scans were obtained at 1, 6, and 12 months and yearly thereafter. RESULTS: A total of 139 (98%) of 142 patients had a successful implantation of the device. Inadequate arterial access was responsible for the 3 failures. The mean DTA size was 64.1 +/- 15.4 mm. Men slightly outnumbered women (57.7%), with an average age of 71 years, and 88% of the patients were white. Ninety percent were American Society of Anesthesiologists category III or IV. One device was used in 44% of patients, and 56% required two or more devices to bridge the thoracic aorta. The left subclavian artery was covered in 28 patients, with planned carotid-subclavian transposition. The procedure time averaged 150 minutes, estimated blood loss averaged 506 mL, intensive care unit stay averaged 2.6 days, and hospital stay averaged 7.6 days. Within 30 days, 45 (32%) patients had at least 1 major adverse event: 5 (4%) experienced a stroke, 4 (3%) demonstrated temporary or permanent paraplegia, 20 (14%) experienced vascular trauma or thrombosis, and 2 (1.5%) died. Mean follow-up was 24.0 months. Four patients had aneurysm-related deaths. Three patients underwent endovascular revisions for endoleak. No ruptures have been reported. Twenty wire fractures have been identified in 19 patients; 18 (90%) of these occurred in the longitudinal spine, and only 1 patient required treatment. At 2 years, aneurysm-related and overall survival rates are 97% and 75%, respectively. CONCLUSIONS: The GORE TAG thoracic endoprosthesis provides a safe alternative for the treatment of DTAs, with low mortality, relatively low morbidity, and excellent 2-year freedom from aneurysm-related death. Longitudinal spine fractures have so far been associated with rare clinical events.

Adult↗
PubMed2005

The relationship between oscillatory activity and motor reaction time in the parkinsonian subthalamic nucleus.

Averaging techniques have demonstrated that movement preparatory cues and movement itself are associated with marked reductions in the oscillatory synchrony of local neuronal populations in the area of the human parkinsonian subthalamic nucleus (STN), as indexed by 8-30 Hz local field potential (LFP) activity. In order to examine the detailed nature and strength of the relationship between reductions in oscillatory activity and movement we examined single-trial LFP activity recorded from the STN area of parkinsonian subjects engaged in a choice reaction task. In this task an initial warning cue was either fully predictive or non-predictive of the hand required to make a later motor response. This motor response was elicited by a second go cue to which data were aligned. We observed a significant linear relationship between the onset time of oscillation reduction after go cues and subsequent motor response time across single trials within subjects. Consistent with this observation we also found a positive correlation of power with response time following go cues. In addition, we observed shorter durations of suppression in fully predictive trials where selection of the response could precede go cue presentation. The results are consistent with the hypothesis that reductions in 8-30 Hz population synchrony in the STN area are related to the processing required for motor preparation, particularly response selection.

Aged↗
PubMed2005

Association of raised titres of antibodies to Chlamydia pneumoniae with a history of pre-eclampsia.

OBJECTIVE: To establish the prevalence of Chlamydia pneumoniae (C. pneumoniae) infection in a pregnant UK population and to investigate whether C. pneumoniae infection is more common in women with a previous history of pre-eclampsia. DESIGN: Prospective study. SETTING: Academic Hospital. POPULATION: Ninety-one pregnant women (54 parous and 37 nulliparous) at 16-22 weeks of gestation were studied. Of the parous women, 32 had a previous history of pre-eclampsia. METHODS: Peripheral blood was drawn for C. pneumoniae antibodies between 16-22 and 28-40 weeks of gestation. C. pneumoniae antibodies were measured using a solid-phase enzyme immunoassay. According to pregnancy outcome, women were categorised into normal, gestational hypertension and pre-eclampsia groups. MAIN OUTCOME MEASURES: Serum levels of IgG, IgA and IgM C. pneumoniae antibodies. RESULTS: Prevalence of seropositivity to C. pneumoniae was 77%. Parous women had significantly higher levels of IgA and IgM C. pneumoniae antibodies than nulliparous women (P < 0.04). Parous women with previous pre-eclampsia were found to have higher levels of antibodies than parous women with a normal obstetric history (P< or = 0.003). There was no difference in the antibody levels in women with different pregnancy outcomes. CONCLUSIONS: The longitudinal data do not indicate an association between C. pneumoniae infection and pre-eclampsia. However, the subgroup analysis of parous women demonstrated raised C. pneumoniae antibodies in the women with previous pre-eclampsia, and therefore suggests that there may be an association between C. pneumoniae and the disease in this group.

