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Biomedical subjects

Richard Walker

Publications and source records attributed to Richard Walker.

18 recordsLinked to original sources
PubMed2006

The prevalence of Parkinson's disease in an area of North Tyneside in the North-East of England.

OBJECTIVES: UK prevalence studies have demonstrated prevalence rates for Parkinson's disease (PD) of 108 to 164 cases per 100,000. we aimed to calculate the prevalence of PD in an area of the North-East of England. MATERIAL AND METHODS: A case finding methodology was used to identify cases in North Tyneside with a population of 108,597 at the 2001 UK census. RESULTS: 161 cases were identified giving crude and age-adjusted prevalence estimates of 148 cases (95% CI 124-174) and 139 cases (95% CI 116-162) per 100,000, respectively. The mean age was 74.1 years (range 44-96 years) with mean disease duration of 5.6 years. CONCLUSIONS: The prevalence of PD in North Tyneside is comparable with that of the rest of the UK. The prevalence of PD in the UK appears not to have changed greatly over the last 30 years.

Adult↗
PubMed2006

Solid-phase microextraction: investigation of the metabolism of substances that may be abused by inhalation.

Purified liquefied petroleum gas (LPG), a mixture of butane, isobutane, and propane, is commonly abused by inhalation. Little is known about the mammalian metabolism of these substances. Metabolism of other hydrocarbons, including n-hexane and cyclohexane, has been studied in vitro using a range of liver preparations, with metabolites analyzed by static headspace techniques. Solid-phase microextraction (SPME) for sampling metabolites in the headspace of incubates of volatile compounds with activated rat liver microsomes is investigated. Cyclohexanol and cyclohexanone were formed from cyclohexane and 1-, 2-, and 3-hexanol and 2-hexanone from n-hexane as predicted. Secondary alcohols are found for the other compounds studied, except for propene and isobutane, together with 2-propanone and 2-butanone from propane and n-butane, respectively. Samples from three individuals who died following LPG abuse contained a range of putative n-butane metabolites: n-butanol, 2-butanol, 2,3-butanediol, 3-hydroxy-2-butanone, and 2,3-butanedione. To our knowledge, the last three compounds have not been proposed as metabolites of n-butane in man. These might be produced through similar metabolic pathways to those of n-hexane and n-heptane. The findings indicate the value of SPME for investigating the metabolism of volatile substances and for detecting and monitoring exposure to these compounds.

Animals↗
PubMed2005

Emergency hospital admissions in idiopathic Parkinson's disease.

Little is known about the hospital inpatient care of patients with idiopathic Parkinson's disease (PD). Here, we describe the features of the emergency hospital admissions of a geographically defined population of PD patients over a 4-year period. Patients with PD were identified from a database for a Parkinson's disease service in a district general hospital with a drainage population of approximately 180,000. All admissions of this patient subgroup to local hospitals were found from the computer administration system. Two clinicians experienced in both general medicine and PD then reviewed the notes to identify reasons for admission. Admission sources and discharge destinations were recorded. Data regarding non-PD patients was compared to PD patients on the same elderly care ward over the same time period. The total number of patients exposed to analysis was 367. There was a total exposure of 775.8 years and a mean duration of 2.11 years per patient. There were 246 emergency admissions to the hospital with a total duration of stay of 4,257 days (mean, 17.3 days). These days were accounted for by 129 patients (mean age, 78 years; 48% male). PD was first diagnosed during 12 (4.9%) of the admissions. The most common reasons for admission were as follows: falls (n=44, 14%), pneumonia (n=37, 11%), urinary tract infection (n=28, 9%), reduced mobility (n=27, 8%), psychiatric (n=26, 8%), angina (n=21, 6%), heart failure (n=20, 6%), fracture (n=14, 4%), orthostatic hypotension (n=13, 4%), surgical (n=13, 4%), upper gastrointestinal bleed (n=10, 3%), stroke/transient ischemic attack (n=8, 2%), and myocardial infarction (n=7, 2%). The mean length of stay for the PD patients on the care of elderly ward specializing in PD care was 21.3 days compared to 17.8 days for non-PD patients. After hospital admission, there was a reduction in those who returned to their own home from 179 to 163 and there was an increase in those requiring nursing home care from 37 to 52. Infections, cardiovascular diseases, falls, reduced mobility, and psychiatric complications accounted for the majority of admissions. By better understanding the way people with PD use hospital services, we may improve quality of care and perhaps prevent some inpatient stays and care-home placements.

Aged↗
PubMed2005

Osteoporosis in Parkinson's disease.

There are few studies of osteoporosis in Parkinson's disease (PD). We assessed the prevalence of osteoporosis in a PD clinic cohort. All subjects with a confirmed diagnosis of PD attending a clinic were invited to participate. All consenting subjects had bone density measured by dual energy X-ray absorptiometry scanning. Further data, including demography, disease duration, and disease severity, were collected. One hundred five subjects participated; median age was 75 (54-92) years. Fifty-one (49%) patients were men. Of the men: median T score, -1.3 (range, -4.7 to 3.8); median Z score, 0.0 (-3.2 to 4.7); diagnostic categories: osteoporosis, 20%; osteopenia, 41%; normal, 39%. Of the women: median T score -2.7 (-4.7 to 1.4); median Z score, -0.25 (-2.6 to 4.2); diagnostic categories: osteoporosis, 63%; osteopenia, 28%; and normal, 9%. Whole sample: osteoporosis, 42%; osteopenia, 34%; and normal, 24%. There were associations between age, depression, disease duration, and osteoporosis but not with disease severity. Female gender was an independent predictor of osteoporosis. The prevalence of osteoporosis/osteopenia is considerable in PD patients but does not exceed that of other people of similar age. Osteoporosis/osteopenia was present in almost all women of this age group with PD.

Age Factors↗
PubMed2005

Molecular identification of a novel deltaproteobacterium as the etiologic agent of epizootic bovine abortion (foothill abortion).

Epizootic bovine abortion (EBA) is endemic in California's coastal range and the foothill regions of the Sierra Nevada, where it has been the primary diagnosed cause of abortion in beef cattle for >50 years. Investigation of these losses has defined a specific fetal syndrome characterized by late-term abortion or birth of weak or dead calves. Although the unusual clinical presentation and unique fetal pathology associated with EBA have been recognized since the 1950s, the identity of the etiologic agent is unknown. In this study, suppression-hybridization PCR was used to identify a fragment of the 16S rRNA gene of a previously undescribed bacterium in thymus tissue derived from affected fetuses. Phylogenetic analysis revealed that this pathogen was a deltaproteobacterium closely related to members of the order Myxococcales. A specific PCR was subsequently developed to detect the presence of this bacterium in DNA extracted from fetal thymuses. Using histopathology as the definitive diagnosis for EBA, this PCR demonstrated 100% specificity and 88% sensitivity. The bacterium was also detected in the argasid tick Ornithodoros coriaceus, which is the recognized vector of EBA. These data imply a close association between this novel agent and the etiology of EBA.

Abortion, Veterinary↗
PubMed2005

Distress in Parkinson's disease: contributions of disease factors and metacognitive style.

Research has suggested that the high levels of depression and anxiety observed in Parkinson's disease are a primary consequence of its pathophysiology. This study aimed to test the hypothesis that a psychological factor, metacognitive style, is significantly associated with distress, independent of previously identified disease-related risk factors. Distress, metacognitive style and disease factors were assessed in 44 people with a diagnosis of Parkinson's disease. People with a specific metacognitive style had an increased vulnerability to distress over and above previously identified disease factors; this suggests future directions for the development of psychological interventions.

Adaptation, Psychological↗
PubMed2005

Developing a Parkinson's Disease service.

People with Parkinson's Disease need information and support if they are to maintain an independent lifestyle. The establishment of a dedicated team in Northumbria for these patients is helping them and their carers to become involved in their care by offering education, counselling and information about medication.

Aged↗
PubMed2003

A structural analysis of the interaction between ncd tail and tubulin protofilaments.

ncd is a minus-end directed, kinesin-like motor, which binds to microtubules with its motor domain and its cargo domain as well. Typical of retrograde motors, the motor domain of ncd locates to the C-terminal end of the polypeptide chain, and hence, the cargo domain constitutes the N-terminal region. To date, several studies have investigated the interaction properties of the motor domain with microtubules, but very few structural data are available about the tail itself or its interaction with microtubules as cargo. Here, we applied cryo-electron microscopy and helical 3D image reconstruction to 15 protofilament microtubules decorated with an ncd tail fragment (N-terminal residues 83-187, named NT6). In our study, the ncd tail shows a behaviour resembling filamentous MAPs such as tau protein, exhibiting a highly flexible structure with no large globular domains. NT6 binds to four different sites on the outer side of microtubules within the proximity of the kinesin motor-binding site. Two of these sites locate within the groove between two neighbouring protofilaments, and appear as strong binding sites, while the other two sites, located at the outer rim, appear to play a secondary role. In addition, the ncd tail fragment induces the formation of large protofilament sheets, suggesting a tail-induced modification of lateral protofilament contacts.