Adult↗
PubMed2005

Bupropion: risks and benefits.

Cigarette smoking represents one of the most preventable causes of death worldwide. However, success rates for stopping smoking are disappointingly low and are associated with high relapse rates. There is a need for a successful form of smoking cessation therapy. Bupropion is an effective therapy for smoking cessation and is recommended as first-line treatment in both US and UK guidelines. Its mechanism of action in smoking cessation is unclear, although it is thought that dopaminergic pathways are involved in the 'reward' circuit of drug dependence. Seizures are an important adverse effect of bupropion and care is needed when used in other conditions or with other medication that can lower the seizure threshold. Bupropion has been shown to be a cost-effective therapy for smoking cessation.

Bupropion↗
PubMed2005

Mechanical signalling: lessons from the past that control the future.

Relative movement between an implanted material and tissues can play a decisive role in generating the host response. As with other components of the biocompatibility of devices, it is essential to control the mechanical signalling associated with this movement if we are to optimise this response.

Animals↗
PubMed2005

Stem cells in medical techonology.

Major ethical and scientific debates surround the potential of stem cells to radically alter therapies in health care. This article provides some basic background on the origins and functions of stem cells.

Animals↗
PubMed2005

Environmentally smart polymers.

Much progress has been made in the synthesis of polymers that emulate certain naturally occurring polymers and demonstrate exquisite sensitivity to environmental factors such as temperature, pH and mechanical stress. This article explains how these are finding use in medical technologies such as drug delivery and cell-sheet tissue engineering.

Absorbable Implants↗
PubMed2005

Business models for biomaterials in regenerative medicine.

The emergence of new therapeutic methods and technologies, including those associated with regenerative medicine, has required new thinking about regulation, reimbursement and business models. Some of the issues that particularly relate to the materials used in these technologies are discussed in this article.

Biocompatible Materials↗
PubMed2005

Acute selenium poisoning: suicide by ingestion.

Selenium is a ubiquitous element in the environment essential to the human diet and widely utilized in industrial processes. Fatal human selenium intoxication is rare. The authors report a case in which investigators recovered a bottle of gun-bluing agent beside a 24-year-old man. He exhibited signs and symptoms typical of acute selenium intoxication presenting with nausea and vomiting, followed by pulmonary edema and rapid cardiovascular collapse approximately 3 to 4 h after ingestion. Classic electrocardiographic (EKG) changes, which have been reported to occur in acute selenium intoxication, included sinus tachycardia with ST wave alteration. Toxicological results confirmed elevated blood and tissue concentrations. The cause of death was ascribed to acute selenium intoxication, which ensued rapidly after oral consumption. The manner of death was suicide. This case report, which presents an overview of acute and chronic selenium poisoning, underscores the value of thorough toxicologic analyses of tissue and body fluids in humans.

Adult↗
PubMed2005

Systemic delivery versus elution of drugs that enhance device performance.

Questions are being raised as to whether it is better to deliver a drug systemically or via a controlled-release mechanism in situations where it is intended that the drug would enhance medical device performance. The issues are addressed here in relation to cardiovascular devices and orthopaedics.

Anti-Bacterial Agents↗
PubMed2005

Phases in titanium alloys.

Titanium (Ti) provides the basis for many alloys used in medical technology. These alloys have been discussed many times in this column over the past decade. In recent years in particular, there have been a number of developments in Ti metallurgy, which suggests that a reappraisal of these alloy systems is timely.

Alloys↗
PubMed2005

Chinese solutions.

Following an extended visit to (China to discuss health (are technologies, a number of issues concerning the rapid growth in the country's biomaterials and medical technology sectors have become apparent. These developments deserve the attention of scientists and industrialists in the West.

Biocompatible Materials↗
PubMed2005

The risks of nanotechnology.

Nanotechnology is extremely fashionable, especially in the medical products sector, but questions are now being asked about the potential for new health risks that are introduced with the products and processes associated with nanotechnology. This article discusses some of the principal findings of a new report on this subject.

Humans↗