Cryoelectron Microscopy↗
PubMed2002

High-performance deep-ultraviolet optics for free-electron lasers.

Working with wavelengths shorter than the deep ultraviolet involves the development of dedicated optics for free-electron lasers with devoted coating techniques and characterizations. High-performance deep-ultraviolet optics are specially developed to create low-loss, high-reflectivity dielectric mirrors with long lifetimes in harsh synchrotron radiation environments. In February 2001, lasing at 189.7 nm, the shortest wavelength obtained so far with free-electron-laser oscillators, was obtained at the European Free-electron-laser project at ELETTRA Synchrotron Light Laboratory, Trieste, Italy. In July 2001, 330-mW extracted power at 250 nm was measured with optimized transmission mirrors. Research and development of coatings correlated to lasing performance are reported.

Journal Article↗
PubMed2002

Colonization of the developing rhizosphere of sugar beet seedlings by potential biocontrol agents applied as seed treatments.

AIMS: Poor colonization of the rhizosphere is a major constraint of seed treatment biological control. The objectives of this study were to; examine the colonization of the rhizosphere of sugar beet seedlings by selected rhizobacteria; determine the influence of the host rhizosphere and percolating water on the distribution of the bacteria; and deliver two biological control agents (BCAs) by co-inoculation. METHODS AND RESULTS: Rifampicin-resistant bacterial strains (Rif +) applied as single treatments to seed sown in columns of field soil produced persistent populations of 5-9 log10 cfu g-1 in the infection court of the damping-off pathogen Aphanomyces cochlioides in a controlled environment. However, isolates varied in their ability to colonize the lower rhizosphere. Percolating water significantly increased the colonization of the upper rhizosphere. Bacterial populations in the soil profiles of "non-rhizosphere" controls declined markedly with time. There was no interaction between the two selected BCAs applied as a seed treatment mixture. CONCLUSIONS: The distribution of the bacteria resulted primarily from root colonization although percolating water may modify the colonization profiles. Co-inoculation of the sugar-beet rhizosphere is a viable proposition. SIGNIFICANCE AND IMPACT OF THE STUDY: Potential BCAs were successfully delivered to the known infection court of A. cochloides and persisted for the infection period. This bioassay can be used as a tool for the selection of BCAs for field trials.

Bacillus megaterium↗
PubMed2002

Genetic redundancy in evolving populations of simulated robots.

A number of authors have argued that redundancy in biological organisms contributes to their evolvability. We investigate this hypothesis via the experimental manipulation of genetic redundancy in evolving populations of simulated robots controlled by artificial neural networks. A genetic algorithm is used to simulate the evolution of robots with the ability to perform a previously studied task. Redundancy is measured using systematic lesioning. In our experiments, populations of robots with larger genotypes achieve systematically higher fitness than populations whose genotypes are smaller. It is shown that, in principle, robots with smaller genotypes have enough computational power to achieve optimal fitness. Populations with larger (redundant) genotypes appear, however, to be more evolvable and display significantly higher diversity. It is argued that this enhanced evolvability is a direct effect of genetic redundancy, which allows populations of redundant robots to explore neutral networks spanning large areas of genotype space. We conjecture that, where cost considerations allow, redundancy in functional or potentially functional components of the genome may make a valuable contribution to evolution in artificial and perhaps in biological systems. The methods described in the article provide a practical way of testing this hypothesis for the artificial case.

Models, Genetic↗
PubMedDate not supplied

Posterior resin-based composite: review of the literature.

The use of direct posterior resin-based composite has increased primarily due to patient esthetic desires and product improvements. Other factors (substantiated or not) contributing to increased use of resin-based composite are environmental and health concerns with dental amalgam. New visible light cured resin-based composite products are introduced yearly, as manufacturers continue to improve this tooth-colored restorative material. This paper will characterize current posterior resin-based composite materials (hybrid, microfill, flowable, and packable), review recent in vitro and clinical research, and recommend indications for these materials. In addition, the literature on compomers will be reviewed and recommendation made for their use. The data indicates that composite resin is a technique sensitive restorative material that can be used in large preparations if proper manipulation and isolation can be maintained. Compomers may also be used as an esthetic posterior restorative if proper isolation is provided.

Bicuspid↗
PubMedDate not supplied

How storage and mixing affect a resin-modified glass ionomer.

This study investigates how the storage time and mixing speed of an older (20+ years old), common brand triturator affect the working time of a resin-modified glass ionomer restorative material. To achieve consistent working times, the correct mixing speed should be used, especially for material near its expiration date.

Analysis of Variance↗